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Coffin AB, Dale E, Molano O, Pederson A, Costa EK, Chen J. Age-related changes in the zebrafish and killifish inner ear and lateral line. Sci Rep 2024; 14:6670. [PMID: 38509148 PMCID: PMC10954678 DOI: 10.1038/s41598-024-57182-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Accepted: 03/14/2024] [Indexed: 03/22/2024] Open
Abstract
Age-related hearing loss (ARHL) is a debilitating disorder for millions worldwide. While there are multiple underlying causes of ARHL, one common factor is loss of sensory hair cells. In mammals, new hair cells are not produced postnatally and do not regenerate after damage, leading to permanent hearing impairment. By contrast, fish produce hair cells throughout life and robustly regenerate these cells after toxic insult. Despite these regenerative abilities, zebrafish show features of ARHL. Here, we show that aged zebrafish of both sexes exhibited significant hair cell loss and decreased cell proliferation in all inner ear epithelia (saccule, lagena, utricle). Ears from aged zebrafish had increased expression of pro-inflammatory genes and significantly more macrophages than ears from young adult animals. Aged zebrafish also had fewer lateral line hair cells and less cell proliferation than young animals, although lateral line hair cells still robustly regenerated following damage. Unlike zebrafish, African turquoise killifish (an emerging aging model) only showed hair cell loss in the saccule of aged males, but both sexes exhibit age-related changes in the lateral line. Our work demonstrates that zebrafish exhibit key features of auditory aging, including hair cell loss and increased inflammation. Further, our finding that aged zebrafish have fewer lateral line hair cells yet retain regenerative capacity, suggests a decoupling of homeostatic hair cell addition from regeneration following acute trauma. Finally, zebrafish and killifish show species-specific strategies for lateral line homeostasis that may inform further comparative research on aging in mechanosensory systems.
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Affiliation(s)
- Allison B Coffin
- College of Arts and Sciences, Washington State University Vancouver, Vancouver, WA, 98686, USA.
- Department of Integrative Physiology and Neuroscience, Washington State University Vancouver, Vancouver, WA, 98686, USA.
| | - Emily Dale
- College of Arts and Sciences, Washington State University Vancouver, Vancouver, WA, 98686, USA
- Neuroimmunology Research, Mayo Clinic, Rochester, MN, 55902, USA
| | - Olivia Molano
- College of Arts and Sciences, Washington State University Vancouver, Vancouver, WA, 98686, USA
- Neuroscience Graduate Program, Brown University, Providence, RI, 02912, USA
| | - Alexandra Pederson
- College of Arts and Sciences, Washington State University Vancouver, Vancouver, WA, 98686, USA
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Emma K Costa
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, 94305, USA
- Neurosciences Interdepartmental Program, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Jingxun Chen
- Department of Genetics, Stanford University, Stanford, CA, 94305, USA
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2
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Choi SW, Abitbol JM, Cheng AG. Hair Cell Regeneration: From Animals to Humans. Clin Exp Otorhinolaryngol 2024; 17:1-14. [PMID: 38271988 PMCID: PMC10933805 DOI: 10.21053/ceo.2023.01382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Revised: 01/07/2024] [Accepted: 01/17/2024] [Indexed: 01/27/2024] Open
Abstract
Cochlear hair cells convert sound into electrical signals that are relayed via the spiral ganglion neurons to the central auditory pathway. Hair cells are vulnerable to damage caused by excessive noise, aging, and ototoxic agents. Non-mammals can regenerate lost hair cells by mitotic regeneration and direct transdifferentiation of surrounding supporting cells. However, in mature mammals, damaged hair cells are not replaced, resulting in permanent hearing loss. Recent studies have uncovered mechanisms by which sensory organs in non-mammals and the neonatal mammalian cochlea regenerate hair cells, and outlined possible mechanisms why this ability declines rapidly with age in mammals. Here, we review similarities and differences between avian, zebrafish, and mammalian hair cell regeneration. Moreover, we discuss advances and limitations of hair cell regeneration in the mature cochlea and their potential applications to human hearing loss.
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Affiliation(s)
- Sung-Won Choi
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA, USA
- Department of Otorhinolaryngology-Head and Neck Surgery and Biomedical Research Institute, Pusan National University Hospital, Busan, Korea
- Department of Otorhinolaryngology-Head and Neck Surgery, Pusan National University School of Medicine, Busan, Korea
| | - Julia M. Abitbol
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA, USA
| | - Alan G. Cheng
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA, USA
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3
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Maurer N, Baltzer J, Schaffeld T, Ruser A, Schnitzler JG, Siebert U. Effects of amplitude and duration of noise exposure on the hearing and anti-predator behaviour of common roach (Rutilus rutilus) and sand goby (Pomatoschistus minutus). THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2023; 154:671-681. [PMID: 37550238 DOI: 10.1121/10.0020535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Accepted: 07/13/2023] [Indexed: 08/09/2023]
Abstract
This study investigates whether an exposure to two different received sound pressure levels at equal cumulative energy affects anti-predator behaviour and auditory detection thresholds of common roach (Rutilus rutilus) and sand goby (Pomatoschistus minutus) differently. This was examined in regard to a vessel slowdown as a management strategy to decrease vessel noise impact on fishes. Using continuous broadband noise, we found significant temporary threshold shifts (TTS) in roach, with 11.9 and 13.4 dB at 250 and 1000 Hz respectively, for the louder exposure. In contrast, gobies exhibited a non-significant shift of 6.6 dB at 125 Hz. Group cohesion increased in roach exposed to an artificial predator in the control group, but not during noise exposures. Gobies showed an initial freezing reaction towards the predator stimulus remaining motionless regardless of treatment. Our results show that a reduction in vessel speed with a corresponding reduction in source level could mitigate the effects on the auditory senses of sensitive fish, but does not appear to have any mitigating effect on their noise-induced behavioural changes. Further studies should investigate the effects of multiple vessel passages, but also the ecological consequences of the described effects on hearing and behaviour at individual and population level.
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Affiliation(s)
- Nina Maurer
- Institute for Terrestrial and Aquatic Wildlife Research (ITAW), University of Veterinary Medicine Hannover, Foundation, Germany
| | - Johannes Baltzer
- Institute for Terrestrial and Aquatic Wildlife Research (ITAW), University of Veterinary Medicine Hannover, Foundation, Germany
| | - Tobias Schaffeld
- Institute for Terrestrial and Aquatic Wildlife Research (ITAW), University of Veterinary Medicine Hannover, Foundation, Germany
| | - Andreas Ruser
- Institute for Terrestrial and Aquatic Wildlife Research (ITAW), University of Veterinary Medicine Hannover, Foundation, Germany
| | - Joseph G Schnitzler
- Institute for Terrestrial and Aquatic Wildlife Research (ITAW), University of Veterinary Medicine Hannover, Foundation, Germany
| | - Ursula Siebert
- Institute for Terrestrial and Aquatic Wildlife Research (ITAW), University of Veterinary Medicine Hannover, Foundation, Germany
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4
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Wijesinghe P, Sastry A, Hui E, Cogan TA, Zheng B, Ho G, Kakal J, Nunez DA. Adult porcine (Sus scrofa) derived inner ear cells: Characteristics in in-vitro cultures. Anat Rec (Hoboken) 2023. [PMID: 36598271 DOI: 10.1002/ar.25149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 11/21/2022] [Accepted: 12/10/2022] [Indexed: 01/05/2023]
Abstract
There is a need for an animal model that closely parallels human cochlea gestational development. This study aims to document porcine inner ear anatomy, and in vitro porcine derived inner ear cell culture characteristics. Twenty-four temporal bone were harvested from 12 adult pigs (Sus scrofa). Six were formalin fixed and their maximal diameters were measured. The cochlea duct length was determined by the insertion length of a Nucleus 22 cochlear implant in two bones. Four formalin fixed bones were sectioned for histology. Cochlear and vestibular tissues were harvested from non-fixed bones, cultured and characterized at different passages (P). Gene and protein expression of multipotent stem/progenitor (Nestin and Sox2), inner ear hair (Myosin VIIa, Prestin) and supporting (Cytokeratin 18 and Vimentin) cell markers were determined. The porcine cochlea was a 3.5 turn spiral. There was a separate vestibular compartment. The cochlear mean maximal diameter and height was 7.99 and 3.77 mm, respectively. Sphere forming cells were identified on phase-contrast microscopy. The relative mRNA expression levels of KRT18, MYO7A and SLC26A5 were significantly positively correlated in cochlear cultures; and MYO7A and SLC26A5; SOX2 and KRT18; NES and SLC26A5 genes were positively correlated in vestibular cultures (p = .037, Spearman correlation [τ] = .900). Inner ear sensory and stem cell characteristics persist in passaged porcine inner ear cells. Further work is required to establish the usefulness of porcine inner ear cell cultures to the study of human inner ear disorders.
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Affiliation(s)
- Printha Wijesinghe
- Division of Otolaryngology, Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada
- Vancouver Coastal Health Research Institute, Vancouver, British Columbia, Canada
| | - Anand Sastry
- Bristol Veterinary School, University of Bristol, Bristol, UK
| | - Elizabeth Hui
- Division of Otolaryngology, Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada
- Vancouver Coastal Health Research Institute, Vancouver, British Columbia, Canada
| | - Tristan A Cogan
- Bristol Veterinary School, University of Bristol, Bristol, UK
| | - Boyuan Zheng
- Division of Otolaryngology, Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada
- Vancouver Coastal Health Research Institute, Vancouver, British Columbia, Canada
| | - Germain Ho
- Division of Otolaryngology, Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada
- Vancouver Coastal Health Research Institute, Vancouver, British Columbia, Canada
| | - Juzer Kakal
- Division of Otolaryngology, Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada
- Vancouver Coastal Health Research Institute, Vancouver, British Columbia, Canada
| | - Desmond A Nunez
- Division of Otolaryngology, Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada
- Vancouver Coastal Health Research Institute, Vancouver, British Columbia, Canada
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Echeverri K. Zebrafishing for enhancers of hearing regeneration. CELL GENOMICS 2022; 2:100178. [PMID: 36778669 PMCID: PMC9903800 DOI: 10.1016/j.xgen.2022.100178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The discovery of regeneration-specific enhancer elements has added an exciting player to the field of regeneration biology. In this issue of Cell Genomics, Jimenez et al.1 demonstrate the power of combining single-cell genomics with the genetically tractable zebrafish to identify modulators of adult hair cell regeneration.
