Feinberg Cardiovascular Research Institute, Northwestern University, Chicago, IL 60611, USA.
Cell Signal. 2012 May;24(5):1031-6. doi: 10.1016/j.cellsig.2011.12.024. Epub 2012 Jan 5.
Fibroblasts are responsible for producing the majority of collagen and other extracellular matrix (ECM) proteins in tissues. In the injured tissue, transforming growth factor-β (TGF-β)-activated fibroblasts or differentiated myofibroblasts synthesize excessive ECM proteins and play a pivotal role in the pathogenesis of fibrosis in heart, kidney and other organs. Recent studies suggest that fibroblast-like cells, derived from endothelial cells by endothelial-to-mesenchymal transition (EndMT), contribute to the pathogenesis of cardiac fibrosis. The molecular basis of EndMT, however, is poorly understood. Here, we investigated the molecular basis of EndMT in mouse cardiac endothelial cells (MCECs) in response to TGF-β2. MCECs exposed to TGF-β2 underwent EndMT as evidenced by morphologic changes, lack of acetylated-low density lipoprotein (Ac-LDL) uptake, and the presence of alpha-smooth muscle actin (α-SMA) staining. Treatment with SB431542, a small molecule inhibitor of TGF-β-receptor I (TβRI) kinase, but not PD98059, a MEK inhibitor, completely blocked TGF-β2-induced EndMT. The transcript and protein levels of α-SMA, Snail and β-catenin as well as acetyltransferase p300 (ATp300) were elevated in EndMT derived fibroblast-like cells. Importantly, microRNA (miRNA) array data revealed that the expression levels of specific miRNAs, known to be dysregulated in different cardiovascular diseases, were altered during EndMT. The protein level of cellular p53, a bonafide target of miR-125b, was downregulated in EndMT-derived fibroblast-like cells. Here, we report for the first time, the differential expression of miRNAs during cardiac EndMT. These results collectively suggest that TβRI serine-threonine kinase-induced TGF-β signaling and microRNAs, the epigenetic regulator of gene expression at the posttranscriptional level, are involved in EndMT and promote profibrotic signaling in EndMT-derived fibroblast-like cells. Pharmacologic agents that restrict the progression of cardiac EndMT, a phenomenon that is found in adults only in the pathological conditions, in targeting specific miRNA may be helpful in preventing and treating cardiac fibrosis.
成纤维细胞负责产生组织中大多数胶原和其他细胞外基质（ECM）蛋白。在受损组织中，转化生长因子-β（TGF-β）激活的成纤维细胞或分化的肌成纤维细胞合成过多的 ECM 蛋白，并在心脏、肾脏和其他器官纤维化的发病机制中发挥关键作用。最近的研究表明，内皮细胞向间充质转化（EndMT）产生的成纤维细胞样细胞有助于心脏纤维化的发病机制。然而，EndMT 的分子基础知之甚少。在这里，我们研究了 TGF-β2 诱导的小鼠心脏内皮细胞（MCEC）中 EndMT 的分子基础。暴露于 TGF-β2 的 MCEC 经历了 EndMT，表现为形态变化、缺乏乙酰化低密度脂蛋白（Ac-LDL）摄取以及α-平滑肌肌动蛋白（α-SMA）染色。用小分子 TGF-β受体 I（TβRI）激酶抑制剂 SB431542 处理，但不是 MEK 抑制剂 PD98059，完全阻断了 TGF-β2 诱导的 EndMT。EndMT 衍生的成纤维细胞样细胞中α-SMA、Snail 和β-catenin 的转录和蛋白水平以及乙酰转移酶 p300（ATp300）升高。重要的是，miRNA 阵列数据显示，在不同心血管疾病中失调的特定 miRNA 的表达水平在 EndMT 期间发生改变。EndMT 衍生的成纤维细胞样细胞中细胞 p53 的蛋白水平，p53 是 miR-125b 的真正靶标，下调。在这里，我们首次报道了心脏 EndMT 期间 miRNA 的差异表达。这些结果共同表明，TβRI 丝氨酸-苏氨酸激酶诱导的 TGF-β 信号和 microRNA，作为转录后水平基因表达的表观遗传调节剂，参与 EndMT，并促进 EndMT 衍生的成纤维细胞样细胞中的促纤维化信号。在靶向特定 miRNA 以限制仅在病理条件下在成人中发现的心脏 EndMT 进展的情况下，药理学药物可能有助于预防和治疗心脏纤维化。
