Mature hepatocytes are the source of small hepatocyte-like progenitor cells in the retrorsine model of liver injury

Background/Aims: Mature hepatocytes divide to restore liver mass after injury. However, when hepatocyte division is impaired by retrorsine poisoning, regeneration proceeds from another cell type: the small hepatocytelike progenitor cells (SHPCs). Our aim was to test whether SHPCs could originate from mature hepatocytes. Methods: Mature hepatocytes were genetically labeled using retroviral vectors harboring the beta-galactosidase gene. After labeling, retrorsine was administered to rats followed by a partial hepatectomy to trigger regeneration. A liver biopsy was performed one month after surgery and rats were sacrificed one month later. Results: We observed the proliferation of small hepatocytes arranged in clusters in liver biopsies. These cells expressed Ki67 antigen and displayed a high mitotic index. At sacrifice, regeneration was completed and clusters had merged. A significant proportion of clusters also expressed beta-galactosidase demonstrating their origin from labeled mature hepatocytes. Finally, the overall proportion of beta-galactosidase positive cells was identical at the time of hepatectomy as well as in liver biopsy and at sacrifice. Conclusions: The constant proportion of beta-galactosidase positive cells during the regeneration process demonstrates that mature hepatocytes are randomly recruited to proliferate and compensate parenchyma loss in this model. Furthermore, mature hepatocytes are the source of SHPC after retrorsine injury. (C) 2004 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.