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Developmental and Functional Hair Cell-Like Cells Induced by Atoh1 Overexpression in the Adult Mammalian Cochlea In Vitro. Neural Plast 2020; 2020:8885813. [PMID: 33204251 PMCID: PMC7661126 DOI: 10.1155/2020/8885813] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 09/17/2020] [Accepted: 10/21/2020] [Indexed: 12/22/2022] Open
Abstract
Hair cells (HCs) in the mammalian cochleae cannot spontaneously regenerate once damaged, resulting in permanent hearing loss. It has been shown that Atoh1 overexpression induces hair cell-like cells (HCLCs) in the cochlea of newborn rodents, but this is hard to achieve in adult mammals. In this study, we used a three-dimensional cochlear culture system and an adenoviral-mediated delivery vector to overexpress Atoh1 in adult mouse cochleae. HCLCs were successfully induced from 3 days after virus infection (3 DVI) in vitro, and the number increased with time. HCLCs were myosin7a positive and distinguishable from remnant HCs in a culture environment. Meanwhile, patch-clamp results showed that noninactive outward potassium currents (sustained outward potassium currents) could be recorded in HCLCs and that their magnitude increased with time, similar to normal HCs. Furthermore, transient HCN currents were recorded in some HCLCs, indicating that the HCLCs experienced a developmental stage similar to normal HCs. We also compared the electrophysiological features of HCLCs from adult mice with native HCs and found the HCLCs gradually matured, similar to the normal HCs. Meanwhile, HCLCs from adult mice possessed the same bundles as developmental HCs. However, these HCLCs did not express prestin, which is a special marker for outer hair cells (OHCs), even at 13 DVI. These results demonstrate that Atoh1 overexpression induces HCLC formation in the adult mammalian cochlea and that these HCLCs were functional and experienced a developmental process similar to that of normal HCs.
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Zheng Y, Luo W, Ma R, Cong N, Ren D, Chi F, Yang J. The Atoh1 expression levels are correlated with the arrangement, ciliary morphology, and electrophysiological characteristics of ectopic hair cell-like cells. Neurosci Lett 2020; 720:134758. [PMID: 31945449 DOI: 10.1016/j.neulet.2020.134758] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 12/15/2019] [Accepted: 01/13/2020] [Indexed: 10/25/2022]
Abstract
Previous reports have suggested that the level and duration of Atoh1 expression are correlated with the survival, arrangement and stereociliary bundle-related morphology of hair cells during development, but whether Atoh1 expression levels are correlated with the arrangement, bundle formation and electrophysiological characteristics of newly formed hair cells is unknown. To address this question, cultured cochlear explants obtained from neonatal rats were treated with different titers of a human adenovirus serotype 5 (Ad5) vector encoding Atoh1 and/or EGFP (EGFP-Atoh1+/-). The results showed that higher EGFP-Atoh1 concentrations led to higher initial Atoh1 mRNA expression levels and induced greater numbers of ectopic hair cell-like cells (EHCLCs) in the lesser epithelial ridge (LER). Furthermore, gradual increases in the number of EHCLCs were associated with the progressive conversion of the LER region similarly to that of hair cells during development. Some of the cilia on EHCLCs with higher Atoh1 expression were regularly arranged in a manner similar to that of normal hair bundles. As demonstrated through patch clamp recordings, high Atoh1 expression was associated with significantly decreased proportions of cells with Ih currents, significantly reduced proportions of transient potassium channel currents, and potassium channel currents with a greatly increased mean amplitude, which indicated that EHCLCs with high Atoh1 expression were more mature than those with low Atoh1 expression. Overall, the evidence suggests that the Atoh1 expression levels affect not only the arrangement and ciliary morphology of hair cells but also the electrophysiological characteristics of Atoh1-induced EHCLCs, and these findings provide important guidance for future therapies aimed at treating deafness.
