The basis of a possible revolution in treating heart attack patients has been laid by three reports of using stem cells from bone marrow to repair heart tissue in animals.
In one of the studies, apparently functional heart tissue was regenerated from the injected cells, the first such success in some two decades of effort. In another, the stem cells morphed into new blood vessels that rescued the heart cells around the damaged area from their usual course of overgrowth and death. In the third, stem cells were used to strengthen pig hearts.
The three groups of researchers, based at Columbia University, New York Medical College in Valhalla, N.Y., the National Institutes of Health, and Osiris Therapeutics of Baltimore, said they were a year or more away from testing their animal techniques in people. Still, heart disease experts believe the stem cell work is highly promising.
"The health care industry would be revolutionized if the treatment of heart failure could be moved from organ transplants down to cell transplants," said Dr. Mark Sussman, a heart researcher at the Children's Hospital and Research Foundation in Cincinnati. The new research opened "some very exciting doors," he said, but required considerable further work to make sure it was as promising as it seemed.
Dr. Eugene Braunwald of Harvard, author of a leading textbook of cardiology, said the idea of putting stem cells into the heart to grow new heart muscle cells was "a very interesting approach."
If their animal techniques work the same way in people, the researchers say, people suffering a heart attack would be treated by having cells extracted from their bone marrow. The cells would be sorted and amplified, then injected either directly into the heart or maybe just into the bloodstream, from which they would home in on damaged heart tissue and on the enlarged heart muscle cells that soon grow around it.
It may even prove possible, though this concept has not yet been tested, to do no more than inject a heart attack patient with a cytokine, a natural protein that stimulates the bone marrow's stem cells to proliferate. The cells would home in on damaged heart tissue, and repair it. Biologists say it is too early to know if the blood-forming stem cells of the bone marrow are also the heart's own stem cells, for which researchers have been looking in vain for years, or if their remarkable ability to repair the heart is just a general property of stem cells.
The new results all depend on the recent finding that the stem cells of the bone marrow are far more versatile than supposed and can generate other tissues besides the red and white blood cells, their best known function. It seems that the cells are a kind of universal clay, so responsive to local cues that if placed in the heart they will develop into heart tissue instead of blood cells.