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Humes LE. Hearing thresholds for "otologically normal" adults from the National Health and Nutrition Examination Surveys 2011-12 and 2015-16. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2023; 154:2512-2529. [PMID: 37870931 DOI: 10.1121/10.0021339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2023] [Accepted: 09/25/2023] [Indexed: 10/25/2023]
Abstract
Hearing threshold levels (HTLs) get worse with advancing age in adults. Publications of nationally representative data from U.S. adults have been confined to HTLs from unscreened individuals. ISO 7029:2017 provides equations for the hearing loss of adults of various ages. Equations were generated from a synthesis of international studies of HTLs for "otologically normal" or screened adults. No nationally representative data for screened U.S. adults were included in the ISO synthesis. This study investigated three different levels of screening rigor, referred to here as Screened, Screened+, and Screened++. Median HTLs are provided for Screened (N = 1545) and Screened++ (N = 795) groups from the National Health and Nutrition Examination Surveys for 2011-12 and 2015-16, the two most recent surveys of adults from 20 to 69 years of age with audiograms. Median HTLs from the Screened and Screened++ groups differed slightly between the sexes, were not affected by race/ethnicity, and increased substantially with age. For young adults, there were no differences in HTLs between screened (any level) and unscreened adults, but such differences in HTLs increased with advancing age, especially at higher frequencies. The default power-function model from ISO 7029:2017 did not provide a good description of the median age-associated HTLs from screened U.S. adults.
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Affiliation(s)
- Larry E Humes
- Department of Speech, Language, and Hearing Sciences, Indiana University, Bloomington, Indiana 47405, USA
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2
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Hoppe U, Hast A, Hocke T. Speech Perception in Bilateral Hearing Aid Users With Different Grades of Asymmetric Hearing Loss. Front Neurosci 2022; 15:715660. [PMID: 35153651 PMCID: PMC8826244 DOI: 10.3389/fnins.2021.715660] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 12/07/2021] [Indexed: 11/27/2022] Open
Abstract
Hearing loss is associated with decreased speech perception as well as with changes in the auditory pathway. The effects of those changes on binaural speech perception with hearing aids are not yet fully understood. To provide further evidence on the functional changes of the auditory pathway, several speech perception tests (unilateral and bilateral, aided and unaided, in quiet, and in noise) were conducted in a population of 370 bilateral hearing aid users covering the entire range of the World Health Organization’s most recent classification of hearing loss. To characterize the effects of asymmetric hearing thresholds, a generalized linear model was used for regression analysis. The model revealed a detrimental effect of the poorer ears’ thresholds on both the unaided and the aided unilateral word recognition scores that were attained by the better ear. Moreover, aided binaural word recognition (in quiet and in noise) was affected to a degree that cannot be explained on the sole basis of bilateral summation. Thus, this study provides evidence that there is reorganization and altered functioning of the afferent and efferent auditory pathways due to asymmetric hearing loss. Consequently, more attention should be paid to provision with a hearing aid as early as possible, and separately for each ear.
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Affiliation(s)
- Ulrich Hoppe
- Department of Audiology, ENT-Clinic, University of Erlangen-Nürnberg, Erlangen, Germany
- *Correspondence: Ulrich Hoppe,
| | - Anne Hast
- Department of Audiology, ENT-Clinic, University of Erlangen-Nürnberg, Erlangen, Germany
| | - Thomas Hocke
- Cochlear Deutschland GmbH & Co. KG, Hanover, Germany
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3
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Zhang L, Chen S, Sun Y. Mechanism and Prevention of Spiral Ganglion Neuron Degeneration in the Cochlea. Front Cell Neurosci 2022; 15:814891. [PMID: 35069120 PMCID: PMC8766678 DOI: 10.3389/fncel.2021.814891] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Accepted: 12/09/2021] [Indexed: 12/14/2022] Open
Abstract
Sensorineural hearing loss (SNHL) is one of the most prevalent sensory deficits in humans, and approximately 360 million people worldwide are affected. The current treatment option for severe to profound hearing loss is cochlear implantation (CI), but its treatment efficacy is related to the survival of spiral ganglion neurons (SGNs). SGNs are the primary sensory neurons, transmitting complex acoustic information from hair cells to second-order sensory neurons in the cochlear nucleus. In mammals, SGNs have very limited regeneration ability, and SGN loss causes irreversible hearing loss. In most cases of SNHL, SGN damage is the dominant pathogenesis, and it could be caused by noise exposure, ototoxic drugs, hereditary defects, presbycusis, etc. Tremendous efforts have been made to identify novel treatments to prevent or reverse the damage to SGNs, including gene therapy and stem cell therapy. This review summarizes the major causes and the corresponding mechanisms of SGN loss and the current protection strategies, especially gene therapy and stem cell therapy, to promote the development of new therapeutic methods.
