Matrix-fragments generated by proteases are known to modulate vascular remodeling. We investigated whether shear stress contributes to release of proteases and whether proteolytic fragments of laminin influence endothelial cell (EC) proliferation and differentiation. EC, which were subjected to shear stress (2h, 20dyn/cm2), showed enhanced elastase activity in conditioned media (16±0.7mU/ml vs. 1±0.03mU/ml, n=8, p<0.05). This went along with increased fragmentation of laminin to its fragment E8 within the matrix identified by western blots. Seeding EC on purified E8 resulted in a reduced proliferation (p<0.05, n=8), quantified with MTT using bFGF as stimulus. EC grown on E8 exhibited a 2-fold higher apoptosis rate (annexin V translocation n=4, p<0.05) and an increased O2- production (DCF, 1.1±0.5nmol vs. 2.3±1nmol/min). Aortic ring sprouting was significantly inhibited by E8 and was revoked by radical scavengers (SOD, catalase).

Conclusion: EC increase elastase activity during shear stress, which degrades laminin to fragments amongst them E8. In contrast to intact laminin, E8 inhibits proliferation and angiogenesis but induces apoptosis and O2- production. These results indicate that during shear stress the matrix is altered post synthesis, a mechanism which might be part of a feed back loop to limit shear stress induced proliferation and differentiation of EC in adaptive vascular remodeling.