Design and Fabrication of a Biomimetic Vascular Scaffold Promoting in Situ Endothelialization and Tunica Media Regeneration

Multilayered vascular scaffolds may be considered advantageous in regenerating vascular tissues due to the nature of mimicking the native structure of a blood vessel. However, there are currently limited small-diameter vascular scaffolds integrating the specific features of native tunica intima (anti-thrombus and rapid endothelialization) and tunica media (the alignment and ingrowth of smooth muscle cells (SMCs), structural elements capable of promoting vascular regeneration and function). To address this limitation, we developed a modified electrospinning method capable of fabricating a bilayer vascular scaffold with a 2-mm inner diameter and investigated the in vivo performance and regenerative capacity using a rat abdominal aorta, with a 2-month implantation period. The vascular scaffold was fabricated from poly(L-lactide-cocaprolactone)/collagen (PLCL/COL) nanofibers and nanofiber yarns, comprising the luminal and medial layers, respectively. Heparin and anti-CD133 antibody (HEP/CD133) were incorporated into the PLCL/COL nanofibers comprising the luminal layer. The mechanical characterization demonstrated compliance of the bilayer scaffold, which was comparable to the human saphenous vein and improved over commercially available e-PTFE grafts. The incorporated components (HEP/CD133) were released over a period of nearly 40 days, during which the nanofibers and nanofiber yarns maintained their structure. Moreover, the released heparin contributed to lumen anticoagulation functionality initially, and the incorporated anti-CD133 antibody promoted the development of a neo-intima. In addition, SMCs proliferated and penetrated throughout the entire nanofiber yarn outer structure. In vivo evaluations demonstrated that a monolayer of endothelial cells (CD31 positive), as well as the aligned and infiltrated smooth muscle tissues (alpha-SMA positive), were regenerated on the inner and outer layers of the fabricated scaffold, respectively, demonstrating the capacity to regenerate structures mimicking native blood vessels. In conclusion, the functionalized bilayer scaffold can be viewed as a promising candidate for in situ vascular tissue regeneration.