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STUDY: Evidence that the organ may indeed harbor stem-cell reserves capable of regenerating damaged tissue.
JOURNAL: The New England Journal of Medicine 2002;346:5-15, 55-56
AUTHORS: Dr. Piero Anversa
ABSTRACT: 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.
COMMENTARY: 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.
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.
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.
The discovery of primitive cells in normal hearts is one of the most intriguing findings of this remarkable study. It does indicate that primitive cells are a component of normal hearts.
And if heart stem cells can indeed form new heart tissue, it is still unclear what "mobilizes" them into action. 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.
The therapeutic implications would be enormous, since at least 600,000 Americans develop heart failure every year and many of them die within 2 to 3 years.