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Chen HK, Wang YH, Lei CS, Guo YR, Tang MC, Tsai TF, Chen YF, Wang CH. Loss of Cisd2 Exacerbates the Progression of Age-Related Hearing Loss. Aging Dis 2024:AD.2024.1036. [PMID: 39226169 DOI: 10.14336/ad.2024.1036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2024] [Accepted: 08/24/2024] [Indexed: 09/05/2024] Open
Abstract
Age-related hearing loss (ARHL) is a disease that impacts human quality of life and contributes to the progression of other neuronal problems. Various stressors induce an increase in free radicals, destroy mitochondria to further contribute to cellular malfunction, and compromise cell viability, ultimately leading to functional decline. Cisd2, a master gene for Marfan syndrome, plays an essential role in maintaining mitochondrial integrity and functions. As shown by our data, specific deletion of Cisd2 in the cochlea exacerbated the hearing impairment of ARHL in C57BL/6 mice. Increased defects in mitochondrial function, potassium homeostasis and synapse activity were observed in the Cisd2-deleted mouse models. These mechanistic phenotypes combined with oxidative stress contribute to cell death in the whole cochlea. Human patients with obviously deteriorated ARHL had low Cisd2 expression; therefore, Cisd2 may be a potential target for designing therapeutic methods to attenuate the disease progression of ARHL.
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Affiliation(s)
- Hang-Kang Chen
- Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei 114201, Taiwan
- Graduate Institute of Microbiology and Immunology, National Defense Medical Center, Taipei 114201, Taiwan
- Department of Otolaryngology-Head and Neck Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei 114202, Taiwan
| | - Yen-Hsin Wang
- The Ph.D. Program for Translational Medicine, Taipei Medical University, Taipei 11031, Taiwan
| | - Cing-Syuan Lei
- Ph.D. Program for Cancer Molecular Biology and Drug Discovery, College of Medical Science and Technology, Taipei Medical University and Academia Sinica, Taipei 11031, Taiwan
| | - Yu-Ru Guo
- The Ph.D. Program for Translational Medicine, Taipei Medical University, Taipei 11031, Taiwan
| | - Ming-Chi Tang
- The Ph.D. Program for Translational Medicine, Taipei Medical University, Taipei 11031, Taiwan
| | - Ting-Fen Tsai
- Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 11221, Taiwan
- Brain Research Center, National Yang-Ming University, Taipei 11221, Taiwan
- Aging and Health Research Center, National Yang-Ming University, Taipei 11221, Taiwan
- Genome Research Center, National Yang-Ming University, Taipei 11221, Taiwan
- Institute of Molecular and Genomic Medicine, National Health Research Institutes, Zhunan 35053, Taiwan
| | - Yi-Fan Chen
- Graduate Institute of Translational Medicine, College of Medical Science and Technology, Taipei Medical University, Taipei 11031, Taiwan
- Master Program in Clinical Genomics and Proteomics, School of Pharmacy, Taipei Medical University, Taipei 11031, Taiwan
- International Ph.D. Program for Translational Science, College of Medical Science and Technology, Taipei Medical University, Taipei 11031, Taiwan
- The Ph.D. Program for Translational Medicine, Taipei Medical University, Taipei 11031, Taiwan
| | - Chih-Hung Wang
- Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei 114201, Taiwan
- Graduate Institute of Microbiology and Immunology, National Defense Medical Center, Taipei 114201, Taiwan
- Department of Otolaryngology-Head and Neck Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei 114202, Taiwan
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Lu M, Xian F, Jin X, Hong G, Fu X, Wang S, Li X, Yang H, Li H, Zhang H, Yang Y, Xiao J, Dong H, Liu Y, Shen H, Lv P. Upregulation of the Ca v1.3 channel in inner hair cells by interleukin 6-dependent inflammaging contributes to age-related hearing loss. Aging Cell 2024:e14305. [PMID: 39148148 DOI: 10.1111/acel.14305] [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: 01/17/2024] [Revised: 07/02/2024] [Accepted: 07/24/2024] [Indexed: 08/17/2024] Open
Abstract
Age-related hearing loss (AHL) is the most common sensory disorder amongst the older population. Inflammaging is a ≈chronic low-grade inflammation that worsens with age and is an early sign of AHL; however, the underlying mechanisms remain unclear. We used electrophysiological and genetic approaches to establish the importance of interleukin 6 (IL-6)-dependent inflammation in AHL. Elevated IL-6 in the cochlea enhanced Cav1.3 calcium channel function in the inner hair cell (IHC) synapse in mice with AHL. IL-6 upregulated the Cav1.3 channel via the Janus kinase-mitogen activated kinase pathway, causing neurotransmitter excitotoxicity and synapse impairment; IL-6 deficiency or the administration of a Cav1.3 channel blocker attenuated this age-related damage, and rescued hearing loss. Thus, IL-6-dependent inflammaging upregulated the Cav1.3 channel in IHCs, contributing to AHL. Our findings could help the comprehensive understanding of inflammaging's effects on AHL, aiding in early intervention to protect against hearing decline.
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Affiliation(s)
- Mingshun Lu
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Fuyu Xian
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Xishuo Jin
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Guodong Hong
- Medical Science and Technology Innovation Center, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, Shandong, China
| | - Xiaolong Fu
- Shandong Provincial Hospital, Medical Science and Technology Innovation Center, College of Clinical and Basic Medicine, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, Shandong, China
- Department of Neurology, Aerospace Center Hospital, School of Life Science, Beijing Institute of Technology, Beijing, China
| | - Shengnan Wang
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Xinyu Li
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Haichao Yang
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Hongchen Li
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Haiwei Zhang
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Yuxin Yang
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Jundan Xiao
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Hui Dong
- Department of Neurology, The Second Hospital of Hebei Medical University, The Key Laboratory of Neurology, Ministry of Education, Hebei Medical University, Neurological Laboratory of Hebei Province, Shijiazhuang, Hebei, China
| | - Yaling Liu
- Department of Neurology, The Second Hospital of Hebei Medical University, The Key Laboratory of Neurology, Ministry of Education, Hebei Medical University, Neurological Laboratory of Hebei Province, Shijiazhuang, Hebei, China
| | - Haitao Shen
- Lab of Pathology, Hebei Medical University,, Shijiazhuang, Hebei, China
- Hebei Collaborative Innovation Center of Tumor Microecological Metabolism Regulation, Affiliated Hospital of Hebei University, Baoding, Hebei, China
| | - Ping Lv
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
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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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Lu Y, Jiang Y, Wang F, Wu H, Hua Y. Electron Microscopic Mapping of Mitochondrial Morphology in the Cochlear Nerve Fibers. J Assoc Res Otolaryngol 2024; 25:341-354. [PMID: 38937328 PMCID: PMC11349726 DOI: 10.1007/s10162-024-00957-y] [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: 01/08/2024] [Accepted: 06/12/2024] [Indexed: 06/29/2024] Open
Abstract
To enable nervous system function, neurons are powered in a use-dependent manner by mitochondria undergoing morphological-functional adaptation. In a well-studied model system-the mammalian cochlea, auditory nerve fibers (ANFs) display distinct electrophysiological properties, which is essential for collectively sampling acoustic information of a large dynamic range. How exactly the associated mitochondrial networks are deployed in functionally differentiated ANFs remains scarcely interrogated. Here, we leverage volume electron microscopy and machine-learning-assisted image analysis to phenotype mitochondrial morphology and distribution along ANFs of full-length in the mouse cochlea inner spiral bundle. This reveals greater variance in mitochondrial size with increased ANF habenula to terminal path length. Particularly, we analyzed the ANF terminal-residing mitochondria, which are critical for local calcium uptake during sustained afferent activities. Our results suggest that terminal-specific enrichment of mitochondria, in addition to terminal size and overall mitochondrial abundance of the ANF, correlates with heterogenous mitochondrial contents of the terminal.
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Affiliation(s)
- Yan Lu
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
- Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yi Jiang
- Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Fangfang Wang
- Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Hao Wu
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
- Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yunfeng Hua
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai, China.
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China.
- Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
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Sijgers L, Röösli C, Bertschinger R, Epprecht L, Veraguth D, Dalbert A, Huber A, Pfiffner F. The Inter-Phase Gap Offset Effect as a Measure of Neural Health in Cochlear Implant Users With Residual Acoustic Hearing. Ear Hear 2024:00003446-990000000-00320. [PMID: 39054580 DOI: 10.1097/aud.0000000000001556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/27/2024]
Abstract
OBJECTIVES The inter-phase gap (IPG) offset effect is defined as the dB offset between the linear parts of electrically evoked compound action potential (ECAP) amplitude growth functions for two stimuli differing only in IPG. The method was recently suggested to represent neural health in cochlear implant (CI) users while being unaffected by CI electrode impedances. Hereby, a larger IPG offset effect should reflect better neural health. The aims of the present study were to (1) examine whether the IPG offset effect negatively correlates with the ECAP threshold and the preoperative pure-tone average (PTA) in CI recipients with residual acoustic hearing and (2) investigate the dependency of the IPG offset effect on hair cell survival and intracochlear electrode impedances. DESIGN Seventeen adult study participants with residual acoustic hearing at 500 Hz undergoing CI surgery at the University Hospital of Zurich were prospectively enrolled. ECAP thresholds, IPG offset effects, electrocochleography (ECochG) responses to 500 Hz tone bursts, and monopolar electrical impedances were obtained at an apical, middle, and basal electrode set during and between 4 and 12 weeks after CI surgery. Pure-tone audiometry was conducted within 3 weeks before surgery and approximately 6 weeks after surgery. Linear mixed regression analyses and t tests were performed to assess relationships between (changes in) ECAP threshold, IPG offset, impedance, PTA, and ECochG amplitude. RESULTS The IPG offset effect positively correlated with the ECAP threshold in intraoperative recordings (p < 0.001) and did not significantly correlate with the preoperative PTA (p = 0.999). The IPG offset showed a postoperative decrease for electrode sets that showed an ECochG amplitude drop. This IPG offset decrease was significantly larger than for electrode sets that showed no ECochG amplitude decrease, t(17) = 2.76, p = 0.014. Linear mixed regression analysis showed no systematic effect of electrode impedance changes on the IPG offset effect (p = 0.263) but suggested a participant-dependent effect of electrode impedance on IPG offset. CONCLUSIONS The present study results did not reveal the expected relationships between the IPG offset effect and ECAP threshold values or between the IPG offset effect and preoperative acoustic hearing. Changes in electrode impedance did not exhibit a direct impact on the IPG offset effect, although this impact might be individualized among CI recipients. Overall, our findings suggest that the interpretation and application of the IPG offset effect in clinical settings should be approached with caution considering its complex relationships with other cochlear and neural health metrics.
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Affiliation(s)
- Leanne Sijgers
- Department of Otorhinolaryngology, Head & Neck Surgery, University Hospital Zurich, University of Zurich, Zurich, Switzerland
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Capshaw G, Diebold CA, Adams DM, Rayner J, Wilkinson GS, Moss CF, Lauer AM. Resistance to age-related hearing loss in the echolocating big brown bat ( Eptesicus fuscus ). BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.15.603592. [PMID: 39071368 PMCID: PMC11275774 DOI: 10.1101/2024.07.15.603592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/30/2024]
Abstract
Hearing mediates many behaviors critical for survival in echolocating bats, including foraging and navigation. Most mammals are susceptible to progressive age-related hearing loss; however, the evolution of biosonar, which requires the ability to hear low-intensity echoes from outgoing sonar signals, may have selected against the development of hearing deficits in echolocating bats. Although many echolocating bats exhibit exceptional longevity and rely on acoustic behaviors for survival to old age, relatively little is known about the aging bat auditory system. In this study, we used DNA methylation to estimate the ages of wild-caught big brown bats ( Eptesicus fuscus ) and measured hearing sensitivity in young and aging bats using auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs). We found no evidence for hearing deficits in aging bats, demonstrated by comparable thresholds and similar ABR wave and DPOAE amplitudes across age groups. We additionally found no significant histological evidence for cochlear aging, with similar hair cell counts, afferent, and efferent innervation patterns in young and aging bats. Here we demonstrate that big brown bats show minimal evidence for age-related loss of peripheral hearing sensitivity and therefore represent informative models for investigating mechanisms that may preserve hearing function over a long lifetime.
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Steenken F, Pektaş A, Köppl C. Age-related changes in olivocochlear efferent innervation in gerbils. Front Synaptic Neurosci 2024; 16:1422330. [PMID: 38887655 PMCID: PMC11180762 DOI: 10.3389/fnsyn.2024.1422330] [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: 04/23/2024] [Accepted: 05/20/2024] [Indexed: 06/20/2024] Open
Abstract
Introduction Age-related hearing difficulties have a complex etiology that includes degenerative processes in the sensory cochlea. The cochlea comprises the start of the afferent, ascending auditory pathway, but also receives efferent feedback innervation by two separate populations of brainstem neurons: the medial olivocochlear and lateral olivocochlear pathways, innervating the outer hair cells and auditory-nerve fibers synapsing on inner hair cells, respectively. Efferents are believed to improve hearing under difficult conditions, such as high background noise. Here, we compare olivocochlear efferent innervation density along the tonotopic axis in young-adult and aged gerbils (at ~50% of their maximum lifespan potential), a classic animal model for age-related hearing loss. Methods Efferent synaptic terminals and sensory hair cells were labeled immunohistochemically with anti-synaptotagmin and anti-myosin VIIa, respectively. Numbers of hair cells, numbers of efferent terminals, and the efferent innervation area were quantified at seven tonotopic locations along the organ of Corti. Results The tonotopic distribution of olivocochlear innervation in the gerbil was similar to that previously shown for other species, with a slight apical cochlear bias in presumed lateral olivocochlear innervation (inner-hair-cell region), and a broad mid-cochlear peak for presumed medial olivocochlear innervation (outer-hair-cell region). We found significant, age-related declines in overall efferent innervation to both the inner-hair-cell and the outer-hair-cell region. However, when accounting for the age-related losses in efferent target structures, the innervation density of surviving elements proved unchanged in the inner-hair-cell region. For outer hair cells, a pronounced increase of orphaned outer hair cells, i.e., lacking efferent innervation, was observed. Surviving outer hair cells that were still efferently innervated retained a nearly normal innervation. Discussion A comparison across species suggests a basic aging scenario where outer hair cells, type-I afferents, and the efferents associated with them, steadily die away with advancing age, but leave the surviving cochlear circuitry largely intact until an advanced age, beyond 50% of a species' maximum lifespan potential. In the outer-hair-cell region, MOC degeneration may precede outer-hair-cell death, leaving a putatively transient population of orphaned outer hair cells that are no longer under efferent control.
