Single-cell transcriptomic landscape of intrahepatic B Cells in MASH.

To understand the heterogeneity of single-B cell responses to Metabolic Dysfunction-Associated Steatohepatitis (MASH), we performed Single-cell RNA sequencing (scRNA-seq) on single-B cells isolated from control and MCD-fed mice livers. Subsequent analyses included clustering, identification of differentially expressed genes (DEGs) and enrichment analysis. The expressions of high specific DEGs were validated using quantitative real-time PCR (qRT-PCR), immunofluorescence staining and function study. Four single-B cell clusters (3, 14, 16 and 20) were identified. The total number and proportion of B cells significantly decreased in MASH mice livers. In cluster 3, the decreasing Fcer2α+ mature B cells were supposed with anti-inflammatory role associated with B cell activation and differentiation of other immune cells in MASH. The DEGs (Fcer2α, Cd22, Cr2 and Fcmr) of cluster 3 were consistently downregulated in B cells cocultued with lipotoxic hepatocytes. And the portal area of livers contained fewer Fcer2α+ B cells in MASH patients and mice compared with controls. Fcer2α+ B cells attenuated lipotoxicity-driven inflammation by enhancing anti-inflammatory factor (IL-10, IL-35) secretion and inhibiting T cell inflammatory factor (IFN-γ, TNF-α, IL-17) production and proliferation. The other 3 clusters (14, 16 and 20) contained small numbers of single-B cell. Tnfrsf17+ plasmacytes (PCs) of cluster 14 were identified with the effect related to endoplasmic reticulum stress and N-Glycan biosynthesis. Klk1+ B cells of cluster 16 were implicated in regulating immune response in MASH. Apol7c+ B cells of cluster 20 participated in apoptosis, NF-κB, TNF and JAK-STAT signaling pathway in MASH. Thus, a subgroup of Fcer2α+ mature B cells, diminished in MASH, may exerted anti-inflammatory or immunosuppressive effects.