Impact of the micromechanical environment on inflammation in AAA progression

描述(由申请人提供)：年龄是腹主动脉瘤(AAA)最重要但最不为人所知的危险因素，腹主动脉瘤是一种常见的进行性血管疾病，致死率很高。血管细胞外基质(ECM)随着年龄的增长而变化，其特征是胶原纤维变硬，组织化程度较低。我们推测，这些与年龄相关的ECM改变不仅通过改变血管的机械性能，而且通过影响浸润性炎症细胞的功能，使老年动脉易患动脉瘤。在这个R21中，我们建议使用转基因小鼠株Col1a1来专门测试与年龄相关的胶原变化如何影响动脉瘤发展过程中的炎症反应。纯合突变动物(Col1a1R/R)表现出过度的胶原堆积和随后的ECM硬化，并加剧了动脉瘤的形成。提出了两个具体目标。在目标1中，我们将通过腔内灌流弹性蛋白酶(AAA)或热灭活弹性蛋白酶(SHAM)对Col1a1突变和野生型(Col1a1/)小鼠进行AAA诱导，以测试ECM硬化是否加速AAA进展并加剧血管炎症。这种所谓的弹性酶模型因其复制了人类AAAs的主要病理特征而被广泛接受。我们将重点放在巨噬细胞介导的炎症上，因为巨噬细胞是动脉瘤性主动脉中发现的主要类型的炎症细胞，被认为是弹性蛋白降解酶的主要来源。除了巨噬细胞的募集，我们将研究巨噬细胞的分化，期望ECM硬化促进促炎亚型或M1巨噬细胞的分化或/和抑制抗炎亚型或M2巨噬细胞的分化。目前，巨噬细胞亚型如何在动脉瘤组织中分布，以及细胞外基质老化对亚型分化的影响还完全不清楚。在目标2中，我们建议将野生型或突变小鼠的单核细胞(巨噬细胞的前体)培养在增加硬度的胶原凝胶中，以研究胶原介导的ECM硬化如何影响炎症细胞的募集和分化。本研究的结果将为理解衰老相关AAA的形成提供新的概念，并为未来的机制研究和药物开发奠定基础。因此，我们的工作意义重大、新颖且具有翻译性。

DESCRIPTION (provided by applicant): Aging is the most important yet least understood risk factor for abdominal aortic aneurysm (AAA), a common, progressive vascular disease with high lethality. The vascular extracellular matrix (ECM) changes with aging, characterized by stiffer and less organized collagen fibers. We hypothesize that these age-related ECM changes predispose older arteries to aneurysm not only by altering vessel mechanical properties but also by influencing the functions of infiltrating inflammatory cells. In this R21, we propose to specifically test how age-related collagen changes affect the inflammatory response during the course of aneurysm development using the transgenic mouse strain Col1a1. The homozygous mutant animals (Col1a1R/R) have been shown to display excessive collagen accumulation and subsequent ECM stiffening as well as exacerbated aneurysm formation. Two Specific Aims are proposed. In Aim 1, we will test whether ECM stiffening accelerates AAA progression and intensifies vascular inflammation by subjecting Col1a1 mutant and wildtype (Col1a1+/+) mice to AAA induction via intraluminal perfusion with elastase (AAA) or heat-inactivated elastase (sham). This so called elastase model is widely accepted for its duplication of major pathological characteristics of human AAAs. We will focus on macrophage-mediated inflammation because macrophages are the predominant type of inflammatory cells found in aneurysmal aorta and are thought to be the major source of elastin degrading proteases. In addition to macrophage recruitment, we will examine macrophage differentiation with the expectation that ECM stiffening facilitates differentiation of the proinflammatory subtype or M1 macrophages or/and suppresses differentiation of the anti-inflammatory subtype or M2 macrophages. Currently, how macrophage subtypes are distributed in aneurysmal tissue and how subtype differentiation may be affected by aging ECM is completely unknown. In Aim 2, we propose culture monocytes (the precursors of macrophages) from wildtype or mutant mice in collagen gels of increasing stiffness to study how collagen-mediated ECM stiffening influences the recruitment and differentiation of inflammatory cells. The results obtained from this study will provide a new concept in understanding aging-associated AAA formation and lay a foundation for future mechanistic studies and drug development. Therefore, our work is significant, novel, and translational.