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Coauthor of retracted stem cell papers commits suicide

According to The Japan Times, Yoshiki Sasai, 52, hanged himself and left behind two suicide notes and three other notes.Kyodo/Reuters/File

The controversy over a high-profile stem cell finding by Japanese and Boston scientists that was retracted last month took a tragic turn Tuesday when a Japanese scientist who coauthored the work committed suicide, Japanese news reports said.

According to The Japan Times, Yoshiki Sasai, 52, hanged himself at the research center where he worked and left two suicide notes and three other notes. One was addressed to Haruko Obokata, the young scientist who led the work and has been accused of scientific misconduct by Japan’s RIKEN institution, where she is now trying to repeat the experiment.

It said, “Be sure to reproduce STAP cells,” sources told the Japan Times.


Sasai oversaw Obokata’s writing, according to the newspaper, which also reported he had been hospitalized in March due to psychological stress.

In a retraction notice last month, the authors noted that an investigation by RIKEN had found extensive errors and “inexplicable discrepancies” that “impair the credibility of the study as a whole.”

The problems with the stem cell research have put Japanese scientists under an intense media spotlight, with several issuing public apologies. Just last month, there were reports that Obokata was chased by reporters on a motorcycle and then through a hotel. She is also said to have been treated at a hospital on and off since errors in the stem cell work began coming to light this year, according to Japanese news reports.

The experiments in one of the papers were designed and overseen by Dr. Charles Vacanti, an anesthesiolgist at Brigham and Women’s Hospital in Boston who originated the idea for the work. In two papers published in the journal Nature in January, the researchers reported that it was possible to create powerful stem cells able to become any type of tissue in the body simply by dipping mature cells in acid. The technique was called STAP, short for stimulus-triggered acquistion of pluripotency.


The stem cell scandal has led to uncertainty in Japan over the future of the Center for Developmental Biology at RIKEN, which an outside committee had suggested may need to be shut down. In a statement released in July when the papers were retracted, Sasai apologized.

“As a deputy director of our center, with responsibility for nurturing young researchers, I feel a deep responsibility for what has happened, and plan to comply with whatever decision RIKEN finally reaches regarding my own status,” Sasai wrote.

RIKEN officials released statements expressing sorrow and shock at his death.

Dr. George Q. Daley, a stem cell scientist at Boston Children’s Hospital, said Sasai’s death was a huge loss and that his contributions had been profound, launching stem cell scientists on a quest to use stem cells to grow miniature versions of organs in a dish.

Initially, many scientists said that it was the fact that stem cell heavyweights such as Sasai were coauthors of the two stem cell papers that gave credence to the acid stem cell papers’ stunning finding.

“Sasai was an expert in coaxing embryonic stem cells to become mini-organs, and in a startling contribution he showed that the retina could self-organize from stem cells in a dish, a breakthrough with tremendous promise for treating blindness,” Daley wrote in an e-mail. “He was a gifted scientist destined to continue to make momentous contributions, and his death is a tragic loss to the scientific community.”


The journal Nature also released a statement: “Yoshiki Sasai was an exceptional scientist and he has left an extraordinary legacy of pioneering work across many fields within stem cell and developmental biology, including organogenesis and neurogenesis.”

Related coverage:

Electrifying stem cell finding retracted

Fraud alleged in findings on stem cells

Scientists discover a new, simpler way to make stem cells

Evan Horowitz: Studies show many studies are false

Nature’s retraction notice

Carolyn Y. Johnson can be reached at johnson@globe.com.