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Oral Administration of TrkB Agonist, 7, 8-Dihydroxyflavone Regenerates Hair Cells and Restores Function after Gentamicin-Induced Vestibular Injury in Guinea Pig. Pharmaceutics 2023; 15:pharmaceutics15020493. [PMID: 36839815 PMCID: PMC9966733 DOI: 10.3390/pharmaceutics15020493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 01/24/2023] [Accepted: 01/30/2023] [Indexed: 02/05/2023] Open
Abstract
The causes of vestibular dysfunction include the loss of hair cells (HCs), synapses beneath the HCs, and nerve fibers. 7, 8-dihydroxyflavone (DHF) mimics the physiological functions of brain-derived neurotrophic factor. We investigated the effects of the orally-administered DHF in the guinea pig crista ampullaris after gentamicin (GM)-induced injury. Twenty animals treated with GM received daily administration of DHF or saline for 14 or 28 days (DHF (+) or DHF (-) group; N = 5, each). At 14 days after GM treatment, almost all of the HCs had disappeared in both groups. At 28 days, the HCs number in DHF (+) and DHF (-) groups was 74% and 49%, respectively, compared to GM-untreated control. In the ampullary nerves, neurofilament 200 positive rate in the DHF (+) group was 91% at 28 days, which was significantly higher than 42% in DHF (-). On day 28, the synaptic connections observed between C-terminal-binding protein 2-positive and postsynaptic density protein-95-positive puncta were restored, and caloric response was significantly improved in DHF (+) group (canal paresis: 57.4% in DHF (+) and 100% in DHF (-)). Taken together, the oral administration of DHF may be a novel therapeutic approach for treating vestibular dysfunction in humans.
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2
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Baumgartner JE, Baumgartner LS, Baumgartner ME, Moore EJ, Messina SA, Seidman MD, Shook DR. Progenitor cell therapy for acquired pediatric nervous system injury: Traumatic brain injury and acquired sensorineural hearing loss. Stem Cells Transl Med 2021; 10:164-180. [PMID: 33034162 PMCID: PMC7848325 DOI: 10.1002/sctm.20-0026] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 08/18/2020] [Accepted: 08/24/2020] [Indexed: 12/16/2022] Open
Abstract
While cell therapies hold remarkable promise for replacing injured cells and repairing damaged tissues, cell replacement is not the only means by which these therapies can achieve therapeutic effect. For example, recent publications show that treatment with varieties of adult, multipotent stem cells can improve outcomes in patients with neurological conditions such as traumatic brain injury and hearing loss without directly replacing damaged or lost cells. As the immune system plays a central role in injury response and tissue repair, we here suggest that multipotent stem cell therapies achieve therapeutic effect by altering the immune response to injury, thereby limiting damage due to inflammation and possibly promoting repair. These findings argue for a broader understanding of the mechanisms by which cell therapies can benefit patients.
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Affiliation(s)
- James E. Baumgartner
- Advent Health for ChildrenOrlandoFloridaUSA
- Department of Neurological SurgeryUniversity of Central Florida College of MedicineOrlandoFloridaUSA
| | | | | | - Ernest J. Moore
- Department of Audiology and Speech Language PathologyUniversity of North TexasDentonTexasUSA
| | | | - Michael D. Seidman
- Advent Health CelebrationCelebrationFloridaUSA
- Department of OtorhinolaryngologyUniversity of Central FloridaOrlandoFloridaUSA
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Kros CJ, Steyger PS. Aminoglycoside- and Cisplatin-Induced Ototoxicity: Mechanisms and Otoprotective Strategies. Cold Spring Harb Perspect Med 2019; 9:cshperspect.a033548. [PMID: 30559254 DOI: 10.1101/cshperspect.a033548] [Citation(s) in RCA: 98] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Ototoxicity refers to damage of inner ear structures (i.e., the cochlea and vestibule) and their function (hearing and balance) following exposure to specific in-hospital medications (i.e., aminoglycoside antibiotics, platinum-based drugs), as well as a variety of environmental or occupational exposures (e.g., metals and solvents). This review provides a narrative derived from relevant papers describing factors contributing to (or increasing the risk of) aminoglycoside and cisplatin-induced ototoxicity. We also review current strategies to protect against ototoxicity induced by these indispensable pharmacotherapeutic treatments for life-threatening infections and solid tumors. We end by highlighting several interventional strategies that are currently in development, as well as the diverse challenges that still need to be overcome to prevent drug-induced hearing loss.
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Affiliation(s)
- Corné J Kros
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, United Kingdom
| | - Peter S Steyger
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, Oregon 97239.,National Center for Rehabilitative Auditory Research, VA Portland Health Care System, Portland, Oregon 97239
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Kinoshita M, Fujimoto C, Iwasaki S, Kashio A, Kikkawa YS, Kondo K, Okano H, Yamasoba T. Alteration of Musashi1 Intra-cellular Distribution During Regeneration Following Gentamicin-Induced Hair Cell Loss in the Guinea Pig Crista Ampullaris. Front Cell Neurosci 2019; 13:481. [PMID: 31708751 PMCID: PMC6824208 DOI: 10.3389/fncel.2019.00481] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Accepted: 10/10/2019] [Indexed: 11/13/2022] Open
Abstract
The mechanism underlying hair cell (HC) regeneration in the mammalian inner ear is still under debate. Understanding what molecules regulate the HC regeneration in mature mammals will be the key to the treatment of the inner ear disorder. Musashi1 (MSI1) is an RNA binding protein associated with asymmetric division and maintenance of stem cell function as a modulator of the Notch-1 signaling pathway. In this study, we investigated the cellular proliferative activity and changes in spatiotemporal pattern of MSI1 expression in the gentamicin (GM)-treated crista ampullaris (CA) in guinea pigs. Although the vestibular HCs in the CA almost disappeared at 14 days after injecting GM in the inner ear, the density of vestibular HCs spontaneously increased by up to 50% relative to controls at 56 days post-GM treatment (PT). The number of the type II HCs was significantly increased at 28 days PT relative to 14 days PT (p < 0.01) while that of type I HCs or supporting cells (SCs) did not change. The number of SCs did not change through the observational period. Administration of bromodeoxyuridine with the same GM treatment showed that the cell proliferation activity was high in SCs between 14 and 28 days PT. The changes in spatiotemporal patterns of MSI1 expression during spontaneous HC regeneration following GM treatment showed that MSI1-immunoreactivity was diffusely spread into the cytoplasm of the SCs during 7–21 days PT whereas the expression of MSI1 was confined to the nucleus of SCs in the other period. The MSI1/MYO7A double-positive cells were observed at 21 days PT. These results suggest that regeneration of vestibular HCs might originate in the asymmetric cell division and differentiation of SCs and that MSI1 might be involved in controlling the process of vestibular HC regeneration.
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Affiliation(s)
- Makoto Kinoshita
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, University of Tokyo, Tokyo, Japan
| | - Chisato Fujimoto
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, University of Tokyo, Tokyo, Japan
| | - Shinichi Iwasaki
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, University of Tokyo, Tokyo, Japan
| | - Akinori Kashio
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, University of Tokyo, Tokyo, Japan
| | - Yayoi S Kikkawa
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, University of Tokyo, Tokyo, Japan
| | - Kenji Kondo
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, University of Tokyo, Tokyo, Japan
| | - Hideyuki Okano
- Department of Physiology, Keio University School of Medicine, Tokyo, Japan
| | - Tatsuya Yamasoba
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, University of Tokyo, Tokyo, Japan
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5
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Omichi R, Shibata SB, Morton CC, Smith RJH. Gene therapy for hearing loss. Hum Mol Genet 2019; 28:R65-R79. [PMID: 31227837 PMCID: PMC6796998 DOI: 10.1093/hmg/ddz129] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 04/15/2019] [Accepted: 06/07/2019] [Indexed: 12/26/2022] Open
Abstract
Sensorineural hearing loss (SNHL) is the most common sensory disorder. Its underlying etiologies include a broad spectrum of genetic and environmental factors that can lead to hearing loss that is congenital or late onset, stable or progressive, drug related, noise induced, age related, traumatic or post-infectious. Habilitation options typically focus on amplification using wearable or implantable devices; however exciting new gene-therapy-based strategies to restore and prevent SNHL are actively under investigation. Recent proof-of-principle studies demonstrate the potential therapeutic potential of molecular agents delivered to the inner ear to ameliorate different types of SNHL. Correcting or preventing underlying genetic forms of hearing loss is poised to become a reality. Herein, we review molecular therapies for hearing loss such as gene replacement, antisense oligonucleotides, RNA interference and CRISPR-based gene editing. We discuss delivery methods, techniques and viral vectors employed for inner ear gene therapy and the advancements in this field that are paving the way for basic science research discoveries to transition to clinical trials.
