Limited Contribution of Hepatic Progenitor Cells to Hepatocyte Replenishment After Acetaminophen Overdose

Liver regeneration is critical determinant of survival following acetaminophen (APAP) overdose, driven primarily by proliferation of surviving hepatocytes. Hepatic progenitor cells (HPCs) are bipotential cells activated when hepatocyte proliferation is impaired. The contribution of HPCs to liver regeneration after APAP overdose remains unclear. This study investigated the contribution of HPCs to hepatocyte repopulation when regeneration is impaired after severe APAP overdose using a lineage-tracing mouse model. Two-month-old male C57BL/6J mice were fasted overnight and then administered a 600 mg/kg overdose of APAP (600APAP). For lineage tracing, male ROSAmT-mG mice were injected with AAV8-TBG-Cre to label hepatocytes. Two weeks after AAV administration, mice were fasted overnight and then administered a 600 mg/kg overdose of APAP. Liver and blood samples were collected multiple times. C57BL/6J mice treated with severe acetaminophen overdose (600APAP) showed substantial liver injury, with peak serum ALT and hepatic necrosis at 72 h, followed by progressive recovery. HPCs activation was evidenced by increased expression of EpCAM, A6. CK19, cholangiocyte marker, increase during the recovery phase. APAP administration to ROSAmT-mG mice induced liver injury and subsequent regeneration and recovery comparable to wild type mice. Detection of HNF4α/tdTomato double-positive cells, hepatocytes originating from a non-parenchymal source, were detected after injury but represented only 0.3–0.6% of total hepatocytes. Taken together, this study indicates that despite an increase of HPC/cholangiocyte markers, HPC/cholangiocyte transdifferentiation contributes minimally to hepatocyte replenishment during an impaired regeneration after severe APAP-induced liver injury.