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Affiliation(s)
- Karen Echeverri
- Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, MA, USA
- Corresponding author
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6
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Montalbano G, Olivotto I, Germanà A, Randazzo B. Evaluation of the hair cell regeneration and claudin b and phoenix gene expression during exposure to low concentrations of cadmium and zinc in early developing zebrafish larvae. Comp Biochem Physiol C Toxicol Pharmacol 2021; 248:109116. [PMID: 34182097 DOI: 10.1016/j.cbpc.2021.109116] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 06/14/2021] [Accepted: 06/18/2021] [Indexed: 12/28/2022]
Abstract
Zebrafish possess hair cells on the body surface similar to that of mammals inner hear, in particular in the neuromasts, and due to its ability in regenerating damaged hair cells, is regularly used as a powerful animal model to study in vivo cytotoxicity. Among the factors leading to hair cell disruption, metal ions are of particular concern since they are important environmental pollutants. To date, several studies on zebrafish hair cell regeneration after metal exposure exist, while no data on regeneration during continuous metal exposure are available. In the present study, neuromast hair cell disruption and regeneration were assessed in zebrafish larvae for the first time during zinc (Zn) and cadmium (Cd) continuous exposure and a visual and molecular approach was adopted. Fluorescent vital dye DASPEI was used to assess hair cell regeneration and the gene expression of claudin b (cldnb) and phoenix (pho), was analyzed. Metallotionein-2 (mt2) gene expression was used as standard molecular marker of metal toxicity and confirmed the higher toxicity of Cd compared to Zn. In addition, Cd caused a delay in hair cell regeneration compared to Zn. Molecular analysis showed cldnb gene expression increased in relation to the metal concentrations used, confirming the involvement of this gene in hair cell regeneration. On the contrary, a dramatic decrease of pho gene expression was observed in Cd exposed groups, suggesting a negative impact of Cd on pho expression, thus negatively interfering with hair cell regeneration in zebrafish larvae exposed to this metal.
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Affiliation(s)
| | - Ike Olivotto
- Polytechnic University of Marche, Department of Life and Environmental Sciences, Ancona, Italy
| | - Antonino Germanà
- Messina Study University, Department of Veterinary Sciences, Messina, Italy
| | - Basilio Randazzo
- Polytechnic University of Marche, Department of Life and Environmental Sciences, Ancona, Italy.
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Hardy K, Amariutei AE, De Faveri F, Hendry A, Marcotti W, Ceriani F. Functional development and regeneration of hair cells in the zebrafish lateral line. J Physiol 2021; 599:3913-3936. [PMID: 34143497 PMCID: PMC7612129 DOI: 10.1113/jp281522] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Accepted: 06/03/2021] [Indexed: 12/22/2022] Open
Abstract
Hair cells are mechanosensory receptors responsible for transducing auditory and vestibular information into electrical signals, which are then transmitted with remarkable precision to afferent neurons. Different from mammals, the hair cells of lower vertebrates, including those present in the neuromasts of the zebrafish lateral line, regenerate following environmental or chemical insults. Here we investigate the time-course of regeneration of hair cells in vivo using electrophysiology, 2-photon imaging and immunostaining applied to wild-type and genetically-encoded fluorescent indicator zebrafish lines. Functional hair cells drive spontaneous action potentials in the posterior lateral line afferent fibres, the frequency of which progressively increases over the first 10-days post-fertilization (dpf). Higher firing-rate fibres are only observed from ~6 dpf. Following copper treatment, newly formed hair cells become functional and are able to drive APs in the afferent fibres within 48 hours in both early-larval (≤8 dpf) and late-larval (12-17 dpf) zebrafish. However, the complete functional regeneration of the entire neuromast is delayed in late-larval compared to early-larval zebrafish. We propose that while individual regenerating hair cells can rapidly become active, the acquisition of fully functional neuromasts progresses faster at early-larval stages, a time when hair cells are still under development. At both ages, the afferent terminals in the regenerating neuromast appear to make initial contact with supporting cells. The ablation of the lateral line afferent neurons prevents the timely regeneration of supporting cells and hair cells. These findings indicate that the afferent system is likely to facilitate or promote the neuromast regeneration process.
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Affiliation(s)
- Katherine Hardy
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Ana E Amariutei
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | | | - Aenea Hendry
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield, UK.,Sheffield Neuroscience Institute, University of Sheffield, Sheffield, UK
| | - Federico Ceriani
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
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8
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Jan TA, Eltawil Y, Ling AH, Chen L, Ellwanger DC, Heller S, Cheng AG. Spatiotemporal dynamics of inner ear sensory and non-sensory cells revealed by single-cell transcriptomics. Cell Rep 2021; 36:109358. [PMID: 34260939 PMCID: PMC8378666 DOI: 10.1016/j.celrep.2021.109358] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 12/25/2020] [Accepted: 06/17/2021] [Indexed: 11/28/2022] Open
Abstract
The utricle is a vestibular sensory organ that requires mechanosensitive hair cells to detect linear acceleration. In neonatal mice, new hair cells are derived from non-sensory supporting cells, yet cell type diversity and mechanisms of cell addition remain poorly characterized. Here, we perform computational analyses on single-cell transcriptomes to categorize cell types and resolve 14 individual sensory and non-sensory subtypes. Along the periphery of the sensory epithelium, we uncover distinct groups of transitional epithelial cells, marked by Islr, Cnmd, and Enpep expression. By reconstructing de novo trajectories and gene dynamics, we show that as the utricle expands, Islr+ transitional epithelial cells exhibit a dynamic and proliferative phase to generate new supporting cells, followed by coordinated differentiation into hair cells. Taken together, our study reveals a sequential and coordinated process by which non-sensory epithelial cells contribute to growth of the postnatal mouse sensory epithelium. The postnatal mouse utricle expands by more than 35% and doubles its number of hair cells during the first 8 days. Using single-cell transcriptomics, Jan et al. show that the surrounding transitional epithelial cells proliferate and contribute to the expansion of the sensory epithelium through a stepwise differentiation mechanism.
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Affiliation(s)
- Taha A Jan
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Palo Alto, CA 94305, USA; Department of Otolaryngology-Head and Neck Surgery, University of California San Francisco, San Francisco, CA 94115, USA
| | - Yasmin Eltawil
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Palo Alto, CA 94305, USA
| | - Angela H Ling
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Palo Alto, CA 94305, USA; Department of Otolaryngology-Head and Neck Surgery, University of California San Francisco, San Francisco, CA 94115, USA
| | - Leon Chen
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Palo Alto, CA 94305, USA
| | - Daniel C Ellwanger
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Palo Alto, CA 94305, USA; Genome Analysis Unit, Amgen Research, Amgen Inc., South San Francisco, CA 94080, USA
| | - Stefan Heller
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Palo Alto, CA 94305, USA.
| | - Alan G Cheng
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Palo Alto, CA 94305, USA.
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Breitzler L, Lau IH, Fonseca PJ, Vasconcelos RO. Noise-induced hearing loss in zebrafish: investigating structural and functional inner ear damage and recovery. Hear Res 2020; 391:107952. [DOI: 10.1016/j.heares.2020.107952] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 02/19/2020] [Accepted: 03/16/2020] [Indexed: 12/20/2022]
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10
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Cheng C, Wang Y, Guo L, Lu X, Zhu W, Muhammad W, Zhang L, Lu L, Gao J, Tang M, Chen F, Gao X, Li H, Chai R. Age-related transcriptome changes in Sox2+ supporting cells in the mouse cochlea. Stem Cell Res Ther 2019; 10:365. [PMID: 31791390 PMCID: PMC6889721 DOI: 10.1186/s13287-019-1437-0] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/29/2019] [Accepted: 10/01/2019] [Indexed: 12/17/2022] Open
Abstract
Background Inner ear supporting cells (SCs) in the neonatal mouse cochlea are a potential source for hair cell (HC) regeneration, but several studies have shown that the regeneration ability of SCs decreases dramatically as mice age and that lost HCs cannot be regenerated in adult mice. To better understand how SCs might be better used to regenerate HCs, it is important to understand how the gene expression profile changes in SCs at different ages. Methods Here, we used Sox2GFP/+ mice to isolate the Sox2+ SCs at postnatal day (P)3, P7, P14, and P30 via flow cytometry. Next, we used RNA-seq to determine the transcriptome expression profiles of P3, P7, P14, and P30 SCs. To further analyze the relationships between these age-related and differentially expressed genes in Sox2+ SCs, we performed gene ontology (GO) analysis. Results Consistent with previous reports, we also found that the proliferation and HC regeneration ability of isolated Sox2+ SCs significantly decreased as mice aged. We identified numerous genes that are enriched and differentially expressed in Sox2+ SCs at four different postnatal ages, including cell cycle genes, signaling pathway genes, and transcription factors that might be involved in regulating the proliferation and HC differentiation ability of SCs. We thus present a set of genes that might regulate the proliferation and HC regeneration ability of SCs, and these might serve as potential new therapeutic targets for HC regeneration. Conclusions In our research, we found several genes that might play an important role in regulating the proliferation and HC regeneration ability of SCs. These datasets are expected to serve as a resource to provide potential new therapeutic targets for regulating the ability of SCs to regenerate HCs in postnatal mammals.
