Stimulation of Apoptosis in Human Granulosa Cells from in Vitro Fertilization Patients and Its Prevention by Dexamethasone: Involvement of Cell Contact and Bcl-2 Expression

Human granulosa cells obtained from in vitro fertilization patients are highly luteinized, but can still be stimulated by LH/cAMP for production of progesterone. This stimulation involved enhancement of apoptosis. Incubation of the cells with dexamethasone (Dex) reduced the apoptotic incidence compared with nontreated cells and completely abolished the increase in apoptosis stimulated by LH or forskolin, concomitantly with a pronounced increase in progesterone production. Organization of the actin cytoskeleton was dramatically reduced after LH/forskolin stimulation. In contrast, Dex prevented disorganization of the actin filament networks. LH and forskolin also decreased the organization of gap junctions, which could be prevented by Dex. However, the intracellular level of connexin 43 was elevated in the presence of LH, forskolin, and Dex. Endogenous levels of the survival gene protein Bcl-2 were significantly elevated in all cultures treated with Dex compared with either nonstimulated cultures or cultures stimulated with LH and forskolin. Our data suggest that LH/cAMP can stimulate steroidogenesis even during the initial stage of apoptosis of human granulosa cells, whereas Dex, which blocks apoptosis, could further elevate progesterone production. Moreover, the integrity of gap junctions and the actin cytoskeleton as well as elevated levels of Bcl-2 may play an important role in the suppression of apoptosis of human granulosa cells.