Studies cast doubt on use of adult stem cells

Two new studies cast doubt on the tantalizing theory that adult stem cells can serve as the body's all-around repairmen, capable of converting into any type of cell to fight disease or replace faulty organs.

The findings, if confirmed, could force scientists to focus more on embryonic stem cells -- whose use is highly controversial because they are taken from embryos that are killed in the process.

The studies could also influence the debate in Washington, where the Senate is expected to take up the issue in the next few weeks of whether to ban the use of cloning to create human embryos for medical research.

Scientists have long known that stem cells from embryos are all-purpose cells that can transform themselves into different kinds of specialized tissue, such as muscle, bone, skin and organs. Researchers hope someday to harness this ability to treat various diseases and injuries.

In recent years, scientists have found surprising evidence that stem cells taken from adult creatures have some of the same transforming properties, or plasticity.

But the two new studies, conducted in separate laboratories in the United States and England and published online Wednesday by the journal Nature, cast doubt on that belief.

In the two studies, embryonic stem cells from mice were put in laboratory dishes with mouse bone marrow and brain cells. But instead of transforming into their neighboring cells, the stem cells simply merged their genetic material with the marrow and brain cells.

The researchers said the same phenomenon may have occurred in studies involving adult stem cells, and may have fooled scientists into thinking the cells had transformed themselves.

The new findings "call into question almost all of the data generated using adult stem cells," said Robert Lanza, medical director of Advanced Cell Technology, a Worcester, Mass., company not involved in the two studies.

He said the findings could influence the political debate.