Rebuilding the heart: marrow cells boost cardiac recovery.

Experimental therapy that infuses a person's bone marrow cells into his or her damaged heart tissue is showing early success, scientists report. First tried in patients 2 years ago, the technique is designed to stimulate the growth of new, healthy heart cells. The treatment could help people who've had recent heart attacks, as well as those who've been battling heart disease for years, researchers said last week at a meeting of the American Heart Association held in Orlando, Fla.

When a coronary artery becomes obstructed in a heart attack, some heart-muscle cells downstream from the blockage die because they're starved of oxygen and nutrients. Other cells linger in a weakened state. The dead and dying tissue limit a person's stamina by restricting how vigorously the heart can pump blood.

Two studies now show that people who have marrow cells inserted into their hearts within days of a heart attack exhibit improvement. In a third investigation, a marrow transfer improved treadmill performance of people with long-term heart disease. A fourth study demonstrated gains in heart output among patients getting a bone marrow-boosting drug, but not marrow cells.

In the first study, a team in Germany enrolled 60 participants who had had heart attacks. All received standard drug treatment and underwent balloon angioplasty, including insertion of a cylindrical mesh stent to prop open a previously blocked artery. Then marrow was extracted from the hipbones of each of 30 of the patients, briefly cleaned, and later that day infused via a catheter into the patient's heart.

Both groups had had about 50 percent of normal heart output immediately after the original angioplasty procedures. After 5 months, magnetic resonance imaging revealed that participants given the marrow cells had improved their output to about 57 percent of normal, while the others averaged 51 percent, says Helmut Drexler of Hannover Medical School.

Another group in Germany conducted a similar study on 40 patients. In 20 people receiving a marrow-cell transfer, the average heart output rose from 55 percent to 65 percent of normal over 3 months. The others showed no change, report Bodo E. Strauer and his colleagues at Heinrich-Heine-University in Dusseldorf.

The third study, presented by Emerson C. Perin of the Texas Heart Institute in Houston, investigated people with severe heart failure who had been in declining health for years. "Many couldn't walk much, even around the house," he said.

The heart's capacity to pump blood through the lungs limits a person's oxygen intake. On treadmill tests, the group averaged oxygen intake of only 18 milliliters per kilogram of body weight per minute, whereas a typical 58-year-old has a rating of 60 ml/kg/min, Perin says. Some of the patients had dipped below 14 ml/kg/min, a reading so low that it made them candidates for a heart transplant.

In Perin's study, ll of the 20 participants underwent marrow transfer. After 6 months, these patients' oxygen intake had risen to 24 ml/kg/min on average, while the control group stayed at about 18 ml/kg/min.

Because these treatments use a person's own bone marrow cells, they avoid the immune rejection that can arise from conventional marrow transplants.

The research on marrow transfer is "very preliminary and not quite ready for widespread clinical use," says Robert O. Bonow of Northwestern University Feinberg School of Medicine in Chicago. "But it has generated a lot of excitement."

Taking a less invasive approach, Christopher A. Glover of the University of Ottawa Heart Institute in Ontario and his colleagues gave five heart attack patients a drug that spurs bone marrow production. The participants' average heart output went from 31 percent of normal to 41 percent in 6 weeks, Glover says.

The drug, a bioengineered form of a natural protein called granulocyte colony stimulating factor, is already used by people who've donated marrow to others and by cancer patients.

The new studies don't reveal how marrow stem cells affect the heart tissues. Animal tests suggest that some of the immature marrow cells transform directly into heart-muscle cells (SN: 1/13/01, p. 30).

Drexler takes a different view. "I think that what is happening is [marrow] cells talk to the residual stem cells in the heart, which can then divide," he says. Some of these activated stem cells in the heart might also differentiate to become new blood vessels to nourish the growing muscle cells, he notes.