Growing muscles from skin cells

For the first time, scientists have grown functional human muscle tissue from skin cells

For many years, scientists have been working on how to grow living tissues and organs in the lab. This process is extremely difficult, as the stem cells used must be kept in very precise conditions to become the right kind of tissue. Additionally, these stem cells are often taken from human embryos, and this raises many ethical concerns.

One of the biggest breakthroughs in this field came when researchers discovered how to turn mature, adult tissues (like skin or blood cells) into stem cells like those found in early embryos.  These cells are called “pluripotent”, meaning they are able to become any kind of cell in the body, and those that are made from mature, adult cells are called “induced pluripotent stem cells” (iPSCs).

Now, for the first time, scientists have managed to grow healthy, functioning muscle tissue from these iPSCs. Nenad Bursac and his team from Duke University in North Carolina published the results in Nature Communications.

The team grew the iPSCs and activated the pax7 gene, which tells stem cells to become muscle-specific stem cells. This had been done before, but these muscle stem cells were not very effective at forming mature tissue. In this study, Bursac’s team decided to grow the cells in 3D conditions. Instead of growing them as a flat layer on a dish, as had been done in the past, they were grown in a firm gel. When provided with specific chemicals, these cells formed mature muscle tissue.

The researchers wanted to test if the muscle tissue they had grown would be able to function normally. They stimulated the tissue with electrical signals and found that it contracted – just like the muscle in the body does when electrically stimulated by nerve cells.  

Next, they implanted the muscle tissue into mice. The tissue was able to survive, integrate into the mouse muscle, and function normally – responding to the mouse nerve cells.

This is the first case of fully functional muscle tissue being grown from iPSCs, and the team hope that this could be a way of growing new muscles for individuals with muscular dystrophy.  The lab-grown muscle could also be used to test the effects of drugs on human muscle tissue, which could reduce the need for animal testing.

This is one of many studies which show the importance of a cell’s physical environment on its behaviour and development. Fully functioning muscle tissue was only able to develop when the cells were grown in 3D conditions, further showing that stem cells respond to both chemical and physical cues.