Researchers have found a surprisingly quick and apparently safe way to transform ordinary skin cells into both stem cells -- the body's master cells -- and muscle cells.

They said on Thursday their method may provide a way to generate tissue in a new science called regenerative medicine, which doctors hope will eventually lead to ways to repair injuries and eventually perhaps even replace whole organs.

Reporting in the journal Cell Stem Cell, Dr. Derrick Rossi of Harvard Medical School and colleagues said they were working on new ways to make induced pluripotent stem cells or iPS cells.

These cells closely resemble embryonic stem cells -- the body's true master cells, which can give rise to all of the body's cells and tissue and which also flourish in the lab.

It takes just 3 or 4 genes to turn back the clock on skin cells or other ordinary cells, and make them behave like stem cells. But most ways of doing this involve using a virus to carry the new genes into the cell, or DNA, and these techniques can lead to other problems, including tumors.

Rossi and colleagues in stem cell leader George Daley's lab tried a new method, using RNA instead. RNA is the compound that carries out DNA's instructions.

To their surprise, RNA from the four stem cell genes worked to transform ordinary skin cells into iPS cells. These cells could, like stem cells, be made to form beating heart cells, nerve cells and other cell types.

They were also able to directly transform skin cells into muscle cells, they reported.

CELL-BASED THERAPIES

We believe that our approach has the potential to become a major and perhaps even central enabling technology for cell-based therapies and regenerative medicine, they wrote.

The methodology described here offers several key advantages over established reprogramming techniques.

They said, for example, it should make it easier for less specialized and experienced scientists to make and work with the cells.

Daley and other researchers also work with human embryonic stem cells and said using iPS cells was not an alternative to the controversial embryonic cells. They said all types of stem cell research were equally important as scientists learn how to use them.

The future of human embryonic stem cell research is being debated in U.S. courts and in Congress. Opponents of the research say it is wrong to destroy a human embryo for any reason, even if the embryos are leftovers from fertility clinics that are destined for destruction.

Opponents of the research have sued the U.S. government and the case is being considered by federal courts. A U.S. appeals court ruled on Tuesday that federal funding for human embryonic stem cell research may continue pending a full appeal.

Members of Congress who support embryonic stem cell research say they are working on legislation to make it clear what the government may pay for.

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