Light-activated neurons restore function to paralysed muscles

The technique developed by UK-based researchers could be ready for human trials in about five years

A technique to artificially control muscles using light, which has the potential to restore function to muscles paralysed by conditions such as motor neuron disease and spinal cord injury, has been developed by UK-based scientists.

Researchers at University College London (UCL) and King’s College London have developed a technique which involves transplanting specially-designed motor neurons created from stem cells into injured nerve branches. These motor neurons are designed to react to pulses of blue light, allowing scientists to fine-tune muscle control by adjusting the intensity, duration and frequency of the light pulses.

In the study, published this week in Science, the team demonstrated the method in mice in which the nerves that supply muscles in the hind legs were injured. They showed that the transplanted stem cell-derived motor neurons grew along the injured nerves to connect successfully with the paralysed muscles, which could then be controlled by pulses of blue light.

Professor Linda Greensmith of the MRC Centre for Neuromuscular Diseases at UCL’s Institute of Neurology, said: “This strategy has significant advantages over existing techniques that use electricity to stimulate nerves, which can be painful and often results in rapid muscle fatigue. Moreover, if the existing motor neurons are lost due to injury or disease, electrical stimulation of nerves is rendered useless as these too are lost.

“Within the next five years or so we hope to undertake the steps that are necessary to take this ground-breaking approach into human trials, potentially to develop treatments for patients with motor neuron disease, many of whom eventually lose the ability to breathe, as their diaphragm muscles gradually become paralysed. We eventually hope to use our method to create a sort of optical pacemaker for the diaphragm to keep these patients breathing,” Greensmith added.