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Affiliation(s)
- Cheng Cheng
- Jiangsu Provincial Key Medical Discipline (Laboratory), Department of Otolaryngology Head and Neck Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, No. 321 Zhongshan Road, Nanjing, 210008, China.,Research Institute of Otolaryngology, No. 321 Zhongshan Road, Nanjing, 210008, China
| | - Yunfeng Wang
- Shanghai Fenyang Vision & Audition Center, Shanghai, China.,ENT Institute and Otorhinolaryngology Department of Affiliated Eye and ENT Hospital, Key Laboratory of Hearing Medicine of NHFPC, Shanghai Engineering Research Centre of Cochlear Implant, State Key Laboratory of Medical Neurobiology, Fudan University, Room 611, Building 9, No. 83, Fenyang Road, Xuhui District, Shanghai, 200031, China
| | - Luo Guo
- ENT Institute and Otorhinolaryngology Department of Affiliated Eye and ENT Hospital, Key Laboratory of Hearing Medicine of NHFPC, Shanghai Engineering Research Centre of Cochlear Implant, State Key Laboratory of Medical Neurobiology, Fudan University, Room 611, Building 9, No. 83, Fenyang Road, Xuhui District, Shanghai, 200031, China
| | - Xiaoling Lu
- ENT Institute and Otorhinolaryngology Department of Affiliated Eye and ENT Hospital, Key Laboratory of Hearing Medicine of NHFPC, Shanghai Engineering Research Centre of Cochlear Implant, State Key Laboratory of Medical Neurobiology, Fudan University, Room 611, Building 9, No. 83, Fenyang Road, Xuhui District, Shanghai, 200031, China
| | - Weijie Zhu
- MOE Key Laboratory for Developmental Genes and Human Disease, State Key Laboratory of Bioelectronics, Co-Innovation Center of Neuroregeneration, Institute of Life Sciences, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, 210096, China
| | - Waqas Muhammad
- MOE Key Laboratory for Developmental Genes and Human Disease, State Key Laboratory of Bioelectronics, Co-Innovation Center of Neuroregeneration, Institute of Life Sciences, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, 210096, China.,Department of Biotechnology, Federal Urdu University of Arts, Science and Technology, Gulshan-e-Iqbal Campus, Karachi, Pakistan
| | - Liyan Zhang
- MOE Key Laboratory for Developmental Genes and Human Disease, State Key Laboratory of Bioelectronics, Co-Innovation Center of Neuroregeneration, Institute of Life Sciences, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, 210096, China
| | - Ling Lu
- Jiangsu Provincial Key Medical Discipline (Laboratory), Department of Otolaryngology Head and Neck Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, No. 321 Zhongshan Road, Nanjing, 210008, China
| | - Junyan Gao
- Jiangsu Rehabilitation Research Center for Hearing and Speech Impairment, Nanjing, 210004, Jiangsu, China
| | - Mingliang Tang
- MOE Key Laboratory for Developmental Genes and Human Disease, State Key Laboratory of Bioelectronics, Co-Innovation Center of Neuroregeneration, Institute of Life Sciences, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, 210096, China
| | - Fangyi Chen
- Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen, China
| | - Xia Gao
- Jiangsu Provincial Key Medical Discipline (Laboratory), Department of Otolaryngology Head and Neck Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, No. 321 Zhongshan Road, Nanjing, 210008, China.
| | - Huawei Li
- ENT Institute and Otorhinolaryngology Department of Affiliated Eye and ENT Hospital, Key Laboratory of Hearing Medicine of NHFPC, Shanghai Engineering Research Centre of Cochlear Implant, State Key Laboratory of Medical Neurobiology, Fudan University, Room 611, Building 9, No. 83, Fenyang Road, Xuhui District, Shanghai, 200031, China.
| | - Renjie Chai
- ENT Institute and Otorhinolaryngology Department of Affiliated Eye and ENT Hospital, Key Laboratory of Hearing Medicine of NHFPC, Shanghai Engineering Research Centre of Cochlear Implant, State Key Laboratory of Medical Neurobiology, Fudan University, Room 611, Building 9, No. 83, Fenyang Road, Xuhui District, Shanghai, 200031, China. .,MOE Key Laboratory for Developmental Genes and Human Disease, State Key Laboratory of Bioelectronics, Co-Innovation Center of Neuroregeneration, Institute of Life Sciences, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, 210096, China. .,Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, 226001, 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, 100069, China.
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11
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Krumm B, Klump G, Köppl C, Langemann U. Barn owls have ageless ears. Proc Biol Sci 2018; 284:rspb.2017.1584. [PMID: 28931742 DOI: 10.1098/rspb.2017.1584] [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: 07/14/2017] [Accepted: 08/14/2017] [Indexed: 11/12/2022] Open
Abstract
We measured the auditory sensitivity of the barn owl (Tyto alba), using a behavioural Go/NoGo paradigm in two different age groups, one younger than 2 years (n = 4) and another more than 13 years of age (n = 3). In addition, we obtained thresholds from one individual aged 23 years, three times during its lifetime. For computing audiograms, we presented test frequencies of between 0.5 and 12 kHz, covering the hearing range of the barn owl. Average thresholds in quiet were below 0 dB sound pressure level (SPL) for frequencies between 1 and 10 kHz. The lowest mean threshold was -12.6 dB SPL at 8 kHz. Thresholds were the highest at 12 kHz, with a mean of 31.7 dB SPL. Test frequency had a significant effect on auditory threshold but age group had no significant effect. There was no significant interaction between age group and test frequency. Repeated threshold estimates over 21 years from a single individual showed only a slight increase in thresholds. We discuss the auditory sensitivity of barn owls with respect to other species and suggest that birds, which generally show a remarkable capacity for regeneration of hair cells in the basilar papilla, are naturally protected from presbycusis.
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Affiliation(s)
- Bianca Krumm
- Cluster of Excellence 'Hearing4all', Animal Physiology and Behaviour Group, Department of Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111 Oldenburg, Germany
| | - Georg Klump
- Cluster of Excellence 'Hearing4all', Animal Physiology and Behaviour Group, Department of Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111 Oldenburg, Germany
| | - Christine Köppl
- Cluster of Excellence 'Hearing4all', Animal Physiology and Behaviour Group, Department of Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111 Oldenburg, Germany
| | - Ulrike Langemann
- Cluster of Excellence 'Hearing4all', Animal Physiology and Behaviour Group, Department of Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111 Oldenburg, Germany
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Bucks SA, Cox BC, Vlosich BA, Manning JP, Nguyen TB, Stone JS. Supporting cells remove and replace sensory receptor hair cells in a balance organ of adult mice. eLife 2017; 6:e18128. [PMID: 28263708 PMCID: PMC5338920 DOI: 10.7554/elife.18128] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 01/20/2017] [Indexed: 01/20/2023] Open
Abstract
Vestibular hair cells in the inner ear encode head movements and mediate the sense of balance. These cells undergo cell death and replacement (turnover) throughout life in non-mammalian vertebrates. However, there is no definitive evidence that this process occurs in mammals. We used fate-mapping and other methods to demonstrate that utricular type II vestibular hair cells undergo turnover in adult mice under normal conditions. We found that supporting cells phagocytose both type I and II hair cells. Plp1-CreERT2-expressing supporting cells replace type II hair cells. Type I hair cells are not restored by Plp1-CreERT2-expressing supporting cells or by Atoh1-CreERTM-expressing type II hair cells. Destruction of hair cells causes supporting cells to generate 6 times as many type II hair cells compared to normal conditions. These findings expand our understanding of sensorineural plasticity in adult vestibular organs and further elucidate the roles that supporting cells serve during homeostasis and after injury.
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Affiliation(s)
- Stephanie A Bucks
- Department of Otolaryngology-Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, United States
| | - Brandon C Cox
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, United States,Department of Surgery, Division of Otolaryngology, Southern Illinois University School of Medicine, Springfield, United States
| | - Brittany A Vlosich
- Department of Otolaryngology-Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, United States
| | - James P Manning
- Department of Otolaryngology-Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, United States
| | - Tot B Nguyen
- Department of Otolaryngology-Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, United States
| | - Jennifer S Stone
- Department of Otolaryngology-Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, United States,
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Nguyen K, Kempfle JS, Jung DH, McKenna CE. Recent advances in therapeutics and drug delivery for the treatment of inner ear diseases: a patent review (2011-2015). Expert Opin Ther Pat 2016; 27:191-202. [PMID: 27855527 DOI: 10.1080/13543776.2017.1252751] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Kim Nguyen
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
| | - Judith S. Kempfle
- Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston, MA, USA
- Eaton Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston, MA, USA
- Department of Otology and Laryngology, Harvard Medical School, Boston, MA, USA
| | - David H. Jung
- Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston, MA, USA
- Eaton Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston, MA, USA
- Department of Otology and Laryngology, Harvard Medical School, Boston, MA, USA
| | - Charles E. McKenna
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
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14
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Role of Wnt and Notch signaling in regulating hair cell regeneration in the cochlea. Front Med 2016; 10:237-49. [PMID: 27527363 DOI: 10.1007/s11684-016-0464-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 06/12/2016] [Indexed: 01/22/2023]
Abstract
Sensory hair cells in the inner ear are responsible for sound recognition. Damage to hair cells in adult mammals causes permanent hearing impairment because these cells cannot regenerate. By contrast, newborn mammals possess limited regenerative capacity because of the active participation of various signaling pathways, including Wnt and Notch signaling. The Wnt and Notch pathways are highly sophisticated and conserved signaling pathways that control multiple cellular events necessary for the formation of sensory hair cells. Both signaling pathways allow resident supporting cells to regenerate hair cells in the neonatal cochlea. In this regard, Wnt and Notch signaling has gained increased research attention in hair cell regeneration. This review presents the current understanding of the Wnt and Notch signaling pathways in the auditory portion of the inner ear and discusses the possibilities of controlling these pathways with the hair cell fate determiner Atoh1 to regulate hair cell regeneration in the mammalian cochlea.
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Chemical Ototoxicity of the Fish Inner Ear and Lateral Line. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 877:419-37. [PMID: 26515324 DOI: 10.1007/978-3-319-21059-9_18] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Hair cell-driven mechanosensory systems are crucial for successful execution of a number of behaviors in fishes, and have emerged as good models for exploring questions relevant to human hearing. This review focuses on ototoxic effects in the inner ear and lateral line system of fishes. We specifically examine studies where chemical ototoxins such as aminoglycoside antibiotics have been employed as tools to disable the lateral line. Lateral line ablation results in alterations to feeding behavior and orientation to water current in a variety of species. However, neither behavior is abolished in the presence of additional sensory cues, supporting the hypothesis that many fish behaviors are driven by multisensory integration. Within biomedical research, the larval zebrafish lateral line has become an important model system for understanding signaling mechanisms that contribute to hair cell death and for developing novel pharmacological therapies that protect hair cells from ototoxic damage. Furthermore, given that fishes robustly regenerate damaged hair cells, ototoxin studies in fishes have broadened our understanding of the molecular and genetic events in an innately regenerative system, offering potential targets for mammalian hair cell regeneration. Collectively, studies of fish mechanosensory systems have yielded insight into fish behavior and in mechanisms of hair cell death, protection, and regeneration.
