Intramyocardial VEGF-B 167 Gene Delivery Delays the Progression Towards Congestive Failure in Dogs With Pacing-Induced Dilated Cardiomyopathy

Abstract

Rationale : Vascular endothelial growth factor (VEGF)-B selectively binds VEGF receptor (VEGFR)-1, a receptor that does not mediate angiogenesis, and is emerging as a major cytoprotective factor. Objective : To test the hypothesis that VEGF-B exerts non-angiogenesis-related cardioprotective effects in nonischemic dilated cardiomyopathy. Methods and Results : AAV-9-carried VEGF-B 167 cDNA (10 12 genome copies) was injected into the myocardium of chronically instrumented dogs developing tachypacing-induced dilated cardiomyopathy. After 4 weeks of pacing, green fluorescent protein-transduced dogs (AAV-control, n=8) were in overt congestive heart failure, whereas the VEGF-B-transduced (AAV-VEGF-B, n=8) were still in a well-compensated state, with physiological arterial P o 2 . Left ventricular (LV) end-diastolic pressure in AAV-VEGF-B and AAV-control was, respectively, 15.0±1.5 versus 26.7±1.8 mm Hg and LV regional fractional shortening was 9.4±1.6% versus 3.0±0.6% (all P <0.05). VEGF-B prevented LV wall thinning but did not induce cardiac hypertrophy and did not affect the density of α-smooth muscle actin-positive microvessels, whereas it normalized TUNEL-positive cardiomyocytes and caspase-9 and -3 activation. Consistently, activated Akt, a major negative regulator of apoptosis, was superphysiological in AAV-VEGF-B, whereas the proapoptotic intracellular mediators glycogen synthase kinase (GSK)-3β and FoxO3a (Akt targets) were activated in AAV-control, but not in AAV-VEGF-B. Cardiac VEGFR-1 expression was reduced 4-fold in all paced dogs, suggesting that exogenous VEGF-B 167 exerted a compensatory receptor stimulation. The cytoprotective effects of VEGF-B 167 were further elucidated in cultured rat neonatal cardiomyocytes exposed to 10 −8 mol/L angiotensin II: VEGF-B 167 prevented oxidative stress, loss of mitochondrial membrane potential, and, consequently, apoptosis. Conclusions : We determined a novel, angiogenesis-unrelated cardioprotective effect of VEGF-B 167 in nonischemic dilated cardiomyopathy, which limits apoptotic cell loss and delays the progression toward failure.