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Affiliation(s)
- Li Zhang
- Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Sen Chen
- Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yu Sun
- Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- Institute of Otorhinolaryngology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- *Correspondence: Yu Sun,
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Le Prell CG. Investigational Medicinal Products for the Inner Ear: Review of Clinical Trial Characteristics in ClinicalTrials.gov. J Am Acad Audiol 2021; 32:670-694. [PMID: 35609594 PMCID: PMC9129919 DOI: 10.1055/s-0041-1735522] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Accepted: 07/21/2020] [Indexed: 12/24/2022]
Abstract
BACKGROUND The previous 30 years have provided information on the mechanisms of cell death in the inner ear after noise exposure, ototoxic drug injury, and during aging, and clinical trials have emerged for all of these acquired forms of hearing loss. Sudden hearing loss is less well understood, but restoration of hearing after sudden hearing loss is also a long-standing drug target, typically using steroids as an intervention but with other agents of interest as well. PURPOSE The purpose of this review was to describe the state of the science regarding clinical testing of investigational medicinal products for the inner ear with respect to treatment or prevention of acquired hearing loss. DATA COLLECTION AND ANALYSIS Comprehensive search and summary of clinical trials listed in the National Library of Medicine (www. CLINICALTRIALS gov) database identified 61 clinical trials. RESULTS Study phase, status, intervention, and primary, secondary, and other outcomes are summarized for studies assessing prevention of noise-induced hearing loss, prevention of drug-induced hearing loss, treatment of stable sensorineural hearing loss, and treatment of sudden sensorineural hearing loss. CONCLUSION This review provides a comprehensive summary of the state of the science with respect to investigational medicinal products for the inner ear evaluated in human clinical trials, and the current challenges for the field.
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MESH Headings
- Cell Death/drug effects
- Cell Death/physiology
- Deafness/chemically induced
- Deafness/drug therapy
- Deafness/prevention & control
- Ear, Inner/pathology
- Hearing Loss, Noise-Induced/drug therapy
- Hearing Loss, Noise-Induced/pathology
- Hearing Loss, Noise-Induced/prevention & control
- Hearing Loss, Sensorineural/chemically induced
- Hearing Loss, Sensorineural/drug therapy
- Hearing Loss, Sensorineural/pathology
- Hearing Loss, Sensorineural/prevention & control
- Hearing Loss, Sudden/chemically induced
- Hearing Loss, Sudden/drug therapy
- Hearing Loss, Sudden/pathology
- Hearing Loss, Sudden/prevention & control
- Humans
- United States
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Affiliation(s)
- Colleen G. Le Prell
- Department of Speech, Language, and Hearing, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas
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Ca v3.2 T-Type Calcium Channels Are Physiologically Mandatory for the Auditory System. Neuroscience 2019; 409:81-100. [PMID: 31029730 DOI: 10.1016/j.neuroscience.2019.04.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2018] [Revised: 04/11/2019] [Accepted: 04/12/2019] [Indexed: 02/07/2023]
Abstract
Voltage-gated Ca2+ channels (VGCCs) play key roles in auditory perception and information processing within the inner ear and brainstem. Pharmacological inhibition of low voltage-activated (LVA) T-type Ca2+ channels is related to both age- and noise induced hearing loss in experimental animals and may represent a promising approach to the treatment of auditory impairment of various etiologies. Within the LVA Ca2+ channel subgroup, Cav3.2 is the most prominently expressed T-type channel entity in the cochlea and auditory brainstem. Thus, we performed a complete gender specific click and tone burst based auditory brainstem