A drug-inducible system for direct reprogramming of human somatic cells to pluripotency

Current approaches to reprogram human somatic cells to pluripotent iPSCs utilize viral transduction of different combinations of transcription factors. These protocols are highly inefficient because only a small fraction of cells carry the appropriate number and stoichiometry of proviral insertions to initiate the reprogramming process. Here we have generated genetically homogeneous secondary somatic cells, which carry the reprogramming factors as defined doxycycline (DOX)-inducible transgenes. These cells were obtained by infecting fibroblasts with DOX-inducible lentiviruses, isolating primary iPSCs in the presence of the drug, and finally differentiating to secondary fibroblasts. When secondary fibroblast lines were cultured in the presence of DOX without further viral infection, up to 2% of the cells were reprogrammed to pluripotent secondary human iPSCs. This system will facilitate the characterization of the reprogramming process and provides a unique platform for genetic or chemical screens to enhance reprogramming or replace individual factors.