Macrophage signaling associates with fibrogenic program activation in periductal fibroblasts in pediatric primary sclerosing cholangitis.

Primary sclerosing cholangitis (PSC) is a chronic, idiopathic cholestatic liver disease characterized by inflammation and fibrosis of the bile ducts, yet the cellular crosstalk driving periductal fibrosis remains poorly defined. This study applied a multiomics approach integrating spatial transcriptomics, RNA-Seq, and proteomics to characterize fibrotic periductal regions and their cell-cell communications. Macrophage subsets, including monocyte-derived macrophages and lipid-associated macrophage-like cells, colocalized with cholangiocytes, lymphocytes, and hepatic stellate cells (HSCs). Cell niche analysis identified periductal regions with elevated fibrotic signals, where cell-cell communication analysis revealed potential macrophage-HSC interactions involving 17 fibrotic driver genes in macrophages, including ITGB2, GRN, and CCL21, and 6 fibrotic effector genes in HSCs. In validation analyses, bulk RNA-Seq data showed higher driver and effector gene expression in PSC with established fibrosis compared with early-stage PSC or healthy controls. Plasma proteins encoded by macrophage driver genes were elevated in PSC and in patients with elevated (≥3.29 kPa) liver stiffness on MR elastography. Immunofluorescence and second harmonic generation imaging showed enrichment of CD68+/CD18+(ITGB2) macrophages in fibrotic regions of PSC liver biopsies. These findings revealed enrichment of monocyte-derived macrophages and lipid-associated macrophage-like cells in fibrotic regions and suggest that they likely contribute to fibrotic activation of nearby HSCs in PSC.