Massage doesn't just make muscles feel better, it makes them heal faster
and stronger
Study in mice confirms link between mechanotherapy and immunotherapy in
muscle regeneration

Date:
October 6, 2021
Source:
Wyss Institute for Biologically Inspired Engineering at Harvard
Summary:
Massages feel good, but do they actually speed muscle
recovery? Turns out, they do. Scientists applied precise, repeated
forces to injured mouse leg muscles and found that they recovered
stronger and faster than untreated muscles, likely because the
compression squeezed inflammation- causing cells out of the muscle
tissue. This work offers a non-invasive, drug-free treatment that
can help regenerate many types of tissues, and confirms a functional
link between mechanotherapy and immunotherapy.



FULL STORY ========================================================================== Massage has been used to treat sore, injured muscles for more
than 3,000 years, and today many athletes swear by massage guns to
rehabilitate their bodies. But other than making people feel good,
do these "mechanotherapies" actually improve healing after severe
injury? According to a new study from researchers at Harvard's Wyss
Institute for Biologically Inspired Engineering and John A.

Paulson School of Engineering and Applied Sciences (SEAS), the answer is
"yes."

========================================================================== Using a custom-designed robotic system to deliver consistent and
tunable compressive forces to mice's leg muscles, the team found
that this mechanical loading (ML) rapidly clears immune cells called neutrophils out of severely injured muscle tissue. This process also
removed inflammatory cytokines released by neutrophils from the muscles, enhancing the process of muscle fiber regeneration. The research is
published in Science Translational Medicine.

"Lots of people have been trying to study the beneficial effects of
massage and other mechanotherapies on the body, but up to this point it
hadn't been done in a systematic, reproducible way. Our work shows a very
clear connection between mechanical stimulation and immune function. This
has promise for regenerating a wide variety of tissues including bone,
tendon, hair, and skin, and can also be used in patients with diseases
that prevent the use of drug-based interventions," said first author Bo
Ri Seo, Ph.D., who is a Postdoctoral Fellow in the lab of Core Faculty
member Dave Mooney, Ph.D. at the Wyss Institute and SEAS.

A more meticulous massage gun Seo and her coauthors started exploring the effects of mechanotherapy on injured tissues in mice several years ago,
and found that it doubled the rate of muscle regeneration and reduced
tissue scarring over the course of two weeks. Excited by the idea that mechanical stimulation alone can foster regeneration and enhance muscle function, the team decided to probe more deeply into exactly how that
process worked in the body, and to figure out what parameters would
maximize healing.

They teamed up with soft robotics experts in the Harvard Biodesign Lab,
led by Wyss Associate Faculty member Conor Walsh, Ph.D., to create a
small device that used sensors and actuators to monitor and control the
force applied to the limb of a mouse. " The device we created allows us
to precisely control parameters like the amount and frequency of force
applied, enabling a much more systematic approach to understanding tissue healing than would be possible with a manual approach," said co-second
author Christopher Payne, Ph.D., a former Postdoctoral Fellow at the Wyss Institute and the Harvard Biodesign Lab who is now a Robotics Engineer
at Viam, Inc.



==========================================================================
Once the device was ready, the team experimented with applying force to
mice's leg muscles via a soft silicone tip and used ultrasound to get
a look at what happened to the tissue in response. They observed that
the muscles experienced a strain of between 10-40%, confirming that
the tissues were experiencing mechanical force. They also used those
ultrasound imaging data to develop and validate a computational model that could predict the amount of tissue strain under different loading forces.

They then applied consistent, repeated force to injured muscles for
14 days.

While both treated and untreated muscles displayed a reduction in the
amount of damaged muscle fibers, the reduction was more pronounced
and the cross- sectional area of the fibers was larger in the treated
muscle, indicating that treatment had led to greater repair and strength recovery. The greater the force applied during treatment, the stronger
the injured muscles became, confirming that mechanotherapy improves
muscle recovery after injury. But how? Evicting neutrophils to enhance regeneration To answer that question, the scientists performed a detailed biological assessment, analyzing a wide range of inflammation-related
factors called cytokines and chemokines in untreated vs. treated
muscles. A subset of cytokines was dramatically lower in treated muscles
after three days of mechanotherapy, and these cytokines are associated
with the movement of immune cells called neutrophils, which play many
roles in the inflammation process.

Treated muscles also had fewer neutrophils in their tissue than untreated muscles, suggesting that the reduction in cytokines that attract them
had caused the decrease in neutrophil infiltration.

The team had a hunch that the force applied to the muscle by the
mechanotherapy effectively squeezed the neutrophils and cytokines out
of the injured tissue.

