机械牵张诱导主动脉夹层血管平滑肌细胞表型转化的机制研究

Hypertension is the most common basical disease for the aortic dissection(AD). However, the mechanism of the AD induced by hypertension is not clear. Supported by the National Natural Science Foundation(NO.81370414), our study had demonstrated that mechanical strain could induce expression of matrix metalloproteinase-9(MMP-9) in vascular smooth muscle cell(VSMC), which was mediated by the stretch activated ion channel(SAC). It has been confirmed that MMP-9 expressed by VSMC is very important in AD , and only synthetic phenotype VSMC can secrete MMP-9. The phenotype of VSMC in normal aorta is contractile phenotype. Therefore, what is the mechanism of mechanical strain induced VSMC phenotypic differentiation via SAC? Our previous study had demonstrated that miRNA 31 was upregulated in AD aortic tissues, while AKT2 was downregulated. AKT2 is very important in VSMC phenotypic differentiation. So we hypothesize that miRNA31 meditating the change of AKT2 signal pathway is the crucial molecular mechanism of mechanical strain induced VSMC phenotypic differentiation via SAC in AD. The object of this study is to demonstrate this hypothesize, which will provide a new target of prevention and treatment of AD .

高血压是主动脉夹层（AD）最常见的基础疾病，但高血压导致AD的具体机制不清楚。血压升高导致血管机械牵张力升高，我们首次发现机械张力通过开放牵张离子通道（SAC）诱导主动脉平滑肌细胞（VSMC）表达基质金属蛋白酶-9（MMP-9）（国自然基金，项目编号：81370414）。已证实主动脉VSMC分泌的MMP-9在AD的发生中起重要作用，但正常主动脉VSMC是收缩表型，只有转化为合成表型才能分泌MMP-9。 是什么机制使机械张力开放SAC促使VSMC表型转变尚不清楚。我们前期预实验表明AD患者主动脉组织miRNA31表达升高、AKT2表达水平下降,且二者呈负相关。而AKT2具有促使VSMC表型转化的作用。因此，我们推测机械张力开放SAC后血管平滑肌细胞表型转化的机制可能是通过miRNA31调控AKT2信号通路来实现的。本项目旨在证实这推测，为寻找新的靶点来防治AD打下坚定的理论基础。

背景：主动脉夹层(AD)是一种灾难性心血管病，其病情严重，死亡率高。高血压是AD最常见的病因，前期研究发现高血压通过异常增高的机械张力开放牵张离子通道（SAC）诱导主动脉平滑肌细胞（VSMC）表达基质金属蛋白酶-9（MMP-9），从而破坏主动脉壁的结构（国家自然科学基金，项目编号：81370414）。然而，只有合成型VSMC才分泌MMP-9，高血压诱导VSMC从收缩型向合成型转变的机制尚不明确。研究发现，AKT2具有促使VSMC表型转化的作用，其受到miRNA的调控,而AD血管壁中miR-31异常高表达。因此，本项目研究机械牵张对VSMC中miR-31和AKT2信号通路的影响，探讨其在高血压诱导AD形成过程中的作用。..研究内容：1.建立SD大鼠AD模型；2.探讨机械牵张是否通过开放SAC引起VSMC表型转变；3.探讨机械牵张开放SAC后是否通过AKT2信号通路引起VSMC表型转变；4.探讨AD组织中miR-31和AKT2磷酸化水平之间的关系；5.探讨机械牵张对主动脉VSMC中miR-31和AKT2磷酸化水平的影响；6.探讨机械牵张开放SAC通道后是否由miR-31调控VSMC中AKT2磷酸化水平的改变，进而影响VSMC表型转变；..结果和结论：1.β-氨基丙腈(BAPN)灌胃联合血管紧张素II腹腔注射能够高效建立SD大鼠AD模型；2.机械牵张通过开放SAC通道从而诱导VSMC发生表型转化；3.机械牵张开放SAC通道后经由AKT2信号通路引起VSMC表型转变；4.AD血管组织中miR-31增多，AKT2的磷酸化水平降低，提示二者的负向调控可能参与了AD的形成；5.机械牵张诱导人VSMC中miR-31-5p增多，PI3KC2a减少，与AD血管的检测结果一致，提示高血压诱导人VSMC中miR-31-5p表达量升高，后者降低PI3KC2a的表达，可能参与了AD的形成；6.机械牵张开放SAC通道后是通过上调miR-31-5p来调控VSMC中AKT2磷酸化水平，进而影响VSMC表型转变。..科学意义：1.运用BAPN灌胃联合AngII腹腔注射的方法建立SD大鼠AD模型，该方法简便、高效，为后期研究AD的发病机制和治疗方法提供了良好的研究基础；2.研究发现高血压通过异常增高的机械张力激活VSMC表面的SAC通道，从而上调miR-31的表达，后者靶向抑制PIK3C2a的合成，从而