More on Exercise and Muscle Stem Cells
As you might imagine, exercise affects the behavior of muscle stem cells: "researchers determined that an adult stem cell present in muscle is responsive to exercise, a discovery that may provide a link between exercise and muscle health. The findings could lead to new therapeutic techniques using these cells to rehabilitate injured muscle and prevent or restore muscle loss with age. Mesenchymal stem cells (MSCs) in skeletal muscle have been known to be important for muscle repair. ... 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. ... The researchers found that MSCs in muscle are very responsive to mechanical strain. They witnessed MSC accumulation in muscle of mice after vigorous exercise. Then, they determined that although MSCs don't directly contribute to building new muscle fibers, they release growth factors that spur other cells in muscle to fuse and generate new muscle, providing the cellular basis for enhanced muscle health following exercise. ... 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."
Link: http://news.illinois.edu/news/12/0206muscle_MarniBoppart.html
The whole feedback cycle whereby muscles become stronger with use is a brilliant illustration of ingenious evolutionary parsimony with stupid consequences for us technological beings. For animals in the natural condition of nutritional scarcity, tissue is expensive and trade-offs are necessary. These days we are surrounded by cheap food energy while our bodies economize to our detriment. Our genetic programs make us work at hard labour to buy warm clothes while we live in mansions of solid gold.
I wonder what would happen if the same growth factors released by MSCs were packaged into slow-release biodegradable nano-particles and injected IM. Things delivered in such a way tend to stay put and most skeletal muscles are not so difficult to reach with a needle. Maybe the regulatory role of MSCs in muscle and thus the need for their specific rejuvenation can be side-stepped.