老龄严重肢体缺血治疗新靶点：mTORC2调控炎症介导的血管生成

Peripheral arterial disease (PAD) continues to be a heavy burden of disease in aging society. Aged PAD displays a much higher risk of critical limb ischemia (CLI) , resulting in disability and poor prognosis. Aging can decrease angiogenesis, which is important for functional compensation and tissue regeneration in the CLI setting. However, the mechanism of action behind aging and angiogenesis is unclear, which severely limits the therapeutic strategies for aged CLI. Our previous in vivo study demonstrated that downregulation of inflammatory response contributed to the insufficient angiogenesis, recently considered together as inflammation-induced angiogenesis, in aged CLI model. Accordingly, it is possible to promote inflammation-induced angiogenesis via regulation of senescence. Our work further indicate that mammalian target of rapamycin complex 2 (mTORC2) may represent a target involved in rejuvenation and inflammation-induced angiogenesis. The present project was designed to assess the role of mTORC2 in the rejuvenation and inflammation-induced angiogenesis in aged murine CLI model using in vivo multimodality molecular imaging strategies. Furthermore, we try to increase the inflammation-induced angiogenesis in aged murine CLI model via mTORC2 genetically-modified murine or human adipose-derived stromal cells transplantation. Based upon the mechanism-driven approach of rejuvenation and angiogenesis, the aim of the project is to provide scientific evidence and strategies for the translation of aged CLI therapy.

周围动脉病（PAD）是老龄化社会沉重的疾病负担。老龄PAD患者易发生严重肢体缺血（CLI），导致高致残率和生活能力丧失。血管生成是CLI重要的代偿修复机制。然而，衰老可导致机体血管生成能力受损，其机制尚不明确，严重制约了老龄CLI的有效治疗。我们通过在体研究发现，衰老可能抑制了炎症介导的下肢血管生成；哺乳动物雷帕霉素靶蛋白复合体2（mTORC2）或为抗衰老靶点，促进炎症介导的下肢血管生成。项目拟应用多模态分子影像方法在体揭示老龄CLI小鼠mTORC2对衰老和炎症介导血管生成的关键调控作用；进一步尝试通过mTORC2基因修饰的小鼠/人脂肪源性血管基质细胞移植干预老龄CLI小鼠炎症介导的血管生成，旨在抗衰老机制研究基础上探索老龄CLI血管再生修复的途径，为老龄CLI治疗的合理转化提供科学依据和策略。

严重肢体缺血（CLI）是老龄化社会沉重的疾病负担，原因在于老年人群CLI发病率高、血管再生修复功能不全和治疗策略有限，最终导致高致残率甚至死亡。衰老可能导致血管生成能力受损，其机制尚不明确，严重制约了老年CLI的有效干预。项目拟评价哺乳动物雷帕霉素靶蛋白复合体2（mTORC2）对年龄相关性血管生成的调控作用，进一步尝试通过mTORC2基因修饰的脂肪源性血管基质细胞（ADSC）干预老龄CLI小鼠炎症介导的血管生成，旨在探索老龄CLI血管再生修复的途径。研究主要应用了多种模态的分子影像学方法进行体外和在体试验。在体报告基因成像显示，老龄CLI小鼠的VEGF/VEGFR2表达水平显著低于年轻CLI小鼠，导致其血管生成受损。机制研究进一步显示，老龄CLI小鼠的mTORC2表达水平较年轻CLI小鼠显著降低，从而抑制了炎症介导的血管生成作用。mTORC2的激活可使IL-1β、TNF-α等炎症因子的表达水平下调和IL-6、IL-10等炎症因子的表达水平上调，并进一步通过调节血管生成信号等机制促进CLI小鼠的血管生成作用；同时，mTORC2的激活能够调节老龄CLI小鼠缺血组织中的炎性细胞（中性粒细胞、巨噬细胞等）水平，从而促进细胞存活，减少细胞凋亡和调节自噬。体外和在体报告基因成像研究显示，以基因修饰等方法使人脂肪源性血管基质细胞（hADSC）过表达mTORC2（hADSCeGFP+Rictor+），能够促进hADSC的功能性存活和旁分泌效应；应用hADSCseGFP+Rictor+移植，联合雷帕霉素、联合用药（沙格雷酯或替格瑞洛）或联合osteopontin预处理等策略，可能上调老龄CLI小鼠的mTORC2表达水平，进一步促进IL-6、IL-10等炎症因子、趋化因子和血管生成因子（VEGF/VEGFR2等）的激活，从而改善老龄CLI小鼠炎症介导的血管生成。研究初步证实了mTORC2可能参与年龄相关性血管生成功能的调节，老龄CLI小鼠mTORC2表达水平的降低可能抑制了炎症介导的血管生成作用；通过调控mTORC2表达或能有效干预炎症反应，从而促进老龄CLI的血管生成，可能发展成为老年、尤其高龄老年CLI患者的有效干预策略。