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Zorio DAR, Jackson CM, Liu Y, Rubel EW, Wang Y. Cellular distribution of the fragile X mental retardation protein in the mouse brain. J Comp Neurol 2017; 525:818-849. [PMID: 27539535 PMCID: PMC5558202 DOI: 10.1002/cne.24100] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Revised: 08/10/2016] [Accepted: 08/11/2016] [Indexed: 11/07/2022]
Abstract
The fragile X mental retardation protein (FMRP) plays an important role in normal brain development. Absence of FMRP results in abnormal neuronal morphologies in a selected manner throughout the brain, leading to intellectual deficits and sensory dysfunction in the fragile X syndrome (FXS). Despite FMRP importance for proper brain function, its overall expression pattern in the mammalian brain at the resolution of individual neuronal cell groups is not known. In this study we used FMR1 knockout and isogenic wildtype mice to systematically map the distribution of FMRP expression in the entire mouse brain. Using immunocytochemistry and cellular quantification analyses, we identified a large number of prominent cell groups expressing high levels of FMRP at the subcortical levels, in particular sensory and motor neurons in the brainstem and thalamus. In contrast, many cell groups in the midbrain and hypothalamus exhibit low FMRP levels. More important, we describe differential patterns of FMRP distribution in both cortical and subcortical brain regions. Almost all major brain areas contain high and low levels of FMRP cell groups adjacent to each other or between layers of the same cortical areas. These differential patterns indicate that FMRP expression appears to be specific to individual neuronal cell groups instead of being associated with all neurons in distinct brain regions, as previously considered. Taken together, these findings support the notion of FMRP differential neuronal regulation and strongly implicate the contribution of fundamental sensory and motor processing at subcortical levels to FXS pathology. J. Comp. Neurol. 525:818-849, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Diego A. R. Zorio
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL 32306, USA
| | - Christine M. Jackson
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL 32306, USA
| | - Yong Liu
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL 32306, USA
| | - Edwin W Rubel
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, University of Washington School of Medicine, Box 357923, Seattle, WA 98195, USA
| | - Yuan Wang
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL 32306, USA
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Weatherstone JH, Kopp-Scheinpflug C, Pilati N, Wang Y, Forsythe ID, Rubel EW, Tempel BL. Maintenance of neuronal size gradient in MNTB requires sound-evoked activity. J Neurophysiol 2016; 117:756-766. [PMID: 27881722 PMCID: PMC5304411 DOI: 10.1152/jn.00528.2016] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 11/21/2016] [Indexed: 12/12/2022] Open
Abstract
Neurons of the medial nucleus of the trapezoid body (MNTB) act as fast-spiking inhibitory interneurons within the auditory brain stem. The MNTB is topographically organized, with low sound frequencies encoded laterally and high frequencies medially. We discovered a cell size gradient along this axis: lateral neurons are larger than medial neurons. The absence of this gradient in deaf mice lacking plasma membrane calcium ATPase 2 suggests an activity-dependent, calcium-mediated mechanism that controls neuronal soma size. The medial nucleus of the trapezoid body (MNTB) is an important source of inhibition during the computation of sound location. It transmits fast and precisely timed action potentials at high frequencies; this requires an efficient calcium clearance mechanism, in which plasma membrane calcium ATPase 2 (PMCA2) is a key component. Deafwaddler (dfw2J) mutant mice have a null mutation in PMCA2 causing deafness in homozygotes (dfw2J/dfw2J) and high-frequency hearing loss in heterozygotes (+/dfw2J). Despite the deafness phenotype, no significant differences in MNTB volume or cell number were observed in dfw2J homozygous mutants, suggesting that PMCA2 is not required for MNTB neuron survival. The MNTB tonotopic axis encodes high to low sound frequencies across the medial to lateral dimension. We discovered a cell size gradient along this axis: lateral neuronal somata are significantly larger than medially located somata. This size gradient is decreased in +/dfw2J and absent in dfw2J/dfw2J. The lack of acoustically driven input suggests that sound-evoked activity is required for maintenance of the cell size gradient. This hypothesis was corroborated by selective elimination of auditory hair cell activity with either hair cell elimination in Pou4f3 DTR mice or inner ear tetrodotoxin (TTX) treatment. The change in soma size was reversible and recovered within 7 days of TTX treatment, suggesting that regulation of the gradient is dependent on synaptic activity and that these changes are plastic rather than permanent. NEW & NOTEWORTHY Neurons of the medial nucleus of the trapezoid body (MNTB) act as fast-spiking inhibitory interneurons within the auditory brain stem. The MNTB is topographically organized, with low sound frequencies encoded laterally and high frequencies medially. We discovered a cell size gradient along this axis: lateral neurons are larger than medial neurons. The absence of this gradient in deaf mice lacking plasma membrane calcium ATPase 2 suggests an activity-dependent, calcium-mediated mechanism that controls neuronal soma size.
