Retrorsine impairs liver regeneration by inducing progenitor cell-senescence via ROS after partial hepatectomy.

BACKGROUND: Hepatic progenitor cells (HPCs) provide an alternative regenerative pathway when hepatocytes are in a senescent state or after chronic liver injury. Yet, their contribution to liver regeneration after partial hepatectomy (PH) remains controversial. The aim of this study is to reveal the regeneration contribution of HPCs after PH when hepatocyte proliferation is totally suppressed. METHODS: Retrorsine (RTS) was administered to suppress hepatocyte proliferation in C57BL/6J mice after PH. The regeneration contribution of HPCs was assessed using HPC-specific lineage tracing mice (Sox9(Cre-ER)Rosa(tdTomato)) after RTS/PH. The effects of RTS on HPCs were analyzed by HPC-enriched organoids in vitro. RESULTS: RTS 0-70 mg/kg dose-dependently reduced the PCNA(+) hepatocyte ratio on day 2 post-PH with hepatocyte proliferation completely suppressed by 70 mg/kg RTS. Yet, the proportion of PCNA(+) HPCs did not increase in these 70 mg/kg RTS/PH mice, suggesting that HPCs were not activated when RTS completely inhibited hepatocyte proliferation. By day 14 post-PH, the 70 mg/kg RTS/PH mice exhibited reduced liver-to-body weight ratios compared to control mice, indicating regeneration failureafter PH. Simultaneously, the tdTomato-positive regenerative foci derived from labeled HPCs were not significantly different from those of the controls, indicating a minimal regeneration contribution from HPCs. RTS increased intracellular ROS levels and β-galactosidase activity of HPC-enriched liver oranoids in vitro, and phospho-H2A.X positive HPCs could be found in 70 mg/kg RTS/PH mouse liver, suggesting RTS-induced HPC senescence. CONCLUSION: When hepatocyte proliferation was completely suppressed by RTS, HPCs contributed minimally to liver regeneration owing to cellular senescence, resulting in regeneration failure.