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Ono M, Ito T. Hearing loss-related altered neuronal activity in the inferior colliculus. Hear Res 2024; 449:109033. [PMID: 38797036 DOI: 10.1016/j.heares.2024.109033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Revised: 05/01/2024] [Accepted: 05/13/2024] [Indexed: 05/29/2024]
Abstract
Hearing loss is well known to cause plastic changes in the central auditory system and pathological changes such as tinnitus and hyperacusis. Impairment of inner ear functions is the main cause of hearing loss. In aged individuals, not only inner ear dysfunction but also senescence of the central nervous system is the cause of malfunction of the auditory system. In most cases of hearing loss, the activity of the auditory nerve is reduced, but that of the successive auditory centers is increased in a compensatory way. It has been reported that activity changes occur in the inferior colliculus (IC), a critical nexus of the auditory pathway. The IC integrates the inputs from the brainstem and drives the higher auditory centers. Since abnormal activity in the IC is likely to affect auditory perception, it is crucial to elucidate the neuronal mechanism to induce the activity changes of IC neurons with hearing loss. This review outlines recent findings on hearing-loss-induced plastic changes in the IC and brainstem auditory neuronal circuits and discusses what neuronal mechanisms underlie hearing-loss-induced changes in the activity of IC neurons. Considering the different causes of hearing loss, we discuss age-related hearing loss separately from other forms of hearing loss (non-age-related hearing loss). In general, the main plastic change of IC neurons caused by both age-related and non-age-related hearing loss is increased central gain. However, plastic changes in the IC caused by age-related hearing loss seem to be more complex than those caused by non-age-related hearing loss.
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Affiliation(s)
- Munenori Ono
- Department of Physiology, School of Medicine, Kanazawa Medical University, Uchinada, Ishikawa 920-0293, Japan.
| | - Tetsufumi Ito
- Systems Function and Morphology, University of Toyama, Toyama 930-0194, Japan.
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2
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Bufalo AJ, Vanderbeck MM, Schmitt J, McGraw HF. EpCAM regulates hair cell development and regeneration in the zebrafish lateral line. MICROPUBLICATION BIOLOGY 2024; 2024:10.17912/micropub.biology.001219. [PMID: 38800699 PMCID: PMC11117072 DOI: 10.17912/micropub.biology.001219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Figures] [Subscribe] [Scholar Register] [Received: 05/01/2024] [Revised: 05/07/2024] [Accepted: 05/08/2024] [Indexed: 05/29/2024]
Abstract
The zebrafish lateral line mechanosensory system shares considerable morphological and molecular similarities with the inner ear. In particular, mechanosensory hair cells are responsible for transducing sensory stimuli in both structures. The epithelia cell adhesion molecule (EpCAM) is expressed in the cells of the inner ear of mammals and in the lateral lines system of fish. EpCAM regulates the many cellular functions including adhesion, migration, proliferation, and differentiation. In this study, we use the epcam jh79 mutant zebrafish line to determine that EpCAM function is required for proper development and regeneration of posterior lateral line hair cells.
