Single-cell landscape of neutrophil activation in primary sclerosing cholangitis.

Primary sclerosing cholangitis (PSC) is a chronic autoimmune cholestatic liver disease characterized by progressive inflammation and fibrosis, but the role of neutrophils in PSC remains poorly understood. To define neutrophil states in the PSC liver microenvironment, we performed single-cell RNA sequencing of leukocytes isolated from liver perfusate obtained from healthy donor grafts and explanted PSC livers. We identified a marked expansion of transcriptionally diverse neutrophil subclusters in PSC liver perfusate. Importantly, PSC livers were enriched for four neutrophil subclusters: RHOB-high, immediate early gene-high, heat shock protein-high, and CXCL8-high liver neutrophil-like subclusters. These PSC-associated neutrophil subclusters showed increased activity of the TNF and IL-17 signaling pathways, consistent with current views of PSC pathogenesis. They also displayed activation of inflammatory transcriptional regulators, including CEBPB, JUN, FOS, and RELA. Pseudotime analysis suggested that RHOB and immediate early gene subsets were derived from immature neutrophils, whereas liver neutrophil-like and heat shock protein-high subsets exhibited more mature and tissue-adapted features. Together, these data reveal previously unrecognized heterogeneity of liver neutrophils in PSC and identify inflammatory neutrophil programs that may contribute to sustained hepatic inflammation and represent potential therapeutic targets.