Abstract Background Intestinal fibrosis, a major challenge in Crohn’s disease (CD), that frequently necessitates surgery due to a lack of effective medical treatments. This study aimed to explore new therapeutic targets for intestinal fibrosis in CD. Methods The single-cell RNA-seq (scRNA-seq) data of full-thickness CD tissue obtained from Prof. Rieder was obtained and reanalyzed. Surgical specimens from stenotic and non-stenotic intestinal sections in CD patients were collected. Bone marrow-derived macrophages (BMDMs) were isolated and stimulated with LPS (100 ng/mL) to induce a S100a8/a9hi phenotype. Small interfering RNA (siRNA) was transfected into BMDM for S100a9 knockdown. An adoptative transfer model of S100A8/A9hi macrophage was established in wild type (WT) mice with dextran sulfate sodium (DSS) insult. Proteomic analysis was performed to elucidate the underlying pro-fibrotic mediators from S100A8/A9hi macrophage. Results scRNA-seq analysis identified a pro-fibrotic S100A8/A9hi macrophage subset. Adoptive transfer of S100a8/a9hi BMDM exacerbated intestinal fibrosis in DSS-induced colitis mice. Proteomic analysis identified mCCL6 as the key pro-fibrotic mediator from S100A8/A9hi macrophage responsible for regulating fibroblasts by CCR1. The CCL6-neutralizing antibody relieved established intestinal fibrosis in chronic DSS murine colitis model. Consistently, hCCL15, the human protein ortholog of mCCL6, exerted comparable pro-fibrotic effects on fibroblasts through CCR1 engagement. Mechanistically, S100A8/A9hi macrophage mediates the generation of mCCL6 via STAT3 activation. Paquinimod, an inhibitor of S100A8/A9, significantly ameliorated fibrosis in colitic mice. Conclusion Our findings revealed that targeting S100A8/A9hi macrophage may be a therapeutic strategy against intestinal fibrosis in CD. Conflict of interest: Ms. Wang, Shu: No conflict of interest Zhao, Xiaojing: No conflict of interest Zhang, Hongjie: No conflict of interest
Wang et al. (Thu,) studied this question.