In mid-February, researchers reported a startling breakthrough: a wide variety of cells could be converted into a very flexible form of stem cell by placing them in a mildly acidic bath and then growing them in carefully controlled conditions. But we've entered a world where post-publication peer review is common, and many readers began to look over the results for problems that the paper's original reviewers may have missed. They quickly found them.

Investigations were quickly launched both by the journal Nature, which published the paper, and RIKEN, the Japanese research organization where a number of its authors worked. On Friday, RIKEN issued a preliminary report where it detailed the six problems it was looking into. It came to conclusions about two of those problems. The report concludes that there have been problems with the handling of images in the paper, but they appear to be accidental and don't rise to the level of research misconduct.

The four issues remaining, however, include plagiarism and the use of images from unrelated research in this paper, both of which could potentially rise to the level of misconduct.

In the mean time, people have continued to try to replicate this technique without success. And the problems have reached the point where one of the authors has called for the work to be retracted until all of the questions have been answered. A number of other authors, however, see little need to do so, which means that we're likely to have to wait either for RIKEN to complete its investigation or for someone else to successfully produce these cells.