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Japanese stem cell scientist Yoshiki Sasai dies

On July 2, 52-year-old Japanese stem cell scientist Yoshiki Sasai wrote a letter expressing great remorse.

He had co-authored two stem cell articles in the journal Nature and was just coming to terms with their retraction and ballooning controversy which was a great embarrassment for his famous research institute.

He also mentioned that he was shamed by his failure as a mentor.

According to the Japanese police he was found hanging from a rope attached to staircase railing by the security guard at Riken in Kobe, Japan. Two hours later, Sasai died at the hospital owning to cardiac arrest. Notes were found near him and one of them was addressed to Haruko Obokata, his star pupil.

This alleged research misconduct occurred during the formulation of "stimulus triggered acquisition of pluripotency" (STAP). Initially this was considered as a major breakthrough which could lead to treatments of illnesses including Parkinson?s disease.

Complications with research appeared almost immediately. The images did not seem original and the language in the study resembled the language of another study which was published a decade before this one. This was followed by accusations of plagiarism and then calls for a retraction.

In a 2012 Nature profile, Sasai was celebrated as the "brainmaker". He also published an article which announced the creation of human eye precursor with stem cells. He was receiving much praises for his work and planned to grow brain parts.

However, around two years later he came forward to give an explanation as to what went wrong with Obokata's STAP cell research. Although he maintained that its founding hypothesis remained viable, he said that the papers should be retracted. He also claimed that he advised Obokata's research when it was in the final stages of work and wasn't aware about the data errors.

An investigative Riken panel cleared him of misconduct but said that he bore heavy responsibility as he failed to catch the mistakes as a senior researcher.

Devastated by the retraction, Sasai wrote in his letter that "it has become increasingly difficult to call the STAP phenomenon even a promising hypothesis."

Meanwhile, Obokata is still trying to replicate the research. She is working under video surveillance at the same institution where his mentor Sasai committed suicide.