Lab-grown human muscle shows how exercise singlehandedly reduces inflammation

DURHAM, N.C. — Inflammation can lead to a slew of dangerous health conditions and cause muscle tissue to waste away. Recent research shows that exercising is an effective way to combat chronic inflammation.

Scientists from Duke University say that inflammation occurs when our body’s immune system responds to tissue damage or bacteria. However, sometimes the immune system overreacts and attacks its own cells, such as the deadly cytokine storms brought on by the COVID-19 virus.

Some diseases, such as arthritis and sarcopenia, lead to what’s known as chronic inflammation, which causes muscles to slowly deteriorate. A molecule, known as interferon gamma, has been identified as one of the culprits behind various types of muscle wasting and dysfunction.

While scientists have found regular exercise can help reduce inflammation, the specific role of muscle cells has remained a mystery. To solve the problem, Duke researchers spent the better part of a decade developing a platform, which allows them to grow human muscles in their laboratory.

“Lots of processes are taking place throughout the human body during exercise, and it is difficult to tease apart which systems and cells are doing what inside an active person. 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,” says study author Nenad Bursac, a professor of biomedical engineering at Duke, in a statement.

The researchers started by growing a functional skeletal human muscle in a petri dish. Immune cells and reservoirs of stem cells were then added to the recipe. Once fully grown, the muscles were “inundated” with high levels of interferon gamma for seven days to mimic the effects of a long-lasting chronic inflammation.

As expected, the lab grown muscles got smaller and lost much of their strength. They then repeated the experiment, but this time put the muscles through a simulated exercise regime using electric shocks. Researchers found that the regime “almost completely” prevented the effects of chronic inflammation by blocking a specific molecular pathway.

“We know that chronic inflammatory diseases induce muscle atrophy, but we wanted to see if the same thing would happen to our engineered human muscles grown in a petri dish. Not only did we confirm that interferon gamma primarily works through a specific signaling pathway, we showed that exercising muscle cells can directly counter this pro-inflammatory signaling independent of the presence of other cell types or tissues,” says the study’s first author Dr. Zhaowei Chen.

Researchers say that exercising had the same anti-inflammatory effect as tofacitinib and baricitinib, two drugs commonly used to treat arthritis. “When exercising, the muscle cells themselves were directly opposing the pro-inflammatory signal induced by interferon gamma, which we did not expect to happen. These results show just how valuable lab-grown human muscles might be in discovering new mechanisms of disease and potential treatments,” explains Bursac.

“There are notions out there that optimal levels and regimes of exercise could fight chronic inflammation while not over stressing the cells. Maybe with our engineered muscle, we can help find out if such notions are true,” he adds.

The findings were published in the journal Science Advances.

SWNS writer Tom Campbell contributed to this report.

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