Effects of Transforming Growth Factor β1 on Astroglial Cells in Culture

The effects of transforming growth factor beta 1 (TGF beta 1) on DNA synthesis and functional differentiation of astroglial cells cultured in serum-free medium were investigated. TGF beta 1 diminished and delayed the peak of DNA synthesis induced by serum. TGF beta 1-treated cells were larger than control cells. This factor delayed the appearance of process-bearing cells induced by acidic fibroblast growth factor treatment and also affected the astrocyte-specific enzyme glutamine synthetase (GS), whose accumulation is under hydrocortisone (HC) control. TGF beta 1 inhibited the induction of GS activity by HC in a dose- and time-dependent manner. Moreover, pretreatment with TGF beta 1 for 4 h maintained the inhibition of GS activity for approximately 16 h after removal of this factor from culture medium. These results suggest that TGF beta 1 may be an important regulator of astrocyte growth and differentiation.