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16
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Yamahara K, Yamamoto N, Nakagawa T, Ito J. Insulin-like growth factor 1: A novel treatment for the protection or regeneration of cochlear hair cells. Hear Res 2015; 330:2-9. [DOI: 10.1016/j.heares.2015.04.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Revised: 04/19/2015] [Accepted: 04/24/2015] [Indexed: 11/15/2022]
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17
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Żak M, Klis SFL, Grolman W. The Wnt and Notch signalling pathways in the developing cochlea: Formation of hair cells and induction of regenerative potential. Int J Dev Neurosci 2015; 47:247-58. [PMID: 26471908 DOI: 10.1016/j.ijdevneu.2015.09.008] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 09/25/2015] [Accepted: 09/26/2015] [Indexed: 12/21/2022] Open
Abstract
The Wnt and Notch signalling pathways control proliferation, specification, and cell fate choices during embryonic development and in adult life. Hence, there is much interest in both signalling pathways in the context of stem cell biology and tissue regeneration. In the developing ear, the Wnt and Notch signalling pathways specify otic cells and refine the ventral boundary of the otic placode. Since both signalling pathways control events essential for the formation of sensory cells, such as proliferation and hair cell differentiation, these pathways could hold promise for the regeneration of hair cells in adult mammalian cochlea. Indeed, modulating either the Wnt or Notch pathways can trigger the regenerative potential of supporting cells. In the neonatal mouse cochlea, Notch-mediated regeneration of hair cells partially depends on Wnt signalling, which implies an interaction between the pathways. This review presents how the Wnt and Notch signalling pathways regulate the formation of sensory hair cells and how modulating their activity induces regenerative potential in the mammalian cochlea.
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Affiliation(s)
- Magdalena Żak
- Department of Otorhinolaryngology and Head & Neck Surgery, Brain Center Rudolf Magnus, University Medical Center Utrecht, Room G.02.531, P.O. Box 85500, 3508 GA, Utrecht, The Netherlands.
| | - Sjaak F L Klis
- Department of Otorhinolaryngology and Head & Neck Surgery, Brain Center Rudolf Magnus, University Medical Center Utrecht, Room G.02.531, P.O. Box 85500, 3508 GA, Utrecht, The Netherlands
| | - Wilko Grolman
- Department of Otorhinolaryngology and Head & Neck Surgery, Brain Center Rudolf Magnus, University Medical Center Utrecht, Room G.02.531, P.O. Box 85500, 3508 GA, Utrecht, The Netherlands
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18
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Monroe JD, Rajadinakaran G, Smith ME. Sensory hair cell death and regeneration in fishes. Front Cell Neurosci 2015; 9:131. [PMID: 25954154 PMCID: PMC4404912 DOI: 10.3389/fncel.2015.00131] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2015] [Accepted: 03/21/2015] [Indexed: 01/31/2023] Open
Abstract
Sensory hair cells are specialized mechanotransductive receptors required for hearing and vestibular function. Loss of hair cells in humans and other mammals is permanent and causes reduced hearing and balance. In the early 1980’s, it was shown that hair cells continue to be added to the inner ear sensory epithelia in cartilaginous and bony fishes. Soon thereafter, hair cell regeneration was documented in the chick cochlea following acoustic trauma. Since then, research using chick and other avian models has led to great insights into hair cell death and regeneration. However, with the rise of the zebrafish as a model organism for studying disease and developmental processes, there has been an increased interest in studying sensory hair cell death and regeneration in its lateral line and inner ears. Advances derived from studies in zebrafish and other fish species include understanding the effect of ototoxins on hair cells and finding otoprotectants to mitigate ototoxin damage, the role of cellular proliferation vs. direct transdifferentiation during hair cell regeneration, and elucidating cellular pathways involved in the regeneration process. This review will summarize research on hair cell death and regeneration using fish models, indicate the potential strengths and weaknesses of these models, and discuss several emerging areas of future studies.
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Affiliation(s)
- Jerry D Monroe
- Department of Biology, Western Kentucky University Bowling Green, KY, USA
| | - Gopinath Rajadinakaran
- Department of Genetics and Genome Sciences, University of Connecticut Health Center Farmington, CT, USA
| | - Michael E Smith
- Department of Biology, Western Kentucky University Bowling Green, KY, USA
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Layman WS, Zuo J. Epigenetic regulation in the inner ear and its potential roles in development, protection, and regeneration. Front Cell Neurosci 2015; 8:446. [PMID: 25750614 PMCID: PMC4285911 DOI: 10.3389/fncel.2014.00446] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Accepted: 12/11/2014] [Indexed: 11/13/2022] Open
Abstract
The burgeoning field of epigenetics is beginning to make a significant impact on our understanding of tissue development, maintenance, and function. Epigenetic mechanisms regulate the structure and activity of the genome in response to intracellular and environmental cues that direct cell-type specific gene networks. The inner ear is comprised of highly specialized cell types with identical genomes that originate from a single totipotent zygote. During inner ear development specific combinations of transcription factors and epigenetic modifiers must function in a coordinated manner to establish and maintain cellular identity. These epigenetic regulatory mechanisms contribute to the maintenance of distinct chromatin states and cell-type specific gene expression patterns. In this review, we highlight emerging paradigms for epigenetic modifications related to inner ear development, and how epigenetics may have a significant role in hearing loss, protection, and regeneration.
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Affiliation(s)
- Wanda S Layman
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital Memphis, TN, USA
| | - Jian Zuo
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital Memphis, TN, USA
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20
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Lush ME, Piotrowski T. Sensory hair cell regeneration in the zebrafish lateral line. Dev Dyn 2014; 243:1187-202. [PMID: 25045019 DOI: 10.1002/dvdy.24167] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 07/12/2014] [Accepted: 07/14/2014] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Damage or destruction of sensory hair cells in the inner ear leads to hearing or balance deficits that can be debilitating, especially in older adults. Unfortunately, the damage is permanent, as regeneration of the inner ear sensory epithelia does not occur in mammals. RESULTS Zebrafish and other non-mammalian vertebrates have the remarkable ability to regenerate sensory hair cells and understanding the molecular and cellular basis for this regenerative ability will hopefully aid us in designing therapies to induce regeneration in mammals. Zebrafish not only possess hair cells in the ear but also in the sensory lateral line system. Hair cells in both organs are functionally analogous to hair cells in the inner ear of mammals. The lateral line is a mechanosensory system found in most aquatic vertebrates that detects water motion and aids in predator avoidance, prey capture, schooling, and mating. Although hair cell regeneration occurs in both the ear and lateral line, most research to date has focused on the lateral line due to its relatively simple structure and accessibility. CONCLUSIONS Here we review the recent discoveries made during the characterization of hair cell regeneration in zebrafish.
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Affiliation(s)
- Mark E Lush
- Stowers Institute for Medical Research, Kansas City, Missouri
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21
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Gene-expression analysis of hair cell regeneration in the zebrafish lateral line. Proc Natl Acad Sci U S A 2014; 111:E1383-92. [PMID: 24706903 DOI: 10.1073/pnas.1402898111] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Deafness caused by the terminal loss of inner ear hair cells is one of the most common sensory diseases. However, nonmammalian animals (e.g., birds, amphibians, and fish) regenerate damaged hair cells. To understand better the reasons underpinning such disparities in regeneration among vertebrates, we set out to define at high resolution the changes in gene expression associated with the regeneration of hair cells in the zebrafish lateral line. We performed RNA-Seq analyses on regenerating support cells purified by FACS. The resulting expression data were subjected to pathway enrichment analyses, and the differentially expressed genes were validated in vivo via whole-mount in situ hybridizations. We discovered that cell cycle regulators are expressed hours before the activation of Wnt/β-catenin signaling following hair cell death. We propose that Wnt/β-catenin signaling is not involved in regulating the onset of proliferation but governs proliferation at later stages of regeneration. In addition, and in marked contrast to mammals, our data clearly indicate that the Notch pathway is significantly down-regulated shortly after injury, thus uncovering a key difference between the zebrafish and mammalian responses to hair cell injury. Taken together, our findings lay the foundation for identifying differences in signaling pathway regulation that could be exploited as potential therapeutic targets to promote either sensory epithelium or hair cell regeneration in mammals.
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22
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Pinto-Teixeira F, Muzzopappa M, Swoger J, Mineo A, Sharpe J, López-Schier H. Intravital imaging of hair-cell development and regeneration in the zebrafish. Front Neuroanat 2013; 7:33. [PMID: 24130521 PMCID: PMC3795300 DOI: 10.3389/fnana.2013.00033] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2013] [Accepted: 09/17/2013] [Indexed: 01/25/2023] Open
Abstract
Direct videomicroscopic visualization of organ formation and regeneration in toto is a powerful strategy to study cellular processes that often cannot be replicated in vitro. Intravital imaging aims at quantifying changes in tissue architecture or subcellular organization over time during organ development, regeneration or degeneration. A general feature of this approach is its reliance on the optical isolation of defined cell types in the whole animals by transgenic expression of fluorescent markers. Here we describe a simple and robust method to analyze sensory hair-cell development and regeneration in the zebrafish lateral line by high-resolution intravital imaging using laser-scanning confocal microscopy (LSCM) and selective plane illumination microscopy (SPIM). The main advantage of studying hair-cell regeneration in the lateral line is that it occurs throughout the life of the animal, which allows its study in the most natural context. We detail protocols to achieve continuous videomicroscopy for up to 68 hours, enabling direct observation of cellular behavior, which can provide a sensitive assay for the quantitative classification of cellular phenotypes and cell-lineage reconstruction. Modifications to this protocol should facilitate pharmacogenetic assays to identify or validate otoprotective or reparative drugs for future clinical strategies aimed at preserving aural function in humans.
