Innovative research and design has created a novel way of allowing muscles to regain movement following paralysis, reports a team from University College London and King’s College London.
The proof-of-principle study was published in this week’s edition of the peer-reviewed scientific journal Science.
What makes this study stand out is the way the researchers allowed muscle movement in the paralyzed tissue. Related to this is The Positive’s recently reported technique of computer interfaces being used to decode neural impulses, which allow the motor cortex situated in the brain of an individual to influence the movement of another individual.
However, the scientists at UCL have managed to regain muscle control by using light.
Every individual undergoes paralysis on a daily basis every time they enter deep sleep. Indeed, during REM sleep, temporary paralysis occurs due to motor neuron inhibition, and typically accounts for a quarter of the time an individual spends asleep each night.
However, permanent muscle paralysis can result from injury to the nervous system, particularly the spinal chord, or due to conditions that affect various nerves, ranging from bacterial sources like botulism to degenerative conditions whereby the nerves begin to lose function.
The human brain, even when the individual is paralyzed, is still capable of thinking out movements that involve a paralyzed muscle group, with the neurons dedicated to the motor cortex still transmitting impulses. The reason why the muscles remain inactive is due to the fact that the nerves linking the muscles to their respective area in the brain are unable to transmit the nerve impulse.
In this case, the scientists used laboratory mice that had nerve injuries situated in the rear limbs.
Stem cells were used to create specialized motor neurons, nerve cells that are tasked with movement and muscular contraction of certain muscle tissue, derived from the embryonic cells of mice.
Importantly, these cells had one particularity as part of their structure: light-sensitive ion channel channelrhodopsin-2, made by Dr. Ivo Lieberam of the MRC Centre for Developmental Neurobiology, King’s College London, derived from algal cells that naturally react to sunlight.
These ion channels would react in the presence of light. This science, called optogenetics, is hailed as a revolutionary new discipline in the field of neurosciences.
These custom made nerve cells were then grafted onto the sciatic nerve in the mice test subjects, a large nerve that originates in the lower back before descending through each buttock and down to the lower leg.
The researchers were pleased to see that these engineered stem cells connected perfectly with the paralyzed musculature, re-innervating the tissue.
Five weeks after grafting, the mice were anaesthetized and their hind limb surgically opened, whereby a blue light was flashed onto the exposed tissue. This optic stimulus resulted in the contraction of the leg muscle.
The light-sensitive ion channels could thus be controlled via a stimulus from pulses of blue light. The scientists noted that the use of light allowed a smooth and controlled contraction, as recalled by Professor Linda Greensmith, team leader of the study, talking to New Scientist.
This proof-of-principle research and experimentation now looks to create a device to produce the necessary impulses, thus making it available for use in humans.
In addition, the team looks to use pluripotent stem cells rather than embryonic stem cells, as these could be created from the skin cells of the patient and have the advantage of being ready to graft sans any immune regulating drugs.
However, the uses of this technology are far reaching. The team mentioned the goal of regaining control of breathing in patients with motor neuron conditions. Prof. Greensmith, during the UCL news release, explained that only one muscle is used in the process, and it’s the next step for this development. Should this work in studies using pigs, the team would look into more complicated movements such as walking.
Where else could the use of light-sensitive cells be used in medical sciences?