Generation of induced pluripotent stem cells from virus-free in vivo reprogramming of BALB/c mouse liver cells

The invivo cell reprogramming of terminally differentiated somatic cells to a pluripotent state by the ectopic expression of defined transcription factors has been previously shown in the BALB/c mouse liver upon plasmid DNA injection with no teratoma formation in the host tissue. Here, we hypothesized that the reprogrammed cells could be extracted from the tissue and cultured invitro. We called these cells invivo induced pluripotent stem (i²PS) cells because they showed pluripotent characteristics equivalent to a standard mouse ES cell line (E14TG2A). The pluripotent character of i²PS cells was determined by a battery of morphological, molecular and functional assays, including their contribution to adult tissues of chimeric mice upon blastocyst injection. These observations further confirm that terminally differentiated somatic cells in wild type, adult animals can be reprogrammed invivo using virus-free methodologies. The reprogrammed cells can generate invitro stem cell colonies that exhibit pluripotency similar to ES cells with numerous implications for the application of invivo reprogramming for tissue regenerative purposes.