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You D, Guo J, Zhang Y, Guo L, Lu X, Huang X, Sun S, Li H. The heterogeneity of mammalian utricular cells over the course of development. Clin Transl Med 2022; 12:e1052. [PMID: 36178017 PMCID: PMC9523683 DOI: 10.1002/ctm2.1052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 08/19/2022] [Accepted: 08/25/2022] [Indexed: 01/28/2023] Open
Abstract
BACKGROUND The inner ear organ is a delicate tissue consisting of hair cells (HCs) and supporting cells (SCs).The mammalian inner ear HCs are terminally differentiated cells that cannot spontaneously regenerate in adults. Epithelial non-hair cells (ENHCs) in the utricle include HC progenitors and SCs, and the progenitors share similar characteristics with SCs in the neonatal inner ear. METHODS We applied single-cell sequencing to whole mouse utricles from the neonatal period to adulthood, including samples from postnatal day (P)2, P7 and P30 mice. Furthermore, using transgenic mice and immunostaining, we traced the source of new HC generation. RESULTS We identified several sensory epithelial cell clusters and further found that new HCs arose mainly through differentiation from Sox9+ progenitor cells and that only a few cells were produced by mitotic proliferation in both neonatal and adult mouse utricles. In addition, we identified the proliferative cells using the marker UbcH10 and demonstrated that in adulthood the mitotically generated HCs were primarily found in the extrastriola. Moreover, we observed that not only Type II, but also Type I HCs could be regenerated by either mitotic cell proliferation or progenitor cell differentiation. CONCLUSIONS Overall, our findings expand our understanding of ENHC cell fate and the characteristics of the vestibular organs in mammals over the course of development.
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Affiliation(s)
- Dan You
- ENT Institute and Otorhinolaryngology Department of Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain ScienceFudan UniversityShanghaiChina,Department of Otorhinolaryngology‐Head and Neck SurgeryZhongshan HospitalFudan UniversityShanghaiChina
| | - Jin Guo
- ENT Institute and Otorhinolaryngology Department of Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain ScienceFudan UniversityShanghaiChina
| | - Yunzhong Zhang
- ENT Institute and Otorhinolaryngology Department of Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain ScienceFudan UniversityShanghaiChina
| | - Luo Guo
- ENT Institute and Otorhinolaryngology Department of Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain ScienceFudan UniversityShanghaiChina
| | - Xiaoling Lu
- ENT Institute and Otorhinolaryngology Department of Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain ScienceFudan UniversityShanghaiChina
| | - Xinsheng Huang
- Department of Otorhinolaryngology‐Head and Neck SurgeryZhongshan HospitalFudan UniversityShanghaiChina
| | - Shan Sun
- ENT Institute and Otorhinolaryngology Department of Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain ScienceFudan UniversityShanghaiChina
| | - Huawei Li
- ENT Institute and Otorhinolaryngology Department of Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain ScienceFudan UniversityShanghaiChina,Institutes of Biomedical SciencesFudan UniversityShanghaiChina,NHC Key Laboratory of Hearing Medicine, Fudan UniversityShanghaiChina,The Institutes of Brain Science and the Collaborative Innovation Center for Brain ScienceFudan UniversityShanghaiChina
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2
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Huang TW, Iyer AA, Manalo JM, Woo J, Bosquez Huerta NA, McGovern MM, Schrewe H, Pereira FA, Groves AK, Ohlemiller KK, Deneen B. Glial-Specific Deletion of Med12 Results in Rapid Hearing Loss via Degradation of the Stria Vascularis. J Neurosci 2021; 41:7171-7181. [PMID: 34253626 PMCID: PMC8387121 DOI: 10.1523/jneurosci.0070-21.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 06/11/2021] [Accepted: 07/05/2021] [Indexed: 11/21/2022] Open
Abstract
Mediator protein complex subunit 12 (Med12) is a core component of the basal transcriptional apparatus and plays a critical role in the development of many tissues. Mutations in Med12 are associated with X-linked intellectual disability syndromes and hearing loss; however, its role in nervous system function remains undefined. Here, we show that temporal conditional deletion of Med12 in astrocytes in the adult CNS results in region-specific alterations in astrocyte morphology. Surprisingly, behavioral studies revealed rapid hearing loss after adult deletion of Med12 that was confirmed by a complete abrogation of auditory brainstem responses. Cellular analysis of the cochlea revealed degeneration of the stria vascularis, in conjunction with disorganization of basal cells adjacent to the spiral ligament and downregulation of key cell adhesion proteins. Physiologic analysis revealed early changes in endocochlear potential, consistent with strial-specific defects. Together, our studies reveal that Med12 regulates auditory function in the adult by preserving the structural integrity of the stria vascularis.SIGNIFICANCE STATEMENT Mutations in Mediator protein complex subunit 12 (Med12) are associated with X-linked intellectual disability syndromes and hearing loss. Using temporal-conditional genetic approaches in CNS glia, we found that loss of Med12 results in severe hearing loss in adult animals through rapid degeneration of the stria vascularis. Our study describes the first animal model that recapitulates hearing loss identified in Med12-related disorders and provides a new system in which to examine the underlying cellular and molecular mechanisms of Med12 function in the adult nervous system.