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Affiliation(s)
- Yu Zheng
- Department of Otology and Skull Base Surgery, Eye Ear Nose and Throat Hospital, Fudan University, Shanghai 200031, China; Shanghai Clinical Medical Center of Hearing Medicine, Shanghai 200031, China; Key Laboratory of Hearing Medicine of National Health Commission of the People's Republic of China, Shanghai 20031, China; Research Institute of Otolaryngology, Fudan University, Shanghai 200031, China
| | - Wenwei Luo
- Department of Otology and Skull Base Surgery, Eye Ear Nose and Throat Hospital, Fudan University, Shanghai 200031, China; Shanghai Clinical Medical Center of Hearing Medicine, Shanghai 200031, China; Key Laboratory of Hearing Medicine of National Health Commission of the People's Republic of China, Shanghai 20031, China; Research Institute of Otolaryngology, Fudan University, Shanghai 200031, China
| | - Rui Ma
- Key Laboratory of Hearing Medicine of National Health Commission of the People's Republic of China, Shanghai 20031, China; Research Institute of Otolaryngology, Fudan University, Shanghai 200031, China
| | - Ning Cong
- Key Laboratory of Hearing Medicine of National Health Commission of the People's Republic of China, Shanghai 20031, China; Research Institute of Otolaryngology, Fudan University, Shanghai 200031, China
| | - Dongdong Ren
- Department of Otology and Skull Base Surgery, Eye Ear Nose and Throat Hospital, Fudan University, Shanghai 200031, China; Shanghai Clinical Medical Center of Hearing Medicine, Shanghai 200031, China; Key Laboratory of Hearing Medicine of National Health Commission of the People's Republic of China, Shanghai 20031, China; Research Institute of Otolaryngology, Fudan University, Shanghai 200031, China.
| | - Fanglu Chi
- Department of Otology and Skull Base Surgery, Eye Ear Nose and Throat Hospital, Fudan University, Shanghai 200031, China; Shanghai Clinical Medical Center of Hearing Medicine, Shanghai 200031, China; Key Laboratory of Hearing Medicine of National Health Commission of the People's Republic of China, Shanghai 20031, China; Research Institute of Otolaryngology, Fudan University, Shanghai 200031, China.
| | - Juanmei Yang
- Department of Otology and Skull Base Surgery, Eye Ear Nose and Throat Hospital, Fudan University, Shanghai 200031, China; Shanghai Clinical Medical Center of Hearing Medicine, Shanghai 200031, China; Key Laboratory of Hearing Medicine of National Health Commission of the People's Republic of China, Shanghai 20031, China; Research Institute of Otolaryngology, Fudan University, Shanghai 200031, China.
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Afferent synaptogenesis between ectopic hair-cell-like cells and neurites of spiral ganglion induced by Atoh1 in mammals in vitro. Neuroscience 2017; 357:185-196. [PMID: 28576729 DOI: 10.1016/j.neuroscience.2017.05.040] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 05/20/2017] [Accepted: 05/23/2017] [Indexed: 11/20/2022]
Abstract
Newly formed ectopic hair-cell-like cells (EHCLCs) induced by overexpression of atonal homolog 1 (Atoh1) in vitro were found to possess features of endogenous hair cells (HCs) in previous reports and in the present study. However, limited information is available regarding whether EHCLCs and native spiral ganglion neurons (SGNs) form afferent synapses, which are important for the restoration of hearing. In the current study, we focused on the afferent synaptogenesis between EHCLCs and SGN-derived dendrites. Cochlear explants of auditory epithelia with native SGNs retained were cultured in vitro, and human adenovirus serotype 5 (Ad5) vectors encoding Atoh1 were used to overexpress Atoh1 and induce EHCLCs. We observed that the neurites of the original SGNs extended toward the lesser epithelial ridge (LER) and innervated the EHCLCs. Immunohistochemical analyses revealed the expression of presynaptic ribbon C-terminal-binding protein 2 (CtBP2) and postsynaptic density protein (PSD)-95 in the nerve endings of SGN-derived neurons adjacent to EHCLCs. PSD-95 was located directly opposite CtBP2-positive puncta in the terminals of branches of SGNs, demonstrating that the neurites of SGNs formed afferent-like synaptic connections with EHCLCs. However, the expression of glutamate receptor type 2 (GluR2) could not be detected in the terminals of branches of SGNs surrounding EHCLCs. In addition, we found that the presynaptic ribbon (CtBP2) formation in EHCLCs preceded neural innervation. Furthermore, CtBP2-positive puncta increased and then decreased in EHCLCs, similar to the changes observed in endogenous HCs in terms of their number and distribution. Our finding of the generation of cochlear afferent synapses between EHCLCs and original SGNs will lay the foundation for regenerative approaches to restoring hearing after hair cell loss.
