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Here's what it looks like when a lab-grown muscle flexes

Duke University researchers have grown a contracting human muscle in a lab and captured it on video.

The muscle acts like one found inside the body would, responding to drugs, electrical pulses and biochemical signals, according to data published in January in the open-access journal eLife by Nenand Bursac and Lauran Madden. The scientists hope to use lab-grown muscles to tailor treatment plans for patients.

The hope for these lab-produced muscles is that they could be used to treat patients. Doctors could grow many reproductions of a patient’s muscle, and then test drugs on each one to see which gets the best results.

Other experts on the subject say this research is more of an incremental accomplishment than a huge advance, because mouse stem cells have previously been used by Bursac's team to grow muscle fibers.

"I would consider it progress, certainly not a breakthrough," says Dr. Jaques Tremblay of Laval University, whose lab researches treatment for muscular dystrophies. This work builds on previous developments, because human cells behave much like mice cells do.

How they did it

The scientists grew the muscles using human cells that had developed slightly past the stem cell stage, but hadn't fully developed into muscle tissue. Stem cells don't have a specialized function, but they can give rise to many different types of specialized cells, like heart muscle cells or red blood cells. In this case, the cells were on their way to becoming muscle cells.

Researchers grew these cells, and placed them into a support made of 3D scaffolding. A nourishing gel lined the scaffolding to help the cells grow into moving muscle fibers.

When tested, the muscles contracted in response to electrical stimuli, which is a first for a lab-grown human muscle. The pathways that would let nerves stimulate the muscle inside the body were also functional, the researchers found.

Bursac’s research team is now trying to grow similar contracting muscles using stem cells too, and not just with cells from a biopsy. The hope here is that doctors could do the same drug tests on lab-grown muscles for patients with diseases that make it difficult to get a biopsy, such as muscular dystrophies. It would be a first with human muscles.