REGULATION OF THE ACTIVIN-BINDING PROTEIN FOLLISTATIN IN CULTURED HUMAN LUTEINIZING GRANULOSA-CELLS - CHARACTERIZATION OF THE EFFECTS OF FOLLICLE-STIMULATING-HORMONE, PROSTAGLANDIN E(2), AND DIFFERENT GROWTH-FACTORS

Regulation of the activin-binding protein follistatin (FS) by recombin ant human (rh) FSH, prostaglandin E(2) (PGE(2)), and several polypepti de growth factors was examined in cultures of human granulosa-luteal ( GL) cells obtained from in-vitro fertilization patients at oocyte retr ieval, Northern and dot blot hybridization analyses demonstrated that both rhFSH and PGE(2) caused stimulatory effects on FS mRNA levels in a culture stage-, time-, and concentration-dependent manner. An 8-h st imulation with rhFSH (100 ng/ml) significantly increased FS mRNA level s on Days 5 and 7 of culture and PGE(2) (10(-6) M) on Days 2, 4, and 7 , The stimulatory effects of rhFSH and PGE(2) on FS mRNA levels were r apid and transient, Maximal inductions occurred 8 h after stimulation, whereas weak or no stimulatory effects were seen at 24 or 48 h, PGF(2 alpha) did not affect FS mRNA levels at any time point studied, Treat ment of the cells with the protein synthesis inhibitor cycloheximide p rior to rhFSH stimulation did not inhibit the rapid induction of FS mR NAs, but it prevented the decline at 24 h, Both rhFSH and PGE(2) clear ly also increased the levels of secreted FS proteins as detected by im munoprecipitation studies with a specific antibody, The effects of the polypeptide growth factors epidermal growth factor (EGF), transformin g growth factor beta(1) (TGF beta 1), and activin A on FS mRNA levels were also examined, TGF beta 1 and activin A had no effect on basal FS expression at any concentration or time point studied, An 8-h stimula tion with EGF increased FS mRNA levels, but the effect was weaker than those caused by rhFSH and PGE(2). We conclude that rhFSH and PGE(2) i nduce FS mRNA and protein in human cultured GL cells, EGF is able to i nduce FS mRNA to a lesser extent than are rhFSH and PGE(2), whereas PG F(2 alpha), TGF beta 1, and activin A do not affect basal FS mRNA leve ls in human cultured GL cells, This study together with our previous r eport on the stimulatory effect of hCG on FS levels suggest that in th e luteal phase of the human menstrual cycle, FS expression in granulos a cells is likely to be positively controlled by luteotropic factors s uch as gonadotropins and PGE(2). Consequently, elevated FS levels may support the survival of the human CL since FS is known to prevent the antisteroidogenic effects of activin in human GL cells.