Endothelialization and smooth muscle cell regeneration capabilities of a bi-layered small diameter vascular graft for blood vessel reconstruction

Despite the tremendous advances in the past few decades, the clinical problems associated with low mechanical strength, thrombosis, and inadequate endothelialization still have not been improved in small diameter vascular grafts. The objective of this study is to design and fabricate a dual layered small-diameter vascular graft by electrospinning process which will mechanically and biologically match the gold standard of blood vessel substitution. The presented graft was composed of polycaprolactone/gelatin (inner layer) and polyurethane/polycaprolactone (outer layer) and fabricated by sequential electrospinning process. Physico-mechanical evaluation, in vitro biocompatibility and hemocompatibility assays were performed for both layers to ensure safe in vivo applications Then, the vascular grafts were successfully implanted into a rat abdominal aorta model. Tubular vascular graft had a nanofibrous and porous outer structure, which provided a conducive micro-environment for smooth muscle cell migration as well as proliferation but the lumen wall had a smooth surface to reduce thrombogenicity and improve endothelialization. Both layers showed excellent biocompatibility and hemocompatibility in all in vitro assays. After three months, the harvested grafts exhibited smooth muscle cell regeneration and complete endothelialization on the graft lumen. The dual layered graft could therefore play a pivotal role in the arena of vascular tissue regeneration application.