Steady Flow Preconditioning of Endothelial Outgrowth Cells on Ex Vivo and In Vivo ePTFE Grafts

Abstract

Endothelialization of vascular graft materials is a promising approach for improving the in vivo performance of vascular grafts, particularly for small diameter applications of less than 4 mm. The ability to incorporate a native endothelium onto a graft may reduce the thrombosis and intimal hyperplasia that limits long-term clinical success of these small diameter grafts. Endothelial outgrowth cells (EOCs), which are isolated from whole blood and expand rapidly in vitro, provide an autologous cell source capable of developing into a biologically active endothelial layer. A preconditioning step may enhance EOCs’ performance on vascular grafts. Mature endothelial cells, isolated from vascular walls, are known to decrease expression of pro-thrombotic and pro-inflammatory markers when exposed to steady fluid shear stress, compared to cells under disturbed flow conditions or static culture. This study examined the hypothesis that steady flow preconditioning of EOCs reduces their in vitro markers of thrombosis and inflammation, reduces platelet and fibrin accumulation on EOC–coated ePTFE grafts in an ex vivo shunt, and reduces initial hyperplasia on EOC–coated ePTFE grafts in an in vivo graft implant. This work was performed using well-established, non-human primate models for testing EOC-coated ePTFE grafts ex vivo and in vivo. These conditions represent a clinically-relevant cell source and biomaterial for determining the effects of fluid shear stress preconditioning on graft performance.