The neurons that restore walking after paralysis

Scientists undertaking multi-year research at the .NeuroRestore research center in Lausanne have identified the neurons that need to be activated and restored through spinal cord stimulation to enable patients with paralysis to stand up, walk and rebuild their muscles. Their results have been recently published in the journal Nature.

The team led by Grégoire Courtine from the Swiss Federal Institute of Technology Lausanne (EPFL) and Jocelyne Bloch from Lausanne University Hospital demonstrated the effectiveness of the therapy in nine patients. Not only did these patients' motor function improve, the improvements persisted after their neurorehabilitation, when electrical stimulation was switched off.

This success indicated that the nerve fibres used for walking had reorganised, explain the researchers. While studying the underlying mechanisms in mice, the team identified a surprising feature in a family of neurons that expresses a gene called Vsx2. These neurons are not needed for walking in healthy mice, but are essential for restoring motor function after spinal cord injury.

For the first time, scientists were able to visualise spinal cord activity in a walking patient, leading to an unexpected discovery. During spinal cord stimulation, patients' neuronal activity decreased when they were walking. The experts suspected that this could be because their neuronal activity

To prove this, they created the first 3D molecular cartography of the spinal cord. The high-precision model allowed the scientists to observe that spinal cord stimulation activates Vsx2 neurons. These Vsx2 spinal cord neurons are not normally needed for walking, as the researchers had also observed in the mice. They are, however, essential for electro-stimulated movement of the legs following a spinal cord injury.