Demonstration of differentiation in hepatocyte progenitor cells using dipeptidyl peptidase IV deficient mutant rats.

The presence of progenitor or stem cells in the adult liver and their potential roles in oncogenesis are unresolved issues. The study of hepatocyte progenitor cells has been limited by a lack of convenient in vivo systems allowing unequivocal cell localization and demonstration of differentiation into hepatocytes. To develop an in vivo progenitor bioassay, early (E14) fetal Fischer 344 rat hepatoblasts were transplanted into the spleen of syngeneic, weaning rats deficient in dipeptidyl peptidase IV (DPPIV) activity. The donor status of transplanted hepatoblasts was demonstrated by DPPIV expression. Localization of hepatoblasts was facilitated by the use of an ectopic site, as well as weanling recipients, which readily allowed identification of very small numbers of transplanted cells. Fetal rat hepatoblasts were demonstrated to undergo cellular differentiation along the hepatocyte lineage by acquiring glucose-6-phosphatase activity within 5 d of transplantation. A critical review of previous transplantation studies of hepatocyte progenitor cells and the role of the local microenvironment at inducing differentiation indicates that this novel bioassay should facilitate analysis of progenitor cells.