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Affiliation(s)
- Jessica H Weatherstone
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, and Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington.,Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, and Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington
| | - Conny Kopp-Scheinpflug
- Department of Neuroscience, Psychology and Behaviour, University of Leicester, Leicester, United Kingdom; .,Division of Neurobiology, Department Biology II, Ludwig-Maximilians University Munich, Planegg-Martinsried, Germany
| | - Nadia Pilati
- Department of Neuroscience, Psychology and Behaviour, University of Leicester, Leicester, United Kingdom.,Autifony Srl Laboratories, Medicines Research Centre, Verona, Italy; and
| | - Yuan Wang
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, and Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington.,Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida
| | - Ian D Forsythe
- Department of Neuroscience, Psychology and Behaviour, University of Leicester, Leicester, United Kingdom
| | - Edwin W Rubel
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, and Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington
| | - Bruce L Tempel
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, and Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington.,Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, and Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington
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Kurioka T, Lee MY, Heeringa AN, Beyer LA, Swiderski DL, Kanicki AC, Kabara LL, Dolan DF, Shore SE, Raphael Y. Selective hair cell ablation and noise exposure lead to different patterns of changes in the cochlea and the cochlear nucleus. Neuroscience 2016; 332:242-57. [PMID: 27403879 DOI: 10.1016/j.neuroscience.2016.07.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2016] [Revised: 06/14/2016] [Accepted: 07/01/2016] [Indexed: 01/21/2023]
Abstract
In experimental animal models of auditory hair cell (HC) loss, insults such as noise or ototoxic drugs often lead to secondary changes or degeneration in non-sensory cells and neural components, including reduced density of spiral ganglion neurons, demyelination of auditory nerve fibers and altered cell numbers and innervation patterns in the cochlear nucleus (CN). However, it is not clear whether loss of HCs alone leads to secondary degeneration in these neural components of the auditory pathway. To elucidate this issue, we investigated changes of central components after cochlear insults specific to HCs using diphtheria toxin receptor (DTR) mice expressing DTR only in HCs and exhibiting complete HC loss when injected with diphtheria toxin (DT). We showed that DT-induced HC ablation has no significant impacts on the survival of auditory neurons, central synaptic terminals, and myelin, despite complete HC loss and profound deafness. In contrast, noise exposure induced significant changes in synapses, myelin and CN organization even without loss of inner HCs. We observed a decrease of neuronal size in the auditory pathway, including peripheral axons, spiral ganglion neurons, and CN neurons, likely due to loss of input from the cochlea. Taken together, selective HC ablation and noise exposure showed different patterns of pathology in the auditory pathway and the presence of HCs is not essential for the maintenance of central synaptic connectivity and myelination.
