Researchers here show that boosting the numbers of the pericyte cell population involved in vascular system growth and activity improves restoration of muscle mass following atrophy. This is particularly interesting in the context of the fact that capillary vessel networks decline in density in tissues with age, the processes of maintenance and blood vessel construction becoming disarrayed, and that this decline is thought to contribute to age-related loss of muscle mass and strength. Muscle is an energy-hungry tissue, and we might thus expect that factors relating to delivery of nutrients and oxygen via the vascular network have some impact on its maintenance and growth. That point is demonstrated here.
By injecting cells that support blood vessel growth into muscles depleted by inactivity, researchers say they are able to help restore muscle mass lost as a result of immobility. The research, conducted in adult mice, involved injections of cells called pericytes, which are known to promote blood vessel growth and dilation in tissues throughout the body. The injections occurred at the end of a two-week period during which the mice were prevented from contracting the muscles in one of their hind legs. "Just as the mice were becoming mobile again, we transplanted the pericytes and we found that there was full recovery of both muscle mass and the vasculature, too."
The team also observed that muscle immobility itself led to a significant decline in the abundance of pericytes in the affected muscle tissues. "We know that if you are under a condition of disuse - for example, as a result of long-term bed rest, or the immobilization of a body part in a cast - you lose muscle mass. And even when you come out of that state of immobility and you start moving your muscles again, there's this really long, slow process of recovery. Older adults might never fully rebuild the lost muscle mass after a period of immobility. They can't recover, they become disabled, and there's this downward spiral. They may become institutionalized and experience early mortality. To my knowledge, no one has demonstrated that anything has been effective in improving the recovery process. We're excited by the new findings because we hope to one day use these cells or biomaterials derived from these cells to help restore lost muscle mass."