Supporting cells in avian vestibular organs proliferate in serum-free culture

Explants of saccules and utricles taken from hatchling chicks were cultured in medium that contained fetal bovine serum and in serum-free medium. The mitotic tracers [³H]thymidine and bromo-deoxyuridine were added to the media to label proliferating cells. High numbers of labeled supporting cells were found in cultures that were maintained in both serum-containing and serum-free media. After seven days in culture, some of the labeled cells had begun to differentiate as hair cells. The results suggest that any mitogenic factors necessary for supporting cell proliferation and the factors required for the initial stages of hair cell differentiation are produced by cells contained within expiants of the vestibular sensory epithelia.