Transforming growth factor-beta effects on morphology of immature rat Leydig cells

Transforming growth factor-beta (TGF beta) has been shown to regulate steroid production and DNA synthesis in rat Leydig cells. We have investigated the effects of TGF beta on the secretion of extracellular matrix (ECM) proteins and on the cytoskeleton of immature rat Leydig cells in vitro. TGF beta caused significant morphological changes in Leydig cells, which were accompanied by significant increases in secretion of fibronectin, laminin and collagen IV and rearrangement of actin filaments in TGF beta-treated cells. The cells cultured on plates pre-coated with fibronectin or fibronectin plus laminin and collagen IV, displayed morphological and cytoskeletal changes similar to those induced by TGF beta. Immunofluorescence localization studies revealed significantly higher fibronectin staining in Leydig cells in adult animals and in LH-treated immature animals than those in untreated immature animals. We conclude that TGF beta participates in the morphological differentiation of immature Leydig cells into adult Leydig cells in the rat testis by inducing the expression of ECM proteins.