Wnt/β-catenin信号通路在血流动力学诱导脑动脉瘤发生中的作用机制研究

Intracranial aneurysms (IA) have posed a great threat to human health, and the study of its pathogenesis has received extensive attention currently. The phenotypic modulation of vascular smooth muscle cells (VSMC) induced by abnormal hemodynamics plays an important role in the development of IA. However, the specific mechanism how mechanical stress initiate the phenotypic modulation of VSMC remains to be elucidated. Our previous study found that the secretory glycoprotein Wnt and the proteins of its downstream signaling pathways were significantly overexpressed in VSMC of intracranial basilar artery when exposed to high blood shear stress. Wnt protein plays an important role in hypertension and other arterial remodeling by regulating cell differentiation and apoptosis, thus, we speculated that Wnt/β-catenin pathway exerts a role in vascular remolding of IA by regulating phenotypic modulation of VSMC, and the specific mechanism remains to be explained. This project, integrating fluid mechanics and molecular biology, will clarify the relationship between fluid mechanics and the expression of Wnt signal pathway in IA by several steps. We will firstly explore the relevance of the two in human specimen and then we share confirm its temporal and spatial relationship in vivo using animal model. Finally, we will study the specific mechanism of Wnt pathway in cytology experiment. We aim to explore the mechanism of this signal pathway in IA by sequential study, which can possible provide us with potential target for drug therapy.

颅内动脉瘤（IA）危害极大，其发病机制的研究成为目前重点。异常血流动力学通过血管平滑肌细胞（VSMC）表型转换介导病理性血管重构在IA发生中起重要作用。但在IA形成中机械应力启动VSMC表型转换的具体机制尚未明确。我们前期研究发现，在高血流应激的基底动脉VSMC中，分泌型糖蛋白Wnt及下游信号通路靶基因显著高表达。鉴于Wnt调控细胞分化与凋亡，参与高血压等动脉重构疾病，我们推测Wnt/β-catenin通路调控VSMC表型转化参与IA发生中的血管重塑，具体机制有待阐明。本项目将整合分析流体力学与血管分子生物学，首先行人IA标本检测并分析流体应力与 Wnt信号通路激活相关性；再以IA动物模型在体验证两者的时空关系；最后通过体外细胞学实验研究流体应力对VSMC 中Wnt/β-catenin信号通路的调控及具体机制；拟通过序贯研究系统探讨该信号通路在IA发生中的作用机制，为药物治疗探寻潜在靶点。

颅内动脉瘤是一类严重威胁人类健康的脑血管疾病，动脉瘤破裂导致的SAH事件仍会伴有高死亡率和残疾率。血管VSMCs的稳态是血管壁发挥功能的基础。VSMCs表型转化在动脉瘤形成中发挥重要的作用。人体标本结果显示与颞浅动脉相比，动脉瘤壁内VSMCs异常增殖、排列紊乱，血管重构明显;α-SMA表达减少(P<0.05),血流动力学分析发现，破裂动脉瘤伴有较低的WSS。大鼠颅内动脉瘤模型中扫描电镜结果显示动脉瘤模型组成瘤率显著增加，信号通路抑制剂组动脉瘤成瘤率下降（p<0.05）; HE显示模型组血管重构现象显著，抑制剂组血管重构现象减轻（p<0.001）；免疫组化显示动脉瘤模型组α-SMA表达减少，抑制剂组α-SMA表达增加；WB发现Wnt1基因（p<0.01）和WISP-1基因（p<0.001）在动脉瘤模型组中表达增加，动脉瘤组中SDF-1α和CXCR4的表达均显著上调(P<0.05)，WB发现动脉瘤模型组MMP-9蛋白表达水平增加（p<0.001）。在离体培养的人脑VSMCs中，与静态组相比，壁面切应力组中SDF-1α和CXCR4表达均上调(P<0.05)，α-SMA表达降低(P<0.01)，而MMP-2表达增高(P<0.05)。给予抑制剂后，α-SMA的表达增高(P<0.05)。rt-PCR显示TNF-α组VSMCs表型转化后；rt-PCR发现Wnt1基因（p<0.01）和WISP-1基因（p<0.001）在炎症刺激组中表达增加，抑制剂组WISP-1基因（p<0.05）在表达下降；rt-PCR，WB发现炎症刺激组MMP-9表达水平增加，抑制剂组表达下降（p<0.05）。研究证实颅内动脉瘤中VSMCs发生表型转化，这一变化可能是通过Wnt1/β-catenin信号通路和SDF-1α/CXCR4信号通路介导的，抑制VSMCs表型转化有望为颅内动脉瘤的治疗带来新的方向。