BETHESDA, MARYLAND - It has been over 6 years since the first person was injected with stem cells to save a heart failure. Hundreds of patients have since followed the example of the 46-year-old German man. But experts are still divided on how the strategy works. During a 2-day symposium on cardiovascular regenerative medicine at the National Institute of Health which ended here today, cardiologists, surgeons, pathologists and other researchers have debated the future cardiac cell therapy. Clinical trials and animal studies provide a wealth of information; so far, the treatment appears safe. But it is not at all clear that stem cells should be given, or by what method -. Or, more importantly, whether patients who get them are more likely to survive
Cardiologists seized on cell therapy as a way to prevent cavities of the heart muscle immediately after a heart attack and restore the muscle long after he was dead. But three of the four largest clinical trials have failed to accomplish what they set out to do - to improve a particular measure of cardiac function, as measured by an increase in the amount of blood pumped, said ejection fraction. In other health measures, however, such as the regeneration of the heart muscle or prevent heart attacks, the tests may have been a success, argued some of those who led them. "It is sad, but it is life" that the tests have failed, said Philippe Menasche, a cardiac surgeon at the Georges Pompidou Hospital in Paris who has tried his hand at transplanting skeletal muscle cells. But "should we be discouraged? Certainly not."
A big problem, Manasseh and others have noted, is that the transplanted cells may be disappearing quickly rather than stick around to do their job. Scientists have seen this happen in animals. Joshua Hare, a cardiologist at the University of Miami in Coral Gables who also heads the Interdisciplinary Institute of stem cells, described the work in pigs showing a "cell washing" in the 8 weeks following the birth. Charles Murry , a pathologist at the University of Washington, Seattle, described how he spent 18 months frustrating trying to keep heart muscle cells derived from living human embryonic stem cells in mice after an induced heart attack. he nearly drove him out the edge, he joked, showing a slide of a white van hanging over a cliff. Finally, his lab found a cocktail of factors that kept the living cells, enabling them to preserve and transplant cardiac function in affected mice. the work appeared in the September issue of Nature Biotechnology .
A side effect could complicate how the cells are delivered. Injecting cells directly into the heart, which facilitates engraftment, may cause arrhythmias. In a speech sobering in which he chided researchers to quickly move into human trials before making comprehensive studies in large animals, Menasché a study published in May Traffic by team Great Britain, showing that rats suffered more arrhythmias if bone marrow was shot directly into the heart. (Clean cell therapy trial Menasché has been plagued by several cases of arrhythmias, which is now not sure were the result of cell therapy.)
Another hot issue: Can injected cells develop in ways that improve heart disease? Scientists working with a different stem cells hodgepodge, some better characterized than others. They understand favored mesenchymal stem cells Hare, who can become bone, muscle, and more; bone marrow cells cocktail used in German trials; and bone cells which express a marker on their surface called bone CD34. A trial in the planning stages, based at Cedars-Sinai Medical Center in Los Angeles, California, and Johns Hopkins University in Baltimore, Maryland, hopes to use a natural pool of cardiac stem cells, while groups such as Murry are interested in coaxing embryonic stem cells into heart cells more defined, but flexible. Identify what each of these cell types can be accomplished in an animal is not easy. "Right now, we are limited to throw them on the plastic" to see what they do, said David Scadden, co-director of the Harvard Stem Cell Institute in Cambridge, Massachusetts, in a speech.
stem cells from the stem is also a problem. Cardiologist Douglas Losordo of Northwestern University in Chicago, Illinois, reviewed published studies indicate that certain stem cells, such as bone marrow, may be less effective when just a heart patient than a healthy person Menasché speculates that conditions such as diabetes or atherosclerosis can alter the function of certain bone marrow stem cells using cells from patients -.. most of what has been tried so far - has other disadvantages, such as cost and complexity Hare described the first trial in cardiac patients to take a different approach and use donor stem cells.. Directed by Hare and sponsored by Osiris Therapeutics in Baltimore, the trial enrolled 53 people who received mesenchymal stem cells within 10 days of a heart attack. In spring, Hare said there were no major security problems, such as mesenchymal stem cells developing in other organs.
And then? One of the biggest fans of cell therapy, Andreas Zeiher of the University of Frankfurt, Germany, said that "it is time to embark on a clinical trial of 1,000 person" to nail once and for all if cell therapy guard heart patients alive and healthier --a challenge tests were far too small to meet. The circulatory diseases targeted by the cardiac cell therapy continues to expand: Losordo hopes to launch a trial in critical limb ischemia, which affects patients with diabetes and other and often leads to amputation and even death. Researchers are aware, too, that heart patients are desperate for new treatments. Some flock to Thailand, where a company now offers cardiac cell therapy -. At a steep cost
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