Arterial Stiffness in the Pathogenesis of Human Pulmonary Arterial Hypertension

描述(申请人提供)：肺动脉高压(PAH)是一种严重的疾病，其特征是抗凋亡的肺动脉内皮细胞(PAEC)和平滑肌细胞(PASMC)过度增殖，进行性肺动脉(PA)硬化，最终导致右心衰竭和死亡。最近的研究表明，PA僵硬的增加显著增加了PAH患者的右室后负荷，并与死亡率的增加有关，然而PA僵硬在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)微压痕技术，在前所未有的微尺度水平上对实验性PAH中的肺动脉僵硬进行了机械表征。我们的初步发现表明，在SU5416/低氧和野百合碱(MCT)诱导的PAH大鼠模型中，远端肺动脉的基质硬度显着增加三倍以上。此外，生长在聚丙烯酰胺基质上的人PASMC和PAEC表现出显著的高增殖表型，环氧合酶(COX)-2的表达减少，前列腺素I2的合成减少，内皮素-1的分泌增加。综上所述，我们的发现表明，PA壁中的基质重塑通过先前未知的基质硬化效应，从根本上偏向于进行性血管重塑的细胞行为。我们假设，PA硬度的增加不仅是血管壁病理改变的结果，而且基质硬度的增加还会触发一种“重塑表型”，其特征是促进肺动脉中细胞的增殖和基质的沉积，促进血管重塑的机械生物学反馈放大。为了检验我们的假设，我们提出了两个具体目标。在特定的目标1中，我们将在微米空间尺度上研究人类PAH组织中肺动脉僵硬病理性增加的程度和分布。我们将使用AFM微压痕来表征来自WHO I组PAH和继发性肺动脉高压患者肺组织中重塑的肺动脉的力学环境，并与来自正常对照组的肺组织中的正常血管进行比较。在具体目标2中，我们将阐明机械环境促进PAH患者PASMC和PAEC病理性重塑行为的机制。与对照组相比，我们将研究基质硬度是否调节来自PAH受试者的PASMC和PAEC的生物学。我们还将确定COX-2衍生的前列腺素生物合成的硬度依赖的衰减是否在机械生物反馈环中驱动进行性血管重构。这些研究将为机械环境在人PAH肺血管重塑中的作用提供新的见解，并将阐明激活人PASMC和PAEC中僵硬依赖的到重塑细胞表型的“切换”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.