Rats with a spinal cord injury learned to walk again.
After a spinal cord injury, most people suffer muscle paralysis and/or loss of sensations. When those symptoms are still detectable months later after the initial injury, the patient's condition is called “chronic spinal cord injury”.
A group of scientists led by the Dr. Grégoire Courtine at the Swiss Federal Institute of Technology (EPFL) managed to restore voluntary control of locomotion on a chronic spinal cord injury model.
The spinal cord of rats was cut in two distinct places, leading to a complete and long lasting paralysis of the animals, but still leaving the spinal cord in one piece. After “bathing” the spinal cord with specific chemicals, the animals were subjected to an electrical stimulation to further facilitate the motor activity. This led to the reawakening of the central pattern generator, which are considered the “spinal brain” and are involved in the stepping process. By submitting animals to an intensive training, using a robotic harness in which rats were supported, and by “pushing” the rats to perform a voluntary movement they were not only able to regain the ability to walk but also to sprint over ground, climb stairs and even pass obstacles.
The extend of this voluntary recovery is surprising knowing that the animal had a full lack of movements before the treatment. The scientists showed this recovery was supported by the creation of new axonal circuits that are spanning across the injury. But even though new nerves have bridged the injury, this regain of voluntary functions can be achieved only while the spinal cord is still being stimulated. The system works as if the “critical amount of stimulation” coming from the brain can be achieved only with the electrical stimulus.
Although this work is still away from a human application, it proves that the recovery from a complete chronic spinal cord injury is possible in general. It also shows that the training has to actively involve the subjects. Indeed simple automated stepping did not lead to any improvements, proving that also the brain has to be somehow “stimulated”. Finally it has a direct impact on human rehabilitation, suggesting that subjects with spinal cord injury might benefit from active participation, while being brought to a “functional state”.
van den Brand R, Heutschi J, Barraud Q, DiGiovanna J, Bartholdi K, Huerlimann M, Friedli L, Vollenweider I, Moraud EM, Duis S, Dominici N, Micera S, Musienko P, Courtine G. Science. 2012 336(6085): 1182-5.