Spinal cord injuries are notoriously difficult to treat, with a break in the spine often leading to permanent loss of feeling and the inability to move. But researchers in China are now reporting that they have successfully repaired acute spinal cord injury in monkeys and restored function to their limbs.  

The experiments were carried out on rhesus macaques by a collaboration of Chinese institutes, with their results published in the Proceedings of the National Academy of Sciences. The study on monkey models raises hopes that the treatment can one day be translated to humans.

The researchers achieved this impressive feat using a mixture of two substances: chitosan and neurotrophin-3. Chitosan is derived from the polysaccharide chitin, the primary component of cell walls in fungi as well as that found in the exoskeletons of arthropods. It forms long strands and has used in the medical field as a drug delivery system, antibacterial agent, and in the reduction of bleeding.

For this particular study, chitosan was used as a matrix scaffold to load neurotrophin-3, which is a neurotrophic factor in the nerve growth factor family. This basically means that it is a molecule – produced naturally by the body – that encourages and stimulates the growth of new neurons from stem cells. In addition to that, it also helps existing neurons to survive and differentiate.

The team paired these together and then inserted it into a 1-centimeter gap created in the spines of rhesus macaques. The structure of chitosan effectively forms a scaffold in which the neurotrophin-3 is slowly released over a period of around 14 weeks. When this was done in rats, researchers found that it encourages neural stem cells to migrate to the site and differentiate to form new neurons, bridging the partial break in the spinal cord.

According to the team, the treatment restored a certain amount of feeling and movement to the monkeys after recovery from surgery. Follow up fMRI scans, magnetic diffusion tensor imaging, electrophysiology, and walking analyses confirmed that the two substances did indeed elicit "robust neural regeneration accompanied by motor and sensory functional recovery."

This is pretty impressive as spinal cord injuries are incredibly difficult to treat. Recovery is often inhibited by inflammatory cytokines that flood the site. It is thought that the chitosan matrix helps to concentrate the neurotrophin-3 at the site of injury and elicit robust regeneration of the spine's neurons.

Due to the success of this treatment in monkeys, the researchers think there is a good chance that it could also be used in humans. However, that is still a long way off.