Understanding and targeting molecular as well as structural events governing right ventricular adaptation, failure and recovery in pulmonary hypertension using repurposed drugs

尽管右心室（RV）在肺动脉高压（PAH）中具有临床重要性，但令人惊讶的是， 关于RV适应性和适应不良重塑的分子和结构机制知之甚少， 转换为RV故障。当RV不是RV故障的主要原因时，这一点尤其重要， 但在主要原因得到解决之前，需要对RV进行临时支持。 使肺血管阻力（PVR）正常化和减少RV后负荷的方法将改善RV 功能和反向RV故障。不幸的是，目前没有可用的药物治疗能够显著地 降低慢性PAH或血栓栓塞性PH（CTEPH）的长期PVR。由于RV故障是最常见的 PAH的死亡原因，支持RV以更好地适应增加的后负荷的方法非常重要。 追捧在本提案中，我们将重点关注两个病理特征，这两个特征使RV具有独特的风险， 衰竭：（1）心脏纤维化，降低RV收缩/舒张功能，破坏心肌结构，以及 损害氧气/营养物的交换和（2）损害微血管适应（=毛细血管稀疏） 导致右心室缺血两者都是有争议的辩论，因为他们的作用，RV适应，以及失败 就像恢复一样。我们使用一种新的小鼠肺动脉结扎（PAB）和去结扎（de-PAB）模型， 使用3-D深部组织成像定量捕获RV中的组织学变化，并将其与心脏 心脏MRI（CMR）作为骨形态发生蛋白受体2（BMPR 2）信号传导的缺陷， 被认为使RV处于失败的风险中，我们评估两种重新使用的药物，他克莫司（FK 506） 和Enzaeurin，以前我们的小组显示，增加BMPR 2信号，通过减少RV， 心脏纤维化和改善血管适应和加速恢复。此外，我们很早就发现， 心脏成纤维细胞中SNAIL 1的RV特异性表达作为改善的有希望的和可药物化的靶点 心脏纤维化我们假设，使用FK 506和Enzaelin抑制Snail并增加BMPR 2， 减轻压力负荷小鼠心肌纤维化，改善毛细血管密度，改善RV功能 RV。我们的建议有三个重要部分，这体现在我们的三个具体目标上：第一，我们将 用遗传工具靶向控制压力超负荷RV中RV纤维化的分子事件， 通过PAB小鼠中的CMR评估，重新利用药物以改善RV功能和应变。二是 表征PAB小鼠和人RV PH组织中RV微血管的适应，构建3- RV微循环的三维模型，用于预测RV结构变化如何影响液体和扩散 第三，我们将研究一种新的去带小鼠RV的组织学和功能恢复 模型通过研究和针对RV适应和失败，我们不仅解决了最重要的问题， 此外，它还有助于改善其他疾病，在这些疾病中，RV具有独特的风险， 例如慢性肺和左心脏病、CTEPH以及先天性心脏病中的衰竭。

Despite the clinical importance of the right ventricle (RV) in pulmonary arterial hypertension (PAH), surprisingly little is known about the molecular and structural mechanisms of RV adaptive and maladaptive remodeling and the transition to RV failure. This is particularly important when the RV is not the primary cause of RV failure, but when a temporary support of the RV would be desirable until the primary cause can be fixed. Approaches that normalize pulmonary vascular resistance (PVR) and reduce RV afterload would improve RV function and reverse RV failure. Unfortunately, no currently available medical therapy is able to significantly reduce PVR long-term in chronic PAH or thromboembolic PH (CTEPH). As RV failure is the most common cause of death in PAH, approaches to support the RV to better adapt to an increased afterload are highly sought after. In this proposal, we will focus on two pathological features that put the RV uniquely at risk for failure: (1) cardiac fibrosis, that reduces RV systolic/diastolic function, disrupts the myocardial architecture, and impairs the exchange of oxygen/nutrients and (2) impaired microvascular adaptation (= capillary rarefaction) that results in RV ischemia. Both are controversially debated as to their role in RV adaptation, failure as well as in recovery. We use a novel mouse model of pulmonary artery banding (PAB) and de-banding (de-PAB) to quantitatively capture histological changes in the RV using 3-D deep tissue imaging and to link them to cardiac function with cardiac MRI (CMR). As a deficiency in Bone morphogenetic protein receptor 2 (BMPR2) signaling is thought to put the RV at risk for failure, we evaluate whether two repurposed drugs, Tacrolimus (FK506) and Enzastaurin, previously shown by our group to increase BMPR2 signaling, assist the RV by reducing cardiac fibrosis and improving vascular adaptation and accelerate recovery. Moreover, we have identified early, RV specific expression of SNAIL1 in cardiac fibroblasts as a promising and druggable target to improved cardiac fibrosis. We hypothesize that Inhibiting Snail and increasing BMPR2 with FK506 and Enzastaurin will reduce cardiac fibrosis, improve capillary density and improve RV function in the pressure overloaded murine RV. Our proposal has three significant parts, which are represented by our three specific aims: First, we will target molecular events that govern RV fibrosis in the pressure overloaded RV with genetic tools and repurposed drugs to improve RV function and strain as assessed by CMR in PAB mice. Second, we will characterize the adaptation of the RV microvasculature in PAB mice and human RV PH tissue, construct a 3- D model of the RV microcirculation to predict how structural changes in the RV influence fluid and diffusion dynamics and third, we will study histological and functional recovery of the RV in a novel de-banding mouse model. By studying and targeting RV adaptation and failure, we not only address the most important cause of mortality in PAH but also help improve other diseases, in which the RV is uniquely at risk for failure such as in chronic lung and left heart disease, CTEPH as well as congenital heart disease.