miR-223在腹主动脉瘤发展和干预中的作用及机制研究

The abdominal aortic aneurysms（AAA）caused by the imbalance of vascular structure/function and the abnormal vascular reconstruction. Mortality following rupture of AAA is high. Current therapeutic options to prevent AAA are restricted to surgical repair, as there remains a lack of validated pharmaceutical approaches. miRNA plays an important role in vascular homeostasis and disease. We performed miRNA-sequencing in abdominal aortic tissue from AAA patients or two AAA mouse models. mir-223 agomir treatment inhibits the development of AAA whereas mir-223 deficiency promotes AAA. mir-223 overexpression promote AKT signals activation in AAA utilizing mRNA-sequencing technology. However, the underlying mechanism is unclear. Using gene overexpression/knockdown and bioinformatics technology, our specific aims are: 1) to determine how the high risk factors of AAA induce increased mir-223 expression; 2) to explore the molecular mechanisms by which mir-223 affects targets genes to regulate AKT signaling, then regulating the function of smooth muscle cells and progression of AAA; and 3) to elucidate the intervention effects of new synthesized AAA-targeting gene vector delivery mir-223 on AAA. The present study will demonstrate the important role of mir-223 in the maintenance of vascular homeostasis and resistance of vascular injury and abnormal remodeling and provide novel gene vector for therapeutic approaches in AAA.

腹主动脉瘤是血管结构/功能稳态失衡导致重构异常的血管疾病，破裂致死率高，缺乏药物干预手段。miRNA在血管稳态和疾病中发挥重要作用。我们前期利用腹主动脉瘤临床标本、疾病动物模型进行miRNA测序，发现mir-223表达升高。mir-223过表达抑制腹主动脉瘤，反之缺失加剧其发展；mRNA测序发现mir-223过表达促进AKT通路上调；但腹主动脉瘤中mir-223表达如何升高，进而通过何种机制抑制腹主动脉瘤的发展等科学问题尚不清楚。本课题将应用基因操作及生物信息等技术，探讨：1）腹主动脉瘤高危因素调节mir-223表达的机制；2）mir-223通过靶基因调控AKT等信号影响平滑肌细胞功能抑制腹主动脉瘤的机制；3）腹主动脉瘤靶向基因载体输送mir-223对其的干预作用。本课题将阐明mir-223在腹主动脉瘤中维持血管稳态、抑制血管损伤/重构异常的保护机制，为其防治提供新的靶点和理论依据。

腹主动脉瘤是血管结构/功能稳态失衡导致重构异常的血管疾病，破裂致死率高，缺乏药物干预手段。miRNA在血管稳态和疾病中发挥重要作用。我们发现mir-223在腹主动脉瘤临床标本、疾病动物模型表达升高。并且小鼠mir-223过表达抑制高脂饮食，联合血管紧张素缓释泵诱导的腹主动脉瘤，缺失反之加剧其发展；利用qPCR及荧光素报告酶实验，我们验证了miR-223与IL6st的结合。同时，miR-223敲除鼠主动脉IL6st的蛋白表达显著升高， IL6st是腹主动脉瘤中miR-223调控的靶基因；并且构建的平滑肌特异性敲除IL6st（IL6st SMC KO）的小鼠与野生型小鼠相比在高脂饮食，联合血管紧张素缓释泵诱导的腹主动脉瘤模型中，成瘤率和最大直径均降低；我们用免疫共沉淀的方法证实，活化IL6st通路影响PDGFRa/MRTFA/SRF信号轴，并降低了下游平滑肌收缩相关基因sm22、asma等表达。与之一致，miR-223敲除鼠主动脉收缩功能下降，收缩相关蛋白表达减少。因此，miR-223通过抑制IL6st信号轴导致平滑肌收缩功能减弱，从而调控腹主动脉瘤进展；使用可溶性IL6st重组蛋白（s IL6st）特异性的结合IL6/IL6R复合体从而阻断IL6st介导的转导通路，能显著抑制AngII诱导的小鼠腹主动脉瘤发生率，降低腹主动脉瘤最大直径，发挥保护作用。因此，mir223，s IL6st可能是潜在的腹主动脉瘤的有效药物。