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Affiliation(s)
- Andrew J. Bufalo
- Division of Biology and Biomedical Systems, University of Missouri–Kansas City, Kansas City, Missouri, United States
| | - Madison M. Vanderbeck
- Division of Biological and Biomedical Systems, University of Missouri–Kansas City, Kansas City, Missouri, United States
| | - Jodie Schmitt
- Division of Biological and Biomedical Systems, University of Missouri–Kansas City, Kansas City, Missouri, United States
| | - Hillary F. McGraw
- Division of Biological and Biomedical Systems, University of Missouri–Kansas City, Kansas City, Missouri, United States
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3
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Coffin AB, Dale E, Molano O, Pederson A, Costa EK, Chen J. Age-related changes in the zebrafish and killifish inner ear and lateral line. Sci Rep 2024; 14:6670. [PMID: 38509148 PMCID: PMC10954678 DOI: 10.1038/s41598-024-57182-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Accepted: 03/14/2024] [Indexed: 03/22/2024] Open
Abstract
Age-related hearing loss (ARHL) is a debilitating disorder for millions worldwide. While there are multiple underlying causes of ARHL, one common factor is loss of sensory hair cells. In mammals, new hair cells are not produced postnatally and do not regenerate after damage, leading to permanent hearing impairment. By contrast, fish produce hair cells throughout life and robustly regenerate these cells after toxic insult. Despite these regenerative abilities, zebrafish show features of ARHL. Here, we show that aged zebrafish of both sexes exhibited significant hair cell loss and decreased cell proliferation in all inner ear epithelia (saccule, lagena, utricle). Ears from aged zebrafish had increased expression of pro-inflammatory genes and significantly more macrophages than ears from young adult animals. Aged zebrafish also had fewer lateral line hair cells and less cell proliferation than young animals, although lateral line hair cells still robustly regenerated following damage. Unlike zebrafish, African turquoise killifish (an emerging aging model) only showed hair cell loss in the saccule of aged males, but both sexes exhibit age-related changes in the lateral line. Our work demonstrates that zebrafish exhibit key features of auditory aging, including hair cell loss and increased inflammation. Further, our finding that aged zebrafish have fewer lateral line hair cells yet retain regenerative capacity, suggests a decoupling of homeostatic hair cell addition from regeneration following acute trauma. Finally, zebrafish and killifish show species-specific strategies for lateral line homeostasis that may inform further comparative research on aging in mechanosensory systems.
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Affiliation(s)
- Allison B Coffin
- College of Arts and Sciences, Washington State University Vancouver, Vancouver, WA, 98686, USA.
- Department of Integrative Physiology and Neuroscience, Washington State University Vancouver, Vancouver, WA, 98686, USA.
| | - Emily Dale
- College of Arts and Sciences, Washington State University Vancouver, Vancouver, WA, 98686, USA
- Neuroimmunology Research, Mayo Clinic, Rochester, MN, 55902, USA
| | - Olivia Molano
- College of Arts and Sciences, Washington State University Vancouver, Vancouver, WA, 98686, USA
- Neuroscience Graduate Program, Brown University, Providence, RI, 02912, USA
| | - Alexandra Pederson
- College of Arts and Sciences, Washington State University Vancouver, Vancouver, WA, 98686, USA
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Emma K Costa
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, 94305, USA
- Neurosciences Interdepartmental Program, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Jingxun Chen
- Department of Genetics, Stanford University, Stanford, CA, 94305, USA
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Smith-Cortinez N, Tan AK, Stokroos RJ, Versnel H, Straatman LV. Regeneration of Hair Cells from Endogenous Otic Progenitors in the Adult Mammalian Cochlea: Understanding Its Origins and Future Directions. Int J Mol Sci 2023; 24:ijms24097840. [PMID: 37175547 PMCID: PMC10177935 DOI: 10.3390/ijms24097840] [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: 03/13/2023] [Revised: 04/20/2023] [Accepted: 04/21/2023] [Indexed: 05/15/2023] Open
Abstract
Sensorineural hearing loss is caused by damage to sensory hair cells and/or spiral ganglion neurons. In non-mammalian species, hair cell regeneration after damage is observed, even in adulthood. Although the neonatal mammalian cochlea carries regenerative potential, the adult cochlea cannot regenerate lost hair cells. The survival of supporting cells with regenerative potential after cochlear trauma in adults is promising for promoting hair cell regeneration through therapeutic approaches. Targeting these cells by manipulating key signaling pathways that control mammalian cochlear development and non-mammalian hair cell regeneration could lead to regeneration of hair cells in the mammalian cochlea. This review discusses the pathways involved in the development of the cochlea and the impact that trauma has on the regenerative capacity of the endogenous progenitor cells. Furthermore, it discusses the effects of manipulating key signaling pathways targeting supporting cells with progenitor potential to promote hair cell regeneration and translates these findings to the human situation. To improve hearing recovery after hearing loss in adults, we propose a combined approach targeting (1) the endogenous progenitor cells by manipulating signaling pathways (Wnt, Notch, Shh, FGF and BMP/TGFβ signaling pathways), (2) by manipulating epigenetic control, and (3) by applying neurotrophic treatments to promote reinnervation.
