Efficacy and mechanisms of vacuum-assisted closure (VAC) therapy in promoting wound healing: a rodent model

Background: The vacuum-assisted closure device (VAC) has revolutionised wound care, although molecular mechanisms are not well understood. We hypothesise that the VAC device induces production of pro-angiogenic factors and promotes formation of granulation tissue and healing. Methods: A novel rodent model of VAC wound healing was established. Excisional wounds were created on rat dorsa. Wounds were dressed with Tegaderm (control group), VAC Granulofoam (R) and Tegaderm(special control group), or VAC Granulofoam (R), T. R. A. C. PAD (R) with 125 mm Hg continuous negative pressure (VAC group). Wound closure rates were calculated as a percentage of initial wound sizes. Rats were sacrificed on postoperative days 3, 5 and 7; harvested tissues were processed for histology [haematoxylin & eosin (H&E), Masson's trichrome, picrosirius red] and Western blot analysis (CD31, vascular endothelial growth factor, basic fibroblast growth factor). Results: Statistically significant wound closure rates were achieved in the experimental group at all measured time points: day 3, 28.1% (VAC) vs 8.2% (control) and 8.8% (special control) (ANOVA, P < 0.0001); day 5, 45.3% ( VAC) vs 23.7% (control) and 22.5% ( special control) (ANOVA, P = 0.0003); day 7, 54.4% (VAC) vs 43.0% (control) and 31.5% (special control) (ANOVA; P < 0.0001). Morphological evaluation by Masson's trichrome stain showed increased collagen organisation and wound maturation in the VAC group. These wounds also showed increased expression of vascular endothelial growth factor and fibroblast growth factor-2 on day 5 by Western blot analysis. Conclusion: A small animal VAC wound model was established. Wounds treated with a VAC device showed accelerated wound closure rates, increased pro-angiogenic growth factor production and improved collagen deposition. Further application of this model may elucidate other mechanisms. (C) 2008 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.