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Pan J, Wang K, Qu J, Chen D, Chen A, You Y, Tang J, Zhang H. Activated tissue-resident macrophages contribute to hair cell insults in noise-induced hearing loss in mice. Commun Biol 2024; 7:1078. [PMID: 39223249 PMCID: PMC11368919 DOI: 10.1038/s42003-024-06768-4] [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: 01/10/2024] [Accepted: 08/21/2024] [Indexed: 09/04/2024] Open
Abstract
Macrophages serve as the primary immune cell population and assume a pivotal role in the immune response within the damaged cochleae. Yet, the origin and role of macrophages in response to noise exposure remain controversial. Here, we take advantage of Ccr2RFP/+ Cx3cr1GFP/+ dual-reporter mice to identify the infiltrated and tissue-resident macrophages. After noise exposure, we reveal that activated resident macrophages change in morphology, increase in abundance, and migrate to the region of hair cells, leading to the loss of outer hair cells and the damage of ribbon synapses. Meanwhile, peripheral monocytes are not implicated in the noise-induced hair cell insults. These noise-induced activities of macrophages are abolished by inhibiting TLR4 signaling, resulting in alleviated insults of hair cells and partial recovery of hearing. Our findings indicate cochlear resident macrophages are pro-inflammatory and detrimental players in acoustic trauma and introduce a potential therapeutic target in noise-induced hearing loss.
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Affiliation(s)
- Jing Pan
- Department of Otolaryngology Head & Neck Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, 510282, China
- Ear Research Institute, Zhujiang Hospital, Southern Medical University, Guangzhou, 510282, China
| | - Kaiye Wang
- Department of Otolaryngology Head & Neck Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, 510282, China
- Ear Research Institute, Zhujiang Hospital, Southern Medical University, Guangzhou, 510282, China
| | - Jiaxi Qu
- Department of Otolaryngology Head & Neck Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, 510282, China
- Ear Research Institute, Zhujiang Hospital, Southern Medical University, Guangzhou, 510282, China
| | - Dongxiu Chen
- Department of Otolaryngology Head & Neck Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, 510282, China
- Ear Research Institute, Zhujiang Hospital, Southern Medical University, Guangzhou, 510282, China
| | - Anning Chen
- Department of Otolaryngology Head & Neck Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, 510282, China
- Ear Research Institute, Zhujiang Hospital, Southern Medical University, Guangzhou, 510282, China
| | - Yunyou You
- Department of Otolaryngology Head & Neck Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, 510282, China
- Ear Research Institute, Zhujiang Hospital, Southern Medical University, Guangzhou, 510282, China
| | - Jie Tang
- Department of Otolaryngology Head & Neck Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, 510282, China.
- Ear Research Institute, Zhujiang Hospital, Southern Medical University, Guangzhou, 510282, China.
- Department of Physiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, 510515, China.
- Key Laboratory of Mental Health of the Ministry of Education, Southern Medical University, Guangzhou, 510515, China.
- Guangdong-Hong Kong Joint Laboratory for Psychiatric Disorders, Southern Medical University, Guangzhou, 510515, China.
| | - Hongzheng Zhang
- Department of Otolaryngology Head & Neck Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, 510282, China.
- Ear Research Institute, Zhujiang Hospital, Southern Medical University, Guangzhou, 510282, China.
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2
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Hussain S, Sedlacek M, Cui R, Zhang-Hooks W, Bergles D, Bum-Shin J, Kindt KS, Kachar B. Spontaneous calcium transients in hair cell stereocilia. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.08.12.607658. [PMID: 39185174 PMCID: PMC11343103 DOI: 10.1101/2024.08.12.607658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 08/27/2024]
Abstract
The hair bundle of auditory and vestibular hair cells converts mechanical stimuli into electrical signals through mechanoelectrical transduction (MET). The MET apparatus is built around a tip link that connects neighboring stereocilia that are aligned in the direction of mechanosensitivity of the hair bundle. Upon stimulation, the MET channel complex responds to changes in tip-link tension and allows a cation influx into the cell. Ca2+ influx in stereocilia has been used as a signature of MET activity. Using genetically encoded Ca2+ sensors (GCaMP3, GCaMP6s) and high-performance fluorescence confocal microscopy, we detect spontaneous Ca2+ transients in individual stereocilia in developing and fully formed hair bundles. We demonstrate that this activity is abolished by MET channel blockers and thus likely originates from putative MET channels. We observe Ca2+ transients in the stereocilia of mice in tissue explants as well as in vivo in zebrafish hair cells, indicating this activity is functionally conserved. Within stereocilia, the origin of Ca2+ transients is not limited to the canonical MET site at the stereocilia tip but is also present along the stereocilia length. Remarkably, we also observe these Ca2+ transients in the microvilli-like structures on the hair cell surface in the early stages of bundle development, prior to the onset of MET. Ca2+ transients are also present in the tallest rows of stereocilia in auditory hair cells, structures not traditionally thought to contain MET channels. We hypothesize that this newly described activity may reflect stochastic and spontaneous MET channel opening. Localization of these transients to other regions of the stereocilia indicates the presence of a pool of channels or channel precursors. Our work provides insights into MET channel assembly, maturation, function, and turnover.
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Affiliation(s)
- Saman Hussain
- Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Miloslav Sedlacek
- Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Runjia Cui
- Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Wendy Zhang-Hooks
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Dwight Bergles
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Department of Otolaryngology-Head & Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Jung Bum-Shin
- Department of Neuroscience, University of Virginia, Charlottesville, VA 22908
| | - Katie S. Kindt
- Laboratory of Cellular Biology, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Bechara Kachar
- Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
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3
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Miyoshi T, Vishwasrao H, Belyantseva I, Sajeevadathan M, Ishibashi Y, Adadey S, Harada N, Shroff H, Friedman T. Live-cell single-molecule fluorescence microscopy for protruding organelles reveals regulatory mechanisms of MYO7A-driven cargo transport in stereocilia of inner ear hair cells. RESEARCH SQUARE 2024:rs.3.rs-4369958. [PMID: 38826223 PMCID: PMC11142366 DOI: 10.21203/rs.3.rs-4369958/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2024]
Abstract
Stereocilia are unidirectional F-actin-based cylindrical protrusions on the apical surface of inner ear hair cells and function as biological mechanosensors of sound and acceleration. Development of functional stereocilia requires motor activities of unconventional myosins to transport proteins necessary for elongating the F-actin cores and to assemble the mechanoelectrical transduction (MET) channel complex. However, how each myosin localizes in stereocilia using the energy from ATP hydrolysis is only partially understood. In this study, we develop a methodology for live-cell single-molecule fluorescence microscopy of organelles protruding from the apical surface using a dual-view light-sheet microscope, diSPIM. We demonstrate that MYO7A, a component of the MET machinery, traffics as a dimer in stereocilia. Movements of MYO7A are restricted when scaffolded by the plasma membrane and F-actin as mediated by MYO7A's interacting partners. Here, we discuss the technical details of our methodology and its future applications including analyses of cargo transportation in various organelles.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Thomas Friedman
- National Institute on Deafness and Other Communication Disorders, NIH
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4
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Yeo XY, Kwon S, Rinai KR, Lee S, Jung S, Park R. A Consolidated Understanding of the Contribution of Redox Dysregulation in the Development of Hearing Impairment. Antioxidants (Basel) 2024; 13:598. [PMID: 38790703 PMCID: PMC11118506 DOI: 10.3390/antiox13050598] [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: 02/22/2024] [Revised: 04/26/2024] [Accepted: 05/09/2024] [Indexed: 05/26/2024] Open
Abstract
The etiology of hearing impairment is multifactorial, with contributions from both genetic and environmental factors. Although genetic studies have yielded valuable insights into the development and function of the auditory system, the contribution of gene products and their interaction with alternate environmental factors for the maintenance and development of auditory function requires further elaboration. In this review, we provide an overview of the current knowledge on the role of redox dysregulation as the converging factor between genetic and environmental factor-dependent development of hearing loss, with a focus on understanding the interaction of oxidative stress with the physical components of the peripheral auditory system in auditory disfunction. The potential involvement of molecular factors linked to auditory function in driving redox imbalance is an important promoter of the development of hearing loss over time.
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Affiliation(s)
- Xin Yi Yeo
- Department of Psychological Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 119228, Singapore;
- Department of Medical Science, College of Medicine, CHA University, Seongnam 13488, Republic of Korea;
| | - Soohyun Kwon
- Department of Medical Science, College of Medicine, CHA University, Seongnam 13488, Republic of Korea;
- Department of BioNanotechnology, Gachon University, Seongnam 13120, Republic of Korea
| | - Kimberley R. Rinai
- Department of Life Science, College of Medicine, CHA University, Seongnam 13488, Republic of Korea;
| | - Sungsu Lee
- Department of Otolaryngology-Head and Neck Surgery, Chonnam National University Hospital and Medical School, Gwangju 61469, Republic of Korea;
| | - Sangyong Jung
- Department of Medical Science, College of Medicine, CHA University, Seongnam 13488, Republic of Korea;
| | - Raekil Park
- Department of Biomedical Science and Engineering, Gwangju Institute of Science & Technology (GIST), Gwangju 61005, Republic of Korea
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5
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Miyoshi T, Vishwasrao HD, Belyantseva IA, Sajeevadathan M, Ishibashi Y, Adadey SM, Harada N, Shroff H, Friedman TB. Live-cell single-molecule fluorescence microscopy for protruding organelles reveals regulatory mechanisms of MYO7A-driven cargo transport in stereocilia of inner ear hair cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.04.590649. [PMID: 38766013 PMCID: PMC11100596 DOI: 10.1101/2024.05.04.590649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
Stereocilia are unidirectional F-actin-based cylindrical protrusions on the apical surface of inner ear hair cells and function as biological mechanosensors of sound and acceleration. Development of functional stereocilia requires motor activities of unconventional myosins to transport proteins necessary for elongating the F-actin cores and to assemble the mechanoelectrical transduction (MET) channel complex. However, how each myosin localizes in stereocilia using the energy from ATP hydrolysis is only partially understood. In this study, we develop a methodology for live-cell single-molecule fluorescence microscopy of organelles protruding from the apical surface using a dual-view light-sheet microscope, diSPIM. We demonstrate that MYO7A, a component of the MET machinery, traffics as a dimer in stereocilia. Movements of MYO7A are restricted when scaffolded by the plasma membrane and F-actin as mediated by MYO7A's interacting partners. Here, we discuss the technical details of our methodology and its future applications including analyses of cargo transportation in various organelles.
