Enhancement of Epigastric Skin Flap Survival by Adenovirus-Mediated VEGF Gene Therapy

Abstract

A novel approach to treat ischemic tissues by using gene therapy has recently been introduced on the basis of the angiogenic potential of certain growth factors. The authors investigated the effect of adenovirus-mediated gene therapy with vascular endothelial growth factor (VEGF) delivered into the subdermal space to treat compromised skin flaps. For this purpose, the epigastric skin flap model in rats, based solely on the right inferior epigastric vessels, was used. Thirty male Sprague-Dawley rats were divided into five groups of six rats each. Viral transfection with 108 plaque-forming units was performed 2 days before the epigastric flap elevation. Rats received subdermal injections of adenovirus encoding VEGF (Ad-VEGF) or green fluorescent protein (Ad-GFP) as treatment control. Another set of animals (n = 6) received no injections and were designated as control. To determine whether site of injection had an impact on flap viability, injections were given into the predicted local ischemic area (Ad-VEGF local, n = 6; Ad-GFP local, n = 6) and into the midline of the flap (Ad-VEGF midline, n = 6; Ad-GFP midline, n = 6). A flap measuring 8 x 8 cm was outlined on the abdominal skin extending from the xiphoid process proximally and the pubic region distally, to the anterior axillary lines bilaterally. Then, the epigastric flap was elevated as an island on the right inferior epigastric vessels and sutured back to its bed. Flap viability was evaluated at 7 and 14 days after the first operation. The epigastric flaps were scanned to the computer and areas of hypoxic and/or necrotic zones relative to total flap surface area were measured and expressed as percentages by using Image Pro Plus software. Specimens were taken for histologic evaluation at day 14 before the animals were killed. Combined area of necrotic and hypoxic zones as well as necrotic zone were decreased to 9.7 +/- 1.4 percent and 1.4 +/- 0.9 percent in Ad-VEGF local, and 11.8 +/- 1.9 percent and 3.5 +/- 1.64 percent in Ad-VEGF midline compared with the control and Ad-GFP treatment groups (control, 23 +/- 3.6 percent and 20.1 +/- 3.3 percent; Ad-GFP local, 24.8 +/- 4.8 percent and 16.2 +/- 5.9 percent; and Ad-GFP midline, 23.4 +/- 6.9 percent and 19.5 +/- 7.7 percent; p < 0.05). Histologic evaluation by light microscopy failed to demonstrate any quantitative difference in vascularity of skin flaps between the treatment groups. In this study, the authors demonstrated that adenovirus-mediated gene therapy using VEGF enhanced epigastric skin flap survival, as confirmed by the significant reduction in combined area of necrotic and hypoxic zones of the flap. Compared with the control, both local and midline subdermal injections of Ad-VEGF showed improvement in overall flap survival by 57.9 and 48.7 percent, respectively. The results of this study raise the possibility of using adenovirus-mediated therapeutic angiogenesis for safer flap surgery in high-risk patients.

AdVEGF165 gene transfer increases survival in overdimensioned skin flaps

“…From a surgical point of view an intraoperative application would be most desirable but angiogenesis and improved perfusion as a consequence will need time to develop. Most previous studies demonstrated increased flap survival, but failed to show evidence of increased VEGF expression, increased flap perfusion or improved angiogenesis [9,24,25]. We show that the delivery of AdVEGF 165 to the preoperative flap site 3 or 7 days before surgery indeed leads to increased VEGF concentration in the skin, increased perfusion of the injected area, and an increased flap survival size together with a reduced necrosis.…”

Efficacy and mechanism of adenovirus-mediated VEGF-165 gene therapy for augmentation of skin flap viability

“…Experimental evidence indicates that VEGF-165 gene therapy is feasible in augmenting skin flap viability. Specifically, local subdermal or subcutaneous injection of liposomal or adenoviral vectors encoding the cDNA of VEGF-165 at 0.5, 2, 3, 7, or 14 days before surgery effectively augmented skin flap viability in the rat, but the mechanism was not studied (9,11,20,21). Local subcutaneous injection of VEGF-165 plasmid DNA 7 days preoperatively also increased skin viability in rat musculocutaneous flaps, and again the mechanism was not studied (49).…”

Transplantation of Adipose-Derived Stem Cells Promotes Formation of Prefabricated Flap in a Rat Model

“…In order to prevent complications like this, several studies have been done to achieve better neovascularization during flap prefabricating process, such as the application of angiogenic cytokines vascular endothelial growth factor (VEGF) (Li et al 2000), basic fibroblast growth factor (bFGF) (Bayati et al 1998), and transforming growth factor (TGF)-β (Iwasawa 1993), or the administration of gene therapy (Lubiatowski et al 2002). However, neither the local application of angiogenic cytokines nor the administration of gene therapy can be effective long-term without obvious side effects.…”