Neurons Identified, Stimulated for Spinal Cord Repair

(Michael Dorausch, Flickr)

10 Nov. 2022. Spinal cord injury patients in a clinical trial received electronic stimulation to a specified set of nerve cells that enabled them to restore walking after rehabilitation. Findings from the trial, testing combined implanted neural stimulation and rehabilitation, developed by a team from the NeuroRestore research center in Lausanne, Switzerland and the health technology company Onward Medical N.V. in Eindhoven, The Netherlands, appears in yesterday’s issue of the journal Nature.

Spinal cord injuries occur after traumatic blows to the spinal column that interrupt transmission of nerve signals to the limbs and organs. These injuries can vary in effect on limb movement and sensation, depending on the severity and location of the blows to the spinal column. Loss of all movement and sensation is called complete injuries, and can affect the legs and pelvic area or arms and legs, depending on how high on the spinal cord the injury occurs.

NeuroRestore is a research and treatment center addressing neurological disorders, affiliated with Ecole Polytechnique Fédérale de Lausanne (EPFL) and University of Lausanne, as well as Lausanne University Hospital and the Defitech Foundation that supports R&D on technologies for assisting people with disabilities. Researchers at NeuroRestore earlier encountered an unexpected finding, of reduced neuronal signals in the lumbar or lower region of the spinal cord by individuals recovering from spinal cord injuries when walking.

By modeling walking movements and spinal cord injuries in mice, and analyzing neural signals that occur, the NeuroRestore team identified precise neurons in the spinal cord sending and receiving signals for walking, but also for repair from injury. This granular analysis revealed different sets of neurons for those specific functions. Further genomic and transcription analysis showed neurons expressing the Vsx2 gene, associated with spinal cord functions, are essential for spinal cord repair, but not for the physical act of walking.

Stimulate precise sets of neurons

Tests with mice induced with spinal cord injuries show stimulating the spinal cord with electronic signals excites neurons to produce Vsx2 proteins, while uninjured mice do not produce those proteins. Thus, electronic stimulation of neurons in the spinal cord must be precisely targeted and calibrated, to stimulate neurons with genes coding for proteins needed for repair, and allow spinal cord patients to walk.

Engineers at NeuroRestore, working with Onward Medical, developed a precise neural stimulation device for implanting in spinal cord injury patients. The Onward Medical device, called ARC-IM implanted in the lumbar region, is programmed to send electronic signals to specific locations to stimulate precise sets of neurons carrying out the desired functions.

The researchers tested the device in a clinical trial with nine individuals in Switzerland with moderate spinal cord injuries affecting their pelvic regions and lower limbs. Participants received the implants in a two-month evaluation and surgical process, then engaged in five months of rehabilitation with robotic assistance that includes various physical exercises of the limbs. After rehab, the study team looked primarily for participants’ ability to walk for ten meters and put weight on their legs. Participants’ performance was evaluated before and after rehabilitation, but the trial had no control or comparison group.

Results show the nine participants were able to regain at least some of their walking abilities, as a result of the implants and rehabilitation. “It’s essential for neuroscientists to be able to understand the specific role that  each neuronal subpopulation plays in a complex activity like walking,” says Jocelyn Bloch, a neurosurgeon at University of Lausanne and one of the senior authors of the paper, in a NeuroRestore statement. “Our new study, in which nine clinical-trial patients were able to recover  some degree of motor function thanks to our implants, is giving us valuable  insight into the reorganization process for spinal cord neurons.”

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