Probing the mechanisms of epithelial barrier restoration in the distal lung

项目摘要 呼吸系统疾病，如急性呼吸窘迫综合征、特发性肺纤维化和慢性 阻塞性肺疾病在全球范围内产生显著的发病率和死亡率。尽管每个 虽然这些疾病是不同的，但它们都有一个共同点，即无法维持或修复肺泡。细牙槽骨 1型（AT 1）细胞覆盖超过95%的肺泡气体交换表面，并散布着 单层上皮中的立方形、分泌表面活性剂的肺泡2型（AT 2）细胞。AT 2细胞的次要亚群 作为主要的干细胞，在整个生命周期中更新肺泡。它们的功能是再生 上皮损伤后，有一些证据表明，他们的功能障碍的基础慢性形式的 呼吸道疾病建立对AT2干细胞生物学的深入理解可能会导致新的 药理学和基于细胞的疗法来治疗这些疾病。尽管最近在肺部疾病方面取得了重大进展， 肺泡干细胞生物学、AT2干细胞的生理行为以及 规范这种行为已被证明是具有挑战性的定义。我们开发了一个老鼠遗传系统来研究 在体内动态激活AT2干细胞，其采用使用白喉毒素的AT1细胞的靶向消融。 正如预期的那样，我们发现AT2细胞的自我复制在AT1细胞消融后被迅速诱导，然而， 在此之前是立即和广泛的AT2到AT1转分化。我们的研究结果显示， （非干）AT2细胞群在快速再生肺泡屏障中的未被重视的作用。我们 假设肺泡修复涉及两步机制，其中AT 2细胞直接转分化 进入AT1细胞最初恢复屏障完整性，随后是AT2干细胞的自我复制。拟议 该项目旨在进一步探索这种超快速恢复的机制和生理重要性， 肺泡气体交换和屏障表面。我们的研究结果将有助于建立一个上皮细胞的基础模型， 再生，并将告知在治疗中操纵AT2干细胞的实用策略 应用.

PROJECT SUMMARY Respiratory diseases like the Acute Respiratory Distress Syndrome, Idiopathic Pulmonary Fibrosis and Chronic Obstructive Pulmonary Disease produce significant morbidity and mortality worldwide. While each of these diseases are distinct, they all have in common a failure to maintain or repair lung alveoli. Thin, delicate alveolar type 1 (AT1) cells encompass greater than 95 percent of the alveolar gas exchange surface, interspersed with cuboidal, surfactant-secreting alveolar type 2 (AT2) cells in a monolayer epithelium. A minor subset of AT2 cells serve as the principal stem cells that renew alveoli throughout the lifetime. They function to regenerate the epithelium after injury, and there is some evidence to suggest that their disfunction underlies chronic forms of respiratory disease. Establishing a deep understanding of the biology of AT2 stem cells may lead to new pharmacological and cell-based therapies to treat these diseases. Despite recent, significant advances in lung alveolar stem cell biology, the physiological behavior of AT2 stem cells and the molecular mechanisms that regulate this behavior have proven to be challenging to define. We developed a mouse genetic system to study dynamic activation of AT2 stem cells in vivo that employs targeted ablation of AT1 cells using Diphtheria toxin. As expected, we found that AT2 cell self-duplication was rapidly induced upon AT1 cell ablation, however, this was preceded by immediate and widespread AT2-to-AT1 transdifferentiation. Our results reveal a previously unappreciated role for a (non-stem) AT2 cell population in rapidly regenerating the alveolar barrier. We hypothesize that alveolar repair involves a two-step mechanism in which direct transdifferentiation of AT2 cells into AT1 cells initially restores barrier integrity and is followed by self-duplication of AT2 stem cells. The proposed project aims to further probe the mechanisms and physiological importance of this ultra-rapid restoration of the alveolar gas exchange and barrier surface. Our findings will help to establish a foundational model of epithelial regeneration in lung alveoli, and will inform practical strategies for manipulating AT2 stem cells in therapeutic applications.