Forging new connections: paralyzed rats walk again

Our brains go through many changes as we grow, learn and experience new situations. Many of these changes are obvious, including maturing as we get older as a result of brain development, acquiring new skills and forming habits. This capacity for growth and change also extends to the entire nervous system. This idea -- called neuroplasticity -- is the basis for the latest breakthrough in spinal cord injury (SCI) rehabilitation.

Currently, despite decades of research and some promising advances, the goal of treatment for paralysis caused by severe SCI is to improve the quality of life for the patient, keeping the body strong despite limitations to prevent further injury. However, ongoing research offers many potential therapies.

On May 31, Swiss researchers announced that rats with legs that were completely paralyzed due to SCI were now walking, and even running, voluntarily due to a new therapy developed in the Courtine Lab at École Polytechnique Fédérale de Lausanne (EFPL) in Switzerland.

The novel method utilizes both pharmacological techniques and electrical-chemical stimulation. Rats severe spinal cord injuries were injected with a chemical solution of monoamine agonists. The chemicals bind to receptors of dopamine, adrenaline and serotonin on the spinal neurons, acting as a replacement for neurotransmitters released by brainstem pathways in healthy patients and triggering cell responses. Following the chemical treatment, the rats were stimulated with electrodes specifically targeting the neurons that control leg movement. When placed on a treadmill, their bodies held up in a device for support, the rats’ legs mimicked a walking pattern involuntarily.

“The spinal cord, even when isolated from the brain, has the capacity to learn the task to which it is exposed,” Dr. Grégoire Courtine, who heads the research, said in a video.

Previously, in 2009, Courtine used similar techniques to achieve this involuntary movement in the rats. Now, however, the rats have reached a new milestone: voluntary walking. Through repeatedly walking involuntarily, new nerve fibers formed and bypassed the damaged area of the spinal cord. It appears that the therapy awakened the “innate intelligence” of the spinal column, as Courtine refers to its capacity to learn. The results of the tests performed in his lab indicate that only a very weak signal from the brain is required to make movement possible, and in turn this allows the potential for that signal to be strengthened.

This method differs from another approach to treating SCI that has recently shown some promise -- stem cell therapy -- in that it does not aim to repair the lesion of the spinal cord, but rather overcome the lesion and disruption in the signals to the brain. The results of another study, which were also released last month, demonstrated success in improving mobility in some patients dealing with the aftermath of SCI, and even appear to have improved lesions according to MRI scans, with transplants of mesenchymal stem cells (MSCs) derived from the patients’ own bone marrow. It was the first study in which MSCs were injected directly into the spinal cord for treatment of SCI.

While a complete restoration of a damaged, even completely severed, spinal cord through stem cell therapy or other means may seem to be the ideal goal of SCI research, the results out of the Courtine lab show that the body may be able to, with minimally-invasive assistance, repair itself and overcome devastating injury. The success of the new method in an animal model speaks to the amazing capacity of the body to bounce back from injury and the degree to which science can amplify this. While electrical stimulation has been used to treat paralysis, if this new type of therapy translates to the human body, it would be a breakthrough. Instead of using electrical signals to assist in specific tasks temporarily, it would allow for the potential to rebuild pathways to restore movement on one’s own accord.