Induction of angiogenesis by cationic lipid-mediated VEGF₁₆₅ gene transfer in the rabbit ischemic hindlimb model

Purpose: The purpose of this study was to test the efficacy of a new cationic lipid formulation coupled with the cDNA encoding for the 165-residue form of vascular endothelial growth factor (VEGF₁₆₅) to induce neovascularization and enhance blood flow in the rabbit ischemic hindlimb model. Methods: Two days after removal of their right femoral arteries, rabbits received intramuscular injections of different concentrations of VEGF₁₆₅ or saline solution in the ischemic thigh. Tissue perfusion and increased neovascularization of the ischemic limb were assessed weekly on the basis of the calf blood pressure ratio for the ischemic/non-ischemic limbs, regional blood flow to the skeletal muscles as measured with radioactive microspheres, postmortem angiography, and histology. Results: At weeks 1 and 2 after surgery, animals treated with 1000 μg of VEGF₁₆₅ had a 1.5-fold increase and a 2.5-fold increase, respectively, in the regional blood flow to both the adductor and gastrocnemius muscles of the ischemic limb. The blood pressure ratio was also greater in the treated animals than in the controls at weeks 2 and 3 after surgery. Early neovascularization in the VEGF₁₆₅ group was further documented at week 1 after surgery by more angiographically recognizable collateral vessels (angioscores were 64.13 ± 2.51 and 38.28 ± 3.82 for VEGF₁₆₅ and saline solution, respectively; P < .001) and by a threefold increase in the number of capillaries (vascular density) relative to the controls (P < .005). Conclusions: Intramuscular administration of a single dose of plasmid-liposomes encoding for VEGF₁₆₅ accelerates angiogenesis and increases blood flow in the rabbit hindlimb ischemic model. Therefore, this nonviral vector could be recommended for further testing for use in therapeutic angiogenesis.