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Affiliation(s)
- Takaomi Kurioka
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA; Department of Otorhinolaryngology-Head and Neck Surgery, National Defense Medical College, Tokorozawa, Saitama, Japan
| | - Min Young Lee
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Amarins N Heeringa
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Lisa A Beyer
- 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
| | - Ariane C Kanicki
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Lisa L Kabara
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - David F Dolan
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Susan E Shore
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, 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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Abstract
From the therapeutic perspective, the etiology and pathophysiology of hearing loss can be classified based on the extent of the primary cause. Hearing loss can have very different consequences for cell preservation in the organ of Corti and the spiral ganglion. These not only have implications for prosthetic therapy outcome, but may also influence the potential for future causal molecular therapies. Etiologies leading to deficits that are limited to one or a few molecules without having an effect on cell survival have the greatest potential for future causal therapy using molecular and cellular approaches. Preliminary success for molecular therapy was recently reported in animal experiments. Unfortunately, the incidence of these types of hearing loss is very low and in the future the therapy of hearing loss will therefore also require several different approaches. In addition to peripheral pathophysiology, hearing loss has consequences on the functioning of the brain, which can vary greatly due to individual adaptation to the situation without hearing. The authors therefore argue for individualization of the diagnostics and therapy that focus not only the symptom of hearing loss, but also the individual pathophysiology and consequences. Only with individualized therapy can the success of treating hearing disorders be significantly improved.
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Kral A, Kronenberger WG, Pisoni DB, O'Donoghue GM. Neurocognitive factors in sensory restoration of early deafness: a connectome model. Lancet Neurol 2016; 15:610-21. [PMID: 26976647 PMCID: PMC6260790 DOI: 10.1016/s1474-4422(16)00034-x] [Citation(s) in RCA: 200] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Revised: 12/15/2015] [Accepted: 01/21/2016] [Indexed: 12/11/2022]
Abstract
Progress in biomedical technology (cochlear, vestibular, and retinal implants) has led to remarkable success in neurosensory restoration, particularly in the auditory system. However, outcomes vary considerably, even after accounting for comorbidity-for example, after cochlear implantation, some deaf children develop spoken language skills approaching those of their hearing peers, whereas other children fail to do so. Here, we review evidence that auditory deprivation has widespread effects on brain development, affecting the capacity to process information beyond the auditory system. After sensory loss and deafness, the brain's effective connectivity is altered within the auditory system, between sensory systems, and between the auditory system and centres serving higher order neurocognitive functions. As a result, congenital sensory loss could be thought of as a connectome disease, with interindividual variability in the brain's adaptation to sensory loss underpinning much of the observed variation in outcome of cochlear implantation. Different executive functions, sequential processing, and concept formation are at particular risk in deaf children. A battery of clinical tests can allow early identification of neurocognitive risk factors. Intervention strategies that address these impairments with a personalised approach, taking interindividual variations into account, will further improve outcomes.
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Affiliation(s)
- Andrej Kral
- Institute of AudioNeuroTechnology and Department of Experimental Otology, ENT Clinics, Medical University Hannover, Hannover, Germany; School of Behavioural and Brain Sciences, The University of Texas at Dallas, Dallas, TX, USA.
| | - William G Kronenberger
- Department of Psychiatry, and DeVault Otologic Research Laboratory, Department of Otolaryngology: Head and Neck Surgery, Indiana University School of Medicine, Indianapolis, IN, USA; Department of Psychological and Brain Sciences, Indiana University, Indianapolis, IN, USA
| | - David B Pisoni
- Department of Psychiatry, and DeVault Otologic Research Laboratory, Department of Otolaryngology: Head and Neck Surgery, Indiana University School of Medicine, Indianapolis, IN, USA; Department of Psychological and Brain Sciences, Indiana University, Indianapolis, IN, USA
| | - Gerard M O'Donoghue
- National Institute of Health Research, Nottingham Hearing Biomedical Research Unit, Nottingham University Hospitals NHS Trust, Nottingham, UK
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Brosel S, Laub C, Averdam A, Bender A, Elstner M. Molecular aging of the mammalian vestibular system. Ageing Res Rev 2016; 26:72-80. [PMID: 26739358 DOI: 10.1016/j.arr.2015.12.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 12/16/2015] [Accepted: 12/21/2015] [Indexed: 12/18/2022]
Abstract
Dizziness and imbalance frequently affect the elderly and contribute to falls and frailty. In many geriatric patients, clinical testing uncovers a dysfunction of the vestibular system, but no specific etiology can be identified. Neuropathological studies have demonstrated age-related degeneration of peripheral and central vestibular neurons, but the molecular mechanisms are poorly understood. In contrast, recent studies into age-related hearing loss strongly implicate mitochondrial dysfunction, oxidative stress and apoptotic cell death of cochlear hair cells. While some data suggest that analogous biological pathomechanisms may underlie vestibular dysfunction, actual proof is missing. In this review, we summarize the available data on the molecular causes of vestibular dysfunction.
