Purpose: The purpose of this study was to investigate the effects of all-trans retinoic acid (RA) and transforming growth factor-beta 1 (TGF-beta 1) on proliferation and melanin synthesis of chick retinal pigment epithelial (RPE) cells in vitro.
Methods: Chick RPE cells were cultured in the presence or absence of RA (10(-5) to 10(-7) M) or TGF-beta 1 (1 to 100 U/ml) for a 10-day period. The effects of RA and TGF-beta 1 on RPE cell proliferation were assessed by counting the number of cells, and their effects on melanin synthesis were evaluated by measuring the melanin content in the cells.
Results: RA significantly inhibited RPE cell proliferation in a time-dependent manner. The most marked inhibition was observed on day 10 of culture, and the most effective concentration of RA was 10(-6) M. Melanin synthesis was increased on day 10, and the most effective concentration of RA was also 10(-6) M. TGF-beta 1 also inhibited RPE cell proliferation and increased melanin synthesis.
Conclusions: These findings indicate that RA and TGF-beta 1 have regulatory effects on the proliferation and differentiation of chick RPE cells in vitro.