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Affiliation(s)
- Ryotaro Omichi
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
- Department of Otolaryngology—Head and Neck Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8558, Japan
| | - Seiji B Shibata
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
- Department of Otolaryngology—Head and Neck Surgery, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Cynthia C Morton
- Departments of Obstetrics and Gynecology and of Pathology, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA 02115, USA
- Manchester Centre for Audiology and Deafness, University of Manchester, Manchester Academic Health Science Centre, Manchester M139NT, UK
- Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA
| | - Richard J H Smith
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
- Department of Otolaryngology—Head and Neck Surgery, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
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Abstract
In sharp contrast to the adult mammalian cochlea, which lacks regenerative ability, the mature avian cochlea, or basilar papilla (BP) is capable of complete recovery from hearing loss after damage. Avian sensory hair cell regeneration relies on rousing quiescent supporting cells to proliferate or transdifferentiate after hair cell death. Unlike mammalian cochlear supporting cells, which have clearly defined subtypes, avian BP supporting cells are deceptively indistinguishable and molecular markers have yet to be identified. Despite the importance of supporting cells as the putative stem cells in avian regeneration, it is unknown whether all supporting cells possess equal capability to give rise to a hair cell or if a specialized subpopulation exists. In this perspective, we reinvigorate the concept of a stem cell in the BP, and form comparisons to other regenerating tissues that show cell-cycle reentry after damage. Special emphasis is given to the structure of the BP and how anatomy informs both the potential, intrinsic heterogeneity of the supporting cell layer as well as the choice between mitotic and nonmitotic regenerative strategies.
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Takeda H, Dondzillo A, Randall JA, Gubbels SP. Challenges in Cell-Based Therapies for the Treatment of Hearing Loss. Trends Neurosci 2018; 41:823-837. [PMID: 30033182 DOI: 10.1016/j.tins.2018.06.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 06/20/2018] [Accepted: 06/21/2018] [Indexed: 12/17/2022]
Abstract
Hearing loss in mammals is an irreversible process caused by degeneration of the hair cells of the inner ear. Current therapies for hearing loss include hearing aids and cochlear implants that provide substantial benefits to most patients, but also have several shortcomings. There is great interest in the development of regenerative therapies to treat deafness in the future. Cell-based therapies, based either on adult, multipotent stem, or other types of pluripotent cells, offer promise for generating differentiated cell types to replace lost or damaged hair cells of the inner ear. In this review, we focus on the methods proposed and avenues for research that seem the most promising for stem cell-based auditory sensory cell regeneration, from work collected over the past 15 years.
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Affiliation(s)
- Hiroki Takeda
- Department of Otolaryngology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA; Department of Otolaryngology-Head and Neck Surgery, Kumamoto University Graduate School of Medicine, Kumamoto City, Japan; These authors contributed equally to this work
| | - Anna Dondzillo
- Department of Otolaryngology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA; These authors contributed equally to this work
| | - Jessica A Randall
- Department of Otolaryngology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA
| | - Samuel P Gubbels
- Department of Otolaryngology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA.
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Scheibinger M, Ellwanger DC, Corrales CE, Stone JS, Heller S. Aminoglycoside Damage and Hair Cell Regeneration in the Chicken Utricle. J Assoc Res Otolaryngol 2017; 19:17-29. [PMID: 29134476 DOI: 10.1007/s10162-017-0646-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 10/30/2017] [Indexed: 12/30/2022] Open
Abstract
In this study, we present a systematic characterization of hair cell loss and regeneration in the chicken utricle in vivo. A single unilateral surgical delivery of streptomycin caused robust decline of hair cell numbers in striolar as well as extrastriolar regions, which in the striola was detected very early, 6 h post-insult. During the initial 12 h of damage response, we observed global repression of DNA replication, in contrast to the natural, mitotic hair cell production in undamaged control utricles. Regeneration of hair cells in striolar and extrastriolar regions occurred via high rates of asymmetric supporting cell divisions, accompanied by delayed replenishment by symmetric division. While asymmetric division of supporting cells is the main regenerative response to aminoglycoside damage, the detection of symmetric divisions supports the concept of direct transdifferentiation where supporting cells need to be replenished after their phenotypic conversion into new hair cells. Supporting cell divisions appear to be well coordinated because total supporting cell numbers throughout the regenerative process were invariant, despite the initial large-scale loss of hair cells. We conclude that a single ototoxic drug application provides an experimental framework to study the precise onset and timing of utricle hair cell regeneration in vivo. Our findings indicate that initial triggers and signaling events occur already within a few hours after aminoglycoside exposure. Direct transdifferentiation and asymmetric division of supporting cells to generate new hair cells subsequently happen largely in parallel and persist for several days.
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Affiliation(s)
- Mirko Scheibinger
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA, 94305, USA.
| | - Daniel C Ellwanger
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - C Eduardo Corrales
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA, 94305, USA
- Department of Otology and Laryngology, Harvard Medical School and Brigham and Woman's Hospital, Boston, MA, 02115, USA
| | - Jennifer S Stone
- Department of Otolaryngology-Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, WA, 98195, USA
| | - Stefan Heller
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA, 94305, USA
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9
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Kelley MW, Stone JS. Development and Regeneration of Sensory Hair Cells. AUDITORY DEVELOPMENT AND PLASTICITY 2017. [DOI: 10.1007/978-3-319-21530-3_2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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10
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He Y, Cai C, Tang D, Sun S, Li H. Effect of histone deacetylase inhibitors trichostatin A and valproic acid on hair cell regeneration in zebrafish lateral line neuromasts. Front Cell Neurosci 2014; 8:382. [PMID: 25431550 PMCID: PMC4230041 DOI: 10.3389/fncel.2014.00382] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 10/27/2014] [Indexed: 11/13/2022] Open
Abstract
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.
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Affiliation(s)
- Yingzi He
- Department of Otorhinolaryngology, Affiliated Eye and ENT Hospital of Fudan University Shanghai, China
| | - Chengfu Cai
- Department of Otolaryngology Head and Neck Surgery, The First Affiliated Hospital of Xiamen University Xiamen, Fujian, China
| | - Dongmei Tang
- Department of Otorhinolaryngology, Affiliated Eye and ENT Hospital of Fudan University Shanghai, China
| | - Shan Sun
- Department of Otorhinolaryngology, Affiliated Eye and ENT Hospital of Fudan University Shanghai, China
| | - Huawei Li
- Department of Otorhinolaryngology, Affiliated Eye and ENT Hospital of Fudan University Shanghai, China ; State Key Laboratory of Medical Neurobiology, Fudan University Shanghai, China ; Institute of Stem Cell and Regeneration Medicine, Institutions of Biomedical Science, Fudan University Shanghai, China ; Key Laboratory of Hearing Science, Ministry of Health, EENT Hospital, Fudan University Shanghai, China
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11
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Sensational placodes: neurogenesis in the otic and olfactory systems. Dev Biol 2014; 389:50-67. [PMID: 24508480 PMCID: PMC3988839 DOI: 10.1016/j.ydbio.2014.01.023] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Revised: 01/27/2014] [Accepted: 01/28/2014] [Indexed: 11/22/2022]
Abstract
For both the intricate morphogenetic layout of the sensory cells in the ear and the elegantly radial arrangement of the sensory neurons in the nose, numerous signaling molecules and genetic determinants are required in concert to generate these specialized neuronal populations that help connect us to our environment. In this review, we outline many of the proteins and pathways that play essential roles in the differentiation of otic and olfactory neurons and their integration into their non-neuronal support structures. In both cases, well-known signaling pathways together with region-specific factors transform thickened ectodermal placodes into complex sense organs containing numerous, diverse neuronal subtypes. Olfactory and otic placodes, in combination with migratory neural crest stem cells, generate highly specialized subtypes of neuronal cells that sense sound, position and movement in space, odors and pheromones throughout our lives.
