Alveoli are the gas-exchanging units of the lung and alveolar barrier is often a key battleground that encounters pathogens, allergens, and other insults from the environment. This is seen in the current COVID-19 pandemic, as alveolar epithelium is one of the major targets of SARS-COV-2, the virus that causes COVID-19. Thus, it is essential to understand the mechanisms to maintain the integrity of alveoli epithelium. Alveolar type II (AT2) cells behave as tissue stem cells that repair alveoli epithelium in steady-state replacement and after injury. However, not all AT2 cells are equal in their ability for self-renewal or differentiation. Through marker gene identification, lineage tracing, and single-cell RNA-sequencing (scRNA-seq), distinct subpopulations of AT2 cells have been identified that play the progenitor role in different context. The revelation of AT2 heterogeneity has brought new insights into the role of AT2 cells in various lung disease settings and potentiates the finding of more therapeutics targets. In this mini review, we discussed the recently identified subpopulations of AT2 cells and their functions under steady state, after injury and in pathological conditions.

中文翻译：

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肺稳态和修复中肺泡 II 型细胞的异质群。


肺泡是肺部的气体交换单位，肺泡屏障通常是遭遇病原体、过敏原和其他环境侵害的关键战场。这在当前的 COVID-19 大流行中就可见一斑，因为肺泡上皮是导致 COVID-19 的病毒 SARS-COV-2 的主要目标之一。因此，了解维持肺泡上皮完整性的机制至关重要。肺泡 II 型 (AT2) 细胞的行为类似于组织干细胞，在稳态替换和损伤后修复肺泡上皮。然而，并非所有 AT2 细胞的自我更新或分化能力都是相同的。通过标记基因鉴定、谱系追踪和单细胞 RNA 测序 (scRNA-seq)，已经鉴定出 AT2 细胞的不同亚群，它们在不同的背景下发挥祖细胞作用。 AT2 异质性的揭示使我们对 AT2 细胞在各种肺部疾病中的作用有了新的认识，并促进了更多治疗靶点的发现。在这篇小综述中，我们讨论了最近发现的 AT2 细胞亚群及其在稳态、损伤后和病理条件下的功能。