VASCULAR ENDOTHELIAL GROWTH FACTOR-C (VEGF-C VEGF-2) PROMOTES ANGIOGENESIS IN THE SETTING OF TISSUE ISCHEMIA/

Recently, vascular endothelial growth factor-C (VEGF-C or VEGF-2) was described as a specific ligand for the endothelial receptor tyrosine k inases VEGFR-2 and VEGFR-3. In vivo data, limited to constitutive over expression in transgenic mice, have been interpreted as evidence that the growth-promoting effects of VEGF-C are restricted to development o f the lymphatic vasculature. The current studies were designed to test the hypothesis that constitutive expression of VEGF-C in adult animal s promotes angiogenesis. In vitro, VEGF-C exhibited a dose-dependent m itogenic and chemotactic effect on endothelial cells, particularly for microvascular endothelial cells (72% and 95% potency, respectively, c ompared with VEGF-A/VEGF-1) VEGF-C stimulated release of nitric oxide from endothelial cells and increased vascular permeability in the Mile s assay; the latter effect was attenuated by pretreatment with the nit ric oxide synthase inhibitor N-omega-nitro-L-arginine methyl ester. Bo th VEGFR-2 and VEGFR-3 receptors were shown to be expressed in human s aphenous vein and internal mammary artery. The potential for VEGF-C to promote angiogenesis in vivo was then tested In. a rabbit ischemic hi ndlimb model. Ten days after ligation of the external iliac artery, VE GF-C was administered as naked plasmid DNA (pcVEGF-C; 500 mu g) from t he polymer coating of an angioplasty balloon (n = 8 each) or as recomb inant human protein (rhVEGF-C; 500 mu g) by direct intra-arterial infu sion. Physiological and anatomical assessments of angiogenesis 30 days later showed evidence of therapeutic angiogenesis for both pcVEGF-C a nd rhVEGF-C, Hindlimb blood pressure ratio (ischemic/normal) after pcV EGF-C increased to 0.83 +/- 0.03 after pcVEGF-C versus 0.59 +/- 0.04 ( P < 0.005) in pGSVLacZ controls and to 0.76 +/- 0.04 after rhVEGF-C ve rsus 0.58 +/- 0.03 (P < 0.01) in control rabbits receiving rabbit seru m albumin. Doppler-derived iliac flow reserve was 2.7 +/- 0.1 versus 2 .0 +/- 0.2 (P < 0.05) for pcVEGF-C versus LacZ controls and 2.9 +/- 0. 3 versus 2.1 +/- 0.2 (P < 0.05) for rhVEGF-C versus albumin controls. Neovascularity was documented by angiography in vivo (angiographic sca res: 0.85 +/- 0.05 versus 0.51 +/- 0.02 (P < 0.001) for plasmid DNA an d 0.74 +/- 0.08 versus 0.53 +/- 0.03 (P < 0.05) for protein), and capi llary density (per mm(2)) was measured at necropsy (252 +/- 12 versus 183 +/- 10 (P < 0.005) for plasmid DNA and 229 a 20 versus 164 +/- 20 (P < 0.05) for protein), In contrast to the results of gene targeting experiments, constitutive expression of VEGF-C in adult animals promot es angiogenesis in the setting of limb ischemia, VEGF-C and its recept ors thus constitute an apparently redundant pathway for postnatal angi ogenesis and may represent an alternative to VEGF-A for strategies of therapeutic angiogenesis in patients with limb and/or myocardial ische mia.