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Affiliation(s)
- Teng-Wei Huang
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, Texas 77030
| | - Amrita A Iyer
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030
- Program in Genetics & Genomics, Baylor College of Medicine, Houston, Texas 77030
| | - Jeanne M Manalo
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030
| | - Junsung Woo
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, Texas 77030
| | - Navish A Bosquez Huerta
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, Texas 77030
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX 77030
| | - Melissa M McGovern
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030
| | - Heinrich Schrewe
- Department of Developmental Genetics, Max Planck Institute for Molecular Genetics, 14195 Berlin, Germany
| | - Fredrick A Pereira
- Huffington Center on Aging, Baylor College of Medicine, Houston, Texas 77030
- Department of Otolaryngology, Baylor College of Medicine, Houston, Texas 77030
| | - Andrew K Groves
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX 77030
- Program in Genetics & Genomics, Baylor College of Medicine, Houston, Texas 77030
| | - Kevin K Ohlemiller
- Department of Otolaryngolgy, Central Institute for the Deaf, Fay and Carl Simons Center for Biology of Hearing and Deafness, Washington University in St. Louis, St. Louis, Missouri 63110
| | - Benjamin Deneen
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, Texas 77030
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX 77030
- Department of Neurosurgery, Baylor College of Medicine, Houston, Texas 77030
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3
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Zhang Y, Zhang S, Zhang Z, Dong Y, Ma X, Qiang R, Chen Y, Gao X, Zhao C, Chen F, He S, Chai R. Knockdown of Foxg1 in Sox9+ supporting cells increases the trans-differentiation of supporting cells into hair cells in the neonatal mouse utricle. Aging (Albany NY) 2020; 12:19834-19851. [PMID: 33099273 PMCID: PMC7655167 DOI: 10.18632/aging.104009] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 08/15/2020] [Indexed: 05/30/2023]
Abstract
Foxg1 plays important roles in regeneration of hair cell (HC) in the cochlea of neonatal mouse. Here, we used Sox9-CreER to knock down Foxg1 in supporting cells (SCs) in the utricle in order to investigate the role of Foxg1 in HC regeneration in the utricle. We found Sox9 an ideal marker of utricle SCs and bred Sox9CreER/+Foxg1loxp/loxp mice to conditionally knock down Foxg1 in utricular SCs. Conditional knockdown (cKD) of Foxg1 in SCs at postnatal day one (P01) led to increased number of HCs at P08. These regenerated HCs had normal characteristics, and could survive to at least P30. Lineage tracing showed that a significant portion of newly regenerated HCs originated from SCs in Foxg1 cKD mice compared to the mice subjected to the same treatment, which suggested SCs trans-differentiate into HCs in the Foxg1 cKD mouse utricle. After neomycin treatment in vitro, more HCs were observed in Foxg1 cKD mice utricle compared to the control group. Together, these results suggest that Foxg1 cKD in utricular SCs may promote HC regeneration by inducing trans-differentiation of SCs. This research therefore provides theoretical basis for the effects of Foxg1 in trans-differentiation of SCs and regeneration of HCs in the mouse utricle.
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Affiliation(s)
- Yuan Zhang
- MOE Key Laboratory for Developmental Genes and Human Disease, School of Life Sciences and Technology, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, China
| | - Shasha Zhang
- MOE Key Laboratory for Developmental Genes and Human Disease, School of Life Sciences and Technology, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, China
| | - Zhonghong Zhang
- Department of Ophthalmology, Zhongda Hospital, Southeast University, Nanjing, China
| | - Ying Dong
- MOE Key Laboratory for Developmental Genes and Human Disease, School of Life Sciences and Technology, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, China
| | - Xiangyu Ma
- MOE Key Laboratory for Developmental Genes and Human Disease, School of Life Sciences and Technology, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, China
| | - Ruiying Qiang
- MOE Key Laboratory for Developmental Genes and Human Disease, School of Life Sciences and Technology, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, China
| | - Yin Chen
- Department of Otolaryngology Head and Neck Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, Jiangsu Provincial Key Medical Discipline (Laboratory), Nanjing, China
| | - Xia Gao
- Department of Otolaryngology Head and Neck Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, Jiangsu Provincial Key Medical Discipline (Laboratory), Nanjing, China
| | - Chunjie Zhao
- MOE Key Laboratory for Developmental Genes and Human Disease, School of Life Sciences and Technology, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, China
| | - Fangyi Chen
- Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen, China
| | - Shuangba He
- Department of Otolaryngology Head and Neck, Nanjing Tongren Hospital, School of Medicine, Southeast University, China
| | - Renjie Chai
- MOE Key Laboratory for Developmental Genes and Human Disease, School of Life Sciences and Technology, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, China
- Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Science, Beijing, China
- Beijing Key Laboratory of Neural Regeneration and Repair, Capital Medical University, Beijing, China
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4
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Shibata SB, West MB, Du X, Iwasa Y, Raphael Y, Kopke RD. Gene therapy for hair cell regeneration: Review and new data. Hear Res 2020; 394:107981. [DOI: 10.1016/j.heares.2020.107981] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 04/19/2020] [Accepted: 04/22/2020] [Indexed: 02/06/2023]
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5
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EGF and a GSK3 Inhibitor Deplete Junctional E-cadherin and Stimulate Proliferation in the Mature Mammalian Ear. J Neurosci 2020; 40:2618-2632. [PMID: 32079647 DOI: 10.1523/jneurosci.2630-19.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 02/02/2020] [Accepted: 02/09/2020] [Indexed: 11/21/2022] Open
Abstract
Sensory hair cell losses underlie the vast majority of permanent hearing and balance deficits in humans, but many nonmammalian vertebrates can fully recover from hearing impairments and balance dysfunctions because supporting cells (SCs) in their ears retain lifelong regenerative capacities that depend on proliferation and differentiation as replacement hair cells. Most SCs in vertebrate ears stop dividing during embryogenesis; and soon after birth, vestibular SCs in mammals transition to lasting quiescence as they develop massively thickened circumferential F-actin bands at their E-cadherin-rich adherens junctions. Here, we report that treatment with EGF and a GSK3 inhibitor thinned the circumferential F-actin bands throughout the sensory epithelium of cultured utricles that were isolated from adult mice of either sex. That treatment also caused decreases in E-cadherin, β-catenin, and YAP in the striola, and stimulated robust proliferation of mature, normally quiescent striolar SCs. The findings suggest that E-cadherin-rich junctions, which are not present in the SCs of the fish, amphibians, and birds which readily regenerate hair cells, are responsible in part for the mammalian ear's vulnerability to permanent balance and hearing deficits.SIGNIFICANCE STATEMENT Millions of people are affected by hearing and balance deficits that arise when loud sounds, ototoxic drugs, infections, and aging cause hair cell losses. Such deficits are permanent for humans and other mammals, but nonmammals can recover hearing and balance after supporting cells regenerate replacement hair cells. Mammalian supporting cells lose the capacity to proliferate around the time they develop unique, exceptionally reinforced, E-cadherin-rich intercellular junctions. Here, we report the discovery of a pharmacological treatment that thins F-actin bands, depletes E-cadherin, and stimulates proliferation in long-quiescent supporting cells within a balance epithelium from adult mice. The findings suggest that high E-cadherin in those supporting cell junctions may be responsible, in part, for the permanence of hair cell loss in mammals.
