iPS cells produce viable mice through tetraploid complementation

Mice from iPS cells Since iPS (induced pluripotent stem) cells arrived on the scene in 2006, their properties have been measured against the yardstick of the true embryonic stem cells that they mimic. A clutch of recent papers, two of them published in this issue, reports the production of viable adult mice from iPS cells, a notable technical feat that shows that these cells are very close indeed to embryonic cells in their potential to produce cells for all tissues and all organs. Zhao et al. used a technique called tetraploid complementation, in which chimaeric mice are generated from injected pluripotent cells, and the embryonic tissue is derived solely from the injected cells. Boland et al. produced fertile adult mice derived entirely from iPS cells generated by inducible genetic reprogramming of mouse embryonic fibroblasts. The availability of these mice will provide a new resource for the study of iPS cell-derived tissues for both research and cell replacement therapy applications.