Hair-cell regeneration in organ cultures of the postnatal chicken inner ear.

The sensory epithelium of the avian inner ear retains into adulthood progenitor cells for inner-ear hair cells and other cell types in the epithelium. Hair cells are produced normally on an ongoing basis in the vestibular sensory epithelium, and hair-cell production is increased after insult in both auditory and vestibular sensory epithelia. The details of postnatal hair-cell production are not understood. In particular, molecular factors involved in the initiation and regulation of hair-cell genesis and differentiation are not known. Studies of this phenomena have been hampered by the lack of cell culture models. An organ culture system was developed which encourages generation and differentiation of hair cells in mature inner-ear sensory epithelia. Continuous labeling with tritiated thymidine showed genesis of both supporting cells and hair cells in normal vestibular epithelia grown in culture, and an increase in hair-cell and supporting-cell proliferation in damaged sensory epithelia grown in culture as compared to undamaged controls. This demonstrates, in vitro, both the division and differentiation of hair-cell progenitor cells in normal vestibular epithelia, and the maintenance of the hair-cell regeneration process in damaged inner-ear epithelia. This culture system should be useful for studies of hair-cell genesis and differentiation as well as studies of hair-cell and supporting-cell functioning in general.