Toward engineering a human neoendothelium with circulating progenitor cells.

Tissue-engineered vascular grafts may one day provide a solution to many of the limitations associated with using synthetic vascular grafts. However, identifying a suitable cell source and polymer scaffold to recreate the properties of a native blood vessel remains a challenge. In this work, we assess the feasibility of using endothelial progenitor cells (EPCs) found in circulating blood to generate a functional endothelium on poly(1,8-octanediol-co-citrate) (POC), a biodegradable elastomeric polyester. EPCs were isolated from human blood and biochemically differentiated into endothelial-like cells (HE-like) in vitro. The differentiated cell phenotype and function was confirmed by the appearance of the characteristic endothelial cell (EC) cobblestone morphology and positive staining for EC markers, von Willebrand factor, vascular endothelial cadherin, flk-1, and CD31. In addition, HE-like cells cultured on POC express endothelial nitric oxide synthase at levels comparable to aortic ECs. Furthermore, as with mature endothelial cells, HE-like cell populations show negligible expression of tissue factor. Similarly, HE-like cells produce and secrete prostacyclin and tissue plasminogen activator at levels comparable to venous and aortic ECs. When compared to fibroblast cells, HE-like cells cultured on POC show a decrease in the rate of plasma and whole-blood clot formation as well as a decrease in platelet adhesion. Finally, the data show that HE-like cells can withstand physiological shear stress of 10 dynes/cm(2) when cultured on POC-modified expanded poly(tetrafluoroethylene) vascular grafts. Collectively, these data are the foundation for future clinical studies in the creation of an autologous endothelial cell-seeded vascular graft.