Reports of a new kind of stem cell, produced by simply stressing mature mouse cells, kicked up a storm of controversy soon after their publication in Nature on 30 January. Duplicated and manipulated images as well as plagiarism were found in the two papers, which led to a verdict of misconduct for the lead author, Haruko Obokata of the RIKEN Center for Developmental Biology in Kobe, Japan. There have also been calls for a retraction (which, for at least one of the papers, looks increasingly likely). But the controversy has left open a key question: does the phenomenon, known as stimulus-triggered acquisition of pluripotency, or STAP, exist?
The answer, according to Japanese media reports today on the results of genetic tests on the cells used in the STAP experiments, is no.
STAP cells were claimed to be made by exposing bodily cells to acid or subjecting them to physical pressure. These cells take on characteristics of embryonic stem cells. If further manipulated, they will also form self-renewing stem cell lines, called STAP stem cells, which share most properties of the embryonic stem cell lines. The Nature papers reported the creation of eight STAP stem cell lines. (Note: Nature’s news and comment team is editorially independent of its research editorial team.)
In March, one of the co-authors of the STAP papers, Teruhiko Wakayama of Yamanashi University, did a simple genetic analysis and found that some of the supposed STAP stem cell lines he had produced outside of the experiments described in the papers did not match the strain of mouse from which they were supposed to have been derived. This would mean that the cells came from a different mouse to that claimed, suggesting contamination. But he did not find a problem with the STAP stem cell lines that were reported in the Nature papers. To verify his results, Wakayama sent some 20 stem cell lines, including samples of the eight reported in the papers, to an independent, but unnamed, genetic analysis team for more precise tests.
According to Japanese media reports quoting “multiple sources”, the results of those tests have now been sent to RIKEN, Obokata’s employer and the institution that found her guilty of misconduct. They conclude that none of the STAP stem cell lines match the original mouse strains from which they were supposedly taken, calling into question whether the STAP phenomenon has ever been demonstrated. Wakayama says he will release detailed results at a press conference soon.
It was also reported that RIKEN will likely enlist Obokata in its ongoing efforts to try to reproduce the STAP results.