整合素α9亚基在主动脉夹层形成中的保护作用及机制研究

Aortic dissection (AD) is a highly lethal vascular disease. The molecular mechanisms and genetic susceptibility of AD are poorly understood. Our pilot results showed that the expression of ITGA9 gene encoding intergrin α9 subunit was significantly decreased in aortic tissue from patients with AD by genome-wide gene expression array profiling and western-blot verification. After down-regulation the expression of Itga9 by siRNA, the phynotype of vascular smooth muscle cell (VSMC) was switched from contractile to synthetic VSMC. Up-regulation of Itga9 reversed the phynotype of VSMC. The present study aims to investigat the protective role of ITGA9 gene against AD formation in the aortic wall. Firstly, we have been creating a mItga9 conditional knockout in C57BL/6 mice and vascular SMC-specific Itga9 transgenic mice in order to investigate the influence of Itga9 in AD development in vivo. We will examine AD formation and aortic histopathological changes in conditional Itga9 knockout mice, Itga9 transgenic mice, and wild type mice by continuous infusion of angiotensin II. Second, we will examine the direct effects of Itga9 on function of VSMC and downstream targeted genes and matrix metalloproteinase-9 expression in cultured aortic VSMCs in vitro. Finally, two case-control studies will be conducted to verify the associations of ITGA9 genetic variations with AD and clinical outcoms. This study will offer insights into the molecular mechanism of AD and provide potential targets for therapeutic intervention and predictive factors of AD.

主动脉夹层的发病机制和临床预警尚不清楚。本团队前期通过全基因转录谱分析发现整合素α9亚基(ITGA9)基因在主动脉夹层病变组织中表达异常降低，敲低Itga9基因表达和过表达Itga9可分别导致大鼠主动脉平滑肌细胞表型发生收缩型与合成型的互换。本项目旨在探讨ITGA9在主动脉夹层中的保护作用，证明ITGA9功能异常参与了主动脉夹层的发病机制。首先，分别采用血管平滑肌组织条件性Itga9敲除小鼠和血管平滑肌特异性Itga9转基因小鼠，通过持续泵入血管紧张素II病理刺激，在体内从正反两方面研究Itga9的缺失或过表达对主动脉夹层/瘤形成的影响；第二，从细胞水平分别采用基因沉默和过表达策略研究Itga9基因的功能和参与主动脉夹层发病的细胞分子及其信号传导机制；最后通过重复病例对照研究探讨ITGA9基因的遗传变异对主动脉夹层发病的预警作用。本申请将为寻找主动脉夹层防治的干预靶点和早期预警提供新线索。

主动脉夹层是严重威胁生命的心血管急重症，但目前其发病机制和遗传危险因素并不清楚。本研究在细胞和动物水平证明了ITGA9基因在主动脉夹层形成中的功能，并对其分子机制作了初步的探究。ITGA9过表达可增加人主动脉平滑肌细胞增殖能力，降低其早期凋亡比例，该作用可能通过激活下游的AKT蛋白信号途径发挥作用。在用β-氨基丙腈（BAPN）诱导的主动脉夹层造模试验中发现血管平滑肌条件性基因敲除小鼠主动脉夹层和主动脉瘤的发病率显著高于阴性对照鼠，提示Itga9基因的表达缺失促使主动脉夹层的发生。同时，本研究通过分析100例Standford A型主动脉夹层全基因组测序结果和临床特征的相关性，发现50%的散发A型主动脉夹层患者中携带主动脉疾病已知致病基因的疑似致病突变。并且与未携带致病突变的患者相比，携带突变患者的升主动脉直径更大，保守治疗的院内预后较差；而携带细胞外基质成分编码基因突变的患者，夹层病变进展撕裂到远端的可能性更大。本研究分析了主动脉夹层患者入院指标与短期和长期预后的相关性，发现入院时白细胞计数升高、血清钾离子水平异常均可增加的急性主动脉夹层患者院内死亡风险。并且发现急性A型主动脉夹层患者的院内死亡风险与发病季节相关，其中秋季发病的患者短期预后最差。