A method for producing mature hepatocytes having functional hepatic enzyme activity from human pluripotent cells is disclosed. The method includes the step of transferring an external vector that includes a microRNA having the seed sequence of the microRNA miR-122, a DNA sequence coding for such a microRNA, a microRNA having the seed sequence of the microRNA miR-let-7c, a DNA sequence coding for such a microRNA, or a combination these, into one or more fetal hepatocytes. The resulting cells differentiate into mature hepatocytes that exhibit functional hepatic enzyme activity, and that can be used in drug metabolism and toxicity testing, in the study of viruses that target hepatic tissue, and as therapeutics.