Cochlear Hair Cell Regeneration from Neonatal Mouse Supporting Cells PDF Download

Author: Naomi F. Bramhall
Publisher:
ISBN:
Category :
Languages : en
Pages : 91

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Book Description
Unlike lower vertebrates, capable of spontaneous hair cell regeneration, mammals experience permanent sensorineural hearing loss following hair cell damage. Although low levels of hair cell regeneration have been demonstrated in the immature mammalian vestibular system, the cochlea has been thought to lack any spontaneous regenerative potential. Inhibition of the Notch pathway can stimulate hair cell generation in neonatal mammals, but the specific source of these new hair cells has been unclear. Here, using in vitro lineage tracing with the supporting cell markers Sox2 and Lgr5, we show that Lgr5-positive inner pillar and 3rd Deiter's cells in gentamicin-damaged organs of Corti from neonatal mice give rise to new hair cells following treatment with a Notch inhibitor. These new hair cells are generated primarily through direct transdifferentiation of supporting cells, although a small number show evidence of proliferation. Inner pillar cells show the greatest transdifferentation capability, giving rise to immature outer hair cells, and transdifferentiating in response to damage even in the absence of Notch inhibition. In vivo pharmacologic inhibition of Notch and in vivo lineage tracing with Sox2 during genetic Notch inhibition provide generally consistent results, although additional new hair cells develop in the inner hair cell region. These data suggest a spontaneous capacity for hair cell regeneration in the neonatal mammalian cochlea. In addition, the data identify Lgr5-positive supporting cells as potential hair cell progenitors, making them an attractive target for future hair cell regeneration treatments.

Author: Mark E. Warchol
Publisher: Springer Nature
ISBN: 3031206614
Category : Medical
Languages : en
Pages : 242

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Book Description
This volume provides a detailed update on progress in the field of hair cell regeneration. This topic is of considerable interest to academicians, clinicians, and commercial entities, including students of auditory and vestibular neuroscience, audiologists, otologists, and industry, all of whom may have interest in hair cell regeneration as a potential future therapy for hearing and balance dysfunction. In 2008, Springer published a SHAR volume on this subject (Hair Cell Regeneration, Repair, and Protection, Editors Richard Salvi and Richard Fay). Since that time, there has been considerable advancement in this field.This book provides a historical perspective on the field, but the emphasis is on more "prospective" views of the various facets of regeneration research, in the hope that the volume will stimulate new projects and approaches, focusing on the limitations of current knowledge and describing promising strategies for future work. The book will include the following key features of hair cell regeneration: • Cellular and molecular control hair cell regeneration in non-mammalian species (in particular zebrafish and chickens) • Our current understanding of the capacity for hair cell replacement in mammals (rodents and humans). • Signals controlling pro-regenerative behaviors in supporting cells, the hair cell progenitors. • New techniques that have been applied to study the genetic and epigenetic regulation of hair cell regeneration in mammals and non-mammals. • Contributions of stem cells toward building new tools to explore how hair cell regeneration is controlled and toward developing cells and tissue for therapeutic transplantation. • Studies that have applied gene and drug therapy to promote regeneration in mammals.

Author: Michael E. Smith
Publisher: Frontiers Media SA
ISBN: 2889450007
Category : Neurosciences. Biological psychiatry. Neuropsychiatry
Languages : en
Pages : 268

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Book Description
Sensory hair cells are the specialized mechanosensory receptors found in vertebrate auditory, vestibular, and lateral line organs that transduce vibratory and acoustic stimuli into the sensations of hearing and balance. Hair cells can be damaged due to such factors as aging, ototoxic chemicals, acoustic trauma, infection, or genetic factors. Loss of these hair cells lead to deficits in hearing and balance, and in mammals, such deficits are permanent. In contrast, non-mammalian vertebrates exhibit the capability to regenerate missing hair cells. Researchers have been examining the process of hair cell death and regeneration in animal models in an attempt to find ways of either preventing hair cell loss or stimulating the production of new hair cells in mammals, with the ultimate goal of finding new therapeutics for human sensorineural hearing and balance deficits. This has led to a wide array of research on sensory hair cells- such as understanding the factors that cause hair cell loss and finding agents that protect them from damage, elucidating the cell signaling pathways activated during hair cell death, examining the genes and cellular pathways that are regulated during the process of hair cell death and regeneration, and characterizing the functional sensory loss and recovery following acoustic or ototoxic insults to the inner ear. This research has involved cell and developmental biologists, physiologists, geneticists, bioinformaticians, and otolaryngologists. In this Research Topic, we have collated reviews of the past progress of hair cell death and regeneration studies and original research articles advancing sensory hair cell death and regeneration research into the future.