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Affiliation(s)
- Takushi Miyoshi
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, 20892, USA
- Division of Molecular and Integrative Physiology, Department of Biomedical Sciences, Southern Illinois University School of Medicine, Carbondale, IL, 62901, USA
| | - Harshad D. Vishwasrao
- Advanced Imaging and Microscopy Resource, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Inna A. Belyantseva
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Mrudhula Sajeevadathan
- Division of Molecular and Integrative Physiology, Department of Biomedical Sciences, Southern Illinois University School of Medicine, Carbondale, IL, 62901, USA
| | - Yasuko Ishibashi
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, 20892, USA
- Inner Ear Gene Therapy Program, National Institute on Deafness and Other Communication Disorders, National Institute of Health, Bethesda, Maryland 20892, USA
| | - Samuel M. Adadey
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Narinobu Harada
- Hearing Research Laboratory, Harada ENT Clinic, Higashi-Osaka, Osaka, 577-0816, Japan
| | - Hari Shroff
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, 20147, USA
| | - Thomas B. Friedman
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, 20892, USA
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6
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Yang W, Zhao X, Chai R, Fan J. Progress on mechanisms of age-related hearing loss. Front Neurosci 2023; 17:1253574. [PMID: 37727326 PMCID: PMC10505809 DOI: 10.3389/fnins.2023.1253574] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Accepted: 08/14/2023] [Indexed: 09/21/2023] Open
Abstract
Age-related hearing loss, or presbycusis, is a common cause of hearing loss in elderly people worldwide. It typically presents as progressive, irreversible, and usually affects the high frequencies of hearing, with a tremendous impact on the quality of life. Presbycusis is a complex multidimensional disorder, in addition to aging, multiple factors including exposure to noise, or ototoxic agents, genetic susceptibility, metabolic diseases and lifestyle can influence the onset and severity of presbycusis. With the aging of the body, its ability to clean up deleterious substances produced in the metabolic process is weakened, and the self-protection and repair function of the body is reduced, which in turn leads to irreversible damage to the cochlear tissue, resulting in the occurrence of presbycusis. Presently, oxidative stress (OS), mitochondrial DNA damage, low-grade inflammation, decreased immune function and stem cell depletion have been demonstrated to play a critical role in developing presbycusis. The purpose of this review is to illuminate the various mechanisms underlying this age-related hearing loss, with the goal of advancing our understanding, prevention, and treatment of presbycusis.
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Affiliation(s)
- Wen Yang
- Department of Otolaryngology Head and Neck Surgery, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
| | - Xiaolong Zhao
- Department of Otolaryngology Head and Neck Surgery, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
| | - Renjie Chai
- Department of Otolaryngology Head and Neck Surgery, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
- State Key Laboratory of Bioelectronics, Department of Otolaryngology Head and Neck Surgery, Zhongda Hospital, School of Life Sciences and Technology, Advanced Institute for Life and Health, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, China
- Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, China
| | - Jiangang Fan
- Department of Otolaryngology Head and Neck Surgery, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
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7
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Yeom J, Park J, Park JY. Fluid dynamic simulation for cellular damage due to lymphatic flow within the anatomical arrangement of the outer hair cells in the cochlea. Comput Biol Med 2023; 161:106986. [PMID: 37230014 DOI: 10.1016/j.compbiomed.2023.106986] [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: 11/25/2022] [Revised: 03/29/2023] [Accepted: 04/27/2023] [Indexed: 05/27/2023]
Abstract
Damage to the sensory hair cells in the cochlea is a major cause of hearing loss since human sensory hair cells do not regenerate naturally after damage. As these sensory hair cells are exposed to a vibrating lymphatic environment, they may be affected by physical flow. It is known that the outer hair cells (OHCs) are physically more damaged by sound than the inner hair cells (IHCs). In this study, the lymphatic flow is compared using computational fluid dynamics (CFD) based on the arrangement of the OHCs, and the effects of such flow on the OHCs is analyzed. In addition, flow visualization is used to validate the Stokes flow. The Stokes flow behavior is attributed to the low Reynolds number, and the same behavior is observed even when the flow direction is reversed. When the distance between the rows of the OHCs is large, each row is independent, but when this distance is short, the flow change in each row influences the other rows. The stimulation caused by flow changes on the OHCs is confirmed through surface pressure and shear stress. The OHCs located at the base with a short distance between the rows receive excess hydrodynamic stimulation, and the tip of the V-shaped pattern receives an excess mechanical force. This study attempts to understand the contributions of lymphatic flow to OHC damage by quantitatively suggesting stimulation of the OHCs and is expected to contribute to the development of OHC regeneration technologies in the future.
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Affiliation(s)
- Jiun Yeom
- School of Mechanical Engineering, College of Engineering, Chung-Ang University, Seoul, 06974, Republic of Korea
| | - Junseon Park
- School of Mechanical Engineering, College of Engineering, Chung-Ang University, Seoul, 06974, Republic of Korea
| | - Joong Yull Park
- School of Mechanical Engineering, College of Engineering, Chung-Ang University, Seoul, 06974, Republic of Korea; Department of Intelligent Energy and Industry, Graduate School, Chung-Ang University, Seoul, 06974, Republic of Korea.
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8
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Natarajan N, Batts S, Stankovic KM. Noise-Induced Hearing Loss. J Clin Med 2023; 12:2347. [PMID: 36983347 PMCID: PMC10059082 DOI: 10.3390/jcm12062347] [Citation(s) in RCA: 32] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 03/10/2023] [Accepted: 03/14/2023] [Indexed: 03/22/2023] Open
Abstract
Noise-induced hearing loss (NIHL) is the second most common cause of sensorineural hearing loss, after age-related hearing loss, and affects approximately 5% of the world's population. NIHL is associated with substantial physical, mental, social, and economic impacts at the patient and societal levels. Stress and social isolation in patients' workplace and personal lives contribute to quality-of-life decrements which may often go undetected. The pathophysiology of NIHL is multifactorial and complex, encompassing genetic and environmental factors with substantial occupational contributions. The diagnosis and screening of NIHL are conducted by reviewing a patient's history of noise exposure, audiograms, speech-in-noise test results, and measurements of distortion product otoacoustic emissions and auditory brainstem response. Essential aspects of decreasing the burden of NIHL are prevention and early detection, such as implementation of educational and screening programs in routine primary care and specialty clinics. Additionally, current research on the pharmacological treatment of NIHL includes anti-inflammatory, antioxidant, anti-excitatory, and anti-apoptotic agents. Although there have been substantial advances in understanding the pathophysiology of NIHL, there remain low levels of evidence for effective pharmacotherapeutic interventions. Future directions should include personalized prevention and targeted treatment strategies based on a holistic view of an individual's occupation, genetics, and pathology.
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Affiliation(s)
- Nirvikalpa Natarajan
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Palo Alto, CA 94304, USA
| | - Shelley Batts
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Palo Alto, CA 94304, USA
| | - Konstantina M. Stankovic
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Palo Alto, CA 94304, USA
- Department of Neurosurgery, Stanford University School of Medicine, Palo Alto, CA 94304, USA
- Wu Tsai Neuroscience Institute, Stanford University, Stanford, CA 94305, USA
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9
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García-Añoveros J, Clancy JC, Foo CZ, García-Gómez I, Zhou Y, Homma K, Cheatham MA, Duggan A. Tbx2 is a master regulator of inner versus outer hair cell differentiation. Nature 2022; 605:298-303. [PMID: 35508658 PMCID: PMC9803360 DOI: 10.1038/s41586-022-04668-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 03/21/2022] [Indexed: 01/03/2023]
Abstract
The cochlea uses two types of mechanosensory cell to detect sounds. A single row of inner hair cells (IHCs) synapse onto neurons to transmit sensory information to the brain, and three rows of outer hair cells (OHCs) selectively amplify auditory inputs1. So far, two transcription factors have been implicated in the specific differentiation of OHCs, whereas, to our knowledge, none has been identified in the differentiation of IHCs2-4. One such transcription factor for OHCs, INSM1, acts during a crucial embryonic period to consolidate the OHC fate, preventing OHCs from transdifferentiating into IHCs2. In the absence of INSM1, embryonic OHCs misexpress a core set of IHC-specific genes, which we predict are involved in IHC differentiation. Here we find that one of these genes, Tbx2, is a master regulator of IHC versus OHC differentiation in mice. Ablation of Tbx2 in embryonic IHCs results in their development as OHCs, expressing early OHC markers such as Insm1 and eventually becoming completely mature OHCs in the position of IHCs. Furthermore, Tbx2 is epistatic to Insm1: in the absence of both genes, cochleae generate only OHCs, which suggests that TBX2 is necessary for the abnormal transdifferentiation of INSM1-deficient OHCs into IHCs, as well as for normal IHC differentiation. Ablation of Tbx2 in postnatal, largely differentiated IHCs makes them transdifferentiate directly into OHCs, replacing IHC features with those of mature and not embryonic OHCs. Finally, ectopic expression of Tbx2 in OHCs results in their transdifferentiation into IHCs. Hence, Tbx2 is both necessary and sufficient to make IHCs distinct from OHCs and maintain this difference throughout development.
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Affiliation(s)
- Jaime García-Añoveros
- Department of Anesthesiology, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA.,Department of Neurology, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA.,Department of Neuroscience, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA.,Hugh Knowles Center for Clinical and Basic Science in Hearing and its Disorders, Northwestern University, Chicago, IL, USA.,These authors jointly supervised this work: Jaime García-Añoveros, Anne Duggan.,Correspondence and requests for materials should be addressed to Jaime García-Añoveros or Anne Duggan. ;
| | - John C. Clancy
- Department of Anesthesiology, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA
| | - Chuan Zhi Foo
- Department of Anesthesiology, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA.,Driskill Graduate Program in Life Sciences, Northwestern University, Chicago, IL, USA
| | - Ignacio García-Gómez
- Department of Anesthesiology, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA
| | - Yingjie Zhou
- Department of Anesthesiology, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA.,Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL, USA
| | - Kazuaki Homma
- Hugh Knowles Center for Clinical and Basic Science in Hearing and its Disorders, Northwestern University, Chicago, IL, USA.,Department of Otolaryngology–Head and Neck Surgery, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA
| | - Mary Ann Cheatham
- Hugh Knowles Center for Clinical and Basic Science in Hearing and its Disorders, Northwestern University, Chicago, IL, USA.,Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL, USA
| | - Anne Duggan
- Department of Anesthesiology, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA.,These authors jointly supervised this work: Jaime García-Añoveros, Anne Duggan.,Correspondence and requests for materials should be addressed to Jaime García-Añoveros or Anne Duggan. ;
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10
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Kim GS, Wang T, Sayyid ZN, Fuhriman J, Jones SM, Cheng AG. Repair of surviving hair cells in the damaged mouse utricle. Proc Natl Acad Sci U S A 2022; 119:e2116973119. [PMID: 35380897 PMCID: PMC9169652 DOI: 10.1073/pnas.2116973119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 02/21/2022] [Indexed: 11/18/2022] Open
Abstract
Sensory hair cells (HCs) in the utricle are mechanoreceptors required to detect linear acceleration. After damage, the mammalian utricle partially restores the HC population and organ function, although regenerated HCs are primarily type II and immature. Whether native, surviving HCs can repair and contribute to this recovery is unclear. Here, we generated the Pou4f3DTR/+; Atoh1CreERTM/+; Rosa26RtdTomato/+ mouse to fate map HCs prior to ablation. After HC ablation, vestibular evoked potentials were abolished in all animals, with ∼57% later recovering responses. Relative to nonrecovery mice, recovery animals harbored more Atoh1-tdTomato+ surviving HCs. In both groups, surviving HCs displayed markers of both type I and type II subtypes and afferent synapses, despite distorted lamination and morphology. Surviving type II HCs remained innervated in both groups, whereas surviving type I HCs first lacked and later regained calyces in the recovery, but not the nonrecovery, group. Finally, surviving HCs initially displayed immature and subsequently mature-appearing bundles in the recovery group. These results demonstrate that surviving HCs are capable of self-repair and may contribute to the recovery of vestibular function.
