Though evidence points to the existence of STAP cells, they are still only a hypothesis worthy of study, a co-author of the papers on the revolutionary but unproved method to create pluripotent stem cells said Wednesday.

In his first public appearance since questions were raised about the alleged discovery of STAP (stimulus-triggered acquisition of pluripotency) cells, Riken researcher Yoshiki Sasai said work must be done to verify the “hypothesis” now that the credibility of the papers has been lost as a result of errors and defects.

“To retract the papers would be the most appropriate step to take for now due to credibility issues,” Sasai said at a press conference in Tokyo.

Sasai is a deputy director of the Riken Center for Developmental Biology, where Haruko Obokata, the lead author of the papers published in the British science journal Nature in late January, is also a researcher.

Sasai’s comments were in stark contrast to those by Obokata.

At her own news conference in Osaka earlier this month, Obokata stood by her claim that she had discovered STAP cells.

She went on to express confidence that other scientists would succeed in reproducing them, if only they acquired “a little know-how.”

That is a limb Sasai appears reluctant to go out on.

At his press conference, Sasai stressed that though the hypothesis was worthwhile, it still needed to be verified.

“STAP cells will have to be replicated by the Riken institute and some other party, but I believe it is worth doing so with respect to the potential of this research,” Sasai told a pack of reporters.

The 52-year-old researcher added that some data were hard to explain in the absence of the phenomenon of stimulus-triggered acquisition of pluripotency.

Because their credibility has been called into question due to various flaws, Sasai said the papers should be retracted, and new unbiased work be carried out to confirm their accuracy.

Sasai denied knowledge of the data errors, saying he mainly advised Obokata as she wrote the papers at a late stage of the project.

He expressed regrets about his failure to notice problems with the STAP cell papers. The project was conducted in an unusual environment involving multiple senior researchers, he said.

An investigative committee set up by the government-backed Riken research institute cleared Sasai of misconduct.

The panel, however, concluded he bore a “heavy responsibility” as a senior researcher for failing to verify the data contained in the papers.

The committee concluded that two points amounted to “research misconduct” by Obokata.

Sasai, a well-known stem cell researcher, was with Obokata at the news conference in Kobe on Jan. 28 when she announced the findings of her research on STAP cells.

Riken is reportedly scheduled to decide later this week whether to review its determination of misconduct by Obokata, as she requested last week.

Obokata denies fabricating or falsifying data in the research papers, and even claimed at the news conference last week in Osaka that she had produced STAP cells “more than 200 times.”

A Riken team, led by Riken researcher Hitoshi Niwa, another co-author of the papers, is in the process of trying to reproduce Obokata’s STAP cell results. These experiments are expected to take a year, according to the institute.

Asked if he believes in the developmental potential of STAP cells, Sasai said, “It is premature to say as a scientist whether I believe it or not at a time when the issue is still under investigation.”

Information from Kyodo and Jiji added

In a time of both misinformation and too much information, quality journalism is more crucial than ever.
By subscribing, you can help us get the story right.