A study which promised a revolutionary way to create stem cells should be quashed after claims its data was faulty, a Japanese research institute has said.
Riken institute head, Ryoji Noyori, who jointly won the Nobel Prize for chemistry in 2001, also heaped criticism on lead researcher Haruko Obokata for her "sloppiness" and warned the controversy could shake the public's faith in research.
The findings, published by 30-year-old Obokata along with other Japanese researchers and a US-based scientist in the January edition of British journal "Nature", outlined a relatively simple way to grow transplant tissue in the lab.
But it faced hard questions as the respected institute, which sponsored the study, launched an inquiry last month over the credibility of its data used in the explosive findings.
Among key concerns was that researchers used erroneous images -- crucial to supporting the study -- which resembled those used in Obokata's doctoral dissertation in 2011.
"I apologise that the papers which Riken researchers recently announced in Nature caused an incident that could hurt the credibility of the scientific community," Noyori told a press briefing.
"This immature researcher handled and collected enormous amounts of research data, and handled it with sloppiness... This must never happen."
Riken did not offer an opinion on whether the results of the study were valid, citing a continuing probe. But the institute itself cannot unilaterally retract the paper.
"I have judged that what is most important was for the paper to be swiftly retracted and to conduct the research again. I have suggested that to the authors," said Masatoshi Takeichi, director of Riken's Centre for Developmental Biology.
"However, retraction of the paper is left to the Nature magazine, upon a full agreement of all of the core authors involved."
- "Hard to believe after so many mistakes" -
Japanese media reports Friday had said Obokata -- who was not at the press briefing -- had agreed that the research should be pulled back, in what would amount to a serious professional embarrassment and deflate hopes of a major advance in the field.
But a joint statement signed by Obokata and two other researchers, released by Riken on Friday, only said the trio were "considering a possible retraction".
The study had been billed as the third great advance in stem cells -- a field that aims to reverse Alzheimer's, cancer and other crippling or lethal diseases.
It took a big hit earlier this week after Teruhiko Wakayama, a Yamanashi University professor who co-authored the article, called for a retraction.
"It's hard to believe the findings any more after so many mistakes in the data," he told broadcaster Nippon Television.
However, another co-author, Charles Vacanti, a tissue engineer at Harvard Medical School and Brigham and Women's Hospital in Boston, has stuck by the results.
"It would be very sad to have such an important paper retracted as a result of peer pressure, when indeed the data and conclusions are honest and valid," he told the Wall Street Journal this week.
Nature has said it has launched its own investigation.
Stem cells are primitive cells that, as they grow, become differentiated into the various specialised cells that make up the brain, heart, kidneys and other organs.
The goal is to create stem cells in the lab and nudge them to grow into these differentiated cells, thus replenishing organs damaged by disease or accident.
The researchers' groundbreaking findings said that white blood cells in newborn mice were returned to a versatile state through a relatively simple process that involved incubating them in a weakly acidic solution for 25 minutes, followed by a five-minute spin in a centrifuge and week-long immersion in a growth culture.
Riken's research held major promise as the next advance in the field after earlier work had come under fire for various reasons, including the use of embryonic stem cells. That method entails destroying the embryo, something opposed by religious conservatives and others.