RNA injections boost muscle strength
Detergent delivers genetic medicine to mice with muscular dystrophy.
A mouse study raises hopes that injections of the DNA-like molecule RNA might one day help to treat the muscle-wasting disease Duchenne muscular dystrophy. For the first time in a live animal, RNA therapy has produced improvements that last for up to three months1.
Duchenne muscular dystrophy is an inherited disease that affects 1 in 3,500 children, mainly boys. Sufferers inherit a fault in the gene encoding the protein dystrophin, causing most to die in early adulthood.
The new approach effectively corrects the flawed gene. It targets RNA - the intermediate between DNA and protein. Snippets of RNA, injected directly into the muscle, help edit out damaged pieces of host RNA. Muscle cells can then produce the missing dystrophin protein.
Qi Long Lu and researchers from the Hammersmith Hospital in London treated more than 30 mice with a form of muscular dystrophy. They gave the animals RNA plus a synthetic detergent that lets ten times more of the RNA into the cell. Three weeks later, protein levels had increased and muscle strength had returned to 70% of normal. "You see the effects very quickly," says Long Lu.
Previous animal studies have been disappointing. Without detergent, only small amounts of RNA can enter the cell. The combination is "efficient and efficacious", says RNA researcher John Rossi of the City of Hope National Medical Center in Duarte, California.
The treatment's local effects wear off after three months, so were it to work in human patients, they would have to re-inject their muscles regularly. Alternatively, the cocktail could be delivered directly into the bloodstream, suggests Long Lu.
- Lu, Q. L. et al. Functional amounts of dystrophin produced by skipping the mutated exon in the mdx dystrophic mouse. Nature Medicine, published online, doi:10.1038/nm897 (2003).