New understanding of how muscles work

August 23, 2017, McGill University
Skeletal muscle tissue. Credit: University of Michigan Medical School

Muscle malfunctions may be as simple as a slight strain after exercise or as serious as heart failure and muscular dystrophy. A new technique developed at McGill now makes it possible to look much more closely at how sarcomeres, the basic building blocks within all skeletal and cardiac muscles, work together. It's a discovery that should advance research into a wide range of muscle malfunctions.

Talk about finicky work

Sarcomeres are the smallest unit within a in which all the molecules responsible for making a muscle work can be found intact. These minuscule structures, about one hundred times smaller in diameter than an average human hair, work cooperatively to produce force during . Scientists have known for some time that when muscles are active many million sarcomeres work together, and that muscle malfunctions can be due, at least in part, to miscommunication between sarcomeres. But how exactly this communication takes place has been a mystery until now. Because no one before has been able to isolate a single sarcomere, watch it in action, and measure what's going on.

"It was very, very tricky and sometimes frustrating for the students working on this project over the last few years," says Dilson Rassier who teaches in the Department of Kinesiology at McGill and is the lead researcher on the study that was recently published in the prestigious journal Proceedings of the National Academy of Sciences of the United States of America. "We used micro-fabricated needles to measure force and high-tech microscopy to isolate the sarcomeres and then watch them contracting. One of our collaborators had to develop a mathematical model to analyze the data because the numbers involved were so minuscule and so precise."

Zooming in on microscopic mini-muscles in action

There are between 2,000 and 2,500 sarcomeres found together in linked coils in each 10 millimetres of . To watch the sarcomeres in action, the researchers first had to isolate a single myofibril (the basic rod-like units which make up ) and then zoom in on an individual sarcomere. They then experimented with different concentrations of calcium (which is responsible for triggering and relaxation) to cause the sarcomeres to contract and measure their force.

What they discovered was that, in a healthy myofibril, all the neighbouring sarcomeres adjust to the activation of one single sarcomere. This finding is new and provocative, showing a cooperative mechanism among sarcomeres in a myofibril that is linked to the specific properties of sarcomeric molecules. This inter-sarcomere dynamic is crucial for the understanding of the molecular mechanism of contraction.

Rassier sounds exultant about the findings: "My group had to work hard to conclude this study, but the results were worth it. The technique opens many possibilities in the muscle field. Since we published our findings a few weeks ago I've been hearing from biophysicists and physiologists from around the world who are excited about it. Our next step is to look into what happens in and other diseases of the muscular system when sarcomeres fail to cooperate."

Explore further: Tension triggers muscle building

More information: Felipe de Souza Leite et al, Microfluidic perfusion shows intersarcomere dynamics within single skeletal muscle myofibrils, Proceedings of the National Academy of Sciences (2017). DOI: 10.1073/pnas.1700615114

Related Stories

Tension triggers muscle building

March 14, 2014
Skeletal muscles are built from small contractile units, the sarcomeres. Many of these sarcomeres are connected in a well-ordered series to form myofibrils that span from one muscle end to the other. Contractions of these ...

A minimally invasive tool to measure muscle impairment

February 28, 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 ...

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.

Atomic structure of key muscle component revealed

July 24, 2014
Actin is the most abundant protein in the body, and when you look more closely at its fundamental role in life, it's easy to see why. It is the basis of most movement in the body, and all cells and components within them ...

Recommended for you

Machine learning can be used to predict which patients require emergency admission

November 20, 2018
Machine learning—a field of artificial intelligence that uses statistical techniques to enable computer systems to 'learn' from data—can be used to analyse electronic health records and predict the risk of emergency hospital ...

Researchers stop 'sneaky' cancer cells in their tracks

November 20, 2018
A new study by University of Minnesota biomedical engineers shows how they stopped cancer cells from moving and spreading, even when the cells changed their movements. The discovery could have a major impact on millions of ...

Researchers hope to be able to replace dysfunctional brain cells

November 20, 2018
A new study by researchers at Karolinska Institutet supports the theory that replacement of dysfunctional immune cells in the brain has therapeutic potential for neurodegenerative diseases like ALS and Alzheimer's disease. ...

RNAi therapy mitigates preeclampsia symptoms

November 19, 2018
A collaboration of scientists from the University of Massachusetts Medical School, Beth Israel Deaconess Medical Center and Western Sydney University, have shown that an innovative new type of therapy using small interfering ...

Skeletal imitation reveals how bones grow atom-by-atom

November 19, 2018
Researchers from Chalmers University of Technology, Sweden, have discovered how our bones grow at an atomic level, showing how an unstructured mass orders itself into a perfectly arranged bone structure. The discovery offers ...

Signal peptides' novel role in glutamate receptor trafficking and neural synaptic activity

November 19, 2018
Glutamate is the major excitatory neurotransmitter in the brain, and the postsynaptic expression level of glutamate receptors is a critical factor in determining the efficiency of information transmission and the activity ...

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.