Origin and Immune Functions of Platelets in Aortic Aneurysms

项目摘要 腹主动脉瘤(Aaa)是一种常见的血管疾病，与炎症和血管表达上调有关。 导致细胞外基质(ECM)局部降解的基质金属蛋白酶(MMPs) 最终导致危及生命的破裂。AAA的发病率高得令人无法接受，而且仍然占很高的比例 死亡率。在导致ECM退化阻碍的机制方面存在重大知识空白 以药物为基础的治疗管道。手术是克服患者负担的唯一选择。这个 在受损的血管壁中存在跨壁巨噬细胞(M？)是AAA的一个重要标志。他们在其中扮演的角色 持续的ECM降解仍然鲜为人知。我们小组之前的工作已经确定 在AAA中促进M？激活的仪器分子信号。新的初步数据表明，M？也可以是 由细胞内的血小板实体通过其非典型的炎症潜在性激活。活化的血小板 起源于肺而不是骨髓(BM)说明了这种调节能力的增强 效果。这项建议的目的是研究免疫活性的血小板在调节 AAA中M？依赖的ECM破坏。中心假说是肺源性血小板是病理性的。 能够协助单核细胞募集和随后激活M？蛋白分解表型的玩家 从而促进AAA。我们的理论是基于重要的观察结果，即血小板的耗尽， 抑制跨壁膜蛋白含量，弹性蛋白碎裂，AAA减少。输注肺血小板，但不输注 BM来源的血管活性物质可加速主动脉扩张，导致主动脉破裂。单细胞RNA AAA和血小板耗竭组织的测序提供了同步的免疫调节网络的前景 通过在血管系统中循环血小板，其中富含亮氨酸的重复蛋白家族成员是 在暴露于血小板耗竭的主动脉中表达最低，并明显富含在肺血小板中 在单核细胞中--血小板聚集在血液中。用一种血小板激活抑制剂治疗小鼠，减少 单核细胞募集、巨噬细胞活化和AAA。在我们的特定目标中，将使用新型遗传血小板减少率 血小板特异性条件性报告小鼠联合骨髓移植模型的建立 有条件地删除已识别的靶点以研究肺和骨髓血小板在促进中的作用 AAA中的病理性炎症。机械论研究将揭示一系列由 最终导致血管壁损伤的肺血小板。拟议的研究具有挑衅性和创新性。 因为我们研究了肺血小板在调节有害的血管重塑中的作用，到目前为止- AAA的发病机制尚不清楚。这一贡献意义重大，因为我们将测试特定的目标是否 肺中富含亮氨酸的蛋白质可以预防AAA，为AAA的发展铺平道路 有希望的预防治疗策略，以遏制AAA。

Project Summary Abdominal aortic aneurysm (AAA) is a common vascular disorder associated with inflammation and upregulation of matrix-metalloproteinases (MMP), which cause the local degradation of the extracellular matrix (ECM) culminating in life-threatening rupture. The incidence of AAA is unacceptably high and still accounts for high death rates. There are major knowledge gaps in the mechanisms that contribute to ECM degradation hindering the pipelines of drug-based therapy. Surgery is the only alternative to overcome the burden of patients. The presence of transmural macrophage (MØ) in the damaged vascular wall is a key hallmark of AAA. Their role in sustaining ECM degradation remains poorly understood. Previous work from our group has identified instrumental molecular signals that foster MØ activation in AAA. New preliminary data show that MØ can also be activated by cellular platelet entities, through their non-canonical inflammatory potential. Activated platelets originating from the lungs but not the bone marrow (BM) illustrated enhanced capacities of mediating such effects. The objective of this proposal is to investigate the contribution of immuno-active platelets in regulating MØ-dependent ECM destruction in AAA. The central hypothesis is that lung-derived platelets are pathological players capable of assisting monocyte recruitment and subsequent activation of MØ proteolytic phenotype thereby promoting AAA. Our rationale is based on important observations that the depletion of platelets, dampened transmural MØ content, elastin fragmentation and reduced AAA. Transfusion of lung platelets but not those originating from the BM accelerated the rate of aortic dilation and induced aortic rupture. Single-cell RNA sequencing of AAA and platelet-depleted tissues provided a vista of immunoregulatory networks synchronized by circulating platelets in the vasculature amongst which leucine-rich repeat protein family member was one of the most downregulated in the aorta exposed to platelet depletion and was distinctly enriched in lung platelets and in monocyte-platelets clusters in the blood. Treatment of mice with an inhibitor of platelet activation, reduced monocyte recruitment, MØ activation and AAA. In our specific aims, will use novel genetic thrombocytopenic mice models combined with BM transplantation of platelet-specific conditional reporter mice as well as conditional deletion of identified target to investigate the contribution of lung and BM platelets in promoting pathological inflammation in AAA. Mechanistic studies will reveal series of pathways and events orchestrated by lung platelets that culminate in injury of the vascular wall. The proposed research is provocative and innovative because we investigate the role of lung platelets in mediating deleterious vascular remodeling, a heretofore- unexamined mechanism in AAA. This contribution is significant since we will test whether specific targeting of leucine-rich protein in platelets from the lungs can protect against AAA and will pave the way for the development of promising preventive therapeutic strategies to curb AAA.