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Affiliation(s)
- Grace S. Kim
- Department of Otolaryngology–Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305
| | - Tian Wang
- Department of Otolaryngology–Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305
| | - Zahra N. Sayyid
- Department of Otolaryngology–Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305
| | - Jessica Fuhriman
- Department of Otolaryngology–Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305
| | - Sherri M. Jones
- Department of Special Education and Communication Disorders, College of Education and Human Sciences, University of Nebraska, Lincoln, NE 68583
| | - Alan G. Cheng
- Department of Otolaryngology–Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305
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11
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Giffen KP, Li Y, Liu H, Zhao XC, Zhang CJ, Shen RJ, Wang T, Janesick A, Chen BB, Gong SS, Kachar B, Jin ZB, He DZ. Mutation of SLC7A14 causes auditory neuropathy and retinitis pigmentosa mediated by lysosomal dysfunction. SCIENCE ADVANCES 2022; 8:eabk0942. [PMID: 35394837 PMCID: PMC8993119 DOI: 10.1126/sciadv.abk0942] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 02/22/2022] [Indexed: 05/13/2023]
Abstract
Lysosomes contribute to cellular homeostasis via processes including macromolecule degradation, nutrient sensing, and autophagy. Defective proteins related to lysosomal macromolecule catabolism are known to cause a range of lysosomal storage diseases; however, it is unclear whether mutations in proteins involved in homeostatic nutrient sensing mechanisms cause syndromic sensory disease. Here, we show that SLC7A14, a transporter protein mediating lysosomal uptake of cationic amino acids, is evolutionarily conserved in vertebrate mechanosensory hair cells and highly expressed in lysosomes of mammalian cochlear inner hair cells (IHCs) and retinal photoreceptors. Autosomal recessive mutation of SLC7A14 caused loss of IHCs and photoreceptors, leading to presynaptic auditory neuropathy and retinitis pigmentosa in mice and humans. Loss-of-function mutation altered protein trafficking and increased basal autophagy, leading to progressive cell degeneration. This study implicates autophagy-lysosomal dysfunction in syndromic hearing and vision loss in mice and humans.
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Affiliation(s)
- Kimberlee P. Giffen
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University/University of Georgia Medical Partnership, Athens, GA 30602, USA
| | - Yi Li
- Beijing Institute of Otorhinolaryngology, Department of Otorhinolaryngology-Head and Neck Surgery, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China
| | - Huizhan Liu
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA
| | - Xiao-Chang Zhao
- Beijing Institute of Otorhinolaryngology, Department of Otorhinolaryngology-Head and Neck Surgery, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China
| | - Chang-Jun Zhang
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Lab, Beijing 100730, China
| | - Ren-Juan Shen
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Lab, Beijing 100730, China
| | - Tianying Wang
- Beijing Institute of Otorhinolaryngology, Department of Otorhinolaryngology-Head and Neck Surgery, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China
| | - Amanda Janesick
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, Stanford, CA 94305, USA
| | - Bo-Bei Chen
- Department of Otorhinolaryngology-Head and Neck Surgery, The Second Affiliated Hospital and Yuying Children’s Hospital of Wenzhou Medical University, Wenzhou 325027, China
| | - Shu-Sheng Gong
- Department of Otorhinolaryngology-Head and Neck Surgery, Friendship Hospital, Capital Medical University, Beijing 100050, China
| | - Bechara Kachar
- Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Zi-Bing Jin
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Lab, Beijing 100730, China
| | - David Z. He
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA
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12
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Miyoshi T, Belyantseva IA, Kitajiri SI, Miyajima H, Nishio SY, Usami SI, Kim BJ, Choi BY, Omori K, Shroff H, Friedman TB. Human deafness-associated variants alter the dynamics of key molecules in hair cell stereocilia F-actin cores. Hum Genet 2022; 141:363-382. [PMID: 34232383 PMCID: PMC11351816 DOI: 10.1007/s00439-021-02304-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 06/15/2021] [Indexed: 12/16/2022]
Abstract
Stereocilia protrude up to 100 µm from the apical surface of vertebrate inner ear hair cells and are packed with cross-linked filamentous actin (F-actin). They function as mechanical switches to convert sound vibration into electrochemical neuronal signals transmitted to the brain. Several genes encode molecular components of stereocilia including actin monomers, actin regulatory and bundling proteins, motor proteins and the proteins of the mechanotransduction complex. A stereocilium F-actin core is a dynamic system, which is continuously being remodeled while maintaining an outwardly stable architecture under the regulation of F-actin barbed-end cappers, severing proteins and crosslinkers. The F-actin cores of stereocilia also provide a pathway for motor proteins to transport cargos including components of tip-link densities, scaffolding proteins and actin regulatory proteins. Deficiencies and mutations of stereocilia components that disturb this "dynamic equilibrium" in stereocilia can induce morphological changes and disrupt mechanotransduction causing sensorineural hearing loss, best studied in mouse and zebrafish models. Currently, at least 23 genes, associated with human syndromic and nonsyndromic hearing loss, encode proteins involved in the development and maintenance of stereocilia F-actin cores. However, it is challenging to predict how variants associated with sensorineural hearing loss segregating in families affect protein function. Here, we review the functions of several molecular components of stereocilia F-actin cores and provide new data from our experimental approach to directly evaluate the pathogenicity and functional impact of reported and novel variants of DIAPH1 in autosomal-dominant DFNA1 hearing loss using single-molecule fluorescence microscopy.
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Affiliation(s)
- Takushi Miyoshi
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Porter Neuroscience Research Center, Room 1F-143A, Bethesda, MD, 20892, USA.
- Department of Otolaryngology-Head and Neck Surgery, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, Japan.
| | - Inna A Belyantseva
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Porter Neuroscience Research Center, Room 1F-143A, Bethesda, MD, 20892, USA
| | - Shin-Ichiro Kitajiri
- Department of Hearing Implant Sciences, Shinshu University School of Medicine, 390-8621, Matsumoto, Japan
| | - Hiroki Miyajima
- Department of Otolaryngology, Shinshu University School of Medicine, Matsumoto, 390-8621, Japan
- Department of Otolaryngology, Aizawa Hospital, Matsumoto, 390-8510, Japan
| | - Shin-Ya Nishio
- Department of Hearing Implant Sciences, Shinshu University School of Medicine, 390-8621, Matsumoto, Japan
| | - Shin-Ichi Usami
- Department of Hearing Implant Sciences, Shinshu University School of Medicine, 390-8621, Matsumoto, Japan
| | - Bong Jik Kim
- Department of Otolaryngology-Head and Neck Surgery, Chungnam National University College of Medicine, Chungnam National University Sejong Hospital, Sejong, 30099, South Korea
- Brain Research Institute, Chungnam National University College of Medicine, Daejeon, 35015, South Korea
| | - Byung Yoon Choi
- Department of Otorhinolaryngology, Seoul National University Bundang Hospital, Seongnam, 13620, South Korea
| | - Koichi Omori
- Department of Otolaryngology-Head and Neck Surgery, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, Japan
| | - Hari Shroff
- Laboratory of High Resolution Optical Imaging, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Thomas B Friedman
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Porter Neuroscience Research Center, Room 1F-143A, Bethesda, MD, 20892, USA
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13
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Holmgren M, Ravicz ME, Hancock KE, Strelkova O, Kallogjeri D, Indzhykulian AA, Warchol ME, Sheets L. Mechanical overstimulation causes acute injury and synapse loss followed by fast recovery in lateral-line neuromasts of larval zebrafish. eLife 2021; 10:69264. [PMID: 34665127 PMCID: PMC8555980 DOI: 10.7554/elife.69264] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 10/18/2021] [Indexed: 12/14/2022] Open
Abstract
Excess noise damages sensory hair cells, resulting in loss of synaptic connections with auditory nerves and, in some cases, hair-cell death. The cellular mechanisms underlying mechanically induced hair-cell damage and subsequent repair are not completely understood. Hair cells in neuromasts of larval zebrafish are structurally and functionally comparable to mammalian hair cells but undergo robust regeneration following ototoxic damage. We therefore developed a model for mechanically induced hair-cell damage in this highly tractable system. Free swimming larvae exposed to strong water wave stimulus for 2 hr displayed mechanical injury to neuromasts, including afferent neurite retraction, damaged hair bundles, and reduced mechanotransduction. Synapse loss was observed in apparently intact exposed neuromasts, and this loss was exacerbated by inhibiting glutamate uptake. Mechanical damage also elicited an inflammatory response and macrophage recruitment. Remarkably, neuromast hair-cell morphology and mechanotransduction recovered within hours following exposure, suggesting severely damaged neuromasts undergo repair. Our results indicate functional changes and synapse loss in mechanically damaged lateral-line neuromasts that share key features of damage observed in noise-exposed mammalian ear. Yet, unlike the mammalian ear, mechanical damage to neuromasts is rapidly reversible.
