Asahi Shimbun/Getty Images

Haruko Obokata, here at a 9 April news conference in Osaka, Japan, was found guilty of misconduct but stands by her claim of having produced stem cells by a novel procedure.

Nature today retracted two controversial papers on stem cells that it published in January1, 2. The retractions agreed to by all of the co-authors come at the end of a whirlwind five months during which various errors were spotted in the papers, attempts to replicate the experiments failed, the lead author was found guilty of misconduct, and the centre where she is employed was threatened with dismantlement. The retraction notice3 includes a handful of problems with the papers that had not been previously considered by institutional investigation teams.

Questions remain over what exactly was the basis for claims that embryonic-like stem cells could be created by exposing bodily cells to stress a technology the authors called stimulus-triggered acquisition of pluripotency, or STAP. But the controversy promises to have lasting impact on science in Japan, global stem-cell research, and the scientific community more broadly including changes in editorial policy at Nature. An Editorial posted today with the retractions notes the need for improvements in publishing procedures: The episode has further highlighted flaws in Natures procedures and in the procedures of institutions that publish with us. (Natures news and comment team is editorially independent of its research editorial team.)

The first of the two papers1 described a method of using acid exposure or physical pressure to convert spleen cells from newborn mice into pluripotent cells cells that can become any cell in the body. The second paper2 further impressed stem-cell scientists with data showing that the STAP process created cells that could differentiate into placenta cells, something that other pluripotent stem cells, such as embryonic stem cells and induced pluripotent stem cells, do not normally do.

But within weeks, duplicated and manipulated images were discovered, focusing attention on the source of data provided by Haruko Obokata, a biochemist at the RIKEN Center for Developmental Biology in Kobe and first author on both papers. Scientists also reported difficulties in replicating the experiments.

A RIKEN investigation team looking into the papers announced on 1 April that Obokata had been found guilty of two counts of scientific misconduct. RIKEN rejected an appeal, and advised her to retract the papers in May. Co-author Teruhiko Wakayama of the University of Yamanishi had been arguing for retraction since March.

Obokata and Charles Vacanti, an anaesthesiologist at the Brigham and Womens Hospital in Boston, Massachusetts, and the senior corresponding author on the first article, both stood by its claims, but later changed their positions after new errors emerged. Obokata gave her consent to the retraction of both papers on 4 June.

The retraction notice published today lists five new errors. The first four note that captions do not describe what is in the corresponding images or figures, without reflecting on how this relates to the experimental data. The fifth, relating to the first paper1, notes that purported STAP cells are of a different genetic background from those supposedly used in the experiments something it calls inexplicable discrepancies.

The notice concludes: These multiple errors impair the credibility of the study as a whole and we are unable to say without doubt whether the STAP-SC [stem cell] phenomenon is real.

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Papers on stress-induced stem cells are retracted