Self-Regenerating Artificial Muscle Tissue a Breakthrough for Bio-Engineers

Artificial muscle tissue grown in a Duke University lab is more lifelike than its predecessors, capable of contracting powerfully and rapidly while also demonstrating the ability to heal itself within a living test environment. The development marks new steps in the process towards growing viable muscle material for treating disease and studying injuries, Duke researchers said.

The lab-grown muscle was implanted on the back of a mouse, and researchers were able to watch the muscle mature and integrate into real tissue through a "window" left open on the mouse's back.

"The muscle we have made represents an important advance for the field," said Nenad Bursac, associate professor of biomedical engineering at Duke. "It's the first time engineered muscle has been created that contracts as strongly as native neonatal skeletal muscle."

Bursac and his collaborators, including graduate student Mark Juhas, determined that to make artificial muscle more viable, two things are key: well-developed contractile muscle fibers and a pool of muscle stem cells, known as satellite cells.

These satellite cells are in every type of muscle, standing on reserve to step and begin the regeneration process if other tissue cells are injured.

The researchers were able to create an artificial environment where these satellite cells can remain on standby, a feat previously unseen in artificial muscle tissue development.

"Simply implanting satellite cells or less-developed muscle doesn't work as well," Juhas said in a statement. "The well-developed muscle we made provides niches for satellite cells to live in, and, when needed, to restore the robust musculature and its function."

Before implanting their artificial tissue in a mouse, the researchers tested it extensively out of body. Using electrical pulses, the bio-engineers measured the the tissue's contractile strength, finding that it was 10 times stronger than any previous engineered muscles. Also before implanting it in a mouse, the researchers damaged the tissue with a toxin found in snake venom to prove the satellite cells could activate, multiply and heal.

After proving the tissue was viable, the researchers implanted it into a specialized chamber bored into a mouse's back. Once implanted, the researchers could monitor the muscle though a glass window covering the chamber.

"We could see and measure in real time how blood vessels grew into the implanted muscle fibers, maturing toward equaling the strength of its native counterpart," said Juhas.

Future research will test whether the artificial muscle can be used to repair actual muscle injuries and disease.

"Can it vascularize, innervate and repair the damaged muscle's function?" asked Bursac. "That is what we will be working on for the next several years."

An article detailing the research is published in the Proceeding of the National Academy of Sciences.