A B S T R A C TPrimary sclerosing cholangitis (PSC) is characterized by increased mast cell (MC) infiltration, biliary damage and hepatic fibrosis. Cholangiocytes secrete stem cell factor (SCF), which is a chemoattractant for c-kit expressed on MCs. We aimed to determine if blocking SCF inhibits MC migration, biliary damage and hepatic fibrosis. Methods: FVB/NJ and Mdr2 −/− mice were treated with Mismatch or SCF Vivo-Morpholinos. We measured (i) SCF expression and secretion; (ii) hepatic damage; (iii) MC migration/activation and histamine signaling; (iv) ductular reaction and biliary senescence; and (v) hepatic fibrosis. In human PSC patients, SCF expression and secretion were measured. In vitro, cholangiocytes were evaluated for SCF expression and secretion. Biliary proliferation/senescence was measured in cholangiocytes pretreated with 0.1% BSA or the SCF inhibitor, ISK03. Cultured HSCs were stimulated with cholangiocyte supernatant and activation measured. MC migration was determined with cholangiocytes pretreated with BSA or ISK03 loaded into the bottom of Boyden chambers and MCs into top chamber. Results: Biliary SCF expression and SCF serum levels increase in human PSC. Cholangiocytes, but not hepatocytes, from SCF Mismatch Mdr2 −/− mice have increased SCF expression and secretion. Inhibition of SCF in Mdr2 −/− mice reduced (i) hepatic damage; (ii) MC migration; (iii) histamine and SCF serum levels; and (iv) ductular reaction/biliary senescence/hepatic fibrosis. In vitro, cholangiocytes express and secrete SCF. Blocking stellate cell; hHSC, human hepatic stellate cell; IBDM, intrahepatic bile duct mass; Ki-67, marker of proliferation; MC, mast cell; Mdr2 −/− , multidrug resistance transporter 2/ABC transporter B family member 2 knock out; mMCP-1, mouse mast cell protease 1; p16, cyclin-dependent kinase inhibitor 2A; p18, Cyclin-dependent kinase 4 inhibitor C; PCNA, proliferating cell nuclear antigen; PSC, primary sclerosing cholangitis; qPCR, quantitative PCR; SASP, senescence-associate secretory phenotype; SCF, stem cell factor; SYP-9, synaptophysin 9; WT, wild type ☆ 0925-4439/ Published by Elsevier B.V.T biliary SCF decreased MC migration, biliary proliferation/senescence, and HSC activation. Conclusion: Cholangiocytes secrete increased levels of SCF inducing MC migration, contributing to biliary damage/hepatic fibrosis. Targeting MC infiltration may be an option to ameliorate PSC progression.