Scientists have moved closer to treatments for people with disabling nerve injuries after successfully re-growing damaged nerves in rats.

The project, led by researchers at St Thomas' Hospital in London, UK, managed to induce the nerves to grow back and join into the spinal cord.

Normally, once a nerve is ripped from the cord, it fails to link up again, and surgery to repair the damage has enjoyed only limited success.

The team used the right combination of "neurotrophic factors" - proteins which encourage natural nerve growth.

Although their experiments only mimic one type of spinal injury, experts say there is no reason why it might not eventually lead to treatments for severed spinal cords.

And it could potentially reduce the severe pain felt constantly by people with damage to nerves.

Natural growth

A damaged nerve outside the spinal column will recover to a certain degree if damaged, but if ripped from the central cord itself, for example in a sudden accident, it cannot grow back inside and join up.

The team reproduced this kind of injury in the sensory nerves of rats - those which send sensations of touch or pain.

They found that, after the neurotrophin treatment, rats were eventually able to feel hot water and withdraw their limb.

A commentary in the journal Nature, which published the research, suggested that their findings should trigger the start of similar studies in humans.

However, it is hard to justify such experiments unless doctors are convinced the treatment can cause no harm, and experts have warned that human treatments could be some years away.

John Kavanagh, of the International Spinal Research Trust, said that doctors had to be sure the doses of neurotrophins would not, for example, cause cancers to develop as well as nerves.

He said: "This is a good step forward, but we are some way off a cure yet."

He said that although this breakthrough applied directly to "peripheral" nerve damage rather than spinal cord injuries themselves, there was no reason why it could not in theory apply to nerve re-growth in any part of the body.