The Wisconsin team got one pluripotent cell for every 10,000 cells.
"We should now be able to generate patient- and disease-specific [induced pluripotent stem] cells and then make various cells, such as cardiac cells, liver cells, and neural cells," team leader Shinya Yamanaka of Kyoto University said in a statement.
Sidney Golub chairs the Human Stem Cell Research Oversight Committee at the University of California, Irvine.
In addition to alleviating concerns over embryonic stem cells, the new techniques may reduce the need to carry out somatic cell nuclear transfer, a controversial technique that uses harvested eggs to clone cells, he said.
Such a procedure is used to create animal clones, such as Dolly the sheep, and is being explored as a way to create human stem cell lines.
"This approach, if generally applicable, may be a good alternative to somatic cell nuclear transfer," he said. "If it turns out to be a good alternative, obtaining donated human oocytes [eggs] may be less important for research progress."
The advance, if it proves generally applicable, will allow the creation of cell lines that are genetically identical to an individual needing stem cell therapy, added Timothy Caulfield, research director of the Health Law Institute at the University of Alberta.
This would eliminate the possibility of tissue rejection, one of several barriers still impeding the development of stem-cell-based medical treatments.
Caulfield said that the findings hold "tremendous amount of potential, but [applications] could be years and years away.
"There are many other issues to consider," he added. "If these cells are truly pluripotent, could they form eggs and sperm? If so, what then?"
The effect of the findings on federal funding is also debatable.
"It is not clear if this work would be eligible for federal funding under the restrictions put in place by President Bush in 2001, as the genes that were transferred were obtained from embryonic stem cells," UC Irvine's Golub said.
"Even if this work was eligible, President Bush's recent veto of the bill containing the NIH appropriation means that little new federal funding will be available for any new research developments," he added.
Caulfield also suggested that the research has a significant downside, because the pluripotent cells are not true stem cells and no one yet knows the true extent of their abilities.
"For those who want to receive federal funding for embryonic stem cell research, it could be a blow," he said.
"This will allow those against the research, particularly politicians, to say that embryonic stem cell work is no longer necessary, so there is no need for federal funds. This, in my view, is a mistake."
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