BMPR2 mutations, Neointimal Transformation and Pulmonary Arterial Hypertension

由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 因肺动脉高压（PH）而死亡的风险。一种特别危险的PH形式，称为 肺动脉高压（PAH）是一种在美国发病率高、生存率低的血管性疾病 老兵PAH的特征是基因变异、慢性炎症和肺动脉阻塞性重塑。 血管内膜（新生内膜）。BMPR 2（骨形态发生蛋白受体）中的杂合生殖系突变 2)是遗传性PAH的主要遗传风险因素。有一个未得到满足的需要， 在其他健康的BMPR 2突变携带者中，环境因素诱导PAH。 我们最近在一个新的“2-hit”大鼠模型中发现，当Bmpr 2突变与肺部炎症结合时， 在其他表型沉默的Bmpr 2 +/-突变大鼠中引发严重PAH。该模型中的PAH具有 具有人类疾病共有特征的增生性和炎性新生内膜。TGF-β阻断 在Bmpr 2 +/-动物中，该治疗改善了晚期PAH和新生内膜转化，并且是一种有前景的临床治疗。 对患病大鼠肺部的试验性单细胞RNA-seq分析显示，Bmpr 2突变和肺部炎症 微环境引起内皮细胞（EC，起源于肺动脉内皮细胞）的“转录会聚”。 动脉、小动脉和毛细血管）以形成转化的新生内膜。基于这些结果，我们假设 PAH发生在Bmpr 2突变体中，因为离散的内皮转录程序被调节， 导致新生内膜发炎 该提案探讨了遗传和环境触发因素如何导致新生内膜形成和PAH， 细胞和分子水平;拟议的研究还寻找驱动EC转化的药物靶点 TGF-β治疗后。具体目标1评估Bmpr 2缺陷如何导致转录 内皮细胞会聚形成PAH新生内膜，并有三个子目标，即建立一个分子 使用尖端单分子技术（Aim 1a）绘制健康和PAH大鼠肺图谱，然后阐明 通过跟踪疾病进展中的特定内皮谱系细胞，研究新生内膜的细胞起源（目的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 1 c）。具体目标2探讨了人肺动脉EC中BMPR 2缺陷如何引发 增殖性内皮炎症，并集中在BMPR 2缺乏对炎性5- 脂氧合酶（5-LO）、NF-κ B和IL-6信号传导。在这里，BMPR 2不足诱导的机制 5-LO表观遗传和翻译后修饰、NF-κ B转录活性和经典或反式IL-6 信号将被评估。特异性目的3测试TGF-β阻断是否通过消除PAH来逆转PAH。 转录会聚EC（即，新生内膜细胞）。这一目标 研究TGF-b抑制是否以及如何通过促进转录“去聚合”逆转PAH。 并探讨了分子靶点的可逆性和潜在的药物作用。这个项目的首要目标是 该提案旨在更好地了解PAH中新生内膜层的形成，这是一种病理性 这一过程导致血管闭塞、肺动脉高压和右心衰竭。这些 研究亦可能为将来的治疗方法提供明确的方向，使我们的退伍军人病人直接受惠。

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.