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12
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Korrapati S, Roux I, Glowatzki E, Doetzlhofer A. Notch signaling limits supporting cell plasticity in the hair cell-damaged early postnatal murine cochlea. PLoS One 2013; 8:e73276. [PMID: 24023676 PMCID: PMC3758270 DOI: 10.1371/journal.pone.0073276] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Accepted: 07/18/2013] [Indexed: 12/02/2022] Open
Abstract
In mammals, auditory hair cells are generated only during embryonic development and loss or damage to hair cells is permanent. However, in non-mammalian vertebrate species, such as birds, neighboring glia-like supporting cells regenerate auditory hair cells by both mitotic and non-mitotic mechanisms. Based on work in intact cochlear tissue, it is thought that Notch signaling might restrict supporting cell plasticity in the mammalian cochlea. However, it is unresolved how Notch signaling functions in the hair cell-damaged cochlea and the molecular and cellular changes induced in supporting cells in response to hair cell trauma are poorly understood. Here we show that gentamicin-induced hair cell loss in early postnatal mouse cochlear tissue induces rapid morphological changes in supporting cells, which facilitate the sealing of gaps left by dying hair cells. Moreover, we provide evidence that Notch signaling is active in the hair cell damaged cochlea and identify Hes1, Hey1, Hey2, HeyL, and Sox2 as targets and potential Notch effectors of this hair cell-independent mechanism of Notch signaling. Using Cre/loxP based labeling system we demonstrate that inhibition of Notch signaling with a γ- secretase inhibitor (GSI) results in the trans-differentiation of supporting cells into hair cell-like cells. Moreover, we show that these hair cell-like cells, generated by supporting cells have molecular, cellular, and basic electrophysiological properties similar to immature hair cells rather than supporting cells. Lastly, we show that the vast majority of these newly generated hair cell-like cells express the outer hair cell specific motor protein prestin.
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Affiliation(s)
- Soumya Korrapati
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Center for Hearing and Balance, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
| | - Isabelle Roux
- Department of Otolaryngology, Head and Neck Surgery, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Center for Hearing and Balance, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
| | - Elisabeth Glowatzki
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Department of Otolaryngology, Head and Neck Surgery, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Center for Hearing and Balance, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
| | - Angelika Doetzlhofer
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Department of Otolaryngology, Head and Neck Surgery, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Center for Hearing and Balance, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- * E-mail:
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13
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Hair cell generation by notch inhibition in the adult mammalian cristae. J Assoc Res Otolaryngol 2013; 14:813-28. [PMID: 23989618 DOI: 10.1007/s10162-013-0414-z] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 08/12/2013] [Indexed: 10/26/2022] Open
Abstract
Balance disorders caused by hair cell loss in the sensory organs of the vestibular system pose a significant health problem worldwide, particularly in the elderly. Currently, this hair cell loss is permanent as there is no effective treatment. This is in stark contrast to nonmammalian vertebrates who robustly regenerate hair cells after damage. This disparity in regenerative potential highlights the need for further manipulation in order to stimulate more robust hair cell regeneration in mammals. In the utricle, Notch signaling is required for maintaining the striolar support cell phenotype into the second postnatal week. Notch signaling has further been implicated in hair cell regeneration after damage in the mature utricle. Here, we investigate the role of Notch signaling in the mature mammalian cristae in order to characterize the Notch-mediated regenerative potential of these sensory organs. For these studies, we used the γ-secretase inhibitor, N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT), in conjunction with a method we developed to culture cristae in vitro. In postnatal and adult cristae, we found that 5 days of DAPT treatment resulted in a downregulation of the Notch effectors Hes1 and Hes5 and also an increase in the total number of Gfi1(+) hair cells. Hes5, as reported by Hes5-GFP, was downregulated specifically in peripheral support cells. Using lineage tracing with proteolipid protein (PLP)/CreER;mTmG mice, we found that these hair cells arose through transdifferentiation of support cells in cristae explanted from mice up to 10 weeks of age. These transdifferentiated cells arose without proliferation and were capable of taking on a hair cell morphology, migrating to the correct cell layer, and assembling what appears to be a stereocilia bundle with a long kinocilium. Overall, these data show that Notch signaling is active in the mature cristae and suggest that it may be important in maintaining the support cell fate in a subset of peripheral support cells.
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14
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Rubel EW, Furrer SA, Stone JS. A brief history of hair cell regeneration research and speculations on the future. Hear Res 2013; 297:42-51. [PMID: 23321648 DOI: 10.1016/j.heares.2012.12.014] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Revised: 12/18/2012] [Accepted: 12/19/2012] [Indexed: 12/24/2022]
Abstract
Millions of people worldwide suffer from hearing and balance disorders caused by loss of the sensory hair cells that convert sound vibrations and head movements into electrical signals that are conveyed to the brain. In mammals, the great majority of hair cells are produced during embryogenesis. Hair cells that are lost after birth are virtually irreplaceable, leading to permanent disability. Other vertebrates, such as fish and amphibians, produce hair cells throughout life. However, hair cell replacement after damage to the mature inner ear was either not investigated or assumed to be impossible until studies in the late 1980s proved this to be false. Adult birds were shown to regenerate lost hair cells in the auditory sensory epithelium after noise- and ototoxic drug-induced damage. Since then, the field of hair cell regeneration has continued to investigate the capacity of the auditory and vestibular epithelia in vertebrates (fishes, birds, reptiles, and mammals) to regenerate hair cells and to recover function, the molecular mechanisms governing these regenerative capabilities, and the prospect of designing biologically-based treatments for hearing loss and balance disorders. Here, we review the major findings of the field during the past 25 years and speculate how future inner ear repair may one day be achieved.
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Affiliation(s)
- Edwin W Rubel
- Virginia Merrill Bloedel Hearing Research Center and Department of Otolaryngology and Head & Neck Surgery, University of Washington, Seattle, WA 98195, USA.
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15
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Mackenzie SM, Raible DW. Proliferative regeneration of zebrafish lateral line hair cells after different ototoxic insults. PLoS One 2012; 7:e47257. [PMID: 23094043 PMCID: PMC3475690 DOI: 10.1371/journal.pone.0047257] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Accepted: 09/11/2012] [Indexed: 11/25/2022] Open
Abstract
Sensory hair cells in the zebrafish lateral line regenerate rapidly and completely after damage. Previous studies have used a variety of ototoxins to kill lateral line hair cells to study different phenomena including mechanisms of hair cell death and regeneration. We sought to directly compare these ototoxins to determine if they differentially affected the rate and amount of hair cell replacement. In addition, previous studies have found evidence of proliferative hair cell regeneration in zebrafish, but both proliferation and non-mitotic direct transdifferentiation have been observed during hair cell regeneration in the sensory epithelia of birds and amphibians. We sought to test whether a similar combination of regenerative mechanisms exist in the fish. We analyzed the time course of regeneration after treatment with different ototoxic compounds and also labeled dividing hair cell progenitors. Certain treatments, including cisplatin and higher concentrations of dissolved copper, significantly delayed regeneration by one or more days. However, cisplatin did not block all regeneration as observed previously in the chick basilar papilla. The particular ototoxin did not appear to affect the mechanism of regeneration, as we observed evidence of recent proliferation in the majority of new hair cells in all cases. Inhibiting proliferation with flubendazole blocked the production of new hair cells and prevented the accumulation of additional precursors, indicating that proliferation has a dominant role during regeneration of lateral line hair cells.