response (ABR) analysis of Cav3.2+/- and Cav3.2-/- mice, including i.a. temporal progression in hearing loss, amplitude growth function and wave latency analysis as well as a cochlear qPCR based evaluation of other VGCCs transcripts. Our results, based on a self-programmed automated wavelet approach, demonstrate that both heterozygous and Cav3.2 null mutant mice exhibit age-dependent increases in hearing thresholds at 5 months of age. In addition, complex alterations in WI-IV amplitudes and latencies were detected that were not attributable to alterations in the expression of other VGCCs in the auditory tract. Our results clearly demonstrate the important physiological role of Cav3.2 VGCCs in the spatiotemporal organization of auditory processing in young adult mice and suggest potential pharmacological targets for interventions in the future.
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Structural changes in thestrial blood-labyrinth barrier of aged C57BL/6 mice. Cell Tissue Res 2015; 361:685-96. [PMID: 25740201 DOI: 10.1007/s00441-015-2147-2] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 11/17/2014] [Indexed: 12/20/2022]
Abstract
Tight control over cochlear blood flow (CoBF) and the blood-labyrinth barrier (BLB) in the striavascularis is critical for maintaining the ionic, fluid and energy balance necessary for hearing function. Inefficient CoBF and disruption of BLB integrity have long been considered major etiologic factors in a variety of hearing disorders. In this study, we investigate structural changes in the BLB of the striavascularis in age-graded C57BL/6 mice (1 to 21 months) with a focus on changes in two blood barrier accessory cells, namely pericytes (PCs) and perivascular-resident macrophage-like melanocytes (PVM/Ms). Decreased capillary density was detectable at 6 months, with significant capillary degeneration seen in 9- to 21-month-old mice. Reduced capillary density was highly correlated with lower numbers of PCs and PVM/Ms. "Drop-out" of PCs and "activation" of PVM/Ms were seen at 6 months, with drastic changes being observed by 21 months. With newly established in vitro three-dimensional cell-based co-culture models, we demonstrate that PCs and PVM/Ms are essential for maintaining cochlear vascular architecture and stability.
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Skjönsberg Å, Duan M, Johnson AC, Ulfendahl M. Effect of auditory stress agents on heterozygous German waltzing guinea pigs. J Otol 2014. [DOI: 10.1016/j.joto.2015.03.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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Zhang Q, Liu H, Soukup GA, He DZZ. Identifying microRNAs involved in aging of the lateral wall of the cochlear duct. PLoS One 2014; 9:e112857. [PMID: 25405349 PMCID: PMC4236067 DOI: 10.1371/journal.pone.0112857] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Accepted: 10/16/2014] [Indexed: 02/07/2023] Open
Abstract
Age-related hearing loss is a progressive sensorineural hearing loss that occurs during aging. Degeneration of the organ of Corti and atrophy of the lateral wall of the cochlear duct (or scala media) in the inner ear are the two primary causes. MicroRNAs (miRNAs), a class of short non-coding RNAs that regulate the expression of mRNA/protein targets, are important regulators of cellular senescence and aging. We examined miRNA gene expression profiles in the lateral wall of two mouse strains, along with exploration of the potential targets of those miRNAs that showed dynamic expression during aging. We show that 95 and 60 miRNAs exhibited differential expression in C57 and CBA mice during aging, respectively. A majority of downregulated miRNAs are known to regulate pathways of cell proliferation and differentiation, while all upregulated miRNAs are known regulators in the pro-apoptotic pathways. By using apoptosis-related gene array and bioinformatic approaches to predict miRNA targets, we identify candidate miRNA-regulated genes that regulate apoptosis pathways in the lateral wall of C57 and CBA mice during aging.
