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Stem Cells Found in the Heart
By Nancy Touchette

A cluster of cardiac stem cells (blue) between heart muscle cells (red) in human heart tissue.

For twenty years or so, scientists have debated whether the human heart can repair itself by regenerating new tissue after injury, such as a heart attack. New research strongly suggests that the heart maintains a reservoir of stem cells that enable the heart to make new cells when it is damaged.

Researchers have isolated cardiac stem cells from rats and showed that when these cells were injected into rat hearts that had been damaged, they reconstituted the injured tissue. The same group has also detected similar cells in human hearts.

The research, done at New York Medical College in Valhalla, could lead to new ways of treating heart disease. For example, the stem cells could be injected into diseased or damaged tissue so that new tissue could grow. The researchers are planning to submit a protocol to the U.S. Food and Drug Administration for a phase I clinical trial to test the safety of injecting cardiac stem cells in humans.

Piero Anversa and his colleagues identified pockets of stem cells in the interstices, or spaces, between muscle cells in the hearts of rats. When the stem cells were cultured and injected into rats with damaged heart tissue, 70 percent of the damaged myocardium was reconstituted within 20 days. These findings were reported in Cell.

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The researchers also found similar cells in humans by examining tissue from patients with heart disease who underwent cardiac surgery. It appeared to the researchers that the accumulated stem cells had been attempting to repair heart damage, they reported in Proceedings of the National Academy of Sciences.

“We have identified where these cells live in the heart,” says Anversa. “The next step is to determine how to mobilize these cells to regenerate cardiac tissue. What can we do to make the cells grow and survive?”

Better yet, researchers could perhaps stimulate cardiac stem cells already living in the heart to grow.

The new findings challenge a longstanding dogma in heart research, Anversa says.

“For years, there has been a general belief that the number of cells in the heart was established at birth,” says Anversa. “But how could anyone believe that the heart could contract for so many years using the same cells? These studies show that there is a pool of cells that repairs damaged heart tissue.”

Previous studies by Anversa and others had shown that bone marrow cells injected into damaged heart muscle could also form new cardiac cells. But this is the first time cardiac stem cells have been used to restore heart function in an animal.

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Beltrami, A.P. et al . Adult cardiac stem cells are multipotent and support myocardial regeneration. Cell 114, 763-776 ( September 19, 2003 ).


Urbanek, K. et al . Intense myocyte formation from cardiac stem cells in human cardiac hypertrophy. Proc. Natl. Acad. Sci. U.S.A. 100, 10440-10445 ( September 2, 2003 ).


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