Scientific breakthrough as normal skin cells 'take on powers' of embryonic cells

Stem cells, found in the adult body and in embryos, are master cells, capable of turning into every sort of tissue.

They offer hope as a "repair kit" for the body, replacing dead, defective and worn-out cells and tissue.

Embryonic stem cells offer the most promise. But their use is mired in controversy, as harvesting them from an embryo in the first days of life leads to its death.

However, the ability to make stem cells from human skin could eventually make the use of embryos redundant, quashing the ethical storm surrounding the issue.

The latest research, hailed by scientists and ethicists, also provides a fast-track route to stem cells matched to the individual.

Stem cell expert Dr Robert Lanza said: "This work represents a tremendous scientific milestone. It's a bit like learning how to turn lead into gold." Two teams of scientists have shown it is possible to reprogramme human skin cells so that they are virtually indistinguishable from embryonic stem cells.

Writing in the journals Cell and Science, they described how cocktails of genes rewound the biological clock of skin cells.

Experiments showed that the rejuvenated cells, like embryonic stem cells, were capable of turning into a variety of cell types, including brain and heart cells.

"The induced cells do all the things embryonic stem cells do," said University of Wisconsin-Madison researcher Professor James Thompson. "It's going to completely change the field."

Kyoto University researcher Dr Shinya Yamanaka said the cells could be used to research diseases and test drugs.

In the long-term, it could allow the generation of replacement organs that are a genetic match to old body parts.

It had been thought that the best way to do this was with cloning - in which a patient's cell is used to create a genetically identical embryo packed with stem cells.

But Professor Ian Wilmut, the British creator of Dolly the sheep, says the new technique is so promising that he is abandoning work on the cloning technique that he pioneered.

Josephine Quintavalle, of campaign group Comment on Reproductive Ethics, said: "The idea that cloning of humans becomes a thing of the past is a great idea."

But others warned reprogramming of adult cells is in its infancy, making it too early to abandon embryo research.