Exercise Triggers Stem Cells in Skeletal Muscle

Mesenchymal stem cells (MSCs) in skeletal muscle have now been shown to be very responsive to mechanical strain from exercise. The findings could lead to new therapeutic techniques using these cells to rehabilitate injured muscle and prevent or restore muscle loss.

Skeletal muscle MSCs have been known to be important for muscle repair in response to nonphysiological injury, mainly from studies of response to chemical injections that significantly damage muscle tissue and induce inflammation.

“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,” said Marni Boppart, PhD, professor at The Department of Kinesiology and Community Health of the University of Illinois at Urbana-Champaign (UIUC; IL, USA), and affiliated with the Beckman Institute for Advanced Science and Technology at UIUC.

In the study published on January 11, 2012, in the online journal PLoS One, researchers witnessed MSC accumulation in muscle of mice after vigorous exercise. They then determined that although MSCs do not directly contribute to building new muscle fibers, they release growth factors that spur other cells in muscle to fuse and generate new muscle, revealing a major aspect underlying the cellular basis for enhanced muscle health following exercise.

A key element of the method was in exercising the mice before isolating the cells to trigger secretion of beneficial growth factors. Then they dyed the cells with a fluorescent marker and injected them into other mice to see how MSCs coordinated with other muscle-building cells.

In addition to examining the cells in vivo, the researchers studied their response to strain on different substrates and found them to be very sensitive to the mechanical environment. For example, in vitro, multiaxial strain upregulated MSC markers in the presence of laminin, but not gelatin, identifying a potential mechanistic basis for the accumulation of these cells in muscle following exercise.

“These findings are important because 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,” senior author Boppart said.

Next, the group hopes to determine whether these cells contribute to the decline in muscle mass over a person’s lifetime. Preliminary data suggest MSCs become deficient in muscle with age. The team hopes to develop a combinatorial therapy that utilizes molecular and stem-cell-based strategies to prevent age-related muscle loss and to preserve significant muscle mass in disability-related atrophy.

Related Links:
University of Illinois at Urbana-Champaign
Beckman Institute for Advanced Science and Technology
The Department of Kinesiology and Community Health