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Mitochondrial Dynamics in Auditory Sensory Cells
Author(s) -
Nuttall Alfred L,
Foster Sarah,
Wilson Teresa
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1015.4
Subject(s) - mitochondrion , organ of corti , cochlea , microbiology and biotechnology , hair cell , inner ear , biology , sound exposure , auditory fatigue , chemistry , anatomy , hearing loss , sound (geography) , noise exposure , audiology , medicine , physics , acoustics
Background The auditory sensory hair cells convert sound vibrations into neuronal impulses. Excessive loud sound exposure can result in the overproduction of oxidative free radicals by the mitochondria in these cells. This can negatively impact hair cell function and viability leading to permanent loss of hearing sensitivity. The mechanisms that initiate this process are thought to include ischemia/reperfusion injury as well as metabolic overstimulation. Despite the importance of auditory hair cells, the basic physiology of the mitochondria in these cells is relatively unknown. Further, whether mitochondrial dynamics and spatial localization are altered to respond to increased energy needs of the cells with loud sound exposure has not been well‐characterized. Objective In this study, our goal was to characterize mitochondrial morphology and spatial distribution in auditory cells under normal and loud sound induced stress conditions. Methods and Results To examine mitochondria in outer hair cells (OHCs), PhAM floxed mice were crossed with prestin‐CreER T2 mice to generate mice that express a mitochondrial‐specific version of the Dendra2 fluorescent protein (mito‐Dendra2) in the mitochondria in OHCs. For examination of mitochondria in all organ of Corti cells, immunolabeling for the mitochondrial outer membrane protein Tom20 was performed. These mice were exposed to damaging levels of loud sound and the cochlea harvested at 24 and 48 hours following noise exposure. Airyscan and super resolution imaging of mito‐Dendra2 and Tom20 fluorescence showed primarily fragmented mitochondria in the OHCs and a mixture of punctate and short rod‐shaped mitochondria in the inner hair cells of normal control animals. Following noise exposure, the mitochondria of the organ of Corti cells were examined for alterations in spatial distribution, number, and morphology, and preliminary results demonstrated changes in the distribution of mitochondria in OHCs. Conclusions Mitochondria are highly dynamic organelles that are maintained by the conserved actions of mitochondrial division, fusion, motility, and tethering. The presence of excessive cellular stress typically results in attenuated fusion processes and increased mitochondrial fragmentation. The presence of fragmented mitochondria in OHCs suggests that the balance of fission and fusion processes are altered, potentially due to a higher oxidant environment being present in these cells. Support or Funding Information Supported by grants 5R01DC000105 (ALN) and P30DC005983.