EFFECTS OF TRANSFORMING GROWTH FACTOR-BETA-1 ON THE EXTRACELLULAR-MATRIX AND CYTOSKELETON OF CULTURED ASTROCYTES

The present study was performed on primary cultures and subcultures of cerebellar astrocytes in order to investigate the effects of transforming growth factor-beta1 (TGFbeta1) on proliferation, extracellular matrix (ECM) components, and cytoskeletal structures in relation to morphological changes. The expression and cellular distribution of the ECM components laminin and fibronectin and the cytoskeletal proteins glial fibrillary acidic protein (GFAP) and actin were investigated by immunoblotting, immunocytochemistry, and phalloidin staining. The proliferation of primary cultures was strongly inhibited by TGFbeta1. Treated cells became enlarged and spread onto the substratum. TGFbeta1 promoted the appearance of actin stress fibers and increased the cell actin content. It elicited a slight increase in GFAP expression and induced dispersion of thin filaments of GFAP. TGFbeta1 also stimulated the production of laminin and fibronectin and their incorporation into the ECM of primary cultures grown in medium with or without serum. Astrocytes grown in serum-containing medium for 1 day after subculturing responded strongly to TGFbeta1. Changes promoted by TGFbeta1 in cell shape, cytoskeleton, and ECM production of cultured astrocytes may have relevance for understanding the mechanisms of action of TGFbeta1 during brain development.