Mechanistic evaluation of a novel Wnt-responsive adult alveolar epithelial progenitor population during regeneration after diffuse alveolar damage

项目总结 哺乳动物肺的肺泡区是一个复杂的、结构精确的组织，是初级肺发育所必需的 呼吸系统、气体交换和组织氧合的功能。对肺泡上皮的损伤 在包括急性呼吸窘迫综合征(ARDS)在内的人类肺部疾病中发挥核心作用 流行的、影响很大的临床疾病，影响高达5%的机械通气患者 发达国家。ARDS的死亡率接近40%，ARDS幸存者的恢复是 艰苦，在接下来的5年或更长时间内继续承受多系统残疾的沉重负担 住院治疗。关键是，虽然许多ARDS幸存者恢复了肺功能，但仍有一部分患者出现 持续性肺功能异常，肺部疤痕形成的影像证据，以及肺部症状 甚至在急性呼吸窘迫综合征之后的几年。到目前为止，还没有关于指导ARDS恢复的机制的数据。 制定策略以改善ARDS后的恢复和促进肺再生的关键要求是 了解肺中的祖细胞种群及其在复杂的地区化性质中的具体作用。 受伤后的再生。我们发现了一组独特的对Wnt有反应的AT2细胞。这些单元格包括 不同的祖细胞亚系，我们称之为AEP(Axin2+肺泡上皮祖细胞)。AEP有能力 在体内和体外产生AT1和AT2细胞的人，在肺泡动态期稳定9个月， 弥漫性肺泡损伤后迅速扩张，再生大部分肺泡上皮。 重要的是，我们已经确定了一种富含AEP的细胞表面受体，它可以标记小鼠和 人类肺，这使得人类AEP作为祖细胞血统的功能验证成为可能。 直接比较来自老鼠和人类AEP的能力提供了对可能的 AEP功能所需的上游信号和下游效应器。这项提议的科学目标是 是直接评估几个这样的候选因子在肺AEP生物学中的需求和作用 再生，特别强调Wnt和成纤维细胞生长因子信号在促进AEP中的组合作用 功能。该提案的目的是1)定义在AEP生物学中对Wnt信号的要求 2)确定FGFR2信号和ETS转录因子在AEP中的作用。 这项提议的另一个关键目标是提供一个有组织的、有重点的培训计划，以便 首席研究员将开发先进的再生生物学研究技术 并允许向独立的成功过渡。

PROJECT SUMMARY The alveolar region of the mammalian lung is a complex, precisely structured tissue required for the primary functions of the respiratory system, gas exchange and tissue oxygenation. Damage to the alveolar epithelium plays a central role in human lung diseases including Acute Respiratory Distress Syndrome (ARDS), a prevalent, high impact clinical disorder that affects up to 5% of mechanically ventilated patients in the developed world. The mortality rate of ARDS approaches 40%, and the recovery for ARDS survivors is arduous, with a substantial burden of multi-system disability continuing 5 or more years following hospitalization. Critically, while many ARDS survivors recover lung function, a subset of patients develops persistently abnormal pulmonary function, imaging evidence of pulmonary scarring, and pulmonary symptoms even years after ARDS. To date, no data exists regarding the mechanisms that guide ARDS recovery. A key requirement for developing strategies to improve recovery after ARDS and promote lung regeneration is to understand progenitor populations in the lung, and their specific roles in the complex, regionalized nature of regeneration after injury. We have found a distinct group of Wnt-responsive AT2 cells. These cells comprise a distinct progenitor sublineage, which we call AEPs (Axin2+ Alveolar Epithelial Progenitors). AEPs are capable of generating both AT1 and AT2 cells in vivo and in vitro, are stable for 9 months during alveolar homeostasis, and expand rapidly to regenerate a majority of the alveolar epithelium after diffuse alveolar damage. Importantly, we have identified an AEP-enriched cell surface receptor that marks AEPs in both mouse and human lung, which has allowed functional validation of human AEPs as a progenitor lineage. The ability to directly compare AEPs from mouse and human has provided specific insight into possible upstream signals and downstream effectors required for AEP function. The scientific objective of this proposal is to directly evaluate the requirement and role for several such candidate factors in AEP biology during lung regeneration, with a specific emphasis on the combinatorial role of Wnt and Fgf signals in promoting AEP function. The Aims of the proposal are 1) Define the requirement for Wnt signaling in AEP biology during alveolar regeneration and 2) Determine the function of FGFR2 signaling and ETS transcription factors in AEPs. The other crucial objective of this proposal is to provide for a structured, focused training plan to allow the primary investigator to develop an advanced armamentarium of research techniques in regenerative biology and allow for a successful transition to independence.