Single-cell RNA Sequencing Reveals the Heterogeneity of Monocyte-derived Macrophages in Liver of Metabolic Dysfunction-associated Steatotic Liver Disease

Monocyte-derived macrophages (MoMFs) orchestrate inflammation and fibrogenesis in metabolic dysfunction-associated steatotic liver disease (MASLD). However, current therapeutic strategies targeting macrophage-mediated inflammation have shown limited clinical efficacy in MASLD. Using single-cell RNA sequencing (scRNA-seq) analysis of liver-infiltrating MoMFs from MASLD mouse models, we identified seven distinct clusters (c0-c6) with unique molecular signatures. Among these, the predominant CD14+CCR2+ (c0) showed multifaceted functions in fibrosis, lipid phagocytosis, and antigen presentation beyond inflammation. We identified two distinct clusters, CCR3+ (c3) and CCR7+ (c4) MoMFs, which exhibited enhanced pro-inflammatory/oxidative stress activity and specialized antigen-presenting capacity, respectively. Pseudotime analysis revealed that the resident basal cluster (c1) could give rise to both CD14+CCR2+ (c0) and CCR7+ (c4) MoMFs during disease progression, challenging the traditional view that CCR2+ MoMFs exclusively originate from bone marrow. Notably, these MoMFs subsets and their dynamic changes during disease progression were conserved between mouse models and human MASLD samples. These findings expand our understanding of MoMFs heterogeneity and suggest new therapeutic strategies for MASLD.