Japan Recent progress in studies on direct cell-fate conversion of differentiated somatic cells into other cell types, which is known as "direct reprogramming", is expected to lead to innovations in health care. In our previous study, we found that three specific combinations of two transcription factors, comprising Hnf4α plus Foxa1, Foxa2, or Foxa3, were able to induce conversion of mouse fibroblasts into functional hepatocyte-like cells. These induced hepatocyte-like (iHep) cells will be

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... l for developing regenerative therapies for liver diseases and examining the pharmacological effects of drugs. However, to evaluate the potential utility of iHep cells, the phenomena involved in the direct conversion of fibroblasts into iHep cells should be examined in detail. Thus, in this study, we sequentially analyzed the early stage of fibroblast conversion into iHep cells after infection with retroviruses expressing Hnf4α and Foxa3. Our data demonstrated that the conversion into iHep cells began within 2 days after introduction of the transgenes into fibroblasts, and the number of iHep cells increased gradually as the culture progressed. The rapid cell-fate conversion of fibroblasts into iHep cells and stable expansion of iHep cells are two pieces of evidence suggesting the utility of iHep cells for cell transplantation therapy, bioartificial liver development, and screening of drugs for patients with liver diseases, which require many hepatocytes within a short period of time.