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This is the VOA Special English SCIENCE REPORT.

Researchers at an American medical center say special stem cells in normal human blood can develop into other kinds of healthy, new tissue. The new findings could become important in forming public policy concerning stem cell research.

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Adult stem cells are unformed cells that exist in the blood and blood-making tissue of the body. Researchers at M-D Cancer Center in Houston, Texas say adult stem cells taken from blood can create new tissue in several organs.

They made the discovery after examining about twelve patients who had received blood from family members. The blood was rich in the rare stem cells that make red and white blood cells.

The patients needed the blood and stem cells after cancer treatments had destroyed the ability of their own bone marrow to make new blood cells. The doctors had thought the stem cells would only restore the patients' ability to make new blood cells.

However, they found that some of the stem cells spread to the patients' livers and began to grow liver cells. Some of the stem cells also grew into skin cells and cells in the intestine. The researchers said some of the stem cells settled into the patients' organs within two weeks.

The research was published in the New England Journal of Medicine.

The doctors who did the research say the tests prove that adult stem cells can become liver, skin and other kinds of cells. The experiment appears to show that adult stem cells are more useful than medical researchers had thought.

Until recently, doctors did not think that adult stem cells could produce new tissue in organs. For this reason, many people have urged Congress to permit research on embryonic stem cells taken from fertilized human eggs. These unformed embryonic stem cells are believed to be able to become any kind of tissue in the body. However, the Bush administration has put limits on embryonic stem cell research. President Bush believes it is not moral to experiment on fertilized human eggs.

If confirmed, the new discovery will add to the debate over stem cells. It will also strengthen the idea that adults have cells that can repair damage to organs. And experts say it could lead to new treatments for diseases based on using the body's own cells.

This VOA Special English SCIENCE REPORT was written by Mario Ritter.