The researchers believe the revolutionary treatment could become the basis of a possible cure for the thousands of children with muscular dystrophy, in which an inherited fault causes muscles to degenerate. But they have also warned that the breakthrough, which may permanently increase the size of a person's muscles, could be wrongly applied for cosmetic improvement or to boost athletic performance.
Experiments on laboratory mice showed that infecting the animals with a genetically engineered virus increased their muscle strength by 15 per cent in young individuals and by up to 27 per cent in older mice - effectively restoring them to their youthful strength.
The virus, which was rendered harmless before extra genes for a muscle- building factor were added, could one day be used on humans who, like mice, also become feeble with age as a result of muscle loss. "Our results show that it may be possible to preserve muscle size and strength in old age using this approach," said Lee Sweeney, Professor of Physiology at the University of Pennsylvania and the head of the research team.
"We're now looking to see whether the technique might also be used to increase muscle strength in diseases such as muscular dystrophy."
Details of the research, which will be published later this month in the Proceedings of the National Academy of Sciences, were released yesterday at the American Society for Cell Biology in San Francisco.
Professor Kay Davies, of Oxford University, an authority on the genetics of muscular dystrophy, said: "This type of therapy is likely to be generally applicable to man and is a very promising development. This approach may also be used to improve muscle strength in muscular dystrophy patients which would greatly improve their quality of life."
The virus used in the experiments, called adeno-associated virus, was engineered with a gene for a substance known to trigger the growth of muscle cells during the repair of damaged tissue. Injecting the muscles of older mice with the virus caused it to infect the animals' cells, introducing the growth-factor gene as it spread within the tissues.
Professor Sweeney said that a number of ethical considerations will have to be addressed before the technique could be used on humans.Reuse content