RGD-MEDIATED ADHESION OF PORCINE GRANULOSA-CELLS MODULATES THEIR DIFFERENTIATION RESPONSE TO FSH IN-VITRO

Porcine granulosa cells cultured in serum-free medium undergo metaboli c and morphologic changes after follicle stimulating hormone (FSH) sti mulation. Under these conditions, granulosa cells differentiate and te nd to round up and their links with the plastic support are reduced. C oating of culture substratum with PepTite-2000, an integrin-binding sy nthetic peptide containing RGD (Arg-Gly-Asp) sequences enhanced the pl ating of granulosa cells. Whether the peptide be present or not, cells cultivated in basal synthetic medium (without FSH) were flattened and attached to the substratum by stress fibers at focal contacts where i ntegrin beta 1, extracellular fibronectin, and urokinase plasminogen a ctivator colocalized. After FSH stimulation, part of the cells rounded up and F-actin took a more uniform, cortical localization. Correlativ ely, extracellular fibronectin aggregated in a clump, while integrin b eta 1 and urokinase plasminogen activator spread over rounded cells. T hese morphological changes elicited by FSH were little affected by the presence of PepTite-2000, yet a larger number of cells remained flatt ened. However, concerning steroidogenesis, increasing concentrations o f peptide seemed to favor progesterone rather than estrogen production , and to restrain luteinizing hormone (LH) receptor expression, sugges ting a premature committment of cells towards luteinization rather tha n completion of follicular preovulatory differentiation.