Hormonal regulation of cytodifferentiation and intercellular communication in cultured granulosa cells

Granulosa cells from immature hypophysectomized diethylstilbestrol-treated rats displayed pronounced intracellular and intercellular changes after 48 hr of exposure to follicle-stimulating hormone (FSH) in vitro. As determined by light and electron microscopy, most of the FSH-treated cells became highly aggregated and grew in multilayered clusters. Numerous gap junctions were seen between cells, indicating the presence of significant intercellular communication. Microvilli densely covered the surface of the hormone-stimulated cells, which contained enlarged mitochondria with convoluted cristae, characteristic of steroidogenic cells. Luteinizing hormone receptors, identified by autoradiography with 125I-labeled human chorionic gonadotropin, were mainly associated with aggregated cells, whereas single cells were usually free of the labeled hormone. Addition of a gonadotropin-releasing hormone agonist prevented the appearance of luteinizing hormone receptors and markedly impaired cyclic AMP and progesterone production, as well as the morphological changes induced by FSH. The majority of the granulosa cells grown in the absence of either hormone assumed a flattened, and smooth shape and grew primarily in monolayers. The maintenance of cellular aggregation and intercellular communication by FSH, and its inhibition by gonadotropin-releasing hormone, may play an important role in the cytodifferentiation of ovarian granulosa cells.