Endothelial-to-mesenchymal transition in human idiopathic dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is characterized by left ventricular dilation and cardiac fibrosis. Emerging evidence indicated that endothelial-to-mesenchymal transition (Endo-MT) is a crucial event during organ fibrosis. This study was performed to clarify whether Endo-MT contributed to the progression of cardiac fibrosis in DCM. Cardiac samples from patients with DCM and control were obtained. The presence of endothelial markers, cluster of differentiation (CD)31 and vascular endothelial (VE)-cadherin, and mesenchymal markers, smooth muscle actin (SMA) and fibroblast-specific protein 1 (FSP1) was performed using immunohistochemistry. Co-localization of endothelial markers and mesenchymal markers were identified using confocal immunofluorescence staining. Serum procollagen type I carboxy-terminal propeptide (PICP) and procollagen type III amino-terminal propeptide (PIIINP) were measured by ELISA. Protein levels of Wnt, -catenin and Snail were determined using western blot analysis. Immunohistochemistry and double-immunofluorescence staining demonstrated that the expression of CD31 and VE-cadherin were significantly decreased in DCM samples, whereas the FSP-1, and SMA were significantly increased. CD31 and VE-cadherin labeling indexes were respectively negatively correlated with left ventricular end-diastolic diameter (LVEDD) (CD31 r=-0.82, P<0.01; VE-cadherin r=-0.73, P<0.01), while FSP-1 and SMA were positively associated with LVEDD (SMA r=0.65, P<0.01, FSP1 r=0.53, P<0.01) and left ventricular ejection fraction (SMA r=-0.18, P<0.05; FSP1 r=-0.21, P<0.05). Furthermore, PICP and PIIINP levels were positively associated with the co-expression labeling indexes (CD31/SMA co-labeling index and PICP r=0.727, P<0.01; CD31/SMA co-labeling index and PIIINP r=0.741, P<0.01; VE-Cadherin/FSP-1 co-labeling index and PICP r=0.716, P<0.01; VE-cadherin/FSP-1 co-labeling index and PIIINP r=0.648, P<0.05). Western blot analysis indicated that proteins levels of Wnt signaling and snail were significantly increased in DCM samples. These results suggested that Endo-MT is potentially implicated in the pathogenesis of myocardial fibrosis and remodeling during the development of DCM, indicating a potential therapeutic target for DCM treatment.