The great promise inherent in stem cell research has taken a huge leap forward with the announcement that stem cells have been produced from ordinary skin cells.
The research by separate groups working in Japan and the US opens the way to virtually limitless supplies of stem cells, which scientists believe can be used to treat intractable diseases.
The findings also mean that personalised treatments are on the way using cells that will not be rejected by the body because they can be made genetically identical to the recipient.
The work by scientists at Kyoto University in Japan and the University of Wisconsin in the US is focused on a new way to produce stem cells, the body's own "starter" cells that can convert into any of its 220 different cell types.
Ethical constraints have hamstrung the advance of stem cell research because the most powerful starter or "pluripotent" cells were previously only available by harvesting them from growing human embryos or by cloning embryos. In both cases this resulted in the destruction of the embryo, a consideration that has blocked stem cell research in Ireland.
Now these ethical constraints have been broken following the research which is published this morning in the journal Cell and in the online version of Science.
Prof Shinya Yamanaka in Japan had previously announced cell reprogramming in mice, the first to have achieved this. Now he has accomplished the same feat using human tissues.
"We just applied the same protocol to human pluripotent cells and it works," the scientist said. "It's amazing. Those cells were skin cells only two to three weeks ago and now they are beating cardiac cells in a dish."
Prof James Tomson, the scientist who in 1998 first extracted embryonic stem cells, led the Wisconsin group. Both teams employed similar methods to reprogramme the cells, using a retrovirus to carry just four genes into the skin cells. Once active, this DNA causes the cell to "forget" how to be a skin cell and changes it back into a stem cell.
The new stem cells were then treated to become different tissues including heart, brain, muscle, fat and cartilage cells using methods already established for growing tissues from embryonic cells.
Research groups at Harvard University and other centres independently confirmed the result.
"More research is necessary to determine how closely related these cells are to embryonic stem cells, but these methods should be useful for developing disease models and for drug development," Prof Thomson's team write in Science. There are also problems related to the use of a virus and the introduced genes, which cause a high proportion of cell lines to become cancerous.
Given these uncertainties both scientists urged continued research into embryonic stem cells in case intractable problems arose using the new technique.
Prof Yamanaka suggested yesterday that the technique could spark new ethical worries and said the introduction of controls to regulate the use of human stem cells was essential.
This was particularly true because the technique was far easier to use than embryo cloning and could easily be repeated in labs around the world.
President George Bush was "very pleased" by yesterday's development, according to White House press secretary Dana Perino.
"By avoiding techniques that destroy life, while vigorously supporting alternative approaches, president Bush is encouraging scientific advancement within ethical boundaries," she said.
Earlier in his administration president Bush had blocked federal research funding for some embryo research because it caused the destruction of the embryo.
The discovery would lead to powerful new medical treatments according Prof Ian Wilmut, the scientist who created Dolly, the cloned sheep. "It will revolutionise the way in which we study and treat human disease," he said.
He has already announced his intention to abandon his work on therapeutic human cloning in favour of this new technique.
"It is a win for science and for ethics," said Richard Doerflinger, deputy director of pro-life activities at the United States Conference of Catholic Bishops. - (additional reporting, Reuters)
