VEGFA and peripheral arterial disease: On the other hand, naked/plasmid DNA and lipofectin were considered not to be superior to viral vector due to low transfection efficiency; however, Isner et al. showed the effect of VEGF on ischemic improvement using easy-to-use treatment with intramuscular injection of plasmid without viral vector [19] and confirmed the effect of plasmid on patients with PAD for the first time in 1996 [12, 20].