Ultrastructural evidence for hair cell regeneration in the mammalian inner ear

TLDR

Hair cell loss in mammalian inner ears was traditionally considered irreversible. Scanning electron micrographs and thin sections of guinea pig utricles revealed that gentamicin‑induced hair cell loss was followed by the appearance of new hair cells, including immature bundles and type‑2‑like cells, demonstrating unexpected regeneration in the mature mammalian inner ear.

Abstract

It has long been thought that hair cell loss from the inner ears of mammals is irreversible. This report presents scanning electron micrographs and thin sections of the utricles from the inner ears of guinea pigs that show that, after hair cell loss caused by treatment with the aminoglycoside gentamicin, hair cells reappeared. Four weeks after the end of treatment, a large number of cells with immature hair bundles in multiple stages of development could be identified in the utricle. Thin sections showed that lost type 1 hair cells were replaced by cells with a morphology similar to that of type 2 hair cells. These results indicate an unexpected capacity for hair cell regeneration in vivo in the mature mammalian inner ear.