Stem cells could be used to reverse symptoms of motor neurone disease

The prospect of treating motor neurone disease and other forms of severe paralysis has come a step closer with a study showing that it is possible to alleviate symptoms with the help of stem cells.

Scientists have shown that human stem cells can be used to treat laboratory rats suffering from the same degeneration of the nerve cells in the spinal cord and brain that causes motor neurone disease in people.

The disease affects about 5,000 people in Britain and life expectancy for most patients is just two to five years. Professor Stephen Hawking, the Cambridge cosmologist and author of A Brief History of Time, is a notable exception, having lived with the condition for more than 35 years.

Motor neurone disease affects the nerves that control muscle movements throughout the body. It leaves people unable to walk, talk or feed themselves, but their intellect usually remains unaffected.

The latest research shows that human stem cells can be grafted into the lower spinal cord of specially bred rats with a genetic defect that mimics the human disease. Stem cells can grow into any of the specialised cells of the body - such as nerves or blood cells - and could be used to treat a range of degenerative diseases.

Vassilis Koliatsos, an associate professor of pathology and neuroscience at Johns Hopkins Medical Institutions in Baltimore, Maryland, said that the transplanted stem cells developed into mature nerve cells and made substantial connections with other cells.

"We were extremely surprised to see that the grafted stem cells were not negatively affected by the degenerating cells around them, as many feared introducing healthy cells into a diseased environment would only kill them," Dr Koliatsos said.

The study, published in the journal Transplantation, showed that rats injected with live human stem cells started to lose weight on average at 59 days and lived for 86 days after injection.

This compared with a second group of "control" animals that were injected with dead stem cells who lost weight at 52 days and lived for 75 days after injection.

Dr Koliatsos said that rats with the live cell transplants were able to retain their muscle control for longer than the second group of controls. A microscopic investigation showed that 70 per cent of the injected stem cells had developed into nerve cells and many of those grew nerve endings connecting to other cells in the rat's spinal cords.

"These stem cells differentiate massively into neurones - a pleasant surprise given that the spinal cord has long been considered an environment unfavourable to this type of transformation," Dr Koliatsos said.

The scientists only injected stem cells into the lower spinal cord, which would not have helped the paralysis of the upper body muscles. Further studies with more extensive transplants are planned before human trials can be carried out.

"The nerves and muscles above the waist, especially those in the chest responsible for breathing, were not helped by these transplanted stem cells," Dr Koliatsos said.