Researchers at École polytechnique fédérale de Lausanne (EPFL) have found a way to awaken a dormant spinal column and enable paralyzed rats with spinal cord injuries to walk and run again.
The brain and spinal cord possess neuroplasticity — the ability to physiologically adapt to moderate injury. However, the plasticity of the spinal cord expressed has been up until now insufficient to handle severe injury. Research led by Grégoire Courtine, who holds the International Paraplegic Foundation (IRP) Chair in Spinal Cord Repair at EPFL, demonstrates that recovery is possible, provided that the innate intelligence and regenerative capacity of the dormant spinal column is awaken first.
This is done by injecting the rats with a monoamine agonist solution. The chemicals in the solution bind to certain dopamine, adrenaline, and serotonin receptors on the spinal neurons, taking the place of neurotransmitters released by brainstem pathways in unparalyzed subjects and exciting neurons controlling leg movement.
After 5-10 minutes, electrodes implanted in the epidural space of the spinal canal electrically stimulated the spinal cord. This stimulation continuously sent electrical signals through nerve fibers to the excited neurons.
In 2009, Courtine already succeeded in restoring involuntary movement to paralyzed rats. Using a treadmill, rats with a stimulated spinal column were able to walk — the treadmill’s movement created sensory feedback and the spinal column’s innate intelligence took over, enabling the rat to walk without the need for a signal from the rat’s brain. This study convinced the scientists that voluntary movement only required a very weak brain signal.
When Courtine replaced the treadmill with a robotic harness and trained the rats using chocolate at the platform’s far end as reward, the rats’ willpower resulted in nerve fibers regrowing throughout the brain and spine. These new fibers bypassed the original spinal damage and transported brain signals to the electrochemically-awakened spine. The signal was strong enough to enable the rats to walk voluntarily towards the reward using their hind legs.
After several weeks of using the harness and electrical-chemical stimulation, the rats were voluntarily walking, sprinting, climbing up stairs and avoiding obstacles while under stimulation.
It is still unclear if such rehabilitation methods could work for humans, but lead author believes that the results give hope that new treatment methods for paralysis can be developed. Courtine hopes to begin human, phase-two trials in 1-2 years at Balgrist University Hospital Spinal Cord Injury Centre in Zurich, Switzerland. EPFL researchers, in the meantime, are working on NeuWalk, a project which involves designing a spinal neuroprosthetic system, similar to the one used with the rats, that can be implanted into humans.