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O'Malley JT, Wu PZ, Kaur C, Gantz BJ, Hansen MR, Quesnel AM, Liberman MC. Delayed hearing loss after cochlear implantation: Re-evaluating the role of hair cell degeneration. Hear Res 2024; 447:109024. [PMID: 38735179 PMCID: PMC11134194 DOI: 10.1016/j.heares.2024.109024] [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: 03/18/2024] [Revised: 04/18/2024] [Accepted: 04/26/2024] [Indexed: 05/14/2024]
Abstract
Delayed loss of residual acoustic hearing after cochlear implantation is a common but poorly understood phenomenon due to the scarcity of relevant temporal bone tissues. Prior histopathological analysis of one case of post-implantation hearing loss suggested there were no interaural differences in hair cell or neural degeneration to explain the profound loss of low-frequency hearing on the implanted side (Quesnel et al., 2016) and attributed the threshold elevation to neo-ossification and fibrosis around the implant. Here we re-evaluated the histopathology in this case, applying immunostaining and improved microscopic techniques for differentiating surviving hair cells from supporting cells. The new analysis revealed dramatic interaural differences, with a > 80 % loss of inner hair cells in the cochlear apex on the implanted side, which can account for the post-implantation loss of residual hearing. Apical degeneration of the stria further contributed to threshold elevation on the implanted side. In contrast, spiral ganglion cell survival was reduced in the region of the electrode on the implanted side, but apical counts in the two ears were similar to that seen in age-matched unimplanted control ears. Almost none of the surviving auditory neurons retained peripheral axons throughout the basal half of the cochlea. Relevance to cochlear implant performance is discussed.
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Affiliation(s)
- Jennifer T O'Malley
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA 02114, USA; Otopathology Laboratory, Massachusetts Eye and Ear, Boston, MA, 02114, USA; Dept of Otolaryngology-Head & Neck Surgery, Harvard Medical School, Boston, MA, 02115, USA
| | - Pei-Zhe Wu
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA 02114, USA; Otopathology Laboratory, Massachusetts Eye and Ear, Boston, MA, 02114, USA; Dept of Otolaryngology-Head & Neck Surgery, Harvard Medical School, Boston, MA, 02115, USA
| | - Charanjeet Kaur
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA 02114, USA; Otopathology Laboratory, Massachusetts Eye and Ear, Boston, MA, 02114, USA; Dept of Otolaryngology-Head & Neck Surgery, Harvard Medical School, Boston, MA, 02115, USA
| | - Bruce J Gantz
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, IA, 52242, USA; Department of Neurosurgery, University of Iowa, Iowa City, IA, 52242
| | - Marlan R Hansen
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, IA, 52242, USA; Department of Neurosurgery, University of Iowa, Iowa City, IA, 52242
| | - Alicia M Quesnel
- Otopathology Laboratory, Massachusetts Eye and Ear, Boston, MA, 02114, USA; Dept of Otolaryngology-Head & Neck Surgery, Harvard Medical School, Boston, MA, 02115, USA
| | - M Charles Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA 02114, USA; Otopathology Laboratory, Massachusetts Eye and Ear, Boston, MA, 02114, USA; Dept of Otolaryngology-Head & Neck Surgery, Harvard Medical School, Boston, MA, 02115, USA.
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Liu Y, Yang L, Singh S, Beyer LA, Prieskorn DM, Swiderski DL, Groves AK, Raphael Y. Combinatorial Atoh1, Gfi1, Pou4f3, and Six1 gene transfer induces hair cell regeneration in the flat epithelium of mature guinea pigs. Hear Res 2024; 441:108916. [PMID: 38103445 DOI: 10.1016/j.heares.2023.108916] [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: 09/05/2023] [Revised: 10/29/2023] [Accepted: 11/14/2023] [Indexed: 12/19/2023]
Abstract
Flat epithelium (FE) is a condition characterized by the loss of both hair cells (HCs) and supporting cells and the transformation of the organ of Corti into a simple flat or cuboidal epithelium, which can occur after severe cochlear insults. The transcription factors Gfi1, Atoh1, Pou4f3, and Six1 (GAPS) play key roles in HC differentiation and survival in normal ears. Previous work using a single transcription factor, Atoh1, to induce HC regeneration in mature ears in vivo usually produced very few cells and failed to produce HCs in severely damaged organs of Corti, especially those with FE. Studies in vitro suggested combinations of transcription factors may be more effective than any single factor, thus the current study aims to examine the effect of co-overexpressing GAPS genes in deafened mature guinea pig cochleae with FE. Deafening was achieved through the infusion of neomycin into the perilymph, leading to the formation of FE and substantial degeneration of nerve fibers. Seven days post neomycin treatment, adenovirus vectors carrying GAPS were injected into the scala media and successfully expressed in the FE. One or two months following GAPS inoculation, cells expressing Myosin VIIa were observed in regions under the FE (located at the scala tympani side of the basilar membrane), rather than within the FE. The number of cells, which we define as induced HCs (iHCs), was not significantly different between one and two months, but the larger N at two months made it more apparent that there were significantly more iHCs in GAPS treated animals than in controls. Additionally, qualitative observations indicated that ears with GAPS gene expression in the FE had more nerve fibers than FE without the treatment. In summary, our results showed that co-overexpression of GAPS enhances the potential for HC regeneration in a severe lesion model of FE.
