Mitochondrial Damage and Necroptosis in Aging Cochlea

Area of Science:

• Otolaryngology
• Neuroscience
• Cell Biology

Background:

• Age-related hearing loss (ARHL) is a progressive neurodegenerative disorder.
• Mitochondrial damage and programmed cell death are implicated in ARHL.
• Necroptosis, a form of programmed cell death, has not been fully explored in ARHL.

Purpose of the Study:

• To investigate the role of mitochondria and necroptosis in the aging cochlea.
• To examine cellular and molecular changes in aged C57BL/6J male mice.
• To provide in vivo evidence for necroptosis in age-related hearing dysfunction.

Main Methods:

• Comparative analysis of young and aged C57BL/6J male mice (20 months old).
• Auditory function tests, hair cell counts, neuronal fiber and synaptic ribbon analysis.
• Ultrastructural analysis, cochlear blood flow measurement, gene expression analysis (cytokines, RIPK1, RIPK3, MLKL), and immunofluorescence (COX1, RIPK3).

Main Results:

• Aged mice showed significant hearing loss, reduced hair cells, neuronal fibers, and synaptic ribbons.
• Cochleae in aged mice exhibited damaged mitochondria, decreased blood flow, and increased pro-inflammatory cytokines (IL-1β, IL-6, TNF-α).
• Increased expression of RIPK1, RIPK3, and MLKL, with RIPK3 localized in necroptotic sensorineural tissues, was observed.

Conclusions:

• The aging cochlea displays mitochondrial dysfunction and enhanced inflammation.
• This study provides novel in vivo evidence of necroptosis occurring in the aging cochlea.
• Mitochondrial damage and necroptosis are key pathophysiological mechanisms in age-related hearing loss.