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Affiliation(s)
- Melanie Holmgren
- Department of Otolaryngology, Washington University School of Medicine, St Louis, United States
| | - Michael E Ravicz
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear, Boston, United States.,Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, United States
| | - Kenneth E Hancock
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear, Boston, United States.,Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, United States
| | - Olga Strelkova
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear, Boston, United States.,Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, United States
| | - Dorina Kallogjeri
- Department of Otolaryngology, Washington University School of Medicine, St Louis, United States
| | - Artur A Indzhykulian
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear, Boston, United States.,Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, United States
| | - Mark E Warchol
- Department of Otolaryngology, Washington University School of Medicine, St Louis, United States.,Department of Neuroscience, Washington University School of Medicine, St Louis, United States
| | - Lavinia Sheets
- Department of Otolaryngology, Washington University School of Medicine, St Louis, United States.,Department of Developmental Biology, Washington University School of Medicine, St. Louis, United States
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14
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Liu H, Giffen KP, Grati M, Morrill SW, Li Y, Liu X, Briegel KJ, He DZ. Transcription co-factor LBH is necessary for the survival of cochlear hair cells. J Cell Sci 2021; 134:237781. [PMID: 33674448 DOI: 10.1242/jcs.254458] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 02/11/2021] [Indexed: 11/20/2022] Open
Abstract
Hearing loss affects ∼10% of adults worldwide. Most sensorineural hearing loss is caused by the progressive loss of mechanosensitive hair cells (HCs) in the cochlea. The molecular mechanisms underlying HC maintenance and loss remain poorly understood. LBH, a transcription co-factor implicated in development, is abundantly expressed in outer hair cells (OHCs). We used Lbh-null mice to identify its role in HCs. Surprisingly, Lbh deletion did not affect differentiation and the early development of HCs, as nascent HCs in Lbh knockout mice had normal looking stereocilia. The stereocilia bundle was mechanosensitive and OHCs exhibited the characteristic electromotility. However, Lbh-null mice displayed progressive hearing loss, with stereocilia bundle degeneration and OHC loss as early as postnatal day 12. RNA-seq analysis showed significant gene enrichment of biological processes related to transcriptional regulation, cell cycle, DNA damage/repair and autophagy in Lbh-null OHCs. In addition, Wnt and Notch pathway-related genes were found to be dysregulated in Lbh-deficient OHCs. Our study implicates, for the first time, loss of LBH function in progressive hearing loss, and demonstrates a critical requirement of LBH in promoting HC survival in adult mice.
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Affiliation(s)
- Huizhan Liu
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA
| | - Kimberlee P Giffen
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA
| | - M'Hamed Grati
- Department of Otorhinolaryngology-Head and Neck Surgery, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Seth W Morrill
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA
| | - Yi Li
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA.,Department of Otorhinolaryngology-Head and Neck Surgery, Beijing Tongren Hospital, Capital Medical University, 100730 Beijing, China
| | - Xuezhong Liu
- Department of Otorhinolaryngology-Head and Neck Surgery, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Karoline J Briegel
- Department of Surgery, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - David Z He
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA
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15
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Wagner EL, Shin JB. Mechanisms of Hair Cell Damage and Repair. Trends Neurosci 2019; 42:414-424. [PMID: 30992136 DOI: 10.1016/j.tins.2019.03.006] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 03/04/2019] [Accepted: 03/13/2019] [Indexed: 01/22/2023]
Abstract
Sensory hair cells of the inner ear are exposed to continuous mechanical stress, causing damage over time. The maintenance of hair cells is further challenged by damage from a variety of other ototoxic factors, including loud noise, aging, genetic defects, and ototoxic drugs. This damage can manifest in many forms, from dysfunction of the hair cell mechanotransduction complex to loss of specialized ribbon synapses, and may even result in hair cell death. Given that mammalian hair cells do not regenerate, the repair of hair cell damage is important for continued auditory function throughout life. Here, we discuss how several key hair cell structures can be damaged, and what is known about how they are repaired.
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Affiliation(s)
- Elizabeth L Wagner
- Department of Neuroscience, University of Virginia-School of Medicine, Charlottesville, VA 22908, USA; Department of Biochemistry and Molecular Genetics, University of Virginia-School of Medicine, Charlottesville, VA 22908, USA
| | - Jung-Bum Shin
- Department of Neuroscience, University of Virginia-School of Medicine, Charlottesville, VA 22908, USA.
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16
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Castañeda R, Natarajan S, Jeong SY, Hong BN, Kang TH. Traditional oriental medicine for sensorineural hearing loss: Can ethnopharmacology contribute to potential drug discovery? JOURNAL OF ETHNOPHARMACOLOGY 2019; 231:409-428. [PMID: 30439402 DOI: 10.1016/j.jep.2018.11.016] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 11/06/2018] [Accepted: 11/06/2018] [Indexed: 06/09/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE In Traditional Oriental Medicine (TOM), the development of hearing pathologies is related to an inadequate nourishment of the ears by the kidney and other organs involved in regulation of bodily fluids and nutrients. Several herbal species have historically been prescribed for promoting the production of bodily fluids or as antiaging agents to treat deficiencies in hearing. AIM OF REVIEW The prevalence of hearing loss has been increasing in the last decade and is projected to grow considerably in the coming years. Recently, several herbal-derived products prescribed in TOM have demonstrated a therapeutic potential for acquired sensorineural hearing loss and tinnitus. Therefore, the aims of this review are to provide a comprehensive overview of the current known efficacy of the herbs used in TOM for preventing different forms of acquired sensorineural hearing loss and tinnitus, and associate the traditional principle with the demonstrated pharmacological mechanisms to establish a solid foundation for directing future research. METHODS The present review collected the literature related to herbs used in TOM or related compounds on hearing from Chinese, Korean, and Japanese herbal classics; library catalogs; and scientific databases (PubMed, Scopus, Google Scholar; and Science Direct). RESULTS This review shows that approximately 25 herbal species and 40 active compounds prescribed in TOM for hearing loss and tinnitus have shown in vitro or in vivo beneficial effects for acquired sensorineural hearing loss produced by noise, aging, ototoxic drugs or diabetes. The inner ear is highly vulnerable to ischemia and oxidative damage, where several TOM agents have revealed a direct effect on the auditory system by normalizing the blood supply to the cochlea and increasing the antioxidant defense in sensory hair cells. These strategies have shown a positive impact on maintaining the inner ear potential, sustaining the production of endolymph, reducing the accumulation of toxic and inflammatory substances, preventing sensory cell death and preserving sensory transmission. There are still several herbal species with demonstrated therapeutic efficacy whose mechanisms have not been deeply studied and others that have been traditionally used in hearing loss but have not been tested experimentally. In clinical studies, Ginkgo biloba, Panax ginseng, and Astragalus propinquus have demonstrated to improve hearing thresholds in patients with sensorineural hearing loss and alleviated the symptoms of tinnitus. However, some of these clinical studies have been limited by small sample sizes, lack of an adequate control group or contradictory results. CONCLUSIONS Current therapeutic strategies have proven that the goal of the traditional oriental medicine principle of increasing bodily fluids is a relevant approach for reducing the development of hearing loss by improving microcirculation in the blood-labyrinth barrier and increasing cochlear blood flow. The potential benefits of TOM agents expand to a multi-target approach on different auditory structures of the inner ear related to increased cochlear blood flow, antioxidant, anti-inflammatory, anti-apoptotic and neuroprotective activities. However, more research is required, given the evidence is very limited in terms of the mechanism of action at the preclinical in vivo level and the scarce number of clinical studies published.
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Affiliation(s)
- Rodrigo Castañeda
- Graduate School of Biotechnology, Kyung Hee University, Republic of Korea; Department of Oriental Medicine Biotechnology, College of Life Sciences, Kyung Hee University, Global Campus, Gyeonggi, Republic of Korea.
| | - Sathishkumar Natarajan
- Graduate School of Biotechnology, Kyung Hee University, Republic of Korea; Department of Oriental Medicine Biotechnology, College of Life Sciences, Kyung Hee University, Global Campus, Gyeonggi, Republic of Korea.
| | - Seo Yule Jeong
- Graduate School of Biotechnology, Kyung Hee University, Republic of Korea; Department of Oriental Medicine Biotechnology, College of Life Sciences, Kyung Hee University, Global Campus, Gyeonggi, Republic of Korea.
| | - Bin Na Hong
- Graduate School of Biotechnology, Kyung Hee University, Republic of Korea.
| | - Tong Ho Kang
- Graduate School of Biotechnology, Kyung Hee University, Republic of Korea; Department of Oriental Medicine Biotechnology, College of Life Sciences, Kyung Hee University, Global Campus, Gyeonggi, Republic of Korea.
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17
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Li Y, Jia S, Liu H, Tateya T, Guo W, Yang S, Beisel KW, He DZZ. Characterization of Hair Cell-Like Cells Converted From Supporting Cells After Notch Inhibition in Cultures of the Organ of Corti From Neonatal Gerbils. Front Cell Neurosci 2018; 12:73. [PMID: 29662441 PMCID: PMC5890164 DOI: 10.3389/fncel.2018.00073] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 03/02/2018] [Indexed: 12/11/2022] Open
Abstract
The senses of hearing and balance depend upon hair cells, the sensory receptors of the inner ear. Hair cells transduce mechanical stimuli into electrical activity. Loss of hair cells as a result of aging or exposure to noise and ototoxic drugs is the major cause of noncongenital hearing and balance deficits. In the ear of non-mammals, lost hair cells can spontaneously be replaced by production of new hair cells from conversion of supporting cells. Although supporting cells in adult mammals have lost that capability, neonatal supporting cells are able to convert to hair cells after inhibition of Notch signaling. We questioned whether Notch inhibition is sufficient to convert supporting cells to functional hair cells using electrophysiology and electron microscopy. We showed that pharmacological inhibition of the canonical Notch pathway in the cultured organ of Corti prepared from neonatal gerbils induced stereocilia formation in supporting cells (defined as hair cell-like cells or HCLCs) and supernumerary stereocilia in hair cells. The newly emerged stereocilia bundles of HCLCs were functional, i.e., able to respond to mechanical stimulation with mechanotransduction (MET) current. Transmission electron microscopy (TEM) showed that HCLCs converted from pillar cells maintained the pillar cell shape and that subsurface cisternae, normally observed underneath the cytoskeleton in outer hair cells (OHCs), was not present in Deiters’ cells-derived HCLCs. Voltage-clamp recordings showed that whole-cell currents from Deiters’ cells-derived HCLCs retained the same kinetics and magnitude seen in normal Deiters’ cells and that nonlinear capacitance (NLC), an electrical hallmark of OHC electromotility, was not detected from any HCLCs measured. Taken together, these results suggest that while Notch inhibition is sufficient for promoting stereocilia bundle formation, it is insufficient to convert neonatal supporting cells to mature hair cells. The fact that Notch inhibition led to stereocilia formation in supporting cells and supernumerary stereocilia in existing hair cells appears to suggest that Notch signaling may regulate stereocilia formation and stability during development.
