Cellular origin of regenerating parenchyma in a mouse model of severe hepatic injury.

Several treatments in rodents, including administration of the alkylating agent dipin, followed by two-thirds partial hepatectomy in mice combine destruction of liver parenchyma with hepatocyte mitoinhibition. These treatments induce proliferation of bile epithelial-like cells (termed oval cells), development of foci composed of small hepatocytes, and eventual replacement of damaged parenchyma by healthy hepatocytes. It has been proposed that these oval cells represent transitional cells in a nonhepatocytic liver facultative stem cell lineage that can give rise to the small hepatocyte foci, and that these foci eventually become confluent and replace liver parenchyma. In this study, we used in vivo cell lineage marking in genetically chimeric livers to test the hypothesis that hepatocytes can serve as the precursor cell type to the small hepatocyte foci that develop in mouse liver after treatment with dipin plus partial hepatectomy. Although we do not exclude the possibility that some small hepatocyte foci may be stem cell-derived, we demonstrate that hepatocyte-derived foci are present after dipin-induced liver damage in mice.