Microangiographic assessment of collateral vessel formation following direct gene transfer of vascular endothelial growth factor in rats

Objective: The development of collateral microvessels following therapeutic angiogenesis with Vascular endothelial growth factor (VEGF) was investigated using a new system of microangiography that employs monochromatic synchrotron radiation (SR) and a high definition video system to visualize arteries with a spatial resolution of 30 mu m. Methods: Ischemia was induced in the hindlimb of 20 rats by excision of the femoral artery, followed by transfection of the plasmid (400 mu g) encoding VEGF or beta-galactosidase (control) into limb muscles. Microangiography was used to assess the development of collaterals in the ischemic limb four weeks after treatment. Results: Gene transfer of VEGF produced morphologically similar, but significantly more extensive, collateral networks at the microvascular level as compared with the naturally occurring collateral arteries in the control animals (angiographic score: 0.88 +/- 0.08 versus 0.54 +/- 0.05, p < 0.01). No adverse vascular effects such as hemangiomas and/or arteriovenous (AV) fistulae were observed following VEGF treatment. The vasodilator effect of papaverine was evident in relatively large vessels in both groups. At the microvascular level (diameter < 100 mu m), however, papaverine induced significant vasodilation in the VEGF-treated animals, and almost no vasodilation in the controls. Conclusions: SR microangiography allowed us to assess the development of small collateral arteries following VEGF-gene transfer. The information obtained may provide new insights regarding the collateral microcirculation and therapeutic angiogenesis. (C) 1997 Elsevier Science B.V.