Reconstructive flaps are a mainstay form of treatment for anatomical defects in plastic surgery, and despite extensive progress in the areas of flap anatomy and design, the mechanism of flap healing and the factors that regulate this process are poorly understood. This thesis investigates the regulation of flap healing, and tests the hypothesis that the introduction of genes for angiogenic growth factors can be used to augment the vascularisation and wound healing of ischaemic flaps. Using a modified McFarlane ischaemic skin flap model in Sprague Dawley rats, endogenous angiogenic regulatory factors that included the VEGF and angiopoietin families and their receptors were investigated. Twelve specific quantitative real-time PCR assays documented a general up-regulation of angiogenic genes and their receptors with time following flap elevation. There was not a readily identifiable master regulator. Angiogenic protein levels were more variable with a decrease VEGF-A and TNF-α levels along the flap. Debridement studies of the necrotic distal flaps demonstrated for the first time that VEGF-A164 and TNF-α protein levels stabilised, while angiogenic genes of VEGF-A164, VEGF-A120, angiopoietins and their receptors were down-regulated and VEGF-B186 and HIF-1α mRNA increased, compared to non-debrided flaps. Leucocyte proteolysis in devitalised tissue is discussed as a possible mechanism for reduced angiogenic proteins levels in ischaemic flaps. The impact of angiogenic gene therapy using adenoviral vectors in the flap model revealed for the first time that recombinant adenoviruses containing the VEGF-B186 transgene could significantly augment neovascularisation and improve flap survival. This neovascularisation correlated with up-regulation of the expression of multiple endogenous angiogenic genes that included VEGF-A164, the angiopoietins and their receptors. Erythematous plaques were documented as a side effect of Ad VEGF-A165 and Ad VEGF-B186 treatment of rat skin, although in the latter treatment they were very mild. Weals induced by the presence of VEGF-A165 transgene were associated with a marked acute inflammatory cell infiltrate and oedema consistent with the increased vascular permeability effects of VEGF-A165. Ad VEGF-A165 plus Ad ANG-1* induced weals were less prominent with reduced oedema highlighting the stabilising effect of Ad ANG-1* on vascular permeability.
| Identifer | oai:union.ndltd.org:ADTP/282491 |
| Date | January 2008 |
| Creators | Roman, Sandrine, Medical Sciences, Faculty of Medicine, UNSW |
| Publisher | Awarded By:University of New South Wales. Medical Sciences |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://unsworks.unsw.edu.au/copyright, http://unsworks.unsw.edu.au/copyright |
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