[Characterization of stem cells derived from the neonatal auditory sensory epithelium].

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Diensthuber, M; Heller, S

2010-11-01

In contrast to regenerating hair cell-bearing organs of nonmammalian vertebrates the adult mammalian organ of Corti appears to have lost its ability to maintain stem cells. The result is a lack of regenerative ability and irreversible hearing loss following auditory hair cell death. Unexpectedly, the neonatal auditory sensory epithelium has recently been shown to harbor cells with stem cell features. The origin of these cells within the cochlea's sensory epithelium is unknown. We applied a modified neurosphere assay to identify stem cells within distinct subregions of the neonatal mouse auditory sensory epithelium. Sphere cells were characterized by multiple markers and morphologic techniques. Our data reveal that both the greater and the lesser epithelial ridge contribute to the sphere-forming stem cell population derived from the auditory sensory epithelium. These self-renewing sphere cells express a variety of markers for neural and otic progenitor cells and mature inner ear cell types. Stem cells can be isolated from specific regions of the auditory sensory epithelium. The distinct features of these cells imply a potential application in the development of a cell replacement therapy to regenerate the damaged sensory epithelium.

REGULATED VESICULAR TRAFFICKING OF SPECIFIC PCDH15 AND VLGR1 VARIANTS IN AUDITORY HAIR CELLS

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Zallocchi, Marisa; Delimont, Duane; Meehan, Daniel T.; Cosgrove, Dominic

2012-01-01

Usher syndrome is a genetically heterogeneous disorder characterized by hearing and balance dysfunction and progressive retinitis pigmentosa. Mouse models carrying mutations for the nine Usher-associated genes have splayed stereocilia and some show delayed maturation of ribbon synapses suggesting these proteins may play different roles in terminal differentiation of auditory hair cells. The presence of the Usher proteins at the basal and apical aspects of the neurosensory epithelia suggests the existence of regulated trafficking through specific transport proteins and routes. Immature mouse cochleae and UB/OC-1 cells were used in this work to address whether specific variants of PCDH15 and VLGR1 are being selectively transported to opposite poles of the hair cells. Confocal co-localization studies between apical and basal vesicular markers and the different PCDH15 and VLGR1 variants along with sucrose density gradients and the use of vesicle trafficking inhibitors show the existence of Usher protein complexes in at least two vesicular sub-pools. The apically trafficked pool co-localized with the early endosomal vesicle marker, rab5, while the basally trafficked pool associates with membrane microdomains and SNAP25. Moreover, co-immunoprecipitation experiments between SNAP25 and VLGR1 show a physical interaction of these two proteins in organ of Corti and brain. Collectively, these findings establish the existence of a differential vesicular trafficking mechanism for specific Usher protein variants in mouse cochlear hair cells, with the apical variants playing a potential role in endosomal recycling and stereocilia development/maintenance and the basolateral variants involved in vesicle docking and/or fusion through SNAP25-mediated interactions. PMID:23035094

Re-Emergent Inhibition of Cochlear Inner Hair Cells in a Mouse Model of Hearing Loss.

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Zachary, Stephen Paul; Fuchs, Paul Albert

2015-07-01

Hearing loss among the elderly correlates with diminished social, mental, and physical health. Age-related cochlear cell death does occur, but growing anatomical evidence suggests that synaptic rearrangements on sensory hair cells also contribute to auditory functional decline. Here we present voltage-clamp recordings from inner hair cells of the C57BL/6J mouse model of age-related hearing loss, which reveal that cholinergic synaptic inputs re-emerge during aging. These efferents are functionally inhibitory, using the same ionic mechanisms as do efferent contacts present transiently before the developmental onset of hearing. The strength of efferent inhibition of inner hair cells increases with hearing threshold elevation. These data indicate that the aged cochlea regains features of the developing cochlea and that efferent inhibition of the primary receptors of the auditory system re-emerges with hearing impairment. Synaptic changes in the auditory periphery are increasingly recognized as important factors in hearing loss. To date, anatomical work has described the loss of afferent contacts from cochlear hair cells. However, relatively little is known about the efferent innervation of the cochlea during hearing loss. We performed intracellular recordings from mouse inner hair cells across the lifespan and show that efferent innervation of inner hair cells arises in parallel with the loss of afferent contacts and elevated hearing threshold during aging. These efferent neurons inhibit inner hair cells, raising the possibility that they play a role in the progression of age-related hearing loss. Copyright © 2015 the authors 0270-6474/15/359701-06$15.00/0.

Frequency locking in auditory hair cells: Distinguishing between additive and parametric forcing

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Edri, Yuval; Bozovic, Dolores; Yochelis, Arik

2016-10-01

The auditory system displays remarkable sensitivity and frequency discrimination, attributes shown to rely on an amplification process that involves a mechanical as well as a biochemical response. Models that display proximity to an oscillatory onset (also known as Hopf bifurcation) exhibit a resonant response to distinct frequencies of incoming sound, and can explain many features of the amplification phenomenology. To understand the dynamics of this resonance, frequency locking is examined in a system near the Hopf bifurcation and subject to two types of driving forces: additive and parametric. Derivation of a universal amplitude equation that contains both forcing terms enables a study of their relative impact on the hair cell response. In the parametric case, although the resonant solutions are 1 : 1 frequency locked, they show the coexistence of solutions obeying a phase shift of π, a feature typical of the 2 : 1 resonance. Different characteristics are predicted for the transition from unlocked to locked solutions, leading to smooth or abrupt dynamics in response to different types of forcing. The theoretical framework provides a more realistic model of the auditory system, which incorporates a direct modulation of the internal control parameter by an applied drive. The results presented here can be generalized to many other media, including Faraday waves, chemical reactions, and elastically driven cardiomyocytes, which are known to exhibit resonant behavior.

Changes in the Adult Vertebrate Auditory Sensory Epithelium After Trauma

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Oesterle, Elizabeth C.

2012-01-01

Auditory hair cells transduce sound vibrations into membrane potential changes, ultimately leading to changes in neuronal firing and sound perception. This review provides an overview of the characteristics and repair capabilities of traumatized auditory sensory epithelium in the adult vertebrate ear. Injured mammalian auditory epithelium repairs itself by forming permanent scars but is unable to regenerate replacement hair cells. In contrast, injured non-mammalian vertebrate ear generates replacement hair cells to restore hearing functions. Non-sensory support cells within the auditory epithelium play key roles in the repair processes. PMID:23178236

miR-96 regulates the progression of differentiation in mammalian cochlear inner and outer hair cells.

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Kuhn, Stephanie; Johnson, Stuart L; Furness, David N; Chen, Jing; Ingham, Neil; Hilton, Jennifer M; Steffes, Georg; Lewis, Morag A; Zampini, Valeria; Hackney, Carole M; Masetto, Sergio; Holley, Matthew C; Steel, Karen P; Marcotti, Walter

2011-02-08

MicroRNAs (miRNAs) are small noncoding RNAs able to regulate a broad range of protein-coding genes involved in many biological processes. miR-96 is a sensory organ-specific miRNA expressed in the mammalian cochlea during development. Mutations in miR-96 cause nonsyndromic progressive hearing loss in humans and mice. The mouse mutant diminuendo has a single base change in the seed region of the Mir96 gene leading to widespread changes in the expression of many genes. We have used this mutant to explore the role of miR-96 in the maturation of the auditory organ. We found that the physiological development of mutant sensory hair cells is arrested at around the day of birth, before their biophysical differentiation into inner and outer hair cells. Moreover, maturation of the hair cell stereocilia bundle and remodelling of auditory nerve connections within the cochlea fail to occur in miR-96 mutants. We conclude that miR-96 regulates the progression of the physiological and morphological differentiation of cochlear hair cells and, as such, coordinates one of the most distinctive functional refinements of the mammalian auditory system.

Pairwise coupling of hair cell transducer channels links auditory sensitivity and dynamic range

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van Netten, Sietse M.; Meulenberg, Cecil J. W.; Lennan, George W. T.; Kros, Corne J.

Hair cells in the inner ear provide the basis for the exquisite hearing capabilities of mammals. These cells transduce sound-induced displacements of their mechanosensitive hair bundle into electrical currents within a fraction of a millisecond and with nanometer fidelity. Excitatory displacements

The Effects of Urethane on Rat Outer Hair Cells

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Mingyu Fu

2016-01-01

Full Text Available The cochlea converts sound vibration into electrical impulses and amplifies the low-level sound signal. Urethane, a widely used anesthetic in animal research, has been shown to reduce the neural responses to auditory stimuli. However, the effects of urethane on cochlea, especially on the function of outer hair cells, remain largely unknown. In the present study, we compared the cochlear microphonic responses between awake and urethane-anesthetized rats. The results revealed that the amplitude of the cochlear microphonic was decreased by urethane, resulting in an increase in the threshold at all of the sound frequencies examined. To deduce the possible mechanism underlying the urethane-induced decrease in cochlear sensitivity, we examined the electrical response properties of isolated outer hair cells using whole-cell patch-clamp recording. We found that urethane hyperpolarizes the outer hair cell membrane potential in a dose-dependent manner and elicits larger outward current. This urethane-induced outward current was blocked by strychnine, an antagonist of the α9 subunit of the nicotinic acetylcholine receptor. Meanwhile, the function of the outer hair cell motor protein, prestin, was not affected. These results suggest that urethane anesthesia is expected to decrease the responses of outer hair cells, whereas the frequency selectivity of cochlea remains unchanged.

Progressive hearing loss and degeneration of hair cell stereocilia in taperin gene knockout mice

International Nuclear Information System (INIS)

Chen, Mo; Wang, Qin; Zhu, Gang-Hua; Hu, Peng; Zhou, Yuan; Wang, Tian; Lai, Ruo-Sha; Xiao, Zi-An; Xie, Ding-Hua

2016-01-01

The TPRN gene encodes taperin, which is prominently present at the taper region of hair cell stereocilia. Mutations in TPRN have been reported to cause autosomal recessive nonsyndromic deafness 79(DFNB 79). To investigate the role of taperin in pathogenesis of hearing loss, we generated TPRN knockout mice using TALEN technique. Sanger sequencing confirmed an 11 bp deletion at nucleotide 177–187 in exon 1 of TPRN, which results in a truncated form of taperin protein. Heterozygous TPRN +/− mice showed apparently normal auditory phenotypes to their wide-type (WT) littermates. Homozygous TPRN −/− mice exhibited progressive sensorineural hearing loss as reflected by auditory brainstem response to both click and tone burst stimuli at postnatal days 15 (P15), 30 (P30), and 60 (P60). Alex Fluor-594 phalloidin labeling showed no obvious difference in hair cell numbers in the cochlea between TPRN −/− mice and WT mice under light microscope. However, scanning electronic microscopy revealed progressive degeneration of inner hair cell stereocilia, from apparently normal at postnatal days 3 (P3) to scattered absence at P15 and further to substantial loss at P30. The outer hair cell stereocilia also showed progressive degeneration, though much less severe, Collectively, we conclude that taperin plays an important role in maintenance of hair cell stereocilia. Establishment of TPRN knockout mice enables further investigation into the function of this gene. - Highlights: • TPRN −/− mice were generated using TALEN technique. • TPRN −/− mice presented progressive hearing loss. • WT and TPRN −/− mice showed no difference in hair cell numbers. • TPRN −/− mice showed progressive degeneration of hair cell stereocilia.

Efferent control of the electrical and mechanical properties of hair cells in the bullfrog's sacculus.

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Manuel Castellano-Muñoz

2010-10-01

Full Text Available Hair cells in the auditory, vestibular, and lateral-line systems respond to mechanical stimulation and transmit information to afferent nerve fibers. The sensitivity of mechanoelectrical transduction is modulated by the efferent pathway, whose activity usually reduces the responsiveness of hair cells. The basis of this effect remains unknown.We employed immunocytological, electrophysiological, and micromechanical approaches to characterize the anatomy of efferent innervation and the effect of efferent activity on the electrical and mechanical properties of hair cells in the bullfrog's sacculus. We found that efferent fibers form extensive synaptic terminals on all macular and extramacular hair cells. Macular hair cells expressing the Ca(2+-buffering protein calretinin contain half as many synaptic ribbons and are innervated by twice as many efferent terminals as calretinin-negative hair cells. Efferent activity elicits inhibitory postsynaptic potentials in hair cells and thus inhibits their electrical resonance. In hair cells that exhibit spiking activity, efferent stimulation suppresses the generation of action potentials. Finally, efferent activity triggers a displacement of the hair bundle's resting position.The hair cells of the bullfrog's sacculus receive a rich efferent innervation with the heaviest projection to calretinin-containing cells. Stimulation of efferent axons desensitizes the hair cells and suppresses their spiking activity. Although efferent activation influences mechanoelectrical transduction, the mechanical effects on hair bundles are inconsistent.

An Analogue VLSI Implementation of the Meddis Inner Hair Cell Model

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McEwan, Alistair; van Schaik, André

2003-12-01

The Meddis inner hair cell model is a widely accepted, but computationally intensive computer model of mammalian inner hair cell function. We have produced an analogue VLSI implementation of this model that operates in real time in the current domain by using translinear and log-domain circuits. The circuit has been fabricated on a chip and tested against the Meddis model for (a) rate level functions for onset and steady-state response, (b) recovery after masking, (c) additivity, (d) two-component adaptation, (e) phase locking, (f) recovery of spontaneous activity, and (g) computational efficiency. The advantage of this circuit, over other electronic inner hair cell models, is its nearly exact implementation of the Meddis model which can be tuned to behave similarly to the biological inner hair cell. This has important implications on our ability to simulate the auditory system in real time. Furthermore, the technique of mapping a mathematical model of first-order differential equations to a circuit of log-domain filters allows us to implement real-time neuromorphic signal processors for a host of models using the same approach.

Hair cell counts in a rat model of sound damage: Effects of tissue preparation & identification of regions of hair cell loss.

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Neal, Christopher; Kennon-McGill, Stefanie; Freemyer, Andrea; Shum, Axel; Staecker, Hinrich; Durham, Dianne

2015-10-01

Exposure to intense sound can damage or kill cochlear hair cells (HC). This loss of input typically manifests as noise induced hearing loss, but it can also be involved in the initiation of other auditory disorders such as tinnitus or hyperacusis. In this study we quantify changes in HC number following exposure to one of four sound damage paradigms. We exposed adult, anesthetized Long-Evans rats to a unilateral 16 kHz pure tone that varied in intensity (114 dB or 118 dB) and duration (1, 2, or 4 h) and sacrificed animals 2-4 weeks later. We compared two different methods of tissue preparation, plastic embedding/sectioning and whole mount dissection, for quantifying hair cell loss as a function of frequency. We found that the two methods of tissue preparation produced largely comparable cochleograms, with whole mount dissections allowing a more rapid evaluation of hair cell number. Both inner and outer hair cell loss was observed throughout the length of the cochlea irrespective of sound damage paradigm. Inner HC loss was either equal to or greater than outer HC loss. Increasing the duration of sound exposures resulted in more severe HC loss, which included all HC lesions observed in an analogous shorter duration exposure. Copyright © 2015 Elsevier B.V. All rights reserved.

Alternative Splice Forms Influence Functions of Whirlin in Mechanosensory Hair Cell Stereocilia

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Seham Ebrahim

2016-05-01

Full Text Available WHRN (DFNB31 mutations cause diverse hearing disorders: profound deafness (DFNB31 or variable hearing loss in Usher syndrome type II. The known role of WHRN in stereocilia elongation does not explain these different pathophysiologies. Using spontaneous and targeted Whrn mutants, we show that the major long (WHRN-L and short (WHRN-S isoforms of WHRN have distinct localizations within stereocilia and also across hair cell types. Lack of both isoforms causes abnormally short stereocilia and profound deafness and vestibular dysfunction. WHRN-S expression, however, is sufficient to maintain stereocilia bundle morphology and function in a subset of hair cells, resulting in some auditory response and no overt vestibular dysfunction. WHRN-S interacts with EPS8, and both are required at stereocilia tips for normal length regulation. WHRN-L localizes midway along the shorter stereocilia, at the level of inter-stereociliary links. We propose that differential isoform expression underlies the variable auditory and vestibular phenotypes associated with WHRN mutations.

An Analogue VLSI Implementation of the Meddis Inner Hair Cell Model

Directory of Open Access Journals (Sweden)

Alistair McEwan

2003-06-01

Full Text Available The Meddis inner hair cell model is a widely accepted, but computationally intensive computer model of mammalian inner hair cell function. We have produced an analogue VLSI implementation of this model that operates in real time in the current domain by using translinear and log-domain circuits. The circuit has been fabricated on a chip and tested against the Meddis model for (a rate level functions for onset and steady-state response, (b recovery after masking, (c additivity, (d two-component adaptation, (e phase locking, (f recovery of spontaneous activity, and (g computational efficiency. The advantage of this circuit, over other electronic inner hair cell models, is its nearly exact implementation of the Meddis model which can be tuned to behave similarly to the biological inner hair cell. This has important implications on our ability to simulate the auditory system in real time. Furthermore, the technique of mapping a mathematical model of first-order differential equations to a circuit of log-domain filters allows us to implement real-time neuromorphic signal processors for a host of models using the same approach.

Retinoic Acid Signaling Mediates Hair Cell Regeneration by Repressing p27kip and sox2 in Supporting Cells.

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Rubbini, Davide; Robert-Moreno, Àlex; Hoijman, Esteban; Alsina, Berta

2015-11-25

During development, otic sensory progenitors give rise to hair cells and supporting cells. In mammalian adults, differentiated and quiescent sensory cells are unable to generate new hair cells when these are lost due to various insults, leading to irreversible hearing loss. Retinoic acid (RA) has strong regenerative capacity in several organs, but its role in hair cell regeneration is unknown. Here, we use genetic and pharmacological inhibition to show that the RA pathway is required for hair cell regeneration in zebrafish. When regeneration is induced by laser ablation in the inner ear or by neomycin treatment in the lateral line, we observe rapid activation of several components of the RA pathway, with dynamics that position RA signaling upstream of other signaling pathways. We demonstrate that blockade of the RA pathway impairs cell proliferation of supporting cells in the inner ear and lateral line. Moreover, in neuromast, RA pathway regulates the transcription of p27(kip) and sox2 in supporting cells but not fgf3. Finally, genetic cell-lineage tracing using Kaede photoconversion demonstrates that de novo hair cells derive from FGF-active supporting cells. Our findings reveal that RA has a pivotal role in zebrafish hair cell regeneration by inducing supporting cell proliferation, and shed light on the underlying transcriptional mechanisms involved. This signaling pathway might be a promising approach for hearing recovery. Hair cells are the specialized mechanosensory cells of the inner ear that capture auditory and balance sensory input. Hair cells die after acoustic trauma, ototoxic drugs or aging diseases, leading to progressive hearing loss. Mammals, in contrast to zebrafish, lack the ability to regenerate hair cells. Here, we find that retinoic acid (RA) pathway is required for hair cell regeneration in vivo in the zebrafish inner ear and lateral line. RA pathway is activated very early upon hair cell loss, promotes cell proliferation of progenitor cells

Alternative Splice Forms Influence Functions of Whirlin in Mechanosensory Hair Cell Stereocilia.

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Ebrahim, Seham; Ingham, Neil J; Lewis, Morag A; Rogers, Michael J C; Cui, Runjia; Kachar, Bechara; Pass, Johanna C; Steel, Karen P

2016-05-03

WHRN (DFNB31) mutations cause diverse hearing disorders: profound deafness (DFNB31) or variable hearing loss in Usher syndrome type II. The known role of WHRN in stereocilia elongation does not explain these different pathophysiologies. Using spontaneous and targeted Whrn mutants, we show that the major long (WHRN-L) and short (WHRN-S) isoforms of WHRN have distinct localizations within stereocilia and also across hair cell types. Lack of both isoforms causes abnormally short stereocilia and profound deafness and vestibular dysfunction. WHRN-S expression, however, is sufficient to maintain stereocilia bundle morphology and function in a subset of hair cells, resulting in some auditory response and no overt vestibular dysfunction. WHRN-S interacts with EPS8, and both are required at stereocilia tips for normal length regulation. WHRN-L localizes midway along the shorter stereocilia, at the level of inter-stereociliary links. We propose that differential isoform expression underlies the variable auditory and vestibular phenotypes associated with WHRN mutations. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Effect of low-level laser treatment on cochlea hair-cell recovery after ototoxic hearing loss

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Rhee, Chung-Ku; He, Peijie; Jung, Jae Yun; Ahn, Jin-Chul; Chung, Phil-Sang; Lee, Min Young; Suh, Myung-Whan

2013-12-01

The primary cause of hearing loss includes damage to cochlear hair cells. Low-level laser therapy (LLLT) has become a popular treatment for damaged nervous systems. Based on the idea that cochlea hair cells and neural cells are from same developmental origin, the effect of LLLT on hearing loss in animal models is evaluated. Hearing loss animal models were established, and the animals were irradiated by 830-nm diode laser once a day for 10 days. Power density of the laser treatment was 900 mW/cm2, and the fluence was 162 to 194 J. The tympanic membrane was evaluated after LLLT. Thresholds of auditory brainstem responses were evaluated before treatment, after gentamicin, and after 10 days of LLLT. Quantitative scanning electron microscopic (SEM) observations were done by counting remaining hair cells. Tympanic membranes were intact at the end of the experiment. No adverse tissue reaction was found. On SEM images, LLLT significantly increased the number of hair cells in middle and basal turns. Hearing was significantly improved by laser irradiation. After LLLT treatment, both the hearing threshold and hair-cell count significantly improved.

Absence of both auditory evoked potentials and auditory percepts dependent on timing cues.

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Starr, A; McPherson, D; Patterson, J; Don, M; Luxford, W; Shannon, R; Sininger, Y; Tonakawa, L; Waring, M

1991-06-01

An 11-yr-old girl had an absence of sensory components of auditory evoked potentials (brainstem, middle and long-latency) to click and tone burst stimuli that she could clearly hear. Psychoacoustic tests revealed a marked impairment of those auditory perceptions dependent on temporal cues, that is, lateralization of binaural clicks, change of binaural masked threshold with changes in signal phase, binaural beats, detection of paired monaural clicks, monaural detection of a silent gap in a sound, and monaural threshold elevation for short duration tones. In contrast, auditory functions reflecting intensity or frequency discriminations (difference limens) were only minimally impaired. Pure tone audiometry showed a moderate (50 dB) bilateral hearing loss with a disproportionate severe loss of word intelligibility. Those auditory evoked potentials that were preserved included (1) cochlear microphonics reflecting hair cell activity; (2) cortical sustained potentials reflecting processing of slowly changing signals; and (3) long-latency cognitive components (P300, processing negativity) reflecting endogenous auditory cognitive processes. Both the evoked potential and perceptual deficits are attributed to changes in temporal encoding of acoustic signals perhaps occurring at the synapse between hair cell and eighth nerve dendrites. The results from this patient are discussed in relation to previously published cases with absent auditory evoked potentials and preserved hearing.

The acquisition of mechano-electrical transducer current adaptation in auditory hair cells requires myosin VI

NARCIS (Netherlands)

Marcotti, Walter; Corns, Laura F.; Goodyear, Richard J.; Rzadzinska, Agnieszka K.; Avraham, Karen B.; Steel, Karen P.; Richardson, Guy P.; Kros, Corne J.

2016-01-01

The transduction of sound into electrical signals occurs at the hair bundles atop sensory hair cells in the cochlea, by means of mechanosensitive ion channels, the mechano-electrical transducer (MET) channels. The MET currents decline during steady stimuli; this is termed adaptation and ensures they

Conditional deletion of pejvakin in adult outer hair cells causes progressive hearing loss in mice.

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Harris, Suzan L; Kazmierczak, Marcin; Pangršič, Tina; Shah, Prahar; Chuchvara, Nadiya; Barrantes-Freer, Alonso; Moser, Tobias; Schwander, Martin

2017-03-06

Mutations in the Pejvakin (Pjvk) gene cause autosomal recessive hearing loss DFNB59 with audiological features of auditory neuropathy spectrum disorder (ANSD) or cochlear dysfunction. The precise mechanisms underlying the variable clinical phenotypes of DFNB59 remain unclear. Here, we demonstrate that mice with conditional ablation of the Pjvk gene in all sensory hair cells or only in outer hair cells (OHCs) show similar auditory phenotypes with early-onset profound hearing loss. By contrast, loss of Pjvk in adult OHCs causes a slowly progressive hearing loss associated with OHC degeneration and delayed loss of inner hair cells (IHCs), indicating a primary role for pejvakin in regulating OHC function and survival. Consistent with this model, synaptic transmission at the IHC ribbon synapse is largely unaffected in sirtaki mice that carry a C-terminal deletion mutation in Pjvk. Using the C-terminal domain of pejvakin as bait, we identified in a cochlear cDNA library ROCK2, an effector for the small GTPase Rho, and the scaffold protein IQGAP1, involved in modulating actin dynamics. Both ROCK2 and IQGAP1 associate via their coiled-coil domains with pejvakin. We conclude that pejvakin is required to sustain OHC activity and survival in a cell-autonomous manner likely involving regulation of Rho signaling. Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

Mammalian Auditory Hair Cell Bundle Stiffness Affects Frequency Tuning by Increasing Coupling along the Length of the Cochlea.

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Dewey, James B; Xia, Anping; Müller, Ulrich; Belyantseva, Inna A; Applegate, Brian E; Oghalai, John S

2018-06-05

The stereociliary bundles of cochlear hair cells convert mechanical vibrations into the electrical signals required for auditory sensation. While the stiffness of the bundles strongly influences mechanotransduction, its influence on the vibratory response of the cochlear partition is unclear. To assess this, we measured cochlear vibrations in mutant mice with reduced bundle stiffness or with a tectorial membrane (TM) that is detached from the sensory epithelium. We found that reducing bundle stiffness decreased the high-frequency extent and sharpened the tuning of vibratory responses obtained postmortem. Detaching the TM further reduced the high-frequency extent of the vibrations but also lowered the partition's resonant frequency. Together, these results demonstrate that the bundle's stiffness and attachment to the TM contribute to passive longitudinal coupling in the cochlea. We conclude that the stereociliary bundles and TM interact to facilitate passive-wave propagation to more apical locations, possibly enhancing active-wave amplification in vivo. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Effect of histone deacetylase inhibitors trichostatin A and valproic acid on hair cell regeneration in zebrafish lateral line neuromasts

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He, Yingzi; Cai, Chengfu; Tang, Dongmei; Sun, Shan; Li, Huawei

2014-01-01

In humans, auditory hair cells are not replaced when injured. Thus, cochlear hair cell loss causes progressive and permanent hearing loss. Conversely, non-mammalian vertebrates are capable of regenerating lost sensory hair cells. The zebrafish lateral line has numerous qualities that make it well-suited for studying hair cell development and regeneration. Histone deacetylase (HDAC) activity has been shown to have an important role in regenerative processes in vertebrates, but its function in hair cell regeneration in vivo is not fully understood. Here, we have examined the role of HDAC activity in hair cell regeneration in the zebrafish lateral line. We eliminated lateral line hair cells of 5-day post-fertilization larvae using neomycin and then treated the larvae with HDAC inhibitors. To assess hair cell regeneration, we used 5-bromo-2-deoxyuridine (BrdU) incorporation in zebrafish larvae to label mitotic cells after hair cell loss. We found that pharmacological inhibition of HDACs using trichostatin A (TSA) or valproic acid (VPA) increased histone acetylation in the regenerated neuromasts following neomycin-induced damage. We also showed that treatment with TSA or VPA decreased the number of supporting cells and regenerated hair cells in response to hair cell damage. Additionally, BrdU immunostaining and western blot analysis showed that TSA or VPA treatment caused a significant decrease in the percentage of S-phase cells and induced p21Cip1 and p27Kip1 expression, both of which are likely to explain the decrease in the amount of newly regenerated hair cells in treated embryos. Finally, we showed that HDAC inhibitors induced no observable cell death in neuromasts as measured by cleaved caspase-3 immunohistochemistry and western blot analysis. Taken together, our results demonstrate that HDAC activity has an important role in the regeneration of hair cells in the lateral line. PMID:25431550

Effect of histone deacetylase inhibitors trichostatin A and valproic acid on hair cell regeneration in zebrafish lateral line neuromasts

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Yingzi eHe

2014-11-01

Full Text Available In humans, auditory hair cells are not replaced when injured. Thus, cochlear hair cell loss causes progressive and permanent hearing loss. Conversely, nonmammalian vertebrates are capable of regenerating lost sensory hair cells. The zebrafish lateral line has numerous qualities that make it well suited for studying hair cell development and regeneration. Histone deacetylase (HDAC activity has been shown to have an important role in regenerative processes in vertebrates, but its function in hair cell regeneration in vivo is not fully understood. Here, we have examined the role of HDAC activity in hair cell regeneration in the zebrafish lateral line. We eliminated lateral line hair cells of 5-day post-fertilization larvae using neomycin and then treated the larvae with HDAC inhibitors. To assess hair cell regeneration, we used 5-bromo-2-deoxyuridine (BrdU incorporation in zebrafish larvae to label mitotic cells after hair cell loss. We found that pharmacological inhibition of HDACs using trichostatin A (TSA or valproic acid (VPA increased histone acetylation in the regenerated neuromasts following neomycin-induced damage. We also showed that treatment with TSA or VPA decreased the number of supporting cells and regenerated hair cells in response to hair cell damage. Additionally, BrdU immunostaining and western blot analysis showed that TSA or VPA treatment caused a significant decrease in the percentage of S-phase cells and induced p21Cip1 and p27Kip1 expression, both of which are likely to explain the decrease in the amount of newly regenerated hair cells in treated embryos. Finally, we showed that HDAC inhibitors induced no observable cell death in neuromasts as measured by cleaved caspase-3 immunohistochemistry and western blot analysis. Taken together, our results demonstrate that HDAC activity has an important role in the regeneration of hair cells in the lateral line.

In Vivo Interplay between p27Kip1, GATA3, ATOH1, and POU4F3 Converts Non-sensory Cells to Hair Cells in Adult Mice

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Bradley J. Walters

2017-04-01

Full Text Available Summary: Hearing loss is widespread and persistent because mature mammalian auditory hair cells (HCs are nonregenerative. In mice, the ability to regenerate HCs from surrounding supporting cells (SCs declines abruptly after postnatal maturation. We find that combining p27Kip1 deletion with ectopic ATOH1 expression surmounts this age-related decline, leading to conversion of SCs to HCs in mature mouse cochleae and after noise damage. p27Kip1 deletion, independent of canonical effects on Rb-family proteins, upregulated GATA3, a co-factor for ATOH1 that is lost from SCs with age. Co-activation of GATA3 or POU4F3 and ATOH1 promoted conversion of SCs to HCs in adult mice. Activation of POU4F3 alone also converted mature SCs to HCs in vivo. These data illuminate a genetic pathway that initiates auditory HC regeneration and suggest p27Kip1, GATA3, and POU4F3 as additional therapeutic targets for ATOH1-mediated HC regeneration. : Auditory hair cells are nonregenerative, resulting in persistent hearing loss upon damage. Walters et al. find that manipulating two genes, p27Kip1 and Atoh1, induces the conversion of nonsensory cells to hair cells in adult mice. This effect is mediated by GATA3 and POU4F3, where POU4F3 alone was found to convert nonsensory cells. Keywords: regeneration, aging, differentiation, proliferation, development, cancer, sensory, cochlea, hearing

Ebselen attenuates cisplatin-induced ROS generation through Nrf2 activation in auditory cells.

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Kim, Se-Jin; Park, Channy; Han, A Lum; Youn, Myung-Ja; Lee, Jeong-Han; Kim, Yunha; Kim, Eun-Sook; Kim, Hyung-Jin; Kim, Jin-Kyung; Lee, Ho-Kyun; Chung, Sang-Young; So, Hongseob; Park, Raekil

2009-05-01

Ebselen, an organoselenium compound that acts as a glutathione peroxidase mimetic, has been demonstrated to possess antioxidant and anti-inflammatory activities. However, the molecular mechanism underlying this effect is not fully understood in auditory cells. The purpose of the present study is to investigate the protective effect of ebselen against cisplatin-induced toxicity in HEI-OC1 auditory cells, organotypic cultures of cochlear explants from two-day postnatal rats (P(2)) and adult Balb/C mice. Pretreatment with ebselen ameliorated apoptotic death induced by cisplatin in HEI-OC1 cells and organotypic cultures of Corti's organ. Ebselen pretreatment also significantly suppressed cisplatin-induced increases in intracellular reactive oxygen species (ROS), intracellular reactive nitrogen species (RNS) and lipid peroxidation levels. Ebselen dose-dependently increased the expression level of an antioxidant response element (ARE)-luciferase reporter in HEI-OC1 cells through the translocation of Nrf2 into the nucleus. Furthermore, we found that pretreatment with ebselen significantly restored Nrf2 function, whereas it ameliorated the cytotoxicity of cisplatin in cells transfectants with either a pcDNA3.1 (control) or a DN-Nrf2 (dominant-negative) plasmid. We also observed that Nrf2 activation by ebselen increased the expression of phase II antioxidant genes, including heme oxygenase (HO-1), NAD(P)H:quinine oxidoreductase, and gamma-glutamylcysteine synthetase (gamma-GCS). Treatment with ebselen resulted in an increased expression of HO-1 and intranuclear Nrf2 in hair cells of organotypic cultured cochlea. After intraperitoneal injection with cisplatin, auditory brainstem responses (ABRs) threshold was measured on 8th day in Balb/C mice. ABR threshold shift was marked occurred in mice injected with cisplatin (16 mg/kg, n=5; Click and 8-kHz stimuli, pebselen was not significantly changed. These results suggest that ebselen activates the Nrf2-ARE signaling pathway

Mutations in ap1b1 cause mistargeting of the Na(+/K(+-ATPase pump in sensory hair cells.

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Rachel Clemens Grisham

Full Text Available The hair cells of the inner ear are polarized epithelial cells with a specialized structure at the apical surface, the mechanosensitive hair bundle. Mechanotransduction occurs within the hair bundle, whereas synaptic transmission takes place at the basolateral membrane. The molecular basis of the development and maintenance of the apical and basal compartments in sensory hair cells is poorly understood. Here we describe auditory/vestibular mutants isolated from forward genetic screens in zebrafish with lesions in the adaptor protein 1 beta subunit 1 (ap1b1 gene. Ap1b1 is a subunit of the adaptor complex AP-1, which has been implicated in the targeting of basolateral membrane proteins. In ap1b1 mutants we observed that although the overall development of the inner ear and lateral-line organ appeared normal, the sensory epithelium showed progressive signs of degeneration. Mechanically-evoked calcium transients were reduced in mutant hair cells, indicating that mechanotransduction was also compromised. To gain insight into the cellular and molecular defects in ap1b1 mutants, we examined the localization of basolateral membrane proteins in hair cells. We observed that the Na(+/K(+-ATPase pump (NKA was less abundant in the basolateral membrane and was mislocalized to apical bundles in ap1b1 mutant hair cells. Accordingly, intracellular Na(+ levels were increased in ap1b1 mutant hair cells. Our results suggest that Ap1b1 is essential for maintaining integrity and ion homeostasis in hair cells.

Mechanoelectrical transduction of adult outer hair cells studied in a gerbil hemicochlea.

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He, David Z Z; Jia, Shuping; Dallos, Peter

2004-06-17

Sensory receptor cells of the mammalian cochlea are morphologically and functionally dichotomized. Inner hair cells transmit auditory information to the brain, whereas outer hair cells (OHC) amplify the mechanical signal, which is then transduced by inner hair cells. Amplification by OHCs is probably mediated by their somatic motility in a mechanical feedback process. OHC motility in vivo is thought to be driven by the cell's receptor potential. The first steps towards the generation of the receptor potential are the deflection of the stereociliary bundle, and the subsequent flow of transducer current through the mechanosensitive transducer channels located at their tips. Quantitative relations between transducer currents and basilar membrane displacements are lacking, as well as their variation along the cochlear length. To address this, we simultaneously recorded OHC transducer currents (or receptor potentials) and basilar membrane motion in an excised and bisected cochlea, the hemicochlea. This preparation permits recordings from adult OHCs at various cochlear locations while the basilar membrane is mechanically stimulated. Furthermore, the stereocilia are deflected by the same means of stimulation as in vivo. Here we show that asymmetrical transducer currents and receptor potentials are significantly larger than previously thought, they possess a highly restricted dynamic range and strongly depend on cochlear location.

Noise-Induced Loss of Hair Cells and Cochlear Synaptopathy Are Mediated by the Activation of AMPK

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Hill, Kayla; Yuan, Hu; Wang, Xianren

2016-01-01

Noise-induced hearing loss (NIHL) is a major unresolved public health problem. Here, we investigate pathomechanisms of sensory hair cell death and suggest a novel target for protective intervention. Cellular survival depends upon maintenance of energy homeostasis, largely by AMP-activated protein kinase (AMPK). In response to a noise exposure in CBA/J mice, the levels of phosphorylated AMPKα increased in hair cells in a noise intensity-dependent manner. Inhibition of AMPK via siRNA or the pharmacological inhibitor compound C attenuated noise-induced loss of outer hair cells (OHCs) and synaptic ribbons, and preserved auditory function. Additionally, noise exposure increased the activity of the upstream AMPK kinase liver kinase B1 (LKB1) in cochlear tissues. The inhibition of LKB1 by siRNA attenuated the noise-increased phosphorylation of AMPKα in OHCs, reduced the loss of inner hair cell synaptic ribbons and OHCs, and protected against NIHL. These results indicate that noise exposure induces hair cell death and synaptopathy by activating AMPK via LKB1-mediated pathways. Targeting these pathways may provide a novel route to prevent NIHL. SIGNIFICANCE STATEMENT Our results demonstrate for the first time that the activation of AMP-activated protein kinase (AMPK) α in sensory hair cells is noise intensity dependent and contributes to noise-induced hearing loss by mediating the loss of inner hair cell synaptic ribbons and outer hair cells. Noise induces the phosphorylation of AMPKα1 by liver kinase B1 (LKB1), triggered by changes in intracellular ATP levels. The inhibition of AMPK activation by silencing AMPK or LKB1, or with the pharmacological inhibitor compound C, reduced outer hair cell and synaptic ribbon loss as well as noise-induced hearing loss. This study provides new insights into mechanisms of noise-induced hearing loss and suggests novel interventions for the prevention of the loss of sensory hair cells and cochlear synaptopathy. PMID:27413159

Noise-Induced Loss of Hair Cells and Cochlear Synaptopathy Are Mediated by the Activation of AMPK.

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Hill, Kayla; Yuan, Hu; Wang, Xianren; Sha, Su-Hua

2016-07-13

Noise-induced hearing loss (NIHL) is a major unresolved public health problem. Here, we investigate pathomechanisms of sensory hair cell death and suggest a novel target for protective intervention. Cellular survival depends upon maintenance of energy homeostasis, largely by AMP-activated protein kinase (AMPK). In response to a noise exposure in CBA/J mice, the levels of phosphorylated AMPKα increased in hair cells in a noise intensity-dependent manner. Inhibition of AMPK via siRNA or the pharmacological inhibitor compound C attenuated noise-induced loss of outer hair cells (OHCs) and synaptic ribbons, and preserved auditory function. Additionally, noise exposure increased the activity of the upstream AMPK kinase liver kinase B1 (LKB1) in cochlear tissues. The inhibition of LKB1 by siRNA attenuated the noise-increased phosphorylation of AMPKα in OHCs, reduced the loss of inner hair cell synaptic ribbons and OHCs, and protected against NIHL. These results indicate that noise exposure induces hair cell death and synaptopathy by activating AMPK via LKB1-mediated pathways. Targeting these pathways may provide a novel route to prevent NIHL. Our results demonstrate for the first time that the activation of AMP-activated protein kinase (AMPK) α in sensory hair cells is noise intensity dependent and contributes to noise-induced hearing loss by mediating the loss of inner hair cell synaptic ribbons and outer hair cells. Noise induces the phosphorylation of AMPKα1 by liver kinase B1 (LKB1), triggered by changes in intracellular ATP levels. The inhibition of AMPK activation by silencing AMPK or LKB1, or with the pharmacological inhibitor compound C, reduced outer hair cell and synaptic ribbon loss as well as noise-induced hearing loss. This study provides new insights into mechanisms of noise-induced hearing loss and suggests novel interventions for the prevention of the loss of sensory hair cells and cochlear synaptopathy. Copyright © 2016 the authors 0270-6474/16/367497-14$15.00/0.

The effect of the inner-hair-cell mediated transduction on the shape of neural tuning curves

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Altoè, Alessandro; Pulkki, Ville; Verhulst, Sarah

2018-05-01

The inner hair cells of the mammalian cochlea transform the vibrations of their stereocilia into releases of neurotransmitter at the ribbon synapses, thereby controlling the activity of the afferent auditory fibers. The mechanical-to-neural transduction is a highly nonlinear process and it introduces differences between the frequency-tuning of the stereocilia and that of the afferent fibers. Using a computational model of the inner hair cell that is based on in vitro data, we estimated that smaller vibrations of the stereocilia are necessary to drive the afferent fibers above threshold at low (≤0.5 kHz) than at high (≥4 kHz) driving frequencies. In the base of the cochlea, the transduction process affects the low-frequency tails of neural tuning curves. In particular, it introduces differences between the frequency-tuning of the stereocilia and that of the auditory fibers resembling those between basilar membrane velocity and auditory fibers tuning curves in the chinchilla base. For units with a characteristic frequency between 1 and 4 kHz, the transduction process yields shallower neural than stereocilia tuning curves as the characteristic frequency decreases. This study proposes that transduction contributes to the progressive broadening of neural tuning curves from the base to the apex.

Evaluation of peripheral compression and auditory nerve fiber intensity coding using auditory steady-state responses

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Encina Llamas, Gerard; M. Harte, James; Epp, Bastian

2015-01-01

. Evaluation of these properties provides information about the health state of the system. It has been shown that a loss of outer hair cells leads to a reduction in peripheral compression. It has also recently been shown in animal studies that noise over-exposure, producing temporary threshold shifts, can....... The results indicate that the slope of the ASSR level growth function can be used to estimate peripheral compression simultaneously at four frequencies below 60 dB SPL, while the slope above 60 dB SPL may provide information about the integrity of intensity coding of low-SR fibers.......The compressive nonlinearity of the auditory system is assumed to be an epiphenomenon of a healthy cochlea and, particularly, of outer-hair cell function. Another ability of the healthy auditory system is to enable communication in acoustical environments with high-level background noises...

Improved biolistic transfection of hair cells.

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Hongyu Zhao

Full Text Available Transient transfection of hair cells has proven challenging. Here we describe modifications to the Bio-Rad Helios Gene Gun that, along with an optimized protocol, improve transfection of bullfrog, chick, and mouse hair cells. The increased penetrating power afforded by our method allowed us to transfect mouse hair cells from the basal side, through the basilar membrane; this configuration protects hair bundles from damage during the procedure. We characterized the efficiency of transfection of mouse hair cells with fluorescently-tagged actin fusion protein using both the optimized procedure and a published procedure; while the efficiency of the two methods was similar, the morphology of transfected hair cells was improved with the new procedure. In addition, using the improved method, we were able to transfect hair cells in the bullfrog sacculus and chick cochlea for the first time. We used fluorescent-protein fusions of harmonin b (USH1C and PMCA2 (ATP2B2; plasma-membrane Ca(2+-ATPase isoform 2 to examine protein distribution in hair cells. While PMCA2-EGFP localization was similar to endogenous PMCA2 detected with antibodies, high levels of harmonin-EGFP were found at stereocilia tapers in bullfrog and chick, but not mouse; by contrast, harmonin-EGFP was concentrated in stereocilia tips in mouse hair cells.

Damage of Inner Ear Sensory Hair Cells via Mitochondrial Loss in a Murine Model of Sleep Apnea With Chronic Intermittent Hypoxia.

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Seo, Young Joon; Ju, Hyun Mi; Lee, Sun Hee; Kwak, Sang Hyun; Kang, Min Jung; Yoon, Joo-Heon; Kim, Chang-Hoon; Cho, Hyung-Ju

2017-09-01

Investigating the exact pathophysiology of obstructive sleep apnea syndrome (OSAS)-induced hearing loss is critical. We sought to verify the hypothesis that a correlation exists between mitochondrial dysfunction in inner ear hair cells and the auditory dysfunction induced by chronic intermittent hypoxia (CIH) in a murine model of sleep apnea. C57BL/6J adult male mice were randomized to 4 weeks of CIH (n = 12) or normoxia (Sham) (n = 12). Hearing threshold was determined by auditory brainstem response. The activity of mitochondria was compared between CIH and Sham mice. Histological assessment and transmission electron microscopy were performed for assessing morphologic changes in mitochondria. The number of mtDNA copies as well as the levels of PGC1-α, Tfam, and VDAC (voltage-dependent anion channel) were determined in the hair cells of CIH mice. We observed that hearing ability in CIH mice was impaired and hair-cell mitochondria in CIH mice were fewer compared to that in Sham and also displayed an aberrant morphology. The mRNA levels of PGC-1α and Tfam were higher in the CIH group than in the Sham group. Moreover, the expression of VDAC was increased in the tectorial membrane, the basilar membrane, and especially in the inner hair cells of CIH mice. This study using CIH mice as a model for OSAS provides evidence of an association between OSAS and auditory function alteration, as well as of mitochondria being part of the pathophysiology of hearing impairment. Further investigation is required to determine whether mitochondria could serve as a valid target for preventive or therapeutic purposes. © Sleep Research Society 2017. Published by Oxford University Press on behalf of the Sleep Research Society. All rights reserved. For permissions, please e-mail journals.permissions@oup.com.

Position-dependent patterning of spontaneous action potentials in immature cochlear inner hair cells

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Johnson, Stuart L.; Eckrich, Tobias; Kuhn, Stephanie; Zampini, Valeria; Franz, Christoph; Ranatunga, Kishani M.; Roberts, Terri P.; Masetto, Sergio; Knipper, Marlies; Kros, Corné J.; Marcotti, Walter

2011-01-01

Spontaneous action potential activity is crucial for mammalian sensory system development. In the auditory system, patterned firing activity has been observed in immature spiral ganglion cells and brain-stem neurons and is likely to depend on cochlear inner hair cell (IHC) action potentials. It remains uncertain whether spiking activity is intrinsic to developing IHCs and whether it shows patterning. We found that action potentials are intrinsically generated by immature IHCs of altricial rodents and that apical IHCs exhibit bursting activity as opposed to more sustained firing in basal cells. We show that the efferent neurotransmitter ACh, by fine-tuning the IHC’s resting membrane potential (Vm), is crucial for the bursting pattern in apical cells. Endogenous extracellular ATP also contributes to the Vm of apical and basal IHCs by activating SK2 channels. We hypothesize that the difference in firing pattern along the cochlea instructs the tonotopic differentiation of IHCs and auditory pathway. PMID:21572434

Neuronal differentiation of hair-follicle-bulge-derived stem cells co-cultured with mouse cochlear modiolus explants.

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Timo Schomann

Full Text Available Stem-cell-based repair of auditory neurons may represent an attractive therapeutic option to restore sensorineural hearing loss. Hair-follicle-bulge-derived stem cells (HFBSCs are promising candidates for this type of therapy, because they (1 have migratory properties, enabling migration after transplantation, (2 can differentiate into sensory neurons and glial cells, and (3 can easily be harvested in relatively high numbers. However, HFBSCs have never been used for this purpose. We hypothesized that HFBSCs can be used for cell-based repair of the auditory nerve and we have examined their migration and incorporation into cochlear modiolus explants and their subsequent differentiation. Modiolus explants obtained from adult wild-type mice were cultured in the presence of EF1α-copGFP-transduced HFBSCs, constitutively expressing copepod green fluorescent protein (copGFP. Also, modiolus explants without hair cells were co-cultured with DCX-copGFP-transduced HFBSCs, which demonstrate copGFP upon doublecortin expression during neuronal differentiation. Velocity of HFBSC migration towards modiolus explants was calculated, and after two weeks, co-cultures were fixed and processed for immunohistochemical staining. EF1α-copGFP HFBSC migration velocity was fast: 80.5 ± 6.1 μm/h. After arrival in the explant, the cells formed a fascicular pattern and changed their phenotype into an ATOH1-positive neuronal cell type. DCX-copGFP HFBSCs became green-fluorescent after integration into the explants, confirming neuronal differentiation of the cells. These results show that HFBSC-derived neuronal progenitors are migratory and can integrate into cochlear modiolus explants, while adapting their phenotype depending on this micro-environment. Thus, HFBSCs show potential to be employed in cell-based therapies for auditory nerve repair.

