In animal experiments, local researchers have for the first time used gene therapy to reverse cardiac damage caused by muscular dystrophy, indicating that a similar technique might work as a treatment for heart failure patients.

Hamsters with the disease that got the gene therapy had stronger hearts and lived as long as healthy animals, said study leader Dr. Xiao Xiao, of the University of Pittsburgh School of Medicine.

"This gene delivery method could be used to deliver other therapeutic genes into the heart to treat general heart failure," he said. The findings were published yesterday in the journal Circulation.

"This is a milestone, really," said Dr. Johnny Huard, a muscular dystrophy researcher and director of the growth and development laboratory at Children's Hospital.

"If it pans out, I think it's extremely exciting," said Dr. Robert Kloner, a cardiac gene and cell therapy expert at the University of Southern California's Keck School of Medicine. Neither he nor Dr. Huard were members of the research team.

Dr. Kloner added, "The results are so amazingly positive, it's the kind of thing you want to see reproduced by several different labs."

In the experiments, the hamsters had a mutation in a gene that makes a muscle protein called sarcoglycan. Their limb muscles are weak, and their enlarged, thin-walled hearts cannot pump blood efficiently. Heart failure cuts their two-year life span to about eight months, Dr. Xiao said.

In the study, a normal sarcoglycan gene was joined to a harmless virus, called adeno-associated virus or AAV, so that it could get inside muscle cells, and then injected into the animals.

The normal gene was incorporated into the muscles of the limbs, diaphragm and heart, and made sarcoglycan protein. Treated hamsters developed stronger hearts, ran easily on treadmills and lived longer, the researchers said.

"If you do a pathology examination, you cannot tell the difference between the normal muscle and the gene therapy-treated muscle," Dr. Xiao said.

Humans have a similar disease, called limb girdle muscular dystrophy. Clinical trials would have to be conducted to see whether gene therapy could treat them, he said.

But before that, other labs should conduct similar animal studies to make sure the results are reproducible, Dr. Kloner cautioned.

The heart specialist said the technique might also be used to treat patients with heart failure, which is a far more common problem than muscular dystrophy.

Different genes would have to be joined with AAV, but other experimental models have shown that gene therapy can improve function, Dr. Kloner said.

"There are quite a few genes that can improve the heart function, but the question is, how do you deliver that gene into the heart?" Dr. Xiao said. "This gene delivery method could be used to deliver other therapeutic genes into the heart to treat general heart failure."

Several heart failure research teams have approached him about the possibility of collaboration, he added.

For the gene therapy to work well in patients, though, much more of the gene-virus combination will be required because humans are bigger than lab animals.

Dr. Huard said that being able to get the treatment gene to all affected muscles through a simple intravenous injection makes the therapy more feasible for muscular dystrophy patients.

"This is very promising," he said. "If we can produce enough virus for human patients ... the door is open."