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-beta 1 (TGF beta 1) 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 TGF beta 1. Treated cells became enlarged and spread onto the substratum. TGF beta 1 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. TGF beta 1 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 TGF beta 1. Changes promoted by TGF beta 1 in cell shape, cytoskeleton, and ECM production of cultured astrocytes may have relevance for understanding the mechanisms of action of TGF beta 1 during brain development.