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Affiliation(s)
- Friederike Steenken
- Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky Universität Oldenburg, Oldenburg, Germany
- Cluster of Excellence “Hearing4all”, Carl von Ossietzky Universität Oldenburg, Oldenburg, Germany
| | - Asli Pektaş
- Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky Universität Oldenburg, Oldenburg, Germany
| | - Christine Köppl
- Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky Universität Oldenburg, Oldenburg, Germany
- Cluster of Excellence “Hearing4all”, Carl von Ossietzky Universität Oldenburg, Oldenburg, Germany
- Research Centre Neurosensory Science, Carl von Ossietzky Universität Oldenburg, Oldenburg, Germany
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Wu PZ, Liberman LD, Liberman MC. Noise-induced synaptic loss and its post-exposure recovery in CBA/CaJ vs. C57BL/6J mice. Hear Res 2024; 445:108996. [PMID: 38547565 PMCID: PMC11024800 DOI: 10.1016/j.heares.2024.108996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 03/11/2024] [Accepted: 03/22/2024] [Indexed: 04/07/2024]
Abstract
Acute noise-induced loss of synapses between inner hair cells (IHCs) and auditory nerve fibers (ANFs) has been documented in several strains of mice, but the extent of post-exposure recovery reportedly varies dramatically. If such inter-strain heterogeneity is real, it could be exploited to probe molecular pathways mediating neural remodeling in the adult cochlea. Here, we compared synaptopathy repair in CBA/CaJ vs. C57BL/6J, which are at opposite ends of the reported recovery spectrum. We evaluated C57BL/6J mice 0 h, 24 h, 2 wks or 8 wks after exposure for 2 h to octave-band noise (8-16 kHz) at either 90, 94 or 98 dB SPL, to compare with analogous post-exposure results in CBA/CaJ at 98 or 101 dB. We counted pre- and post-synaptic puncta in immunostained cochleas, using machine learning to classify paired (GluA2 and CtBP2) vs. orphan (CtBP2 only) puncta, and batch-processing to quantify immunostaining intensity. At 98 dB, both strains show ongoing loss of ribbons and synapses between 0 and 24 h, followed by partial recovery, however the extent and degree of these changes were greater in C57BL/6J. Much of the synaptic recovery is due to transient reduction in GluA2 intensity in synaptopathic regions. In contrast, CtBP2 intensity showed only transient increases (at 2 wks). Neurofilament staining revealed transient extension of ANF terminals in C57BL/6J, but not in CBA/CaJ, peaking at 24 h and reverting by 2 wks. Thus, although interstrain differences in synapse recovery are dominated by reversible changes in GluA2 receptor levels, the neurite extension seen in C57BL/6J suggests a qualitative difference in regenerative capacity.
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Affiliation(s)
- Pei-Zhe Wu
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA 02114, USA; Department of Otolaryngology, Harvard Medical School, Boston, MA 02115, USA
| | - Leslie D Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA 02114, USA
| | - M Charles Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA 02114, USA; Department of Otolaryngology, Harvard Medical School, Boston, MA 02115, USA.
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Bovee S, Klump GM, Pyott SJ, Sielaff C, Köppl C. Cochlear Ribbon Synapses in Aged Gerbils. Int J Mol Sci 2024; 25:2738. [PMID: 38473985 DOI: 10.3390/ijms25052738] [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: 12/30/2023] [Revised: 02/15/2024] [Accepted: 02/21/2024] [Indexed: 03/14/2024] Open
Abstract
In mammalian hearing, type-I afferent auditory nerve fibers comprise the basis of the afferent auditory pathway. They are connected to inner hair cells of the cochlea via specialized ribbon synapses. Auditory nerve fibers of different physiological types differ subtly in their synaptic location and morphology. Low-spontaneous-rate auditory nerve fibers typically connect on the modiolar side of the inner hair cell, while high-spontaneous-rate fibers are typically found on the pillar side. In aging and noise-damaged ears, this fine-tuned balance between auditory nerve fiber populations can be disrupted and the functional consequences are currently unclear. Here, using immunofluorescent labeling of presynaptic ribbons and postsynaptic glutamate receptor patches, we investigated changes in synaptic morphology at three different tonotopic locations along the cochlea of aging gerbils compared to those of young adults. Quiet-aged gerbils showed about 20% loss of afferent ribbon synapses. While the loss was random at apical, low-frequency cochlear locations, at the basal, high-frequency location it almost exclusively affected the modiolar-located synapses. The subtle differences in volumes of pre- and postsynaptic elements located on the inner hair cell's modiolar versus pillar side were unaffected by age. This is consistent with known physiology and suggests a predominant, age-related loss in the low-spontaneous-rate auditory nerve population in the cochlear base, but not the apex.
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Affiliation(s)
- Sonny Bovee
- Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany
| | - Georg M Klump
- Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany
- Cluster of Excellence "Hearing4all", Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany
- Research Centre Neurosensory Science, Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany
| | - Sonja J Pyott
- Department of Otorhinolaryngology/Head and Neck Surgery, University Medical Center Groningen, University of Groningen, P.O. Box 30.001, 9700 RB Groningen, The Netherlands
| | - Charlotte Sielaff
- Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany
- Fraunhofer Institute for Toxicology and Experimental Medicine (ITEM), 30625 Hannover, Germany
| | - Christine Köppl
- Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany
- Cluster of Excellence "Hearing4all", Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany
- Research Centre Neurosensory Science, Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany
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Lu Y, Liu J, Li B, Wang H, Wang F, Wang S, Wu H, Han H, Hua Y. Spatial patterns of noise-induced inner hair cell ribbon loss in the mouse mid-cochlea. iScience 2024; 27:108825. [PMID: 38313060 PMCID: PMC10835352 DOI: 10.1016/j.isci.2024.108825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 10/16/2023] [Accepted: 01/03/2024] [Indexed: 02/06/2024] Open
Abstract
In the mammalian cochlea, moderate acoustic overexposure leads to loss of ribbon-type synapse between the inner hair cell (IHC) and its postsynaptic spiral ganglion neuron (SGN), causing a reduced dynamic range of hearing but not a permanent threshold elevation. A prevailing view is that such ribbon loss (known as synaptopathy) selectively impacts the low-spontaneous-rate and high-threshold SGN fibers contacting predominantly the modiolar IHC face. However, the spatial pattern of synaptopathy remains scarcely characterized in the most sensitive mid-cochlear region, where two morphological subtypes of IHC with distinct ribbon size gradients coexist. Here, we used volume electron microscopy to investigate noise exposure-related changes in the mouse IHCs with and without ribbon loss. Our quantifications reveal that IHC subtypes differ in the worst-hit area of synaptopathy. Moreover, we show relative enrichment of mitochondria in the surviving SGN terminals, providing key experimental evidence for the long-proposed role of SGN-terminal mitochondria in synaptic vulnerability.
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Affiliation(s)
- Yan Lu
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People’s Hospital, Shanghai 200125, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai 200125, China
- Shanghai Institute of Precision Medicine, Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China
| | - Jing Liu
- Laboratory of Brain Atlas and Brain-inspired Intelligence, Institute of Automation, Chinese Academy of Sciences, Beijing 100190, China
| | - Bei Li
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People’s Hospital, Shanghai 200125, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai 200125, China
| | - Haoyu Wang
- Shanghai Institute of Precision Medicine, Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China
| | - Fangfang Wang
- Shanghai Institute of Precision Medicine, Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China
| | - Shengxiong Wang
- Shanghai Institute of Precision Medicine, Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China
| | - Hao Wu
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People’s Hospital, Shanghai 200125, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai 200125, China
- Shanghai Institute of Precision Medicine, Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China
| | - Hua Han
- Laboratory of Brain Atlas and Brain-inspired Intelligence, Institute of Automation, Chinese Academy of Sciences, Beijing 100190, China
- School of Future Technology, University of Chinese Academy of Sciences, Beijing 101408, China
- State Key Laboratory of Multimodal Artificial Intelligence Systems, Institute of Automation, Chinese Academy of Sciences, Beijing 100190, China
| | - Yunfeng Hua
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People’s Hospital, Shanghai 200125, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai 200125, China
- Shanghai Institute of Precision Medicine, Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China
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11
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Moverman DJ, Liberman LD, Kraemer S, Corfas G, Liberman MC. Ultrastructure of noise-induced cochlear synaptopathy. Sci Rep 2023; 13:19456. [PMID: 37945811 PMCID: PMC10636047 DOI: 10.1038/s41598-023-46859-6] [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: 08/25/2023] [Accepted: 11/06/2023] [Indexed: 11/12/2023] Open
Abstract
Acoustic overexposure can eliminate synapses between inner hair cells (IHCs) and auditory nerve fibers (ANFs), even if hair-cell function recovers. This synaptopathy has been extensively studied by confocal microscopy, however, understanding the nature and sequence of damage requires ultrastructural analysis. Here, we used focused ion-beam scanning electron microscopy to mill, image, segment and reconstruct ANF terminals in mice, 1 day and 1 week after synaptopathic exposure (8-16 kHz, 98 dB SPL). At both survivals, ANF terminals were normal in number, but 62% and 53%, respectively, lacked normal synaptic specializations. Most non-synapsing fibers (57% and 48% at 1 day and 1 week) remained in contact with an IHC and contained healthy-looking organelles. ANFs showed a transient increase in mitochondrial content (51%) and efferent innervation (34%) at 1 day. Fibers maintaining synaptic connections showed hypertrophy of pre-synaptic ribbons at both 1 day and 1 week. Non-synaptic fibers were lower in mitochondrial content and typically on the modiolar side of the IHC, where ANFs with high-thresholds and low spontaneous rates are normally found. Even 1 week post-exposure, many ANF terminals remained in IHC contact despite loss of synaptic specializations, thus, regeneration efforts at early post-exposure times should concentrate on synaptogenesis rather than neurite extension.
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Affiliation(s)
- Daniel J Moverman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, 243 Charles St., Boston, MA, 02114-3096, USA
| | - Leslie D Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, 243 Charles St., Boston, MA, 02114-3096, USA
| | - Stephan Kraemer
- Center for Nanoscale Systems, Harvard College, Cambridge, MA, 02138, USA
| | - Gabriel Corfas
- Department of Otolaryngology-Head and Neck Surgery, Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI, USA
| | - M Charles Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, 243 Charles St., Boston, MA, 02114-3096, USA.
- Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, MA, 02115, USA.
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12
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Wu PZ, O'Malley JT, Liberman MC. Neural Degeneration in Normal-Aging Human Cochleas: Machine-Learning Counts and 3D Mapping in Archival Sections. J Assoc Res Otolaryngol 2023; 24:499-511. [PMID: 37957485 PMCID: PMC10695900 DOI: 10.1007/s10162-023-00909-y] [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: 01/12/2023] [Accepted: 09/03/2023] [Indexed: 11/15/2023] Open
Abstract
Quantifying the survival patterns of spiral ganglion cells (SGCs), the cell bodies of auditory-nerve fibers, is critical to studies of sensorineural hearing loss, especially in human temporal bones. The classic method of manual counting is tedious, and, although stereology approaches can be faster, they can only be used to estimate total cell numbers per cochlea. Here, a machine-learning algorithm that automatically identifies, counts, and maps the SGCs in digitized images of semi-serial human temporal-bone sections not only speeds the analysis, with no loss of accuracy, but also allows 3D visualization of the SGCs and fine-grained mapping to cochlear frequency. Applying the algorithm to 62 normal-aging human ears shows significantly faster degeneration of SGCs in the basal than the apical half of the cochlea. Comparison to fiber counts in the same ears shows that the fraction of surviving SGCs lacking a peripheral axon steadily increases with age, reaching more than 50% in the apical cochlea and almost 66% in basal regions.
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Affiliation(s)
- Pei-Zhe Wu
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA, 02114-3096, USA.
- Department of Otolaryngology, Harvard Medical School, Boston, MA, 02115, USA.
| | - Jennifer T O'Malley
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA, 02114-3096, USA
- Department of Otolaryngology, Harvard Medical School, Boston, MA, 02115, USA
| | - M Charles Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA, 02114-3096, USA
- Department of Otolaryngology, Harvard Medical School, Boston, MA, 02115, USA
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13
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Michanski S, Kapoor R, Steyer AM, Möbius W, Früholz I, Ackermann F, Gültas M, Garner CC, Hamra FK, Neef J, Strenzke N, Moser T, Wichmann C. Piccolino is required for ribbon architecture at cochlear inner hair cell synapses and for hearing. EMBO Rep 2023; 24:e56702. [PMID: 37477166 PMCID: PMC10481675 DOI: 10.15252/embr.202256702] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 06/30/2023] [Accepted: 07/06/2023] [Indexed: 07/22/2023] Open
Abstract
Cochlear inner hair cells (IHCs) form specialized ribbon synapses with spiral ganglion neurons that tirelessly transmit sound information at high rates over long time periods with extreme temporal precision. This functional specialization is essential for sound encoding and is attributed to a distinct molecular machinery with unique players or splice variants compared to conventional neuronal synapses. Among these is the active zone (AZ) scaffold protein piccolo/aczonin, which is represented by its short splice variant piccolino at cochlear and retinal ribbon synapses. While the function of piccolo at synapses of the central nervous system has been intensively investigated, the role of piccolino at IHC synapses remains unclear. In this study, we characterize the structure and function of IHC synapses in piccolo gene-trap mutant rats (Pclogt/gt ). We find a mild hearing deficit with elevated thresholds and reduced amplitudes of auditory brainstem responses. Ca2+ channel distribution and ribbon morphology are altered in apical IHCs, while their presynaptic function seems to be unchanged. We conclude that piccolino contributes to the AZ organization in IHCs and is essential for normal hearing.
