Vascular grafts coated with endothelial cells (ECs) have shown great potential in preventing acute thrombosis compared with other agents. As ECs continuously undergo shear stress, they stimulate the release of nitric oxide by endothelial nitric oxide synthase, which triggers vasodilation, inhibits platelet aggregation, reduces restenosis, and enhances human umbilical vein EC adhesion (Figure ). When a polyurethane vascular grafts coated with a polymer containing a nitric oxide donor was evaluated in a sheep arteriovenous bridge-graft model, there was no platelet adhesion or thrombus formation after 21 days. In contrast, uncoated grafts exhibited adherent thrombi and red blood cell and inflammatory cell infiltration into the graft wall.