Efforts to replicate the STAP cell findings have not been successful so far, the RIKEN Institute has reported.
Dr Hitoshi Niwa, who leads a team that has been trying to verify the stimulus-triggered acquisition of pluripotency or STAP phenomenon since April, said: 'We're still midway, but there's a possibility that STAP cells don't exist'. Dr Niwa is a co-author in the STAP studies and a principal investigator at the RIKEN Center for Developmental Biology in Kobe.
The research, originally published in Nature in January this year, claimed that a simple acid bath is able to trigger conversion of a type of blood cells into pluripotent stem cells that can develop into any cell type in mice. The work attracted worldwide attention and was considered a breakthrough in regenerative medicine, but quickly faced criticism due to a number of errors.
A RIKEN investigating committee found lead author Dr Haruko Obokata guilty of research misconduct, but cleared other co-authors. Eventually, the articles were retracted at the beginning of July.
For the verification experiments, the team at RIKEN have been following the procedure to create STAP cells as detailed in the original articles, using 'acid baths' of spleen mouse cells. However, no activity from genes signifying that stem cells have been created has been detected. The attempts will continue and other conditions, such as use of other type of mice, organs and chemical stresses, will be tested. Dr Obokata has also been given the chance of replicating her work within RIKEN, but in a separate effort to Dr Niwa's team.
However, the lack of validity so far comes as another blow to the STAP saga. Dr Yoshiki Sasai, who was the deputy director of the RIKEN Center for Development Biology and also a co-author of the STAP studies, committed suicide at the beginning of August.
The work is expected to be completed by March 2015, and the results of both investigations will be collated in a report assessing the fidelity of the original STAP publications. The latest interim report does not include information about the progress of Dr Obokata's work.
RIKEN has addressed the negative publicity of STAP research and its consequences by announcing its plan to downsize the Center for Developmental Biology, renaming it and re-launching it in November 2014 under new management. It has since reported that the reform plan would be carried out 'not for the sake of RIKEN, but for the sake of the society as a whole'.