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Affiliation(s)
- Susann Michanski
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Center for Biostructural Imaging of NeurodegenerationUniversity Medical Center GöttingenGöttingenGermany
- Collaborative Research Center 889 “Cellular Mechanisms of Sensory Processing”GöttingenGermany
- Multiscale Bioimaging of Excitable Cells, Cluster of ExcellenceGöttingenGermany
| | - Rohan Kapoor
- Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Auditory Neuroscience and Synaptic Nanophysiology GroupMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
- IMPRS Molecular Biology, Göttingen Graduate School for Neuroscience and Molecular BiosciencesUniversity of GöttingenGöttingenGermany
| | - Anna M Steyer
- Electron Microscopy Core Unit, Department of NeurogeneticsMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
| | - Wiebke Möbius
- Multiscale Bioimaging of Excitable Cells, Cluster of ExcellenceGöttingenGermany
- Electron Microscopy Core Unit, Department of NeurogeneticsMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
| | - Iris Früholz
- Developmental, Neural, and Behavioral Biology Master ProgramUniversity of GöttingenGöttingenGermany
| | | | - Mehmet Gültas
- Faculty of AgricultureSouth Westphalia University of Applied SciencesSoestGermany
| | - Craig C Garner
- German Center for Neurodegenerative DiseasesBerlinGermany
- NeuroCureCluster of ExcellenceCharité – UniversitätsmedizinBerlinGermany
| | - F Kent Hamra
- Department of Obstetrics and GynecologyUniversity of Texas Southwestern Medical CenterDallasTXUSA
| | - Jakob Neef
- Collaborative Research Center 889 “Cellular Mechanisms of Sensory Processing”GöttingenGermany
- Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Auditory Neuroscience and Synaptic Nanophysiology GroupMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
| | - Nicola Strenzke
- Collaborative Research Center 889 “Cellular Mechanisms of Sensory Processing”GöttingenGermany
- Auditory Systems Physiology Group, Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
| | - Tobias Moser
- Collaborative Research Center 889 “Cellular Mechanisms of Sensory Processing”GöttingenGermany
- Multiscale Bioimaging of Excitable Cells, Cluster of ExcellenceGöttingenGermany
- Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Auditory Neuroscience and Synaptic Nanophysiology GroupMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
| | - Carolin Wichmann
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Center for Biostructural Imaging of NeurodegenerationUniversity Medical Center GöttingenGöttingenGermany
- Collaborative Research Center 889 “Cellular Mechanisms of Sensory Processing”GöttingenGermany
- Multiscale Bioimaging of Excitable Cells, Cluster of ExcellenceGöttingenGermany
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14
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Michanski S, Henneck T, Mukhopadhyay M, Steyer AM, Gonzalez PA, Grewe K, Ilgen P, Gültas M, Fornasiero EF, Jakobs S, Möbius W, Vogl C, Pangršič T, Rizzoli SO, Wichmann C. Age-dependent structural reorganization of utricular ribbon synapses. Front Cell Dev Biol 2023; 11:1178992. [PMID: 37635868 PMCID: PMC10447907 DOI: 10.3389/fcell.2023.1178992] [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: 03/03/2023] [Accepted: 07/17/2023] [Indexed: 08/29/2023] Open
Abstract
In mammals, spatial orientation is synaptically-encoded by sensory hair cells of the vestibular labyrinth. Vestibular hair cells (VHCs) harbor synaptic ribbons at their presynaptic active zones (AZs), which play a critical role in molecular scaffolding and facilitate synaptic release and vesicular replenishment. With advancing age, the prevalence of vestibular deficits increases; yet, the underlying mechanisms are not well understood and the possible accompanying morphological changes in the VHC synapses have not yet been systematically examined. We investigated the effects of maturation and aging on the ultrastructure of the ribbon-type AZs in murine utricles using various electron microscopic techniques and combined them with confocal and super-resolution light microscopy as well as metabolic imaging up to 1 year of age. In older animals, we detected predominantly in type I VHCs the formation of floating ribbon clusters, mostly consisting of newly synthesized ribbon material. Our findings suggest that VHC ribbon-type AZs undergo dramatic structural alterations upon aging.
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Affiliation(s)
- Susann Michanski
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience, InnerEarLab and Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
- Collaborative Research Center 889, University of Göttingen, Göttingen, Germany
- Multiscale Bioimaging Cluster of Excellence (MBExC), University of Göttingen, Göttingen, Germany
| | - Timo Henneck
- Biology Bachelor Program, University of Göttingen, Göttingen, Germany
| | - Mohona Mukhopadhyay
- Experimental Otology Group, InnerEarLab, Department of Otolaryngology, Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen, Germany
| | - Anna M. Steyer
- Electron Microscopy-City Campus, Department of Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
- Center Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), University of Göttingen, Göttingen, Germany
| | - Paola Agüi Gonzalez
- Department for Neuro-and Sensory Physiology, University Medical Center Göttingen, Center for Biostructural Imaging of Neurodegeneration (BIN), Göttingen, Germany
| | - Katharina Grewe
- Department for Neuro-and Sensory Physiology, University Medical Center Göttingen, Center for Biostructural Imaging of Neurodegeneration (BIN), Göttingen, Germany
| | - Peter Ilgen
- Clinic of Neurology, University Medical Center Göttingen, Göttingen, Germany
- Department of NanoBiophotonics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
- Fraunhofer Institute for Translational Medicine and Pharmacology ITMP, Translational Neuroinflammation and Automated Microscopy TNM, Göttingen, Germany
| | - Mehmet Gültas
- Faculty of Agriculture, South Westphalia University of Applied Sciences, Soest, Germany
| | - Eugenio F. Fornasiero
- Department for Neuro-and Sensory Physiology, University Medical Center Göttingen, Center for Biostructural Imaging of Neurodegeneration (BIN), Göttingen, Germany
| | - Stefan Jakobs
- Clinic of Neurology, University Medical Center Göttingen, Göttingen, Germany
- Department of NanoBiophotonics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
- Fraunhofer Institute for Translational Medicine and Pharmacology ITMP, Translational Neuroinflammation and Automated Microscopy TNM, Göttingen, Germany
| | - Wiebke Möbius
- Multiscale Bioimaging Cluster of Excellence (MBExC), University of Göttingen, Göttingen, Germany
- Electron Microscopy-City Campus, Department of Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Christian Vogl
- Collaborative Research Center 889, University of Göttingen, Göttingen, Germany
- Presynaptogenesis and Intracellular Transport in Hair Cells Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
- Auditory Neuroscience Group, Institute of Physiology, Medical University Innsbruck, Innsbruck, Austria
| | - Tina Pangršič
- Collaborative Research Center 889, University of Göttingen, Göttingen, Germany
- Multiscale Bioimaging Cluster of Excellence (MBExC), University of Göttingen, Göttingen, Germany
- Experimental Otology Group, InnerEarLab, Department of Otolaryngology, Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen, Germany
| | - Silvio O. Rizzoli
- Department for Neuro-and Sensory Physiology, University Medical Center Göttingen, Center for Biostructural Imaging of Neurodegeneration (BIN), Göttingen, Germany
| | - Carolin Wichmann
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience, InnerEarLab and Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
- Collaborative Research Center 889, University of Göttingen, Göttingen, Germany
- Multiscale Bioimaging Cluster of Excellence (MBExC), University of Göttingen, Göttingen, Germany
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15
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Sodero AO, Castagna VC, Elorza SD, Gonzalez-Rodulfo SM, Paulazo MA, Ballestero JA, Martin MG, Gomez-Casati ME. Phytosterols reverse antiretroviral-induced hearing loss, with potential implications for cochlear aging. PLoS Biol 2023; 21:e3002257. [PMID: 37619212 PMCID: PMC10449472 DOI: 10.1371/journal.pbio.3002257] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Accepted: 07/18/2023] [Indexed: 08/26/2023] Open
Abstract
Cholesterol contributes to neuronal membrane integrity, supports membrane protein clustering and function, and facilitates proper signal transduction. Extensive evidence has shown that cholesterol imbalances in the central nervous system occur in aging and in the development of neurodegenerative diseases. In this work, we characterize cholesterol homeostasis in the inner ear of young and aged mice as a new unexplored possibility for the prevention and treatment of hearing loss. Our results show that cholesterol levels in the inner ear are reduced during aging, an effect that is associated with an increased expression of the cholesterol 24-hydroxylase (CYP46A1), the main enzyme responsible for cholesterol turnover in the brain. In addition, we show that pharmacological activation of CYP46A1 with the antiretroviral drug efavirenz reduces the cholesterol content in outer hair cells (OHCs), leading to a decrease in prestin immunolabeling and resulting in an increase in the distortion product otoacoustic emissions (DPOAEs) thresholds. Moreover, dietary supplementation with phytosterols, plant sterols with structure and function similar to cholesterol, was able to rescue the effect of efavirenz administration on the auditory function. Altogether, our findings point towards the importance of cholesterol homeostasis in the inner ear as an innovative therapeutic strategy in preventing and/or delaying hearing loss.
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Affiliation(s)
- Alejandro O. Sodero
- Instituto de Investigaciones Biomédicas, Pontificia Universidad Católica Argentina, Consejo Nacional de Investigaciones Científicas y Técnicas (BIOMED, UCA-CONICET), Buenos Aires, Argentina
| | - Valeria C. Castagna
- Instituto de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Dr. Héctor N. Torres, Consejo Nacional de Investigaciones Científicas y Técnicas (INGEBI-CONICET), Buenos Aires, Argentina
| | - Setiembre D. Elorza
- Laboratorio de Neurobiología, Instituto de Investigaciones Médicas Mercedes y Martín Ferreyra, Consejo Nacional de Investigaciones Científicas y Técnicas (INIMEC-CONICET-UNC), Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Sara M. Gonzalez-Rodulfo
- Instituto de Investigaciones Biomédicas, Pontificia Universidad Católica Argentina, Consejo Nacional de Investigaciones Científicas y Técnicas (BIOMED, UCA-CONICET), Buenos Aires, Argentina
| | - María A. Paulazo
- Instituto de Investigaciones Biomédicas, Pontificia Universidad Católica Argentina, Consejo Nacional de Investigaciones Científicas y Técnicas (BIOMED, UCA-CONICET), Buenos Aires, Argentina
| | - Jimena A. Ballestero
- Instituto de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Mauricio G. Martin
- Laboratorio de Neurobiología, Instituto de Investigaciones Médicas Mercedes y Martín Ferreyra, Consejo Nacional de Investigaciones Científicas y Técnicas (INIMEC-CONICET-UNC), Universidad Nacional de Córdoba, Córdoba, Argentina
| | - María Eugenia Gomez-Casati
- Instituto de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
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16
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Ryugo DK, Milinkeviciute G. Differential projections from the cochlear nucleus to the inferior colliculus in the mouse. Front Neural Circuits 2023; 17:1229746. [PMID: 37554670 PMCID: PMC10405501 DOI: 10.3389/fncir.2023.1229746] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Accepted: 06/26/2023] [Indexed: 08/10/2023] Open
Abstract
The cochlear nucleus (CN) is often regarded as the gateway to the central auditory system because it initiates all ascending pathways. The CN consists of dorsal and ventral divisions (DCN and VCN, respectively), and whereas the DCN functions in the analysis of spectral cues, circuitry in VCN is part of the pathway focused on processing binaural information necessary for sound localization in horizontal plane. Both structures project to the inferior colliculus (IC), which serves as a hub for the auditory system because pathways ascending to the forebrain and descending from the cerebral cortex converge there to integrate auditory, motor, and other sensory information. DCN and VCN terminations in the IC are thought to overlap but given the differences in VCN and DCN architecture, neuronal properties, and functions in behavior, we aimed to investigate the pattern of CN connections in the IC in more detail. This study used electrophysiological recordings to establish the frequency sensitivity at the site of the anterograde dye injection for the VCN and DCN of the CBA/CaH mouse. We examined their contralateral projections that terminate in the IC. The VCN projections form a topographic sheet in the central nucleus (CNIC). The DCN projections form a tripartite set of laminar sheets; the lamina in the CNIC extends into the dorsal cortex (DC), whereas the sheets to the lateral cortex (LC) and ventrolateral cortex (VLC) are obliquely angled away. These fields in the IC are topographic with low frequencies situated dorsally and progressively higher frequencies lying more ventrally and/or laterally; the laminae nestle into the underlying higher frequency fields. The DCN projections are complementary to the somatosensory modules of layer II of the LC but both auditory and spinal trigeminal terminations converge in the VLC. While there remains much to be learned about these circuits, these new data on auditory circuits can be considered in the context of multimodal networks that facilitate auditory stream segregation, signal processing, and species survival.
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Affiliation(s)
- David K. Ryugo
- Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
- School of Biomedical Sciences, University of New South Wales, Kensington, NSW, Australia
- Department of Otolaryngology, Head and Neck and Skull Base Surgery, St. Vincent’s Hospital, Darlinghurst, NSW, Australia
| | - Giedre Milinkeviciute
- Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
- School of Biomedical Sciences, University of New South Wales, Kensington, NSW, Australia
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17
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Zhang Y, Hiel H, Vincent PF, Wood MB, Elgoyhen AB, Chien W, Lauer A, Fuchs PA. Engineering olivocochlear inhibition to reduce acoustic trauma. Mol Ther Methods Clin Dev 2023; 29:17-31. [PMID: 36941920 PMCID: PMC10023855 DOI: 10.1016/j.omtm.2023.02.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 02/22/2023] [Indexed: 02/27/2023]
Abstract
Efferent brain-stem neurons release acetylcholine to desensitize cochlear hair cells and can protect the inner ear from acoustic trauma. That protection is absent from knockout mice lacking efferent inhibition and is stronger in mice with a gain-of-function point mutation of the hair cell-specific nicotinic acetylcholine receptor. The present work uses viral transduction of gain-of-function receptors to restore acoustic prophylaxis to the knockout mice. Widespread postsynaptic expression of the transgene was visualized in excised tissue with a fluorophore-conjugated peptide toxin that binds selectively to hair cell acetylcholine receptors. Viral transduction into efferent knockout mice reduced the temporary hearing loss measured 1 day post acoustic trauma. The acoustic evoked-response waveform (auditory brain-stem response) recovered more rapidly in treated mice than in control mice. Thus, both cochlear amplification by outer hair cells (threshold shift) and afferent signaling (evoked-response amplitude) in knockout mice were protected by viral transduction of hair cell acetylcholine receptors. Gene therapy to strengthen efferent cochlear feedback could be complementary to existing and future therapies to prevent hearing loss, including ear coverings, hearing aids, single-gene repair, or small-molecule therapies.
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Affiliation(s)
- Yuanyuan Zhang
- The Center for Hearing and Balance, Otolaryngology–Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Hakim Hiel
- The Center for Hearing and Balance, Otolaryngology–Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Philippe F.Y. Vincent
- The Center for Hearing and Balance, Otolaryngology–Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Megan B. Wood
- The Center for Hearing and Balance, Otolaryngology–Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Ana B. Elgoyhen
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular Dr. Héctor N. Torres (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), C1428ADN CABA, Buenos Aires, Argentina
| | - Wade Chien
- The Center for Hearing and Balance, Otolaryngology–Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Inner Ear Gene Therapy Program, National Institute on Deafness and Other Communication Disorders (NIDCD), National Institutes of Health, Bethesda, MD 20892, USA
| | - Amanda Lauer
- The Center for Hearing and Balance, Otolaryngology–Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Paul A. Fuchs
- The Center for Hearing and Balance, Otolaryngology–Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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18
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Liu H, Liu H, Wang L, Song L, Jiang G, Lu Q, Yang T, Peng H, Cai R, Zhao X, Zhao T, Wu H. Cochlear transcript diversity and its role in auditory functions implied by an otoferlin short isoform. Nat Commun 2023; 14:3085. [PMID: 37248244 DOI: 10.1038/s41467-023-38621-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Accepted: 05/10/2023] [Indexed: 05/31/2023] Open
Abstract
Isoforms of a gene may contribute to diverse biological functions. In the cochlea, the repertoire of alternative isoforms remains unexplored. We integrated single-cell short-read and long-read RNA sequencing techniques and identified 236,012 transcripts, 126,612 of which were unannotated in the GENCODE database. Then we analyzed and verified the unannotated transcripts using RNA-seq, RT-PCR, Sanger sequencing, and MS-based proteomics approaches. To illustrate the importance of identifying spliced isoforms, we investigated otoferlin, a key protein involved in synaptic transmission in inner hair cells (IHCs). Upon deletion of the canonical otoferlin isoform, the identified short isoform is able to support normal hearing thresholds but with reduced sustained exocytosis of IHCs, and further revealed otoferlin functions in endocytic membrane retrieval that was not well-addressed previously. Furthermore, we found that otoferlin isoforms are associated with IHC functions and auditory phenotypes. This work expands our mechanistic understanding of auditory functions at the level of isoform resolution.
