Cells in heart can regenerate dead tissue.

Stem cells in parts of the heart that have survived a heart attack can be prodded to regenerate tissue that was killed by the attack, recent experiments suggest. Doctors ultimately might use a battery of stem cell-stimulating molecules "to limit the devastating effects of heart failure" says Piero Anversa of New York Medical College in Valhalla.

The condition called heart failure can develop after a nonfatal heart attack kills portions of the organ's muscle. Drugs can sustain the injured heart for a time, but many patients eventually die or require a transplant.

To see whether the heart has untapped potential to resuscitate itself, Anversa and his colleagues studied cardiac stem cells in 52 hearts that had been removed from people during heart transplantation or shortly after death from a heart attack or another cause. Such cells can give rise to heart muscle, arteries, and other tissue.

Heart stem cells were nearly 10 times as abundant in people receiving heart transplants and nearly 20 times as abundant in people who had died of heart attacks as they were in people whose deaths had been unrelated to heart injury, the researchers report in the June 14 Proceedings of the National Academy of Sciences (PNAS).

But while the results indicate that stem cells multiply in response to heart injury, Anversa says, they appear to do little to repair the organ.

Cardiac stem cells can be prompted in that direction, however, according to tests on dogs that have had heart attacks. In the June 21 PNAS, Anversa and his team report injecting two growth-inducing proteins into the animals' hearts. The treatment stimulated stem cells to migrate to dead areas of the dogs' hearts and, once there, to regenerate muscle and arteries.--B.H.