Background and Aims: In cholestatic liver diseases, ductular reactive (DR) cells extend into the hepatic parenchyma and promote inflammation and fibrosis. We have previously observed that multidrug-resistant 2 (Mdr2−/−) double knockout (DKO) mice lacking tumor necrosis factor–related apoptosis-inducing ligand receptor (Tr−/−) display a more extensive ductular reaction and hepatic fibrosis compared to Mdr2−/− mice. This observation suggests that the magnitude of the DR-cell population may be regulated by apoptosis. Approach and Results: To examine this concept, we cultured epithelial cell adhesion molecule–positive reactive cholangioids (ERCs) obtained from wild-type (WT), Tr−/−, Mdr2−/− and DKO mice. Single-cell transcriptomics and immunostaining of both WT and DKO ERCs confirmed their DR-cell phenotype. Moreover, DKO ERCs displayed a unique translational cluster with expression of chemokines, indicating a reactive state. Incubation with the myeloid cell leukemia 1 (MCL1) inhibitor S63845, a proapoptotic BH3-mimetic therapy, significantly decreased DKO and Mdr2−/− ERC viability compared to WT. Intravenous administration of S63845 significantly reduced the DR-cell population and markers of inflammation and liver fibrosis in Mdr2−/− and DKO mice. Furthermore, DKO mice treated with S63845 displayed a significant decrease in hepatic B lymphocytes compared to untreated mice as assessed by high-definition mass cytometry by time-of-flight. Coculture of bone marrow–derived macrophages with ERCs from DKO mouse livers up-regulated expression of the B cell–directed chemokine (C-C motif) ligand 5. Finally, DR cells were noted to be primed for apoptosis with Bcl-2 homologous antagonist/killer activation in vitro and in vivo in primary sclerosing cholangitis liver specimens. Conclusions: DR cells appear to play a key role in recruiting immune cells to the liver to actively create an inflammatory and profibrogenic microenvironment. Pharmacologic targeting of MCL1 in a mouse model of chronic cholestasis reduces DR-cell and B-cell populations and hepatic fibrosis.
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