BMPR2 mutations, Neointimal Transformation and Pulmonary Arterial Hypertension

退伍军人健康管理局服务的患有慢性心肺疾病的患者处于高水平 因肺动脉高压(PH)而死亡的风险。一种特别危险的PH，被称为 肺动脉高压(PAH)在美国是一种发病率高、存活率低的血管疾病 退伍军人。PAH的特征是基因变异、慢性炎症和阻塞性血管重构。 血管内膜(新生内膜)。骨形态发生蛋白受体BMPR2基因杂合性胚系突变 2)是遗传性PAH的主要遗传危险因素。有一种尚未得到满足的需求，需要了解如何 环境提示在其他健康的BMPR2突变携带者中诱导PAH。 我们最近在一种新的两次打击大鼠模型中表明，当Bmpr2突变与肺部炎症相结合时， 在其他表型沉默的Bmpr2+/-突变大鼠中诱导严重的PAH。此型号中的PAH具有 增殖性和炎症性新生内膜，具有人类疾病的共同特征。转化生长因子-β的阻断 改善晚期PAH和Bmpr2+/-动物的新生内膜转化，是一种有前途的临床治疗方法。 对疾病大鼠肺部的飞行员单细胞RNA-seq分析显示，Bmpr2突变和肺部发炎 微环境导致内皮细胞(ECs)转录趋同，来源于肺 动脉、小动脉和毛细血管)形成转化的新生内膜。基于这些结果，我们假设 在Bmpr2突变体中出现PAH是因为离散的内皮转录程序被调节 并导致新生内膜发炎。 这项建议探讨了遗传和环境因素如何导致动脉内膜新生和肺动脉高压。 细胞和分子水平；拟议的研究还寻找推动EC转化的可用药靶点 在接受转化生长因子-b治疗后。特定目标1评估Bmpr2缺乏如何导致转录 内皮细胞汇聚形成PAH新生内膜，并有三个亚目标，即建立一个分子 使用尖端单分子技术的健康和PAH大鼠肺图谱(目标1a)，然后阐明 通过追踪疾病发展中的特定内皮系细胞来研究新生内膜的细胞起源(目标1b)，以及 最后确定负责血管病变形成和维持的分子程序(目的 1C)。特定目标2探讨人肺动脉内皮细胞BMPR2缺乏是如何引起 增殖性内皮细胞炎症，重点关注BMPR2缺乏对炎性5-羟色胺的影响 脂氧合酶(5-LO)、核因子-kB和IL-6信号转导。在这里，BMPR2不足导致的机制 5-LO表观遗传和翻译后修饰、核因子-kB转录活性和经典或反式IL-6 将对信号进行评估。特定目标3测试转化生长因子-b阻断是否通过消除 Bmpr2基因突变大鼠肺内转录聚集性内皮细胞(即新生内膜细胞)。这一目标 研究转化生长因子-b的抑制是否以及如何通过促进转录“去逆转”逆转PAH。 并探索分子靶标的可逆性和潜在的可药性。这件事的首要目标是 建议更好地了解PAH新生内膜的形成，这是一种病理性的 导致血管闭塞、肺动脉高压和右心衰竭的过程。这些 研究还可能为未来直接受益于我们的退伍军人患者的治疗途径提供明确的方向。

Patients served by the Veterans Health Administration who have chronic cardiopulmonary conditions are at high risk for death because of pulmonary hypertension (PH). A particularly dangerous form of PH, referred to as pulmonary arterial hypertension (PAH), is a vascular disease with high prevalence and poor survival among US veterans. PAH is characterized by gene variants, chronic inflammation and an occlusive remodeling of the vascular intima (neointima). Heterozygous germline mutations in BMPR2 (bone morphogenetic protein receptor 2) is the principle genetic risk factor for hereditary PAH. There is an unmet need to understand how environmental cues induce PAH in otherwise healthy BMPR2 mutation carriers. We recently showed in a new ‘2-hit’ rat model that Bmpr2 mutations, when coupled with pulmonary inflammation, elicit severe PAH in otherwise phenotypically-silent Bmpr2+/- mutant rats. PAH in this model features a proliferative and inflammatory neointima with characteristics shared by human disease. TGF-b blockade ameliorates advanced PAH and neointimal transformation in Bmpr2+/- animals and is a promising clinical therapy. Pilot single cell RNA-seq analyses of the disease rat lungs revealed that Bmpr2 mutations and an inflamed lung microenvironment cause a ‘transcriptional convergence’ of endothelial cells (ECs, originating from pulmonary arteries, arterioles and capillaries) to form the transformed neointima. Based on these results, we postulate that PAH occurs in Bmpr2 mutants because discrete endothelial transcriptional programs are modulated and result in an inflamed neointima. This proposal explores how genetic and environmental triggers may lead to neointimal formation and PAH at the cellular and molecular levels; proposed studies also search for druggable targets driving EC transformation following TGF-b treatment. Specific Aim 1 evaluates how Bmpr2 deficiency causes transcriptional convergence of ECs to form the PAH neointima and has three subaims which are to establish a molecular atlas of rat lungs in health and PAH using cutting-edge single molecular techniques (Aim 1a), then to elucidate the cellular origins of neointima by tracking specific endothelial lineage cells in evolving disease (Aim 1b), and finally to identify molecular programs responsible for the formation and maintenance of vascular lesions (Aim 1c). Specific Aim 2 explores how BMPR2 deficiency in human pulmonary arterial ECs provokes proliferative endothelial inflammation and focuses on the influence of BMPR2 deficiency on inflammatory 5- lipoxygenase (5-LO), NF-kB and IL-6 signaling. Here, the mechanisms by which BMPR2 insufficiency induces 5-LO epigenetic and post-translational modification, NF-kB transcriptional activities and classical- or trans-IL-6 signaling will be assessed. Specific Aim 3 tests whether TGF-b blockade reverses PAH by eliminating transcriptionally-convergent ECs (i.e., neointimal cells) in the lungs of Bmpr2 mutant rats. This aim investigates whether and how TGF-b inhibition reverses PAH by promoting the transcriptional ‘deconvergence’ of ECs and explores the reversibility and potential druggability of molecular targets. The overarching goal of this proposal is to create a better understanding about the formation of the neointimal layer in PAH, a pathological process responsible for vascular occlusion, high pulmonary artery pressures and right heart failure. These studies may also offer clear directions for future therapeutic avenues of direct benefit to our veteran patients.