Mice paralysed by spinal injuries have been able to walk again thanks to a treatment developed by scientists in the US. The therapy uses proteins that self-assemble into nanofibres at the site of the injury, encouraging nerves to regrow. 

'Spinal cord injury is rather like cutting a telephone cable,' says John Kessler, leader of the team at Northwestern University, Illinois. 'It's not about replacing cells; it's about reconnecting the wires properly.' But in the spinal cord, although severed nerve fibres are capable of repairing themselves, glial cells that surround the damaged nerves form a scar that blocks the two ends from reconnecting. 

A) Schematic picture showing the structure of the nanofibres; B) The assembled scaffold of nanofibres

The new treatment involves injecting specially-designed peptides with long hydrophobic tails directly into the site of the injury. 

'When these peptides come into contact with an aqueous solution - such as fluids in the body - the charges in the tails line up and point inwards, forming radial spokes and producing long cylindrical nanofibres,' Kessler explains. 'These nanofibres act as a scaffold that serves a dual purpose, both limiting the amount of glial scarring that occurs and stimulating the nerves to grow out and reconnect.' 

The team used their therapy to treat mice with crushed spines 24 hours after they had received the injury. Six weeks later the mice had regained the ability to control their hind legs and walk, showing that both motor and sensory nerve fibres had healed. But, Kessler adds, there is still a lot of work to be done before the treatment can enter human clinical trials.  

'I think this is a pretty significant development,' says Michael Beattie, a specialist in central nervous system injury and repair at the University of California. 'The team have combined clever polymer chemistry with some good outcome measures to achieve impressive results.' 

'Right now there is a lot of excitement about using stem cells or progenitor cells to treat brain or spinal cord injury,' he adds. 'These could be combined with this kind of treatment and I should expect to see human trials in years rather than decades.' 

Kessler's team are also confident that this technology will not be limited to injuries of the nervous system. There is a huge potential for applying this technique to other health problems, the researchers say, such as stimulating regrowth of blood vessels or regenerating organs with stem cells. 

Lewis Brindley 

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