Skeletal muscle accounts for 40 percent of most people's body weight. Muscle consumes about 30 percent of the body's energy intake, and more during exercise. The health of a person's metabolism is linked to the amount and health of his or her skeletal muscle.
Many people experience temporary muscle fatigue and pain, but some people have serious muscular diseases, such as muscular dystrophy. Aging adults are at risk for developing sarcopenia, a wasting away of skeletal muscle. Excessive muscle loss in patients with certain chronic diseases can cause a wasting condition called cachexia. Many of these disorders don't have cures.
NIH-supported researchers are developing a device called a muscle on a chip to study the function of human skeletal muscle in the laboratory and to test the effectiveness and toxicity of drugs on muscle. The goal is to use the system to screen potential new drugs to treat skeletal muscle and blood vessel disorders. Many drugs used to treat diabetes, high cholesterol and other conditions have side effects on muscle, and the new device might help researchers predict such side effects before patients take the drugs.
Muscle on a Chip
A team of NIH-supported scientists at Duke University collected muscle cells from volunteers. The scientists grew the muscle cells to multiply and self-organize into bio-engineered muscle bundles.
But do these laboratory systems act like human muscle? The researchers applied electrical impulses and chemicals to mimic the brain messages that normally would transmit through the nerves of the body that tell muscles to contract. The researchers found that small electrical currents caused the muscle bundles to twitch and larger currents caused more forceful contractions. The team also found that the muscle bundles release calcium during contraction, just like the muscles of the body do.
Duke University scientists are developing a miniaturized 3-D system for growing human muscle bundles, as shown in this video.
This video is a microscopic view of a muscle bundle after electrical stimulation, which causes the muscle to contract and release calcium, visualized as white particles.
NIH-supported researchers have observed that the muscle on a chip acts much like the skeletal muscle of the body. Researchers already are testing the device with various drugs to see whether the lab-grown muscle bundles respond the same way as human muscle does.
The scientists also are culturing blood vessel cells from umbilical cord blood and from adult stem cells and growing them with the muscle bundles in a system that closely resembles the situation in the human body. Stem cells have the remarkable potential to develop into many different cell types. Stem cells are important during early life and for embryonic growth; in adults, stem cells function in tissue repair and maintenance.
Scientists could use this new device to learn more about muscular diseases. In addition, the chip might enable scientists to gather data to accelerate the drug approval process and to enable researchers to create new treatments for patients.
In the future, scientists may be able to link this muscle device with other tissue chips, such as blood vessels or liver, to get more comprehensive information about how a given drug is processed and transported throughout the body and to better predict a drug's toxic effects.