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A major clinical trial will investigate whether stem cells can be safely used to treat multiple sclerosis (MS).

It is hoped eventually to slow, stop or even reverse the damage MS causes to the brain and spinal cord.

The trial, involving up to 150 patients across Europe, is due to start later this year.

Dr Paolo Muraro from Imperial College London said: "There is very strong pre-clinical evidence that stem cells might be an effective treatment."

Researchers will collect stem cells from the bone marrow of patients, grow them in the laboratory and then re-inject them into their blood.

The stem cells will make their way to the brain where it is hoped that they will repair the damage caused by MS.

The research has been part-funded by the UK's MS Society, which is concerned about the availability of unproven stem cell treatments.

In recent years many people living with MS have been attracted to overseas stem cell clinics which claim to cure long-term conditions in exchange for large amounts of money.

But there is no proven stem cell therapy available for MS anywhere in the world.

The MS Society hopes these new trials will eventually lead to a proven treatment - and a reduction in the draw of overseas treatments.

Common condition

MS is the most common neurological condition to affect young people in the UK.

Three million people are thought to be affected worldwide and up to 100,000 in the UK.

The condition is caused by the body's own immune system attacking and damaging a substance called myelin in the brain and nerve cells.

The myelin damage disrupts messages from the brain to the body which leads to a number of symptoms such as sight loss, bladder and bowel problems, muscle stiffness and eventually physical disability.

Drugs are available to alleviate the symptoms - but they do not prevent the progression of the condition.

Experiments in test tubes and laboratory animals suggest stem cells extracted from bone marrow may be able to offer a more effective treatment.

Their role in the bone marrow is to protect the cells that make blood. But they also seem to protect myelin from attack by the immune system.

There is also some evidence that these cells might also be able to repair damaged tissue.

Hold potential

Dr Doug Brown, of the MS Society, said: "These experiments have confirmed that these stem cells hold that potential - but these need to be confirmed in large scale clinical trials."

There is some way to go, however, before laboratory promise can be translated into a treatment that can be offered to patients.

The international team will begin so-called phase two clinical trials in six months' time designed to determine whether the treatment is safe and effective.

It will take five years to carry out and assess the results of the trials after which large phase three trials may be required.

But Dr Muraro believes that the stem cell approach has real potential.

He said: "The great hope is the fact that we are exploiting a biological system that has evolved over millions of years and harnessing it for treatment that takes advantage of the stem cells' flexibility."

Sir Richard Sykes, chair of the UK Stem Cell Foundation, said Dr Muraro's research was the first of its kind to take place in the UK.

"Given the high incidence of MS in the UK in comparison to other countries, I am delighted that we have at last progressed stem cell research to this stage, which will bring much-needed hope to so many people affected by this devastating condition."

Correction 29 July 2011: This story has been amended after the MS Society corrected a statement it had made suggesting stem cells from the brains of aborted foetuses had been used in research it was funding. The society said that adult neural cells were in fact being used.