Li Yinzhen, Zhou Chen, Sun Jiaxing, Wang Enhao, Wang Chunmei, Liu Xuan, Zhou Xiaohui, Bai Jianwen
Department of Emergency Medicine and Critical Care, School of Medicine, Shanghai East Hospital, Tongji University, Shanghai, 200092, China.
Research Center for Translational Medicine, School of Medicine, Shanghai East Hospital, Tongji University, Shanghai, 200092, China.
Respir Res. 2025 May 16;26(1):188. doi: 10.1186/s12931-025-03264-z.
Idiopathic pulmonary fibrosis (IPF) is a devastating age-related disease with unknown causes and limited effective treatment. Dysregulation of Alveolar Type 2 (AT2) cells facilitates the initiation of IPF. While differentiation of AT2 into AT1 is necessary for restoring alveolar epithelium. Delta-like non-canonical Notch ligand 1 (DLK1) is a paternally imprinted gene that controls stem cell differentiation. However, the role of DLK1 on AT2 during lung fibrosis remains unclear.
Lung specimens from 11 patients with IPF or contemporaneous non-IPF controls were collected to determine DLK1 expression. The murine model of bleomycin (BLM) -induced pulmonary fibrosis and cell models of transforming growth factor-beta (TGF-β)-treated A549, MRC5 or primary lung fibroblasts (PLFs) were established. Epithelial DLK1 knockdown mice were constructed by an alveolar epithelial -specific adeno-associated virus (AAV) 6 vector system. Besides, primary AT2 cells were isolated from SPC-EGFP mice and cultured in 2D and 3D organoids.
In the present study, we found that DLK1, predominantly expressed in AT2 cells, was upregulated in both IPF lungs and the murine fibrotic lung induced by BLM. AAV-mediated epithelial-specific knockdown of DLK1 promoted the proliferation and differentiation of AT2 into AT1 and alleviated the established lung fibrosis in murine BLM-induced models. In addition, recombinant DLK1 inhibited the renewal of AT2 and aggravated TGF-β-induced fibrosis in vitro, which can be rescued by si-DLK1 intervention. Mechanically, conditional knockdown of DLK1 upregulated TTF-1, a transcriptional factor that controls AT2 differentiation via CLDN6.
DLK1 inhibition regulates AT2 differentiation and contributes to the mitigation of established fibrosis via TTF-1/CLDN6 pathway, which suggests that DLK1 may be a therapeutic target for IPF.
特发性肺纤维化（IPF）是一种与年龄相关的毁灭性疾病，病因不明且有效治疗方法有限。2型肺泡上皮细胞（AT2）的失调促进了IPF的发生。而AT2向AT1的分化对于恢复肺泡上皮至关重要。类Delta非经典Notch配体1（DLK1）是一个父系印记基因，控制干细胞分化。然而，DLK1在肺纤维化过程中对AT2的作用仍不清楚。
收集11例IPF患者或同期非IPF对照者的肺组织标本，以确定DLK1的表达。建立博来霉素（BLM）诱导的肺纤维化小鼠模型以及转化生长因子-β（TGF-β）处理的A549、MRC5或原代肺成纤维细胞（PLF）的细胞模型。通过肺泡上皮特异性腺相关病毒（AAV）6载体系统构建上皮DLK1基因敲低小鼠。此外，从SPC-EGFP小鼠中分离出原代AT2细胞，并在二维和三维类器官中培养。
在本研究中，我们发现主要在AT2细胞中表达的DLK1在IPF肺组织以及BLM诱导的小鼠纤维化肺组织中均上调。AAV介导的上皮特异性敲低DLK1促进了AT2的增殖和向AT1的分化，并减轻了小鼠BLM诱导模型中已形成的肺纤维化。此外，重组DLK1在体外抑制了AT2的更新并加重了TGF-β诱导的纤维化，而si-DLK1干预可挽救这种情况。机制上，条件性敲低DLK1上调了甲状腺转录因子-1（TTF-1），这是一种通过紧密连接蛋白6（CLDN6）控制AT2分化的转录因子。
抑制DLK1可调节AT2分化，并通过TTF-1/CLDN6途径有助于减轻已形成的纤维化，这表明DLK1可能是IPF的一个治疗靶点。
