Targeted Apoptosis Of Ductular Reactive Cells Reduces Hepatic Fibrosis In A Mouse Model of Cholestasis

BACKGROUND AND AIMS: In cholestatic liver diseases, ductular reactive (DR) cells extend into the hepatic parenchyma promoting inflammation and fibrosis. We have previously observed that Mdr2(-/-) mice lacking TRAIL receptor (Mdr2(-/-) Tr(-/-) double knockout, DKO) 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: To examine this concept, we cultured EpCAM-positive reactive cholangioids (ERC) obtained from wild-type (WT), Tr(-/-) , Mdr2(-/-) and DKO mice. RESULTS: Single-cell transcriptomics and immunostaining of both WT and DKO ERC confirmed their DR cell phenotype. Moreover, DKO ERC displayed a unique translational cluster with expression of chemokines indicating a reactive state. Incubation with the MCL1 inhibitor S63845, a pro-apoptotic BH3-mimetic therapy significantly decreased DKO and Mdr2(-/-) ERC viability compared to WT. Intravenous administration of S63845 significantly reduced the DR cell population, 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 (CyTOF). Co-culture of bone-marrow derived macrophages with ERC from DKO mouse livers upregulated expression of the B-cell directed chemokine CCL5/RANTES. Finally, DR cells were noted to be primed for apoptosis with BAK activation in vitro and in vivo in PSC liver specimens. CONCLUSION: DR cells appear to play a key role in recruiting immune cells to the liver to actively create an inflammatory and pro-fibrogenic microenvironment. Pharmacologic targeting of MCL1 in a mouse model of chronic cholestasis reduces DR and B cell populations and hepatic fibrosis.