Calcium-Induced calcium release during action potential firing in developing inner hair cells.

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Iosub, Radu; Avitabile, Daniele; Grant, Lisa; Tsaneva-Atanasova, Krasimira; Kennedy, Helen J

2015-03-10

In the mature auditory system, inner hair cells (IHCs) convert sound-induced vibrations into electrical signals that are relayed to the central nervous system via auditory afferents. Before the cochlea can respond to normal sound levels, developing IHCs fire calcium-based action potentials that disappear close to the onset of hearing. Action potential firing triggers transmitter release from the immature IHC that in turn generates experience-independent firing in auditory neurons. These early signaling events are thought to be essential for the organization and development of the auditory system and hair cells. A critical component of the action potential is the rise in intracellular calcium that activates both small conductance potassium channels essential during membrane repolarization, and triggers transmitter release from the cell. Whether this calcium signal is generated by calcium influx or requires calcium-induced calcium release (CICR) is not yet known. IHCs can generate CICR, but to date its physiological role has remained unclear. Here, we used high and low concentrations of ryanodine to block or enhance CICR to determine whether calcium release from intracellular stores affected action potential waveform, interspike interval, or changes in membrane capacitance during development of mouse IHCs. Blocking CICR resulted in mixed action potential waveforms with both brief and prolonged oscillations in membrane potential and intracellular calcium. This mixed behavior is captured well by our mathematical model of IHC electrical activity. We perform two-parameter bifurcation analysis of the model that predicts the dependence of IHCs firing patterns on the level of activation of two parameters, the SK2 channels activation and CICR rate. Our data show that CICR forms an important component of the calcium signal that shapes action potentials and regulates firing patterns, but is not involved directly in triggering exocytosis. These data provide important insights

Artificial Cochlear Sensory Epithelium with Functions of Outer Hair Cells Mimicked Using Feedback Electrical Stimuli

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Tetsuro Tsuji

2018-05-01

Full Text Available We report a novel vibration control technique of an artificial auditory cochlear epithelium that mimics the function of outer hair cells in the organ of Corti. The proposed piezoelectric and trapezoidal membrane not only has the acoustic/electric conversion and frequency selectivity of the previous device developed mainly by one of the authors and colleagues, but also has a function to control local vibration according to sound stimuli. Vibration control is achieved by applying local electrical stimuli to patterned electrodes on an epithelium made using micro-electro-mechanical system technology. By choosing appropriate phase differences between sound and electrical stimuli, it is shown that it is possible to both amplify and dampen membrane vibration, realizing better control of the response of the artificial cochlea. To be more specific, amplification and damping are achieved when the phase difference between the membrane vibration by sound stimuli and electrical stimuli is zero and π , respectively. We also demonstrate that the developed control system responds automatically to a change in sound frequency. The proposed technique can be applied to mimic the nonlinear response of the outer hair cells in a cochlea, and to realize a high-quality human auditory system.

Hair cell regeneration or the expression of related factors that regulate the fate specification of supporting cells in the cochlear ducts of embryonic and posthatch chickens.

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Jiang, Lingling; Jin, Ran; Xu, Jincao; Ji, Yubin; Zhang, Meiguang; Zhang, Xuebo; Zhang, Xinwen; Han, Zhongming; Zeng, Shaoju

2016-02-01

Hair cells in posthatch chickens regenerate spontaneously through mitosis or the transdifferentiation of supporting cells in response to antibiotic injury. However, how embryonic chicken cochleae respond to antibiotic treatment remains unknown. This study is the first to indicate that unlike hair cells in posthatch chickens, the auditory epithelium was free from antibiotic injury (25-250 mg gentamicin/kg) in embryonic chickens, although FITC-conjugated gentamicin actually reached embryonic hair cells. Next, we examined and counted the cells and performed labeling for BrdU, Sox2, Atoh1/Math1, PV or p27(kip1) (triple or double labeling) in the injured cochlea ducts after gentamicin treatment at 2 h (h), 15 h, 24 h, 2 days (d), 3 d and 7 d after BrdU treatment in posthatch chickens. Our results indicated that following gentamicin administration, proliferating cells (BrdU+) were labeled for Atoh1/Math1 in the damaged areas 3d after gentamicin administration, whereas hair cells (PV+) renewed through mitosis (BrdU+) or direct transdifferentiation (BrdU-) were evident only after 5 d of gentamicin administration. In addition, Sox2 expression was up-regulated in triggered supporting cells at an early stage of regeneration, but stopped at the advent of mature hair cells. Our study also indicated that p27(kip1) was expressed in both hair cells and supporting cells but was down-regulated in a subgroup of the supporting cells that gave rise to hair cells. These data and the obtained dynamic changes of the cells labeled for BrdU, Sox2, Atoh1/Math1, PV or p27(kip1) are useful for understanding supporting cell behaviors and their fate specification during hair cell regeneration. Copyright © 2015 Elsevier B.V. All rights reserved.

Position-dependent patterning of spontaneous action potentials in immature cochlear inner hair cells.

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Johnson, Stuart L; Eckrich, Tobias; Kuhn, Stephanie; Zampini, Valeria; Franz, Christoph; Ranatunga, Kishani M; Roberts, Terri P; Masetto, Sergio; Knipper, Marlies; Kros, Corné J; Marcotti, Walter

2011-06-01

Spontaneous action potential activity is crucial for mammalian sensory system development. In the auditory system, patterned firing activity has been observed in immature spiral ganglion and brain-stem neurons and is likely to depend on cochlear inner hair cell (IHC) action potentials. It remains uncertain whether spiking activity is intrinsic to developing IHCs and whether it shows patterning. We found that action potentials were intrinsically generated by immature IHCs of altricial rodents and that apical IHCs showed bursting activity as opposed to more sustained firing in basal cells. We show that the efferent neurotransmitter acetylcholine fine-tunes the IHC's resting membrane potential (V(m)), and as such is crucial for the bursting pattern in apical cells. Endogenous extracellular ATP also contributes to the V(m) of apical and basal IHCs by triggering small-conductance Ca(2+)-activated K(+) (SK2) channels. We propose that the difference in firing pattern along the cochlea instructs the tonotopic differentiation of IHCs and auditory pathway.

The pluripotency of hair follicle stem cells.

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Hoffman, Robert M

2006-02-01

The hair follicle bulge area is an abundant, easily accessible source of actively growing, pluripotent adult stem cells. Nestin, a protein marker for neural stem cells, is also expressed in follicle stem cells as well as their immediate differentiated progeny. The nestin-expressing hair follicle stem cells differentiated into neurons, glial cells, keratinocytes and smooth muscle cells in vitro. Hair-follicle stem cells were implanted into the gap region of a severed sciatic nerve. The hair follicle stem cells greatly enhanced the rate of nerve regeneration and the restoration of nerve function. The follicle stem cells transdifferentiated largely into Schwann cells which are known to support neuron regrowth. Function of the rejoined sciatic nerve was measured by contraction of the gastrocnemius muscle upon electrical stimulation. After severing the tibial nerve and subsequent transplantation of hair-follicle stem cells, the transplanted mice recovered the ability to walk normally. These results suggest that hair-follicle stem cells provide an important accessible, autologous source of adult stem cells for regenerative medicine.

Rescue of Outer Hair Cells with Antisense Oligonucleotides in Usher Mice Is Dependent on Age of Treatment.

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Ponnath, Abhilash; Depreux, Frederic F; Jodelka, Francine M; Rigo, Frank; Farris, Hamilton E; Hastings, Michelle L; Lentz, Jennifer J

2018-02-01

The absence of functional outer hair cells is a component of several forms of hereditary hearing impairment, including Usher syndrome, the most common cause of concurrent hearing and vision loss. Antisense oligonucleotide (ASO) treatment of mice with the human Usher mutation, Ush1c c.216G>A, corrects gene expression and significantly improves hearing, as measured by auditory-evoked brainstem responses (ABRs), as well as inner and outer hair cell (IHC and OHC) bundle morphology. However, it is not clear whether the improvement in hearing achieved by ASO treatment involves the functional rescue of outer hair cells. Here, we show that Ush1c c.216AA mice lack OHC function as evidenced by the absence of distortion product otoacoustic emissions (DPOAEs) in response to low-, mid-, and high-frequency tone pairs. This OHC deficit is rescued by treatment with an ASO that corrects expression of Ush1c c.216G>A. Interestingly, although rescue of inner hairs cells, as measured by ABR, is achieved by ASO treatment as late as 7 days after birth, rescue of outer hair cells, measured by DPOAE, requires treatment before post-natal day 5. These results suggest that ASO-mediated rescue of both IHC and OHC function is age dependent and that the treatment window is different for the different cell types. The timing of treatment for congenital hearing disorders is of critical importance for the development of drugs such ASO-29 for hearing rescue.

Induction of Functional Hair-Cell-Like Cells from Mouse Cochlear Multipotent Cells

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Quanwen Liu

2016-01-01

Full Text Available In this paper, we developed a two-step-induction method of generating functional hair cells from inner ear multipotent cells. Multipotent cells from the inner ear were established and induced initially into progenitor cells committed to the inner ear cell lineage on the poly-L-lysine substratum. Subsequently, the committed progenitor cells were cultured on the mitotically inactivated chicken utricle stromal cells and induced into hair-cell-like cells containing characteristic stereocilia bundles. The hair-cell-like cells exhibited rapid permeation of FM1-43FX. The whole-cell patch-clamp technique was used to measure the membrane currents of cells differentiated for 7 days on chicken utricle stromal cells and analyze the biophysical properties of the hair-cell-like cells by recording membrane properties of cells. The results suggested that the hair-cell-like cells derived from inner ear multipotent cells were functional following differentiation in an enabling environment.

Hair follicle stem cell proliferation, Akt and Wnt signaling activation in TPA-induced hair regeneration.

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Qiu, Weiming; Lei, Mingxing; Zhou, Ling; Bai, Xiufeng; Lai, Xiangdong; Yu, Yu; Yang, Tian; Lian, Xiaohua

2017-06-01

Regeneration of hair follicles relies on activation of hair follicle stem cells during telogen to anagen transition process in hair cycle. This process is rigorously controlled by intrinsic and environmental factors. 12-o-tetradecanoylphorbol-13-acetate (TPA), a tumor promoter, accelerates reentry of hair follicles into anagen phase. However, it is unclear that how TPA promotes the hair regeneration. In the present study, we topically applied TPA onto the dorsal skin of 2-month-old C57BL/6 female mice to examine the activity of hair follicle stem cells and alteration of signaling pathways during hair regeneration. We found that refractory telogen hair follicles entered anagen prematurely after TPA treatment, with the enhanced proliferation of CD34-positive hair follicle stem cells. Meanwhile, we observed Akt signaling was activated in epidermis, hair infundibulum, bulge and hair bulb, and Wnt signaling was also activated after hair follicle stem cells proliferation. Importantly, after overexpression of DKK1, a specific Wnt signaling inhibitor, the accelerated reentry of hair follicles into anagen induced by TPA was abolished. Our data indicated that TPA-induced hair follicle regeneration is associated with activation of Akt and Wnt/β-catenin signaling.

Direct effects of music in non-auditory cells in culture

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Nathalia dos Reis Lestard

2013-01-01

Full Text Available The biological effects of electromagnetic waves are widely studied, especially due to their harmful effects, such as radiation-induced cancer and to their application in diagnosis and therapy. However, the biological effects of sound, another physical agent to which we are frequently exposed have been considerably disregarded by the scientific community. Although a number of studies suggest that emotions evoked by music may be useful in medical care, alleviating stress and nociception in patients undergoing surgical procedures as well as in cancer and burned patients, little is known about the mechanisms by which these effects occur. It is generally accepted that the mechanosensory hair cells in the ear transduce the sound-induced mechanical vibrations into neural impulses, which are interpreted by the brain and evoke the emotional effects. In the last decade; however, several studies suggest that the response to music is even more complex. Moreover, recent evidence comes out that cell types other than auditory hair cells could response to audible sound. However, what is actually sensed by the hair cells, and possible by other cells in our organism, are physical differences in fluid pressure induced by the sound waves. Therefore, there is no reasonable impediment for any cell type of our body to respond to a pure sound or to music. Hence, the aim of the present study was to evaluate the response of a human breast cancer cell line, MCF7, to music. The results′ obtained suggest that music can alter cellular morpho-functional parameters, such as cell size and granularity in cultured cells. Moreover, our results suggest for the 1 st time that music can directly interfere with hormone binding to their targets, suggesting that music or audible sounds could modulate physiological and pathophysiological processes.

Adipose-derived stromal cells enhance auditory neuron survival in an animal model of sensory hearing loss.

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Schendzielorz, Philipp; Vollmer, Maike; Rak, Kristen; Wiegner, Armin; Nada, Nashwa; Radeloff, Katrin; Hagen, Rudolf; Radeloff, Andreas

2017-10-01

A cochlear implant (CI) is an electronic prosthesis that can partially restore speech perception capabilities. Optimum information transfer from the cochlea to the central auditory system requires a proper functioning auditory nerve (AN) that is electrically stimulated by the device. In deafness, the lack of neurotrophic support, normally provided by the sensory cells of the inner ear, however, leads to gradual degeneration of auditory neurons with undesirable consequences for CI performance. We evaluated the potential of adipose-derived stromal cells (ASCs) that are known to produce neurotrophic factors to prevent neural degeneration in sensory hearing loss. For this, co-cultures of ASCs with auditory neurons have been studied, and autologous ASC transplantation has been performed in a guinea pig model of gentamicin-induced sensory hearing loss. In vitro ASCs were neuroprotective and considerably increased the neuritogenesis of auditory neurons. In vivo transplantation of ASCs into the scala tympani resulted in an enhanced survival of auditory neurons. Specifically, peripheral AN processes that are assumed to be the optimal activation site for CI stimulation and that are particularly vulnerable to hair cell loss showed a significantly higher survival rate in ASC-treated ears. ASC transplantation into the inner ear may restore neurotrophic support in sensory hearing loss and may help to improve CI performance by enhanced AN survival. Copyright © 2017 International Society for Cellular Therapy. Published by Elsevier Inc. All rights reserved.

Sensory hair cell death and regeneration in fishes

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Jerry D. Monroe

2015-04-01

Full Text Available Sensory hair cells are specialized mechanotransductive receptors required for hearing and vestibular function. Loss of hair cells in humans and other mammals is permanent and causes reduced hearing and balance. In the early 1980’s, it was shown that hair cells continue to be added to the inner ear sensory epithelia in cartilaginous and bony fishes. Soon thereafter, hair cell regeneration was documented in the chick cochlea following acoustic trauma. Since then, research using chick and other avian models has led to great insights into hair cell death and regeneration. However, with the rise of the zebrafish as a model organism for studying disease and developmental processes, there has been an increased interest in studying sensory hair cell death and regeneration in its lateral line and inner ears. Advances derived from studies in zebrafish and other fish species include understanding the effect of ototoxins on hair cells and finding otoprotectants to mitigate ototoxin damage, the role of cellular proliferation versus direct transdifferentiation during hair cell regeneration, and elucidating cellular pathways involved in the regeneration process. This review will summarize research on hair cell death and regeneration using fish models, indicate the potential strengths and weaknesses of these models, and discuss several emerging areas of future studies.

The very large G-protein-coupled receptor VLGR1: a component of the ankle link complex required for the normal development of auditory hair bundles.

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McGee, Joann; Goodyear, Richard J; McMillan, D Randy; Stauffer, Eric A; Holt, Jeffrey R; Locke, Kirsten G; Birch, David G; Legan, P Kevin; White, Perrin C; Walsh, Edward J; Richardson, Guy P

2006-06-14

Sensory hair bundles in the inner ear are composed of stereocilia that can be interconnected by a variety of different link types, including tip links, horizontal top connectors, shaft connectors, and ankle links. The ankle link antigen is an epitope specifically associated with ankle links and the calycal processes of photoreceptors in chicks. Mass spectrometry and immunoblotting were used to identify this antigen as the avian ortholog of the very large G-protein-coupled receptor VLGR1, the product of the Usher syndrome USH2C (Mass1) locus. Like ankle links, Vlgr1 is expressed transiently around the base of developing hair bundles in mice. Ankle links fail to form in the cochleae of mice carrying a targeted mutation in Vlgr1 (Vlgr1/del7TM), and the bundles become disorganized just after birth. FM1-43 [N-(3-triethylammonium)propyl)-4-(4-(dibutylamino)styryl) pyridinium dibromide] dye loading and whole-cell recordings indicate mechanotransduction is impaired in cochlear, but not vestibular, hair cells of early postnatal Vlgr1/del7TM mutant mice. Auditory brainstem recordings and distortion product measurements indicate that these mice are severely deaf by the third week of life. Hair cells from the basal half of the cochlea are lost in 2-month-old Vlgr1/del7TM mice, and retinal function is mildly abnormal in aged mutants. Our results indicate that Vlgr1 is required for formation of the ankle link complex and the normal development of cochlear hair bundles.

Modeling auditory perception of individual hearing-impaired listeners

DEFF Research Database (Denmark)

Jepsen, Morten Løve; Dau, Torsten

showed that, in most cases, the reduced or absent cochlear compression, associated with outer hair-cell loss, quantitatively accounts for broadened auditory filters, while a combination of reduced compression and reduced inner hair-cell function accounts for decreased sensitivity and slower recovery from...... selectivity. Three groups of listeners were considered: (a) normal hearing listeners; (b) listeners with a mild-to-moderate sensorineural hearing loss; and (c) listeners with a severe sensorineural hearing loss. A fixed set of model parameters were derived for each hearing-impaired listener. The simulations...

Motility of vestibular hair cells in the chick.

Science.gov (United States)

Ogata, Y; Sekitani, T

1993-01-01

Recent studies of the outer hair cells in cochlea have demonstrated active motilities. However, very little study has been done on the vestibular hair cells (VHCs). The present study shows the motile response of the VHCs induced by application of Ca2+/ATP promoting contraction. Reversible cell shape changes could be shown in 10 of 16 isolated type I hair cells and 9 of 15 isolated type II hair cells by applying the contraction solution. Furthermore, the sensory hair bundles in the utricular epithelium pivoted around the base and stood perpendicularly to the apical borderline of the epithelium in response to the application of the same solution. It is suggested that the contraction of the isolated VHCs may be transferred to tension which causes the sensory hair bundles to restrict their motion in normal tissue, instead of changing the cell shape.

Activation of CHK1 in Supporting Cells Indirectly Promotes Hair Cell Survival

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Azadeh Jadali

2017-05-01

Full Text Available The sensory hair cells of the inner ear are exquisitely sensitive to ototoxic insults. Loss of hair cells after exposure to ototoxic agents causes hearing loss. Chemotherapeutic agents such as cisplatin causes hair cell loss. Cisplatin forms DNA mono-adducts as well as intra- and inter-strand DNA crosslinks. DNA cisplatin adducts are repaired through the DNA damage response. The decision between cell survival and cell death following DNA damage rests on factors that are involved in determining damage tolerance, cell survival and apoptosis. Cisplatin damage on hair cells has been the main focus of many ototoxic studies, yet the effect of cisplatin on supporting cells has been largely ignored. In this study, the effects of DNA damage response in cochlear supporting cells were interrogated. Supporting cells play a major role in the development, maintenance and oto-protection of hair cells. Loss of supporting cells may indirectly affect hair cell survival or maintenance. Activation of the Phosphoinositide 3-Kinase (PI3K signaling was previously shown to promote hair cell survival. To test whether activating PI3K signaling promotes supporting cell survival after cisplatin damage, cochlear explants from the neural subset (NS Cre Pten conditional knockout mice were employed. Deletion of Phosphatase and Tensin Homolog (PTEN activates PI3K signaling in multiple cell types within the cochlea. Supporting cells lacking PTEN showed increased cell survival after cisplatin damage. Supporting cells lacking PTEN also showed increased phosphorylation of Checkpoint Kinase 1 (CHK1 levels after cisplatin damage. Nearest neighbor analysis showed increased numbers of supporting cells with activated PI3K signaling in close proximity to surviving hair cells in cisplatin damaged cochleae. We propose that increased PI3K signaling promotes supporting cell survival through phosphorylation of CHK1 and increased survival of supporting cells indirectly increases hair cell

The relation between otoacoustic emissions and the broadening of the auditory filter for higher levels

NARCIS (Netherlands)

Leeuw, A. R.; Dreschler, W. A.

1998-01-01

The active behaviour of outer hair cells (OHCs) is often used to explain two phenomena, namely otoacoustic emissions (OAEs) and the level dependence of auditory filters. Correlations between these two phenomena may contribute to the evidence of these hypotheses. In this study auditory filters were

Defining the cellular environment in the organ of Corti following extensive hair cell loss: a basis for future sensory cell replacement in the Cochlea.

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Ruth R Taylor

Full Text Available BACKGROUND: Following the loss of hair cells from the mammalian cochlea, the sensory epithelium repairs to close the lesions but no new hair cells arise and hearing impairment ensues. For any cell replacement strategy to be successful, the cellular environment of the injured tissue has to be able to nurture new hair cells. This study defines characteristics of the auditory sensory epithelium after hair cell loss. METHODOLOGY/PRINCIPAL FINDINGS: Studies were conducted in C57BL/6 and CBA/Ca mice. Treatment with an aminoglycoside-diuretic combination produced loss of all outer hair cells within 48 hours in both strains. The subsequent progressive tissue re-organisation was examined using immunohistochemistry and electron microscopy. There was no evidence of significant de-differentiation of the specialised columnar supporting cells. Kir4.1 was down regulated but KCC4, GLAST, microtubule bundles, connexin expression patterns and pathways of intercellular communication were retained. The columnar supporting cells became covered with non-specialised cells migrating from the outermost region of the organ of Corti. Eventually non-specialised, flat cells replaced the columnar epithelium. Flat epithelium developed in distributed patches interrupting regions of columnar epithelium formed of differentiated supporting cells. Formation of the flat epithelium was initiated within a few weeks post-treatment in C57BL/6 mice but not for several months in CBA/Ca's, suggesting genetic background influences the rate of re-organisation. CONCLUSIONS/SIGNIFICANCE: The lack of dedifferentiation amongst supporting cells and their replacement by cells from the outer side of the organ of Corti are factors that may need to be considered in any attempt to promote endogenous hair cell regeneration. The variability of the cellular environment along an individual cochlea arising from patch-like generation of flat epithelium, and the possible variability between individuals

l-N-acetylcysteine protects outer hair cells against TNFα initiated ototoxicity in vitro.

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Tillinger, Joshua A; Gupta, Chhavi; Ila, Kadri; Ahmed, Jamal; Mittal, Jeenu; Van De Water, Thomas R; Eshraghi, Adrien A

2018-03-07

The present study is aimed at determining the efficacy and exploring the mechanisms by which l-N-acetylcysteine (l-NAC) provides protection against tumor necrosis factor-alpha (TNFα)-induced oxidative stress damage and hair cell loss in 3-day-old rat organ of Corti (OC) explants. Previous work has demonstrated a high level of oxidative stress in TNFα-challenged OC explants. TNFα can potentially play a significant role in hair cell loss following an insult to the inner ear. l-NAC has shown to provide effective protection against noise-induced hearing loss in laboratory animals but mechanisms of this otoprotective effect are not well-defined. Rat OC explants were exposed to either: (1) saline control (N = 12); (2) TNFα (2 μg/ml, N = 12); (3) TNFα+l-NAC (5 mM, N = 12); (4) TNFα+l-NAC (10 mM, N = 12); or (5) l-NAC (10 mM, N = 12). Outer hair cell (OHC) density, levels of reactive oxygen species (ROS), lipid peroxidation of cell membranes, gluthathione activity, and mitochondrial viability were assayed. l-NAC (5 and 10 mM) provided protection for OHCs from ototoxic level of TNFα in OC explants. Groups treated with TNFα+l-NAC (5 mM) showed a highly significant reduction of both ROS (p l-NAC (5 mM) treated explants (p l-NAC is a promising treatment for protecting auditory HCs from TNFα-induced oxidative stress and subsequent loss via programmed cell death.

JP-8 jet fuel can promote auditory impairment resulting from subsequent noise exposure in rats.

Science.gov (United States)

Fechter, Laurence D; Gearhart, Caroline; Fulton, Sherry; Campbell, Jerry; Fisher, Jeffrey; Na, Kwangsam; Cocker, David; Nelson-Miller, Alisa; Moon, Patrick; Pouyatos, Benoit

2007-08-01

We report on the transient and persistent effects of JP-8 jet fuel exposure on auditory function in rats. JP-8 has become the standard jet fuel utilized in the United States and North Atlantic Treaty Organization countries for military use and it is closely related to Jet A fuel, which is used in U.S. domestic aviation. Rats received JP-8 fuel (1000 mg/m(3)) by nose-only inhalation for 4 h and half of them were immediately subjected to an octave band of noise ranging between 97 and 105 dB in different experiments. The noise by itself produces a small, but permanent auditory impairment. The current permissible exposure level for JP-8 is 350 mg/m(3). Additionally, a positive control group received only noise exposure, and a fourth group consisted of untreated control subjects. Exposures occurred either on 1 day or repeatedly on 5 successive days. Impairments in auditory function were assessed using distortion product otoacoustic emissions and compound action potential testing. In other rats, tissues were harvested following JP-8 exposure for assessment of hydrocarbon levels or glutathione (GSH) levels. A single JP-8 exposure by itself at 1000 mg/m(3) did not disrupt auditory function. However, exposure to JP-8 and noise produced an additive disruption in outer hair cell function. Repeated 5-day JP-8 exposure at 1000 mg/m(3) for 4 h produced impairment of outer hair cell function that was most evident at the first postexposure assessment time. Partial though not complete recovery was observed over a 4-week postexposure period. The adverse effects of repeated JP-8 exposures on auditory function were inconsistent, but combined treatment with JP-8 + noise yielded greater impairment of auditory function, and hair cell loss than did noise by itself. Qualitative comparison of outer hair cell loss suggests an increase in outer hair cell death among rats treated with JP-8 + noise for 5 days as compared to noise alone. In most instances, hydrocarbon constituents of the fuel

Mechanically Gated Ion Channels in Mammalian Hair Cells

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Xufeng Qiu

2018-04-01

Full Text Available Hair cells in the inner ear convert mechanical stimuli provided by sound waves and head movements into electrical signal. Several mechanically evoked ionic currents with different properties have been recorded in hair cells. The search for the proteins that form the underlying ion channels is still in progress. The mechanoelectrical transduction (MET channel near the tips of stereociliary in hair cells, which is responsible for sensory transduction, has been studied most extensively. Several components of the sensory mechanotransduction machinery in stereocilia have been identified, including the multi-transmembrane proteins tetraspan membrane protein in hair cell stereocilia (TMHS/LHFPL5, transmembrane inner ear (TMIE and transmembrane channel-like proteins 1 and 2 (TMC1/2. However, there remains considerable uncertainty regarding the molecules that form the channel pore. In addition to the sensory MET channel, hair cells express the mechanically gated ion channel PIEZO2, which is localized near the base of stereocilia and not essential for sensory transduction. The function of PIEZO2 in hair cells is not entirely clear but it might have a role in damage sensing and repair processes. Additional stretch-activated channels of unknown molecular identity and function have been found to localize at the basolateral membrane of hair cells. Here, we review current knowledge regarding the different mechanically gated ion channels in hair cells and discuss open questions concerning their molecular composition and function.

Reduced sensory stimulation alters the molecular make-up of glutamatergic hair cell synapses in the developing cochlea.

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Barclay, M; Constable, R; James, N R; Thorne, P R; Montgomery, J M

2016-06-14

Neural activity during early development is known to alter innervation pathways in the central and peripheral nervous systems. We sought to examine how reduced sound-induced sensory activity in the cochlea affected the consolidation of glutamatergic synapses between inner hair cells (IHC) and the primary auditory neurons as these synapses play a primary role in transmitting sound information to the brain. A unilateral conductive hearing loss was induced prior to the onset of sound-mediated stimulation of the sensory hair cells, by rupturing the tympanic membrane and dislocating the auditory ossicles in the left ear of P11 mice. Auditory brainstem responses at P15 and P21 showed a 40-50-dB increase in thresholds for frequencies 8-32kHz in the dislocated ear relative to the control ear. Immunohistochemistry and confocal microscopy were subsequently used to examine the effect of this attenuation of sound stimulation on the expression of RIBEYE, which comprises the presynaptic ribbons, Shank-1, a postsynaptic scaffolding protein, and the GluA2/3 and 4 subunits of postsynaptic AMPA receptors. Our results show that dislocation did not alter the number of pre- or postsynaptic protein puncta. However, dislocation did increase the size of RIBEYE, GluA4, GluA2/3 and Shank-1 puncta, with postsynaptic changes preceding presynaptic changes. Our data suggest that a reduction in sound stimulation during auditory development induces plasticity in the molecular make-up of IHC glutamatergic synapses, but does not affect the number of these synapses. Up-regulation of synaptic proteins with sound attenuation may facilitate a compensatory increase in synaptic transmission due to the reduced sensory stimulation of the IHC. Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.

Regeneration of hair cells in the mammalian vestibular system.

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Li, Wenyan; You, Dan; Chen, Yan; Chai, Renjie; Li, Huawei

2016-06-01

Hair cells regenerate throughout the lifetime of non-mammalian vertebrates, allowing these animals to recover from hearing and balance deficits. Such regeneration does not occur efficiently in humans and other mammals. Thus, balance deficits become permanent and is a common sensory disorder all over the world. Since Forge and Warchol discovered the limited spontaneous regeneration of vestibular hair cells after gentamicininduced damage in mature mammals, significant efforts have been exerted to trace the origin of the limited vestibular regeneration in mammals after hair cell loss. Moreover, recently many strategies have been developed to promote the hair cell regeneration and subsequent functional recovery of the vestibular system, including manipulating the Wnt, Notch and Atoh1. This article provides an overview of the recent advances in hair cell regeneration in mammalian vestibular epithelia. Furthermore, this review highlights the current limitations of hair cell regeneration and provides the possible solutions to regenerate functional hair cells and to partially restore vestibular function.

Cockayne syndrome group B (Csb) and group a (Csa) deficiencies predispose to hearing loss and cochlear hair cell degeneration in mice.

Science.gov (United States)

Nagtegaal, A Paul; Rainey, Robert N; van der Pluijm, Ingrid; Brandt, Renata M C; van der Horst, Gijsbertus T J; Borst, J Gerard G; Segil, Neil

2015-03-11

Sensory hair cells in the cochlea, like most neuronal populations that are postmitotic, terminally differentiated, and non-regenerating, depend on robust mechanisms of self-renewal for lifelong survival. We report that hair cell homeostasis requires a specific sub-branch of the DNA damage nucleotide excision repair pathway, termed transcription-coupled repair (TCR). Cockayne syndrome (CS), caused by defects in TCR, is a rare DNA repair disorder with a broad clinical spectrum that includes sensorineural hearing loss. We tested hearing and analyzed the cellular integrity of the organ of Corti in two mouse models of this disease with mutations in the Csb gene (CSB(m/m) mice) and Csa gene (Csa(-/-) mice), respectively. Csb(m/m) and Csa(-/-) mice manifested progressive hearing loss, as measured by an increase in auditory brainstem response thresholds. In contrast to wild-type mice, mutant mice showed reduced or absent otoacoustic emissions, suggesting cochlear outer hair cell impairment. Hearing loss in Csb(m/m) and Csa(-/-) mice correlated with progressive hair cell loss in the base of the organ of Corti, starting between 6 and 13 weeks of age, which increased by 16 weeks of age in a basal-to-apical gradient, with outer hair cells more severely affected than inner hair cells. Our data indicate that the hearing loss observed in CS patients is reproduced in mouse models of this disease. We hypothesize that accumulating DNA damage, secondary to the loss of TCR, contributes to susceptibility to hearing loss. Copyright © 2015 the authors 0270-6474/15/354280-07$15.00/0.

Sensory Hair Cells: An Introduction to Structure and Physiology.

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McPherson, Duane R

2018-06-18

Sensory hair cells are specialized secondary sensory cells that mediate our senses of hearing, balance, linear acceleration, and angular acceleration (head rotation). In addition, hair cells in fish and amphibians mediate sensitivity to water movement through the lateral line system, and closely related electroreceptive cells mediate sensitivity to low-voltage electric fields in the aquatic environment of many fish species and several species of amphibian.Sensory hair cells share many structural and functional features across all vertebrate groups, while at the same time they are specialized for employment in a wide variety of sensory tasks. The complexity of hair cell structure is large, and the diversity of hair cell applications in sensory systems exceeds that seen for most, if not all, sensory cell types. The intent of this review is to summarize the more significant structural features and some of the more interesting and important physiological mechanisms that have been elucidated thus far. Outside vertebrates, hair cells are only known to exist in the coronal organ of tunicates. Electrical resonance, electromotility, and their exquisite mechanical sensitivity all contribute to the attractiveness of hair cells as a research subject.

LSD1 is Required for Hair Cell Regeneration in Zebrafish.

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He, Yingzi; Tang, Dongmei; Cai, Chengfu; Chai, Renjie; Li, Huawei

2016-05-01

Lysine-specific demethylase 1 (LSD1/KDM1A) plays an important role in complex cellular processes such as differentiation, proliferation, apoptosis, and cell cycle progression. It has recently been demonstrated that during development, downregulation of LSD1 inhibits cell proliferation, modulates the expression of cell cycle regulators, and reduces hair cell formation in the zebrafish lateral line, which suggests that LSD1-mediated epigenetic regulation plays a key role in the development of hair cells. However, the role of LSD1 in hair cell regeneration after hair cell loss remains poorly understood. Here, we demonstrate the effect of LSD1 on hair cell regeneration following neomycin-induced hair cell loss. We show that the LSD1 inhibitor trans-2-phenylcyclopropylamine (2-PCPA) significantly decreases the regeneration of hair cells in zebrafish after neomycin damage. In addition, immunofluorescent staining demonstrates that 2-PCPA administration suppresses supporting cell proliferation and alters cell cycle progression. Finally, in situ hybridization shows that 2-PCPA significantly downregulates the expression of genes related to Wnt/β-catenin and Fgf activation. Altogether, our data suggest that downregulation of LSD1 significantly decreases hair cell regeneration after neomycin-induced hair cell loss through inactivation of the Wnt/β-catenin and Fgf signaling pathways. Thus, LSD1 plays a critical role in hair cell regeneration and might represent a novel biomarker and potential therapeutic approach for the treatment of hearing loss.

Study of inner ear and lateral line hair cell regeneration

OpenAIRE

Piqué Borràs, Maria Riera

2013-01-01

Death of sensory hair cells in the inner ear results in two global health problems that millions of people around the world suffer: hearing loss and balance disorders. Hair cells convert sound vibrations and head movements into electrical signals that are conveyed to the brain, and as a result of aging, exposure to noise, modern drugs or genetic predisposition, hair cells die. In mammals, the great majority of hair cells are produced during embryogenesis, and hair cells that ar...

Myc and Fgf Are Required for Zebrafish Neuromast Hair Cell Regeneration.

Science.gov (United States)

Lee, Sang Goo; Huang, Mingqian; Obholzer, Nikolaus D; Sun, Shan; Li, Wenyan; Petrillo, Marco; Dai, Pu; Zhou, Yi; Cotanche, Douglas A; Megason, Sean G; Li, Huawei; Chen, Zheng-Yi

2016-01-01

Unlike mammals, the non-mammalian vertebrate inner ear can regenerate the sensory cells, hair cells, either spontaneously or through induction after hair cell loss, leading to hearing recovery. The mechanisms underlying the regeneration are poorly understood. By microarray analysis on a chick model, we show that chick hair cell regeneration involves the activation of proliferation genes and downregulation of differentiation genes. Both MYC and FGF are activated in chick hair cell regeneration. Using a zebrafish lateral line neuromast hair cell regeneration model, we show that the specific inhibition of Myc or Fgf suppresses hair cell regeneration, demonstrating that both pathways are essential to the process. Rapid upregulation of Myc and delayed Fgf activation during regeneration suggest a role of Myc in proliferation and Fgf in differentiation. The dorsal-ventral pattern of fgfr1a in the neuromasts overlaps with the distribution of hair cell precursors. By laser ablation, we show that the fgfr1a-positive supporting cells are likely the hair cell precursors that directly give rise to new hair cells; whereas the anterior-posterior fgfr1a-negative supporting cells have heightened proliferation capacity, likely to serve as more primitive progenitor cells to replenish lost precursors after hair cell loss. Thus fgfr1a is likely to mark compartmentalized supporting cell subtypes with different capacities in renewal proliferation and hair cell regeneration. Manipulation of c-MYC and FGF pathways could be explored for mammalian hair cell regeneration.

Stem cell plasticity enables hair regeneration following Lgr5+ cell loss.

Science.gov (United States)

Hoeck, Joerg D; Biehs, Brian; Kurtova, Antonina V; Kljavin, Noelyn M; de Sousa E Melo, Felipe; Alicke, Bruno; Koeppen, Hartmut; Modrusan, Zora; Piskol, Robert; de Sauvage, Frederic J

2017-06-01

Under injury conditions, dedicated stem cell populations govern tissue regeneration. However, the molecular mechanisms that induce stem cell regeneration and enable plasticity are poorly understood. Here, we investigate stem cell recovery in the context of the hair follicle to understand how two molecularly distinct stem cell populations are integrated. Utilizing diphtheria-toxin-mediated cell ablation of Lgr5 + (leucine-rich repeat-containing G-protein-coupled receptor 5) stem cells, we show that killing of Lgr5 + cells in mice abrogates hair regeneration but this is reversible. During recovery, CD34 + (CD34 antigen) stem cells activate inflammatory response programs and start dividing. Pharmacological attenuation of inflammation inhibits CD34 + cell proliferation. Subsequently, the Wnt pathway controls the recovery of Lgr5 + cells and inhibition of Wnt signalling prevents Lgr5 + cell and hair germ recovery. Thus, our study uncovers a compensatory relationship between two stem cell populations and the underlying molecular mechanisms that enable hair follicle regeneration.

Feathers and fins: non-mammalian models for hair cell regeneration.

Science.gov (United States)

Brignull, Heather R; Raible, David W; Stone, Jennifer S

2009-06-24

Death of mechanosensory cells in the inner ear results in two profound disabilities: hearing loss and balance disorders. Although mammals lack the capacity to regenerate hair cells, recent studies in mice and other rodents have offered valuable insight into strategies for stimulating hair cell regeneration in mammals. Investigations of model organisms that retain the ability to form new hair cells after embryogenesis, such as fish and birds, are equally important and have provided clues as to the cellular and molecular mechanisms that may block hair cell regeneration in mammals. Here, we summarize studies on hair cell regeneration in the chicken and the zebrafish, discuss specific advantages of each model, and propose future directions for the use of non-mammalian models in understanding hair cell regeneration.

Sensory hair cell regeneration in the zebrafish lateral line.

Science.gov (United States)

Lush, Mark E; Piotrowski, Tatjana

2014-10-01

Damage or destruction of sensory hair cells in the inner ear leads to hearing or balance deficits that can be debilitating, especially in older adults. Unfortunately, the damage is permanent, as regeneration of the inner ear sensory epithelia does not occur in mammals. Zebrafish and other non-mammalian vertebrates have the remarkable ability to regenerate sensory hair cells and understanding the molecular and cellular basis for this regenerative ability will hopefully aid us in designing therapies to induce regeneration in mammals. Zebrafish not only possess hair cells in the ear but also in the sensory lateral line system. Hair cells in both organs are functionally analogous to hair cells in the inner ear of mammals. The lateral line is a mechanosensory system found in most aquatic vertebrates that detects water motion and aids in predator avoidance, prey capture, schooling, and mating. Although hair cell regeneration occurs in both the ear and lateral line, most research to date has focused on the lateral line due to its relatively simple structure and accessibility. Here we review the recent discoveries made during the characterization of hair cell regeneration in zebrafish. Copyright © 2014 Wiley Periodicals, Inc.

SENSORY HAIR CELL REGENERATION IN THE ZEBRAFISH LATERAL LINE

Science.gov (United States)

Lush, Mark E.; Piotrowski, Tatjana

2014-01-01

Damage or destruction of sensory hair cells in the inner ear leads to hearing or balance deficits that can be debilitating, especially in older adults. Unfortunately, the damage is permanent, as regeneration of the inner ear sensory epithelia does not occur in mammals. Zebrafish and other non-mammalian vertebrates have the remarkable ability to regenerate sensory hair cells and understanding the molecular and cellular basis for this regenerative ability will hopefully aid us in designing therapies to induce regeneration in mammals. Zebrafish not only possess hair cells in the ear but also in the sensory lateral line system. Hair cells in both organs are functionally analogous to hair cells in the inner ear of mammals. The lateral line is a mechanosensory system found in most aquatic vertebrates that detects water motion and aids in predator avoidance, prey capture, schooling and mating. Although hair cell regeneration occurs in both the ear and lateral line, most research to date has focused on the lateral line due to its relatively simple structure and accessibility. Here we review the recent discoveries made during the characterization of hair cell regeneration in zebrafish. PMID:25045019

Mammalian cochlear supporting cells can divide and trans-differentiate into hair cells.

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White, Patricia M; Doetzlhofer, Angelika; Lee, Yun Shain; Groves, Andrew K; Segil, Neil

2006-06-22

Sensory hair cells of the mammalian organ of Corti in the inner ear do not regenerate when lost as a consequence of injury, disease, or age-related deafness. This contrasts with other vertebrates such as birds, where the death of hair cells causes surrounding supporting cells to re-enter the cell cycle and give rise to both new hair cells and supporting cells. It is not clear whether the lack of mammalian hair cell regeneration is due to an intrinsic inability of supporting cells to divide and differentiate or to an absence or blockade of regenerative signals. Here we show that post-mitotic supporting cells purified from the postnatal mouse cochlea retain the ability to divide and trans-differentiate into new hair cells in culture. Furthermore, we show that age-dependent changes in supporting cell proliferative capacity are due in part to changes in the ability to downregulate the cyclin-dependent kinase inhibitor p27(Kip1) (also known as Cdkn1b). These results indicate that postnatal mammalian supporting cells are potential targets for therapeutic manipulation.

 Hair follicle as a novel source of stem cells

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Romana Joachimiak

2012-04-01

Full Text Available  Tissue engineering as a rapidly developing branch of science offers hope for the use of its products in medical practice. Among the components of tissue substitutes are different types of cells, especially stem cells. A promising source of adult stem cells is hair follicles. Development of follicles in the skin takes place even during fetal life. They arise due to the impact of epidermal and mesenchymal cells. The next steps in the formation of hair follicles are under the control of many factors. Hair follicles are the niche of various stem cell populations and are a major source of cells responsible for regeneration of the hair, sebaceous glands and epidermis. The term „hair follicle stem cells” is most often used in relation to the epithelial cell population. Hair follicle stem cell studies are complicated by the fact that these stem cells divide relatively rarely.The aim of this study is to present the characteristics of cells isolated from the hair follicle in the light of recent research.

Stimulation of hair cells with ultraviolet light

Science.gov (United States)

Azimzadeh, Julien B.; Fabella, Brian A.; Hudspeth, A. J.

2018-05-01

Hair bundles are specialized organelles that transduce mechanical inputs into electrical outputs. To activate hair cells, physiologists have resorted to mechanical methods of hair-bundle stimulation. Here we describe a new method of hair-bundle stimulation, irradiation with ultraviolet light. A hair bundle illuminated by ultraviolet light rapidly moves towards its tall edge, a motion typically associated with excitatory stimulation. The motion disappears upon tip-link rupture and is associated with the opening of mechanotransduction channels. Hair bundles can be induced to move sinusoidally with oscillatory modulation of the stimulation power. We discuss the implications of ultraviolet stimulation as a novel hair-bundle stimulus.

Development and regeneration of vestibular hair cells in mammals.

Science.gov (United States)

Burns, Joseph C; Stone, Jennifer S

2017-05-01

Vestibular sensation is essential for gaze stabilization, balance, and perception of gravity. The vestibular receptors in mammals, Type I and Type II hair cells, are located in five small organs in the inner ear. Damage to hair cells and their innervating neurons can cause crippling symptoms such as vertigo, visual field oscillation, and imbalance. In adult rodents, some Type II hair cells are regenerated and become re-innervated after damage, presenting opportunities for restoring vestibular function after hair cell damage. This article reviews features of vestibular sensory cells in mammals, including their basic properties, how they develop, and how they are replaced after damage. We discuss molecules that control vestibular hair cell regeneration and highlight areas in which our understanding of development and regeneration needs to be deepened. Copyright © 2016 Elsevier Ltd. All rights reserved.

Local Mechanisms for Loud Sound-Enhanced Aminoglycoside Entry into Outer Hair Cells

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Hongzhe eLi

2015-04-01

Full Text Available Loud sound exposure exacerbates aminoglycoside ototoxicity, increasing the risk of permanent hearing loss and degrading the quality of life in affected individuals. We previously reported that loud sound exposure induces temporary threshold shifts (TTS and enhances uptake of aminoglycosides, like gentamicin, by cochlear outer hair cells (OHCs. Here, we explore mechanisms by which loud sound exposure and TTS could increase aminoglycoside uptake by OHCs that may underlie this form of ototoxic synergy.Mice were exposed to loud sound levels to induce TTS, and received fluorescently-tagged gentamicin (GTTR for 30 minutes prior to fixation. The degree of TTS was assessed by comparing auditory brainstem responses before and after loud sound exposure. The number of tip links, which gate the GTTR-permeant mechanoelectrical transducer (MET channels, was determined in OHC bundles, with or without exposure to loud sound, using scanning electron microscopy.We found wide-band noise (WBN levels that induce TTS also enhance OHC uptake of GTTR compared to OHCs in control cochleae. In cochlear regions with TTS, the increase in OHC uptake of GTTR was significantly greater than in adjacent pillar cells. In control mice, we identified stereociliary tip links at ~50% of potential positions in OHC bundles. However, the number of OHC tip links was significantly reduced in mice that received WBN at levels capable of inducing TTS.These data suggest that GTTR uptake by OHCs during TTS occurs by increased permeation of surviving, mechanically-gated MET channels, and/or non-MET aminoglycoside-permeant channels activated following loud sound exposure. Loss of tip links would hyperpolarize hair cells and potentially increase drug uptake via aminoglycoside-permeant channels expressed by hair cells. The effect of TTS on aminoglycoside-permeant channel kinetics will shed new light on the mechanisms of loud sound-enhanced aminoglycoside uptake, and consequently on ototoxic

Live cell imaging of Arabidopsis root hairs

NARCIS (Netherlands)

Ketelaar, T.

2014-01-01

Root hairs are tubular extensions from the root surface that expand by tip growth. This highly focused type of cell expansion, combined with position of root hairs on the surface of the root, makes them ideal cells for microscopic observation. This chapter describes the method that is routinely used

Hair cell regeneration in the bullfrog vestibular otolith organs following aminoglycoside toxicity

Science.gov (United States)

Baird, Richard A.; Torres, M. A.; Schuff, N. R.

1994-01-01

Adult bullfrogs were given single intraotic injections of the aminoglycoside antibiotic gentamicin sulfate and sacrificed at postinjection times ranging from 0.5 to 9 days. The saccular and utricular maculae of normal and injected animals were examined in wholemount and cross-section. Intraotic 200 (mu) M gentamicin concentrations resulted in the uniform destruction of the hair bundles and, at later times, the cell bodies of saccular hair cells. In the utriculus, striolar hair cells were selectively damaged while extrastriolar hair cells were relatively unaffected. Regenerating hair cells, identified in sectioned material by their small cell bodies and short, well-formed hair bundles, were seen in the saccular and utricular maculae as early as 24-48 h postinjection. Immature versions of mature hair cell types in both otolith organs were recognized by the presence of absence of a bulbed kinocilia and the relative lengths of their kinocilia and longest sterocilia. Utricular hair cell types with kinocilia longer than their longest stereocilia were observed at earlier times than hair cell types with shorter kinocilia. In the same sacculus, the hair bundles of gentamicin-treated animals, even at 9 days postinjection, were significantly smaller than those of normal animals. The hair bundles of utricular hair cells, on the other hand, reached full maturity within the same time period.

Paraquat initially damages cochlear support cells leading to anoikis-like hair cell death.

