IN-VITRO TESTING OF ENDOTHELIAL-CELL MONOLAYERS UNDER DYNAMIC CONDITIONS INSIDE A BEATING VENTRICULAR PROSTHESIS

Thromboembolic complications remain a major problem associated with th e long-term clinical use of cardiac prostheses. A promising approach t oward resolving this predicament is lining the blood contacting surfac es with a functional monolayer of endothelial cells (EC). In developin g an endothelialized cardiac prosthesis, the authors in the past focus ed on establishing a confluent EC monolayer on the luminal surface of ventricular blood sacs. In this study, the authors concentrated on exp osing the post confluent monolayers to the dynamic conditions inside a beating ventricle. The cells, derived from either bovine aortae or ju gular veins, were grown to post confluence inside fully assembled vent ricles on fibronectin or plasma cryoprecipitate coated, textured surfa ces. After 11 days of culturing under static conditions, the endotheli alized ventricles were connected to a mock loop that was run for 6 and 24 hr at 60 bpm and mean flow rate of 3.2 L/min. The status of the mo nolayer was evaluated by Alamar Blue assay before and after each run, and the extent of surface coverage was determined visually using brigh t field microscopic study after cell staining with KMnO4 and toluidine blue. In addition, morphometric information on cells/polyurethane sur face was obtained with a scanning electron microscope. After 6 hr of p umping, cell staining revealed signs of moderate cell loss in fibronec tin coated blood sacs, whereas in cryoprecipitate coated bladders the signs of denudation were marginal. In seven ventricles operated for 24 hr, Alamar Blue measurements indicated 35 +/- 16% of cell loss from m onolayers established on fibronectin coating, but only 4.8 +/- 6.25% o n cryoprecipitate. Thus, the current study demonstrates the feasibilit y of maintaining an intact endothelial surface in a beating ventricula r prosthesis and indicates that the integrity of the endothelial linin g is dependent upon a proper choice of surface macrostructure and prot ein coating.