Coaxial double‐tubular compliant arterial graft prosthesis: Time‐dependent morphogenesis and compliance changes after implantation

Abstract

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.

Characterization and preparation of bioinspired resorbable conduits for vascular reconstruction

“…An artery easily inflates in the low pressure regions (0 to ~60 mmHg), moderately inflates in the physiological pressure region (~60 to 140 mmHg), and hardly inflates in the high pressure regions (approximately > 140 mmHg). 20 The single elastomeric tube made of PLCL generally exhibits high elasticity and does not mimic stress-strain behavior of native arteries. To overcome this problem, our conceptual design and fabrication technology are based on the two component system: low-stiffness, mechano-elastic PLCL and high-stiffness PDO fibers that were assembled by custom-designed spinning setup and salt leaching, and experimentally this type of graft mimicked the 'J curve', as shown in Figure 3.…”

“…electrospinning and casting), and various composite designs via different approaches. [19][20][21][22][23][24][25] In addition, the mechanical properties of various fabricated scaffolds made from blends of elastin, collagen, and synthetic polymers have been reported. 24,25 However, there remains a need for tissue-engineered scaffolds that are capable of recapitulating the 'J-shaped' stress-strain behavior, and methods for making such scaffolds.…”

Mechanical behavior of bilayered small-diameter nanofibrous structures as biomimetic vascular grafts

“…The recruitment of nanofibers with increasing pressure induced a nolinear response, where stiffness increased as more fibers supported the load, as seen in uniaxial tensile tests (Section 3.2) for deformations under 10%. Besides, in the same way as the design presented by Sonoda et al, the internal layer is the responsible for supporting the internal pressure at low pressure ranges, and after a certain deformation is achieved, the internal and external layers support the pressure together (Sonoda et al, 2001;Sonoda et al, 2003).…”

“…Sonoda et al developed an adaptable concentric two-layered graft designed with a gap between each layer, where the mechanical behavior of the artery could be mimicked by selecting the layers properties and the distance between them (Sonoda et al, 2001;Sonoda et al, 2003). At low pressures the internal layer alone mimics the pressure resistance, while at high pressures both layers copy the response together.…”

Fabrication of biodegradable scaffold by powder sintering process

“…Materials used for the scaffold are desired to degrade after implantation. So, the materials are shifting from biocompatible to biodegradable [5].…”