Tumor necrosis factor-alpha-mutant mice exhibit high frequency hearing loss

Area of Science:

• Oto-neurology
• Immunology
• Genetics

Background:

• Exogenous tumor necrosis factor-alpha (TNF-α) contributes to auditory hair cell death via apoptosis.
• The role of TNF-α in normal hair cell physiology remains largely uncharacterized.

Purpose of the Study:

• To investigate the function of TNF-α in cochlear morphology and auditory function.
• To analyze the auditory performance and inner ear structure of TNF-α-deficient mice.

Main Methods:

• Auditory evoked brainstem response (ABR) testing to assess hearing thresholds.
• Analysis of cochlear morphology, including the organ of Corti and hair cell stereocilia via scanning electron microscopy.
• Distortion product otoacoustic emissions (DPOAEs) measurement to evaluate outer hair cell function.

Main Results:

• TNF-α-deficient mice exhibited significantly higher ABR thresholds, particularly at high frequencies, indicating early hearing loss.
• No gross morphological differences were observed in the cochlea or auditory ossicles between mutant and wild-type mice.
• Reduced DPOAE amplitudes suggested outer hair cell dysfunction, with stereocilia loss or malformation observed in the basal and middle turns of the cochlea.

Conclusions:

• TNF-α plays a crucial role in maintaining normal auditory function and hair cell integrity.
• Stereocilia abnormalities in outer hair cells are a key factor contributing to hearing loss in TNF-α-deficient mice.
• Further research into TNF-α's physiological role is warranted for understanding hearing preservation.