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Affiliation(s)
- Sonja Brosel
- German Center for Vertigo and Balance Disorders, Department of Neurology, Klinikum Grosshadern, Ludwig-Maximilians-University, Marchioninistr. 15, 81377 Munich, Germany.
| | - Christoph Laub
- Department of Neurology with Friedrich-Baur-Institute, Klinikum Grosshadern, Ludwig-Maximilians-University, Marchioninistr. 15, 81377 Munich, Germany
| | - Anne Averdam
- Department of Neurology with Friedrich-Baur-Institute, Klinikum Grosshadern, Ludwig-Maximilians-University, Marchioninistr. 15, 81377 Munich, Germany
| | - Andreas Bender
- Department of Neurology, Therapiezentrum Burgau, Kapuzinerstr.34, 89331 Burgau, Germany
| | - Matthias Elstner
- Department of Neurology with Friedrich-Baur-Institute, Klinikum Grosshadern, Ludwig-Maximilians-University, Marchioninistr. 15, 81377 Munich, Germany; Department of Neurology and Clinical Neurophysiology, Academic Hospital Munich-Bogenhausen, Technical University of Munich, Englschalkingerstr. 77, 81925 Munich, Germany
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Fractalkine Signaling Regulates Macrophage Recruitment into the Cochlea and Promotes the Survival of Spiral Ganglion Neurons after Selective Hair Cell Lesion. J Neurosci 2016; 35:15050-61. [PMID: 26558776 DOI: 10.1523/jneurosci.2325-15.2015] [Citation(s) in RCA: 97] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
UNLABELLED Macrophages are recruited into the cochlea in response to injury caused by acoustic trauma or ototoxicity, but the nature of the interaction between macrophages and the sensory structures of the inner ear remains unclear. The present study examined the role of fractalkine signaling in regulating the injury-evoked behavior of macrophages following the selective ablation of cochlear hair cells. We used a novel transgenic mouse model in which the human diphtheria toxin receptor (huDTR) is selectively expressed under the control of Pou4f3, a hair cell-specific transcription factor. Administration of diphtheria toxin (DT) to these mice resulted in nearly complete ablation of cochlear hair cells, with no evident pathology among supporting cells, spiral ganglion neurons, or cells of the cochlear lateral wall. Hair cell death led to an increase in macrophages associated with the sensory epithelium of the cochlea. Their numbers peaked at 14 days after DT and then declined at later survival times. Increased macrophages were also observed within the spiral ganglion, but their numbers remained elevated for (at least) 56 d after DT. To investigate the role of fractalkine signaling in macrophage recruitment, we crossed huDTR mice to a mouse line that lacks expression of the fractalkine receptor (CX3CR1). Disruption of fractalkine signaling reduced macrophage recruitment into both the sensory epithelium and spiral ganglion and also resulted in diminished survival of spiral ganglion neurons after hair cell death. Our results suggest a fractalkine-mediated interaction between macrophages and the neurons of the cochlea. SIGNIFICANCE STATEMENT It is known that damage to the inner ear leads to recruitment of inflammatory cells (macrophages), but the chemical signals that initiate this recruitment and the functions of macrophages in the damaged ear are unclear. Here we show that fractalkine signaling regulates macrophage recruitment into the cochlea and also promotes the survival of cochlear afferents after selective hair cell lesion. Because these afferent neurons carry sound information from the cochlea to the auditory brainstem, their survival is a key determinant of the success of cochlear prosthetics. Our data suggest that fractalkine signaling in the cochlea is neuroprotective, and reveal a previously uncharacterized interaction between cells of the cochlea and the innate immune system.
