Advanced Non-invasive Imaging in the Investigation of Aortic Stenosis Pathobiology

摘要 主动脉狭窄(AS)是一种严重的疾病，影响2%-4%的老年人，并对美国的医疗保健负责 每年超过60亿美元的支出，主要归因于瓣膜更换程序。通常，就像现在一样 在病情严重或有症状之前，通过非侵入性成像进行诊断。然而，目前还没有药物疗法。 延缓疾病的发展。AS的病理生物学涉及肌成纤维细胞和成骨细胞 参与基质重塑和钙化的瓣膜间质细胞(VIC)的转化。多数人 影响VICS的事件和信号通路的缺失是缺乏有效药物治疗的原因之一。vbl.使用 在活体分子成像的主动脉根部和全面的超声心动图，我们发现，小鼠 缺乏从内皮细胞表面切割von Willebrand因子(VWF)多聚体的能力 进行性动脉粥样硬化和负荷性左心室肥厚。这些动物的瓣叶证明了 血小板和血小板胞外小泡的内皮黏附以及VIC增殖的典型模式 和转型。这些发现与血小板通过结合VWF促进AS的观点是一致的。 并通过局部释放血小板衍生生长因子、细胞因子和反应性细胞因子而发挥旁分泌作用 已知能刺激VIC转化的氧物种(ROS)。相应地，抑制血小板 与VWF在瓣膜内皮细胞表面的相互作用可以阻止许多平行信号的激活 导致动脉粥样硬化的途径。我们的总体目标是将非侵入性成像与组织学相结合， 转录学和血液标记物来表征这一潜在的AS治疗机制。在目标1中，我们将 通过对缺陷小鼠的纵向评估，提供明确的证据表明，血小板黏附有助于AS 对于从内皮细胞表面切割剪切激活的VWF的ADAMTS13蛋白酶。我们会调查的 是否删除vWF的反配体--血小板GPIB；以及用重组ADAMTS13治疗。 由于血小板-内皮细胞黏附也会导致血管僵硬，系统生物学方法将是 用于动脉顺应性、左室重构和负荷相关指数的无创性成像 功能。在目标2中，我们将测试减少过度内皮细胞的新药理学方法- 相关的VWF多聚体抑制AS和LV在小鼠模型中的重构。治疗方法 将包括(I)抑制VWF自结合的N-乙酰半胱氨酸，以及(Ii)NOX2的乙酰香草酮抑制剂 这减少了ROS的产生，从而减少了过量的内皮相关VWF。在《目标3》中，有一个证据- 将在轻度或中度患者中进行概念外前瞻性临床试验，以确定 VWF蛋白分解和血小板衍生信号因子异常的血液标志物预测快速进展性AS 和动脉不顺应性。这些数据将与瓣膜剪切的新超声心动图特征相结合。 基于已知的血小板GPIB的VWF A1结构域“打开”的剪切力依赖性 血小板信号分子的结合和剪切相关转录调控

SUMMARY Aortic stenosis (AS) is a serious condition that affects 2-4% of the elderly, and is responsible for U.S. healthcare expenditures of over $6 billion annually attributable mostly to valve replacement procedures. Frequently, AS is diagnosed by non-invasive imaging before it is severe or symptomatic. Yet there are no pharmacologic therapies to slow progression of disease. The pathobiology of AS involves the myofibroblastic and osteoblastic transformation of valvular interstitial cells (VICs) that mediate matrix remodeling and calcification. The plurality of events and signaling pathways that influence VICs is one reason for lack of effective medical therapy. Using in vivo molecular imaging of the aortic root and comprehensive echocardiography, we have found that mice that lack the ability to cleave von Willebrand Factor (VWF) multimers from the endothelial surface develop progressive AS and load-related left ventricular hypertrophy. Valve leaflets from these animals demonstrate endothelial adhesion of platelets and platelet extracellular vesicles, and also typical patterns of VIC proliferation and transformation. These findings are consistent with the idea that platelets contribute to AS by binding VWF and acting in a juxtracrine fashion through local release of platelet-derived growth factors, cytokines, and reactive oxygen species (ROS) which are known to stimulate VIC transformation. Accordingly, inhibiting platelet interaction with VWF at the valve endothelial surface could prevent the activation of many parallel signaling pathways that contribute to AS. Our overall goal is to integrate non-invasive imaging with histology, transcriptomics, and blood markers to characterize this potentially treatable mechanism for AS. In Aim 1, we will provide definitive evidence that platelet adhesion contributes to AS by longitudinal assessment of mice deficient for the ADAMTS13 protease that cleaves shear-activated VWF from the endothelial surface. We will investigate whether deletion of platelet GPIb, the counterligand for VWF; and treatment with recombinant ADAMTS13. Because platelet-endothelial adhesion also contributes to vascular stiffness, a systems-biology approach will be used with non-invasive imaging of arterial compliance, LV remodeling, and load-dependent indices of LV function. In Aim 2, we will test whether novel pharmacologic approaches that reduce excess endothelial- associated VWF multimers suppress the development of AS and LV remodeling in the murine models. Therapies will include (i) n-acetylcysteine which inhibits VWF self-association, and (ii) an acetovanillone inhibitor of Nox2 which reduces the generation of ROS and, consequently, excess endothelial-associated VWF. In Aim 3, a proof- of-concept prospective clinical trial will be performed in patients with mild or moderate AS to determine whether blood markers of abnormal VWF proteolysis and platelet-derived signaling factors predict rapidly progressive AS and arterial non-compliance. These data will be integrated with novel echocardiographic features of valve shear based on the known shear-dependency of “opening” of the otherwise cryptic VWF A1 domain for platelet GPIb binding and shear-related transcriptomic control of platelet signaling molecules