长链非编码RNA MEG3介导磷酸鞘胺醇参与肝纤维化相关的血管新生

Angiogenesis is an important pathophysiological process closely associated with liver fibrosis. The hyperplasia of a large amount of fibrous tissue needs new blood vessels to provide nutritional support. However, the molecular mechanism of liver fibrosis-associated angiogenesis remains incompletely defined. Our previous studies have reported that sphingosine1-phosphate (S1P) stimulation induced the expression of angiopoietin 1(Ang1), a kind of pro-angiogenic cytokines in HSC, thus contributing to liver fibrosis-associated angiogenesis. But the specific molecular mechanism remains unknown. According to our preliminary results, the expression of materally expressed gene3 (MEG3), a long non-coding RNA, was significantly down-regulated in BDL or CCl4-treated liver. And there was a negative correlation between the expression of MEG3 and angiogenic marker Ang1. In HSC, S1P stimulation induced the down-regulation of MEG3 and up-regulation of Ang1. The present study proposed MEG3 as the research object, with S1P system and Ang1 as targets, aiming to explore the molecular mechanism underlying the effects of S1P on Ang1 expression and secretion via MEG3 during angiogenesis. Our results will provide new insights into the pro-angiogenic and pro-fibrotic mechanism of S1P, as well as a new therapeutic target for liver fibrosis.

肝脏在纤维化过程中往往伴随新生血管的形成，但是肝纤维化相关血管新生的分子机理尚不清楚。我们以往的研究报道磷酸鞘胺醇(S1P)可以诱导小鼠肝星状细胞(HSC)中一种促血管生成因子——血管生成素1(Ang1)表达的上调，从而参与肝纤维化相关的血管新生，但其具体的分子机制仍然未知。预实验结果表明：长链非编码RNA——母系表达基因3(MEG3)在纤维化肝脏中表达下调，且和Ang1呈现负相关；在体外HSC中，S1P诱导MEG3表达下调及Ang1表达上调。因此我们提出假说：S1P通过下调MEG3，促进HSC中Ang1的表达和分泌，从而发挥促血管新生的作用。本课题拟以MEG3为研究对象，以S1P和Ang1为靶分子，研究S1P通过MEG3作用于Ang1从而促进血管新生的分子机理。期待从一个新的视角研究并阐述肝纤维化相关血管新生的发生机制，为寻找治疗肝纤维化的药物新靶点提供理论依据。

肝脏在纤维化过程中往往伴随新生血管的形成，但是肝纤维化相关血管新生的分子机理尚不清楚。本课题组前期工作证实，在小鼠肝星状细胞（周细胞）中通过上调血管生成素1的表达，可以促进肝纤维化相关的血管新生。但其具体的分子机制以及肝纤维化时这些周细胞的来源仍然未知。本课题即探讨LncMEG3作为miR-26b-5p海绵，在周细胞分化以及肝纤维化相关血管新生中的作用机制。结果证实：（1）在MCDHF诱导的纤维化小鼠模型中，周细胞标志蛋白PDGFR-b表达显著上调，且和纤维化标志物、血管新生标志物存在高度正相关；（2）在体内和体外骨髓来源的间充质干细胞（BMSC）可分化为PDGFR-b阳性周细胞；（3）LncMEG3可直接调控PDGFR-b，促进BMSC向PDGFR-b阳性周细胞分化；（4）miR-26b-5p通过靶向PDGFR-b，抑制BMSC向PDGFR-b阳性周细胞的分化；（5）LncMEG3作为miR-26b-5p的“分子海绵”，抑制miR-26b-5p对靶基因PDGFR-b的负调控作用，加强PDGFR-b表达，进而促进BMSC分化为PDGFR-b阳性周细胞；（6）在MCDHF小鼠，注射miR-26b-5p模拟物抑制PDGFR-b阳性周细胞分化，抑制肝脏纤维化及血管新生。本课题以LncMEG3为研究对象，结合细胞学、分子生物学和动物学实验，系统完整地研究了LncMEG3参与肝纤维化时BMSC分化为PDGFR-b阳性周细胞及肝纤维化相关血管新生的分子机制。