Exercise is widely recognized for its multitude of benefits on physical health, from strengthening muscles to enhancing bone density, improving blood circulation, and boosting immune function. However, recent research by MIT engineers reveals that the positive effects of exercise extend to our very neurons.
During exercise, muscle contractions release a range of biochemical signals known as myokines. In intriguing findings, researchers discovered that neurons exposed to myokines grew four times farther compared to those without this biochemical stimulation. This groundbreaking research indicates that exercise may play a significant role in promoting nerve growth at a cellular level.
What might surprise you is that neurons also respond to the physical forces present during exercise. Researchers noted that when neurons are subjected to the same pulling and stretching actions as muscles during exercise, they exhibit growth comparable to that induced by myokines.
This revelation challenges previous assumptions by demonstrating that both biochemical signals and mechanical forces are critical for nerve growth, marking a substantial advancement in understanding muscle and nerve interactions during physical activity. The comprehensive study, featured in the journal Advanced Healthcare Materials, opens up new possibilities for exercise-related therapies aimed at repairing and regenerating damaged nerves.
“Now that we understand this dialogue between muscles and nerves, it could lead us to innovative treatments for nerve injuries where communication is disrupted,” explains Ritu Raman, the Eugene Bell Career Development Assistant Professor of Mechanical Engineering at MIT. “By stimulating the muscle, we may encourage nerve healing and help restore mobility for individuals affected by traumatic injuries or neurodegenerative conditions.”
Raman’s research team includes notable contributors such as Angel Bu, Ferdows Afghah, Nicolas Castro, Maheera Bawa, Sonika Kohli, Karina Shah, and Brandon Rios from MIT’s Department of Mechanical Engineering, alongside Vincent Butty from MIT’s Koch Institute for Integrative Cancer Research.
Exploring Muscle-Nerve Communication
In a related study earlier this year, Raman and her team successfully restored mobility in mice suffering from traumatic muscle injuries. They initially implanted muscle tissue at the injury site and then stimulated this tissue via light to mimic exercise. Over time, the electrically stimulated grafted muscle produced biochemical signals crucial for nerve and blood vessel growth, leading to significant recovery of motor function in the mice.
Raman emphasizes the importance of understanding the communication between nerves and muscles, stating, “Traditionally, we think of nerves directing muscle activity, but muscles also signal back to nerves.” Recognizing this bidirectional communication prompted the researchers to further explore the impact of muscle activity on nerve growth amid the complexity of other cell types present.
In their latest experiment, the team concentrated strictly on muscle and nerve cells. They grew mouse muscle cells into long fibers that fused to create a mature muscle tissue sheet the size of a quarter.
By genetically modifying the muscle to contract in response to light, researchers could simulate exercise through a controlled flashing process. To maintain the muscle’s health during stimulation, a specially-designed gel mat was utilized, ensuring the muscle remained anchored and functional.
The surrounding fluid collected during muscle exercise was rich in myokines, suggesting these biochemical mediators hold significant potential for nerve health. “Think of myokines as a cocktail of substances that muscles release, some of which may directly benefit nerve cells,” Raman explains further, highlighting that exercised muscles produce a greater quantity of these signals.
Exercise as a Therapeutic Approach
To investigate the effects of these myokines, researchers transferred the collected solution to a dish containing motor neurons, sourced from mouse stem cells. Upon exposure to the myokine-rich environment, these neurons grew significantly faster—four times, to be precise—than those that did not receive the biochemical treatment.
“The speed and extent of their growth were remarkable,” notes Raman. To further understand the underlying changes, the team conducted genetic analyses which revealed that many of the genes activated in response to myokines were linked not only to growth but also to functional maturity and communication capabilities with muscle fibers.
Intrigued, the researchers then explored the purely physical effects of exercise by employing a novel method of stretching the neurons mechanically. By embedding tiny magnets in a gel mat, the team used a stronger external magnet to move the mat and, consequently, the neurons back and forth for 30-minute sessions, simulating physical activity.
To their astonishment, this mechanical stimulation resulted in neuron growth comparable to that induced by myokines, reinforcing the notion that both biochemical signals and physical movements play critical roles in neurological development.
With compelling evidence pointing to the advantages of muscle exercise in promoting nerve growth, the researchers plan to delve deeper into targeted muscle stimulation strategies to treat nerve damage and improve mobility in individuals suffering from neurodegenerative diseases like ALS.
“This research is just the initial phase of harnessing exercise as a medical intervention,” Raman concludes.
Photo credit & article inspired by: Massachusetts Institute of Technology