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Affiliation(s)
- Filipe Pinto-Teixeira
- Centre for Genomic Regulation (CRG) Barcelona, Spain ; Universitat Pompeu Fabra (UPF) Barcelona, Spain
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23
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Gallardo VE, Behra M. Fluorescent activated cell sorting (FACS) combined with gene expression microarrays for transcription enrichment profiling of zebrafish lateral line cells. Methods 2013; 62:226-31. [PMID: 23791746 DOI: 10.1016/j.ymeth.2013.06.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Revised: 06/05/2013] [Accepted: 06/10/2013] [Indexed: 10/26/2022] Open
Abstract
Transgenic lines carrying fluorescent reporter genes like GFP have been of great value in the elucidation of developmental features and physiological processes in various animal models, including zebrafish. The lateral line (LL), which is a fish specific superficial sensory organ, is an emerging organ model for studying complex cellular processes in the context of the whole living animal. Cell migration, mechanosensory cell development/differentiation and regeneration are some examples. This sensory system is made of superficial and sparse small sensory patches called neuromasts, with less than 50 cells in any given patch. The paucity of cells is a real problem in any effort to characterize those cells at the transcriptional level. We describe here a method which we applied to efficiently separate subpopulation of cells of the LL, using two distinct stable transgenic zebrafish lines, Tg(cldnb:gfp) and Tg(tnks1bp1:EGFP). In both cases, the GFP positive (GFP+) cells were separated from the remainder of the animal by using a Fluorescent Activated Cell Sorter (FACS). The transcripts of the GFP+ cells were subsequently analyzed on gene expression microarrays. The combination of FACS and microarrays is an efficient method to establish a transcriptional signature for discrete cell populations which would otherwise be masked in whole animal preparation.
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Affiliation(s)
- Viviana E Gallardo
- National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
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24
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Behra M, Gallardo VE, Bradsher J, Torrado A, Elkahloun A, Idol J, Sheehy J, Zonies S, Xu L, Shaw KM, Satou C, Higashijima SI, Weinstein BM, Burgess SM. Transcriptional signature of accessory cells in the lateral line, using the Tnk1bp1:EGFP transgenic zebrafish line. BMC DEVELOPMENTAL BIOLOGY 2012; 12:6. [PMID: 22273551 PMCID: PMC3305402 DOI: 10.1186/1471-213x-12-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 01/24/2012] [Indexed: 11/10/2022]
Abstract
Background Because of the structural and molecular similarities between the two systems, the lateral line, a fish and amphibian specific sensory organ, has been widely used in zebrafish as a model to study the development/biology of neuroepithelia of the inner ear. Both organs have hair cells, which are the mechanoreceptor cells, and supporting cells providing other functions to the epithelium. In most vertebrates (excluding mammals), supporting cells comprise a pool of progenitors that replace damaged or dead hair cells. However, the lack of regenerative capacity in mammals is the single leading cause for acquired hearing disorders in humans. Results In an effort to understand the regenerative process of hair cells in fish, we characterized and cloned an egfp transgenic stable fish line that trapped tnks1bp1, a highly conserved gene that has been implicated in the maintenance of telomeres' length. We then used this Tg(tnks1bp1:EGFP) line in a FACsorting strategy combined with microarrays to identify new molecular markers for supporting cells. Conclusions We present a Tg(tnks1bp1:EGFP) stable transgenic line, which we used to establish a transcriptional profile of supporting cells in the zebrafish lateral line. Therefore we are providing a new set of markers specific for supporting cells as well as candidates for functional analysis of this important cell type. This will prove to be a valuable tool for the study of regeneration in the lateral line of zebrafish in particular and for regeneration of neuroepithelia in general.
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Affiliation(s)
- Martine Behra
- National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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25
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Ramcharitar J, Selckmann GM. Differential ablation of sensory receptors underlies ototoxin-induced shifts in auditory thresholds of the goldfish (Carassius auratus). J Appl Toxicol 2011; 30:536-41. [PMID: 20809542 DOI: 10.1002/jat.1523] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In recent years, fish models have become popular for investigations of ototoxic agents. However, the vast majority of such studies have focused on anatomical changes in lateral line hair cells after drug administration. Using the goldfish (Carassius auratus), we confirm that the acquisition of auditory evoked potentials offers a rapid and non-invasive method for quantifying ototoxin-induced changes in hearing sensitivity. Gentamicin (100 mg ml(-1)) was the drug of choice as it is a well-studied human ototoxin. Auditory threshold elevation was observed between 300 and 600 Hz and was accompanied by significant reductions in hair cell ciliary bundle densities in specific regions of the utricle and saccule. The correlations between structure and function suggest that differential susceptibility of sensory hair cells to acute gentamicin treatment underlies the frequency-specific elevation of auditory thresholds. We propose that fish auditory systems should be used alongside the lateral line, for the assessment of ototoxicity in new-developed drugs.
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Affiliation(s)
- John Ramcharitar
- St Mary's College of Maryland, Department of Biology, 18952 E. Fisher Road, St Mary's City, MD 20686, USA.
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26
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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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27
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Bell TJ, Oberholtzer JC. cAMP-induced auditory supporting cell proliferation is mediated by ERK MAPK signaling pathway. J Assoc Res Otolaryngol 2010; 11:173-85. [PMID: 20107853 DOI: 10.1007/s10162-009-0205-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2009] [Accepted: 12/16/2009] [Indexed: 11/28/2022] Open
Abstract
Sensorineural hearing deficiencies result from the loss of auditory hair cells. This hearing loss is permanent in humans and mammals because hair cells are not spontaneously replaced. In other animals such as birds, this is not the case. Damage to the avian cochlea evokes proliferation of supporting cells and the generation of functionally competent replacement hair cells. Signal transduction pathways are clinically useful as potential therapeutic targets, so there is significant interest in identifying the key signal transduction pathways that regulate the formation of replacement hair cells. In a previous study from our lab, we showed that forskolin (FSK) treatment induces auditory supporting cell proliferation and formation of replacement hair cells in the absence of sound or aminoglycoside treatment. Here, we show that FSK-induced supporting cell proliferation is mediated by cell-specific accumulation of cyclic adenosine monophosphate (cAMP) in avian supporting cells and the extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) pathway. By a combination of immunostaining and pharmacological analyses, we show that FSK treatment increases cAMP levels in avian auditory supporting cells and that several ERK MAP inhibitors effectively block FSK-induced supporting cell proliferation. Next, we demonstrate by Western blotting and immunostaining analyses the expression of several ERK MAPK signaling molecules in the avian auditory epithelium and the cell-specific expression of B-Raf in avian auditory supporting cells. Collectively, these data suggest that FSK-induced supporting cell proliferation in the avian auditory epithelium is mediated by increases of cAMP levels in supporting cells and the cell-specific expression of the ERK MAPK family member B-Raf in supporting cells.
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Affiliation(s)
- Thomas J Bell
- Division of Neuropathology, Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
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28
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McDermott BM, Asai Y, Baucom JM, Jani SD, Castellanos Y, Gomez G, McClintock JM, Starr CJ, Hudspeth AJ. Transgenic labeling of hair cells in the zebrafish acousticolateralis system. Gene Expr Patterns 2010; 10:113-8. [PMID: 20085825 DOI: 10.1016/j.gep.2010.01.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2009] [Revised: 01/07/2010] [Accepted: 01/09/2010] [Indexed: 02/01/2023]
Abstract
The zebrafish provides a useful experimental system for investigations of aural development. To permit the controlled expression of transgenes in developing hair cells, we isolated the genomic control regions of the parvalbumin 3a (pvalb3a) and parvalbumin 3b (pvalb3b) genes. Deletion analysis and somatic-cell transgenesis restricted the cis-acting control regions for hair cells to as little as 484base pairs for pvalb3a and 650base pairs for pvalb3b. Using both meganuclease-mediated and standard methods, we produced transgenic animals that transmit transgenes through their germ lines. These fish express GFP in hair cells in the inner ear and lateral line. Two stable transgenic lines express GFP prior to hair-bundle formation, so the associated promoter constructs are suitable for manipulating gene expression during bundle development. We additionally identified a transgenic line that offers variable labeling of supporting cells.
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Affiliation(s)
- Brian M McDermott
- Laboratory of Sensory Neuroscience and Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue New York, NY 10065, USA
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29
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McCullar JS, Ty S, Campbell S, Oesterle EC. Activin potentiates proliferation in mature avian auditory sensory epithelium. J Neurosci 2010; 30:478-90. [PMID: 20071511 PMCID: PMC2975606 DOI: 10.1523/jneurosci.5154-09.2010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2009] [Accepted: 11/12/2009] [Indexed: 01/17/2023] Open
Abstract
Humans and other mammals are highly susceptible to permanent hearing and balance deficits due to an inability to regenerate sensory hair cells lost to inner ear trauma. In contrast, nonmammalian vertebrates, such as birds, robustly regenerate replacement hair cells and restore hearing and balance functions to near-normal levels. There is considerable interest in understanding the cellular mechanisms responsible for this difference in regenerative capacity. Here we report on involvement of the TGFbeta superfamily type II activin receptors, Acvr2a and Acvr2b, in regulating proliferation in mature avian auditory sensory epithelium. Cultured, posthatch avian auditory sensory epithelium treated with Acvr2a and Acvr2b inhibitors shows decreased proliferation of support cells, the cell type that gives rise to new hair cells. Conversely, addition of activin A, an Acvr2a/b ligand, potentiates support cell proliferation. Neither treatment (inhibitor or ligand) affected hair cell survival, suggesting a specific effect of Acvr2a/b signaling on support cell mitogenicity. Using immunocytochemistry, Acvr2a, Acvr2b, and downstream Smad effector proteins were differentially localized in avian and mammalian auditory sensory epithelia. Collectively, these data suggest that signaling through Acvr2a/b promotes support cell proliferation in mature avian auditory sensory epithelium and that this signaling pathway may be incomplete, or actively blocked, in the adult mammalian ear.
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Affiliation(s)
- Jennifer S. McCullar
- Department of Otolaryngology-Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, Washington 98195-7923
| | - Sidya Ty
- Department of Otolaryngology-Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, Washington 98195-7923
| | - Sean Campbell
- Department of Otolaryngology-Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, Washington 98195-7923
| | - Elizabeth C. Oesterle
- Department of Otolaryngology-Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, Washington 98195-7923
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Millimaki BB, Sweet EM, Riley BB. Sox2 is required for maintenance and regeneration, but not initial development, of hair cells in the zebrafish inner ear. Dev Biol 2009; 338:262-9. [PMID: 20025865 DOI: 10.1016/j.ydbio.2009.12.011] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Revised: 12/08/2009] [Accepted: 12/08/2009] [Indexed: 12/19/2022]
Abstract
Sox2 has been variously implicated in maintenance of pluripotent stem cells or, alternatively, early stages of cell differentiation, depending on context. In the developing inner ear, Sox2 initially marks all cells in the nascent sensory epithelium and, in mouse, is required for sensory epithelium formation. Sox2 is eventually downregulated in hair cells but is maintained in support cells, the functional significance of which is unknown. Here we describe regulation and function of sox2 in the zebrafish inner ear. Expression of sox2 begins after the onset of sensory epithelium development and is regulated by Atoh1a/b, Fgf and Notch. Knockdown of sox2 does not prevent hair cell production, but the rate of accumulation is reduced due to sporadic death of differentiated hair cells. We next tested the capacity for hair cell regeneration following laser ablation of mature brn3c:gfp-labeled hair cells. In control embryos, regeneration of lost hair cells begins by 12 h post-ablation and involves transdifferentiation of support cells rather than asymmetric cell division. In contrast, regeneration does not occur in sox2-depleted embryos. These data show that zebrafish sox2 is required for hair cell survival, as well as for transdifferentiation of support cells into hair cells during regeneration.
