Cholangiocytes contribute to hepatocyte regeneration after partial liver injury in larval zebrafish

Liver possesses robust regenerative ability, characterized by flexibility in the cellular source of regeneration based on the extent of the injury. After partial hepatectomy or minor injuries, hepatocytes, the primary liver cells, undergo self-duplication to replenish the liver mass. In contrast, when the damage is extensive, or hepatocyte proliferation is impaired, cholangiocytes contribute to hepatocyte recovery. This current paradigm of regenerative flexibility in the liver has been established for animals with little or no growth. However, the regenerative mechanisms during periods of growth in young animals remain unexplored. Here, we establish two new partial liver injury protocols in the zebrafish model of rapid growth during late larval stage and observe emergence of de novo hepatocytes in the presence of spared hepatocytes. Using single-cell RNA sequencing and lineage tracing, we identify cholangiocytes as the source of de novo hepatocytes. Our study offers a new perspective on the current paradigm of liver regenerating by proposing cholangiocyte-to-hepatocyte transdifferentiation as the default mechanism of hepatocyte recovery in late larval stage zebrafish. We conducted single-cell RNA Sequencing using the 10x platform of larval zebrafish liver. This was performed in the basal state (Control1, Control2), after partial ablation (MTZ_0dppa, MTZ_1dppa and MTZ_9dppa) and after partial hepatectomy (PHx_4dpi and PHx_11dpi). The two control samples were not treated with 4-OHT, and were also not injured. The control samples are from 13 dpf zebrafish raised under normal rearing condition. For all experiments Tg(fabp10a:CellCousin) line was used.