Broad Distribution of Hepatocyte Proliferation in Liver Homeostasis and Regeneration

Abstract

Hepatocyte proliferation is the principal mechanism for generating new hepatocytes in liver homeostasis and regeneration. Recent studies have suggested that this ability is not equally distributed among hepatocytes but concentrated in a small subset of hepatocytes acting like stem cells, located around the central vein or distributed throughout the liver lobule and exhibiting active WNT signaling or high telomerase activity, respectively. These findings were obtained by utilizing components of these growth regulators as markers for genetic lineage tracing. Here, we used random lineage tracing to localize and quantify clonal expansion of hepatocytes in normal and injured liver. We found that modest proliferation of hepatocytes distributed throughout the lobule maintains the hepatocyte mass and that most hepatocytes proliferate to regenerate it, with diploidy providing a growth advantage over polyploidy. These results show that the ability to proliferate is broadly distributed among hepatocytes rather than limited to a rare stem cell-like population. Chen et al. investigate potential differences in how much hepatocytes in the different zones of the liver lobule contribute to hepatocyte replacement in normal and injured liver. They find that, in principle, location and extent of hepatocyte proliferation are broadly distributed, with specific effects of type of injury and ploidy.