THE search for a cure for motor neurone disease has taken an important step forward, after the nerve cells that go wrong in the condition were successfully grown for the first time.

Scientists in the United States have coaxed human embryonic stem (ES) cells to develop into spinal motor neurones, paving the way for new therapies for the wasting disease that has afflicted Professor Stephen Hawking, the actor David Niven and the former England football manager Don Revie. The work will also assist research into paralysis caused by spinal cord injuries.

The landmark achievement suggests it may be possible to treat patients with the disorder by growing replacements for their damaged spinal motor neurones, though experts said this remains a long way off.

It will bring more immediate therapeutic benefits by providing researchers with the best laboratory model yet available for developing new drugs and testing their effectiveness. The disease affects about 5,000 people in Britain, there is no cure, and most patients die within five years of diagnosis.

The new work at the University of Wisconsin-Madison will also help a British team that is seeking to clone human embryos to investigate the disease. A group led by Professor Ian Wilmut, of the Roslin Institute, the scientist who created Dolly the sheep, has applied for a licence to produce clones from patients with the condition, which would be used to study its causes and development and to screen new drugs.

If permission is granted by the Human Fertilisation and Embryology Authority, the Wisconsin results would help Professor Wilmut to turn cloned ES cells into the mature motor neurones he will need for his research. ES cells have never before been turned into spinal motor neurones — the long nerves that transmit messages from the brain and spinal cord to the muscles. The task is considered challenging because these motor neurones are among the first nerves to develop in the embryo, and previous efforts to grow them have failed, even in mice.

The Wisconsin group, led by Suchun Zhang, has now identified that there is a narrow window of opportunity during which ES cells can be steered to make spinal motor neurones, if they are bathed in the correct cocktail of chemicals.

“You need to teach the cells to change step by step, where each step has different conditions and a strict window of time,” Dr Zhang said. “Otherwise it just won’t work.”

He used the procedure to generate motor neurones that show electrical activity — a sign that they are functional. The cells have survived in culture in the laboratory for more than three months.

The success, described in the journal Nature Biotechnology, has several possible implications for treating motor neurone diseases such as amyotrophic lateral sclerosis (ALS). In theory, scientists could use stem cells to replace the dying motor neurones of patients with ALS, though this is likely to be difficult in practice. The more realistic prospect is of growing motor neurones in the laboratory as a tool for examining how diseases such as ALS work, and for developing effective drug treatments.

FATAL FLAW

It commonly starts in middle age, though it can strike down young people

Symptoms are speech problems, difficulty chewing, swallowing and breathing, and paralysis. Muscles weaken and waste away. Death is usually a result of respiratory failure

Most sufferers die within 5 years of diagnosis, and 50 per cent are dead within 14 months

A defect in the SOD-1 gene causes about 2 per cent of cases; otherwise the cause is unknown

There is no cure. Treatment focuses on managing symptoms

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