α 2(VIII) collagen substrata enhance endothelial cell retention under acute shear stress flow via an α 2β 1 integrin-dependent mechanism: An in vitro and in vivo study

BACKGROUND - Essential to tissue-engineered vascular grafts is the formation of a functional endothelial monolayer capable of resisting the forces of blood flow. This study targeted α2(VIII) collagen, a major component of the subendothelial matrix, and examined the ability of and mechanisms by which endothelial cells attach to this collagen under static and dynamic conditions both in vitro and in vivo. METHODS AND RESULTS - Attachment of human endothelial cells to recombinant α2(VIII) collagen was assessed in vitro under static and shear conditions of up to 100 dyne/cm. α2(VIII) collagen supported endothelial cell attachment in a dose-dependent manner, with an 18-fold higher affinity for endothelial cells compared with fibronectin. Cell attachment was significantly inhibited by function-blocking anti-α2 (56%) and -β1 (98%) integrin antibodies but was not RGD dependent. Under flow, endothelial cells were retained at significantly higher levels on α2(VIII) collagen (53% and 51%) than either fibronectin (23% and 16%) or glass substrata (7% and 1%) at shear rates of 30 and 60 dyne/cm, respectively. In vivo studies, using endothelialized polyurethane grafts, demonstrated significantly higher cell retention rates to α2(VIII) collagen-coated than to fibronectin-coated prostheses in the midgraft area (P