Treatment could one day help humans
Paralyzed rats learned to walk again after a combination of electro-chemical stimulation to their injured spines and intensive rehabilitation therapy.
Researchers say the treatment “woke up” dormant or sleeping neurons in their spinal cords, and formed new connections to the brain. Scientists hope the treatment might someday help paralyzed humans.
Researchers at the University of Zurich in Switzerland, injected a mixture of chemicals to stimulate the rats' spinal nerve cells, which communicate with the brain. Ten minutes later, they used electrodes just below the cord injury to "wake up" the otherwise healthy nerve cells involved in walking, but which had became inactive following the injury to the spine.
The rats were also placed in a robotic device that looks like a little vest, to support their weight. The device, which helped with the rehabilitation, kept the animals upright, and was activated only when the rats started to lose their balance.
During the first few weeks after the treatment, lead researcher Grégoire Courtine at the Swiss Federal Institute of Technology of Lausanne says the rats did not move their legs. But after three weeks, the rodents took one or two steps and, with the vest, supported themselves on their weakened legs.
At the end of six to seven weeks, Courtine says, the rats were able to sprint up stairs, achieving what he calls 100 percent recuperation of voluntary movement.
“We really observed a reorganization of neuronal connections," Courtine said. "And it was really fascinating because it was not predicted when we started the experiments.”
Investigators used chocolate as a reward to induce the rats to walk, encouraging what
Courtine calls willpower-based training that led to neuronal plasticity, or nerve regrowth, throughout the rats' nervous systems. There was a four-fold increase in nerve fibers, not only in the rats' spines, but also throughout their brains. The newly formed fibers bypassed the spinal injuries, so signals from the brain could reach the reawakened neurons.
But the robotic vest will always be necessary to keep the rats upright when they walk.
Courtine says scientists have proven the enormous potential of neuroplasticity, which previously had been thought to occur only on a limited basis in patients with brain and spinal cord injuries. But he cautions that this approach might not be able to bring about the same degree of movement in paralyzed humans.
“We may be able to improve the functional recovery in humans," Courtine said. "But this is really too early to say anything.”