It's an unfortunate fact of life that as we get older, our cells gradually lose the ability to heal themselves. Thankfully, at least one aspect of that might be treatable in the near future, if new work from Georgia Tech pans out. Researchers have developed a hydrogel that holds muscle stem cells, and by injecting this near the site of a muscle injury they can get to work repairing it. The team says the technique could be effective at treating injuries in the elderly and people with muscular dystrophy.

The stem cells involved are known as muscle satellite cells (MuSCs), and in young people they're common in muscle strands throughout the body, ready to patch up any damage that occurs. But sadly those days don't last – as we age the number of these stem cells goes down, and at the same time those that remain get weaker. As a result, older people have a harder time repairing injured tissue.

In past studies, scientists have tried injecting more of these MuSCs directly into damaged muscle tissue, with poor results. One of the main problems, say the Georgia Tech researchers, is that the immune system damages the new cells, so that less than 20 percent of them get where they need to be.

"Any muscle injury is going to attract immune cells," says Young Jang, one of the principal investigators on the study. "Typically, this would help muscle stem cells repair damage. But in aged or dystrophic muscles, immune cells lead to the release of a lot of toxic chemicals like cytokines and free radicals that kill the new stem cells."

To give the MuSCs a fighting chance, the Georgia Tech team mixed them into a biocompatible hydrogel. As a kind of net structure suspended in water, the gel holds the muscle satellite cells in place, and protects them from the dangers of the immune cells and keeps them from self-destructing, as they tend to do when left alone and free-floating.

This hydrogel can then be applied to an injured muscle, where it sets into a kind of patch that transfers the MuSCs to the muscle.

"The stem cells keep multiplying and thriving in the gel after it is applied," says Jang. "Then the hydrogel degrades and leaves behind the cells engrafted onto muscle tissue the way natural stem cells usually would be."

In tests on mice, the team found that the method successfully boosted the healing process. It was found to be effective on both elderly mice and those that had a genetic muscle tissue deficiency, similar to Duchene muscular dystrophy in humans.

"With this system we engineered, we think we can introduce donor cells to enhance the repair mechanism in injured older patients," says Woojin Han, first author of the study. "We also want to get this to work in patients with Duchene muscular dystrophy."

While the method is promising so far, further work needs to be done before human trials can begin. One challenge in particular is the potential for patients to reject donated cells.

The research was published in the journal Science Advances.

Source: Georgia Tech

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