Bioactive lipid mediated Endothelial niche regulation of alveolar epithelial repair

摘要 肺泡上皮暴露在环境和病原体中，因此非常容易感染 受伤。肺泡上皮的修复需要肺泡上皮干细胞通过下列信号激活 它们周围的壁龛。值得注意的是，肺微血管内皮细胞(LMVECs)在这方面的作用 人们对修复工作知之甚少。在这项建议中，我们通过关注一种新的机制来解决这一知识差距 生物活性脂质介导的肺微血管内皮细胞与肺泡的相互作用 修复窝内的上皮细胞(AEC)。肺微血管内皮细胞占肺细胞总数的40%。他们并列在一起 AECs(肺泡I型细胞(AT1)和II型细胞(AT2))，并在调节其修复方面发挥重要作用， 尽管强调的机制仍不清楚。AT1有一个细长的扁平形状，占据 &gt；肺泡表面积的95%，并介导O2-CO2交换。AT2只占表面积的5%，但 发挥多重作用，包括产生表面活性物质，更重要的是，充当成人组织干细胞进行修复 肺泡受伤。包括我们在内的研究表明，虽然AT2通常是静止的，但它们可以做出反应 到周围壁龛释放的信号，并通过分化成AT1来启动修复程序。然而， 调节AT2干细胞功能的信号仍不清楚(S)。最近的研究表明，AT1也表现出 一定程度的可塑性，但AT1是否以及如何参与肺修复几乎是完全未知的 受伤后。在初步研究中，我们建立了一种内皮细胞(EC)特异性缺失的小鼠模型 鞘氨醇激酶1(Sphk1)，负责产生脊髓磷脂-1-磷酸(S1P)的酶。这些 突变小鼠表现出标准化铜绿假单胞菌的AECs修复明显缺陷 细菌性肺损伤模型。我们进一步证明，S1P通过其受体S1PR2在AT2中表达而发挥作用， 导致转录调节因子YAP的核移位，YAP介导 AT2向AT1的分化及损伤肺泡的修复此外，我们观察到，作为对S1P的响应， AT1经历了实质性的改变，这可能有助于修复过程。这些基本原则 观察结果引出了我们的中心假设：LMVECs构成了一个利基，当被肺泡激活时 损伤，释放生物活性脂质因子S1P，它通过S1PR作用于AT2和AT1，促进它们的 修复肺泡上皮所需的修复能力。为了检验这一假设，我们提出了三个假设 具体目标：目标1：确定S1P介导的EC生态位和AEC之间对肺所需的相互作用 修理。目的：明确S1P-S1PR2-YAP信号轴在调节AT2为AT1中的功能意义 过渡性和介导性牙槽骨修复。目的3：检验S1P导致AT1改变导联的假设 到牙槽修复。这项研究计划将为推动肺修复的基本机制提供新的线索 在受伤后，具有创新治疗方法的长期潜力。

Abstract The lung alveolar epithelium is exposed to the environment and pathogens and is thus highly susceptible to injury. Repair of the alveolar epithelium requires the activation of alveolar epithelial stem cells by signals from their surrounding niche. Significantly, the role of lung microvascular endothelial cells (LMVECs) in mediating this repair is poorly understood. In this proposal we address this gap in knowledge by focusing on a novel mechanism of bioactive lipid mediated interaction between lung microvascular endothelial cells (LMVEC) and alveoli epithelial cells (AEC) in the reparative niche. LMVECs account for >40% of total lung cells. They are juxtaposed to AECs (both alveolar type I cells (AT1) and type II cells (AT2)) and play essential roles in regulating their repair, although the underlining mechanisms remain unclear. AT1s have a thin and extended squamous shape, occupy > 95% of the alveoli surface area and mediate O2–CO2 exchange. AT2 occupy only 5% of the surface area, but play multiples roles, including producing surfactant and, importantly, acting as adult tissue stem cells to repair injured alveoli. Studies, including ours, have shown that while AT2s are normally quiescent, they can respond to signals released by surrounding niches and initiate a repair program by differentiating into AT1. However, the signals that regulate AT2 stem cell function(s) remain unclear. Recent studies suggest that AT1 also exhibit a certain degree of plasticity, but it is almost completely unknown whether and how AT1s participate in lung repair after injury. In preliminary studies, we generated a mouse model with endothelial cell (EC)-specific deletion of sphingosine kinase 1 (Sphk1), the enzyme responsible for spinhgosine-1-phosphate (S1P) production. These mutant mice manifest a significantly defective repair of AECs in the standardized Pseudomonas aeruginosa bacterial lung injury model. We further showed that S1P functions through its receptor S1PR2 expressed in AT2, leading to nuclear translocation of the transcriptional regulator Yes-Associated Protein (YAP), which mediates the differentiation of AT2 to AT1 and repair of injured alveoli. Furthermore, we observed that in response to S1P, AT1s undergo substantive alteration which likely contribute to the repair process. These fundamental observations led to our central hypothesis: that LMVECs constitute a niche that, when activated by alveolar injury, releases the bioactive lipid factor, S1P, which acts via S1PRs on both AT2 and AT1 to promote their reparative capacity required for the restoration of alveolar epithelium. To test this hypothesis, we propose three specific aims: Aim 1: To determine S1P-mediated interactions between the EC niche and AEC required for lung repair. Aim2: To define the functional significance of S1P-S1PR2-YAP signaling axis in regulating AT2 to AT1 transition and mediating alveolar repair. Aim 3: To test the hypothesis that S1P induces AT1 alteration leading to alveolar repair. This research program will throw new light on the fundamental mechanisms driving lung repair after injury, with the long term potential for innovative therapeutic approaches.