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Discredited STAP cells were likely embryonic stem cells

TOKYO—Tying up a loose end of a long-running stem cell research fiasco, yet another RIKEN investigating committee released yet another report in Tokyo today. It concludes that the so-called stimulus-triggered acquisition of pluripotency (STAP) stem cells, as well as the chimeric mice and teratomas supposedly derived from those cells, "all originated in cultures contaminated with (embryonic stem) cells, a fact that refutes all of the main conclusions of the two papers" that reported the the supposed breakthrough method of reprogramming adult cells. Those two papers, an article and a letter, appeared online in Nature on 29 January.

The committee determined that three supposed STAP stem cell lines were actually likely to be three previously existing embryonic stem (ES) cell lines. "It is unlikely that there was accidental contamination by three different ES cells, and it is suspected that the contamination may have occurred artificially," the committee concluded in a report released today. However the panel could not find conclusive evidence of deliberate contamination, nor of who might be responsible. "We cannot, therefore, conclude that there was research misconduct in this instance," the committee reported.

However, the committee did find "research misconduct involving fabrication" in the production of two images in the article that had no supporting experimental data. The images are Fig. 5c: Growth curves of STAP stem cells and Fig. 2c: DNA methylation. The committee laid responsibility for the fabrications on Haruko Obokata, the lead author of both papers.

The committee's announcement came a week after a separate RIKEN group announced it could not reproduce the STAP cell method even with Obokata's help. The same day, Obokata resigned from the RIKEN Center for Developmental Biology (CDB) in Kobe, home to most of the research team.

A previous investigating committee had looked at the papers and reported on 1 April that Obokata was guilty of two counts of misconduct for fabricating and falsifying images. That committee only investigated six specific allegations of image manipulation. Nature retracted the papers in July. This second investigating committee was formed in September to take a closer look at the papers in response to additional allegations of problematic images. It relied on sequencing and other genetic analyses of materials taken from the Wakayama and Obokata labs; a review of notebooks, documents, and e-mails; and interviews with involved researchers.

While blaming Obokata for the misconduct, the committee cited two senior researchers as bearing "heavy responsibility" for lax oversight. One is Teruhiko Wakayama, who headed the RIKEN laboratory in which Obokata worked; the other is Yoshiki Sasai, who had a major role in writing the papers. Wakayama, now at the University of Yamanashi in Kofu, previously said that he would accept some sort of disciplinary action for his role in the scandal. Sasai committed suicide in August as investigations were under way. Only one senior author is still at RIKEN, Hitoshi Niwa. A separate disciplinary committee will decide if he or any higher-ups should be disciplined. RIKEN, which manages a network of national laboratories, has already restructured CDB, cutting its staff by nearly half.

One of the papers' co-authors has been beyond the reach of RIKEN investigators: Charles Vacanti, a tissue engineer at Brigham and Women’s Hospital in Boston, an affiliate of Harvard Medical School. Obokata initiated her work on STAP cells while a postdoc in Vacanti's lab. Mutsuhiro Arinobu, a RIKEN executive director, said that although they have been in contact with Harvard, input from Vacanti "is not included in this investigation."