April 17, 2014 3:49 am JST

STAP cells hold promise despite problems with papers: co-author

Yoshiki Sasai, co-author of controversial research papers on stem cells and mentor of lead author Haruko Obokata, apologizes at a new conference.

OSAKA -- Research papers detailing a new method for creating stem cells should be retracted because of credibility issues, but the studies are worth exploring further, a co-author of the controversial research papers said Wednesday.

     Yoshiki Sasai, deputy director of the Riken Center for Developmental Biology, was one of the authors of the pair of papers published in the Jan. 30 issue of the scientific journal Nature. He is also a mentor of Riken's Haruko Obokata, lead author of the articles describing a phenomenon called stimulus-triggered acquisition of pluripotency, or STAP.

     In his first appearance in front of the press since irregularities were pointed out about the articles, Sasai started the news conference in Tokyo by apologizing for helping write papers that have aroused suspicion. The problems in the papers and an investigative committee's conclusion that research misconduct took place "damaged confidence in Japan's science and technology as a whole," he said.

     The papers should be retracted "given that there are cracks in the parts of the handicraft," he said, referring to the papers.

     But Sasai stressed that the STAP cell research cannot be completely ignored, noting that there are some things that cannot be easily explained unless STAP cells are assumed to exist. "It's a promising hypothesis, and it needs to be verified," he said, indicating that he will wait to see the results of experiments being conducted by Riken.

     Sasai listed several reasons why he believes that the existence of STAP cells is a highly plausible hypothesis. There is video shot with a microscope of STAP cells being created, and genes showing that they are pluripotent can be observed, he said, adding that manipulation of the video is impossible.

     Sasai brushed aside speculation that he had looked at embryonic stem cells without realizing it. "Embryonic stem cells and STAP cells are clearly different in size," he said.

     He also argued that the images of STAP cells allegedly growing into a placenta cannot be explained with cells other than STAP cells.

     Sasai has been regarded as a gifted researcher since he was young, becoming a full professor at Kyoto University at the age of 36. After transferring to Riken, he has conducted cutting-edge research on embryonic stem cells and several of his papers have been published in Nature and other respected journals.

     Obokata has appealed the conclusion of Riken's investigative committee that she engaged in misconduct by fabricating and falsifying parts of the STAP cell papers. The committee is expected to decide soon whether to reopen the investigation.