Functional and Structural Changes in the Inner Ear and Cochlear Hair Cell Loss Induced by Hypergravity

Area of Science:

• Space biology
• Neuroscience
• Otolaryngology

Background:

• Gravitational changes impact multiple body systems, yet inner ear responses to altered gravity are understudied.
• The vestibule and cochlea share structures and neural pathways, necessitating research into auditory nerve cell changes under hypergravity.

Purpose of the Study:

• To investigate functional and structural changes in the inner ear following hypergravity exposure.
• To analyze auditory brainstem responses (ABRs) and cochlear integrity under simulated gravitational stress.

Main Methods:

• Exposure to hypergravity stimuli.
• Analysis of auditory brainstem responses (ABRs) including click thresholds, tone burst amplitudes, and latencies.
• Histological examination for hair cell loss and nerve damage on the cochlear surface.

Main Results:

• Hypergravity exposure led to increased click thresholds across all frequencies.
• Reduced amplitudes and delayed latencies in tone burst ABRs were observed, especially at high frequencies.
• Significant hair cell loss in the cochlea's middle and basal turns and cochlear nerve damage were evident after 4 weeks of 4G exposure.

Conclusions:

• Prolonged hypergravity exposure induces functional and structural damage to the inner ear.
• The cochlea, particularly mid and high-frequency regions, is vulnerable to hypergravity.
• Findings highlight potential risks for auditory function in altered gravitational environments.