Our results demonstrate that the ectopic expression of four transcription factors is sufficient to globally reset the epigenetic landscape of fibroblasts into that of pluripotent cells that are remarkably similar to embryonic stem cells, explains Dr. Hochedlinger. Dr. Plath adds The fact that our induced pluripotent cells are epigenetically similar to ES cells suggests that epigenetic abnormalities will not pose a problem for the potential therapeutic applications of induced pluripotent cells. The researchers went on to show that the induced pluripotent cells could differentiate into numerous cell types, including blood cells in culture and oocytes in animals. Importantly, two related papers being published in the journal Nature demonstrate that similar induced pluripotent cells can also give rise to fertilized embryos and viable offspring, respectively. Future studies are needed to examine whether direct reprogramming of human cells follows these promising patterns observed in mice.

These studies and other recent advances in strategies aimed at generating patient-specific stem cell lines are discussed in the review article by Dr. Shinya Yamanaka in the current issue of Cell Stem Cell.