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Affiliation(s)
- Natalia Smith-Cortinez
- Department of Otorhinolaryngology and Head & Neck Surgery, University Medical Center Utrecht, Utrecht University, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
- UMC Utrecht Brain Center, Utrecht University, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
| | - A Katherine Tan
- Department of Otorhinolaryngology and Head & Neck Surgery, University Medical Center Utrecht, Utrecht University, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
- UMC Utrecht Brain Center, Utrecht University, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
| | - Robert J Stokroos
- Department of Otorhinolaryngology and Head & Neck Surgery, University Medical Center Utrecht, Utrecht University, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
- UMC Utrecht Brain Center, Utrecht University, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
| | - Huib Versnel
- Department of Otorhinolaryngology and Head & Neck Surgery, University Medical Center Utrecht, Utrecht University, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
- UMC Utrecht Brain Center, Utrecht University, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
| | - Louise V Straatman
- Department of Otorhinolaryngology and Head & Neck Surgery, University Medical Center Utrecht, Utrecht University, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
- UMC Utrecht Brain Center, Utrecht University, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
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Schvartz-Leyzac KC, Colesa DJ, Swiderski DL, Raphael Y, Pfingst BE. Cochlear Health and Cochlear-implant Function. J Assoc Res Otolaryngol 2023; 24:5-29. [PMID: 36600147 PMCID: PMC9971430 DOI: 10.1007/s10162-022-00882-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 11/24/2022] [Indexed: 01/06/2023] Open
Abstract
The cochlear implant (CI) is widely considered to be one of the most innovative and successful neuroprosthetic treatments developed to date. Although outcomes vary, CIs are able to effectively improve hearing in nearly all recipients and can substantially improve speech understanding and quality of life for patients with significant hearing loss. A wealth of research has focused on underlying factors that contribute to success with a CI, and recent evidence suggests that the overall health of the cochlea could potentially play a larger role than previously recognized. This article defines and reviews attributes of cochlear health and describes procedures to evaluate cochlear health in humans and animal models in order to examine the effects of cochlear health on performance with a CI. Lastly, we describe how future biologic approaches can be used to preserve and/or enhance cochlear health in order to maximize performance for individual CI recipients.
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Affiliation(s)
- Kara C Schvartz-Leyzac
- Department of Otolaryngology-Head and Neck Surgery, Michigan Medicine, Kresge Hearing Research Institute, University of Michigan, 1150 Medical Center Drive, Ann Arbor, MI, 48109-5616, USA
- Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, 135 Rutledge Ave, Charleston, SC, 29425, USA
| | - Deborah J Colesa
- Department of Otolaryngology-Head and Neck Surgery, Michigan Medicine, Kresge Hearing Research Institute, University of Michigan, 1150 Medical Center Drive, Ann Arbor, MI, 48109-5616, USA
| | - Donald L Swiderski
- Department of Otolaryngology-Head and Neck Surgery, Michigan Medicine, Kresge Hearing Research Institute, University of Michigan, 1150 Medical Center Drive, Ann Arbor, MI, 48109-5616, USA
| | - Yehoash Raphael
- Department of Otolaryngology-Head and Neck Surgery, Michigan Medicine, Kresge Hearing Research Institute, University of Michigan, 1150 Medical Center Drive, Ann Arbor, MI, 48109-5616, USA
| | - Bryan E Pfingst
- Department of Otolaryngology-Head and Neck Surgery, Michigan Medicine, Kresge Hearing Research Institute, University of Michigan, 1150 Medical Center Drive, Ann Arbor, MI, 48109-5616, USA.
