Comparative analysis of liver tissues from heahtly mice and mice suffering from cholangitis

The goal of the study was to compare the transcriptomic signature (by bulk RNA-sequencing) of hepatic tissues of mice either healthy/normal or affected with primary sclerosing cholangitis (PSC) or primary biliary cholangitis mouse (PBC) (Paillet et al, J Exp Med, 2021). Transcriptomic analyses revealed mostly convergent alterations in the gene expression patterns when PBC and PSC were compared to normal, age- and sex-matched controls. Gene Ontology (GO) term analyses of the modulated mRNAs revealed a significant enrichment of genes involved in inflammation, immune response and chemotaxis of different leukocyte subsets . The expression of genes listed under the GO terms “inflammation” and “neutrophil” was not significantly different (p>0.5, Student t-test) between PBC and PSC. In sharp contrast, genes listed under the GO terms “T cell” and “B cell” were significantly (p<0.05, Student t-test) upregulated in PBC compared to PSC livers. Deeper analysis of the aforementioned liver RNA-seq dataset indicated that several genes specifically involved in Th1 and Tc1 responses were upregulated in PBC livers with respect to controls and, in some cases also with respect to PSC. Especially, this applies to Tc1-related genes encoding the markers CD8a, CD274 (best known as PD-L1), UL16 binding protein 1 (ULBP1), IFNγ, G Protein-Coupled Receptor 18 (GPR18), the transcription factor suppressor of cytokine signaling 1 (SOCS1), and the cytotoxic protease granzyme B (GzmB) (Paillet et al, J Exp Med, 2021). Autoimmune primary biliary cholangitis (PBC) was induced in C57Bl/6 mice as described before: Chang et al., 2014; Wakabayashi et al., 2008. Briefly, mice were immunized with 100 µg of 2-octynoic acid BSA conjugate (2OA-BSA) intraperitoneally (i.p.) in a mix of PBS and complete Freund’s adjuvant (CFA, Sigma-Aldrich) at day 0 and were reboosted at days 14 and 28 with 2OA-BSA and incomplete Freund’s Adjuvant (IFA, Sigma Aldrich). Concomitantly with the two first injections of 2OA-BSA, mice were also injected intravenously (i.v.) with 2 μg of α-galactosylceramide (α-GalCer, Abcam) in PBS. Non-autoimmune primary sclerosing cholangitis model (PSC) was induced in C57Bl/6 mice as previously published: Fickert et al., 2007; Ikenaga et al., 2017. They were fed the SAFE A04 diet (SAFE™) containing 0.089% (in weight) of 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC, Sigma-Aldrich) for 2 weeks (from day 0 to 14). After one week of recovery with the regular diet, mice were fed again with the DDC-supplemented diet for one more week. For bulk mRNA-sequecing, 4 healthy/normal mouse livers, 3 PBC mouse livers, and 3 PSC mouse livers were collected at day 35 post-cholangitis induction (Paillet et al, J Exp Med, 2021).