Perlecan inhibits smooth muscle cell adhesion to fibronectin: Role of heparan sulfate

Smooth muscle cell migration, proliferation, and deposition of extracellula r matrix are key events in atherogenesis and restenosis development. To exp lore the mechanisms that regulate smooth muscle cell function, we have inve stigated whether perlecan, a basement membrane heparan sulfate proteoglycan , modulates interaction between smooth muscle cells and other matrix compon ents. A combined substrate of fibronectin and perlecan showed a reduced adh esion of rat aortic smooth muscle cells by 70-90% in comparison to fibronec tin alone. In contrast, perlecan did not interfere with cell adhesion to la minin. Heparinase treated perlecan lost 60% of its anti-adhesive effect. Fu rthermore, heparan sulfate as well as heparin reduced smooth muscle cell ad hesion when combined with fibronectin whereas neither hyaluronan nor chondr oitin sulfate had any anti-adhesive effects. Addition of heparin as a secon d coating to a preformed fibronectin matrix did not affect cell adhesion. C ell adhesion to the 105- and 120 kDa cell-binding fragments of fibronectin, lacking the main heparin-binding domains, was also inhibited by heparin. I n addition, co-coating of fibronectin and H-3-heparin showed that heparin w as not even incorporated in the substrate. Morphologically, smooth muscle c ells adhering to a substrate prepared by co-coating of fibronectin and perl ecan or heparin were small, rounded, lacked focal contacts, and showed poor ly developed stress fibers of actin. The results show that the heparan sulf ate chains of perlecan lead to altered interactions between smooth muscle c ells and fibronectin, possibly due to conformational changes in the fibrone ctin molecule. Such interactions may influence smooth muscle cell function in atherogenesis and vascular repair processes, (C) 2001 Wiley-Liss, Inc.