Scientists discover how to knit severed spinal cords back together

Published on Sunday 2 August 2009 22:46

SCIENTISTS have taken a major step towards helping people paralysed by spinal injuries by reconnecting the severed nerves of rats with broken backs.

A team has shown that regenerating nerve fibres can reform connections in the spine after being guided to the right targets.

Back and neck injuries often result in the person becoming paralysed because, unlike peripheral nerves, the "wires" of the spinal cord do not naturally mend themselves. The breakthrough could one day help the hundreds of people paralysed in the UK each year.

Currently, more than 40,000 people are living with a spinal cord injury. Recently scientists have shown that the severed fibres – called axons – can be made to regenerate into and beyond injury sites. But, like the wires in a wall plug, nerve fibres have to be attached to the right places.

A key problem has been how to ensure regenerating fibres join up with their correct cell targets when faced with millions of potential alternatives.

Another stumbling block is the formation of functional nerve-connection points, called synapses.

In the new research, scientists working at the University of California in San Diego regenerated axons in injured rats.

They showed that the nerve fibres could be guided to their correct targets using a biological chemical to promote growth.

The chemical, neurotrophin-3 (NT-3), not only steered the "wires" the right way, but also supported synapse formation.

Two other treatments were needed at the same time – a cell "bridge" placed across the spinal cord injury site and a "conditioning" stimulus to turn on regeneration genes for new growth.

When NT-3 was inserted in the right sites, axons grew into it and formed synapses. Placed in the wrong sites, the nerve fibres grew into the wrong region.

The scientists, writing in the journal Nature Neuroscience, used high-resolution imaging to observe what was going on and found that guided regenerating axons were precisely on target.

Researcher Professor Mark Tuszynski said: "The ability to guide regenerating axons to a correct target after spinal cord injury has always been a point of crucial importance in contemplating translation of regeneration therapies to humans.

"While our findings are very encouraging in this respect, they also highlight the complexity of restoring function in the injured spinal cord."

The researchers will continue their work to make the connections "electrically active" to allow the spinal cord to work.

The breakthrough would have laid the groundwork to aid patients such as the late Superman actor Christopher Reeve, paralysed in a riding accident.

Despite crossing a major hurdle, the team failed to create electrically active and functioning spinal cord connections.

Further investigation revealed the probable cause. The regenerated axons were not covered in myelin, the essential insulating fatty sheath that coats nerve fibres.

This will be the next step in the team's research.

GAMES THAT ENDED IN TRAGEDY FOR TEENAGERS

A RISE in the number of teenagers suffering serious spinal injures while playing rugby last year sparked a government investigation.

One of those injured was Ciaran Pryce, pictured right, who was just 15 when his dreams of playing at national level were cut short. The teenager was paralysed from the neck down following an accident on the pitch.

Ciaran, who had been playing for Cathkin High School, Cambuslang, was rushed to hospital in October 2007 after a violent clash of heads during a game against Kilmarnock.

The accident left him tetraplegic – paralysed from the neck down, with only limited movement of his upper limbs.

The Ciaran Pryce Appeal was set up to raise money for his long-term needs.

Ciaran is not the only young player to have suffered crippling injuries.

In September, a 17-year-old pupil at Merchiston Castle, Edinburgh sustained severe spinal injuries during a match against another private school.

An expert group has now been set up by the Spinal Injuries Unit in Glasgow to analyse the recent cases.