The government-funded Riken institute on May 8 turned down an appeal by researcher Haruko Obokata to reinvestigate her controversial papers on so-called STAP cells. Riken also formally recommended that one of the two papers that Obokata wrote with a team of Japanese and U.S. scientists, which were published in January in the British scientific journal Nature, be withdrawn. But Riken's 21-page final report on the controversy is inadequate because it fails to delve into the question of why and how the research misconduct occurred. Without doing this it will be difficult for the institute to establish a system to prevent the recurrence of similar problems.

In the two papers, the 14-member research team headed by Obokata reported that some lymph corpuscles taken from 7-day-old mice and soaked in mildly acidic liquid for about 30 minutes developed into nerve and muscle tissues. They named this new way of reprogramming adult cells into pluripotent cells "stimulus-triggered acquisition of pluripotency" or STAP. The papers attracted worldwide attention, but later raised many questions.

On April 1, Riken's investigative' committee announced that Obokata committed two cases of research misconduct: fabrication and manipulation of data. Regarding images intended to show that STAP cells have the ability to change into various cells, the panel said that Obokata had used images "that very closely resembled images in her doctoral thesis" for Waseda University, which were created under different research conditions, and concluded there was "an act of research misconduct involving fabrication." Thus it rejected the authenticity of crucial evidence for the discovery of STAP cells.