(CNN) -- Researchers managed to create embryonic stem cells through cloning, a breakthrough in the field that was announced May 15 in the journal Cell. That study is now being called into question -- but not necessarily on scientific grounds.
It appears that the study authors, led by Shoukhrat Mitalipov at Oregon Health & Science University, made some errors in the graphical presentations when they submitted the manuscript. A commenter on the PubPeer website noticed some duplication of figures (the data plots, graphics and images in a scientific paper) and apparent errors in labeling.
Mitalipov acknowledged that the commenter made some valid points but told Nature.com, "The results are real, the cell lines are real, everything is real."
Emilie Marcus, editor-in-chief of Cell, posted a statement on the study in the comments on the Cell website:
"Based on our own initial in-house assessment of issues raised and in initial discussions with the authors, it seems that there were some minor errors made by the authors when preparing the figures for initial submission. While we are continuing discussions with the authors, we do not believe these errors impact the scientific findings of the paper in any way."
The study has received several comments relating to how fast it was reviewed for publication at the journal. The review process is not being questioned, Marcus said, and the paper was not considered any less thoroughly than usual despite its being published relatively quickly. According to Nature.com, the study was accepted three days after it was submitted, and it was published 12 days later.
Oregon Health & Science University released this statement:
"In response to the issues raised in PubPeer, OHSU has had several discussions with the journal which published the paper, Cell. Based on OHSU's own initial reviews and the original assessments by Cell, OHSU agrees that there were some minor errors made when preparing the figures for initial submission. Neither OHSU nor Cell editors believe these errors impact the scientific findings of the paper in any way. We also do not believe there was any wrongdoing."
The researchers are also sending more information to Cell, including photos and original data. "Our shared goal is to publish a correction noting the errors and correcting the photos as soon as both OHSU and Cell feel the issues are fully investigated," the statement said.
A South Korean scientist in 2004 claimed to have cloned human embryonic stem cells. Reports of Hwang Woo-suk's studies attracted worldwide attention and enthusiasm from researchers and patients, but in 2006 he acknowledged faking his findings after questions of impropriety emerged.
Hwang was convicted in 2009 of embezzling money and illegally buying human eggs, according to state media. He was sentenced to a two-year prison term suspended for three years.
Here's how the OHSU experiment in question actually worked:
Normally, an embryo is created when sperm enters the egg and it starts to divide. But, in the Cell study, Mitalipov and colleagues began with skin cells from an 8-month-old baby that had a genetic disease. They did not use sperm.
To create each embryo, they took the DNA out of an egg so that it was hollow and replaced it with the skin cell's DNA instead. The baby's DNA was the only genetic material being used.
With the help of chemicals, the egg started to divide just like a normal fertilized egg would. Then, within several days, embryos genetically identical to the baby were created, from which stem cells were derived. Researchers made more than 120 embryos using this method.
Embryonic stems research is inherently controversial because in order to use the stem cells for science, the embryo, which is a collection of cells that could develop into a fully formed human, is destroyed, even though embryos in these procedures are left over from in vitro fertilization.
However, Mitalipov said the embryos created in his study, from skin cells and eggs, would not grow babies. That would have required additional technology, and it wasn't part of the study.