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Xia P, Liu Y, Chen J, Cheng Z. Cell Cycle Proteins as Key Regulators of Postmitotic Cell Death. THE YALE JOURNAL OF BIOLOGY AND MEDICINE 2019; 92:641-650. [PMID: 31866779 PMCID: PMC6913832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Cell cycle progression in dividing cells, characterized by faithful replication of the genomic materials and duplication of the original cell, is fundamental for growth and reproduction of all mammalian organisms. Functional maturation of postmitotic cells, however, requires cell cycle exit and terminal differentiation. In mature postmitotic cells, many cell cycle proteins remain to be expressed, or can be induced and reactivated in pathological conditions such as traumatic injury and degenerative diseases. Interestingly, elevated levels of cell cycle proteins in postmitotic cells often do not induce proliferation, but result in aberrant cell cycle reentry and cell death. At present, the cell cycle machinery is known predominantly for regulating cell cycle progression and cell proliferation, albeit accumulating evidence indicates that cell cycle proteins may also control cell death, especially in postmitotic tissues. Herein, we provide a brief summary of these findings and hope to highlight the connection between cell cycle reentry and postmitotic cell death. In addition, we also outline the signaling pathways that have been identified in cell cycle-related cell death. Advanced understanding of the molecular mechanisms underlying cell cycle-related death is of paramount importance because this knowledge can be applied to develop protective strategies against pathologies in postmitotic tissues. Moreover, a full-scope understanding of the cell cycle machinery will allow fine tuning to favor cell proliferation over cell death, thereby potentially promoting tissue regeneration.
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Affiliation(s)
| | | | | | - Zhaokang Cheng
- To whom all correspondence should be addressed: Zhaokang Cheng, PhD, Department of Pharmaceutical Sciences, Washington State University, PBS 423, 412 E. Spokane Falls Blvd. Spokane, WA 99202-2131; Tel: 509-358-7741,
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7
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Washausen S, Knabe W. Lateral line placodes of aquatic vertebrates are evolutionarily conserved in mammals. Biol Open 2018; 7:bio.031815. [PMID: 29848488 PMCID: PMC6031350 DOI: 10.1242/bio.031815] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Placodes are focal thickenings of the surface ectoderm which, together with neural crest, generate the peripheral nervous system of the vertebrate head. Here we examine how, in embryonic mice, apoptosis contributes to the remodelling of the primordial posterior placodal area (PPA) into physically separated otic and epibranchial placodes. Using pharmacological inhibition of apoptosis-associated caspases, we find evidence that apoptosis eliminates hitherto undiscovered rudiments of the lateral line sensory system which, in fish and aquatic amphibia, serves to detect movements, pressure changes or electric fields in the surrounding water. Our results refute the evolutionary theory, valid for more than a century that the whole lateral line was completely lost in amniotes. Instead, those parts of the PPA which, under experimental conditions, escape apoptosis have retained the developmental potential to produce lateral line placodes and the primordia of neuromasts that represent the major functional units of the mechanosensory lateral line system. Summary: Inhibition of apoptosis in mouse embryos reveals rudiments of the lateral line system, a sensory system common to fish and aquatic amphibia, but hypothesized to be completely lost in amniotes.
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Affiliation(s)
- Stefan Washausen
- Department Prosektur Anatomie, Westfälische Wilhelms-University, 48149 Münster, Germany
| | - Wolfgang Knabe
- Department Prosektur Anatomie, Westfälische Wilhelms-University, 48149 Münster, Germany
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8
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Stone JS, Wisner SR, Bucks SA, Mellado Lagarde MM, Cox BC. Characterization of Adult Vestibular Organs in 11 CreER Mouse Lines. J Assoc Res Otolaryngol 2018; 19:381-399. [PMID: 29869046 DOI: 10.1007/s10162-018-0676-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Accepted: 05/07/2018] [Indexed: 10/14/2022] Open
Abstract
Utricles are vestibular sense organs that encode linear head movements. They are composed of a sensory epithelium with type I and type II hair cells and supporting cells, sitting atop connective tissue, through which vestibular nerves project. We characterized utricular Cre expression in 11 murine CreER lines using the ROSA26tdTomato reporter line and tamoxifen induction at 6 weeks of age. This characterization included Calbindin2CreERT2, Fgfr3-iCreERT2, GFAP-A-CreER™, GFAP-B-CreER™, GLAST-CreERT2, Id2CreERT2, OtoferlinCreERT2, ParvalbuminCreERT2, Prox1CreERT2, Sox2CreERT2, and Sox9-CreERT2. OtoferlinCreERT2 mice had inducible Cre activity specific to hair cells. GLAST-CreERT2, Id2CreERT2, and Sox9-CreERT2 had inducible Cre activity specific to supporting cells. Sox2CreERT2 had inducible Cre activity in supporting cells and most type II hair cells. ParvalbuminCreERT2 mice had small numbers of labeled vestibular nerve afferents. Calbindin2CreERT2 mice had labeling of most type II hair cells and some type I hair cells and supporting cells. Only rare (or no) tdTomato-positive cells were detected in utricles of Fgfr3-iCreERT2, GFAP-A-CreER™, GFAP-B-CreER™, and Prox1CreERT2 mice. No Cre leakiness (tdTomato expression in the absence of tamoxifen) was observed in OtoferlinCreERT2 mice. A small degree of leakiness was seen in GLAST-CreERT2, Id2CreERT2, Sox2CreERT2, and Sox9-CreERT2 lines. Calbindin2CreERT2 mice had similar tdTomato expression with or without tamoxifen, indicating lack of inducible control under the conditions tested. In conclusion, 5 lines-GLAST-CreERT2, Id2CreERT2, OtoferlinCreERT2, Sox2CreERT2, and Sox9-CreERT2-showed cell-selective, inducible Cre activity with little leakiness, providing new genetic tools for researchers studying the vestibular periphery.
