Development of Small-Diameter Artificial Vascular Grafts Using Transgenic Silk Fibroin

Silk fibroin (SF) is a suitable material for vascular prostheses for small arteries. SF is useful not only as a base material for artificial vascular grafts but also as a coating material. This study prepared three types of transgenic SF (vascular endothelial growth factor (VEGF), Arg-Glu-Asp-Val (REDV), and Tyr-Ile-Gly-Ser-Arg (YIGSR)) incorporating expression factors that are thought to be effective for endothelialization as coating materials. We compared the contribution of these materials to early endothelialization in vivo when using them as a porous transgenic SF coating. A porous coating of transgenic SF containing VEGF, REDV, and YIGSR was applied to a silk small-diameter artificial vascular graft base with a diameter of 1.5 mm and a length of 3 cm. Two and four weeks after implantation of these artificial grafts into the abdominal aorta of rats, they were removed and evaluated by histologic examination. Transgenic SF coating incorporating VEGF and REDV demonstrated higher tissue infiltration and continuous endothelialization in the center of the graft compared to YIGSR at 4 weeks after implantation. VEGF and REDV are capable of endothelialization as early as 4 weeks after implantation, confirming the usefulness of transgenic SF when used as a porous coating.