A Golden Retriever pup has hit the medical headlines after taking part in successful tests to treat muscular dystrophy.
Five month old Azor was already limping as a result of the disease, but, after five consecutive injections of stem cells extracted from adult muscle, he was able to bound around like his peers.As a result of this remarkable series of experiments reported last week, stem-cell treatment for the degenerative and fatal disease muscular dystrophy could be available for testing on patients within two years.
Muscular dystrophy comes in at least 20 forms and causes muscle wasting, progressive paralysis and eventually death, affecting about 30,000 people in Britain alone. There are no effective treatments but now an Italian team reports success in experiments on dogs that have a form of Duchenne muscular dystrophy, which is caused by a lack of the protein dystrophin in muscle fibres.
Golden Retrievers have also suffered from the genetic disease, the result of a naturally occurring mutation and have been specially bred because they are the most accurate animal model of the human disease.
The dramatic results of stem-cell therapy on the animals are reported in the journal Nature by Prof Giulio Cossu, the director of the Stem Cell Research Institute of San Raffaele Scientific Institute of Milan. The work shows that it is possible to halt this devastating disease and possibly even reverse it to a degree.
The therapy was described as ‘a very significant advance, perhaps even a breakthrough’ by Prof George Dickson of Royal Holloway, University of London.
Dr Marita Pohlschmidt, the director of research at the Muscular Dystrophy Campaign, said: ‘If it does prove to be successful in humans, this technology has the potential to develop into an efficient and ground breaking treatment.’
Working with the University of Pavia and the Veterinarian School of Macon Alfort in Paris, Prof Cossu's team transplanted cells called mesoangioblasts ˜ stem cells gathered from small blood vessels in muscle ˜ that are programmed to develop into muscle cells.
The cells came from healthy dogs and were multiplied in the laboratory to sufficient quantities. These were injected into the blood stream of dogs with the disease and their immune systems were suppressed to stop the stem cells from being rejected.
‘That worked,’ said Prof Cossu last week. The cells were carried around the body to the affected muscles and increased their strength, which in turn improved the ability of the dogs to walk.
To see if it was also possible to correct the dogs' own cells, so they would not need anti-rejection drugs, stem cells were isolated from affected dogs and a type of virus - a lentivirus - used to insert into the cells a corrected copy of the faulty dystrophin protein, actually a stripped down version of the human gene.
Other animals - around four months and already limping - were injected five times at monthly intervals with their own modified stem cells but there was no improvement, even though the gene therapy seemed to work at the molecular level. In the long-term, this type of transplant would be preferable because it would do away with a lifetime of immune suppression: without this, some dogs in the trial that received stem cells from another animal rapidly lost the ability to walk.
Prof Cossu has already discussed human transplants with an Italian charity and is planning clinical trials. The first attempt is likely to use stem cells from a donor with a similar tissue type, the method that succeeded with the dogs.
The professor estimated that another year or two will be necessary to get a patient's own genetically modified stem cells to work.