The laboratory of Marni D. Boppart at the Beckman Inst. for Advanced Science and Technology in Urbana, Illinois has published a very interesting study that shows that injections of mesenchymal stem cells (MSCs) into mice after they have exercised increases the number of new blood vessels formed in skeletal muscle.
Early last year, Boppart’s laboratory showed that exercise in mice induces a population of mesenchymal stem cells located near blood vessels (pericytes) to migrate into muscles and form new muscle fibers. A particular adhesion molecule known as integrin α7 is responsible for the movement of MSCs into the muscle. Boppart and his colleagues showed that engineering mice that made extra α7 integrin had muscles that were filled with more stem cells making new muscle than their normal litter mates after exercise.
More recently, Boppart and his colleagues have injected cultured MSCs into the muscles of mice after the mice had exercised by running downhill. The mice injected with MSCs had more blood vessels in their muscles than mice than received no such injections. The blood vessels in the MSC-injected mice were also larger. Further work showed that the MSCs produced a veritable smorgasbord of angiogenic factors, which are molecules that induce the formation of blood vessels.
Thus MSCs, in response to exercise, can increase muscle mass as a result of exercise and increase the density and diameter of blood vessels.
Dr. Centeno at the Regenexx blog site wonders if stem-cell doping will be the next trick athletes will use to increase their muscle size and strength. Such a trick would be completely undetectable with contemporary technology, and it seems as though this might be a genuine possibility.
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.