Regulation of type II cells in the repair ofalveolar epithelial injury

肺泡上皮损伤修复中II型细胞的调节 摘要 在美国，每年约有200,000例急性肺损伤(ALI)和急性呼吸系统疾病 窘迫综合征(ARDS)。修复受损的肺泡上皮屏障是解决肺泡炎的关键 ALI/ARDS。然而，目前缺乏旨在促进修复的针对性治疗。 上皮细胞恢复屏障功能。本项目的目标是了解信号事件对 以促进内源性牙槽骨修复过程，并找出潜在的药物靶点，加速修复。肺泡 内有两种上皮细胞：肺泡I型细胞(AT1)和II型细胞(AT2)。AT1覆盖率~95% 由于其薄而扁平的形状和负责血气交换的表面积。 AT2具有多种功能，包括分泌表面活性物质，也能够作为祖细胞， 肺损伤后增殖并转化为AT1以恢复肺泡上皮屏障。然而， 负责调节AT2介导的修复的信号事件仍然知之甚少。我们的预赛 数据表明，在AT2中需要一个非正则Notch配体Dlk1(对于Delta-like 1同系物) 至AT1分化。我们发现Dlk1表达的动态变化与AT2到AT1相关 维修过程中的过渡。使用Dlk1在AT2中被特定打乱的小鼠模型，我们发现 突变细胞不能分化为AT1，同时Notch异常升高 发信号。基于这些数据，我们假设动态调节的Notch信令是必不可少的 为了AT2的正常祖细胞功能以及Dlk1在AT2到AT1中扮演重要角色 抑制Notch信号在牙槽骨修复过程中的转变。我们打算追求以下具体目标 目的：目的1：检验Dlk1调节肺泡发育所需的AT2到AT1转变的假设 修理。我们将确定Dlk1在恢复上皮屏障完整性和气体交换功能中的作用 受伤后。我们将定义Dlk1调节的AT2到AT1转换的详细步骤和识别因素 Dlk1的下游和上游。目的2：检验Dlk1依赖的动力学假设 在AT2介导的肺泡修复过程中，规范的Notch信号通路的调节是必不可少的。 我们将确定Notch信号在AT2中的作用，在牙槽骨修复的不同阶段和 研究Dlk1与Notch受体和配体之间的分子相互作用。最后，我们会 通过引入Dlk1等Notch调节剂促进牙槽骨修复的研究 并将进一步测试Notch/Dlk1在人类AT2和人iPSC衍生的AT2中的作用。 在这些研究的结论中，我们将填补关于分子的一个重要的知识空白 肺泡修复的潜在机制。我们相信，这些研究将导致发现治疗性 目标是加速肺部修复，防止因恢复不当而导致的慢性病理情况。

Title: Regulation of type II cells in the repair of alveolar epithelial injury ABSTRACT Each year in the United States, there are ~ 200,000 cases of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) . Repair of the injured alveolar epithelial barrier is essential for the resolution of ALI/ARDS. However, there is currently a lack of targeted therapies aimed at promoting the repair of the epithelium to restore barrier function. The goal of this project is to understand the signaling events contributing to the endogenous alveolar repair process and identify potential drug targets to accelerate repair. Lung alveoli are lined with two types of epithelial cells: Alveolar Type I cells (AT1) and Type II cells (AT2). AT1 cover ~95% of the surface area because of their thin and squamous shape and are responsible for blood-gas exchange. AT2 have multiple functions including the secretion of surfactant and are also able to act as progenitor cells, proliferating and converting to AT1 after lung injury to restore the alveolar epithelial barrier. However, the signaling events responsible for regulating AT2-mediated repair remain poorly understood. Our preliminary data demonstrated the requirement of a non-canonical Notch ligand Dlk1 (For delta-like 1 homolog) in the AT2 to AT1 differentiation. We found that a dynamic change in Dlk1 expression is correlated with the AT2 to AT1 transition during repair. Using a mouse model in which Dlk1 was specifically disrupted in AT2, we found that the mutant cells were unable to differentiate into AT1 and at mean time had abnormally elevated Notch signaling. Based on these data, we hypothesize that dynamically regulated Notch signaling is essential for the proper progenitor function of AT2 and that Dlk1 plays an essential role in the AT2 to AT1 transition during alveolar repair by inhibiting Notch signaling. We intend to pursue the following specific aims: Aim 1: To test the hypothesis that Dlk1 regulates the AT2 to AT1 transition required for alveolar repair. We will determine the function of Dlk1 in restoring epithelial barrier integrity and gas-exchange function post-injury. We will define the detailed steps in the Dlk1 regulated AT2 to AT1 transition and identifying factors downstream and upstream of Dlk1. Aim 2: To test the hypothesis that the Dlk1-dependent dynamic regulation of the canonical Notch signaling pathway is essential during AT2-mediated alveolar repair. We will determine the role of Notch signaling activity in AT2 at different phases of alveolar repair and investigate the molecular interactions between Dlk1 and Notch receptors and ligands. Finally, we will investigate the effects of improving alveolar repair through the introduction of Dlk1 and other Notch-regulating molecules into alveoli and will further test the roles of Notch/Dlk1 in human AT2 and human iPSC derived AT2. At the conclusion of these studies, we will have filled an important gap in knowledge about the molecular mechanisms underlying alveolar repair. We believe that these studies will lead to the discovery of therapeutic targets to accelerate lung repair and prevent chronic pathological conditions resulting from improper recovery.