Meis2在退行性瓣膜病发病中的作用与机制研究

The morbidity of degenerative valve disease of our country has been increasing last years, and the conventional surgical therapy was costly and risky for the patients. However, the pathogenesis of this disease still remains to be elucidated which restrains the explorations for the etiological treatment. Several studies made it clear that endothelial-to-mesenchymal transition (EMT) occurred in valve endothelial cells was an important pathological process in the pathogenesis of degenerative valve disease. EMT is a key process of valve development in the embryo and a transcription factor, Meis2, was reported to play an important role in the developmental EMT. For mice, lacking of MEIS2 gene in the embryonic period would leads to death; for human beings, MEIS2 gene deficiency may be related to the congenital heart disease. Our previous studies indicated that meis2 expressed in the patients' valve endothelial cells and these cells tended to move inward. This evidences suggest that meis2 may relate to the pathogenesis of degenerative valve disease via some involvement in the EMT process. This proposal is based on our previous studies. We hypothesize that meis2 is involved in the EMT process and then plays an important role in the pathogenesis of degenerative valve disease. We will do the research from following aspects: Studying the valve tissues of patients to find the different expression of meis2 and EMT markers, and to seek the relationship between the expressions of them; Exploring the function of meis2 in EMT process and the pathogenesis of degenerative valve disease with human valve endothelial cells model and the animal model.

退行性瓣膜病的发病机制尚不明确，瓣膜发育期的内皮间质转换（EMT）重新启动可能是发病的始动因素。课题组前期研究发现，Meis2基因在胚胎期EMT过程中发挥重要作用，并在退行性瓣膜病的瓣膜内皮细胞（VECs）上高表达，表达Meis2的细胞倾向于向瓣膜内部迁移。因此我们假设，Meis2能够通过调控心脏瓣膜内皮细胞的EMT过程而引起成人退行性瓣膜病的发生。本研究应用退行性瓣膜病患者病变瓣膜组织，通过免疫荧光等方法进一步确认病变瓣膜中EMT的现象；应用Meis2过表达/抑制的瓣膜内皮细胞模型，证明Meis2对EMT过程的作用，并在转基因/基因敲除动物模型研究进一步证明Meis2通过调节EMT导致退行性瓣膜病。通过研究Meis2在退行性瓣膜病发病中的作用和机理，为该病的病因治疗提供的重要理论基础及干预靶点。

主动脉瓣疾病（aortic valve disease，AVD）是最主要的心脏瓣膜疾病。随着人口老龄化的加剧，退行性主动脉瓣疾病已成为欧美国家AVD的首要病因，在我国成人AVD患者中的比例也逐年增加。钙化性主动脉瓣疾病（calcific aortic valve disease，CAVD）是退行性主动脉瓣疾病的主要病理类型之一，表现为瓣叶增厚、钙质沉积和活动异常。目前，瓣膜置换手术仍然是CAVD的主要治疗方式，缺乏有效药物治疗方案。因此，探索CAVD发病机制是退行性瓣膜病防治研究的关键。.主动脉瓣由瓣膜内皮细胞和瓣膜间质细胞（valve interstitial cells，VICs）组成。瓣膜发育阶段VICs来源于胚胎内皮细胞的内皮间质转化（endothelial-to-mesenchymal transition，EMT），以及心脏神经嵴细胞（neural crest cells，NCCs）的迁移。成熟瓣膜VICs的成骨转化是CAVD的关键环节，既往研究发现，Notch1可以通过调控BMP2的表达影响CAVD的发生。然而，发生成骨转化的VICs来源及相应机制尚不清楚。.Meis蛋白是HOX同源的转录因子。Meis2在心脏发育过程中具有重要作用，参与调控斑马鱼的心管形成和心脏扭转。小鼠模型中，条件性敲除Meis2会导致心脏NCCs发育异常。同时，人类Meis2基因变异个体可以表现为房间隔缺损，室间隔缺损等先天性心脏病。Meis/Pbx复合物可以调节NOTCH信号通路的水平。但是Meis2在CAVD过程中对于VICs成骨转化和Notch1信号通路的影响尚不明确。.因此，本研究利用CAVD患者主动脉瓣组织对Meis2水平进行了检测，同时利用猪主动脉瓣间质细胞（PAVICs）对Meis2在成骨转化过程中的调控作用与机制进行了研究。.通过对总计60例人类主动脉瓣组织（正常30例，CAVD 30例）的Meis2蛋白和mRNA水平进行检测，发现CAVD主动脉瓣瓣膜组织Meis2表达水平明显低于正常瓣膜。利用siRNAs降低Meis2表达水平后，PAVICs的Notch1和Twist1水平下降，成骨转化反应增强。.本研究结果提示，Meis2通过Notch1/Twist1信号通路抑制主动脉瓣VICs的成骨转化过程。Meis2可能成为CAVD防治的新的干预靶点。