A CELL-ADHESION RECEPTOR ANTISERUM ABOLISHES, WHEREAS LAMININ AND FIBRONECTIN GLYCOPROTEIN COMPONENTS OF EXTRACELLULAR-MATRIX PROMOTE, LUTEINIZATION OF CULTURED RAT GRANULOSA-CELLS

We recently showed that structural regression is marked by an endocrine-induced increase in matrix metalloproteinase activity specific for basement membrane, which suggests that extracellular matrix (ECM) may play an important role in sustaining luteal cell function. Such a role for ECM has been demonstrated for cultured mammary epithelial cells,hepatocytes, and keratinocytes. To test this hypothesis, granulosa cells from preovulatory follicles that were induced to luteinize by gonadotropin stimulation in vivo were examined. Initial studies established that cells cultured on plastic in medium supplemented with 1% fetal bovine serum, LH (100 pg/ml), PRL (1 mu g/ml), and insulin-like growth factor-I (5 ng/ml) showed a time-dependent increase in the secretion of progesterone (P-4) and total progestin (P-4 plus 20 alpha-dihydroprogesterone) for at least 10 days and that replacement of fetal bovine serum with 0.1% BSA stimulated P-4 secretion and reduced the 20 alpha-dihydroprogesterone to P-4 ratio from 10:1 to as low as 3:1. The inclusion of an anticell adhesion receptor subunit sera (Lenny IV, against the integrin beta(1)-subunit) in the culture medium for the first 2 days resulted in an irreversible loss of progestin secretion by the cultured granulosa cells, but the inclusion of a bacterial collagenase (form III) had no effect. Granulosa cells from preovulatory follicles cultured on ECM (Matrigel matrix) formed cell aggregates and projected cellular sprouts, but secreted less P-4 than those cultured on plastic. The inclusion of laminin in the culture medium or laminin coating the culture wells stimulated P-4 secretion by granulosa cells and promoted the enlargement of steroidogenic cells (3 beta-hydroxysteroid dehydrogenase). Fibronectin-coated, but not collagen-I-coated wells similarly promoted P-4 secretion. These results suggest that a cell adhesion receptor (an integrin), and laminin and fibronectin, major glycoprotein components of ECM, play important roles in the differentiation of granulosa cells to luteal cells.