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Affiliation(s)
- Scott M. Mackenzie
- Department of Biological Structure, University of Washington, Seattle, Washington, United States of America
- Graduate Program in Neurobiology and Behavior, University of Washington, Seattle, Washington, United States of America
| | - David W. Raible
- Department of Biological Structure, University of Washington, Seattle, Washington, United States of America
- Graduate Program in Neurobiology and Behavior, University of Washington, Seattle, Washington, United States of America
- * E-mail:
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Lewis RM, Hume CR, Stone JS. Atoh1 expression and function during auditory hair cell regeneration in post-hatch chickens. Hear Res 2012; 289:74-85. [PMID: 22543087 PMCID: PMC3371146 DOI: 10.1016/j.heares.2012.04.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 04/06/2012] [Accepted: 04/11/2012] [Indexed: 11/24/2022]
Abstract
Loss of hair cells in humans leads to irreversible hearing deficits, since auditory hair cells are not replaced. In contrast, hair cells are regenerated in the auditory epithelium of mature birds after damage by non-sensory supporting cells that transdifferentiate into hair cells by mitotic and/or non-mitotic mechanisms. Factors controlling these processes are poorly understood. The basic helix-loop-helix transcription factor ATOH1 is both necessary and sufficient for developmental hair cell differentiation, but it is unclear if it plays the same role in the mitotic and non-mitotic pathways in hair cell regeneration. We examined Atoh1 expression and function during hair cell regeneration in chickens. Atoh1 transcripts were increased in many supporting cells in the damaged auditory epithelium shortly after ototoxin administration and later became restricted to differentiating hair cells. Fate-mapping in vitro using an Atoh1 enhancer reporter demonstrated that only 56% of the supporting cells that spontaneously upregulate Atoh1 enhancer activity after damage acquired the hair cell fate. Inhibition of notch signaling using a gamma secretase antagonist stimulated an increase in Atoh1 reporter activity and induced a higher proportion of supporting cells with Atoh1 activity (73%) to differentiate as hair cells. Forced overexpression of Atoh1 in supporting cells triggered 66% of them to acquire the hair cell fate and nearly tripled their likelihood of cell cycle entry. These findings demonstrate that Atoh1 is broadly upregulated in supporting cells after damage, but a substantial proportion of supporting cells with Atoh1 activation fails to acquire hair cell features, in part due to gamma secretase-dependent activities.
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Affiliation(s)
- Rebecca M. Lewis
- Department of Speech and Hearing Sciences, University of Washington, Seattle, WA, USA
| | - Clifford R. Hume
- Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, WA, USA
- Department of Otolaryngology e Head and Neck Surgery, University of Washington, Seattle, WA, USA
| | - Jennifer S. Stone
- Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, WA, USA
- Department of Otolaryngology e Head and Neck Surgery, University of Washington, Seattle, WA, USA
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Bermingham-McDonogh O, Reh TA. Regulated reprogramming in the regeneration of sensory receptor cells. Neuron 2011; 71:389-405. [PMID: 21835338 DOI: 10.1016/j.neuron.2011.07.015] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/22/2011] [Indexed: 12/15/2022]
Abstract
Vision, olfaction, hearing, and balance are mediated by receptors that reside in specialized sensory epithelial organs. Age-related degeneration of the photoreceptors in the retina and the hair cells in the cochlea, caused by macular degeneration and sensorineural hearing loss, respectively, affect a growing number of individuals. Although sensory receptor cells in the mammalian retina and inner ear show only limited or no regeneration, in many nonmammalian vertebrates, these sensory epithelia show remarkable regenerative potential. We summarize the current state of knowledge of regeneration in the specialized sense organs in both nonmammalian vertebrates and mammals and discuss possible areas where new advances in regenerative medicine might provide approaches to successfully stimulate sensory receptor cell regeneration. The field of regenerative medicine is still in its infancy, but new approaches using stem cells and reprogramming suggest ways in which the potential for regeneration may be restored in individuals suffering from sensory loss.
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Affiliation(s)
- Olivia Bermingham-McDonogh
- Department of Biological Structure, Institute for Stem Cells and Regenerative Medicine, University of Washington, Seattle, WA 98195, USA.
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Hair cell fate decisions in cochlear development and regeneration. Hear Res 2010; 266:18-25. [PMID: 20438823 DOI: 10.1016/j.heares.2010.04.012] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Revised: 04/26/2010] [Accepted: 04/27/2010] [Indexed: 11/28/2022]
Abstract
The discovery of avian cochlear hair cell regeneration in the late 1980s and the concurrent development of new techniques in molecular and developmental biology generated a renewed interest in understanding the genetic mechanisms that regulate hair cell development in the embryonic avian and mammalian cochlea and regeneration in the mature avian cochlea. Research from many labs has demonstrated that the development of the inner ear utilizes a complex series of genetic signals and pathways to generate the endorgans, specify cell identities, and establish innervation patterns found in the inner ear. Recent studies have shown that the Notch signaling pathway, the Atoh1/Hes signaling cascade, the stem cell marker Sox2, and some of the unconventional myosin motor proteins are utilized to regulate distinct steps in inner ear development. While many of the individual genes involved in these pathways have been identified from studies of mutant and knockout mouse cochleae, the interplay of all these signals into a single systemic program that directs this process needs to be explored. We need to know not only what genes are involved, but understand how their gene products interact with one another in a structural and temporal framework to guide hair cell and supporting cell differentiation and maturation.
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Abstract
Cisplatin is a chemotherapeutic agent that is widely used in the treatment of solid tumors. Ototoxicity is a common side effect of cisplatin therapy and often leads to permanent hearing loss. The sensory organs of the avian ear are able to regenerate hair cells after aminoglycoside ototoxicity. This regenerative response is mediated by supporting cells, which serve as precursors to replacement hair cells. Given the antimitotic properties of cisplatin, we examined whether the avian ear was also capable of regeneration after cisplatin ototoxicity. Using cell and organ cultures of the chick cochlea and utricle, we found that cisplatin treatment caused apoptosis of both auditory and vestibular hair cells. Hair cell death in the cochlea occurred in a unique pattern, progressing from the low-frequency (distal) region toward the high-frequency (proximal) region. We also found that cisplatin caused a dose-dependent reduction in the proliferation of cultured supporting cells as well as increased apoptosis in those cells. As a result, we observed no recovery of hair cells after ototoxic injury caused by cisplatin. Finally, we explored the potential for nonmitotic hair cell recovery via activation of Notch pathway signaling. Treatment with the gamma-secretase inhibitor N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester failed to promote the direct transdifferentiation of supporting cells into hair cells in cisplatin-treated utricles. Taken together, our data show that cisplatin treatment causes maintained changes to inner ear supporting cells and severely impairs the ability of the avian ear to regenerate either via proliferation or by direct transdifferentiation.
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Shang J, Cafaro J, Nehmer R, Stone J. Supporting cell division is not required for regeneration of auditory hair cells after ototoxic injury in vitro. J Assoc Res Otolaryngol 2010; 11:203-22. [PMID: 20165896 DOI: 10.1007/s10162-009-0206-7] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2009] [Accepted: 12/22/2009] [Indexed: 01/16/2023] Open
Abstract
In chickens, nonsensory supporting cells divide and regenerate auditory hair cells after injury. Anatomical evidence suggests that supporting cells can also transdifferentiate into hair cells without dividing. In this study, we characterized an organ culture model to study auditory hair cell regeneration, and we used these cultures to test if direct transdifferentiation alone can lead to significant hair cell regeneration. Control cultures (organs from posthatch chickens maintained without streptomycin) showed complete hair cell loss in the proximal (high-frequency) region by 5 days. In contrast, a 2-day treatment with streptomycin induced loss of hair cells from all regions by 3 days. Hair cell regeneration proceeded in culture, with the time course of supporting cell division and hair cell differentiation generally resembling in vivo patterns. The degree of supporting cell division depended upon the presence of streptomycin, the epithelial region, the type of culture media, and serum concentration. On average, 87% of the regenerated hair cells lacked the cell division marker BrdU despite its continuous presence, suggesting that most hair cells were regenerated via direct transdifferentiation. Addition of the DNA polymerase inhibitor aphidicolin to culture media prevented supporting cell division, but numerous hair cells were regenerated nonetheless. These hair cells showed signs of functional maturation, including stereociliary bundles and rapid uptake of FM1-43. These observations demonstrate that direct transdifferentiation is a significant mechanism of hair cell regeneration in the chicken auditory after streptomycin damage in vitro.
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Affiliation(s)
- Jialin Shang
- Department of Otolaryngology/Head and Neck Surgery, The Virginia Merrill Bloedel Hearing Research Center, University of Washington School of Medicine, Seattle, WA 98195-7923, USA
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Abstract
PURPOSE OF REVIEW In evaluating strategies to preserve or regenerate the cochlea, understanding the process of labyrinthine injury on a cellular and molecular level is crucial. Examination of inner ear injury reveals mechanism-specific types of damage, often at specific areas within the cochlea. Site-specific interventions can then be considered. RECENT FINDINGS The review will briefly summarize the historical perspective of advancements in hearing science through 2006. Areas of research covered include hair cell protection, hair cell regeneration, spiral ganglion cell regeneration, and stria vascularis metabolic regulation. SUMMARY The review will briefly summarize the early development of a few such site-specific interventions for inner ear functional rehabilitation, for work done prior to 2006. The outstanding reviews of cutting edge research from this year's and last year's Hearing Science section of Current Opinion in Otolaryngology - Head and Neck Surgery can then be understood and appreciated in a more informed manner.
