Using mechanical forces — including massage — to stimulate tissue healing has been a form of physical therapy for decades. However, the biological basis and optimal settings for noninvasive mechanotherapies are still poorly understood, especially with respect to elderly patients.
A new multidisciplinary study has investigated whether elderly patients can benefit from tailored mechanotherapy for severely injured muscles the same way that young patients can.
The study was performed by researchers at the Wyss Institute for Biologically Inspired Engineering and the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), led by Wyss core faculty member David Mooney in collaboration with associate faculty member and Paul A. Maeder Professor of Engineering and Applied Sciences Conor Walsh. In previous work, the collaborators used Walsh’s lab to develop a robotic mechanotherapy device that functions like a highly advanced massage gun. This technology enabled precise delivery of mechanotherapy to injured muscles in mice, allowing the team to measure its biological effects.
In young animals, the researchers found mechanotherapy accelerated muscle healing by mitigating inflammation. However, on aged muscle, the researchers found that the same treatment actually had the opposite effect — the settings that promoted healing in young muscle exacerbated injury in old muscle.
Searching for an explanation, the team found that mechanotherapy amplified inflammation in aged muscle, hindering the normal healing process by disrupting the behavior of muscle stem cells, a subset of cells responsible for replacing damaged muscle tissue.
The researchers next asked if controlling inflammation along with delivering mechanotherapy could help heal aged muscles. They found that this was indeed the case: combining mechanotherapy with anti-inflammatory treatment significantly improved healing in aged muscles and was superior to anti-inflammatory treatment alone. This work, published in Science Robotics, opens an exciting, noninvasive therapeutic avenue for elderly patients.
“Our study highlights critical differences in how muscle stem cells and immune cells respond to mechanical forces in the context of age, and how upregulated inflammation additionally compromises the function of aged stem cells needed for the regeneration of old muscles,” said Mooney who also is the Robert P. Pinkas Family Professor of Bioengineering at SEAS. “Muscle mechanotherapies likely thus won’t be a ‘one-size-fits-all.’ To realize their benefits, they will have to be tailored to patient populations, and specifically for aged individuals, it will be key to modulate inflammation.”
