ADAMTS2通过调控VSMC表型转化稳定血管内环境抑制腹主动脉瘤形成的机制研究

Abdominal aortic aneurysm is defined as local aortic expansion for the destruction in the structure of aortic wall which is concealed and high-mortality. To date there has been no effective methods for early interventions. Vascular smooth muscle cells give priority to forming the vascular microenvironment which takes part in maintaining the normal structure and function of aortic wall. The activation of PI3K-Akt signaling pathway causes VSMC phenotypic modulation which is the main reason leading to the destruction of vascular microenvironment and the development of abdominal aortic aneurysm, but the exactly regulatory mechanism upstream is still unclear. Previous reports proved that metalloprotease ADAMTS2 could take part in the vascular disease process. Preliminary experiment suggested that ADAMTS2 could modulate PI3K-Akt signaling pathway via integrating with DKK3. Loss of ADAMTS2 could reduce the expression of contractile VSMC, elevate the expression of CD68, MMP2, MMP9, and accelerate the extent of vascular microenvironment destruction and mice abdominal aortic aneurysm. Herein we indicated that ADAMTS2 might inactive the PI3K-Akt signaling pathway via integrating with DKK3, inhibit the VSMC phenotypic modulation to stabilize the vascular microenvironment, and prevent the development of abdominal aortic aneurysm eventually. We will start our investigation to verify the scientific hypothesis and explore the application perspectives with the use of animal models, cultured cells and human bodies, and attempt to provide experimental basis and a new therapy target for the prevention and treatment of the abdominal aortic aneurysm.

腹主动脉瘤（AAA）是因主动脉壁结构破坏造成的局部病理性扩张，发病隐匿且死亡率高，至今尚无有效的早期干预手段。以血管平滑肌细胞（VSMC）为主体构成的血管微环境参与维持正常主动脉壁结构及功能，而外界刺激引起PI3K-Akt信号通路激活造成VSMC表型转化会破坏血管微环境诱发腹主动脉瘤形成，但其上游具体调控机制仍未知。既往研究揭示金属蛋白酶ADAMTS2参与血管性疾病形成，预实验显示其可作用于DKK3调控PI3K-Akt信号通路，该基因缺失降低收缩型VSMC表达，增加CD68及MMP2、MMP9表达，加速血管微环境破坏及小鼠腹主动脉瘤形成。因此我们推测ADAMTS2可能通过作用于DKK3，抑制PI3K-Akt信号通路的激活及VSMC表型转化，稳定血管微环境，最终防止腹主动脉瘤形成。项目组拟从动物、细胞及人体水平验证该科学假说并探索其应用前景，为腹主动脉瘤的防治提供新的理论依据和治疗靶点。

腹主动脉瘤（AAA）是因主动脉壁结构破坏造成的局部病理性扩张，发病隐匿且死亡率高，至今尚无有效的早期干预手段。以血管平滑肌细胞（VSMC）为主体构成的血管微环境参与维持正常主动脉壁结构及功能，而外界刺激引起PI3K-Akt信号通路激活造成VSMC表型转化会破坏血管微环境诱发腹主动脉瘤形成，但其上游具体调控机制仍未知。既往研究揭示金属蛋白酶ADAMTS2参与血管性疾病形成，预实验显示其可作用于DKK3调控PI3K-Akt信号通路，该基因缺失降低收缩型VSMC表达，增加CD68及MMP2、MMP9表达，加速血管微环境破坏及小鼠腹主动脉瘤形成。我们通过收集人动脉瘤患者的组织标本与构建小鼠腹主动脉瘤模型进行HE、Masson、免疫组化染色和Western Blot检测，发现主动脉瘤患者的主动脉组织标本与小鼠腹主动脉瘤组织标本中ADAMTS2表达量较对照组显著升高，且主要集中在中膜层。另外，组织标本中α-SMA表达量较正常组织减少，相反，OPN表达量显著增高。与此同时，DKK3在组织标本中表达量增高，且与ADAMTS2的表达存在共定位现象。我们进一步通过血管紧张素II（AngII）刺激小鼠主动脉平滑肌细胞系（MOVAS），建立腹主动脉瘤的细胞模型，使用特异性小干扰RNA（siRNA）转染MOVAS敲降ADAMTS2的表达水平，用RT-qPCR法检测转染效率，用Western blot法检测Caspase-1、IL-1β、IL-6、α-SMA、SMα-22、DKK3的表达情况，用免疫荧光染色法检测Osteopontin、Vimentin在MOVAS中的表达情况。发现ADAMTS2 siRNA转染MOVAS敲降ADAMTS2的效果显著；与未敲降的MOVAS相比，敲降ADAMTS2可增强AngII诱导的Caspase-1、IL-1β及IL6的过表达，并使AngII诱导的α-SMA、SMα-22表达下调，Osteopontin、Vimentin表达上调更显著；且敲降ADAMTS2后，可以使DKK3表达水平不再随AngII的刺激作用下降。因此我们推测ADAMTS2与腹主动脉瘤的发生发展存在关联，并可能是通过调控重要底物DKK3实现的。下调ADAMTS2表达可加重VSMC凋亡和炎症反应，导致其由收缩型向分泌型转化，ADAMTS2在腹主动脉瘤的病理生理过程中可能具有保护作用。