Stem cells with the capacity to form any type of tissue can be created from adult cells without destroying embryos, according to new research that suggests a way of sidestepping ethical controversy over the field.

Three separate teams of scientists have used genetic trickery to wind back the biological clock of mature skin cells from mice, to give them the unlimited potential of stem cells that are normally found only in embryos.

Though it remains uncertain whether the same technique would work in humans, the successes raise the prospect that powerful master cells for use in medicine and research could one day be created from adult bodies, removing any need to use embryos.

Scientists pointed out, however, that even if this does prove possible, research into embryonic stem cells (ESCs) will remain essential in the medium term to study how the reprogrammed cells work.

ESCs are found only in early-stage embryos, and are attractive to medical researchers as they are “plutipotent” — they can give rise to all the 200 or so tissue types found in the human body. The goal is to find ways of directing their growth so they can be used to provide replacement tissue for treating conditions such as Parkinson’s, diabetes and spinal paralysis.

While research using these cells is legal under licence in Britain, it is opposed by some religious groups as ESCs can be harvested only by destroying embryos.

The United States currently bans federal funding for such work, and President Bush is expected to veto a congressional bill seeking to lift the ban. A key vote on the issue is to be held in the US House of Representatives on Thrusday.

Stem cells are also found in adult tissue, but these are normally more limited in their potential than embryonic cells. In August last year, however, a team at Kyoto University in Japan reported that by activating four genes in mouse skin cells, it was possible to make stem cells that appeared as pluripotent as ESCs.

That work has now been repeated by three teams, at Kyoto University, and the Whitehead Institute and the Harvard Stem Cell Institute in Massachusetts, whose results are published in the journals Nature and Cell Stem Cell.

Each group has confirmed more fully than was previously possible that the reprogrammed cells, which began as a kind of skin cell known as fibroblasts, are fully pluripotent. When injected into mouse embryos, the cells contribute to every cell type, and are passed on to the next generation.

“These reprogrammed cells, by all criteria that we can apply, are indistinguishable from embryonic stem cells,” said Professor Rudolf Jaenisch, who led the Whitehead team. “Germline transmission is the final and definitive proof that these cells can do anything a traditionally derived embryonic stem cell can do.”

He cautioned, though, that while it was hoped that the same technique would work in humans, that would not be known for several years.

“All these results are preliminary and proof of principle. It will be a while before we know what can and can’t be done in humans. Human embryonic stem cells remain the gold standard for pluripotent cells, and it is a necessity to continue studying embryonic stem cells through traditional means.”

British stem cell experts agreed that while the work is encouraging, it does not mean that ESC research is unnecessary.

Robin Lovell-Badge, of the National Institute for Medical Research in London, said: “This work emphasises that if scientists reasonably up-to-date with current knowledge in the field can not guess what is just around the corner, then it is extremely unlikely that politicians will be able to do so – a good reason why regulation is better than laws based on prohibition.

“Clearly the work offers hope that similar methods can be applied to human somatic cells, obtained from patients, to turn them directly into ES-like cells for research and eventually for cell-based therapies. There is still a long way to go, however.”

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