STRETCHING neurons on the rack might seem like torture, but it could be the key to repairing spinal cords.

By gradually pulling apart bunches of neurons, Douglas Smith and his colleagues at the University of Pennsylvania in Philadelphia have persuaded the cells' processes, or axons, to grow up to a centimetre in just 10 days. "For an axon just a micron wide, that's an enormous distance," Smith says.

The researchers say these nerve cells could be used to bridge the gap between damaged nerves in the spinal cords of people who are paralysed. They have already begun trials in animals. "You can think about what we have as jumper cables," Smith says.

While it's too early to know if the approach will work for people with spinal cord injuries, Smith thinks it is a viable alternative to other strategies. For example, many researchers are trying to encourage nerve cells to ...