Background: The cross-talk between vascular endothelial growth factor (VEGF)-A, angiopoietin (Ang), and VE-cadherin coregulates endothelial cell (EC) survival. Cardiac expression of VEGF-A but not its receptor KDR is blunted in dilated cardiomyopathy (DCM). Whether VE-cadherin/Ang function is affected in DCM is unknown.
Methods and results: The myocardial expression of VE-cadherin/beta-catenin, Ang-1, Ang-2, and their receptor Tie-2 was examined in DCM, ischemic cardiomyopathy (ICM), and in control subjects through the use of real-time RT-PCR, Western blotting, and immunocytochemistry. EC degeneration was quantified by TEM. RNA interference against VE-cadherin and VEGF deprivation and stimulation were applied to cultured DCM myocardium and human microvascular ECs to examine the interplay between VEGF, VE-cadherin/beta-catenin, and Ang-2. Analysis of tissue sections with similar rates of EC degeneration in both patient groups showed that VE-cadherin/beta-catenin expression was downregulated in DCM only (P<0.05). Although Ang-1 was not changed, Ang-2 expression was downregulated and Tie-2 protein expression was upregulated both in DCM and ICM (P<0.05). The ratio of degenerated to normal ECs was significantly higher in DCM versus ICM (P<0.05). Targeted VE-cadherin gene silencing in cultured human ECs resulted in similar degenerative effects observed in myocardial ECs of DCM patients. In vitro experiments indicated that VE-cadherin/beta-catenin expression is independent of VEGF.
Conclusions: These results indicate for the first time that the EC survival is impaired in myocardium of patients with DCM involving VE-cadherin/beta-catenin, probably independent of VEGF. Targeting VE-cadherin might be of benefit to counteract the selective EC pathology in DCM.