It is known that blocking myostatins activity increases muscle mass and strength, but also makes muscle fibers more vulnerable to injury. The U-M team broke new ground by asking if myostatin also affected the make-up and performance of tendons, the fibrous, tough tissues that connect muscle to bone.
Tendons are stiffer than muscles to begin with, and get stiffer with age. If tendons are brittle and short, as they were in myostatin-lacking mice in the study, they cant adequately do their important job of buffering against muscle injuries.
The tendon acts like a spring, Faulkner says, to reduce some of the force on the muscle in a lengthening contraction. Contraction-induced injury is the most common way we injure our muscles. This type of injury already occurs frequently in people with muscular dystrophy so short, brittle tendons could aggravate the problem if myostatin inhibitors turn out to cause the effect in people.
The research team conducted a series of studies using a strain of laboratory mice that lacked the ability to produce myostatin. They tested the mechanical properties of tendons, compared to tendons in a strain of normal laboratory mice. They isolated and treated tendon cells with myostatin and examined what genes control tendon activity. They were able to identify tendon genes that respond to myostatin, which is produced in muscles, showing that myostatin acts as a hormone to promote strong, flexible tendons.
The findings in mice that lack myostatin are very preliminary and will need to be tested in other mouse strains before seeing if they hold true in people, the researchers say. Its also necessary to explore whether tendon brittleness is a problem if myostatin is merely reduced.
In the meantime, the results are intriguing and cautionary for the variety of people interested in the pot
|Contact: Anne Rueter|
University of Michigan Health System