Author: Richard J. Salvi
Publisher: Springer Science & Business Media
ISBN: 0387733647
Category : Science
Languages : en
Pages : 323

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Book Description
Not male pattern baldness, but the loss of sensory hair, is a very serious topic. Sensory hair cells convert sound and motion into our sense of hearing, movement, and head position. In mammals, the loss of hair cells is irreversible. Or is it? Hair cells in other vertebrates are capable of regenerating and recovering partial or complete function. This book provides a comprehensive survey of the regeneration of sensory hair cells.

Author: Melissa M. McGovern
Publisher:
ISBN:
Category : Cell differentiation
Languages : en
Pages : 328

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Book Description
One of the most common disabilities in the US, hearing loss, is reported by The National Institutes of Health to affect approximately 36 million Americans. One of the major contributing factors to this loss in hearing is the loss of the sensory hair cells (HCs) within the cochlea. Also in the mammalian cochlea, six major groups of supporting cell (SC) subtypes reside in close proximity to HCs and may have the potential to regenerate HCs after damage. These subtypes include cells of the greater epithelial ridge, inner phalangeal/border cells, inner and outer pillar cells, Deiters' cells, Hensen cells, and Claudius cells. During embryonic development, progenitor cells differentiate into HCs or one of the SC subtypes by Notch-mediated lateral inhibition. In the neonatal mouse cochlea, many studies have shown that inhibition of Notch signaling allows SCs to convert into HCs in both normal undamaged cochleae, as well as in drug-damaged cochlear explants. This mechanism is also implicated during spontaneous HC regeneration that occurs in non-mammalian vertebrates. We and others have recently observed that spontaneous HC regeneration can also occur in the neonatal mouse cochlea. However, little is known about the molecular mechanism or the SC subtypes which act as the source of regenerated HCs. In the neonatal mouse cochlea, HCs were killed in vivo at birth using a genetically-modified mouse model to express a toxin in HCs. Subsequently, SCs formed new HCs by either direct transdifferentiation, where no cell division occurred, or by mitotic regeneration. My dissertation investigated the role of Notch signaling in the ability of SC subtypes to regenerate HCs after damage. My central hypothesis is that after HC ablation is induced at birth, Notch signaling is partially eliminated and therefore lateral inhibition is lost in neonatal SCs in a subtype specific manner, which allows some SCs, but not others, to differentiate into and regenerate HCs. Aim 1 focused on changes in the Notch signaling pathway in response to HC damage during the window of spontaneous HC regeneration. Changes in the expression of genes in the Notch pathway were measured using real time qPCR, immunostaining, and in situ hybridization. The Notch effector HeyL was increased in the apical one-third of the cochlea while other Notch players are decreased. The most notable example is the Notch effector Hes5, which is directly responsible for inhibiting HC fate, and was reduced in outer pillar cells and Deiters' cells, but not in other SC subtypes. From this we conclude that Notch signaling is reduced differentially among SC subtypes. In Aim 2 we investigated whether inhibition of Notch signaling is required for spontaneous HC regeneration to occur by maintaining active Notch signaling in all SCs in the context of HC damage. We hypothesized that maintaining active Notch signaling after HC damage will prevent SC-to-HC conversion thus preventing HC regeneration. We found significantly fewer regenerated HCs while maintaining Notch expression compared to controls with HC damage and no manipulation of Notch signaling. Therefore we conclude loss of Notch mediated lateral inhibition is required for the majority of spontaneous HC regeneration. In Aim 3 we investigated the ability of different SC subtypes to regenerate HCs by fate-mapping SC subtypes during the HC regeneration process. Since fate-mapping creates a permanent label in targeted cells, we can track their potential change in cell fate or reentry in the cell cycle after HC damage. We hypothesized that pillar cells and Deiters' cells are the source for spontaneously regenerated HC within the neonatal mouse cochlea based on our results from Aim 1. We used three CreER mouse lines to fate-map distinct groups of SC subtypes during the HC damage and regeneration process. More pillar and Deiters' cells regenerated HCs after damage than other SC populations. We found that outer pillar cells and Deiters' cells are capable of downregulating the cell cycle inhibitor, p27Kip1, after HC damage. Therefore we investigated the ability of SC subtypes to mitotically regenerate HCs by including a mitotic tracer along with fate-mapping. A larger proportion of mitotically regenerated HCs came from pillar and Deiters' cells. From these experiments, we conclude that outer pillar and Deiters' cells are the source for the majority of spontaneously regenerated HCs in vivo. This knowledge will allow targeted investigation into outer pillar cells and Deiters' cells that maintain regenerative plasticity at postnatal ages. Understanding how these cells change with age will inform efforts to induce HC regeneration in more mature cochleae. Additionally, understanding how Notch signaling regulates this regenerative plasticity will lead to the development of potential targets for the treatment of hearing loss.

