Regulation of human granulosa-luteal cell progesterone production and proliferation by gonadotropins and growth factors.

The effects of human chorionic gonadotropin (hCG), follicle-stimulating hormone (FSH), fibroblast growth factor (FGF), and epidermal growth factor (EGF) on human granulosa-luteal cell proliferation and progesterone (P) production were studied in vitro. The cells were obtained from an in vitro fertilization protocol and were cultured for 2 to 12 days on plastic culture dishes or on dishes coated with extracellular matrix (ECM). During the first 2 to 4 days of culture, basal P production was high and could not be further stimulated with gonadotropins. Thereafter, basal P production decreased and could be stimulated by both hCG and FSH. The cells growing on ECM produced less P than the cells growing on plastic. EGF and FGF significantly increased cell proliferation on both substrates. FGF did not influence P production, while EGF clearly increased basal P production of the cells cultured on plastic. The high P production in cultured human granulosa cells obtained from follicles stimulated in vivo indicates that at least some of the cells were luteinized. The present data also demonstrate that EGF and FGF are mitogenic for human granulosa-luteal cells, and EGF regulates their biosynthesis in vitro. These results suggest that growth factors may also regulate granulosa cell function in vivo.

Leydig cell desensitization by human chorionic gonadotropin does not occur in the human fetal testis.

In vivo data concerning human fetal testicular testosterone production as well as in vitro findings in fetal and neonatal rats suggest that fetal Leydig cells may be capable of responding to gonadotropins and secreting testosterone at high levels for prolonged periods, in contrast to adult testes which reportedly become desensitized after high dose gonadotropin administration. To evaluate fetal testicular testosterone production during long term, high dose gonadotropic stimulation, we cultured human, rhesus monkey, and rabbit fetal testes in organ and cell cultures. After 24 h of culture with different concentrations of hCG (0-100 ng/ml, physiological fetal concentrations during human gestation), the fetal testes were still able to respond to a second hCG stimulus (no desensitization). The 24-h incubation with hCG (0-100 ng/ml) also increased the capacity of the cultures to secrete testosterone during a second incubation in a dose-dependent manner even in the absence of hCG (steroidogenic enzyme induction). Furthermore, hCG increased thymidine incorporation into DNA by the human fetal testis. The results of this study substantiate the role of hCG in the regulation of fetal Leydig cells. They suggest that long term effects via nuclear mechanisms (RNA and DNA synthesis) may be important aspects of this regulation, and that fetal Leydig cells are able to respond to sustained concentrations of gonadotropin without being desensitized.