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Affiliation(s)
- Huihui Liu
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, 200011, China
| | - Hongchao Liu
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, 200011, China
| | - Longhao Wang
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, 200011, China
| | - Lei Song
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, 200011, China
| | - Guixian Jiang
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, 200011, China
| | - Qing Lu
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, 200011, China
- Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Ministry of Education, Bio-X Institutes, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Tao Yang
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, 200011, China
| | - Hu Peng
- Department of Otolaryngology-Head and Neck Surgery, Changzheng Hospital, Second Military Medical University, Shanghai, 200003, China
| | - Ruijie Cai
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, 200011, China
| | - Xingle Zhao
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, 200011, China
| | - Ting Zhao
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, 200011, China
| | - Hao Wu
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China.
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China.
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, 200011, China.
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Heuermann ML, Matos S, Hamilton D, Cox BC. Regenerated hair cells in the neonatal cochlea are innervated and the majority co-express markers of both inner and outer hair cells. Front Cell Neurosci 2022; 16:841864. [PMID: 36187289 PMCID: PMC9524252 DOI: 10.3389/fncel.2022.841864] [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: 12/22/2021] [Accepted: 08/29/2022] [Indexed: 11/30/2022] Open
Abstract
After a damaging insult, hair cells can spontaneously regenerate from cochlear supporting cells within the first week of life. While the regenerated cells express several markers of immature hair cells and have stereocilia bundles, their capacity to differentiate into inner or outer hair cells, and ability to form new synaptic connections has not been well-described. In addition, while multiple supporting cell subtypes have been implicated as the source of the regenerated hair cells, it is unclear if certain subtypes have a greater propensity to form one hair cell type over another. To investigate this, we used two CreER mouse models to fate-map either the supporting cells located near the inner hair cells (inner phalangeal and border cells) or outer hair cells (Deiters’, inner pillar, and outer pillar cells) along with immunostaining for markers that specify the two hair cell types. We found that supporting cells fate-mapped by both CreER lines responded early to hair cell damage by expressing Atoh1, and are capable of producing regenerated hair cells that express terminal differentiation markers of both inner and outer hair cells. The majority of regenerated hair cells were innervated by neuronal fibers and contained synapses. Unexpectedly, we also found that the majority of the laterally positioned regenerated hair cells aberrantly expressed both the outer hair cell gene, oncomodulin, and the inner hair cell gene, vesicular glutamate transporter 3 (VGlut3). While this work demonstrates that regenerated cells can express markers of both inner and outer hair cells after damage, VGlut3 expression appears to lack the tight control present during embryogenesis, which leads to its inappropriate expression in regenerated cells.
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Affiliation(s)
- Mitchell L. Heuermann
- Department of Otolaryngology, Southern Illinois University School of Medicine, Springfield, IL, United States
| | - Sophia Matos
- Department of Otolaryngology, Southern Illinois University School of Medicine, Springfield, IL, United States
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, United States
| | - Deborah Hamilton
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, United States
| | - Brandon C. Cox
- Department of Otolaryngology, Southern Illinois University School of Medicine, Springfield, IL, United States
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, United States
- *Correspondence: Brandon C. Cox,
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Li Y, Yu H, Zhou X, Jin L, Li W, Li GL, Shen X. Multiple Sevoflurane Exposures During the Neonatal Period Cause Hearing Impairment and Loss of Hair Cell Ribbon Synapses in Adult Mice. Front Neurosci 2022; 16:945277. [PMID: 35911996 PMCID: PMC9329801 DOI: 10.3389/fnins.2022.945277] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 06/24/2022] [Indexed: 11/13/2022] Open
Abstract
Objectives This study aims to investigate the effects of multiple sevoflurane exposures in neonatal mice on hearing function in the later life and explores the underlying mechanisms and protective strategies. Materials and Methods Neonatal Kunming mice were exposed to sevoflurane for 3 days. Auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) tests, immunofluorescence, patch-clamp recording, and quantitative real-time PCR were performed to observe hearing function, hair cells, ribbon synapses, nerve fibers, spiral ganglion neurons, and oxidative stress. Results Compared to control group, multiple sevoflurane exposures during the neonatal time significantly elevated ABR thresholds at 8 kHz (35.42 ± 1.57 vs. 41.76 ± 1.97 dB, P = 0.0256), 16 kHz (23.33 ± 1.28 vs. 33.53 ± 2.523 dB, P = 0.0012), 24 kHz (30.00 ± 2.04 vs. 46.76 ± 3.93 dB, P = 0.0024), and 32 kHz (41.25 ± 2.31 vs. 54.41 ± 2.94 dB, P = 0.0028) on P30, caused ribbon synapse loss on P15 (13.10 ± 0.43 vs. 10.78 ± 0.52, P = 0.0039) and P30 (11.24 ± 0.56 vs. 8.50 ± 0.84, P = 0.0141), and degenerated spiral ganglion neuron (SGN) nerve fibers on P30 (110.40 ± 16.23 vs. 55.04 ± 8.13, P = 0.0073). In addition, the Vhalf of calcium current become more negative (−21.99 ± 0.70 vs. −27.17 ± 0.60 mV, P < 0.0001), exocytosis was reduced (105.40 ± 19.97 vs. 59.79 ± 10.60 fF, P < 0.0001), and Lpo was upregulated (P = 0.0219) in sevoflurane group than those in control group. N-acetylcysteine (NAC) reversed hearing impairment induced by sevoflurane. Conclusion The findings suggest that multiple sevoflurane exposures during neonatal time may cause hearing impairment in adult mice. The study also demonstrated that elevated oxidative stress led to ribbon synapses impairment and SGN nerve fibers degeneration, and the interventions of antioxidants alleviated the sevoflurane-induced hearing impairment.
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Affiliation(s)
- Yufeng Li
- Department of Anesthesiology, Eye & ENT Hospital, Fudan University, Shanghai, China
| | - Huiqian Yu
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, Fudan University, Shanghai, China
| | - Xuehua Zhou
- Department of Anesthesiology, Eye & ENT Hospital, Fudan University, Shanghai, China
| | - Lin Jin
- Department of Anesthesiology, Eye & ENT Hospital, Fudan University, Shanghai, China
| | - Wen Li
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, Fudan University, Shanghai, China
| | - Geng-Lin Li
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, Fudan University, Shanghai, China
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
- *Correspondence: Geng-Lin Li,
| | - Xia Shen
- Department of Anesthesiology, Eye & ENT Hospital, Fudan University, Shanghai, China
- Xia Shen,
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21
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Mukhopadhyay M, Pangrsic T. Synaptic transmission at the vestibular hair cells of amniotes. Mol Cell Neurosci 2022; 121:103749. [PMID: 35667549 DOI: 10.1016/j.mcn.2022.103749] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2021] [Revised: 05/09/2022] [Accepted: 06/01/2022] [Indexed: 11/19/2022] Open
Abstract
A harmonized interplay between the central nervous system and the five peripheral end organs is how the vestibular system helps organisms feel a sense of balance and motion in three-dimensional space. The receptor cells of this system, much like their cochlear equivalents, are the specialized hair cells. However, research over the years has shown that the vestibular endorgans and hair cells evolved very differently from their cochlear counterparts. The structurally unique calyceal synapse, which appeared much later in the evolutionary time scale, and continues to intrigue researchers, is now known to support several forms of synaptic neurotransmission. The conventional quantal transmission is believed to employ the ribbon structures, which carry several tethered vesicles filled with neurotransmitters. However, the field of vestibular hair cell synaptic molecular anatomy is still at a nascent stage and needs further work. In this review, we will touch upon the basic structure and function of the peripheral vestibular system, with the focus on the various modes of neurotransmission at the type I vestibular hair cells. We will also shed light on the current knowledge about the molecular anatomy of the vestibular hair cell synapses and vestibular synaptopathy.
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Affiliation(s)
- Mohona Mukhopadhyay
- Experimental Otology Group, InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, and Institute for Auditory Neuroscience, 37075 Göttingen, Germany
| | - Tina Pangrsic
- Experimental Otology Group, InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, and Institute for Auditory Neuroscience, 37075 Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute for Multidisciplinary Sciences, 37075 Göttingen, Germany; Collaborative Research Center 889, University of Göttingen, Göttingen, Germany; Multiscale Bioimaging Cluster of Excellence (MBExC), University of Göttingen, 37075 Göttingen, Germany.
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22
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Liu Z, Luo Y, Guo R, Yang B, Shi L, Sun J, Guo W, Gong S, Jiang X, Liu K. Head and Neck Radiotherapy Causes Significant Disruptions of Cochlear Ribbon Synapses and Consequent Sensorineural Hearing Loss. Radiother Oncol 2022; 173:207-214. [DOI: 10.1016/j.radonc.2022.05.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 05/13/2022] [Accepted: 05/25/2022] [Indexed: 10/18/2022]
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Harris KC, Bao J. Optimizing non-invasive functional markers for cochlear deafferentation based on electrocochleography and auditory brainstem responses. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2022; 151:2802. [PMID: 35461487 PMCID: PMC9034896 DOI: 10.1121/10.0010317] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 03/22/2022] [Accepted: 04/08/2022] [Indexed: 06/14/2023]
Abstract
Accumulating evidence suggests that cochlear deafferentation may contribute to suprathreshold deficits observed with or without elevated hearing thresholds, and can lead to accelerated age-related hearing loss. Currently there are no clinical diagnostic tools to detect human cochlear deafferentation in vivo. Preclinical studies using a combination of electrophysiological and post-mortem histological methods clearly demonstrate cochlear deafferentation including myelination loss, mitochondrial damages in spiral ganglion neurons (SGNs), and synaptic loss between inner hair cells and SGNs. Since clinical diagnosis of human cochlear deafferentation cannot include post-mortem histological quantification, various attempts based on functional measurements have been made to detect cochlear deafferentation. So far, those efforts have led to inconclusive results. Two major obstacles to the development of in vivo clinical diagnostics include a lack of standardized methods to validate new approaches and characterize the normative range of repeated measurements. In this overview, we examine strategies from previous studies to detect cochlear deafferentation from electrocochleography and auditory brainstem responses. We then summarize possible approaches to improve these non-invasive functional methods for detecting cochlear deafferentation with a focus on cochlear synaptopathy. We identify conceptual approaches that should be tested to associate unique electrophysiological features with cochlear deafferentation.
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Affiliation(s)
- Kelly C Harris
- Department of Otolaryngology, Head & Neck Surgery, Medical University of South Carolina, 135 Rutledge Avenue, MSC 550, Charleston, South Carolina 29425, USA
| | - Jianxin Bao
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, Ohio 44272, USA
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24
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Seicol BJ, Lin S, Xie R. Age-Related Hearing Loss Is Accompanied by Chronic Inflammation in the Cochlea and the Cochlear Nucleus. Front Aging Neurosci 2022; 14:846804. [PMID: 35418849 PMCID: PMC8995794 DOI: 10.3389/fnagi.2022.846804] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Accepted: 03/07/2022] [Indexed: 12/24/2022] Open
Abstract
Age-related hearing loss (ARHL) is a major hearing impairment characterized by pathological changes in both the peripheral and central auditory systems. Low-grade inflammation was observed in the cochlea of deceased human subjects with ARHL and animal models of early onset ARHL, which suggests that inflammation contributes to the development of ARHL. However, it remains elusive how chronic inflammation progresses during normal aging in the cochlea, and especially the accompanying changes of neuroinflammation in the central auditory system. To address this, we investigated chronic inflammation in both the cochlea and the cochlear nucleus (CN) of CBA/CaJ mice, an inbred mouse strain that undergoes normal aging and develops human, like-late-onset ARHL. Using immunohistochemistry, confocal microscopy, and quantitative image processing, we measured the accumulation and activation of macrophages in the cochlea and microglia in the CN using their shared markers: ionized calcium binding adaptor molecule 1 (Iba1) and CD68-a marker of phagocytic activity. We found progressive increases in the area covered by Iba1-labeled macrophages and enhanced CD68 staining in the osseous spiral lamina of the cochlea that correlated with elevated ABR threshold across the lifespan. During the process, we further identified significant increases in microglial activation and C1q deposition in the CN, indicating increased neuroinflammation and complement activation in the central auditory system. Our study suggests that during normal aging, chronic inflammation occurs in both the peripheral and the central auditory system, which may contribute in coordination to the development of ARHL.
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Affiliation(s)
- Benjamin J. Seicol
- Department of Otolaryngology—Head and Neck Surgery, The Ohio State University, Columbus, OH, United States
- Department of Neuroscience, The Ohio State University, Columbus, OH, United States
| | - Shengyin Lin
- Department of Otolaryngology—Head and Neck Surgery, The Ohio State University, Columbus, OH, United States
| | - Ruili Xie
- Department of Otolaryngology—Head and Neck Surgery, The Ohio State University, Columbus, OH, United States
- Department of Neuroscience, The Ohio State University, Columbus, OH, United States
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25
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Andresen NS, Winslow MK, Gregg L, Seal SM, Lehar M, Ward BK, Lauer AM. Insights into Presbycusis From the First Temporal Bone Laboratory Within the United States. Otol Neurotol 2022; 43:400-408. [PMID: 35061640 PMCID: PMC8852250 DOI: 10.1097/mao.0000000000003466] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The Johns Hopkins Otologic Research Laboratory was founded in 1924 as the first human temporal bone laboratory within the United States. To better understand the contributions of the Johns Hopkins Otologic Research Laboratory to our understanding of presbycusis, we consulted with a medical librarian and archivist to search the Alan Mason Chesney Medical Archives, PubMed, JSTOR, and Johns Hopkins Bulletin for published and unpublished works from the lab. Between 1924 and 1938, Samuel J. Crowe, the Chairman of Otolaryngology, and anatomist Stacy R. Guild amassed a collection of ∼1,800 temporal bones. This collection allowed for an unprecedented period of discovery related to otologic disease. They combined hearing thresholds measured by the recently invented audiometer with new techniques for temporal bone decalcification, sectioning, and staining, and a method for the graphic reconstruction of the cochlea. Crowe and Guild used this unique opportunity to correlate otopathology with hearing and to make the first detailed descriptions of the otopathology of presbycusis. In 1931 and 1934, they observed spiral ganglion neuron and outer hair cell loss in the basal turn of the cochlea in individuals with high-frequency hearing loss. These were the first studies to reveal that stria vascularis degeneration and middle ear pathology were not the most common causes for high-frequency hearing loss. Aside from revealing the primary driving factors of presbycusis, this work provided insight into the tonotopic organization of the cochlea. After initially being recruited to help raise money for the laboratory, medical illustrator Max Brödel used the vertical histologic cross-sections of the cochlea to produce illustrations of the ear. The decision to produce histologic sections in the plane of the superior semicircular canal likely influenced Brödel's illustrations that share a similar orientation and would later become widely circulated. Significant contributions from the Otologic Research Laboratory were also made by Mary Hardy, D.Sc., a woman who has previously received little recognition for her work. The sectioning of temporal bones was stopped in 1938 due to World War II, but much of Crowe's and Guild's work continued into the 1940s until a rift between the two resulted in the temporary closure of the laboratory in 1949. Nearly 100 years after its founding, discoveries from the Johns Hopkins Otologic Research Laboratory remain relevant and emphasize the importance of continued human temporal bone research to improve our understanding and treatment of otologic disease.