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Schuck JB, Smith ME. Cell proliferation follows acoustically-induced hair cell bundle loss in the zebrafish saccule. Hear Res 2009; 253:67-76. [PMID: 19327392 DOI: 10.1016/j.heares.2009.03.008] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 03/11/2009] [Accepted: 03/16/2009] [Indexed: 10/21/2022]
Abstract
Fishes are capable of regenerating sensory hair cells in the inner ear after acoustic trauma. However, a time course of auditory hair cell regeneration has not been established for zebrafish. Adult zebrafish (Danio rerio) were exposed to a 100 Hz pure tone at 179 dB re 1 microPa RMS for 36 h and then allowed to recover for 0-14 days before morphological analysis. Hair cell bundle loss and recovery were determined using phalloidin to visualize hair bundles. Cell proliferation was quantified through bromodeoxyuridine (BrdU) labeling. Immediately following sound exposure, zebrafish saccules exhibited significant hair bundle damage (e.g., splayed, broken, and missing stereocilia) and loss (i.e., missing bundles and lesions in the epithelia) in the caudal region. Hair bundle counts increased over the course of the experiment, reaching pre-treatment levels at 14 days post-sound exposure (dpse). Low levels of proliferation were observed in untreated controls, indicating that some cells of the zebrafish saccule are mitotically active in the absence of a damaging event. In sound-exposed fish, cell proliferation peaked two dpse in the caudal region, and to a lesser extent in the rostral region. This proliferation was followed by an increase in numbers of cuticular plates with rudimentary stereocilia and immature-like hair bundles at 7 and 14 dpse, suggesting that at least some of the saccular cell proliferation resulted in newly formed hair cells. This study establishes a time course of hair cell bundle regeneration in the zebrafish inner ear and demonstrates that cell proliferation is associated with the regenerative process.
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Affiliation(s)
- Julie B Schuck
- Department of Biology and Biotechnology Center, Western Kentucky University, 1906 College Heights Blvd. #11080, Bowling Green, KY 42104-1080, USA
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Li–dong Z, Jun L, Yin–yan H, Jian–he S, Shi–ming Y. Supporting Cells–a New Area in Cochlear Physiology Study. J Otol 2008. [DOI: 10.1016/s1672-2930(08)50002-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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WDR1 presence in the songbird basilar papilla. Hear Res 2008; 240:102-11. [PMID: 18514449 DOI: 10.1016/j.heares.2008.03.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2007] [Revised: 02/26/2008] [Accepted: 03/21/2008] [Indexed: 11/16/2022]
Abstract
WD40 repeat 1 protein (WDR1) was first reported in the acoustically injured chicken inner ear, and bioinformatics revealed that WDR1 has numerous WD40 repeats, important for protein-protein interactions. It has significant homology to actin interacting protein 1 (Aip1) in several lower species such as yeast, roundworm, fruitfly and frog. Several studies have shown that Aip1 binds cofilin/actin depolymerizing factor, and that these interactions are pivotal for actin disassembly via actin filament severing and actin monomer capping. However, the role of WDR1 in auditory function has yet to be determined. WDR1 is typically restricted to hair cells of the normal avian basilar papilla, but is redistributed towards supporting cells after acoustic overstimulation, suggesting that WDR1 may be involved in inner ear response to noise stress. One aim of the present study was to resolve the question as to whether stress factors, other than intense sound, could induce changes in WDR1 presence in the affected avian inner ear. Several techniques were used to assess WDR1 presence in the inner ears of songbird strains, including Belgian Waterslager (BW) canary, an avian strain with degenerative hearing loss thought to have a genetic basis. Reverse transcription, followed by polymerase chain reactions with WDR1-specific primers, confirmed WDR1 presence in the basilar papillae of adult BW, non-BW canaries, and zebra finches. Confocal microscopy examinations, following immunocytochemistry with anti-WDR1 antibody, localized WDR1 to the hair cell cytoplasm along the avian sensory epithelium. In addition, little, if any, staining by anti-WDR1 antibody was observed among supporting cells in the chicken or songbird ear. The present observations confirm and extend the early findings of WDR1 localization in hair cells, but not in supporting cells, in the normal avian basilar papilla. However, unlike supporting cells in the acoustically damaged chicken basilar papilla, the inner ear of the BW canary showed little, if any, WDR1 up-regulation in supporting cells. This may be due to the fact that the BW canary already has established hearing loss and/or to the possibility that the mechanism(s) involved in BW hearing loss may not be related to WDR1.
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Smith ME, Coffin AB, Miller DL, Popper AN. Anatomical and functional recovery of the goldfish (Carassius auratus) ear following noise exposure. ACTA ACUST UNITED AC 2007; 209:4193-202. [PMID: 17050834 DOI: 10.1242/jeb.02490] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Fishes can regenerate lateral line and inner ear sensory hair cells that have been lost following exposure to ototoxic antibiotics. However, regenerative capabilities following noise exposure have not been explored in fish. Moreover, nothing is known about the functional relationship between hair cell damage and hearing loss, or the time course of morphological versus functional recovery in fishes. This study examines the relationship between hair cell damage and physiological changes in auditory responses following noise exposure in the goldfish (Carassius auratus). Goldfish were exposed to white noise (170 dB re. 1 muPa RMS) for 48 h and monitored for 8 days after exposure. Auditory thresholds were determined using the auditory evoked potential technique, and morphological hair cell damage was analyzed using phalloidin and DAPI labeling to visualize hair cell bundles and nuclei. A TUNEL assay was used to identify apoptotic cells. Following noise exposure, goldfish exhibited a significant temporary threshold shift (TTS; ranging from 13 to 20 dB) at all frequencies tested (from 0.2-2 kHz). By 7 days post-exposure, goldfish hearing recovered significantly (mean TTS<4 dB). Increased apoptotic activity was observed in the saccules and lagenae between 0 and 2 days post-exposure. Immediately after noise exposure, the central and caudal regions of saccules exhibited significant loss of hair bundles. Hair bundle density in the central saccule recovered by the end of the experiment (8 days post-exposure) while bundle density in the caudal saccule did not return to control levels in this time frame. These data demonstrate that goldfish inner ear epithelia show damage following noise exposure and that they are capable of significant regenerative responses similar to those seen following ototoxic drug treatment. Interestingly, functional recovery preceded morphological recovery in the goldfish saccule, suggesting that only a subset of hair cells are necessary for normal auditory responses, at least to the extent that hearing was measured in this study.
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Affiliation(s)
- Michael E Smith
- Department of Biology and Center for Comparative and Evolutionary Biology of Hearing, University of Maryland, College Park, MD 20742, USA.
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Taylor RR, Forge A. Hair cell regeneration in sensory epithelia from the inner ear of a urodele amphibian. J Comp Neurol 2005; 484:105-20. [PMID: 15717301 DOI: 10.1002/cne.20450] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
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.
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Affiliation(s)
- Ruth R Taylor
- UCL Centre for Auditory Research, University College London, London WC1X 8EE, United Kingdom.
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Abstract
The publication of a paper entitled "Direct transdifferentiation gives rise to the earliest new hair cells in regenerating avian auditory epithelium" in the Journal of Neuroscience Research offers the opportunity to call attention to a well-developed line of research on the auditory receptor of birds, which should be of interest to students of regeneration and plasticity of the mature nervous system in higher vertebrates, including mammals. Although hair cell proliferation normally stops before hatching, destruction of the auditory receptors of the chicken may be followed by complete regeneration of hair cells. Most of the new hair cells arise from a new wave of proliferation, but Roberson et al. show that about one-third of the new hair cells are formed without undergoing cell division and thus may differentiate from so-called supporting cells or cells with an "intermediate morphology." This finding suggests some models for regeneration of this neuroepithelium, including the possibility that mature supporting cells could transform directly into hair cells. The present Mini-Review discusses some of the models for neural regeneration that future studies might address in the light of our current knowledge and the new report. The possibility is raised that transitional forms of hair cell and supporting cell precursors may reside in the inner ear in a quiescent state until stimulated by damage.
