Coaxial double-tubular compliant arterial graft prosthesis: time-dependent morphogenesis and compliance changes after implantation

In order to reduce the compliance mismatch between the native artery and the artificial graft, we have developed a coaxial double-tubular compliant graft, using multiply micropored segmented polyurethane (SPU) thin films, which mimics the relationship between the intraluminal pressure and vessel internal diameter (P-D) of the native artery (termed "J" curve). The graft was coaxially assembled by inserting a high-compliance inner tube with a heparin-immobilized photocured gelatin coating layer into a low-compliance outer tube with a photocured hydrophilic polymer coating layer. Twenty-eight coaxial double-tubular compliant grafts were implanted into the canine common carotid arteries in an end-to-end fashion for up to 12 months. The overall patency rate was 86% (24/28), and neither rupture nor aneurysmal formation was observed. A neoarterial wall was formed via transanastomotic and transmural tissue ingrowth, resulting in neoarterial tissue formation on the luminal surface and into the intertubular space of the double-tubular graft, accompanied by mainly myofibroblasts and inflammatory cells in the early stage and endothelialization and collagen-rich extracellular matrices in the late stage of implantation. Surrounding-tissue adhesion with the outer tube was prevented by the hydrophilic polymer coating. Although the J curve of the implanted prototype model was preserved 1 month after implantation, the impaired J curves were observed because of tissue ingrowth and tissue adhesion between the outer surface of the inner tube and the surrounding tissues 3 and 6 months after implantation. At 12 months after implantation, however, the implanted coaxial double-tubular graft exhibited high compliance due to biodegradation of the SPU films.