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MARCH 11, 2005
By Carol Marie Cropper Stem Cells, Minus the Furor Researchers are hoping cells taken from patients themselves will grow fresh, healthy muscle in ailing hearts
Former President Bill Clinton is expected to recover quickly from his Mar. 10 surgery to remove scar tissue formed around the lung after an earlier, heart-bypass operation. But for thousands of Americans, scar tissue can't be removed. It results from heart attacks and becomes part of the heart itself. But hope is rising. Doctors are experimenting with procedures to coax stem cells or related progenitor cells -- taken from elsewhere in the patient's body -- to build new heart muscle where scarring has replaced normal tissue. If it works, the new procedure could save the hundreds of thousands who die each year because their hearts have lost the ability to efficiently pump blood. Right now, the only effective treatment for the condition, called congestive heart failure, is a transplant. "LIKE DROWNING." When a patient suffers a massive heart attack, heart muscle cells are stunned and deprived of oxygen. "It's like taking a sledge hammer to the heart," explains Doris Taylor, director of the Center for Cardiovascular Repair at the University of Minnesota and one of the earliest researchers into the possibility of injecting cells into damaged hearts. After the heart attack, muscle cells and blood vessels die -- usually those in the left ventricle -- and are replaced by tough scar tissue incapable of beating like healthy heart muscle. Over time, the heart's walls grow thin and floppy, and the heart ceases to pump properly. Sufferers feel fatigued and short of breath as blood fluids back up in tissues and seep into the lungs. "It's dreadful. It's like drowning," Dr. Nicholas Chronos, chief medical officer at the American Cardiovascular Research Institute, one of the centers testing the stem cell procedure in patients. "It's a disease that will kill you quickly." And while tens of thousands could benefit from a transplant, only about 2,000 hearts become available each year, says Dr. Timothy Gardner, a cardiac surgeon and national spokesperson for the American Heart Assn. The demand for an effective treatment has researchers rushing to try the new stem cell therapies in the sickest patients. Unlike the cells taken from embryos, adult stem cells raise no highly charged religious and moral issues and fall outside government funding restrictions. In fact, adult stem cells have been deployed since the 1960s, when doctors began harvesting them from bone marrow to inject into leukemia patients after radiation treatments. Stem cell therapy is now used to treat other forms of cancer, such as lymphoma, as well and for such autoimmune diseases as lupus and Crohn's disease. THIGH MUSCLE. Now researchers are testing adult stem cells and stem cells derived from umbilical cord blood to regenerate such things as spinal cord nerves, skin for burn victims, and insulin-producing islet cells in diabetic patients. But the area furthest along is the use of cells to repair human hearts, says Dr. Andrew Pecora, a hematologist oncologist at Hackensack University Medical Center, which has one of the largest stem cell transplant programs in the nation. In the heart trials, cells are harvested from the patient's thigh, spinal cord, or blood, then injected into the heart in hopes they'll grow into new heart muscle or blood vessel cells. If the process works, within four to six years, stem cells could become part of the treatment regimen for patients with damaged hearts, Pecora predicts. Human trials began five years ago in France and have been focused in Europe, where fewer regulatory hurdles exist. But clinical tests are moving into U.S. hospitals. Five American medical centers, including Mount Sinai Hospital in Manhattan and the Mayo Clinic in Rochester, Minn., are involved in a clinical trial that involves injecting cells grown from thigh muscle into ailing hearts. SERIOUS RISKS? At the Texas Heart Institute in Houston, doctors are using stem cells harvested from bone marrow. At St. Elizabeth's Medical Center in Boston, doctors are stimulating bone marrow to release stem cells into the blood, then collecting the cells to inject into the heart. And more basic research is looking inside the heart itself to find stem cells or progenitor cells, which are one step further along toward becoming a specific type of cell than the endlessly adaptable stem cell. Last month, researchers at the University of California, San Diego, reported finding cardiac progenitor cells -- cells programmed to form heart muscle during the fetal stage -- living in newborn hearts. It's too soon to tell how well these therapies will work. And, of course, the medical community has serious concerns about possible drawbacks. What if the bone marrow stem cells grow into something else -- like cartilage -- when placed inside the heart? asks Dr. Gardner. Will the new cells beat like heart cells? If they do, will those taken from thigh muscle wear out when called upon to contract dozens of times per minute as heart muscle does? A study published in the Journal of the American College of Cardiology by the the French group that did the first testing in humans reported that 63% of the scars in eight patients receiving cell implants showed improvement. But four patients developed heart arrhythmias and needed defibrillators implanted. HEART OF THE MATTER. In December, a 65-year-old Atlanta man, Joseph De Sieno, became the third person to receive muscle progenitor cells, or myoblasts, as part of the the multisite U.S. study involving thigh muscle cells. Doctors cut a 3-inch by 2-inch section of muscle from his thigh, and the myoblasts were isolated and grown in a laboratory. Two months later, they were injected via a catheter inserted into an artery in De Sieno's groin and snaked up to his heart and into the damaged area. The former UPS (UPS ) deliveryman says he feels stronger and less apt to grow tired or short of breath. But it will take another three months before tests can show whether his heart has improved. Right now, the only way heart patients can benefit from this research is by volunteering for a clinical trial. But if the research goes well, the promise of stem cell technology could finally be realized in regenerating new organ tissue. In the heart. Not a bad place to start.  Cropper is a Personal Business editor for BusinessWeek in New York Edited by Beth Belton
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