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Affiliation(s)
- D Kent Morest
- Department of Neuroscience, The University of Connecticut Health Center, Farmington, CT 06030, USA.
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Roberson DW, Alosi JA, Cotanche DA. Direct transdifferentiation gives rise to the earliest new hair cells in regenerating avian auditory epithelium. J Neurosci Res 2004; 78:461-71. [PMID: 15372572 DOI: 10.1002/jnr.20271] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The avian auditory epithelium is capable of complete regeneration after hair cell (HC) loss. Most new HCs arise via cell division, but approximately one-third of new HCs arise via direct transdifferentiation (DT), in which supporting cells (SCs) alter their phenotype without dividing. In this study, we used synchronous, gentamicin-induced near-total HC loss in the basal end of the epithelium and continuous infusion of the cell division marker bromodeoxyuridine (BrdU) to identify the origin of each individual regenerating HC. Early new HCs were identified by immunolabeling for the HC-specific marker myosin-VIIa, and mitotic cells with BrdU immunolabeling. The first new HCs arising via DT appear 72-96 hr after gentamicin, 24-48 hr earlier than the first new mitotic HCs. After Day 6, however, most new HCs are mitotic. The "intermediate" morphology that has been suggested to be characteristic of DT is seen in HCs arising via both pathways. These findings suggest that DT is a simpler, more rapid process that produces the first new HCs, and that mitotic regeneration is somewhat slower but ultimately produces most new HCs. The identical morphology of regenerating HCs from both pathways suggests that once HC fate is established, all new HCs follow similar cellular processes during differentiation and reorganization into the regenerated epithelium.
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Affiliation(s)
- David W Roberson
- Department of Otolaryngology, Children's Hospital Boston, Boston, Massachusetts 02115, USA.
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Yamasoba T, Kondo K, Miyajima C, Suzuki M. Changes in cell proliferation in rat and guinea pig cochlea after aminoglycoside-induced damage. Neurosci Lett 2003; 347:171-4. [PMID: 12875913 DOI: 10.1016/s0304-3940(03)00675-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Cell proliferation in the cochleae of guinea pigs and rats was investigated after systemic application of kanamycin sulfate (KM) and ethacrynic acid (EA). Bromodeoxyuridine (BrdU) was injected daily for 10 days, after which the number of BrdU-positive cells was counted in paraffin sections of the cochlea. Only a few BrdU-positive cells were present in the spiral ligament and among the acoustic nerve fibers in the non-deafened control animals. Animals treated with KM and EA had profound hearing loss and significant increases in the number of BrdU-positive cells in the spiral ligament and among the acoustic nerve fibers. No BrdU-positive cells were found in the auditory sensory epithelium of any animal. These findings suggest that in the mature mammalian cochlea cell proliferation increases in nonsensory regions after ototoxic damage but may not occur in the auditory sensory epithelium.
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Affiliation(s)
- Tatsuya Yamasoba
- Department of Otolaryngology and Head and Neck Surgery, University of Tokyo, 113-8665, Tokyo, Japan.
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Berggren D, Liu W, Frenz D, Van De Water T. Spontaneous hair-cell renewal following gentamicin exposure in postnatal rat utricular explants. Hear Res 2003; 180:114-25. [PMID: 12782359 DOI: 10.1016/s0378-5955(03)00112-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We have established an in vitro model of long-time culture of 4-day-old rat utricular maculae to study aminoglycoside-induced vestibular hair-cell renewal in the mammalian inner ear. The explanted maculae were cultured for up to 28 days on the surface of a membrane insert system. In an initial series of experiments utricles were exposed to 1 mM of gentamicin for 48 h and then allowed to recover in unsupplemented medium or in medium supplemented with the anti-mitotic drug aphidicolin. In a parallel control series, explants were not exposed to gentamicin. Utricles were harvested at specified time points from the second through the 28th day in vitro. Whole-mount utricles were stained with phalloidin-fluorescein isothiocyanate and their stereociliary bundles visualized and counted. In a second experimental series 2'-bromo-5'deoxyuridine labeling was used to confirm the antimitotic efficacy of aphidicolin. Loss of hair-cell stereociliary bundles was nearly complete 3 days after exposure to gentamicin, with the density of stereociliary bundles only 3-4% of their original density. Renewal of hair-cell bundles was abundant (i.e. 15x increase) in cultures in unsupplemented medium, with a peak of stereociliary bundle renewal reached after 21 days in vitro. A limited amount of hair-cell renewal also occurred in the presence of the anti-mitotic drug, aphidicolin. These results suggest that spontaneous renewal of hair-cell stereociliary bundles following gentamicin damage in utricular explants predominantly follows a pathway that includes mitotic events, but that a small portion of the hair-cell stereociliary bundle renewal does not require mitotic activity.
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Affiliation(s)
- Diana Berggren
- Department of Otolaryngology, Albert Einstein College of Medicine, New York, NY, USA
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Affiliation(s)
- Allen F Ryan
- Department of Surgery/Otolaryngology, University of California San Diego School of Medicine and San Diego Veterans Administration Medical Center, La Jolla, California 92093, USA
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Oh SH, Adler HJ, Raphael Y, Lomax MI. WDR1 colocalizes with ADF and actin in the normal and noise-damaged chick cochlea. J Comp Neurol 2002; 448:399-409. [PMID: 12115702 DOI: 10.1002/cne.10265] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Auditory hair cells of birds, unlike hair cells in the mammalian organ of Corti, can regenerate following sound-induced loss. We have identified several genes that are upregulated following such an insult. One gene, WDR1, encodes the vertebrate homologue of actin-interacting protein 1, which interacts with actin depolymerization factor (ADF) to enhance the rate of actin filament cleavage. We examined WDR1 expression in the developing, mature, and noise-damaged chick cochlea by in situ hybridization and immunocytochemistry. In the mature cochlea, WDR1 mRNA was detected in hair cells, homogene cells, and cuboidal cells, all of which contain high levels of F-actin. In the developing inner ear, WDR1 mRNA was detected in homogene cells and cuboidal cells by embryonic day 7, in the undifferentiated sensory epithelium by day 9, and in hair cells at embryonic day 16. We also demonstrated colocalization of WDR1, ADF, and F-actin in all three cell types in the normal and noise-damaged cochlea. Immediately after acoustic overstimulation, WDR1 mRNA was seen in supporting cells. These cells contribute to the structural integrity of the basilar papilla, the maintenance of the ionic barrier at the reticular lamina, and the generation of new hair cells. These results indicate that one of the immediate responses of the supporting cell after noise exposure is to induce WDR1 gene expression and thus to increase the rate of actin filament turnover. These results suggest that WDR1 may play a role either in restoring cytoskeletal integrity in supporting cells or in a cell signaling pathway required for regeneration.
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Affiliation(s)
- Seung-Ha Oh
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, The University of Michigan Medical School, Ann Arbor, MI 48109-0506, USA
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Hossler FE, Olson KR, Musil G, McKamey MI. Ultrastructure and blood supply of the tegmentum vasculosum in the cochlea of the duckling. Hear Res 2002; 164:155-65. [PMID: 11950535 DOI: 10.1016/s0378-5955(01)00427-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The tegmentum vasculosum of the duckling consists of a highly folded epithelium which extends over the dorsal and lateral walls of the cochlear duct, separating the scala media from the scala vestibuli. This epithelium consists of two distinct cell types, dark cells and light cells, and is well vascularized. The surface of the epithelium is formed by a mosaic of alternating dark and light cells. The goblet-shaped dark cells have an electron-dense, organelle-rich cytoplasm, and are expanded basally by extensive basolateral plasma membrane infoldings, within which are numerous mitochondria. Dark cells are isolated from each other and from the capillaries within the epithelium by intervening light cells. In contrast, columnar light cells exhibit an electron-lucent, organelle-poor cytoplasm and may extend from the underlying capillaries to the endolymphatic surface. Light cells contain abundant, coated endocytic vesicles on their apical surfaces and are bound, apically, to other light cells or to dark cells by tight junctions and desmosomes. Laterally, light cells are linked to each other either by complex, fluid-filled membrane interdigitations or by extensive gap junctions. Plasma membrane interdigitations and obvious, fluid-filled intercellular spaces characterize the lateral borders between light and dark cells. Vascular corrosion casting reveals the three-dimensional anatomy of the cochlear vasculature. A continuous arteriolar loop fed by anterior and posterior cochlear arterioles encircles the cochlear duct. The rich capillary beds of the tegmentum vasculosum are supplied by arching arterioles arising from this loop. These capillaries are the continuous type and are situated primarily within the core of the epithelium or along its border with the scala vestibuli. The structure and blood supply of the tegmentum vasculosum are characteristic of an epithelium involved in active transport.