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Affiliation(s)
- Yi Li
- Department of Otorhinolaryngology, Beijing Tongren Hospital, Beijing Capital Medical University, Beijing, China.,Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE, United States
| | - Shuping Jia
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE, United States
| | - Huizhan Liu
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE, United States
| | - Tomoko Tateya
- Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Weiwei Guo
- Department of Otorhinolaryngology, PLA General Hospital, Beijing, China
| | - Shiming Yang
- Department of Otorhinolaryngology, PLA General Hospital, Beijing, China
| | - Kirk W Beisel
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE, United States
| | - David Z Z He
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE, United States
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18
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Jiang QQ, Yu N, Yang SM. A hypothesis study on bionic active noise reduction of auditory organs. Mil Med Res 2018; 5:8. [PMID: 29502534 PMCID: PMC6389082 DOI: 10.1186/s40779-018-0155-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 02/08/2018] [Indexed: 11/21/2022] Open
Abstract
BACKGROUND Noise exposure can lead to hearing loss and multiple system dysfunctions. As various forms of noise exist in our living environments, and our auditory organs are very sensitive to acoustic stimuli, it is a challenge to protect our hearing system in certain noisy environments. PRESENTATION OF THE HYPOTHESIS Herein, we propose that our hearing organ could serve as a noise eliminator for high intensity noise and enhance acoustic signal processing abilities by increasing the signal-noise ratio. For suprathreshold signals, the hearing system is capable of regulating the middle ear muscles and other structures to actively suppress the sound level to a safe range. TESTING THE HYPOTHESIS To test our hypothesis, both mathematic model analyses and animal model studies are needed. Based on a digital 3D reconstructed model, every structure in the auditory system can be analyzed and tested for its contribution to the process of noise reduction. Products manufactured by this bionic method could be used and verified in animal models and volunteers. IMPLICATIONS By mimicking the noise-reduction effect of the sophisticated structures in the hearing system, we may be able to provide a model that establishes a new active-sound-suppression mode. This innovative method may overcome the limited capabilities of current noise protection options and become a promising possibility for noise prevention.
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Affiliation(s)
- Qing-Qing Jiang
- Department of Otolaryngology Head and Neck Surgery, Institute of Otolaryngology, Chinese PLA General Hospital; Key Laboratory of Hearing Impairment Science, Ministry of Education; Beijing Key Laboratory of Hearing Impairment Prevention and Treatment, Beijing, 100853, China
| | - Ning Yu
- Department of Otolaryngology Head and Neck Surgery, Institute of Otolaryngology, Chinese PLA General Hospital; Key Laboratory of Hearing Impairment Science, Ministry of Education; Beijing Key Laboratory of Hearing Impairment Prevention and Treatment, Beijing, 100853, China
| | - Shi-Ming Yang
- Department of Otolaryngology Head and Neck Surgery, Institute of Otolaryngology, Chinese PLA General Hospital; Key Laboratory of Hearing Impairment Science, Ministry of Education; Beijing Key Laboratory of Hearing Impairment Prevention and Treatment, Beijing, 100853, China.
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19
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Barta CL, Liu H, Chen L, Giffen KP, Li Y, Kramer KL, Beisel KW, He DZ. RNA-seq transcriptomic analysis of adult zebrafish inner ear hair cells. Sci Data 2018; 5:180005. [PMID: 29406519 PMCID: PMC5800389 DOI: 10.1038/sdata.2018.5] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 12/11/2017] [Indexed: 02/03/2023] Open
Abstract
Although hair cells are the sensory receptors of the auditory and vestibular systems in the ears of all vertebrates, hair cell properties are different between non-mammalian vertebrates and mammals. To understand the basic biological properties of hair cells from non-mammalian vertebrates, we examined the transcriptome of adult zebrafish auditory and vestibular hair cells. GFP-labeled hair cells were isolated from inner-ear sensory epithelia of a pou4f3 promoter-driven GAP-GFP line of transgenic zebrafish. One thousand hair cells and 1,000 non-sensory surrounding cells (nsSCs) were separately collected for each biological replicate, using the suction pipette technique. RNA sequencing of three biological replicates for the two cell types was performed and analyzed. Comparisons between hair cells and nsSCs allow identification of enriched genes in hair cells, which may underlie hair cell specialization. Our dataset provides an extensive resource for understanding the molecular mechanisms underlying morphology, function, and pathology of adult zebrafish hair cells. It also establishes a framework for future characterization of genes expressed in hair cells and the study of hair cell evolution.
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Affiliation(s)
- Cody L Barta
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska 68178, USA
| | - Huizhan Liu
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska 68178, USA
| | - Lei Chen
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska 68178, USA.,Chongqing Academy of Animal Science, Chongqing 402460, China
| | - Kimberlee P Giffen
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska 68178, USA
| | - Yi Li
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska 68178, USA.,Department of Otorhinolaryngology-Head and Neck Surgery, Beijing Tonren Hospital, Capital Medical University, Beijing 100730, China
| | - Kenneth L Kramer
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska 68178, USA
| | - Kirk W Beisel
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska 68178, USA
| | - David Z He
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska 68178, USA
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20
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Pathophysiology of the inner ear after blast injury caused by laser-induced shock wave. Sci Rep 2016; 6:31754. [PMID: 27531021 PMCID: PMC4987642 DOI: 10.1038/srep31754] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 07/25/2016] [Indexed: 11/08/2022] Open
Abstract
The ear is the organ that is most sensitive to blast overpressure, and ear damage is most frequently seen after blast exposure. Blast overpressure to the ear results in sensorineural hearing loss, which is untreatable and is often associated with a decline in the quality of life. In this study, we used a rat model to demonstrate the pathophysiological and structural changes in the inner ear that replicate pure sensorineural hearing loss associated with blast injury using laser-induced shock wave (LISW) without any conductive hearing loss. Our results indicate that threshold elevation of the auditory brainstem response (ABR) after blast exposure was primarily caused by outer hair cell dysfunction induced by stereociliary bundle disruption. The bundle disruption pattern was unique; disturbed stereocilia were mostly observed in the outermost row, whereas those in the inner and middle rows stereocilia remained intact. In addition, the ABR examination showed a reduction in wave I amplitude without elevation of the threshold in the lower energy exposure group. This phenomenon was caused by loss of the synaptic ribbon. This type of hearing dysfunction has recently been described as hidden hearing loss caused by cochlear neuropathy, which is associated with tinnitus or hyperacusis.
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21
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Zhou Y, Hu Z. Epigenetic DNA Demethylation Causes Inner Ear Stem Cell Differentiation into Hair Cell-Like Cells. Front Cell Neurosci 2016; 10:185. [PMID: 27536218 PMCID: PMC4971107 DOI: 10.3389/fncel.2016.00185] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 07/12/2016] [Indexed: 12/17/2022] Open
Abstract
The DNA methyltransferase (DNMT) inhibitor 5-azacytidine (5-aza) causes genomic demethylation to regulate gene expression. However, it remains unclear whether 5-aza affects gene expression and cell fate determination of stem cells. In this study, 5-aza was applied to mouse utricle sensory epithelia-derived progenitor cells (MUCs) to investigate whether 5-aza stimulated MUCs to become sensory hair cells. After treatment, MUCs increased expression of hair cell genes and proteins. The DNA methylation level (indicated by percentage of 5-methylcytosine) showed a 28.57% decrease after treatment, which causes significantly repressed DNMT1 protein expression and DNMT activity. Additionally, FM1-43 permeation assays indicated that the permeability of 5-aza-treated MUCs was similar to that of sensory hair cells, which may result from mechanotransduction channels. This study not only demonstrates a possible epigenetic approach to induce tissue specific stem/progenitor cells to become sensory hair cell-like cells, but also provides a cell model to epigenetically modulate stem cell fate determination.
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Affiliation(s)
- Yang Zhou
- Department of Otolaryngology-Head and Neck Surgery, Wayne State University School of Medicine Detroit, MI, USA
| | - Zhengqing Hu
- Department of Otolaryngology-Head and Neck Surgery, Wayne State University School of Medicine Detroit, MI, USA
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22
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Tang PC, Smith KM, Watson GM. Repair of traumatized mammalian hair cells via sea anemone repair proteins. ACTA ACUST UNITED AC 2016; 219:2265-70. [PMID: 27489215 DOI: 10.1242/jeb.135459] [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: 11/30/2015] [Accepted: 05/18/2016] [Indexed: 12/25/2022]
Abstract
Mammalian hair cells possess only a limited ability to repair damage after trauma. In contrast, sea anemones show a marked capability to repair damaged hair bundles by means of secreted repair proteins (RPs). Previously, it was found that recovery of traumatized hair cells in blind cavefish was enhanced by anemone-derived RPs; therefore, the ability of anemone RPs to assist recovery of damaged hair cells in mammals was tested here. After a 1 h incubation in RP-enriched culture media, uptake of FM1-43 by experimentally traumatized murine cochlear hair cells was restored to levels comparable to those exhibited by healthy controls. In addition, RP-treated explants had significantly more normally structured hair bundles than time-matched traumatized control explants. Collectively, these results indicate that anemone-derived RPs assist in restoring normal function and structure of experimentally traumatized hair cells of the mouse cochlea.
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Affiliation(s)
- Pei-Ciao Tang
- Department of Biology, University of Louisiana at Lafayette, Lafayette, LA 70503, USA
| | - Karen Müller Smith
- Department of Biology, University of Louisiana at Lafayette, Lafayette, LA 70503, USA
| | - Glen M Watson
- Department of Biology, University of Louisiana at Lafayette, Lafayette, LA 70503, USA
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23
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Taura A, Taura K, Koyama Y, Yamamoto N, Nakagawa T, Ito J, Ryan AF. Hair cell stereociliary bundle regeneration by espin gene transduction after aminoglycoside damage and hair cell induction by Notch inhibition. Gene Ther 2016; 23:415-23. [PMID: 26886463 PMCID: PMC4860107 DOI: 10.1038/gt.2016.12] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 09/27/2015] [Accepted: 10/23/2015] [Indexed: 12/20/2022]
Abstract
Once inner ear hair cells (HCs) are damaged by drugs, noise or aging, their apical structures including the stereociliary arrays are frequently the first cellular feature to be lost. Although this can be followed by progressive loss of HC somata, a significant number of HC bodies often remain even after stereociliary loss. However, in the absence of stereocilia they are nonfunctional. HCs can sometimes be regenerated by Atoh1 transduction or Notch inhibition, but they also may lack stereociliary bundles. It is therefore important to develop methods for the regeneration of stereocilia, in order to achieve HC functional recovery. Espin is an actin-bundling protein known to participate in sterociliary elongation during development. We evaluated stereociliary array regeneration in damaged vestibular sensory epithelia in tissue culture, using viral vector transduction of two espin isoforms. Utricular HCs were damaged with aminoglycosides. The utricles were then treated with a γ-secretase inhibitor, followed by espin or control transduction and histochemistry. Although γ-secretase inhibition increased the number of HCs, few had stereociliary arrays. In contrast, 46 h after espin1 transduction, a significant increase in hair-bundle-like structures was observed. These were confirmed to be immature stereociliary arrays by scanning electron microscopy. Increased uptake of FM1-43 uptake provided evidence of stereociliary function. Espin4 transduction had no effect. The results demonstrate that espin1 gene therapy can restore stereocilia on damaged or regenerated HCs.
