Long term performance of polycaprolactone vascular grafts in a rat abdominal aorta replacement model

In the active field of vascular graft research, polycaprolactone is often used because of its good mechanical strength and its biocompatibility. It is easily processed into micro and nano-fibers by electrospinning to form a porous, cell-friendly scaffold. However, long term in vivo performance of polycaprolactone vascular grafts had yet to be investigated. In this study, polycaprolactone micro and nano-fiber based vascular grafts were evaluated in the rat abdominal aorta replacement model for 1.5, 3, 6, 12, and 18 months (n = 3 for each time point). The grafts were evaluated for patency, thrombosis, compliance, tissue regeneration, and material degradation. Results show excellent structural integrity throughout the study, with no aneurysmal dilation, and perfect patency with no thrombosis and limited intimal hyperplasia. Endothelialization, cell invasion, and neovascularization of the graft wall rapidly increased until 6 months, but at 12 and 18 months, a cellular regression is observed. On the medium term, chondroid metaplasia takes place in the intimal hyperplasia layers, which contributes to calcification of the grafts. This study presents issues with degradable vascular grafts that cannot be identified with short implantation times or in vitro studies. Such findings should allow for better design of next generation vascular grafts.