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Affiliation(s)
- Nicholas S. Andresen
- Department of Otolaryngology-Head and Neck Surgery and Center for Hearing and Balance, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Marjorie Kehoe Winslow
- Alan Mason Chesney Medical Archives, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Lydia Gregg
- Department of Art as Applied to Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Stella M. Seal
- Welch Medical Library, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Mohamed Lehar
- Department of Otolaryngology-Head and Neck Surgery and Center for Hearing and Balance, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Bryan K. Ward
- Department of Otolaryngology-Head and Neck Surgery and Center for Hearing and Balance, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Amanda M. Lauer
- Department of Otolaryngology-Head and Neck Surgery and Center for Hearing and Balance, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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26
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Lin X, Luo J, Tan J, Yang L, Wang M, Li P. Experimental animal models of drug-induced sensorineural hearing loss: a narrative review. ANNALS OF TRANSLATIONAL MEDICINE 2021; 9:1393. [PMID: 34733945 PMCID: PMC8506545 DOI: 10.21037/atm-21-2508] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 05/16/2021] [Accepted: 08/16/2021] [Indexed: 01/19/2023]
Abstract
Objective This narrative review describes experimental animal models of sensorineural hearing loss (SNHL) caused by ototoxic agents. Background SNHL primarily results from damage to the sensory organ within the inner ear or the vestibulocochlear nerve (cranial nerve VIII). The main etiology of SNHL includes genetic diseases, presbycusis, ototoxic agents, infection, and noise exposure. Animal models with functional and anatomic damage to the sensory organ within the inner ear or the vestibulocochlear nerve mimicking the damage seen in humans are employed to explore the mechanism and potential treatment of SNHL. These animal models of SNHL are commonly established using ototoxic agents. Methods A literature search of PubMed, Embase, and Web of Science was performed for research articles on hearing loss and ototoxic agents in animal models of hearing loss. Conclusions Common ototoxic medications such as aminoglycoside antibiotics (AABs) and platinum antitumor drugs are extensively used to induce SNHL in experimental animals. The effect of ototoxic agents in vivo is influenced by the chemical mechanisms of the ototoxic agents, the species of animal, routes of administration of the ototoxic agents, and the dosage of ototoxic agents. Animal models of drug-induced SNHL contribute to understanding the hearing mechanism and reveal the function of different parts of the auditory system in humans.
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Affiliation(s)
- Xuexin Lin
- Department of Otolaryngology Head and Neck Surgery, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China
| | - Jia Luo
- Department of Otolaryngology Head and Neck Surgery, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China
| | - Jingqian Tan
- Department of Otolaryngology Head and Neck Surgery, The Eighth Affiliated Hospital of Sun Yat-sen University, Shenzhen, China
| | - Luoying Yang
- Department of Otolaryngology Head and Neck Surgery, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China
| | - Mitian Wang
- Department of Otolaryngology Head and Neck Surgery, The Third Affiliated Hospital of Sun Yat-sen University Yuedong Hospital, Meizhou, China
| | - Peng Li
- Department of Otolaryngology Head and Neck Surgery, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China
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27
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Peineau T, Belleudy S, Pietropaolo S, Bouleau Y, Dulon D. Synaptic Release Potentiation at Aging Auditory Ribbon Synapses. Front Aging Neurosci 2021; 13:756449. [PMID: 34733152 PMCID: PMC8558230 DOI: 10.3389/fnagi.2021.756449] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 09/21/2021] [Indexed: 11/13/2022] Open
Abstract
Age-related hidden hearing loss is often described as a cochlear synaptopathy that results from a progressive degeneration of the inner hair cell (IHC) ribbon synapses. The functional changes occurring at these synapses during aging are not fully understood. Here, we characterized this aging process in IHCs of C57BL/6J mice, a strain which is known to carry a cadherin-23 mutation and experiences early hearing loss with age. These mice, while displaying a large increase in auditory brainstem thresholds due to 50% loss of IHC synaptic ribbons at middle age (postnatal day 365), paradoxically showed enhanced acoustic startle reflex suggesting a hyperacusis-like response. The auditory defect was associated with a large shrinkage of the IHCs' cell body and a drastic enlargement of their remaining presynaptic ribbons which were facing enlarged postsynaptic AMPAR clusters. Presynaptic Ca2+ microdomains and the capacity of IHCs to sustain high rates of exocytosis were largely increased, while on the contrary the expression of the fast-repolarizing BK channels, known to negatively control transmitter release, was decreased. This age-related synaptic plasticity in IHCs suggested a functional potentiation of synaptic transmission at the surviving synapses, a process that could partially compensate the decrease in synapse number and underlie hyperacusis.
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Affiliation(s)
- Thibault Peineau
- Neurophysiologie de la Synapse Auditive, INSERM UMRS 1120, Bordeaux Neurocampus, Université de Bordeaux, Bordeaux, France.,Institut de l'Audition, Centre Institut Pasteur/Inserm, Paris, France
| | - Séverin Belleudy
- Neurophysiologie de la Synapse Auditive, INSERM UMRS 1120, Bordeaux Neurocampus, Université de Bordeaux, Bordeaux, France
| | | | - Yohan Bouleau
- Neurophysiologie de la Synapse Auditive, INSERM UMRS 1120, Bordeaux Neurocampus, Université de Bordeaux, Bordeaux, France.,Institut de l'Audition, Centre Institut Pasteur/Inserm, Paris, France
| | - Didier Dulon
- Neurophysiologie de la Synapse Auditive, INSERM UMRS 1120, Bordeaux Neurocampus, Université de Bordeaux, Bordeaux, France.,Institut de l'Audition, Centre Institut Pasteur/Inserm, Paris, France
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28
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Salam SA, Mostafa F, Alnamshan MM, Elshewemi SS, Sorour JM. Thymoquinone ameliorates age-related hearing loss in C57BL/6J mice by modulating Sirt1 activity and Bak1 expression. Biomed Pharmacother 2021; 143:112149. [PMID: 34507120 DOI: 10.1016/j.biopha.2021.112149] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 08/27/2021] [Accepted: 08/31/2021] [Indexed: 01/10/2023] Open
Abstract
Age-related hearing loss (AHL) is the most common sensory disorder of aged population. Currently, one of the most important sources of experimental medicine for AHL is medicinal plants. This study performed the first investigation of the effect of thymoquinone (TQ), a potent antioxidant, on AHL. Here, we used inbred C57BL/6J mice (B6 mice) as a successful experimental model of the early onset of AHL. The behavioral assessment of hearing revealed that the injection of a high dose of TQ (40 mg/kg; TQ40) significantly improved the auditory sensitivity of B6 mice at all tested frequencies (8, 16 and 22 kHz). Histological sections of cochlea from B6 mice injected with a low dose (20 mg/kg; TQ20) and high dose showed relatively less degenerative signs in the modiolus, hair cells and spiral ligaments, the main constituents of the cochlea. In addition, TQ40 completely restored the normal pattern of hair cells in B6 mice, as shown in scanning electron micrographs. Our data indicated that TQ20 and TQ40 reduced levels of Bak1-mediated apoptosis in the cochlea of B6 mice. Interestingly, the level of Sirt1, a positive regulator of autophagy, was significantly increased in B6 mice administered TQ40. In conclusion, TQ relieves the symptoms of AHL by downregulating Bak1 and activating Sirt1 in the cochlea of B6 mice.
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Affiliation(s)
- Sherine Abdel Salam
- Department of Zoology, Faculty of Science, Alexandria University, Alexandria 21511, Egypt.
| | - Fatma Mostafa
- Department of Zoology, Faculty of Science, Alexandria University, Alexandria 21511, Egypt.
| | - Mashael M Alnamshan
- Department of Biology, College of Science, Imam Abdulrahman Bin Faisal University, P.O. Box 1982, Dammam 31441, Saudi Arabia.
| | - Salma S Elshewemi
- Department of Zoology, Faculty of Science, Alexandria University, Alexandria 21511, Egypt.
| | - Jehan M Sorour
- Department of Zoology, Faculty of Science, Alexandria University, Alexandria 21511, Egypt.
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Settibhaktini H, Heinz MG, Chintanpalli A. Modeling the effects of age and hearing loss on concurrent vowel scores. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2021; 150:3581. [PMID: 34852572 PMCID: PMC8594952 DOI: 10.1121/10.0007046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 10/09/2021] [Accepted: 10/12/2021] [Indexed: 06/13/2023]
Abstract
A difference in fundamental frequency (F0) between two vowels is an important segregation cue prior to identifying concurrent vowels. To understand the effects of this cue on identification due to age and hearing loss, Chintanpalli, Ahlstrom, and Dubno [(2016). J. Acoust. Soc. Am. 140, 4142-4153] collected concurrent vowel scores across F0 differences for younger adults with normal hearing (YNH), older adults with normal hearing (ONH), and older adults with hearing loss (OHI). The current modeling study predicts these concurrent vowel scores to understand age and hearing loss effects. The YNH model cascaded the temporal responses of an auditory-nerve model from Bruce, Efrani, and Zilany [(2018). Hear. Res. 360, 40-45] with a modified F0-guided segregation algorithm from Meddis and Hewitt [(1992). J. Acoust. Soc. Am. 91, 233-245] to predict concurrent vowel scores. The ONH model included endocochlear-potential loss, while the OHI model also included hair cell damage; however, both models incorporated cochlear synaptopathy, with a larger effect for OHI. Compared with the YNH model, concurrent vowel scores were reduced across F0 differences for ONH and OHI models, with the lowest scores for OHI. These patterns successfully captured the age and hearing loss effects in the concurrent-vowel data. The predictions suggest that the inability to utilize an F0-guided segregation cue, resulting from peripheral changes, may reduce scores for ONH and OHI listeners.
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Affiliation(s)
- Harshavardhan Settibhaktini
- Department of Electrical and Electronics Engineering, Birla Institute of Technology and Science, Pilani Campus, Vidya Vihar, Pilani, Rajasthan 333031, India
| | - Michael G Heinz
- Department of Speech, Language and Hearing Sciences, and Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana 47907-2028, USA
| | - Ananthakrishna Chintanpalli
- Department of Electrical and Electronics Engineering, Birla Institute of Technology and Science, Pilani Campus, Vidya Vihar, Pilani, Rajasthan 333031, India
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30
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Prior Acoustic Trauma Alters Type II Afferent Activity in the Mouse Cochlea. eNeuro 2021; 8:ENEURO.0383-21.2021. [PMID: 34607806 PMCID: PMC8589282 DOI: 10.1523/eneuro.0383-21.2021] [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: 09/20/2021] [Accepted: 09/23/2021] [Indexed: 01/11/2023] Open
Abstract
Auditory stimuli travel from the cochlea to the brainstem through type I and type II cochlear afferents. While type I afferents convey information about the frequency, intensity, and timing of sounds, the role of type II afferents remains unresolved. Limited recordings of type II afferents from cochlear apex of prehearing rats reveal they are activated by widespread outer hair cell stimulation, ATP, and by the rupture of nearby outer hair cells. Altogether, these lines of evidence suggest that type II afferents sense loud, potentially damaging levels of sound. To explore this hypothesis further, calcium imaging was used to determine the impact of acoustic trauma on the activity of type II cochlear afferents of young adult mice of both sexes. Two known marker genes (Th, Drd2) and one new marker gene (Tac1), expressed in type II afferents and some other cochlear cell types, drove GCaMP6f expression to reveal calcium transients in response to focal damage in the organ of Corti in all turns of the cochlea. Mature type II afferents responded to acute photoablation damage less often but at greater length compared with prehearing neurons. In addition, days after acoustic trauma, acute photoablation triggered a novel response pattern in type II afferents and surrounding epithelial cells, delayed bursts of activity occurring minutes after the initial response subsided. Overall, calcium imaging can report type II afferent responses to damage even in mature and noise-exposed animals and reveals previously unknown tissue hyperactivity subsequent to acoustic trauma.
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31
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Peixoto Pinheiro B, Adel Y, Knipper M, Müller M, Löwenheim H. Auditory Threshold Variability in the SAMP8 Mouse Model of Age-Related Hearing Loss: Functional Loss and Phenotypic Change Precede Outer Hair Cell Loss. Front Aging Neurosci 2021; 13:708190. [PMID: 34408646 PMCID: PMC8366269 DOI: 10.3389/fnagi.2021.708190] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Accepted: 07/09/2021] [Indexed: 11/13/2022] Open
Abstract
Age-related hearing loss (ARHL) is the most common sensory deficit in aging society, which is accompanied by increased speech discrimination difficulties in noisy environments, social isolation, and cognitive decline. The audiometric degree of ARHL is largely correlated with sensory hair cell loss in addition to age-related factors not captured by histopathological analysis of the human cochlea. Previous studies have identified the senescence-accelerated mouse prone strain 8 (SAMP8) as a model for studying ARHL and age-related modifications of the cochlear redox environment. However, the SAMP8 population exhibits a large variability in auditory function decline over age, whose underlying cause remains unknown. In this study, we analyzed auditory function of SAMP8 mice by measuring auditory brainstem response (ABR) thresholds at the age of 6 weeks (juvenile), 12 weeks (young adult), and 24 weeks (adult). Consistent with previous studies, SAMP8 mice exhibit an early progressive, age-related decline of hearing acuity. However, a spatiotemporal cytohistological analysis showed that the significant increase in threshold variability was not concurrently reflected in outer hair cell (OHC) loss observed in the lower and upper quartiles of the ABR threshold distributions over age. This functional loss was found to precede OHC loss suggesting that age-related phenotypic changes may be contributing factors not represented in cytohistological analysis. The expression of potassium channels KCNQ4 (KV7.4), which mediates the current IK,n crucial for the maintenance of OHC membrane potential, and KCNQ1 (KV7.1), which is an essential component in potassium circulation and secretion into the endolymph generating the endocochlear potential, showed differences between these quartiles and age groups. This suggests that phenotypic changes in OHCs or the stria vascularis due to variable oxidative deficiencies in individual mice may be predictors of the observed threshold variability in SAMP8 mice and their progressive ARHL. In future studies, further phenotypic predictors affected by accumulated metabolic challenges over age need to be investigated as potentially underlying causes of ARHL preceding irreversible OHC loss in the SAMP8 mouse model.
