They create a model with light to return mobility to people with paralysis

Ensure that people who suffer from paralysis or limb amputation Being able to move with precision again is closer thanks to a new advance in optogenetics, a revolutionary technique that combines optical and genomic sciences.

Optogenetics consists of genetically editing neuronal cells so that they express light-sensitive proteins, which allows controlling the activity of these cells when exposing them to light,” explains Mexican researcher, Guillermo Herrera-Arcos.

Herrera-Arcos is a biomechatronics researcher at the Massachusetts Institute of Technology (MIT), the university where this technique was invented a decade ago, and where this new advance reported in the journal Science Robotics comes from.

The co-author of this study, the prestigious MIT bionics researcher, Hugh Herr, He had both of his legs amputated at the age of 17. due to an accident while climbing.

Overcome barriers

So far, electrical stimulation and neuroprostheses have made enormous progress so that amputees or with paralysis recover mobility.

Among others, it has been known that 43 quadriplegics could move their hands again, and, a few months ago, a Parkinson's patient who had been suffering from Parkinson's for 25 years was seen walking again thanks to this technique.

The problem with electrostimulation of neurons to control the muscles of the body is that it tends to activate the entire muscle at the same time, and as it requires too much effort, muscle control ends up being lost, due to exhaustion, between 5 and 10 minutes after having “The movement has started,” says Herrera-Arcos.

To overcome this difficulty, MIT researchers have replaced the electrodes with optical molecular technologies in order to control muscles through optogenetics.

To do this, they turned to mice genetically modified with a light-sensitive protein (channelrhodopsin-2) and implanted a small light source near the main nerve of the tibia, which controls the muscles of the lower leg.

The result was that as the light drive increased, the strength of the muscle also increased.

Unlike electrical stimulation, which activates the entire muscle at once, optogenetic control produces a constant and gradual increase in muscle contraction.

As we change the optical stimulation we deliver to the nerve, we can proportionally, almost linearly, control the strength of the muscle. The process is similar to the way our brain moves muscles, hence the control is greater than with electrical stimulation,” he adds.

Based on their experiments, the researchers have created a mathematical model of optogenetic muscle control that adjusts light stimulation of the muscle to achieve the desired muscle strength.

Thanks to him, they have achieved stimulate muscles for more than an hour without tiring them, something that electrical electrostimulation has only achieved for 15 minutes.

Application to people

Asked how this finding would be applied to people in the future, Herrera-Arcos says that “the patient would receive an injection with a genetic therapy, in which the gene responsible for the cells responding to light would be inserted, and would have it implanted in the “area to move a chip that can be stimulated through light pulses.”

The idea, he adds, is that using a mobile phone, smart watch or similar, a person can activate, through light pulses, the nerve that connects with the muscle they want to exercise and can move it with great precision.

The challenge now is “introduce photosensitive proteins into human tissue safely”the researcher emphasizes, since years ago they saw, in experiments with rats, that these light-sensitive proteins can trigger an immune response that inactivates them and can even lead to muscle and cellular damage.

Our goal is to design new light-sensitive proteins and strategies to train them without triggering an unwanted immune response,” he concludes.

The researchers are convinced that their findings will benefit people who have suffered strokes in the future, limb amputation and spinal cord injuries, as well as others who have reduced ability to control their extremities.

(With information from EFE)