OHCs

OHCs, or outer hair cells, are specialized sensory cells located in the organ of Corti within the mammalian cochlea. They are arranged in three rows and lie between the tectorial membrane and the basilar membrane, alongside the inner hair cells that primarily transduce sound into neural signals. The main role of OHCs is to act as mechanical amplifiers that enhance the motion of the basilar membrane, improving auditory sensitivity and frequency selectivity, especially for softer sounds.

The amplification arises from electromotility, a rapid change in the length of the cells in response to voltage changes across the cell membrane. This motion is driven by the motor protein prestin and allows OHCs to boost the movement of the inner ear structures in real time, increasing the response to a wide range of frequencies.

Anatomically, OHCs have hair bundles of stereocilia on their apical surfaces and receive efferent innervation from the brain, enabling dynamic feedback control of amplification. In contrast, inner hair cells are the primary transducers of mechanical energy into neural signals; OHCs serve to enhance and sharpen the cochlear response.

Damage or loss of OHC function raises hearing thresholds and reduces frequency discrimination, even when inner hair cells and neurons are intact. OHCs are particularly vulnerable to noise exposure, ototoxic drugs (such as certain antibiotics and platinum-based chemotherapy), aging, and other cochlear insults. Mammals have limited regenerative capacity for hair cells, so such damage is often permanent.

Clinically, while cochlear implants bypass damaged hair cells to stimulate the auditory nerve, the preserved function of remaining OHCs can influence outcomes by affecting residual amplification and sensitivity.