The role of hair cell regeneration in an avian model of inner ear injury and repair from acoustic trauma.

The auditory system of young chicks (Gallus domesticus)is an important model for studying the structure and function of the inner ear. For over 20 years this model has gained interest because of the discovery that birds, and perhaps lower vertebrates in general, are capable of generating new hair cells to replace those lost to ototrauma, a capacity that is absent along the mammalian organ of Corti. Accompanying this remarkable capacity is the nearly complete restoration of auditory function to the chick peripheral ear. This article presents a review of findings on the toxic effect of exposure to extremely loud sound on the young chick ear, and the subsequent recovery from inner ear structural damage and accompanying recovery of auditory function. The evidence, surprisingly, suggests that the role of the regenerated hair cells in the latter may be minimal and that multiple other factors play more important roles. There is also a section on the unique problems encountered in using chicks as laboratory animal subjects in experiments designed to understand the consequences of acoustic trauma. The conclusion summarizes some of the issues that need to be addressed in future research.