T3 affects cerebellar astrocyte proliferation, GFAP and fibronectin organization.

Thyroid hormone T3 and conditioned medium from cerebellar T3-treated astrocytes induced proliferation in astroglial cells. In addition, T3 treatment promoted alterations in the organization of cytoskeleton (GFAP) and extracellular matrix (fibronectin) in these cerebellar astrocytes in culture. GFAP filaments that normally spread in the cytoplasm of astrocytes became organized around the cell nucleus. Fibronectin that had a punctate distribution on control cell surface, became diffused in T3-treated astrocytes. This hormone also induced growth factor(s) secretion by astrocytes. These results suggest that T3 may be an important regulator of astrocyte growth and differentiation.