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Affiliation(s)
- Qian Zhang
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska, United States of America
| | - Huizhan Liu
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska, United States of America
| | - Garrett A. Soukup
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska, United States of America
- * E-mail: (GS); (DH)
| | - David Z. Z. He
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska, United States of America
- * E-mail: (GS); (DH)
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Mannström P, Ulfhake B, Kirkegaard M, Ulfendahl M. Dietary restriction reduces age-related degeneration of stria vascularis in the inner ear of the rat. Exp Gerontol 2013; 48:1173-9. [DOI: 10.1016/j.exger.2013.07.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 06/13/2013] [Accepted: 07/09/2013] [Indexed: 10/26/2022]
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Humes LE, Busey TA, Craig J, Kewley-Port D. Are age-related changes in cognitive function driven by age-related changes in sensory processing? Atten Percept Psychophys 2013; 75:508-24. [PMID: 23254452 PMCID: PMC3617348 DOI: 10.3758/s13414-012-0406-9] [Citation(s) in RCA: 154] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Although there has been keen interest in the association among measures of sensory function and cognitive function for many years, in general, measures of sensory function have been confined to one or two senses and measures of threshold sensitivity (acuity). In this study, rigorous psychophysical measures of threshold sensitivity, temporal gap detection, temporal order identification, and temporal masking have been obtained, in hearing, vision, and touch. In addition, all subjects completed 15 subtests of the Wechsler Adult Intelligence Scale, 3rd edition (WAIS-III). Data were obtained from 245 adults (18-87 years old) for the WAIS-III and for 40 measures of threshold sensitivity and temporal processing. The focus in this report is on individual differences in performance for the entire data set. Principal-components (PC) factor analysis reduced the 40 psychophysical measures to eight correlated factors, which were reduced further to a single global sensory processing factor. Similarly, PC factor analysis of the 15 WAIS-III scores resulted in three correlated factors that were further reduced to a single global cognitive function factor. Age, global sensory processing, and global cognitive function were all moderately and significantly correlated with one another. However, paired partial correlations, controlling for the third of these three measures, revealed that the moderate correlation between age and global cognitive function went to zero when global sensory processing was controlled for; the other two partial correlations remained intact. Structural models confirmed this result. These analyses suggest that the long-standing observation of age-related changes in cognitive function may be mediated by age-related changes in global sensory processing.
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Affiliation(s)
- Larry E Humes
- Department of Speech & Hearing Sciences, Indiana University, Bloomington, IN 47405-7002, USA.
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11
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Humes LE, Dubno JR, Gordon-Salant S, Lister JJ, Cacace AT, Cruickshanks KJ, Gates GA, Wilson RH, Wingfield A. Central presbycusis: a review and evaluation of the evidence. J Am Acad Audiol 2012; 23:635-66. [PMID: 22967738 DOI: 10.3766/jaaa.23.8.5] [Citation(s) in RCA: 238] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND The authors reviewed the evidence regarding the existence of age-related declines in central auditory processes and the consequences of any such declines for everyday communication. PURPOSE This report summarizes the review process and presents its findings. DATA COLLECTION AND ANALYSIS The authors reviewed 165 articles germane to central presbycusis. Of the 165 articles, 132 articles with a focus on human behavioral measures for either speech or nonspeech stimuli were selected for further analysis. RESULTS For 76 smaller-scale studies of speech understanding in older adults reviewed, the following findings emerged: (1) the three most commonly studied behavioral measures were speech in competition, temporally distorted speech, and binaural speech perception (especially dichotic listening); (2) for speech in competition and temporally degraded speech, hearing loss proved to have a significant negative effect on performance in most of the laboratory studies; (3) significant negative effects of age, unconfounded by hearing loss, were observed in most of the studies of speech in competing speech, time-compressed speech, and binaural speech perception; and (4) the influence of cognitive processing on speech understanding has been examined much less frequently, but when included, significant