Abstract：
Reciprocal interactions between alveolar fibroblasts and epithelial cells are crucial for lung homeostasis, injury repair, and fibrogenesis, but underlying mechanisms remain unclear. To investigate, we administered the fibroblast-selective TGFβ1 signaling inhibitor, epigallocatechin gallate (EGCG), to Interstitial Lung Disease (ILD) patients undergoing diagnostic lung biopsy and conducted single-cell RNA sequencing on spare tissue. Biopsies from untreated patients showed higher fibroblast TGFβ1 signaling compared to non-disease donor or end-stage ILD tissues. In vivo, EGCG downregulated TGFβ1 signaling and several pro-inflammatory and stress pathways in biopsy samples. Notably, EGCG reduced fibroblast secreted frizzle-like receptor protein 2 (sFRP2), an unrecognized TGFβ1 fibroblast target gene induced near type II alveolar epithelial cells (AEC2s) in situ. Using AEC2-fibroblast coculture organoids and precision cut lung slices (PCLS) from non-diseased donors, we found TGFβ1 signaling promotes a spread AEC2 KRT17+ basaloid state, whereupon sFRP2 then activates a mature Krt5+ basal cell program. Wnt-receptor Frizzled 5 (Fzd5) expression and downstream calcineurin signaling were required for sFRP2-induced nuclear NFATc3 accumulation and KRT5 expression. These findings highlight stage-specific TGFβ1 signaling in ILD, the therapeutic potential of EGCG in reducing IPF-related transcriptional changes, and identify TGFβ1-non-canonical Wnt pathway crosstalk via sFRP2 as a novel mechanism for dysfunctional epithelial signaling in Idiopathic Pulmonary Fibrosis/ILD.
摘要：
肺泡成纤维细胞和上皮细胞之间的相互作用对肺稳态至关重要。损伤修复,和纤维发生，但潜在的机制仍不清楚。为了调查，我们给予成纤维细胞选择性TGFβ1信号抑制剂，表没食子儿茶素没食子酸酯（EGCG），间质性肺病（ILD）患者接受诊断性肺活检，并对备用组织进行单细胞RNA测序。与非疾病供体或终末期ILD组织相比，未治疗患者的活检显示出更高的成纤维细胞TGFβ1信号传导。在体内,EGCG下调活检样品中的TGFβ1信号传导和几种促炎和应激途径。值得注意的是,EGCG减少成纤维细胞分泌的卷曲样受体蛋白2（sFRP2），未识别的TGFβ1成纤维细胞靶基因原位诱导II型肺泡上皮细胞（AEC2s）附近。使用AEC2-成纤维细胞共培养的类器官和来自非患病供体的精确切割的肺切片（PCLS），我们发现TGFβ1信号传导促进了AEC2KRT17+基底细胞状态的扩散，然后sFRP2激活成熟的Krt5+基础细胞程序。sFRP2诱导的核NFATc3积累和KRT5表达需要Wnt受体卷曲蛋白5(Fzd5)表达和下游钙调磷酸酶信号传导。这些发现强调了ILD中的阶段特异性TGFβ1信号传导，EGCG在减少IPF相关转录变化方面的治疗潜力，并通过sFRP2鉴定TGFβ1-非经典Wnt通路串扰是特发性肺纤维化/ILD中功能失调的上皮信号传导的新机制。
