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Scientists Use Circulating Stem Cells to Repair Fetal Mouse Hearts - 2004-10-07

It may one day be possible to repair broken hearts, literally. Scientists have discovered a way to correct congenital heart defects in mouse pups using embryonic stems cells injected into mouse mothers. The technology holds promise for the repair of a number of other organ systems.

Scientists already knew that stem cells, the body's master cells, could be coaxed to grow into any cell to replace diseased tissue, potentially curing people with a variety of ailments. But until now, they have not achieved much success.

Researchers are reporting a breakthrough in the use of embryonic stem cells, or ES cells, to cure unborn mice with congenital heart disease. They have discovered that stem cells injected into the blood circulation of pregnant mice can repair the hearts of their offspring with lethal heart disease.

In experiments at Memorial Sloan-Kettering Cancer Center in New York, scientists genetically altered unborn mice so that they would die of lethal heart disease within a couple of days after being born. But researchers "rescued" some of the mice by injecting their mothers with embryonic stem cells that found their way to the defective hearts and repaired the damage. The offspring of the mothers injected with ES cells were born in healthy condition.

The study's lead author, Diego Fraidenraich, says the results were unexpected. "And it provides a new function, an unexpected function of the ES cells, that is why it is so exciting, because again it is not only the cells,? he says. ?The cells are also a vehicle, a carrier, of biological factors that can correct ... defective tissues in the vicinity of defective cells."

The technology has the potential to provide therapy to correct an unlimited range of diseases that begin in the womb.

"So in a way, the aura of influence is much broader, it is not the cells themselves, it is the influence that these cells can provide," says Dr. Fraidenraich.

The work by Dr. Fraidenraich and colleagues is published in the journal Science.

Kenneth Chien is director of the Institute of Molecular Biology at the University of California in San Diego. Commenting on the research in Science, Dr. Chien says the work takes therapeutic stem cell research to the next level.

"So for the scientist, it is exciting because ES cells for regenerative medicine have been looked at primarily as tools to repopulate degenerative organ systems: so heart failure, then you would put in cardiac stem cells or other degenerative diseases of the brain, Alzheimer's, you put in neural stem cells,? he says. ?This has been one of the approaches that has been thought about.?

The use of circulating embryonic stem cells may also be a new way of identifying and treating disease. Dr. Chien says the ES cells secrete different growth factors depending upon which organ they are targeting for repair.

"What one could envision, since ES cells have many different cell types, secrete many different factors, you could take another animal that had say a neural defect, a brain defect that was lethal, and then try the same thing and see if it modified the effect and then eventually if it did, use modern tools of the genome to identify them," he says.

Experts say embryonic stem cell therapy involving the treatment of human embryos with congenital disease is at least 10 years away.