Scientists already know that it’s possible for damaged axons within the nerve cells to be restored, however they’ve never really understood how this happens. Now a study carried out by a team of researchers at the University of Wisconsin-Madison has been able to shed more light on the process.
Axons are the long fibres found on neurons whose role is to transmit impulses along the nerve. If they are damaged, the peripheral nervous system is able to regenerate destroyed axons to some degree, but the process is often drawn out and may not result in a full repair. How this happened has always been a bit of a mystery. Now scientists have found that Schwann cells, which are present in the peripheral nervous system, are able to transform themselves so that they can accelerate the repair process. Schwann cells are normally responsible for creating the myelin sheath that insulates and speeds transmission of impulses through the nerves. However, once they’re triggered into repair mode, they’re also able to stimulate nerve regrowth too.
To find out more about this transformation, senior author of the study, Professor John Svaren and his team made a comparison of the activation of genes in Schwann cells in both mice with intact axons and mice with axons that had been cut. From their comparison they observed that a set of latent genes were activated in the mice with the cut axons, which triggered the Schwann cells to adopt a repair mode and perform several functions to enable the axons to regrow.
While in repair mode, the Schwann cells start to dissolve the myelin which, although essential for the nerve cells to function properly, actually hinders regeneration following an injury to the cells.
They also begin to send signals summoning extra blood cells to help with the clean-up, and plan the pathway for the repaired axon. Once this has been done, they then return to their normal role and grow a new myelin sheath around the repaired axon. It’s hoped that this study could help researchers to find new ways to help repair damaged axons, particularly in light of the fact that it’s now known that Schwann cells don’t just make myelin, but that they also have another function that enables them to regenerate axons too.
The study was published in a recent edition of the online Journal of Neuroscience.