Science.gov (United States)

Zhang, Jianhui; Sun, Hong; Salvi, Richard; Ding, Dalian

2018-07-01

Paraquat (PQ), one of the most widely used herbicides, is extremely dangerous because it generates the highly toxic superoxide radical. When paraquat was applied to cochlear organotypic cultures, it not only damaged the outer hair cells (OHCs) and inner hair cells (IHCs), but also caused dislocation of the hair cell rows. We hypothesized that the dislocation arose from damage to the support cells (SCs) that anchors hair cells within the epithelium. To test this hypothesis, rat postnatal cochlear cultures were treated with PQ. Shortly after PQ treatment, the rows of OHCs separated from one another and migrated radially away from IHCs suggesting loss of cell-cell adhesion that hold the hair cells in proper alignment. Hair cells dislocation was associated with extensive loss of SCs in the organ of Corti, loss of tympanic border cells (TBCs) beneath the basilar membrane, the early appearance of superoxide staining and caspase-8 labeling in SCs below the OHCs and disintegration of E-cadherin and β-catenin in the organ of Corti. Damage to the TBCs and SCs occurred prior to loss of OHC or IHC loss suggesting a form of detachment-induced apoptosis referred to as anoikis. Copyright © 2018 Elsevier B.V. All rights reserved.

A Review of Gene Delivery and Stem Cell Based Therapies for Regenerating Inner Ear Hair Cells

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Michael S. Detamore

2011-09-01

Full Text Available Sensory neural hearing loss and vestibular dysfunction have become the most common forms of sensory defects, affecting millions of people worldwide. Developing effective therapies to restore hearing loss is challenging, owing to the limited regenerative capacity of the inner ear hair cells. With recent advances in understanding the developmental biology of mammalian and non-mammalian hair cells a variety of strategies have emerged to restore lost hair cells are being developed. Two predominant strategies have developed to restore hair cells: transfer of genes responsible for hair cell genesis and replacement of missing cells via transfer of stem cells. In this review article, we evaluate the use of several genes involved in hair cell regeneration, the advantages and disadvantages of the different viral vectors employed in inner ear gene delivery and the insights gained from the use of embryonic, adult and induced pluripotent stem cells in generating inner ear hair cells. Understanding the role of genes, vectors and stem cells in therapeutic strategies led us to explore potential solutions to overcome the limitations associated with their use in hair cell regeneration.

A review of gene delivery and stem cell based therapies for regenerating inner ear hair cells.

Science.gov (United States)

Devarajan, Keerthana; Staecker, Hinrich; Detamore, Michael S

2011-09-13

Sensory neural hearing loss and vestibular dysfunction have become the most common forms of sensory defects, affecting millions of people worldwide. Developing effective therapies to restore hearing loss is challenging, owing to the limited regenerative capacity of the inner ear hair cells. With recent advances in understanding the developmental biology of mammalian and non-mammalian hair cells a variety of strategies have emerged to restore lost hair cells are being developed. Two predominant strategies have developed to restore hair cells: transfer of genes responsible for hair cell genesis and replacement of missing cells via transfer of stem cells. In this review article, we evaluate the use of several genes involved in hair cell regeneration, the advantages and disadvantages of the different viral vectors employed in inner ear gene delivery and the insights gained from the use of embryonic, adult and induced pluripotent stem cells in generating inner ear hair cells. Understanding the role of genes, vectors and stem cells in therapeutic strategies led us to explore potential solutions to overcome the limitations associated with their use in hair cell regeneration.

Usher protein functions in hair cells and photoreceptors

OpenAIRE

Cosgrove, Dominic; Zallocchi, Marisa

2013-01-01

The 10 different genes associated with the deaf/blind disorder, Usher syndrome, encode a number of structurally and functionally distinct proteins, most expressed as multiple isoforms/protein variants. Functional characterization of these proteins suggests a role in stereocilia development in cochlear hair cells, likely owing to adhesive interactions in hair bundles. In mature hair cells, homodimers of the Usher cadherins, cadherin 23 and protocadherin 15, interact to form a structural fiber,...

Usher protein functions in hair cells and photoreceptors.

Science.gov (United States)

Cosgrove, Dominic; Zallocchi, Marisa

2014-01-01

The 10 different genes associated with the deaf/blind disorder, Usher syndrome, encode a number of structurally and functionally distinct proteins, most expressed as multiple isoforms/protein variants. Functional characterization of these proteins suggests a role in stereocilia development in cochlear hair cells, likely owing to adhesive interactions in hair bundles. In mature hair cells, homodimers of the Usher cadherins, cadherin 23 and protocadherin 15, interact to form a structural fiber, the tip link, and the linkages that anchor the taller stereocilia's actin cytoskeleton core to the shorter adjacent stereocilia and the elusive mechanotransduction channels, explaining the deafness phenotype when these molecular interactions are perturbed. The conundrum is that photoreceptors lack a synonymous mechanotransduction apparatus, and so a common theory for Usher protein function in the two neurosensory cell types affected in Usher syndrome is lacking. Recent evidence linking photoreceptor cell dysfunction in the shaker 1 mouse model for Usher syndrome to light-induced protein translocation defects, combined with localization of an Usher protein interactome at the periciliary region of the photoreceptors suggests Usher proteins might regulate protein trafficking between the inner and outer segments of photoreceptors. A distinct Usher protein complex is trafficked to the ribbon synapses of hair cells, and synaptic defects have been reported in Usher mutants in both hair cells and photoreceptors. This review aims to clarify what is known about Usher protein function at the synaptic and apical poles of hair cells and photoreceptors and the prospects for identifying a unifying pathobiological mechanism to explain deaf/blindness in Usher syndrome. Copyright © 2013 Elsevier Ltd. All rights reserved.

Protein biosynthesis in cultured human hair follicle cells.

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Weterings, P J; Vermorken, A J; Bloemendal, H

1980-10-31

A new technique has been used for culturing human keratinocytes. The cells grow on the basement membrane-like capsules of bovine lenses. Lens cells were removed from the capsules by rigid trypsinization. In order to exclude any contamination with remaining living cells the isolated capsules were irradiated with X-rays at a dose of 10,000 rad. In this way human epithelial cells can be brought in culture from individual hair follicles. Since feeder cells are not used in this culture technique, the biosynthesis of keratinocyte proteins can be studied in these cultures. The newly synthesized proteins can be separated into a water-soluble, a urea-soluble, and a urea-insoluble fraction. Product analysis has been performed on the first two fractions revealing protein patterns identical to those of intact hair follicles. Product analysis of the urea-soluble fractions of microdissected hair follicles shows that the protein pattern of the cultured keratinocytes resembles the protein pattern of the hair follicle sheath. Studies on the metabolism of benzo(a)pyrene revealed that the enzyme aryl hydrocarbon hydroxylase (AHH) is present in cultured hair follicle cells. A possible use of our culture system for eventual detection of inherited predisposition for smoking-dependent lung cancer is discussed.

Streptomycin ototoxicity and hair cell regeneration in the adult pigeon utricle

Science.gov (United States)

Frank, T. C.; Dye, B. J.; Newlands, S. D.; Dickman, J. D.

1999-01-01

OBJECTIVE: The purpose of this study was to develop a technique to investigate the regeneration of utricular hair cells in the adult pigeon (Columba livia) following complete hair cell loss through administration of streptomycin. STUDY DESIGN: Experimental animal study. METHODS: Animals were divided into four groups. Group 1 received 10 to 15 days of systemic streptomycin injections. Animals in Groups 2 and 3 received a single direct placement of a 1-, 2-, 4-, or 8-mg streptomycin dose into the perilymphatic space. Animals in Groups 1 and 2 were analyzed within 1 week from injection to investigate hair cell destruction, whereas Group 3 was investigated at later dates to study hair cell recovery. Group 4 animals received a control injection of saline into the perilymphatic space. Damage and recovery were quantified by counting hair cells in isolated utricles using scanning electron microscopy. RESULTS: Although systemic injections failed to reliably achieve complete utricular hair cell destruction, a single direct placement of a 2-, 4-, or 8-mg streptomycin dose caused complete destruction within the first week. Incomplete hair cell loss was observed with the 1-mg dose. Over the long term, regeneration of the hair cells was seen with the 2-mg dose but not the 8-mg dose. Control injections of saline into the perilymphatic space caused no measurable hair cell loss. CONCLUSIONS: Direct placement of streptomycin into the perilymph is an effective, reliable method for complete destruction of utricular hair cells while preserving the regenerative potential of the neuroepithelium.

Coenzyme Q10 protects hair cells against aminoglycoside.

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Kazuma Sugahara

Full Text Available It is well known that the production of free radicals is associated with sensory cell death induced by an aminoglycoside. Many researchers have reported that antioxidant reagents protect sensory cells in the inner ear, and coenzyme Q10 (CoQ10 is an antioxidant that is consumed as a health food in many countries. The purpose of this study was to investigate the role of CoQ10 in mammalian vestibular hair cell death induced by aminoglycoside. Cultured utricles of CBA/CaN mice were divided into three groups (control group, neomycin group, and neomycin + CoQ10 group. In the neomycin group, utricles were cultured with neomycin (1 mM to induce hair cell death. In the neomycin + CoQ10 group, utricles were cultured with neomycin and water-soluble CoQ10 (30-0.3 µM. Twenty-four hours after exposure to neomycin, the cultured tissues were fixed, and vestibular hair cells were labeled using an anti-calmodulin antibody. Significantly more hair cells survived in the neomycin + CoQ10 group than in the neomycin group. These data indicate that CoQ10 protects sensory hair cells against neomycin-induced death in the mammalian vestibular epithelium; therefore, CoQ10 may be useful as a protective drug in the inner ear.

Stem cell dynamics in the hair follicle niche

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Rompolas, Panteleimon; Greco, Valentina

2014-01-01

Hair follicles are skin appendages of the mammalian skin that have the ability to periodically and stereotypically regenerate in order to continuously produce new hair over our lifetime. The ability of the hair follicle to regenerate is due to the presence of stem cells that along with other cell populations and non-cellular components, including molecular signals and extracellular material, make up a niche microenvironment. Mounting evidence suggests that the niche is critical for regulating stem cell behavior and thus the process of regeneration. Here we review the literature concerning past and current studies that have utilized mouse genetic models, combined with other approaches to dissect the molecular and cellular composition of the hair follicle niche. We also discuss our current understanding of how stem cells operate within the niche during the process of tissue regeneration and the factors that regulate their behavior. PMID:24361866

The activity of spontaneous action potentials in developing hair cells is regulated by Ca(2+-dependence of a transient K+ current.

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Snezana Levic

Full Text Available Spontaneous action potentials have been described in developing sensory systems. These rhythmic activities may have instructional roles for the functional development of synaptic connections. The importance of spontaneous action potentials in the developing auditory system is underpinned by the stark correlation between the time of auditory system functional maturity, and the cessation of spontaneous action potentials. A prominent K(+ current that regulates patterning of action potentials is I(A. This current undergoes marked changes in expression during chicken hair cell development. Although the properties of I(A are not normally classified as Ca(2+-dependent, we demonstrate that throughout the development of chicken hair cells, I(A is greatly reduced by acute alterations of intracellular Ca(2+. As determinants of spike timing and firing frequency, intracellular Ca(2+ buffers shift the activation and inactivation properties of the current to more positive potentials. Our findings provide evidence to demonstrate that the kinetics and functional expression of I(A are tightly regulated by intracellular Ca(2+. Such feedback mechanism between the functional expression of I(A and intracellular Ca(2+ may shape the activity of spontaneous action potentials, thus potentially sculpting synaptic connections in an activity-dependent manner in the developing cochlea.

Sonic Hedgehog Initiates Cochlear Hair Cell Regeneration through Downregulation of Retinoblastoma Protein

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Lu, Na; Chen, Yan; Wang, Zhengmin; Chen, Guoling; Lin, Qin; Chen, Zheng-Yi; Li, Huawei

2013-01-01

Cell cycle re-entry by cochlear supporting cells and/or hair cells is considered one of the best approaches for restoring hearing loss as a result of hair cell damage. To identify mechanisms that can be modulated to initiate cell cycle re-entry and hair cell regeneration, we studied the effect of activating the sonic hedgehog (Shh) pathway. We show that Shh signaling in postnatal rat cochleae damaged by neomycin leads to renewed proliferation of supporting cells and hair cells. Further, proliferating supporting cells are likely to transdifferentiate into hair cells. Shh treatment leads to inhibition of retinoblastoma protein (pRb) by increasing phosphorylated pRb and reducing retinoblastoma gene transcription. This results in upregulation of cyclins B1, D2, and D3, and CDK1. These results suggest that Shh signaling induces cell cycle re-entry in cochlear sensory epithelium and the production of new hair cells, in part by attenuating pRb function. This study provides an additional route to modulate pRb function with important implications in mammalian hair cell regeneration. PMID:23211596

Effects of Microbubble Size on Ultrasound-Mediated Gene Transfection in Auditory Cells

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Ai-Ho Liao

2014-01-01

Full Text Available Gene therapy for sensorineural hearing loss has recently been used to insert genes encoding functional proteins to preserve, protect, or even regenerate hair cells in the inner ear. Our previous study demonstrated a microbubble- (MB-facilitated ultrasound (US technique for delivering therapeutic medication to the inner ear. The present study investigated whether MB-US techniques help to enhance the efficiency of gene transfection by means of cationic liposomes on HEI-OC1 auditory cells and whether MBs of different sizes affect such efficiency. Our results demonstrated that the size of MBs was proportional to the concentration of albumin or dextrose. At a constant US power density, using 0.66, 1.32, and 2.83 μm albumin-shelled MBs increased the transfection rate as compared to the control by 30.6%, 54.1%, and 84.7%, respectively; likewise, using 1.39, 2.12, and 3.47 μm albumin-dextrose-shelled MBs increased the transfection rates by 15.9%, 34.3%, and 82.7%, respectively. The results indicate that MB-US is an effective technique to facilitate gene transfer on auditory cells in vitro. Such size-dependent MB oscillation behavior in the presence of US plays a role in enhancing gene transfer, and by manipulating the concentration of albumin or dextrose, MBs of different sizes can be produced.

Artificial induction of Sox21 regulates sensory cell formation in the embryonic chicken inner ear.

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Stephen D Freeman

Full Text Available During embryonic development, hair cells and support cells in the sensory epithelia of the inner ear derive from progenitors that express Sox2, a member of the SoxB1 family of transcription factors. Sox2 is essential for sensory specification, but high levels of Sox2 expression appear to inhibit hair cell differentiation, suggesting that factors regulating Sox2 activity could be critical for both processes. Antagonistic interactions between SoxB1 and SoxB2 factors are known to regulate cell differentiation in neural tissue, which led us to investigate the potential roles of the SoxB2 member Sox21 during chicken inner ear development. Sox21 is normally expressed by sensory progenitors within vestibular and auditory regions of the early embryonic chicken inner ear. At later stages, Sox21 is differentially expressed in the vestibular and auditory organs. Sox21 is restricted to the support cell layer of the auditory epithelium, while it is enriched in the hair cell layer of the vestibular organs. To test Sox21 function, we used two temporally distinct gain-of-function approaches. Sustained over-expression of Sox21 from early developmental stages prevented prosensory specification, and abolished the formation of both hair cells and support cells. However, later induction of Sox21 expression at the time of hair cell formation in organotypic cultures of vestibular epithelia inhibited endogenous Sox2 expression and Notch activity, and biased progenitor cells towards a hair cell fate. Interestingly, Sox21 did not promote hair cell differentiation in the immature auditory epithelium, which fits with the expression of endogenous Sox21 within mature support cells in this tissue. These results suggest that interactions among endogenous SoxB family transcription factors may regulate sensory cell formation in the inner ear, but in a context-dependent manner.

Repair of traumatized mammalian hair cells via sea anemone repair proteins.

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Tang, Pei-Ciao; Smith, Karen Müller; Watson, Glen M

2016-08-01

Mammalian hair cells possess only a limited ability to repair damage after trauma. In contrast, sea anemones show a marked capability to repair damaged hair bundles by means of secreted repair proteins (RPs). Previously, it was found that recovery of traumatized hair cells in blind cavefish was enhanced by anemone-derived RPs; therefore, the ability of anemone RPs to assist recovery of damaged hair cells in mammals was tested here. After a 1 h incubation in RP-enriched culture media, uptake of FM1-43 by experimentally traumatized murine cochlear hair cells was restored to levels comparable to those exhibited by healthy controls. In addition, RP-treated explants had significantly more normally structured hair bundles than time-matched traumatized control explants. Collectively, these results indicate that anemone-derived RPs assist in restoring normal function and structure of experimentally traumatized hair cells of the mouse cochlea. © 2016. Published by The Company of Biologists Ltd.

Seasonal plasticity of auditory saccular sensitivity in "sneaker" type II male plainfin midshipman fish, Porichthys notatus.

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Bhandiwad, Ashwin A; Whitchurch, Elizabeth A; Colleye, Orphal; Zeddies, David G; Sisneros, Joseph A

2017-03-01

Adult female and nesting (type I) male midshipman fish (Porichthys notatus) exhibit an adaptive form of auditory plasticity for the enhanced detection of social acoustic signals. Whether this adaptive plasticity also occurs in "sneaker" type II males is unknown. Here, we characterize auditory-evoked potentials recorded from hair cells in the saccule of reproductive and non-reproductive "sneaker" type II male midshipman to determine whether this sexual phenotype exhibits seasonal, reproductive state-dependent changes in auditory sensitivity and frequency response to behaviorally relevant auditory stimuli. Saccular potentials were recorded from the middle and caudal region of the saccule while sound was presented via an underwater speaker. Our results indicate saccular hair cells from reproductive type II males had thresholds based on measures of sound pressure and acceleration (re. 1 µPa and 1 ms -2 , respectively) that were ~8-21 dB lower than non-reproductive type II males across a broad range of frequencies, which include the dominant higher frequencies in type I male vocalizations. This increase in type II auditory sensitivity may potentially facilitate eavesdropping by sneaker males and their assessment of vocal type I males for the selection of cuckoldry sites during the breeding season.

Lgr5 marks cycling, yet long-lived, hair follicle stem cells.

NARCIS (Netherlands)

Jaks, V.; Barker, N.; Kasper, M.; van Es, J.H.; Snippert, H.J.G.; Clevers, H.; Toftgard, R.

2008-01-01

In mouse hair follicles, a group of quiescent cells in the bulge is believed to have stem cell activity. Lgr5, a marker of intestinal stem cells, is expressed in actively cycling cells in the bulge and secondary germ of telogen hair follicles and in the lower outer root sheath of anagen hair

Sonic hedgehog initiates cochlear hair cell regeneration through downregulation of retinoblastoma protein

International Nuclear Information System (INIS)

Lu, Na; Chen, Yan; Wang, Zhengmin; Chen, Guoling; Lin, Qin; Chen, Zheng-Yi; Li, Huawei

2013-01-01

Highlights: ► Shh activation in neonatal cochleae enhances sensory cell proliferation. ► Proliferating supporting cells can transdifferentiate into hair cells. ► Shh promotes proliferation by transiently modulating pRb activity. ► Shh inhibits pRb by inhibiting transcription and increasing phosphorylation of pRb. -- Abstract: Cell cycle re-entry by cochlear supporting cells and/or hair cells is considered one of the best approaches for restoring hearing loss as a result of hair cell damage. To identify mechanisms that can be modulated to initiate cell cycle re-entry and hair cell regeneration, we studied the effect of activating the sonic hedgehog (Shh) pathway. We show that Shh signaling in postnatal rat cochleae damaged by neomycin leads to renewed proliferation of supporting cells and hair cells. Further, proliferating supporting cells are likely to transdifferentiate into hair cells. Shh treatment leads to inhibition of retinoblastoma protein (pRb) by increasing phosphorylated pRb and reducing retinoblastoma gene transcription. This results in upregulation of cyclins B1, D2, and D3, and CDK1. These results suggest that Shh signaling induces cell cycle re-entry in cochlear sensory epithelium and the production of new hair cells, in part by attenuating pRb function. This study provides an additional route to modulate pRb function with important implications in mammalian hair cell regeneration.

Melatonin mitigates neomycin-induced hair cell injury in zebrafish.

Science.gov (United States)

Oh, Kyoung Ho; Rah, Yoon Chan; Hwang, Kyu Ho; Lee, Seung Hoon; Kwon, Soon Young; Cha, Jae Hyung; Choi, June

2017-10-01

Ototoxicity due to medications, such as aminoglycosides, is irreversible, and free radicals in the inner ear are assumed to play a major role. Because melatonin has an antioxidant property, we hypothesize that it might mitigate hair cell injury by aminoglycosides. The objective of this study was to evaluate whether melatonin has an alleviative effect on neomycin-induced hair cell injury in zebrafish (Danio rerio). Various concentrations of melatonin were administered to 5-day post-fertilization zebrafish treated with 125 μM neomycin for 1 h. Surviving hair cells within four neuromasts were compared with that of a control group. Apoptosis was assessed via terminal deoxynucleotidyl transferase dUTP nick-end labeling assay. The changes of ultrastructure were confirmed using a scanning electron microscope. Melatonin alleviated neomycin-induced hair cell injury in neuromasts (neomycin + melatonin 100 μM: 13.88 ± 0.91 cells, neomycin only: 7.85 ± 0.90 cells; n = 10, p melatonin for 1 h in SEM findings. Melatonin is effective in alleviating aminoglycoside-induced hair cell injury in zebrafish. The results of this study demonstrated that melatonin has the potential to reduce apoptosis induced by aminoglycosides in zebrafish.

Progressive hearing loss and gradual deterioration of sensory hair bundles in the ears of mice lacking the actin-binding protein Eps8L2.

Science.gov (United States)

Furness, David N; Johnson, Stuart L; Manor, Uri; Rüttiger, Lukas; Tocchetti, Arianna; Offenhauser, Nina; Olt, Jennifer; Goodyear, Richard J; Vijayakumar, Sarath; Dai, Yuhai; Hackney, Carole M; Franz, Christoph; Di Fiore, Pier Paolo; Masetto, Sergio; Jones, Sherri M; Knipper, Marlies; Holley, Matthew C; Richardson, Guy P; Kachar, Bechara; Marcotti, Walter

2013-08-20

Mechanotransduction in the mammalian auditory system depends on mechanosensitive channels in the hair bundles that project from the apical surface of the sensory hair cells. Individual stereocilia within each bundle contain a core of tightly packed actin filaments, whose length is dynamically regulated during development and in the adult. We show that the actin-binding protein epidermal growth factor receptor pathway substrate 8 (Eps8)L2, a member of the Eps8-like protein family, is a newly identified hair bundle protein that is localized at the tips of stereocilia of both cochlear and vestibular hair cells. It has a spatiotemporal expression pattern that complements that of Eps8. In the cochlea, whereas Eps8 is essential for the initial elongation of stereocilia, Eps8L2 is required for their maintenance in adult hair cells. In the absence of both proteins, the ordered staircase structure of the hair bundle in the cochlea decays. In contrast to the early profound hearing loss associated with an absence of Eps8, Eps8L2 null-mutant mice exhibit a late-onset, progressive hearing loss that is directly linked to a gradual deterioration in hair bundle morphology. We conclude that Eps8L2 is required for the long-term maintenance of the staircase structure and mechanosensory function of auditory hair bundles. It complements the developmental role of Eps8 and is a candidate gene for progressive age-related hearing loss.

Feathers and Fins: Non-mammalian models for hair cell regeneration

OpenAIRE

Brignull, Heather R.; Raible, David W.; Stone, Jennifer S.

2009-01-01

Death of mechanosensory cells in the inner ear results in two profound disabilities: hearing loss and balance disorders. Although mammals lack the capacity to regenerate hair cells, recent studies in mice and other rodents have offered valuable insight into strategies for stimulating hair cell regeneration in mammals. Investigations of model organisms that retain the ability to form new hair cells after embryogenesis, such as fish and chicks, are equally important and have provided clues as t...

Sonic hedgehog initiates cochlear hair cell regeneration through downregulation of retinoblastoma protein

Energy Technology Data Exchange (ETDEWEB)

Lu, Na [Otology Skull Base Surgery Department, Hearing Research Institute, Eye and ENT Hospital of Shanghai Medical School, Fudan University, Shanghai 200031 (China); Department of Otolaryngology and Program in Neuroscience, Harvard Medical School and Eaton Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston, MA 02114 (United States); Chen, Yan [Central Laboratory, Hearing Research Institute, Eye and ENT Hospital of Shanghai Medical School, Fudan University, Shanghai 200031 (China); Wang, Zhengmin [Otology Skull Base Surgery Department, Hearing Research Institute, Eye and ENT Hospital of Shanghai Medical School, Fudan University, Shanghai 200031 (China); Institute of Biomedical Sciences, Fudan University, Shanghai 200032 (China); Chen, Guoling [Otology Skull Base Surgery Department, Hearing Research Institute, Eye and ENT Hospital of Shanghai Medical School, Fudan University, Shanghai 200031 (China); Lin, Qin [Otology Skull Base Surgery Department, Hearing Research Institute, Eye and ENT Hospital of Shanghai Medical School, Fudan University, Shanghai 200031 (China); Department of Otolaryngology, First Affiliated Hospital of Fujian Medical University, Otolaryngology Institute of Fujian Province, Fuzhou (China); Chen, Zheng-Yi, E-mail: Zheng-yi_chen@meei.harvard.edu [Department of Otolaryngology and Program in Neuroscience, Harvard Medical School and Eaton Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston, MA 02114 (United States); Li, Huawei, E-mail: hwli@shmu.edu.cn [Otology Skull Base Surgery Department, Hearing Research Institute, Eye and ENT Hospital of Shanghai Medical School, Fudan University, Shanghai 200031 (China); Institute of Biomedical Sciences, Fudan University, Shanghai 200032 (China)

2013-01-11

Highlights: Black-Right-Pointing-Pointer Shh activation in neonatal cochleae enhances sensory cell proliferation. Black-Right-Pointing-Pointer Proliferating supporting cells can transdifferentiate into hair cells. Black-Right-Pointing-Pointer Shh promotes proliferation by transiently modulating pRb activity. Black-Right-Pointing-Pointer Shh inhibits pRb by inhibiting transcription and increasing phosphorylation of pRb. -- Abstract: Cell cycle re-entry by cochlear supporting cells and/or hair cells is considered one of the best approaches for restoring hearing loss as a result of hair cell damage. To identify mechanisms that can be modulated to initiate cell cycle re-entry and hair cell regeneration, we studied the effect of activating the sonic hedgehog (Shh) pathway. We show that Shh signaling in postnatal rat cochleae damaged by neomycin leads to renewed proliferation of supporting cells and hair cells. Further, proliferating supporting cells are likely to transdifferentiate into hair cells. Shh treatment leads to inhibition of retinoblastoma protein (pRb) by increasing phosphorylated pRb and reducing retinoblastoma gene transcription. This results in upregulation of cyclins B1, D2, and D3, and CDK1. These results suggest that Shh signaling induces cell cycle re-entry in cochlear sensory epithelium and the production of new hair cells, in part by attenuating pRb function. This study provides an additional route to modulate pRb function with important implications in mammalian hair cell regeneration.

Spontaneous hair cell regeneration in the mouse utricle following gentamicin ototoxicity.

Science.gov (United States)

Kawamoto, Kohei; Izumikawa, Masahiko; Beyer, Lisa A; Atkin, Graham M; Raphael, Yehoash

2009-01-01

Whereas most epithelial tissues turn-over and regenerate after a traumatic lesion, this restorative ability is diminished in the sensory epithelia of the inner ear; it is absent in the cochlea and exists only in a limited capacity in the vestibular epithelium. The extent of regeneration in vestibular hair cells has been characterized for several mammalian species including guinea pig, rat, and chinchilla, but not yet in mouse. As the fundamental model species for investigating hereditary disease, the mouse can be studied using a wide variety of genetic and molecular tools. To design a mouse model for vestibular hair cell regeneration research, an aminoglycoside-induced method of complete hair cell elimination was developed in our lab and applied to the murine utricle. Loss of utricular hair cells was observed using scanning electron microscopy, and corroborated by a loss of fluorescent signal in utricles from transgenic mice with GFP-positive hair cells. Regenerative capability was characterized at several time points up to six months following insult. Using scanning electron microscopy, we observed that as early as two weeks after insult, a few immature hair cells, demonstrating the characteristic immature morphology indicative of regeneration, could be seen in the utricle. As time progressed, larger numbers of immature hair cells could be seen along with some mature cells resembling surface morphology of type II hair cells. By six months post-lesion, numerous regenerated hair cells were present in the utricle, however, neither their number nor their appearance was normal. A BrdU assay suggested that at least some of the regeneration of mouse vestibular hair cells involved mitosis. Our results demonstrate that the vestibular sensory epithelium in mice can spontaneously regenerate, elucidate the time course of this process, and identify involvement of mitosis in some cases. These data establish a road map of the murine vestibular regenerative process, which can be

Hair cell regeneration in sensory epithelia from the inner ear of a urodele amphibian.

Science.gov (United States)

Taylor, Ruth R; Forge, Andrew

2005-03-28

The capacity of urodele amphibians to regenerate a variety of body parts is providing insight into mechanisms of tissue regeneration in vertebrates. In this study the ability of the newt, Notophthalmus viridescens, to regenerate inner ear hair cells in vitro was examined. Intact otic capsules were maintained in organotypic culture. Incubation in 2 mM gentamicin for 48 hours resulted in ablation of all hair cells from the saccular maculae. Thus, any hair cell recovery was not due to repair of damaged hair cells. Immature hair cells were subsequently observed at approximately 12 days posttreatment. Their number increased over the following 7-14 days to reach approximately 30% of the normal number. Following incubation of damaged tissue with bromodeoxyuridine (BrdU), labeled nuclei were confined strictly within regions of hair cell loss, indicating that supporting cells entered S-phase. Double labeling of tissue with two different hair cell markers and three different antibodies to BrdU in various combinations, however, all showed that the nuclei of cells that labeled with hair cell markers did not label for BrdU. This suggested that the new hair cells were not derived from those cells that had undergone mitosis. When mitosis was blocked with aphidicolin, new hair cells were still generated. The results suggest that direct phenotypic conversion of supporting cells into hair cells without an intervening mitotic event is a major mechanism of hair cell regeneration in the newt. A similar mechanism has been proposed for the hair cell recovery phenomenon observed in the vestibular organs of mammals. Copyright 2005 Wiley-Liss, Inc.

Semicircular canals circumvent Brownian Motion overload of mechanoreceptor hair cells

DEFF Research Database (Denmark)

Muller, Mees; Heeck, Kier; Elemans, Coen P H

2016-01-01

Vertebrate semicircular canals (SCC) first appeared in the vertebrates (i.e. ancestral fish) over 600 million years ago. In SCC the principal mechanoreceptors are hair cells, which as compared to cochlear hair cells are distinctly longer (70 vs. 7 μm), 10 times more compliant to bending (44 vs. 500...... nN/m), and have a 100-fold higher tip displacement threshold (hair cells where the bundle is approximated as a stiff, cylindrical elastic rod subject to friction and thermal agitation. Our models suggest that the above...... differences aid SCC hair cells in circumventing the masking effects of Brownian motion noise of about 70 nm, and thereby permit transduction of very low frequency (

Artifactual voltage response recorded from hair cells with patch-clamp amplifiers.

Science.gov (United States)

Masetto, S; Weng, T; Valli, P; Correia, M J

1999-06-23

Patch-clamp amplifiers (PCAs) are commonly used to characterize voltage- and current-clamp responses in the same cell. However, the cell membrane voltage response can be severely distorted by PCAs working in the current-clamp mode. Here we compare the voltage response of pigeon semicircular canal hair cells in situ, recorded with two different PCAs, and with a classic microelectrode bridge amplifier (BA). We found that the voltage response of hair cells recorded with PCAs differed significantly from that recorded with the BA. The true hair cell membrane voltage response to positive current steps was characterized by a strongly damped oscillation, whose frequency and duration depended on hair cell location in the sensory crista ampullaris.

Outer hair cell piezoelectricity: frequency response enhancement and resonance behavior.

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Weitzel, Erik K; Tasker, Ron; Brownell, William E

2003-09-01

Stretching or compressing an outer hair cell alters its membrane potential and, conversely, changing the electrical potential alters its length. This bi-directional energy conversion takes place in the cell's lateral wall and resembles the direct and converse piezoelectric effects both qualitatively and quantitatively. A piezoelectric model of the lateral wall has been developed that is based on the electrical and material parameters of the lateral wall. An equivalent circuit for the outer hair cell that includes piezoelectricity shows a greater admittance at high frequencies than one containing only membrane resistance and capacitance. The model also predicts resonance at ultrasonic frequencies that is inversely proportional to cell length. These features suggest all mammals use outer hair cell piezoelectricity to support the high-frequency receptor potentials that drive electromotility. It is also possible that members of some mammalian orders use outer hair cell piezoelectric resonance in detecting species-specific vocalizations.

Neuromast hair cells retain the capacity of regeneration during heavy metal exposure.

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Montalbano, G; Capillo, G; Laurà, R; Abbate, F; Levanti, M; Guerrera, M C; Ciriaco, E; Germanà, A

2018-07-01

The neuromast is the morphological unit of the lateral line of fishes and is composed of a cluster of central sensory cells (hair cells) surrounded by support and mantle cells. Heavy metals exposure leads to disruption of hair cells within the neuromast. It is well known that the zebrafish has the ability to regenerate the hair cells after damage caused by toxicants. The process of regeneration depends on proliferation, differentiation and cellular migration of sensory and non-sensory progenitor cells. Therefore, our study was made in order to identify which cellular types are involved in the complex process of regeneration during heavy metals exposure. For this purpose, adult zebrafish were exposed to various heavy metals (Arsenic, cadmium and zinc) for 72h. After acute (24h) exposure, immunohistochemical localization of S100 (a specific marker for hair cells) in the neuromasts highlighted the hair cells loss. The immunoreaction for Sox2 (a specific marker for stem cells), at the same time, was observed in the support and mantle cells, after exposure to arsenic and cadmium, while only in the support cells after exposure to zinc. After chronic (72h) exposure the hair cells were regenerated, showing an immunoreaction for S100 protein. At the same exposure time to the three metals, a Sox2 immunoreaction was expressed in support and mantle cells. Our results showed for the first time the regenerative capacity of hair cells, not only after, but also during exposure to heavy metals, demonstrated by the presence of different stem cells that can diversify in hair cells. Copyright © 2018 Elsevier GmbH. All rights reserved.

A simple method for purification of vestibular hair cells and non-sensory cells, and application for proteomic analysis.

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Herget, Meike; Scheibinger, Mirko; Guo, Zhaohua; Jan, Taha A; Adams, Christopher M; Cheng, Alan G; Heller, Stefan

2013-01-01

Mechanosensitive hair cells and supporting cells comprise the sensory epithelia of the inner ear. The paucity of both cell types has hampered molecular and cell biological studies, which often require large quantities of purified cells. Here, we report a strategy allowing the enrichment of relatively pure populations of vestibular hair cells and non-sensory cells including supporting cells. We utilized specific uptake of fluorescent styryl dyes for labeling of hair cells. Enzymatic isolation and flow cytometry was used to generate pure populations of sensory hair cells and non-sensory cells. We applied mass spectrometry to perform a qualitative high-resolution analysis of the proteomic makeup of both the hair cell and non-sensory cell populations. Our conservative analysis identified more than 600 proteins with a false discovery rate of Analysis of proteins exclusively detected in either population revealed 64 proteins that were specific to hair cells and 103 proteins that were only detectable in non-sensory cells. Statistical analyses extended these groups by 53 proteins that are strongly upregulated in hair cells versus non-sensory cells and vice versa by 68 proteins. Our results demonstrate that enzymatic dissociation of styryl dye-labeled sensory hair cells and non-sensory cells is a valid method to generate pure enough cell populations for flow cytometry and subsequent molecular analyses.

Regional analysis of whole cell currents from hair cells of the turtle posterior crista.

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Brichta, Alan M; Aubert, Anne; Eatock, Ruth Anne; Goldberg, Jay M

2002-12-01

The turtle posterior crista is made up of two hemicristae, each consisting of a central zone containing type I and type II hair cells and a surrounding peripheral zone containing only type II hair cells and extending from the planum semilunatum to the nonsensory torus. Afferents from various regions of a hemicrista differ in their discharge properties. To see if afferent diversity is related to the basolateral currents of the hair cells innervated, we selectively harvested type I and II hair cells from the central zone and type II hair cells from two parts of the peripheral zone, one near the planum and the other near the torus. Voltage-dependent currents were studied with the whole cell, ruptured-patch method and characterized in voltage-clamp mode. We found regional differences in both outwardly and inwardly rectifying voltage-sensitive currents. As in birds and mammals, type I hair cells have a distinctive outwardly rectifying current (I(K,L)), which begins activating at more hyperpolarized voltages than do the outward currents of type II hair cells. Activation of I(K,L) is slow and sigmoidal. Maximal outward conductances are large. Outward currents in type II cells vary in their activation kinetics. Cells with fast kinetics are associated with small conductances and with partial inactivation during 200-ms depolarizing voltage steps. Almost all type II cells in the peripheral zone and many in the central zone have fast kinetics. Some type II cells in the central zone have large outward currents with slow kinetics and little inactivation. Although these currents resemble I(K,L), they can be distinguished from the latter both electrophysiologically and pharmacologically. There are two varieties of inwardly rectifying currents in type II hair cells: activation of I(K1) is rapid and monoexponential, whereas that of I(h) is slow and sigmoidal. Many type II cells either have both inward currents or only have I(K1); very few cells only have I(h). Inward currents are

Limited hair cell induction from human induced pluripotent stem cells using a simple stepwise method.

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Ohnishi, Hiroe; Skerleva, Desislava; Kitajiri, Shin-ichiro; Sakamoto, Tatsunori; Yamamoto, Norio; Ito, Juichi; Nakagawa, Takayuki

2015-07-10

Disease-specific induced pluripotent stem cells (iPS) cells are expected to contribute to exploring useful tools for studying the pathophysiology of inner ear diseases and to drug discovery for treating inner ear diseases. For this purpose, stable induction methods for the differentiation of human iPS cells into inner ear hair cells are required. In the present study, we examined the efficacy of a simple induction method for inducing the differentiation of human iPS cells into hair cells. The induction of inner ear hair cell-like cells was performed using a stepwise method mimicking inner ear development. Human iPS cells were sequentially transformed into the preplacodal ectoderm, otic placode, and hair cell-like cells. As a first step, preplacodal ectoderm induction, human iPS cells were seeded on a Matrigel-coated plate and cultured in a serum free N2/B27 medium for 8 days according to a previous study that demonstrated spontaneous differentiation of human ES cells into the preplacodal ectoderm. As the second step, the cells after preplacodal ectoderm induction were treated with basic fibroblast growth factor (bFGF) for induction of differentiation into otic-placode-like cells for 15 days. As the final step, cultured cells were incubated in a serum free medium containing Matrigel for 48 days. After preplacodal ectoderm induction, over 90% of cultured cells expressed the genes that express in preplacodal ectoderm. By culture with bFGF, otic placode marker-positive cells were obtained, although their number was limited. Further 48-day culture in serum free media resulted in the induction of hair cell-like cells, which expressed a hair cell marker and had stereocilia bundle-like constructions on their apical surface. Our results indicate that hair cell-like cells are induced from human iPS cells using a simple stepwise method with only bFGF, without the use of xenogeneic cells. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Generation of inner ear organoids containing functional hair cells from human pluripotent stem cells.

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Koehler, Karl R; Nie, Jing; Longworth-Mills, Emma; Liu, Xiao-Ping; Lee, Jiyoon; Holt, Jeffrey R; Hashino, Eri

2017-06-01

The derivation of human inner ear tissue from pluripotent stem cells would enable in vitro screening of drug candidates for the treatment of hearing and balance dysfunction and may provide a source of cells for cell-based therapies of the inner ear. Here we report a method for differentiating human pluripotent stem cells to inner ear organoids that harbor functional hair cells. Using a three-dimensional culture system, we modulate TGF, BMP, FGF, and WNT signaling to generate multiple otic-vesicle-like structures from a single stem-cell aggregate. Over 2 months, the vesicles develop into inner ear organoids with sensory epithelia that are innervated by sensory neurons. Additionally, using CRISPR-Cas9, we generate an ATOH1-2A-eGFP cell line to detect hair cell induction and demonstrate that derived hair cells exhibit electrophysiological properties similar to those of native sensory hair cells. Our culture system should facilitate the study of human inner ear development and research on therapies for diseases of the inner ear.

Membrane properties of chick semicircular canal hair cells in situ during embryonic development.

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Masetto, S; Perin, P; Malusà, A; Zucca, G; Valli, P

2000-05-01

The electrophysiological properties of developing vestibular hair cells have been investigated in a chick crista slice preparation, from embryonic day 10 (E10) to E21 (when hatching would occur). Patch-clamp whole-cell experiments showed that different types of ion channels are sequentially expressed during development. An inward Ca(2+) current and a slow outward rectifying K(+) current (I(K(V))) are acquired first, at or before E10, followed by a rapid transient K(+) current (I(K(A))) at E12, and by a small Ca-dependent K(+) current (I(KCa)) at E14. Hair cell maturation then proceeds with the expression of hyperpolarization-activated currents: a slow I(h) appears first, around E16, followed by the fast inward rectifier I(K1) around E19. From the time of its first appearance, I(K(A)) is preferentially expressed in peripheral (zone 1) hair cells, whereas inward rectifying currents are preferentially expressed in intermediate (zone 2) and central (zone 3) hair cells. Each conductance conferred distinctive properties on hair cell voltage response. Starting from E15, some hair cells, preferentially located at the intermediate region, showed the amphora shape typical of type I hair cells. From E17 (a time when the afferent calyx is completed) these cells expressed I(K, L), the signature current of mature type I hair cells. Close to hatching, hair cell complements and regional organization of ion currents appeared similar to those reported for the mature avian crista. By the progressive acquisition of different types of inward and outward rectifying currents, hair cell repolarization after both positive- and negative-current injections is greatly strengthened and speeded up.

A hardware model of the auditory periphery to transduce acoustic signals into neural activity

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Takashi eTateno

2013-11-01

Full Text Available To improve the performance of cochlear implants, we have integrated a microdevice into a model of the auditory periphery with the goal of creating a microprocessor. We constructed an artificial peripheral auditory system using a hybrid model in which polyvinylidene difluoride was used as a piezoelectric sensor to convert mechanical stimuli into electric signals. To produce frequency selectivity, the slit on a stainless steel base plate was designed such that the local resonance frequency of the membrane over the slit reflected the transfer function. In the acoustic sensor, electric signals were generated based on the piezoelectric effect from local stress in the membrane. The electrodes on the resonating plate produced relatively large electric output signals. The signals were fed into a computer model that mimicked some functions of inner hair cells, inner hair cell–auditory nerve synapses, and auditory nerve fibers. In general, the responses of the model to pure-tone burst and complex stimuli accurately represented the discharge rates of high-spontaneous-rate auditory nerve fibers across a range of frequencies greater than 1 kHz and middle to high sound pressure levels. Thus, the model provides a tool to understand information processing in the peripheral auditory system and a basic design for connecting artificial acoustic sensors to the peripheral auditory nervous system. Finally, we discuss the need for stimulus control with an appropriate model of the auditory periphery based on auditory brainstem responses that were electrically evoked by different temporal pulse patterns with the same pulse number.

Characterization of Rat Hair Follicle Stem Cells Selected by Vario Magnetic Activated Cell Sorting System

International Nuclear Information System (INIS)

Huang, Enyi; Lian, Xiaohua; Chen, Wei; Yang, Tian; Yang, Li

2009-01-01

Hair follicle stem cells (HfSCs) play crucial roles in hair follicle morphogenesis and hair cycling. These stem cells are self-renewable and have the multi-lineage potential to generate epidermis, sebaceous glands, and hair follicle. The separation and identification of hair follicle stem cells are important for further research in stem cell biology. In this study, we report on the successful enrichment of rat hair follicle stem cells through vario magnetic activated cell sorting (Vario MACS) and the biological characteristics of the stem cells. We chose the HfSCs positive surface markers CD34, α6-integrin and the negative marker CD71 to design four isolation strategies: positive selection with single marker of CD34, positive selection with single marker of α6-integrin, CD71 depletion followed by CD34 positive selection, and CD71 depletion followed by α6-integrin positive selection. The results of flow cytometry analysis showed that all four strategies had ideal effects. Specifically, we conducted a series of researches on HfSCs characterized by their high level of CD34, termed CD34 bri cells, and low to undetectable expression of CD34, termed CD34 dim cells. CD34 bri cells had greater proliferative potential and higher colony-forming ability than CD34 dim cells. Furthermore, CD34 bri cells had some typical characteristics as progenitor cells, such as large nucleus, obvious nucleolus, large nuclear:cytoplasmic ratio and few cytoplasmic organelles. Our findings clearly demonstrated that HfSCs with high purity and viability could be successfully enriched with Vario MACS

Signal detection by active, noisy hair bundles

Science.gov (United States)

O'Maoiléidigh, Dáibhid; Salvi, Joshua D.; Hudspeth, A. J.

2018-05-01

Vertebrate ears employ hair bundles to transduce mechanical movements into electrical signals, but their performance is limited by noise. Hair bundles are substantially more sensitive to periodic stimulation when they are mechanically active, however, than when they are passive. We developed a model of active hair-bundle mechanics that predicts the conditions under which a bundle is most sensitive to periodic stimulation. The model relies only on the existence of mechanotransduction channels and an active adaptation mechanism that recloses the channels. For a frequency-detuned stimulus, a noisy hair bundle's phase-locked response and degree of entrainment as well as its detection bandwidth are maximized when the bundle exhibits low-amplitude spontaneous oscillations. The phase-locked response and entrainment of a bundle are predicted to peak as functions of the noise level. We confirmed several of these predictions experimentally by periodically forcing hair bundles held near the onset of self-oscillation. A hair bundle's active process amplifies the stimulus preferentially over the noise, allowing the bundle to detect periodic forces less than 1 pN in amplitude. Moreover, the addition of noise can improve a bundle's ability to detect the stimulus. Although, mechanical activity has not yet been observed in mammalian hair bundles, a related model predicts that active but quiescent bundles can oscillate spontaneously when they are loaded by a sufficiently massive object such as the tectorial membrane. Overall, this work indicates that auditory systems rely on active elements, composed of hair cells and their mechanical environment, that operate on the brink of self-oscillation.

Six1 is essential for differentiation and patterning of the mammalian auditory sensory epithelium.

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Ting Zhang

2017-09-01

Full Text Available The organ of Corti in the cochlea is a two-cell layered epithelium: one cell layer of mechanosensory hair cells that align into one row of inner and three rows of outer hair cells interdigitated with one cell layer of underlying supporting cells along the entire length of the cochlear spiral. These two types of epithelial cells are derived from common precursors in the four- to five-cell layered primordium and acquire functionally important shapes during terminal differentiation through the thinning process and convergent extension. Here, we have examined the role of Six1 in the establishment of the auditory sensory epithelium. Our data show that prior to terminal differentiation of the precursor cells, deletion of Six1 leads to formation of only a few hair cells and defective patterning of the sensory epithelium. Previous studies have suggested that downregulation of Sox2 expression in differentiating hair cells must occur after Atoh1 mRNA activation in order to allow Atoh1 protein accumulation due to antagonistic effects between Atoh1 and Sox2. Our analysis indicates that downregulation of Sox2 in the differentiating hair cells depends on Six1 activity. Furthermore, we found that Six1 is required for the maintenance of Fgf8 expression and dynamic distribution of N-cadherin and E-cadherin in the organ of Corti during differentiation. Together, our analyses uncover essential roles of Six1 in hair cell differentiation and formation of the organ of Corti in the mammalian cochlea.

Reduced systemic toxicity and preserved vestibular toxicity following co-treatment with nitriles and CYP2E1 inhibitors: a mouse model for hair cell loss.

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Saldaña-Ruíz, Sandra; Boadas-Vaello, Pere; Sedó-Cabezón, Lara; Llorens, Jordi

2013-10-01

Several nitriles, including allylnitrile and cis-crotononitrile, have been shown to be ototoxic and cause hair cell degeneration in the auditory and vestibular sensory epithelia of mice. However, these nitriles can also be lethal due in large part to the microsomal metabolic release of cyanide, which is mostly dependent on the activity of the 2E1 isoform of the cytochrome P450 (CYP2E1). In this study, we co-administered mice with a nitrile and, to reduce their lethal effects, a selective CYP2E1 inhibitor: diallylsulfide (DAS) or trans-1,2-dichloroethylene (TDCE). Both in female 129S1/SvImJ (129S1) mice co-treated with DAS and cis-crotononitrile and in male RjOrl:Swiss/CD-1 (Swiss) mice co-treated with TDCE and allylnitrile, the nitrile caused a dose-dependent loss of vestibular function, as assessed by a specific behavioral test battery, and of hair cells, as assessed by hair bundle counts using scanning electron microscopy. In the experiments, the CYP2E1 inhibitors provided significant protection against the lethal effects of the nitriles and did not diminish the vestibular toxicity as assessed by behavioral effects in comparison to animals receiving no inhibitor. Additional experiments using a single dose of allylnitrile demonstrated that TDCE does not cause hair cell loss on its own and does not modify the vestibular toxicity of the nitrile in either male or female 129S1 mice. In all the experiments, high vestibular dysfunction scores in the behavioral test battery predicted extensive to complete loss of hair cells in the utricles. This provides a means of selecting animals for subsequent studies of vestibular hair cell regeneration or replacement.

