Hepatocytes make up 80% of the mass of the liver and play a critical role in the organ’s function and regeneration. Primary human hepatocytes provide a useful platform to investigate human-specific liver biology as an alternative to using mouse models. However, their capacity to proliferate and maintain their cell identity in culture is limited. Advances in cell culture techniques have enabled the generation of 3D liver organoids from patients’ bile ducts, which can then be further differentiated towards hepatocytes. These organoid-derived hepatocytes provide exciting potential for disease modelling and drug screening, but they do not completely resemble mature primary hepatocytes. Determining the mechanisms underpinning these differences could improve in vitro culture systems for use in disease research.
Wu, Bártfai, Marks and colleagues performed single-cell RNA sequencing to compare gene expression in primary and organoid-derived hepatocytes. They integrated bioinformatic approaches with analysis of potential transcription factor binding sites to reveal that the two different types of hepatocyte use different transcription factor regulatory networks, likely accounting for the observed differences in hepatocyte maturation between organoid-derived and primary cells. Notably, they found the transcription factor ELF3 (involved in a variety of processes including proliferation, apoptosis and migration) to be a key driver of differences between the two hepatocyte states. Depletion of ELF3 in organoids led to higher expression of hepatocyte markers, suggesting that ELF3 prevents organoids from maturing to the same stage as the primary hepatocytes. Additionally, the authors found that AP-1 transcription factors (commonly associated with proliferation, among other roles) likely cooperate with liver-specific transcription factors to support cell identity in primary hepatocytes.
Understanding fundamental features of hepatocyte function and cell identity provides an essential basis for further research into liver biology. The findings of this study could lead to improved organoid differentiation protocols to generate hepatocytes in vitro that are more representative of the in vivo state, aiding the study of liver disease and the development of novel therapeutics.
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