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Affiliation(s)
- Jennifer S Stone
- Department of Otolaryngology-Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, WA, USA
| | - Serena R Wisner
- Department of Otolaryngology-Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, WA, USA
| | - Stephanie A Bucks
- Department of Otolaryngology-Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, WA, USA
| | - Marcia M Mellado Lagarde
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Brandon C Cox
- Departments of Pharmacology and Surgery, Division of Otolaryngology, Southern Illinois University School of Medicine, Springfield, IL, USA.
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Gnedeva K, Jacobo A, Salvi JD, Petelski AA, Hudspeth AJ. Elastic force restricts growth of the murine utricle. eLife 2017; 6. [PMID: 28742024 PMCID: PMC5550282 DOI: 10.7554/elife.25681] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2017] [Accepted: 07/21/2017] [Indexed: 12/30/2022] Open
Abstract
Dysfunctions of hearing and balance are often irreversible in mammals owing to the inability of cells in the inner ear to proliferate and replace lost sensory receptors. To determine the molecular basis of this deficiency we have investigated the dynamics of growth and cellular proliferation in a murine vestibular organ, the utricle. Based on this analysis, we have created a theoretical model that captures the key features of the organ’s morphogenesis. Our experimental data and model demonstrate that an elastic force opposes growth of the utricular sensory epithelium during development, confines cellular proliferation to the organ’s periphery, and eventually arrests its growth. We find that an increase in cellular density and the subsequent degradation of the transcriptional cofactor Yap underlie this process. A reduction in mechanical constraints results in accumulation and nuclear translocation of Yap, which triggers proliferation and restores the utricle’s growth; interfering with Yap’s activity reverses this effect. DOI:http://dx.doi.org/10.7554/eLife.25681.001
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Affiliation(s)
- Ksenia Gnedeva
- Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, New York, United States.,Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research, Keck School of Medicine of the University of Southern California, Los Angeles, United States
| | - Adrian Jacobo
- Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, New York, United States
| | - Joshua D Salvi
- Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, New York, United States
| | - Aleksandra A Petelski
- Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, New York, United States
| | - A J Hudspeth
- Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, New York, United States
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10
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Burns JC, Stone JS. Development and regeneration of vestibular hair cells in mammals. Semin Cell Dev Biol 2017; 65:96-105. [PMID: 27864084 PMCID: PMC5423856 DOI: 10.1016/j.semcdb.2016.11.001] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 11/03/2016] [Indexed: 10/20/2022]
Abstract
Vestibular sensation is essential for gaze stabilization, balance, and perception of gravity. The vestibular receptors in mammals, Type I and Type II hair cells, are located in five small organs in the inner ear. Damage to hair cells and their innervating neurons can cause crippling symptoms such as vertigo, visual field oscillation, and imbalance. In adult rodents, some Type II hair cells are regenerated and become re-innervated after damage, presenting opportunities for restoring vestibular function after hair cell damage. This article reviews features of vestibular sensory cells in mammals, including their basic properties, how they develop, and how they are replaced after damage. We discuss molecules that control vestibular hair cell regeneration and highlight areas in which our understanding of development and regeneration needs to be deepened.
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Affiliation(s)
- Joseph C Burns
- Decibel Therapeutics, 215 First St., Suite 430, Cambridge, MA 02142, USA.
| | - Jennifer S Stone
- Department of Otolaryngology/Head and Neck Surgery and The Virginia Merrill Bloedel Hearing Research Center, University of Washington School of Medicine, Box 357923, Seattle, WA 98195-7923, USA.
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11
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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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12
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Li W, You D, Chen Y, Chai R, Li H. Regeneration of hair cells in the mammalian vestibular system. Front Med 2016; 10:143-51. [DOI: 10.1007/s11684-016-0451-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 04/11/2016] [Indexed: 11/25/2022]
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13
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Brosel S, Laub C, Averdam A, Bender A, Elstner M. Molecular aging of the mammalian vestibular system. Ageing Res Rev 2016; 26:72-80. [PMID: 26739358 DOI: 10.1016/j.arr.2015.12.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 12/16/2015] [Accepted: 12/21/2015] [Indexed: 12/18/2022]
Abstract
Dizziness and imbalance frequently affect the elderly and contribute to falls and frailty. In many geriatric patients, clinical testing uncovers a dysfunction of the vestibular system, but no specific etiology can be identified. Neuropathological studies have demonstrated age-related degeneration of peripheral and central vestibular neurons, but the molecular mechanisms are poorly understood. In contrast, recent studies into age-related hearing loss strongly implicate mitochondrial dysfunction, oxidative stress and apoptotic cell death of cochlear hair cells. While some data suggest that analogous biological pathomechanisms may underlie vestibular dysfunction, actual proof is missing. In this review, we summarize the available data on the molecular causes of vestibular dysfunction.
