• Kyodo


A co-author of two controversial stem cell papers questioned the claims they made Monday, saying a new study showed that the cells purportedly used in the experiments did not appear to be STAP cells after all.

“There is no proof as to the existence of STAP cells,” University of Yamanashi professor Teruhiko Wakayama told a news conference. “All the results of the analysis are moving toward denying the existence of STAP cells but I cannot say that the cells absolutely do not exist.”

Wakayama added that he tried a dozen times to create STAP cells at his university but failed.

The headline-making papers and subsequent questions about their integrity rocked the scientific community in Japan and around the world. The papers claimed to have developed stem cells with “stimulus-triggered acquisition of pluripotency,” meaning that they can theoretically develop into any kind of tissue, at least in mice.

At the center of the scandal is lead author Haruko Obokata, whose papers, which were published by the British science journal Nature in January, said that she had successfully produced STAP cells using an astonishingly simple process.

After several discrepancies and allegations of misconduct surfaced, Obokata eventually agreed to retract the papers. But she has maintained throughout that her research remains valid and that the STAP condition did exist.

That assertion is now challenged by Wakayama’s revelation. The analysis he cited was conducted by a third-party entity using STAP cells that he had kept in storage.

Wakayama said the tests showed the cells did not match the mouse strains supposedly used in the research, which could suggest Obokata created STAP cells but based on a different mouse strain.

Asked whether he would continue his research on STAP, Wakayama said he could not verify the existence of such cells and that, at the moment, only Obokata has the capacity to re-create the phenomenon.

Wakayama also said that Obokata had access to embryonic stem cells. There are growing suspicions in the scientific community that the STAP cells may have actually been ES cells.

Obokata said she produced STAP cells more than 200 times using mice, but Wakayama said he could not replicate what she did because doing it 200 times on newborn mice would mean that he would need 1,000 mice for the study.

Wakayama also said he regrets not reading Obokata’s lab notes because if he had, he would have realized that her data management methods were “sloppy.”

The professor said he continues to communicate with his fellow co-authors but has only heard from Obokata once.

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