Post-transcriptional modifications of VEGF-A mRNA in non-ischemic dilated cardiomyopathy

Vascular endothelial growth factor (VEGF-A) is one of the most important proangiogenic factors. It has many isoforms encoded by one gene. The occurrence of these isoforms is associated with the process of alternative splicing of mRNA. Some of the splice forms are perceived as tissue specific. The aim of this study was to determine the alternative splicing of VEGF-A mRNA in dilated cardiomyopathy, especially at the level of particular myocardial layers. The assessment of post-transcriptional modifications of VEGF-A mRNA was made on specimens taken from the explanted hearts of patients undergoing cardiac transplantation. Molecular and histopathological studies were perfomed on particular layers of the myocardial muscle (endocardium, myocardium, epicardium). A molecular analysis of cardiac samples was performed by quantitative analysis of the mRNA of the studied VEGF-A isoforms (VEGF121, -145, -165, -183, -189, and -206) using QRTPCR with an ABI-PRISM 7700-TaqMan sequence detector. 72 cardiac specimens taken from the explanted hearts were analyzed. Each of the studied VEGF-A splice forms was present in the evaluated hearts, but the types of alternative splicing of mRNA were different in particular layers. Quantitative analysis revealed different amounts of the studied isoforms. Generally, significantly increased expression of the VEGF-A isoforms was observed in samples taken from hearts with post-inflammatory etiology of cardiomyopathy. Our conclusions are: 1. All the studied VEGF-A isoforms were found in the human hearts, including those thusfar considered characteristic for other tissues. 2. Significant differences were observed in the expression of the VEGF-A splice forms with respect to the myocardial layers and the location of the cardiac biopsy. 3. Repetitive and comparable results for samples with post-inflammatory etiology were obtained, and they revealed considerably higher amounts of VEGF-A isoforms compared to specimens with idiopathic etiology.