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Affiliation(s)
- Sonja Brosel
- German Center for Vertigo and Balance Disorders, Department of Neurology, Klinikum Grosshadern, Ludwig-Maximilians-University, Marchioninistr. 15, 81377 Munich, Germany.
| | - Christoph Laub
- Department of Neurology with Friedrich-Baur-Institute, Klinikum Grosshadern, Ludwig-Maximilians-University, Marchioninistr. 15, 81377 Munich, Germany
| | - Anne Averdam
- Department of Neurology with Friedrich-Baur-Institute, Klinikum Grosshadern, Ludwig-Maximilians-University, Marchioninistr. 15, 81377 Munich, Germany
| | - Andreas Bender
- Department of Neurology, Therapiezentrum Burgau, Kapuzinerstr.34, 89331 Burgau, Germany
| | - Matthias Elstner
- Department of Neurology with Friedrich-Baur-Institute, Klinikum Grosshadern, Ludwig-Maximilians-University, Marchioninistr. 15, 81377 Munich, Germany; Department of Neurology and Clinical Neurophysiology, Academic Hospital Munich-Bogenhausen, Technical University of Munich, Englschalkingerstr. 77, 81925 Munich, Germany
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14
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DNA damage signaling regulates age-dependent proliferative capacity of quiescent inner ear supporting cells. Aging (Albany NY) 2015; 6:496-510. [PMID: 25063730 PMCID: PMC4100811 DOI: 10.18632/aging.100668] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Supporting cells (SCs) of the cochlear (auditory) and vestibular (balance) organs hold promise as a platform for therapeutic regeneration of the sensory hair cells. Prior data have shown proliferative restrictions of adult SCs forced to re-enter the cell cycle. By comparing juvenile and adult SCs in explant cultures, we have here studied how proliferative restrictions are linked with DNA damage signaling. Cyclin D1 overexpression, used to stimulate cell cycle re-entry, triggered higher proliferative activity of juvenile SCs. Phosphorylated form of histone H2AX (γH2AX) and p53 binding protein 1 (53BP1) were induced in a foci-like pattern in SCs of both ages as an indication of DNA double-strand break formation and activated DNA damage response. Compared to juvenile SCs, γH2AX and the repair protein Rad51 were resolved with slower kinetics in adult SCs, accompanied by increased apoptosis. Consistent with the in vitro data, in a Rb mutant mouse model in vivo, cell cycle re-entry of SCs was associated with γH2AX foci induction. In contrast to cell cycle reactivation, pharmacological stimulation of SC-to-hair-cell transdifferentiation in vitro did not trigger γH2AX. Thus, DNA damage and its prolonged resolution are critical barriers in the efforts to stimulate proliferation of the adult inner ear SCs.
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Slattery EL, Oshima K, Heller S, Warchol ME. Cisplatin exposure damages resident stem cells of the mammalian inner ear. Dev Dyn 2014; 243:1328-37. [PMID: 24888499 DOI: 10.1002/dvdy.24150] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Revised: 04/29/2014] [Accepted: 05/10/2014] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Cisplatin is a widely used chemotherapeutic agent that can also cause ototoxic injury. One potential treatment for cisplatin-induced hearing loss involves the activation of endogenous inner ear stem cells, which may then produce replacement hair cells. In this series of experiments, we examined the effects of cisplatin exposure on both hair cells and resident stem cells of the mouse inner ear. RESULTS Treatment for 24 hr with 10 µM cisplatin caused significant loss of hair cells in the mouse utricle, but such damage was not evident until 4 days after the cisplatin exposure. In addition to killing hair cells, cisplatin treatment also disrupted the actin cytoskeleton in remaining supporting cells, and led to increased histone H2AX phosphorylation within the sensory epithelia. Finally, treatment with 10 µM cisplatin appeared to have direct toxic effects on resident stem cells in the mouse utricle. Exposure to cisplatin blocked the proliferation of isolated stem cells and prevented sphere formation when those cells were maintained in suspension culture. CONCLUSION The results suggest that inner ear stem cells may be injured during cisplatin ototoxicity, thus limiting their ability to mediate sensory repair.
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Affiliation(s)
- Eric L Slattery
- Department of Otolaryngology, Washington University School of Medicine, Saint Louis, Missouri
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16
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Disrupting the interaction between retinoblastoma protein and Raf-1 leads to defects in progenitor cell proliferation and survival during early inner ear development. PLoS One 2013; 8:e83726. [PMID: 24391814 PMCID: PMC3877085 DOI: 10.1371/journal.pone.0083726] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 11/07/2013] [Indexed: 11/19/2022] Open
Abstract
The retinoblastoma protein (pRb) is required for cell-cycle exit of embryonic mammalian hair cells but is not required for hair cell fate determination and early differentiation, and this provides a strategy for hair cell regeneration by manipulating the pRb pathway. To reveal the mechanism of pRb functional modification in the inner ear, we compared the effects of attenuated pRb phosphorylation by an inhibitor of the Mitogen-Activated Protein (MAP) kinase pathway and an inhibitor of the Rb-Raf-1 interaction on cultured chicken otocysts. We demonstrated that the activity of pRb is correlated with its phosphorylation state, which is regulated by a newly established cell cycle-independent pathway mediated by the physical interaction between Raf-1 and pRb. The phosphorylation of pRb plays an important role during the early stage of inner ear development, and attenuated phosphorylation in progenitor cells leads to cell cycle arrest and increased apoptosis along with a global down-regulation of the genes involved in cell cycle progression. Our study provides novel routes to modulate pRb function for hair cell regeneration.
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Ectopic expression of activated notch or SOX2 reveals similar and unique roles in the development of the sensory cell progenitors in the mammalian inner ear. J Neurosci 2013; 33:16146-57. [PMID: 24107947 DOI: 10.1523/jneurosci.3150-12.2013] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Hearing impairment or vestibular dysfunction in humans often results from a permanent loss of critical cell types in the sensory regions of the inner ear, including hair cells, supporting cells, or cochleovestibular neurons. These important cell types arise from a common sensory or neurosensory progenitor, although little is known about how these progenitors are specified. Studies have shown that Notch signaling and the transcription factor Sox2 are required for the development of these lineages. Previously we and others demonstrated that ectopic activation of Notch can direct nonsensory cells to adopt a sensory fate, indicating a role for Notch in early specification events. Here, we explore the relationship between Notch and SOX2 by ectopically activating these factors in nonsensory regions of the mouse cochlea, and demonstrate that, similar to Notch, SOX2 can specify sensory progenitors, consistent with a role downstream of Notch signaling. However, we also show that Notch has a unique role in promoting the proliferation of the sensory progenitors. We further demonstrate that Notch can only induce ectopic sensory regions within a certain time window of development, and that the ectopic hair cells display specialized stereocilia bundles similar to endogenous hair cells. These results demonstrate that Notch and SOX2 can both drive the sensory program in nonsensory cells, indicating these factors may be useful in cell replacement strategies in the inner ear.
