['Angiopoietin-1 (Ang1) and angiopoietin-2 (Ang2) have recently been identified as ligands for the endothelial cell-specific Tie2 receptor. Little is known regarding the impact of these Tie2 ligands on postnatal neovascularization. Accordingly, we tested the hypothesis that gene transfer of plasmid DNA encoding Ang1 and Ang2 could modulate collateral vessel development in a rabbit model of hindlimb ischemia.', 'pAng1* (n=15), pJFE control (no Ang1* insert) (n=9), pAng2 (n=9), pcDNA3 control (no Ang2 insert) (n=10), or saline (n=5) was injected intramuscularly into the rabbit ischemic hindlimb. Collateral vessel development and limb perfusion were assessed before and 30 days after treatment. Calf blood pressure ratio (ischemic to normal hindlimb) was increased 30 days after Ang1* gene transfer versus controls (Ang1*, 0.90+/-0.02; pJFE, 0.76+/-0.05; saline, 0.77+/-0. 03; P<0.05). Angiographic score was higher (P<0.05) in the pAng1* group (0.63+/-0.02) than in the pJFE (0.51+/-0.03) or saline (0. 52+/-0.02) group. Maximal (postpapaverine) blood flow in the ischemic limb was higher (P<0.05) after pAng1* (67.8+/-4.9 mL/min) than pJFE (51.2+/-4.4 mL/min) or saline (52.9+/-4.9 mL/min). Capillary density and capillary/muscle fiber ratio (242+/-12/mm2 and 0.89+/-0.06, respectively) were higher (P<0.01) with pAng1* than pJFE (172+/-11/mm2 and 0.64+/-0.05) or saline (166+/-10/mm2 and 0. 67+/-0.05). Neovascularization was not enhanced with pAng2.'] Does direct intramuscular injection of plasmid DNA encoding angiopoietin-1 but not angiopoietin-2 augment revascularization in the rabbit ischemic hindlimb?