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Affiliation(s)
- Barbara Peixoto Pinheiro
- Translational Hearing Research, Tübingen Hearing Research Center, Department of Otolaryngology, Head and Neck Surgery, University of Tübingen, Tübingen, Germany
| | - Youssef Adel
- Translational Hearing Research, Tübingen Hearing Research Center, Department of Otolaryngology, Head and Neck Surgery, University of Tübingen, Tübingen, Germany
| | - Marlies Knipper
- Molecular Physiology of Hearing, Tübingen Hearing Research Center, Department of Otolaryngology, Head and Neck Surgery, University of Tübingen, Tübingen, Germany
| | - Marcus Müller
- Translational Hearing Research, Tübingen Hearing Research Center, Department of Otolaryngology, Head and Neck Surgery, University of Tübingen, Tübingen, Germany
| | - Hubert Löwenheim
- Translational Hearing Research, Tübingen Hearing Research Center, Department of Otolaryngology, Head and Neck Surgery, University of Tübingen, Tübingen, Germany
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Walia A, Lee C, Hartsock J, Goodman SS, Dolle R, Salt AN, Lichtenhan JT, Rutherford MA. Reducing Auditory Nerve Excitability by Acute Antagonism of Ca 2+-Permeable AMPA Receptors. Front Synaptic Neurosci 2021; 13:680621. [PMID: 34290596 PMCID: PMC8287724 DOI: 10.3389/fnsyn.2021.680621] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 05/31/2021] [Indexed: 11/13/2022] Open
Abstract
Hearing depends on glutamatergic synaptic transmission mediated by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs). AMPARs are tetramers, where inclusion of the GluA2 subunit reduces overall channel conductance and Ca2+ permeability. Cochlear afferent synapses between inner hair cells (IHCs) and auditory nerve fibers (ANFs) contain the AMPAR subunits GluA2, 3, and 4. However, the tetrameric complement of cochlear AMPAR subunits is not known. It was recently shown in mice that chronic intracochlear delivery of IEM-1460, an antagonist selective for GluA2-lacking AMPARs [also known as Ca2+-permeable AMPARs (CP-AMPARs)], before, during, and after acoustic overexposure prevented both the trauma to ANF synapses and the ensuing reduction of cochlear nerve activity in response to sound. Surprisingly, baseline measurements of cochlear function before exposure were unaffected by chronic intracochlear delivery of IEM-1460. This suggested that cochlear afferent synapses contain GluA2-lacking CP-AMPARs alongside GluA2-containing Ca2+-impermeable AMPA receptors (CI-AMPARs), and that the former can be antagonized for protection while the latter remain conductive. Here, we investigated hearing function in the guinea pig during acute local or systemic delivery of CP-AMPAR antagonists. Acute intracochlear delivery of IEM-1460 or systemic delivery of IEM-1460 or IEM-1925 reduced the amplitude of the ANF compound action potential (CAP) significantly, for all tone levels and frequencies, by > 50% without affecting CAP thresholds or distortion product otoacoustic emissions (DPOAE). Following systemic dosing, IEM-1460 levels in cochlear perilymph were ~ 30% of blood levels, on average, consistent with pharmacokinetic properties predicting permeation of the compounds into the brain and ear. Both compounds were metabolically stable with half-lives >5 h in vitro, and elimination half-lives in vivo of 118 min (IEM-1460) and 68 min (IEM-1925). Heart rate monitoring and off-target binding assays suggest an enhanced safety profile for IEM-1925 over IEM-1460. Compound potency on CAP reduction (IC50 ~ 73 μM IEM-1460) was consistent with a mixture of GluA2-lacking and GluA2-containing AMPARs. These data strongly imply that cochlear afferent synapses of the guinea pig contain GluA2-lacking CP-AMPARs. We propose these CP-AMPARs may be acutely antagonized with systemic dosing, to protect from glutamate excitotoxicity, while transmission at GluA2-containing AMPARs persists to mediate hearing during the protection.
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Affiliation(s)
- Amit Walia
- Department of Otolaryngology, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
| | - Choongheon Lee
- Department of Otolaryngology, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
| | - Jared Hartsock
- Department of Otolaryngology, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
| | - Shawn S Goodman
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, United States
| | - Roland Dolle
- Department of Biochemistry and Molecular Biophysics, Washington University Center for Drug Discovery, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
| | - Alec N Salt
- Department of Otolaryngology, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
| | - Jeffery T Lichtenhan
- Department of Otolaryngology, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
| | - Mark A Rutherford
- Department of Otolaryngology, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
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33
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Payne SA, Joens MS, Chung H, Skigen N, Frank A, Gattani S, Vaughn K, Schwed A, Nester M, Bhattacharyya A, Iyer G, Davis B, Carlquist J, Patel H, Fitzpatrick JAJ, Rutherford MA. Maturation of Heterogeneity in Afferent Synapse Ultrastructure in the Mouse Cochlea. Front Synaptic Neurosci 2021; 13:678575. [PMID: 34220482 PMCID: PMC8248813 DOI: 10.3389/fnsyn.2021.678575] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 05/11/2021] [Indexed: 12/11/2022] Open
Abstract
Auditory nerve fibers (ANFs) innervating the same inner hair cell (IHC) may have identical frequency tuning but different sound response properties. In cat and guinea pig, ANF response properties correlate with afferent synapse morphology and position on the IHC, suggesting a causal structure-function relationship. In mice, this relationship has not been fully characterized. Here we measured the emergence of synaptic morphological heterogeneities during maturation of the C57BL/6J mouse cochlea by comparing postnatal day 17 (p17, ∼3 days after hearing onset) with p34, when the mouse cochlea is mature. Using serial block face scanning electron microscopy and three-dimensional reconstruction we measured the size, shape, vesicle content, and position of 70 ribbon synapses from the mid-cochlea. Several features matured over late postnatal development. From p17 to p34, presynaptic densities (PDs) and post-synaptic densities (PSDs) became smaller on average (PDs: 0.75 to 0.33; PSDs: 0.58 to 0.31 μm2) and less round as their short axes shortened predominantly on the modiolar side, from 770 to 360 nm. Membrane-associated synaptic vesicles decreased in number from 53 to 30 per synapse from p17 to p34. Anatomical coupling, measured as PSD to ribbon distance, tightened predominantly on the pillar side. Ribbons became less spherical as long-axes lengthened only on the modiolar side of the IHC, from 372 to 541 nm. A decreasing gradient of synaptic ribbon size along the modiolar-pillar axis was detected only at p34 after aligning synapses of adjacent IHCs to a common reference frame (median volumes in nm3 × 106: modiolar 4.87; pillar 2.38). The number of ribbon-associated synaptic vesicles scaled with ribbon size (range 67 to 346 per synapse at p34), thus acquiring a modiolar-pillar gradient at p34, but overall medians were similar at p17 (120) and p34 (127), like ribbon surface area (0.36 vs. 0.34 μm2). PD and PSD morphologies were tightly correlated to each other at individual synapses, more so at p34 than p17, but not to ribbon morphology. These observations suggest that PDs and PSDs mature according to different cues than ribbons, and that ribbon size may be more influenced by cues from the IHC than the surrounding tissue.
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Affiliation(s)
- Shelby A. Payne
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States
| | - Matthew S. Joens
- Center for Cellular Imaging, Washington University in St. Louis, St. Louis, MO, United States
- TESCAN USA, Inc., Warrendale, PA, United States
| | - Heather Chung
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Natalie Skigen
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Adam Frank
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Sonali Gattani
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Kya Vaughn
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Allison Schwed
- Graduate Program in Audiology and Communications Sciences, Washington University School of Medicine, St. Louis, MO, United States
| | - Matt Nester
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Atri Bhattacharyya
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Guhan Iyer
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Bethany Davis
- Graduate Program in Audiology and Communications Sciences, Washington University School of Medicine, St. Louis, MO, United States
| | - Jason Carlquist
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Honey Patel
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - James A. J. Fitzpatrick
- Center for Cellular Imaging, Washington University in St. Louis, St. Louis, MO, United States
- Department of Neuroscience, Washington University School of Medicine, St. Louis, MO, United States
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, United States
- Department of Biomedical Engineering, Washington University School of Medicine, St. Louis, MO, United States
| | - Mark A. Rutherford
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States
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34
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Kitcher SR, Pederson AM, Weisz CJC. Diverse identities and sites of action of cochlear neurotransmitters. Hear Res 2021; 419:108278. [PMID: 34108087 DOI: 10.1016/j.heares.2021.108278] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 04/30/2021] [Accepted: 05/18/2021] [Indexed: 11/18/2022]
Abstract
Accurate encoding of acoustic stimuli requires temporally precise responses to sound integrated with cellular mechanisms that encode the complexity of stimuli over varying timescales and orders of magnitude of intensity. Sound in mammals is initially encoded in the cochlea, the peripheral hearing organ, which contains functionally specialized cells (including hair cells, afferent and efferent neurons, and a multitude of supporting cells) to allow faithful acoustic perception. To accomplish the demanding physiological requirements of hearing, the cochlea has developed synaptic arrangements that operate over different timescales, with varied strengths, and with the ability to adjust function in dynamic hearing conditions. Multiple neurotransmitters interact to support the precision and complexity of hearing. Here, we review the location of release, action, and function of neurotransmitters in the mammalian cochlea with an emphasis on recent work describing the complexity of signaling.
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Affiliation(s)
- Siân R Kitcher
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, United States
| | - Alia M Pederson
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, United States
| | - Catherine J C Weisz
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, United States.
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35
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Primary Neural Degeneration in Noise-Exposed Human Cochleas: Correlations with Outer Hair Cell Loss and Word-Discrimination Scores. J Neurosci 2021; 41:4439-4447. [PMID: 33883202 DOI: 10.1523/jneurosci.3238-20.2021] [Citation(s) in RCA: 59] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 03/23/2021] [Accepted: 03/27/2021] [Indexed: 11/21/2022] Open
Abstract
Animal studies suggest that cochlear nerve degeneration precedes sensory cell degeneration in both noise-induced hearing loss (NIHL) and age-related hearing loss (ARHL), producing a hearing impairment that is not reflected in audiometric thresholds. Here, we investigated the histopathology of human ARHL and NIHL by comparing loss of auditory nerve fibers (ANFs), cochlear hair cells and the stria vascularis in a group of 52 cases with noise-exposure history against an age-matched control group. Although strial atrophy increased with age, there was no effect of noise history. Outer hair cell (OHC) loss also increased with age throughout the cochlea but was unaffected by noise history in the low-frequency region (<2 kHz), while greatly exacerbated at high frequencies (≥2 kHz). Inner hair cell (IHC) loss was primarily seen at high frequencies but was unaffected by noise at either low or high frequencies. ANF loss was substantial at all cochlear frequencies and was exacerbated by noise throughout. According to a multivariable regression model, this loss of neural channels contributes to poor word discrimination among those with similar audiometric threshold losses. The histopathological patterns observed also suggest that, whereas the low-frequency OHC loss may be an unavoidable consequence of aging, the high-frequency loss, which produces the classic down-sloping audiogram of ARHL, may be partially because of avoidable ear abuse, even among those without a documented history of acoustic overexposure.SIGNIFICANCE STATEMENT As regenerative therapeutics in sensorineural hearing loss enter clinical trials, it becomes critical to infer which cochlear pathologies are present in addition to hair cell loss. Here, by analyzing human autopsy material, we show that acoustic injury accelerates age-related primary neural degeneration, but not strial degeneration, neither of which can be inferred from audiometric thresholds. It exacerbates outer hair cell (OHC) loss only in the high-frequency half of the cochlea, suggesting that the apical loss is age-related, whereas the basal loss is partially noise induced, and therefore avoidable. Statistical analysis suggests that neural loss helps explain differences in word-recognition ability among individuals with similar audiometric thresholds. The surprising correlation between neural loss and OHC loss in the cochlea's speech region also implicates neural loss in the well-known decline in word scores as thresholds deteriorate with age.
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36
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Wang H, Wang S, Lu Y, Chen Y, Huang W, Qiu M, Wu H, Hua Y. Cytoarchitecture and innervation of the mouse cochlear amplifier revealed by large-scale volume electron microscopy. J Comp Neurol 2021; 529:2958-2969. [PMID: 33719053 PMCID: PMC8252425 DOI: 10.1002/cne.25137] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 03/02/2021] [Accepted: 03/03/2021] [Indexed: 12/31/2022]
Abstract
In mammalian cochlea, sound‐induced vibration is amplified by a three‐row lattice of Y‐shaped microstructures consisting of electromotile outer hair cell and supporting Deiters cell. This highly organized structure is thought to be essential for hearing of low‐level sounds. Prior studies reported differences in geometry and synaptic innervation of the outer hair cells between rows, but how these fine features are achieved at subcellular level still remains unclear. Using serial block‐face electron microscopy, we acquired few‐hundred‐micron‐sized cytoarchitecture of mouse organ of Corti at nanometer resolution. Structural quantifications were performed on the Y‐shapes as well as afferent and efferent projections to outer hair cells (OHCs). Several new features, which support the previously observed inter‐row heterogeneity, are described. Our result provides structural bases for the gradient of mechanical properties and diverse centrifugal regulation of OHC rows.