Author: Amber D. Slowik
Publisher:
ISBN:
Category :
Languages : en
Pages : 190

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Book Description
The sensory modalities of hearing and balance are mediated by the six sensory organs of the inner ear that are each comprised of the same two main cell types, support cells and mechanosensory hair cells. Loss of the sensory hair cells from these organs causes permanent hearing loss and/or balance disorders, as there is currently no therapeutic treatment for hair cell loss. In developing organs, hair cells can be generated through the transdifferentiation of support cells caused by inhibition of the Notch signaling pathway, which is normally required to determine and maintain the precise ratio of hair cells and support cells through lateral inhibition. Although the efficacy of this method declines as the organs mature and Notch signaling is downregulated, previous research has shown that the Notch downstream effector, Hes5, is present in the adult cristae, suggesting that Notch signaling may be active and that the cristae of the adult mouse may retain some regenerative ability. In this dissertation, I tested this hypothesis and showed that Notch signaling is active in the peripheral region of the adult cristae and, using hair cell counts and lineage tracing, that supernumerary hair cells can be generated through inhibition of Notch signaling in vitro. Further, through an analysis of the spatial distribution of hair cell birth in the developing cristae, I showed that there is a correlation between the regions that maintain regenerative competence in the adult and the last regions to exit the cell cycle. In addition, to aid future regenerative studies, I identified a new support cell marker that can be used to lineage trace support cells and have used this marker to characterize spontaneous hair cell regeneration in the adult cristae in vivo. I also created standard protocols for lesioning hair cells in vivo in two common mouse strains using the known ototoxin 3,3'--Iminodipropionitrile (IDPN) and for quantifiably assaying vestibular behavior in mice with varying degrees of hair cell lesion. Together, this work establishes the previously uncharacterized mouse cristae as an additional model for studying the mechanisms of hair cell regeneration and provides some of the tools necessary for future studies. Supplemental Movie 1.1 The inner ear contains six distinct sensory organs: The cochlea, utricle, saccule, posterior cristae, horizontal cristae, and anterior cristae. These organs be seen in an intact E15.5 inner ear labeled for the sensory regions with Sox2 (white) and in a color coded model of the position of the Sox2-labeled sensory organs created by 3-dimensionally rendering tracings of the Sox2 regions in the individual confocal slices. Supplemental Movie 2.1 Cristae are highly three-dimensional, composed of two saddle-shaped hemicristae separated by the eminentia cruciatum. Sox9 (red) labels support cells as well as non-sensory cells in the eminentia cruciatum and throughout the ampulla and semicircular canals. Gfi1 (white) labels all hair cells in the sensory epithelium. Hes5-GFP is expressed in a subset of support cells in the Calretinin-negative peripheral zone. Note that while the overall structure of the sensory epithelium was preserved, the normally dome-like Sox9+ ampulla flattened onto the sensory epithelium. Dimensions in [unknown scientific symbol]m (w x h x d) - 544.9 x 272.5 x 75.5. Supplemental Movie 2.2 An example of a lineage traced transitional cell from the mTmG mouse (see Figure7B-B"). The GFP+ cell expressed Gfi1, but had an elongated body similar to a support cell. The nucleus was lifting off of the basement membrane and the apical part of the cell had an unusual appearance unlike a normal hair cell or support cell. There was also another GFP+ support cell that spans the sensory epithelium as well as several non-sensory cells in view. Dimensions in [unknown scientific symbol]m (w x h x d) - 36.4 x 61.2 x 6.9. Supplemental Movie 2.3 An example of a lineage traced transitional cell from the mTmG mouse (see Fig. 7CC"). The GFP+ cell expresses Gfi1 and overall has a normal appearance for a hair cell, except for a thin foot-like projection that extends to the basement membrane. Also in view are two support cells, one of which is directly next to the hair cell. Dimensions in [unknown scientific symbol]m (w x h x d) - 43.3 x 52.6 x 13.0. Supplemental Movie 2.4 An example of a lineage traced hair cell with a kinocilium from the mTmG mouse (see Fig. 7D-D"). The GFP+ cell expressed Gfi1 (red) and had a flask shape with a rounded bottom and a thin neck. A long kinocilium extended up from the apical surface. Nuclei are labeled with Hoechst 33342 (white) and had prominent nucleoli at this fluorescent intensity. Also in view were a couple of GFP+ support cells and a non-sensory cell. Dimensions in [unknown scientific symbol]m (w x h x d) - 28.7 x 64.2 x 13.5.

