Reactive cholangiocyte-derived ORM2 drives a pathogenic modulation of the injured biliary niche through macrophage reprogramming

Abstract

Background: Injured or reactive biliary epithelial cells participate in most chronic liver injuries in a process referred to as ductular reaction, which involves multicellular interactions with marked local infiltration of macrophages and fibrogenic cell activation. The direct roles of biliary epithelial cells in shaping their cellular niche remain unknown.

Objective: We aimed at investigating the effects of biliary epithelial cell-derived acute phase response protein orosomucoid 2 (ORM2) in shaping monocyte/macrophage response to liver injury.

Design: Transcriptome data sets from human and mouse livers were used, results were confirmed with multiplex immunofluorescence. A multicellular biliary-niche-on-a-chip derived from primary liver and blood cells (wild-type, Mdr2 ^-/- mice) was established to model ductular reaction. Human blood cells collected from healthy donors and intrahepatic cholangiocyte organoids derived from normal and cirrhotic liver patients were used.

Results: Our transcriptome data set and multiplex immunofluorescence analyses indicated a previously unrecognised involvement of the acute phase response protein ORM2 in ductular reactions in both human and mouse livers. ORM2 gene expression was increased in biliatresone-challenged, bile acid-challenged and acetaminophen-challenged cholangiocytes. Cholangiocyte-derived ORM2 induced unique transcriptome changes and functional adaptation of liver macrophages. ORM2-activated macrophages exacerbated cholangiocyte cell stress and Orm2 expression, but also tended to promote fibrogenic activation of hepatic stellate cells. Mechanistically, ORM2 effects were mediated by an inositol 1,4,5-trisphosphate receptor type 2-dependent calcium pathway.

Conclusion: This study reveals a paracrine communication circuit during ductular reaction, in which reactive cholangiocyte-derived ORM2 reprogrammes liver macrophages, participating in a pathogenic remodelling of the immune biliary niche.

Keywords: BILIARY EPITHELIUM; BILIARY PHYSIOLOGY; CHOLESTATIC LIVER DISEASES; LIVER IMMUNOLOGY; MACROPHAGES.