A point mutation in the hair cell nicotinic cholinergic receptor prolongs cochlear inhibition and enhances noise protection.

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Julian Taranda

2009-01-01

Full Text Available The transduction of sound in the auditory periphery, the cochlea, is inhibited by efferent cholinergic neurons projecting from the brainstem and synapsing directly on mechanosensory hair cells. One fundamental question in auditory neuroscience is what role(s this feedback plays in our ability to hear. In the present study, we have engineered a genetically modified mouse model in which the magnitude and duration of efferent cholinergic effects are increased, and we assess the consequences of this manipulation on cochlear function. We generated the Chrna9L9'T line of knockin mice with a threonine for leucine change (L9'T at position 9' of the second transmembrane domain of the alpha9 nicotinic cholinergic subunit, rendering alpha9-containing receptors that were hypersensitive to acetylcholine and had slower desensitization kinetics. The Chrna9L9'T allele produced a 3-fold prolongation of efferent synaptic currents in vitro. In vivo, Chrna9L9'T mice had baseline elevation of cochlear thresholds and efferent-mediated inhibition of cochlear responses was dramatically enhanced and lengthened: both effects were reversed by strychnine blockade of the alpha9alpha10 hair cell nicotinic receptor. Importantly, relative to their wild-type littermates, Chrna9(L9'T/L9'T mice showed less permanent hearing loss following exposure to intense noise. Thus, a point mutation designed to alter alpha9alpha10 receptor gating has provided an animal model in which not only is efferent inhibition more powerful, but also one in which sound-induced hearing loss can be restrained, indicating the ability of efferent feedback to ameliorate sound trauma.

Age-related auditory pathology in the CBA/J mouse

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Sha, Su-Hua; Kanicki, Ariane; Dootz, Gary; Talaska, Andra E.; Halsey, Karin; Dolan, David; Altschuler, Richard; Schacht, Jochen

2008-01-01

Commercially obtained aged male CBA/J mice presented a complex pattern of hearing loss and morphological changes. A significant threshold shift in auditory brainstem responses (ABR) occurred at 3 months of age at 4 kHz without apparent loss of hair cells, rising slowly at later ages accompanied by loss of apical hair cells. A delayed high-frequency deficit started at 24 kHz around the age of 12 months. At 20 to 26 months, threshold shifts at 12 and 24 kHz and the accompanying hair cell loss at the base of the cochlea were highly variable with some animals appearing almost normal and others showing large deficits. Spiral ganglion cells degenerated by 18 months in all regions of the cochlea, with cell density reduced by approximately 25%. There was no degeneration of the stria vascularis and the endocochlear potential remained stable from 3 to 25 months of age regardless of whether the animals had normal or highly elevated ABR thresholds. The slow high frequency hearing loss combined with a modest reduction of ganglion cell density and an unchanged endocochlear potential suggest sensorineural presbycusis. The superimposed early hearing loss at low frequencies, which is not seen in animals bred in-house, may complicate the use of these animals as a presbycusis model. PMID:18573325

Comparison of peripheral compression estimates using auditory steady-state responses (ASSR) and distortion product otoacoustic emissions (DPOAE)

DEFF Research Database (Denmark)

Encina Llamas, Gerard; Epp, Bastian; Dau, Torsten

The healthy auditory system shows a compressive input/output (I/O) function as a result of healthy outer-hair cell function. Hearing impairment often leads to a decrease in sensitivity and a reduction of compression, mainly caused by loss of inner and/or outer hair cells. Compression is commonly...... (DPOAEs) recordings. Results show compressive ASSR I/O functions for NH subjects. For HI subjects, ASSR reveal the loss of sensitivity at low stimulus levels. Growth slopes are smaller (more compressive) in ASSR than in DPOAE I/O functions....

Making sense of Wnt signaling – linking hair cell regeneration to development

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Lina eJansson

2015-03-01

Full Text Available Wnt signaling is a highly conserved pathway crucial for development and homeostasis of multicellular organisms. Secreted Wnt ligands bind Frizzled receptors to regulate diverse processes such as axis patterning, cell division, and cell fate specification. They also serve to govern self-renewal of somatic stem cells in several adult tissues. The complexity of the pathway can be attributed to the myriad of Wnt and Frizzled combinations as well as its diverse context-dependent functions. In the developing mouse inner ear, Wnt signaling plays diverse roles, including specification of the otic placode and patterning of the otic vesicle. At later stages, its activity governs sensory hair cell specification, cell cycle regulation, and hair cell orientation. In regenerating sensory organs from non-mammalian species, Wnt signaling can also regulate the extent of proliferative hair cell regeneration. This review describes the current knowledge of the roles of Wnt signaling and Wnt-responsive cells in hair cell development and regeneration. We also discuss possible future directions and the potential application and limitation of Wnt signaling in augmenting hair cell regeneration.

Correlation between auditory brainstem recordings and morphology as seen through the scanning electron microscope

International Nuclear Information System (INIS)

Hultcrantz, M.

1988-01-01

Pregnant CBA/CBA mice were exposed to 0.5, 1 and 2 Grey (Gy), (1 Gy = 100 rad) in single doses with whole body gamma-irradiation on the 12th, 13th and 16th gestational days, respectively. The animals were tested at an age of one month for vestibular and cochlear function. Thereafter the inner ears were analyzed with scanning electron microscopy. A morphological analysis with cytocochleograms was performed. Morphological changes in the vestibular part showed gross malformations in the cristae ampullares. Hair cells of type I seemed to be more severely changed than hair cells type II. The macula utriculi also showed malformations of the otoconia. All these changes were more pronounced when the irradiation was given early during pregnancy and with the highest doses used, except the otoconia which were more injured when irradiated day 16 of gestation. No disturbances of the equilibrium reflexes were noted. In the cochlea a dose-dependent, time-related damage pattern was demonstrated with pathological changes of outer (OHC) and inner (IHC) hair cells. When tested electrophysiologically for auditory function with auditory brainstem recordings (ABR), elevated thresholds were revealed different in shape depending on when during pregnancy irradiation took place. A good correlation existed between the morphological changes as seen in the cytocochleograms and the functional changes documented with the ABR

Correlation between auditory brainstem recordings and morphology as seen through the scanning electron microscope

Energy Technology Data Exchange (ETDEWEB)

Hultcrantz, M.

1988-09-01

Pregnant CBA/CBA mice were exposed to 0.5, 1 and 2 Grey (Gy), (1 Gy = 100 rad) in single doses with whole body gamma-irradiation on the 12th, 13th and 16th gestational days, respectively. The animals were tested at an age of one month for vestibular and cochlear function. Thereafter the inner ears were analyzed with scanning electron microscopy. A morphological analysis with cytocochleograms was performed. Morphological changes in the vestibular part showed gross malformations in the cristae ampullares. Hair cells of type I seemed to be more severely changed than hair cells type II. The macula utriculi also showed malformations of the otoconia. All these changes were more pronounced when the irradiation was given early during pregnancy and with the highest doses used, except the otoconia which were more injured when irradiated day 16 of gestation. No disturbances of the equilibrium reflexes were noted. In the cochlea a dose-dependent, time-related damage pattern was demonstrated with pathological changes of outer (OHC) and inner (IHC) hair cells. When tested electrophysiologically for auditory function with auditory brainstem recordings (ABR), elevated thresholds were revealed different in shape depending on when during pregnancy irradiation took place. A good correlation existed between the morphological changes as seen in the cytocochleograms and the functional changes documented with the ABR.

Genetically induced cell death in bulge stem cells reveals their redundancy for hair and epidermal regeneration.

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Driskell, Iwona; Oeztuerk-Winder, Feride; Humphreys, Peter; Frye, Michaela

2015-03-01

Adult mammalian epidermis contains multiple stem cell populations in which quiescent and more proliferative stem and progenitor populations coexist. However, the precise interrelation of these populations in homeostasis remains unclear. Here, we blocked the contribution of quiescent keratin 19 (K19)-expressing bulge stem cells to hair follicle formation through genetic ablation of the essential histone methyltransferase Setd8 that is required for the maintenance of adult skin. Deletion of Setd8 eliminated the contribution of bulge cells to hair follicle regeneration through inhibition of cell division and induction of cell death, but the growth and morphology of hair follicles were unaffected. Furthermore, ablation of Setd8 in the hair follicle bulge blocked the contribution of K19-postive stem cells to wounded epidermis, but the wound healing process was unaltered. Our data indicate that quiescent bulge stem cells are dispensable for hair follicle regeneration and epidermal injury in the short term and support the hypothesis that quiescent and cycling stem cell populations are equipotent. © 2014 AlphaMed Press.

Fractalkine Signaling Regulates Macrophage Recruitment into the Cochlea and Promotes the Survival of Spiral Ganglion Neurons after Selective Hair Cell Lesion.

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Kaur, Tejbeer; Zamani, Darius; Tong, Ling; Rubel, Edwin W; Ohlemiller, Kevin K; Hirose, Keiko; Warchol, Mark E

2015-11-11

selective hair cell lesion. Because these afferent neurons carry sound information from the cochlea to the auditory brainstem, their survival is a key determinant of the success of cochlear prosthetics. Our data suggest that fractalkine signaling in the cochlea is neuroprotective, and reveal a previously uncharacterized interaction between cells of the cochlea and the innate immune system. Copyright © 2015 the authors 0270-6474/15/3515050-12$15.00/0.

Natural bizbenzoquinoline derivatives protect zebrafish lateral line sensory hair cells from aminoglycoside toxicity

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Matthew eKruger

2016-03-01

Full Text Available Moderate to severe hearing loss affects 360 million people worldwide and most often results from damage to sensory hair cells. Hair cell damage can result from aging, genetic mutations, excess noise exposure, and certain medications including aminoglycoside antibiotics. Aminoglycosides are effective at treating infections associated with cystic fibrosis and other life-threatening conditions such as sepsis, but cause hearing loss in 20-30% of patients. It is therefore imperative to develop new therapies to combat hearing loss and allow safe use of these potent antibiotics. We approach this drug discovery question using the larval zebrafish lateral line because zebrafish hair cells are structurally and functionally similar to mammalian inner ear hair cells and respond similarly to toxins. We screened a library of 502 natural compounds in order to identify novel hair cell protectants. Our screen identified four bisbenzylisoquinoline derivatives: berbamine, E6 berbamine, hernandezine, and isotetrandrine, each of which robustly protected hair cells from aminoglycoside-induced damage. Using fluorescence microscopy and electrophysiology, we demonstrated that the natural compounds confer protection by reducing antibiotic uptake into hair cells and showed that hair cells remain functional during and after incubation in E6 berbamine. We also determined that these natural compounds do not reduce antibiotic efficacy. Together, these natural compounds represent a novel source of possible otoprotective drugs that may offer therapeutic options for patients receiving aminoglycoside treatment.

Involvement of p53 and Bcl-2 in sensory cell degeneration in aging rat cochleae.

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Xu, Yang; Yang, Wei Ping; Hu, Bo Hua; Yang, Shiming; Henderson, Donald

2017-06-01

p53 and Bcl-2 (B-cell lymphoma 2) are involved in the process of sensory cell degeneration in aging cochleae. To determine molecular players in age-related hair cell degeneration, this study examined the changes in p53 and Bcl-2 expression at different stages of apoptotic and necrotic death of hair cells in aging rat cochleae. Young (3-4 months) and aging (23-24 months) Fisher 344/NHsd rats were used. The thresholds of the auditory brainstem response (ABR) were measured to determine the auditory function. Immunolabeling was performed to determine the expression of p53 and Bcl-2 proteins in the sensory epithelium. Propidium iodide staining was performed to determine the morphologic changes in hair cell nuclei. Aging rats exhibited a significant elevation in ABR thresholds at all tested frequencies (p aging hair cells showing the early signs of apoptotic changes in their nuclei. The Bcl-2 expression increase was also observed in hair cells displaying early signs of necrosis. As the hair cell degenerative process advanced, p53 and Bcl-2 immunoreactivity became reduced or absent. In the areas where no detectable nuclear staining was present, p53 and Bcl-2 immunoreactivity was absent.

Unleashing the potential of the root hair cell as a single plant cell type model in root systems biology

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Zhenzhen eQiao

2013-11-01

Full Text Available Plant root is an organ composed of multiple cell types with different functions. This multicellular complexity limits our understanding of root biology because –omics studies performed at the level of the entire root reflect the average responses of all cells composing the organ. To overcome this difficulty and allow a more comprehensive understanding of root cell biology, an approach is needed that would focus on one single cell type in the plant root. Because of its biological functions (i.e. uptake of water and various nutrients; primary site of infection by nitrogen-fixing bacteria in legumes, the root hair cell is an attractive single cell model to study root cell response to various stresses and treatments. To fully study their biology, we have recently optimized procedures in obtaining root hair cell samples. We culture the plants using an ultrasound aeroponic system maximizing root hair cell density on the entire root systems and allowing the homogeneous treatment of the root system. We then isolate the root hair cells in liquid nitrogen. Isolated root hair yields could be up to 800 to 1000 mg of plant cells from 60 root systems. Using soybean as a model, the purity of the root hair was assessed by comparing the expression level of genes previously identified as soybean root hair specific between preparations of isolated root hair cells and stripped roots, roots devoid in root hairs. Enlarging our tests to include other plant species, our results support the isolation of large quantities of highly purified root hair cells which is compatible with a systems biology approach.

Distribution and time course of hair cell regeneration in the pigeon utricle

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Dye, B. J.; Frank, T. C.; Newlands, S. D.; Dickman, J. D.

1999-01-01

Vestibular and cochlear regeneration following ototoxic insult from aminoglycoside antibiotics has been well documented, particularly in birds. In the present study, intraotic application of a 2 mg streptomycin paste was used to achieve complete vestibular hair cell destruction in pigeons (Columba livia) while preserving regenerative ability. Scanning electron microscopy was used to quantify hair cell density longitudinally during regeneration in three different utricular macula locations, including the striola, central and peripheral regions. The utricular epithelium was void of stereocilia (indicating hair cell loss) at 4 days after intraotic treatment with streptomycin. At 2 weeks the stereocilia began to appear randomly and mostly in an immature form. However, when present most kinocilia were polarized toward the developing striola. Initially, regeneration occurred more rapidly in the central and peripheral regions of the utricle as compared to the striola. As regeneration proceeded from 2 to 12 weeks, hair cell density in the striola region equaled the density noted in the central and peripheral regions. At 24 weeks, hair cell density of the central and peripheral regions was equal to normal values, however the striola region had a slightly greater hair cell density than that observed for normal animals.

Enhancement of cell wall protein SRPP expression during emergent root hair development in Arabidopsis.

Science.gov (United States)

Uno, Hiroshi; Tanaka-Takada, Natsuki; Sato, Ryosuke; Maeshima, Masayoshi

2017-10-03

SRPP is a protein expressed in seeds and root hairs and is significantly induced in root hairs under phosphate (Pi)-deficient conditions. Root hairs in the knockout mutant srpp-1 display defects, i.e., suppression of cell growth and cell death. Here, we analyzed the expression profile of SRPP during cell elongation of root hairs and compared the transcript levels in several mutants with short root hairs. The mRNA level was increased in wild-type plants and decreased in mutants with short root hairs. Induction of SRPP expression by Pi starvation occurred one or two days later than induction of Pi-deficient sensitive genes, such as PHT1 and PHF1. These results indicate that the expression of SRPP is coordinated with root hair elongation. We hypothesize that SRPP is essential for structural robustness of the cell walls of root hairs.

Thermal noise and the incessant vibration of the outer hair cells in the cochlea

Directory of Open Access Journals (Sweden)

W. Fritze

1998-01-01

Full Text Available The continual exposure of outer hair cells (OHCs to thermal noise causes vibrations in resonant frequency. As these vibrations are backprojected, they should be recordable as audiofrequencies in the outer ear canal. But even though they are likely to be amplified in some areas by clustering in terms of the chaos theory, they cannot be picked up in the outer ear canal by currently available recording technologies. Conditions change in the presence of pathology, e.g. loss of OHCs and fibrous replacement: Clusters grow in size and amplitudes become larger so that the vibrations can be picked up as spontaneous oto-acoustic emissions (SOAEs in the outer ear canal. Efforts are needed to demonstrate the presence of physiological OHC vibrations (emission by incessant vibration, EIV by processing auditory recordings with statistical methods.

Daunomycin accumulation and induction of programmed cell death in rat hair follicles

DEFF Research Database (Denmark)

Shin, Masashi; Larsson, Lars-Inge; Hougaard, David M.

2009-01-01

The anthracycline antibiotic daunomycin (DM) is useful for the treatment of leukemia but has side-effects such as alopecia. Using immunocytochemistry, we show that, after a single i.v. injection, DM accumulates in the nuclei of matrix cells and in the outer root sheath of hair follicles. DM......-positive matrix cells are detectable up to 48 h after injection and exhibit a characteristic granular morphology, which is not observed in saline-injected controls. TUNEL-staining has revealed that DM injection induces programmed cell death (PCD) in rat hair follicles. Cells undergoing PCD are detectable as late...... (PCD type 2). Interestingly, little, if any, DM accumulation or apoptosis has been detected in the dermal hair papillae. This may have a bearing on potential regeneration of the hair follicles. Thus, DM accumulates in a characteristic pattern in hair follicles. This accumulation is associated...

Implanted hair follicle stem cells form Schwann cells that support repair of severed peripheral nerves.

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Amoh, Yasuyuki; Li, Lingna; Campillo, Raul; Kawahara, Katsumasa; Katsuoka, Kensei; Penman, Sheldon; Hoffman, Robert M

2005-12-06

The hair follicle bulge area is an abundant, easily accessible source of actively growing, pluripotent adult stem cells. Nestin, a protein marker for neural stem cells, also is expressed in follicle stem cells and their immediate, differentiated progeny. The fluorescent protein GFP, whose expression is driven by the nestin regulatory element in transgenic mice, served to mark the follicle cell fate. The pluripotent nestin-driven GFP stem cells are positive for the stem cell marker CD34 but negative for keratinocyte marker keratin 15, suggesting their relatively undifferentiated state. These cells can differentiate into neurons, glia, keratinocytes, smooth muscle cells, and melanocytes in vitro. In vivo studies show the nestin-driven GFP hair follicle stem cells can differentiate into blood vessels and neural tissue after transplantation to the subcutis of nude mice. Equivalent hair follicle stem cells derived from transgenic mice with beta-actin-driven GFP implanted into the gap region of a severed sciatic nerve greatly enhance the rate of nerve regeneration and the restoration of nerve function. The follicle cells transdifferentiate largely into Schwann cells, which are known to support neuron regrowth. Function of the rejoined sciatic nerve was measured by contraction of the gastrocnemius muscle upon electrical stimulation. After severing the tibial nerve and subsequent transplantation of hair follicle stem cells, walking print length and intermediate toe spread significantly recovered, indicating that the transplanted mice recovered the ability to walk normally. These results suggest that hair follicle stem cells provide an important, accessible, autologous source of adult stem cells for regenerative medicine.

A Review of Gene Delivery and Stem Cell Based Therapies for Regenerating Inner Ear Hair Cells

OpenAIRE

Michael S. Detamore; Keerthana Devarajan; Hinrich Staecker

2011-01-01

Sensory neural hearing loss and vestibular dysfunction have become the most common forms of sensory defects, affecting millions of people worldwide. Developing effective therapies to restore hearing loss is challenging, owing to the limited regenerative capacity of the inner ear hair cells. With recent advances in understanding the developmental biology of mammalian and non-mammalian hair cells a variety of strategies have emerged to restore lost hair cells are being developed. Two predominan...

Association of intracellular and synaptic organization in cochlear inner hair cells revealed by 3D electron microscopy.

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Bullen, Anwen; West, Timothy; Moores, Carolyn; Ashmore, Jonathan; Fleck, Roland A; MacLellan-Gibson, Kirsty; Forge, Andrew

2015-07-15

The ways in which cell architecture is modelled to meet cell function is a poorly understood facet of cell biology. To address this question, we have studied the cytoarchitecture of a cell with highly specialised organisation, the cochlear inner hair cell (IHC), using multiple hierarchies of three-dimensional (3D) electron microscopy analyses. We show that synaptic terminal distribution on the IHC surface correlates with cell shape, and the distribution of a highly organised network of membranes and mitochondria encompassing the infranuclear region of the cell. This network is juxtaposed to a population of small vesicles, which represents a potential new source of neurotransmitter vesicles for replenishment of the synapses. Structural linkages between organelles that underlie this organisation were identified by high-resolution imaging. Taken together, these results describe a cell-encompassing network of membranes and mitochondria present in IHCs that support efficient coding and transmission of auditory signals. Such techniques also have the potential for clarifying functionally specialised cytoarchitecture of other cell types. © 2015. Published by The Company of Biologists Ltd.

Hair regrowth in alopecia areata patients following Stem Cell Educator therapy.

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Li, Yanjia; Yan, Baoyong; Wang, Hepeng; Li, Heng; Li, Quanhai; Zhao, Dong; Chen, Yana; Zhang, Ye; Li, Wenxia; Zhang, Jun; Wang, Shanfeng; Shen, Jie; Li, Yunxiang; Guindi, Edward; Zhao, Yong

2015-04-20

Alopecia areata (AA) is one of the most common autoimmune diseases and targets the hair follicles, with high impact on the quality of life and self-esteem of patients due to hair loss. Clinical management and outcomes are challenged by current limited immunosuppressive and immunomodulating regimens. We have developed a Stem Cell Educator therapy in which a patient's blood is circulated through a closed-loop system that separates mononuclear cells from the whole blood, allows the cells to briefly interact with adherent human cord blood-derived multipotent stem cells (CB-SC), and returns the "educated" autologous cells to the patient's circulation. In an open-label, phase 1/phase 2 study, patients (N = 9) with severe AA received one treatment with the Stem Cell Educator therapy. The median age was 20 years (median alopecic duration, 5 years). Clinical data demonstrated that patients with severe AA achieved improved hair regrowth and quality of life after receiving Stem Cell Educator therapy. Flow cytometry revealed the up-regulation of Th2 cytokines and restoration of balancing Th1/Th2/Th3 cytokine production in the peripheral blood of AA subjects. Immunohistochemistry indicated the formation of a "ring of transforming growth factor beta 1 (TGF-β1)" around the hair follicles, leading to the restoration of immune privilege of hair follicles and the protection of newly generated hair follicles against autoimmune destruction. Mechanistic studies revealed that co-culture with CB-SC may up-regulate the expression of coinhibitory molecules B and T lymphocyte attenuator (BTLA) and programmed death-1 receptor (PD-1) on CD8β(+)NKG2D(+) effector T cells and suppress their proliferation via herpesvirus entry mediator (HVEM) ligands and programmed death-1 ligand (PD-L1) on CB-SCs. Current clinical data demonstrated the safety and efficacy of the Stem Cell Educator therapy for the treatment of AA. This innovative approach produced lasting improvement in hair regrowth in

The genetics of hair-cell function in zebrafish.

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Nicolson, Teresa

2017-09-01

Our ears are remarkable sensory organs, providing the important senses of balance and hearing. The complex structure of the inner ear, or 'labyrinth', along with the assorted neuroepithelia, have evolved to detect head movements and sounds with impressive sensitivity. The rub is that the inner ear is highly vulnerable to genetic lesions and environmental insults. According to National Institute of Health estimates, hearing loss is one of the most commonly inherited or acquired sensorineural diseases. To understand the causes of deafness and balance disorders, it is imperative to understand the underlying biology of the inner ear, especially the inner workings of the sensory receptors. These receptors, which are termed hair cells, are particularly susceptible to genetic mutations - more than two dozen genes are associated with defects in this cell type in humans. Over the past decade, a substantial amount of progress has been made in working out the molecular basis of hair-cell function using vertebrate animal models. Given the transparency of the inner ear and the genetic tools that are available, zebrafish have become an increasingly popular animal model for the study of deafness and vestibular dysfunction. Mutagenesis screens for larval defects in hearing and balance have been fruitful in finding key components, many of which have been implicated in human deafness. This review will focus on the genes that are required for hair-cell function in zebrafish, with a particular emphasis on mechanotransduction. In addition, the generation of new tools available for the characterization of zebrafish hair-cell mutants will be discussed.

Heat pulse excitability of vestibular hair cells and afferent neurons.

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Rabbitt, Richard D; Brichta, Alan M; Tabatabaee, Hessam; Boutros, Peter J; Ahn, JoongHo; Della Santina, Charles C; Poppi, Lauren A; Lim, Rebecca

2016-08-01

In the present study we combined electrophysiology with optical heat pulse stimuli to examine thermodynamics of membrane electrical excitability in mammalian vestibular hair cells and afferent neurons. We recorded whole cell currents in mammalian type II vestibular hair cells using an excised preparation (mouse) and action potentials (APs) in afferent neurons in vivo (chinchilla) in response to optical heat pulses applied to the crista (ΔT ≈ 0.25°C per pulse). Afferent spike trains evoked by heat pulse stimuli were diverse and included asynchronous inhibition, asynchronous excitation, and/or phase-locked APs synchronized to each infrared heat pulse. Thermal responses of membrane currents responsible for APs in ganglion neurons were strictly excitatory, with Q10 ≈ 2. In contrast, hair cells responded with a mix of excitatory and inhibitory currents. Excitatory hair cell membrane currents included a thermoelectric capacitive current proportional to the rate of temperature rise (dT/dt) and an inward conduction current driven by ΔT An iberiotoxin-sensitive inhibitory conduction current was also evoked by ΔT, rising in protein biophysics and manipulate cellular excitability. Copyright © 2016 the American Physiological Society.

Guided genetic screen to identify genes essential in the regeneration of hair cells and other tissues.

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Pei, Wuhong; Xu, Lisha; Huang, Sunny C; Pettie, Kade; Idol, Jennifer; Rissone, Alberto; Jimenez, Erin; Sinclair, Jason W; Slevin, Claire; Varshney, Gaurav K; Jones, MaryPat; Carrington, Blake; Bishop, Kevin; Huang, Haigen; Sood, Raman; Lin, Shuo; Burgess, Shawn M

2018-01-01

Regenerative medicine holds great promise for both degenerative diseases and traumatic tissue injury which represent significant challenges to the health care system. Hearing loss, which affects hundreds of millions of people worldwide, is caused primarily by a permanent loss of the mechanosensory receptors of the inner ear known as hair cells. This failure to regenerate hair cells after loss is limited to mammals, while all other non-mammalian vertebrates tested were able to completely regenerate these mechanosensory receptors after injury. To understand the mechanism of hair cell regeneration and its association with regeneration of other tissues, we performed a guided mutagenesis screen using zebrafish lateral line hair cells as a screening platform to identify genes that are essential for hair cell regeneration, and further investigated how genes essential for hair cell regeneration were involved in the regeneration of other tissues. We created genetic mutations either by retroviral insertion or CRISPR/Cas9 approaches, and developed a high-throughput screening pipeline for analyzing hair cell development and regeneration. We screened 254 gene mutations and identified 7 genes specifically affecting hair cell regeneration. These hair cell regeneration genes fell into distinct and somewhat surprising functional categories. By examining the regeneration of caudal fin and liver, we found these hair cell regeneration genes often also affected other types of tissue regeneration. Therefore, our results demonstrate guided screening is an effective approach to discover regeneration candidates, and hair cell regeneration is associated with other tissue regeneration.

Distinct roles of Eps8 in the maturation of cochlear and vestibular hair cells.

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Tavazzani, Elisa; Spaiardi, Paolo; Zampini, Valeria; Contini, Donatella; Manca, Marco; Russo, Giancarlo; Prigioni, Ivo; Marcotti, Walter; Masetto, Sergio

2016-07-22

Several genetic mutations affecting the development and function of mammalian hair cells have been shown to cause deafness but not vestibular defects, most likely because vestibular deficits are sometimes centrally compensated. The study of hair cell physiology is thus a powerful direct approach to ascertain the functional status of the vestibular end organs. Deletion of Epidermal growth factor receptor pathway substrate 8 (Eps8), a gene involved in actin remodeling, has been shown to cause deafness in mice. While both inner and outer hair cells from Eps8 knockout (KO) mice showed abnormally short stereocilia, inner hair cells (IHCs) also failed to acquire mature-type ion channels. Despite the fact that Eps8 is also expressed in vestibular hair cells, Eps8 KO mice show no vestibular deficits. In the present study we have investigated the properties of vestibular Type I and Type II hair cells in Eps8-KO mice and compared them to those of cochlear IHCs. In the absence of Eps8, vestibular hair cells show normally long kinocilia, significantly shorter stereocilia and a normal pattern of basolateral voltage-dependent ion channels. We have also found that while vestibular hair cells from Eps8 KO mice show normal voltage responses to injected sinusoidal currents, which were used to mimic the mechanoelectrical transducer current, IHCs lose their ability to synchronize their responses to the stimulus. We conclude that the absence of Eps8 produces a weaker phenotype in vestibular hair cells compared to cochlear IHCs, since it affects the hair bundle morphology but not the basolateral membrane currents. This difference is likely to explain the absence of obvious vestibular dysfunction in Eps8 KO mice. Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.

Causes and Consequences of Sensory Hair Cell Damage and Recovery in Fishes.

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Smith, Michael E; Monroe, J David

2016-01-01

Sensory hair cells are the mechanotransductive receptors that detect gravity, sound, and vibration in all vertebrates. Damage to these sensitive receptors often results in deficits in vestibular function and hearing. There are currently two main reasons for studying the process of hair cell loss in fishes. First, fishes, like other non-mammalian vertebrates, have the ability to regenerate hair cells that have been damaged or lost via exposure to ototoxic chemicals or acoustic overstimulation. Thus, they are used as a biomedical model to understand the process of hair cell death and regeneration and find therapeutics that treat or prevent human hearing loss. Secondly, scientists and governmental natural resource managers are concerned about the potential effects of intense anthropogenic sounds on aquatic organisms, including fishes. Dr. Arthur N. Popper and his students, postdocs and research associates have performed pioneering experiments in both of these lines of fish hearing research. This review will discuss the current knowledge regarding the causes and consequences of both lateral line and inner ear hair cell damage in teleost fishes.

2,3-Dihydroxybenzoic acid attenuates kanamycin-induced volume reduction in mouse utricular type I hair cells

DEFF Research Database (Denmark)

Severinsen, Stig Åvall; Kirkegaard, Mette; Nyengaard, Jens Randel

2006-01-01

injection. Total volume of the utricle, as well as total number of hair and supporting cells, were estimated on light microscopic sections. Total volume and mean volume of hair cell types I and II and supporting cells were estimated on digital transmission electron micrographs. Total volume of the utricular...... macula, hair cell type I and supporting cells decreased significantly in animals injected with kanamycin but not in animals co-treated with DHB. Hair and supporting cell numbers remained unchanged in all three groups. In conclusion, the kanamycin-induced volume reduction of type I hair cells...

BDNF Increases Survival and Neuronal Differentiation of Human Neural Precursor Cells Cotransplanted with a Nanofiber Gel to the Auditory Nerve in a Rat Model of Neuronal Damage

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Yu Jiao

2014-01-01

Full Text Available Objectives. To study possible nerve regeneration of a damaged auditory nerve by the use of stem cell transplantation. Methods. We transplanted HNPCs to the rat AN trunk by the internal auditory meatus (IAM. Furthermore, we studied if addition of BDNF affects survival and phenotypic differentiation of the grafted HNPCs. A bioactive nanofiber gel (PA gel, in selected groups mixed with BDNF, was applied close to the implanted cells. Before transplantation, all rats had been deafened by a round window niche application of β-bungarotoxin. This neurotoxin causes a selective toxic destruction of the AN while keeping the hair cells intact. Results. Overall, HNPCs survived well for up to six weeks in all groups. However, transplants receiving the BDNF-containing PA gel demonstrated significantly higher numbers of HNPCs and neuronal differentiation. At six weeks, a majority of the HNPCs had migrated into the brain stem and differentiated. Differentiated human cells as well as neurites were observed in the vicinity of the cochlear nucleus. Conclusion. Our results indicate that human neural precursor cells (HNPC integration with host tissue benefits from additional brain derived neurotrophic factor (BDNF treatment and that these cells appear to be good candidates for further regenerative studies on the auditory nerve (AN.

Elementary properties of CaV1.3 Ca2+ channels expressed in mouse cochlear inner hair cells

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Zampini, Valeria; Johnson, Stuart L; Franz, Christoph; Lawrence, Neil D; Münkner, Stefan; Engel, Jutta; Knipper, Marlies; Magistretti, Jacopo; Masetto, Sergio; Marcotti, Walter

2010-01-01

Mammalian cochlear inner hair cells (IHCs) are specialized to process developmental signals during immature stages and sound stimuli in adult animals. These signals are conveyed onto auditory afferent nerve fibres. Neurotransmitter release at IHC ribbon synapses is controlled by L-type CaV1.3 Ca2+ channels, the biophysics of which are still unknown in native mammalian cells. We have investigated the localization and elementary properties of Ca2+ channels in immature mouse IHCs under near-physiological recording conditions. CaV1.3 Ca2+ channels at the cell pre-synaptic site co-localize with about half of the total number of ribbons present in immature IHCs. These channels activated at about −70 mV, showed a relatively short first latency and weak inactivation, which would allow IHCs to generate and accurately encode spontaneous Ca2+ action potential activity characteristic of these immature cells. The CaV1.3 Ca2+ channels showed a very low open probability (about 0.15 at −20 mV: near the peak of an action potential). Comparison of elementary and macroscopic Ca2+ currents indicated that very few Ca2+ channels are associated with each docked vesicle at IHC ribbon synapses. Finally, we found that the open probability of Ca2+ channels, but not their opening time, was voltage dependent. This finding provides a possible correlation between presynaptic Ca2+ channel properties and the characteristic frequency/amplitude of EPSCs in auditory afferent fibres. PMID:19917569

Elementary properties of CaV1.3 Ca(2+) channels expressed in mouse cochlear inner hair cells.

Science.gov (United States)

Zampini, Valeria; Johnson, Stuart L; Franz, Christoph; Lawrence, Neil D; Münkner, Stefan; Engel, Jutta; Knipper, Marlies; Magistretti, Jacopo; Masetto, Sergio; Marcotti, Walter

2010-01-01

Mammalian cochlear inner hair cells (IHCs) are specialized to process developmental signals during immature stages and sound stimuli in adult animals. These signals are conveyed onto auditory afferent nerve fibres. Neurotransmitter release at IHC ribbon synapses is controlled by L-type Ca(V)1.3 Ca(2+) channels, the biophysics of which are still unknown in native mammalian cells. We have investigated the localization and elementary properties of Ca(2+) channels in immature mouse IHCs under near-physiological recording conditions. Ca(V)1.3 Ca(2+) channels at the cell pre-synaptic site co-localize with about half of the total number of ribbons present in immature IHCs. These channels activated at about 70 mV, showed a relatively short first latency and weak inactivation, which would allow IHCs to generate and accurately encode spontaneous Ca(2+) action potential activity characteristic of these immature cells. The Ca(V)1.3 Ca(2+) channels showed a very low open probability (about 0.15 at 20 mV: near the peak of an action potential). Comparison of elementary and macroscopic Ca(2+) currents indicated that very few Ca(2+) channels are associated with each docked vesicle at IHC ribbon synapses. Finally, we found that the open probability of Ca(2+) channels, but not their opening time, was voltage dependent. This finding provides a possible correlation between presynaptic Ca(2+) channel properties and the characteristic frequency/amplitude of EPSCs in auditory afferent fibres.

SENSORY HAIR CELL REGENERATION IN THE ZEBRAFISH LATERAL LINE

OpenAIRE

Lush, Mark E.; Piotrowski, Tatjana

2014-01-01

Damage or destruction of sensory hair cells in the inner ear leads to hearing or balance deficits that can be debilitating, especially in older adults. Unfortunately, the damage is permanent, as regeneration of the inner ear sensory epithelia does not occur in mammals. Zebrafish and other non-mammalian vertebrates have the remarkable ability to regenerate sensory hair cells and understanding the molecular and cellular basis for this regenerative ability will hopefully aid us in designing ther...

Monitoring intracellular calcium ion dynamics in hair cell populations with Fluo-4 AM.

Directory of Open Access Journals (Sweden)

Kateri J Spinelli

Full Text Available We optimized Fluo-4 AM loading of chicken cochlea to report hair-bundle Ca(2+ signals in populations of hair cells. The bundle Ca(2+ signal reported the physiological state of the bundle and cell; extruding cells had very high bundle Fluo-4 fluorescence, cells with intact bundles and tip links had intermediate fluorescence, and damaged cells with broken tip links had low fluorescence. Moreover, Fluo-4 fluorescence in the bundle correlated with Ca(2+ entry through transduction channels; mechanically activating transduction channels increased the Fluo-4 signal, while breaking tip links with Ca(2+ chelators or blocking Ca(2+ entry through transduction channels each caused bundle and cell-body Fluo-4 fluorescence to decrease. These results show that when tip links break, bundle and soma Ca(2+ decrease, which could serve to stimulate the hair cell's tip-link regeneration process. Measurement of bundle Ca(2+ with Fluo-4 AM is therefore a simple method for assessing mechanotransduction in hair cells and permits an increased understanding of the interplay of tip links, transduction channels, and Ca(2+ signaling in the hair cell.

Tauroursodeoxycholic acid attenuates gentamicin-induced cochlear hair cell death in vitro.

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Jia, Zhanwei; He, Qiang; Shan, Chunguang; Li, Fengyi

2018-09-15

Gentamycin is one of the most clinically used aminoglycoside antibiotics which induce intrinsic apoptosis of hair cells. Tauroursodeoxycholic acid (TUDCA) is known as safe cell-protective agent in disorders associated with apoptosis. We aimed to investigate the protective effects of TUDCA against gentamicin-induced ototoxicity. House Ear Institute-Organ of Corti 1(HEI-OC1) cells and explanted cochlear tissue were treated with gentamicin and TUDCA, followed by serial analyses including cell viability assay, hair cell staining, qPCR, ELISA and western blotting to determine the cell damage by the parameters relevant to cell apoptosis and endoplasmic reticulum stress. TUDCA significantly attenuated gentamicin-induced cell damage in cultured HEI-OC1 cells and explanted cochlear hair cells. TUDCA alleviated gentamicin-induced cell apoptosis, supported by the decreased Bax/Bcl2 ratio compared with that of gentamicin treated alone. TUDCA decreased gentamicin-induced nitric oxide production and protein nitration in both models. In addition, TUDCA suppressed gentamicin-induced endoplasmic reticulum stress as reflected by inversing the expression levels of Binding immunoglobulin protein (Bip), CCAAT/-enhancer-binding protein homologous protein (CHOP) and Caspase 3. TUDCA attenuated gentamicin-induced hair cell death by inhibiting protein nitration activation and ER stress, providing new insights into the new potential therapies for sensorineural deafness. Copyright © 2018 Elsevier B.V. All rights reserved.

Heat pulse excitability of vestibular hair cells and afferent neurons

Science.gov (United States)

Brichta, Alan M.; Tabatabaee, Hessam; Boutros, Peter J.; Ahn, JoongHo; Della Santina, Charles C.; Poppi, Lauren A.; Lim, Rebecca

2016-01-01

In the present study we combined electrophysiology with optical heat pulse stimuli to examine thermodynamics of membrane electrical excitability in mammalian vestibular hair cells and afferent neurons. We recorded whole cell currents in mammalian type II vestibular hair cells using an excised preparation (mouse) and action potentials (APs) in afferent neurons in vivo (chinchilla) in response to optical heat pulses applied to the crista (ΔT ≈ 0.25°C per pulse). Afferent spike trains evoked by heat pulse stimuli were diverse and included asynchronous inhibition, asynchronous excitation, and/or phase-locked APs synchronized to each infrared heat pulse. Thermal responses of membrane currents responsible for APs in ganglion neurons were strictly excitatory, with Q10 ≈ 2. In contrast, hair cells responded with a mix of excitatory and inhibitory currents. Excitatory hair cell membrane currents included a thermoelectric capacitive current proportional to the rate of temperature rise (dT/dt) and an inward conduction current driven by ΔT. An iberiotoxin-sensitive inhibitory conduction current was also evoked by ΔT, rising in heat pulse excitability in vestibular sensory organs and provide quantitative methods for rational application of optical heat pulses to examine protein biophysics and manipulate cellular excitability. PMID:27226448

ACh-induced hyperpolarization and decreased resistance in mammalian type II vestibular hair cells.

Science.gov (United States)

Poppi, Lauren A; Tabatabaee, Hessam; Drury, Hannah R; Jobling, Phillip; Callister, Robert J; Migliaccio, Americo A; Jordan, Paivi M; Holt, Joseph C; Rabbitt, Richard D; Lim, Rebecca; Brichta, Alan M

2018-01-01

In the mammalian vestibular periphery, electrical activation of the efferent vestibular system (EVS) has two effects on afferent activity: 1) it increases background afferent discharge and 2) decreases afferent sensitivity to rotational stimuli. Although the cellular mechanisms underlying these two contrasting afferent responses remain obscure, we postulated that the reduction in afferent sensitivity was attributed, in part, to the activation of α9- containing nicotinic acetylcholine (ACh) receptors (α9*nAChRs) and small-conductance potassium channels (SK) in vestibular type II hair cells, as demonstrated in the peripheral vestibular system of other vertebrates. To test this hypothesis, we examined the effects of the predominant EVS neurotransmitter ACh on vestibular type II hair cells from wild-type (wt) and α9-subunit nAChR knockout (α9 -/- ) mice. Immunostaining for choline acetyltransferase revealed there were no obvious gross morphological differences in the peripheral EVS innervation among any of these strains. ACh application onto wt type II hair cells, at resting potentials, produced a fast inward current followed by a slower outward current, resulting in membrane hyperpolarization and decreased membrane resistance. Hyperpolarization and decreased resistance were due to gating of SK channels. Consistent with activation of α9*nAChRs and SK channels, these ACh-sensitive currents were antagonized by the α9*nAChR blocker strychnine and SK blockers apamin and tamapin. Type II hair cells from α9 -/- mice, however, failed to respond to ACh at all. These results confirm the critical importance of α9nAChRs in efferent modulation of mammalian type II vestibular hair cells. Application of exogenous ACh reduces electrical impedance, thereby decreasing type II hair cell sensitivity. NEW & NOTEWORTHY Expression of α9 nicotinic subunit was crucial for fast cholinergic modulation of mammalian vestibular type II hair cells. These findings show a multifaceted

The passive cable properties of hair cell stereocilia and their contribution to somatic capacitance measurements.

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Breneman, Kathryn D; Highstein, Stephen M; Boyle, Richard D; Rabbitt, Richard D

2009-01-01

Somatic measurements of whole-cell capacitance are routinely used to understand physiologic events occurring in remote portions of cells. These studies often assume the intracellular space is voltage-clamped. We questioned this assumption in auditory and vestibular hair cells with respect to their stereocilia based on earlier studies showing that neurons, with radial dimensions similar to stereocilia, are not always isopotential under voltage-clamp. To explore this, we modeled the stereocilia as passive cables with transduction channels located at their tips. We found that the input capacitance measured at the soma changes when the transduction channels at the tips of the stereocilia are open compared to when the channels are closed. The maximum capacitance is felt with the transducer closed but will decrease as the transducer opens due to a length-dependent voltage drop along the stereocilium length. This potential drop is proportional to the intracellular resistance and stereocilium tip conductance and can produce a maximum capacitance error on the order of fF for single stereocilia and pF for the bundle.

Protective effects of edaravone against cisplatin-induced hair cell damage in zebrafish.

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Hong, Seok Jin; Im, Gi Jung; Chang, Jiwon; Chae, Sung Won; Lee, Seung Hoon; Kwon, Soon Young; Jung, Hak Hyun; Chung, Ah Young; Park, Hae Chul; Choi, June

2013-06-01

Edaravone is known to have a potent free radical scavenging effect. The objective of the present study was to evaluate the effects of edaravone on cisplatin-induced ototoxicity in transgenic zebrafish (Brn3C: EGFP). Five day post-fertilization zebrafish larvae were exposed to 1000 μM cisplatin and 50 μM, 100 μM, 250 μM, 500 μM, 750 μM, and 1000 μM concentrations of edaravone for 4h. Hair cells within neuromasts of the supraorbital (SO1 and SO2), otic (O1), and occipital (OC1) lateral lines were analyzed by fluorescence microscopy and confocal microscopy (n=10). Hair cell survival was calculated as a percentage of the hair cells in the control group that were not exposed to cisplatin. Ultrastructural changes were evaluated using scanning electron microscopy and transmission electron microscopy. Edaravone protected cisplatin-induced hair cell loss of neuromasts (edaravone 750 μM: 8.7 ± 1.5 cells, cisplatin 1000 μM only: 3.7 ± 0.9 cells; n=10, pedaravone for 4h. Edaravone attenuated cisplatin-induced hair cell damage in zebrafish. The results of the current study suggest that cisplatin induces apoptosis, and the apoptotic cell death can be prevented by treatment with edaravone in zebrafish. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Up-to-date Clinical Trials of Hair Regeneration Using Conditioned Media of Adipose-Derived Stem Cells in Male and Female Pattern Hair Loss.

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Shin, Hyoseung; Won, Chong Hyun; Chung, Woon-Kyung; Park, Byung-Soon

2017-01-01

The primary roles of mesenchymal stem cells (MSCs) are to maintain the stem cell niche, facilitate recovery after injury, and ensure healthy aging and the homeostasis of organ and tissues. MSCs have recently emerged as a new therapeutic option for hair loss. Since adipose-derived stem cells (ADSCs) are the most accessible sources of MSCs, ADSCbased hair regeneration is investigated. Besides replacing degenerated cells in affected organs, ADSCs exhibit their beneficial effects through the paracrine actions of various cytokines and growth factors. Several laboratory experiments and animal studies have shown that ADSC-related proteins can stimulate hair growth. In addition, we introduce our clinical pilot studies using conditioned media of ADSCs for pattern hair loss in men and women. We believe that conditioned media of ADSCs represents a promising alternative therapeutic strategy for hair loss. We also discuss practical therapeutic challenges and the direction of future research. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Zebrafish Models for the Mechanosensory Hair Cell Dysfunction in Usher Syndrome 3 Reveal That Clarin-1 Is an Essential Hair Bundle Protein.

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Gopal, Suhasini R; Chen, Daniel H-C; Chou, Shih-Wei; Zang, Jingjing; Neuhauss, Stephan C F; Stepanyan, Ruben; McDermott, Brian M; Alagramam, Kumar N

2015-07-15

Usher syndrome type III (USH3) is characterized by progressive loss of hearing and vision, and varying degrees of vestibular dysfunction. It is caused by mutations that affect the human clarin-1 protein (hCLRN1), a member of the tetraspanin protein family. The missense mutation CLRN1(N48K), which affects a conserved N-glycosylation site in hCLRN1, is a common causative USH3 mutation among Ashkenazi Jews. The affected individuals hear at birth but lose that function over time. Here, we developed an animal model system using zebrafish transgenesis and gene targeting to provide an explanation for this phenotype. Immunolabeling demonstrated that Clrn1 localized to the hair cell bundles (hair bundles). The clrn1 mutants generated by zinc finger nucleases displayed aberrant hair bundle morphology with diminished function. Two transgenic zebrafish that express either hCLRN1 or hCLRN1(N48K) in hair cells were produced to examine the subcellular localization patterns of wild-type and mutant human proteins. hCLRN1 localized to the hair bundles similarly to zebrafish Clrn1; in contrast, hCLRN1(N48K) largely mislocalized to the cell body with a small amount reaching the hair bundle. We propose that this small amount of hCLRN1(N48K) in the hair bundle provides clarin-1-mediated function during the early stages of life; however, the presence of hCLRN1(N48K) in the hair bundle diminishes over time because of intracellular degradation of the mutant protein, leading to progressive loss of hair bundle integrity and hair cell function. These findings and genetic tools provide an understanding and path forward to identify therapies to mitigate hearing loss linked to the CLRN1 mutation. Mutations in the clarin-1 gene affect eye and ear function in humans. Individuals with the CLRN1(N48K) mutation are born able to hear but lose that function over time. Here, we develop an animal model system using zebrafish transgenesis and gene targeting to provide an explanation for this phenotype

microRNA-183 is Essential for Hair Cell Regeneration after Neomycin Injury in Zebrafish.

