Single-cell landscape of alcohol-related hepatitis reveals serum amyloid a hepatocytes as key drivers of disease pathogenesis

BACKGROUND AIMS: Alcohol-related hepatitis (AH) is a severe form of alcohol-related liver disease (ALD). The cellular subpopulations that contribute to AH and dynamics remain poorly understood. This study aimed to identify key cellular subpopulations and their interactions in AH and explore key mechanisms contributing to disease pathogenesis. APPROACH RESULTS: Single-cell RNA sequencing was performed starting from liver biopsies from patients with AH, early-stage ALD, and healthy individuals. Immunofluorescence was used to validate protein expression of selected markers. Liver biopsy-derived organoids were generated and exposed to a conditioned medium recapitulating AH (AH-medium) to assess serum amyloid A (SAA) secretion by ELISA. Circulating SAA levels were measured in plasma samples obtained from patients at different stages of ALD. Our analysis revealed an atlas of several cell subpopulations of AH, including hepatocytes expressing SAA, scar-associated (SA) endothelial cells, Fibulin-3+ mesenchymal cells, SA-macrophages expressing MMP19, activated CD4+ and stressed/effector CD8+ T cell subsets, and hyperactivated neutrophils expressing FPR2. Cell-communication analysis predicted a strong SAA-FPR2 interaction between hepatocyte and neutrophil subpopulations in AH. We confirmed that AH-hepatocytes secreted SAA in organoid cultures after stimulation with AH-medium. We also found out that circulating SAA levels were elevated in AH and were associated with reduced survival. CONCLUSIONS: The SAA-FPR2 pathway emerges as a potential mediator of inflammation in AH, offering potential therapeutic targets for this severe disease. This study provides new insights into the cellular heterogeneity and dynamics in ALD progression, dissecting AH at a single-cell level.