Scientists have obtained some promising results by treating mice bred to develop a form of motor neuron disease that affect children, with injections of stem cells into the spinal cord.
Giacomo Comi, of the University of Milan in Italy, has revealed that the treatment extended the lives of the mice beyond and kept them more mobile, giving hope that similar approaches might work in humans as well.
The lead research has revealed that the treated mice were bred to have a form of motor neuron disease called spinal muscular atrophy with respiratory distress type 1 (SMARD 1), which affects 1 or 2 in every 100,000 children.
Since diaphragms of infants with the disease stop working, they need mechanical ventilators to stay alive.
The condition also affects nerves in muscles of the extremities, gradually limiting movement of hands and feet.
"At present there is no cure for this disorder, besides ventilation and prevention of infections," New Scientist magazine quoted Comi as saying.
Cells in the spinal cords of children with the disease rapidly die, and scientists have to date not been successful in finding out why.
Thus, Comi extracted stem cells that grow into neurons from the spinal cords of mouse embryos.
The cells were normal, except that they had been genetically engineered to make green fluorescent proteinMovie Camera, a substance from jellyfish that glows bright green under ultraviolet light.
Doing so made it possible for the researchers to see what happened to the 10,000 cells transplanted into the spinal cords of each mouse with the mouse form of SMARD1.
Their study showed that the mice treated with the cells alone lived 30 per cent longer than untreated mice.
The researchers observed that untreated mice lost 60 per cent of their neurons during the experiment, but cell-treated rats gained neurons, with donated cells and increased numbers of native neurons each making up a quarter of the total.
According to them, the results were even better in a group of mice that received the stem cells plus a cocktail of drugs to help neurons grow and develop axons, so forming connections with muscles.
The team said that such mice lived 40 per cent longer than the controls, with donated and new native cells each making up a third of the total number of neurons.
The treated mice also retained the mobility that untreated mice began to lose rapidly at around 5 weeks of life.
By week eight, both sets of treated rats could still perform the "rotorod" test, a standard test of mobility similar to a human treadmill, except that the mice place their front paws on a revolving drum.
"For the first time in an animal model of a human motor neuron disease, there was functional restoration opening up new possibilities for therapeutic interventions with transplanted motor neurons," says Comi.
Brian Dickie, director of research at the British Motor Neurone Disease Association, hailed the study's findings by saying: "This is very promising work. Not only have the researchers managed to direct transplanted motor neurons to connect with their target muscles in appreciable numbers, but they've also been able to demonstrate an improvement in motor function and survival."
He, however, insisted that there's a world of difference between treating mice and humans.
"Establishing new neuromuscular connections over distances of a couple of centimeters in a young mouse is very different from attempting the same in human motor neuron diseases, especially in adults where the transplanted neurons may have to grow up to a meter to reach their target. That is a substantial hurdle that we still need to overcome," he says.
Comi admits that there are many hurdles ahead, including selection of the most suitable type of cell for treating humans.
"At the moment, we're not planning to start a trial," he said.
A research article on the study has been published in The Journal of Neuroscience.