positive associations with speech understanding were observed. For 36 smaller-scale studies of the perception of nonspeech stimuli by older adults reviewed, the following findings emerged: (1) the three most frequently studied behavioral measures were gap detection, temporal discrimination, and temporal-order discrimination or identification; (2) hearing loss was seldom a significant factor; and (3) negative effects of age were almost always observed. For 18 studies reviewed that made use of test batteries and medium-to-large sample sizes, the following findings emerged: (1) all studies included speech-based measures of auditory processing; (2) 4 of the 18 studies included nonspeech stimuli; (3) for the speech-based measures, monaural speech in a competing-speech background, dichotic speech, and monaural time-compressed speech were investigated most frequently; (4) the most frequently used tests were the Synthetic Sentence Identification (SSI) test with Ipsilateral Competing Message (ICM), the Dichotic Sentence Identification (DSI) test, and time-compressed speech; (5) many of these studies using speech-based measures reported significant effects of age, but most of these studies were confounded by declines in hearing, cognition, or both; (6) for nonspeech auditory-processing measures, the focus was on measures of temporal processing in all four studies; (7) effects of cognition on nonspeech measures of auditory processing have been studied less frequently, with mixed results, whereas the effects of hearing loss on performance were minimal due to judicious selection of stimuli; and (8) there is a paucity of observational studies using test batteries and longitudinal designs. CONCLUSIONS Based on this review of the scientific literature, there is insufficient evidence to confirm the existence of central presbycusis as an isolated entity. On the other hand, recent evidence has been accumulating in support of the existence of central presbycusis as a multifactorial condition that involves age- and/or disease-related changes in the auditory system and in the brain. Moreover, there is a clear need for additional research in this area.
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Affiliation(s)
- Larry E Humes
- Department of Speech and Hearing Sciences, Indiana University, Bloomington, IN, USA.
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12
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Abstract
Normal blood supply to the cochlea is critically important for establishing the endocochlear potential and sustaining production of endolymph. Abnormal cochlear microcirculation has long been considered an etiologic factor in noise-induced hearing loss, age-related hearing loss (presbycusis), sudden hearing loss or vestibular function, and Meniere's disease. Knowledge of the mechanisms underlying the pathophysiology of cochlear microcirculation is of fundamental clinical importance. A better understanding of cochlear blood flow (CoBF) will enable more effective management of hearing disorders resulting from aberrant blood flow. This review focuses on recent discoveries and findings related to the physiopathology of the cochlear microvasculature.
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Affiliation(s)
- Xiaorui Shi
- Oregon Hearing Research Center (NRC04), Department of Otolaryngology/Head & Neck Surgery, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA.
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14
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Lei D, Gao X, Perez P, Ohlemiller KK, Chen CC, Campbell KP, Hood AY, Bao J. Anti-epileptic drugs delay age-related loss of spiral ganglion neurons via T-type calcium channel. Hear Res 2011; 278:106-12. [PMID: 21640179 PMCID: PMC3152691 DOI: 10.1016/j.heares.2011.05.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2010] [Revised: 04/29/2011] [Accepted: 05/11/2011] [Indexed: 12/26/2022]
Abstract
Loss of spiral ganglion neurons is a major cause of age-related hearing loss (presbycusis). Despite being the third most prevalent condition afflicting elderly persons, there are no known medications to prevent presbycusis. Because calcium signaling has long been implicated in age-related neuronal death, we investigated T-type calcium channels. This family is comprised of three members (Ca(v)3.1, Ca(v)3.2, and Ca(v)3.3), based on their respective main pore-forming alpha subunits: α1G, α1H, and α1I. In the present study, we report a significant delay of age-related loss of cochlear function and preservation of spiral ganglion neurons in α1H null and heterozygous mice, clearly demonstrating an important role for Ca(v)3.2 in age-related neuronal loss. Furthermore, we show that anticonvulsant drugs from a family of T-type calcium channel blockers can significantly preserve spiral ganglion neurons during aging. To our knowledge, this is the first report of drugs capable of diminishing age-related loss of spiral ganglion neurons.
