Cells and transfection
Primary mouse hepatocytes were isolated from BALB/c mice by following a two-step perfusion protocol as previously described [16, 17], and cultured in Hepato-Stim Hepatocyte Defined medium (BD Biosciences). Primary human hepatocytes were cultured as previously described [18, 19]. IL-21 mRNA transfection was performed using TurboFect Transfection Reagent (Thermo Fisher Scientific) according to the manufacturer’s instructions. For LNP transfection, LNP particles were diluted in serum free medium at a ratio of 1:5 and kept for 20 minutes at room temperature, and then added into the cultured cells. Medium was changed at 6-8 hours post transfection.