US scientists have found a way to reverse muscular dystrophy (MD) in mice, offering hope of a cure for humans with muscle-wasting diseases.
MD affects the muscles of the body
The animals in the Nature Genetics study had myotonic dystrophy - the most common form of MD in adults.
The therapy targets a particular kind of toxic molecule to "silence" its presence in the diseased muscle.
The University of Virginia team showed the treatment fully restored heart and skeletal muscle function in mice.
In myotonic dystrophy, like the other types of MD, faulty DNA is to blame for the abnormalities that occur.
Myotonic dystrophy occurs because of a large expansion of DNA code, which most likely causes an accumulation of toxic messenger RNA molecules in cells.
Messenger or mRNA is a copy of the information carried by a gene on the DNA. If the DNA code is faulty then the mRNA will be faulty too.
These abnormalities lead to the progressive muscle weakness and wasting and heart problems seen in myotonic dystrophy.
Dr Mani Mahadevan and his team reasoned that eliminating the toxic mRNA molecules might help reverse the disease.
They created mice with faulty DNA that could be turned on and off by adding or removing an antibiotic to their drinking water.
In the "on" phase the mice showed all the cardinal features of myotonic dystrophy. When the DNA was turned off, normal skeletal and cardiac muscle function was restored in many, but not all of the mice.
Proof of principle
Although the treatment was not 100% effective, the researchers believe their results provide the proof scientists have been waiting for to demonstrate that it might be possible to reverse muscular dystrophy.
They said: "The results represent the first in vivo proof of principle for a therapeutic strategy for treatment of myotonic dystrophy by ablating or silencing expression of the toxic RNA molecules."
Their work also suggests that it is indeed the toxic mRNA that causes the pathology.
They said: "The fact that the course of the disease can be reversed both overtly and at the molecular level suggests that the toxic RNA functions as a reversible metabolic toxin."
Dr Marita Pohlschmidt, of the Muscular Dystrophy Campaign, UK, said: "The results of the research are encouraging for finding a treatment for myotonic dystrophy.
"It might be possible to reverse the symptoms of myotonic dystrophy when the toxic substance causing the condition is neutralised.
"However, there is still a lot that needs to be done before we can be sure that this will be successful."