Author: Juichi Ito
Publisher: Springer
ISBN: 4431548629
Category : Medical
Languages : en
Pages : 311

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Book Description
The research described in this book represents important steps toward understanding the development of inner ear medicine and new perspectives in regenerative medicine, including efficacy in cochlear implants and various other treatments. The book depicts the mechanisms that underlie inner ear diseases, their experimental models, and proposals for new strategies to treat their symptoms. As well, the exciting future prospects for dealing with the very common problem of inner ear diseases are explained. These disorders occur among many people and include sensorineural hearing loss (SNHL), sudden deafness, senile deafness, noise-induced deafness, tinnitus, dizziness–vertigo, and Ménière’s disease. In Japan alone, there are more than 6 million deaf patients including those with middle-range deafness. There is currently no effective treatment, and regardless of the underlying cause, the damage has been considered irreversible. However, the results of recent research show that these patients actually can recover. The study of hair cells, spiral ganglion neurons, and stem cells for inner ear diseases such as SNHL, tinnitus, dizziness, and vertigo is at the forefront of regenerative medicine and may provide solutions to some of these problems. The information presented here makes this book a valuable professional reference work for all doctors and researchers in the field of otolaryngology who focus on regenerative treatments for inner ear diseases.

Author: M.E. Lutman
Publisher: Academic Press
ISBN: 1483295168
Category : Medical
Languages : en
Pages : 353

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Book Description
Hearing Science and Hearing Disorders focuses on the nature of the processes in the inner ear and the nervous system that mediate hearing. Organized into eight chapters, this book first discusses the nature of speech communication, the extent of hearing problems, and the pathophysiology of hearing. Four core chapters follow, in which four areas of central importance to understanding hearing disorders and their effects are covered. These areas are assessment of auditory function, the scope for technological solutions, the nature of audio-visual speech perception, and the effects of deafness upon speech production. This book will be valuable to students; to academic and professional workers concerned with hearing, speech, and their disorders; and to scientifically or medically literate people in general.

