Molecular mechanisms of lung branching morphogenesis

项目摘要/摘要 新生儿呼吸窘迫仍然是新生儿死亡和发病的重要原因。大多数人 4例由表面活性物质缺乏和随后的新生儿呼吸适应异常引起。 然而，导致围产期肺成熟受损和表面活性物质缺乏的原因机制 还没有完全被理解。我们的初步研究表明，BMP信号对新生儿的呼吸至关重要， 也可能有助于糖皮质激素增强的表面活性物质蛋白的表达。确定了 骨形态发生蛋白信号促进围产期肺成熟和适应的相关机制 产前干预糖皮质激素对肺生长的刺激作用将有助于突破关键 预防和治疗新生儿呼吸窘迫的屏障。因此，我们提出了三个具体目标 验证假设：外周肺上皮细胞中的BMP信号对围产期肺成熟至关重要 上调促进内源性表面活性物质产生与新生儿呼吸适应 NFATc3和Lpcat1的表达，进而促进糖皮质激素促进的肺成熟。因此， 骨形态发生蛋白信号缺陷可能导致新生儿呼吸衰竭。 目的1.确定外周肺上皮细胞中的BMP信号是否对围产儿是必需的 肺成熟与新生儿呼吸适应BMP信号活动的动态变化将是 测定与围产期小鼠肺生长和肺功能相关的表面活性物质的产生和功能 适应。BMP信号在新生儿呼吸中的作用将在体内通过基因缺失BMP来确定 受体(Alk3)或下游的Smad1，或通过给予专门针对BMP的小分子抑制剂 小鼠体内的受体Alk3。此外，应用BMP信号激活治疗可提高疗效 外源性BMP4也将决定围产期小鼠肺组织中表面活性物质的产生 给药或通过诱导结构性活性的Alk3转基因过表达。 目的2.确定BMP正向信号转导的转录调控机制 调节NFATc3和Lpcat1的表达。我们的初步数据表明，BMP-Smad1可能直接 调节NFATc3和Lpcat1的基因表达，这两个基因在促进表面活性蛋白的表达中起重要作用 和卵磷脂的合成。因此，这些基因的转录调控机制是通过 Smad1，包括Smad1-启动子DNA的相互作用，将在围产期肺上皮细胞中被确定。 目的3.确定BMP信号在介导糖皮质激素促进作用中的作用 围产期肺成熟。糖皮质激素治疗是否增强肺BMP信号传导 途径将在体内确定。骨形态发生蛋白途径激活在介导糖皮质激素刺激中的作用 然后将确定Alk3或Smad1基因敲除的围产期小鼠对表面活性物质产生的影响。 相关的分子机制将在肺泡上皮细胞中被剖析。

Project Summary/Abstract Neonatal respiratory distress remains an important cause of neonatal mortality and morbidity. The majority of cases are caused by surfactant deficiency and subsequent abnormality in neonatal respiratory adaptation. However, the causative mechanisms leading to impaired perinatal lung maturation and surfactant deficiency are not fully understood. Our preliminary studies suggest that BMP signaling is critical to neonatal respiration, and may also contribute to glucocorticoid-augmented surfactant protein expression. Determination of the related mechanisms of BMP signaling in enhancing perinatal lung maturation and adaptation, as well as in mediating antenatal glucocorticoid's stimulatory effects on lung growth will help to break through the critical barrier for prevention and treatment of neonatal respiratory distress. Thus, we propose three specific aims to test the Hypothesis: BMP signaling in peripheral lung epithelial cells is essential for perinatal lung maturation and neonatal respiratory adaptation by promoting endogenous surfactant production through upregulating Nfatc3 and Lpcat1 expression, which in turn contributes to glucocorticoid-enhanced lung maturation. Thus, deficient BMP signaling may result in neonatal respiratory failure. Aim 1. To determine whether BMP signaling in peripheral lung epithelial cells is essential for perinatal lung maturation and neonatal respiratory adaptation. Dynamic changes in BMP signaling activity will be determined in association with surfactant production and function during perinatal mouse lung growth and adaptation. The role of BMP signaling in neonatal respiration will be defined in vivo by genetically deleting BMP receptor (Alk3) or downstream Smad1, or by administering a small molecule inhibitor specifically against BMP receptor Alk3 in mice. In addition, the efficacy of therapeutic application of BMP signal activation to increase surfactant production in perinatal mouse lung tissue will also be determined by exogenous BMP4 administration or by induction of constitutively active Alk3 transgenic overexpression. Aim 2. To determine the transcriptional regulatory mechanisms by which BMP signaling positively regulates Nfatc3 and Lpcat1 expression. Our preliminary data suggest that BMP-Smad1 may directly regulate gene expression of Nfatc3 and Lpcat1, which are important in promoting surfactant protein expression and phosphatidylcholine synthesis. Therefore, the transcriptional regulatory mechanisms of these genes by Smad1, including Smad1-promoter DNA interaction, will be determined in perinatal lung epithelial cells. Aim 3. To determine the role of BMP signaling in mediating glucocorticoid effects on promoting perinatal lung maturation. Whether glucocorticoid treatment enhances the pulmonary BMP signaling pathway will be determined in vivo. The role of BMP pathway activation in mediating glucocorticoid stimulatory effects on surfactant production will then be determined in perinatal mice with Alk3 or Smad1 gene knockout. Related molecular mechanisms will be dissected in alveolar epithelial cells.