软骨寡聚基质蛋白COMP对巨噬细胞极化和动脉粥样硬化发生发展的调控及其机制的研究

Macrophage polarization, the programming among different phenotypes of macrophages, plays a critical role in atherosclerosis. Thus the modulation of polarization could be a potential way to prevent and cure atherosclerosis. Macrophage polarization is regulated by lots of stimulators in microenvironment of macrophages, but the relationship of polarization with the extracellular matrix (ECM), one major component of microenvironment, is still unknown. Our preliminary data demonstrated that macrophages expressed cartilage oligomeric matrix protein (COMP), and that COMP could promote M2 but inhibited M1 markers expression. Moreover,we also found that atherosclerotic lesions were increased on ApoE-/- and COMP-/- mice compared with ApoE-/- mice. Based on these we hypothesize that COMP can inhibit atherosclerosis through regulating macrophage polarization. To validate our hypothesis, we firstly plan to confirm the effects of COMP on polarization by changing COMP expression level in macrophages. Secondly we design to detect the atherosclerosis and then identify COMP from different cell types affects the polarization and atherosclerosis in vivo through gene knockout animal and bone marrow reconstitution. Thirdly, we arrange to explore the mechanism by detecting whether integrin beta 1 or 3, the receptor of ECM, involves in the COMP-regulated macrophage polarization. In this project, we expect to clarify the role of ECM in macrophage polarization as a novel mechanism of atherosclerosis.

巨噬细胞不同表型变化，即极化参与了动脉粥样硬化（AS）的发生和发展。因此，调节极化成为治疗和预防AS的潜在手段。巨噬细胞极化与其微环境中的多种刺激因素密切相关，而目前作为微环境成分之一的细胞外基质对极化的作用却鲜有报道。我们预实验显示巨噬细胞表达软骨寡聚基质蛋白COMP；COMP能促进巨噬细胞M2而抑制M1表型分子的表达；ApoE小鼠敲除COMP后加重AS。因此，我们提出假说：胞外基质- - COMP通过调节巨噬细胞极化而减缓AS的进展。为了证明该假说，我们首先改变巨噬细胞COMP水平以确定其在巨噬细胞极化中的作用；再通过基因敲除小鼠和骨髓移植以明确COMP对极化和AS的影响以及不同来源COMP所起的作用；进而在机制上探讨COMP通过胞外基质的受体- - 整合素beta1或3参与极化的调控。该项目将从胞外基质参与巨噬细胞极化调控的角度为AS发生发展的机制研究提供新的实验依据。

动脉粥样硬化斑块钙化和血栓的形成与斑块稳定性和疾病的转归密切相关。血管细胞外基质蛋白——软骨寡聚基质蛋白COMP已知可抑制血管中膜钙化、维持平滑肌的收缩表型及抑制血管损伤后再狭窄，而本课题主要研究COMP对斑块钙化和血栓形成的调控作用。我们发现巨噬细胞来源的COMP通过和膜表面受体integrin beta 3的相互作用，抑制巨噬细胞向致动脉粥样硬化和促成骨表型的转化，从而减轻了小鼠动脉粥样硬化斑块的形成和钙化（Fu et al. Circ Res. 2016，封面故事），该杂志同期述评：我们的研究提示了COMP相关的基质分泌(matricrine)信号通路在血管钙化中起了重要的作用。此外，我们还发现COMP可直接与凝血酶结合抑制其激活血小板与切割纤维蛋白原的活性，是一种天然的凝血酶抑制剂，并且COMP可在血小板中表达和分泌。采用骨髓移植和血小板回输实验发现，血小板来源而非血管壁来源的COMP 能够抑制凝血。该工作被发表在Blood上（Liang et al. Blood 2015），杂志对我们的工作进行了相关述评：我们的工作证实COMP是一种内源性凝血酶抑制剂，是止血和血栓形成的负调节因子。

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