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18
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Burns JC, Collado MS, Oliver ER, Corwin JT. Specializations of intercellular junctions are associated with the presence and absence of hair cell regeneration in ears from six vertebrate classes. J Comp Neurol 2013; 521:1430-48. [PMID: 23124808 DOI: 10.1002/cne.23250] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Revised: 10/10/2012] [Accepted: 10/25/2012] [Indexed: 01/12/2023]
Abstract
Sensory hair cell losses lead to hearing and balance deficits that are permanent for mammals, but temporary for nonmammals because supporting cells in their ears give rise to replacement hair cells. In mice and humans, vestibular supporting cells grow exceptionally large circumferential F-actin belts and their junctions express E-cadherin in patterns that strongly correlate with postnatal declines in regeneration capacity. In contrast, chicken supporting cells retain thin F-actin belts throughout life and express little E-cadherin. To determine whether the junctions in chicken ears might be representative of other ears that also regenerate hair cells, we investigated inner ears from dogfish sharks, zebrafish, bullfrogs, Xenopus, turtles, and the lizard, Anolis. As in chickens, the supporting cells in adult zebrafish, Xenopus, and turtle ears retained thin circumferential F-actin belts and expressed little E-cadherin. Supporting cells in adult sharks and bullfrogs also retained thin belts, but were not tested for E-cadherin. Supporting cells in adult Anolis exhibited wide, but porous webs of F-actin and strong E-cadherin expression. Anolis supporting cells also showed some cell cycle reentry when cultured. The results reveal that the association between thin F-actin belts and low E-cadherin is shared by supporting cells in anamniotes, turtles, and birds, which all can regenerate hair cells. Divergent junctional specializations in supporting cells appear to have arisen independently in Anolis and mammals. The presence of webs of F-actin at the junctions in Anolis appears compatible with supporting cell proliferation, but the solid reinforcement of the F-actin belts in mammals is associated with its absence.
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Affiliation(s)
- Joseph C Burns
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA
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19
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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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20
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Qi L, Toyoda H, Shankar V, Sakurai N, Amano K, Kihira K, Iwasa T, Deguchi T, Hori H, Azuma E, Gabazza EC, Komada Y. Heterogeneity of neuroblastoma cell lines in insulin-like growth factor 1 receptor/Akt pathway-mediated cell proliferative responses. Cancer Sci 2013; 104:1162-71. [PMID: 23710710 DOI: 10.1111/cas.12204] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Revised: 05/08/2013] [Accepted: 05/15/2013] [Indexed: 12/18/2022] Open
Abstract
Insulin-like growth factor 1 receptor (IGF-1R) is critical for cancer cell proliferation; however, recent clinical anti-IGF-1R trials did not show clear clinical benefit in cancer therapy. We hypothesized that IGF-1R signaling-mediated proliferative response is heterogeneous in neuroblastoma (NB) cells, and analyzed the cell growth of 31 NB cell lines cultured in three different media, including Hybridoma-SFM medium (with insulin) and RPMI1640 with/without 10% FBS. Three growth patterns were found. In response to IGF and insulin, cell proliferation and Akt phosphorylation were upregulated in 13 cell lines, and suppressed by MK2206 (Akt inhibitor) and picropodophyllin (IGF-1R inhibitor). Interestingly, 3 of these 13 cell lines showed Akt self-phosphorylation and cell proliferation in RPMI1640; their proliferation was downregulated by anti-IGF-1 or anti-IGF-2 neutralizing antibody, suggesting the existence of an autocrine loop in the IGF-1R/Akt pathway. Eighteen NB cell lines did not proliferate in RPMI1640, even though Akt phosphorylation was upregulated by IGF and insulin. Based on the heterogeneous response of the IGF-1R/Akt pathway, the 31 NB cell lines could be classified into group 1 (autocrine IGF-mediated), group 2 (exogenous IGF-mediated) and group 3 (partially exogenous IGF-mediated) NB cell lines. In addition, group 3 NB cell lines were different from group 1 and 2, in terms of serum starvation-induced caspase 3 cleavage and picropodophyllin-induced G2/M arrest. These results indicate that the response of the IGF-1R/Akt pathway is an important determinant of the sensitivity to IGF-1R antagonists in NB. To our knowledge, this is the first report describing heterogeneity in the IGF-1R/Akt-mediated proliferation of NB cells.
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Affiliation(s)
- Lei Qi
- Department of Pediatrics and Developmental Science, Graduate School of Medicine, Mie University, Tsu, Japan
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21
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Coupling the cell cycle to development and regeneration of the inner ear. Semin Cell Dev Biol 2013; 24:507-13. [PMID: 23665151 DOI: 10.1016/j.semcdb.2013.04.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Accepted: 04/23/2013] [Indexed: 12/19/2022]
Abstract
Cell cycle exit and acquirement of a postmitotic state is essential for the proper development of organs. In the present review, we examine the role of the cell cycle control in the sensory epithelia of the mammalian inner ear. We describe the roles of the core cell cycle regulators in the proliferation of prosensory cells and in the initiation and maintenance of terminal mitosis of the sensory epithelia. We also discuss how other intracellular signalling may influence the cell cycle. Finally, we address the question of whether manipulations of the cell cycle may have the potential to create replacement cells for the damaged inner sensory epithelia.
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22
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Inner ear supporting cells: rethinking the silent majority. Semin Cell Dev Biol 2013; 24:448-59. [PMID: 23545368 DOI: 10.1016/j.semcdb.2013.03.009] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Accepted: 03/21/2013] [Indexed: 11/21/2022]
Abstract
Sensory epithelia of the inner ear contain two major cell types: hair cells and supporting cells. It has been clear for a long time that hair cells play critical roles in mechanoreception and synaptic transmission. In contrast, until recently the more abundant supporting cells were viewed as serving primarily structural and homeostatic functions. In this review, we discuss the growing information about the roles that supporting cells play in the development, function and maintenance of the inner ear, their activities in pathological states, their potential for hair cell regeneration, and the mechanisms underlying these processes.
