HDAC3非常规剪接介导内皮间充质转化在心肌纤维化中的机制研究

Excessive fibrosis in the cardiac tissue results in increased mechanical stiffness and diastolic dysfunction. It also disrupts the electric coupling of cardiomyocyte, leading to impaired cardiac contraction and arhythmia. Recent studies have reported that the endothelial-mesenchymal transition (EndMT) pays a major contribution to cardiac fibroblasts and ventricular remodeling under pathological conditions. Our recent studies revealed that chronic pressure overload via transverse aortic constriction induced myocardial fibrosis in a mouse model. During this process, histone deacetylase (HDAC) 3 underwent unconventional splicing. The occurrence of HDAC3α isoform is concomitant with the up-regulation of FSP1/SMA and down-regulation of VE-cadherin expression. In vitro study showed that over-expression of HDAC3α increased FSP1/SMA expression and collagen IV/periostin secretion while decreased PECAM-1 expression in mature endothelial cells, indicating an EndMT phenotype. Therefore, we hypothesize that HDAC3 unconventional splicing plays important role in EndMT and myocardial fibrosis. We will establish a transgenic mouse model to confirm that EndMT is truly involved in myocardial fibrosis. After investigating the detailed mechanism of HDAC3 splicing and subsequent signaling pathway, we hope to find the new insights into the mechanisms of myocardial fibrosis, and provide a new therapeutic target for preventing ventricular remodeling under pathological conditions.

心肌纤维化是心室重构的主要病理机制，它不仅能引起心脏局部运动不协调、舒张功能障碍等问题，而且干扰正常的心肌细胞电活动，导致心肌收缩异常及心律失常。已有研究发现内皮间充质转化（EndMT）会引起心肌成纤维细胞增多、心室重构。课题组在小鼠主动脉缩窄模型的左心室组织中发现HDAC3可发生非常规剪接，同时内皮细胞开始表达间充质组织标志物，而内皮特异标志物表达下调。在成熟内皮细胞上过表达HDAC3非常规剪接产物α亚型也可诱导EndMT。因此，我们推断HDAC3非常规剪接介导的EndMT在心室重塑中具有重要意义。我们将首先在动物模型中证实EndMT在心肌纤维化中的作用，然后对HDAC3非常规剪接的分子生物学机制和下游通路进行研究，最后在动物模型中，抑制关键信号分子，检验干预HDAC3非常规剪接及EndMT对心肌纤维化的治疗意义。该课题将为心肌纤维化的病理机制研究和临床治疗提供新的理论基础和解决思路。

心肌纤维化可以减小心室顺应性和电解偶联，进而引起心肌舒缩功能障碍，最终导致心力衰竭加重。我们此前在离体及在体模型中证实了内皮间充质转化（EndMT）在心肌正常发育和纤维化中的作用，并对组蛋白去乙酰化酶3（HDAC3）非常规剪接的分子生物学机制和下游通路进行初步探索，检验了干预HDAC3非常规剪接及EndMT对心肌纤维化的影响，发现了HDAC3非常规剪接对内皮细胞功能维护及多种病理生理机制有重要作用。在此基础之上，课题组深入探讨了HDAC3非常规剪接在 EndMT中的生理现象，发现HDAC3剪接所产生的一种亚型HDAC3α不仅参与了鼠胚动脉发育过程中的内皮向平滑肌细胞的转化，并和鸡胚心内膜内皮细胞向间质细胞的转化有关。进一步通过HDAC3α过表达证实其通过PI3K/AKt和TGFβ信号通路诱导EndMT，具体机制又涉及了HDAC3α诱导TGFβ2的分泌和与Akt 1的直接作用。最终也在上述研究成果基础上证实的各种信号传导通路拮抗剂在小鼠主动脉缩窄模型中的作用，观察到影响HDAC3非常规剪接下游传导通路对心肌纤维化的干预作用。研究成果将为临床治疗心肌纤维化提供重要的理论依据以及新的治疗思路。