The discovery of a defined set of transcription factors that can induce reprogramming of somatic cells to pluripotent stem cells (iPSCs) had a unprecedented impact on our view on future, cell transplantation-based regenerative medicine. Somatic cell reprogramming is a several weeks long process through which the cells reach the developmental state similar to embryonic stem cells. This cascade of events and the driving forces behind the phenomenon are very poorly understood. It is, however, crucial to uncover the fine details of this process in order to comprehend the true property of iPSCs and so better tailor their future therapeutic use.
We have recently developed a reprogramming method utilizing a transposon-mediated delivery of the reprogramming transgenes. This system has several advantages over the viral delivery-based alternative. Most notably, it allows for a seamless removal of the transgenes once pluripotent stem cells have been generated and they are no longer needed for stem cell self renewal. We also combined the doxycycline inducible transgene expression system with the transposon delivery-based reprogramming and found that these transgenes are very efficiently regulatable by adding or withdrawing doxycycline. In vivo differentiated somatic cells derived from iPSCs can be reprogrammed to “secondary” iPSCs (2ºiPSc) by simply adding doxycycline to the culture medium. Somatic cell lines produced with this method frequently return to 2ºiPSc in a "population" manner, which allows us to study the cascade of molecular events during the entire process of reprogramming. In this talk the current status of our multi-platform molecular characterization of the reprogramming process will be presented. We expect that utilizing genetic, epigenetic and proteomic profiling of the reprogramming process at a high definition level will give us answers to pivotal questions essential for the future potential and use of iPSCs in human medicine.