There are several ways you can build bigger, stronger muscles. You can take the approach favored by our former Governor, Arnold Schwarzenegger, and pump iron till your biceps are as inflated as a birthday balloon. Or you could follow the lead of a research team we are funding and try to use stem cells to do the trick.

Our muscles contain a group of stem cells called satellite cells. These normally lie dormant until the muscle is damaged and then they spring into action to repair the injury. However, satellite cells are relatively rare and are hidden in the muscle itself, making them hard to find and notoriously difficult to study. In the past researchers have struggled to get these satellite cells to grow outside the body, which made it difficult to study muscle regeneration and develop new ways of treating muscle problems.

Finding a solution

Now a team at the University of California, San Francisco has found a solution to the problem. They started by analyzing samples of 7 different kinds of muscles (in the body, legs and head) from 43 patients. In all but two samples they found that the gene PAX7 was specifically turned on in satellite cells and the PAX7 protein was present with little variation from one muscle group to another.

Upon further sleuthing, they discovered that PAX7-positive satellite cells were the real deal because they also expressed two common cell surface markers of human satellite cells: CD29 and CD56.

The researchers then transplanted PAX7-positive cells into mice that had experienced muscle injuries. As they report in the journal Stem Cell Reports these cells not only engrafted in the mice but they also created hundreds of human-derived muscle fibers. This finding shows that satellite cells were regenerating and potentially helping to heal the damaged muscle.

What’s next

As always, anything done in mice is interesting but still needs to be replicated in people before we know for sure we are on to something.

In their conclusion the team freely admit this is just a first step but, compared to where we were before, it’s a very important step. As senior author Jason Pomerantz says:

“This is the first definitive experimental description of adult human endogenous muscle stem cell function.”

Harnessing the power of satellite cells would be of tremendous benefit to people suffering from facial paralysis, loss of hand function or muscle-wasting diseases such as sarcopenia, and could even be used as a way to deliver gene therapy to people with muscular dystrophies.

Using satellite cells to do all that, would be out of this world.