Single-cell RNA sequencing of peripheral blood mononuclear cells in patients with acutely decompensated cirrhosis reveals a specific monocyte subset associated with an increased risk of progression to ACLF

Background & AimsPatients with acute decompensation (AD) of cirrhosis are at a high risk of developing acute-on-chronic liver failure (ACLF), a syndrome characterized by multi-organ failure and high short-term mortality. Prospective studies addressing the cellular mechanisms that drive the transition from AD to ACLF are lacking. In this study, we aimed to determine whether peripheral immune cell subsets at hospital admission predict the progression from AD to ACLF and to delineate underlying molecular mechanisms. Approach & ResultsWe prospectively enrolled 63 patients with AD and 15 healthy donors across five European centers, with a 90-day follow-up. Single-cell RNA sequencing was performed on peripheral blood mononuclear cells (PBMCs) from 16 patients with distinct trajectories and 4 controls. Progression to ACLF was associated with expansion of classical monocytes, particularly subcluster "C2", which specifically displayed impaired energy metabolism with reduced oxidative phosphorylation. Genes encoding respiratory chain Complex IV were markedly downregulated. A C2-derived gene signature was enriched in two large international whole-blood cohorts (PREDICT, n=689; ACLARA, n=521), particularly in patients with bacterial infections, those developing ACLF, and non-survivors. Functional validation by respirometry in an independent AD cohort confirmed declining monocyte Complex IV-dependent oxygen consumption in patients with pre-ACLF. ConclusionsWe identified and validated a distinct monocyte subpopulation with defective energy metabolism in patients with AD with poor outcomes, suggesting a mechanistic link to ACLF development.