Effects of local gene transfer of VEGF on neointima formation after balloon injury in hypercholesterolemic rabbits

Abstract

Enhancement of the generation of nitric oxide (NO) and vascular endothelial growth factor (VEGF) are suggested to prevent restenosis after angioplasty. Accordingly, we tested whether the local delivery of L-arginine (L-Arg), a substrate for NO generation and the VEGF gene, alone or in combination, can influence neointima formation in hypercholesterolemic rabbits. Balloon injury of the iliac arteries was performed in 24 New Zealand White rabbits fed a 1% cholesterol diet for 3 weeks followed by a local infusion of: (1) pSG5VEGF₁₆₅ plasmid alone (1000 μg); (2) pSG5VEGF₁₆₅ (1000 μg) with L-Arg (800 mg); (3) L-Arg (800 mg) alone; and (4) L-Arg (800 mg) with naked pSVβ-gal plasmid (1000 μg). The animals were kept on the hypercholesterolemic diets for a further 28 days, when vessels were taken for morphometric analysis and immunocytochemistry. Endogenous rabbit VEGF concentration in the plasma increased significantly at 7 days after injury (17.06 ± 1.57 vs 23.01 ± 1.9 pg/ml; p < 0.02) and remained elevated for up to 28 days (28.46 ± 5.24; p < 0.01). Injured arteries exhibited strong immunocytochemical staining for rabbit VEGF. Rabbits that received a VEGF gene transfer revealed more prominent neointima formation, whereas treatment with L-Arg was associated with significantly less intimal thickness (p < 0.05). Local transfer of the VEGF gene does not inhibit neointima formation in hypercholesterolemic rabbits. Our results suggest that VEGF gene therapy applied locally in atherosclerotic arteries may not be beneficial.