Induced pluripotent stem cells (iPSCs) hold enormous promise for regenerative medicine: they have the potential to develop into cells of any type, just as embryonic stem cells do, but do not require the controversial use of human embryos. Until now, the most efficient way to make iPSCs from human skin cells required a virus to ferry four 'reprogramming' factors into cells.

Edward Morrisey at the University of Pennsylvania in Philadelphia and his colleagues describe a recipe for making iPSCs that does not require these four factors, and boosts the efficiency of the reprogramming process. By infusing cells with a viral vector encoding certain small, RNA strands called microRNAs, the team was able to reprogram human skin cells two orders of magnitude more efficiently than is possible with the standard method.

Cell Stem Cell 8 376–388 (2011)