Age reduces the stem cells' capacity to repair damage, according to a recent study.

Researchers from the Ottawa Hospital Research Institute and University of Ottawa found that as muscle stem cells age, their reduced function is a result of a progressive increase in the activation of a specific signaling pathway. Such pathways transmit information to a cell from the surrounding tissue. The particular culprit identified by Dr. Rudnicki and his team is called the JAK/STAT signaling pathway.

"What's really exciting to our team is that when we used specific drugs to inhibit the JAK/STAT pathway, the muscle stem cells in old animals behaved the same as those found in young animals," Dr. Michael Rudnicki, a world leader in muscle stem cell research, said in a statement. "These inhibitors increased the older animals' ability to repair injured muscle and to build new tissue."

"What's happening is that our skeletal muscle stem cells are not being instructed to maintain their population. As we get older, the activity of the JAK/STAT pathway shoots up and this changes how muscle stem cells divide. To maintain a population of these stem cells, which are called satellite cells, some have to stay as stem cells when they divide," researchers said in the study.

 With increased activity of the JAK/STAT pathway, fewer divide to produce two satellite cells (symmetric division) and more commit to cells that eventually become muscle fiber. This reduces the population of these regenerating satellite cells, which results in a reduced capacity to repair and rebuild muscle tissue.

While this discovery is still at early stages, Rudnicki's team is exploring the therapeutic possibilities of drugs to treat muscle-wasting diseases such as muscular dystrophy. The drugs used in this study are commonly used for chemotherapy, the team is now looking for less toxic molecules that would have the same effect.

The findings were recently published by the journal Nature Medicine.