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31.05.12 – Scientists recover mobility of the lower limbs by awakening the injured spinal cord. Performed on rats, this work gives hope big improvements for people with spinal paralysis.
Rats with spinal cord injuries and severe paralysis can now walk and run. EPFL scientists have published these findings in the journal Science on 1 June 2012.
Their work shows that it is possible to reactivate the functions of the spinal cord, even badly damaged, awakening regenerative capacity using electrical and chemical stimuli. The study began five years ago, at the University of Zurich.
IRP Chair in Spinal Cord Repair at EPFL
According to Grégoire Courtine, holder of the IRP Chair in Spinal Cord Repair at EPFL, it is not yet certain that similar rehabilitation techniques have results in humans. But the regeneration of injured nerve fibers in rats suggests new methods to improve recovery in paralyzed people. “Thanks to the combined effects of stimulation and training with a vertical support system, our rats found voluntary march a few weeks. They can quickly start running, climbing stairs or avoid obstacles, “explains Grégoire Courtine.
Waking the spinal cord is known that the nervous system can recover and readjust after moderate injury – a phenomenon designated by the name of “neuroplasticity”. But in severe cases, the spinal cord shows very limited recovery capabilities, resulting disabilities without hope of remission. Grégoire Courtine’s research proves that it is possible to initiate a healing process, combining rehabilitation sessions and electrochemical stimuli designed to awaken the inactive portion of the spinal cord below the injury.
First step. Grégoire Courtine and his team inject pharmacological agents to rats suffering from paralysis of the lower limbs. These substances, called “agonists monoamine” bind dopamine, epinephrine and serotonin receptor neurons in the spinal cord. This cocktail replaces neurotransmitters issued by brainstem pathways in healthy subjects. It stimulates the neurons of the spinal cord to prepare them to coordinate lower limb movements. Second step.
Five to ten minutes after injection, scientists stimulate the spinal cord with electrodes implanted in the epidural space. These two stimuli, the chemical, the other electric, are a first step towards the restoration of voluntary work.
“This localized epidural stimulation sends continuous electrical signals to neurons that control movement of the legs. We are left then have to initiate movement, “
explains Rubia van den Brand, co-author of the Science paper.
The innate intelligence of the spine In 2009, Grégoire Courtine has shown that it can restore mobility but involuntarily. By stimulating the portion of the spinal cord below the lesion, the researcher noticed surprising developments. At this point, the nervous system of the brain is isolated. However, he began to perform again the modulation of walking. On a treadmill, the previously paralyzed rats to walk was recovering. – Without really intending These experiments show that the movement of the treadmill created sensory feedback, which triggered the march without the intervention of the brain.
It was as if the neurons of the spinal cord were equipped with their own intelligence. These results suggested to researchers that a very small brain signal was enough to trigger a voluntary movement. To test this theory, the researchers removed the treadmill. They have developed a support system to maintain the rats upright during the exercise sessions. This system intervenes only to help paralyzed subjects to keep their balance. Sufficiently motivating conditions for the animals, also tempted by a piece of chocolate, try to move along a platform.
After some time and by dint of successive trials, voluntary movement is restored – provided that the electrochemical stimulation is always active. Even more surprising, the nerve fibers grow back, not only in the spinal cord – they create that bypass relay injury – but also in the brain. “Based on the will, that learning test resulted in an increase in nerve fibers in the brain and spread the column – a regeneration which demonstrates the enormous potential of neuroplasticity even after severe nervous system injury central, “says Janine Heutschi, co-author. First rehabilitation; a promising way for man According to Grégoire Courtine, this regeneration of nerve fibers can be compared to the development phase in the child – for example when it learns to walk. Nerve fibers grow and generate new connections. In rats, the researchers found that the new fibers were circumventing the lesion and allowed signals from the brain to transmit their orders.
When many voluntary movements only last activity time of the electrochemical stimulation, the impressive regrowth nerve fibers suggests that a promising path opens to enhance the recovery of people with spinal cord injury. “This is the World Cup of neurorehabilitation, says Grégoire Courtine. Our rats have become athletes, even though they were completely paralyzed few weeks ago.
I speak of a 100% recovery of voluntary movement abilities. “Phase II human trials will begin in a year or two at Balgrist University Hospital Spinal Cord Injury Centre in Zurich, Switzerland. Meanwhile, the EPFL researchers are coordinating a project called nine million euros NeuWalk whose goal is to create a fully operational neuroprostheses system for the spine, similar to that used on rats, in order to a use in humans.