Endothelial c-Maf protects against liver fibrosis by regulating chromatin accessibility to suppress pathogenic microvascular cell subsets

Liver sinusoidal endothelial cells (LSEC) are highly specialized within the hepatic vascular niche, controlling liver function and disease pathogenesis by angiocrine signaling. Recently, we identified GATA4 as a major transcription factor controlling LSEC development and protecting against liver fibrosis. As the transcription factor c-Maf was strongly downregulated in Gata4-deficient LSEC, we hypothesized that c-Maf might be an important downstream effector of GATA4 in LSEC differentiation and liver fibrogenesis. Clec4g-iCre/Maffl/fl mice (MafLSEC-KO) mice with LSEC-specific Maf deficiency were generated and liver tissue was analyzed by histology, immunofluorescence, and in situ-hybridization at the age of three months. LSECs were isolated for RNA-, ATAC-seq, and single-cell RNA-seq (scRNA-seq) analysis. The expression of MAF and its targets were analyzed in published human scRNA-seq data. Endothelial Maf deficiency resulted in perisinusoidal liver fibrosis without affecting metabolic liver zonation, accompanied by a switch from sinusoidal to continuous endothelial differentiation. Furthermore, endothelial Maf deficiency caused hepatic endothelial proliferation and expression of profibrotic angiocrine factors such as Pdgfb, Igfbp5, Sparcl-1, and Flrt2. scRNA-seq revealed replacement of zonated LSEC subpopulations by capillarized, proliferative, sprouting and secretory endothelial cell subsets promoting liver fibrogenesis and angiogenesis. This fundamental dysregulation of LSEC gene expression and differentiation was caused by changes in chromatin accessibility and transcription factor network alterations at promoter and enhancer regions following loss of Maf. Notably, endothelial MAF expression was also significantly reduced in human liver cirrhosis patients. Hepatic endothelial c-Maf protects against metabolic dysfunction-associated steatohepatitis-like liver fibrosis and regulates endothelial differentiation and zonation by controlling chromatin opening. Notably, our findings may open up new avenues to develop angiotargeted strategies for hepatic disease prevention and liver repair.