EVIDENCE FOR THE PRODUCTION OF A GROWTH-INHIBITORY FACTOR BY HUMAN GRANULOSA-LUTEAL CELLS

The factors involved in the inhibition of ovarian follicular cellular growth after the luteinizing hormone (LH) surge are poorly established . The aim of this study was to investigate the production of an inhibi tory growth factor by human ovarian cells. Luteinized granulosa cells were obtained from an assisted fertilization program and were cultured in the presence or absence of follicle-stimulating hormone (FSH) and estradiol. Data obtained by cell counting showed that the number of hu man luteinized granulosa cells cultured in the presence of fetal bovin e serum (10%) increased 1.8-fold within a 2-day period. In serum-free medium, human luteinized granulosa cells were able to incorporate H-3- thymidine, measured during consecutive 48 h periods. During all the pe riods tested (up to 7 days), low basal levels of thymidine incorporati on were measured and were further reduced in the presence of FSH (200 ng/ml) and estradiol (500 ng/ml). To elucidate the possible production of an inhibitory growth factor, H-3-thymidine incorporation by rat gr anulosa cell cultures was measured in the presence of conditioned medi a (CM; from human granulosa cell cultures). In this system, FSH and es tradiol elicited a tenfold increase in thymidine incorporation. The ad dition of CM (10% v/v collected on day 2) to FSH- and estradiol-treate d granulosa cell cultures produced an inhibition (61%) of thymidine in corporation. The active factor in CM withstood freeze-thawing, was sta ble for several weeks at -20-degrees-C, became unstable at 4-degrees-C , and was heat labile and sensitive to proteolysis. Ultrafiltration us ing membranes with different molecular weight cutoffs suggested that t he factor had a molecular weight >30,000 dalton. We suggest that an in hibitory growth factor produced by human luteinized granulosa cells co uld be involved in the differentiation of growing follicles to corpus luteum. (C) 1993 Wiley-Liss, Inc.