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Affiliation(s)
- Fred E Hossler
- Department of Anatomy and Cell Biology, J.H. Quillen College of Medicine, Box 70582, East Tennessee State University, Johnson City 37614, USA.
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Bermingham-McDonogh O, Stone JS, Reh TA, Rubel EW. FGFR3 expression during development and regeneration of the chick inner ear sensory epithelia. Dev Biol 2001; 238:247-59. [PMID: 11784008 DOI: 10.1006/dbio.2001.0412] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Several studies suggest fibroblast growth factor receptor 3 (FGFR3) plays a role in the development of the auditory epithelium in mammals. We undertook a study of FGFR3 in the developing and mature chicken inner ear and during regeneration of this epithelium to determine whether FGFR3 shows a similar pattern of expression in birds. FGFR3 mRNA is highly expressed in most support cells in the mature chick basilar papilla but not in vestibular organs of the chick. The gene is expressed early in the development of the basilar papilla. Gentamicin treatment sufficient to destroy hair cells in the basilar papilla causes a rapid, transient downregulation of FGFR3 mRNA in the region of damage. In the initial stages of hair cell regeneration, the support cells that reenter the mitotic cycle in the basilar papilla do not express detectable levels of FGFR3 mRNA. However, once the hair cells have regenerated in this region, the levels of FGFR3 mRNA and protein expression rapidly return to approximate those in the undamaged epithelium. These results indicate that FGFR3 expression changes after drug-induced hair cell damage to the basilar papilla in an opposite way to that found in the mammalian cochlea and may be involved in regulating the proliferation of support cells.
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Affiliation(s)
- O Bermingham-McDonogh
- Virginia Merrill Bloedel Hearing Research Center, University of Washington School of Medicine, Seattle, Washington 98195, USA.
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Ibsch M, Anken RH, Vöhringer P, Rahmann H. Vesicular bodies in fish maculae are artifacts not contributing to otolith growth. Hear Res 2001; 153:80-90. [PMID: 11223298 DOI: 10.1016/s0378-5955(00)00258-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The presence, morphology and possible origin of vesicle-like bodies (VBs) within the inner ear macular otolithic membrane of developmental stages of cichlid fish Oreochromis mossambicus and neonate (i.e. functionally fully developed except the reproductive organs) swordtail fish Xiphophorus helleri were analyzed by means of transmission and scanning electron microscopy (TEM and SEM, respectively) employing various fixation procedures. Some authors believe that these VBs are involved in the formation of the organic phase of inner ear otoliths (or statoliths in birds and mammals). Decreasing the osmolarity of the fixation medium from a value rather close to that of native fresh water fish tissue (i.e. 250 mOsm and 290--300 mOsm, respectively) to a value of fixatives mostly employed in TEM studies (ca. 190 mOsm), the amount of VBs increased and the components of sensory inner ear tissue increasingly dilated. Whilst a conventional prefixation with aldehydes followed by osmium tetroxide postfixation yielded numerous VBs, only few of them were observed when the tissue was fixed with aldehydes and osmium tetroxide simultaneously. Therefore, the results demonstrate that inner ear sensory epithelia are extremely sensitive to altering fixation media. On this background it must be concluded that VBs are fixative (i.e. glutaraldehyde) induced artificial structures, so-called membrane blisters. Thus, the protein matrix of otoliths (and possibly that of statoliths in higher vertebrates) is rather provided by secretion processes than by the release of vesicles.
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Affiliation(s)
- M Ibsch
- Zoological Institute, University of Stuttgart-Hohenheim, Garbenstr. 30, D-70593 Stuttgart, Germany
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Kevetter GA, Blumberg KR, Correia MJ. Hair cell and supporting cell density and distribution in the normal and regenerating posterior crista ampullaris of the pigeon. Int J Dev Neurosci 2000; 18:855-67. [PMID: 11154855 DOI: 10.1016/s0736-5748(00)00029-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The numbers of supporting cells and the numbers and types of hair cells in three distinct longitudinal regions through the posterior canal cristae of control and streptomycin-treated pigeons were determined using stereological techniques. For control cristae, type I (3758) and type II (3517) hair cells occurred in approximately equal numbers. However, the proportions varied in different longitudinal zones: Zone I (peripheral region) had four times more type II hair cells (2083) than type I (483), while Zone II (intermediate region) had almost seven times more type I (2517) than type II (367) hair cells and Zone III (central region) had relatively equal numbers of type I (758) and type II (1067) hair cells. Novel findings included the following: (1) immediately after the post-injection sequence (PIS) of streptomycin, there was a significant reduction in both hair cells (-93%) and supporting cells (-45%); (2) by 70 days after the PIS, the population of type I hair cells returned to control values (however, the normal complement of complex calyces took 1 year to recover); (3) during the first 143 days after the PIS, the number of type I and type II hair cells across all zones returned linearly with about the same slope (46 and 43 cells per day, respectively), although the rate of return differed significantly in different zones; (4) there was a massive overproduction of hair cells (+150%) and supporting cells (+120%) during the first 5 months of recovery; and (5) during the first year after the PIS, both hair cells and supporting cells increased and their increases in numbers were correlated (r = 0.88, P < 0.01). Knowledge of the sequence and numbers of regenerating hair cells may help elucidate common modes of cell survival, recovery, and compensation from neural insult.
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Affiliation(s)
- G A Kevetter
- Department of Otolaryngology, University of Texas Medical Branch, Galveston 77555-1063, USA.
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Baird RA, Burton MD, Lysakowski A, Fashena DS, Naeger RA. Hair cell recovery in mitotically blocked cultures of the bullfrog saccule. Proc Natl Acad Sci U S A 2000; 97:11722-9. [PMID: 11050201 PMCID: PMC34341 DOI: 10.1073/pnas.97.22.11722] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Hair cells in many nonmammalian vertebrates are regenerated by the mitotic division of supporting cell progenitors and the differentiation of the resulting progeny into new hair cells and supporting cells. Recent studies have shown that nonmitotic hair cell recovery after aminoglycoside-induced damage can also occur in the vestibular organs. Using hair cell and supporting cell immunocytochemical markers, we have used confocal and electron microscopy to examine the fate of damaged hair cells and the origin of immature hair cells after gentamicin treatment in mitotically blocked cultures of the bullfrog saccule. Extruding and fragmenting hair cells, which undergo apoptotic cell death, are replaced by scar formations. After losing their bundles, sublethally damaged hair cells remain in the sensory epithelium for prolonged periods, acquiring supporting cell-like morphology and immunoreactivity. These modes of damage appear to be mutually exclusive, implying that sublethally damaged hair cells repair their bundles. Transitional cells, coexpressing hair cell and supporting cell markers, are seen near scar formations created by the expansion of neighboring supporting cells. Most of these cells have morphology and immunoreactivity similar to that of sublethally damaged hair cells. Ultrastructural analysis also reveals that most immature hair cells had autophagic vacuoles, implying that they originated from damaged hair cells rather than supporting cells. Some transitional cells are supporting cells participating in scar formations. Supporting cells also decrease in number during hair cell recovery, supporting the conclusion that some supporting cells undergo phenotypic conversion into hair cells without an intervening mitotic event.
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Affiliation(s)
- R A Baird
- Fay and Carl Simons Center for Biology of Hearing and Deafness, Central Institute for the Deaf, 4560 Clayton Road, St. Louis, MO 63110, USA.
