A Japanese scientist called on Monday for his own headline-grabbing study on stem cells to be withdrawn from publication, saying its findings had been thrown into too much doubt.
The research - hailed when it came out in January as a breakthrough that could herald a new era of medical biology - was covered widely in Japan and across the world after it was published in the highly reputable science journal Nature.
But since then, there have been reports that other scientists have been unable to replicate the Japanese team's results and that there may have been problems with its data and images.
"It is no longer clear what is right," Teruhiko Wakayama, a professor at Japan's University of Yamanashi who was part of the researcher team, told public broadcaster NHK.
The study, described as game changing by independent experts when it was published, appeared to show a simple way to reprogram mature animal cells back into an embryonic-like state that would allow them to generate many types of tissue.
The results appeared to offer a promise that human cells might in future be simply and cheaply reprogramed back into embryonic cell-like cells - in this case cells dubbed Stimulus-Triggered Acquisition of Pluripotency, or STAP, cells - suggesting a simple way to replace damaged cells or grow new organs for sick and injured people.
"When conducting the experiment, I believed it was absolutely right," Wakayama said.
"But now that many mistakes have emerged, I think it is best to withdraw the research paper and, using correct data and correct pictures, to prove once again the paper is right. If it turns out to be wrong, we would need to make it clear why a thing like this happened."
A Nature spokesperson said "issues relating to this paper" had been brought to the journal's attention and it was conducting an investigation, but made no further comment.
Robin Lovell-Badge, a stem cell expert at Britain's National Institute for Medical Research, cautioned against premature assumptions on whether the research was flawed.
The Japanese researchers, joined by others from Brigham and Women's Hospital and Harvard Medical School in the United States, took skin and blood cells, let them multiply, then subjected them to stress "almost to the point of death," they explained, by exposing them to various events, including trauma, low oxygen levels and acidic environments.
In one test, they bathed the cells in a weak acid solution for around 30 minutes. Within days, the scientists said they had found that the cells had not only survived, but had recovered by naturally reverting into a state similar to that of an embryonic stem cell.
Yet no other research team has yet been able to replicate the findings.
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