Bone marrow stem cells help mend broken hearts

Human trials yield promising results
27 April 2004

HELEN R. PILCHER

Stem cell therapy might help repair ailing hearts, a clinical trial suggests.

Researchers harvested stem cells from patients with cardiac failure, and then transplanted the cells into their damaged hearts. Six months later, the hearts functioned significantly better than those of patients who had not received the therapy.

The results suggest that stem cell transplants are a good way to treat heart failure, researchers told the American Association for Thoracic Surgery meeting in Toronto this week.

But the study will fuel the ongoing debate over the usefulness of stem cell therapy for cardiac problems. Animal and human studies have yielded conflicting results, leading some to question the effectiveness and safety of the technique.

Marrow harvest

Amit Patel from the University of Pittsburgh School of Medicine and colleagues studied 20 patients undergoing bypass surgery for heart failure in South America. Half received stem cell therapy, in which adult stem cells were harvested from the patient’s own bone marrow and then injected into the heart.

Patients received up to 30 injections into sites where there was obvious muscle damage. Subsequently, their hearts were able to pump more blood than those who had surgery alone.

It is thought that the stem cells help damaged heart muscle to regrow and may also stimulate the formation of new blood vessels.

Recipients also had higher levels of a protein called connexin 43, which is important for cell communication. "We do not know if this increase was due to the growth of new heart muscle cells resulting from the stem cell injections or whether the stem cells coaxed existing cells to come out of hibernation," says Patel.

Critically, there seemed to be no side-effects or complications. Earlier this year, a stem cell trial in South Korea was halted after some heart attack patients began to develop abnormal growths in their arteries.

The study is also at odds with earlier rat studies, says stem cell researcher Malcolm Alison from Imperial College London. A few months ago, two teams concluded that stem cells transplanted into damaged rat hearts were unable to replace heart cells.

An estimated 23 million people worldwide are affected by heart failure. The South American trials are continuing.