While massage has been used to treat muscle pain and injury for thousands of years, it is only now that a study has scientifically confirmed that it improves recovery and strength gains. Intriguingly, the mechanism behind this is mechanically clearing out of immune cells from the injury site after they have done their job.
Using a custom-designed robotic system massage system for mice, 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, PhD.
Dr Seo and her colleagues previously found in mouse studies that mechanical massage of injured muscles doubled the rate of muscle regeneration and reduced tissue scarring over the course of two weeks. With a new device inspired by soft robotics, the researchers sought to confirm these results. They found that the greater the force applied, the stronger the injured muscles became.
In vitro experiments suggested that neutrophil-secreted factors stimulate the growth of muscle cells, but the prolonged presence of those factors impairs the production of new muscle fibres. In vivo testing showed that stronger muscle fibre types predominated in treated, injured muscle types. Depleting neutrophils in mice after the third day resulted in greater strength recovery, indicating that they are important in the initial recovery period but removing them from the injury site early leads to improved muscle regeneration.
“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 Don Ingber, MD, PhD, founding director of the Wyss Institute for Biologically Inspired Engineering at Harvard.
Source: Wyss Institute for Biologically Inspired Engineering at Harvard