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Affiliation(s)
- A Taura
- Department of Otolaryngology-Head and Neck Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - K Taura
- Department of Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Y Koyama
- Department of Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - N Yamamoto
- Department of Otolaryngology-Head and Neck Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - T Nakagawa
- Department of Otolaryngology-Head and Neck Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - J Ito
- Department of Otolaryngology-Head and Neck Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - A F Ryan
- Department of Otolaryngology-Head and Neck Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan.,Divison of Otolaryngology, Department of Surgery, UCSD School of Medicine, La Jolla, CA, USA.,VA Medical Center, San Diego, CA, USA.,Department of Neurosciences, UCSD School of Medicine, La Jolla, CA, USA
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24
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Hwang P, Chou SW, Chen Z, McDermott BM. The Stereociliary Paracrystal Is a Dynamic Cytoskeletal Scaffold In Vivo. Cell Rep 2015; 13:1287-1294. [PMID: 26549442 DOI: 10.1016/j.celrep.2015.10.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Revised: 07/30/2015] [Accepted: 10/02/2015] [Indexed: 12/31/2022] Open
Abstract
Permanency of mechanosensory stereocilia may be the consequence of low protein turnover or rapid protein renewal. Here, we devise a system, using optical techniques in live zebrafish, to distinguish between these mechanisms. We demonstrate that the stereocilium's abundant actin cross-linker fascin 2b exchanges, without bias or a phosphointermediate, orders of magnitude faster (t1/2 of 76.3 s) than any other known hair bundle protein. To establish the logic of fascin 2b's exchange, we examine whether filamentous actin is dynamic and detect substantial β-actin exchange within the stereocilium's paracrystal (t1/2 of 4.08 hr). We propose that fascin 2b's behavior may enable cross-linking at fast timescales of stereocilia vibration while noninstructively facilitating the slower process of actin exchange. Furthermore, tip protein myosin XVa fully exchanges in hours (t1/2 of 11.6 hr), indicating that delivery of myosin-associated cargo occurs in mature stereocilia. These findings suggest that stereocilia permanency is underpinned by vibrant protein exchange.
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Affiliation(s)
- Philsang Hwang
- Department of Otolaryngology-Head and Neck Surgery, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA; Department of Biology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Shih-Wei Chou
- Department of Otolaryngology-Head and Neck Surgery, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA; Department of Biology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Zongwei Chen
- Department of Otolaryngology-Head and Neck Surgery, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA; Department of Biology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Brian M McDermott
- Department of Otolaryngology-Head and Neck Surgery, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA; Department of Biology, Case Western Reserve University, Cleveland, OH 44106, USA; Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA; Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA.
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25
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Tang PC, Watson GM. Proteomic identification of hair cell repair proteins in the model sea anemone Nematostella vectensis. Hear Res 2015; 327:245-56. [PMID: 26183436 DOI: 10.1016/j.heares.2015.07.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2015] [Revised: 06/15/2015] [Accepted: 07/09/2015] [Indexed: 12/26/2022]
Abstract
Sea anemones have an extraordinary capability to repair damaged hair bundles, even after severe trauma. A group of secreted proteins, named repair proteins (RPs), found in mucus covering sea anemones significantly assists the repair of damaged hair bundle mechanoreceptors both in the sea anemone Haliplanella luciae and the blind cavefish Astyanax hubbsi. The polypeptide constituents of RPs must be identified in order to gain insight into the molecular mechanisms by which repair of hair bundles is accomplished. In this study, several polypeptides of RPs were isolated from mucus using blue native PAGE and then sequenced using LC-MS/MS. Thirty-seven known polypeptides were identified, including Hsp70s, as well as many polypeptide subunits of the 20S proteasome. Other identified polypeptides included those involved in cellular stress responses, protein folding, and protein degradation. Specific inhibitors of Hsp70s and the 20S proteasome were employed in experiments to test their involvement in hair bundle repair. The results of those experiments suggested that repair requires biologically active Hsp70s and 20S proteasomes. A model is proposed that considers the function of extracellular Hsp70s and 20S proteasomes in the repair of damaged hair cells.
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Affiliation(s)
- Pei-Ciao Tang
- Department of Biology, University of Louisiana Lafayette, USA
| | - Glen M Watson
- Department of Biology, University of Louisiana Lafayette, USA.
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26
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Tumor Necrosis Factor-α-Induced Ototoxicity in Mouse Cochlear Organotypic Culture. PLoS One 2015; 10:e0127703. [PMID: 26000970 PMCID: PMC4441368 DOI: 10.1371/journal.pone.0127703] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 04/17/2015] [Indexed: 12/20/2022] Open
Abstract
Tumor necrosis factor (TNF)-α is a cytokine involved in acute inflammatory phase reactions, and is the primary upstream mediator in the cochlear inflammatory response. Treatment of the organ of Corti with TNF-α can induce hair cell damage. However, the resulting morphological changes have not been systematically examined. In the present study, cochlear organotypic cultures from neonatal mice were treated with various concentrations and durations of TNF-α to induce inflammatory responses. Confocal microscopy was used to evaluate the condition of hair cells and supporting cells following immunohistochemical staining. In addition, the ultrastructure of the stereocilia bundle, hair cells, and supporting cells were examined by scanning and transmission electron microscopy. TNF-α treatment resulted in a fusion and loss of stereocilia bundles in hair cells, swelling of mitochondria, and vacuolation and degranulation of the endoplasmic reticulum. Disruption of tight junctions between hair cells and supporting cells was also observed at high concentrations. Hair cell loss was preceded by apoptosis of Deiters' and pillar cells. Taken together, these findings detail the morphological changes in the organ of Corti after TNF-α treatment, and provide an in vitro model of inflammatory-induced ototoxicity.
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27
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Sanz L, Murillo-Cuesta S, Cobo P, Cediel-Algovia R, Contreras J, Rivera T, Varela-Nieto I, Avendaño C. Swept-sine noise-induced damage as a hearing loss model for preclinical assays. Front Aging Neurosci 2015; 7:7. [PMID: 25762930 PMCID: PMC4329813 DOI: 10.3389/fnagi.2015.00007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Accepted: 01/19/2015] [Indexed: 11/27/2022] Open
Abstract
Mouse models are key tools for studying cochlear alterations in noise-induced hearing loss (NIHL) and for evaluating new therapies. Stimuli used to induce deafness in mice are usually white and octave band noises that include very low frequencies, considering the large mouse auditory range. We designed different sound stimuli, enriched in frequencies up to 20 kHz (“violet” noises) to examine their impact on hearing thresholds and cochlear cytoarchitecture after short exposure. In addition, we developed a cytocochleogram to quantitatively assess the ensuing structural degeneration and its functional correlation. Finally, we used this mouse model and cochleogram procedure to evaluate the potential therapeutic effect of transforming growth factor β1 (TGF-β1) inhibitors P17 and P144 on NIHL. CBA mice were exposed to violet swept-sine noise (VS) with different frequency ranges (2–20 or 9–13 kHz) and levels (105 or 120 dB SPL) for 30 min. Mice were evaluated by auditory brainstem response (ABR) and otoacoustic emission tests prior to and 2, 14 and 28 days after noise exposure. Cochlear pathology was assessed with gross histology; hair cell number was estimated by a stereological counting method. Our results indicate that functional and morphological changes induced by VS depend on the sound level and frequency composition. Partial hearing recovery followed the exposure to 105 dB SPL, whereas permanent cochlear damage resulted from the exposure to 120 dB SPL. Exposure to 9–13 kHz noise caused an auditory threshold shift (TS) in those frequencies that correlated with hair cell loss in the corresponding areas of the cochlea that were spotted on the cytocochleogram. In summary, we present mouse models of NIHL, which depending on the sound properties of the noise, cause different degrees of cochlear damage, and could therefore be used to study molecules which are potential players in hearing loss protection and repair.