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Affiliation(s)
- Haoyu Wang
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai, China.,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China.,Shanghai Institute of Precision Medicine, Shanghai Ninth People's Hospital, Shanghai, China
| | - Shengxiong Wang
- Shanghai Institute of Precision Medicine, Shanghai Ninth People's Hospital, Shanghai, China.,Putuo People's Hospital, Tongji University, Shanghai, China
| | - Yan Lu
- Shanghai Institute of Precision Medicine, Shanghai Ninth People's Hospital, Shanghai, China
| | - Ying Chen
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai, China.,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Wenqing Huang
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai, China.,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China.,Shanghai Institute of Precision Medicine, Shanghai Ninth People's Hospital, Shanghai, China
| | - Miaoxin Qiu
- Putuo People's Hospital, Tongji University, Shanghai, China
| | - Hao Wu
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai, China.,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China.,Shanghai Institute of Precision Medicine, Shanghai Ninth People's Hospital, Shanghai, China
| | - Yunfeng Hua
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai, China.,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China.,Shanghai Institute of Precision Medicine, Shanghai Ninth People's Hospital, Shanghai, China
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37
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Hintze A, Gültas M, Semmelhack EA, Wichmann C. Ultrastructural maturation of the endbulb of Held active zones comparing wild-type and otoferlin-deficient mice. iScience 2021; 24:102282. [PMID: 33851098 PMCID: PMC8022229 DOI: 10.1016/j.isci.2021.102282] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 01/18/2021] [Accepted: 03/03/2021] [Indexed: 11/13/2022] Open
Abstract
Endbulbs of Held are located in the anteroventral cochlear nucleus and present the first central synapses of the auditory pathway. During development, endbulbs mature functionally to enable rapid and powerful synaptic transmission with high temporal precision. This process is accompanied by morphological changes of endbulb terminals. Loss of the hair cell-specific protein otoferlin (Otof) abolishes neurotransmission in the cochlea and results in the smaller endbulb of Held terminals. Thus, peripheral hearing impairment likely also leads to alterations in the morphological synaptic vesicle (SV) pool size at individual endbulb of Held active zones (AZs). Here, we investigated endbulb AZs in pre-hearing, young, and adult wild-type and Otof−/− mice. During maturation, SV numbers at endbulb AZs increased in wild-type mice but were found to be reduced in Otof−/− mice. The SV population at a distance of 0–15 nm was most strongly affected. Finally, overall SV diameters decreased in Otof−/− animals during maturation. Maturation of wt endbulb of Held active zones leads to more synaptic vesicles At endbulbs of otoferlin knockout mice, synaptic vesicles decline with age Mainly two distinct synaptic vesicle populations are affected Synaptic vesicles sizes are reduced in six-month-old otoferlin knockout animals
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Affiliation(s)
- Anika Hintze
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience, InnerEarLab and Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, 37075 Göttingen, Germany.,Collaborative Research Center 1286, University of Göttingen, Göttingen, Germany.,Göttingen Graduate School for Neurosciences, Biophysics and Molecular Biosciences, University of Göttingen, Göttingen, Germany
| | - Mehmet Gültas
- Breeding Informatics Group, Department of Animal Sciences, Georg-August-University Göttingen, Göttingen, Germany
| | - Esther A Semmelhack
- Developmental, Neural, and Behavioral Biology MSc/PhD Program, University of Göttingen, Göttingen, Germany
| | - Carolin Wichmann
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience, InnerEarLab and Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, 37075 Göttingen, Germany.,Collaborative Research Center 1286, University of Göttingen, Göttingen, Germany
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Hua Y, Ding X, Wang H, Wang F, Lu Y, Neef J, Gao Y, Moser T, Wu H. Electron Microscopic Reconstruction of Neural Circuitry in the Cochlea. Cell Rep 2021; 34:108551. [PMID: 33406431 DOI: 10.1016/j.celrep.2020.108551] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 08/25/2020] [Accepted: 12/03/2020] [Indexed: 02/02/2023] Open
Abstract
Recent studies reveal great diversity in the structure, function, and efferent innervation of afferent synaptic connections between the cochlear inner hair cells (IHCs) and spiral ganglion neurons (SGNs), which likely enables audition to process a wide range of sound pressures. By performing an extensive electron microscopic (EM) reconstruction of the neural circuitry in the mature mouse organ of Corti, we demonstrate that afferent SGN dendrites differ in abundance and composition of efferent innervation in a manner dependent on their afferent synaptic connectivity with IHCs. SGNs that sample glutamate release from several presynaptic ribbons receive more efferent innervation from lateral olivocochlear projections than those driven by a single ribbon. Next to the prevailing unbranched SGN dendrites, we found branched SGN dendrites that can contact several ribbons of 1-2 IHCs. Unexpectedly, medial olivocochlear neurons provide efferent innervation of SGN dendrites, preferring those forming single-ribbon, pillar-side synapses. We propose a fine-tuning of afferent and efferent SGN innervation.
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Affiliation(s)
- Yunfeng Hua
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai, China; Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China; Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Department of Connectomics, Max Planck Institute for Brain Research, Frankfurt/Main, Germany.
| | - Xu Ding
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai, China; Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Haoyu Wang
- Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Fangfang Wang
- Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yan Lu
- Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jakob Neef
- Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Yunge Gao
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai, China; Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Tobias Moser
- Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine, Göttingen, Germany; Multiscale Bioimaging Cluster of Excellence, University of Göttingen, Göttingen, Germany.
| | - Hao Wu
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai, China; Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China; Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
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Jeng JY, Carlton A, Johnson SL, Brown SDM, Holley MC, Bowl MR, Marcotti W. Biophysical and morphological changes in inner hair cells and their efferent innervation in the ageing mouse cochlea. J Physiol 2021; 599:269-287. [PMID: 33179774 PMCID: PMC7612127 DOI: 10.1113/jp280256] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 10/01/2020] [Indexed: 09/18/2023] Open
Abstract
KEY POINTS Age-related hearing loss is a progressive hearing loss involving environmental and genetic factors, leading to a decrease in hearing sensitivity, threshold and speech discrimination. We compared age-related changes in inner hair cells (IHCs) between four mouse strains with different levels of progressive hearing loss. The surface area of apical coil IHCs (9-12 kHz cochlear region) decreases by about 30-40% with age. The number of BK channels progressively decreases with age in the IHCs from most mouse strains, but the basolateral membrane current profile remains unchanged. The mechanoelectrical transducer current is smaller in mice harbouring the hypomorphic Cdh23 allele Cdh23ahl (C57BL/6J; C57BL/6NTac), but not in Cdh23-repaired mice (C57BL/6NTacCdh23+ ), indicating that it could contribute to the different progression of hearing loss among mouse strains. The degree of efferent rewiring onto aged IHCs, most likely coming from the lateral olivocochlea fibres, was correlated with hearing loss in the different mouse strains. ABSTRACT Inner hair cells (IHCs) are the primary sensory receptors of the mammalian cochlea, transducing acoustic information into electrical signals that are relayed to the afferent neurons. Functional changes in IHCs are a potential cause of age-related hearing loss. Here, we have investigated the functional characteristics of IHCs from early-onset hearing loss mice harbouring the allele Cdh23ahl (C57BL/6J and C57BL/6NTac), from late-onset hearing loss mice (C3H/HeJ), and from mice corrected for the Cdh23ahl mutation (C57BL/6NTacCdh23+ ) with an intermediate hearing phenotype. There was no significant loss of IHCs in the 9-12 kHz cochlear region up to at least 15 months of age, but their surface area decreased progressively by 30-40% starting from ∼6 months of age. Although the size of the BK current decreased with age, IHCs retained a normal KCNQ4 current and resting membrane potential. These basolateral membrane changes were most severe for C57BL/6J and C57BL/6NTac, less so for C57BL/6NTacCdh23+ and minimal or absent in C3H/HeJ mice. We also found that lateral olivocochlear (LOC) efferent fibres re-form functional axon-somatic connections with aged IHCs, but this was seen only sporadically in C3H/HeJ mice. The efferent post-synaptic SK2 channels appear prior to the establishment of the efferent contacts, suggesting that IHCs may play a direct role in re-establishing the LOC-IHC synapses. Finally, we showed that the size of the mechanoelectrical transducer (MET) current from IHCs decreased significantly with age in mice harbouring the Cdh23ahl allele but not in C57BL/6NTacCdh23+ mice, indicating that the MET apparatus directly contributes to the progression of age-related hearing loss.
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Affiliation(s)
- Jing-Yi Jeng
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Adam Carlton
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Stuart L. Johnson
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
- Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
| | - Steve D. M. Brown
- Mammalian Genetics Unit, MRC Harwell Institute, Oxfordshire, OX11 0RD, UK
| | - Matthew C. Holley
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Michael R. Bowl
- Mammalian Genetics Unit, MRC Harwell Institute, Oxfordshire, OX11 0RD, UK
| | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
- Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
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Cochlear homeostasis: a molecular physiological perspective on maintenance of sound transduction and auditory neurotransmission with noise and ageing. CURRENT OPINION IN PHYSIOLOGY 2020. [DOI: 10.1016/j.cophys.2020.09.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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41
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Carcagno S, Plack CJ. Effects of age on psychophysical measures of auditory temporal processing and speech reception at low and high levels. Hear Res 2020; 400:108117. [PMID: 33253994 PMCID: PMC7812372 DOI: 10.1016/j.heares.2020.108117] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 10/18/2020] [Accepted: 11/17/2020] [Indexed: 01/21/2023]
Abstract
We found little evidence of greater age-related hearing declines at high sound levels. There are age-related temporal-processing declines independent of hearing loss. No evidence of age-related speech-reception deficits independent of hearing loss.
Age-related cochlear synaptopathy (CS) has been shown to occur in rodents with minimal noise exposure, and has been hypothesized to play a crucial role in age-related hearing declines in humans. It is not known to what extent age-related CS occurs in humans, and how it affects the coding of supra-threshold sounds and speech in noise. Because in rodents CS affects mainly low- and medium-spontaneous rate (L/M-SR) auditory-nerve fibers with rate-level functions covering medium-high levels, it should lead to greater deficits in the processing of sounds at high than at low stimulus levels. In this cross-sectional study the performance of 102 listeners across the age range (34 young, 34 middle-aged, 34 older) was assessed in a set of psychophysical temporal processing and speech reception in noise tests at both low, and high stimulus levels. Mixed-effect multiple regression models were used to estimate the effects of age while partialing out effects of audiometric thresholds, lifetime noise exposure, cognitive abilities (assessed with additional tests), and musical experience. Age was independently associated with performance deficits on several tests. However, only for one out of 13 tests were age effects credibly larger at the high compared to the low stimulus level. Overall these results do not provide much evidence that age-related CS, to the extent to which it may occur in humans according to the rodent model of greater L/M-SR synaptic loss, has substantial effects on psychophysical measures of auditory temporal processing or on speech reception in noise.
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Affiliation(s)
- Samuele Carcagno
- Department of Psychology, Lancaster University, Lancaster, LA1 4YF, United Kingdom.
| | - Christopher J Plack
- Department of Psychology, Lancaster University, Lancaster, LA1 4YF, United Kingdom; Manchester Centre for Audiology and Deafness, University of Manchester, Academic Health Science Centre, M13 9PL, United Kingdom
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Voorn RA, Vogl C. Molecular Assembly and Structural Plasticity of Sensory Ribbon Synapses-A Presynaptic Perspective. Int J Mol Sci 2020; 21:E8758. [PMID: 33228215 PMCID: PMC7699581 DOI: 10.3390/ijms21228758] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 11/16/2020] [Accepted: 11/17/2020] [Indexed: 12/13/2022] Open
Abstract
In the mammalian cochlea, specialized ribbon-type synapses between sensory inner hair cells (IHCs) and postsynaptic spiral ganglion neurons ensure the temporal precision and indefatigability of synaptic sound encoding. These high-through-put synapses are presynaptically characterized by an electron-dense projection-the synaptic ribbon-which provides structural scaffolding and tethers a large pool of synaptic vesicles. While advances have been made in recent years in deciphering the molecular anatomy and function of these specialized active zones, the developmental assembly of this presynaptic interaction hub remains largely elusive. In this review, we discuss the dynamic nature of IHC (pre-) synaptogenesis and highlight molecular key players as well as the transport pathways underlying this process. Since developmental assembly appears to be a highly dynamic process, we further ask if this structural plasticity might be maintained into adulthood, how this may influence the functional properties of a given IHC synapse and how such plasticity could be regulated on the molecular level. To do so, we take a closer look at other ribbon-bearing systems, such as retinal photoreceptors and pinealocytes and aim to infer conserved mechanisms that may mediate these phenomena.
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MESH Headings
- Alcohol Oxidoreductases/genetics
- Alcohol Oxidoreductases/metabolism
- Animals
- Co-Repressor Proteins/genetics
- Co-Repressor Proteins/metabolism
- Cytoskeletal Proteins/genetics
- Cytoskeletal Proteins/metabolism
- Cytoskeleton/metabolism
- Cytoskeleton/ultrastructure
- Gene Expression Regulation, Developmental
- Hair Cells, Auditory, Inner/metabolism
- Hair Cells, Auditory, Inner/ultrastructure
- Hair Cells, Auditory, Outer/metabolism
- Hair Cells, Auditory, Outer/ultrastructure
- Hair Cells, Vestibular/metabolism
- Hair Cells, Vestibular/ultrastructure
- Mechanotransduction, Cellular
- Mice
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/metabolism
- Neuronal Plasticity/genetics
- Neuropeptides/genetics
- Neuropeptides/metabolism
- Rats
- Synapses/metabolism
- Synapses/ultrastructure
- Synaptic Transmission/genetics
- Synaptic Vesicles/metabolism
- Synaptic Vesicles/ultrastructure
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Affiliation(s)
- Roos Anouk Voorn
- Presynaptogenesis and Intracellular Transport in Hair Cells Junior Research Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Goettingen, 37075 Goettingen, Germany;
- Göttingen Graduate Center for Neurosciences, Biophysics and Molecular Biosciences, 37075 Goettingen, Germany
- Collaborative Research Center 889 “Cellular Mechanisms of Sensory Processing”, 37075 Goettingen, Germany
| | - Christian Vogl
- Presynaptogenesis and Intracellular Transport in Hair Cells Junior Research Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Goettingen, 37075 Goettingen, Germany;
- Collaborative Research Center 889 “Cellular Mechanisms of Sensory Processing”, 37075 Goettingen, Germany
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Wood MB, Nowak N, Mull K, Goldring A, Lehar M, Fuchs PA. Acoustic Trauma Increases Ribbon Number and Size in Outer Hair Cells of the Mouse Cochlea. J Assoc Res Otolaryngol 2020; 22:19-31. [PMID: 33151428 PMCID: PMC7822997 DOI: 10.1007/s10162-020-00777-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 10/19/2020] [Indexed: 01/01/2023] Open
Abstract
Outer hair cells (OHCs) in the mouse cochlea are contacted by up to three type II afferent boutons. On average, only half of these are postsynaptic to presynaptic ribbons. Mice of both sexes were subjected to acoustic trauma that produced a threshold shift of 44.2 ± 9.1 dB 7 days after exposure. Ribbon synapses of OHCs were quantified in post-trauma and littermate controls using immunolabeling of CtBP2. Visualization with virtual reality was used to determine 3-D cytoplasmic localization of CtBP2 puncta to the synaptic pole of OHCs. Acoustic trauma was associated with a statistically significant increase in the number of synaptic ribbons per OHC. Serial section TEM was carried out on similarly treated mice. This also showed a significant increase in the number of ribbons in post-trauma OHCs, as well as a significant increase in ribbon volume compared to ribbons in control OHCs. An increase in OHC ribbon synapses after acoustic trauma is a novel observation that has implications for OHC:type II afferent signaling. A mathematical model showed that the observed increase in OHC ribbons considered alone could produce a significant increase in action potentials among type II afferent neurons during strong acoustic stimulation.
