Scientists believe the animal experiments show that gene therapy - injecting healthy genes into patients - for muscular dystrophy is now more than a theoretical possibility, although researchers emphasise in today's issue of the journal Nature that more work needs to be done.
Duchenne muscular dystrophy affects about one in every 3,500 boys and is one of the most common genetic diseases with no cure. Females rarely develop the symptoms but can be carriers. The signs of muscle wasting first appear at about three years old. Children are often confined to wheelchairs by the age of 11 and develop severe respiratory and heart problems that frequently prove lethal by their mid-twenties.
Ever since the gene for muscular dystrophy was discovered in 1986, scientists have thought that gene therapy could provide a cure, but the problems of inserting such a large gene - it is 100 times the size of a typical gene - into all affected muscle cells seemed insurmountable.
Jeffrey Chamberlain, assistant professor of human genetics at the University of Michigan Medical School, United States, who led the research team, said the work demonstrated for the first time that a cure was possible: 'We have clearly shown that if you can get the gene into the muscle you can cure the disease.'
He warned that the method used to cure the mice could not be used on humans because genetic manipulation of the very early embryo was too dangerous. 'If you can find an effective way to get the gene into humans, and you can control it properly, then you may have a cure. In this study we found a way to control the gene once it's in the muscle; now we need to find a way to deliver it (to muscles).'
Dr Chamberlain's group is attempting to insert the healthy gene into the influenza virus which can then be used to 'infect' muscle cells of the lungs with the correct gene form.
Kay Davies, a medical geneticist who will soon become head of the Medical Research Council's new Clinical Research Centre at Hammersmith, London, and who helped to discover the muscular dystrophy gene, said at the International Congress of Genetics at Birmingham yesterday that Dr Chamberlain's work showed that such gene therapy does not produce toxic side-effects.
'It's a very important experiment (because) we need to know what range of toxicity there might be,' she said. 'This is a valuable contribution but we still have a long way to go before we get a method that is efficient at getting at all the respiratory cells.'
Although muscular dystrophy is inherited, about a third of cases result from spontaneous mutations in early life, so pre-natal diagnosis cannot eliminate it completely, which is why gene therapy is important.
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