Mice with muscular dystrophy bulk up when injected with a gene that's responsible for making a specific protein, according to a new study in the Proceedings of the National Academy of Sciences.

Researchers say the results should now be tested in human clinical trials associated with muscle wasting, including Duchenne muscular dystrophy, which is the most prevalent form of the childhood disorder.

In the study, mice of varying ages with disorders similar to Duchenne muscular dystrophy were injected with a safe virus that contained the protein follistatin. The protein inhibits the activity of myostatin, which previous studies demonstrated to lessen muscle growth. Both young and old mice that were treated with the therapy showed increases in muscle mass and boosts in strength.

Because the older mice in the study responded well to the protein, the treatment might also work on older patients who have few treatment options once their muscles have gone through progressive degeneration, said principal investigator Brian Kaspar, an assistant professor of pediatrics at Ohio State University.

"Many studies don't evaluate a therapy over a two-year time span. In our studies, the beneficial effects persisted over the two years we evaluated," Kaspar said. "Furthermore, this long-term study shows that there were no obvious safety problems with either the gene therapy virus or the therapeutic protein, follistatin."