SRP374597 PRJNA836922 GSE202676 Bulk RNA-seq in cholangiocytes from mouse model of primary biliary cholangitis Background & Aims: Late-stage primary biliary cholangitis (PBC) is defined by bile duct loss, ductular reaction, peribiliary inflammation and fibrosis. Loss of anion exchanger 2 (AE2), the 'bicarbonate umbrella' and ductulo-canalicular junctions (DCJ) are hypothesized to promote PBC progression. The secretin (Sct)/secretin receptor (SR) axis controls cystic fibrosis transmembrane receptor (CFTR) activation and AE2 opening, and controls choleresis. We aimed to define the impact of Sct/SR signaling on biliary secretory processes and subsequent injury in late-stage PBC mouse model and human samples. Methods: Female and male wild-type (WT) and dominant-negative transforming growth factor beta receptor II (dnTGFßRII, late-stage PBC model) at 32 wks of age were treated with Sct for 1 wk or 8 wks. Pathways mediated by Sct were identified by RNA-seq in isolated cholangiocytes. Sct/SR/CFTR/AE2 expression and MUC1 levels were evaluated in human control and late-stage PBC. Results: Biliary Sct, SR, CFTR and AE2 expression is reduced in late-stage PBC mouse models and human samples. Sct treatment decreased bile duct loss, ductular reaction, inflammation and fibrosis in late-stage PBC models, as well as hepatic bile acid release and DCJ formation. RNA-seq identified that Sct promoted mature epithelial cell marker expression, specifically anterior grade 2 (Agr2, expressed only in cholangiocytes). Late-stage PBC models and human samples had reduced biliary MUC1, which was enhanced with Sct treatment. Conclusion: Loss of the Sct/SR pathway in late-stage PBC results in a faulty 'bicarbonate umbrella' and reduced Agr2 and mucin production. Sct restores cholangiocyte secretory processes and DCJ formation through enhanced mature cholangiocyte phenotypes and healthy bile duct growth. The Sct/SR axis may be a therapeutic target for late-stage PBC patients. Overall design: intrahepatic cholangiocytes analyzed from WT, WT+secretin 8 wk, PBC model (dnTGFBRII), and PBC model + secretin 8 wk. WT cholangiocytes are the control sample. We analyzed male and female samples separately. 6-8 mice per treatment group were pooled to extract cholangiocytes, and total RNA from this pooled population of cholangiocytes was sequenced in triplicate at GeneWiz using an Illumina platform. GSE202676 pubmed 35987275