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Affiliation(s)
- Lorena Sanz
- Institute for Biomedical Research "Alberto Sols" (IIBM), Spanish National Research Council-Autonomous University of Madrid (CSIC-UAM) Madrid, Spain ; Centre for Biomedical Network Research (CIBER), Institute of Health Carlos III (ISCIII) Madrid, Spain ; Príncipe de Asturias University Hospital, University of Alcalá, Alcalá de Henares Madrid, Spain
| | - Silvia Murillo-Cuesta
- Institute for Biomedical Research "Alberto Sols" (IIBM), Spanish National Research Council-Autonomous University of Madrid (CSIC-UAM) Madrid, Spain ; Centre for Biomedical Network Research (CIBER), Institute of Health Carlos III (ISCIII) Madrid, Spain ; Hospital La Paz Institute for Health Research (IdiPAZ) Madrid, Spain
| | - Pedro Cobo
- Institute for Physical and Information Technologies (ITEFI), Spanish National Research Council (CSIC) Madrid, Spain
| | - Rafael Cediel-Algovia
- Institute for Biomedical Research "Alberto Sols" (IIBM), Spanish National Research Council-Autonomous University of Madrid (CSIC-UAM) Madrid, Spain ; Centre for Biomedical Network Research (CIBER), Institute of Health Carlos III (ISCIII) Madrid, Spain ; Veterinary Faculty, Complutense University of Madrid Madrid, Spain
| | - Julio Contreras
- Institute for Biomedical Research "Alberto Sols" (IIBM), Spanish National Research Council-Autonomous University of Madrid (CSIC-UAM) Madrid, Spain ; Centre for Biomedical Network Research (CIBER), Institute of Health Carlos III (ISCIII) Madrid, Spain ; Veterinary Faculty, Complutense University of Madrid Madrid, Spain
| | - Teresa Rivera
- Institute for Biomedical Research "Alberto Sols" (IIBM), Spanish National Research Council-Autonomous University of Madrid (CSIC-UAM) Madrid, Spain ; Centre for Biomedical Network Research (CIBER), Institute of Health Carlos III (ISCIII) Madrid, Spain ; Príncipe de Asturias University Hospital, University of Alcalá, Alcalá de Henares Madrid, Spain
| | - Isabel Varela-Nieto
- Institute for Biomedical Research "Alberto Sols" (IIBM), Spanish National Research Council-Autonomous University of Madrid (CSIC-UAM) Madrid, Spain ; Centre for Biomedical Network Research (CIBER), Institute of Health Carlos III (ISCIII) Madrid, Spain ; Hospital La Paz Institute for Health Research (IdiPAZ) Madrid, Spain
| | - Carlos Avendaño
- Hospital La Paz Institute for Health Research (IdiPAZ) Madrid, Spain ; Department of Anatomy, Histology and Neuroscience, Medical School, Autónoma University of Madrid Madrid, Spain
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28
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Gannouni N, Lenoir M, Ben Rhouma K, El May M, Tebourbi O, Puel JL, Mhamdi A. Cochlear neuropathy in the rat exposed for a long period to moderate-intensity noises. J Neurosci Res 2015; 93:848-58. [DOI: 10.1002/jnr.23567] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 01/06/2015] [Indexed: 12/20/2022]
Affiliation(s)
- Noura Gannouni
- Laboratory of Toxicology; Ergonomics and Occupational Environment, Faculty of Medicine of Tunis, Tunis El-Manar University; Tunis Tunisia
- Laboratory of Integrated Physiology; Faculty of Sciences of Bizerte; Carthage University; Tunis Tunisia
| | - Marc Lenoir
- INSERM Unit 1051. Deafness; Tinnitus and Therapies Research Unit. Institute of Neurosciences of Montpellier; Montpellier France
| | - Khemais Ben Rhouma
- Laboratory of Integrated Physiology; Faculty of Sciences of Bizerte; Carthage University; Tunis Tunisia
| | - Michèle El May
- Research Unit 01/UR/08-07, Department of Histology, Embryology and Cell Biology; Faculty of Medicine of Tunis, Tunis El-Manar University; Tunis Tunisia
| | - Olfa Tebourbi
- Laboratory of Integrated Physiology; Faculty of Sciences of Bizerte; Carthage University; Tunis Tunisia
| | - Jean Luc Puel
- INSERM Unit 1051. Deafness; Tinnitus and Therapies Research Unit. Institute of Neurosciences of Montpellier; Montpellier France
| | - Abada Mhamdi
- Laboratory of Toxicology; Ergonomics and Occupational Environment, Faculty of Medicine of Tunis, Tunis El-Manar University; Tunis Tunisia
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Inhibition of H3K4me2 Demethylation Protects Auditory Hair Cells from Neomycin-Induced Apoptosis. Mol Neurobiol 2014; 52:196-205. [PMID: 25132091 DOI: 10.1007/s12035-014-8841-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 07/30/2014] [Indexed: 12/26/2022]
Abstract
Aminoglycoside-induced hair cell loss is a major cause of hearing impairment in children and deserves more attention in medical research. Epigenetic mechanisms have been shown to protect hair cells from ototoxic drugs. In this study, we focused on the role of dimethylated histone H3K4 (H3K4me2) in hair cell survival. To investigate the effects of lysine-specific demethylase 1 (LSD1)--the histone demethylase primarily responsible for demethylating H3K4me2--on neomycin-induced hair cell loss, isolated cochleae were pretreated with LSD1 inhibitors followed by neomycin exposure. There was a severe loss of hair cells in the organ of Corti after neomycin exposure, and inhibition of LSD1 significantly protected against neomycin-induced hair cell loss. H3K4me2 expression in the nuclei of hair cells decreased after exposure to neomycin, and blocking the decreased expression of H3K4me2 with LSD1 inhibitors prevented hair cell loss. Local delivery of these inhibitors in vivo also protected hair cells from neomycin-induced ototoxicity and maintained the hearing threshold in mice as determined by auditory brain stem response. This inhibition of neomycin-induced apoptosis occurs via reduced caspase-3 activation. Together, our findings demonstrate the protective role for H3K4me2 against neomycin-induced hair cell loss and hearing loss.
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30
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Bremer HG, Versnel H, Hendriksen FG, Topsakal V, Grolman W, Klis SF. Does Vestibular End-Organ Function Recover after Gentamicin-Induced Trauma in Guinea Pigs? ACTA ACUST UNITED AC 2014; 19:135-50. [DOI: 10.1159/000357587] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Accepted: 11/26/2013] [Indexed: 11/19/2022]
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Abstract
Isl1 is a LIM-homeodomain transcription factor that is critical in the development and differentiation of multiple tissues. In the mouse inner ear, Isl1 is expressed in the prosensory region of otocyst, in young hair cells and supporting cells, and is no longer expressed in postnatal auditory hair cells. To evaluate how continuous Isl1 expression in postnatal hair cells affects hair cell development and cochlear function, we created a transgenic mouse model in which the Pou4f3 promoter drives Isl1 overexpression specifically in hair cells. Isl1 overexpressing hair cells develop normally, as seen by morphology and cochlear functions (auditory brainstem response and otoacoustic emissions). As the mice aged to 17 months, wild-type (WT) controls showed the progressive threshold elevation and outer hair cell loss characteristic of the age-related hearing loss (ARHL) in the background strain (C57BL/6J). In contrast, the Isl1 transgenic mice showed significantly less threshold elevation with survival of hair cells. Further, the Isl1 overexpression protected the ear from noise-induced hearing loss (NIHL): both ABR threshold shifts and hair cell death were significantly reduced when compared with WT littermates. Our model suggests a common mechanism underlying ARHL and NIHL, and provides evidence that hair cell-specific Isl1 expression can promote hair cell survival and therefore minimize the hearing impairment that normally occurs with aging and/or acoustic overexposure.
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Du X, Li W, Gao X, West MB, Saltzman WM, Cheng CJ, Stewart C, Zheng J, Cheng W, Kopke RD. Regeneration of mammalian cochlear and vestibular hair cells through Hes1/Hes5 modulation with siRNA. Hear Res 2013; 304:91-110. [PMID: 23850665 DOI: 10.1016/j.heares.2013.06.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Revised: 05/16/2013] [Accepted: 06/27/2013] [Indexed: 12/31/2022]
Abstract
The Notch pathway is a cell signaling pathway determining initial specification and subsequent cell fate in the inner ear. Previous studies have suggested that new hair cells (HCs) can be regenerated in the inner ear by manipulating the Notch pathway. In the present study, delivery of siRNA to Hes1 and Hes5 using a transfection reagent or siRNA to Hes1 encapsulated within poly(lactide-co-glycolide acid) (PLGA) nanoparticles increased HC numbers in non-toxin treated organotypic cultures of cochleae and maculae of postnatal day 3 mouse pups. An increase in HCs was also observed in cultured cochleae and maculae of mouse pups pre-conditioned with a HC toxin (4-hydroxy-2-nonenal or neomycin) and then treated with the various siRNA formulations. Treating cochleae with siRNA to Hes1 associated with a transfection reagent or siRNA to Hes1 delivered by PLGA nanoparticles decreased Hes1 mRNA and up-regulated Atoh1 mRNA expression allowing supporting cells (SCs) to acquire a HC fate. Experiments using cochleae and maculae of p27(kip1)/-GFP transgenic mouse pups demonstrated that newly generated HCs trans-differentiated from SCs. Furthermore, PLGA nanoparticles are non-toxic to inner ear tissue, readily taken up by cells within the tissue of interest, and present a synthetic delivery system that is a safe alternative to viral vectors. These results indicate that when delivered using a suitable vehicle, Hes siRNAs are potential therapeutic molecules that may have the capacity to regenerate new HCs in the inner ear and possibly restore human hearing and balance function.
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Affiliation(s)
- Xiaoping Du
- Hough Ear Institute, P.O. Box 23206, Oklahoma City, OK 73112, USA
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Oesterle EC. Changes in the adult vertebrate auditory sensory epithelium after trauma. Hear Res 2013; 297:91-8. [PMID: 23178236 PMCID: PMC3637947 DOI: 10.1016/j.heares.2012.11.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Revised: 10/30/2012] [Accepted: 11/06/2012] [Indexed: 01/12/2023]
Abstract
Auditory hair cells transduce sound vibrations into membrane potential changes, ultimately leading to changes in neuronal firing and sound perception. This review provides an overview of the characteristics and repair capabilities of traumatized auditory sensory epithelium in the adult vertebrate ear. Injured mammalian auditory epithelium repairs itself by forming permanent scars but is unable to regenerate replacement hair cells. In contrast, injured non-mammalian vertebrate ear generates replacement hair cells to restore hearing functions. Non-sensory support cells within the auditory epithelium play key roles in the repair processes.
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Affiliation(s)
- Elizabeth C Oesterle
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, CHDD CD176, Box 357923, Univ. of Washington, Seattle, WA 98195-7923, USA.
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34
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Integrity and regeneration of mechanotransduction machinery regulate aminoglycoside entry and sensory cell death. PLoS One 2013; 8:e54794. [PMID: 23359017 PMCID: PMC3554584 DOI: 10.1371/journal.pone.0054794] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Accepted: 12/14/2012] [Indexed: 12/04/2022] Open
Abstract
Sound perception requires functional hair cell mechanotransduction (MET) machinery, including the MET channels and tip-link proteins. Prior work showed that uptake of ototoxic aminoglycosides (AG) into hair cells requires functional MET channels. In this study, we examined whether tip-link proteins, including Cadherin 23 (Cdh23), regulate AG entry into hair cells. Using time-lapse microscopy on cochlear explants, we found rapid uptake of gentamicin-conjugated Texas Red (GTTR) into hair cells from three-day-old Cdh23+/+ and Cdh23v2J/+ mice, but failed to detect GTTR uptake in Cdh23v2J/v2J hair cells. Pre-treatment of wildtype cochleae with the calcium chelator 1,2-bis(o-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid (BAPTA) to disrupt tip-links also effectively reduced GTTR uptake into hair cells. Both Cdh23v2J/v2J and BAPTA-treated hair cells were protected from degeneration caused by gentamicin. Six hours after BAPTA treatment, GTTR uptake remained reduced in comparison to controls; by 24 hours, drug uptake was comparable between untreated and BAPTA-treated hair cells, which again became susceptible to cell death induced by gentamicin. Together, these results provide genetic and pharmacologic evidence that tip-links are required for AG uptake and toxicity in hair cells. Because tip-links can spontaneously regenerate, their temporary breakage offers a limited time window when hair cells are protected from AG toxicity.
