Proliferation of resident glomerular cells and the accumulation of mesangial matrix are histologic abnormalities which are observed in the course of many progressive glomerular diseases. We explored the potential regulatory effects of transforming growth factor-β (TGF-β) on these processes. We found that cultured mouse glomerular endothelial, mesangial, and epithelial cells as well as isolated intact rat glomeruli possess high-affinity receptors for TGF-β. We also found that, although TGF-β consistently inhibited the proliferation of glomerular endothelial and epithelial cells, it acted as a bifunctional regulator of mesangial cell proliferation. TGF-β-significantly increased the production of collagen and fibronectin by glomerular mesangial cells whereas only fibronectin production was augmented in glomerular epithelial cells. The presence of TGF-β receptors on intact glomeruli and on each glomerular cell type and the demonstrated responsiveness of these cells to TGF-β combine to suggest that potentially important interactions may occur between resident glomerular cells and TGF-β in vivo.
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