Hair cell regeneration in the avian inner ear

The postembryonic production of hair cells in fish and reptiles has been known for several decades. Until recently it was assumed that this capacity was absent in the more highly specialized inner ears of birds and mammals. Recent research has shown, however, that birds have the capacity to rebuild a damaged inner ear. Summarized here are studies conducted in our laboratory which address the following questions: (1) Which are the precursors of the regenerated hair cells? (2) Are the new hair cells functional? (3) What are the ultrastructural properties of regenerated hair cells? and (4) Can the level of proliferation be regulated? Both the auditory and the vestibular systems of the avian inner ear were studied. Our results provide some answers to these questions. The implications of the results are discussed.