Arterial Stiffness in the Pathogenesis of Human Pulmonary Arterial Hypertension

描述（由申请人提供）：肺动脉高压（PAH）是一种严重的疾病，其特征是抗凋亡肺动脉内皮细胞（PAEC）和平滑肌细胞（PASMC）过度增殖，进行性肺动脉（PA）硬化，最终导致右心衰和死亡。最近的研究表明，PA僵硬度的增加显著增加了PAH患者的右心室后负荷，并与死亡率的增加有关，然而，PA僵硬度在PAH发病机制中的作用尚未完全阐明。我们使用原子力显微镜（AFM）微压痕在实验PAH中前所未有的微观尺度上机械表征肺动脉的刚度。我们的初步研究结果表明，在SU5416/缺氧和单氯胆碱（MCT）诱导的PAH大鼠模型中，肺动脉远端基质硬度显著增加3倍以上。此外，在聚丙烯酰胺基质上生长的人PASMC和PAEC具有重塑肺动脉的刚度，表现出惊人的高增殖表型，环氧化酶(COX)-2表达降低，前列腺素I2合成减少，内皮素-1分泌增加。综上所述，我们的研究结果表明，通过之前未被认识到的基质硬化效应，PA壁的基质重塑从根本上使细胞行为倾向于进行性血管重塑。我们假设PA刚度的增加不仅仅是血管壁病理改变的结果，而是基质刚度的增加引发了“重塑表型”，其特征是细胞增殖和肺动脉基质沉积增强，促进血管重塑的机械生物学反馈放大。为了验证我们的假设，我们提出了两个具体目标。在Specific Aim 1中，我们将在微米空间尺度上研究人类多环芳烃组织中肺动脉硬度病理性增加的幅度和分布。我们将使用AFM微凹痕来表征来自WHO I组PAH和继发性肺动脉高压受试者的肺组织中重建肺动脉的机械环境，并与来自对照受试者的肺组织中正常血管进行比较。在Specific Aim 2中，我们将阐明机械环境促进PAH患者的PASMC和PAEC的病理重塑行为的机制。与对照组相比，我们将研究基质刚度是否调节PAH患者近端和远端PASMC和PAEC的生物学特性。我们还将确定COX-2衍生的前列腺素生物合成的刚度依赖性衰减是否在机械生物学反馈回路中驱动进行性血管重构。拟议的研究将为人类PAH中机械环境在肺血管重塑中的作用提供新的见解，并将阐明在人类PASMC和PAEC中激活刚度依赖“开关”到重塑细胞表型的机制。

DESCRIPTION (provided by applicant): Pulmonary arterial hypertension (PAH) is a severe disease characterized by excessive proliferation of apoptosis-resistant pulmonary artery endothelial cells (PAEC) and smooth muscle cells (PASMC), progressive pulmonary arterial (PA) stiffening, and ultimately right heart failure and death. Recent studies suggest that increased PA stiffness contributes significantly to increased right ventricular afterload and is associated with increased mortality in PAH patients, however the role of PA stiffening in the pathogenesis of PAH has not yet been fully elucidated. We have used atomic force microscopy (AFM) microindentation to mechanically characterize the stiffness of pulmonary arteries at an unprecedented micro-scale level in experimental PAH. Our preliminary findings demonstrate that distal pulmonary arteries develop significant increases in matrix stiffness by more than three-fold in the rat models of SU5416/hypoxia and monocrotaline (MCT)-induced PAH. Furthermore, human PASMC and PAEC grown on polyacrylamide substrates with the stiffness of remodeled pulmonary arteries develop a striking hyperproliferative phenotype, decreased expression of cyclooxygenase (COX)-2, reduced prostaglandin I2 synthesis, and increased secretion of endothelin-1. Taken together, our findings suggest that matrix remodeling in the PA wall fundamentally biases cellular behavior towards progressive vascular remodeling via previously unrecognized effects of matrix stiffening. We hypothesize that increases in PA stiffness are not merely a consequence of pathological alterations in the vessel wall, but rather that increases in matrix stiffness trigger a "remodeling phenotype" characterized by enhanced cellular proliferation and matrix deposition in pulmonary arteries, promoting mechanobiological feedback amplification of vascular remodeling. To test our hypothesis, we propose two specific aims. In Specific Aim 1, we will investigate the magnitude and distribution of pathological increases in pulmonary arterial stiffness at the micron spatial scale in human PAH tissue. We will use AFM microindentation to characterize the mechanical environment of remodeled pulmonary arteries in lung tissue derived from subjects with WHO Group I PAH and secondary pulmonary hypertension compared with normal vessels in lung tissue from control subjects. In Specific Aim 2, we will elucidate the mechanisms by which the mechanical environment promotes pathologic remodeling behaviors in PASMC and PAEC derived from subjects with PAH. We will investigate whether matrix stiffness regulates the biology of proximal and distal PASMC and PAEC derived from subjects with PAH compared with control subjects. We will also determine whether stiffness-dependent attenuation of COX-2- derived prostanoid biosynthesis drives progressive vascular remodeling in a mechanobiological feedback loop. The proposed studies will provide novel insights into the role of the mechanical environment in pulmonary vascular remodeling in human PAH and will elucidate the mechanisms activating the stiffness-dependent "switch" to a remodeling cellular phenotype in human PASMC and PAEC. PUBLIC HEALTH RELEVANCE: Pulmonary arterial hypertension (PAH) is a severe disease characterized by abnormal growth of cells within the pulmonary artery wall, which may lead to irreversible vascular remodeling, stiffening of the pulmonary arteries, failure of the right side o the heart, and death. We hypothesize that increases in pulmonary artery stiffness trigger a "remodeling phenotype" in the cells of the vessel wall which promotes further vascular remodeling. The goal of our proposed studies is to measure arterial stiffness in human lung tissue and perform a rigorous analysis of the stiffness-dependent "switch" which causes human pulmonary artery cells to behave abnormally and lead to pulmonary vascular remodeling. Our research has the potential to discover new pathways for targeted therapy to prevent irreversible vascular remodeling, right heart failure, and death in patients with PAH.