The rapid expansion of the elderly population has led to the recent epidemic of age-related diseases, including increased incidence and mortality of chronic lung diseases, such as Idiopathic Pulmonary Fibrosis (IPF). Cellular senescence is a major hallmark of aging and has a higher occurrence in IPF. The lung epithelium represents a major site of tissue injury, cellular senescence and aberrant activity of developmental pathways such as the WNT/β-catenin pathway in IPF. The potential impact of WNT/β-catenin signaling on alveolar epithelial senescence in general as well as in IPF, however, remains elusive. Here, we characterized alveolar epithelial cells of aged mice and assessed the contribution of chronic WNT/β-catenin signaling on alveolar epithelial type (AT) II cell senescence. Whole lungs from old (16-24 months) versus young (3 months) mice had relatively less epithelial (EpCAM+) but more inflammatory (CD45+) cells, as assessed by flow cytometry. Compared to young ATII cells, old ATII cells showed decreased expression of the ATII cell marker Surfactant Protein C along with increased expression of the ATI cell marker Hopx, accompanied by increased WNT/β-catenin activity. Notably, when placed in an organoid assay, old ATII cells exhibited decreased progenitor cell potential. Chronic canonical WNT/β-catenin activation for up to 7 days in primary ATII cells as well as alveolar epithelial cell lines induced a robust cellular senescence, whereas the non-canonical ligand WNT5A was not able to induce cellular senescence. Moreover, chronic WNT3A treatment of precision-cut lung slices (PCLS) further confirmed ATII cell senescence. Simultaneously, chronic but not acute WNT/β-catenin activation induced a profibrotic state with increased expression of the impaired ATII cell marker Keratin 8. These results suggest that chronic WNT/β-catenin activity in the IPF lung contributes to increased ATII cell senescence and reprogramming. In the fibrotic environment, WNT/β-catenin signaling thus might lead to further progenitor cell dysfunction and impaired lung repair.

中文翻译：

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慢性 WNT/β-catenin 信号传导诱导肺上皮细胞中的细胞衰老。

老年人口的快速扩张导致近期与年龄有关的疾病流行，包括特发性肺纤维化（IPF）等慢性肺病的发病率和死亡率增加。细胞衰老是衰老的主要标志，在 IPF 中发生率更高。肺上皮代表组织损伤、细胞衰老和发育通路异常活动的主要部位，例如 IPF 中的 WNT/β-连环蛋白通路。然而，WNT/β-连环蛋白信号传导对肺泡上皮衰老以及 IPF 的潜在影响仍然难以捉摸。在这里，我们对老年小鼠的肺泡上皮细胞进行了表征，并评估了慢性 WNT/β-连环蛋白信号对肺泡上皮类型 (AT) II 细胞衰老的贡献。通过流式细胞术评估，老年（16-24 个月）与年轻（3 个月）小鼠的全肺上皮细胞 (EpCAM+) 相对较少，但炎症细胞 (CD45+) 较多。与年轻的 ATII 细胞相比，旧的 ATII 细胞显示 ATII 细胞标志物表面活性剂蛋白 C 的表达降低，同时 ATI 细胞标志物 Hopx 的表达增加，同时 WNT/β-连环蛋白活性增加。值得注意的是，当置于类器官试验中时，旧的 ATII 细胞表现出降低的祖细胞潜力。在原代 ATII 细胞和肺泡上皮细胞系中长达 7 天的慢性经典 WNT/β-连环蛋白活化诱导了强烈的细胞衰老，而非经典配体 WNT5A 不能诱导细胞衰老。而且，精密切割肺切片 (PCLS) 的慢性 WNT3A 治疗进一步证实了 ATII 细胞衰老。同时，慢性但非急性 WNT/β-catenin 激活诱导促纤维化状态，受损 ATII 细胞标志物角蛋白 8 的表达增加。这些结果表明，IPF 肺中的慢性 WNT/β-catenin 活性有助于增加 ATII 细胞衰老和重新编程。在纤维化环境中，WNT/β-连环蛋白信号可能导致进一步的祖细胞功能障碍和肺修复受损。