Biodegradable extremely-small-diameter vascular graft made of silk fibroin can be implanted in mice

Abstract

Aim: Synthetic vascular grafts are widely used in surgical revascularization, mainly for medium-to large-sized vessels. However, synthetic grafts smaller than 6 mm in diameter are associated with a high incidence of throm-bosis. In this study, we evaluated silk fibroin, a major protein of silk, with high biocompatibility and biodegrad-ability, as a useful material for extremely-small-diameter vascular grafts. Methods: A small-sized (0.9 mm inner diameter) graft was braided from a silk fibroin thread. The right carotid arteries of 8-to 14-week-old male C57BL/6 mice were cut at the midpoint, and fibroin grafts (5-to 7-mm in length) were transplanted using a cuff technique with polyimide cuffs. The grafts were harvested at different time points and analyzed histologically. Results: CD31＋endothelial cells had already started to proliferate at 2 weeks after implantation. At 4 weeks, neointima had formed with α-smooth muscle actin+ cells, and the luminal surface was covered with CD31＋ endothelial cells. Mac3＋ macrophages were accumulated in the grafts. Graft patency was confirmed at up to 6 months after implantation. Conclusion: This mouse model of arterial graft implantation enables us to analyze the remodeling process and biocompatibility of extremely-small-diameter vascular grafts. Biodegradable silk fibroin might be applicable for further researches using genetically modified mice.