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Neuronal Cytoglobin in the Auditory Brainstem of Rat and Mouse: Distribution, Cochlear Projection, and Nitric Oxide Production. Brain Sci 2023; 13:brainsci13010107. [PMID: 36672088 PMCID: PMC9856379 DOI: 10.3390/brainsci13010107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 12/07/2022] [Accepted: 12/28/2022] [Indexed: 01/08/2023] Open
Abstract
Cytoglobin (Cygb), a hemoprotein of the globin family, is expressed in the supportive tissue cells of the fibroblast lineage and in distinct neuronal cell populations. The expression pattern and regulatory parameters of fibroblasts and related cells were studied in organs such as the kidney and liver in a variety of animal models. In contrast, knowledge about cytoglobin-expressing neurons is sparse. Only a few papers described the distribution in the brain as ubiquitous with a restricted number of neurons in focal regions. Although there is evidence for cytoglobin involvement in neuronal hypoxia tolerance, its presence in the auditory system was not studied despite high metabolism rates and oxygen demands of the cochlea and related brainstem centers. In a continuation of a previous study demonstrating Cygb-neurons in, inter alia, auditory regions of the mouse brain, we concentrated on the superior olivary complex (SOC) in the present study. We sought to investigate the distribution, projection pattern and neurochemistry of Cygb-neurons in the SOC. We conducted immunohistochemistry using a Cygb antibody and found that this brainstem region, functionally competent for bilateral hearing and providing cochlear hair cell innervation, contains a considerable number of Cygb-expressing neurons (averaging 2067 ± 211 making up 10 ±1% percent of total neuron number) in rats, and 514 ± 138 (6 ± 1%) in mice. They were observed in all regions of the SOC. Retrograde neuronal tract tracing with Fluorogold injected into the cochlea demonstrated that 1243 ± 100 (6 ± 1% of total neuron number in rat SOC)) were olivocochlear neurons. Approximately 56% of total Cygb neurons were retrogradely labelled, while the majority of olivocochlear neurons of both lateral and medial systems were Cygb-immunoreactive. We also conducted double immunofluorescence staining for Cygb and neuronal nitric oxide synthase (nNOS), the enzyme responsible for nitric oxide production, and observed that cytoglobin in the SOC frequently co-localized with nNOS. Our findings suggest that cytoglobin plays an important physiologic role in the oxygen homeostasis of the peripheral and central auditory nervous system. Further studies, also including transgenic animal models, are required to shed more light on the function(s) of Cygb in neurons, in particular of the auditory system.
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Hou S, Zhang J, Wu Y, Junmin C, Yuyu H, He B, Yang Y, Hong Y, Chen J, Yang J, Li S. FGF22 deletion causes hidden hearing loss by affecting the function of inner hair cell ribbon synapses. Front Mol Neurosci 2022; 15:922665. [PMID: 35966010 PMCID: PMC9366910 DOI: 10.3389/fnmol.2022.922665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 07/04/2022] [Indexed: 12/04/2022] Open
Abstract
Ribbon synapses are important structures in transmitting auditory signals from the inner hair cells (IHCs) to their corresponding spiral ganglion neurons (SGNs). Over the last few decades, deafness has been primarily attributed to the deterioration of cochlear hair cells rather than ribbon synapses. Hearing dysfunction that cannot be detected by the hearing threshold is defined as hidden hearing loss (HHL). The relationship between ribbon synapses and FGF22 deletion remains unknown. In this study, we used a 6-week-old FGF22 knockout mice model (Fgf22–/–) and mainly focused on alteration in ribbon synapses by applying the auditory brainstem response (ABR) test, the immunofluorescence staining, the patch-clamp recording, and quantitative real-time PCR. In Fgf22–/– mice, we found the decreased amplitude of ABR wave I, the reduced vesicles of ribbon synapses, and the decreased efficiency of exocytosis, which was suggested by a decrease in the capacitance change. Quantitative real-time PCR revealed that Fgf22–/– led to dysfunction in ribbon synapses by downregulating SNAP-25 and Gipc3 and upregulating MEF2D expression, which was important for the maintenance of ribbon synapses’ function. Our research concluded that FGF22 deletion caused HHL by affecting the function of IHC ribbon synapses and may offer a novel therapeutic target to meet an ever-growing demand for deafness treatment.
