Enhancement of epigastric skin flap survival by adenovirus-mediated VEGF gene therapy.

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.