Platelet-derived growth factor modulates rat vascular smooth muscle cell responses on laminin-5 via mitogen-activated protein kinase-sensitive pathways

Using a system of in vitro assays we assessed rat vascular smooth muscle cell (rVSMC) responses plated on laminin-5 to the addition of exogenous, soluble PDGF-BB. Our results indicate that although laminin-5 induces haptotactic migration of rVSMC, the addition of PDGF-BB significantly increases rVSMC migration on laminin-5, which is inhibited in a dose-dependent manner by the MAPK inhibitor, PD98059, and transforming growth factor (TGF-β1). In addition, PDGF-BB greatly reduces rVSMC adhesion to laminin-5, an effect that is reversible by MAPK inhibition or the addition of TGF-β1. In addition, this reduction in adhesion is less significant on another ECM substrate, fibronectin and is reversible using TGF-β1 but not MAPK inhibition. PDGF-BB also strongly increased rVSMC proliferation on laminin-5, but had no effect on rVSMC plated on fibronectin. Finally, plating rVSMC on laminin-5 did not induce an increase in MAPK activation, while plating on fibronectin or the addition of soluble PDGF-BB did.These results suggest that rVSMC binding to laminin-5 activates integrin-dependent intracellular signaling cascades that are different from those of fibronectin or PDGF-BB, causing rVSMC to respond more acutely to the inhibition of MAPK. In contrast, our results suggest that fibronectin and PDGF-BB may activate parallel, reinforcing intracellular signaling cascades that converge in the activation of MAPK and are therefore less sensitive to MAPK inhibition. These results suggest a partial mechanism to explain the regulation of rVSMC behaviors, including migration, adhesion, and proliferation that may be responsible for the progression of restenosis.Angioplasty is a procedure designed to treat vascular stenosis, blockage(s), or atherosclerotic lesions, but it may also, simultaneously, cause damage to the integrity of the blood vessel wall. Restenosis is the subsequent narrowing and occlusion of the blood vessel in response to the injury or damage sustained during angioplastic proc