炎症小体调控血管炎症及干细胞功能进而介导CABG术后静脉桥重塑的机制研究

As the graft vessel of coronary artery bypass grafting (CABG), saphenous vein underwent remodeling to adapt to the arterial flow environment. But the excessive remodeling caused graft stenosis could lead to CABG failure. Immune response could regulate the vascular remodeling. Stem cells in vascular adventitia differentiated to endothelia cells and smooth muscle cells to participate in vein graft remodeling. Our preliminary studies suggested that the production of inflammasome activation IL-1β and IL-18 increased in the grafted vein; the Nlrp3 knockout mouse, which was deficiency in inflammasome activation, exhibited less intimal hyperplasia and vascular remodeling. However, the underlined mechanism is remained unclear. In this project, we hypothesis that during the vein graft remodeling, the inflammasome in macrophages was activated and secreted IL-1β and IL-18, which could promote the Sca-1+ stem cells differentiated to endothelia cells and smooth muscle cells by activating intracellular signaling pathway. To verify this hypothesis, we will reveal the molecular mechanism of inflammasome activation in vein graft remodeling using Nlrp3 knockout mouse and Nlrp3 inhibitor in vivo and stem cells co-culture in vitro, and explore the relationship between the degrees of vein graft stenosis and inflammasome activation. Our research will provide the new theoretical and experimental basis for intervention of vein graft stenosis after CABG.

大隐静脉是冠脉旁路移植术的主要桥血管之一，其术后过度重塑将引起管腔狭窄。炎症反应可以调控血管重塑，血管外膜干细胞分化为内皮细胞和平滑肌细胞参与血管重塑。我们前期研究发现静脉桥血管组织中炎症小体活化，IL-1β和IL-18表达增加，炎症小体关键基因Nlrp3敲除小鼠的静脉血管重塑程度显著低于对照野生型，但其作用机制尚不清楚。据此本课题组提出科学假说：在静脉动脉化血管重塑中，巨噬细胞炎症小体激活释放IL-1β和IL-18，通过激活Sca1+干细胞内信号通路促进其向平滑肌细胞和内皮细胞分化并加速内膜新生和血管重塑。本课题拟使用小鼠静脉动脉移植模型、Nlrp3敲除小鼠和炎症小体活化抑制剂探讨其对静脉动脉化重塑的影响，结合体外干细胞分化和细胞共培养等方法明确炎症小体在血管重塑中分子机制，同时使用CABG术后患者随访资料分析炎症小体活化与桥血管再狭窄相关性，为桥血管再狭窄预防和治疗提供新靶点。

大隐静脉是冠脉旁路移植术(coronary artery bypass grafting,CABG)最常用的血管移植材料，其术后过度重塑将引起管腔狭窄。NLRP3炎症小体是先天免疫系统中重要的免疫调节因子，其可能参与了静脉移植术后静脉桥血管重塑的发生和发展过程。本研究通过体内和体外实验观察了NLRP3炎症小体在静脉移植术后静脉桥血管重塑中的表达及活化。结果发现（1）静脉移植术后静脉桥内膜增厚，管腔狭窄。（2）通过免疫组化SMA及Calponin染色发现静脉移植术后静脉桥血管壁中血管平滑肌细胞与正常对照组相比显著增加，这提示术后血管重塑可能是血管平滑肌细胞增殖所致。（3）静脉移植术后静脉桥血管中NLRP3炎症小体的活化产物Caspase-1、ASC、白介素-1β（IL-1β）和白介素-18（IL-18）的表达水平均显著升高。（4）采用血小板衍生因子（PDGF-BB）刺激血管平滑肌细胞增殖后发现，促增殖后的血管平滑肌细胞中NLRP3的表达水平与未加PDGF-BB刺激的对照组相比显著升高，这提示NLRP3与血管平滑肌细胞的增殖之间具有一定的相关性。这些研究结果表明静脉移植术后静脉桥会发生血管重塑过程，血管重塑主要是由于血管平滑肌细胞的增殖所致，NLRP3炎症小体与血管平滑肌细胞的增殖密切相关，参与静脉桥血管重塑的过程。这一发现为桥血管再狭窄预防和治疗提供了新的潜在靶点。