Diploid Hepatocytes Resist Acetaminophen-Induced Liver Injury Through Suppressed JNK Signaling.

BACKGROUND & AIMS: The liver contains both diploid and polyploid hepatocytes, but their functional differences remain poorly understood. Emerging evidence suggests that each ploidy state contributes to regeneration in an injury-specific manner. We hypothesized that diploid hepatocytes promote healing after acetaminophen (APAP)-induced liver injury.

APPROACH & RESULTS: To study ploidy populations , we utilized mice with a lifelong liver-specific knockout of / (LKO), which are enriched in diploid hepatocytes (>70%) but otherwise normal. Control and LKO mice were treated with APAP (300 or 600 mg/kg), and injury was assessed over 0-96 hours. Although both groups sustained injury, LKO mice showed improved survival, lower serum liver enzyme levels, and reduced necrosis and DNA fragmentation, indicating resistance to APAP-induced injury. To determine if resistance was due to loss or increased diploidy, we deleted in adult hepatocytes (HKO), a model that does not alter ploidy. Injury was similar between controls and HKO, ruling out gene deletion as the protective factor. Transcriptomic and protein analyses revealed minimal baseline differences; however, following APAP treatment, LKO livers exhibited reduced JNK activation and less mitochondrial injury. Finally, APAP-treated wild-type hepatocytes exhibited a shift toward lower ploidy, supporting the idea that diploid cells are more resistant to injury.

CONCLUSIONS

Diploid hepatocytes resist APAP-induced liver injury through reduced JNK activation and mitochondrial damage. These findings highlight hepatocyte ploidy as a key determinant of injury response and suggest a protective role for diploid hepatocytes in promoting liver resilience and regeneration.