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35
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Noise-induced alterations in cochlear mechanics, electromotility, and cochlear amplification. Pflugers Arch 2012; 465:907-17. [DOI: 10.1007/s00424-012-1198-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Revised: 11/19/2012] [Accepted: 12/02/2012] [Indexed: 11/25/2022]
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36
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Regeneration of stereocilia of hair cells by forced Atoh1 expression in the adult mammalian cochlea. PLoS One 2012; 7:e46355. [PMID: 23029493 PMCID: PMC3459923 DOI: 10.1371/journal.pone.0046355] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Accepted: 08/29/2012] [Indexed: 02/02/2023] Open
Abstract
The hallmark of mechanosensory hair cells is the stereocilia, where mechanical stimuli are converted into electrical signals. These delicate stereocilia are susceptible to acoustic trauma and ototoxic drugs. While hair cells in lower vertebrates and the mammalian vestibular system can spontaneously regenerate lost stereocilia, mammalian cochlear hair cells no longer retain this capability. We explored the possibility of regenerating stereocilia in the noise-deafened guinea pig cochlea by cochlear inoculation of a viral vector carrying Atoh1, a gene critical for hair cell differentiation. Exposure to simulated gunfire resulted in a 60-70 dB hearing loss and extensive damage and loss of stereocilia bundles of both inner and outer hair cells along the entire cochlear length. However, most injured hair cells remained in the organ of Corti for up to 10 days after the trauma. A viral vector carrying an EGFP-labeled Atoh1 gene was inoculated into the cochlea through the round window on the seventh day after noise exposure. Auditory brainstem response measured one month after inoculation showed that hearing thresholds were substantially improved. Scanning electron microscopy revealed that the damaged/lost stereocilia bundles were repaired or regenerated after Atoh1 treatment, suggesting that Atoh1 was able to induce repair/regeneration of the damaged or lost stereocilia. Therefore, our studies revealed a new role of Atoh1 as a gene critical for promoting repair/regeneration of stereocilia and maintaining injured hair cells in the adult mammal cochlea. Atoh1-based gene therapy, therefore, has the potential to treat noise-induced hearing loss if the treatment is carried out before hair cells die.
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Zhang DS, Piazza V, Perrin BJ, Rzadzinska AK, Poczatek JC, Wang M, Prosser HM, Ervasti JM, Corey DP, Lechene CP. Multi-isotope imaging mass spectrometry reveals slow protein turnover in hair-cell stereocilia. Nature 2012; 481:520-4. [PMID: 22246323 PMCID: PMC3267870 DOI: 10.1038/nature10745] [Citation(s) in RCA: 166] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Accepted: 12/01/2011] [Indexed: 11/09/2022]
Abstract
Hair cells of the inner ear are not normally replaced during an animal's life, and must continually renew components of their various organelles. Among these are the stereocilia, each with a core of several hundred actin filaments that arise from their apical surfaces and that bear the mechanotransduction apparatus at their tips. Actin turnover in stereocilia has previously been studied by transfecting neonatal rat hair cells in culture with a β-actin-GFP fusion, and evidence was found that actin is replaced, from the top down, in 2-3 days. Overexpression of the actin-binding protein espin causes elongation of stereocilia within 12-24 hours, also suggesting rapid regulation of stereocilia lengths. Similarly, the mechanosensory 'tip links' are replaced in 5-10 hours after cleavage in chicken and mammalian hair cells. In contrast, turnover in chick stereocilia in vivo is much slower. It might be that only certain components of stereocilia turn over quickly, that rapid turnover occurs only in neonatal animals, only in culture, or only in response to a challenge like breakage or actin overexpression. Here we quantify protein turnover by feeding animals with a (15)N-labelled precursor amino acid and using multi-isotope imaging mass spectrometry to measure appearance of new protein. Surprisingly, in adult frogs and mice and in neonatal mice, in vivo and in vitro, the stereocilia were remarkably stable, incorporating newly synthesized protein at <10% per day. Only stereocilia tips had rapid turnover and no treadmilling was observed. Other methods confirmed this: in hair cells expressing β-actin-GFP we bleached fiducial lines across hair bundles, but they did not move in 6 days. When we stopped expression of β- or γ-actin with tamoxifen-inducible recombination, neither actin isoform left the stereocilia, except at the tips. Thus, rapid turnover in stereocilia occurs only at the tips and not by a treadmilling process.
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Affiliation(s)
- Duan-Sun Zhang
- Department of Neurobiology, Harvard Medical School and Howard Hughes Medical Institute, Boston, MA, USA
| | - Valeria Piazza
- Department of Neurobiology, Harvard Medical School and Howard Hughes Medical Institute, Boston, MA, USA
| | - Benjamin J. Perrin
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | | | - J. Collin Poczatek
- National Resource for Imaging Mass Spectrometry, Division of Genetics Brigham and Women's Hospital and Harvard Medical School, Cambridge, MA, USA
| | - Mei Wang
- National Resource for Imaging Mass Spectrometry, Division of Genetics Brigham and Women's Hospital and Harvard Medical School, Cambridge, MA, USA
| | - Haydn M. Prosser
- The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, UK
| | - James M. Ervasti
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - David P. Corey
- Department of Neurobiology, Harvard Medical School and Howard Hughes Medical Institute, Boston, MA, USA
| | - Claude P. Lechene
- National Resource for Imaging Mass Spectrometry, Division of Genetics Brigham and Women's Hospital and Harvard Medical School, Cambridge, MA, USA
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Dynamic changes in hair cell stereocilia and cochlear transduction after noise exposure. Biochem Biophys Res Commun 2011; 409:616-21. [PMID: 21616058 DOI: 10.1016/j.bbrc.2011.05.049] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Accepted: 05/10/2011] [Indexed: 01/13/2023]
Abstract
The structures of cochlear transduction include stereocilia at the apical surface of hair cells and their connection to the tectorial membrane. The transduction site is one of the loci for noise-induced cochlear damage. Although stereocilia are susceptible to noise, it has been found that in the inner ears of avians, this fragile structure is largely self-repairing and is associated with recovery of hearing sensitivity after noise exposure, as observed in the difference between the temporal threshold shift (TTS) and the permanent threshold shift (PTS). In the mammalian cochleae, however, threshold shifts measured in the auditory brainstem responses (ABR) did not parallel the chronological changes in the stereocilia on hair cells. It is unclear how the morphological recovery of the stereocilia on the mammalian hair cells is correlated with the changes in cochlear transduction that can be assessed by measuring receptor potential. In the present study, guinea pigs were exposed to a broadband noise of 110 dB SPL for 2h. Auditory sensitivity was evaluated using ABR and cochlear transduction was assessed using cochlear microphonics (CM). Stereocilia morphology was quantified at different time points after the noise and compared with the control. The noise produced a TTS of 55.69 ± 14.13 dB in frequency-averaged ABR thresholds. The threshold shift was reduced to 9.58 ± 11.75 dB SPL 1 month later with virtually no loss of hair cells. Damage to the stereocilia immediately after noise exposure was found to be associated with depression of CM amplitude. Virtually no abnormal stereocilia were observed 1month after the noise in association with a fully recovered CM.
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Supporting cells eliminate dying sensory hair cells to maintain epithelial integrity in the avian inner ear. J Neurosci 2010; 30:12545-56. [PMID: 20844149 DOI: 10.1523/jneurosci.3042-10.2010] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Epithelial homeostasis is essential for sensory transduction in the auditory and vestibular organs of the inner ear, but how it is maintained during trauma is poorly understood. To examine potential repair mechanisms, we expressed β-actin-enhanced green fluorescent protein (EGFP) in the chick inner ear and used live-cell imaging to study how sensory epithelia responded during aminoglycoside-induced hair cell trauma. We found that glial-like supporting cells used two independent mechanisms to rapidly eliminate dying hair cells. Supporting cells assembled an actin cable at the luminal surface that extended around the pericuticular junction and constricted to excise the stereocilia bundle and cuticular plate from the hair cell soma. Hair bundle excision could occur within 3 min of actin-cable formation. After bundle excision, typically with a delay of up to 2-3 h, supporting cells engulfed and phagocytosed the remaining bundle-less hair cell. Dual-channel recordings with β-actin-EGFP and vital dyes revealed phagocytosis was concurrent with loss of hair cell integrity. We conclude that supporting cells repaired the epithelial barrier before hair cell plasmalemmal integrity was lost and that supporting cell activity was closely linked to hair cell death. Treatment with the Rho-kinase inhibitor Y-27632 did not prevent bundle excision but prolonged phagocytic engulfment and resulted in hair cell corpses accumulating within the epithelium. Our data show that supporting cells not only maintain epithelial integrity during trauma but suggest they may also be an integral part of the hair cell death process itself.
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Development and regeneration of sensory transduction in auditory hair cells requires functional interaction between cadherin-23 and protocadherin-15. J Neurosci 2010; 30:11259-69. [PMID: 20739546 DOI: 10.1523/jneurosci.1949-10.2010] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Tip links are extracellular filaments that connect pairs of hair cell stereocilia and convey tension to mechanosensitive channels. Recent evidence suggests that tip links are formed by calcium-dependent interactions between the N-terminal domains of cadherin-23 (CDH23) and protocadherin-15 (PCDH15). Mutations in either CDH23 or PCDH15 cause deafness in mice and humans, indicating the molecules are required for normal inner ear function. However, there is little physiological evidence to support a direct role for CDH23 and PCDH15 in hair cell mechanotransduction. To investigate the contributions of CDH23 and PCDH15 to mechanotransduction and tip-link formation, we examined outer hair cells of mouse cochleas during development and after chemical disruption of tip links. We found that tip links and mechanotransduction with all the qualitative properties of mature transduction recovered within 24 h after disruption. To probe tip-link formation, we measured transduction currents after extracellular application of recombinant CDH23 and PCDH15 fragments, which included putative interaction domains (EC1). Both fragments inhibited development and regeneration of transduction but did not disrupt transduction in mature cells. PCDH15 fragments that carried a mutation in EC1 that causes deafness in humans did not inhibit transduction development or regeneration. Immunolocalization revealed wild-type fragments bound near the tips of hair cell stereocilia. Scanning electron micrographs revealed that hair bundles exposed to fragments had a reduced number of linkages aligned along the morphological axis of sensitivity of the bundle. Together, the data provide direct evidence implicating CDH23 and PCDH15 proteins in the formation of tip links during development and regeneration of mechanotransduction.
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