RESUMO
OBJECTIVE: The introduction of 4 transcription factors-c-MYC, OCT3/4, SOX2, and KLF4--can reprogram somatic cells back to pluripotency. However, some of the factors used are oncogenic, making therapeutic application unfeasible. Although the use of adult stem cells expressing high endogenous levels of some of these factors allows for reprogramming with fewer exogenous genes, such cells are rare and may have accumulated genetic mutations. Our goal was to reprogram human somatic cells without oncogenic factors. We found that high endogenous expression of KLF4 in human umbilical vein endothelial cells (HUVECs) allows for generation of induced pluripotent stem cells (iPSCs) with just 2 nononcogenic factors, OCT3/4 and SOX2. METHODS AND RESULTS: HUVECs were infected with lentivirus containing OCT4 and SOX2 for generation of iPSCs. These 2-factor HUVEC iPSCs were morphologically similar to embryonic stem cells, express endogenous pluripotency markers postreprogramming, and can differentiate toward lineages of all 3 germ layers both in vitro and in vivo. CONCLUSIONS: iPSCs can be generated from HUVECs with only 2 nononcogenic factors. The use of fetal cells for reprogramming without oncogenic factors may provide an efficient in vitro model for human iPSC research, as well as a novel source for possible therapeutic use.