Clinical performance of vascular grafts lined with endothelial cells

The replacement of arteries with purely synthetic vascular prostheses often leads to the failure of such reconstructions when small-diameter or low-flow locations are concerned, due in part to the thrombogenicity of the internal graft surface. In order to improve long-term patency of these grafts, the concept of endothelial cell seeding has been suggested because this metabolically active endothelial surface plays major roles in preventing in vivo blood thrombosis and because vascular grafts placed in humans do not spontaneously form an endothelial monolayer whereas they do in animal models. The composite structure resulting from the combination of biologically active cells to prosthetic materials thus creates more biocompatible Vascular substitutes. To achieve endothelialization of synthetic vascular grafts, previous efforts aimed at "one-stage" procedure (adding autologous endothelial cells to the graft at the time of implantation) in the 1980's seemed clinically feasible but results of reported clinical trials were controversial and mostly disappointing. An alternative method is an in vitro complete and preformed endothelial lining at the time of implantation: the "two-stage" procedure which implies harvest and culture of autologous endothelial cells. Up to date, the latter approach demonstrated its superiority in terms of significantly increased patency of the grafts that underwent endothelialization eight years earlier. Due to difficulties of cell procurement for the building of these tissue-engineered vascular grafts, additional cell sources are under study in experimental works and will be mentioned as perspectives.