Stem cells from the bone marrow are being studied in many clinical trials for heart failure, but evidence of a lasting benefit is unclear. Publishing in the Journal of the American Medical Association, Douwe Atsma and colleagues at Leiden University Medical Center in the Netherlands describe what they call the first double-blind, randomized, placebo-controlled study of its kind1. They injected bone marrow cells into patients with a form of chronic heart failure called myocardial ischemia, which is caused by decreased blood flow to the heart. In assessments made three and six months after the procedure, the researchers found improvements in heart function and decreases in chest pain.

Patients were an average age of 64 years old and lacked other treatment options. Bone marrow cells were isolated from each patient, who was then randomly assigned to either a treatment or placebo group. Each patient was given eight injections of either 100 million bone marrow cells or placebo solution. At the three-month follow-up, a summed stress score, used to assess heart blood flow, and a magnetic resonance image, used to measure left ventricle function, showed a modest but significant improvement in patients receiving bone marrow cells. At the six-month follow-up, these patients had fewer complaints of chest pain, increased exercise tolerance and an improvement in the quality of life score that was roughly twice that reported for the placebo group.

Only two prior small-sized, randomized, controlled studies have formally tested the effect of bone marrow cell injection in patients with chronic myocardial ischemia, says Atsma, and the results were inconclusive. Michael Schneider, head of cardiovascular science at the National Heart and Lung Institute of Imperial College London, says the advantage of this study is the objectively measured endpoints, particularly the demonstration of increased perfusion, or blood flow within the heart. He further points out that the study design means the effect of the cells alone can be assessed because the cell therapy was not complicated by concurrent interventions like angioplasty or stenting.

Exactly how these injected cells improve heart function is another active area of current research. Recent animal studies suggest that, rather than differentiating into heart tissue, injected cells likely contribute to endogenous angiogenesis, thereby leading to improvements in perfusion and heart function. However, Atsma says that how these results relate to human patients is unclear. Larger-scale trials that assess patient survival will be necessary to evaluate stem cell therapy in treating chronic myocardial ischemia.

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