Gene therapy may work to help treat Duchenne muscular dystrophy, a deadly inherited disease that causes a painful degeneration of the muscles, researchers said.

Working with dogs that have a similar disease, a US government team said they had used a special kind of gene therapy to treat the animals.

They hope their work can translate into humans, but it can take years to try something on people that has worked in animals.

Richard Bartlett and colleagues at the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), one of the National Institutes of Health, reported in the journal Nature Biotechnology that they used a golden retriever bred to have a form of Duchenne muscular dystrophy, which is the most common childhood form of MD in humans.

Gene therapy for MD has been difficult because the gene is so large it cannot be delivered easily using a virus or direct injection of DNA.

Bartlett's team tried making the genes repair themselves using a chimeric oligonucleotide, which is made in the lab and includes both DNA -- the genetic code -- and RNA, which is the working molecule that actually causes the production of proteins by cells based on DNA's instructions.

The idea was to get the cells in the dog to go to work repairing the DNA damage seen in MD.

This approach, also known as antisense, acts as kind of a chemical instruction to the cell to alter the gene in the desired way.

The oligonucleotide is designed to attach itself to the gene right where a change is needed. The researchers were advised in this part of their work by Newtown, Pa.- based Kimeragen Inc., which specializes in making oligonucleotides it calls chimeraplasts.

Bartlett's team said their oligonucleotide got the cell to use its own repair mechanism to fix the ``bad'' gene. The dog's cells produced normal dystrophin. It was killed after 11 months and examination showed the cells had repaired themselves, they reported.

Duchenne MD is the most common lethal genetic disease of childhood.

Caused by a defect in the gene that codes for dystrophin protein, which attaches to other proteins in muscle cells and helps anchor muscles to connective tissues, it occurs in one out of every 3,500 births -- one in 5,000 where at-risk pregnant women can be tested.

It causes weakness in the muscles of the legs, hips, shoulders, and spine.

It is an X-linked recessive disease, meaning females who carry the mutation do not usually have any symptoms because they have two X chromosomes and the "good'' one can kick in to overcome the defective one.

But boys only have one X chromosome and a male child of a woman who carries the Duchenne dystrophy defect has a 50 percent chance having the disease.

Because it is caused by such a simple defect, it was an early target for gene therapy.