Fig 1: Macrophage-derived FTH1 binds fibroblast SCARA5 to inhibit fibrosis.A. Re-clustering of fibroblasts from single-cell RNA-seq data identifies distinct subpopulations in human BAS granulation tissue. B. Pseudotime trajectory analysis reveals fibroblast differentiation converging on pro-fibrotic Cluster 2. C. CellChat interaction analysis predicts FTH1 (from ACOD1+ macrophages) binding to SCARA5 (on Cluster 2 fibroblasts) as the top ligand-receptor pair. D. Representative immunofluorescence images of FTH1(green), SCARA5(yellow) and Vimentin (red) in normal trachea group and granulation group. Scale bars indicate 50 μm and 20 μm. E. Co-immunoprecipitation (Co-IP) confirms FTH1 binding to SCARA5 in fibroblasts co-cultured with LPS+4-OI-treated macrophages. F,G. Representative tracheal immunofluorescence images of FTH1 (green), GPX4(yellow), SCARA5(red) and VIMENTIN(pink) in mouse trachea and quantitative of mean fluorescence of FTH1 and GPX4 in the control, BAS and BAS+4-OI group(n = 3 mice per group). Scale bars indicate 200 μm and 50 μm. H. Schematic diagram of the experimental design for 4-OI and Anti-SCARA5 treatment. I,J. Representative immunofluorescence images and mean fluorescence intensity of αSMA (red) and COL1(green) in four group: Control, BAS,BAS+4-OI,BAS+4-OI + Anti-SCARA5 (n = 3 mice per group). Scale bars indicate 200 μm and 50 μm. Data are presented as the mean ± SEM. One-way ANOVA analysis followed by Tukey post hoc multi-comparison test was used in G, J.