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Maraslioglu-Sperber A, Blanc F, Heller S. Murine cochlear damage models in the context of hair cell regeneration research. Hear Res 2024; 447:109021. [PMID: 38703432 DOI: 10.1016/j.heares.2024.109021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2023] [Revised: 04/16/2024] [Accepted: 04/26/2024] [Indexed: 05/06/2024]
Abstract
Understanding the complex pathologies associated with hearing loss is a significant motivation for conducting inner ear research. Lifelong exposure to loud noise, ototoxic drugs, genetic diversity, sex, and aging collectively contribute to human hearing loss. Replicating this pathology in research animals is challenging because hearing impairment has varied causes and different manifestations. A central aspect, however, is the loss of sensory hair cells and the inability of the mammalian cochlea to replace them. Researching therapeutic strategies to rekindle regenerative cochlear capacity, therefore, requires the generation of animal models in which cochlear hair cells are eliminated. This review discusses different approaches to ablate cochlear hair cells in adult mice. We inventoried the cochlear cyto- and histo-pathology caused by acoustic overstimulation, systemic and locally applied drugs, and various genetic tools. The focus is not to prescribe a perfect damage model but to highlight the limitations and advantages of existing approaches and identify areas for further refinement of damage models for use in regenerative studies.
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Affiliation(s)
- Ayse Maraslioglu-Sperber
- Department of Otolaryngology - Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA, USA; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Fabian Blanc
- Department of Otolaryngology - Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA, USA; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Otolaryngology - Head & Neck Surgery, University Hospital Gui de Chauliac, University of Montpellier, Montpellier, France
| | - Stefan Heller
- Department of Otolaryngology - Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA, USA; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA.
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2
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Sato MP, Benkafadar N, Heller S. Hair cell regeneration, reinnervation, and restoration of hearing thresholds in the avian hearing organ. Cell Rep 2024; 43:113822. [PMID: 38393948 PMCID: PMC11068303 DOI: 10.1016/j.celrep.2024.113822] [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: 07/19/2023] [Revised: 12/13/2023] [Accepted: 02/02/2024] [Indexed: 02/25/2024] Open
Abstract
Hearing starts, at the cellular level, with mechanoelectrical transduction by sensory hair cells. Sound information is then transmitted via afferent synaptic connections with auditory neurons. Frequency information is encoded by the location of hair cells along the cochlear duct. Loss of hair cells, synapses, or auditory neurons leads to permanent hearing loss in mammals. Birds, in contrast, regenerate auditory hair cells and functionally recover from hearing loss. Here, we characterized regeneration and reinnervation in sisomicin-deafened chickens and found that afferent neurons contact regenerated hair cells at the tips of basal projections. In contrast to development, synaptic specializations are established at these locations distant from the hair cells' bodies. The protrusions then contracted as regenerated hair cells matured and became functional 2 weeks post-deafening. We found that auditory thresholds recovered after 4-5 weeks. We interpret the regeneration-specific synaptic reestablishment as a location-preserving process that might be needed to maintain tonotopic fidelity.
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Affiliation(s)
- Mitsuo P Sato
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Otolaryngology-Head and Neck Surgery, Kindai University School of Medicine, Osaka, Japan
| | - Nesrine Benkafadar
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Stefan Heller
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA.
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3
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Krumm B, Klump G, Köppl C, Langemann U. Barn owls have ageless ears. Proc Biol Sci 2018; 284:rspb.2017.1584. [PMID: 28931742 DOI: 10.1098/rspb.2017.1584] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 08/14/2017] [Indexed: 11/12/2022] Open
Abstract
We measured the auditory sensitivity of the barn owl (Tyto alba), using a behavioural Go/NoGo paradigm in two different age groups, one younger than 2 years (n = 4) and another more than 13 years of age (n = 3). In addition, we obtained thresholds from one individual aged 23 years, three times during its lifetime. For computing audiograms, we presented test frequencies of between 0.5 and 12 kHz, covering the hearing range of the barn owl. Average thresholds in quiet were below 0 dB sound pressure level (SPL) for frequencies between 1 and 10 kHz. The lowest mean threshold was -12.6 dB SPL at 8 kHz. Thresholds were the highest at 12 kHz, with a mean of 31.7 dB SPL. Test frequency had a significant effect on auditory threshold but age group had no significant effect. There was no significant interaction between age group and test frequency. Repeated threshold estimates over 21 years from a single individual showed only a slight increase in thresholds. We discuss the auditory sensitivity of barn owls with respect to other species and suggest that birds, which generally show a remarkable capacity for regeneration of hair cells in the basilar papilla, are naturally protected from presbycusis.
