Retention of endothelium on ovine collagen biomatrix vascular conduits under physiological shear stress

This study evaluates the adhesion of endothelial cells to 4 mm internal diameter, ovine collagen biomatrix vascular conduits. The biomatrix conduit is formed in a living animal and the wall consists of a complete, naturally produced matrix reinforced with polyester mesh. We propose that the microarchitecture of the matrix lining the lumen may promote endothelial cell attachment without pretreatment with adhesive proteins or extra cellular matrix components. Endothelial cell adhesion to the biomatrix surface was assessed by subjecting conduits seeded with ovine aortic endothelial cells (OAEC) to physiological range shear stresses of 16 and 32 dyn/cm2 in vitro. OAECs were isolated, cultured and seeded (1 x 10(6) cells/ml) by rotation onto the luminal surface of 20 cm lengths of biomatrix vascular conduits (n = 36). The seeded conduits were divided into three groups and cultured either for 24 h (n = 12), 48 h (n = 12) or 72 h (n = 12). Following culture, the conduits from each group were subjected to flow rates of either 240 ml/min (n = 6) or 480 ml/min (n = 6) with heparinized sheep blood for 1 h. Luminal surface cell cover was determined pre- and post-flow from Datura stramonium lectin labeled en face preparations. Histological analysis demonstrated that OAECs attach to the luminal surface of biomatrix conduits and form confluent monolayers within 24-48 h. Flow testing revealed that, for both flow rates and independent of the time in culture, there was no significant decrease in cell cover after flow (p = 0.13). The results support the hypothesis that a vascular conduit, engineered from a naturally formed biomatrix, provides a suitable substrate for the formation of flow resistant endothelium.