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MESH Headings
- Aging/drug effects
- Aging/metabolism
- Aging/pathology
- Animals
- Anticonvulsants/pharmacology
- Base Sequence
- Calcium Channel Blockers/pharmacology
- Calcium Channels, T-Type/deficiency
- Calcium Channels, T-Type/genetics
- Calcium Channels, T-Type/metabolism
- Evoked Potentials, Auditory, Brain Stem/drug effects
- Hair Cells, Auditory, Inner/pathology
- Hair Cells, Auditory, Outer/pathology
- Mice
- Mice, Congenic
- Mice, Knockout
- Neurons/drug effects
- Neurons/metabolism
- Neurons/pathology
- Presbycusis/metabolism
- Presbycusis/pathology
- Presbycusis/prevention & control
- RNA/genetics
- RNA/metabolism
- Spiral Ganglion/drug effects
- Spiral Ganglion/innervation
- Spiral Ganglion/metabolism
- Spiral Ganglion/pathology
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Affiliation(s)
- Debin Lei
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, Missouri, 63110, USA
- Center for Aging, Washington University School of Medicine, St. Louis, Missouri, 63110, USA
| | - Xia Gao
- Department of Otolaryngology, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China 210008
| | - Philip Perez
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, Missouri, 63110, USA
- Center for Aging, Washington University School of Medicine, St. Louis, Missouri, 63110, USA
| | - Kevin K Ohlemiller
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, Missouri, 63110, USA
| | - Chien-Chang Chen
- Howard Hughes Medical Institute, University of Iowa, Iowa City, Iowa, 60153, USA
| | - Kevin P. Campbell
- Howard Hughes Medical Institute, University of Iowa, Iowa City, Iowa, 60153, USA
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa, 60153, USA
- Department of Neurology, University of Iowa, Iowa City, Iowa, 60153, USA
- Department of Internal Medicine, University of Iowa, Iowa City, Iowa, 60153, USA
| | - Aizhen Yang Hood
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, Missouri, 63110, USA
- Center for Aging, Washington University School of Medicine, St. Louis, Missouri, 63110, USA
| | - Jianxin Bao
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, Missouri, 63110, USA
- Center for Aging, Washington University School of Medicine, St. Louis, Missouri, 63110, USA
- The Division of Biology & Biomedical Science and Neuroscience Program, Washington University School of Medicine, St. Louis, Missouri, 63110, USA
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15
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Fu B, Le Prell C, Simmons D, Lei D, Schrader A, Chen AB, Bao J. Age-related synaptic loss of the medial olivocochlear efferent innervation. Mol Neurodegener 2010; 5:53. [PMID: 21110869 PMCID: PMC3000387 DOI: 10.1186/1750-1326-5-53] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Accepted: 11/26/2010] [Indexed: 01/26/2023] Open
Abstract
Age-related functional decline of the nervous system is consistently observed, though cellular and molecular events responsible for this decline remain largely unknown. One of the most prevalent age-related functional declines is age-related hearing loss (presbycusis), a major cause of which is the loss of outer hair cells (OHCs) and spiral ganglion neurons. Previous studies have also identified an age-related functional decline in the medial olivocochlear (MOC) efferent system prior to age-related loss of OHCs. The present study evaluated the hypothesis that this functional decline of the MOC efferent system is due to age-related synaptic loss of the efferent innervation of the OHCs. To this end, we used a recently-identified transgenic mouse line in which the expression of yellow fluorescent protein (YFP), under the control of neuron-specific elements from the thy1 gene, permits the visualization of the synaptic connections between MOC efferent fibers and OHCs. In this model, there was a dramatic synaptic loss between the MOC efferent fibers and the OHCs in older mice. However, age-related loss of efferent synapses was independent of OHC status. These data demonstrate for the first time that age-related loss of efferent synapses may contribute to the functional decline of the MOC efferent system and that this synaptic loss is not necessary for age-related loss of OHCs.
