In vivo regeneration of elastic lamina on fibroin biodegradable vascular scaffold

PURPOSE: There is an increasing need for vascular grafts in the field of surgical revascularization. Artificial grafts offer alternative strategies to autologous tissue, however, small caliber (diameter <6 mm) 
vascular prosthesis are associated with a high incidence of thrombosis and early failure. Despite promising results, vascular tissue engineering is not yet a clinical reality due to the complexity of this approach. We aimed at investigating the use of fibroin, a biodegradable protein derived from silk, as an acellular vascular graft for in vivo recellularization. 
 METHODS: We produced small caliber fibroin matrices by electrospinning to replace small arterial segments. Electrospun fibroin scaffolds were implanted into the abdominal aorta of Lewis rats by end-
to-end anastomosis. Seven days after implantation, fibroin matrices were recovered and processed for histological and immunohistochemical analysis.
 RESULTS: Fibroin matrices allowed host cell infiltration, extracellular matrix remodeling, and ensured good patency of the grafts in the short term. Endothelial cells and smooth muscle cells were present in the explanted construct. Development of an elastic lamina adjacent to the lumen of the scaffold was observed with organization of intima and media layers. Vasa-vasorum were also present in the outer layer of the fibroin material.
 CONCLUSIONS: Our results indicate that formation of vascular tissue containing elastin occurs already 
at 7 days after implantation on fibroin scaffold without in vitro cellularization. The use of an acellular electrospun silk fibroin tubular scaffold could be a promising strategy for in vivo regeneration of vascular tissue in the clinical reality.