Two leading UK stem cell scientists, Azim Surani, and Anne McLaren, have given top marks to the Japanese discovery that adult cells can be reprogrammed to revert to an embryonic stem cell-like state. In an article earlier this year in the journal Cell, Shinya Yamanaka and Kazutoshi Takahashi, of Kyoto University, found that when four factors were turned on, adult mouse cells reverted to ES-like cells. In principle, say their British colleagues in Nature, the technique should also work with human cells.

If so, it could eventually be used to deliver all of the promised benefits of the ethically more contentious cells derived from human embryos: cellular therapies and greater understanding of how genetic factors influence diseases like diabetes. In an upbeat conclusion to their review, they write: "This approach may eventually eliminate the need to use early embryos for deriving stem cells -- an enticing objective, but one that will require extensive research on both mouse and human ES cells."