Somatic mtDNA mutations cause progressive hearing loss in the mouse.

Area of Science:

• Gerontology
• Neuroscience
• Genetics

Background:

• Age-associated hearing loss (presbycusis) is common and linked to mitochondrial dysfunction.
• Mitochondrial DNA (mtDNA) mutations accumulate with age and can cause premature aging phenotypes.

Purpose of the Study:

• To investigate the impact of elevated somatic mtDNA mutations on the auditory system using mtDNA mutator mice.
• To determine if mtDNA mutations contribute to the pathology observed in presbycusis.

Main Methods:

• Utilized mtDNA mutator mice exhibiting increased somatic mtDNA point mutations.
• Assessed auditory function using auditory brainstem response (ABR) thresholds.
• Performed quantitative histological analysis of the cochlea, spiral ganglion, stria vascularis, and cochlear nucleus.

Main Results:

• mtDNA mutator mice displayed progressive hearing impairment (elevated ABR thresholds).
• No significant hair cell loss was observed in the cochlea.
• Progressive apoptotic cell loss occurred in the spiral ganglion and increased pathology in the stria vascularis with age.
• Accelerated neuronal degeneration was noted in the cochlear nucleus of mutator mice compared to controls.
• Auditory system pathology in mutator mice closely resembled human presbycusis.

Conclusions:

• Elevated somatic mtDNA mutations lead to progressive auditory system degeneration in mice.
• The findings suggest a strong link between mitochondrial dysfunction and presbycusis.
• Further human studies are warranted to confirm the role of mtDNA mutations in age-related hearing loss.