[Mechanism study of S100A4 influencing pulmonary fibrosis through the lncRNA MEG3/miR-147 pathway]

Objective: To investigate the effect of S100A4 on pulmonary fibrosis and elucidate its underlying mechanism involving the long non-coding RNA MEG3 (lncRNA MEG3) /microRNA-147 (miR-147) pathway. Methods: In November 2024, a model of S100A4-overexpressing mouse alveolar macrophages (MH-S cells) was established. A Transwell co-culture system was set up with mouse lung fibroblasts. The control group consisted of MH-S cells transfected with an empty plasmid co-cultured with mouse lung fibroblasts, while the transfection group consisted of S100A4-overexpressing MH-S cells co-cultured with mouse lung fibroblasts. The S100A4 level in the supernatant was detected by western blotting. The proliferation activity of co-cultured mouse lung fibroblasts was measured by CCK-8 assay. Cell cycle distribution was analyzed by PI staining flow cytometry, and the apoptosis rate was determined by Annexin V-FITC/PI double staining flow cytometry. Cell migration ability was assessed using Transwell chambers. Western blotting was employed to detect S100A4 expression in MH-S cells, as well as the expressions of Janus kinase 2 (JAK2), phosphorylated JAK2 (p-JAK2), signal transducer and activator of transcription 3 (STAT3), and phosphorylated STAT3 (p-STAT3) in mouse lung fibroblasts. Quantitative real time polymerase chain reaction (qPCR) was used to measure the levels of LncRNA MEG3, miR-147, and α-smooth muscle actin (α-SMA) mRNA. Immunofluorescence was used to detect α-SMA protein expression. The levels of transforming growth factor-β1 (TGF-β1) and tumor necrosis factor-α (TNF-α) were measured by enzyme-linked immunosorbent assay (ELISA). All results were normally distributed measurement data, and comparisons between groups were performed using one way analysis of variance (ANOVA) . Results: Compared with the control group, the transfection group exhibited a significantly increased S100A4 level in the supernatant. In mouse lung fibroblasts co-cultured with S100A4-overexpressing MH-S cells, proliferation activity was significantly enhanced, the apoptosis rate was significantly decreased, and the proportion in G2/M phase was increased, the ratios of p-JAK2/JAK2 and p-STAT3/STAT3, as well as S100A4 expression in MH-S cells, were significantly increased. The expression of α-SMA was also increased. lncRNA MEG3 and α-SMA mRNA levels were significantly elevated, while miR-147 was significantly decreased. Both TGF-β1 and TNF-α levels were significantly increased (all P<0.05) . Conclusion: S100A4 overexpression in macrophages upregulates LncRNA MEG3, which may act as a sponge for miR-147, leading to increased p-JAK2/JAK2 and p-STAT3/STAT3 ratios as well as elevated release of TGF-β1 and TNF-α. This activates the pulmonary inflammatory microenvironment and promotes lung fibroblast proliferation, thereby inducing pulmonary fibrosis.