Identification of hepatocytic and bile ductular cell lineages and candidate stem cells in bipolar ductular reactions in cirrhotic human liver.

Hepatocyte function and regeneration are severely compromised in severe liver disease, and a common sequela is cirrhosis. Structural changes caused by cirrhosis create a cellular environment conducive to the formation of ductular reactions (DRs). Ductular reactions are primarily composed of oval cells also known as "intermediate hepatobiliary cells". We have conducted single, double, and triple staining to study lineages of oval cells present in DRs. Staining with NCAM, CK19, and HepPar1 has revealed a distinctly bipolar structure to DRs that are embedded in cirrhotic tissue. Spatial analysis of cells that are singly HepPar1-positive, or CK19-positive, has revealed hepatocytic and biliary poles, respectively, in the DRs. Also, the location of singly NCAM-positive cells in DRs suggests that they may be bipotent liver stem/progenitor cells. The locations of other intermediate hepatobiliary cells, which have combinations of markers, suggest that CK19+/NCAM+ cells are transitional cells in the biliary lineage and that rare cells that are negative for all three markers are transitional cells in the hepatocytic lineage. A working cell lineage model for DRs is presented.