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Affiliation(s)
- Bonny B Millimaki
- Biology Department, Texas A&M University, College Station, TX 77843-3258, USA
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31
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Phoenix is required for mechanosensory hair cell regeneration in the zebrafish lateral line. PLoS Genet 2009; 5:e1000455. [PMID: 19381250 PMCID: PMC2662414 DOI: 10.1371/journal.pgen.1000455] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Accepted: 03/16/2009] [Indexed: 11/19/2022] Open
Abstract
In humans, the absence or irreversible loss of hair cells, the sensory mechanoreceptors in the cochlea, accounts for a large majority of acquired and congenital hearing disorders. In the auditory and vestibular neuroepithelia of the inner ear, hair cells are accompanied by another cell type called supporting cells. This second cell population has been described as having stem cell-like properties, allowing efficient hair cell replacement during embryonic and larval/fetal development of all vertebrates. However, mammals lose their regenerative capacity in most inner ear neuroepithelia in postnatal life. Remarkably, reptiles, birds, amphibians, and fish are different in that they can regenerate hair cells throughout their lifespan. The lateral line in amphibians and in fish is an additional sensory organ, which is used to detect water movements and is comprised of neuroepithelial patches, called neuromasts. These are similar in ultra-structure to the inner ear's neuroepithelia and they share the expression of various molecular markers. We examined the regeneration process in hair cells of the lateral line of zebrafish larvae carrying a retroviral integration in a previously uncharacterized gene, phoenix (pho). Phoenix mutant larvae develop normally and display a morphologically intact lateral line. However, after ablation of hair cells with copper or neomycin, their regeneration in pho mutants is severely impaired. We show that proliferation in the supporting cells is strongly decreased after damage to hair cells and correlates with the reduction of newly formed hair cells in the regenerating phoenix mutant neuromasts. The retroviral integration linked to the phenotype is in a novel gene with no known homologs showing high expression in neuromast supporting cells. Whereas its role during early development of the lateral line remains to be addressed, in later larval stages phoenix defines a new class of proteins implicated in hair cell regeneration.
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33
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Warchol ME, Richardson GP. Expression of the Pax2 transcription factor is associated with vestibular phenotype in the avian inner ear. Dev Neurobiol 2009; 69:191-202. [PMID: 19130600 DOI: 10.1002/dneu.20684] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The paired-domain transcription factor Pax2 is involved in many facets of inner ear development, but relatively little is known about the expression or function of Pax2 in the mature ear. In this study, we have used immunohistochemical methods to characterize the expression patterns of Pax2 in the sensory organs of inner ears from posthatch chicks. Immunoreactivity for Pax2 was observed in the nuclei of most hair cells and supporting cells in the vestibular organs. In contrast, Pax2 expression in the chick cochlea was limited to hair cells located in the very distal (low frequency) region. We then used organotypic cultures of the chick utricle to examine changes in Pax2 expression in response to ototoxic injury and during hair cell regeneration. Treatment with streptomycin resulted in the loss of most Pax2 immunoreactivity from the lumenal (hair cell) stratum of the utricle. During the early phases of regeneration, moderate Pax2 expression was maintained in the nuclei of proliferating supporting cells. Expression of Pax2 in the hair cell stratum recovered in parallel with hair cell regeneration. The results indicate that Pax2 continues to be expressed in the mature avian ear, and that its expression pattern is correlated with a vestibular phenotype.
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Affiliation(s)
- Mark E Warchol
- Fay and Carl Simons Center for the Biology of Hearing and Deafness, Washington University School of Medicine, St. Louis, MO 63110, USA.
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Epigenetic influences on sensory regeneration: histone deacetylases regulate supporting cell proliferation in the avian utricle. J Assoc Res Otolaryngol 2009; 10:341-53. [PMID: 19340485 DOI: 10.1007/s10162-009-0166-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2008] [Accepted: 02/16/2009] [Indexed: 10/20/2022] Open
Abstract
The sensory hair cells of the cochlea and vestibular organs are essential for normal hearing and balance function. The mammalian ear possesses a very limited ability to regenerate hair cells and their loss can lead to permanent sensory impairment. In contrast, hair cells in the avian ear are quickly regenerated after acoustic trauma or ototoxic injury. The very different regenerative abilities of the avian vs. mammalian ear can be attributed to differences in injury-evoked expression of genes that either promote or inhibit the production of new hair cells. Gene expression is regulated both by the binding of cis-regulatory molecules to promoter regions as well as through structural modifications of chromatin (e.g., methylation and acetylation). This study examined effects of histone deacetylases (HDACs), whose main function is to modify histone acetylation, on the regulation of regenerative proliferation in the chick utricle. Cultures of regenerating utricles and dissociated cells from the utricular sensory epithelia were treated with the HDAC inhibitors valproic acid, trichostatin A, sodium butyrate, and MS-275. All of these molecules prevent the enzymatic removal of acetyl groups from histones, thus maintaining nuclear chromatin in a "relaxed" (open) configuration. Treatment with all inhibitors resulted in comparable decreases in supporting cell proliferation. We also observed that treatment with the HDAC1-, 2-, and 3-specific inhibitor MS-275 was sufficient to reduce proliferation and that two class I HDACs--HDAC1 and HDAC2--were expressed in the sensory epithelium of the utricle. These results suggest that inhibition of specific type I HDACs is sufficient to prevent cell cycle entry in supporting cells. Notably, treatment with HDAC inhibitors did not affect the differentiation of replacement hair cells. We conclude that histone deacetylation is a positive regulator of regenerative proliferation but is not critical for avian hair cell differentiation.
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Brignull HR, Raible DW, Stone JS. Feathers and fins: non-mammalian models for hair cell regeneration. Brain Res 2009; 1277:12-23. [PMID: 19245801 DOI: 10.1016/j.brainres.2009.02.028] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Revised: 02/09/2009] [Accepted: 02/11/2009] [Indexed: 11/18/2022]
Abstract
Death of mechanosensory cells in the inner ear results in two profound disabilities: hearing loss and balance disorders. Although mammals lack the capacity to regenerate hair cells, recent studies in mice and other rodents have offered valuable insight into strategies for stimulating hair cell regeneration in mammals. Investigations of model organisms that retain the ability to form new hair cells after embryogenesis, such as fish and birds, are equally important and have provided clues as to the cellular and molecular mechanisms that may block hair cell regeneration in mammals. Here, we summarize studies on hair cell regeneration in the chicken and the zebrafish, discuss specific advantages of each model, and propose future directions for the use of non-mammalian models in understanding hair cell regeneration.
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Affiliation(s)
- Heather R Brignull
- Department of Biological Structure, University of Washington, WA 98195-7420, USA.
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36
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Cochlear stem/progenitor cells from a postnatal cochlea respond to Jagged1 and demonstrate that notch signaling promotes sphere formation and sensory potential. Mech Dev 2008; 125:674-86. [PMID: 18571907 DOI: 10.1016/j.mod.2008.05.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2007] [Revised: 04/23/2008] [Accepted: 05/09/2008] [Indexed: 01/07/2023]
Abstract
Hair cells and supporting cells of the mammalian cochlea terminally differentiate during development. Recent in vitro evidence suggests the presence of hair cell progenitors in the postnatal cochlea. Phenotypic properties of these cells and factors that promote their ability to generate spheres in aggregate cultures have not been reported. We define an in vitro system that allows stem/progenitor cells harvested from the early postnatal cochlea to develop into spheres. These spheres contain Abcg2, Jagged1 and Notch1 positive progenitor cells that can divide and generate new hair cell-like cells, i.e. immunopositive for specific hair cell markers, including Myosin VI, Myosin VIIa, Math1 and ability to uptake FM1-43. We demonstrate that reducing Notch signaling with a gamma secretase inhibitor decreases the number of spheres generated following treatment of the stem/progenitor cell cultures. Additionally, activation of Notch by an exogenous soluble form of a Notch ligand, i.e. Jagged1 protein, promotes sphere formation and the sensory potential of cochlear stem/progenitor cells. Our findings suggest that Notch1/Jagged1 signaling plays a role in maintaining a population of Abcg2 sensory stem/progenitor cells in the postnatal cochlea.
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37
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Rapid cell-cycle reentry and cell death after acute inactivation of the retinoblastoma gene product in postnatal cochlear hair cells. Proc Natl Acad Sci U S A 2008; 105:781-5. [PMID: 18178626 DOI: 10.1073/pnas.0708061105] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Unlike lower vertebrates, mammals are unable to replace damaged mechanosensory hair cells (HCs) in the cochlea. Recently, ablation of the retinoblastoma protein (Rb) in undifferentiated mouse HC precursors was shown to cause cochlear HC proliferation and the generation of new HCs, raising the hope that inactivation of Rb in postmitotic HCs could trigger cell division and regenerate functional HCs postnatally. Here, we acutely inactivated Rb in nearly all cochlear HCs of newborn mice, using a newly developed HC-specific inducible Cre mouse line. Beginning 48 h after Rb deletion, approximately 40% of HCs were in the S and M phases of the cell cycle, demonstrating an overriding role for Rb in maintaining the quiescent state of postnatal HCs. Unlike Rb-null HC precursors, such HCs failed to undergo cell division and died rapidly. HC clusters were restricted to the less differentiated cochlear regions, consistent with differentiation-dependent roles of Rb. Moreover, outer HCs expressed the maturation marker prestin, suggesting an embryonic time window for Rb-dependent HC specification. We conclude that Rb plays essential and age-dependent roles during HC proliferation and differentiation, and, in contrast to previous hypotheses, cell death after forced cell-cycle reentry presents a major challenge for mammalian HC regeneration from residual postnatal HCs.
