The spontaneous appearance of hair cell-like cells in the mammalian cochlea following aminoglycoside ototoxicity

YOUNG rats (in vivo) and cochleas from neonatal rats (in vitro) were treated with ototoxic antibiotics. Scanning electron microscope observations of the cicatricial epithelium of the former outer hair cell region revealed cells with a tuft of microvilli at their apical surface that could contain actin filaments, as observed by phalloidin staining. The apical organization of these hair cell-like cells was reminiscent of fetal hair cells topped with a bundle of microvilli. During both in vivo and in vitro observations, and despite the use of several growth factors in vitro, these hair cell-like cells did not differentiate into mature sensory cells. These hair cell-like cells might represent an attempt by the former sensory epithelium to regenerate.