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Affiliation(s)
- Megan B Wood
- Department of Otolaryngology - Head and Neck, Surgery, Johns Hopkins University School of Medicine, 820 Richard Starr Ross Research Building, 720 Rutland Ave, Baltimore, MD, 21205, USA.
| | - Nathaniel Nowak
- Department of Otolaryngology - Head and Neck, Surgery, Johns Hopkins University School of Medicine, 820 Richard Starr Ross Research Building, 720 Rutland Ave, Baltimore, MD, 21205, USA
| | - Keira Mull
- Department of Otolaryngology - Head and Neck, Surgery, Johns Hopkins University School of Medicine, 820 Richard Starr Ross Research Building, 720 Rutland Ave, Baltimore, MD, 21205, USA
| | - Adam Goldring
- Department of Otolaryngology - Head and Neck, Surgery, Johns Hopkins University School of Medicine, 820 Richard Starr Ross Research Building, 720 Rutland Ave, Baltimore, MD, 21205, USA.,Sutter Instrument, Co. 1 Digital Drive, Novato, CA, 94949, USA
| | - Mohamed Lehar
- Department of Otolaryngology - Head and Neck, Surgery, Johns Hopkins University School of Medicine, 820 Richard Starr Ross Research Building, 720 Rutland Ave, Baltimore, MD, 21205, USA
| | - Paul Albert Fuchs
- Department of Otolaryngology - Head and Neck, Surgery, Johns Hopkins University School of Medicine, 820 Richard Starr Ross Research Building, 720 Rutland Ave, Baltimore, MD, 21205, USA
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44
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Carcagno S, Plack CJ. Effects of age on electrophysiological measures of cochlear synaptopathy in humans. Hear Res 2020; 396:108068. [PMID: 32979760 PMCID: PMC7593961 DOI: 10.1016/j.heares.2020.108068] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 08/11/2020] [Accepted: 08/31/2020] [Indexed: 12/19/2022]
Abstract
Age-related cochlear synaptopathy (CS) has been shown to occur in rodents with minimal noise exposure, and has been hypothesized to play a crucial role in age-related hearing declines in humans. Because CS affects mainly low-spontaneous rate auditory nerve fibers, differential electrophysiological measures such as the ratio of the amplitude of wave I of the auditory brainstem response (ABR) at high to low click levels (WIH/WIL), and the difference between frequency following response (FFR) levels to shallow and deep amplitude modulated tones (FFRS-FFRD), have been proposed as CS markers. However, age-related audiometric threshold shifts, particularly prominent at high frequencies, may confound the interpretation of these measures in cross-sectional studies of age-related CS. To address this issue, we measured WIH/WIL and FFRS-FFRD using highpass masking (HP) noise to eliminate the contribution of high-frequency cochlear regions to the responses in a cross-sectional sample of 102 subjects (34 young, 34 middle-aged, 34 older). WIH/WIL in the presence of the HP noise did not decrease as a function of age. However, in the absence of HP noise, WIH/WIL showed credible age-related decreases even after partialing out the effects of audiometric threshold shifts. No credible age-related decreases of FFRS-FFRD were found. Overall, the results do not provide evidence of age-related CS in the low-frequency region where the responses were restricted by the HP noise, but are consistent with the presence of age-related CS in higher frequency regions.
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Affiliation(s)
- Samuele Carcagno
- Department of Psychology, Lancaster University, Lancaster, LA1 4YF, United Kingdom.
| | - Christopher J Plack
- Department of Psychology, Lancaster University, Lancaster, LA1 4YF, United Kingdom; Manchester Centre for Audiology and Deafness, University of Manchester, Manchester Academic Health Science Centre, M13 9PL, United Kingdom
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45
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Kobrina A, Schrode KM, Screven LA, Javaid H, Weinberg MM, Brown G, Board R, Villavisanis DF, Dent ML, Lauer AM. Linking anatomical and physiological markers of auditory system degeneration with behavioral hearing assessments in a mouse (Mus musculus) model of age-related hearing loss. Neurobiol Aging 2020; 96:87-103. [PMID: 32950782 DOI: 10.1016/j.neurobiolaging.2020.08.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2020] [Revised: 08/03/2020] [Accepted: 08/19/2020] [Indexed: 12/13/2022]
Abstract
Age-related hearing loss is a very common sensory disability, affecting one in three older adults. Establishing a link between anatomical, physiological, and behavioral markers of presbycusis in a mouse model can improve the understanding of this disorder in humans. We measured age-related hearing loss for a variety of acoustic signals in quiet and noisy environments using an operant conditioning procedure and investigated the status of peripheral structures in CBA/CaJ mice. Mice showed the greatest degree of hearing loss in the last third of their lifespan, with higher thresholds in noisy than in quiet conditions. Changes in auditory brainstem response thresholds and waveform morphology preceded behavioral hearing loss onset. Loss of hair cells, auditory nerve fibers, and signs of stria vascularis degeneration were observed in old mice. The present work underscores the difficulty in ascribing the primary cause of age-related hearing loss to any particular type of cellular degeneration. Revealing these complex structure-function relationships is critical for establishing successful intervention strategies to restore hearing or prevent presbycusis.
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Affiliation(s)
| | - Katrina M Schrode
- Department of Otolaryngology-Head and Neck Surgery and Center for Hearing and Balance, Johns Hopkins University, Baltimore, MD, USA
| | - Laurel A Screven
- Department of Otolaryngology-Head and Neck Surgery and Center for Hearing and Balance, Johns Hopkins University, Baltimore, MD, USA
| | - Hamad Javaid
- Department of Otolaryngology-Head and Neck Surgery and Center for Hearing and Balance, Johns Hopkins University, Baltimore, MD, USA
| | - Madison M Weinberg
- Department of Otolaryngology-Head and Neck Surgery and Center for Hearing and Balance, Johns Hopkins University, Baltimore, MD, USA
| | - Garrett Brown
- Department of Otolaryngology-Head and Neck Surgery and Center for Hearing and Balance, Johns Hopkins University, Baltimore, MD, USA
| | - Ryleigh Board
- Department of Otolaryngology-Head and Neck Surgery and Center for Hearing and Balance, Johns Hopkins University, Baltimore, MD, USA
| | - Dillan F Villavisanis
- Department of Otolaryngology-Head and Neck Surgery and Center for Hearing and Balance, Johns Hopkins University, Baltimore, MD, USA
| | - Micheal L Dent
- Department of Psychology, University at Buffalo SUNY, Buffalo, NY, USA
| | - Amanda M Lauer
- Department of Otolaryngology-Head and Neck Surgery and Center for Hearing and Balance, Johns Hopkins University, Baltimore, MD, USA.
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46
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Jeng JY, Ceriani F, Olt J, Brown SDM, Holley MC, Bowl MR, Johnson SL, Marcotti W. Pathophysiological changes in inner hair cell ribbon synapses in the ageing mammalian cochlea. J Physiol 2020; 598:4339-4355. [PMID: 32710572 DOI: 10.1113/jp280018] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 07/24/2020] [Indexed: 12/16/2022] Open
Abstract
KEY POINTS Age-related hearing loss (ARHL) is associated with the loss of inner hair cell (IHC) ribbon synapses, lower hearing sensitivity and decreased ability to understand speech, especially in a noisy environment. Little is known about the age-related physiological and morphological changes that occur at ribbon synapses. We show that the differing degrees of ARHL in four selected mouse stains is correlated with the loss of ribbon synapses, being most severe for the strains C57BL/6NTac and C57BL/6J, less so for C57BL/6NTacCdh23+ -Repaired and lowest for C3H/HeJ. Despite the loss of ribbon synapses with age, the volume of the remaining ribbons increased and the size and kinetics of Ca2+ -dependent exocytosis in IHCs was unaffected, indicating the presence of a previously unknown degree of functional compensation at ribbon synapses. Although the age-related morphological changes at IHC ribbon synapses contribute to the different progression of ARHL, without the observed functional compensation hearing loss could be greater. ABSTRACT Mammalian cochlear inner hair cells (IHCs) are specialized sensory receptors able to provide dynamic coding of sound signals. This ability is largely conferred by their ribbon synapses, which tether a large number of vesicles at the IHC's presynaptic active zones, allowing high rates of sustained synaptic transmission onto the afferent fibres. How the physiological and morphological properties of ribbon synapses change with age remains largely unknown. Here, we have investigated the biophysical and morphological properties of IHC ribbon synapses in the ageing cochlea (9-12 kHz region) of four mouse strains commonly used in hearing research: early-onset progressive hearing loss (C57BL/6J and C57BL/6NTac) and 'good hearing' strains (C57BL/6NTacCdh23+ and C3H/HeJ). We found that with age, both modiolar and pillar sides of the IHC exhibited a loss of ribbons, but there was an increased volume of those that remained. These morphological changes, which only occurred after 6 months of age, were correlated with the level of hearing loss in the different mouse strains, being most severe for C57BL/6NTac and C57BL/6J, less so for C57BL/6NTacCdh23+ and absent for C3H/HeJ strains. Despite the age-related reduction in ribbon number in three of the four strains, the size and kinetics of Ca2+ -dependent exocytosis, as well as the replenishment of synaptic vesicles, in IHCs was not affected. The degree of vesicle release at the fewer, but larger, individual remaining ribbon synapses colocalized with the post-synaptic afferent terminals is likely to increase, indicating the presence of a previously unknown degree of functional compensation in the ageing mouse cochlea.
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Affiliation(s)
- Jing-Yi Jeng
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK.,Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
| | - Federico Ceriani
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK.,Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
| | - Jennifer Olt
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Steve D M Brown
- Mammalian Genetics Unit, MRC Harwell Institute, Oxfordshire, UK
| | - Matthew C Holley
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Michael R Bowl
- Mammalian Genetics Unit, MRC Harwell Institute, Oxfordshire, UK
| | - Stuart L Johnson
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK.,Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
| | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK.,Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
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Yuan X, Liu H, Li Y, Li W, Yu H, Shen X. Ribbon Synapses and Hearing Impairment in Mice After in utero Sevoflurane Exposure. DRUG DESIGN DEVELOPMENT AND THERAPY 2020; 14:2685-2693. [PMID: 32753847 PMCID: PMC7354911 DOI: 10.2147/dddt.s253031] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 06/18/2020] [Indexed: 12/12/2022]
Abstract
Introduction In utero, exposure to sevoflurane (a commonly used inhalation anesthetic) can lead to hearing impairment in offspring mice, but the underlying impairment mechanism is not known. Materials and Methods Day-15 pregnant mice were treated with 2.5% sevoflurane for 2 h to investigate sevoflurane ototoxicity. Cochleae from offspring mice were harvested for hair-cell and ribbon-synapse assessments. Hearing in offspring mice was assessed at postnatal day 30 using an auditory brainstem-response (ABR) test. Cochlear-explant cultures from offspring mice were exposed to 2.5% sevoflurane for 6 h. Immediately after treatment, explants were assessed for hair-cell morphology, mitochondrial oxidative stress, and autophagy. Results In utero, sevoflurane exposure impaired hearing in the offspring is demonstrated by a decrease in ABR wave I amplitudes, a marker for ribbon-synapse functionality. Sevoflurane exposure caused no obvious damage to hair cells, but cochlear ribbon synapses were reduced in postnatal day 15 offspring, and partially recovered by postnatal day 30. Sevoflurane treatment also increased mitochondrial reactive-oxygen species stress and decreased autophagy in the cochlear explants. Conclusion These results suggest that oxidative stress and reduced autophagy may underly ribbon-synapse involvement in sevoflurane-induced hearing loss.
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Affiliation(s)
- Xia Yuan
- Department of Anesthesiology, Shanghai Eye, Ear, Nose, and Throat Hospital, Fudan University, Shanghai 200031, People's Republic of China
| | - Hongjun Liu
- Department of Anesthesiology, Shanghai Eye, Ear, Nose, and Throat Hospital, Fudan University, Shanghai 200031, People's Republic of China
| | - Yufeng Li
- Department of Anesthesiology, Shanghai Eye, Ear, Nose, and Throat Hospital, Fudan University, Shanghai 200031, People's Republic of China
| | - Wen Li
- Research Center, Shanghai Eye, Ear, Nose, and Throat Hospital, Fudan University, Shanghai 200031, People's Republic of China
| | - Huiqian Yu
- Department of Otorhinolaryngology, Shanghai Eye, Ear, Nose, and Throat Hospital, Fudan University, Shanghai 200031, People's Republic of China
| | - Xia Shen
- Department of Anesthesiology, Shanghai Eye, Ear, Nose, and Throat Hospital, Fudan University, Shanghai 200031, People's Republic of China
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Preventing presbycusis in mice with enhanced medial olivocochlear feedback. Proc Natl Acad Sci U S A 2020; 117:11811-11819. [PMID: 32393641 DOI: 10.1073/pnas.2000760117] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
"Growing old" is the most common cause of hearing loss. Age-related hearing loss (ARHL) (presbycusis) first affects the ability to understand speech in background noise, even when auditory thresholds in quiet are normal. It has been suggested that cochlear denervation ("synaptopathy") is an early contributor to age-related auditory decline. In the present work, we characterized age-related cochlear synaptic degeneration and hair cell loss in mice with enhanced α9α10 cholinergic nicotinic receptors gating kinetics ("gain of function" nAChRs). These mediate inhibitory olivocochlear feedback through the activation of associated calcium-gated potassium channels. Cochlear function was assessed via distortion product otoacoustic emissions and auditory brainstem responses. Cochlear structure was characterized in immunolabeled organ of Corti whole mounts using confocal microscopy to quantify hair cells, auditory neurons, presynaptic ribbons, and postsynaptic glutamate receptors. Aged wild-type mice had elevated acoustic thresholds and synaptic loss. Afferent synapses were lost from inner hair cells throughout the aged cochlea, together with some loss of outer hair cells. In contrast, cochlear structure and function were preserved in aged mice with gain-of-function nAChRs that provide enhanced olivocochlear inhibition, suggesting that efferent feedback is important for long-term maintenance of inner ear function. Our work provides evidence that olivocochlear-mediated resistance to presbycusis-ARHL occurs via the α9α10 nAChR complexes on outer hair cells. Thus, enhancement of the medial olivocochlear system could be a viable strategy to prevent age-related hearing loss.
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Han S, Du Z, Liu K, Gong S. Nicotinamide riboside protects noise-induced hearing loss by recovering the hair cell ribbon synapses. Neurosci Lett 2020; 725:134910. [PMID: 32171805 DOI: 10.1016/j.neulet.2020.134910] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 02/18/2020] [Accepted: 03/10/2020] [Indexed: 12/16/2022]
Abstract
OBJECTIVE Nicotinamide riboside (NR) has been proved to protect the hearing. To achieve animal models of temporary threshold shift (TTS) and permanent threshold shift (PTS) respectively, evaluate the dynamic change of ribbon synapse before and after NR administration. METHODS Mice were divided into control group, noise exposure (NE) group and NR group. The noise was exposed to NE and NR group, and NR was injected before noise exposure. Auditory brainstem response (ABR), ribbon synapse count and cochlear morphology were tested, as well as the concentration of hydrogen peroxide (H2O2) and ATP. RESULTS Ribbon synapse count decrease with the intensity of noise exposure, and the cochlear morphology remains stable during TTS and was damaged during PTS. NR promotes the oxidation resistance to protect the synapse and the inner ear morphology. CONCLUSION Our findings suggest that TTS mice are more vulnerable to noise, and NR can promote the recovery of the synapse count to protect the animals' hearing.
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Affiliation(s)
- Shuguang Han
- Department of Otolaryngology Head and Neck Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China.
| | - Zhengde Du
- Department of Otolaryngology Head and Neck Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China.
| | - Ke Liu
- Department of Otolaryngology Head and Neck Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China.
| | - Shusheng Gong
- Department of Otolaryngology Head and Neck Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China.
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Garrett M, Verhulst S. Applicability of subcortical EEG metrics of synaptopathy to older listeners with impaired audiograms. Hear Res 2019; 380:150-165. [DOI: 10.1016/j.heares.2019.07.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 06/24/2019] [Accepted: 07/01/2019] [Indexed: 01/12/2023]
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