Hair cell regeneration in the chicken cochlea following aminoglycoside toxicity

Hair cell loss in the avian cochlea partially recovers following both acoustic trauma and aminoglycoside intoxication. DNA labeling with tritiated thymidine has shown that the restoration of cell number following acoustic trauma results from the production of new hair cells by mitotic division. The purpose of the present study was to determine if mitosis also contributes to the recovery of hair cell number which occurs following aminoglycoside intoxication. Chickens received daily injections of either gentamicin sulfate or distilled water for 10 consecutive days. During the latter 7 days of this period, all birds were also injected with [3H]thymidine. Following postinjection survival periods of 3 or 6 days, one papilla from each bird was processed for autoradiography and the other for scanning electron microscopy (SEM). Incorporation of [3H]thymidine was seen over hair cells and support cells in experimental papillae in regions of hair cell loss. No labeling was seen outside of damaged regions or in the papillae of control birds. SEM showed that damaged regions in experimental birds contained cells similar in appearance to developing auditory hair cells in avian embryos. These results show that the restoration of hair cell number following aminoglycoside toxicity results from the production of new cells by mitosis.