They confirmed this theory by injecting fluorescent molecules into
the muscles and observing that the movement of the molecules was more significant with force application, supporting the idea that it helped
to flush out the muscle tissue.



==========================================================================
To pick apart what effect the neutrophils and their associated
cytokines have on regenerating muscle fibers, the scientists performed in vitrostudies in which they grew muscle progenitor cells (MPCs) in a medium
in which neutrophils had previously been grown. They found that the number
of MPCs increased, but the rate at which they differentiated (developed
into other cell types) decreased, suggesting that neutrophil-secreted
factors stimulate the growth of muscle cells, but the prolonged presence
of those factors impairs the production of new muscle fibers.

"Neutrophils are known to kill and clear out pathogens and damaged
tissue, but in this study we identified their direct impacts on
muscle progenitor cell behaviors," said co-second author Stephanie
McNamara, a former Post-Graduate Fellow at the Wyss Institute who is
now an M.D.-Ph.D. student at Harvard Medical School (HMS). "While the inflammatory response is important for regeneration in the initial stages
of healing, it is equally important that inflammation is quickly resolved
to enable the regenerative processes to run its full course." Seo and her colleagues then turned back to their in vivomodel and analyzed the types
of muscle fibers in the treated vs. untreated mice 14 days after injury.

They found that type IIX fibers were prevalent in healthy muscle and
treated muscle, but untreated injured muscle contained smaller numbers of
type IIX fibers and increased numbers of type IIA fibers. This difference explained the enlarged fiber size and greater force production of treated muscles, as IIX fibers produce more force than IIA fibers.

Finally, the team homed in on the optimal amount of time for neutrophil presence in injured muscle by depleting neutrophils in the mice on
the third day after injury. The treated mice's muscles showed larger
fiber size and greater strength recovery than those in untreated mice, confirming that while neutrophils are necessary in the earliest stages
of injury recovery, getting them out of the injury site early leads to
improved muscle regeneration.

"These findings are remarkable because they indicate that we can influence
the function of the body's immune system in a drug-free, non-invasive
way," said Walsh, who is also the Paul A. Maeder Professor of Engineering
and Applied Science at SEAS and whose group is experienced in developing wearable technology for diagnosing and treating disease. "This provides
great motivation for the development of external, mechanical interventions
to help accelerate and improve muscle and tissue healing that have
the potential to be rapidly translated to the clinic." The team is
continuing to investigate this line of research with multiple projects in
the lab. They plan to validate this mechanotherpeutic approach in larger animals, with the goal of being able to test its efficacy on humans.

They also hope to test it on different types of injuries, age-related
muscle loss, and muscle performance enhancement.

"The fields of mechanotherapy and immunotherapy rarely interact with each other, but this work is a testament to how crucial it is to consider both physical and biological elements when studying and working to improve
human health," said Mooney, who is the corresponding author of the paper
and the Robert P. Pinkas Family Professor of Bioengineering at SEAS.

"The idea that mechanics influence cell and tissue function was ridiculed
until the last few decades, and while scientists have made great strides
in establishing acceptance of this fact, we still know very little about
how that process actually works at the organ level. This research has
revealed a previously unknown type of interplay between mechanobiology
and immunology that is critical for muscle tissue healing, in addition
to describing a new form of mechanotherapy that potentially could be as
potent as chemical or gene therapies, but much simpler and less invasive,"
said Wyss Founding Director Don Ingber, M.D., Ph.D., who is also the
Judah Folkman Professor of Vascular Biology at (HMS) and the Vascular
Biology Program at Boston Children's Hospital, as well as Professor of Bioengineering at SEAS.

This research was supported by the National Institute of Dental &
Craniofacial Research under Award Number R01DE013349, the Eunice Kennedy Shriver National Institute of Child Health & Human Development under Award Number P2CHD086843, the Materials and Research Science and Engineering
Centers grant award DMR- 1420570 from the National Science Foundation,
the National Institute of Arthritis and Musculoskeletal and Skin Diseases,
the National Institute of Health (F32 AG057135), and the National Cancer Institute (U01CA214369).

========================================================================== Story Source: Materials provided
by Wyss_Institute_for_Biologically_Inspired_Engineering_at
Harvard. Original written by Lindsay Brownell. Note: Content may be
edited for style and length.


========================================================================== Journal Reference:
1. Bo Ri Seo et al. Skeletal muscle regeneration with robotic
actuation-
mediated clearance of neutrophils. Science Translational Medicine,
2021 DOI: 10.1126/scitranslmed.abe8868 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211006143446.htm

--- up 4 weeks, 6 days, 8 hours, 25 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)