Meox1在血管损伤后新生内膜形成中的作用及其分子机制

Meox1 and Meox2 are two members of Meox (Mesoderm/Mesenchyme homeobox gene) subfamily. The role of Meox2 (also known as Gax) in the vasculature has been extensively studied, Meox2 is involved in the neointimal hyperplasia after vascular injury, vessel remodeling, pulmonary arterial hypertension, hepatic portal hypertension and angiogenesis. However, very little is known about the role of Meox1 in these processes. Our preliminary data demonstrated that Meox1 expression was up-regulated in vascular smooth muscle cells (VSMCs) treated with PDGF-BB inducing VSMCs migration and proliferation and previous reports confirmed that Meox2 was down-regulated in VSMCs treated with PDGF-BB, we speculate the function of Meox1 is likely to be opposite to that of Meox2 in the vasculature. This project will focus on determining Meox1 expression in rat balloon-injured carotid arteries and the effect of Meox1 knockdown by using RNA interference on the neointima formation after vascular injury. In Vitro, we will investigate the role of Meox1 in VSMCs proliferation, migration and apoptosis. Furthermore, we will explore the molecular mechanism about the phenotypic modulation of VSMCs involving Meox1. This work will elucidate the role of Meox1 in the neointima formation after vascular injury and provide a novel therapeutic strategy for restenosis after vascular angioplasty and stenting.

Meox1和Meox2是中胚层/间充质同源异形盒基因亚家族的两个成员。Meox2(又称Gax)在心血管系统的作用研究得比较深入，其在血管损伤后新生内膜形成， 血管重塑，肺动脉高压，门脉高压和血管生成中起重要作用。但是，关于Meox1在心血管系统中的作用几乎没有报道。我们的前期工作发现诱导血管平滑肌细胞(VSMCs)迁移和增殖的PDGF-BB处理VSMCs后，Meox1的表达上调，而以往的研究证明Meox2在PDGF-BB处理VSMCs后表达下调，我们推测Meox1的功能和可能与Meox2的相反。本课题拟观察大鼠颈总动脉损伤后Meox1的表达情况及采用RNA干扰技术下调Meox1的表达后对新生内膜形成和对VSMCs增殖，迁移和凋亡的影响，并探讨Meox1对VSMCs生物学行为影响的分子机制。本课题的完成将阐明Meox1在血管损伤后新生内膜形成中的作用，为血管成形后再狭窄找到新的干预策略。

近年来，冠心病的发病率和死亡率逐年上升，已成为威胁中国公众健康的重要疾病。PCI术后再狭窄是影响其远期疗效的重要制约因素。平滑肌细胞向内膜下迁移和随后的增生及细胞外基质的产生在内膜再狭窄的形成中发挥着重要的作用。Meoxl基因(Mesoderm/Mesenchyme homeobox gene1) 是非成簇排列的同源异形盒基因(Meox)亚家族中的一个亚型，其编码的蛋白可能作用于调控体节发育的分子信号网络中。本课题组通过免疫荧光共定位，实时荧光定量PCR和Western印迹检测发现，体外通过血小板衍生的生长因子-BB（PDGF-BB）刺激或体内球囊损伤引起的血管平滑肌细胞表型转变过程中，Meox1表达上调。此外，当腺病毒介导的Meox1在血管平滑肌细胞中的异位表达能够引起血管平滑肌细胞收缩功能的典型标志物的减少，如平滑肌α-肌动蛋白的表达，平滑肌22α，钙调素和Smoothelin等。同时，Meox1过表达能够诱导VSMCs的自噬。这一过程可以被PD98059和自噬抑制剂3-甲基腺嘌呤逆转。Meox1过表达引起的血管平滑肌细胞增殖和迁移效应可被ERK1 / 2抑制剂PD98059或FAK抑制剂PF573228显著抑制。相反地，通过腺病毒介导的短发夹RNA干扰Meox1表达（Ad-shMeox1），会促进血管平滑肌细胞收缩标记基因的表达，同时抑制PDGF-BB诱导的血管平滑肌细胞的增殖和迁移，以及大鼠颈总动脉球囊损伤引起的血管损伤后新生内膜的病变。有趣的是，Ad-shMeox1可以通过激活血管内皮生长因子（VEGF）在血管平滑肌细胞中的表达和释放促进损伤血管再内皮的过程。因此，Meox1 Meox1作为一种新型调节剂，能够通过激活ERK1/2信号通路介导自噬调节血管平滑肌细胞表型转换。这些研究结果，为通过靶向血管平滑肌细胞中的Meox1来治疗血管相关疾病，从自噬的角度提供了一个非常具有吸引力的方法。