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Affiliation(s)
- Yujie Liu
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA; Department of Otolaryngology-Head and Neck Surgery, Beijing Tongren Hospital, Capital Medical University, Ministry of Education Key Laboratory of Otolaryngology-Head and Neck Surgery, Beijing 100730, China
| | - Lin Yang
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA; Department of Otolaryngology-Head and Neck Surgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China
| | - Sunita Singh
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas, USA
| | - Lisa A Beyer
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Diane M Prieskorn
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Donald L Swiderski
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Andrew K Groves
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
| | - Yehoash Raphael
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA.
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Kaur C, Wu PZ, O'Malley JT, Liberman MC. Predicting Atrophy of the Cochlear Stria Vascularis from the Shape of the Threshold Audiogram. J Neurosci 2023; 43:8801-8811. [PMID: 37863653 PMCID: PMC10727192 DOI: 10.1523/jneurosci.1138-23.2023] [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: 06/20/2023] [Revised: 10/02/2023] [Accepted: 10/10/2023] [Indexed: 10/22/2023] Open
Abstract
Several lines of evidence have suggested that steeply sloping audiometric losses are caused by hair cell degeneration, while flat audiometric losses are caused by strial atrophy, but this concept has never been rigorously tested in human specimens. Here, we systematically compare audiograms and cochlear histopathology in 160 human cases from the archival collection of celloidin-embedded temporal bones at the Massachusetts Eye and Ear. The dataset included 106 cases from a prior study of normal-aging ears, and an additional 54 cases selected by combing the database for flat audiograms. Audiogram shapes were classified algorithmically into five groups according to the relation between flatness (i.e., SD of hearing levels across all frequencies) and low-frequency pure-tone average (i.e., mean at 0.25, 0.5, and 1.0 kHz). Outer and inner hair cell losses, neural degeneration, and strial atrophy were all quantified as a function of cochlear location in each case. Results showed that strial atrophy was worse in the apical than the basal half of the cochlea and was worse in females than in males. The degree of strial atrophy was uncorrelated with audiogram flatness. Apical atrophy was correlated with low-frequency thresholds and basal atrophy with high-frequency thresholds, and the former correlation was higher. However, a multivariable regression with all histopathological measures as predictors and audiometric thresholds as the outcome showed that strial atrophy was a significant predictor of threshold shift only in the low-frequency region, and, even there, the contribution of outer hair cell damage was larger.SIGNIFICANCE STATEMENT Cochlear pathology can only be assessed postmortem; thus, human cochlear histopathology is critical to our understanding of the mechanisms of hearing loss. Dogma holds that relative damage to sensory cells, which transduce mechanical vibration into electrical signals, versus the stria vascularis, the cellular battery that powers transduction, can be inferred by the shape of the audiogram, that is, down-sloping (hair cell damage) versus flat (strial atrophy). Here we quantified hair cell and strial atrophy in 160 human specimens to show that it is the degree of low-frequency hearing loss, rather than the audiogram slope, that predicts strial atrophy. Results are critical to the design of clinical trials for hearing-loss therapeutics, as current drugs target only hair cell, not strial, regeneration.
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Affiliation(s)
- Charanjeet Kaur
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, Massachusetts 02114
- Department of Otolaryngology-Head & Neck Surgery, Harvard Medical School, Boston, Massachusetts 02115
| | - Pei-Zhe Wu
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, Massachusetts 02114
- Department of Otolaryngology-Head & Neck Surgery, Harvard Medical School, Boston, Massachusetts 02115
| | - Jennifer T O'Malley
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, Massachusetts 02114
- Otopathology Laboratory, Massachusetts Eye and Ear, Boston, Massachusetts 02114
| | - M Charles Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, Massachusetts 02114
- Otopathology Laboratory, Massachusetts Eye and Ear, Boston, Massachusetts 02114
- Department of Otolaryngology-Head & Neck Surgery, Harvard Medical School, Boston, Massachusetts 02115
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