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.
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