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23
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Burns JC, Corwin JT. A historical to present-day account of efforts to answer the question: "what puts the brakes on mammalian hair cell regeneration?". Hear Res 2013; 297:52-67. [PMID: 23333259 PMCID: PMC3594491 DOI: 10.1016/j.heares.2013.01.005] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2012] [Revised: 12/20/2012] [Accepted: 01/07/2013] [Indexed: 12/17/2022]
Abstract
Hearing and balance deficits often affect humans and other mammals permanently, because their ears stop producing hair cells within a few days after birth. But production occurs throughout life in the ears of sharks, bony fish, amphibians, reptiles, and birds allowing them to replace lost hair cells and quickly recover after temporarily experiencing the kinds of sensory deficits that are irreversible for mammals. Since the mid 1970s, researchers have been asking what puts the brakes on hair cell regeneration in mammals. Here we evaluate the headway that has been made and assess current evidence for alternative mechanistic hypotheses that have been proposed to account for the limits to hair cell regeneration in mammals.
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Affiliation(s)
- Joseph C Burns
- Department of Neuroscience, University of Virginia, School of Medicine, Charlottesville, VA 22908, USA.
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24
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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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26
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Anttonen T, Kirjavainen A, Belevich I, Laos M, Richardson WD, Jokitalo E, Brakebusch C, Pirvola U. Cdc42-dependent structural development of auditory supporting cells is required for wound healing at adulthood. Sci Rep 2012; 2:978. [PMID: 23248743 PMCID: PMC3523287 DOI: 10.1038/srep00978] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 11/14/2012] [Indexed: 11/20/2022] Open
Abstract
Cdc42 regulates the initial establishment of cytoskeletal and junctional structures, but only little is known about its role at later stages of cellular differentiation. We studied Cdc42′s role in vivo in auditory supporting cells, epithelial cells with high structural complexity. Cdc42 inactivation was induced early postnatally using the Cdc42loxP/loxP;Fgfr3-iCre-ERT2 mice. Cdc42 depletion impaired elongation of adherens junctions and F-actin belts, leading to constriction of the sensory epithelial surface. Fragmented F-actin belts, junctions containing ectopic lumens and misexpression of a basolateral membrane protein in the apical domain were observed. These defects and changes in aPKCλ/ι expression suggested that apical polarization is impaired. Following a lesion at adulthood, supporting cells with Cdc42 loss-induced maturational defects collapsed and failed to remodel F-actin belts, a process that is critical to scar formation. Thus, Cdc42 is required for structural differentiation of auditory supporting cells and this proper maturation is necessary for wound healing in adults.
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Affiliation(s)
- Tommi Anttonen
- Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
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MYC gene delivery to adult mouse utricles stimulates proliferation of postmitotic supporting cells in vitro. PLoS One 2012; 7:e48704. [PMID: 23119091 PMCID: PMC3484123 DOI: 10.1371/journal.pone.0048704] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Accepted: 10/01/2012] [Indexed: 01/01/2023] Open
Abstract
The inner ears of adult humans and other mammals possess a limited capacity for regenerating sensory hair cells, which can lead to permanent auditory and vestibular deficits. During development and regeneration, undifferentiated supporting cells within inner ear sensory epithelia can self-renew and give rise to new hair cells; however, these otic progenitors become depleted postnatally. Therefore, reprogramming differentiated supporting cells into otic progenitors is a potential strategy for restoring regenerative potential to the ear. Transient expression of the induced pluripotency transcription factors, Oct3/4, Klf4, Sox2, and c-Myc reprograms fibroblasts into neural progenitors under neural-promoting culture conditions, so as a first step, we explored whether ectopic expression of these factors can reverse supporting cell quiescence in whole organ cultures of adult mouse utricles. Co-infection of utricles with adenoviral vectors separately encoding Oct3/4, Klf4, Sox2, and the degradation-resistant T58A mutant of c-Myc (c-MycT58A) triggered significant levels of supporting cell S-phase entry as assessed by continuous BrdU labeling. Of the four factors, c-MycT58A alone was both necessary and sufficient for the proliferative response. The number of BrdU-labeled cells plateaued between 5–7 days after infection, and then decreased ∼60% by 3 weeks, as many cycling cells appeared to enter apoptosis. Switching to differentiation-promoting culture medium at 5 days after ectopic expression of c-MycT58A temporarily attenuated the loss of BrdU-labeled cells and accompanied a very modest but significant expansion of the sensory epithelium. A small number of the proliferating cells in these cultures labeled for the hair cell marker, myosin VIIA, suggesting they had begun differentiating towards a hair cell fate. The results indicate that ectopic expression of c-MycT58A in combination with methods for promoting cell survival and differentiation may restore regenerative potential to supporting cells within the adult mammalian inner ear.
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Regulation of p27Kip1 by Sox2 maintains quiescence of inner pillar cells in the murine auditory sensory epithelium. J Neurosci 2012; 32:10530-40. [PMID: 22855803 DOI: 10.1523/jneurosci.0686-12.2012] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Sox2 plays critical roles in cell fate specification during development and in stem cell formation; however, its role in postmitotic cells is largely unknown. Sox2 is highly expressed in supporting cells (SCs) of the postnatal mammalian auditory sensory epithelium, which unlike non-mammalian vertebrates remains quiescent even after sensory hair cell damage. Here, we induced the ablation of Sox2, specifically in SCs at three different postnatal ages (neonatal, juvenile and adult) in mice. In neonatal mice, Sox2-null inner pillar cells (IPCs, a subtype of SCs) proliferated and generated daughter cells, while other SC subtypes remained quiescent. Furthermore, p27(Kip1), a cell cycle inhibitor, was absent in Sox2-null IPCs. Similarly, upon direct deletion of p27(Kip1), p27(Kip1)-null IPCs also proliferated but retained Sox2 expression. Interestingly, cell cycle control of IPCs by Sox2-mediated expression of p27(Kip1) gradually declined with age. In addition, deletion of Sox2 or p27(Kip1) did not cause a cell fate change. Finally, chromatin immunoprecipitation with Sox2 antibodies and luciferase reporter assays with the p27(Kip1) promoter support that Sox2 directly activates p27(Kip1) transcription in postmitotic IPCs. Hence, in contrast to the well known activity of Sox2 in promoting proliferation and cell fate determination, our data demonstrate that Sox2 plays a novel role as a key upstream regulator of p27(Kip1) to maintain the quiescent state of postmitotic IPCs. Our studies suggest that manipulating Sox2 or p27(Kip1) expression is an effective approach to inducing proliferation of neonatal auditory IPCs, an initial but necessary step toward restoring hearing in mammals.