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Affiliation(s)
- Bianca Krumm
- Cluster of Excellence 'Hearing4all', Animal Physiology and Behaviour Group, Department of Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111 Oldenburg, Germany
| | - Georg Klump
- Cluster of Excellence 'Hearing4all', Animal Physiology and Behaviour Group, Department of Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111 Oldenburg, Germany
| | - Christine Köppl
- Cluster of Excellence 'Hearing4all', Animal Physiology and Behaviour Group, Department of Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111 Oldenburg, Germany
| | - Ulrike Langemann
- Cluster of Excellence 'Hearing4all', Animal Physiology and Behaviour Group, Department of Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111 Oldenburg, Germany
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Russo G, Calzi D, Gioglio L, Botta L, Polimeni M, Zucca G, Martini M, Contini D, Fesce R, Rossi M, Prigioni I. Analysis of pre- and postsynaptic activity in the frog semicircular canal following ototoxic insult: differential recovery of background and evoked afferent activity. Neuroscience 2009; 163:1327-39. [DOI: 10.1016/j.neuroscience.2009.07.026] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2008] [Revised: 07/13/2009] [Accepted: 07/13/2009] [Indexed: 11/29/2022]
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Radeloff A, Smolders JWT. Brain-derived neurotrophic factor treatment does not improve functional recovery after hair cell regeneration in the pigeon. Acta Otolaryngol 2006; 126:452-9. [PMID: 16698693 DOI: 10.1080/00016480500437344] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
CONCLUSIONS Brain-derived neurotrophic factor (BDNF) supply to the inner ear does not improve the time course or the extent of functional recovery after hair cell regeneration. Specifically it does not improve the residual threshold elevation observed after the completion of spontaneous recovery. OBJECTIVE The avian inner ear is capable of hair cell regeneration and substantial functional recovery, but residual hearing deficits remain. We investigated whether functional recovery can be improved by intracochlear application of BDNF, which plays an important role in auditory ontogenesis and maintenance during adult life. METHODS Hair cells in adult pigeons were destroyed by local application of gentamicin. After 3 days either BDNF or control solution was administered to the scala tympani by implanted osmotic minipumps for 8 weeks. Auditory brain stem responses (ABR) to tone pips were used to assess recovery of hearing thresholds in both groups. RESULTS The application of gentamicin caused a frequency-dependent hearing loss that ranged from 24.8 dB SPL at low frequencies to 66.2 dB SPL at high frequencies. After day 10 substantial recovery was observed, but a significant threshold shift remained. The time course of recovery in the control and BDNF-treated groups was similar, without significant residual threshold differences in any frequency range.
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Affiliation(s)
- A Radeloff
- Physiologisches Institut II, Zentrum der Hals-Nasen-Ohrenheilkunde, Frankfurt am Main, Germany
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Nordang L, Anniko M. Nitro-L-arginine methyl ester: a potential protector against gentamicin ototoxicity. Acta Otolaryngol 2005; 125:1033-8. [PMID: 16298782 DOI: 10.1080/00016480510038022] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The nitric oxide (NO) inhibitor nitro-L-arginine methyl ester (L-NAME) may act as an otoprotectant against high-frequency hearing loss caused by gentamicin, but further studies are needed to confirm this.Aminoglycoside antibiotics are still widely used by virtue of their efficacy and low cost. Their ototoxicity is a serious health problem and, as their ototoxic mechanism involves the production of NO, we need to assess the use of NO inhibitors for the prevention of aminoglycoside-induced sensorineural hearing loss. In this experimental study we used 30 Sprague-Dawley rats, 27 of which had gentamicin instilled into the middle ear. The otoprotectant L-NAME was administered topically to 12/27 animals. Its effect was determined in terms of attenuation of hearing loss, measured by shifts in the auditory brainstem response threshold. L-NAME reduced gentamicin-induced hearing loss in the high-frequency range, but gave no protection in the middle or low frequencies.
