Electrospun vein grafts with high cell infiltration for vascular tissue engineering

Demand is increasing for functional small-diameter vascular grafts (diameter < 6 mm) for clinical arterial replacement. In the present study, we develop a bilayer poly(epsilon-caprolactone, PCL) fibrous vascular graft consisting of a thin internal layer made of longitudinally aligned fibers and a relatively thick highly porous external layer. The internal layer provides a scaffold with the necessary mechanical strength and enhances the growth of endothelial cells, whereas the external layer enhances cell motility through the scaffold bulk. The biocompatibility and biological performance of bilayer fibrous scaffolds are evaluated by in vivo experiments, molecular biology, and histology studies. Our bilayer scaffolds demonstrate much better fiber alignment and higher porosity than do normal electrospun vascular grafts with randomly distributed fibers. The results suggest that the proposed grafts can overcome limitations owing to the inadequate porosity, small pores, and poor cell infiltration of scaffolds fabricated by conventional electrospinning. The unique structure of bilayer scaffolds is satisfactory and promotes cell proliferation, collagen fiber deposition, and ingrowth of smooth muscle cells and endothelial cells in vivo. The results of this study illustrate the strong potential of such bilayer fibrous scaffolds for vascular tissue engineering and regeneration.