RESUMO
We hypothesize that combining angiopoietin-1 (ANG-1) or ANG-2 with vascular endothelial growth factor (VEGF) improves myocardial perfusion and contractile function by modulating vascular adaptation of neoangiogenic microvessels in a chronic ischemic swine model. Four weeks after occlusion of the left circumflex coronary artery (LCx), animals were injected with AdVEGF(165) (n=6), AdVEGF(165)+AdANG-1 (n=6), AdVEGF(165)+AdANG-2 (n=6) or control vector (n=5) into the left ventricular posterolateral wall. Regional perfusion by fluorescent microspheres and segmental myocardial tissue velocity by tissue Doppler imaging (TDI) were assessed at baseline, 4 weeks post occlusion and 4 weeks post therapy. Despite similar vascular growth following VEGF+ANG-1 and VEGF+ANG-2 treatments, transmural myocardial contractility improved only when VEGF was paired with ANG-1. In contrast, regional systolic function deteriorated uniformly across subepicardial, mid-myocardial and subendocardial segments in VEGF and VEGF+ANG-2 treated groups. Contractile improvement was associated with enhanced vascular stability through augmented arteriole formation, tight structural integration between VE-cadherin and beta-catenin at endothelial junctions and improved cross-talk between endothelium and myocardium. Structural stability of developing intramyocardial microvessels contributes to systolic function during ischemic neovascularization. Coordinated regulation of angiogenic revascularization that supports vascular stability is a key aspect in improving therapeutic outcomes in ischemic myocardium.
Assuntos
Adenoviridae , Angiopoietina-1/biossíntese , Angiopoietina-2/biossíntese , Isquemia Miocárdica/metabolismo , Neovascularização Fisiológica , Recuperação de Função Fisiológica , Fator A de Crescimento do Endotélio Vascular/biossíntese , Angiopoietina-1/genética , Angiopoietina-2/genética , Animais , Antígenos CD/metabolismo , Arteríolas/metabolismo , Arteríolas/patologia , Caderinas/metabolismo , Doença Crônica , Circulação Coronária/genética , Vasos Coronários/metabolismo , Vasos Coronários/patologia , Modelos Animais de Doenças , Ecocardiografia Doppler , Endotélio/metabolismo , Feminino , Terapia Genética/métodos , Masculino , Contração Miocárdica/genética , Isquemia Miocárdica/diagnóstico por imagem , Isquemia Miocárdica/patologia , Isquemia Miocárdica/terapia , Miocárdio/metabolismo , Miocárdio/patologia , Neovascularização Fisiológica/genética , Recuperação de Função Fisiológica/genética , Suínos , Fatores de Tempo , Fator A de Crescimento do Endotélio Vascular/genética , beta Catenina/metabolismoRESUMO
This study investigates the long-term angiogenic effects of ANG-1 and VEGF in a swine chronic myocardial ischemia model. Four-weeks after gradual occlusion of the left circumflex coronary artery by ameroid constrictor, animals were injected with recombinant adenoviral vectors carrying either human ANG-1 (n=9), human VEGF(165) (n=10) or empty vector (n=7) into the left ventricle free wall supplied by the constricted artery. Left ventricular perfusion in animals that received AdANG-1 (3.25+/-0.16 ml/min/g, p<0.05) recovered robustly 4 weeks after gene transfer while ischemia persisted in the AdVEGF (1.09+/-0.13 ml/min/g) and empty vector (1.20+/-0.03 ml/min/g) groups. Microvascular densities in the left ventricles of animals that received AdANG-1 (19.61+/-1.76/0.572 mm(2) myocardial tissue, p<0.05) and AdVEGF (18.17+/-1.43/0.572 mm(2) myocardial tissue, p<0.05) were significantly higher than animals that received empty vector (13.53+/-0.92/0.572 mm(2) myocardial tissue) 12 weeks after gene transfer. ANG-1, but not VEGF, contributed to enhanced regional perfusion by increasing arteriolar density (1.9+/-0.4/0.572 mm(2) myocardial tissue vs. 0.7+/-0.2/0.572 mm(2) myocardial tissue, p<0.05) of large-sized (50-100 microm) arterioles. These data demonstrate that gene transfer of ANG-1 and VEGF enhances angiogenesis, but ANG-1 promotes sustained improvement of ventricular perfusion that expedites recovery of ischemic myocardium via arteriogenesis.
