'Building nerve bridges'

How nerve regeneration works

"The nerve is made up of many thousands of fibres like you can see in a telephone cable.

"These need to be reconnected for the telephone to ring."

Dr Gary Coulton, of St George's Hospital Medical School in London is one of the leading experts treating nerve damage, suffered by thousands of people each year.

The causes can range from household accidents to stabbing, or casualties in war - and are notoriously difficult to treat and slow to heal.

Now Dr Coulton and his colleagues have discovered key proteins which are essential for nerve regeneration.

BBC News Online investigates how scientists plan to "bridge the gap".

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Nerve damage can cause long-term problems.

The exact nature of the damage depends on where the affected nerves are, but injuries tend to heal very poorly and cause extensive disability, often wrecking patients' lives.

And the longer patients wait for their injury to be treated, the smaller the possibility of successful treatment.

At the moment, nerve damage is repaired either by sewing the nerve ends back together or by a graft of a nerve from the lower leg, which causes more damage, prolonging the recovery time.

This could be useful for any patient who is undergoing nerve repair

Dr Giorgio Terenghi,
Royal Free and University College Medical School

But scientists at the Royal Free and St George's Hospitals in London are hoping key scientific discoveries will improve patients' chances.

Special proteins have been identified which encourage growth, speeding up the repair process.

Two have been identified - NGF and NT-3.

NGF increases the number of nerve fibres reaching the skin, which improves the sensitivity of skin.

NT-3 seems to act on the nerve cells responsible for fast contracting muscles.

The researchers say this means there must be another growth factor responsible for slow contracting, weight-bearing muscles, which are responsible for posture.

Therapy

Action Research says more information about how specific nerve cells work will help surgeons repairing nerves.

A member of the research team, Dr Giorgio Terenghi, head of the Nerve Regeneration Group at the Blond McIndoe Centre, Royal Free and University College Medical School, added: "It could be useful for any patient who is undergoing nerve repair.

"Although this new therapy will be applicable only to recent nerve injury, we cannot exclude that development in this field might eventually lead to the treatment of patients who have suffered nerve injury in the past."

Scientists had already developed "bridges" - very small tubes that can link healthy and damaged nerves - which can be filled with the growth factor proteins.

The team have also carried out further work into the use of special genetically modified cells called Schwann cells.

These wrap around nerve fibres, helping one cell communicate with another via electrical impulses.

Schwann cells can be injected into the "bridges", producing extra amounts of growth factors.

Because they can be labelled and identified, they can be tracked once they are transplanted.

Dr Coulton added: "Identification of all these different factors contributing to nerve regeneration will be a crucial step forward."