Preventing presbycusis in mice with enhanced medial olivocochlear feedback

Area of Science:

• Neuroscience
• Otolaryngology
• Gerontology

Background:

• Age-related hearing loss (ARHL), or presbycusis, commonly impacts speech comprehension in noise.
• Cochlear synaptic degeneration (synaptopathy) is implicated as an early factor in ARHL.
• The medial olivocochlear (MOC) system provides efferent feedback to the cochlea.

Purpose of the Study:

• To investigate the role of cochlear synaptic degeneration in ARHL.
• To assess the impact of enhanced α9α10 nicotinic acetylcholine receptors (nAChRs) on cochlear structure and function during aging.
• To determine if enhanced efferent feedback can prevent age-related auditory decline.

Main Methods:

• Characterized age-related changes in cochlear structure and function in wild-type and genetically modified mice.
• Utilized distortion product otoacoustic emissions and auditory brainstem responses to assess cochlear function.
• Employed confocal microscopy on immunolabeled cochlear whole mounts to quantify cellular and synaptic components.

Main Results:

• Aged wild-type mice exhibited elevated hearing thresholds, synaptic loss at inner hair cells, and some outer hair cell loss.
• Aged mice with enhanced α9α10 nAChRs showed preserved cochlear structure and function.
• Synaptic integrity and hair cell populations were maintained in aged mice with enhanced olivocochlear inhibition.

Conclusions:

• Enhanced olivocochlear feedback via α9α10 nAChRs protects against age-related cochlear synaptic degeneration and hearing loss.
• The medial olivocochlear system plays a crucial role in maintaining inner ear function during aging.
• Enhancing the MOC system represents a potential therapeutic strategy for preventing presbycusis.