血管紧张素II促进骨髓间充质干细胞跨肺微血管内皮迁移的机制研究

间充质干细胞（MSC）促进肺损伤细胞修复是急性肺损伤（ALI）重要治疗方向，但MSC向损伤肺组织归巢率低，跨内皮迁移是其向肺实质归巢的关键。研究发现血管紧张素Ⅱ（AngⅡ）可促进肿瘤细胞跨内皮迁移，ALI时肺组织内AngⅡ水平明显高于血液；预实验结果表明AngⅡ可增强MSC纵向迁移，且MSC表达AngⅡ的受体AT1R，推测AngⅡ可能通过AT1R促进MSC跨内皮迁移。本研究拟①用氯沙坦阻断MSC的AT1R，观察AngⅡ对MSC跨内皮迁移、黏着斑的形成和细胞骨架排列的影响；②对AT1R胞内信号途径进行干预，证实黏着斑激酶是AngⅡ促进MSC跨内皮迁移的重要分子，并可调控RhoA和Rac1参与细胞骨架的重排；③体内试验明确高表达AT1R的MSC移植可促进MSC向损伤肺组织归巢，修复损伤细胞的同时降低肺内AngⅡ的水平，抑制炎症反应。本研究通过探讨MSC归巢机制，为ALI修复提供新的治疗途径。

Mesenchymal stem cells (MSC) based cell therapy is a hopeful treatment of acute lung injury（ALI）.However,the rate of engraftment is very low. The mechanisms determining MSC recruitment to the lung remain unclear,but the transendothelial migration of MSC may play the most important role in the process of engraftment because MSC are large cells and this may will cause the cells to be held up in the capillary beds of lungs for a while.The process of transendothelial migration will be determined by the functions of migration and adhesion of MSC which will be influenced by the local microenvironment of injuried lungs.Recently,A number of studies have showed that Angiotensin Ⅱ(AngⅡ) which is highly expressed in the injuried lung tissues and acts as an pro-inflammatory cytokine plays an important role in the process of cancer metastasis by increasing transendothelial migration. Interestingly, in our previous study, we found that AngⅡ can promote the migration of MSC by Transwell migration assay.Besides,there was expression of angiotensin Ⅱ receptor 1 (AT1R) on MSC.So it can be hypothesized that AngⅡ particpate in the transendothelial migration of MSC in the lung. In this study, We investigate the role of AngII and its receptor AT1R by using AT1R's blocker in the homing process especially the transendothelial migration of MSC and identify its mechinism whether it is associated with the regulation of focal adhesion comeplexes and the rearrangement of actin cytoskeleton in vitro study. In addition,we will demonstrate that focal adhesion kinase (FAK) is the key regulator of focal adhesion comeplexes and can also activate its downstream signaling protein especially the RhoA and Rac1 pathway to make the actin remode and contract,and then to increase the transendothelial migration of MSC.What's more, in vivo mouse model, the LPS-induced lung injury, we quantify the migration and engraftment of MSC carrying AT1R to the injured lung and the expression of AngⅡ and also evaluate the injuried lung restoration to demostrate the protective effect of AT1R pretreated MSC for ALI.