Locally Administered Vascular Endothelial Growth Factor cDNA Increases Survival of Ischemic Experimental Skin Flaps

Abstract

Microvascular surgery has emerged as an attractive area for recent advances in the field of gene therapy. The present study investigated the survival of ischemic, experimental skin flaps after treatment with the gene encoding vascular endothelial growth factor (VEGF). In 30 Sprague-Dawley rats, anterior abdominal skin flaps supplied by the epigastric artery and vein were created. Ten animals were treated with a mixture of liposomes and the cDNA encoding the 121-amino acid isoform of VEGF. Another 10 animals were treated with control plasmid DNA and liposome transfection medium; a third group of 10 animals was given physiologic saline. Each solution was injected directly into the femoral artery distal to the origin of the epigastric pedicle supplying the flap. Four days after injection, the pedicle was ligated and blood flow in the flap was approximated using dye fluorescence. Seven days later, the amount of viable tissue within the flap was measured by planimetry. After the animals were killed, specimens from both the operated and nonoperated sides of the abdomen were harvested for immunohistologic evidence of VEGF protein expression. Average dye fluorescence indices of the three groups (VEGF cDNA, control plasmid, and saline) 2 hours after pedicle ligation were 35.9, 23.9, and 53.9 percent, respectively (p < 0.05). Compared with the two control groups, flaps receiving VEGF cDNA had significantly greater tissue viability at the end of 7 days: 93.9 versus 28.1 percent for the control plasmid DNA group and 31.9 percent for the saline group (p < 0.05). Immunohistochemical staining documented increased deposition of VEGF protein in flaps that were infused with the VEGF cDNA versus saline alone (p < 0.05). The results indicated that the survival of ischemic tissues can be enhanced by administration of a cDNA encoding VEGF, a protein known to be important in the process of angiogenesis and wound healing.

Genetically Modified Mouse Models in Studies on Cutaneous Wound Healing

“…Surprisingly, in these mice the prominent GFP expressing cell type appeared to be the fibroblast, which stands in contrast to a keratinocyte dominated VEGF expression other groups have reported previously (Frank et al 1995). A cutaneous study on intra-arterial liposomal gene transfer to experimental skin flaps prior to exposure to ischaemia revealed an increased tissue viability after treatment with VEGF expression vector cDNA in correlation with increased VEGF protein expression (Taub et al 1998). The angiopoietins form a second family of growth factors essential for the regulation of vascular development (Holash et al 1999).…”

Regulation of scar formation by vascular endothelial growth factor

“…[34][35][36][37] The benefits of enhanced angiogenesis have primarily been shown in models of impaired wound healing 28,32,33 or severe injury. [29][30][31] In contrast, several reports have shown that modulation of angiogenesis does not affect epidermal healing rates or overall wound closure to a great degree, [38][39][40][41][42][43] and some studies have even reported enhanced healing with reduced angiogenesis. 44 Thus, although there are many studies examining angiogenesis and wound repair, the degree to which angiogenesis actually facilitates healing under normal circumstances is still not known.…”

“…It is not surprising then, that many studies have found angiogenesis to be beneficial for wound repair. Stimulation of angiogenesis can enhance healing rates, [27][28][29][30][31][32][33] whereas a reduction in angiogenesis can impair the same. [34][35][36][37] The benefits of enhanced angiogenesis have primarily been shown in models of impaired wound healing 28,32,33 or severe injury.…”

Delivery of FGF-2 but not VEGF by encapsulated genetically engineered myoblasts improves survival and vascularization in a model of acute skin flap ischemia

“…52 The site of VEGF delivery may not have been optimal, since a separate study revealed that intravascular delivery of naked DNA encoding VEGF improved the survival of skin flaps containing vessels arising from a single artery. 53 It is worth noting that in the clinic it is seldom that flaps are vascularized in this manner.…”