Mounting evidence indicates that the function of members of the vascular endothelial growth factor (VEGF) family extends beyond blood vessel formation. Here, we show that the prolonged intramyocardial expression of VEGF-A(165) and VEGF-B(167) on adeno-associated virus-mediated gene delivery determined a marked improvement in cardiac function after myocardial infarction in rats, by promoting cardiac contractility, preserving viable cardiac tissue, and preventing remodeling of the left ventricle (LV) over time. Consistent with this functional outcome, animals treated with both factors showed diminished fibrosis and increased contractile myocardium, which were more pronounced after expression of the selective VEGF receptor-1 (VEGFR-1) ligand VEGF-B, in the absence of significant induction of angiogenesis. We found that cardiomyocytes expressed VEGFR-1, VEGFR-2, and neuropilin-1 and that, in particular, VEGFR-1 was specifically up-regulated in hypoxia and on exposure to oxidative stress. VEGF-B exerted powerful antiapoptotic effect in both cultured cardiomyocytes and after myocardial infarction in vivo. Finally, VEGFR-1 activation by VEGF-B was found to elicit a peculiar gene expression profile proper of the compensatory, hypertrophic response, consisting in activation of alphaMHC and repression of betaMHC and skeletal alpha-actin, and an increase in SERCA2a, RYR, PGC1alpha, and cardiac natriuretic peptide transcripts, both in cultured cardiomyocytes and in infarcted hearts. The finding that VEGFR-1 activation by VEGF-B prevents loss of cardiac mass and promotes maintenance of cardiac contractility over time has obvious therapeutic implications.

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-B167 cDNA (1012 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 PO2. 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-B167 exerted a compensatory receptor stimulation. The cytoprotective effects of VEGF-B167 were further elucidated in cultured rat neonatal cardiomyocytes exposed to 10−8 mol/L angiotensin II: VEGF-B167 prevented oxidative stress, loss of mitochondrial membrane potential, and, consequently, apoptosis. Conclusions We determined a novel, angiogenesis-unrelated cardioprotective effect of VEGF-B167 in nonischemic dilated cardiomyopathy, which limits apoptotic cell loss and delays the progression toward failure.

The developed microsurgical chamber provides a highly vascular, isolated tool for in vivo tissue engineering.