2 June 2003
Spinal cord repair: pilot trials "within sight"
When the brain and spinal cord are injured, the damage is permanent, because the tissues cannot repair themselves in the way that bone and skin can. Writing in the June Journal of the Royal Society of Medicine, Dr Geoffrey Raisman describes encouraging results from a new approach to the problem, which he believes will make it possible to plan a pilot trial involving human patients. Dr Raisman led a team at the National Institute for Medical Research which successfully healed the injured spinal cord of an adult rat. They were able to grow a bridge of olfactory nerve cells across the scar tissue, which acted as a guide so the severed nerve fibres could find their way to the right targets in the rat's brain.
How nerve fibres 'get lost'
Soon
after birth the nerve fibres in our brain and spinal cord
stop being able to repair themselves properly. Some experts
suggest that this is because the fibres lose their ability
to form new connections, others believe that the adult nervous
system produces molecules which stop nerve fibres from growing.
Dr Raisman disputes both theories. He points out that the
brain changes all the time as we learn throughout life, and
that cut nerves "sprout vigorously", just not in the right
direction. Dr Raisman suggests that adult nerve fibres fail
to regenerate because they have to contend with much greater
distances and much more complex pathways than those in the
embryo.
A bridge made of nose nerves
Another problem with injuries to the spinal cord is scarring.
During development, nerves grow along glial cells, types
of supporting tissue arranged in regular networks and channels.
When the glial cells are damaged, each type behaves differently
- some swell up, some die and some move into the damaged
area, which is swamped with blood cells. This creates a scar
which nerve fibres cannot find their way past. Dr Raisman's
team got round this problem by grafting a culture of glial
cells from the olfactory nerves - which regularly regenerate
even in adults - onto the scarred Section, where they grew
into a "bridge". The cut nerve fibres were able to follow
the bridge pathway over the scar, growing safely inside a
sheath of graft cells.
Curing human spine injuries: the final obstacles
Dr Raisman's team successfully restored nerve functions in
rats with partially-severed spinal cords, and they believe
their method "really is predictive of human repair". More
work needs to be done on sourcing enough suitable graft cells
and refining the implantation technique, and suitable patients
must be found for a pilot trial. Dr Raisman is hopeful that
he will be able to overcome these final obstacles in the
near future. He is currently in discussions with the Institute
of Neurology at University College London about a possible
trial at the National Hospital for Neurology and Neurosurgery.
[ends]
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