Researchers design a cellular exercise mat that could help scientists understand the mechanical effects of exercise at a microscopic level Researchers have created a gel pad containing magnets that can simulate the mechanical forces that muscle cells experience during exercise. This novel "exercise mat" could be useful for testing treatments in patients with muscle injuries and neuromuscular diseases, or for growing artificial muscles for use in soft robots.
In the human body, cells communicate through a combination of chemical, electrical, and mechanical signals, especially during exercise. Making lifelike mechanical cell-cell contacts can be difficult for lab-made cells because it often causes damage to the cells.
MIT researchers have created a damage-free way to simulate the mechanical impacts skeletal muscle cells receive during exercise—think of it like a fitness mat for the cells.
"Here, we wanted to separate the two main factors of movement - chemical and mechanical - and see how the muscles respond purely to the mechanical forces of movement," said Ritu Raman, corresponding author of the study.
Researchers looked at magnets as a way to enable muscle cells to withstand mechanical force regularly and repeatedly without causing damage. The researchers mixed commercially available magnetic nanoparticles with a rubbery silicone solution, then solidified the mixture into sheets and cut them into very thin strips. We built a prototype pad consisting of four magnetic rods spaced slightly wider apart, sandwiched between two layers of hydrogel.
By placing muscle cells on the surface of the mat, the round cells gradually elongate and fuse with neighboring cells to form fibers. Underneath the gel pad, the researchers placed an external magnet on the track and programmed it to move back and forth. The magnets embedded in the gel move, causing the gel to oscillate and create forces similar to those in actual movement of cells. They "exercised" the cells for 30 minutes a day for 10 days. A group of unexercised muscle cells served as a control.
"Then we zoomed in and took pictures of the gel and found that the mechanically stimulated cells looked very different from the control cells," Raman said.
They found that the exercised cells grew longer and into fibers aligned in the same direction. In contrast, control cells tended to remain round and disorganized. Under normal circumstances, muscle cells contract in response to electrical impulses from nerves, but under laboratory conditions this can damage the cells. So the researchers genetically engineered the cells to shrink when exposed to blue light.
"When we shine a light on a muscle, you can see the control cells beating, but some of the fibers are beating this way and some are beating that, creating a very asynchronous twitch overall," Raman said. "With fibers that are aligned, they're pulling and beating in the same direction at the same time."
Researchers say the new "exercise gel" could serve as a quick, non-invasive way to sculpt muscle fibers and study their response to exercise, which could lead to treatments to help people recover from muscle injuries and neuromuscular diseases. They also plan to grow other types of cells on the gel and study their response to 'exercise'.
"Biological evidence shows that many types of cells respond to mechanical stimuli. This is a new tool for studying interactions," Raman said.
The research was published in the journal Devices.