Exercising muscle may ward off chronic inflammation on its own

The study, published in the journal Science Advances, indicates that inflammation is not inherently good or bad. When the body is injured, an initial low-level inflammation response clears away debris and helps tissue rebuild. 

"Our engineered muscle platform is modular, meaning we can mix and match various types of cells and tissue components if we want to. But in this case, we discovered that the muscle cells were capable of taking anti-inflammatory actions all on their own," said researcher Nenad Bursac, Professor at Duke University. 

Among many molecules that can cause inflammation, one pro-inflammatory molecule in particular, interferon gamma, has been associated with various types of muscle wasting and dysfunction. 

While previous research in humans and animals has shown that exercise can help mitigate the effects of inflammation in general, it has been difficult to distinguish what role the muscle cells themselves might play, let alone how they interact with specific offending molecules, such as interferon gamma. 

To prove that muscle alone is capable of blocking interferon gamma's destructive powers, the team turned to an engineered muscle platform that the laboratory has been developing for nearly a decade. 

They were first to grow contracting, functional human skeletal muscle in a Petri dish, and since then the lab has been improving its processes by, for example, adding immune cells and reservoirs of stem cells to the recipe. 

In the current study, the researchers took these fully functional, lab-grown muscles and inundated them with relatively high levels of interferon gamma for seven days to mimic the effects of a long-lasting chronic inflammation. As expected, the muscle got smaller and lost much of its strength. 

The researchers then applied interferon gamma again, but this time also put the muscle through a simulated exercise regime by stimulating it with a pair of electrodes. 

While they expected the procedure to induce some muscle growth, as shown in their previous studies, they were surprised to discover that it almost completely prevented the effects of the chronic inflammation.