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Luo WW, Han Z, Ren DD, Wang XW, Chi FL, Yang JM. Notch pathway inhibitor DAPT enhances Atoh1 activity to generate new hair cells in situ in rat cochleae. Neural Regen Res 2017; 12:2092-2099. [PMID: 29323051 PMCID: PMC5784360 DOI: 10.4103/1673-5374.221169] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
Atoh1 overexpression in cochlear epithelium induces new hair cell formation. Use of adenovirus-mediated Atoh1 overexpression has mainly focused on the rat lesser epithelial ridge and induces ectopic hair cell regeneration. The sensory region of rat cochlea is difficult to transfect, thus new hair cells are rarely produced in situ in rat cochlear explants. After culturing rat cochleae in medium containing 10% fetal bovine serum, adenovirus successfully infected the sensory region as the width of the supporting cell area was significantly increased. Adenovirus encoding Atoh1 infected the sensory region and induced hair cell formation in situ. Combined application of the Notch inhibitor DAPT and Atoh1 increased the Atoh1 expression level and decreased hes1 and hes5 levels, further promoting hair cell generation. Our results demonstrate that DAPT enhances Atoh1 activity to promote hair cell regeneration in rat cochlear sensory epithelium in vitro.
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Affiliation(s)
- Wen-Wei Luo
- Department of Otolaryngology, Eye & ENT Hospital of Fudan University; Research Institute of Otolaryngology, Fudan University, Shanghai, China
| | - Zhao Han
- Department of Otolaryngology, Eye & ENT Hospital of Fudan University; Research Institute of Otolaryngology, Fudan University, Shanghai, China
| | - Dong-Dong Ren
- Department of Otolaryngology, Eye & ENT Hospital of Fudan University; Research Institute of Otolaryngology, Fudan University, Shanghai, China
| | - Xin-Wei Wang
- Department of Otolaryngology, Eye & ENT Hospital of Fudan University; Research Institute of Otolaryngology, Fudan University, Shanghai, China
| | - Fang-Lu Chi
- Department of Otolaryngology, Eye & ENT Hospital of Fudan University; Research Institute of Otolaryngology, Fudan University, Shanghai, China
| | - Juan-Mei Yang
- Department of Otolaryngology, Eye & ENT Hospital of Fudan University; Research Institute of Otolaryngology, Fudan University, Shanghai, China
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Analysis of the Damage Mechanism Related to CO 2 Laser Cochleostomy on Guinea Pig Cochlea. Neural Plast 2016; 2016:5982397. [PMID: 28070426 PMCID: PMC5192333 DOI: 10.1155/2016/5982397] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 11/14/2016] [Indexed: 12/03/2022] Open
Abstract
Different types of lasers have been used in inner ear surgery. Therefore, it is of the utmost importance to avoid damage to the inner ear (e.g., hyperthermia and acoustic effects) caused by the use of such lasers. The aim of this study was to use a high powered fibre-enabled CO2 laser (10 W, 606 J/cm2) to perform cochleostomies on guinea pig cochlea and to investigate the possible laser-induced damage mechanisms. The temperature changes in the round window membrane, auditory evoked brainstem response, and morphological of the hair cells were measured and recorded before and after laser application. All of the outcomes differed in comparison with the control group. A rise in temperature and subsequent increased hearing loss were observed in animals that underwent surgery with a 10 W CO2 laser. These findings correlated with increased injury to the cochlear ultrastructure and a higher positive expression of E-cadherin and β-catenin in the damaged organ of Corti. We assume that enhanced cell-cell adhesion and the activated β-catenin-related canonical Wnt-signalling pathway may play a role in the protection of the cochlea to prevent further damage.
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Su YX, Hou CC, Yang WX. Control of hair cell development by molecular pathways involving Atoh1, Hes1 and Hes5. Gene 2014; 558:6-24. [PMID: 25550047 DOI: 10.1016/j.gene.2014.12.054] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Revised: 11/23/2014] [Accepted: 12/25/2014] [Indexed: 01/14/2023]
Abstract
Atoh1, Hes1 and Hes5 are crucial for normal inner ear hair cell development. They regulate the expression of each other in a complex network, while they also interact with many other genes and pathways, such as Notch, FGF, SHH, WNT, BMP and RA. This paper summarized molecular pathways that involve Atoh1, Hes1, and Hes5. Some of the pathways and gene regulation mechanisms discussed here were studied in other tissues, yet they might inspire studies in inner ear hair cell development. Thereby, we presented a complex regulatory network involving these three genes, which might be crucial for proliferation and differentiation of inner ear hair cells.
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Affiliation(s)
- Yi-Xun Su
- The Sperm Laboratory, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - Cong-Cong Hou
- The Sperm Laboratory, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - Wan-Xi Yang
- The Sperm Laboratory, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
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