Molecular Mechanisms of Aneurysmal Degeneration

描述(由申请人提供)： 腹主动脉瘤(AAA)是一种常见且危及生命的疾病。本项目的目的是利用我们实验室以前建立的弹性酶诱导的AAA小鼠模型，阐明导致主动脉壁退变的细胞和分子机制。该模型概括了人类AAA的许多重要特征，包括非单核巨噬细胞对主动脉壁的跨壁渗透，局部炎性细胞因子和基质金属蛋白酶(MMPs)的增加。以及弹性蛋白和胶原蛋白的逐渐降解。我们已经证明，靶向删除基质金属蛋白酶-9可以抑制弹性蛋白酶诱导的AAA，从而抑制弹性蛋白的降解，而在缺乏内源性基质金属蛋白酶抑制剂TIMP-1的情况下，AAA会被增强。因为我们发现在缺乏基质金属蛋白酶-9和基质金属蛋白酶-1的小鼠体内AAA的增强作用更大，所以需要更详细地了解基质金属蛋白酶-9、基质金属蛋白酶-1和其他弹性溶解基质金属蛋白酶之间的体内相互作用，以及基质金属蛋白酶-9在主动脉弹性蛋白降解中的具体作用。同样重要的是要考虑，对胶原酶介导的间质胶原降解有抵抗力的小鼠，或者缺乏主要胶原酶之一的胶原酶-3(MMP13)表达的小鼠，是否会发生AAAs易感性的改变。由于我们已经观察到通过靶向缺失组织蛋白酶-S(Cst-S)抑制弹性酶诱导的AAA，Cst-S是一种弹性和胶原分解半胱氨酸蛋白酶，其促进动脉瘤变性的机制也需要确定。这些问题将通过实现以下三个具体目标来解决：(1)阐明MMP-9、TIMP-1和其他弹性溶解MMPs如何影响Eastase诱导的AAA的发展，是否在体内直接导致主动脉壁弹性蛋白的降解，以及是否需要基质溶素(MMP7)来实现动脉瘤样变性；(2)确定在实验性AAA的发展过程中是否需要基质(I型)胶原的降解，以及是否在这一过程中MMP13是必需的；(3)确定在弹性酶诱导的AAA形成过程中，Cat-S的重要细胞来源，以及Cat-S靶向基因缺失抑制动脉瘤变性的分子机制。综上所述，这些研究将对动脉瘤变性中细胞外基质降解的潜在机制提供重要的新信息。

DESCRIPTION (provided by applicant): Abdominal aortic aneurysms (AAAs) are a common and life-threatening condition. The goal of this project is to elucidate cellular and molecular mechanisms responsible for aortic wall degeneration using a mouse model of elastase-induced AAAs previously characterized in our laboratory. This model recapitulates many critical features of human AAAs, including transmural infiltration of the aortic wall by rnononuclear phagocytes, increased local production of proinflammatory cytokines and matrix metalloproteinases (MMPs). and progressive degradation of elastin and collagen. We have shown that targeted deletion of MMP-9 inhibits elastase-induced AAAs with suppression of elastin degradation, whereas AAAs are enhanced in the absence of the endogenous MMP inhibitor, TIMP-1. Because we found even greater enhancement of AAAs in mice lacking both MMP-9 and TIMP-1, more detailed knowledge is needed regarding the in vivo interactions between MMP-9, TIMP-1, and other elastolytic MMPs, and the specific role of MMP-9 in aortic elastin degradation. It is also important to consider if altered susceptibility to AAAs will occur in mice with resistance to collagenase-mediated degradation of interstitial collagen or in mice lacking expression of coilagenase-3 (MMP-13), one of the principal MMP-collagenases. Because we have observed suppression of elastase-induced AAAs in mice with targeted deletion of cathepsin-S (Cst-S), an elastolytic and collagenolytic cysteine protease, the mechanisms by which Cat-S promotes aneurysmal degeneration also need to be defined. These issues will be addressed by accomplishing the following three specific aims: (1) Clarify how MMP-9, TIMP-1 and other elastolytic MMPs influence the development of eiastase-induced AAAs, if MMP-9 is directly responsible for aortic wall elastin degradation in vivo, and if matrilysin (MMP-7) is required for aneurysmal degeneration; (2) Establish if MMP-mediated degradation of interstitial (type I) collagen is required in the development of experimental AAAs and if MMP-13 is essential in this process; and (3) Identify the functionally important cellular sources of Cat-S during the development of elastaseinduced AAAs and the molecular mechanisms by which targeted gene deletion of Cat-S suppresses aneurysmal degeneration. Taken together, these studies will contribute important new information on the mechanisms underlying extracellular matrix degradation in aneurysmal degeneration.