Stem cells can cure severe heart disease? Study suggests early reports may be oversold

| May 6, 2014
Decellularized pig heart.
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The experimental treatment of injecting stem cells into the hearts of patients with severe heart disease or who are recovering from heart attacks has been under investigation in clinical trials for a few years. In a study published in The Lancet in 2011 scientists grew stem cells from patients’ own hearts after the patients had suffered serious heart attacks. These were patients who had serious, irreversible heart damage. Fourteen of the 16 patients had improved heart function after four months, and the results were even better after one year. The stems cells grew into new, functioning heart cells.

Just last week, the Cochrane Collaboration published a review of 23 trials, all of them attempting stem cell therapy for heart disease. The trials looked at the use of bone marrow stem cells in patients whose hearts were failing. Unlike the 2011 study, which looked at heart attack patients, these studies looked at patients with advanced heart disease who had not suffered a heart attack. The results: overall, stem cell treatments reduced the risk of death and improved heart function, though the benefits were not as dramatic as in the patients with heart attacks.

Overall, the therapy has been promising enough that more than 100 preliminary studies have been done, and some companies are already offering the treatment for profit.

But a review of the evidence on the stem cell treatment in the British Medical Journal (BMJ) identified some large errors in a majority of the studies. And, the studies that they reviewed without errors showed the treatment had no effect. A summary of the methodological errors from Scientist magazine:

Examining 133 different reports from 49 clinical trials for the use of autologous bone marrow transplants to treat heart disease, a team of researchers in the U.K. has revealed hundreds of discrepancies in the data: numbers that don’t add up, misclassification of a trial as prospective randomized rather than retrospective/observational, patients whose sex was misreported or who were listed as both dead and alive. In addition to calling into question the validity of this well-researched therapy, some errors are raising concerns of scientific misconduct.

The original mechanism of effect proposed by researchers–that the stem cells replaced damaged cells– has also recently been disputed. New evidence point towards enhanced healing of cardiac tissue. From Alison Abbott at Nature:

Therapies that use adult stem cells typically involve collecting mesenchymal stem cells from bone marrow taken from the patient’s hip bone. The cells are then injected back into the patient, to help repair damaged tissue. Original claims that they differentiated into replacement cells have been rejected, and many clinicians now believe that the cells act by releasing molecules that cause inflammation, with an attendant growth of oxygen-delivering small blood vessels, in the damaged tissue.

The editorial staff at Nature commented that, at the very least, evidence of error and the lack of effect in the error-free studies should be cause for pause before starting hugely expensive phase III trials (currently recruiting subjects). It might be more beneficial to take a step back and fund studies to examine the basic science behind the stem cell treatments, the editorial argues. But, now that treatments are becoming commercialized, that seems unlikely to happen:

When it comes to stem-cell therapies, the stakes are high — but not as high as the hopes of people who are severely ill. Over the past few years, dozens of small, early-phase clinical trials have tested the value of adult stem cells in treating debilitating or life-threatening heart disease. Results have been mixed, but most peer-reviewed academic reports have hinted that patients may be helped. This has, understandably, encouraged clinicians to move potential therapies into large and expensive phase III trials to establish whether the treatments can fulfil their promise.

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