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Kim, Chang Woo; Han, Ji Hyuk; Wu, Ling; Choi, Jae Young

2018-01-01

microRNAs (miRNAs) are non-coding RNAs composed of 20 to 22 nucleotides that regulate development and differentiation in various organs by silencing specific RNAs and regulating gene expression. In the present study, we show that the microRNA (miR)-183 cluster is upregulated during hair cell regeneration and that its inhibition reduces hair cell regeneration following neomycin-induced ototoxicity in zebrafish. miRNA expression patterns after neomycin exposure were analyzed using microarray chips. Quantitative polymerase chain reaction was performed to validate miR-183 cluster expression patterns following neomycin exposure (500 μM for 2 h). After injection of an antisense morpholino (MO) to miR-183 (MO-183) immediately after fertilization, hair cell regeneration after neomycin exposure in neuromast cells was evaluated by fluorescent staining (YO-PRO1). The MO-183 effect also was assessed in transgenic zebrafish larvae expressing green fluorescent protein (GFP) in inner ear hair cells. Microarray analysis clearly showed that the miR-183 cluster (miR-96, miR-182, and miR-183) was upregulated after neomycin treatment. We also confirmed upregulated expression of the miR-183 cluster during hair cell regeneration after neomycin-induced ototoxicity. miR-183 inhibition using MO-183 reduced hair cell regeneration in both wild-type and GFP transgenic zebrafish larvae. Our work demonstrates that the miR-183 cluster is essential for the regeneration of hair cells following ototoxic injury in zebrafish larvae. Therefore, regulation of the miR-183 cluster can be a novel target for stimulation of hair cell regeneration. © Copyright: Yonsei University College of Medicine 2018

[Presbycusis: neural degeneration and aging on the auditory receptor of C57/BL6J mice].

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Castillo, E; Carricondo, F; Bartolomé, M V; Vicente-Torres, A; Poch Broto, J; Gil-Loyzaga, P

2006-11-01

Presbycusis is a progressive hearing impairment associated with aging, characterized by hearing loss and a degeneration of cochlear structures. In this paper we analyze the effects of aging on the auditory system of C57/BL6J mice, with electrophysiological and morphological studies. With this aim the auditory potentials of mice aging 1, 3, 6, 9, 12, 15, 18, 21 and 24 months were recorded, and then the morphology of the cochleal were analyzed. Auditory potentials revealed an increase in wave latencies, as well as a decrease in their amplitudes during aging. Morphological results showed a total Corti's organ degeneration, being replaced by a flat epithelial layer, and a total absence of hair cells.

A Model for the representation of Speech Signals in Normal and Impaired Ears

DEFF Research Database (Denmark)

Christiansen, Thomas Ulrich

2004-01-01

hearing was modelled as a combination of outer- and inner hair cell loss. The percentage of dead inner hair cells was calculated based on a new computational method relating auditory nerve fibre thresholds to behavioural thresholds. Finally, a model of the entire auditory nerve fibre population......A model of human auditory periphery, ranging from the outer ear to the auditory nerve, was developed. The model consists of the following components: outer ear transfer function, middle ear transfer function, basilar membrane velocity, inner hair cell receptor potential, inner hair cell probability...... of neurotransmitter release and auditory nerve fibre refractoriness. The model builds on previously published models, however, parameters for basilar membrane velocity and inner hair cell probability of neurotransmitter release were successfully fitted to model data from psychophysical and physiological data...

A role for CSLD3 during cell-wall synthesis in apical plasma membranes of tip-growing root-hair cells.

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Park, Sungjin; Szumlanski, Amy L; Gu, Fangwei; Guo, Feng; Nielsen, Erik

2011-07-17

In plants, cell shape is defined by the cell wall, and changes in cell shape and size are dictated by modification of existing cell walls and deposition of newly synthesized cell-wall material. In root hairs, expansion occurs by a process called tip growth, which is shared by root hairs, pollen tubes and fungal hyphae. We show that cellulose-like polysaccharides are present in root-hair tips, and de novo synthesis of these polysaccharides is required for tip growth. We also find that eYFP-CSLD3 proteins, but not CESA cellulose synthases, localize to a polarized plasma-membrane domain in root hairs. Using biochemical methods and genetic complementation of a csld3 mutant with a chimaeric CSLD3 protein containing a CESA6 catalytic domain, we provide evidence that CSLD3 represents a distinct (1→4)-β-glucan synthase activity in apical plasma membranes during tip growth in root-hair cells.

The design, calibration, and use of a water microjet for stimulating hair cell sensory hair bundles.

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Saunders, J C; Szymko, Y M

1989-11-01

The design, calibration, and use of a noninvasive, noncontact device for stimulating hair cell hair bundles in vitro are described. This device employed a piezoelectric crystal, driven at high frequencies, to generate sinusoidal pressure in a contained fluid volume. The pressure was propagated to the tip of a glass micropipette and the oscillating water jet stimulus produced at the tip was used to stimulate sensory hair bundles. The movements of glass microbeads, caught in the oscillating pressure field of the water jet, provided a means of calibrating this stimulus. The linearity of the jet, its waveform and frequency response, the influence of pipette shape and tip diameter, as well as models to explain the operation of the water jet, are described. The use of this stimulus for measuring hair bundle micromechanics at high frequencies is then demonstrated.

Numerical simulation of the hair formation -modeling of hair cycle

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Kajihara, Narumichi; Nagayama, Katsuya

2018-01-01

In the recent years, the fields of study of anti-aging, health and beauty, cosmetics, and hair diseases have attracted significant attention. In particular, human hair is considered to be an important aspect with regard to an attractive appearance. To this end, many workers have sought to understand the formation mechanism of the hair root. However, observing growth in the hair root is difficult, and a detailed mechanism of the process has not yet been elucidated. Hair repeats growth, retraction, and pause cycles (hair cycle) in a repetitive process. In the growth phase, hair is formed through processes of cell proliferation and differentiation (keratinization). During the retraction phase, hair growth stops, and during the resting period, hair fall occurs and new hair grows. This hair cycle is believed to affect the elongation rate, thickness, strength, and shape of hair. Therefore, in this study, we introduce a particle model as a new method to elucidate the unknown process of hair formation, and to model the hair formation process accompanying the proliferation and differentiation of the hair root cells in all three dimensions. In addition, to the growth period, the retraction and the resting periods are introduced to realize the hair cycle using this model.

Selective Inner Hair Cell Dysfunction in Chinchillas Impairs Hearing-in-Noise in the Absence of Outer Hair Cell Loss.

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Lobarinas, Edward; Salvi, Richard; Ding, Dalian

2016-04-01

Poorer hearing in the presence of background noise is a significant problem for the hearing impaired. Ototoxic drugs, ageing, and noise exposure can damage the sensory hair cells of the inner ear that are essential for normal hearing sensitivity. The relationship between outer hair cell (OHC) loss and progressively poorer hearing sensitivity in quiet or in competing background noise is supported by a number of human and animal studies. In contrast, the effect of moderate inner hair cell (IHC) loss or dysfunction shows almost no impact on behavioral measures of hearing sensitivity in quiet, when OHCs remain intact, but the relationship between selective IHC loss and hearing in noise remains relatively unknown. Here, a moderately high dose of carboplatin (75 mg/kg) that produced IHC loss in chinchillas ranging from 40 to 80 % had little effect on thresholds in quiet. However, when tested in the presence of competing broadband (BBN) or narrowband noise (NBN), thresholds increased significantly. IHC loss >60 % increased signal-to-noise ratios (SNRs) for tones (500-11,300 Hz) in competing BBN by 5-10 dB and broadened the masking function under NBN. These data suggest that IHC loss or dysfunction may play a significant role in listening in noise independent of OHC integrity and that these deficits may be present even when thresholds in quiet are within normal limits.

Falsification of the ionic channel theory of hair cell transduction.

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Rossetto, Michelangelo

2013-11-01

The hair cell provides the transduction of mechanical vibrations in the balance and acoustic sense of all vertebrates that swim, walk, or fly. The current theory places hair cell transduction in a mechanically controlled ion channel. Although the theory of a mechanical input modulating the flow of ions through an ion pore has been a useful tool, it is falsified by experimental data in the literature and can be definitively falsified by a proposed experiment.

Intraoperative Electrocochleographic Characteristics of Auditory Neuropathy Spectrum Disorder in Cochlear Implant Subjects

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William J. Riggs

2017-07-01

Full Text Available Auditory neuropathy spectrum disorder (ANSD is characterized by an apparent discrepancy between measures of cochlear and neural function based on auditory brainstem response (ABR testing. Clinical indicators of ANSD are a present cochlear microphonic (CM with small or absent wave V. Many identified ANSD patients have speech impairment severe enough that cochlear implantation (CI is indicated. To better understand the cochleae identified with ANSD that lead to a CI, we performed intraoperative round window electrocochleography (ECochG to tone bursts in children (n = 167 and adults (n = 163. Magnitudes of the responses to tones of different frequencies were summed to measure the “total response” (ECochG-TR, a metric often dominated by hair cell activity, and auditory nerve activity was estimated visually from the compound action potential (CAP and auditory nerve neurophonic (ANN as a ranked “Nerve Score”. Subjects identified as ANSD (45 ears in children, 3 in adults had higher values of ECochG-TR than adult and pediatric subjects also receiving CIs not identified as ANSD. However, nerve scores of the ANSD group were similar to the other cohorts, although dominated by the ANN to low frequencies more than in the non-ANSD groups. To high frequencies, the common morphology of ANSD cases was a large CM and summating potential, and small or absent CAP. Common morphologies in other groups were either only a CM, or a combination of CM and CAP. These results indicate that responses to high frequencies, derived primarily from hair cells, are the main source of the CM used to evaluate ANSD in the clinical setting. However, the clinical tests do not capture the wide range of neural activity seen to low frequency sounds.

Deletion of PDZD7 disrupts the Usher syndrome type 2 protein complex in cochlear hair cells and causes hearing loss in mice.

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Zou, Junhuang; Zheng, Tihua; Ren, Chongyu; Askew, Charles; Liu, Xiao-Ping; Pan, Bifeng; Holt, Jeffrey R; Wang, Yong; Yang, Jun

2014-05-01

Usher syndrome type 2 (USH2) is the predominant form of USH, a leading genetic cause of combined deafness and blindness. PDZD7, a paralog of two USH causative genes, USH1C and USH2D (WHRN), was recently reported to be implicated in USH2 and non-syndromic deafness. It encodes a protein with multiple PDZ domains. To understand the biological function of PDZD7 and the pathogenic mechanism caused by PDZD7 mutations, we generated and thoroughly characterized a Pdzd7 knockout mouse model. The Pdzd7 knockout mice exhibit congenital profound deafness, as assessed by auditory brainstem response, distortion product otoacoustic emission and cochlear microphonics tests, and normal vestibular function, as assessed by their behaviors. Lack of PDZD7 leads to the disorganization of stereocilia bundles and a reduction in mechanotransduction currents and sensitivity in cochlear outer hair cells. At the molecular level, PDZD7 determines the localization of the USH2 protein complex, composed of USH2A, GPR98 and WHRN, to ankle links in developing cochlear hair cells, likely through its direct interactions with these three proteins. The localization of PDZD7 to the ankle links of cochlear hair bundles also relies on USH2 proteins. In photoreceptors of Pdzd7 knockout mice, the three USH2 proteins largely remain unchanged at the periciliary membrane complex. The electroretinogram responses of both rod and cone photoreceptors are normal in knockout mice at 1 month of age. Therefore, although the organization of the USH2 complex appears different in photoreceptors, it is clear that PDZD7 plays an essential role in organizing the USH2 complex at ankle links in developing cochlear hair cells. GenBank accession numbers: KF041446, KF041447, KF041448, KF041449, KF041450, KF041451.

Neural Hyperactivity of the Central Auditory System in Response to Peripheral Damage

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Yi Zhao

2016-01-01

Full Text Available It is increasingly appreciated that cochlear pathology is accompanied by adaptive responses in the central auditory system. The cause of cochlear pathology varies widely, and it seems that few commonalities can be drawn. In fact, despite intricate internal neuroplasticity and diverse external symptoms, several classical injury models provide a feasible path to locate responses to different peripheral cochlear lesions. In these cases, hair cell damage may lead to considerable hyperactivity in the central auditory pathways, mediated by a reduction in inhibition, which may underlie some clinical symptoms associated with hearing loss, such as tinnitus. Homeostatic plasticity, the most discussed and acknowledged mechanism in recent years, is most likely responsible for excited central activity following cochlear damage.

Cytoplasm localization of aminopeptidase M1 and its functional activity in root hair cells and BY-2 cells.

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Lee, Ok Ran; Cho, Hyung-Taeg

2012-12-01

Aminopeptidase M1 (APM1) was the first M1 metallopeptidase family member identified in Arabidopsis, isolated by its affinity for the auxin transport inhibitor N-1-naphthylphthalamic acid (NPA). A loss-of-function mutation showed various developmental defects in cell division and auxin transport. APM1 was shown to be localized in endomembrane structures, the cytoplasm, and the plasma membrane. These previous results suggested that APM1 has diverse functional roles in different cell and tissue types. Here we report that APM1 localized to the cytoplasm, and its over-expression in the root hair cell caused longer root hair phenotypes. Treatment of aminopeptidase inhibitors caused internalization of auxin efflux PIN-FORMED proteins in root hair cells and suppressed short root hair phenotype of PIN3 overexpression line (PIN3ox). APM1 also localized to the cytoplasm in tobacco BY-2 cells, its over-expression had little effect on auxin transport in these cells.

Intercellular K⁺ accumulation depolarizes Type I vestibular hair cells and their associated afferent nerve calyx.

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Contini, D; Zampini, V; Tavazzani, E; Magistretti, J; Russo, G; Prigioni, I; Masetto, S

2012-12-27

Mammalian vestibular organs contain two types of sensory receptors, named Type I and Type II hair cells. While Type II hair cells are contacted by several small afferent nerve terminals, the basolateral surface of Type I hair cells is almost entirely enveloped by a single large afferent nerve terminal, called calyx. Moreover Type I, but not Type II hair cells, express a low-voltage-activated outward K(+) current, I(K,L), which is responsible for their much lower input resistance (Rm) at rest as compared to Type II hair cells. The functional meaning of I(K,L) and associated calyx is still enigmatic. By combining the patch-clamp whole-cell technique with the mouse whole crista preparation, we have recorded the current- and voltage responses of in situ hair cells. Outward K(+) current activation resulted in K(+) accumulation around Type I hair cells, since it induced a rightward shift of the K(+) reversal potential the magnitude of which depended on the amplitude and duration of K(+) current flow. Since this phenomenon was never observed for Type II hair cells, we ascribed it to the presence of a residual calyx limiting K(+) efflux from the synaptic cleft. Intercellular K(+) accumulation added a slow (τ>100ms) depolarizing component to the cell voltage response. In a few cases we were able to record from the calyx and found evidence for intercellular K(+) accumulation as well. The resulting depolarization could trigger a discharge of action potentials in the afferent nerve fiber. Present results support a model where pre- and postsynaptic depolarization produced by intercellular K(+) accumulation cooperates with neurotransmitter exocytosis in sustaining afferent transmission arising from Type I hair cells. While vesicular transmission together with the low Rm of Type I hair cells appears best suited for signaling fast head movements, depolarization produced by intercellular K(+) accumulation could enhance signal transmission during slow head movements. Copyright �

The Rho GTPase Cdc42 regulates hair cell planar polarity and cellular patterning in the developing cochlea

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Anna Kirjavainen

2015-03-01

Full Text Available Hair cells of the organ of Corti (OC of the cochlea exhibit distinct planar polarity, both at the tissue and cellular level. Planar polarity at tissue level is manifested as uniform orientation of the hair cell stereociliary bundles. Hair cell intrinsic polarity is defined as structural hair bundle asymmetry; positioning of the kinocilium/basal body complex at the vertex of the V-shaped bundle. Consistent with strong apical polarity, the hair cell apex displays prominent actin and microtubule cytoskeletons. The Rho GTPase Cdc42 regulates cytoskeletal dynamics and polarization of various cell types, and, thus, serves as a candidate regulator of hair cell polarity. We have here induced Cdc42 inactivation in the late-embryonic OC. We show the role of Cdc42 in the establishment of planar polarity of hair cells and in cellular patterning. Abnormal planar polarity was displayed as disturbances in hair bundle orientation and morphology and in kinocilium/basal body positioning. These defects were accompanied by a disorganized cell-surface microtubule network. Atypical protein kinase C (aPKC, a putative Cdc42 effector, colocalized with Cdc42 at the hair cell apex, and aPKC expression was altered upon Cdc42 depletion. Our data suggest that Cdc42 together with aPKC is part of the machinery establishing hair cell planar polarity and that Cdc42 acts on polarity through the cell-surface microtubule network. The data also suggest that defects in apical polarization are influenced by disturbed cellular patterning in the OC. In addition, our data demonstrates that Cdc42 is required for stereociliogenesis in the immature cochlea.

Inactivation of STAT3 Signaling Impairs Hair Cell Differentiation in the Developing Mouse Cochlea.

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Chen, Qianqian; Quan, Yizhou; Wang, Naitao; Xie, Chengying; Ji, Zhongzhong; He, Hao; Chai, Renjie; Li, Huawei; Yin, Shankai; Chin, Y Eugene; Wei, Xunbin; Gao, Wei-Qiang

2017-07-11

Although STAT3 signaling is demonstrated to regulate sensory cell differentiation and regeneration in the zebrafish, its exact role is still unclear in mammalian cochleae. Here, we report that STAT3 and its activated form are specifically expressed in hair cells during mouse cochlear development. Importantly, conditional cochlear deletion of Stat3 leads to an inhibition on hair cell differentiation in mice in vivo and in vitro. By cell fate analysis, inactivation of STAT3 signaling shifts the cell division modes from asymmetric to symmetric divisions from supporting cells. Moreover, inhibition of Notch signaling stimulates STAT3 phosphorylation, and inactivation of STAT3 signaling attenuates production of supernumerary hair cells induced by a Notch pathway inhibitor. Our findings highlight an important role of the STAT3 signaling during mouse cochlear hair cell differentiation and may have clinical implications for the recovery of hair cell loss-induced hearing impairment. Copyright © 2017 International Society for Stem Cell Research. Published by Elsevier Inc. All rights reserved.

Effect of JNK inhibitor SP600125 on hair cell regeneration in zebrafish (Danio rerio) larvae

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Sun, Shaoyang; Wang, Xu; Li, Wenyan; Li, Huawei

2016-01-01

The c-Jun amino-terminal kinase (JNK) proteins are a subgroup of the mitogen-activated protein kinase family. They play a complex role in cell proliferation, survival, and apoptosis. Here, we report a novel role of JNK signalling in hair cell regeneration. We eliminated hair cells of 5-day post-fertilization zebrafish larvae using neomycin followed by JNK inhibition with SP600125. JNK inhibition strongly decreased the number of regenerated hair cells in response to neomycin damage. These changes were associated with reduced proliferation. JNK inhibition also increased cleaved caspase-3 activity and induced apoptosis in regenerating neuromasts. Finally, JNK inhibition with SP600125 decreased the expression of genes related to Wnt. Over-activation of the Wnt signalling pathway partly rescued the hair cell regeneration defects induced by JNK inhibition. Together, our findings provide novel insights into the function of JNK and show that JNK inhibition blocks hair cell regeneration by controlling the Wnt signalling pathway. PMID:27438150

Investigation of the mechanism of soft tissue conduction explains several perplexing auditory phenomena.

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Adelman, Cahtia; Chordekar, Shai; Perez, Ronen; Sohmer, Haim

2014-09-01

Soft tissue conduction (STC) is a recently expounded mode of auditory stimulation in which the clinical bone vibrator delivers auditory frequency vibratory stimuli to skin sites on the head, neck, and thorax. Investigation of the mechanism of STC stimulation has served as a platform for the elucidation of the mechanics of cochlear activation, in general, and to a better understanding of several perplexing auditory phenomena. This review demonstrates that it is likely that the cochlear hair cells can be directly activated at low sound intensities by the fluid pressures initiated in the cochlea; that the fetus in utero, completely enveloped in amniotic fluid, hears by STC; that a speaker hears his/her own voice by air conduction and by STC; and that pulsatile tinnitus is likely due to pulsatile turbulent blood flow producing fluid pressures that reach the cochlea through the soft tissues.

Inactivation of STAT3 Signaling Impairs Hair Cell Differentiation in the Developing Mouse Cochlea

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Qianqian Chen

2017-07-01

Full Text Available Although STAT3 signaling is demonstrated to regulate sensory cell differentiation and regeneration in the zebrafish, its exact role is still unclear in mammalian cochleae. Here, we report that STAT3 and its activated form are specifically expressed in hair cells during mouse cochlear development. Importantly, conditional cochlear deletion of Stat3 leads to an inhibition on hair cell differentiation in mice in vivo and in vitro. By cell fate analysis, inactivation of STAT3 signaling shifts the cell division modes from asymmetric to symmetric divisions from supporting cells. Moreover, inhibition of Notch signaling stimulates STAT3 phosphorylation, and inactivation of STAT3 signaling attenuates production of supernumerary hair cells induced by a Notch pathway inhibitor. Our findings highlight an important role of the STAT3 signaling during mouse cochlear hair cell differentiation and may have clinical implications for the recovery of hair cell loss-induced hearing impairment.

A synthetic prestin reveals protein domains and molecular operation of outer hair cell piezoelectricity.

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Schaechinger, Thorsten J; Gorbunov, Dmitry; Halaszovich, Christian R; Moser, Tobias; Kügler, Sebastian; Fakler, Bernd; Oliver, Dominik

2011-06-24

Prestin, a transporter-like protein of the SLC26A family, acts as a piezoelectric transducer that mediates the fast electromotility of outer hair cells required for cochlear amplification and auditory acuity in mammals. Non-mammalian prestin orthologues are anion transporters without piezoelectric activity. Here, we generated synthetic prestin (SynPres), a chimera of mammalian and non-mammalian prestin exhibiting both, piezoelectric properties and anion transport. SynPres delineates two distinct domains in the protein's transmembrane core that are necessary and sufficient for generating electromotility and associated non-linear charge movement (NLC). Functional analysis of SynPres showed that the amplitude of NLC and hence electromotility are determined by the transport of monovalent anions. Thus, prestin-mediated electromotility is a dual-step process: transport of anions by an alternate access cycle, followed by an anion-dependent transition generating electromotility. The findings define structural and functional determinants of prestin's piezoelectric activity and indicate that the electromechanical process evolved from the ancestral transport mechanism.

Maintained expression of the planar cell polarity molecule Vangl2 and reformation of hair cell orientation in the regenerating inner ear.

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Warchol, Mark E; Montcouquiol, Mireille

2010-09-01

The avian inner ear possesses a remarkable ability to regenerate sensory hair cells after ototoxic injury. Regenerated hair cells possess phenotypes and innervation that are similar to those found in the undamaged ear, but little is known about the signaling pathways that guide hair cell differentiation during the regenerative process. The aim of the present study was to examine the factors that specify the orientation of hair cell stereocilia bundles during regeneration. Using organ cultures of the chick utricle, we show that hair cells are properly oriented after having regenerated entirely in vitro and that orientation is not affected by surgical removal of the striolar reversal zone. These results suggest that the orientation of regenerating stereocilia is not guided by the release of a diffusible morphogen from the striolar reversal zone but is specified locally within the regenerating sensory organ. In order to determine the nature of the reorientation cues, we examined the expression patterns of the core planar cell polarity molecule Vangl2 in the normal and regenerating utricle. We found that Vangl2 is asymmetrically expressed on cells within the sensory epithelium and that this expression pattern is maintained after ototoxic injury and throughout regeneration. Notably, treatment with a small molecule inhibitor of c-Jun-N-terminal kinase disrupted the orientation of regenerated hair cells. Both of these results are consistent with the hypothesis that noncanonical Wnt signaling guides hair cell orientation during regeneration.

Perceptual consequences of disrupted auditory nerve activity.

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Zeng, Fan-Gang; Kong, Ying-Yee; Michalewski, Henry J; Starr, Arnold

2005-06-01

Perceptual consequences of disrupted auditory nerve activity were systematically studied in 21 subjects who had been clinically diagnosed with auditory neuropathy (AN), a recently defined disorder characterized by normal outer hair cell function but disrupted auditory nerve function. Neurological and electrophysical evidence suggests that disrupted auditory nerve activity is due to desynchronized or reduced neural activity or both. Psychophysical measures showed that the disrupted neural activity has minimal effects on intensity-related perception, such as loudness discrimination, pitch discrimination at high frequencies, and sound localization using interaural level differences. In contrast, the disrupted neural activity significantly impairs timing related perception, such as pitch discrimination at low frequencies, temporal integration, gap detection, temporal modulation detection, backward and forward masking, signal detection in noise, binaural beats, and sound localization using interaural time differences. These perceptual consequences are the opposite of what is typically observed in cochlear-impaired subjects who have impaired intensity perception but relatively normal temporal processing after taking their impaired intensity perception into account. These differences in perceptual consequences between auditory neuropathy and cochlear damage suggest the use of different neural codes in auditory perception: a suboptimal spike count code for intensity processing, a synchronized spike code for temporal processing, and a duplex code for frequency processing. We also proposed two underlying physiological models based on desynchronized and reduced discharge in the auditory nerve to successfully account for the observed neurological and behavioral data. These methods and measures cannot differentiate between these two AN models, but future studies using electric stimulation of the auditory nerve via a cochlear implant might. These results not only show the unique

Mobilizing Transit-Amplifying Cell-Derived Ectopic Progenitors Prevents Hair Loss from Chemotherapy or Radiation Therapy.

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Huang, Wen-Yen; Lai, Shih-Fan; Chiu, Hsien-Yi; Chang, Michael; Plikus, Maksim V; Chan, Chih-Chieh; Chen, You-Tzung; Tsao, Po-Nien; Yang, Tsung-Lin; Lee, Hsuan-Shu; Chi, Peter; Lin, Sung-Jan

2017-11-15

Genotoxicity-induced hair loss from chemotherapy and radiotherapy is often encountered in cancer treatment, and there is a lack of effective treatment. In growing hair follicles (HF), quiescent stem cells (SC) are maintained in the bulge region, and hair bulbs at the base contain rapidly dividing, yet genotoxicity-sensitive transit-amplifying cells (TAC) that maintain hair growth. How genotoxicity-induced HF injury is repaired remains unclear. We report here that HFs mobilize ectopic progenitors from distinct TAC compartments for regeneration in adaptation to the severity of dystrophy induced by ionizing radiation (IR). Specifically, after low-dose IR, keratin 5 + basal hair bulb progenitors, rather than bulge SCs, were quickly activated to replenish matrix cells and regenerated all concentric layers of HFs, demonstrating their plasticity. After high-dose IR, when both matrix and hair bulb cells were depleted, the surviving outer root sheath cells rapidly acquired an SC-like state and fueled HF regeneration. Their progeny then homed back to SC niche and supported new cycles of HF growth. We also revealed that IR induced HF dystrophy and hair loss and suppressed WNT signaling in a p53- and dose-dependent manner. Augmenting WNT signaling attenuated the suppressive effect of p53 and enhanced ectopic progenitor proliferation after genotoxic injury, thereby preventing both IR- and cyclophosphamide-induced alopecia. Hence, targeted activation of TAC-derived progenitor cells, rather than quiescent bulge SCs, for anagen HF repair can be a potential approach to prevent hair loss from chemotherapy and radiotherapy. Cancer Res; 77(22); 6083-96. ©2017 AACR . ©2017 American Association for Cancer Research.

Cochlear injury and adaptive plasticity of the auditory cortex

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ANNA R. eFETONI

2015-02-01

Full Text Available Growing evidence suggests that cochlear stressors as noise exposure and aging can induce homeostatic/maladaptive changes in the central auditory system from the brainstem to the cortex. Studies centered on such changes have revealed several mechanisms that operate in the context of sensory disruption after insult (noise trauma, drug- or age-related injury. The oxidative stress is central to current theories of induced sensory neural hearing loss and aging, and interventions to attenuate the hearing loss are based on antioxidant agent. The present review addresses the recent literature on the alterations in hair cells and spiral ganglion neurons due to noise-induced oxidative stress in the cochlea, as well on the impact of cochlear damage on the auditory cortex neurons. The emerging image emphasizes that noise-induced deafferentation and upward spread of cochlear damage is associated with the altered dendritic architecture of auditory pyramidal neurons. The cortical modifications may be reversed by treatment with antioxidants counteracting the cochlear redox imbalance. These findings open new therapeutic approaches to treat the functional consequences of the cortical reorganization following cochlear damage.

Type I hair cell degeneration in the utricular macula of the waltzing guinea pig

DEFF Research Database (Denmark)

Severinsen, Stig A; Raarup, Merete Krog; Ulfendahl, Mats

2008-01-01

Waltzing guinea pigs are an inbred guinea pig strain with a congenital and progressive balance and hearing disorder. A unique rod-shaped structure is found in the type I vestibular hair cells, that traverses the cell in an axial direction, extending towards the basement membrane. The present study...... estimates the total number of utricular hair cells and supporting cells in waltzing guinea pigs and age-matched control animals using the optical fractionator method. Animals were divided into four age groups (1, 7, 49 and 343 day-old). The number of type I hair cells decreased by 20% in the 343 day......-old waltzing guinea pigs compared to age-matched controls and younger animals. Two-photon confocal laser scanning microscopy using antibodies against fimbrin and betaIII-tubulin showed that the rods were exclusive to type I hair cells. There was no significant change in the length of the filament rods with age...

XIRP2, an Actin-Binding Protein Essential for Inner Ear Hair-Cell Stereocilia

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Déborah I. Scheffer

2015-03-01

Full Text Available Hair cells of the inner ear are mechanoreceptors for hearing and balance, and proteins highly enriched in hair cells may have specific roles in the development and maintenance of the mechanotransduction apparatus. We identified XIRP2/mXinβ as an enriched protein likely to be essential for hair cells. We found that different isoforms of this protein are expressed and differentially located: short splice forms (also called XEPLIN are targeted more to stereocilia, whereas two long isoforms containing a XIN-repeat domain are in both stereocilia and cuticular plates. Mice lacking the Xirp2 gene developed normal stereocilia bundles, but these degenerated with time: stereocilia were lost and long membranous protrusions emanated from the nearby apical surfaces. At an ultrastructural level, the paracrystalline actin filaments became disorganized. XIRP2 is apparently involved in the maintenance of actin structures in stereocilia and cuticular plates of hair cells, and perhaps in other organs where it is expressed.

Hearing after congenital deafness: central auditory plasticity and sensory deprivation.

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Kral, A; Hartmann, R; Tillein, J; Heid, S; Klinke, R

2002-08-01

The congenitally deaf cat suffers from a degeneration of the inner ear. The organ of Corti bears no hair cells, yet the auditory afferents are preserved. Since these animals have no auditory experience, they were used as a model for congenital deafness. Kittens were equipped with a cochlear implant at different ages and electro-stimulated over a period of 2.0-5.5 months using a monopolar single-channel compressed analogue stimulation strategy (VIENNA-type signal processor). Following a period of auditory experience, we investigated cortical field potentials in response to electrical biphasic pulses applied by means of the cochlear implant. In comparison to naive unstimulated deaf cats and normal hearing cats, the chronically stimulated animals showed larger cortical regions producing middle-latency responses at or above 300 microV amplitude at the contralateral as well as the ipsilateral auditory cortex. The cortex ipsilateral to the chronically stimulated ear did not show any signs of reduced responsiveness when stimulating the 'untrained' ear through a second cochlear implant inserted in the final experiment. With comparable duration of auditory training, the activated cortical area was substantially smaller if implantation had been performed at an older age of 5-6 months. The data emphasize that young sensory systems in cats have a higher capacity for plasticity than older ones and that there is a sensitive period for the cat's auditory system.

FGF signalling controls the specification of hair placode-derived SOX9 positive progenitors to Merkel cells.

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Nguyen, Minh Binh; Cohen, Idan; Kumar, Vinod; Xu, Zijian; Bar, Carmit; Dauber-Decker, Katherine L; Tsai, Pai-Chi; Marangoni, Pauline; Klein, Ophir D; Hsu, Ya-Chieh; Chen, Ting; Mikkola, Marja L; Ezhkova, Elena

2018-06-13

Merkel cells are innervated mechanosensory cells responsible for light-touch sensations. In murine dorsal skin, Merkel cells are located in touch domes and found in the epidermis around primary hairs. While it has been shown that Merkel cells are skin epithelial cells, the progenitor cell population that gives rise to these cells is unknown. Here, we show that during embryogenesis, SOX9-positive (+) cells inside hair follicles, which were previously known to give rise to hair follicle stem cells (HFSCs) and cells of the hair follicle lineage, can also give rise to Merkel Cells. Interestingly, while SOX9 is critical for HFSC specification, it is dispensable for Merkel cell formation. Conversely, FGFR2 is required for Merkel cell formation but is dispensable for HFSCs. Together, our studies uncover SOX9(+) cells as precursors of Merkel cells and show the requirement for FGFR2-mediated epithelial signalling in Merkel cell specification.

Investigation of hair dye deposition, hair color loss, and hair damage during multiple oxidative dyeing and shampooing cycles.

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Zhang, Guojin; McMullen, Roger L; Kulcsar, Lidia

2016-01-01

Color fastness is a major concern for consumers and manufacturers of oxidative hair dye products. Hair dye loss results from multiple wash cycles in which the hair dye is dissolved by water and leaches from the hair shaft. In this study, we carried out a series of measurements to help us better understand the kinetics of the leaching process and pathways associated with its escape from the fiber. Hair dye leaching kinetics was measured by suspending hair in a dissolution apparatus and monitoring the dye concentration in solution (leached dye) with an ultraviolet-visible spectrophotometer. The physical state of dye deposited in hair fibers was evaluated by a reflectance light microscopy technique, based on image stacking, allowing enhanced depth of field imaging. The dye distribution within the fiber was monitored by infrared spectroscopic imaging of hair fiber cross sections. Damage to the ultrafine structure of the hair cuticle (surface, endocuticle, and cell membrane complex) and cortex (cell membrane complex) was determined in hair cross sections and on the hair fiber surface with atomic force microscopy. Using differential scanning calorimetry, we investigated how consecutive coloring and leaching processes affect the internal proteins of hair. Further, to probe the surface properties of hair we utilized contact angle measurements. This study was conducted on both pigmented and nonpigmented hair to gain insight into the influence of melanin on the hair dye deposition and leaching processes. Both types of hair were colored utilizing a commercial oxidative hair dye product based on pyrazole chemistry.

The Hair Follicle: An Underutilized Source of Cells and Materials for Regenerative Medicine.

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Kiani, Mehrdad T; Higgins, Claire A; Almquist, Benjamin D

2018-04-09

The hair follicle is one of only two structures within the adult body that selectively degenerates and regenerates, making it an intriguing organ to study and use for regenerative medicine. Hair follicles have been shown to influence wound healing, angiogenesis, neurogenesis, and harbor distinct populations of stem cells; this has led to cells from the follicle being used in clinical trials for tendinosis and chronic ulcers. In addition, keratin produced by the follicle in the form of a hair fiber provides an abundant source of biomaterials for regenerative medicine. In this review, we provide an overview of the structure of a hair follicle, explain the role of the follicle in regulating the microenvironment of skin and the impact on wound healing, explore individual cell types of interest for regenerative medicine, and cover several applications of keratin-based biomaterials.

Gene therapy in the inner ear using adenovirus vectors.

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Husseman, Jacob; Raphael, Yehoash

2009-01-01

Therapies for the protection and regeneration of auditory hair cells are of great interest given the significant monetary and lifestyle impact of hearing loss. The past decade has seen tremendous advances in the use of adenoviral vectors to achieve these aims. Preliminary data demonstrated the functional capacity of this technique as adenoviral-induced expression of neurotrophic and growth factors protected hair cells and spiral ganglion neurons from ototoxic insults. Subsequent efforts confirmed the feasibility of adenoviral transfection of cells in the auditory neuroepithelium via cochleostomy into the scala media. Most recently, efforts have focused on regeneration of depleted hair cells. Mammalian hearing loss is generally considered a permanent insult as the auditory epithelium lacks a basal layer capable of producing new hair cells. Recently, the transcription factor Atoh1 has been found to play a critical role in hair cell differentiation. Adenoviral-mediated overexpression of Atoh1 in culture and in vivo have shown the ability to regenerate auditory and vestibular hair cells by causing transdifferentiation of neighboring epithelial-supporting cells. Functional recovery of both the auditory and vestibular systems has been documented following adenoviral induced Atoh1 overexpression. Copyright (c) 2009 S. Karger AG, Basel.

ROOT HAIR DEFECTIVE SIX-LIKE Class I Genes Promote Root Hair Development in the Grass Brachypodium distachyon.

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Chul Min Kim

2016-08-01

Full Text Available Genes encoding ROOT HAIR DEFECTIVE SIX-LIKE (RSL class I basic helix loop helix proteins are expressed in future root hair cells of the Arabidopsis thaliana root meristem where they positively regulate root hair cell development. Here we show that there are three RSL class I protein coding genes in the Brachypodium distachyon genome, BdRSL1, BdRSL2 and BdRSL3, and each is expressed in developing root hair cells after the asymmetric cell division that forms root hair cells and hairless epidermal cells. Expression of BdRSL class I genes is sufficient for root hair cell development: ectopic overexpression of any of the three RSL class I genes induces the development of root hairs in every cell of the root epidermis. Expression of BdRSL class I genes in root hairless Arabidopsis thaliana root hair defective 6 (Atrhd6 Atrsl1 double mutants, devoid of RSL class I function, restores root hair development indicating that the function of these proteins has been conserved. However, neither AtRSL nor BdRSL class I genes is sufficient for root hair development in A. thaliana. These data demonstrate that the spatial pattern of class I RSL activity can account for the pattern of root hair cell differentiation in B. distachyon. However, the spatial pattern of class I RSL activity cannot account for the spatial pattern of root hair cells in A. thaliana. Taken together these data indicate that that the functions of RSL class I proteins have been conserved among most angiosperms-monocots and eudicots-despite the dramatically different patterns of root hair cell development.

Inositol bisphosphate and inositol trisphosphate inhibit cell-to-cell passage of carboxyfluorescein in staminal hairs ofSetcreasea purpurea.

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Tucker, E B

1988-06-01

pH-buffered carboxyfluorescein (Buffered-CF) alone (control), or Buffered-CF solutions containing one of the following: (1)D-myo-inositol (I); (2)D-myo-inositol 2-monophosphate (IP1); (3)D-myo-inositol 1,4-bisphosphate (IP2); (4)D-myo-inositol 1,4,5-trisphosphate (IP3); (5)D-fructose 2,6-diphosphate (F-2,6P2) were microinjected into the terminal cells of staminal hairs ofSetcreasea purpurea Boom. Passage of the CF from this terminal cell along the chain of cells towards the filament was monitored for 5 min using fluorescence microscopy and quantified using computer-assisted fluorescence-intensity video analysis. Cell-to-cell transport of CF in hairs microinjected with Buffered-CF containing either I, IP1 or F-2,6P2 was similar to that in hairs microinjected with Buffered-CF only. On the other hand, cell-to-cell transport of CF in hairs microinjected with Buffered-CF containing either IP2 or IP3 was inhibited. These results indicate that polyphosphoinositols may be involved in the regulation of intercellular transport of low-molecular-weight, hydrophilic molecules in plants.

Developing an active artificial hair cell using nonlinear feedback control

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Joyce, Bryan S.; Tarazaga, Pablo A.

2015-09-01

The hair cells in the mammalian cochlea convert sound-induced vibrations into electrical signals. These cells have inspired a variety of artificial hair cells (AHCs) to serve as biologically inspired sound, fluid flow, and acceleration sensors and could one day replace damaged hair cells in humans. Most of these AHCs rely on passive transduction of stimulus while it is known that the biological cochlea employs active processes to amplify sound-induced vibrations and improve sound detection. In this work, an active AHC mimics the active, nonlinear behavior of the cochlea. The AHC consists of a piezoelectric bimorph beam subjected to a base excitation. A feedback control law is used to reduce the linear damping of the beam and introduce a cubic damping term which gives the AHC the desired nonlinear behavior. Model and experimental results show the AHC amplifies the response due to small base accelerations, has a higher frequency sensitivity than the passive system, and exhibits a compressive nonlinearity like that of the mammalian cochlea. This bio-inspired accelerometer could lead to new sensors with lower thresholds of detection, improved frequency sensitivities, and wider dynamic ranges.

The delayed rectifier, IKI, is the major conductance in type I vestibular hair cells across vestibular end organs

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Ricci, A. J.; Rennie, K. J.; Correia, M. J.

1996-01-01

Hair cells were dissociated from the semicircular canal, utricle, lagena and saccule of white king pigeons. Type I hair cells were identified morphologically based on the ratios of neck width to cuticular plate width (NPR rectifier characterized previously in semicircular canal hair cells as IKI.

S-nitrosoglutathione promotes cell wall remodelling, alters the transcriptional profile and induces root hair formation in the hairless root hair defective 6 (rhd6) mutant of Arabidopsis thaliana.

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Moro, Camila Fernandes; Gaspar, Marilia; da Silva, Felipe Rodrigues; Pattathil, Sivakumar; Hahn, Michael G; Salgado, Ione; Braga, Marcia Regina

2017-03-01

Nitric oxide (NO) exerts pleiotropic effects on plant development; however, its involvement in cell wall modification during root hair formation (RHF) has not yet been addressed. Here, mutants of Arabidopsis thaliana with altered root hair phenotypes were used to assess the involvement of S-nitrosoglutathione (GSNO), the primary NO source, in cell wall dynamics and gene expression in roots induced to form hairs. GSNO and auxin restored the root hair phenotype of the hairless root hair defective 6 (rhd6) mutant. A positive correlation was observed between increased NO production and RHF induced by auxin in rhd6 and transparent testa glabra (ttg) mutants. Deposition of an epitope within rhamnogalacturonan-I recognized by the CCRC-M2 antibody was delayed in root hair cells (trichoblasts) compared with nonhair cells (atrichoblasts). GSNO, but not auxin, restored the wild-type root glycome and transcriptome profiles in rhd6, modulating the expression of a large number of genes related to cell wall composition and metabolism, as well as those encoding ribosomal proteins, DNA and histone-modifying enzymes and proteins involved in post-translational modification. Our results demonstrate that NO plays a key role in cell wall remodelling in trichoblasts and suggest that it also participates in chromatin modification in root cells of A. thaliana. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Ca(2+) currents and voltage responses in Type I and Type II hair cells of the chick embryo semicircular canal.

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Masetto, Sergio; Zampini, Valeria; Zucca, Giampiero; Valli, Paolo

2005-11-01

Type I and Type II hair cells, and Type II hair cells located in different zones of the semicircular canal crista, express different patterns of voltage-dependent K channels, each one specifically shaping the hair cell receptor potential. We report here that, close to hatching, chicken embryo semicircular canal Type I and Type II hair cells express a similar voltage-dependent L-type calcium current (I(Ca)), whose main features are: activation above -60 mV, fast activation kinetics, and scarce inactivation. I(Ca) should be already active at rest in Zone 1 Type II hair cells, whose resting membrane potential was on average slightly less negative than -60 mV. Conversely, I(Ca) would not be active at rest in Type II hair cells from Zone 2 and 3, nor in Type I hair cells, since their resting membrane potential was significantly more negative than -60 mV. However, even small depolarising currents would activate I(Ca) steadily in Zone 2 and 3 Type II hair cells, but not in Type I hair cells because of the robust repolarising action of their specific array of K(+) currents. The implications of the present findings in the afferent discharge are discussed.

Minoxidil Promotes Hair Growth through Stimulation of Growth Factor Release from Adipose-Derived Stem Cells

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Nahyun Choi

2018-02-01

Full Text Available Minoxidil directly promotes hair growth via the stimulation of dermal papilla (DP and epithelial cells. Alternatively, there is little evidence for indirect promotion of hair growth via stimulation of adipose-derived stem cells (ASCs. We investigated whether minoxidil stimulates ASCs and if increased growth factor secretion by ASCs facilitates minoxidil-induced hair growth. Telogen-to-anagen induction was examined in mice. Cultured DP cells and vibrissae hair follicle organ cultures were used to further examine the underlying mechanisms. Subcutaneous injection of minoxidil-treated ASCs accelerated telogen-to-anagen transition in mice, and increased hair weight at day 14 post-injection. Minoxidil did not alter ASC proliferation, but increased migration and tube formation. Minoxidil also increased the secretion of growth factors from ASCs, including chemokine (C-X-C motif ligand 1 (CXCL1, platelet-derived endothelial cell growth factor (PD-ECGF, and platelet-derived growth factor-C (PDGF-C. Minoxidil increased extracellular signal–regulated kinases 1/2 (ERK1/2 phosphorylation, and concomitant upregulation of PD-ECGF and PDGF-C mRNA levels were attenuated by an ERK inhibitor. Subcutaneous injection of CXCL1, PD-ECGF, or PDGF-C enhanced anagen induction in mice, and both CXCL1 and PDGF-C increased hair length in ex vivo organ culture. Treatment with CXCL1, PD-ECGF, or PDGF-C also increased the proliferation index in DP cells. Finally, topical application of CXCL1, PD-ECGF, or PDGF-C with 2% minoxidil enhanced anagen induction when compared to minoxidil alone. Minoxidil stimulates ASC motility and increases paracrine growth factor signaling. Minoxidil-stimulated secretion of growth factors by ASCs may enhance hair growth by promoting DP proliferation. Therefore, minoxidil can be used as an ASC preconditioning agent for hair regeneration.

Minoxidil Promotes Hair Growth through Stimulation of Growth Factor Release from Adipose-Derived Stem Cells

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Choi, Nahyun; Shin, Soyoung; Song, Sun U.; Sung, Jong-Hyuk

2018-01-01

Minoxidil directly promotes hair growth via the stimulation of dermal papilla (DP) and epithelial cells. Alternatively, there is little evidence for indirect promotion of hair growth via stimulation of adipose-derived stem cells (ASCs). We investigated whether minoxidil stimulates ASCs and if increased growth factor secretion by ASCs facilitates minoxidil-induced hair growth. Telogen-to-anagen induction was examined in mice. Cultured DP cells and vibrissae hair follicle organ cultures were used to further examine the underlying mechanisms. Subcutaneous injection of minoxidil-treated ASCs accelerated telogen-to-anagen transition in mice, and increased hair weight at day 14 post-injection. Minoxidil did not alter ASC proliferation, but increased migration and tube formation. Minoxidil also increased the secretion of growth factors from ASCs, including chemokine (C-X-C motif) ligand 1 (CXCL1), platelet-derived endothelial cell growth factor (PD-ECGF), and platelet-derived growth factor-C (PDGF-C). Minoxidil increased extracellular signal–regulated kinases 1/2 (ERK1/2) phosphorylation, and concomitant upregulation of PD-ECGF and PDGF-C mRNA levels were attenuated by an ERK inhibitor. Subcutaneous injection of CXCL1, PD-ECGF, or PDGF-C enhanced anagen induction in mice, and both CXCL1 and PDGF-C increased hair length in ex vivo organ culture. Treatment with CXCL1, PD-ECGF, or PDGF-C also increased the proliferation index in DP cells. Finally, topical application of CXCL1, PD-ECGF, or PDGF-C with 2% minoxidil enhanced anagen induction when compared to minoxidil alone. Minoxidil stimulates ASC motility and increases paracrine growth factor signaling. Minoxidil-stimulated secretion of growth factors by ASCs may enhance hair growth by promoting DP proliferation. Therefore, minoxidil can be used as an ASC preconditioning agent for hair regeneration. PMID:29495622

The structural and functional differentiation of hair cells in a lizard's basilar papilla suggests an operational principle of amniote cochleas.

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Chiappe, M Eugenia; Kozlov, Andrei S; Hudspeth, A J

2007-10-31

The hair cells in the mammalian cochlea are of two distinct types. Inner hair cells are responsible for transducing mechanical stimuli into electrical responses, which they forward to the brain through a copious afferent innervation. Outer hair cells, which are thought to mediate the active process that sensitizes and tunes the cochlea, possess a negligible afferent innervation. For every inner hair cell, there are approximately three outer hair cells, so only one-quarter of the hair cells directly deliver information to the CNS. Although this is a surprising feature for a sensory system, the occurrence of a similar innervation pattern in birds and crocodilians suggests that the arrangement has an adaptive value. Using a lizard with highly developed hearing, the tokay gecko, we demonstrate in the present study that the same principle operates in a third major group of terrestrial animals. We propose that the differentiation of hair cells into signaling and amplifying classes reflects incompatible strategies for the optimization of mechanoelectrical transduction and of an active process based on active hair-bundle motility.

