Building more muscle could help soldiers and sailors returning from Iraq and Afghanistan mend shattered arms and legs, a Medical College of Georgia researcher said.
Mark Hamrick has a three-year, $1.2 million grant from the Navy to look at using compounds that block a muscle-limiting growth factor called myostatin. Mice specially bred not to have it pack on lean muscle and limit fat.
"In the absence of myostatin, muscle regenerates more quickly," said Kathryn R. Wagner, a neurologist at Johns Hopkins Hospital and one of the first to run a clinical trial on a compound that limits myostatin, which is called myostatin inhibitor.
That could help the military, particularly with the high rate of limb injuries. Of those injured in Iraq, 75 percent were from explosions and 54 percent had an "extremity injury," such as an injured arm or leg, according to a study last year in the Journal of Orthopaedic Trauma . And 26 percent of those injuries were fractures.
"We've improved a lot with protection for the (chest) and the head, so that people are surviving a lot of things they wouldn't have survived, yet you've still got this huge preponderance of musculoskeletal injuries," Dr. Hamrick said. "It's orthopedic trauma."
Healing those fractures can be tricky.
"The key factor in healing bone is the health of the surrounding soft tissue," such as muscle, he said. "In cases where the muscle is really damaged, it is going to impair bone healing. Our theory was if you can improve the health of the soft tissues, preferably muscle, by enhancing the regeneration with myostatin inhibitors, you'll help facilitate bone healing."
Myostatin inhibitors have been tried in patients with degenerative muscle disease, such as muscular dystrophy, and were proven to be safe, Dr. Wagner said. Because they also have implications for age-related muscle loss, myostatin inhibitors also are getting a lot of attention from pharmaceutical companies, she said.
"It has moved things along much more quickly than if it were in academia alone," said Dr. Wagner, who is part of the Sen. Paul D. Wellstone Cooperative Researcher Center, a joint effort between Johns Hopkins and the University of Pennsylvania to study muscle regeneration.
The military is putting millions into research in regenerative medicine, and that has been a boon to Dr. Hamrick and other researchers, particularly at a time when the National Institutes of Health funding has been flat.
"It's a big area of interest for the military, but it's something that can translate over nicely into the civilian sector as well," he said.
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WHAT IS MYOSTATIN?
The body often uses positive and negative factors to keep in check different systems, such as bone formation and muscle regeneration. Myostatin is a growth factor that helps to limit muscle growth. Scientists are hoping to exploit that system in patients whose muscles are degenerating or severely injured by inhibiting myostatin to provide an extra boost to muscles. Many companies are looking to develop new drugs based on this idea. Dr. Mark Hamrick, of Medical College of Georgia, is working with a company called MetaMorphix in Beltsville, Md., that is looking at applications in livestock. Dr. Hamrick is working right now with mice.
Dr. Kathryn R. Wagner, of Johns Hopkins Hospital, is looking at both limiting myostatin and adding a positive growth factor called IGF-1 that boosts muscle growth for patients with diseases such as muscular dystrophy.