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Affiliation(s)
- Leif Nordang
- Department of Otolaryngology and Head and Neck Surgery, University Hospital (Akademiska sjukhuset), Uppsala, Sweden.
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Heydt JL, Cunningham LL, Rubel EW, Coltrera MD. Round window gentamicin application: an inner ear hair cell damage protocol for the mouse. Hear Res 2004; 192:65-74. [PMID: 15157964 DOI: 10.1016/j.heares.2004.01.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2003] [Accepted: 01/08/2004] [Indexed: 11/23/2022]
Abstract
It is important to develop an inner ear damage protocol for mice that avoids systemic toxicity and produces damage in a relatively rapid fashion, allowing for study of early cellular and molecular mechanisms responsible for hair cell death and those that underlie the lack of hair cell regeneration in mammals. Ideally, this damage protocol would reliably produce both partial and complete lesions of the sensory epithelium. We present a method for in vivo induction of hair cell damage in the mouse via placement of gentamicin-soaked Gelfoam in the round window niche of the inner ear, an adaptation of a method developed to study hair cell regeneration in chicks. A total of 82 subjects underwent the procedure. Variable doses of gentamicin were used (25, 50, 100 and 200 microg). Saline-soaked Gelfoam, sham-operations and the contralateral, non-operated cochlea were used as controls. Survival periods were 1, 3 and 14 days. Damage was assessed on scanning electron microscopy. We found that this method produces relatively rapid hair cell damage that varies with dose and can extend the entire length of the sensory epithelium. In addition, this protocol produces no systemic toxicity and preserves the contralateral ear as a control.
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MESH Headings
- Animals
- Dyneins
- Gelatin Sponge, Absorbable
- Gentamicins/administration & dosage
- Gentamicins/toxicity
- Hair Cells, Auditory/drug effects
- Hair Cells, Auditory/injuries
- Hair Cells, Auditory/metabolism
- Hair Cells, Auditory/ultrastructure
- Hair Cells, Auditory, Inner/drug effects
- Hair Cells, Auditory, Inner/injuries
- Hair Cells, Auditory, Inner/metabolism
- Hair Cells, Auditory, Inner/ultrastructure
- Hair Cells, Auditory, Outer/drug effects
- Hair Cells, Auditory, Outer/injuries
- Hair Cells, Auditory, Outer/metabolism
- Hair Cells, Auditory, Outer/ultrastructure
- Immunohistochemistry
- Male
- Mice
- Mice, Inbred CBA
- Microscopy, Electron, Scanning
- Myosin VIIa
- Myosins/metabolism
- Round Window, Ear/drug effects
- Time Factors
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Affiliation(s)
- Jennifer L Heydt
- Department of Otolaryngology-Head and Neck Surgery, University of Washington, Box 356515, Seattle, WA 98195-7923, USA
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Harris JA, Cheng AG, Cunningham LL, MacDonald G, Raible DW, Rubel EW. Neomycin-induced hair cell death and rapid regeneration in the lateral line of zebrafish (Danio rerio). J Assoc Res Otolaryngol 2003; 4:219-34. [PMID: 12943374 PMCID: PMC3202713 DOI: 10.1007/s10162-002-3022-x] [Citation(s) in RCA: 351] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2002] [Accepted: 10/05/2002] [Indexed: 10/26/2022] Open
Abstract
Mechanoreceptive hair cells are extremely sensitive to aminoglycoside antibiotics, including neomycin. Hair cell survival was assessed in larval wild-type zebrafish lateral line neuromasts 4 h after initial exposure to a range of neomycin concentrations for 1 h. Each of the lateral line neuromasts was scored in live fish for the presence or absence of hair cells using the fluorescent vital dye DASPEI to selectively label hair cells. All neuromasts were devoid of DASPEI-labeled hair cells 4 h after 500 microM neomycin exposure. Vital DASPEI staining was proportional to the number of hair cells per neuromast identified in fixed larvae using immunocytochemistry for acetylated tubulin and phalloidin labeling. The time course of hair cell regeneration in the lateral line neuromasts was also analyzed following neomycin-induced damage. Regenerated hair cells were first observed using live DASPEI staining 12 and 24 h following neomycin treatment. The potential role of proliferation in regenerating hair cells was analyzed. A 1 h pulse-fix protocol using bromodeoxyuridine (BrdU) incorporation was used to identify S-phase cells in neuromasts. BrdU incorporation in neomycin-damaged neuromasts did not differ from control neuromasts 4 h after drug exposure but was dramatically upregulated after 12 h. The proliferative cells identified during a 1 h period at 12 h after neomycin treatment were able to give rise to new hair cells by 24-48 h after drug treatment. The results presented here provide a standardized preparation for studying and identifying genes that influence vertebrate hair cell death, survival, and regeneration following ototoxic insults.