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Kopecky B, Fritzsch B. The myc road to hearing restoration. Cells 2012; 1:667-98. [PMID: 24710525 PMCID: PMC3901154 DOI: 10.3390/cells1040667] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Revised: 08/12/2012] [Accepted: 09/14/2012] [Indexed: 01/01/2023] Open
Abstract
Current treatments for hearing loss, the most common neurosensory disorder, do not restore perfect hearing. Regeneration of lost organ of Corti hair cells through forced cell cycle re-entry of supporting cells or through manipulation of stem cells, both avenues towards a permanent cure, require a more complete understanding of normal inner ear development, specifically the balance of proliferation and differentiation required to form and to maintain hair cells. Direct successful alterations to the cell cycle result in cell death whereas regulation of upstream genes is insufficient to permanently alter cell cycle dynamics. The Myc gene family is uniquely situated to synergize upstream pathways into downstream cell cycle control. There are three Mycs that are embedded within the Myc/Max/Mad network to regulate proliferation. The function of the two ear expressed Mycs, N-Myc and L-Myc were unknown less than two years ago and their therapeutic potentials remain speculative. In this review, we discuss the roles the Mycs play in the body and what led us to choose them to be our candidate gene for inner ear therapies. We will summarize the recently published work describing the early and late effects of N-Myc and L-Myc on hair cell formation and maintenance. Lastly, we detail the translational significance of our findings and what future work must be performed to make the ultimate hearing aid: the regeneration of the organ of Corti.
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Affiliation(s)
- Benjamin Kopecky
- Department of Biology, 143 Biology Building, University of Iowa, Iowa City, IA 52242, USA.
| | - Bernd Fritzsch
- Department of Biology, 143 Biology Building, University of Iowa, Iowa City, IA 52242, USA.
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Abstract
The regeneration of mechanoreceptive hair cells occurs throughout life in non-mammalian vertebrates and allows them to recover from hearing and balance deficits that affect humans and other mammals permanently. The irreversibility of comparable deficits in mammals remains unexplained, but often has been attributed to steep embryonic declines in cellular production. However, recent results suggest that gravity-sensing hair cells in murine utricles may increase in number during neonatal development, raising the possibility that young mice might retain sufficient cellular plasticity for mitotic hair cell regeneration. To test for this we used neomycin to kill hair cells in utricles cultured from mice of different ages and found that proliferation increased tenfold in damaged utricles from the youngest neonates. To kill hair cells in vivo, we generated a novel mouse model that uses an inducible, hair cell-specific CreER allele to drive expression of diphtheria toxin fragment A (DTA). In newborns, induction of DTA expression killed hair cells and resulted in significant, mitotic hair cell replacement in vivo, which occurred days after the normal cessation of developmental mitoses that produce hair cells. DTA expression induced in 5-d-old mice also caused hair cell loss, but no longer evoked mitotic hair cell replacement. These findings show that regeneration limits arise in vivo during the postnatal period when the mammalian balance epithelium's supporting cells differentiate unique cytological characteristics and lose plasticity, and they support the notion that the differentiation of those cells may directly inhibit regeneration or eliminate an essential, but as yet unidentified pool of stem cells.
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Pan N, Kopecky B, Jahan I, Fritzsch B. Understanding the evolution and development of neurosensory transcription factors of the ear to enhance therapeutic translation. Cell Tissue Res 2012; 349:415-32. [PMID: 22688958 DOI: 10.1007/s00441-012-1454-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Accepted: 05/18/2012] [Indexed: 01/08/2023]
Abstract
Reconstructing a functional organ of Corti is the ultimate target towards curing hearing loss. Despite the impressive technical gains made over the last few years, many complications remain ahead for the two main restoration avenues: in vitro transformation of pluripotent cells into hair cell-like cells and adenovirus-mediated gene therapy. Most notably, both approaches require a more complete understanding of the molecular networks that ensure specific cell types form in the correct places to allow proper function of the restored organ of Corti. Important to this understanding are the basic helix-loop-helix (bHLH) transcription factors (TFs) that are highly diverse and serve to increase functional complexity but their evolutionary implementation in the inner ear neurosensory development is less conspicuous. To this end, we review the evolutionary and developmentally dynamic interactions of the three bHLH TFs that have been identified as the main players in neurosensory evolution and development, Neurog1, Neurod1 and Atoh1. These three TFs belong to the neurogenin/atonal family and evolved from a molecular precursor that likely regulated single sensory cell development in the ectoderm of metazoan ancestors but are now also expressed in other parts of the body, including the brain. They interact extensively via intracellular and intercellular cross-regulation to establish the two main neurosensory cell types of the ear, the hair cells and sensory neurons. Furthermore, the level and duration of their expression affect the specification of hair cell subtypes (inner hair cells vs. outer hair cells). We propose that appropriate manipulation of these TFs through their characterized binding sites may offer a solution by itself, or in conjunction with the two other approaches currently pursued by others, to restore the organ of Corti.
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Affiliation(s)
- Ning Pan
- Department of Biology, University of Iowa, College of Liberal Arts and Sciences, Iowa City, IA 52242, USA
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