Peribiliary Glands Are Key in Regeneration of the Human Biliary Epithelium After Severe Bile Duct Injury

Abstract

Peribiliary glands (PBG) are a source of stem/progenitor cells organized in a cellular network encircling large bile ducts. Severe cholangiopathy with loss of luminal biliary epithelium has been proposed to activate PBG, resulting in cell proliferation and differentiation to restore biliary epithelial integrity. However, formal evidence for this concept in human livers is lacking. We therefore developed an ex vivo model using precision‐cut slices of extrahepatic human bile ducts obtained from discarded donor livers, providing an intact anatomical organization of cell structures, to study spatiotemporal differentiation and migration of PBG cells after severe biliary injury. Postischemic bile duct slices were incubated in oxygenated culture medium for up to a week. At baseline, severe tissue injury was evident with loss of luminal epithelial lining and mural stroma necrosis. In contrast, PBG remained relatively well preserved and different reactions of PBG were noted, including PBG dilatation, cell proliferation, and maturation. Proliferation of PBG cells increased after 24 hours of oxygenated incubation, reaching a peak after 72 hours. Proliferation of PBG cells was paralleled by a reduction in PBG apoptosis and differentiation from a primitive and pluripotent (homeobox protein Nanog+/ sex‐determining region Y‐box 9+) to a mature (cystic fibrosis transmembrane conductance regulator+/secretin receptor+) and activated phenotype (increased expression of hypoxia‐inducible factor 1 alpha, glucose transporter 1, and vascular endothelial growth factor A). Migration of proliferating PBG cells in our ex vivo model was unorganized, but resulted in generation of epithelial monolayers at stromal surfaces. Conclusion: Human PBG contain biliary progenitor cells and are able to respond to bile duct epithelial loss with proliferation, differentiation, and maturation to restore epithelial integrity. The ex vivo spatiotemporal behavior of human PBG cells provides evidence for a pivotal role of PBG in biliary regeneration after severe injury.

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

“…Taken together, our data indicate an active contribution by SOX9 + PBG cells in the restoration of SE after injury and their capability to differentiate into mature cholangiocytes. Our findings are in keeping with the evidence that the regeneration of ischemic injured SE is ensured by BTSC activation in a human ex vivo model …”

“…PBGs can produce Notch ligands themselves, thus suggesting an autocrine effect and a further paracrine effect on neighboring (myo‐)fibroblasts. Interestingly, previous evidence indicated that, in human biliary disease, PBGs can secrete vascular endothelial growth factors (VEGFs), influencing the modification of peribiliary vascular plexus in PSC and hypoxic conditions . Taken together with previous studies, our results indicate that the activation of PBG niche represents a consequence of toxic or inflammatory biliary damage (Fig.…”

“…In the DDC model, Notch and Wnt signaling pathways are turned off once the toxic agent is interrupted, thus determining a progressive restoration to the normal condition. In PSC, chronic inflammation continuously triggers PBG niche activation; in turn, chronically activated PBGs start to produce growth factors (VEGFs), signals (sonic hedgehog, Notch ligands), and inflammatory cytokines (interleukin‐6, transforming growth factor‐β), which further stimulate fibrogenetic and inflammatory cells. Therefore, this secretory phenotype of PBGs in PSC configures a sort of vicious cycle that is more prone to developing concentric fibrosis than furnishing coordinated signals for restitutio ad integrum .…”

Gallbladder wall abnormality in biliary atresia of mouse Sox17+/− neonates and human infants

“…The PBGs/PPGs secrete mucus and immunoglobulin, thus contributing to the protection of the apical surface of the bile duct epithelia from bile salt toxicity (DiPaola et al, 2013;Hopwood et al, 1988;Sugiura and Nakanuma, 1989). PBGs also contain epithelial cells expressing several biliary and hepatic stem cell markers (including Sox9, Sox17, Pdx1 and Lgr5), and it has therefore been suggested that they may be the reservoir of epithelial stem/progenitor cells in the biliary tract (Furuyama et al, 2011;Cardinale et al, 2012;Carpino et al, 2012;DiPaola et al, 2013;Lanzoni et al, 2016;Matsui et al, 2018;de Jong et al, 2018de Jong et al, , 2019. Therefore, it is possible that the metaplastic PBG/PPG-like glands may serve as a positive response to regenerate the epithelial structure in the BA gallbladders following stress/inflammation during late fetal and perinatal periods.…”

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 ).…”