13 research outputs found
Ductular hepatocytes
Ductular hepatocytes are observed in the
livers of both experimental animals and man under
various conditions of severe toxin-, carcinogen- or viralinduced
hepatic injury with prominent loss of
parenchymal hepatocytes. These unique hepatic
epithelial cells are characterized by phenotypic traits that
are intermediate between those of hepatocytes and
intrahepatic biliary epithelium. The origin of ductular
hepatocytes is controversial, but it has been
hypothesized that they may represent a transitional cell
stage associated with either (1) a ductular metaplasia of
parenchymal hepatocytes into intrahepatic biliary
epithelium, (2) a metaplastic conversion of intrahepatic
bile duct or ductular epithelium into hepatocytes, or (3)
differentiation of a putative liver stem cell along the
hepatocyte lineage. Depending on the liver disease state
being investigated, evidence is presented to support al1
three of these possibilities. Of particular interest is the
increasing evidence supporting the existence of a
facultative pluripotent stem-like cell associated with the
intrahepatic biliary tract, which appears capable of
differentiating into various gut endoderm-derived cell
types, including hepatocytes, small intestinal mucosa1
cells, and pancreatic acinar cells. Ductular cells of
pancreas have also been demonstrated to alter their differentiation commitment under various induced
conditions of pancreatic injury and regeneration, so as to
give rise to pancreatic hepatocytes. The presence of a
putative stem-like cell in liver together with the
plasticity exhibited by some hepatocytes and biliary
epithelial cells in various forms of severe hepatic and
biliary tract injury can have important implications for
carcinogenesis and aberrant regenerative responses in
liver. In addition, novel in vivo and cell culture models
have been developed, which are serving as potentially
powerful tools for investigating the effects of specific
growth factors, extracellular matrix components,
hormones and other agents on the ability of nonparenchymal
epithelial liver cell types to differentiate
into hepatocyte-like cells