New questions have arisen over a human stem cell experiment that was hailed as a tremendous advance when it was announced in May.
Hwang Woo Suk, the South Korean researcher whose laboratory performed the experiment, told the journal Science yesterday that he was correcting some of the photographs that appeared as an online supplement to an article reporting a highly efficient recipe for producing human embryos through cloning, and then extracting their stem cells.
His co-author, Gerald P. Schatten of the University of Pittsburgh, said through a spokeswoman that Dr. Hwang had not informed him of the problem and that he had asked the university's Office of Research Integrity to conduct an inquiry.
An effort to reach Dr. Hwang by e-mail yesterday was unsuccessful.
The two scientists' article, published June 17, attracted considerable attention because it reported the first step toward the proposed goal of therapeutic cloning, the idea of treating patients with new tissues generated from their own cells. Dr. Hwang said he had converted the adult cells of 11 patients suffering from various diseases into embryonic form, in each case by transferring the nucleus of an adult cell into an unfertilized human egg. Scientists hope that tissues developed from such embryonic cells could be used to treat a wide range of serious diseases.
Dr. Hwang's team at Seoul National University, working around the clock and under fewer restrictions than those borne by American university researchers, has achieved three prominent firsts: the first cloning of a human adult cell last year, the development of the 11 embryonic stem cell lines this year, and the first cloning of a dog.
But last month Dr. Schatten announced he was severing relations with Dr. Hwang over the source of the human eggs used in his experiments. Dr. Hwang had assured him the donors of the eggs had not been paid, but Dr. Schatten apparently learned this was not the case and chose on those grounds to end their collaboration. Dr. Hwang stepped down as director of a new research center a few days later, saying members of his laboratory had donated their eggs under false names after he had refused their offers.
Dr. Schatten also cited an error in a table in the June article, saying it had made no difference to the overall findings. He did not make clear at the time, but wrote later in an e-mail message, that Dr. Hwang had called his attention to the error.
The new problem, raised over the past few days by Internet discussion groups in South Korea, is that photos of the cell colonies said to have been derived from the 11 patients in several instances show the same colony.
Yesterday Dr. Hwang sent Science an e-mail message stating that some of the photographs that the journal had published online, as a supplement to the article, had been "erroneously duplicated," said Katrina L. Kelner, the journal's deputy editor for life sciences.
But she added that a review of the journal's files had shown that in Dr. Hwang's original submission, the photos of the 11 human cell colonies were all different. The journal's referees were sent the original submission, so they could not have spotted the duplicate cell colony photos that were later published.
The duplicates must have been substituted at some later stage, but how the change occurred is not yet known. "Dr. Hwang has no idea how this happened," Dr. Kelner said. Presumably the error could have occurred in the publication process. "We can't reconstruct how it did happen," Dr. Kelner said.
The journal is about to publish a correction to a table in the same paper and a correction to Dr. Hwang's 2004 article, on the cloning of a human adult cell, which said that donors of the human eggs had not been compensated. The correction will say that each donor was paid a sum equivalent to $1,400, Dr. Kelner said.
Errors in scientific papers are not uncommon, and most mistakes are minor. But a few turn out to be signs of manipulation or otherwise serious misstatements that invalidate the conclusion. The editor of Science, Donald Kennedy, said yesterday that he was discussing with colleagues what corrections needed to be made with respect to the photos, but that so far he did not think Dr. Hwang's request for changes raised issues about the scientific validity of this work.
"How seriously I am bothered depends on what turns up as we examine these requests," he said.
Dr. Schatten declined to be interviewed about the photo duplication but said through a spokeswoman, Lisa Rossi, that he did not yet know if it would alter the study's conclusions. Ms. Rossi said Dr. Schatten's decision not to give interviews was supported by the dean of the Pittsburgh medical school, Dr. Arthur Levine. "There is no need to give an interview at this time because we need to move on," she said.
