A senior Japanese scientist embroiled in a stem-cell research scandal has been found dead in an apparent suicide.

Yoshiki Sasai had supervised and co-authored stem cell research papers that had to be retracted due to falsified contents. Hyogo prefectural police said Sasai, 52, was found on Tuesday at the government-affiliated science institute Riken, in Kobe, western Japan. Sasai was deputy chief of Riken’s Centre for Developmental Biology.

A security guard found Sasai suffering from cardiac arrest. He was taken to hospital and pronounced dead two hours later.

Police said Sasai left what appeared to be suicide notes but they refused to disclose their contents. The public broadcaster NHK said there were letters addressed to other researchers and senior scientists at the centre.

Sasai’s team retracted the research papers from the British science journal Nature over co-author Haruko Obokata’s alleged malpractice, which she has contested.

Retractions of papers in major scientific journals are extremely rare and the scandal was a major embarrassment to Japanese scientific research.

In two papers published earlier this year in the journal Nature the researchers reported that they had successfully transformed ordinary mouse cells into stem cells by exposing them to a mildly acidic environment. Scientists hope to harness stem cells to grow replacement tissue for treating a variety of diseases.

Riken later held Obokata, a main author of the research, responsible for falsifying data. The investigation also focused on Sasai and two other employees, though those three were not accused of research misconduct.



Sasai had said he was “deeply ashamed” over the problems in the papers.