LONDON — The need to clone embryos could be removed by a method to transform skin cells into versatile stem cells capable of overcoming the effects of disease.

Along with a second study published today, the research also shows that the proposal to use animal eggs for cloning human DNA could become redundant as science advances and throws up alternatives.

Embryonic stem cells — parent cells of all the 200 or so types in the body — could be used to generate unlimited supplies of cells and tissues, even organs in the distant future. They can be generated by cloning a tiny week-old embryo from a patient’s own cells.

But while some scientists want to use the resulting cells to avoid problems of rejection, there is an intense search for alternatives because of pressure from the anti-abortion lobby, the opposition of President Bush, and ethical concerns.

Now, pioneering work by a Japanese team to turn adult cells into an embryonic state, without having to create an embryo, has been extended by the Japanese team and reproduced by a second group in America.

This work suggests that after a heart attack, for example, skin cells from a patient might be turned by growth factors into muscle cells to repair damage to the heart.

Ian Wilmut, who led the team that cloned Dolly the sheep and first showed how the process of cloning can rejuvenate adult cells, said the latest work was “extremely exciting and astonishing.”

The new work by Shinya Yamanaka of Kyoto University underlines that the dream of converting adult cells into those that can grow into many different types can be realized remarkably easily.

Scientists have been racing to understand what it is about the process used to clone Dolly [nuclear transfer] that enables an adult cell to be returned to an embryonic state. They then try to mimic those events in the lab to change cells from one type to another.

Fibroblasts — a common cell type found in connective tissue — can be coaxed back into a state similar to an embryonic stem cell with a little genetic trickery, Mr. Yamanaka reports in Nature. The improved method, which sees a handful of genes added back to the cells by gene therapy before selection for a stem cell marker, means that no embryos are harmed in the creation of these cells.

When they studied how genes are used in these reprogrammed cells, they were typical of the activity seen in an embryo. In the test tube, the new cells look and grow like embryonic stem cells.

Both teams were also able to generate viable chimaeras from the cells, where the embryo cells created by the new method could be mixed with those of a mouse embryo to grow into a viable adult chimaeric mouse, which could pass on the DNA of the reprogrammed cells to the next generation.

Although the revised method still needs some tweaking, the research has caused tremendous excitement because it offers the prospect of making customized embryonic stem cells for patient-specific cell treatment from a simple skin biopsy.

Mr. Wilmut of Edinburgh University said, “Yamanaka’s work is extremely exciting, and it is encouraging to see it being repeated in another laboratory. They have shown some astonishing effects.”