LAUSR

BACKGROUND AIMS The progression of chronic liver diseases towards liver cirrhosis is accompanied by drastic tissue changes. This study combines elaborate transcriptomic and histological methods aiming at spatially resolving the hepatic immune microenvironment in non-alcoholic fatty liver disease (NAFLD) (including non-alcoholic steatohepatitis [NASH)]), primary sclerosing cholangitis (PSC), primary biliary cholangitis (PBC), and severe alcoholic hepatitis (AH). APPROACH RESULTS Human liver samples were subjected to RNA-sequencing (n=225), and imaging cytometry (n=99) across three independent patient cohorts. Liver samples from AH and PBC patients were used for comparison. Myeloid populations were further characterized in corresponding mouse models. Imaging, clinical and phenotypical data were combined for multidimensional analysis. NAFLD/NASH and PSC disease stages were associated with loss of parenchymal areas, increased ductular cell accumulation, and infiltration of immune cells. NASH patients predominantly exhibited myeloid cell accumulation, whereas PSC patients additionally had pronounced lymphoid cell responses. Correlating to disease stage, both etiologies displayed intense IBA1 + CD16 low CD163 low macrophage aggregation in non-parenchymal areas, with a distinct spatial proximity to ductular cells. Mouse models revealed that disease-associated IBA1 + hepatic macrophages originated from bone marrow-derived monocytes. Using an unbiased, machine learning-based algorithm, IBA1 in combination with hepatocyte and ductular cell immunostaining predicted advanced cirrhosis in human NASH, PSC, and AH. CONCLUSIONS Loss of hepatocytes and increased ductular reaction are tightly associated with monocyte-derived macrophage accumulation and represent the most prominent common immunological feature revealing the progression of NAFLD, PSC, PBC and AH, suggesting IBA1 + CD163 low macrophages are key pathogenic drivers of human liver disease progression across diverse etiologies.