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Affiliation(s)
- Benjamin Fu
- Department of Otolaryngology, Washington University, St, Louis, MO, 63110, USA.
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16
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Ohlemiller KK, Dahl AR, Gagnon PM. Divergent aging characteristics in CBA/J and CBA/CaJ mouse cochleae. J Assoc Res Otolaryngol 2010; 11:605-23. [PMID: 20706857 DOI: 10.1007/s10162-010-0228-1] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Accepted: 07/21/2010] [Indexed: 11/24/2022] Open
Abstract
Two inbred mouse strains, CBA/J and CBA/CaJ, have been used nearly interchangeably as 'good hearing' standards for research in hearing and deafness. We recently reported, however, that these two strains diverge after 1 year of age, such that CBA/CaJ mice show more rapid elevation of compound action potential (CAP) thresholds at high frequencies (Ohlemiller, Brain Res. 1277: 70-83, 2009). One contributor is progressive decline in endocochlear potential (EP) that appears only in CBA/CaJ. Here, we explore the cellular bases of threshold and EP disparities in old CBA/J and CBA/CaJ mice. Among the major findings, both strains exhibit a characteristic age (∼18 months in CBA/J and 24 months in CBA/CaJ) when females overtake males in sensitivity decline. Strain differences in progression of hearing loss are not due to greater hair cell loss in CBA/CaJ, but instead appear to reflect greater neuronal loss, plus more pronounced changes in the lateral wall, leading to EP decline. While both male and female CBA/CaJ show these pathologies, they are more pronounced in females. A novel feature that differed sharply by strain was moderate loss of outer sulcus cells (or 'root' cells) in spiral ligament of the upper basal turn in old CBA/CaJ mice, giving rise to deep indentations and void spaces in the ligament. We conclude that CBA/CaJ mice differ both quantitatively and qualitatively from CBA/J in age-related cochlear pathology, and model different types of presbycusis.
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Affiliation(s)
- Kevin K Ohlemiller
- Program in Audiology and Communication Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA.
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Bao J, Ohlemiller KK. Age-related loss of spiral ganglion neurons. Hear Res 2010; 264:93-7. [PMID: 19854255 PMCID: PMC2868093 DOI: 10.1016/j.heares.2009.10.009] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Revised: 10/14/2009] [Accepted: 10/16/2009] [Indexed: 01/12/2023]
Abstract
Spiral ganglion neurons (SGNs) are the relay station for auditory information between hair cells and central nervous system. Age-related decline of auditory function due to SGN loss can not be ameliorated by hearing aids or cochlear implants. Recent findings clearly indicate that survival of SGNs during aging depends on genetic and environmental interactions, which can be demonstrated at the systemic, tissue, cellular, and molecular levels. At the systemic level, both insulin/insulin-like growth factor-1 and lipophilic/steroid hormone pathways influence SGN survival during aging. At the level of organ of the Corti, it is difficult to determine whether age-related SGN loss is primary or secondary degeneration. However, a late stage of SGN degeneration may be independent of age-related loss of hair cells. At the cellular and molecular level, several pathways, particularly free radical and calcium signaling pathways, can influence age-related SGN loss, and further studies should determine how these pathways contribute to SGN loss, such as whether they directly or indirectly act on SGNs. With the advancement of recent genetic and pharmacologic tools, we should not only understand how SGNs die during aging, but also find ways to delay this loss.
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Affiliation(s)
- Jianxin Bao
- Fay and Carl Simmons Center for the Biology of Hearing and Deafness, Department of Otolaryngology, Washington University Medical School, 660 S. Euclid, St. Louis, MO 63110, USA.
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