IMPROVING ENDOTHELIAL-CELL ADHESION TO VASCULAR GRAFT SURFACES - CLINICAL NEED AND STRATEGIES

Synthetic vascular grafts do not spontaneously endothelialize in human s and require some form of anticoagulation to maintain patency. Presee ding synthetic graft materials such as expanded polytetrafluoroethylen e (ePTFE) and polyethylene terephthalate (PET) with endothelial cells (EC) has been examined in various in vitro and in vivo models. Althoug h various studies provide encouraging results, clinical trials for EC seeding on synthetic grafts have not been equally successful. This pap er provides a brief review of the various reports on EC seeding in ani mal and clinical studies. We discuss the inefficiencies associated wit h the EC seeding process and examine plasma protein treatment of the g raft surfaces as a viable option for improving EC attachment, retentio n and spreading. As an alternative to exsisting therapies we present d ata on a heterogeneous ligand treatment of fibronectin (Fn) and avidin -biotin for enhanced human umbilical vein endothelial cell (HUVEC) adh esion to ePTFE graft surfaces. Control consisted of HUVECs seeded on F n treated ePTFE graft surfaces. Functionality of HUVECs was assessed b y measuring prostacyclin production of cells on both homogeneous and h eterogeneous ligand treated surfaces. Laminar flow studies with a vari able width flow chamber and scanning electron microscopy were used to measure initial cell retention and observe initial cell spreading on e PTFE surfaces, respectively. HUVEC retention on heterogeneous ligand t reated graft surface was significantly (p < 0.001) higher compared to homogeneous ligand treated surfaces for shear stress in the range of 1 0-30 dyn cm(-2) HUVEC showed more cellular spreading on the heterogene ous ligand treated surface after seeding for 1-2 h. In vivo experiment ation was performed in immune deficient (nude) rats by replacing a sec tion of both the femoral arteries with 8 mm long, 1 mm internal diamet er denucleated ePTFE grafts treated with homogeneous and heterogeneous ligands respectively Both grafts were seeded with similar cell densit y for 15 min prior to implantation. EC attachment and retention was me asured by staining EC with hematoxylin and counting the cells before a nd after flow using light microscopy. The results indicate that a hete rogeneous ligand treatment of graft surfaces using avidin-biotin and F n-integrin attachment mechanisms increase cell seeding efficiency, ini tial cell retention and cellular spreading.