Endothelialization of the luminal sac in artificial cardiac prostheses: a challenge for both biologists and engineers

Thromboembolic complications are a major obstacle for the permanent use of artificial cardiac prostheses. Many of these complications are caused by the intrinsic thrombogenicity of the biomaterials, which are used to cast the luminal blood sac. Numerous attempts have been made to improve the hemocompatibility of the new generation of totally implantable blood pumps, mainly by physico-chemical modifications of the biopolymeric materials and the blood contacting surfaces. We, on the other hand, believe that the most promising and challenging approach, from both the biologists' and engineers' point of view, is to coat the luminal surfaces of cardiac prostheses with a functional monolayer of autologous endothelial cells (ECs) and thus reproduce "nature's biocompatible blood container." The key to lining an artificial heart with a nonthrombogenic monolayer of endothelial cells is to explore the molecular and cellular mechanisms which render the EC lining inside the beating ventricle nonthrombogenic and resistant to flow-induced shear stresses and cyclic, tensional deformations. This knowledge has then to be translated into biotechnological know-how, in order to maintain an intact EC monolayer inside the blood sac of an artificial device. In this paper we emphasize some of the bioengineering issues associated with the endothelialization of the luminal sac, and also discuss some aspects related to the blood sac itself.