Transforming growth factor‐βs inhibit mitogen‐stimulated proliferation of astrocytes

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Abstract
We have studied the influence of three members of the transforming growth factor-β (TGF-β) family of multifunctional growth factors on the proliferation of cultured astrocytes isolated from newborn mouse cerebral cortex. Although TGF-βs 1, 2, and 3 cause only a small reduction in the low level of astrocyte proliferation occurring in chemically defined medium, they each inhibit the effects of five astrocyte mitogens (bFGF, EGF, PDGF, IL-1α, and IL-2). Inhibition is observed when astrocytes are exposed to mitogen and TGF-r3 at the same time and when they are exposed to TGF-β prior to, and separately from, mitogen. This latter effect appears to be due to the binding of TGF-βs to astrocyte-secreted extracellular matrix. These findings raise the possibility that TGF-β may co-operate with other growth factors to control astrocyte proliferation in vivo.