DIRECT INTRAMUSCULAR GENE-TRANSFER OF NAKED DNA ENCODING VASCULAR ENDOTHELIAL GROWTH-FACTOR AUGMENTS COLLATERAL DEVELOPMENT AND TISSUE PERFUSION

Background Striated muscle has been shown to be capable of taking up a nd expressing foreign genes transferred in the form of naked plasmid D NA, although typically with a low level of gene expression. In the cas e of genes that encode secreted proteins, however, low transfection ef ficiency may not preclude bioactivity of the secreted gene product. Ac cordingly, we investigated the hypothesis that intramuscular (IM) gene therapy with naked plasmid DNA encoding vascular endothelial growth f actor (VEGF) could augment collateral development and tissue perfusion in an animal model of hindlimb ischemia. Methods and Results Ten days after ischemia was induced in one rabbit hindlimb, 500 mu g of phVEGF (165), or the reporter gene LacZ, was injected IM into the ischemic hi ndlimb muscles. Thirty days later, angiographically recognizable colla teral vessels and histologically identifiable capillaries were increas ed in VEGF transfectants compared with controls. This augmented vascul arity improved perfusion to the ischemic limb, documented by a superio r calf blood pressure ratio for phVEGF(165) (0.85+/-0.05) versus contr ols (0.64+/-0.05, P<.01), improved blood flow in the ischemic limb (me asured with an intra-arterial Doppler wire) at rest (phVEGF(165)=21.3/-3.9 mL/min, control=14.6+/-1.6 mL/min, P<.01) and after a vasodilato r (phVEGF(165)=54.2+/-12.0 mL/min, control=37.3+/-8.9 mL/min, P<.01) a nd increased microspheres in the adductor (phVEGF(165)=4.3+/-1.6 mL . min(-1) . 100 g of tissue(-1), control=2.9+/-1.2 mL . min(-1) . 100 g of tissue(-1), P<.05) and gastrocnemius (phVEGF(165)=3.9+/-1.0 mL . mi n(-1) . 100 g of tissue(-1), control=2.8+/-1.4 mL . min(-1) . 100 g of tissue(-1), P<.05) muscles of the ischemic limb. Conclusions Ischemic skeletal muscle represents a promising target for gene therapy with n aked plasmid DNA. IM transfection of genes encoding angiogenic cytokin es, particularly those that are naturally secreted by intact cells, ma y constitute an alternative treatment strategy for patients with exten sive peripheral vascular disease in whom the use of intravascular cath eter-based gene transfer is compromised and/or prohibited.