Rat walk: Electrodes stimulated the spinal nerves (Image: courtesy of EPFL)





Video: Paralysed rat walks again after treatment

Rats paralysed by severe spinal cord injuries have recovered the ability to walk, sprint and even climb stairs, thanks to a rehabilitating robot and a chocolate treat.

Grégoire Courtine at the Swiss Federal Institute of Technology in Lausanne, Switzerland and colleagues previously restored movement to rats with spinal injuries similar to those causing lower-body paralysis in humans, by using a cocktail of chemicals and direct stimulation of spinal nerves.


The team injected chemicals similar to those released in a healthy rat by the brainstem pathways that activate nerves controlling lower body movement. The team then stimulated the spinal cord using electrodes which send a continuous electrical signal to nerves that control rhythmic leg movement. This allowed the animals to walk supported on a treadmill just one week after their injury. “That looks great, but it is completely involuntary,” says Courtine.

Now his team have replaced the treadmill with a robotic harness that holds the rat up on its hind legs, supporting it when it falls over but otherwise allowing it to stand and move independently – Courtine compares it to being held on either side by a pair of burly men.

They also added a chocolate treat just out of reach of the rats. This encouraged each rat to send messages from its brain to its legs, willing them to move. This top-down motivation appeared to kick-start the spinal nerves’ growth. After two to three weeks the rats were able to make their first voluntary steps. A further few weeks saw the rats walking voluntarily on their hind legs for extended periods of time.

More nerve fibres

The rats saw a four-fold increase in nerve fibres throughout their brain and spine, with the new fibres bypassing the original injury and allowing signals from the brain to reach the spine. In comparison, rats given the same chemical and electrical treatment but trained on a treadmill were unable to move voluntarily as there was no regrowth of nerve fibres.

Courtine plans to begin human trials of the technique in the next two years. “We have huge cognitive capacity to invest, and the desire to recover is stronger than a rat, so the recovery may be more extensive. That’s my feeling,” he says, though he stresses that the treatment works best on recent, rather than long-standing, injuries.

“It is a determined attempt to see whether electrical and chemical means can enhance the formation of new functional connections among non-damaged fibres in rats, with implications for the same procedure in clinical trials,” says Geoffrey Raisman, who researches spinal repair at University College London.

It is not yet clear, however, whether the new, bypassing nerve fibres can completely restore motor function, he adds. “We don’t know to what extent this would be limited by the fact that the original connections are still lost.”

Journal reference: Science, DOI: 10.1126/science.1217416