Figure 1. Model of the hepatic stem cell niche in the canals of Hering.

Label-retaining cells (black nuclei) represent putative stem cells and are located in the canals of Hering as keratin-expressing cells. Also, cholangiocytes of intralobular bile ducts, small hepatocytes, and less-characterized null cells retain the BrdU label after acetaminophen treatment of mice (50). Coexpression of keratin 19 and albumin in small hepatocytes at the interface of cholangiocytes and hepatocytes in the canals of Hering indicate that hepatocytes are generated at this site by stem/progenitor cells (116). A continuous production of hepatocytes within the portal field is supported by SOX9 fate-mapping analysis (54). Small cholangiocytes lining the canals of Hering and ductules may represent cholangiocyte precursors, which potentially contribute to the cholangiocyte population of larger bile ducts (116) and could explain the presence of label-retaining cholangiocytes at this site (50).