Stria vascularis and cochlear hair cell changes in syphilis: A human temporal bone study.

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Hızlı, Ömer; Kaya, Serdar; Hızlı, Pelin; Paparella, Michael M; Cureoglu, Sebahattin

2016-12-01

To observe any changes in stria vascularis and cochlear hair cells in patients with syphilis. We examined 13 human temporal bone samples from 8 patients with syphilis (our syphilis group), as well as 12 histopathologically normal samples from 9 age-matched patients without syphilis (our control group). We compared, between the two groups, the mean area of the stria vascularis (measured with conventional light microscopy connected to a personal computer) and the mean percentage of cochlear hair cell loss (obtained from cytocochleograms). In our syphilis group, only 1 (7.7%) of the 13 samples had precipitate in the endolymphatic or perilymphatic spaces; 8 (61.5%) of the samples revealed the presence of endolymphatic hydrops (4 cochlear, 4 saccular). The mean area of the stria vascularis did not significantly differ, in any turn of the cochlea, between the 2 groups (P>0.1). However, we did find significant differences between the 2 groups in the mean percentage of outer hair cells in the apical turn (Psyphilis group, we observed either complete loss of the organ of Corti or a flattened organ of Corti without any cells in addition to the absence of both outer and inner hair cells. In this study, syphilis led either to complete loss of the organ of Corti or to significant loss of cochlear hair cells, in addition to cochleosaccular hydrops. But the area of the stria vascularis did not change. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Organ-level quorum sensing directs regeneration in hair stem cell populations

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Chen, Chih-Chiang; Wang, Lei; Plikus, Maksim V.; Jiang, Ting Xin; Murray, Philip J.; Ramos, Raul; Guerrero-Juarez, Christian F.; Hughes, Michael W; Lee, Oscar K.; Shi, Songtao; Widelitz, Randall B.; Lander, Arthur D.; Chuong, Cheng Ming

2015-01-01

SUMMARY Coordinated organ behavior is crucial for an effective response to environmental stimuli. By studying regeneration of hair follicles in response to patterned hair removal, we demonstrate that organ-level quorum sensing allows coordinated responses to skin injury. Removing hair at different densities leads to a regeneration of up to 5 times more neighboring, unplucked resting hairs, indicating activation of a collective decision-making process. Through data modeling, the range of the quorum signal was estimated to be on the order of 1 mm, greater than expected for a diffusible molecular cue. Molecular and genetic analysis uncovered a two-step mechanism, where release of CCL2 from injured hairs leads to recruitment of TNF-α secreting macrophages, which accumulate and signal to both plucked and unplucked follicles. By coupling immune response with regeneration, this mechanism allows skin to respond predictively to distress, disregarding mild injury, while meeting stronger injury with full-scale cooperative activation of stem cells. PMID:25860610

Ethanol extract of Piper longum L. attenuates gentamicin-induced hair cell loss in neonatal cochlea cultures.

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Du, Xiao Fei; Song, Jae-Jun; Hong, Seungug; Kim, Jihye

2012-06-01

Piper longum L. (PL), also as known as long pepper, a well-known spice and traditional medicine in Asia and Pacific islands, has been reported to exhibit wide spectrum activity including antioxidant activity. However, little information is available on its protective effect on gentamicin (GM) induced ototoxicity which is commonly regarded as being mediated by reactive oxygen species and reactive nitrogen species. This study was undertaken to investigate the protective effect of PL ethanol extract on gentamicin-induced hair cell loss in neonatal cochlea cultures. Cochlea cultures from postnatal day 2-3 mice were used for analysis of the protective effects of PL against gentamicin-induced hair cell loss by phalloidin staining. E. coil cultures were used to determine whether PL interferes with the antibiotic activity of GM. Nitric oxide (NO)-scavenging activity of PL was also measured in vitro. GM induced significant dose-dependent hair cell loss in cochlea cultures. However, without interfering with the antibiotic activity of GM, PL showed a significant and concentration-dependent protective effect against GM-induced hair cell loss, and hair cells retained their stereocilia well. In addition, PL expressed direct scavenging activity toward NO radical liberated within solution of sodium nitroprusside. These findings demonstrate the protective effect of PL on GM-induced hair cell loss in neonatal cochlea cultures, and suggest that it might be of therapeutic benefit for treatment of GM-induced ototoxicity.

Continuous Hair Cell Turnover in the Inner Ear Vestibular Organs of a Mammal, the Daubenton's Bat (Myotis daubentonii)

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Kirkegaard, M.; Jørgensen, J. M.

In both humans and mice the number of hair cells in the inner ear sensory epithelia declines with age, indicating cell death (Park et al. 1987; Rosenhall 1973). However, recent reports demonstrate the ability of the vestibular sensory epithelia to regenerate after injury (Forge et al. 1993, 1998; Kuntz and Oesterle 1998; Li and Forge 1997; Rubel et al. 1995; Tanyeri et al. 1995). Still, a continuous hair cell turnover in the vestibular epithelia has not previously been demonstrated in mature mammals. Bats are the only flying mammals, and they are known to live to a higher age than animals of equal size. The maximum age of many species is 20years, with average lifespans of 4-6years (Schober and Grimmberger 1989). Further, the young are fully developed and able to fly at the age of 2months, and thus the vestibular organs are thought to be differentiated at that age. Consequently, long-lived mammals such as bats might compensate for the loss of hair cells by producing new hair cells in their postembryonic life. Here we show that the utricular macula of adult Daubenton's bats (more than 6months old) contains innervated immature hair cells as well as apoptotic hair cells, which strongly indicates a continuous turnover of hair cells, as previously demonstrated in birds.

Effect of N-Acetylcysteine in Protecting from Simultaneous Noise and Carbon Monoxide Induced Hair Cell Loss

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Akram Pourbakht

2011-06-01

Full Text Available Background and Aim: N-acetylcysteine, a glutathione precursor and reactive oxygen species scavenger, is reported to be effective in reducing noise-induced hearing loss. Many workers in industry are exposed simultaneously to noise and chemical pollutants such as carbon monoxide. We investigated effectiveness of N-acetylcysteine in protecting the cochlea from simultaneous noise and carbon monoxide damages.Methods: Twelve rabbits were exposed simeltaneously to 100 dB sound pressure level of broad band noise and carbon monoxide 8 hours a day for 5 days. One hour before exposure, experimental group received 325 mg/kg of N-acetylcysteine while normal saline was administered for the control group. The protective effect of N-acetylcysteine was evaluated 3 weeks after exposure by histological assessment of the hair cells.Results: Simultaneous exposure to noise and carbon monoxide resulted in a considerable damage to the outer hair cells; however, the inner hair cells and the pillar cells remained intact. Use of N-acetylcysteine in the experimental group significantly reduced the extent of outer hair cell loss.Conclusion: N-acetylcysteine attenuates simultaneous noise and carbon monoxide induced hair cell damage in rabbits.

Expression and localization of VEGFR-2 in hair follicles during induced hair growth in mice.

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Wu, Xian-Jie; Jing, Jing; Lu, Zhong-Fa; Zheng, Min

2018-06-16

Recently, VEGFR-2 has been detected not only in vascular and lymphatic endothelial cells but also in some non-vascular endothelial cells, particularly human hair follicles, sebaceous glands, and sweat glands. In addition, VEGFR-2 has been confirmed to play direct roles in hair follicle keratinocyte regulation beyond simply angiogenesis. To elucidate whether VEGFR-2 activation plays a role in hair follicle cycling regulation, immunofluorescence of VEGFR-2 expression was performed during hair cycling of the dorsum of the mouse induced by hair plucking. We observed that staining for VEGFR-2 in hair follicles during anagen II and IV was much stronger than during anagen VI, catagen and telogen. During anagen II, intense staining for VEGFR-2 was observed on the keratinocyte strands of the hair follicle. Subsequently, we detected intense staining for VEGFR-2 in the ORS, IRS and hair bulb during anagen IV. Moderate staining for VEGFR-2 was detected in the ORS and hair bulb, but staining was most intense in IRS during anagen VI. During catagen, staining for VEGFR-2 in the IRS remained intense, while staining in the ORS and hair bulb was significantly weakened and was negative in the dermal papilla. During telogen, we detected VEGFR-2 in germ cells, cap, and club hair adjoining the epidermis. In conclusion, VEGFR-2 was expressed on the hair follicles of the dorsum of the mouse and varied in expression on the mouse hair follicles during hair cycling, suggesting that VEGFR-2 may exert roles in hair cycle regulation in hair follicles on the dorsum of mice.

ER stress inhibitor attenuates hearing loss and hair cell death in Cdh23erl/erl mutant mice.

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Hu, Juan; Li, Bo; Apisa, Luke; Yu, Heping; Entenman, Shami; Xu, Min; Stepanyan, Ruben; Guan, Bo-Jhih; Müller, Ulrich; Hatzoglou, Maria; Zheng, Qing Yin

2016-11-24

Hearing loss is one of the most common sensory impairments in humans. Mouse mutant models helped us to better understand the mechanisms of hearing loss. Recently, we have discovered that the erlong (erl) mutation of the cadherin23 (Cdh23) gene leads to hearing loss due to hair cell apoptosis. In this study, we aimed to reveal the molecular pathways upstream to apoptosis in hair cells to exploit more effective therapeutics than an anti-apoptosis strategy. Our results suggest that endoplasmic reticulum (ER) stress is the earliest molecular event leading to the apoptosis of hair cells and hearing loss in erl mice. We also report that the ER stress inhibitor, Salubrinal (Sal), could delay the progression of hearing loss and preserve hair cells. Our results provide evidence that therapies targeting signaling pathways in ER stress development prevent hair cell apoptosis at an early stage and lead to better outcomes than those targeting downstream factors, such as tip-link degeneration and apoptosis.

Role for a Novel Usher Protein Complex in Hair Cell Synaptic Maturation

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Zallocchi, Marisa; Meehan, Daniel T.; Delimont, Duane; Rutledge, Joseph; Gratton, Michael Anne; Flannery, John; Cosgrove, Dominic

2012-01-01

The molecular mechanisms underlying hair cell synaptic maturation are not well understood. Cadherin-23 (CDH23), protocadherin-15 (PCDH15) and the very large G-protein coupled receptor 1 (VLGR1) have been implicated in the development of cochlear hair cell stereocilia, while clarin-1 has been suggested to also play a role in synaptogenesis. Mutations in CDH23, PCDH15, VLGR1 and clarin-1 cause Usher syndrome, characterized by congenital deafness, vestibular dysfunction and retinitis pigmentosa. Here we show developmental expression of these Usher proteins in afferent spiral ganglion neurons and hair cell synapses. We identify a novel synaptic Usher complex comprised of clarin-1 and specific isoforms of CDH23, PCDH15 and VLGR1. To establish the in vivo relevance of this complex, we performed morphological and quantitative analysis of the neuronal fibers and their synapses in the Clrn1−/− mouse, which was generated by incomplete deletion of the gene. These mice showed a delay in neuronal/synaptic maturation by both immunostaining and electron microscopy. Analysis of the ribbon synapses in Ames waltzerav3J mice also suggests a delay in hair cell synaptogenesis. Collectively, these results show that, in addition to the well documented role for Usher proteins in stereocilia development, Usher protein complexes comprised of specific protein isoforms likely function in synaptic maturation as well. PMID:22363448

Role for a novel Usher protein complex in hair cell synaptic maturation.

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Marisa Zallocchi

Full Text Available The molecular mechanisms underlying hair cell synaptic maturation are not well understood. Cadherin-23 (CDH23, protocadherin-15 (PCDH15 and the very large G-protein coupled receptor 1 (VLGR1 have been implicated in the development of cochlear hair cell stereocilia, while clarin-1 has been suggested to also play a role in synaptogenesis. Mutations in CDH23, PCDH15, VLGR1 and clarin-1 cause Usher syndrome, characterized by congenital deafness, vestibular dysfunction and retinitis pigmentosa. Here we show developmental expression of these Usher proteins in afferent spiral ganglion neurons and hair cell synapses. We identify a novel synaptic Usher complex comprised of clarin-1 and specific isoforms of CDH23, PCDH15 and VLGR1. To establish the in vivo relevance of this complex, we performed morphological and quantitative analysis of the neuronal fibers and their synapses in the Clrn1-/- mouse, which was generated by incomplete deletion of the gene. These mice showed a delay in neuronal/synaptic maturation by both immunostaining and electron microscopy. Analysis of the ribbon synapses in Ames waltzer(av3J mice also suggests a delay in hair cell synaptogenesis. Collectively, these results show that, in addition to the well documented role for Usher proteins in stereocilia development, Usher protein complexes comprised of specific protein isoforms likely function in synaptic maturation as well.

Noise-induced and age-related hearing loss:  new perspectives and potential therapies [version 1; referees: 4 approved

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M Charles Liberman

2017-06-01

Full Text Available The classic view of sensorineural hearing loss has been that the primary damage targets are hair cells and that auditory nerve loss is typically secondary to hair cell degeneration. Recent work has challenged that view. In noise-induced hearing loss, exposures causing only reversible threshold shifts (and no hair cell loss nevertheless cause permanent loss of >50% of the synaptic connections between hair cells and the auditory nerve. Similarly, in age-related hearing loss, degeneration of cochlear synapses precedes both hair cell loss and threshold elevation. This primary neural degeneration has remained a “hidden hearing loss” for two reasons: 1 the neuronal cell bodies survive for years despite loss of synaptic connection with hair cells, and 2 the degeneration is selective for auditory nerve fibers with high thresholds. Although not required for threshold detection when quiet, these high-threshold fibers are critical for hearing in noisy environments. Research suggests that primary neural degeneration is an important contributor to the perceptual handicap in sensorineural hearing loss, and it may be key to the generation of tinnitus and other associated perceptual anomalies. In cases where the hair cells survive, neurotrophin therapies can elicit neurite outgrowth from surviving auditory neurons and re-establishment of their peripheral synapses; thus, treatments may be on the horizon.

No Correlates for Somatic Motility in Freeze-Fractured Hair-Cell Membranes of Lizards and Birds

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Köppl, C.; Forge, A.; Manley, G. A.

2003-02-01

It is not known whether active processes in mammals and non-mammals are due to the same underlying mechanism. To address this, we studied the size and density of particles in hair-cell membranes in mammals, in a lizard, the Tokay gecko, and in a bird, the barn owl. We surmised that if the prominent particles described in mammalian outer-hair-cell membranes are responsible for cochlear motility, a similar occurrence in non-mammalian hair cells would argue for similar mechanisms. Particle densities differed, however, substantially from those of mammals, suggesting that non-mammals have no membrane-based motility.

Macrophage-Mediated Glial Cell Elimination in the Postnatal Mouse Cochlea

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LaShardai N. Brown

2017-12-01

Full Text Available Hearing relies on the transmission of auditory information from sensory hair cells (HCs to the brain through the auditory nerve. This relay of information requires HCs to be innervated by spiral ganglion neurons (SGNs in an exclusive manner and SGNs to be ensheathed by myelinating and non-myelinating glial cells. In the developing auditory nerve, mistargeted SGN axons are retracted or pruned and excessive cells are cleared in a process referred to as nerve refinement. Whether auditory glial cells are eliminated during auditory nerve refinement is unknown. Using early postnatal mice of either sex, we show that glial cell numbers decrease after the first postnatal week, corresponding temporally with nerve refinement in the developing auditory nerve. Additionally, expression of immune-related genes was upregulated and macrophage numbers increase in a manner coinciding with the reduction of glial cell numbers. Transient depletion of macrophages during early auditory nerve development, using transgenic CD11bDTR/EGFP mice, resulted in the appearance of excessive glial cells. Macrophage depletion caused abnormalities in myelin formation and transient edema of the stria vascularis. Macrophage-depleted mice also showed auditory function impairment that partially recovered in adulthood. These findings demonstrate that macrophages contribute to the regulation of glial cell number during postnatal development of the cochlea and that glial cells play a critical role in hearing onset and auditory nerve maturation.

The structural and functional differentiation of hair cells in a lizard’s basilar papilla suggests an operational principle of amniote cochleas

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Chiappe, M. Eugenia; Kozlov, Andrei S.; Hudspeth, A. J.

2007-01-01

The hair cells in the mammalian cochlea are of two distinct types. Inner hair cells are responsible for transducing mechanical stimuli into electrical responses, which they forward to the brain through a copious afferent innervation. Outer hair cells, which are thought to mediate the active process that sensitizes and tunes the cochlea, possess a negligible afferent innervation. For every inner hair cell there are approximately three outer hair cells, so only a quarter of the hair cells directly deliver information to the central nervous system. Although this is a surprising feature for a sensory system, the occurrence of a similar innervation pattern in birds and crocodilians suggests that the arrangement has an adaptive value. Using a lizard with highly developed hearing, the tokay gecko, we demonstrate in the present study that the same principle operates in a third major group of terrestrial animals. We propose that the differentiation of hair cells into signaling and amplifying classes reflects incompatible strategies for the optimization of mechanoelectrical transduction and of an active process based on active hair-bundle motility. PMID:17978038

The function and molecular identity of inward rectifier channels in vestibular hair cells of the mouse inner ear

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Levin, Michaela E.

2012-01-01

Inner ear hair cells respond to mechanical stimuli with graded receptor potentials. These graded responses are modulated by a host of voltage-dependent currents that flow across the basolateral membrane. Here, we examine the molecular identity and the function of a class of voltage-dependent ion channels that carries the potassium-selective inward rectifier current known as IK1. IK1 has been identified in vestibular hair cells of various species, but its molecular composition and functional contributions remain obscure. We used quantitative RT-PCR to show that the inward rectifier gene, Kir2.1, is highly expressed in mouse utricle between embryonic day 15 and adulthood. We confirmed Kir2.1 protein expression in hair cells by immunolocalization. To examine the molecular composition of IK1, we recorded voltage-dependent currents from type II hair cells in response to 50-ms steps from −124 to −54 in 10-mV increments. Wild-type cells had rapidly activating inward currents with reversal potentials close to the K+ equilibrium potential and a whole-cell conductance of 4.8 ± 1.5 nS (n = 46). In utricle hair cells from Kir2.1-deficient (Kir2.1−/−) mice, IK1 was absent at all stages examined. To identify the functional contribution of Kir2.1, we recorded membrane responses in current-clamp mode. Hair cells from Kir2.1−/− mice had significantly (P < 0.001) more depolarized resting potentials and larger, slower membrane responses than those of wild-type cells. These data suggest that Kir2.1 is required for IK1 in type II utricle hair cells and contributes to hyperpolarized resting potentials and fast, small amplitude receptor potentials in response to current inputs, such as those evoked by hair bundle deflections. PMID:22496522

Minocycline attenuates streptomycin-induced cochlear hair cell death by inhibiting protein nitration and poly (ADP-ribose) polymerase activation.

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Wang, Ping; Li, Haonan; Yu, Shuyuan; Jin, Peng; Hassan, Abdurahman; Du, Bo

2017-08-24

This study aimed to elucidate the protective effect of minocycline against streptomycin-induced damage of cochlear hair cells and its mechanism. Cochlear membranes were isolated from newborn Wistar rats and randomly divided into control, 500μmol/L streptomycin, 100μmol/L minocycline, and streptomycin and minocycline treatment groups. Hair cell survival was analyzed by detecting the expression of 3-nitrotyrosine (3-NT) in cochlear hair cells by immunofluorescence and an enzyme-linked immunosorbent assay. Expression of 3-NT and inducible nitric oxide synthase (iNOS), and poly (ADP-Ribose) polymerase (PARP) and caspase-3 activation were evaluated by western blotting. The results demonstrated hair cell loss at 24h after streptomycin treatment. No change was found in supporting cells of the cochleae. Minocycline pretreatment improved hair cell survival and significantly reduced the expression of iNOS and 3-NT in cochlear tissues compared with the streptomycin treatment group. PARP and caspase-3 activation was increased in the streptomycin treatment group compared with the control group, and pretreatment with minocycline decreased cleaved PARP and activated caspase-3 expression. Minocycline protected cochlear hair cells from injury caused by streptomycin in vitro. The mechanism underlying the protective effect may be associated with the inhibition of excessive formation of nitric oxide, reduction of the nitration stress reaction, and inhibition of PARP and caspase-3 activation in cochlear hair cells. Combined minocycline therapy can be applied to patients requiring streptomycin treatment. Copyright © 2017. Published by Elsevier B.V.

Transplantation and survival of mouse inner ear progenitor/stem cells in the organ of Corti after cochleostomy of hearing-impaired guinea pigs: preliminary results

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L.C.M. Barboza Jr.

2016-01-01

Full Text Available In mammals, damage to sensory receptor cells (hair cells of the inner ear results in permanent sensorineural hearing loss. Here, we investigated whether postnatal mouse inner ear progenitor/stem cells (mIESCs are viable after transplantation into the basal turns of neomycin-injured guinea pig cochleas. We also examined the effects of mIESC transplantation on auditory functions. Eight adult female Cavia porcellus guinea pigs (250-350g were deafened by intratympanic neomycin delivery. After 7 days, the animals were randomly divided in two groups. The study group (n=4 received transplantation of LacZ-positive mIESCs in culture medium into the scala tympani. The control group (n=4 received culture medium only. At 2 weeks after transplantation, functional analyses were performed by auditory brainstem response measurement, and the animals were sacrificed. The presence of mIESCs was evaluated by immunohistochemistry of sections of the cochlea from the study group. Non-parametric tests were used for statistical analysis of the data. Intratympanic neomycin delivery damaged hair cells and increased auditory thresholds prior to cell transplantation. There were no significant differences between auditory brainstem thresholds before and after transplantation in individual guinea pigs. Some mIESCs were observed in all scalae of the basal turns of the injured cochleas, and a proportion of these cells expressed the hair cell marker myosin VIIa. Some transplanted mIESCs engrafted in the cochlear basilar membrane. Our study demonstrates that transplanted cells survived and engrafted in the organ of Corti after cochleostomy.

Diverse Roles of Axonemal Dyneins in Drosophila Auditory Neuron Function and Mechanical Amplification in Hearing.

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Karak, Somdatta; Jacobs, Julie S; Kittelmann, Maike; Spalthoff, Christian; Katana, Radoslaw; Sivan-Loukianova, Elena; Schon, Michael A; Kernan, Maurice J; Eberl, Daniel F; Göpfert, Martin C

2015-11-26

Much like vertebrate hair cells, the chordotonal sensory neurons that mediate hearing in Drosophila are motile and amplify the mechanical input of the ear. Because the neurons bear mechanosensory primary cilia whose microtubule axonemes display dynein arms, we hypothesized that their motility is powered by dyneins. Here, we describe two axonemal dynein proteins that are required for Drosophila auditory neuron function, localize to their primary cilia, and differently contribute to mechanical amplification in hearing. Promoter fusions revealed that the two axonemal dynein genes Dmdnah3 (=CG17150) and Dmdnai2 (=CG6053) are expressed in chordotonal neurons, including the auditory ones in the fly's ear. Null alleles of both dyneins equally abolished electrical auditory neuron responses, yet whereas mutations in Dmdnah3 facilitated mechanical amplification, amplification was abolished by mutations in Dmdnai2. Epistasis analysis revealed that Dmdnah3 acts downstream of Nan-Iav channels in controlling the amplificatory gain. Dmdnai2, in addition to being required for amplification, was essential for outer dynein arms in auditory neuron cilia. This establishes diverse roles of axonemal dyneins in Drosophila auditory neuron function and links auditory neuron motility to primary cilia and axonemal dyneins. Mutant defects in sperm competition suggest that both dyneins also function in sperm motility.

Gating energies and forces of the mammalian hair cell transducer channel and related hair bundle mechanics

NARCIS (Netherlands)

van Netten, SM; Kros, CJ

2000-01-01

We quantified the molecular energies and forces involved in opening and closing of mechanoelectrical transducer channels in hair cells using a novel generally applicable method. It relies on a thermodynamic description of the free energy of an ion channel in terms of its open probability. The

Hair cosmetics and camouflage technics

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Zahide Eriş Eken

2014-06-01

Full Text Available Hair is composed of a mixture of trace elements in small quantities, proteins, lipids and water. Proteins consist of helical polypeptide amino acid molecules. In the hair cells; polypeptide chains of keratin protein would be organized in filaments. In recent years, hair cosmetics showed a significant change and development. The content of shampoos which is used to cleanse the hair has enhanced significantly. Hair conditioner, hair styling products, pomades, brilliantine, and gloss sprays, hair protective products, camouflage products are most commonly used hair cosmetics. Hair shaping procedures are frequently applied.

Gene therapy restores auditory and vestibular function in a mouse model of Usher syndrome type 1c.

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Pan, Bifeng; Askew, Charles; Galvin, Alice; Heman-Ackah, Selena; Asai, Yukako; Indzhykulian, Artur A; Jodelka, Francine M; Hastings, Michelle L; Lentz, Jennifer J; Vandenberghe, Luk H; Holt, Jeffrey R; Géléoc, Gwenaëlle S

2017-03-01

Because there are currently no biological treatments for hearing loss, we sought to advance gene therapy approaches to treat genetic deafness. We focused on Usher syndrome, a devastating genetic disorder that causes blindness, balance disorders and profound deafness, and studied a knock-in mouse model, Ush1c c.216G>A, for Usher syndrome type IC (USH1C). As restoration of complex auditory and balance function is likely to require gene delivery systems that target auditory and vestibular sensory cells with high efficiency, we delivered wild-type Ush1c into the inner ear of Ush1c c.216G>A mice using a synthetic adeno-associated viral vector, Anc80L65, shown to transduce 80-90% of sensory hair cells. We demonstrate recovery of gene and protein expression, restoration of sensory cell function, rescue of complex auditory function and recovery of hearing and balance behavior to near wild-type levels. The data represent unprecedented recovery of inner ear function and suggest that biological therapies to treat deafness may be suitable for translation to humans with genetic inner ear disorders.

HCN channels are not required for mechanotransduction in sensory hair cells of the mouse inner ear.

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Geoffrey C Horwitz

Full Text Available The molecular composition of the hair cell transduction channel has not been identified. Here we explore the novel hypothesis that hair cell transduction channels include HCN subunits. The HCN family of ion channels includes four members, HCN1-4. They were originally identified as the molecular correlates of the hyperpolarization-activated, cyclic nucleotide gated ion channels that carry currents known as If, IQ or Ih. However, based on recent evidence it has been suggested that HCN subunits may also be components of the elusive hair cell transduction channel. To investigate this hypothesis we examined expression of mRNA that encodes HCN1-4 in sensory epithelia of the mouse inner ear, immunolocalization of HCN subunits 1, 2 and 4, uptake of the transduction channel permeable dye, FM1-43 and electrophysiological measurement of mechanotransduction current. Dye uptake and transduction current were assayed in cochlear and vestibular hair cells of wildtype mice exposed to HCN channel blockers or a dominant-negative form of HCN2 that contained a pore mutation and in mutant mice that lacked HCN1, HCN2 or both. We found robust expression of HCNs 1, 2 and 4 but little evidence that localized HCN subunits in hair bundles, the site of mechanotransduction. Although high concentrations of the HCN antagonist, ZD7288, blocked 50-70% of the transduction current, we found no reduction of transduction current in either cochlear or vestibular hair cells of HCN1- or HCN2- deficient mice relative to wild-type mice. Furthermore, mice that lacked both HCN1 and HCN2 also had normal transduction currents. Lastly, we found that mice exposed to the dominant-negative mutant form of HCN2 had normal transduction currents as well. Taken together, the evidence suggests that HCN subunits are not required for mechanotransduction in hair cells of the mouse inner ear.

Selective deletion of cochlear hair cells causes rapid age-dependent changes in spiral ganglion and cochlear nucleus neurons.

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Tong, Ling; Strong, Melissa K; Kaur, Tejbeer; Juiz, Jose M; Oesterle, Elizabeth C; Hume, Clifford; Warchol, Mark E; Palmiter, Richard D; Rubel, Edwin W

2015-05-20

During nervous system development, critical periods are usually defined as early periods during which manipulations dramatically change neuronal structure or function, whereas the same manipulations in mature animals have little or no effect on the same property. Neurons in the ventral cochlear nucleus (CN) are dependent on excitatory afferent input for survival during a critical period of development. Cochlear removal in young mammals and birds results in rapid death of target neurons in the CN. Cochlear removal in older animals results in little or no neuron death. However, the extent to which hair-cell-specific afferent activity prevents neuronal death in the neonatal brain is unknown. We further explore this phenomenon using a new mouse model that allows temporal control of cochlear hair cell deletion. Hair cells express the human diphtheria toxin (DT) receptor behind the Pou4f3 promoter. Injections of DT resulted in nearly complete loss of organ of Corti hair cells within 1 week of injection regardless of the age of injection. Injection of DT did not influence surrounding supporting cells directly in the sensory epithelium or spiral ganglion neurons (SGNs). Loss of hair cells in neonates resulted in rapid and profound neuronal loss in the ventral CN, but not when hair cells were eliminated at a more mature age. In addition, normal survival of SGNs was dependent on hair cell integrity early in development and less so in mature animals. This defines a previously undocumented critical period for SGN survival. Copyright © 2015 the authors 0270-6474/15/357878-14$15.00/0.

Diffusion tensor imaging of the auditory nerve in patients with acquired single-sided deafness

DEFF Research Database (Denmark)

Vos, Sjoerd; Haakma, Wieke; Versnel, Huib

2015-01-01

following cochlear hair cell loss, and the amount of degeneration may considerably differ between the two ears, also in patients with bilateral deafness. A measure that reflects the nerve's condition would help to assess the best of both nerves and decide accordingly which ear should be implanted......A cochlear implant (CI) can restore hearing in patients with profound sensorineural hearing loss by direct electrical stimulation of the auditory nerve. Therefore, the viability of the auditory nerve is vitally important in successful hearing recovery. However, the nerve typically degenerates...... single-sided sensorineural hearing loss. A specialized acquisition protocol was designed for a 3 T MRI scanner to image the small nerve bundle. The nerve was reconstructed using fiber tractography and DTI metrics - which reflect the nerve's microstructural properties - were computed per tract. Comparing...

Possible biological dosimeters in skin and hair

International Nuclear Information System (INIS)

Potten, C.S.

1986-01-01

The hair follicle, when producing hair, contains rapidly proliferating cells, some of which are very sensitive to radiation. These can be detected by studying the incidence of dead or dying (apoptotic) cells which reach peak yields 12 h after irradiation. The yield of apoptotic cells in the follicle has been studied after various doses. The response is dose-dependent and sensitive down to levels of a few cGy. Any reduction in cell production resulting from mitotic delay or cell death might be expressed as a reduction in the width of the hair. This has been studied and the abnormality referred to as dysplasia of the hair. The fraction of dysplastic hairs is strongly dose dependent over the range 2-10 Gy. More detailed studies using higher magnification and numerous measurements of hair width should make this end-point an even more sensitive assay for radiation exposure. Preliminary measurements on the average width at a critical point along the length of the hair illustrate that doses between 1.0 and 1.5 Gy can be detected. The width of the hair is dose dependent. The length of the affected region of the hair is also probably dose dependent. Estimates for the full reduction in volume of hair should increase the sensitivity further. (orig./MG)

Biotechnology in the Treatment of Sensorineural Hearing Loss: Foundations and Future of Hair Cell Regeneration

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Parker, Mark A.

2011-01-01

Purpose: To provide an overview of the methodologies involved in the field of hair cell regeneration. First, the author provides a tutorial on the biotechnological foundations of this field to assist the reader in the comprehension and interpretation of the research involved in hair cell regeneration. Next, the author presents a review of stem…

Targeted inactivation of integrin-linked kinase in hair follicle stem cells reveals an important modulatory role in skin repair after injury.

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Nakrieko, Kerry-Ann; Rudkouskaya, Alena; Irvine, Timothy S; D'Souza, Sudhir J A; Dagnino, Lina

2011-07-15

Integrin-linked kinase (ILK) is key for normal epidermal morphogenesis, but little is known about its role in hair follicle stem cells and epidermal regeneration. Hair follicle stem cells are important contributors to newly formed epidermis following injury. We inactivated the Ilk gene in the keratin 15--expressing stem cell population of the mouse hair follicle bulge. Loss of ILK expression in these cells resulted in impaired cutaneous wound healing, with substantially decreased wound closure rates. ILK-deficient stem cells produced very few descendants that moved toward the epidermal surface and into the advancing epithelium that covers the wound. Furthermore, those few mutant cells that homed in the regenerated epidermis exhibited a reduced residence time. Paradoxically, ILK-deficient bulge stem cells responded to anagen growth signals and contributed to newly regenerated hair follicles during this phase of hair follicle growth. Thus ILK plays an important modulatory role in the normal contribution of hair follicle stem cell progeny to the regenerating epidermis following injury.

Na+ currents in vestibular type I and type II hair cells of the embryo and adult chicken.

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Masetto, S; Bosica, M; Correia, M J; Ottersen, O P; Zucca, G; Perin, P; Valli, P

2003-08-01

In birds, type I and type II hair cells differentiate before birth. Here we describe that chick hair cells, from the semicircular canals, begin expressing a voltage-dependent Na current (INa) from embryonic day 14 (E14) and continue to express the current up to hatching (E21). During this period, INa was present in most (31/43) type I hair cells irrespective of their position in the crista, in most type II hair cells located far from the planum semilunatum (48/63), but only occasionally in type II hair cells close to the planum semilunatum (2/35). INa activated close to -60 mV, showed fast time- and voltage-dependent activation and inactivation, and was completely, and reversibly, blocked by submicromolar concentrations of tetrodotoxin (Kd = 17 nM). One peculiar property of INa concerns its steady-state inactivation, which is complete at -60 mV (half-inactivating voltage = -96 mV). INa was found in type I and type II hair cells from the adult chicken as well, where it had similar, although possibly not identical, properties and regional distribution. Current-clamp experiments showed that INa could contribute to the voltage response provided that the cell membrane was depolarized from holding potentials more negative than -80 mV. When recruited, INa produced a significant acceleration of the cell membrane depolarization, which occasionally elicited a large rapid depolarization followed by a rapid repolarization (action-potential-like response). Possible physiological roles for INa in the embryo and adult chicken are discussed.

A novel Atoh1 "self-terminating" mouse model reveals the necessity of proper Atoh1 level and duration for hair cell differentiation and viability.

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Ning Pan

Full Text Available Atonal homolog1 (Atoh1 is a bHLH transcription factor essential for inner ear hair cell differentiation. Targeted expression of Atoh1 at various stages in development can result in hair cell differentiation in the ear. However, the level and duration of Atoh1 expression required for proper hair cell differentiation and maintenance remain unknown. We generated an Atoh1 conditional knockout (CKO mouse line using Tg(Atoh1-cre, in which the cre expression is driven by an Atoh1 enhancer element that is regulated by Atoh1 protein to "self-terminate" its expression. The mutant mice show transient, limited expression of Atoh1 in all hair cells in the ear. In the organ of Corti, reduction and delayed deletion of Atoh1 result in progressive loss of almost all the inner hair cells and the majority of the outer hair cells within three weeks after birth. The remaining cells express hair cell marker Myo7a and attract nerve fibers, but do not differentiate normal stereocilia bundles. Some Myo7a-positive cells persist in the cochlea into adult stages in the position of outer hair cells, flanked by a single row of pillar cells and two to three rows of disorganized Deiters cells. Gene expression analyses of Atoh1, Barhl1 and Pou4f3, genes required for survival and maturation of hair cells, reveal earlier and higher expression levels in the inner compared to the outer hair cells. Our data show that Atoh1 is crucial for hair cell mechanotransduction development, viability, and maintenance and also suggest that Atoh1 expression level and duration may play a role in inner vs. outer hair cell development. These genetically engineered Atoh1 CKO mice provide a novel model for establishing critical conditions needed to regenerate viable and functional hair cells with Atoh1 therapy.

Wnt1a maintains characteristics of dermal papilla cells that induce mouse hair regeneration in a 3D preculture system.

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Dong, Liang; Hao, Haojie; Liu, Jiejie; Tong, Chuan; Ti, Dongdong; Chen, Deyun; Chen, Li; Li, Meirong; Liu, Huiling; Fu, Xiaobing; Han, Weidong

2017-05-01

Hair follicle morphogenesis and regeneration depend on intensive but well-orchestrated interactions between epithelial and mesenchymal components. Therefore, an alternative strategy to reproduce the process of epithelial-mesenchymal interaction in vitro could use a 3D system containing appropriate cell populations. The 3D air-liquid culture system for reproducibly generating hair follicles from dissociated epithelial and dermal papilla (DP) cells combined with a collagen-chitosan scaffold is described in this study. Wnt-CM was prepared from the supernatant of Wnt1a-expressing bone marrow mesenchymal stem cells (BM-MSCs) that maintain the hair-inducing gene expression of DP cells. The collagen-chitosan scaffold cells (CCS cells) were constructed using a two-step method by inoculating the Wnt-CM-treated DP cells and epidermal (EP) cells into the CCS. The cells in the air-liquid culture formed dermal condensates and a proliferative cell layer in vitro. The CCS cells were able to induce hair regeneration in nude mice. The results demonstrate that Wnt-CM can maintain the hair induction ability of DP cells in expansion cultures, and this approach can be used for large-scale preparation of CCS cells in vitro to treat hair loss. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Micronucleus frequency in exfoliated buccal cells from hairdresser who expose to hair products

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Koh Hui Yee

2015-06-01

Full Text Available Background: Hairdresser is one of the fastest growing occupations in today’s society. Hairdresser help styling, cutting, colouring, perming, curling, straightening hair and various treatment to customer. Somehow, hairdresser are constantly exposed to chemical substances such as aromatic amines, hydrogen peroxide, thioglycolic acid, formaldehyde in hair products which can cause damage to human’s genome. Micronucleus is one of the effective biomarker for processes associated with the induction of DNA damage. Purpose: The aim of this study was to determine the micronucleus frequencies in buccal mucosa epithelial cells of hairdresser who were exposed to chemical of hair products. Method: This study was conducted on twenty female subjects, who were divided into 2 groups: exposed and non-exposed (control group. All subjects recruited were working in the same beauty salon. Buccal cells were obtained from each individual by using cytobrush. The cells were stained with modified Feulgen-Ronssenback method and counting of micronucleus per 1000 cell was done under light microscope. The data were analyzed using independent t-test and one-way Anova (p<0.05. Result: The result showed a significant difference in micronucleus frequency between 2 groups. There were a significantly increase of micronucleus frequency in hairdressers and increase of  micronucleus frequency with the longer duration of exposure. Conclusion: It concluded that the chemical substances of hair products had affected the micronucleus frequency ofthe epithelial cells in buccal mucosa of hairdressers.

Cyclic dermal BMP signalling regulates stem cell activation during hair regeneration.

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Plikus, Maksim V; Mayer, Julie Ann; de la Cruz, Damon; Baker, Ruth E; Maini, Philip K; Maxson, Robert; Chuong, Cheng-Ming

2008-01-17

In the age of stem cell engineering it is critical to understand how stem cell activity is regulated during regeneration. Hairs are mini-organs that undergo cyclic regeneration throughout adult life, and are an important model for organ regeneration. Hair stem cells located in the follicle bulge are regulated by the surrounding microenvironment, or niche. The activation of such stem cells is cyclic, involving periodic beta-catenin activity. In the adult mouse, regeneration occurs in waves in a follicle population, implying coordination among adjacent follicles and the extrafollicular environment. Here we show that unexpected periodic expression of bone morphogenetic protein 2 (Bmp2) and Bmp4 in the dermis regulates this process. This BMP cycle is out of phase with the WNT/beta-catenin cycle, thus dividing the conventional telogen into new functional phases: one refractory and the other competent for hair regeneration, characterized by high and low BMP signalling, respectively. Overexpression of noggin, a BMP antagonist, in mouse skin resulted in a markedly shortened refractory phase and faster propagation of the regenerative wave. Transplantation of skin from this mutant onto a wild-type host showed that follicles in donor and host can affect their cycling behaviours mutually, with the outcome depending on the equilibrium of BMP activity in the dermis. Administration of BMP4 protein caused the competent region to become refractory. These results show that BMPs may be the long-sought 'chalone' inhibitors of hair growth postulated by classical experiments. Taken together, results presented in this study provide an example of hierarchical regulation of local organ stem cell homeostasis by the inter-organ macroenvironment. The expression of Bmp2 in subcutaneous adipocytes indicates physiological integration between these two thermo-regulatory organs. Our findings have practical importance for studies using mouse skin as a model for carcinogenesis, intra-cutaneous drug

Inexhaustible hair-cell regeneration in young and aged zebrafish

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Filipe Pinto-Teixeira

2015-07-01

Full Text Available Animals have evolved two general strategies to counter injury and maintain physiological function. The most prevalent is protection by isolating vital organs into body cavities. However, protection is not optimal for sensory systems because their external components need to be exposed to the environment to fulfill their receptive function. Thus, a common strategy to maintain sensory abilities against persistent environmental insult involves repair and regeneration. However, whether age or frequent injuries affect the regenerative capacity of sensory organs remains unknown. We have found that neuromasts of the zebrafish lateral line regenerate mechanosensory hair cells after recurrent severe injuries and in adulthood. Moreover, neuromasts can reverse transient imbalances of Notch signaling that result in defective organ proportions during repair. Our results reveal inextinguishable hair-cell regeneration in the lateral line, and suggest that the neuromast epithelium is formed by plastic territories that are maintained by continuous intercellular communication.

A method for culturing human hair follicle cells.

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Weterings, P J; Vermorken, A J; Bloemendal, H

1981-01-01

For the first time a method for culturing human hair follicle cells is described. The bovine eye lens capsule, a basement membrane-like structure, is used as the substrate for the cultures. In a culture medium supplemented with hydrocortisone and insulin about 70% of the original follicles will form growing colonies of diploid keratinocytes.

An allosteric gating model recapitulates the biophysical properties of IK,L expressed in mouse vestibular type I hair cells.

Science.gov (United States)

Spaiardi, Paolo; Tavazzani, Elisa; Manca, Marco; Milesi, Veronica; Russo, Giancarlo; Prigioni, Ivo; Marcotti, Walter; Magistretti, Jacopo; Masetto, Sergio

2017-11-01

Vestibular type I and type II hair cells and their afferent fibres send information to the brain regarding the position and movement of the head. The characteristic feature of type I hair cells is the expression of a low-voltage-activated outward rectifying K + current, I K,L , whose biophysical properties and molecular identity are still largely unknown. In vitro, the afferent nerve calyx surrounding type I hair cells causes unstable intercellular K + concentrations, altering the biophysical properties of I K,L . We found that in the absence of the calyx, I K,L in type I hair cells exhibited unique biophysical activation properties, which were faithfully reproduced by an allosteric channel gating scheme. These results form the basis for a molecular and pharmacological identification of I K,L . Type I and type II hair cells are the sensory receptors of the mammalian vestibular epithelia. Type I hair cells are characterized by their basolateral membrane being enveloped in a single large afferent nerve terminal, named the calyx, and by the expression of a low-voltage-activated outward rectifying K + current, I K,L . The biophysical properties and molecular profile of I K,L are still largely unknown. By using the patch-clamp whole-cell technique, we examined the voltage- and time-dependent properties of I K,L in type I hair cells of the mouse semicircular canal. We found that the biophysical properties of I K,L were affected by an unstable K + equilibrium potential (V eq K + ). Both the outward and inward K + currents shifted V eq K + consistent with K + accumulation or depletion, respectively, in the extracellular space, which we attributed to a residual calyx attached to the basolateral membrane of the hair cells. We therefore optimized the hair cell dissociation protocol in order to isolate mature type I hair cells without their calyx. In these cells, the uncontaminated I K,L showed a half-activation at -79.6 mV and a steep voltage dependence (2.8 mV). I K,L also

Expression and function of scleraxis in the developing auditory system.

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Zoe F Mann

Full Text Available A study of genes expressed in the developing inner ear identified the bHLH transcription factor Scleraxis (Scx in the developing cochlea. Previous work has demonstrated an essential role for Scx in the differentiation and development of tendons, ligaments and cells of chondrogenic lineage. Expression in the cochlea has been shown previously, however the functional role for Scx in the cochlea is unknown. Using a Scx-GFP reporter mouse line we examined the spatial and temporal patterns of Scx expression in the developing cochlea between embryonic day 13.5 and postnatal day 25. Embryonically, Scx is expressed broadly throughout the cochlear duct and surrounding mesenchyme and at postnatal ages becomes restricted to the inner hair cells and the interdental cells of the spiral limbus. Deletion of Scx results in hearing impairment indicated by elevated auditory brainstem response (ABR thresholds and diminished distortion product otoacoustic emission (DPOAE amplitudes, across a range of frequencies. No changes in either gross cochlear morphology or expression of the Scx target genes Col2A, Bmp4 or Sox9 were observed in Scx(-/- mutants, suggesting that the auditory defects observed in these animals may be a result of unidentified Scx-dependent processes within the cochlea.

Resveratrol attenuates CoCl2-induced cochlear hair cell damage through upregulation of Sirtuin1 and NF-κB deacetylation.

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Ping Wang

Full Text Available The goals of this study were to investigate the effects of hypoxia on cochlear hair cell damage, and to explore the role of sirtuin1 in hypoxia-induced hair cell damage. Cochlear organotypic cultures from postnatal day 4 rats were used in this study. Hypoxia was induced by treating cochlear explants with CoCl2. Cochlear cultures were treated with CoCl2 alone or in combination with the sirtuin1 activator resveratrol and the sirtuin1 inhibitor sirtinol. Hair cell damage was identified by phalloidin staining and imaged using scanning electron microscopy. RT-PCR and Western blot analyses were used to detect the expression of sirtuin1 and acetylated nuclear factor-κB (NF-κB. Low concentrations of CoCl2 (100-200 μM did not cause an obvious change in the number and morphology of hair cells, whereas higher concentrations of CoCl2 (300-400 μM induced swelling of hair cells, accompanied by cell loss. Increased sirtuin1 expression was induced by CoCl2 at 100 to 200 μM, but not at 400 μM. NF-κB acetylation was significantly increased in explants treated with 400 μM CoCl2. Pretreatment with resveratrol prevented CoCl2-induced hair cell loss and acetylation of NF-κB. The protective effect of resveratrol was significantly reduced by sirtinol. CoCl2 induces hair cell damage in organotypic cochleae cultures. Resveratrol attenuates CoCl2-induced cochlear hair cell damage possibly via activation of sirtuin1, which deacetylates NF-κB.

Confirming a Role for α9nAChRs and SK Potassium Channels in Type II Hair Cells of the Turtle Posterior Crista

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Xiaorong Xu Parks

2017-11-01

Full Text Available In turtle posterior cristae, cholinergic vestibular efferent neurons (VENs synapse on type II hair cells, bouton afferents innervating type II hair cells, and afferent calyces innervating type I hair cells. Electrical stimulation of VENs releases acetylcholine (ACh at these synapses to exert diverse effects on afferent background discharge including rapid inhibition of bouton afferents and excitation of calyx-bearing afferents. Efferent-mediated inhibition is most pronounced in bouton afferents innervating type II hair cells near the torus, but becomes progressively smaller and briefer when moving longitudinally through the crista toward afferents innervating the planum. Sharp-electrode recordings have inferred that efferent-mediated inhibition of bouton afferents requires the sequential activation of alpha9-containing nicotinic ACh receptors (α9*nAChRs and small-conductance, calcium-dependent potassium channels (SK in type II hair cells. Gradations in the strength of efferent-mediated inhibition across the crista likely reflect variations in α9*nAChRs and/or SK activation in type II hair cells from those different regions. However, in turtle cristae, neither inference has been confirmed with direct recordings from type II hair cells. To address these gaps, we performed whole-cell, patch-clamp recordings from type II hair cells within a split-epithelial preparation of the turtle posterior crista. Here, we can easily visualize and record hair cells while maintaining their native location within the neuroepithelium. Consistent with α9*nAChR/SK activation, ACh-sensitive currents in type II hair cells were inward at hyperpolarizing potentials but reversed near −90 mV to produce outward currents that typically peaked around −20 mV. ACh-sensitive currents were largest in torus hair cells but absent from hair cells near the planum. In current clamp recordings under zero-current conditions, ACh robustly hyperpolarized type II hair cells. ACh

Unravelling hair follicle-adipocyte communication.

