Durability of Endothelial Cell Monolayers Inside a Beating Cardiac Prosthesis

Abstract

Thromboembolic complications associated with the use of cardiac prostheses might be alleviated by lining the blood-contacting surfaces of these devices with a functional monolayer of endothelial cells. In the current study, we tested our hypothesis that precoating textured surfaces of artificial ventricles with various plasma proteins could enhance the resistance of endothelial cell monolayers to hemodynamic forces generated within an in vitro mock circulatory loop system. Bovine jugular vein endothelial cells were grown to confluence on the luminal surface of artificial ventricles constructed of textured, medical grade polyurethane (Biospan), which had been precoated with either fibronectin or plasma cryoprecipitate. Following 7 days of culturing under static conditions, the endothelialized ventricles were connected to a mock loop system, and exposed to pulsatile flow for 6 and 24h (60bpm, 3.21/min mean flow rate, 150mmHg ejection pressure). Retention of endothelial cells was evaluated by Alamar Blue assay before and after each run. Monolayer integrity and additional morphometric parameters were also assessed by direct visualization, employing various light and electron microscopic techniques. In ventricles which had been precoated with fibronectin, Alamar Blue assay indicated cellular retention to be 77% ± 4% and 72% ± 5% of static controls, after 6 and 24h, respectively. In marked contrast, cryoprecipitate-coated ventricles retained over 90% of their endothelial cell lining through 24 h of exposure to physiological hemodynamic conditions. These findings were confirmed by visual inspection. Our study demonstrates the feasibility of maintaining an intact endothelial surface in a beating ventricular prosthesis, and that the durability of the cell layer is highly dependent upon the selection of biomaterial surface topography and protein coating.