Arterial replacement with compliant hierarchic hybrid vascular graft: biomechanical adaptation and failure

Two types of hybrid vascular grafts were hierarchically structured with an autologous smooth muscle cell (SMC)-inoculated collagen gel layer and an endothelial cell (EC) monolayer, and wrapped with different elasomeric scaffolds. Type A graft was wrapped with poly(urethane)-nylon mesh, and type B graft was wrapped with an excimer laser-directed microporous segmented polyurethane (SPU) film as the scaffold. Type A graft was more compliant than canine carotid arteries, whereas compliance of type B graft was close to that of native arteries. After implantation into canine carotid arteries for 1 month, all type A grafts were dilated due to loosening of the mesh, resulting in loss of prelined ECs and thrombus formation. In contrast, type B grafts developed a well-organized neoarterial wall composed of a confluent EC monolayer and SMC-resided medial tissue, resulting in only slightly appreciable thrombus and minimal tissue ingrowth 6 months after implantation. Compliance of type B graft was reduced at 6 month's implantation, which is mostly due to encapsulated connective tissue formed around the graft.