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Schmidt, Barbara; Horsley, Valerie

2012-11-01

Here, we explore the established and potential roles for intradermal adipose tissue in communication with hair follicle biology. The hair follicle delves deep into the rich dermal macroenvironment as it grows to maturity where it is surrounded by large lipid-filled adipocytes. Intradermal adipocytes regenerate with faster kinetics than other adipose tissue depots and in parallel with the hair cycle, suggesting an interplay exists between hair follicle cells and adipocytes. While adipocytes have well-established roles in metabolism and energy storage, until recently, they were overlooked as niche cells that provide important growth signals to neighbouring skin cells. We discuss recent data supporting adipocytes as niche cells for the skin and skin pathologies that may be related to alterations in skin adipose tissue defects. © 2012 John Wiley & Sons A/S.

d-Tubocurarine and Berbamine: Alkaloids That Are Permeant Blockers of the Hair Cell's Mechano-Electrical Transducer Channel and Protect from Aminoglycoside Toxicity

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Nerissa K. Kirkwood

2017-09-01

Full Text Available Aminoglycoside antibiotics are widely used for the treatment of life-threatening bacterial infections, but cause permanent hearing loss in a substantial proportion of treated patients. The sensory hair cells of the inner ear are damaged following entry of these antibiotics via the mechano-electrical transducer (MET channels located at the tips of the hair cell's stereocilia. d-Tubocurarine (dTC is a MET channel blocker that reduces the loading of gentamicin-Texas Red (GTTR into rat cochlear hair cells and protects them from gentamicin treatment. Berbamine is a structurally related alkaloid that reduces GTTR labeling of zebrafish lateral-line hair cells and protects them from aminoglycoside-induced cell death. Both compounds are thought to reduce aminoglycoside entry into hair cells through the MET channels. Here we show that dTC (≥6.25 μM or berbamine (≥1.55 μM protect zebrafish hair cells in vivo from neomycin (6.25 μM, 1 h. Protection of zebrafish hair cells against gentamicin (10 μM, 6 h was provided by ≥25 μM dTC or ≥12.5 μM berbamine. Hair cells in mouse cochlear cultures are protected from longer-term exposure to gentamicin (5 μM, 48 h by 20 μM berbamine or 25 μM dTC. Berbamine is, however, highly toxic to mouse cochlear hair cells at higher concentrations (≥30 μM whilst dTC is not. The absence of toxicity in the zebrafish assays prompts caution in extrapolating results from zebrafish neuromasts to mammalian cochlear hair cells. MET current recordings from mouse outer hair cells (OHCs show that both compounds are permeant open-channel blockers, rapidly and reversibly blocking the MET channel with half-blocking concentrations of 2.2 μM (dTC and 2.8 μM (berbamine in the presence of 1.3 mM Ca2+ at −104 mV. Berbamine, but not dTC, also blocks the hair cell's basolateral K+ current, IK,neo, and modeling studies indicate that berbamine permeates the MET channel more readily than dTC. These studies reveal key properties of

Inner hair cell stereocilia movements captured in-situ by a high-speed camera with subpixel image processing

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Wang, Yanli; Puria, Sunil; Steele, Charles R.; Ricci, Anthony J.

2018-05-01

Mechanical stimulation of the stereocilia hair bundles of the inner and outer hair cells (IHCs and OHCs, respectively) drives IHC synaptic release and OHC electromotility. The modes of hair-bundle motion can have a dramatic influence on the electrophysiological responses of the hair cells. The in vivo modes of motion are, however, unknown for both IHC and OHC bundles. In this work, we are developing technology to investigate the in situ hair-bundle motion in excised mouse cochleae, for which the hair bundles of the OHCs are embedded in the tectorial membrane but those of the IHCs are not. Motion is generated by pushing onto the stapes at 1 kHz with a glass probe coupled to a piezo stack, and recorded using a high-speed camera at 10,000 frames per second. The motions of individual IHC stereocilia and the cell boundary are analyzed using 2D and 1D Gaussian fitting algorithms, respectively. Preliminary results show that the IHC bundle moves mainly in the radial direction and exhibits a small degree of splay, and that the stereocilia in the second row move less than those in the first row, even in the same focal plane.

Protective effect of hexane and ethanol extract of piper longum L. On gentamicin-induced hair cell loss in neonatal cultures.

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Yadav, Mukesh Kumar; Choi, June; Song, Jae-Jun

2014-03-01

Gentamicin (GM) is a commonly used aminoglycoside antibiotic that generates free oxygen radicals within the inner ear, which can cause vestibulo-cochlear toxicity and permanent damage to the sensory hair cells and neurons. Piper longum L. (PL) is a well-known spice and traditional medicine in Asia and Pacific islands, which has been reported to exhibit a wide spectrum of activity, including antioxidant activity. In this study, we evaluated the effect of hexane:ethanol (2:8) PL extract (subfraction of PL [SPL] extract) on GM-induced hair cell loss in basal, middle and apical regions in a neonatal cochlea cultures. The protective effects of SPL extract were measured by phalloidin staining of cultures from postnatal day 2-3 mice with GM-induced hair cell loss. The anti-apoptosis activity of SPL extract was measured using double labeling by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and myosin-7a staining. The radical-scavenging activity of SPL extract was assessed using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. SPL extract at a concentration of 1 µg/mL significantly inhibited GM-induced hair cell loss at basal and middle region of cochlea, while 5 µg/mL was effective against apical region hair cell loss. The protective effect of SPL extract was concentration dependent and hair cells retained their stereocilia in explants treated with SPL extract prior to treatment with 0.3 mM GM. SPL extract decreased GM-induced apoptosis of hair cells as assessed by TUNEL staining. The outer hair and inner hair counts were not decreased in SPL extract treated groups in compare to GM treated explants. Additionally, SPL extract showed concentration dependent radical scavenging activity in a DPPH assay. An anti-apoptosis effect and potent radical scavenger activity of SPL extract protects from GM-induced hair cell loss at basal, middle and apical regions in neonatal cochlea cultures.

A central to peripheral progression of cell cycle exit and hair cell differentiation in the developing mouse cristae.

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Slowik, Amber D; Bermingham-McDonogh, Olivia

2016-03-01

The inner ear contains six distinct sensory organs that each maintains some ability to regenerate hair cells into adulthood. In the postnatal cochlea, there appears to be a relationship between the developmental maturity of a region and its ability to regenerate as postnatal regeneration largely occurs in the apical turn, which is the last region to differentiate and mature during development. In the mature cristae there are also regional differences in regenerative ability, which led us to hypothesize that there may be a general relationship between the relative maturity of a region and the regenerative competence of that region in all of the inner ear sensory organs. By analyzing adult mouse cristae labeled embryonically with BrdU, we found that hair cell birth starts in the central region and progresses to the periphery with age. Since the peripheral region of the adult cristae also maintains active Notch signaling and some regenerative competence, these results are consistent with the hypothesis that the last regions to develop retain some of their regenerative ability into adulthood. Further, by analyzing embryonic day 14.5 inner ears we provide evidence for a wave of hair cell birth along the longitudinal axis of the cristae from the central regions to the outer edges. Together with the data from the adult inner ears labeled with BrdU as embryos, these results suggest that hair cell differentiation closely follows cell cycle exit in the cristae, unlike in the cochlea where they are uncoupled. Copyright © 2016 Elsevier Inc. All rights reserved.

Hair Follicle and Sebaceous Gland De Novo Regeneration With Cultured Epidermal Stem Cells and Skin-Derived Precursors.

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Wang, Xiaoxiao; Wang, Xusheng; Liu, Jianjun; Cai, Ting; Guo, Ling; Wang, Shujuan; Wang, Jinmei; Cao, Yanpei; Ge, Jianfeng; Jiang, Yuyang; Tredget, Edward E; Cao, Mengjun; Wu, Yaojiong

2016-12-01

: Stem cell-based organ regeneration is purported to enable the replacement of impaired organs in the foreseeable future. Here, we demonstrated that a combination of cultured epidermal stem cells (Epi-SCs) derived from the epidermis and skin-derived precursors (SKPs) was capable of reconstituting functional hair follicles and sebaceous glands (SG). When Epi-SCs and SKPs were mixed in a hydrogel and implanted into an excisional wound in nude mice, the Epi-SCs formed de novo epidermis along with hair follicles, and SKPs contributed to dermal papilla in the neogenic hair follicles. Notably, a combination of culture-expanded Epi-SCs and SKPs derived from the adult human scalp were sufficient to generate hair follicles and hair. Bone morphogenetic protein 4, but not Wnts, sustained the expression of alkaline phosphatase in SKPs in vitro and the hair follicle-inductive property in vivo when SKPs were engrafted with neonatal epidermal cells into excisional wounds. In addition, Epi-SCs were capable of differentiating into sebocytes and formed de novo SGs, which excreted lipids as do normal SGs. Thus our results indicate that cultured Epi-SCs and SKPs are sufficient to generate de novo hair follicles and SGs, implying great potential to develop novel bioengineered skin substitutes with appendage genesis capacity. In postpartum humans, skin appendages lost in injury are not regenerated, despite the considerable achievement made in skin bioengineering. In this study, transplantation of a combination of culture-expanded epidermal stem cells and skin-derived progenitors from mice and adult humans led to de novo regeneration of functional hair follicles and sebaceous glands. The data provide transferable knowledge for the development of novel bioengineered skin substitutes with epidermal appendage regeneration capacity. ©AlphaMed Press.

Metabolic changes in the auditory cortex in presbycusis demonstrated by MR spectroscopy.

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Profant, Oliver; Balogová, Zuzana; Dezortová, Monika; Wagnerová, Dita; Hájek, Milan; Syka, Josef

2013-08-01

In humans, aging is accompanied by the deterioration of the hearing function--presbycusis. The major etiology for presbycusis is the loss of hair cells in the inner ear; less well known are changes in the central auditory system. Therefore, we used 1H magnetic resonance spectroscopy at 3T tomograph to examine metabolite levels in the auditory cortex of three groups of subjects: young healthy subjects less than 30 years old and subjects older than 65 years either with mild presbycusis corresponding to their age or with expressed presbycusis. Hearing function in all subjects was examined by pure tone audiometry (125-16,000 Hz). Significant differences were found in the concentrations of glutamate and N-acetylaspartate, with lower levels in aged subjects. Lactate was particularly increased in subjects with expressed presbycusis. Significant differences were not found in other metabolites, including GABA, between young and elderly subjects. The results demonstrate that the age-related changes of the inner ear are accompanied by a decrease in the excitatory neurotransmitter glutamate as well as a lactate increase in the auditory cortex that is more expressed in elderly subjects with large hearing threshold shifts. Copyright © 2013 Elsevier Inc. All rights reserved.

Coding of auditory temporal and pitch information by hippocampal individual cells and cell assemblies in the rat.

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Sakurai, Y

2002-01-01

This study reports how hippocampal individual cells and cell assemblies cooperate for neural coding of pitch and temporal information in memory processes for auditory stimuli. Each rat performed two tasks, one requiring discrimination of auditory pitch (high or low) and the other requiring discrimination of their duration (long or short). Some CA1 and CA3 complex-spike neurons showed task-related differential activity between the high and low tones in only the pitch-discrimination task. However, without exception, neurons which showed task-related differential activity between the long and short tones in the duration-discrimination task were always task-related neurons in the pitch-discrimination task. These results suggest that temporal information (long or short), in contrast to pitch information (high or low), cannot be coded independently by specific neurons. The results also indicate that the two different behavioral tasks cannot be fully differentiated by the task-related single neurons alone and suggest a model of cell-assembly coding of the tasks. Cross-correlation analysis among activities of simultaneously recorded multiple neurons supported the suggested cell-assembly model.Considering those results, this study concludes that dual coding by hippocampal single neurons and cell assemblies is working in memory processing of pitch and temporal information of auditory stimuli. The single neurons encode both auditory pitches and their temporal lengths and the cell assemblies encode types of tasks (contexts or situations) in which the pitch and the temporal information are processed.

Implanted hair follicle stem cells form Schwann cells that support repair of severed peripheral nerves

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Amoh, Yasuyuki; Li, Lingna; Campillo, Raul; Kawahara, Katsumasa; Katsuoka, Kensei; Penman, Sheldon; Hoffman, Robert M.

2005-01-01

The hair follicle bulge area is an abundant, easily accessible source of actively growing, pluripotent adult stem cells. Nestin, a protein marker for neural stem cells, also is expressed in follicle stem cells and their immediate, differentiated progeny. The fluorescent protein GFP, whose expression is driven by the nestin regulatory element in transgenic mice, served to mark the follicle cell fate. The pluripotent nestin-driven GFP stem cells are positive for the stem cell marker CD34 but ne...

Hair Follicle Dermal Sheath Derived Cells Improve Islet Allograft Survival without Systemic Immunosuppression

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Xiaojie Wang

2015-01-01

Full Text Available Immunosuppressive drugs successfully prevent rejection of islet allografts in the treatment of type I diabetes. However, the drugs also suppress systemic immunity increasing the risk of opportunistic infection and cancer development in allograft recipients. In this study, we investigated a new treatment for autoimmune diabetes using naturally immune privileged, hair follicle derived, autologous cells to provide localized immune protection of islet allotransplants. Islets from Balb/c mouse donors were cotransplanted with syngeneic hair follicle dermal sheath cup cells (DSCC, group 1 or fibroblasts (FB, group 2 under the kidney capsule of immune-competent, streptozotocin induced, diabetic C57BL/6 recipients. Group 1 allografts survived significantly longer than group 2 (32.2 ± 12.2 versus 14.1 ± 3.3 days, P<0.001 without administration of any systemic immunosuppressive agents. DSCC reduced T cell activation in the renal lymph node, prevented graft infiltrates, modulated inflammatory chemokine and cytokine profiles, and preserved better beta cell function in the islet allografts, but no systemic immunosuppression was observed. In summary, DSCC prolong islet allograft survival without systemic immunosuppression by local modulation of alloimmune responses, enhancing of beta cell survival, and promoting of graft revascularization. This novel finding demonstrates the capacity of easily accessible hair follicle cells to be used as local immunosuppression agents in islet transplantation.

The actin-binding proteins eps8 and gelsolin have complementary roles in regulating the growth and stability of mechanosensory hair bundles of mammalian cochlear outer hair cells.

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Jennifer Olt

Full Text Available Sound transduction depends upon mechanosensitive channels localized on the hair-like bundles that project from the apical surface of cochlear hair cells. Hair bundles show a stair-case structure composed of rows of stereocilia, and each stereocilium contains a core of tightly-packed and uniformly-polarized actin filaments. The growth and maintenance of the stereociliary actin core are dynamically regulated. Recently, it was shown that the actin-binding protein gelsolin is expressed in the stereocilia of outer hair cells (OHCs and in its absence they become long and straggly. Gelsolin is part of a whirlin scaffolding protein complex at the stereocilia tip, which has been shown to interact with other actin regulatory molecules such as Eps8. Here we investigated the physiological effects associated with the absence of gelsolin and its possible overlapping role with Eps8. We found that, in contrast to Eps8, gelsolin does not affect mechanoelectrical transduction during immature stages of development. Moreover, OHCs from gelsolin knockout mice were able to mature into fully functional sensory receptors as judged by the normal resting membrane potential and basolateral membrane currents. Mechanoelectrical transducer current in gelsolin-Eps8 double knockout mice showed a profile similar to that observed in the single mutants for Eps8. We propose that gelsolin has a non-overlapping role with Eps8. While Eps8 is mainly involved in the initial growth of stereocilia in both inner hair cells (IHCs and OHCs, gelsolin is required for the maintenance of mature hair bundles of low-frequency OHCs after the onset of hearing.

Tissue-engineered skin preserving the potential of epithelial cells to differentiate into hair after grafting.

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Larouche, Danielle; Cuffley, Kristine; Paquet, Claudie; Germain, Lucie

2011-03-01

The aim of this study was to evaluate whether tissue-engineered skin produced in vitro was able to sustain growth of hair follicles in vitro and after grafting. Different tissues were designed. Dissociated newborn mouse keratinocytes or newborn mouse hair buds (HBs) were added onto dermal constructs consisting of a tissue-engineered cell-derived matrix elaborated from either newborn mouse or adult human fibroblasts cultured with ascorbic acid. After 7-21 days of maturation at the air-liquid interface, no hair was noticed in vitro. Epidermal differentiation was observed in all tissue-engineered skin. However, human fibroblast-derived tissue-engineered dermis (hD) promoted a thicker epidermis than mouse fibroblast-derived tissue-engineered dermis (mD). In association with mD, HBs developed epithelial cyst-like inclusions presenting outer root sheath-like attributes. In contrast, epidermoid cyst-like inclusions lined by a stratified squamous epithelium were present in tissues composed of HBs and hD. After grafting, pilo-sebaceous units formed and hair grew in skin elaborated from HBs cultured 10-26 days submerged in culture medium in association with mD. However, the number of normal hair follicles decreased with longer culture time. This hair-forming capacity after grafting was not observed in tissues composed of hD overlaid with HBs. These results demonstrate that epithelial stem cells can be kept in vitro in a permissive tissue-engineered dermal environment without losing their potential to induce hair growth after grafting.

Effects of neuroactive steroids on cochlear hair cell death induced by gentamicin.

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Nakamagoe, Mariko; Tabuchi, Keiji; Nishimura, Bungo; Hara, Akira

2011-12-11

As neuroactive steroids, sex steroid hormones have non-reproductive effects. We previously reported that 17β-estradiol (βE2) had protective effects against gentamicin (GM) ototoxicity in the cochlea. In the present study, we examined whether the protective action of βE2 on GM ototoxicity is mediated by the estrogen receptor (ER) and whether other estrogens (17α-estradiol (αE2), estrone (E1), and estriol (E3)) and other neuroactive steroids, dehydroepiandrosterone (DHEA) and progesterone (P), have similar protective effects. The basal turn of the organ of Corti was dissected from Sprague-Dawley rats and cultured in a medium containing 100 μM GM for 48h. The effects of βE2 and ICI 182,780, a selective ER antagonist, were examined. In addition, the effects of other estrogens, DHEA and P were tested using this culture system. Loss of outer hair cells induced by GM exposure was compared among groups. βE2 exhibited a protective effect against GM ototoxicity, but its protective effect was antagonized by ICI 182,780. αE2, E1, and E3 also protected hair cells against gentamicin ototoxicity. DHEA showed a protective effect; however, the addition of ICI 182,780 did not affect hair cell loss. P did not have any effect on GM-induced outer hair cell death. The present findings suggest that estrogens and DHEA are protective agents against GM ototoxicity. The results of the ER antagonist study also suggest that the protective action of βE2 is mediated via ER but that of DHEA is not related to its conversion to estrogen and binding to ER. Further studies on neuroactive steroids may lead to new insights regarding cochlear protection. Copyright © 2011 Elsevier Inc. All rights reserved.

Age-related hair pigment loss.

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Tobin, Desmond J

2015-01-01

Humans are social animals that communicate disproportionately via potent genetic signals imbued in the skin and hair, including racial, ethnic, health, gender, and age status. For the vast majority of us, age-related hair pigment loss becomes the inescapable signal of our disappearing youth. The hair follicle (HF) pigmentary unit is a wonderful tissue for studying mechanisms generally regulating aging, often before this becomes evident elsewhere in the body. Given that follicular melanocytes (unlike those in the epidermis) are regulated by the hair growth cycle, this cycle is likely to impact the process of aging in the HF pigmentary unit. The formal identification of melanocyte stem cells in the mouse skin has spurred a flurry of reports on the potential involvement of melanocyte stem cell depletion in hair graying (i.e., canities). Caution is recommended, however, against simple extrapolation of murine data to humans. Regardless, hair graying in both species is likely to involve an age-related imbalance in the tissue's oxidative stress handling that will impact not only melanogenesis but also melanocyte stem cell and melanocyte homeostasis and survival. There is some emerging evidence that the HF pigmentary unit may have regenerative potential, even after it has begun to produce white hair fibers. It may therefore be feasible to develop strategies to modulate some aging-associated changes to maintain melanin production for longer. © 2015 S. Karger AG, Basel.

3-Deoxysappanchalcone Promotes Proliferation of Human Hair Follicle Dermal Papilla Cells and Hair Growth in C57BL/6 Mice by Modulating WNT/β-Catenin and STAT Signaling

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Kim, Young Eun; Choi, Hyung Chul; Lee, In-Chul; Yuk, Dong Yeon; Lee, Hyosung; Choi, Bu Young

2016-01-01

3-Deoxysappanchalcone (3-DSC) has been reported to possess anti-allergic, antiviral, anti-inflammatory and antioxidant activities. In the present study, we investigated the effects of 3-DSC on the proliferation of human hair follicle dermal papilla cells (HDPCs) and mouse hair growth in vivo. A real-time cell analyzer system, luciferase assay, Western blot and real-time polymerase chain reaction (PCR) were employed to measure the biochemical changes occurring in HDPCs in response to 3-DSC treatment. The effect of 3-DSC on hair growth in C57BL/6 mice was also examined. 3-DSC promoted the proliferation of HDPCs, similar to Tofacitinib, an inhibitor of janus-activated kinase (JAK). 3-DSC promoted phosphorylation of β-catenin and transcriptional activation of the T-cell factor. In addition, 3-DSC potentiated interleukin-6 (IL-6)-induced phosphorylation and subsequent transactivation of signal transducer and activator of transcription-3 (STAT3), thereby increasing the expression of cyclin-dependent kinase-4 (Cdk4), fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF). On the contrary, 3-DSC attenuated STAT6 mRNA expression and IL4-induced STAT6 phosphorylation in HDPCs. Finally, we observed that topical application of 3-DSC promoted the anagen phase of hair growth in C57BL/6 mice. 3-DSC stimulates hair growth possibly by inducing proliferation of follicular dermal papilla cells via modulation of WNT/β-catenin and STAT signaling. PMID:27795451

Neomycin damage and regeneration of hair cells in both mechanoreceptor and electroreceptor lateral line organs of the larval Siberian sturgeon (Acipenser baerii).

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Fan, Chunxin; Zou, Sha; Wang, Jian; Zhang, Bo; Song, Jiakun

2016-05-01

The lateral line found in some amphibians and fishes has two distinctive classes of sensory organs: mechanoreceptors (neuromasts) and electroreceptors (ampullary organs). Hair cells in neuromasts can be damaged by aminoglycoside antibiotics and they will regenerate rapidly afterward. Aminoglycoside sensitivity and the capacity for regeneration have not been investigated in ampullary organs. We treated Siberian sturgeon (Acipenser baerii) larvae with neomycin and observed loss and regeneration of sensory hair cells in both organs by labeling with DASPEI and scanning electron microscopy (SEM). The numbers of sensory hair cells in both organs were reduced to the lowest levels at 6 hours posttreatment (hpt). New sensory hair cells began to appear at 12 hpt and were regenerated completely in 7 days. To reveal the possible mechanism for ampullary hair cell regeneration, we analyzed cell proliferation and the expression of neural placodal gene eya1 during regeneration. Both cell proliferation and eya1 expression were concentrated in peripheral mantle cells and both increased to the highest level at 12 hpt, which is consistent with the time course for regeneration of the ampullary hair cells. Furthermore, we used Texas Red-conjugated gentamicin in an uptake assay following pretreatment with a cation channel blocker (amiloride) and found that entry of the antibiotic was suppressed in both organs. Together, our results indicate that ampullary hair cells in Siberian sturgeon larvae can be damaged by neomycin exposure and they can regenerate rapidly. We suggest that the mechanisms for aminoglycoside uptake and hair cell regeneration are conserved for mechanoreceptors and electroreceptors. J. Comp. Neurol. 524:1443-1456, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

External light activates hair follicle stem cells through eyes via an ipRGC-SCN-sympathetic neural pathway.

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Fan, Sabrina Mai-Yi; Chang, Yi-Ting; Chen, Chih-Lung; Wang, Wei-Hung; Pan, Ming-Kai; Chen, Wen-Pin; Huang, Wen-Yen; Xu, Zijian; Huang, Hai-En; Chen, Ting; Plikus, Maksim V; Chen, Shih-Kuo; Lin, Sung-Jan

2018-06-29

Changes in external light patterns can alter cell activities in peripheral tissues through slow entrainment of the central clock in suprachiasmatic nucleus (SCN). It remains unclear whether cells in otherwise photo-insensitive tissues can achieve rapid responses to changes in external light. Here we show that light stimulation of animals' eyes results in rapid activation of hair follicle stem cells with prominent hair regeneration. Mechanistically, light signals are interpreted by M1-type intrinsically photosensitive retinal ganglion cells (ipRGCs), which signal to the SCN via melanopsin. Subsequently, efferent sympathetic nerves are immediately activated. Increased norepinephrine release in skin promotes hedgehog signaling to activate hair follicle stem cells. Thus, external light can directly regulate tissue stem cells via an ipRGC-SCN autonomic nervous system circuit. Since activation of sympathetic nerves is not limited to skin, this circuit can also facilitate rapid adaptive responses to external light in other homeostatic tissues.

Kölliker’s Organ and the Development of Spontaneous Activity in the Auditory System: Implications for Hearing Dysfunction

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M. W. Nishani Dayaratne

2014-01-01

Full Text Available Prior to the “onset of hearing,” developing cochlear inner hair cells (IHCs and primary auditory neurons undergo experience-independent activity, which is thought to be important in retaining and refining neural connections in the absence of sound. One of the major hypotheses regarding the origin of such activity involves a group of columnar epithelial supporting cells forming Kölliker’s organ, which is only present during this critical period of auditory development. There is strong evidence for a purinergic signalling mechanism underlying such activity. ATP released through connexin hemichannels may activate P2 purinergic receptors in both Kölliker’s organ and the adjacent IHCs, leading to generation of electrical activity throughout the auditory system. However, recent work has suggested an alternative origin, by demonstrating the ability of IHCs to generate this spontaneous activity without activation by ATP. Regardless, developmental abnormalities of Kölliker’s organ may lead to congenital hearing loss, considering that mutations in ion channels (hemichannels, gap junctions, and calcium channels involved in Kölliker’s organ activity share strong links with such types of deafness.

The role of hair cells, cilia and ciliary motility in otolith formation in the zebrafish otic vesicle.

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Stooke-Vaughan, Georgina A; Huang, Peng; Hammond, Katherine L; Schier, Alexander F; Whitfield, Tanya T

2012-05-01

Otoliths are biomineralised structures required for the sensation of gravity, linear acceleration and sound in the zebrafish ear. Otolith precursor particles, initially distributed throughout the otic vesicle lumen, become tethered to the tips of hair cell kinocilia (tether cilia) at the otic vesicle poles, forming two otoliths. We have used high-speed video microscopy to investigate the role of cilia and ciliary motility in otolith formation. In wild-type ears, groups of motile cilia are present at the otic vesicle poles, surrounding the immotile tether cilia. A few motile cilia are also found on the medial wall, but most cilia (92-98%) in the otic vesicle are immotile. In mutants with defective cilia (iguana) or ciliary motility (lrrc50), otoliths are frequently ectopic, untethered or fused. Nevertheless, neither cilia nor ciliary motility are absolutely required for otolith tethering: a mutant that lacks cilia completely (MZovl) is still capable of tethering otoliths at the otic vesicle poles. In embryos with attenuated Notch signalling [mindbomb mutant or Su(H) morphant], supernumerary hair cells develop and otolith precursor particles bind to the tips of all kinocilia, or bind directly to the hair cells' apical surface if cilia are absent [MZovl injected with a Su(H)1+2 morpholino]. However, if the first hair cells are missing (atoh1b morphant), otolith formation is severely disrupted and delayed. Our data support a model in which hair cells produce an otolith precursor-binding factor, normally localised to tether cell kinocilia. We also show that embryonic movement plays a minor role in the formation of normal otoliths.

Bioconversion of Scutellaria baicalensis extract can increase recovery of auditory function in a mouse model of noise-induced hearing loss.

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Rodriguez, Isabel; Hong, Bin Na; Nam, Youn Hee; Kim, Eun Young; Park, Geun Ha; Ji, Min Gun; Kang, Tong Ho

2017-09-01

In noise-induced hearing loss (NIHL), noise exposure damages cochlear sensory hair cells, which lack the capacity to regenerate. Following noise insult, intense metabolic activity occurs, resulting in a cochlear free radical imbalance. Oxidative stress and antioxidant enzyme alterations, including lipoxygenase upregulation, have been linked to chronic inflammation, which contributes to hearing impairment. We previously proposed Scutellaria baicalensis (SB) extract as an alternative therapeutic for preventing NIHL and attributed its pharmacological effects to baicalein. Although baicalein was most effective, its concentration in SB extract is much lower compared to baicalin. In this study, we performed enzymatic bioconversion using an Sumizyme (SM) enzyme to increase baicalein concentration in SB extract and consequently improve its therapeutic efficacy. HPLC analysis revealed that baicalein concentration in SB extract after bioconversion (BSB) was significantly increased. Moreover, BSB-treated mice exhibited significantly improved auditory function compared with control mice and tended to have improved auditory function compared with SB-treated mice. We also demonstrated that BSB effectively stimulates hair cell regeneration compared to SB that did not achieve the same effect in a zebrafish model. Finally, when compared the abilities of SB and BSB to inhibit lipoxygenase (LOX), BSB showed a greater efficacy. Cumulatively, our data suggest that BSB exhibits improved pharmacological properties for treating NIHL compared with SB. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Frequency response for electromotility of isolated outer hair cells of the guinea pig

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Wit, HP; vanDijk, P; Segenhout, HM

1996-01-01

Frequency and impulse responses were determined for isolated guinea pig outer hair cells by electrically stimulating the cells between two wire electrodes with white noise. Cells were attached to the bottom of a small culture dish at one end while the other end was freely moving. Results have the

Cilia-driven fluid flow as an epigenetic cue for otolith biomineralization on sensory hair cells of the inner ear.

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Yu, Xianwen; Lau, Doreen; Ng, Chee Peng; Roy, Sudipto

2011-02-01

Ciliary motility is necessary for many developmental and physiological processes in animals. In zebrafish, motile cilia are thought to be required for the deposition of otoliths, which comprise crystals of protein and calcium carbonate, on hair cells of the inner ear. The identity of the motile cilia and their role in otolith biogenesis, however, remain controversial. Here, we show that the ear vesicle differentiates numerous motile cilia, the spatial distribution of which changes as a function of the expression pattern of the ciliogenic gene foxj1b. By contrast, the hair cells develop immotile kinocilia that serve as static tethers for otolith crystallization. In ears devoid of all cilia, otoliths can form but they are of irregular shapes and sizes and appear to attach instead to the hair cell apical membranes. Moreover, overproduction of motile cilia also disrupts otolith deposition through sustained agitation of the precursor particles. Therefore, the correct spatial and temporal distribution of the motile cilia is crucial for proper otolith formation. Our findings support the view that the hair cells express a binding factor for the otolith precursors, while the motile cilia ensure that the precursors do not sediment prematurely and are efficiently directed towards the hair cells. We also provide evidence that the kinocilia are modified motile cilia that depend on Foxj1b for their differentiation. We propose that in hair cells, a Foxj1b-dependent motile ciliogenic program is altered by the proneural Atoh proteins to promote the differentiation of immotile kinocilia.

Squamous cell carcinoma of the external auditory canal: computed tomography findings in six cases

International Nuclear Information System (INIS)

Gonzalez, Fabio Mota; Paes Junior, Ademar Jose de Oliveira; Tornin, Olger de Souza; Souza, Ricardo Pires de

2005-01-01

Objective: to evaluate the role of computed tomography in the assessment of deep extension of squamous cell carcinoma of the external auditory canal. Materials and methods: in the period between May 1995 and December 2003 six patients with squamous cell carcinoma of the external auditory canal were submitted to computed tomography scan at 'Hospital Heliopolis', Sao Paulo, SP, Brazil, including axial and coronal slices with soft tissue and bone algorithms. Results: thickening of the soft tissue of the external auditory canal was seen in all patients, bone erosion and invasion of the middle ear in five (83.3%), invasion of the mastoid and parotid gland in four (66.7%), invasion of the temporomandibular joint in three (50%), and invasion of the middle cranial fossa, carotid canal and cervical lymph node enlargement in two (33.3%) patients. Conclusion: assessment of deep extension of squamous cell carcinoma of the external auditory canal using computed tomography is useful for clinical staging of the disease allowing better therapeutic planning for these patients. (author)

Early transcriptional response to aminoglycoside antibiotic suggests alternate pathways leading to apoptosis of sensory hair cells in the mouse inner ear

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Neil eSegil

2015-05-01

Full Text Available Aminoglycoside antibiotics are the drug of choice for treating many bacterial infections, but their administration results in hearing loss in nearly one fourth of the patients who receive them. Several biochemical pathways have been implicated in aminoglycoside antibiotic ototoxicity; however, little is known about how hair cells respond to aminoglycoside antibiotics at the transcriptome level. Here we have investigated the genome-wide response to the aminoglycoside antibiotic gentamicin. Using organotypic cultures of the perinatal organ of Corti, we performed RNA sequencing using cDNA libraries obtained from FACS-purified hair cells. Within 3 hours of gentamicin treatment, the messenger RNA level of more than three thousand genes in hair cells changed significantly. Bioinformatic analysis of these changes highlighted several known signal transduction pathways, including the JNK pathway and the NF-κB pathway, in addition to genes involved in the stress response, apoptosis, cell cycle control, and DNA damage repair. In contrast, only 698 genes, mainly involved in cell cycle and metabolite biosynthetic processes, were significantly affected in the non-hair cell population. The gene expression profiles of hair cells in response to gentamicin share a considerable similarity with those previously observed in gentamicin-induced nephrotoxicity. Our findings suggest that previously observed early responses to gentamicin in hair cells in specific signaling pathways are reflected in changes in gene expression. Additionally, the observed changes in gene expression of cell cycle regulatory genes indicate a disruption of the postmitotic state, which may suggest an alternative pathway regulating gentamicin-induced hair cell death. This work provides a more comprehensive view of aminoglycoside antibiotic ototoxicity, and thus contribute to identifying potential pathways or therapeutic targets to alleviate this important side effect of aminoglycoside

Molecular Conversations and the Development of the Hair Follicle and Basal Cell Carcinoma

OpenAIRE

Harris, Pamela Jo; Takebe, Naoko; Ivy, S. Percy

2010-01-01

The understanding of the anatomy and development of fetal and adult hair follicles and molecular study of the major embryonic pathways that regulate the hair follicle have led to exciting discoveries concerning the development of basal cell carcinoma (BCC). These studies have shed light on the major roles of Sonic hedgehog (Shh) signaling and its interactions with the insulin-like growth factor (IGF) axis in BCC development. New work, for example, explores a link between Shh signaling and IGF...

Partial Aminoglycoside Lesions in Vestibular Epithelia Reveal Broad Sensory Dysfunction Associated with Modest Hair Cell Loss and Afferent Calyx Retraction.

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Sultemeier, David R; Hoffman, Larry F

2017-01-01

Although the effects of aminoglycoside antibiotics on hair cells have been investigated for decades, their influences on the dendrites of primary afferent neurons have not been widely studied. This is undoubtedly due to the difficulty in disassociating pathology to dendritic processes from that resulting from loss of the presynaptic hair cell. This was overcome in the present investigation through development of a preparation using Chinchilla laniger that enabled direct perilymphatic infusion. Through this strategy we unmasked gentamicin's potential effects on afferent calyces. The pathophysiology of the vestibular neuroepithelia after post-administration durations of 0.5 through 6 months was assessed using single-neuron electrophysiology, immunohistochemistry, and confocal microscopy. Hair cell densities within cristae central zones (0.5-, 1-, 2-, and 6-months) and utricle peri- and extrastriola (6-months) regions were determined, and damage to calretinin-immunoreactive calyces was quantified. Gentamicin-induced hair cell loss exhibited a profile that reflected elimination of a most-sensitive group by 0.5-months post-administration (18.2%), followed by loss of a second group (20.6%) over the subsequent 5.5 months. The total hair cell loss with this gentamicin dose (approximately 38.8%) was less than the estimated fraction of type I hair cells in the chinchilla's crista central zone (approximately 60%), indicating that viable type I hair cells remained. Extensive lesions to afferent calyces were observed at 0.5-months, though stimulus-evoked modulation was intact at this post-administration time. Widespread compromise to calyx morphology and severe attenuation of stimulus-evoked afferent discharge modulation was found at 1 month post-administration, a condition that persisted in preparations examined through the 6-month post-administration interval. Spontaneous discharge was robust at all post-administration intervals. All calretinin-positive calyces had retracted

Root hair defective4 encodes a phosphatidylinositol-4-phosphate phosphatase required for proper root hair development in Arabidopsis thaliana

NARCIS (Netherlands)

Thole, J.M.; Vermeer, J.E.M.; Zhang, Y.; Gadella, Th.W.J.; Nielsen, E.

2008-01-01

Polarized expansion of root hair cells in Arabidopsis thaliana is improperly controlled in root hair-defective rhd4-1 mutant plants, resulting in root hairs that are shorter and randomly form bulges along their length. Using time-lapse fluorescence microscopy in rhd4-1 root hairs, we analyzed

Three-dimensional architecture of hair-cell linkages as revealedby electron-microscopic tomography

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Auer, Manfred; Koster, Bram; Ziese, Ulrike; Bajaj, Chandrajit; Volkmann, Niels; Wang, Da Neng; Hudspeth, A. James

2006-07-28

The senses of hearing and balance rest upon mechanoelectrical transduction by the hair bundles of hair cells in the inner ear. Located at the apical cellular surface, each hair bundle comprises several tens of stereocilia and a single kinocilium that are interconnected by extracellular proteinaceous links. Using electron-microscopic tomography of bullfrog saccular sensory epithelia, we examined the three-dimensional structures of ankle or basal links, kinociliary links, and tip links. We observed clear differences in the dimensions and appearances of the three links. We found two distinct populations of tip links suggestive of the involvement of two proteins or splice variants. We noted auxiliary links connecting the upper portions of tip links to the taller stereocilia. Tip links and auxiliary links show a tendency to adopt a globular conformation when disconnected from the membrane surface.

Serenoa repens extracts promote hair regeneration and repair of hair loss mouse models by activating TGF-β and mitochondrial signaling pathway.

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Zhu, H-L; Gao, Y-H; Yang, J-Q; Li, J-B; Gao, J

2018-06-01

Plenty of plant extracts have been used for treating hair loss. This study aims to investigate the effects of liposterolic extracts of Serenoa repens (LSESr) on hair cell growth and regeneration of hair, and clarify the associated mechanisms. Human keratinocyte cells (HACAT) were cultured, incubated with dihydrotestosterone (DHT) and treated with LSESr. Cell viability was examined by using 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H- tetrazolium bromide (MTT) assay. Hair loss C57BL/6 mouse model was established by inducing with DHT. Hair growth, density, and thickness were evaluated. Back skin samples were collected and stained with hematoxylin and eosin (HE) assay. B-cell lymphoma-2 (Bcl-2), Bcl-2 associated protein X (Bax), cleaved caspase 3 and transforming growth factor β2 (TGF-β2) were examined using Western blot assay. LSESr treatment significantly increased HACAT cell viabilities compared to DHT-only treated cells (p<0.05). LSESr treatment post injection of DHT significantly converted skin color from pink to gray and increased hair density, weight and thickness compared to DHT-only treated mice (p<0.05). LSESr treatment significantly triggered follicle growth and decreased inflammatory response. LSESr treatment significantly decreased TGF-β2 and cleaved caspase 3 expression of hair loss mouse models compared to that of DHT treated mice (p<0.05). LSESr treatment significantly enhanced Bcl-2 expression and reduced Bax expression compared to that of DHT treated mice (p<0.05). Meanwhile, effects of LSESr were substantial even achieving to the potential of finasteride. LSESr promoted the hair regeneration and repair of hair loss mouse models by activating TGF-β signaling and mitochondrial signaling pathway.

A new path in defining light parameters for hair growth: Discovery and modulation of photoreceptors in human hair follicle.

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Buscone, Serena; Mardaryev, Andrei N; Raafs, Bianca; Bikker, Jan W; Sticht, Carsten; Gretz, Norbert; Farjo, Nilofer; Uzunbajakava, Natallia E; Botchkareva, Natalia V

2017-09-01

Though devices for hair growth based on low levels of light have shown encouraging results, further improvements of their efficacy is impeded by a lack of knowledge on the exact molecular targets that mediate physiological response in skin and hair follicle. The aim of this study was to investigate the expression of selected light-sensitive receptors in the human hair follicle and to study the impact of UV-free blue light on hair growth ex vivo. The expression of Opsin receptors in human skin and hair follicles has been characterized using RT-qPCR and immunofluorescence approaches. The functional significance of Opsin 3 was assessed by silencing its expression in the hair follicle cells followed by a transcriptomic profiling. Proprietary LED-based devices emitting two discrete visible wavelengths were used to access the effects of selected optical parameters on hair growth ex vivo and outer root sheath cells in vitro. The expression of OPN2 (Rhodopsin) and OPN3 (Panopsin, Encephalopsin) was detected in the distinct compartments of skin and anagen hair follicle. Treatment with 3.2 J/cm 2 of blue light with 453 nm central wavelength significantly prolonged anagen phase in hair follicles ex vivo that was correlated with sustained proliferation in the light-treated samples. In contrast, hair follicle treatment with 3.2 J/cm 2 of 689 nm light (red light) did not significantly affect hair growth ex vivo. Silencing of OPN3 in the hair follicle outer root sheath cells resulted in the altered expression of genes involved in the control of proliferation and apoptosis, and abrogated stimulatory effects of blue light (3.2 J/cm 2 ; 453 nm) on proliferation in the outer root sheath cells. We provide the first evidence that (i) OPN2 and OPN3 are expressed in human hair follicle, and (ii) A 453 nm blue light at low radiant exposure exerts a positive effect on hair growth ex vivo, potentially via interaction with OPN3. Lasers Surg. Med. 49:705-718, 2017. © 2017 Wiley

Titrated extract of Centella asiatica increases hair inductive property through inhibition of STAT signaling pathway in three-dimensional spheroid cultured human dermal papilla cells.

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Choi, Yeong Min; An, Sungkwan; Lee, Junwoo; Lee, Jae Ho; Lee, Jae Nam; Kim, Young Sam; Ahn, Kyu Joong; An, In-Sook; Bae, Seunghee

2017-12-01

Dermal papilla (DP) is a pivotal part of hair follicle, and the smaller size of the DP is related with the hair loss. In this study, we investigated the effect of titrated extract of Centella asiatica (TECA) on hair growth inductive property on 3D spheroid cultured human DP cells (HDP cells). Significantly increased effect of TECA on cell viability was only shown in 3D sphered HPD cells, not in 2D cultured HDP cells. Also, TECA treatment increased the sphere size of HDP cells. The luciferase activity of STAT reporter genes and the expression of STAT-targeted genes, SOCS1 and SOCS3, were significantly decreased. Also, TECA treatment increased the expression of the hair growth-related signature genes in 3D sphered HDP cells. Furthermore, TECA led to downregulation of the level of phosphorylated STAT proteins in 3D sphered HDP cells. Overall, TECA activates the potential of hair inductive capacity in HDP cells.

The mechanosensory structure of the hair cell requires clarin-1, a protein encoded by Usher syndrome III causative gene.

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Geng, Ruishuang; Melki, Sami; Chen, Daniel H-C; Tian, Guilian; Furness, David N; Oshima-Takago, Tomoko; Neef, Jakob; Moser, Tobias; Askew, Charles; Horwitz, Geoff; Holt, Jeffrey R; Imanishi, Yoshikazu; Alagramam, Kumar N

2012-07-11

Mutation in the clarin-1 gene (Clrn1) results in loss of hearing and vision in humans (Usher syndrome III), but the role of clarin-1 in the sensory hair cells is unknown. Clarin-1 is predicted to be a four transmembrane domain protein similar to members of the tetraspanin family. Mice carrying null mutation in the clarin-1 gene (Clrn1(-/-)) show loss of hair cell function and a possible defect in ribbon synapse. We investigated the role of clarin-1 using various in vitro and in vivo approaches. We show by immunohistochemistry and patch-clamp recordings of Ca(2+) currents and membrane capacitance from inner hair cells that clarin-1 is not essential for formation or function of ribbon synapse. However, reduced cochlear microphonic potentials, FM1-43 [N-(3-triethylammoniumpropyl)-4-(4-(dibutylamino)styryl) pyridinium dibromide] loading, and transduction currents pointed to diminished cochlear hair bundle function in Clrn1(-/-) mice. Electron microscopy of cochlear hair cells revealed loss of some tall stereocilia and gaps in the v-shaped bundle, although tip links and staircase arrangement of stereocilia were not primarily affected by Clrn1(-/-) mutation. Human clarin-1 protein expressed in transfected mouse cochlear hair cells localized to the bundle; however, the pathogenic variant p.N48K failed to localize to the bundle. The mouse model generated to study the in vivo consequence of p.N48K in clarin-1 (Clrn1(N48K)) supports our in vitro and Clrn1(-/-) mouse data and the conclusion that CLRN1 is an essential hair bundle protein. Furthermore, the ear phenotype in the Clrn1(N48K) mouse suggests that it is a valuable model for ear disease in CLRN1(N48K), the most prevalent Usher syndrome III mutation in North America.

The effect of noise exposure during the developmental period on the function of the auditory system.

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Bureš, Zbyněk; Popelář, Jiří; Syka, Josef

2017-09-01

Recently, there has been growing evidence that development and maturation of the auditory system depends substantially on the afferent activity supplying inputs to the developing centers. In cases when this activity is altered during early ontogeny as a consequence of, e.g., an unnatural acoustic environment or acoustic trauma, the structure and function of the auditory system may be severely affected. Pathological alterations may be found in populations of ribbon synapses of the inner hair cells, in the structure and function of neuronal circuits, or in auditory driven behavioral and psychophysical performance. Three characteristics of the developmental impairment are of key importance: first, they often persist to adulthood, permanently influencing the quality of life of the subject; second, their manifestations are different and sometimes even contradictory to the impairments induced by noise trauma in adulthood; third, they may be 'hidden' and difficult to diagnose by standard audiometric procedures used in clinical practice. This paper reviews the effects of early interventions to the auditory system, in particular, of sound exposure during ontogeny. We summarize the results of recent morphological, electrophysiological, and behavioral experiments, discuss the putative mechanisms and hypotheses, and draw possible consequences for human neonatal medicine and noise health. Copyright © 2016 Elsevier B.V. All rights reserved.

Structural and functional effects of acoustic exposure in goldfish: evidence for tonotopy in the teleost saccule

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Gilley Ronald R

2011-02-01

Full Text Available Abstract Background Mammalian and avian auditory hair cells display tonotopic mapping of frequency along the length of the cochlea and basilar papilla. It is not known whether the auditory hair cells of fishes possess a similar tonotopic organization in the saccule, which is thought to be the primary auditory receptor in teleosts. To investigate this question, we determined the location of hair cell damage in the saccules of goldfish (Carassius auratus following exposure to specific frequencies. Subjects were divided into six groups of six fish each (five treatment groups plus control. The treatment groups were each exposed to one of five tones: 100, 400, 800, 2000, and 4000 Hz at 176 dB re 1 μPa root mean squared (RMS for 48 hours. The saccules of each fish were dissected and labeled with phalloidin in order to visualize hair cell bundles. The hair cell bundles were counted at 19 specific locations in each saccule to determine the extent and location of hair cell damage. In addition to quantification of anatomical injury, hearing tests (using auditory evoked potentials were performed on each fish immediately following sound exposure. Threshold shifts were calculated by subtracting control thresholds from post-sound exposure thresholds. Results All sound-exposed fish exhibited significant hair cell and hearing loss following sound exposure. The location of hair cell loss varied along the length of the saccule in a graded manner with the frequency of sound exposure, with lower and higher frequencies damaging the more caudal and rostral regions of the saccule, respectively. Similarly, fish exposed to lower frequency tones exhibited greater threshold shifts at lower frequencies, while high-frequency tone exposure led to hearing loss at higher frequencies. In general, both hair cell and hearing loss declined as a function of increasing frequency of exposure tone, and there was a significant linear relationship between hair cell loss and hearing

Inhibition of nitrogen-fixing activity of the cyanobiont affects the localization of glutamine synthetase in hair cells of Azolla.