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Affiliation(s)
- Shule Hou
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Jifang Zhang
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Yan Wu
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Chen Junmin
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Huang Yuyu
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Baihui He
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Yan Yang
- Liaoning Medical Device Test Institute, Shenyang, China
| | - Yuren Hong
- Laboratory of Electron Microscope Center, Shanghai Medical College, Fudan University, Shanghai, China
| | - Jiarui Chen
- Department of Otorhinolaryngology-Head and Neck Surgery, Shanghai Children’s Hospital, Shanghai Jiao Tong University, Shanghai, China
- *Correspondence: Jiarui Chen,
| | - Jun Yang
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
- Jun Yang,
| | - Shuna Li
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
- Shuna Li,
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8
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Hearing loss drug discovery and medicinal chemistry: Current status, challenges, and opportunities. PROGRESS IN MEDICINAL CHEMISTRY 2022; 61:1-91. [PMID: 35753714 DOI: 10.1016/bs.pmch.2022.05.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Hearing loss is a severe high unmet need condition affecting more than 1.5 billion people globally. There are no licensed medicines for the prevention, treatment or restoration of hearing. Prosthetic devices, such as hearing aids and cochlear implants, do not restore natural hearing and users struggle with speech in the presence of background noise. Hearing loss drug discovery is immature, and small molecule approaches include repurposing existing drugs, combination therapeutics, late-stage discovery optimisation of known chemotypes for identified molecular targets of interest, phenotypic tissue screening and high-throughput cell-based screening. Hearing loss drug discovery requires the integration of specialist therapeutic area biology and otology clinical expertise. Small molecule drug discovery projects in the global clinical portfolio for hearing loss are here collated and reviewed. An overview is provided of human hearing, inner ear anatomy, inner ear delivery, types of hearing loss and hearing measurement. Small molecule experimental drugs in clinical development for hearing loss are reviewed, including their underpinning biology, discovery strategy and activities, medicinal chemistry, calculated physicochemical properties, pharmacokinetics and clinical trial status. SwissADME BOILED-Egg permeability modelling is applied to the molecules reviewed, and these results are considered. Non-small molecule hearing loss assets in clinical development are briefly noted in this review. Future opportunities in hearing loss drug discovery for human genomics and targeted protein degradation are highlighted.
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Ma X, Zhang S, Qin S, Guo J, Yuan J, Qiang R, Zhou S, Cao W, Yang J, Ma F, Chai R. Transcriptomic and epigenomic analyses explore the potential role of H3K4me3 in neomycin-induced cochlear Lgr5+ progenitor cell regeneration of hair cells. Hum Cell 2022; 35:1030-1044. [DOI: 10.1007/s13577-022-00727-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2022] [Accepted: 05/17/2022] [Indexed: 12/14/2022]
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Clinard CG, Lawlor KJ, Thorne AP, Piker EG. Nonlinearity in bone-conducted amplitude-modulated cervical vestibular evoked myogenic potentials: Harmonic distortion products. J Neurophysiol 2022; 127:791-800. [PMID: 35171737 DOI: 10.1152/jn.00347.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Otolith organs of the balance system, the saccule and utricle, encode linear acceleration. Integrity of the saccule is commonly assessed using cervical vestibular evoked myogenic potentials (cVEMPs) arising from an inhibitory reflex along the vestibulospinal pathway. Conventional approaches to eliciting these responses use brief, transient sounds to elicit onset responses. Here we used long-duration amplitude-modulated (AM) tones to elicit cVEMPs (AMcVEMPs) and analyzed their spectral content for evidence of nonlinear processing consistent with known characteristics of vestibular hair cells. Twelve young adults (ages 21-25) with no hearing or vestibular pathologies participated in this study. AMcVEMPs were elicited by bone-conducted AM tones with a 500 Hz carrier frequency. Eighteen modulation frequencies were used between 7 and 403 Hz. All participants had robust distortion products at harmonics of the modulation frequency. Total harmonic distortion ranged from approximately 10 to 80%. AMcVEMPs contain harmonic distortion products consistent with vestibular hair cell nonlinearities, and this new approach to studying the otolith organs may provide a non-invasive, in vivo method to study nonlinearity of vestibular hair cells in humans.
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Affiliation(s)
- Christopher G Clinard
- Communication Sciences and Disorders, James Madison University, Harrisonburg, VA, United States
| | - Kerri J Lawlor
- Communication Sciences and Disorders, James Madison University, Harrisonburg, VA, United States
| | - Andrew P Thorne
- Communication Sciences and Disorders, James Madison University, Harrisonburg, VA, United States
| | - Erin G Piker
- Communication Sciences and Disorders, James Madison University, Harrisonburg, VA, United States
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