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Affiliation(s)
- Julie A. Harris
- Virginia Merrill Bloedel Hearing Research Center and Department of Otolaryngology–Head and Neck Surgery, University of Washington, Seattle, WA 98195, USA
- Graduate Program in Neurobiology and Behavior, University of Washington, Seattle, WA 98195, USA
| | - Alan G. Cheng
- Virginia Merrill Bloedel Hearing Research Center and Department of Otolaryngology–Head and Neck Surgery, University of Washington, Seattle, WA 98195, USA
| | - Lisa L. Cunningham
- Virginia Merrill Bloedel Hearing Research Center and Department of Otolaryngology–Head and Neck Surgery, University of Washington, Seattle, WA 98195, USA
| | - Glen MacDonald
- Virginia Merrill Bloedel Hearing Research Center and Department of Otolaryngology–Head and Neck Surgery, University of Washington, Seattle, WA 98195, USA
- Core for Communication Research, University of Washington, Box 357923, Seattle, WA 98195, USA
| | - David W. Raible
- Graduate Program in Neurobiology and Behavior, University of Washington, Seattle, WA 98195, USA
- Department of Biological Structure, University of Washington, Seattle, WA 98195, USA
| | - Edwin W Rubel
- Virginia Merrill Bloedel Hearing Research Center and Department of Otolaryngology–Head and Neck Surgery, University of Washington, Seattle, WA 98195, USA
- Graduate Program in Neurobiology and Behavior, University of Washington, Seattle, WA 98195, USA
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Abstract
The discovery of hair cell regeneration in the inner ear of birds provides new optimism that there may be a treatment for hearing and balance disorders. In this review we describe the process of hair cell regeneration in birds; including restoration of function, recovery of perception and what is currently known about molecular events, such as growth factors and signalling systems. We examine some of the key recent findings in both birds and mammals.
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Affiliation(s)
- Olivia Bermingham-McDonogh
- Virginia Merrill Bloedel Hearing Research Center and Department of Otolaryngology-HNS, University of Washington Medical School, Box 357923, Seattle, Washington 98195-7923, USA.
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10
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Abstract
Two types of chickens are commercially available. Broiler birds are bred to develop quickly for meat production, while egg layers are bred to attain a smaller adult size. Because we have observed breed differences in the response of central auditory neurons to cochlear ablation in adult birds [Edmonds et al. (1999) Hear. Res. 127, 62-76], we examined cochleae from the two breeds for differences in integrity. We evaluated cochlear hair cell structure using scanning electron microscopy and cochlear hair cell function using distortion product otoacoustic emissions (DPOAEs) and the auditory brainstem response. We observed striking breed differences in cochlear integrity in adult but not hatchling birds. In adult broiler birds, all cochleae showed damage, encompassing at least the basal 29% of the cochlea. In 15 of 18 broiler ears, damage was observed throughout the basal 60% of the cochlea. In contrast, cochleae from egg layer adults were largely normal. Two thirds of egg layer ears showed no anatomical abnormalities, while in the remainder cochlear damage was seen within the basal 48% of the cochlea. DPOAEs recorded from egg layer birds showed loss of high frequency emissions in every ear for which the cochlea displayed anatomical damage. Average sound pressure levels in both commercial facilities were 90 dB, suggesting these two breeds may exhibit differential susceptibility to noise damage.
