Harvard University: Massage can indeed help injured muscles heal faster and stronger

Massages feel good, but can they really speed up muscle recovery? Facts have proved that it is true
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Scientists from the Wyss Institute and Harvard University’s School of Engineering and Applied Sciences applied precise and repeated force to the injured mouse leg muscles and found that they recovered stronger and faster than untreated muscles, which may be due to stress Squeeze the cells that cause inflammation out of muscle tissue

Researchers at Harvard Wyss Bio-Inspired Engineering and SEAS Institute used a custom-designed robotic system to provide consistent and adjustable compression force to mouse leg muscles, and found that this mechanical load (ML) can quickly clear severely damaged muscle tissue The immune cells are called neutrophils
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This process also eliminates the inflammatory cytokines released by neutrophils in the muscles, and enhances the process of muscle fiber regeneration

"Many people have been trying to study the beneficial effects of massage and other mechanical therapies on the body, but so far, they have not been done in a systematic and reproducible way," said first author Bo Ri Seo, who is the Wyss Institute and SEAS.
Postdoctoral researcher in Dave Mooney's laboratory
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"Our research shows that there is a very clear connection between mechanical stimulation and immune function

A finer massage gun

Seo and her co-authors began to explore the effects of mechanical therapy on damaged tissues in mice a few years ago, and found that within two weeks, mechanical therapy can double the rate of muscle regeneration and reduce tissue scars
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Since mechanical stimulation itself can promote regeneration and strengthen muscle function, the research team decided to explore more in-depth how this process works in the body and find out which parameters can maximize healing

They collaborated with soft robotics experts in the Harvard Biodesign Lab, and under the leadership of Wyss associate professor Conor Walsh, they developed a small device that uses sensors and actuators to monitor and control the effects on the limbs of mice.
Force
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The research team applied a soft silicone tip to the mouse’s leg muscles and used ultrasound to observe the tissue’s response

"This drug can also be widely used to treat various skin diseases and tendon regeneration
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Then, they applied continuous and repeated force to the injured muscle for 14 days
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Although both treated and untreated muscles showed a decrease in the number of damaged muscle fibers, in the treated muscles, the decrease in the number of damaged muscle fibers was more pronounced, and the cross-sectional area of ​​the fibers was larger, indicating that the treatment resulted in For greater repair and strength recovery

Expel neutrophils to promote regeneration

To answer this question, the scientists conducted a detailed biological evaluation and analyzed a series of inflammation-related factors called cytokines and chemokines in untreated and untreated muscle
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After three days of mechanical treatment, some of the cytokines in the treated muscle were significantly reduced.

The research team has a hunch that the force exerted by mechanical therapy on the muscles effectively squeezes neutrophils and cytokines out of the injured tissue
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They confirmed this theory by injecting fluorescent molecules into the muscles and observing that the movement of the molecules was more pronounced when force was applied, supporting the idea that fluorescent molecules help flush muscle tissue
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In order to distinguish the effects of neutrophils and their related cytokines on regenerating muscle fibers, the scientists conducted an in vitro study.
In this study, they cultured muscle progenitor cells ( MPCs)
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They found that the number of MPCs increased, but their rate of differentiation (developing into other cell types) decreased, indicating that neutrophils secrete factors to stimulate muscle cell growth, but the long-term existence of these factors can impair the production of new muscle fibers
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"Neutrophils are known to kill and remove pathogens and damaged tissues, but in this study, we determined their direct effects on the behavior of muscle progenitor cells," second author Stephanie McNamara (Stephanie McNamara) McNamara) said that she was a graduate student at the Wyss Institute and is now a doctoral student in Harvard Medical School and the Graduate School of Arts and Sciences
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"Although the inflammatory response is very important for regeneration in the initial stage of healing, it is equally important that inflammation should be eliminated quickly so that the regeneration process can proceed throughout the process
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Seo and her colleagues then returned to their in vivo model and analyzed the types of muscle fibers in mice that received treatment 14 days after injury and mice that did not receive treatment
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They found that type IIX fibers are common in healthy muscles and treated muscles, but the number of type IIX fibers in untreated injured muscles is less, and the number of type IIA fibers increases
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This difference explains the increased fiber size and greater force generation of the treated muscle, because IIX fibers generate more force than IIA fibers
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Finally, the research team determined the best time for the existence of neutrophils in the injured muscle by depleting the neutrophils in the mice on the third day after injury
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Compared with untreated mice, the muscles of treated mice showed larger fiber size and greater strength recovery, confirming that although neutrophils are necessary in the early stages of injury recovery, it should be as early as possible Removing it from the injured site can improve muscle regeneration
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Walsh said: "These findings are very significant because they show that we can affect the function of the human immune system in a drug-free and non-invasive way.

Professor Paul Maeder is an experienced marine disease diagnosis and treatment expert, and also a marine disease expert.
Experts in diagnosis and treatment
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This provides a huge impetus for the development of external mechanical interventions to help accelerate and improve the healing of muscles and tissues, and it may be quickly transformed into the clinic
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The team is continuing to investigate this research route through multiple projects in the laboratory
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They plan to validate this mechanical therapy method in large animals, with the goal of being able to test its efficacy on humans
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They also hope to test on different types of injuries, age-related muscle loss, and muscle performance enhancement
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"The fields of mechanical therapy and immunotherapy rarely interact, but this work demonstrates how important it is to consider physical and biological elements when researching and working to improve human health
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" Mooney said
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He is the corresponding author of this paper and the Robert P.
Pinkas family professor of marine bioengineering
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Original Search: Skeletal muscle regeneration with robotic actuation–mediated clearance of neutrophils

DOI: 10.
1126/scitranslmed.
abe8868