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-fl ow locations are concerned, due in part to the thrombogenicity of the inter nal graft surface. In order to improve long-term patency of these grafts, the concept of endot helial cell seeding has been suggested because this metabolically active en dothelial surface plays major roles in preventing in vivo blood thrombosis and because vascular grafts placed in humans do not spontaneously form an e ndothelial monolayer whereas they do in animal models. The composite struct ure resulting from the combination of biologically active cells to prosthet ic materials thus creates more biocompatible Vascular substitutes. To achieve endothelialization of synthetic vascular grafts, previous effort s aimed at "one-stage" procedure (adding autologous endothelial cells to th e graft at the time of implantation) in the 1980's seemed clinically feasib le but results of reported clinical trials were controversial and mostly di sappointing. An alternative method is an in vitro complete and preformed en dothelial lining at the time of implantation: the "two-stage" procedure whi ch 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 ye ars earlier. Due to difficulties of cell procurement for the building of these tissue-en gineered vascular grafts, additional cell sources are under study in experi mental works and will be mentioned as perspectives.