title: Acute local subcutaneous VEGF165 injection for augmentation of skin flap viability: efficacy and mechanism.
abstract: Distal skin ischemic necrosis is a common complication in skin flap surgery. The pathogenesis of skin flap ischemic necrosis is unclear, and there is no clinical treatment available. Here, we used the 4 x 10 cm rat dorsal skin flap model to test our hypothesis that subcutaneous injection of vascular endothelial growth factor 165 (VEGF165) in skin flaps at the time of surgery is effective in augmentation of skin flap viability, which is associated with an increase in nitric oxide (NO) production, and the mechanism involves 1) an increase in skin flap blood flow in the early stage after surgery and 2) enhanced angiogenesis subsequently to sustain increased skin flap blood flow and viability. We observed that subcutaneous injection of VEGF165 in skin flaps at the time of surgery increased skin flap viability in a dose-dependent manner. Subcutaneous injection of VEGF165 at the dose of 2 microg/flap increased skin flap viability by 28% (P < 0.05; n = 8). Over 80% of this effect was blocked by intramuscular injection of the NO synthase (NOS) inhibitor Nomega-nitro-L-arginine (13 mg/kg) 45 min before surgery (P < 0.05; n = 8). The VEGF165 treatment also increased skin flap blood flow (2.68 +/- 0.63 ml x min(-1) x 100 g(-1)) compared with the control (1.26 +/- 0.10 ml x min(-1) x 100 g(-1); P < 0.05, n = 6) assessed 6 h postoperatively. There was no change in skin flap capillary density at this time point. VEGF165-induced increase in capillary density (32.2 +/- 1.1 capillaries/mm2; P < 0.05, n = 7) compared with control (24.6 +/- 1.4 capillaries/mm2) was seen 7 days postoperatively. There was also evidence to indicate that VEGF165-induced NO production in skin flaps was stimulated by activation of NOS activity followed by upregulation of NOS protein expression. These observations support our hypothesis and for the first time provide an important insight into the mechanism of acute local VEGF165 protein therapy in mitigation of skin flap ischemic necrosis.
authors.affiliation: Research Institute, The Hospital for Sick Children, University of Toronto, Ontario, Canada M5G 1X8.
authors.forename: Asim
authors.initials: A
authors.lastname: Khan
authors.forename: Homa
authors.initials: H
authors.lastname: Ashrafpour
authors.forename: Ning
authors.initials: N
authors.lastname: Huang
authors.forename: Peter C
authors.initials: PC
authors.lastname: Neligan
authors.forename: Christopher
authors.initials: C
authors.lastname: Kontos
authors.forename: Anguo
authors.initials: A
authors.lastname: Zhong
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Forrest
authors.forename: Cho Y
authors.initials: CY
authors.lastname: Pang
mesh_terms: D000199:Actins / Q000096:biosynthesis; D000818:Animals; D015153:Blotting, Western; D002199:Capillary Permeability / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000378:metabolism; D007279:Injections, Subcutaneous; D008297:Male; D008833:Microcirculation / Q000502:physiology; D009336:Necrosis; D018919:Neovascularization, Physiologic / Q000187:drug effects; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow / Q000187:drug effects; D012867:Skin / Q000098:blood supply / Q000187:drug effects / Q000473:pathology; D013524:Surgical Flaps / Q000098:blood supply / Q000473:pathology / Q000502:physiology*; D042461:Vascular Endothelial Growth Factor A / Q000008:administration & dosage / Q000494:pharmacology*; D014664:Vasodilation / Q000187:drug effects
chemical_list: D000199:Actins; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496318:Nos2 protein, rat; C496316:Nos3 protein, rat; D011451:Prostaglandin-Endoperoxide Synthases