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MESH Headings
- Aging/pathology
- Aging/physiology
- Animals
- Breeding
- Chickens/anatomy & histology
- Chickens/physiology
- Evoked Potentials, Auditory, Brain Stem
- Female
- Hair Cells, Auditory/abnormalities
- Hair Cells, Auditory/physiology
- Hair Cells, Auditory/ultrastructure
- Hearing Loss, Noise-Induced/pathology
- Hearing Loss, Noise-Induced/physiopathology
- Microscopy, Electron, Scanning
- Otoacoustic Emissions, Spontaneous
- Regeneration
- Species Specificity
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Affiliation(s)
- Dianne Durham
- Department of Otolaryngology and the Smith Mental Retardation Research Center, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160-7380, USA.
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Woolley SM, Wissman AM, Rubel EW. Hair cell regeneration and recovery of auditory thresholds following aminoglycoside ototoxicity in Bengalese finches. Hear Res 2001; 153:181-95. [PMID: 11223308 DOI: 10.1016/s0378-5955(00)00217-3] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Birds regenerate auditory hair cells when original hair cells are lost. Regenerated hair cells become innervated and restore hearing function. Functional recovery during hair cell regeneration is particularly interesting in animals that depend on hearing for vocal communication. Bengalese finches are songbirds that depend on auditory feedback for normal song learning and maintenance. We examined the structural and functional recovery of the Bengalese finch basilar papilla after aminoglycoside ototoxicity. Birds were treated with the ototoxic aminoglycoside, amikacin, daily for 1 week. Treatment resulted in hair cell loss across the basal half of the basilar papilla and corresponding high frequency hearing loss. Hair cell regeneration and recovery of auditory brainstem responses were compared in the same animals. Survival times following treatment were between 1 day and 12 weeks. Analysis of structural recovery at weekly intervals indicated that hair cells in the Bengalese finch papilla require a maximum of 1 week to regenerate and appear with immature morphology at the epithelial surface. An additional 6 days are required for adult-like morphology to develop. Repopulation of the damaged region was complete by 8 weeks. Recovery of auditory thresholds began 1 week after treatment and reached asymptote by 4 weeks. Slight residual threshold shifts at 2.0 kHz and above were observed up to 12 weeks after treatment. Direct comparison of structural and functional recovery indicates that auditory thresholds recover maximally before a full complement of hair cells has regenerated.
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Affiliation(s)
- S M Woolley
- Neurobiology and Behavior Program, Department of Otolaryngology-HNS and Virginia Merrill Bloedel Hearing Research Center, P.O. Box 357923, University of Washington, Seattle, WA 98195, USA
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12
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Girod DA, Park RH, Park DL, Durham D. Changes in the avian cochlea after single high-dose gentamicin. Am J Otolaryngol 2000; 21:379-88. [PMID: 11115522 DOI: 10.1053/ajot.2000.18866] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE Define the time course of functional and anatomical damage and subsequent recovery (by regeneration) of hair cells in the chicken inner ear after a single high-dose of gentamicin. MATERIALS AND METHODS Broiler chicks were given a single intraperitoneal dose (200 mg/kg) of gentamicin (n = 39) or saline (n = 39). Functional status was evaluated with auditory brainstem response (ABR) thresholds before injection and before sacrifice at 2, 5, 9, 16, 21, 28, and 70 days postinjection. The cochleae were then examined with scanning electron microscopy (SEM) to assess the extent of damage along the cochlea and absolute hair cell numbers in the basal 15% of the cochlea (high-frequency region). RESULTS Considerable variability between animals was seen for both ABR and SEM changes. Damage was maximal at 5 days postinjection with an average ABR threshold shift of 12 dB (range -10 to 50 dB) and basal cochlear damage of 28% (range 12%-57%). Hair cell counts were significantly decreased in the basal 15% of the cochlea at 5 days. Hair cell regeneration resulted in rapid anatomical and functional recovery, but evidence of hair cell disorganization persisted at 70 days despite improved thresholds. CONCLUSION A single high dose of gentamicin produces a significant but variable anatomical and functional insult in the chick cochlea. Hair cell regeneration results in rapid but incomplete recovery.
