Efficient episomal reprogramming of blood mononuclear cells and differentiation to hepatocytes with functional drug metabolism

• Episomal reprogramming of blood mononuclear cells (MNC) to pluripotent cells.
• Episomal reprogramming of non-adherent fetal liver cells.
• Using a feeder-free system, a reprogramming efficiency of up to 0.033% was achieved.
• The iPS cell lines exhibited typical characteristics of pluripotent cells.
• The iPS could be differentiated into hepatocytes with drug metabolic function.

The possibility of converting cells from blood mononuclear cells (MNC) to liver cells provides promising opportunities for the study of diseases and the assessment of new drugs. However, clinical applications have to meet GMP requirements and the methods for generating induced pluripotent cells (iPCs) have to avoid insertional mutagenesis, a possibility when using viral vehicles for the delivery of reprogramming factors. We have developed an efficient non-integration method for reprogramming fresh or frozen blood MNC, maintained in an optimised cytokine cocktail, to generate induced pluripotent cells. Using electroporation for the effective delivery of episomal transcription factors (Oct4, Sox2, Klf4, L-Myc, and Lin28) in a feeder-free system, without any requirement for small molecules, we achieved a reprogramming efficiency of up to 0.033% (65 colonies from 2×105 seeded MNC). Applying the same cytokine cocktail and reprogramming methods to cord blood or fetal liver-derived CD34+ cells, we obtained 148 iPS colonies from 105 seeding cells (0.148%). The iPS cell lines we generated maintained typical characteristics of pluripotent cells and could be successfully differentiated into hepatocytes with drug metabolic function.