Timothy C. Hain, MD
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Many processes that affect the inner ear kill the main sensory part of the ear, hair cells. While it would seem reasonable that hair cells should be replaced when they are lost, this seems to be species specific. Hair cells of birds, both auditory and vestibular, regenerate but hair cells of humans are generally felt to not regenerate. In birds, auditory hair cells regenerate after exposure to ototoxic aminoglycoside antibiotics, and noise. Vestibular hair cells also regenerate in birds, with both the vestibulocollic and vestibuloocular reflexes recovering full functionality after aminoglycoside exposure in chickens (Goode et al, 1999; Carey et al, 1996; Boyle et al, 2001).
If birds can regenerate their hair cells, it seems reasonable that people might also be able to do this, perhaps with the correct growth factor trigger. This is an ongoing subject of research.
A recent study indicated that sterocilia, a part of the hair cell, "turns over" in cell cultures of rat inner ears over roughly 48 hours (Schneider and others, 2002). It is not surprising to find that damaged cells can repair themselves and this process offers evidence for short-term repair processes in the ear.