Fig. 8: Summary of the distinctions in anatomy and in the location of the stem/progenitor niches in the human versus porcine biliary trees.

a Illustration of the lobule patterns for porcine liver, biliary tree, and pancreas. Abbreviation for enlarged liver lobes: CL caudate lobe, RLL right lateral lobe, RML right medial lobe, LML left medial lobe, LLL left lateral lobe, G gallbladder; Abbreviation for enlarged pancreas: S stomach, D duodenum, H head of pancreas, T tail of pancreas, Pr Descending process; UB upper bridge, LB lower bridge. b Locations of the stem/progenitor cell niches. The highest numbers of the hepato/pancreatic co-stem/progenitor niches are in the submucosal duodenal glands (also called Brunner’s Glands), in peribiliary glands (PBGs) throughout the biliary tree and in the accessory duct to the dorsal pancreas; the ones in PBGs near the liver transition to hepatic stem cell niches in the canals of Hering connecting into the parenchyma in the liver acinar plates. The major distinctions between pigs and humans are that humans, but not pigs, have the hepato/pancreatic common duct connecting the duodenum to the ventral pancreas. It is the location of the highest number of stem/progenitor cell niches in the biliary tree in all mammals, other than pigs or ox. Pigs, but not humans, have stem cell niches in the pancreatic duct glands (PDGs) within the pancreas proper, those PDGs that are in regions near the duodenum. Both humans and pigs have committed bipotent and unipotent progenitors, but not the stem cells, in PDGs elsewhere in the pancreas. There are also progenitors in the gallbladder, though the ones in the human gallbladder retain some traits of stemness albeit muted relative to the traits in the cells at the base of the PBGs (near the fibromuscular layer), the presumptive stem cell niches in the biliary tree. Further details are provided in Supplementary Figure 6.