Baez-Faria, Michelle

Abstract Introduction Primary sclerosing cholangitis (PSC) is an immune-mediated chronic fibrotic liver disease with no effective medical therapies. We showed that bile duct epithelial cells, called cholangiocytes, express IL-17C, a cytokine that modulates immune responses. Mucosal-associated invariant T cells (MAITs) have been implicated in fibrosis, but their mechanistic role in PSC remains unknown. SPARC (secreted protein acidic and rich in cysteine) is an extracellular matrix protein whose role in hepatic fibrosis is unexplored. Methods Flow cytometry, RNAscope, ELISA, RNA sequencing, immunofluorescence, immunocytochemistry, spheroid culture. Results Flow cytometry of bile duct brushings from PSC patients (n = 8) revealed that 41.32% of T cells were MAITs, indicating their proximity to cholangiocytes within the epithelial-immune niche. MAITs co-cultured with PSC patients-derived cholangiocytes showed increased activation than with normal human cholangiocytes (p = 0.018, n = 4). RNAscope on human livers identified increased IL17C expression in PSC cholangiocytes compared to controls (p = 0.064, n = 3), and IL-17C levels were elevated in PSC bile (p = 0.035, n = 25). Surprisingly, the receptor of IL-17C is enriched in MAITs in PSC (re-analysis of single cell-RNA seq, PMID: 33774059). Bulk RNA sequencing of IL-17C-treated peripheral blood MAITs revealed upregulation of T cell activation markers and pathways associated with hepatic fibrosis. Moreover, IL-17C-treated MAITs increased SPARC secretion (p = 0.025, n = 7), an effect attenuated by IL-17C blockade. Consistently, conditioned media from IL-17C—treated MAITs activated hepatic fibroblasts (HF), evidenced by increased PDGFRβ expression (p = 0.048, n = 6). SPARC directly promoted HF activation, marked by increased α-SMA (p = 0.039, n = 5). Co-culture of primary human HF, MAITs and cholangiocytes in the presence of IL-17C enhanced HF activation. Conclusion IL-17C drives MAITs toward a profibrogenic phenotype in PSC, promoting HF activation through SPARC. Funding Source C-SIG P30DK084567 Topic Categories Immune Mechanisms of Human Disease (HUM)

Abstract Description Background Primary sclerosing cholangitis (PSC) is an immune-mediated liver disease characterized by chronic inflammation and fibrosis of the bile ducts. The primary cells impacted in PSC are bile duct epithelial cells called cholangiocytes. Mucosal associated invariant T (MAIT) cells are enriched in human liver and associated with fibrosis. We hypothesize that cholangiocyte-activated MAIT cells drive fibrosis in PSC. Results Flow cytometry of PSC patient bile duct brushings show that 30% of T cells are MAIT cells, suggesting their co-existence with cholangiocytes within the peri-biliary environment. Re-analysis of single cell RNA sequencing data of PSC patient cholangiocyte organoids reveals upregulation of MR1 gene, indicating their enhanced ability to activate MAIT cells. Proteomics of human MAIT cells identify the expression of multiple profibrotic factors including secreted protein acidic and rich in cysteine (SPARC). Flow cytometry of TCR-activated MAIT cells show a significant and dose-dependent increase in a SPARClow MAIT population, indicating release of SPARC. Re-analysis of Olink proteomics on supernatant of PSC cholangiocyte organoids show IL-17C secretion. IL-17C treatment of TCR-activated MAIT cells result in significant upregulation of SPARC gene. Conclusion MAIT cells secrete profibrogenic mediators and MAIT cell profibrogenicity is enhanced by IL-17C, a novel cytokine released by cholangiocytes in PSC. Funding Sources C-SIG P30DK084567 Topic Categories Mucosal and Regional Immunology (MUC)