Optogenetics: Restoring Movement for Physical Disabilities
Oct 01, 2010
Like something straight out of Science Fiction or comic books, scientists from Stanford University have been able to more accurately induce proper firing order in the muscles of bioengineered mice with nothing more than blue light. Their hope is that one day this technique will allow people with paralysis from traumatic brain and spinal cord injuries to move their limbs again and help counteract the debilitating spastic twitches of people living with cerebral palsy. The “secret ingredient” in all of this is algae.
Stanford’s Schools of Medicine and of Engineering have been collaborating to develop the new technology for the study of optogenetics — a new field of science invented at Stanford that involves taking specialized genes derived from algae and inserting them into the genomes of other creatures. The gene then encodes a light-sensitive protein onto the surface of nerve cells, which are then capable of responding to certain wavelengths of light (i.e. blue), which can be used to modify cell firing patterns via a band of tiny LEDs placed around the sciatic nerve. This has allowed researchers to control which muscles receive the impulse to move via which lights are turned on and off. The experimental procedure has only been tested on animals, and this latest experiment marks the first time it was tested on mammals (mice), but the results are extremely promising.
What makes the results different from previous ones involving electrical impulses to control muscles is the degree of control over the order in which the muscles are firing. In previous functional electrical stimulation (FES), paralyzed individuals have been able to walk with the help of an electrical band around the sciatic nerve, but only for a few minutes. This is because the larger, fast-twitch nerve fibers responded well to the electrical impulses, but the smaller, fatigue-resistant, slow-twitch nerve fibers often lagged behind or did not respond at all. Because the slow-twitch muscles control more refined movement, the lack of those muscles moving first (or at all) gave the individual a very jerky movement and resulted in muscle fatigue very quickly.
With the blue LED lights able to penetrate deep into the nerve, the Stanford scientists have been able to access the slow-twitch nerves and incite them to contract before the fast-twitch nerves, giving fluidity of movement back to the test animals and greatly reducing muscle fatigue. In addition, each muscle contraction could be sustained for longer periods with optical stimulation than with electrical stimulation.
The same research team is now conducting similar experiments with a different light-sensitive protein that could help inhibit nerve fibers rather than trigger them, and thus helping individuals suffering from spasticity, like the kind that occurs from cerebral palsy. The researchers are not completely convinced that optical stimulation alone will result in walking for paralyzed individuals, because that movement is based on an incredibly complicated set of muscle systems. However, they do see this as a step in the right direction.
The findings were published in Nature Medicine.
If you’re interested in learning more about optogenetic research, watch this lecture from one of this study’s head scientists: