In vitro endothelialization of expanded polytetrafluoroethylene grafts: A clinical case report after 41 months of implantation

Purpose: Forty-one months after we performed bilateral implantation of in vitro endothelialized femoropopliteal bypass grafts in a 69-year-old patient, we obtained a central graft segment for histologic and ultrastructural investigation. Methods: Before implantation the grafts were confluently lined with autologous first passage mass cultures of pure cephalic vein endothelial cells. The precoating of the expanded polytetrafluoroethylene prosthesis was done with fibrinolytically inhibited fibrin glue. Reoperation became necessary because of symptomatic unilateral atherosclerotic lesions located in the center of one of the two in vitro lined grafts. A 21 cm long graft segment was removed and replaced by a new in vitro endothelialized expanded polytetrafluoroethylene graft. Results: On scanning electron microscopy a confluently covering mature endothelium was found throughout the whole length of the removed prosthesis. The endothelial identity was confirmed by a positive immunohistochemical CD 34, von Willebrand factor-staining, and the ultrastructural demonstration of Weibel Pallade bodies. The endothelium rested on a collagen IV positive basement membrane. Histologic cross sections revealed uniformly developed subintimal tissue of 1.21 +/- 0.19 mm thickness, which was separated from the intima by a distinct internal elastic membrane. The cells of this cell-rich matrix stained strongly positive for actin. Ultrastructurally, this matrix was dominated by highly contractile myofibroblasts loaded with peripherally located well-developed actin fillaments. A number of these cells also showed signs of secretory cells with a distinct endoplasmic reticulum and a Golgi complex. In areas of atherosclerotic lesions the subendothelial matrix was partially exposed, and the internal elastic membrane had to a certain extent disintegrated. Only in these areas KP-1 and MG-M1 positive foamy macrophages and CD 34 positive capillaries were found. The myofibroblasts of this diseased part of the subintimal tissue contained large lipid vacuoles. Conclusions: We conclude that the confluent in vitro lining of synthetic vascular grafts with pure autologous endothelial cells facilitates graft healing, which may result in a hybrid structure with features of a native vessel.