Improved endothelialization of small-diameter ePTFE vascular grafts through growth factor therapy

Abstract

Background Prosthetic vascular grafts in humans characteristically lack confluent endothelialization regardless of the duration of implantation. Use of high-porosity grafts has been proposed as a way to induce endothelialization through transgraft capillarization, although early experiments failed to show increased healing in man. Objectives We hypothesized that transduction of tissues around the prosthetic conduit with vectors encoding VEGF receptor-2 (VEGFR2) ligands would augment transinterstitial capillarization and induce luminal endothelialization of high-porosity ePTFE grafts. Methods Fifty-two NZW rabbits received 87 ePTFE uni- or bilateral end-to-end interposition grafts in carotid arteries. Rabbits were randomized to local therapy with adenoviruses encoding AdVEGF-A165, AdVEGF-A109 or control AdLacZ and analyzed at 6 and 28 days after surgery by contrast-enhanced ultrasound and histology. Results AdVEGF-A165 and AdVEGF-A109 dramatically increased perfusion in perigraft tissues at 6 days (14.2 ± 3.6 or 16.7 ± 2.6-fold increases, P < 0.05 and P < 0.01). At 28 days, the effect was no longer significantly higher than baseline. At 6 days, no luminal endothelialization was observed in any of the groups. At 28 days, AdVEGF-A109- and AdVEGF-A165-treated animals showed enhanced ingrowth of transinterstitial capillaries (66.0 ± 13.7% and 77.4 ± 15.7% of graft thickness vs 44.7 ± 24.4% in controls, P < 0.05) and improved luminal endothelialization (11.2 ± 26.3% and 11.4 ± 22.2%, AdVEGF-A109 and AdVEGF-A165 vs 0% in controls, P < 0.05). No increased stenosis was observed in the treatment groups as compared to LacZ controls. Conclusions This study suggests that transient local overexpression of VEGFR2 ligands in the peri-implant tissues at the time of graft implantation is a novel strategy to increase endothelialization of high-porosity ePTFE vascular grafts and improve the patency of small-diameter vascular prostheses.