Scientists have grown the first functioning muscles using stem cells created from skin.
Duke University researchers have grown the first functional human skeletal muscle tissue entirely from induced human pluripotent stem cells (hPSCs). The achievement could feasibly allow scientists to generate skeletal muscle tissue for disease modeling and drug studies, and potentially for developing hPSC-based therapies for rare muscle-wasting diseases.
Muscles were grown using skin cells that had been “reprogrammed” to an original state, in which they are referred to as pluripotent stem cells. These cells can then be encouraged to grow into muscle cells by flooding them with a substance called Pax7.
The new research was published in the journal Nature Communications.
"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," said Dr Lingjun Rao, a biomedical engineer at Duke University who co-authored the study.
Having produced muscle cells in this way, the scientists provided them with structural support and nourishment that allowed them to become functioning muscle.
Not only did this muscle respond to chemical and electrical signals just like living muscle, the scientists were able to implant it into mice, with some success.
Though the muscle was not as strong as conventional muscle tissue, it functioned within the mice and began to integrate into pre-existing mouse muscle.
"The prospect of studying rare diseases is especially exciting for us," said Professor Nenad Bursac, who co-authored the study.
In previous work, Professor Bursac and his colleagues had successfully grown muscle from immature muscle cells called “myoblasts”.
However, if applied in humans this method would involve taking muscle tissue from a patient already suffering from a muscular disease, which could cause further damage.
The lab-grown muscle fibers were put to the test when they were implanted into adult mice. Small ‘windows’ grafted on the backs of the mice allowed the researchers to observe how the muscles they’ve grown behaved inside the rodents. The muscles survived and functioned for at least three weeks, during which it progressively integrated with native tissue through vascularisation.
A stained cross section of the new muscle fibers. The red cells are muscle cells, the green areas are receptors for neuronal input, and the blue patches are cell nuclei.
Credit: Image courtesy of Duke University
The new technique could allow medics to grow new muscle without causing additional harm to their patients.
“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 fibres to test,” said Professor Bursac.
According to Professor Bursac, the new method should allow them to create “an unlimited number” of potential muscle cells.
Stem cells have the potential to benefit many aspects of human health, with research suggesting they could be used to help reverse the ageing process and create a “limitless supply” of blood.
However, much of their potential in clinical practice still remains to be seen.
Using this new technique, the researchers think it might be possible to grow healthy muscle in patients with genetic diseases affecting their muscles, such as Duchenne muscular dystrophy.
The scientists also hope to create models of such diseases that can be used to discover new treatments