Author: Matthew Kelley
Publisher: Springer Science & Business Media
ISBN: 0387306781
Category : Science
Languages : en
Pages : 250

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Book Description
The Springer Handbook of Auditory Research presents a series of compreh- sive and synthetic reviews of the fundamental topics in modern auditory - search. The volumes are aimed at all individuals with interests in hearing research including advanced graduate students, postdoctoral researchers, and clinical investigators. The volumes are intended to introduce new investigators to important aspects of hearing science and to help established investigators to betterunderstandthefundamentaltheoriesanddatain?eldsofhearingthatthey may not normally follow closely. Each volume presents a particular topic comprehensively, and each servesas a synthetic overview and guide to the literature. As such, the chapters present neither exhaustive data reviews nor original research that has not yet appeared in peer-reviewed journals. The volumes focus on topics that have developed a solid data and conceptual foundation rather than on those for which a literature is only beginning to develop. New research areas will be covered on a timely basis in the series as they begin to mature. Eachvolumeintheseriesconsistsofafewsubstantialchaptersonaparticular topic. In some cases, the topics will be ones of traditional interest for which there is a substantial body of data and theory, such as auditory neuroanatomy (Vol. 1) and neurophysiology (Vol. 2). Other volumes in the series deal with topics that have begun to mature more recently, suchasdevelopment,plasticity, and computational models of neural processing. In many cases, the series - itorsarejoinedbyaco-editorhavingspecialexpertiseinthetopicofthevolume.

Author: Rebecca M. Lewis
Publisher:
ISBN:
Category :
Languages : en
Pages : 96

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Book Description
Sensorineural hearing loss is irreversible in all mammals, including humans, since neither hair cells nor neurons are regenerated. In contrast to mammals, non-mammalian vertebrates replace hair cells after damage. In the avian basilar papilla, hair cell injury activates neighboring supporting cells to undergo direct transdifferentiation or mitotic division, both of which contribute to regeneration of hair cells. The molecules that enable hair cell regeneration in birds are not well understood. This dissertation presents a series of experiments to evaluate whether Atoh1, a transcription factor required for hair cell development, is sufficient for hair cell differentiation in avian basilar papilla during regeneration after aminoglycoside damage and to determine if the bone morphogenetic factor BMP4, a protein required for development of auditory epithelia, inhibits Atoh1 mRNA expression and subsequent hair cell differentiation after damage. In the first study, I tracked the activity of the Atoh1 enhancer in cultured basilar papillae to determine if it is an accurate predictor of hair cell fate, and I forced expression of mouse Atoh1 in supporting cells to test the hypothesis that higher levels of Atoh1 push supporting cells to divide or transdifferentiate. This first study determined that about half of supporting cells with Atoh1 enhancer activity do not differentiate into hair cells, but relief from notch-mediated lateral inhibition or forced overexpression of Atoh1 significantly increase the likelihood that a supporting cell will differentiate as a hair cell or proliferate. In the second study, I used in situ hybridization to determine that Bmp4 mRNA is expressed in hair cells in mature chicken basilar papilla. BMP4 receptors are transcribed in supporting cells and hair cells, while inhibitor of DNA binding (Id) mRNA, a downstream effector of BMP4, is enriched in supporting cells in control tissues. Upon hair cell loss, Bmp4 mRNA expression is lost, while Atoh1 mRNA is upregulated in supporting cells. Concurrently, downstream Id effectors and receptors to BMP4 are upregulated in the area of damage. Given the observation that Bmp4 and Atoh1 have opposing expression patterns after hair cell loss, damaged basilar papillae were cultured with BMP4 protein or its inhibitor noggin after hair cell loss to determine if BMP4 antagonizes Atoh1 expression and subsequent hair cell differentiation. BMP4 eliminated Atoh1 transcripts along the length of the basilar papilla, while noggin increased Atoh1 expression. Further, BMP4 application significantly decreased the number of regenerated hair cells, while noggin application significantly increased them. These findings suggest BMP4 antagonizes hair cell regeneration by reducing Atoh1 transcripts in supporting cells, preventing them from dividing or transdifferentiating. My results are consistent with other investigators’ observations that Atoh1 is necessary for hair cell differentiation during development but additional factors such as notch ligands and BMP4 limit ATOH1’s expression. These are important considerations as investigators examine the potential for ATOH1 to stimulate auditory hair cell regeneration in humans.