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Scientists Report Advance in Stem Cell Alternative

Hochedlinger said his team is working to streamline the conversion, perhaps by supplementing the introduced genes with chemicals that flip biological switches. Many researchers suspect they will eventually find ways to transform cells much more cleanly without transferring genes at all.

Although additional work will be necessary to prove that the new approach will work with human cells, Hochedlinger said he is confident it will.

"There's no reason to believe it would not work," he said.

Lanza said the advance should unleash a flurry of work on iPS cells.

"Although the advent of iPS cells has been exciting, it has been extremely frustrating not being able to use these cells clinically to help people. Clinical translation has been dead in its tracks," he said. "The use of iPS cells to treat or even cure human disease may not be far away."

Critics of embryonic stem cell research said the work offered yet more evidence that research on embryonic cells is unnecessary. Last month, another Harvard team announced that it had converted adult cells directly into another type of adult cell, possibly offering another less contentious alternative.

"This is the latest in a line of studies showing that the practical problems associated with using 'reprogrammed' adult cells are rapidly being solved," Richard Doerflinger of the U.S. Conference of Catholic Bishops said in an e-mail.

But Hochedlinger and others said it is important to continue to work on embryonic stem cells as well as adult stem cells and reprogrammed adult cells, because it remains far from clear which will eventually prove most effective.

"We just don't know yet which ones will be useful for which types of treatment," said Mark A. Kay, a gene therapy researcher at Stanford University.

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