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Cyr JL, Bell AM, Hudspeth AJ. Identification with a recombinant antibody of an inner-ear cytokeratin, a marker for hair-cell differentiation. Proc Natl Acad Sci U S A 2000; 97:4908-13. [PMID: 10758152 PMCID: PMC18331 DOI: 10.1073/pnas.070050797] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Extensive biochemical characterization of cells in the inner ear has been hampered by a lack of tools with which to identify inner-ear proteins. By using a single-chain antibody fragment isolated from a bacteriophage-displayed library, we have identified a cytokeratin that is abundant in nonsensory cells of the frog inner ear. Although the progenitors of hair cells exhibit strong immunoreactivity to this cytokeratin, the signal declines in immature hair cells and vanishes as the cells mature. The correlation between diminished immunoreactivity and hair-cell differentiation indicates that the cytokeratin is down-regulated during the transition from a nonsensory to a sensory cell and suggests that the marker is an early index of hair-cell differentiation.
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Affiliation(s)
- J L Cyr
- Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, 1230 York Avenue, New York, NY 10021-6399, USA
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Ibsch M, Vohringer P, Anken RH, Rahmann H. Electronmicroscopic investigations on the role of vesicle-like bodies in inner ear maculae for fish otolith growth. ADVANCES IN SPACE RESEARCH : THE OFFICIAL JOURNAL OF THE COMMITTEE ON SPACE RESEARCH (COSPAR) 2000; 25:2031-2034. [PMID: 11542853 DOI: 10.1016/s0273-1177(99)01011-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The presence, morphology and possible origin of vesicle-like bodies (VBs) within the inner ear otolithic membrane of developmental stages of cichlid fish Oreochromis mossambicus and adult swordtail fish Xiphophorus helleri was analysed by means of transmission and scanning electron microscopy (TEM and SEM, respectively) employing various fixation procedures. The VBs are believed to be involved in the formation of the otolith (or statolith in birds and mammals) regarding the supply of the otolith's organic material. Increasing the osmolarity of the fixation medium decreased the number of VBs seen. Decalcification ended up in a complete disappearance of the VBs. Whilst a fixation with glutaraldehyde followed by OSO4 fixation yielded numerous VBs, only few of them were observed when the tissue was fixed with glutaraldehyde and OSO4 simultaneously. Therefore, the results strongly suggest that the VBs are fixative (i.e., glutaraldehyde) induced artifacts, so-called blisters. With this, the supply of an oto- or statolith's organic material remains obscure. Possibly, it is provided by secretion from the supporting cells as has been hypothesized earlier.
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Affiliation(s)
- M Ibsch
- Zoological Institute, University of Stuttgart-Hohenheim, Stuttgart, Germany
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Immunocytochemical and morphological evidence for intracellular self-repair as an important contributor to mammalian hair cell recovery. J Neurosci 1999. [PMID: 10066269 DOI: 10.1523/jneurosci.19-06-02161.1999] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Although recent studies have provided evidence for hair cell regeneration in mammalian inner ears, the mechanism underlying this regenerative process is still under debate. Here we report immunocytochemical, histological, electron microscopic, and autoradiographic evidence that, in cultured postnatal rat utricles, a substantial number of hair cells can survive gentamicin insult even their stereocilia are lost. These partially damaged hair cells can survive for a prolonged time and regrow the stereocilia. Although the number of stereocilia-bearing hair cells increases over time after gentamicin insult, hair cell and supporting cell numbers remain essentially unchanged. Tritiated thymidine autoradiography and bromodeoxyuridine immunocytochemistry of the cultures demonstrate that cell proliferation in the sensory epithelium is very limited and is far below the number of recovered hair cells. Furthermore, terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling analysis indicates that gentamicin-induced apoptosis in the sensory epithelium occurs mainly during a 2 d treatment period, and additional cell death is minimal 2-11 d after treatment. Considered together, intracellular repair of partially damaged hair cells can be an important contributor to spontaneous hair cell recovery in mammalian inner ears.
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Adler HJ, Winnicki RS, Gong TW, Lomax MI. A gene upregulated in the acoustically damaged chick basilar papilla encodes a novel WD40 repeat protein. Genomics 1999; 56:59-69. [PMID: 10036186 DOI: 10.1006/geno.1998.5672] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The chick WDR1 gene is expressed at higher levels in the chick basilar papilla after acoustic overstimulation. The 3.3-kb WDR1 cDNA encodes a novel 67-kDa protein containing nine WD40 repeats, motifs that mediate protein-protein interactions. The predicted WDR1 protein has high sequence identity to WD40-repeat proteins in budding yeast (Saccharomyces cerevisiae), two slime molds (Dictyostelium discoideum and Physarum polycephalum), and the roundworm (Caenorhabditis elegans). The yeast and P. polycephalum proteins bind actin, suggesting that the novel chick protein may be an actin-binding protein. Sequence database comparisons identified mouse and human cDNAs with high sequence identity to the chick WDR1 cDNA. The mouse Wdr1 and human WDR1 proteins showed 95% sequence identity to each other and 86% identity to the chick WDR1 protein. Northern blot analysis of total RNA from the chick basilar papilla after noise trauma revealed increased levels of a 3.1-kb transcript in the lesioned area. The WDR1 gene was mapped to human chromosome 4, between 22 and 24 cM from the telomere of 4p.
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Affiliation(s)
- H J Adler
- Department of Otolaryngology/Head-Neck Surgery, University of Michigan, Ann Arbor, Michigan, 48109, USA
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43
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Abstract
Sensory organs of the vertebrate inner ear contain two major cell types: hair cells (HCs) and supporting cells (SCs). To study the lineage relationships between these two populations, replication-defective retroviral vectors encoding marker genes were delivered to the otic vesicle of the chicken embryo. The resulting labeled clones were analyzed in the hearing organ of the chicken, called the basilar papilla (BP), after cellular differentiation. BPs were allowed to develop for 2 weeks after delivery of the retrovirus, were removed, and were processed histochemically as whole mounts to identify clones of cells. Clusters of labeled cells were evident in the sensory epithelium, the nonsensory epithelium, and in adjacent tissues. Labeled cell types included HCs, two morphologically distinct types of SCs, homogene cells, border cells, hyaline cells, ganglion cells, and connective tissue cells. Each clone was sectioned and cell-type identification was performed on sensory clones expressing retrovirally transduced beta-galactosidase. Cell composition was determined for 41 sensory clones, most of which contained both HCs and SCs. Clones containing one HC and one SC were observed, suggesting that a common progenitor exists that can remain bipotential up to its final mitotic division. The possibility that these two cell types may also arise from a mitotic precursor during HC regeneration in the mature basilar papilla is consistent with their developmental history.
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44
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Kuntz A, Oesterle E. Transforming growth factor ? with insulin stimulates cell proliferation in vivo in adult rat vestibular sensory epithelium. J Comp Neurol 1998. [DOI: 10.1002/(sici)1096-9861(19980928)399:3<413::aid-cne9>3.0.co;2-3] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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45
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Staecker H, Van De Water TR. Factors controlling hair-cell regeneration/repair in the inner ear. Curr Opin Neurobiol 1998; 8:480-7. [PMID: 9751665 DOI: 10.1016/s0959-4388(98)80035-4] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Damaged hair cells in the avian basilar papilla are replaced by regenerative proliferation of supporting cells and transdifferentiation of supporting cells into hair cells. In the mammalian vestibular system, transdifferentiation and, possibly, the repair of damaged hair cells appear to play significant roles. Several growth factors have been found to be associated with the regeneration/repair process: insulin, insulin-like growth factor 1 (IGF-1), and fibroblast growth factors are important for avian inner ear regeneration/repair, whereas epidermal growth factor, transforming growth factor alpha, insulin, IGF-1, and IGF-2 are important for regeneration/repair in the mammalian labyrinth. Increasing evidence suggests that regeneration/repair of mammalian auditory hair cells is possible during the early neonatal period and may exist to a very limited degree at later times.
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Affiliation(s)
- H Staecker
- Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston 02114, USA
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Stone JS, Oesterle EC, Rubel EW. Recent insights into regeneration of auditory and vestibular hair cells. Curr Opin Neurol 1998; 11:17-24. [PMID: 9484612 DOI: 10.1097/00019052-199802000-00004] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Advances in hair cell regeneration are progressing at a rapid rate. This review will highlight and critique recent attempts to understand some of the cellular and molecular mechanisms underlying hair cell regeneration in non-mammalian vertebrates and efforts to induce regeneration in the mammalian inner ear sensory epithelium.
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Affiliation(s)
- J S Stone
- Department of Otolaryngology, University of Washington School of Medicine, Seattle, USA
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