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Affiliation(s)
- D A Girod
- Department of Otolaryngology--Head and Neck Surgery, University of Kansas Medical Center, Kansas City, KS 66160, USA
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13
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Roberson DW, Alosi JA, Messana EP, Cotanche DA. Effect of violation of the labyrinth on the sensory epithelium in the chick cochlea. Hear Res 2000; 141:155-64. [PMID: 10713503 DOI: 10.1016/s0378-5955(99)00218-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Models in which a single large systemic dose of gentamicin is used to cause near-synchronous hair cell (HC) loss in the basal end of the chick cochlea have proven increasingly useful in the study of HC regeneration. We quantified the amount of HC death, as a percentage of the length of the basilar papilla, following single doses of 200 mg/kg and 300 mg/kg of gentamicin in 23-day-old chicks. Following 200 mg/kg of gentamicin, there was total HC loss in the basal 18.0% of the sensory epithelium and partial HC loss in the basal 26.3%. Following 300 mg/kg of gentamicin, there was total HC loss in the basal 30.5% of the epithelium and partial HC loss in the basal 40.9%. The second goal of this study was to determine whether cannula implantation in the inner ear, and infusion of bromodeoxyuridine causes HC damage. We found that creation of a fistula in the labyrinth is not associated with HC damage, but that cannula implantation can cause HC death, and can also cause potentiation of gentamicin-induced HC death. Revision of the cannula and surgical technique to ensure minimal penetration into the labyrinth almost entirely eliminated these effects. We conclude that surgical technique is critical in experimental models in which the labyrinth is violated.
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Affiliation(s)
- D W Roberson
- Department of Otolaryngology, Fegan-9, Boston Children's Hospital, 300 Longwood Ave., Boston, MA, USA.
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Müller M, Smolders JW. Responses of auditory nerve fibers innervating regenerated hair cells after local application of gentamicin at the round window of the cochlea in the pigeon. Hear Res 1999; 131:153-69. [PMID: 10355612 DOI: 10.1016/s0378-5955(99)00029-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Hair cells in the basilar papilla of birds have the capacity to regenerate after injury. There is also functional recovery of hearing after regeneration of the hair cells. The present study was undertaken to determine the effect of local aminoglycoside application on the physiology of auditory nerve fibers innervating regenerated hair cells. Collagen sponges loaded with gentamicin were placed at the round window of the cochlea in adult pigeons. The local application of gentamicin-loaded collagen sponges resulted in total hair cell loss over at least the basal 62% of the basilar papilla. According to the pigeon cochlear place-frequency map (Smolders, Ding-Pfennigdorff and Klinke, Hear. Res. 92 (1995) 151-169), frequencies above 0.3 kHz are represented in this area. Physiological data on single auditory nerve fibers were obtained 14 weeks after gentamicin treatment. The response properties showed the following characteristics when compared to control data: CF thresholds (CF = characteristic frequency) were elevated in units with CF above 0.15 kHz, sharpness of tuning (Q10dB) was reduced in units with CF above 0.38 kHz, low-frequency slopes of the tuning curves were reduced in units with CF above 0.25 kHz, high frequency slopes of the tuning curves were reduced in units with CF above 0.4 kHz, spontaneous firing rate was reduced in units with CF above 0.38 kHz, dynamic range of rate-intensity functions at CF was reduced in units with CF above 0.4 kHz and the slopes of these rate-intensity functions were elevated in units with CF above 0.4 kHz. Maximum discharge rate was the only parameter that remained unchanged in regenerated ears. The results show that the response properties of auditory nerve fibers which innervate areas of the papilla that were previously devoid of hair cells are poorer than the controls, but that action potential generation in the afferent fibers is unaffected. This suggests that despite structural regeneration of the basilar papilla, functional recovery of the auditory periphery is incomplete at the level of the hair cell or the hair cell-afferent synapse.
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Affiliation(s)
- M Müller
- Klinikum der J.W. Goethe-Universität, Physiologisches Institut III, Frankfurt am Main, Germany
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