Huppert, S. S. | bioRxiv Science

bioRxiv2024

Cholestasis alters polarization and suppressor function of hepatic regulatory T cells.

Fibrosing cholangiopathies, including biliary atresia and primary sclerosing cholangitis, involve immune-mediated bile duct epithelial injury and hepatic bile acid (BA) retention (cholestasis). Regulatory T-cells (Tregs) can prevent auto-reactive lymphocyte activation, yet the effects of BA on this CD4 lymphocyte subset are unknown. Gene regulatory networks for hepatic CD4 lymphocytes in a murine cholestasis model revealed Tregs are polarized to Th17 during cholestasis. Following bile duct ligation, Stat3 deletion in CD4 lymphocytes preserved hepatic Treg responses. While pharmacological reduction of hepatic BA in MDR2-/- mice prompted Treg expansion and diminished liver injury, this improvement subsided with Treg depletion. A cluster of patients diagnosed with biliary atresia showed both increased hepatic Treg responses and improved 2-year native liver survival, supporting that Tregs might protect against neonatal bile duct obstruction. Together, these findings suggest liver BA determine Treg function and should be considered as a therapeutic target to restore protective hepatic immune responses.

immunology↗

bioRxiv2024

Rbpj deletion in hepatic progenitor cells attenuates endothelial responses in a mouse model of cholestatic liver disease

BackgroundAs the role of hepatic progenitor cells (HPCs) constituting ductular reactions in pathogenesis remains ambiguous, we aimed to establish the in vivo cause-and-effect relationship between HPCs and chronic liver disease progression. We previously demonstrated that peritumoral ductules are associated with angiogenesis in liver tumors and forkhead box L1 (Foxl1)-expressing murine HPCs secrete angiogenic factors in vitro. Therefore, we hypothesized that HPCs are capable of remodeling the portal vascular microenvironment and regulating overall liver disease progression, and this function of HPCs is dependent on recombination signal binding protein for immunoglobulin kappa J region (RBPJ), a key effector of the Notch signaling pathway. Methods and ResultsWe generated HPC-specific Rbpj conditional knockout mice (CKO) using Foxl1-Cre and treated them with the DDC diet to induce chronic liver disease. CKO mice exhibited a significant reduction in serum levels of liver injury markers, ductular reactions, vascular and fibrotic areas, and hepatic expression of fibrosis and inflammation markers compared to control mice (WT). Single-nucleus RNA sequencing comparing CKO and WT livers detected transcriptome changes across multiple cell types, including endothelial cells, hepatic stellate cells, and cholangiocytes. Expression of several reactive cholangiocyte markers, including vascular cell adhesion molecule 1 (VCAM1), in HPCs was significantly downregulated in response to anti-Rbpj shRNAs in vitro. Immunofluorescence analysis indicated that the percentage of VCAM1+ cells was reduced in both HPC and cholangiocyte populations in CKO compared to WT in vivo. ConclusionsOur findings reveal Rbpj-dependent expression of reactive cholangiocyte markers in HPCs and demonstrate that Rbpj deletion in HPCs attenuates not only endothelial responses but also liver injury, fibrosis, and VCAM1 expression in cholangiocytes, highlighting the crucial role of HPCs in pathogenic progression.

cell biology↗