It has been years since Nenad Bursac has been trying to make human muscle from scratch. While a biological engineer at Duke, Bursac first approached success in 2015. That year, his lab managed to grow “functional” human skeletal muscle in a culture. The tissues could contract and even generate force in response to certain stimuli like electrical pulses or chemical shots.
However, in order to make this first prototype, the team used pea-sized globules of real muscle so it was not like they were starting completely from scratch. Basically, the lab grew muscle from existing muscle (taken from human subjects). It was quite an accomplishment but biopsied cells don’t survive well in a laboratory setting. Furthermore, Bursac designed the experiment in an attempt to study and treat muscular disorders and taking biopsies from patients who already have weak muscles is unethical.
He explains, “In a lot of people with rare, congenital diseases, their muscles are already damaged, so you don’t want to biopsy on top of that and cause further damage. The ideal scenario is to take a skin, blood, or urine sample, use that to generate stem cells, and use that to generate functional muscles.”
In essence, then, he wanted to reprogram skin or blood cells to act more like undifferentiated stem cells.
And that is what Bursac’s team has finally done. Reporting in the the science journal Nature Communications, study co-author Lingjun Rao notes, “It’s taken years of trial and error, making educated guesses and taking baby steps to finally produce functioning human muscle from pluripotent stem cells.”
The Duke University professor of biomedical engineering explains, “Starting with pluripotent stem cells that are not muscle cells, but can become all existing cells in our body, allows us to grow an unlimited number of myogenic progenitor cells. These progenitor cells resemble adult muscle stem cells called ‘satellite cells’ that can theoretically grow an entire muscle starting from a single cell.”
Furthermore, Bursac comments on the progress: “The prospect of studying rare diseases is especially exciting for us. When a child’s muscles are already withering away from something like Duchenne muscular dystrophy, it would not be ethical to take muscle samples from them and do further damage.”
This breakthrough could continue to lead to improved genetic and/or cell-based therapies. It could also lead to more investigations into potential causes and possible treatment of/for muscular disorders.
Bursac concludes: “With this technique, we can just take a small sample of non-muscle tissue — like skin or blood — revert the obtained cells to a pluripotent state, and eventually grow an endless amount of functioning muscle fibers to test.”