First, tissue source influences the efficiency and fidelity of reprogramming91011. From aged mice, blood cells were reprogrammed more closely to fESC than dermal fibroblasts, which yielded only incompletely reprogrammed cells. Neural progenitor-derived iPSC were most similar to fESC, consistent with evidence that such cells can be reprogrammed with fewer transcription factors38. Whereas neural progenitors are not readily accessible, iPSC can be generated by direct reprogramming of human blood39.
