New findings from researchers from the University of Illinois showed that adult stem cells in muscle are responsive to exercise. This discovery might provide a link between exercise and muscle health, and could provide the impetus for therapeutic techniques that use muscle-specific stem cells to heal injured muscles and prevent or restore muscle loss with age.
Mesenchymal stem cells (MSCs) in skeletal muscles have been known to be important for muscle repair in response to injury. Experiments that demonstrate the roles of mesenchymal stem cells in muscle repair have use chemical-induced injuries that initiate damage muscle tissue and inflammation. However, exercise also stresses muscle, and a research group led by kinesiology and community health professor Marni Boppart investigated whether MSCs also responded to exercise-induced stress.
According to Boppart, “Since exercise can induce some injury as part of the remodeling process following mechanical strain, we wondered if MSC accumulation was a natural response to exercise and whether these cells contributed to the beneficial regeneration and growth process that occurs post-exercise.”
Boppart’s group found that muscle-based MSCs respond to mechanical strain. In fact, mice subjected to vigorous exercise showed robust accumulation after exercise. They also found that MSCs do not directly contribute to new muscle fibers, but, instead, they release growth factors that spur other cells in muscle to fuse and generate new muscle.
Boppart’s research group isolated muscle-based MSCs after the mice exercised, and then they stained the MSCs with a fluorescent marker and injected them into other mice to see how they coordinated with other muscle-building cells. In addition to examining MSCs in vivo, Boppart’s laboratory examined the response of MSCs to strain on different substrates. They discovered that MSC response is very sensitive to the mechanical environment, indicating that conditions under which muscles are strained affects the activity of the cells.
Boppart added, “We’ve identified an adult stem cell in muscle that may provide the basis for muscle health with exercise and enhanced muscle healing with rehabilitation/movement therapy. The fact that MSCs in muscle have the potential to release high concentrations of growth factor into the circulatory system during exercise also makes us wonder if they provide a critical link between enhanced whole-body health and participation in routine physical activity.”
Since, preliminary data suggest MSCs become deficient in muscle with age; the group hopes to determine if these cells contribute to the decline in muscle mass over a person’s lifetime. The team hopes to develop a combinatorial therapy that utilizes molecular and stem-cell-based strategies to prevent age-related muscle loss.