Extracellular matrix contraction by cultured mesangial cells: modulation by transforming growth factor-beta and matrix components.

Cultured glomerular mesangial cells (MCs) have the ability to contract the surrounding collagen gel matrix (CGM). To investigate this phenomenon, we examined the effect of growth factors and extracellular matrix (ECM) components. Among some growth factors tested, transforming growth factor-beta (TGF-beta) and fetal calf serum (FCS) enhanced CGM contraction dose dependently. These factors acted through distinct mechanisms because: (1) when growth-arrested MCs were used, the effect of FCS was inhibited partially but that of TGF-beta was not; and (2) anti-TGF-beta had no influence on CGM contraction induced by FCS. Among the ECM components such as laminin, fibronectin, type IV collagen, and heparin-like proteoglycans (heparan sulfate and heparin), which were each mixed separately with CGM before gelling, heparin-like proteoglycans and type IV collagen inhibited contraction by MCs. The inhibitory effect of heparin was mediated by the interaction both with CGM and with MCs because: (1) when heparin was added to the culture medium, not into the gel, the inhibitory effect was diminished but still noted; and (2) using growth-arrested MCs, the inhibitory effect of heparin in the medium was reduced but still observed. This culture assay is useful for elucidating the tensional interaction between MCs and surrounding ECM.