The effect of growth factors on rVSMC proliferation in vitro . The addition of PDGF-BB stimulated proliferation of rVSMC on laminin-5 and to some extent on naked plastic, but not on fibronectin. The presence of fibronectin alone was able to stimulate proliferation of rVSMC. The proliferative response of rVSMC to presence of laminin-5 with PDGF-BB or to fibronectin was suppressed by the addition of TGF-β1. Figure 3b The ECM induces differential rVSMC proliferation responses in vitro. The plating of rVSMC on fibronectin, but not laminin, induced increases in proliferation over four days. The addition of PDGF-BB, however, increased rVSMC migration on laminin-5, but not on fibronectin. The addition of TGF-β1 was sufficient to suppress rVSMC proliferation on both laminin-5 and fibronectin.