Effects of BMPRII Mutations in Pulmonary Hypertension

描述（由申请人提供）：原发性肺动脉高压（PPH）是一种以肺血管收缩和血管重构为特征的潜在致命性疾病，涉及成纤维细胞、平滑肌和内皮细胞的异常增殖。2000年，2型骨形态发生蛋白受体（BMPR2）的突变被确定为家族性PPH和约30%散发性PPH的遗传基础。以前没有发现BMP信号与肺动脉高压有关，其机制联系也不清楚。我们假设在正常个体中，BMP通路下调炎症细胞因子介导的正反馈回路和血管平滑肌细胞增殖。在BMPR2突变个体中，BMP通路活性不足导致这些自调节回路阻尼不足，从而导致PPH表型。我们在细胞培养系统中提供了支持这一假设的初步证据，并构建了一系列独特的转基因小鼠来进一步验证这一假设。这些小鼠使用四环素基因开关系统表达人类显性阴性BMPR2 (dnBMPR2)，允许空间和时间控制表达。我们已经成功培育了平滑肌细胞和上皮细胞特异性表达dnBMPR2的小鼠，目前正在构建内皮细胞特异性表达小鼠。使用我们的体外和转基因模型，我们将验证以下三个具体目标：1：验证BMP途径是PA SMC中细胞因子白介素-6 （IL-6）的负调节因子，导致IL-6介导的信号传导和增殖减少的假设。2：验证SM22-dnBMPR2转基因小鼠PA SMC BMPR2功能丧失导致体内肺动脉高压反应夸大的假设。3：验证除SMC外肺细胞类型BMPR2功能丧失也有助于肺动脉高压发生的假设。在完成我们的研究后，我们将验证BMP信号与肺动脉高压之间的联系涉及关键细胞因子IL-6的调节以及平滑肌细胞增殖的调节这一假设。我们还将测试四种肺细胞类型，平滑肌细胞、内皮细胞、气道上皮细胞和巨噬细胞在BMPR2和肺动脉高压之间的联系中的作用。

DESCRIPTION (provided by applicant): Primary pulmonary hypertension (PPH) is a potentially lethal disorder characterized by pulmonary vasoconstriction and vascular remodeling involving abnormal proliferation of fibroblasts, smooth muscle and endothelial cells. In the year 2000, mutations in the type 2 bone morphogenic protein receptor (BMPR2) were identified as the genetic basis for familial PPH and about 30% of sporadic PPH. BMP signaling had not previously been connected to pulmonary hypertension, and the mechanistic linkage is unknown. We hypothesize that in normal individuals the BMP pathway acts to down-regulate both inflammatory cytokine-mediated positive feedback loops and vascular smooth muscle cell proliferation. Insufficient BMP pathway activity in individuals with BMPR2 mutations leads to insufficient damping of these auto-regulatory loops, resulting in the PPH phenotype. We provide preliminary evidence in cell culture systems supporting this hypothesis and have constructed a unique series of transgenic mice to further test the hypothesis. These mice express a human dominant-negative BMPR2 (dnBMPR2) using the tetracycline gene switch system, allowing both spatial and temporal control of expression. We have successfully bred smooth muscle cell and epithelial cell specific dnBMPR2 expressing mice, and are constructing endothelial cell specific mice at this time. Using our in vitro and transgenic models we will test the following three specific aims: 1: Test the hypothesis that the BMP pathway is a negative modulator of the cytokine interleukin-6 (IL-6) in PA SMC, leading to reduced IL-6-mediated signaling and proliferation. 2: Test the hypothesis that loss of PA SMC BMPR2 function in SM22-dnBMPR2 transgenic mice leads to an exaggerated pulmonary hypertensive response in vivo. 3: Test the hypothesis that loss of BMPR2 function in lung cell types other than SMC also contributes to the development of pulmonary hypertension. Upon completion of our studies, we will have tested the hypothesis that the link between BMP signaling and pulmonary hypertension involves both regulation of the critical cytokine, IL-6, as well as modulation of smooth muscle cell proliferation. We will have also tested the role of four pulmonary cell types, smooth muscle, endothelium, airway epithelium and macrophages in the link between BMPR2 and pulmonary hypertension.