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  • Title: Transforming growth factor-β-induced endothelial-to-mesenchymal transition is partly mediated by microRNA-21.
    Author: Kumarswamy R, Volkmann I, Jazbutyte V, Dangwal S, Park DH, Thum T.
    Journal: Arterioscler Thromb Vasc Biol; 2012 Feb; 32(2):361-9. PubMed ID: 22095988.
    Abstract:
    OBJECTIVE: MicroRNAs are a class of small ribonucleotides regulating gene/protein targets by transcript degradation or translational inhibition. Transforming growth factor-β (TGF-β) is involved in cardiac fibrosis partly by stimulation of endothelial-to-mesenchymal transition (EndMT). Here, we investigated whether microRNA (miR)-21, a microRNA enriched in fibroblasts and involved in general fibrosis, has a role in cardiac EndMT. METHODS AND RESULTS: TGF-β treatment of endothelial cells significantly increased miR-21 expression and induced EndMT characterized by suppression of endothelial and increase of fibroblast markers. Overexpression of miR-21 alone also stimulated EndMT. Importantly, miR-21 blockade by transfection of specific microRNA inhibitors partly prevented TGF-β-induced EndMT. Mechanistically, miR-21 silenced phosphatase and tensin homolog in endothelial cells, resulting in activation of the Akt-pathway. Akt inhibition partly restored TGF-β-mediated loss of endothelial markers during EndMT. In vivo, pressure overload of the left ventricle led to increased expression of miR-21 in sorted cardiac endothelial cells, which displayed molecular and phenotypic signs of EndMT. This was attenuated by treatment of mice subjected to left ventricular pressure overload with an antagomir against miR-21. CONCLUSIONS: TGF-β-mediated EndMT is regulated at least in part by miR-21 via the phosphatase and tensin homolog/Akt pathway. In vivo, antifibrotic effects of miR-21 antagonism are partly mediated by blocking EndMT under stress conditions.
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