Laboratory-grown human muscle shows that exercise can “almost completely” prevent chronic inflammation that causes tissue dissipation
- Inflammation comes from the excessive reaction of the body’s immune system
- Chronic inflammation can cause dissipation and loss of muscle tissue structure
- Experts believe that a molecule called “interferon gamma” is behind this waste
- However, it was unclear how this worked and why exercise seemed to alleviate it.
- To make it easier to investigate, American researchers grew their own muscles in the laboratory
- This allowed them to reach zero in the cells to focus on the relevant processes
Exercise can “almost completely” prevent chronic inflammation that causes muscle loss, according to a study conducted in human tissue grown in the laboratory.
Inflammation occurs when our body’s immune system responds to damage to bacteria or tissues – but sometimes it can overreact and end up attacking its own cells.
And some diseases – such as arthritis and sarcopenia – can lead to long-term “chronic inflammation” that causes muscle wasting.
It is believed that a molecule known as “interferon gamma” is one of the culprits behind various types of muscle wasting and dysfunction.
Previous studies have shown that exercise can alleviate the effects of inflammation in general – but it has not been clear what role muscle cells and gamma interferon play.
To find out, researchers at Duke University in the US have developed a platform to allow them to develop their own human muscles in the laboratory.
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Exercise can “almost completely” prevent chronic inflammation that causes muscle loss, according to a study conducted in human tissue grown in the laboratory. In the picture: long, thin, well-defined muscle fibers (upper left) lose their structure after a prolonged inflammation (upper right), but not when they are subjected to exercise (lower left). The same goes for resistance (bottom right)
“A lot of processes take place throughout the human body during exercise and it is difficult to destroy what systems and cells do what they do inside an active person,” said the author of the paper and biological engineer Nenad Bursac.
“Our designed muscle platform is modular, which means we can mix and match various cell types and tissue components if we wish.”
But in this case, we found that muscle cells were able to take anti-inflammatory action on their own.
For their studies, the researchers began by growing functional human skeletal muscles in a Petri dish – to which they then added immune cells and stem cell reservoirs.
When the muscles were fully grown, the team “flooded” them with high levels of interferon gamma for seven days to mimic the effects of long-term chronic inflammation.
As expected, the muscles grown in the laboratory shrank and lost much of their strength.
Then they repeated the experiment, but this time they put the muscles through a regime of simulated exercises using electric shocks.
The researchers found that the “almost complete” regimen 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 human muscles grown in a Petri dish,” said the author of the paper and biomedical engineer Zhaowei Chen.
“Not only have we confirmed that gamma interferon works primarily through a specific signaling pathway,” he continued.
We have shown that exercising muscle cells can directly counteract this pro-inflammatory signaling regardless of the presence of other cell types or tissues.
Exercise had the same anti-inflammatory effect as tofacitinib and baricitinib, two drugs commonly used to treat arthritis, the researchers found.
“When exercising, the muscle cells themselves were directly opposed to the pro-inflammatory signal induced by interferon gamma, which we did not expect to happen,” said Professor Bursac.
These results show how valuable human muscles grown in the laboratory could be in discovering new disease mechanisms and potential treatments.
“There are notions out there that optimal exercise levels and regimes could fight chronic inflammation without stressing the cells.”
“Maybe with the help of our projected muscles, we can help find out if such notions are true.”
The full results of the study were published in the journal Science Advances.