Extracellular Matrix Metabolism in Thoracic Aortic Aneurysm and Dissection

描述（申请人提供）：虽然胸主动脉瘤及夹层（TAAD）不像某些血管疾病如冠状动脉疾病那样常见，但它是一种临床隐匿性疾病，病死率高。如果不及时治疗，70%的患者会发生破裂，导致94%的死亡率，这使得它在人群和个人层面上都是一个影响很大的健康问题。适当的手术治疗可显著提高长期生存率。然而，何时以及如何治疗这些患者仍然是经验，而不是基于证据的临床实践。如果出现以下一种或多种情况，TAAD会发生在主动脉：1)原有主动脉结构太弱；2)破坏力太强；3)修复机制不称职。虽然这三个方面在疾病发展中都至关重要，但本项目要验证的中心假设是，细胞外基质（ECM）在主动脉壁的产生和组织决定了主动脉对基质蛋白酶激活不足的反应，从而形成动脉瘤或夹层。我们有四个具体目标：(1)研究ECM代谢在TAAD患者中的作用。我们将定性和定量地检测TAAD患者主动脉样本中的胶原蛋白和弹性蛋白，以及参与胶原蛋白和弹性蛋白合成、分泌和降解的酶，并与正常主动脉进行比较。(2)验证TAAD患者主动脉平滑肌细胞（SMCs）产生ECM能力可能受损的假设。我们将通过培养TAAD患者的主动脉SMCs，并与正常主动脉SMCs进行比较，建立体外模型。(3)探讨正常对照和TAAD患者主动脉内皮成纤维细胞在ECM生成中的作用。除了常驻内皮层的SMCs外，外皮层成纤维细胞可能迁移到内皮层或留在外皮层，并参与ECM的整体代谢。我们将遵循与Aim 2相同的实验设计，并评估从正常和TAAD主动脉收集的成纤维细胞的潜在差异。(4)评价动脉壁ECM的产生与体内动脉瘤发育的关系。为了证明ECM产生与主动脉壁动脉瘤样变化之间的因果关系，我们将使用单基因敲除或转基因小鼠模型，并测量其对主动脉壁定量变化的影响。我们将通过局部CaCl2刺激再生TAAD， CaCl2激活基质金属蛋白酶（MMPs）并导致主动脉瘤。我们目前的项目将在体内（患者研究和动物模型）和体外（细胞培养模型）研究ECM产生决定TAAD发展易感性的新假设。我们的项目将为TAAD的外科和/或医学治疗建立循证指南。凭借我们对大量TAAD患者的独特访问以及细胞和动物模型的专业知识，我们的项目是可行的。

DESCRIPTION (provided by applicant): Although thoracic aortic aneurysm and dissection (TAAD) are not as common as some forms of vascular diseases, e.g. coronary artery disease, it is a clinically insidious disease with high fatality. If untreated, rupture occurs in 70% of patients resulting in a 94% mortality rate, which makes it a high impact health problem at both population and individual levels. Appropriate surgical therapy dramatically improves long-term survival. However, when and how to treat these patients is still experience- rather than evidence-based clinical practice. TAAD will occur in an aorta if one or more of the following conditions are present: 1) original aortic structure is too weak; 2) destructive forces are too powerful; 3) repair mechanisms are not competent. While all three aspects are critical in the disease development, the central hypothesis to be tested in this project is that extracellular matrix (ECM) production and organization in aortic wall determine how aorta will respond to inadequate matrix protease activation, hence formation of aneurysm or dissection. We have developed four Specific Aims: (1) To investigate the role of ECM metabolism in patients with TAAD. We will examine qualitatively and quantitatively the collagen and elastin, enzymes involved in collagen and elastin synthesis and secretion, and degradation in aortic samples of TAAD patients and compare with normal aortas. (2) To examine the hypothesis that ECM production capacity by aortic smooth muscle cells (SMCs) may be compromised in TAAD patients. We will use in vitro model by culturing aortic SMCs from TAAD patients and comparing with SMCs of normal aortas. (3) To examine the role aortic adventitial fibroblasts in ECM production in aortas from normal control and TAAD patients. In addition to resident medial layer SMCs, adventitial fibroblasts may either migrate to medial layer or stay in adventitial layer and contribute to the overall ECM metabolism. We will follow the same experimental design as those in the Aim 2 and evaluate the potential differences in fibroblasts collected from normal and TAAD aortas. (4) To evaluate the involvement of arterial wall ECM production in aneurysm development in vivo. To provide evidence for the causal relationship between the ECM production and aneurysm-like changes in aortic wall, we will use single gene knockout or transgenic mouse models and measure the impact on quantitative changes in aortic wall. We will regenerate TAAD by local CaCl2 challenge, which activates matrix metalloproteinases (MMPs) and causes aortic aneurysms. Our current project will investigate this novel hypothesis that ECM production determines the susceptibility to TAAD development, in vivo (patient study and animal model) and in vitro (cell culture model). Our project will lead to the establishment of evidence-based guides for surgical and/or medical treatments of TAAD. With our unique access to a large number of TAAD patients and expertise in cell and animal models, our project is feasible.