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Stem Cells Can Help Lungs and Hearts

Researchers see promise in bone marrow

MONDAY, Nov. 10, 2003 (HealthDayNews) -- Researchers experimenting with bone marrow stem cells are discovering procedures that may one day hold promise for patients with various heart and lung conditions.

These reports are being presented this week at the American Heart Association's annual conference in Orlando, Fla.

One study, conducted in Toronto, may raise hope for people with a relatively rare condition known as pulmonary hypertension. The condition is characterized by the loss of microvessels in the lungs.

These particular microvessels appear to be extremely fragile and therefore highly susceptible to damage. Study author Duncan Stewart had proposed that regenerating the blood vessels would be helpful. "This was quite a heretical hypothesis when we proposed it because there were concerns that, for at least some forms of pulmonary hypertension, abnormal growth might be a problem." As it turned out, though, Stewart was correct.

Stewart and his colleagues cultured rat endothelial progenitor cells, or cells which are normally present in the bone marrow and which can differentiate into endothelial cells, which make up the lining of blood vessels, to help repair and regenerate blood vessels. Once the cells had started to differentiate into endothelial cells, the investigators injected a large number directly into the lungs of rats.

Three weeks later, blood pressure had improved, there was a reduction in the thickening of the heart wall (indicating larger vessels were being repaired), and the cells could be seen forming into new blood vessels.

"We are harnessing these cells to try to repair the tiny blood vessels," Stewart explains. "We are really, really boosting the system."

The work only involved animals yet "raises some cautious optimism," Stewart adds. "If vessels can be regenerated in humans with this problem, this might be the first real approach to turn around the disease and restore some function."

In another study, a team led by Dr. Young Sup Yoon of Tufts University and St. Elizabeth's Medical Center in Boston managed to produce both blood vessels and heart muscles from human bone marrow stem cells.

In the past, scientists had only been able to coax one or the other out of a particular stem cell.

Yoon and his colleagues started with a single cell, grew it into hundreds of thousand of cells, and then put 800,000 new cells into animals that had suffered heart attacks. This resulted in the growth of blood vessels and of heart muscles and also an improvement in the animals' heart function. The stem cells were also more resilient than in previous studies and secreted growth factors that let them interact with host cells and prevent cell death.

The procedure may one day help regenerate human hearts damaged by heart attacks or other forms of heart failure. It may also have applications for people with hypertension, diabetes and other blood vessel diseases.

A third study involved 20 heart attack patients. Four to eight days after the heart attack, investigators took bone marrow cells from the patients, cultured them and then infused them into the damaged heart the following day while the balloon angioplasty was performed.

After three months, the average area of damage in the study participants decreased from 33 percent of the left ventricle's circumference to 14 percent. The contraction speed of the heart doubled and the heart was pumping better.

A final study, this one conducted at the Texas Heart Institute, injected bone marrow cells into 11 patients with heart failure. These cells can differentiate into tissue and new blood vessels. At two months, the live heart muscle tissue not getting enough blood flow was reduced by about one third. Although there was no change in the amount of scar tissue, patients became much more active in their daily lives. One even climbed eight flights of stairs during a blackout.

More information

The American Heart Association has more on heart attacks. The National Institutes of Health has a basic primer on stem cells.

SOURCES: Duncan Stewart, M.D., director, cardiology, University of Toronto, and head, cardiology, St. Michael's Hospital, Toronto; Young-Sup Yoon, M.D., Ph.D., assistant professor, medicine, Tufts University, Boston; Nov. 10-12, 2003, presentations, American Heart Association Scientific Sessions 2003, Orlando, Fla.
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