Authors say conclusions still valid
The authors of a controversial paper on stem cells publish a correction of their work in this week's issue of Nature (see page 880), but say their overall conclusions still stand.
The paper in question, published in 2002, claimed to find evidence for so-called 'multipotent adult progenitor cells', or MAPCs, in mouse bone marrow (Y. Jiang et al. Nature 418, 41–49; 2002). The work was led by Catherine Verfaillie, now director of the Stem Cell Institute at the Catholic University of Leuven, in Belgium.
The correction states that figures showing proteins on the surface of the MAPCs contained many errors, including duplications. Verfaillie's group provides replacement data and says that the correction does not undermine the paper's conclusion that MAPCs can give rise to a wide range of different cell types.
The paper challenged the prevailing idea that only stem cells derived from embryos were highly flexible. Some of its results have been reproduced by other labs, but no one has been able to replicate the work independently in its entirety.
“I believe that despite the hype over the mistake, we and Nature made the conclusion that the final findings of the paper still stand,” says Verfaillie.
This February, an investigation convened by the University of Minnesota — Verfaillie's former institution — found that her group had used incorrect procedures in the Nature paper, and that some of the data contained in it might be flawed. The investigation was a response to questions from a reporter from the magazine New Scientist, who pointed out that the figure corrected today was partly reproduced with different labels in another paper in the journal Experimental Hematology (Y. Jiang et al. Exp. Hematol. 30, 896–904; 2002).
In response to the investigation, Nature convened a peer-review panel to analyse the data from the 2002 paper. According to Nature, the experts concluded that although the figure data were flawed, the paper's conclusions are still valid.
No allegations of fraud or misconduct have been levelled at Verfaillie or anyone from her group. There are still two investigations ongoing — one at the University of Minnesota and one at the Catholic University of Leuven — into a second set of allegations raised by New Scientist. These concern data from a paper in the journal Blood (M. Reyes et al. Blood 98, 2615–2625; 2001) and data in a US patent filing.
Verfaillie says her group cannot explain how the errors in the Nature paper occurred: “Why this happened, we have not been able to determine,” she says.
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