To study the cellular level of living humans, you usually have to cut out a sample of tissue to study it under a microscope, which means you aren’t studying living tissue. Obviously, being able to do that would have enormous benefits—like helping scientists to better understand and treat certain diseases.
Researchers from Stanford have found a solution to this problem: They have created the world’s first microscope that allows them to look at muscle in action.
Understanding muscle movement
“When it comes to muscle microstructure and dynamics, we have not been able to visualize normal muscle, and we don’t know how it changes with disease,” said co-author Scott Delp, a Stanford professor of bioengineering, of mechanical engineering and, by courtesy, of orthopaedic surgery, in a statement.
“With this microscope, we have opened up a new window to how muscles change with strokes and diseases like ALS or muscular dystrophy. We can immediately use it in humans; it’s very low risk, and it gives us a new way to examine muscle microstructure and dynamics.”
Muscle contraction relies on the electrically-driven firing of units called sarcomeres found within muscle fibers. Thousands of sarcomeres within the muscle contract when triggered, causing the entire muscle to shorten and pull (usually) on a bone, allowing you to move a part of your body.
The length of a sarcomere greatly affects its efficacy—if it’s too long or too short, it doesn’t pull the muscle fiber together as efficiently. Because of this, many scientists believe that certain neuromuscular disorders cause the sarcomeres to lose their ideal length, which in turn results in muscle weakness.
“We stand to gain important insights by visualizing the contractions of individual motor units in live patients,” said co-author Mark Schnitzer, an associate professor of biology and of applied physics at Stanford.
Miniaturized optics
According to their paper published in Neuron, this new microscope is a miniaturized version of previously-developed technology—it can fit neatly into a bedside pushcart. This unit contains a small optical needle which is inserted into the patient’s muscle.
The needle beams out an ultrafast infrared light (100-femtosecond pulses) onto the muscle, which, through a process known as harmonic generation, converts the infrared light into green light. The light then re-enters the needle and is interpreted by the unit’s computer into images.
The end result is an image of sarcomere activation, as well as precise measurements of the duration of muscle twitch.
“The size of the needle is similar to a flu shot, but it has optics in it, and produces the same optical performance as the table-size systems with an equivalent objective,” explained said co-author Gabriel Sanchez.
The potential uses for this technology are staggering.
“We see this as a very useful companion diagnostic to track disease progression and, in the future, help personalize medicine by gauging how a person responds to a drug,” said Sanchez.
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Image credit: Stanford/YouTube Screenshot
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