Impact of endothelial cell seeding on long-term patency and subendothelial proliferation in a small-caliber highly porous polytetrafluoroethylene graft

Abstract

Previous reports have demonstrated that endothelial cell seeding of polytetrafluoroethylene (PTFE) grafts enhances short-term patency. This experiment was undertaken to study its impact on the long-term patency of a highly porous, experimental PTFE graft and to determine whether increasing the internodal distance of the graft material resulted in increased proliferation of the subendothelium. Ten centimeter long, 4 mm internal diameter segments of an unreinforced, experimental PTFE graft were implanted into 36 mongrel dogs as carotid interpositions. In each animal, one graft was seeded with autologous endothelial cells, enzymatically derived from the external jugular veins, whereas the contralateral graft was treated in identical fashion except that endothelial cells were not added to the preclot mixture. Nineteen animals were killed at 12 weeks; six at 22 weeks; eight at 26 weeks; and three at 52 weeks. The mean follow-up period was 20.1 weeks. The overall patency rate was 58.3% (21 of 36 grafts) for seeded grafts vs. 27.8% (10 of 36 grafts) for control grafts (p < 0.01). The thrombus-free area was planimetrically measured at 83.4% ± 4.5% in seeded grafts vs. 55.1% ± 9.7% in control grafts (p < 0.05). Scanning electron microscopy confirmed the presence of a confluent cellular monolayer in seeded grafts, whereas control grafts exhibited a variable coagulum of fibrin, platelets, and endothelial cells. The thickness of the subendothelial layer varied from 56 to 95 μm with no progressive increase in thickness between 12 and 52 weeks. The presence of endothelium was confirmed by immunoperoxidase staining for canine factor VIII—related antigen in both seeded and control grafts. Endothelial seeding of the porous, experimental PTFE graft in this model significantly increased thrombus-free, luminal surface area and long-term patency compared with nonseeded control grafts. The increased porosity of our graft was not associated with progressive subendothelial proliferation, as had been feared, and may instead have been partially responsible for the finding of endothelium in the midportion of those long-term, control grafts that remained patent.