A developmental biologist in Hong Kong says that he has succeeded in reproducing a method of reprogramming cells to an embryonic-like state by applying mechanical stress. The development, which the author describes as a “megatwist”, took place on 1 April, the same day that the Japanese researcher who invented the method was found guilty of scientific misconduct. The new claim, however, has been greeted with scepticism.
The technology, known as stimulus-triggered acquisition of pluripotency (STAP), has been under attack after two papers published on 30 January in Nature claimed that it worked in mouse cells. Numerous attempts to replicate the results have failed, forcing the authors to back away from their initial characterization of their method as one that is simple to implement. Multiple flaws were also found in the papers, and on 1 April an investigation committee found the lead author, Haruko Obokata of the RIKEN Center for Developmental Biology in Kobe, Japan, guilty of scientific misconduct.
When others were giving up after repeated failures to reproduce the results by using a number of approaches, Kenneth Lee of the Chinese University of Hong Kong tried to precisely follow Obokata’s protocol, which stressed cells with an acidic solution to trigger the reprogramming. It didn’t work. When she released a modified protocol, he tried again, in vain.
Then Obokata’s former mentor and a co-author on the STAP papers, Charles Vacanti of Harvard Medical School in Boston, released his own protocol. It depended more on physically stressing the cell membranes — by passing them through narrow glass pipettes — than on acid.
Lee set up a team of four and made 150- and 75-micrometre pipettes. After three days of regular pipetting, the cells looked unhealthy and “yucky”, says Lee. “They looked dead.”
But when he carried out a genetic analysis on the cells, he found that three genes normally expressed in pluripotent cells were elevated, leading him to believe that pluripotency had been achieved. “I couldn’t believe it.” He posted his findings as a single bar graph on ResearchGate, a social-networking site for researchers (see ‘The new dilemma of online peer review: too many places to post?‘).
However one US-based stem-cell researcher, who did not want to be mentioned by name, worries that the results may be over-interpreted, noting that “in real pluripotent cells the markers are expressed at levels 1,000-fold higher than controls”. The expression in Lee’s cells was only ten-fold higher.
Andrés M Bratt-Leal, a research associate at the Scripps Research Institute in La Jolla, California, commented on Lee’s post that the numbers didn’t necessarily add up to “significant gene expression” and recommended that Lee make a better-controlled comparison.
Lee himself recognizes the possibility that “the expression of these pluripotent markers could be the by-product of unregulated gene expression by the dying or stressed cells”. Lee did the experiment only once, although he ran the genetic tests four times to assure himself of the result. He plans to repeat the experiment. In response to the sceptics, he asks other laboratories to give it a try.
He then adds: “I am not claiming that ‘STAP’ cells exist, only presenting the results of our research as it is — which is open to interpretation.”