Nov. 18, 2002 By Lisa Ellis
InteliHealth News Service
CHICAGO — Injection of a person's own muscle or bone marrow cells into damaged areas of heart muscle appears to be safe and shows promise as a way to repair dead heart tissue, researchers reported here in some of the earliest studies involving humans.
The five studies, from the United States and Europe, were described at a news conference and will be presented to participants in the annual Scientific Sessions of the American Heart Association (AHA).
The cell-transplant approach, studied in animals for several years, aims to improve heart function after heart attack, which kills an area of heart muscle by shutting off its oxygen supply. Heart muscle does not repair itself.
If successful, the technique could help to prevent heart failure, in which a severely damaged heart loses much of its pumping ability. Some heart failure patients eventually require a transplant.
"This is really new, and I think it's pretty exciting," said Timothy Gardner, M.D., a professor of cardiac surgery at the University of Pennsylvania Medical School. Dr. Gardner was moderator of the news conference but was not involved in any of the studies. "The thing that's exciting is that it's a whole new treatment pathway."
More than 1 million Americans suffer heart attacks — and thus heart damage — each year, according to the AHA. About 5 million Americans suffer from heart failure.
The work presented here is very preliminary, involving only a few dozen patients and designed only to assess safety and decide on an appropriate dose. Larger studies to examine whether the technique works have just begun or will begin next year.
Many questions remain. For example, the studies presented here showed improvements in heart function, but researchers do not know for sure if the transplants caused the improvements. All of the patients also had the transplants at the same time they were undergoing either coronary bypass surgery, which itself improves heart function, or installation of a device that assists the heart in pumping.
All of the patients' hearts had sharply diminished pumping ability because of damage. Pumping ability (known as ejection fraction) is expressed as a percentage, equal to 50 percent or more in people with normal hearts. Patients in the studies had pumping ability in the 20s or lower 30s.
Three of the studies involved injection of the dead scar tissue in the heart with millions of cells called myoblasts, obtained from a tiny section of muscle in the patient's own body and then grown in the laboratory into millions of cells.
Unlike heart muscle, muscle in other parts of the body can repair itself because it contains myoblasts — immature cells that can develop into various types of muscle cells. The researchers are testing whether they also can become heart muscle.
Here are the results so far:
- Philippe Menasche, M.D., of Hospital Bichat in Paris, who reported the first muscle cell transplant into a human heart two years ago, now has treated 10 patients. One died of a stroke after 18 months. In the others, researchers examined what happened to the scar tissue after the injections. About two-thirds of the formerly dead areas showed thickening caused by new growth of cells. Four patients, however, needed drugs to control dangerous irregular heart rhythms.
- In a study at six U.S. medical centers, 16 patients were transplanted with myoblast cells that were stained so they could be traced later, said lead author Nabil Dib, M.D., director of cardiovascular research at the Arizona Heart Institute in Phoenix. The cells stayed in place, and examination of three patients showed the scar area had thickened from growth of new tissue. There were no heart-rhythm problems, and average pumping ability improved from 22.7 percent to 35.8 percent after three months.
- Ten patients received myoblast transplants at the University School of Medical Science in Poznan, Poland, said Tomasz Siminiak, M.D., Ph.D., lead author. Patients were given drugs to prevent irregular heart rhythm (arrhythmia), but they were discontinued after three months. There were no other problems in six months of follow-up.
Two other studies used cells from the patient's own bone marrow, which is known to contain stem cells that can develop into all types of blood cells. Many researchers are trying to determine to what extent these cells also can become other types of cells.
Here are the results from these two studies:
- Investigators at the University of Leicester in the United Kingdom treated 14 patients with injections of diluted bone marrow, said Manuel Galinanes, M.D., lead author. After six weeks, they showed significantly less irregular motion of the heart walls, and this benefit remained 10 months after treatment. There were no arrhythmias or other problems.
- A similar approach was tried with 11 patients at Rostock University in Rostock, Germany, said lead author Christof Stamm, M.D. Patients showed improvements in heart pumping ability and better flow to previously blood-starved areas of the heart.
Researchers still don't know for sure that the transplanted cells turn into heart muscle cells or whether they work as effectively as normal heart cells. Dr. Gardner said the cases of irregular heart rhythm in some studies are a concern, but he noted that patients with severe heart damage are susceptible to rhythm problems anyway.
Researchers agreed that patients also need some procedure, such as bypass surgery, to restore blood supply to the heart. And it’s unclear what the appropriate dose may be. The studies used widely varying doses, from tens of millions to billions of cells.
But if these techniques are shown to work, transplants of a patient's own cells offer many advantages, researchers noted. They are relatively easy to obtain, they will not be rejected because they come from the same patient, and they do not present the ethical problems associated with another type of cell transplant — using stem cells taken from embryos.
Dr. Dib said myoblasts actually show more promise than stem cells for repairing heart tissue. "Stem cells get their signals from the environment. If you put them into scar tissue, they make more scar [tissue]."
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