South Korean cloning expert Hwang Woo-suk yesterday countered claims by a colleague that he faked stem-cell research.
He said at a press conference in Seoul that he could prove his team of researchers had produced human embryonic stem-cell lines tailored to specific patients.
The research was reported in May in the journal Science, but one of the study's co-authors, Roh Sung-il, charged Thursday that most, and possibly all, of the stem-cell cultures produced in the research were fabricated.
Hwang admitted some "human errors".
"The fact remains that our research team was successful in creating stem cells from patients' skin cells," said the 52-year-old scientist whose research has made him a national hero.
"Still, there were mistakes made, human errors, in taking photographs and in the preservation of the stem cells," he said.
Because the study contains faulty data, Hwang said, he will ask the permission of his 24 co-authors to withdraw the study.
Roh, who provided human eggs for Hwang's research, said in interviews on South Korean television Thursday night that he had met Thursday with Hwang who had admitted that his own stem cells in the research under question had died and he had used ones from Roh's laboratory at the MizMedi Hospital in Seoul for the paper published in Science.
The revelation was the latest to call into question Hwang's research, once called revolutionary.
Hwang and his team at Seoul National University reported last year that they had become the first scientists to clone a human embryo.
This year, they reported the first cloned dog and, in the research questioned by Roh, the first stem-cell lines created from cloned human embryos and, therefore, tailored to specific patients.
The most recent research was hailed as offering potential breakthroughs for incurable diseases, such as Parkinson's and Alzheimer's as well as diabetes in which replacement cells could be genetically matched to patients, thereby removing the fear of tissue rejection.
The work also led Hwang in October to launch the World Stem Cell Foundation as part of a large consortium of scientists on three continents working on stem-cell research for therapeutic use.
However, Roh threw Hwang's work into question by saying that nine of the 11 stem-cell lines in the Science study had been faked and the authenticity of the other two could not be confirmed.
His comments followed Hwang's resignation last month from Seoul National University after Hwang admitted that his team had obtained eggs for its work from junior researchers or from paid donors, violating global ethics guidelines.
Hwang and his researchers have denied allegations of research manipulation as doubts have grown about the authenticity of the work on the cloned human stem-cell cultures.
Last month, the lead US partner in the South Korean research, Gerald Schatten of the University of Pittsburgh, said he was ending his nearly two-year work with Hwang, and this week, Schatten asked Science to remove his name from the author list of the May article.
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