Lab-made muscle repairs itself in supermouse

Duke University researchers create living skeletal muscle that looks and acts very much like the real thing -- even down to repairing itself. Then they attack it.

The engineered muscle fibers that were implanted, stained to show detail. Pratt School of Engineering, Duke
I get to write about a lot of cool scientific breakthroughs here at Crave, but rarely do I get to report on a story from the cutting edge of medicine that involves not one, but three, mind-blowing components. Yet that's what those geniuses over at Duke delivered this week -- a story involving superstrong self-healing artificial muscle, snake venom, and a window in a mouse's back. Kapow!

First the fake muscle.

Apparently, previous attempts to grow human-like muscle in a lab have created fibers that are simply too weak and can't repair themselves from tears and other damages. The Duke team, which included Nenad Bursac, associate professor of biomedical engineering, and graduate student Mark Juhas, solved this problem by making sure their artificial muscle had a supply of muscle stem cells, known as satellite cells.

In the body, these satellite cells are always at the ready, and rush in to repair muscles when they are injured. But just adding them to the fake muscle wasn't enough -- they needed to be kept in a special microenvironment known as a niche.

"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." It's like a reservoir of tiny medics that rush out onto the battlefield when they're needed.

Once the artificial muscle and accompanying niche were created and found to be stable, it was time to test it. To do so, the researchers zapped it with electrical pulses and found that it was 10 times stronger than any engineered muscle that came before it. Then -- and here's the second cool part of the study -- they injected it with a toxin found in snake venom. Go snakes!

As you might imagine, the venom damaged the muscle fibers, but that was just the point. The engineers wanted to see if their new muscle could recover from such an attack -- but not just in a lab dish, in a living subject. So first they genetically modified the muscle to produce fluorescent flashes whenever it contracted. Then they implanted the fake muscle inside a mouse's back and -- ready for "cool science thing" No. 3? -- they closed it in with a window that let them watch the muscle's progress over time.

The progression of veins growing into the artificial muscle. Pratt School of Engineering, Duke
What they could then see through the tiny window in the mouse was that the flashes got brighter as the muscle repaired itself and got stronger. Not only that, but blood vessels from the mouse actually grew into the fake muscle, effectively incorporating it into its own body. "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," Juhas said.

There you have it. Manufactured muscle that heals itself, snake venom, and a window in a mouse's back. It almost makes a science writer like me a little teary-eyed. The results of the research were published in the Proceedings of the National Academy of Sciences Early Edition the week of March 31.

The next step for the researchers is to see if their engineered product could repair damage from muscle injuries or disease in the body. "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."

I wonder if they need any volunteers? For now, I guess I'll just have to pretend I'm there peeking through that mouse window thanks to this short video Duke put out that shows how the fake muscle took on very real blood vessels.

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