Human Heart Can Repair Itself, Study Suggests

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Wednesday January 2 5:22 PM ET

Human Heart Can Repair Itself, Study Suggests

By Amy Norton

NEW YORK (Reuters Health) - In a study that turns on its head the traditional

view that the heart cannot help heal itself, scientists have found evidence that

the organ may indeed harbor stem-cell reserves capable of regenerating damaged

tissue.

Their study of men who received heart transplants from female donors revealed

that primitive cells from the recipients migrated into the donor hearts, after

which new muscle cells and small blood vessels formed. The researchers were able

to pin down the phenomenon by finding a considerable number of cells in the

donor heart that bore the Y chromosome--the ``male'' sex chromosome, which could

only have come from the transplant recipients themselves.

Dr. Piero Anversa of New York Medical College in Valhalla said his team believes

primitive cells moved to the donor hearts from the remaining portions of the

transplant recipients' own hearts, although the study does not prove this.

Anversa explained that his team could not rule out the possibility that the

cells traveled to the heart from the bone marrow, which contains the stem cells

that give rise to blood.

Still, he told Reuters Health, the study ``indicates that the heart possesses a

population of cardiac stem cells...implying that the heart has the capacity to

regenerate itself.''

And that idea, Anversa noted, is at odds with the cardiology ``dogma'' that

there is no such thing as cardiac stem cells--populations of immature cells

within the heart that have the potential to divide, proliferate and replace

mature cells killed off by heart attack and disease.

Now that there is strong evidence of the heart's regenerative capacity,

scientists can study the possibility of harnessing this self-healing potential

to treat damaged hearts, according to Anversa.

He and his colleagues report their findings in the January 3rd issue of The New

England Journal of Medicine (news - web sites).

The study looked at autopsied tissue from eight men who died sometime after

receiving a heart from a female donor. The patients had lived with their new

hearts for anywhere from 4 to 552 days.

Anversa's team found that up to 20% of the cells in the men's heart muscle and

small blood vessels called arterioles and capillaries bore the Y chromosome.

Even the patient who died 4 days after his transplant had Y-bearing cells in the

donor heart.

According to the researchers, this suggests that the recipients' own primitive

cells moved into the foreign heart and matured to aid in the ``remodeling'' of

the organ.

In addition, when they looked at a small group of autopsied normal hearts, the

investigators found small populations of immature cells. This gives further

evidence that there is a ''stem-cell population normally there that helps

regenerate the heart,'' Anversa explained.

``The discovery of primitive cells in normal hearts is one of the most

intriguing findings of this remarkable study,'' Dr. o Bolli of the

University of Louisville in Kentucky told Reuters Health. ``It does indicate

that primitive cells are a component of normal hearts.''

However, Bolli, who wrote an editorial accompanying the report, cautioned that

many questions remain. He explained that although Anversa's team found Y-bearing

cells with markers that identify them as stem cells, this does not prove that

they gave rise to the new muscle and blood vessel tissue that formed in the

donor hearts.

And if heart stem cells can indeed form new heart tissue, it is still unclear

what ``mobilizes'' them into action, Anversa said. His team is currently using

animal models to study what signaling mechanisms--such as growth factors--are

needed.

If researchers can figure out how to mobilize self-repair cells in the heart,

they could become an important weapon against a ``host of disorders'' including

coronary artery disease and heart muscle conditions, according to Bolli.

``The therapeutic implications would be enormous,'' he said, ''since at least

600,000 Americans develop heart failure every year and many of them die within 2

to 3 years.''

SOURCE: The New England Journal of Medicine 2002;346:5-15, 55-56.