Melanogenesis by human uveal melanocytes in vitro.

PURPOSE To study melanogenesis by cultured human uveal melanocytes, and the relationship between melanin production by uveal melanocytes in vitro with the degree of iris pigmentation in vivo. METHODS Melanin content, melanin production, and tyrosinase activity of cultured uveal melanocytes derived from eyes of various iris color were measured at different stages of cultivation. RESULTS Cultured uveal melanocytes maintained a constant level of melanin content, expressed tyrosinase activity, and produced measurable amounts of melanin in vitro. Melanosomes in different stages were seen ultrastructurally. Melanin production correlated directly with the degree of iris pigmentation of the eyes from which the uveal melanocytes were isolated. Tyrosinase activity of cultured uveal melanocytes from black versus white donors was significantly different, but, among white donors, there was no correlation with iris pigmentation or with melanin production in vitro. CONCLUSION Cultured uveal melanocytes can produce melanin in vitro. Cultured uveal melanocytes isolated from eyes of different iris color maintained their inherent capacity for melanogenesis. Therefore, cultured uveal melanocytes are an excellent model system for studying melanogenesis in uveal melanocytes in vitro.