One form of stem cell therapy for heart attack patients appears to have little effect, German researchers report. The team, based at the German Heart Centre in Munich, carried out the largest trial designed to test the therapy to date. The results, published in the Journal of the American Medical Association, show that boosting bone marrow-derived stem cells in people who have had a heart attack does not improve their recovery. However, an accompanying editorial called for larger well-controlled studies to investigate the effect of other stem cell treatments. 'I, for one, am not ready to give up on this technology', said author Robert Kloner, director of the Heart Institute at the Good Samaritan Hospital in Los Angeles.
Heart attacks damage the heart muscle and associated blood vessels, which stop it working effectively. Previous research suggested that injections of stem cells derived from bone marrow can trigger the growth of new heart muscle, although scientists do not clearly understand how this happens. Last year, a German trial involving 60 patients showed that stem cells taken from the bone marrow increase the efficiency of hearts that have been damaged by heart attacks.
In the latest study, the scientists tested the effect of injecting patients with a substance called granulocyte colony-stimulating factor (G-CSF), which promotes stem cell production in bone marrow. The trial included 114 patients - 56 of whom received regular G-CSF injections for five days after they had experienced a heart attack, while 58 received a placebo. But although the number of stem cells in the blood of those given G-CSF injections increased, check-ups carried out at four and six months after the treatment revealed no difference in the heart function of the two groups.
However, study leader Dietlind Zohlnhofer said that in contrast to other some studies, the trial showed no increased risk of potentially harmful side effects. The scientists think that the treatment might have failed to work because the stem cells didn't home in on the damaged heart tissue. In his accompanying editorial, Robert Kloner said that while some investigators may be 'disappointed' with the trial, it highlighted the importance of large, controlled, carefully designed studies. He said this was the only way 'to differentiate between the hype often generated by smaller, less well-controlled trials and reality'.