Muscular monkeys prompt sports doping fearsLinda Geddes, reporter

A gene therapy that appears to bulk up muscle mass and strength in monkeys - reported today in Science Translational Medicine - will undoubtedly raise fresh concerns about the potential for gene doping in sport.

We already know that some athletes use drugs like erythropoietin to increase the amount of oxygen their blood delivers, and steroids to bulk up muscle mass.

The big advantage with gene doping is that it should be harder to detect. That's because it's difficult to test for a protein that the body already produces, especially when its levels naturally vary between individuals - which might explain why some people are inherently better at sports than others.

In the new study, Janaiah Kota and colleagues at Nationwide Children's Hospital in Columbus, Ohio, used gene therapy to add extra copies of the follistatin gene into the leg muscles of monkeys. Follistatin has been previously shown in mice to block myostatin, a protein that decreases muscle mass, resulting in bulked up "mighty mice". Monkeys injected with the gene also seemed to bulk up, and when Kota's team analyzed their leg muscles with a device that measures force, they found that the muscles injected with the follistatin gene were also stronger than normal muscles.

They hope the approach could eventually be used to treat the severe muscle weakness associated with neuromuscular disorders like muscular dystrophy and multiple sclerosis.

Indeed, the drugs companies Amgen and Wyeth are already experimenting with drugs called myostatin inhibitors in humans, with some promising early results.

Such studies have already prompted fears about the potential for myostatin inhibitors to be abused by athletes hoping to gain the competitive edge. If gene therapy can achieve similar outcomes in humans, such modifications will be even harder to detect.

The World Anti-Doping Authority has already prohibited the use of gene doping within their World Anti-Doping code, and while there is currently no hard evidence of athletes using gene doping to improve performance, there are strong suspicions that they will start doing so soon - unless someone figures out a reliable way of detecting it.