TUESDAY, Feb. 28, 2006 (HealthDay News) -- One method of using bone marrow stem cells to repair the damage caused by a heart attack did not work in the largest trial of the therapy so far, German researchers report.
But U.S. experts say there is still a lot of promise in other stem cell therapies that are being tested.
"This should not dismay people or make them think stem cells will not work," said Dr. Robert E. Michler, chairmanof the Department of Cardiothoracic Surgery at Montefiore MedicalCenter in New York City, who also works in this field.
The German researchers described how a molecule that stimulates stem cell activity was given to half of 114 patients in the 12 hours after their heart attack was diagnosed. The molecule, granulocyte colony-stimulating factor (G-CSF), was given in daily doses for five days.
The G-CSF therapy did mobilize stem cells, said the physicians at the Technische Universitat in Munich, where the study was done. But there was no difference in the amount of heart damage or the heart-pumping ability in the patients who got the treatment and those who did not.
"I, for one, am not ready to give up on this technology," said Dr. Robert A. Kloner, who wrote an editorial accompanying the German report in the March 1 issue of the Journal of the American Medical Association.
The study design was praised by Kloner, who is director of the Heart Institute at Good Samaritan Hospital in Los Angeles, and a professor of medicine at the University of Southern California. "Previous to this there have been few large, well-controlled studies," Kloner said. But the negative results aren't especially discouraging, he said.
"The basic concept that stem cells may someday be used to treat heart attacks is exciting," Kloner said.
However, a great deal of research remains to be done, Michler said. "The field is so complex at this time and there is limited understanding of which cells are most important, how many cells are needed to have a desired effect and what is the best vehicle to deliver them to the site of a myocardial infarction [heart attack]," he said.
Scientists believe stem cells have the potential to develop into many different cell types in the body, potentially offering treatments -- even cures -- for a variety of diseases and health conditions.
Michler said he is planning a human trial of a stem-cell therapy for heart attack that cannot be described yet because it is undergoing regulatory approval. Several approaches are being tried, he said -- injecting stem cells into the coronary artery or putting them into the heart muscle surgically.
Several human trials are under way, Kloner said. "Some studies are using stem cells injected directly into the heart muscle, some use intracoronary artery injection, some use bone marrow stem cells. What we need now are larger, well-controlled studies."
And the technique used in the German study might still prove useful for some heart attack patients, said Dr. Amit Patel, director of cardiac stem cell therapies at the University of Pittsburgh's McGowan Institute. He noted that the study did not show the adverse effects of the treatment that had been reported in earlier, smaller trials.
"Because there was no benefit in these patients, you can't generalize to say G-CSF is of no benefit at all," Patel said. It may ultimately be useful for patients who are not helped by other treatments, he said.
Kloner said he has done animal studies whose results show that stem cells can help rebuild a damaged heart.
"Now the question is how you do it in people," he said, adding that his work was too preliminary to warrant a human trial. It will take four or five years for the technique to prove its worth, he said.
Basic information about stem cell therapy is provided by the U.S. National Institutes of Health.