Effects of BMPRII Mutations in Pulmonary Hypertension

描述(申请人提供)：原发性肺动脉高压(PPH)是一种潜在的致命性疾病，其特征是肺血管收缩和血管重构，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)基因突变被认为是家族性PPH和散发性PPH的遗传基础。BMP信号在此之前并未与肺动脉高压联系在一起，其机制也不清楚。我们假设，在正常人中，BMP途径起到下调炎症细胞因子介导的正反馈环和血管平滑肌细胞增殖的作用。具有BMPR2突变的个体中BMP途径活性不足导致这些自动调节环抑制不足，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说的初步证据，并构建了一系列独特的转基因小鼠来进一步检验这一假说。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)，允许在空间和时间上控制表达。我们已经成功培育了表达dnBMPR2的平滑肌细胞和上皮细胞特异性小鼠，目前正在构建内皮细胞特异性小鼠。利用我们的体外和转基因模型，我们将测试以下三个特定目标：1：验证BMP途径是PA SMC中细胞因子IL-6的负调控因子的假设，导致IL-6介导的信号和增殖减少。2：验证SM22-dnBMPR2转基因小鼠PA、SMC、BMPR2功能缺失导致体内过度的肺动脉高压反应的假说。3：验证SMC以外的肺细胞BMPR2功能丧失也参与肺动脉高压发生的假说。在我们的研究完成后，我们将检验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的假设。我们还将测试四种类型的肺细胞，即平滑肌细胞、内皮细胞、呼吸道上皮细胞和巨噬细胞在BMPR2与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.