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Tillein J, Hubka P, Kral A. Monaural Congenital Deafness Affects Aural Dominance and Degrades Binaural Processing. Cereb Cortex 2016; 26:1762-77. [PMID: 26803166 PMCID: PMC4785956 DOI: 10.1093/cercor/bhv351] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Cortical development extensively depends on sensory experience. Effects of congenital monaural and binaural deafness on cortical aural dominance and representation of binaural cues were investigated in the present study. We used an animal model that precisely mimics the clinical scenario of unilateral cochlear implantation in an individual with single-sided congenital deafness. Multiunit responses in cortical field A1 to cochlear implant stimulation were studied in normal-hearing cats, bilaterally congenitally deaf cats (CDCs), and unilaterally deaf cats (uCDCs). Binaural deafness reduced cortical responsiveness and decreased response thresholds and dynamic range. In contrast to CDCs, in uCDCs, cortical responsiveness was not reduced, but hemispheric-specific reorganization of aural dominance and binaural interactions were observed. Deafness led to a substantial drop in binaural facilitation in CDCs and uCDCs, demonstrating the inevitable role of experience for a binaural benefit. Sensitivity to interaural time differences was more reduced in uCDCs than in CDCs, particularly at the hemisphere ipsilateral to the hearing ear. Compared with binaural deafness, unilateral hearing prevented nonspecific reduction in cortical responsiveness, but extensively reorganized aural dominance and binaural responses. The deaf ear remained coupled with the cortex in uCDCs, demonstrating a significant difference to deprivation amblyopia in the visual system.
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Affiliation(s)
- Jochen Tillein
- Cluster of Excellence Hearing4all, Institute of AudioNeuroTechnology and Department of Experimental Otology of the ENT Clinics, Hannover Medical School, Hannover, Germany Department of Otorhinolaryngology, J.W. Goethe University, Frankfurt am Main, Germany MED-EL GmbH, Innsbruck, Austria
| | - Peter Hubka
- Cluster of Excellence Hearing4all, Institute of AudioNeuroTechnology and Department of Experimental Otology of the ENT Clinics, Hannover Medical School, Hannover, Germany
| | - Andrej Kral
- Cluster of Excellence Hearing4all, Institute of AudioNeuroTechnology and Department of Experimental Otology of the ENT Clinics, Hannover Medical School, Hannover, Germany School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, TX, USA
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Luo C, Omelchenko I, Manson R, Robbins C, Oesterle EC, Cao GZ, Shen I, Hume CR. Direct Intracochlear Acoustic Stimulation Using a PZT Microactuator. Trends Hear 2015; 19:2331216515616942. [PMID: 26631107 PMCID: PMC4771031 DOI: 10.1177/2331216515616942] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Combined electric and acoustic stimulation has proven to be an effective strategy to improve hearing in some cochlear implant users. We describe an acoustic microactuator to directly deliver stimuli to the perilymph in the scala tympani. The 800 µm by 800 µm actuator has a silicon diaphragm driven by a piezoelectric thin film (e.g., lead-zirconium-titanium oxide or PZT). This device could also be used as a component of a bimodal acoustic-electric electrode array. In the current study, we established a guinea pig model to test the actuator for its ability to deliver auditory signals to the cochlea in vivo. The actuator was placed through the round window of the cochlea. Auditory brainstem response (ABR) thresholds, peak latencies, and amplitude growth were calculated for an ear canal speaker versus the intracochlear actuator for tone burst stimuli at 4, 8, 16, and 24 kHz. An ABR was obtained after removal of the probe to assess loss of hearing related to the procedure. In some animals, the temporal bone was harvested for histologic analysis of cochlear damage. We show that the device is capable of stimulating ABRs in vivo with latencies and growth functions comparable to stimulation in the ear canal. Further experiments will be necessary to evaluate the efficiency and safety of this modality in long-term auditory stimulation and its ability to be integrated with conventional cochlear implant arrays.