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38
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Lu Z, Corwin JT. The influence of glycogen synthase kinase 3 in limiting cell addition in the mammalian ear. Dev Neurobiol 2008; 68:1059-75. [DOI: 10.1002/dneu.20635] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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39
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Ozeki H, Oshima K, Senn P, Kurihara H, Kaga K. Development and regeneration of hair cells. Acta Otolaryngol 2007:38-44. [PMID: 18340569 DOI: 10.1080/03655230701597200] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The vertebrate inner ear is derived from the otic placode and undergoes a complicated series of morphogenetic processes to differentiate into an elaborate structure harboring mechanosensory epithelia featuring hair cells, the mechanoreceptors of hearing and balance. Recently, the principal mechanisms producing hair cells and the key molecules involved in their fate determination and differentiation have been gradually unveiled. The in-depth understanding of hair cell development is consequently providing clues to strategies for mammalian hair cell regeneration. Among them, the identification and characterization of progenitor cells for the hair cell lineage, which is just emerging, is of particular interest. Herein, we review the molecular mechanisms of inner ear development with particular focus on perspectives for hair cell regeneration.
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40
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Kharlamova A, Aarts NL. A Review of Past and Present Hair Cell Regeneration Techniques. ACTA ACUST UNITED AC 2007. [DOI: 10.1044/cicsd_34_f_134] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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41
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Hu Z, Corwin JT. Inner ear hair cells produced in vitro by a mesenchymal-to-epithelial transition. Proc Natl Acad Sci U S A 2007; 104:16675-80. [PMID: 17895386 PMCID: PMC1994140 DOI: 10.1073/pnas.0704576104] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sensory hair cell loss is a major contributor to disabling hearing and balance deficits that affect >250 million people worldwide. Sound exposures, infections, drug toxicity, genetic disorders, and aging all can cause hair cell loss and lead to permanent sensory deficits. Progress toward treatments for these deficits has been limited, in part because hair cells have only been obtainable via microdissection of the anatomically complex internal ear. Attempts to produce hair cells in vitro have resulted in reports of some success but have required transplantation into embryonic ears or coculturing with other tissues. Here, we show that avian inner ear cells can be cultured and passaged for months, frozen, and expanded to large numbers without other tissues. At any point from passage 6 up to at least passage 23, these cultures can be fully dissociated and then aggregated in suspension to induce a mesenchymal-to-epithelial transition that reliably yields new polarized sensory epithelia. Those epithelia develop numerous hair cells that are crowned by hair bundles, composed of a single kinocilium and an asymmetric array of stereocilia. These hair cells exhibit rapid permeance to FM1-43, a dye that passes through open mechanotransducing channels. Because a vial of frozen cells can now provide the capacity to produce bona fide hair cells completely in vitro, these discoveries should open new avenues of research that may ultimately contribute to better treatments for hearing loss and other inner ear disorders.
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Affiliation(s)
- Zhengqing Hu
- Department of Neuroscience, University of Virginia School of Medicine, 409 Lane Road, Charlottesville, VA 22908-1392; and Marine Biological Laboratory, Woods Hole, MA 02543
- *To whom correspondence may be addressed. E-mail:
or
| | - Jeffrey T. Corwin
- Department of Neuroscience, University of Virginia School of Medicine, 409 Lane Road, Charlottesville, VA 22908-1392; and Marine Biological Laboratory, Woods Hole, MA 02543
- *To whom correspondence may be addressed. E-mail:
or
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42
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Gu R, Montcouquiol M, Marchionni M, Corwin JT. Proliferative responses to growth factors decline rapidly during postnatal maturation of mammalian hair cell epithelia. Eur J Neurosci 2007; 25:1363-72. [PMID: 17425563 DOI: 10.1111/j.1460-9568.2007.05414.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Millions of lives are affected by hearing and balance deficits that arise as a consequence of sensory hair cell loss. Those deficits affect mammals permanently, but hearing and balance recover in nonmammals after epithelial supporting cells divide and produce replacement hair cells. Hair cells are not effectively replaced in mammals, but balance epithelia cultured from the ears of rodents and adult humans can respond to hair cell loss with low levels of supporting cell proliferation. We have sought to stimulate vestibular proliferation; and we report here that treatment with glial growth factor 2 (rhGGF2) yields a 20-fold increase in cell proliferation within sheets of pure utricular hair cell epithelium explanted from adult rats into long-term culture. In epithelia from neonates, substantially greater proliferation responses are evoked by rhGGF2 alone, insulin alone and to a lesser degree by serum even during short-term cultures, but all these responses progressively decline during the first 2 weeks of postnatal maturation. Thus, sheets of utricular epithelium from newborn rats average > 40% labelling when cultured for 72 h with bromo-deoxyuridine (BrdU) and either rhGGF2 or insulin. Those from 5- and 6-day-olds average 8-15%, 12-day-olds average < 1% and after 72 h there is little or no labelling in epithelia from 27- and 35-day-olds. These cells are the mammalian counterparts of the progenitors that produce replacement hair cells in nonmammals, so the postnatal quiescence described here is likely to be responsible for at least part of the mammalian ear's unique vulnerability to permanent sensory deficits.
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Affiliation(s)
- Rende Gu
- Department of Neuroscience, University of Virginia, School of Medicine, HSC Box 801392, MR-4 Bldg., Rm 5150, Lane Road, Charlottesville, VA 22908, USA
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43
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Buttitta LA, Katzaroff AJ, Perez CL, de la Cruz A, Edgar BA. A double-assurance mechanism controls cell cycle exit upon terminal differentiation in Drosophila. Dev Cell 2007; 12:631-43. [PMID: 17419999 DOI: 10.1016/j.devcel.2007.02.020] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2006] [Revised: 02/13/2007] [Accepted: 02/27/2007] [Indexed: 10/23/2022]
Abstract
Terminal differentiation is often coupled with permanent exit from the cell cycle, yet it is unclear how cell proliferation is blocked in differentiated tissues. We examined the process of cell cycle exit in Drosophila wings and eyes and discovered that cell cycle exit can be prevented or even reversed in terminally differentiating cells by the simultaneous activation of E2F1 and either Cyclin E/Cdk2 or Cyclin D/Cdk4. Enforcing both E2F and Cyclin/Cdk activities is required to bypass exit because feedback between E2F and Cyclin E/Cdk2 is inhibited after cells differentiate, ensuring that cell cycle exit is robust. In some differentiating cell types (e.g., neurons), known inhibitors including the retinoblastoma homolog Rbf and the p27 homolog Dacapo contribute to parallel repression of E2F and Cyclin E/Cdk2. In other cell types, however (e.g., wing epithelial cells), unknown mechanisms inhibit E2F and Cyclin/Cdk activity in parallel to enforce permanent cell cycle exit upon terminal differentiation.
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Affiliation(s)
- Laura A Buttitta
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
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44
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Cafaro J, Lee GS, Stone JS. Atoh1 expression defines activated progenitors and differentiating hair cells during avian hair cell regeneration. Dev Dyn 2007; 236:156-70. [PMID: 17096404 DOI: 10.1002/dvdy.21023] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
In the avian inner ear, nonsensory supporting cells give rise to new sensory hair cells through two distinct processes: mitosis and direct transdifferentiation. Regulation of supporting cell behavior and cell fate specification during avian hair cell regeneration is poorly characterized. Expression of Atoh1, a proneural transcription factor necessary and sufficient for developmental hair cell specification, was examined using immunofluorescence in quiescent and regenerating hair cell epithelia of mature chickens. In untreated birds, Atoh1 protein was not detected in the auditory epithelium, which is quiescent. In contrast, numerous Atoh1-positive nuclei were seen in the utricular macula, which undergoes continual hair cell turnover. Atoh1-positive nuclei emerged in the auditory epithelium by 15 hr post-ototoxin administration, before overt hair cell damage and supporting cell re-entry into the cell cycle. Subsequently, Atoh1 labeling was seen in 15% of dividing supporting cells. During cell division, Atoh1 was distributed symmetrically to daughter cells, but Atoh1 levels were dramatically regulated shortly thereafter. After cellular differentiation, Atoh1 labeling was confined to hair cells regenerated through either mitosis or direct transdifferentiation. However, Atoh1 expression in dividing progenitors did not necessarily predict hair cell fate specification in daughter cells. Finally, predominant modes of hair cell regeneration varied significantly across the radial axis of the auditory epithelium, with mitosis most frequent neurally and direct transdifferentiation most frequent abneurally. These observations suggest a role for Atoh1 in re-specifying supporting cells and in biasing postmitotic cells toward the hair cell fate during hair cell regeneration in the mature chicken ear.
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Affiliation(s)
- Jon Cafaro
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology and Head and Neck Surgery, University of Washington, Seattle, Washington 98195-7923, USA
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45
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Oshima K, Grimm CM, Corrales CE, Senn P, Martinez Monedero R, Géléoc GS, Edge A, Holt JR, Heller S. Differential distribution of stem cells in the auditory and vestibular organs of the inner ear. J Assoc Res Otolaryngol 2007; 8:18-31. [PMID: 17171473 PMCID: PMC2538418 DOI: 10.1007/s10162-006-0058-3] [Citation(s) in RCA: 237] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2006] [Accepted: 10/03/2006] [Indexed: 12/26/2022] Open
Abstract
The adult mammalian cochlea lacks regenerative capacity, which is the main reason for the permanence of hearing loss. Vestibular organs, in contrast, replace a small number of lost hair cells. The reason for this difference is unknown. In this work we show isolation of sphere-forming stem cells from the early postnatal organ of Corti, vestibular sensory epithelia, the spiral ganglion, and the stria vascularis. Organ of Corti and vestibular sensory epithelial stem cells give rise to cells that express multiple hair cell markers and express functional ion channels reminiscent of nascent hair cells. Spiral ganglion stem cells display features of neural stem cells and can give rise to neurons and glial cell types. We found that the ability for sphere formation in the mouse cochlea decreases about 100-fold during the second and third postnatal weeks; this decrease is substantially faster than the reduction of stem cells in vestibular organs, which maintain their stem cell population also at older ages. Coincidentally, the relative expression of developmental and progenitor cell markers in the cochlea decreases during the first 3 postnatal weeks, which is in sharp contrast to the vestibular system, where expression of progenitor cell markers remains constant or even increases during this period. Our findings indicate that the lack of regenerative capacity in the adult mammalian cochlea is either a result of an early postnatal loss of stem cells or diminishment of stem cell features of maturing cochlear cells.
