689. Therapeutic Angiogenesis for Prefabrication of Ischemic Flaps with Multiple Growth Factor Gene Transfers: A Study in a Rat Model

Abstract

Top of pageAbstract Purpose: Necrosis of transferred flaps is a major problem in reconstructive surgery and is primarily due to insufficient angiogenesis in the transferred flaps. Enhancement of angiogenesis by flap prefabrication has been a focus of investigations and remains a challenge to both researchers and surgeons. The objective of this study was to investigate the efficacy of combination gene therapy with multiple growth factor cDNAs to enhance survival of ischemic skin in a rat model. Materials and Methods: Sixty Sprague-Dawley rats were divided into 6 groups. Varying combinations of VEGF-, PDGF-, and bFGF-plasmids were injected to prefabricate the flaps. Random skin flaps were raised on the dorsal aspect of rats following prefabrication with growth factor cDNAs. Flap viability was determined by measurement of percentage area of survival. The efficacy of gene therapy was evaluated by flap survival and neovascularization of representative histologic sections stained immunohistologically with antibody to von Willebrand Factor. Results: The VEGF plus bFGF cDNAs enhanced the viability of the flap and neovascularization most effectively; the flap survival area was 64.3 +//0 8.7 % after transfer of these 2 growth factor genes. Addition of PDGF cDNA is deleterious to the effects of combined VEGF and bFGF, leading to a significant decrease in flap viability (44.9 +//0 2.7 %). Viability of the flaps with combined VEGF and bFGF cDNA transfer was significantly greater than that of the flaps with VEGF transfer alone (57.6 +//0 5.2 %) or sham plasmid control (52.3 +//0 5.0 %). Discussion: Transfer of a single angiogenic growth factor gene, VEGF or PDGF, significantly improved viability of ischemic flaps in previous studies of the authors' and other groups. Transfer of multiple genes encoding angiogenic growth factors to ischemic flaps has not been reported. An important and intriguing finding of our current study is that combined transfer of 2 growth factor genes (VEGF and bFGF) significantly improved flap survival, but in contrast 3 growth factor genes (VEGF, bFGF, and PDGF) drastically worsened the viability of the flap. Transfer of 3 growth factor genes to ischemic flaps appears not advantageous because of interactions between these genes or increases in production of multiple growth factors may not lead to functional improvement of vascular supplies to the flaps and decreases the effectiveness of angiogenesis. Conclusions: Combined transfer of VEGF and bFGF cDNA is the most effective combination of multiple growth factor genes to improve flap viability in this model. Simultaneous transfer of 3 growth factor genes (VEGF, PDGF, and bFGF) is deleterious to flap survival.