A minimally invasive tool to measure muscle impairment

February 28, 2017, Cell Press
This figures shows a minimally invasive sarcomere length profiler. A laser source continuously sweeps across wavelength and illuminates muscle through a 250-mm-diameter fiber optic probe. The same optical probe collects muscle resonant reflections that are combined with the reference arm and sent to a detector. Resonant reflection spectra are encodedinto interferograms and used to calculate sarcomere length with nanometer resolution and ~1 ms time resolution. Credit: Young et al./Biophysical Journal 2017

A minimally invasive, fiber-optic technique that accurately measures the passive stretch and twitch contraction of living muscle tissue could someday be an alternative to the painful muscle biopsies used to diagnose and treat a wide range of movement disorders, researchers report February 28 in Biophysical Journal. In a fraction of a millisecond, the tool measures the length of thousands of sarcomeres—the contractile units of muscle tissue—making it possible to quickly identify issues and develop personalized treatment plans for patients.

"This approach enables measurement of previously unobtainable properties by combining advances in telecommunications technology with a deep understanding of , biomechanics, and pathology," says senior author Richard Lieber, a physiologist at the Rehabilitation Institute of Chicago. "This bioengineering innovation will permit new studies of human muscle function and pathology and permit efficacy testing of muscle treatments." His group has applied for a patent on the technology.

Muscle impairment is common in a wide range of disorders, including stroke, traumatic brain injury, spinal cord injury, Parkinson's disease, and cerebral palsy. Currently, the gold standard for diagnosing neuromuscular problems involves clinical exams or painful and sometimes impossible muscle biopsies. The most direct and highest-resolution approach for characterizing human muscle health is to measure the movements of sarcomeres, which are responsible for generating .

While a couple of tools are available to measure sarcomere length in patients, they are not suitable for common clinical evaluation of muscle health. For example, laser diffraction requires surgery, damages tissue, and is not compatible with movement. Meanwhile, microendoscopy does not rapidly collect simultaneous, real-time, high-resolution samples across a large amount of muscle tissue.

To address these shortcomings, Lieber and his collaborators recently developed a technique called resonant reflection spectroscopy (RRS). Here's how it works: a laser source continuously sweeps across and illuminates muscle through a very thin (1/4 millimeter) fiber optic probe, which is inserted directly into the muscle belly and positioned parallel to sarcomeres. The same optical probe collects reflected light from the muscle, and these data are then used to calculate sarcomere length.

In the new study, the researchers applied this method to living muscle tissue for the first time. They demonstrated that RSS could simultaneously sample 4,200 sarcomeres spanning millimeters of in one-tenth of a millisecond, capturing nanometer-scale changes in sarcomere length during passive stretch and electrically stimulated twitch contractions of lower leg muscles in rabbits. In theory, the technique could enable the complete 3D reconstruction of sarcomere proteins for studying muscle diseases.

"Our findings demonstrate a new method to measure protein-scale interactions during ," Lieber says. "To our knowledge, this method achieves sample sizes, resolutions, and compatibility with human movements that no other current or proposed technique can match."

To make the tool suitable for routine clinical use, Lieber and his collaborators are currently addressing technical challenges, such as developing a new optical source and optical probe, and they will also work on making the method more affordable. "We plan to use this technology in both fundamental and clinical studies of human movement and movement disorders," Lieber says. "We hope that these new experiments lead to better understanding and maintenance of human muscle health."

Explore further: 3-D imaging of muscles points to potential treatments for muscle diseases and injuries

More information: Biophysical Journal, Young et al.: "In Vivo Sarcomere Length Measurement in Whole Muscles during Passive Stretch and Twitch Contractions" http://www.cell.com/biophysj/fulltext/S0006-3495(17)30040-1 , DOI: 10.1016/j.bpj.2016.12.046

Related Stories

3-D imaging of muscles points to potential treatments for muscle diseases and injuries

November 17, 2016
Eight million people per year in the UK suffer from muscular diseases and injuries including muscular dystrophy, cerebral palsy, exercise-related injuries, rotator cuff tears, and age-related muscle loss.

Regenerating muscle from stem cells

October 28, 2016
A microscopic image of a mouse leg that has been reconstructed with a stem cell transplant shows what may one day help patients regrow new muscle after a major surgery.

New mechanism controlling proper organization of the muscle contractile units indentified

November 7, 2014
Muscle-specific protein cofilin-2 controls the length of actin filaments in muscle cells.

Gene could play role in body's muscle mass

January 9, 2017
Scientists have identified a gene they think could play a role in determining a person's muscle mass - which is linked to a number of health factors, including how long someone lives.

Poor thigh muscle strength may increase women's risk of knee osteoarthritis

February 8, 2017
A new study has found that poor strength in the thigh muscles may increase the risk of knee osteoarthritis in women but not men. This relationship was confounded by body mass index (BMI), which itself is known as a risk factor ...

Recommended for you

Using DeepMind's neural network learning system to diagnose eye diseases

August 14, 2018
Three institutions working together have applied DeepMind's neural network learning system to the task of discovering and diagnosing eye diseases. Moorfields Eye Hospital has been working with Google's DeepMind Health subsidiary ...

Artificial intelligence platform screens for acute neurological illnesses

August 13, 2018
An artificial intelligence platform designed to identify a broad range of acute neurological illnesses, such as stroke, hemorrhage, and hydrocephalus, was shown to identify disease in CT scans in 1.2 seconds, faster than ...

Researchers create specialized delivery methods to help treat cancer, other disorders

August 13, 2018
More than 100 years ago, German Nobel laureate Paul Ehrlich popularized the "magic bullet" concept—a method that clinicians might one day use to target invading microbes without harming other parts of the body. Although ...

Scientists identify why some kidney transplants don't work

August 13, 2018
Scientists have discovered a 'molecular signature' for the allostatic load – or 'wear and tear' of kidneys – which could help clinicians understand why some kidney transplants don't work as well as expected.

3-D printed biomaterials for bone tissue engineering

August 13, 2018
When skeletal defects are unable to heal on their own, bone tissue engineering (BTE), a developing field in orthopedics can combine materials science, tissue engineering and regenerative medicine to facilitate bone repair. ...

Tiny fruit flies unravelling the secrets to end of life

August 10, 2018
We are used to seeing them dive-bombing our glass of wine or hovering around the fruit bowl.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.