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Uheda, Eiji; Maejima, Kazuhiro

2009-10-15

In the Azolla-Anabaena association, the host plant Azolla efficiently incorporates and assimilates ammonium ions that are released from the nitrogen-fixing cyanobiont, probably via glutamine synthetase (GS; EC 6.3.1.2) in hair cells, which are specialized cells protruding into the leaf cavity. In order to clarify the regulatory mechanism underlying ammonium assimilation in the Azolla-Anabaena association, Azolla plants were grown under an argon environment (Ar), in which the nitrogen-fixing activity of the cyanobiont was inhibited specifically and completely. The localization of GS in hair cells was determined by immunoelectron microscopy and quantitative analysis of immunogold labeling. Azolla plants grew healthily under Ar when nitrogen sources, such as NO(3)(-) and NH(4)(+), were provided in the growth medium. Both the number of cyanobacterial cells per leaf and the heterocyst frequency of the plants under Ar were similar to those of plants in a nitrogen environment (N(2)). In hair cells of plants grown under Ar, regardless of the type of nitrogen source provided, only weak labeling of GS was observed in the cytoplasm and in chloroplasts. In contrast, in hair cells of plants grown under N(2), abundant labeling of GS was observed in both sites. These findings indicate that specific inhibition of the nitrogen-fixing activity of the cyanobiont affects the localization of GS isoenzymes. Ammonium fixed and released by the cyanobiont could stimulate GS synthesis in hair cells. Simultaneously, the abundant GS, probably GS1, in these cells, could assimilate ammonium rapidly.

Expression of EFR3A in the mouse cochlea during degeneration of spiral ganglion following hair cell loss.

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Chen Nie

Full Text Available Retrograde degeneration of spiral ganglion cells in the cochlea following hair cell loss is similar to dying back in pathology. The EFR3A gene has recently been discovered to be involved in the pathogenesis of dying back. The relationship of EFR3A and spiral ganglion degeneration, however, was rarely investigated. In this study, we destroyed the hair cells of the mouse cochlea by co-administration of kanamycin and furosemide and then investigated the EFR3A expression during the induced spiral ganglion cell degeneration. Our results revealed that co-administration of kanamycin and furosemide quickly induced hair cell loss in the C57BL/6J mice and then resulted in progressive degeneration of the spiral ganglion beginning at day 5 following drug administration. The number of the spiral ganglion cells began to decrease at day 15. The expression of EFR3A increased remarkably in the spiral ganglion at day 5 and then decreased to near normal level within the next 10 days. Our study suggested that the change of EFR3A expression in the spiral ganglion was coincident with the time of the spiral ganglion degeneration, which implied that high expression of EFR3A may be important to prompt initiation of spiral ganglion degeneration following hair cell loss.

Loss of Slc4a1b chloride/bicarbonate exchanger function protects mechanosensory hair cells from aminoglycoside damage in the zebrafish mutant persephone.

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Dale W Hailey

Full Text Available Mechanosensory hair cell death is a leading cause of hearing and balance disorders in the human population. Hair cells are remarkably sensitive to environmental insults such as excessive noise and exposure to some otherwise therapeutic drugs. However, individual responses to damaging agents can vary, in part due to genetic differences. We previously carried out a forward genetic screen using the zebrafish lateral line system to identify mutations that alter the response of larval hair cells to the antibiotic neomycin, one of a class of aminoglycoside compounds that cause hair cell death in humans. The persephone mutation confers resistance to aminoglycosides. 5 dpf homozygous persephone mutants are indistinguishable from wild-type siblings, but differ in their retention of lateral line hair cells upon exposure to neomycin. The mutation in persephone maps to the chloride/bicarbonate exchanger slc4a1b and introduces a single Ser-to-Phe substitution in zSlc4a1b. This mutation prevents delivery of the exchanger to the cell surface and abolishes the ability of the protein to import chloride across the plasma membrane. Loss of function of zSlc4a1b reduces hair cell death caused by exposure to the aminoglycosides neomycin, kanamycin, and gentamicin, and the chemotherapeutic drug cisplatin. Pharmacological block of anion transport with the disulfonic stilbene derivatives DIDS and SITS, or exposure to exogenous bicarbonate, also protects hair cells against damage. Both persephone mutant and DIDS-treated wild-type larvae show reduced uptake of labeled aminoglycosides. persephone mutants also show reduced FM1-43 uptake, indicating a potential impact on mechanotransduction-coupled activity in the mutant. We propose that tight regulation of the ionic environment of sensory hair cells, mediated by zSlc4a1b activity, is critical for their sensitivity to aminoglycoside antibiotics.

Age-related hearing loss: Aquaporin 4 gene expression changes in the mouse cochlea and auditory midbrain

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Christensen, Nathan; D'Souza, Mary; Zhu, Xiaoxia; Frisina, Robert D.

2009-01-01

Presbycusis – age-related hearing loss, is the number one communication disorder, and one of the top three chronic medical conditions of our aged population. Aquaporins, particularly aquaporin 4 (Aqp4), are membrane proteins with important roles in water and ion flux across cell membranes, including cells of the inner ear and pathways of the brain used for hearing. To more fully understand the biological bases of presbycusis, 39 CBA mice, a well-studied animal model of presbycusis, underwent non-invasive hearing testing as a function of sound frequency (auditory brainstem response – ABR thresholds, and distortion-product otoacoustic emission – DPOAE magnitudes), and were clustered into four groups based on age and hearing ability. Aqp4 gene expression, as determined by genechip microarray analysis and quantitative real-time PCR, was compared to the young adult control group in the three older groups: middle aged with good hearing, old age with mild presbycusis, and old age with severe presbycusis. Linear regression and ANOVA showed statistically significant changes in Aqp4 gene expression and ABR and DPOAE hearing status in the cochlea and auditory midbrain – inferior colliculus. Down-regulation in the cochlea was seen, and an initial down-, then up-regulation was discovered for the inferior colliculus Aqp4 expression. It is theorized that these changes in Aqp4 gene expression represent an age-related disruption of ion flux in the fluids of the cochlea that are responsible for ionic gradients underlying sound transduction in cochlear hair cells necessary for hearing. In regard to central auditory processing at the level of the auditory midbrain, aquaporin gene expression changes may affect neurotransmitter cycling involving supporting cells, thus impairing complex sound neural processing with age. PMID:19070604

Dose-dependent effects of ouabain on spiral ganglion neurons and Schwann cells in mouse cochlea.

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Zhang, Zhi-Jian; Guan, Hong-Xia; Yang, Kun; Xiao, Bo-Kui; Liao, Hua; Jiang, Yang; Zhou, Tao; Hua, Qing-Quan

2017-10-01

This study aimed in fully investigating the toxicities of ouabain to mouse cochlea and the related cellular environment, and providing an optimal animal model system for cell transplantation in the treatment of auditory neuropathy (AN) and sensorineural hearing loss (SNHL). Different dosages of ouabain were applied to mouse round window. The auditory brainstem responses and distortion product otoacoustic emissions were used to evaluate the cochlear function. The immunohistochemical staining and cochlea surface preparation were performed to detect the spiral ganglion neurons (SGNs), Schwann cells and hair cells. Ouabain at the dosages of 0.5 mM, 1 mM and 3 mM selectively and permanently destroyed SGNs and their functions, while leaving the hair cells relatively intact. Ouabain at 3 mM resulted in the most severe SGNs loss and induced significant loss of Schwann cells started as early as 7 days and with further damages at 14 and 30 days after ouabain exposure. The application of ouabain to mouse round window induces damages of SGNs and Schwann cells in a dose- and time-dependent manner, this study established a reliable and accurate animal model system of AN and SNHL.

Drive mechanisms to the inner and outer hair cell stereocilia

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Maftoon, Nima; Motallebzadeh, Hamid; Guinan, John J.; Puria, Sunil

2018-05-01

It has been long believed that inner hair cell (IHC) stimulation can be gleaned from the classic ter-Kuile shear motion between the reticular lamina (RL) and tectorial membrane (TM). The present study explores this and other IHC stimulation mechanisms using a finite-element-model representation of an organ of Corti (OoC) cross section with fluid-structure interaction. A 3-D model of a cross section of the OoC including soft tissue and the fluid in the sub-tectorial space, tunnel of Corti and above the TM was formulated based on anatomical measurements from the gerbil apical turn. The outer hair cells (OHCs), Deiter's cells and their phalangeal processes are represented as Y-shaped building-block elements. Each of the IHC and OHC bundles is represented by a single sterocilium. Linearized Navier-Stokes equations coupled with linear-elastic equations discretized with tetrahedral elements are solved in the frequency domain. We evaluated the dynamic changes in the OoC motion including sub-tectorial gap dimensions for 0.1 to 10 kHz input frequencies. Calculations show the classic ter-Kuile motion but more importantly they show that the gap-height changes which produce oscillatory radial flow in the subtectorial space. Phase changes in the stereocilia across OHC rows and the IHC are also observed.

Round window administration of gentamicin: a new method for the study of ototoxicity of cochlear hair cells.

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Husmann, K R; Morgan, A S; Girod, D A; Durham, D

1998-11-01

Damage to inner ear sensory hair cells after systemic administration of ototoxic drugs has been documented in humans and animals. Birds have the ability to regenerate new hair cells to replace those damaged by drugs or noise. Unfortunately, the systemic administration of gentamicin damages both ears in a variable fashion with potentially confounding systemic drug effects. We developed a method of direct application of gentamicin to one cochlea of hatchling chickens, allowing the other ear to serve as a within-animal control. We tested variables including the vehicle for application, location of application, dosage, and duration of gentamicin exposure. After 5 or 28 days survival, the percent length damage to the cochlea and regeneration of hair cells was evaluated using scanning electron microscopy. Controls consisted of the opposite unexposed cochlea and additional animals which received saline instead of gentamicin. Excellent damage was achieved using gentamicin-soaked Gelfoam pledgets applied to the round window membrane. The percent length damage could be varied from 15 to 100% by changing the dosage of gentamicin, with exposures as short as 30 min. No damage was observed in control animals. Regeneration of hair cells was observed in both the base and apex by 28 days survival.

Auditory midbrain processing is differentially modulated by auditory and visual cortices: An auditory fMRI study.

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Gao, Patrick P; Zhang, Jevin W; Fan, Shu-Juan; Sanes, Dan H; Wu, Ed X

2015-12-01

The cortex contains extensive descending projections, yet the impact of cortical input on brainstem processing remains poorly understood. In the central auditory system, the auditory cortex contains direct and indirect pathways (via brainstem cholinergic cells) to nuclei of the auditory midbrain, called the inferior colliculus (IC). While these projections modulate auditory processing throughout the IC, single neuron recordings have samples from only a small fraction of cells during stimulation of the corticofugal pathway. Furthermore, assessments of cortical feedback have not been extended to sensory modalities other than audition. To address these issues, we devised blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) paradigms to measure the sound-evoked responses throughout the rat IC and investigated the effects of bilateral ablation of either auditory or visual cortices. Auditory cortex ablation increased the gain of IC responses to noise stimuli (primarily in the central nucleus of the IC) and decreased response selectivity to forward species-specific vocalizations (versus temporally reversed ones, most prominently in the external cortex of the IC). In contrast, visual cortex ablation decreased the gain and induced a much smaller effect on response selectivity. The results suggest that auditory cortical projections normally exert a large-scale and net suppressive influence on specific IC subnuclei, while visual cortical projections provide a facilitatory influence. Meanwhile, auditory cortical projections enhance the midbrain response selectivity to species-specific vocalizations. We also probed the role of the indirect cholinergic projections in the auditory system in the descending modulation process by pharmacologically blocking muscarinic cholinergic receptors. This manipulation did not affect the gain of IC responses but significantly reduced the response selectivity to vocalizations. The results imply that auditory cortical

Isolation of hair follicle bulge stem cells from YFP-expressing reporter mice.

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Nakrieko, Kerry-Ann; Irvine, Timothy S; Dagnino, Lina

2013-01-01

In this article we provide a method to isolate hair follicle stem cells that have undergone targeted gene inactivation. The mice from which these cells are isolated are bred into a Rosa26-yellow fluorescent protein (YFP) reporter background, which results in YFP expression in the targeted stem cell population. These cells are isolated and purified by fluorescence-activated cell sorting, using epidermal stem cell-specific markers in conjunction with YFP fluorescence. The purified cells can be used for gene expression studies, clonogenic experiments, and biological assays, such as viability and capacity for directional migration.

Characterisation of cell cycle arrest and terminal differentiation in a maximally proliferative human epithelial tissue: Lessons from the human hair follicle matrix.

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Purba, Talveen S; Brunken, Lars; Peake, Michael; Shahmalak, Asim; Chaves, Asuncion; Poblet, Enrique; Ceballos, Laura; Gandarillas, Alberto; Paus, Ralf

2017-09-01

Human hair follicle (HF) growth and hair shaft formation require terminal differentiation-associated cell cycle arrest of highly proliferative matrix keratinocytes. However, the regulation of this complex event remains unknown. CIP/KIP family member proteins (p21 CIP1 , p27 KIP1 and p57 KIP2 ) regulate cell cycle progression/arrest, endoreplication, differentiation and apoptosis. Since they have not yet been adequately characterized in the human HF, we asked whether and where CIP/KIP proteins localise in the human hair matrix and pre-cortex in relation to cell cycle activity and HF-specific epithelial cell differentiation that is marked by keratin 85 (K85) protein expression. K85 expression coincided with loss or reduction in cell cycle activity markers, including in situ DNA synthesis (EdU incorporation), Ki-67, phospho-histone H3 and cyclins A and B1, affirming a post-mitotic state of pre-cortical HF keratinocytes. Expression of CIP/KIP proteins was found abundantly within the proliferative hair matrix, concomitant with a role in cell cycle checkpoint control. p21 CIP1 , p27 KIP1 and cyclin E persisted within post-mitotic keratinocytes of the pre-cortex, whereas p57 KIP2 protein decreased but became nuclear. These data imply a supportive role for CIP/KIP proteins in maintaining proliferative arrest, differentiation and anti-apoptotic pathways, promoting continuous hair bulb growth and hair shaft formation in anagen VI. Moreover, post-mitotic hair matrix regions contained cells with enlarged nuclei, and DNA in situ hybridisation showed cells that were >2N in the pre-cortex. This suggests that CIP/KIP proteins might counterbalance cyclin E to control further rounds of DNA replication in a cell population that has a propensity to become tetraploid. These data shed new light on the in situ-biography of human hair matrix keratinocytes on their path of active cell cycling, arrest and terminal differentiation, and showcase the human HF as an excellent, clinically

ILK modulates epithelial polarity and matrix formation in hair follicles.

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Rudkouskaya, Alena; Welch, Ian; Dagnino, Lina

2014-03-01

Hair follicle morphogenesis requires coordination of multiple signals and communication between its epithelial and mesenchymal constituents. Cell adhesion protein platforms, which include integrins and integrin-linked kinase (ILK), are critical for hair follicle formation. However, their precise contribution to this process is poorly understood. We show that in the absence of ILK, the hair follicle matrix lineage fails to develop, likely due to abnormalities in development of apical-basal cell polarity, as well as in laminin-511 and basement membrane assembly at the tip of the hair bud. These defects also result in impaired specification of hair matrix and absence of precortex and inner sheath root cell lineages. The molecular pathways affected in ILK-deficient follicles are similar to those in the absence of epidermal integrin β1 and include Wnt, but not sonic hedgehog, signaling. ILK-deficient hair buds also show abnormalities in the dermal papilla. Addition of exogenous laminin-511 restores morphological and molecular markers associated with hair matrix formation, indicating that ILK regulates hair bud cell polarity and functions upstream from laminin-511 assembly to regulate the developmental progression of hair follicles beyond the germ stage.

Effect of inner and outer hair cell lesions on electrically evoked otoacoustic emissions.

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Reyes, S; Ding, D; Sun, W; Salvi, R

2001-08-01

When the cochlea is stimulated by a sinusoidal current, the inner ear emits an acoustic signal at the stimulus frequency, termed the electrically evoked otoacoustic emission (EEOAE). Recent studies have found EEOAEs in birds lacking outer hair cells (OHCs), raising the possibility that other types of hair cells, including inner hair cells (IHCs), may generate EEOAEs. To determine the relative contribution of IHCs and OHCs to the generation of the EEOAE, we measured the amplitude of EEOAEs, distortion product otoacoustic emissions (DPOAEs), the cochlear microphonic (CM) and the compound action potential (CAP) in normal chinchillas and chinchillas with IHC lesions or IHC plus OHC lesions induced by carboplatin. Selective IHC loss had little or no effect on CM amplitude and caused a slight reduction in mean DPOAE amplitude. However, IHC loss resulted in a massive reduction in CAP amplitude. Importantly, selective IHC lesions did not reduce EEOAE amplitude, but instead, EEOAE amplitude increased at high frequencies. When both IHCs and OHCs were destroyed, the amplitude of the CM, DPOAE and EEOAE all decreased. The increase in EEOAE amplitude seen with IHC loss may be due to (1) loss of tonic efferent activity to the OHCs, (2) change in the mechanical properties of the cochlea or (3) elimination of EEOAEs produced by IHCs in phase opposition to those from OHCs.

Three-dimensional Organotypic Cultures of Vestibular and Auditory Sensory Organs.

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Gnedeva, Ksenia; Hudspeth, A J; Segil, Neil

2018-06-01

The sensory organs of the inner ear are challenging to study in mammals due to their inaccessibility to experimental manipulation and optical observation. Moreover, although existing culture techniques allow biochemical perturbations, these methods do not provide a means to study the effects of mechanical force and tissue stiffness during development of the inner ear sensory organs. Here we describe a method for three-dimensional organotypic culture of the intact murine utricle and cochlea that overcomes these limitations. The technique for adjustment of a three-dimensional matrix stiffness described here permits manipulation of the elastic force opposing tissue growth. This method can therefore be used to study the role of mechanical forces during inner ear development. Additionally, the cultures permit virus-mediated gene delivery, which can be used for gain- and loss-of-function experiments. This culture method preserves innate hair cells and supporting cells and serves as a potentially superior alternative to the traditional two-dimensional culture of vestibular and auditory sensory organs.

Functional anatomy of the hair follicle: The Secondary Hair Germ.

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Panteleyev, Andrey A

2018-07-01

The secondary hair germ (SHG)-a transitory structure in the lower portion of the mouse telogen hair follicle (HF)-is directly involved in anagen induction and eventual HF regrowth. Some crucial aspects of SHG functioning and ontogenetic relations with other HF parts, however, remain undefined. According to recent evidence (in contrast to previous bulge-centric views), the SHG is the primary target of anagen-inducing signalling and a source of both the outer root sheath (ORS) and ascending HF layers during the initial (morphogenetic) anagen subphase. The SHG is comprised of two functionally distinct cell populations. Its lower portion (originating from lower HF cells that survived catagen) forms all ascending HF layers, while the upper SHG (formed by bulge-derived cells) builds up the ORS. The predetermination of SHG cells to a specific morphogenetic fate contradicts their attribution to the "stem cell" category and supports SHG designation as a "germinative" or a "founder" cell population. The mechanisms of this predetermination driving transition of the SHG from "refractory" to the "competent" state during the telogen remain unknown. Functionally, the SHG serves as a barrier, protecting the quiescent bulge stem cell niche from the extensive follicular papilla/SHG signalling milieu. The formation of the SHG is a prerequisite for efficient "precommitment" of these cells and provides for easier sensing and a faster response to anagen-inducing signals. In general, the formation of the SHG is an evolutionary adaptation, which allowed the ancestors of modern Muridae to acquire a specific, highly synchronized pattern of hair cycling. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Trace element distribution in the hair of some sickle cell anemia patients and controls

International Nuclear Information System (INIS)

Oluwole, A.F.; Asubiojo, O.I.; Adekile, A.D.; Filby, R.H.; Bragg, A.; Grimm, C.I.

1990-01-01

Hair samples of some young sickle cell anemia (SCA) and Control patients in Nigeria were analyzed for 12 elements, viz, Se, Hg, Cr, Fe, Zn, Co, Cu, Br, As, Sb, Na, and Sc, using instrumental Neutron Activation Analysis (INAA). With the exception of Cu, which was found to be significantly higher in the hair of SCA patients (at the 0.05 level of the t-test), there were generally no significant differences in elemental concentrations within the two groups. A preliminary study of the elemental contents of the fingernails of the same subjects showed a higher abundance of most of the elements in nail than in hair. These preliminary results were compared with similar studies form some other parts of the world

Serial cultivation of human scalp hair follicle keratinocytes.

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Weterings, P J; Roelofs, H M; Vermorken, A J; Bloemendal, H

1983-01-01

A method is described for the serial cultivation of adult human hair follicle keratinocytes. Plucked scalp hair follicles, placed on bovine eye lens capsules as a growth substrate, give rise to quickly expanding colonies within a few days. After trypsinization, the cells are replated with irradiated 3T3 cells as 'feeders'. Using this combination of techniques the keratinocytes can be subcultured up to four times. In this way about 10(7) keratinocytes can be generated from one single hair follicle. Moreover, the technique enables cryogenic storage of the cells, allowing for instance, convenient transportation. Subcultured hair follicle keratinocytes can be plated on glass coverslips. This allows immunofluorescence studies. The keratin cytoskeletons visualized using an antiserum against human keratin.

Mutations in Three Genes Encoding Proteins Involved in Hair Shaft Formation Cause Uncombable Hair Syndrome

DEFF Research Database (Denmark)

Ü Basmanav, F Buket; Cau, Laura; Tafazzoli, Aylar

2016-01-01

Uncombable hair syndrome (UHS), also known as "spun glass hair syndrome," "pili trianguli et canaliculi," or "cheveux incoiffables" is a rare anomaly of the hair shaft that occurs in children and improves with age. UHS is characterized by dry, frizzy, spangly, and often fair hair that is resistant...... in the majority of UHS case subjects. The two enzymes PADI3 and TGM3, responsible for posttranslational protein modifications, and their target structural protein TCHH are all involved in hair shaft formation. Elucidation of the molecular outcomes of the disease-causing mutations by cell culture experiments...... and tridimensional protein models demonstrated clear differences in the structural organization and activity of mutant and wild-type proteins. Scanning electron microscopy observations revealed morphological alterations in hair coat of Padi3 knockout mice. All together, these findings elucidate the molecular genetic...

Calcium-loaded 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid blocks cell-to-cell diffusion of carboxyfluorescein in staminal hairs of Setcreasea purpurea.

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Tucker, E B

1990-08-01

The effect of microinjected calcium-loaded 1,2-bis(2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid (CaBAPTA) on cell-to-cell diffusion of carboxyfluorescein (CF) was examined in staminal hairs of S. purpurea Boom. The CaBAPTA was microinjected into the cytoplasm of the staminal hairs either with CF or prior to a subsequent microinjection of CF. The cell-to-cell diffusion of CF along the hair was monitored using enhanced-fluorescence video microscopy. Cytoplasmic streaming stopped in cells treated with CaBAPTA, indicating that intracellular Ca(2+) had increased. Cell-to-cell diffusion of CF was blocked in cells treated with Ca-BAPTA. An inhibition of cytoplasmic streaming and cell-to-cell diffusion was observed in the cells adjoining the CaBAPTA-microinjected cell, indicating that the Ca-BAPTA appeared to pass through plasmodesmata. While cytoplasmic streaming resumed 5-10 min after CaBAPTA treatment, cell-to-cell diffusion did not resume until 30-120 min later. These data support an involvement of calcium in the regulation of cell-to-cell communication in plants.

The hair follicle bulge: a niche for adult stem cells.

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Pasolli, Hilda Amalia

2011-08-01

Adult stem cells (SCs) are essential for tissue homeostasis and wound repair. They have the ability to both self-renew and differentiate into multiple cell types. They often reside in specialized microenvironments or niches that preserve their proliferative and tissue regenerative capacity. The murine hair follicle (HF) has a specialized and permanent compartment--the bulge, which safely lodges SCs and provides the necessary molecular cues to regulate their function. The HF undergoes cyclic periods of destruction, regeneration, and rest, making it an excellent system to study SC biology.

Hey2 functions in parallel with Hes1 and Hes5 for mammalian auditory sensory organ development

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Chin Michael T

2008-02-01

Full Text Available Abstract Background During mouse development, the precursor cells that give rise to the auditory sensory organ, the organ of Corti, are specified prior to embryonic day 14.5 (E14.5. Subsequently, the sensory domain is patterned precisely into one row of inner and three rows of outer sensory hair cells interdigitated with supporting cells. Both the restriction of the sensory domain and the patterning of the sensory mosaic of the organ of Corti involve Notch-mediated lateral inhibition and cellular rearrangement characteristic of convergent extension. This study explores the expression and function of a putative Notch target gene. Results We report that a putative Notch target gene, hairy-related basic helix-loop-helix (bHLH transcriptional factor Hey2, is expressed in the cochlear epithelium prior to terminal differentiation. Its expression is subsequently restricted to supporting cells, overlapping with the expression domains of two known Notch target genes, Hairy and enhancer of split homolog genes Hes1 and Hes5. In combination with the loss of Hes1 or Hes5, genetic inactivation of Hey2 leads to increased numbers of mis-patterned inner or outer hair cells, respectively. Surprisingly, the ectopic hair cells in Hey2 mutants are accompanied by ectopic supporting cells. Furthermore, Hey2-/-;Hes1-/- and Hey2-/-;Hes1+/- mutants show a complete penetrance of early embryonic lethality. Conclusion Our results indicate that Hey2 functions in parallel with Hes1 and Hes5 in patterning the organ of Corti, and interacts genetically with Hes1 for early embryonic development and survival. Our data implicates expansion of the progenitor pool and/or the boundaries of the developing sensory organ to account for patterning defects observed in Hey2 mutants.

Hair curvature: a natural dialectic and review.

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Nissimov, Joseph N; Das Chaudhuri, Asit Baran

2014-08-01

Although hair forms (straight, curly, wavy, etc.) are present in apparently infinite variations, each fibre can be reduced to a finite sequence of tandem segments of just three types: straight, bent/curly, or twisted. Hair forms can thus be regarded as resulting from genetic pathways that induce, reverse or modulate these basic curvature modes. However, physical interconversions between twists and curls demonstrate that strict one-to-one correspondences between them and their genetic causes do not exist. Current hair-curvature theories do not distinguish between bending and twisting mechanisms. We here introduce a multiple papillary centres (MPC) model which is particularly suitable to explain twisting. The model combines previously known features of hair cross-sectional morphology with partially/completely separated dermal papillae within single follicles, and requires such papillae to induce differential growth rates of hair cortical material in their immediate neighbourhoods. The MPC model can further help to explain other, poorly understood, aspects of hair growth and morphology. Separate bending and twisting mechanisms would be preferentially affected at the major or minor ellipsoidal sides of fibres, respectively, and together they exhaust the possibilities for influencing hair-form phenotypes. As such they suggest dialectic for hair-curvature development. We define a natural-dialectic (ND) which could take advantage of speculative aspects of dialectic, but would verify its input data and results by experimental methods. We use this as a top-down approach to first define routes by which hair bending or twisting may be brought about and then review evidence in support of such routes. In particular we consider the wingless (Wnt) and mammalian target of rapamycin (mTOR) pathways as paradigm pathways for molecular hair bending and twisting mechanisms, respectively. In addition to the Wnt canonical pathway, the Wnt/Ca(2+) and planar cell polarity (PCP) pathways

Localization of calcium in the sensory cells of the Dionaea trigger hair by laser micro-mass analysis (LAMMA)

International Nuclear Information System (INIS)

Buchen, B.; Schröder, W.H.

1986-01-01

In Dionaea, mechanical bending of the trigger hair induces action potentials which spread over the trap lobes to the motor cells (review Bentrup 1979). The perception of the stimulus and its transformation into a physiological signal occurs in a ring of specialized epidermal cells in the indentation zone of the trigger hair. These sensory cells (Haberlandt 1906) are characterized by a highly evolved ER complex at the apical and the basal cell pole. The ER surrounds several vacuoles containing poly phenols (Buchen et al. 1983). In order to study the function of these cell structures in sensory transduction, we examined the development of the trigger hair (Casser et al. 1985). During its development, a change in the membrane potential could be measured for the first time when the structural polarity of the sensory cell was established. Yet the short action potentials which are necessary for trap closure were fired only if the typical ER complex in the cell poles was visible. Since membrane potential changes are mediated by ions, we tried to identify and to localize ions possibly involved in these processes. Here we present the first results

Single-channel L-type Ca2+ currents in chicken embryo semicircular canal type I and type II hair cells.

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Zampini, Valeria; Valli, Paolo; Zucca, Giampiero; Masetto, Sergio

2006-08-01

Few data are available concerning single Ca channel properties in inner ear hair cells and particularly none in vestibular type I hair cells. By using the cell-attached configuration of the patch-clamp technique in combination with the semicircular canal crista slice preparation, we determined the elementary properties of voltage-dependent Ca channels in chicken embryo type I and type II hair cells. The pipette solutions included Bay K 8644. With 70 mM Ba(2+) in the patch pipette, Ca channel activity appeared as very brief openings at -60 mV. Ca channel properties were found to be similar in type I and type II hair cells; therefore data were pooled. The mean inward current amplitude was -1.3 +/- 0.1 (SD) pA at - 30 mV (n = 16). The average slope conductance was 21 pS (n = 20). With 5 mM Ba(2+) in the patch pipette, very brief openings were already detectable at -80 mV. The mean inward current amplitude was -0.7 +/- 0.2 pA at -40 mV (n = 9). The average slope conductance was 11 pS (n = 9). The mean open time and the open probability increased significantly with depolarization. Ca channel activity was still present and unaffected when omega-agatoxin IVA (2 microM) and omega-conotoxin GVIA (3.2 microM) were added to the pipette solution. Our results show that types I and II hair cells express L-type Ca channels with similar properties. Moreover, they suggest that in vivo Ca(2+) influx might occur at membrane voltages more negative than -60 mV.

Effects of ultraviolet-visible irradiation in the presence of melanin isolated from human black or red hair upon Ehrlich ascites carcinoma cells

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Menon, I.A.; Persad, S.; Ranadive, N.S.; Haberman, H.F.

1983-07-01

The present study is an attempt to investigate the possibility that ultraviolet irradiation in the presence of pheomelanin may be more harmful to cells than the irradiation in the presence of eumelanin. The effects of UV-visible irradiation upon Ehrlich ascites carcinoma cells in the presence of the melanin isolated from human black hair (eumelanin) or from red hair (pheomelanin) were investigated. Irradiation of these cells was found to produce cell lysis, as observed by leakage of 51Cr from labeled cells and intracellular lactic dehydrogenase from the cells and decrease in cell viability demonstrated by the trypan blue exclusion test. The three parameters were quantitatively parallel to one another under various experimental conditions, namely different periods of irradiation and irradiation in the presence of different concentrations of melanin. The above effects were more pronounced when the irradiation was carried out in the presence of melanin from red hair than in the presence of black-hair melanin. In the absence of either melanin, the irradiation did not produce any significant effect in cell viability or cell lysis. Irradiation of the cells in the presence of red-hair melanin also decreased the transplantability of these cells. These observations clearly show that irradiation of cells in the presence of pheomelanin could produce cytotoxic effects. The present experimental design may have application in the development of in vitro models for the study of UV radiation-induced cutaneous carcinogenesis. The reactions of pheomelanin may be related to the susceptibility of ''Celtic'' skin to UV radiation-induced skin damage and carcinogenesis.

Is there any relationship between decreased AgNOR protein synthesis and human hair loss?

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Eroz, R; Tasdemir, S; Dogan, H

2012-11-01

Argyrophilic nucleolar organizing region associated proteins (AgNORs) play roles in cell proliferation and a variety of diseases. We attempted to determine whether decreased NOR protein synthesis causes human hair loss. We studied 21 healthy males who suffered hair loss on the frontal/vertex portion of the head. Hair root cells from normal and hair loss sites were stained for AgNOR. One hundred nuclei per site were evaluated and the AgNOR number and NORa/TNa proportions of individual cells were determined using a computer program. The cells from normal sites had significantly higher AgNOR counts than those from hair loss sites. Also, the cells from the normal sites had significantly higher NORa/TNa than cells from the hair loss sites. In the normal sites, the cells demonstrated more NOR protein synthesis than cells in hair loss sites. Therefore, decreased NOR protein synthesis appears to be related to hair loss in humans.

Multifunctional Merkel cells: their roles in electromagnetic reception, finger-print formation, Reiki, epigenetic inheritance and hair form.

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Irmak, M Kemal

2010-08-01

Merkel cells are located in glabrous and hairy skin and in some mucosa. They are characterized by dense-core secretory granules and cytoskeletal filaments. They are attached to neighboring keratinocytes by desmosomes and contain melanosomes similar to keratinocytes. They are excitable cells in close contact with sensory nerve endings but their function is still unclear. In this review, following roles are attributed for the first time to the Merkel cells: (1) melanosomes in Merkel cells may be involved in mammalian magnetoreception. In this model melanosome as a biological magnetite is connected by cytoskeletal filaments to mechanically gated ion channels embedded in the Merkel cell membrane. The movement of melanosome with the changing electromagnetic field may open ion channels directly producing a receptor potential that can be transmitted to brain via sensory neurons. (2) Merkel cells may be involved in finger-print formation: Merkel cells in glabrous skin are located at the base of the epidermal ridges the type of which defines the finger-print pattern. Finger-print formation starts at the 10th week of pregnancy after the arrival of Merkel cells. Keratinocyte proliferation and the buckling process observed in the basal layer of epidermis resulting in the epidermal ridges may be controlled and formed by Merkel cells. (3) Brain-Merkel cell connection is bi-directional and Merkel cells not only absorb but also radiate the electromagnetic frequencies. Hence, efferent aspects of the palmar and plantar Merkel nerve endings may form the basis of the biofield modalities such as Reiki, therapeutic touch and telekinesis. (4) Adaptive geographic variations such as skin color, craniofacial morphology and hair form result from interactions between environmental factors and epigenetic inheritance system. While environmental factors produce modifications in the body, they simultaneously induce epigenetic modifications in the oocytes and in this way adaptive changes could be

Espins and the actin cytoskeleton of hair cell stereocilia and sensory cell microvilli

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Sekerková, Gabriella; Zheng, Lili; Loomis, Patricia A.; Mugnaini, Enrico; Bartles, James R.

2008-01-01

The espins are novel actin-bundling proteins that are produced in multiple isoforms from a single gene. They are present at high concentration in the parallel actin bundle of hair cell stereocilia and are the target of deafness mutations in mice and humans. Espins are also enriched in the microvilli of taste receptor cells, solitary chemoreceptor cells, vomeronasal sensory neurons and Merkel cells, suggesting that espins play important roles in the microvillar projections of vertebrate sensory cells. Espins are potent actin-bundling proteins that are not inhibited by Ca2+. In cells, they efficiently elongate parallel actin bundles and, thereby, help determine the steady-state length of microvilli and stereocilia. Espins bind actin monomer via their WH2 domain and can assemble actin bundles in cells. Certain espin isoforms can also bind phosphatidylinositol 4,5-bisphosphate, profilins or SH3 proteins. These biological activities distinguish espins from other actin-bundling proteins and may make them well-suited to sensory cells. PMID:16909209

Increased root hair density by loss of WRKY6 in Arabidopsis thaliana

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Markus G. Stetter

2017-01-01

Full Text Available Root hairs are unicellular elongations of certain rhizodermal cells that improve the uptake of sparingly soluble and immobile soil nutrients. Among different Arabidopsis thaliana genotypes, root hair density, length and the local acclimation to low inorganic phosphate (Pi differs considerably, when analyzed on split agar plates. Here, genome-wide association fine mapping identified significant single nucleotide polymorphisms associated with the increased root hair density in the absence of local phosphate on chromosome 1. A loss-of-functionmutant of the candidate transcription factor gene WRKY6, which is involved in the acclimation of plants to low phosphorus, had increased root hair density. This is partially explained by a reduced cortical cell diameter in wrky6-3, reducing the rhizodermal cell numbers adjacent to the cortical cells. As a consequence, rhizodermal cells in positions that are in contact with two cortical cells are found more often, leading to higher hair density. Distinct cortical cell diameters and epidermal cell lengths distinguish other Arabidopsis accessions with distinct root hair density and −Pi response from diploid Col-0, while tetraploid Col-0 had generally larger root cell sizes, which explain longer hairs. A distinct radial root morphology within Arabidopsis accessions and wrky6-3explains some, but not all, differences in the root hair acclimation to –Pi.

Thinning Hair and Hair Loss: Could it be Female Pattern Hair Loss?

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... mcat1=de12", ]; for (var c = 0; c Thinning hair and hair loss: Could it be female pattern hair loss? Female pattern hair loss: Without treatment, female ... can I tell if I have female pattern hair loss? It’s best to make an appointment to ...

mTOR signaling promotes stem cell activation via counterbalancing BMP-mediated suppression during hair regeneration.

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Deng, Zhili; Lei, Xiaohua; Zhang, Xudong; Zhang, Huishan; Liu, Shuang; Chen, Qi; Hu, Huimin; Wang, Xinyue; Ning, Lina; Cao, Yujing; Zhao, Tongbiao; Zhou, Jiaxi; Chen, Ting; Duan, Enkui

2015-02-01

Hair follicles (HFs) undergo cycles of degeneration (catagen), rest (telogen), and regeneration (anagen) phases. Anagen begins when the hair follicle stem cells (HFSCs) obtain sufficient activation cues to overcome suppressive signals, mainly the BMP pathway, from their niche cells. Here, we unveil that mTOR complex 1 (mTORC1) signaling is activated in HFSCs, which coincides with the HFSC activation at the telogen-to-anagen transition. By using both an inducible conditional gene targeting strategy and a pharmacological inhibition method to ablate or inhibit mTOR signaling in adult skin epithelium before anagen initiation, we demonstrate that HFs that cannot respond to mTOR signaling display significantly delayed HFSC activation and extended telogen. Unexpectedly, BMP signaling activity is dramatically prolonged in mTOR signaling-deficient HFs. Through both gain- and loss-of-function studies in vitro, we show that mTORC1 signaling negatively affects BMP signaling, which serves as a main mechanism whereby mTORC1 signaling facilitates HFSC activation. Indeed, in vivo suppression of BMP by its antagonist Noggin rescues the HFSC activation defect in mTORC1-null skin. Our findings reveal a critical role for mTOR signaling in regulating stem cell activation through counterbalancing BMP-mediated repression during hair regeneration. © The Author (2015). Published by Oxford University Press on behalf of Journal of Molecular Cell Biology, IBCB, SIBS, CAS. All rights reserved.

Molecular mechanisms involved in cochlear implantation trauma and the protection of hearing and auditory sensory cells by inhibition of c-Jun-N-terminal kinase signaling.

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Eshraghi, Adrien A; Gupta, Chhavi; Van De Water, Thomas R; Bohorquez, Jorge E; Garnham, Carolyn; Bas, Esperanza; Talamo, Victoria Maria

2013-03-01

To investigate the molecular mechanisms involved in electrode insertion trauma (EIT) and to test the otoprotective effect of locally delivered AM-111. An animal model of cochlear implantation. Guinea pigs' hearing thresholds were measured by auditory brainstem response (ABR) before and after cochlear implantation in four groups: EIT; pretreated with hyaluronate gel 30 minutes before EIT (EIT+Gel); pretreated with hyaluronate gel/AM-111 30 minutes before EIT (EIT+AM-111); and unoperated contralateral ears as controls. Neurofilament, synapsin, and fluorescein isothiocyanate (FITC)-phalloidin staining for hair cell counts were performed at 90 days post-EIT. Immunostaining for 4-hydroxy-2-nonenal (HNE), activated caspase-3, CellROX, and phospho-c-Jun were performed at 24 hours post-EIT. ABR thresholds increased post-EIT in the cochleae of EIT only and EIT+Gel treated animals. There was no significant increase in hearing thresholds in cochleae from either EIT+AM-111 treated or unoperated control ears. AM-111 protection of organ of Corti sensory elements (i.e., hair cells [HCs], supporting cells [SCs], nerve fibers, and synapses) was documented at 3 months post-EIT. Immunostaining of 24-hour post-EIT specimens demonstrated increased levels of HNE in HCs and SCs; increased levels of CellROX and activation of caspase-3 was observed only in SCs, and phosphorylation of c-Jun occurred only in HCs of the EIT-only and EIT+Gel specimens. There was no immunostaining for either HNE, CellROX, caspase-3, or phospho-c-Jun in the organ of Corti specimens from AM-111 treated cochleae. Molecular mechanisms involved in programmed cell death of HCs are different than the ones involved in programmed cell death of SCs. Local delivery of AM-111 provided a significant level of protection against EIT-induced hearing losses, HC losses, and damage to neural elements. Copyright © 2012 The American Laryngological, Rhinological, and Otological Society, Inc.

Constitutive transgene expression of Stem Cell Antigen-1 in the hair follicle alters the sensitivity to tumor formation and progression

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Rikke Christensen

2017-08-01

Full Text Available The cell surface protein Stem Cell Antigen-1 (Sca-1 marks stem or progenitor cells in several murine tissues and is normally upregulated during cancer development. Although the specific function of Sca-1 remains unknown, Sca-1 seems to play a role in proliferation, differentiation and cell migration in a number of tissues. In the skin epithelium, Sca-1 is highly expressed in the interfollicular epidermis but is absent in most compartments of the hair follicle; however, the function of Sca-1 in the skin has not been investigated. To explore the role of Sca-1 in normal and malignant skin development we generated transgenic mice that express Sca-1 in the hair follicle stem cells that are normally Sca-1 negative. Development of hair follicles and interfollicular epidermis appeared normal in Sca-1 mutant mice; however, follicular induction of Sca-1 expression in bulge region and isthmus stem cells reduced the overall yield of papillomas in a chemical carcinogenesis protocol. Despite that fewer papillomas developed in transgenic mice a higher proportion of the papillomas underwent malignant conversion. These findings suggest that overexpression of Sca-1 in the hair follicle stem cells contributes at different stages of tumour development. In early stages, overexpression of Sca-1 decreases tumour formation while at later stages overexpression of Sca-1 seems to drive tumours towards malignant progression.

The Mechanosensory Structure of the Hair Cell Requires Clarin-1, a Protein Encoded by Usher Syndrome III Causative Gene

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Geng, Ruishuang; Melki, Sami; Chen, Daniel H.-C.; Tian, Guilian; Furness, David; Oshima-Takago, Tomoko; Neef, Jakob; Moser, Tobias; Askew, Charles; Horwitz, Geoff; Holt, Jeffrey; Imanishi, Yoshikazu; Alagramam, Kumar N.

2012-01-01

Mutation in the clarin-1 gene results in loss of hearing and vision in humans (Usher syndrome III), but the role of clarin-1 in the sensory hair cells is unknown. Clarin-1 is predicted to be a four transmembrane domain protein similar to members of the tetraspanin family. Mice carrying null mutation in the clarin-1 (Clrn1−/−) gene show loss of hair cell function and a possible defect in ribbon synapse. We investigated the role of clarin-1 using various in vitro and in vivo approaches. We show by immunohistochemistry and patch-clamp recordings of Ca2+ currents and membrane capacitance from IHCs that clarin-1 is not essential for formation or function of ribbon synapse. However, reduced cochlear microphonic potentials, FM1-43 loading and transduction currents pointed to diminished cochlear hair bundle function in Clrn1−/− mice. Electron microscopy of cochlear hair cells revealed loss of some tall stereocilia and gaps in the v-shaped bundle, although tip-links and staircase arrangement of stereocilia were not primarily affected by Clrn1−/− mutation. Human clarin-1 protein expressed in transfected mouse cochlear hair cells localized to the bundle; however, the pathogenic variant, p.N48K, failed to localize to the bundle. The mouse model generated to study the in vivo consequence of p. N48K in clarin-1 (Clrn1N48K) supports our in vitro and Clrn1−/− mouse data and the conclusion that CLRN1 is an essential hair bundle protein. Further, the ear phenotype in the Clrn1N48K mouse suggests that it is a valuable model for ear disease in CLRN1N48K, the most prevalent Usher III mutation in North America. PMID:22787034

Mammalian Cochlear Hair Cell Regeneration and Ribbon Synapse Reformation

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Xiaoling Lu

2016-01-01

Full Text Available Hair cells (HCs are the sensory preceptor cells in the inner ear, which play an important role in hearing and balance. The HCs of organ of Corti are susceptible to noise, ototoxic drugs, and infections, thus resulting in permanent hearing loss. Recent approaches of HCs regeneration provide new directions for finding the treatment of sensor neural deafness. To have normal hearing function, the regenerated HCs must be reinnervated by nerve fibers and reform ribbon synapse with the dendrite of spiral ganglion neuron through nerve regeneration. In this review, we discuss the research progress in HC regeneration, the synaptic plasticity, and the reinnervation of new regenerated HCs in mammalian inner ear.

Hair Dye and Hair Relaxers

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... For Consumers Consumer Information by Audience For Women Hair Dye and Hair Relaxers Share Tweet Linkedin Pin it More sharing ... products. If you have a bad reaction to hair dyes and relaxers, you should: Stop using the ...

The microRNA-200 family coordinately regulates cell adhesion and proliferation in hair morphogenesis.

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Hoefert, Jaimee E; Bjerke, Glen A; Wang, Dongmei; Yi, Rui

2018-06-04

The microRNA (miRNA)-200 (miR-200) family is highly expressed in epithelial cells and frequently lost in metastatic cancer. Despite intensive studies into their roles in cancer, their targets and functions in normal epithelial tissues remain unclear. Importantly, it remains unclear how the two subfamilies of the five-miRNA family, distinguished by a single nucleotide within the seed region, regulate their targets. By directly ligating miRNAs to their targeted mRNA regions, we identify numerous miR-200 targets involved in the regulation of focal adhesion, actin cytoskeleton, cell cycle, and Hippo/Yap signaling. The two subfamilies bind to largely distinct target sites, but many genes are coordinately regulated by both subfamilies. Using inducible and knockout mouse models, we show that the miR-200 family regulates cell adhesion and orientation in the hair germ, contributing to precise cell fate specification and hair morphogenesis. Our findings demonstrate that combinatorial targeting of many genes is critical for miRNA function and provide new insights into miR-200's functions. © 2018 Hoefert et al.

Hair follicle proteoglycans

DEFF Research Database (Denmark)

Couchman, J R

1993-01-01

that are present in the epithelial and stromal compartments of hair follicles. However, the transmembrane proteoglycan syndecan may be important in follicle morphogenesis, both with respect to the epithelium and dermal papilla cells. Syndecan may possess both heparan and chondroitin sulfate chains, interacts...... basement membranes, including those surrounding the epithelial compartment of hair follicles. Additionally, and quite unlike the dermis, the dermal papilla is enriched in basement-membrane components, especially a chondroitin 6-sulfate-containing proteoglycan, BM-CSPG. The function of this proteoglycan...... is not known, but developmental studies indicate that it may have a role in stabilizing basement membranes. In the hair cycle, BM-CSPG decreases through catagen and is virtually absent from the telogen papilla. One or more heparan sulfate proteoglycans, including perlecan, are also present in papilla...

Hair growth promoting effect of white wax and policosanol from white wax on the mouse model of testosterone-induced hair loss.

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Wang, Zhan-di; Feng, Ying; Ma, Li-Yi; Li, Xian; Ding, Wei-Feng; Chen, Xiao-Ming

2017-05-01

White wax (WW) has been traditionally used to treat hair loss in China. However there has been no reporter WW and its extract responsible for hair growth-promoting effect on androgenetic alopecia. In this paper, we examined the hair growth-promoting effects of WW and policosanol of white wax (WWP) on model animal of androgenetic alopecia and the potential target cell of WW and WWP. WW (1, 10 and 20%) and WWP (0.5, 1 and 2%) were applied topically to the backs of mice. Finasteride (2%) was applied topically as a positive control. MTS assays were performed to evaluate cell proliferation in culture human follicle dermal papilla cells (HFDPCs). The inhibition of WW and WWP for 5α- reductase were tested in Vitro. Results showed more lost hairs were clearly seen in mice treated with TP only and TP plus vehicle. Mice which received TP plus WW and WWP showed less hair loss. WW and WWP showed an outstanding hair growth-promoting activity as reflected by the follicular length, follicular density, A/T ratio, and hair bulb diameter. The optimal treatment effect was observed at 10% WW and 1% WWP, which were better than 2% finasteride treatment. MTS assay results suggested that WW and WWP remarkably increased the proliferation of HFDPCs. Inhibitor assay of 5α- reductase showed that WW and WWP inhibited significantly the conversion of testosterone to dihydrotesterone, and the IC 50 values of WW and WWP were higher than that of finasteride. In Conclusion, WW and WWP could act against testosterone-induced alopecia in mice, and they promoted hair growth by inhibiting 5α-reductase activity and HFDPCs proliferation. DPCs is the target cell of WW and WWP. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Discrimination between basal cell carcinoma and hair follicles in skin tissue sections by Raman micro-spectroscopy