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Scientists Improve Heart Function in Sheep with Mouse Stem Cells

Heart failure, a life-threatening condition long seen in developed countries, is quickly becoming more prevalent in emerging countries.

It can be caused by coronary artery disease, where the heart does not get enough oxygen because the vessels that feed it are blocked by plaque. Heart failure can also be caused by conditions that overwork the heart, like diabetes and kidney failure. And the heart can begin to fail after heart attack.

Whatever the cause, a heart that becomes diseased has to work harder to pump blood throughout the body. There are few remedies for heart failure. Current prescriptions include lifestyle changes or, in the worst cases, surgery.

Now, in experiments they hope will eventually work in humans, French researchers have repaired the diseased hearts of sheep using the embryonic stem cells of mice.

Stem cells are master cells that can be made to transform into any cell in the body. Embryos are a rich source of stem cells.

Using 18 sheep with heart failure, the researchers gave half the animals a substance that did not contain the mouse stem cells. The rest of the sheep received stem cells grown from the mouse embryos.

One month after transplantation, scientists noted that the heart function worsened by ten percent among sheep that did not get the stem cells, compared to a six percent improvement in heart function among the group of treated sheep.

Another significant finding: half of the sheep that got better did so without drugs to suppress their immune systems. So-called immunosuppression drugs are given to organ recipients to keep them from rejecting a donor organ. But such drugs have many unpleasant side effects.

Michel Puceat is director of research at the National Institute for Health and Medical Research in France. Dr. Puceat says the use of mouse cells to treat sheep has implications for human heart patients.

"We think that if we can cross the species barriers with embryonic cells, there is a good chance for human stem cells to be tolerated in human patients, or at least to be tolerated with probably very little immunosuppression treatment," he said.

Dr. Puceat and his colleagues are starting work using human embryonic stem cells to repair the diseased hearts of baboons, which are primates like humans.

Dr. Puceat acknowledges this is a controversial area of research. Removing stem cells from a human embryos for research results in the destruction of the embryos, which opponents say amounts to the destruction of human life even if it is at a very early stage. But Dr. Puceat believes the procedure, if successful, will gain support.

"I think if somebody can prove that it can work, in terms of clinical work, it will be easier for people who are against the use of human embryonic stem cells to be convinced that it's worth trying," he explained.

The study on the repair of sheep hearts with mouse embryonic stem cells appears in the September 17 issue of the Lancet.