Peribiliary Gland Niche Participates in Biliary Tree Regeneration in Mouse and in Human Primary Sclerosing Cholangitis

Abstract

Background and Aims Mechanisms underlying the repair of extrahepatic biliary tree (EHBT) after injury have been scarcely explored. The aims of this study were to evaluate, by using a lineage tracing approach, the contribution of peribiliary gland (PBG) niche in the regeneration of EHBT after damage and to evaluate, in vivo and in vitro, the signaling pathways involved. Approach and Results Bile duct injury was induced by the administration of 3,5‐diethoxycarbonyl‐1,4‐dihydrocollidine (DDC) diet for 14 days to Krt19CreTdTomatoLSL mice. Human biliary tree stem/progenitor cells (BTSC) within PBGs were isolated from EHBT obtained from liver donors. Hepatic duct samples (n = 10) were obtained from patients affected by primary sclerosing cholangitis (PSC). Samples were analyzed by histology, immunohistochemistry, western blotting, and polymerase chain reaction. DDC administration causes hyperplasia of PBGs and periductal fibrosis in EHBT. A PBG cell population (Cytokeratin19‐/SOX9+) is involved in the renewal of surface epithelium in injured EHBT. The Wnt signaling pathway triggers human BTSC proliferation in vitro and influences PBG hyperplasia in vivo in the DDC‐mediated mouse biliary injury model. The Notch signaling pathway activation induces BTSC differentiation in vitro toward mature cholangiocytes and is associated with PBG activation in the DDC model. In human PSC, inflammatory and stromal cells trigger PBG activation through the up‐regulation of the Wnt and Notch signaling pathways. Conclusions We demonstrated the involvement of PBG cells in regenerating the injured biliary epithelium and identified the signaling pathways driving BTSC activation. These results could have relevant implications on the pathophysiology and treatment of cholangiopathies.

The Spectrum of Reactive Cholangiocytes in Primary Sclerosing Cholangitis

“…On the other hand, frequently used markers to identify DRCs, such as epithelial cell adhesion molecule, SOX9, and cytokeratins 7 and 19, lack specificity as they are not exclusively expressed by DRCs but also by normal cholangiocytes and, in some cases, SCs. Nevertheless, recent lineage‐tracing studies have demonstrated that DRCs in biliary injury are mainly derived from the expansion of proliferative cholangiocytes (particularly of a select population with persistent proliferative activity) and/or activation of biliary tree progenitor/stem cells in the peribiliary gland niche . This etiology‐dependent origin of DRCs likely affects their interaction with nonparenchymal cells within the ductular reaction, as demonstrated by a recent study that compared the transcriptomic profile of DRCs/HPCs from hepatitis C virus–infected and PSC livers as models for hepatocellular or biliary injury, respectively.…”

“…Nevertheless, recent lineage-tracing studies have demonstrated that DRCs in biliary injury are mainly derived from the expansion of proliferative cholangiocytes (particularly of a select population with persistent proliferative activity) and/or activation of biliary tree progenitor/ stem cells in the peribiliary gland niche. (13,16,17) This etiology-dependent origin of DRCs likely affects their interaction with nonparenchymal cells within the ductular reaction, as demonstrated by a recent study that compared the transcriptomic profile of DRCs/HPCs from hepatitis C virus-infected and PSC livers as models for hepatocellular or biliary injury, respectively. The study identified significant differences in the expression of over 300 genes between the DRCs of the two diseases and defined how these differences influence the recruiting and homing of inflammatory cells.…”

Distinct EpCAM-Positive Stem Cell Niches Are Engaged in Chronic and Neoplastic Liver Diseases

“…Altogether, these findings are confirmed by single-cell transcriptomic analysis in human, with the identification of an EpCAM pos / TROP2 int / MUC6 high progenitor compartment with prominent stem cell features ( 9 ). Moreover, the contribution of PBG cells in the regeneration of mature biliary epithelium has been demonstrated in experimental conditions and by an ex vivo human model of biliary regeneration, which have disclosed that PBG cells can repopulate the surface epithelium of bile ducts by proliferation and differentiation into mature cholangiocytes ( 25 , 28 , 29 ).…”

“…PBGs are tubulo-alveolar mucous glands, in continuity with the surface epithelium of the bile duct ( 22 , 23 ). Intriguingly, the EpCAM pos cell population within PBGs showed stem/progenitor properties, including organoid formation and plasticity to differentiate into hepatocytes, cholangiocytes, and endocrine pancreatic cells ( Figure 2 , panel B) ( 21 , 24 , 25 ). PBG cells have been collectively named biliary tree stem/progenitor cells (BTSC) and, embryologically, they represent the remnant of the common bilio-pancreatic progenitors of the ventral endoderm ( 23 , 24 ).…”

“…Therefore, these cells could be distinguished from cholangiocytes that populate interlobular bile ducts, the latter expressing TROP 2 and mucin family genes. However, a TROP int cell fraction among the EpCAM pos compartment was proven to have high stemness properties; thus, this fraction resides more likely into peribiliary glands than in bile ductules, given also its high mucin family gene expression (e.g., MUC5A and MUC6) and low CK19 and CFTR levels ( 25 , 30 ).…”