Grafted muscle cells aid damaged hearts.

Some survivors of heart attacks suffer years of failing health as their hearts strain to pump adequate quantities of blood. Now researchers report that damaged heart muscle in rabbits can get a boost from muscle cells transplanted from their legs, a finding that may lead to new therapies for patients.

Scientists at Duke University Medical Center in Durham, N.C., froze portions of the hearts of 12 rabbits, killing about the same number of heart cells as die in the kind of heart attacks that lead to the prolonged decline in heart function known as heart failure. The researchers then transplanted 10 million muscle cells from a leg of each animal into its heart.

After receiving the transplants, pumping efficiency rose significantly in five of the seven hearts in which the transplants became established, the team reports in the August Nature Medicine. The most successful transplant gave a fourfold boost. The researchers don't know why the transplants were unsuccessful in five of the rabbits, says Doris A. Taylor, one of the Duke researchers.

The study is the first to show that muscle cells contract after being transplanted into a working heart, says Ray C.J. Chiu, a cardiac surgeon at McGill University and Montreal General Hospital, both in Quebec. The Duke team "has made an important contribution," he says.

Among the seven rabbits in which the transplants survived, the pumping capacity increased twofold on average. However, it reached only 50 percent that of healthy animals, Taylor says. Still, similar grafts in patients may keep them alive until they can receive new hearts through transplantation, she adds.

The researchers have applied to the Food and Drug Administration for permission to test muscle cell transplantation in people. Clinical studies are needed to determine whether it will yield any benefit in patients, and if so, for how long, Taylor says.

The researchers monitored the rabbits for only 2 to 6 weeks after transplantation because implanted sensors that measure pumping efficiency become less effective after a few weeks, producing less reliable data, Taylor says. However, the grafted cells persisted in some of the animals for a longer time, she notes.

Last month, Piero Anversa at New York Medical College in Valhalla and his colleagues observed cell division among surviving muscle cells in damaged hearts (SN: 07/25/98, p. 54), which might replenish the heart muscle without the aid of transplants. However, those results remain controversial.

In previous studies, researchers have transplanted into animal hearts muscle cells taken from the animal's limbs. have also transplanted cells from e,. bryos and fetuses. However, none of those reports established that the transplanted cells began contracting in a working heart, Chiu says.

Unlike foreign fetal or embryonic cells, grafts taken from an animal's own body do not trigger an immunological reaction, Chiu notes. Ethical issues surrounding use of human embryonic and fetal tissues make them less likely to be available than a patient's own muscle, he adds.