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A malfunctioning heart could be restored to health with the help of stem cells taken from the patient's own body, according to a study of how to repair the effects of cardiac failure.
Scientists have shown that it is possible to grow cardiac stem cells in the laboratory before transplanting them back into a patient to replace damaged heart tissue.
The findings demonstrate the possibility of rebuilding cardiac muscle that had been destroyed during a heart attack, offering an alternative treatment to a complete heart-transplant operation.
The experiment was carried out on pigs but the researchers involved said that the animal's heart is so similar to the human heart that clinical trials on people could begin in 12 months' time.
Professor Eduardo Marban, head of cardiology at the Johns Hopkins University School of Medicine in Baltimore, Maryland, said that the technique involves taking a small biopsy - a sample of living heart muscle - that is no bigger than a grain of rice.
Stem cells present in the biopsy would be grown in the laboratory and then infused back into the animal's heart using a standard method of accessing the organ through a catheter inserted into an artery in the leg.
"This is a relatively simple method of stem cell extraction that can be used in any community-based clinic, and if further studies show the same kind of organ repair that we see in pigs, it could be performed on an outpatient basis," Professor Marban said.
"Starting with just a small amount of tissue, we demonstrated that it was possible, very soon after a heart attack, to use the healthy parts of the heart to regenerate some of the damaged parts," he said.
The stem cells in the experiment were cultured for up to a month in the laboratory and were labelled with a coloured dye so that the scientists could see where they became integrated into the structure of the heart.
About a million stem cells were extracted from the biopsy and, after growing them in the laboratory, about 10 million cells were injected back into the heart, where they were still embedded in functioning tissue two months later.
Professor Marban said that the purpose of the experiment was to see whether or not the integration occurred, rather than measuring the physical benefits - a feature that will form the next stage of the experiment.
"But we have proof of principle, and we are planning to use larger numbers of cells implanted in different sites of the heart to test whether we can restore function as well," Professor Marban said.
"If the answer is yes, we could see the first phase of studies in people in later 2007," he said.
Stem cells are the undifferentiated cells of the body and are capable of forming specialised tissues, such as cardiac muscle.
Taking adult stem cells from a patient's own heart could provide an alternative to using stem cells taken from a cloned human embryo.
The other advantage of using a patient's own stem cells is that the transplanted tissue will not be rejected by the body's immune system, which avoids the need to use potentially damaging drugs.
"The goal is to repair heart muscle weakened not only by heart attack but by heart failure, perhaps averting the need for heart transplants," said Peter Johnston of the Hopkins' Heart Institute.
"By using a patient's own adult stem cell rather than a donor's, there would be not risk of triggering an immune response that could cause rejection," he said.
The results of the study were released yesterday at the American Heart Association's annual meeting in Chicago.
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