Activin a in JEG-3 cells: Potential role as an autocrine regulator of steroidogenesis in humans

Activin A has been shown to exert several regulatory functions on human pla centa. in the present study, we tested the hypothesis that activin A is an autocrine regulator of trophoblast using a choriocarcinoma cell line, JEG-3 , as a model. Messenger RNAs for activin beta(A) subunit, activin binding p rotein (follistatin), and various activin receptors, including ActR-IA, Act R-IB, ActR-IIA, and ActR-IIB, were detected in JEG-3 cells by reverse trans cription-polymerase chain reaction. The expression of activin A in JEG-3 ce lls was further confirmed by Western blot analysis using an antibody agains t activin beta(A) subunit. Using Northern blot analysis, Smad-2 and Smad-4 mRNAs were also observed in JEG-3 cells. These data suggest that JEG-3 cell s produce activin A and express activin binding proteins and receptors, as well as potential downstream signals. In cultured JEG-3 cells, basal proges terone production was stimulated by activin A but inhibited by follistatin- 288. Similarly, in the presence of androstenedione, estradiol production wa s enhanced by activin A but decreased by follistatin-288. On the other hand , neither activin A nor follistatin affected JEG-3 cell growth. Taken toget her, these findings strongly suggest that activin A is an autocrine factor that is involved in the regulation of progesterone and estradiol production in JEG-3 cells.