P5377Biodegradable extremely small diameter vascular graft made of silk fibroin leads rapid vascular remodeling; a preliminary evaluation

Abstract

Background: Synthetic grafts are widely used in surgical revascularization mainly in medium to large size vessels. There is an increasing need for small size grafts, however, grafts under 5mm in diameter are associated with a high incidence of thrombosis. Recently, biodegradable tissue engineered grafts, which were made of poly(glycerol sebacate) and polylactic acid, were examined. However, it is difficult to make graft of enough strength for arterial pressure with biodegradable materials. Purpose(s): We evaluated the short term efficacy of biodegradable extremely small size graft made of silk fibroin which exhibits high biocompatibility. Method(s): A small size (0.9mm in diameter) graft was braided from silk fibroin thread. The grafts were implanted in left carotid arteries of eight-week-old male C57BL/6 mice with cuff technique. The left common carotid artery of a mouse was ligated with sutures at the midpoint and divided. The polyimide cuffs were covered at the proximal and distal artery ends and the both ends were everted over the tubular body portion of the cuffs. The graft, in 5 to 6mm length, was then sleeved over the artery cuffs, tied with sutures and fixed. The implanted grafts were harvested after 4 weeks, fixed in formalin, embedded in paraffin to make tissue sections. Result(s): The graft patency was detected at 4 weeks. In these grafts, neointimae were formed with alpha-smooth muscle actin positive cells. The luminal surface of the neointima was covered with spindle like cells which are likely endothelial cells. Mac3 positive macrophages were accumulated in the grafts to absorb silk fibroin. Conclusion(s): Biodegradable silk fibroin might have potential to be the ideal material of extremely small size synthetic graft.