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Affiliation(s)
- Chuan Luo
- Department of Mechanical Engineering, University of Washington, Seattle, WA, USA
- Department of Precision Instruments, Tsinghua University, Beijing, China
| | - Irina Omelchenko
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology–Head and Neck Surgery, University of Washington, Seattle, WA, USA
| | - Robert Manson
- Department of Mechanical Engineering, University of Washington, Seattle, WA, USA
| | - Carol Robbins
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology–Head and Neck Surgery, University of Washington, Seattle, WA, USA
| | - Elizabeth C. Oesterle
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology–Head and Neck Surgery, University of Washington, Seattle, WA, USA
| | - Guo Zhong Cao
- Department of Materials Science, University of Washington, Seattle, WA, USA
| | - I.Y. Shen
- Department of Mechanical Engineering, University of Washington, Seattle, WA, USA
| | - Clifford R. Hume
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology–Head and Neck Surgery, University of Washington, Seattle, WA, USA
- VA Puget Sound, Seattle, WA, USA
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Kaur T, Hirose K, Rubel EW, Warchol ME. Macrophage recruitment and epithelial repair following hair cell injury in the mouse utricle. Front Cell Neurosci 2015; 9:150. [PMID: 25954156 PMCID: PMC4406144 DOI: 10.3389/fncel.2015.00150] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 04/01/2015] [Indexed: 11/13/2022] Open
Abstract
The sensory organs of the inner ear possess resident populations of macrophages, but the function of those cells is poorly understood. In many tissues, macrophages participate in the removal of cellular debris after injury and can also promote tissue repair. The present study examined injury-evoked macrophage activity in the mouse utricle. Experiments used transgenic mice in which the gene for the human diphtheria toxin receptor (huDTR) was inserted under regulation of the Pou4f3 promoter. Hair cells in such mice can be selectively lesioned by systemic treatment with diphtheria toxin (DT). In order to visualize macrophages, Pou4f3-huDTR mice were crossed with a second transgenic line, in which one or both copies of the gene for the fractalkine receptor CX3CR1 were replaced with a gene for GFP. Such mice expressed GFP in all macrophages, and mice that were CX3CR1(GFP/GFP) lacked the necessary receptor for fractalkine signaling. Treatment with DT resulted in the death of ∼70% of utricular hair cells within 7 days, which was accompanied by increased numbers of macrophages within the utricular sensory epithelium. Many of these macrophages appeared to be actively engulfing hair cell debris, indicating that macrophages participate in the process of 'corpse removal' in the mammalian vestibular organs. However, we observed no apparent differences in injury-evoked macrophage numbers in the utricles of CX3CR1(+/GFP) mice vs. CX3CR1(GFP/GFP) mice, suggesting that fractalkine signaling is not necessary for macrophage recruitment in these sensory organs. Finally, we found that repair of sensory epithelia at short times after DT-induced hair cell lesions was mediated by relatively thin cables of F-actin. After 56 days recovery, however, all cell-cell junctions were characterized by very thick actin cables.
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Affiliation(s)
- Tejbeer Kaur
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO USA
| | - Keiko Hirose
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO USA
| | - Edwin W Rubel
- The Virginia Merrill Bloedel Hearing Research Center and Department of Otolaryngology - Head and Neck Surgery, University of Washington School of Medicine Seattle, WA, USA
| | - Mark E Warchol
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO USA
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