Hepatocyte transplantation has been used to treat liver disease. The availability of cells for these procedures is quite limited. hESCs and hiPSCs may be a useful source of hepatocytes for basic research and transplantation if efficient and effective differentiation protocols were developed and problems with tumorigenicity could be overcome. Recent evidence suggests that the cell of origin may affect hiPSC differentiation. Thus, hiPSCs generated from hepatocytes may differentiate back to hepatocytes more efficiently than hiPSCs from other cell types. We examined the efficiency of reprogramming adult and fetal human hepatocytes. The present studies report the generation of 40 hiPSC lines from primary human hepatocytes under feeder-free conditions (37 from fetal hepatocytes, 2 from normal adult hepatocytes and 1 from adult hepatocytes of a patient with Crigler-Najjar Syndrome, Type-1). All lines were confirmed reprogrammed and expressed markers of pluripotency by gene expression, flow cytometry, immunofluorescence, and teratoma formation. Fetal hepatocytes were reprogrammed at a frequency over 50-fold higher than adult hepatocytes. Adult hepatocytes were only reprogrammed with 6 factors, while fetal hepatocytes could be reprogrammed with 3 or 4 factors. The increased reprogramming efficiency of fetal cells was not due to increased transduction efficiency or vector toxicity.
We also report the transplantation and differentiation of human fetal hepatocyte-derived iPSCs. We show preliminary data that undifferentiated cells can engraft in mouse livers of FRG and NOD/SCID mice. Engraftment was based on human DNA presence in liver tissue. Furthermore we differentiated these cells to definitive endoderm and transplanted them to FRG mice. Human DNA and human albumin were present in mouse livers and mouse serum respectively. Finally, full hepatic differentiation was performed, although we show limited results in terms of the cells’ ability to express liver specific genes and perform liver-specific metabolism. Taken together, these studies confirm that hiPSCs can be generated from adult and fetal hepatocytes, including those with genetic diseases, and differentiated back to the hepatocyte lineage. Fetal hepatocytes reprogram much more efficiently than adult, although both could serve as useful sources of hiPSC-derived hepatocytes for basic research or transplantation if an efficient hepatic differentiation protocol could be developed
