The human body is a bit cruel sometimes. “Use it or lose it” applies to muscles, but unfortunately so does “don’t use it too much or lose it.” Now, researchers at Temple University have tested a drug that appears to reverse muscle damage from overuse injuries in rats.
Movements involving high force or high repetition will make tiny tears in muscle fibers, and normally the body will patch them up just fine. But the problems arise when these injuries continue for long periods of time, say for athletes or manual laborers. Eventually the muscle tissue begins to be replaced with connective tissue – a condition called fibrosis, which can be painful and leave muscles weakened.
“The accumulation of scar tissue from muscle fibrosis is the primary cause of muscle weakness that arises following overuse injury, also known as repetitive strain injury,” says Mary Barbe, lead researcher on the study. “If we can successfully reverse muscle fibrosis in humans, we will be able to provide relief and help workers with overuse injury eventually return to their jobs.”
The key to the new study was a drug called FG-3019, which was recently approved by the US FDA. This drug blocks the activity of CCN2, a protein that promotes the growth of connective tissue. FG-3019 was designed as a potential treatment for muscular dystrophy, but the researchers on the new study wondered whether it could also be put to work on other fibrosis-related conditions.
To test it out, the team trained rats to perform a high-force, high-repetition task – reaching for and pulling a lever to receive a reward. After 18 weeks, they had developed muscle fibrosis as a result of overuse. One group of animals was then given FG-3019, while another group received a placebo and another had no treatment.
After six weeks of treatment, fibrotic damage had been reversed in the treated rats and they showed improvements to grip strength and other tests. They also had lower levels of CCN2 and collagen than the untreated or placebo groups, which put them on similar ground to a control group of rats that hadn’t performed the repetitive task at all.
With this promising animal study completed, the researchers hope to move onto clinical trials in humans. After all, the drug has already been approved and is in the testing stage for other conditions.
“FG-3019 is already in clinical trials for other diseases involving fibrosis, including pulmonary fibrosis and kidney fibrosis,” says Barbe. “Our work adds to the relevance of this drug in treating fibrotic diseases, with the novel application for muscle fibrosis associated with overuse injury.”
The research was published in The FASEB Journal.
Source: Temple University
