Regulation of mesangial cell growth by polypeptide mitogens. Inhibitory role of transforming growth factor beta.

Proliferation of mesangial cells is a common histologic abnormality in glomerular diseases. In vivo studies suggest a role for platelets and monocytes-macrophages in mediating glomerular hypercellularity. The authors recently reported that several peptide growth factors stimulate DNA synthesis and growth of human mesangial cells. This article reports that transforming growth factor beta (TGF-beta), a peptide released by inflammatory cells and platelets, inhibits DNA synthesis and growth of human mesangial cells. The stimulatory and inhibitory effects of these mitogens on DNA synthesis and growth was confirmed by autoradiography and cell counting. The inhibitory effect of TGF-beta is not mediated at the receptor level because TGF-beta did not inhibit the binding of epidermal growth factor (EGF) or platelet-derived growth factor (PDGF) to mesangial cells. Because peptide growth factors that stimulate DNA synthesis in mesangial cells induce expression of PDGF mRNAs, the effect of TGF-beta on PDGF mRNAs expression induced by peptide growth factors was studied. TGF-beta did not lower the increased levels of PDGF mRNAs caused by EGF or PDGF. These data show that TGF-beta is a potent inhibitor of DNA synthesis and growth of mesangial cells. The mechanism of the inhibitory effect of TGF-beta remains to be determined.