IL22 supports Long-Term Expansion of Mouse and Human Hepatocytes in vitro.

Hepatocytes have wide applications in drug development, disease modeling, and cell therapy. However, to expand hepatocytes in large quantities in vitro without losing their functions remains a challenging task. Here we report that IL22, a cytokine highly upregulated after partial hepatectomy or hepatocyte transplantation, could support long-term expansion (>30 passages, with theoretical expansion of ~1030 times within ~150 days) of mice hepatocytes in vitro by dedifferentiate hepatocytes into hepatocyte progenitor cells (HPCs), which maintain the capacity of differentiation into mature hepatocytes. With transcriptomic analysis and lineage-specific deletion, we uncover the critical involvement of STAT3 pathway in IL22-mediated hepatocyte to HPC conversion. Two key transcription factors (TFs) down-stream of STAT3 pathway, Bhlha15 and Arntl2, govern IL22-induced hepatic dedifferentiation. Expression of these two TFs directly initiates the dedifferentiation of hepatocytes into HPCs, which could be expanded in long-term without the supplement of IL22. IL22 also supports human hepatocyte growth in simple culture condition. Within 30 days, human hepatocytes could be expanded by more than 10,000-fold by dedifferentiation into HPCs, which maintain the full capacity of maturation. Collectively, this study provides a simple culture system enables large-scale expansion of both mice and human hepatocytes in vitro, and elucidates the critical pathways and TFs involved in these processes.