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Affiliation(s)
- Kazuo Oshima
- Departments of Otolaryngology—Head & Neck Surgery and Molecular & Cellular Physiology, Stanford University School of Medicine, 801 Welch Road, Stanford, CA 94305-5739 USA
- Marine Biological Laboratory, Woods Hole, MA 02543 USA
| | - Christian M. Grimm
- Departments of Otolaryngology—Head & Neck Surgery and Molecular & Cellular Physiology, Stanford University School of Medicine, 801 Welch Road, Stanford, CA 94305-5739 USA
| | - C. Eduardo Corrales
- Departments of Otolaryngology—Head & Neck Surgery and Molecular & Cellular Physiology, Stanford University School of Medicine, 801 Welch Road, Stanford, CA 94305-5739 USA
- Marine Biological Laboratory, Woods Hole, MA 02543 USA
| | - Pascal Senn
- Departments of Otolaryngology—Head & Neck Surgery and Molecular & Cellular Physiology, Stanford University School of Medicine, 801 Welch Road, Stanford, CA 94305-5739 USA
| | - Rodrigo Martinez Monedero
- Department of Otolaryngology and Program in Neuroscience, Harvard Medical School and Eaton Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston, MA 02114 USA
| | - Gwenaëlle S.G. Géléoc
- Departments of Neuroscience and Otolaryngology, University of Virginia School of Medicine, Charlottesville, VA 22908 USA
| | - Albert Edge
- Department of Otolaryngology and Program in Neuroscience, Harvard Medical School and Eaton Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston, MA 02114 USA
| | - Jeffrey R. Holt
- Departments of Neuroscience and Otolaryngology, University of Virginia School of Medicine, Charlottesville, VA 22908 USA
| | - Stefan Heller
- Departments of Otolaryngology—Head & Neck Surgery and Molecular & Cellular Physiology, Stanford University School of Medicine, 801 Welch Road, Stanford, CA 94305-5739 USA
- Marine Biological Laboratory, Woods Hole, MA 02543 USA
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Davies D, Magnus C, Corwin JT. Developmental changes in cell-extracellular matrix interactions limit proliferation in the mammalian inner ear. Eur J Neurosci 2007; 25:985-98. [PMID: 17331195 DOI: 10.1111/j.1460-9568.2007.05355.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hair cell losses can produce severe hearing and balance deficits in mammals and nonmammals alike, but nonmammals recover after epithelial supporting cells divide and give rise to replacement hair cells. Here, we describe cellular changes that appear to underlie the permanence of hair cell deficits in mammalian vestibular organs. In sensory epithelia isolated from the utricles of embryonic day 18 (E18) mice, supporting cells readily spread and proliferated, but spreading and proliferation were infrequent in supporting cells from postnatal day 6 (P6) mice. Cellular spreading and proliferation were dependent on alpha6 integrin, which disappeared from lateral cell membranes by P6 and colocalized with beta4 integrin near the basement membrane at both ages. In the many well-spread, proliferating E18 supporting cells, beta4 was localized at cell borders, but it was localized to hemidesmosome-like structures in the columnar, nondividing supporting cells that were prevalent in P6 cultures. We treated cultures with phorbol myristate acetate (PMA) to activate protein kinase C (PKC) in an initial test of the possibility that maturational changes in supporting cell cytoskeletons or their anchorage might restrict the proliferation of these progenitor cells in the developing mammalian inner ear. That treatment triggered the disassembly of the hemidesmosome-like beta4 structures and resulted in significantly increased cellular spreading and S-phase entry in the P6 epithelia. The results suggest that maturational changes in cytoskeletal organization and anchorage restrict proliferation of mammalian supporting cells whose counterparts are the progenitors of replacement hair cells in nonmammals, thereby leaving mammals vulnerable to persistent sensory deficits caused by hair cell loss.
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Affiliation(s)
- Dawn Davies
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.
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47
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Warchol ME, Speck JD. Expression of GATA3 and tenascin in the avian vestibular maculae: normative patterns and changes during sensory regeneration. J Comp Neurol 2007; 500:646-57. [PMID: 17154269 DOI: 10.1002/cne.21153] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Sensory receptors in the vestibular organs of birds can regenerate after ototoxic injury. Notably, this regenerative process leads to the restoration of the correct patterning of hair cell phenotype and afferent innervation within the repaired sensory epithelium. The molecular signals that specify cell phenotype and regulate neuronal guidance during sensory regeneration are not known, but they are likely to be similar to the signals that direct these processes during embryonic development. The present study examined the recovery of hair cell phenotype during regeneration in the avian utricle, a vestibular organ that detects linear acceleration and head orientation. First, we show that Type I hair cells in the avian vestibular maculae are immunoreactive for the extracellular matrix molecule tenascin and that treatment with the ototoxic antibiotic streptomycin results in a nearly complete elimination of tenascin immunoreactivity. Cells that express tenascin begin to recover after about 2 weeks and are then contacted by calyx terminals of vestibular neurons. In addition, our previous work had shown that the zinc finger transcription factor GATA3 is uniquely expressed within the striolar reversal zone of the utricle (Hawkins et al. [2003] Hum Mol Genet 12:1261-1272), and we show here that this regionalized expression of GATA3 is maintained after severe hair cell lesions and after transplantation of the sensory epithelium onto a chemically defined substrate. In contrast, the expression of three other supporting cell markers--alpha- and beta-tectorin and SCA--is reduced following ototoxic injury. These observations suggest that GATA3 expression may maintain positional information in the maculae during sensory regeneration.
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Affiliation(s)
- Mark E Warchol
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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Savary E, Hugnot JP, Chassigneux Y, Travo C, Duperray C, Van De Water T, Zine A. Distinct Population of Hair Cell Progenitors Can Be Isolated from the Postnatal Mouse Cochlea Using Side Population Analysis. Stem Cells 2007; 25:332-9. [PMID: 17038670 DOI: 10.1634/stemcells.2006-0303] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In mammals, the permanence of hearing loss is due mostly to the incapacity of the cochlea to replace lost mechano-receptor cells (i.e., hair cells [HCs]). The generation of new HCs from a renewable source of progenitors is a principal requirement for developing a cell therapy within this sensory organ. A subset of stem cells, termed side population (SP), has been identified in several tissues of mammals. The ATP-binding cassette transporter Abcg2/Bcrp1 contributes to the specification of the SP phenotype and is proposed as a universal marker for stem/progenitor cells. A defining character of these SP cells is a high efflux capacity for Hoechst dye. Here, we demonstrate that Abcg2 transporter is expressed with two other stem/progenitor cell markers (i.e., Nestin and Musashi1) in distinct and overlapping domains of the supporting cells within the postnatal cochlea. We have developed and describe a fluorescence-activated cell sorting (FACS) technique that enables the purification of a discrete subpopulation of SP-supporting cells from the early postnatal mouse cochlea based on their ability to exclude Hoechst dye. These FACS-isolated cells can divide and express markers of stem/progenitor cells such as Abcg2, a determinant of the SP phenotype, and Musashi1, a neural stem/progenitor cell marker. These markers can differentiate cells expressing markers of HCs and supporting cells in vitro. Our observation that these SP cells are capable of differentiating into HC-like cells implies a possible use for such cells (i.e., the replacement of lost auditory HCs within damaged cochlea).
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Affiliation(s)
- Etienne Savary
- Institute of Neuroscience, INSERM U.583, Montpellier, France
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Martinez-Monedero R, Oshima K, Heller S, Edge ASB. The potential role of endogenous stem cells in regeneration of the inner ear. Hear Res 2007; 227:48-52. [PMID: 17321086 PMCID: PMC2020819 DOI: 10.1016/j.heares.2006.12.015] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2006] [Revised: 12/20/2006] [Accepted: 12/22/2006] [Indexed: 01/10/2023]
Abstract
Stem cells in various mammalian organs retain the capacity to renew themselves and may be able to restore damaged tissue. Their existence has been proven by genetic tracer studies that demonstrate their differentiation into multiple tissue types and by their ability to self-renew through proliferation. Stem cells from the adult nervous system proliferate to form clonal floating colonies called spheres in vitro, and recent studies have demonstrated sphere formation by cells in the cochlea in addition to the vestibular system and the auditory ganglia, indicating that these tissues contain cells with stem cell properties. The presence of stem cells in the inner ear raises the hope of regeneration of mammalian inner ear cells but is difficult to correlate with the lack of spontaneous regeneration seen in the inner ear after tissue damage. Loss of stem cells postnatally in the cochlea may correlate with the loss of regenerative capacity and may limit our ability to stimulate regeneration. Retention of sphere forming ability in adult vestibular tissues suggests that the limited capacity for repair may be attributed to the continued presence of progenitor cells. Future strategies for regeneration must consider the distribution of endogenous stem cells in the inner ear and whether the tissue retains cells with the capacity for regeneration.
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Schlosser G. Development and evolution of lateral line placodes in amphibians I. Development. ZOOLOGY 2006; 105:119-46. [PMID: 16351862 DOI: 10.1078/0944-2006-00058] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2002] [Accepted: 05/30/2002] [Indexed: 11/18/2022]
Abstract
Lateral line placodes are specialized regions of the ectoderm that give rise to the receptor organs of the lateral line system as well as to the sensory neurons innervating them. The development of lateral line placodes has been studied in amphibians since the early 1900s. This paper reviews these older studies and tries to integrate them with more recent findings. Lateral line placodes are probably induced in a multistep process from a panplacodal area surrounding the neural plate. The time schedule of these inductive processes has begun to be unravelled, but little is known yet about their molecular basis. Subsequent pattern formation, morphogenesis and differentiation of lateral line placodes proceeds in most respects relatively autonomously: Onset and polarity of migration of lateral line primordia, the type, spacing, size and number of receptor organs formed, as well as the patterned differentiation of different cell types occur normally even in ectopic locations. Only the pathways for migration of lateral line primordia depend on external cues. Thus, lateral line placodes act as integrated and relatively context-insensitive developmental modules.
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