In vivo optical imaging of expression of vascular endothelial growth factor following laser incision in skin

Background and Objective: Laser-tissue interaction studies have focused on laser-induced secondary effects on tissue and the postmortem histological a nalysis of laser wounds. In this study we addressed wound healing and possi ble impairment of wound healing due to collateral tissue damage by in vivo imaging of gene expression. Study Design/Material and Methods: We used a transgenic mouse model contain ing a VEGF promoter driving a GFP reporter gene to image VEGF expression in vivo. Twenty-two mice received two full thickness incisions in the dorsal skin: one with the Free Electron Laser (lambda = 6.45 mum, 52.9 mJ/mm(2)) a nd one with a scalpel. Mice were imaged for GFP expression at 3 days, 1, 2, 3, and 4 weeks. Confocal microscopic imaging was performed at 2 weeks. Results: Peak GFP expression was seen at 2-3 weeks and was localized in fib roblasts. FEL lesions showed more total GFP expression than scalpel lesions but this was only statistically significant (P < 0.05) at 2 and 4 weeks. T he full-width half-max (FWHM) of the GFP expression was always larger for t he FEL lesion compared to the scalpel lesion but was only statistically sig nificant (P < 0.05) at 2 and 3 weeks. At 2 weeks the extent of the GFP expr ession in the laser lesion was on average 55 mum beyond that seen in the sc alpel lesion but correlated with the number of laser passes. Conclusions: Feasibility of using transgenic mice carrying photoactive repo rter genes for studying cellular process of laser-inflicted wound repair in a noninvasive, in vivo manner was shown. GFP expression mediated by the VE GF promoter in fibroblast showed minimal impairment of wound healing due to the laser. (C) 2001 Wiley-Liss, Inc.