Skeletal Muscle Stem Cell Niche from Birth to Old Age

Stem cells are defined as undifferentiated cells that are able to unlimitedly renew themselves within controlled conditions and to differentiate into a multitude of mature cell types. Skeletal muscle stem cells, represented predominantly by satellite cells, show a variable capability of self-renewal and myogenic differentiation. They were found to be involved not only in the growth of myofibers during neonatal and juvenile life but also in the regeneration of skeletal muscles after an injury. The microenvironment in which stem cells are nourished and maintained dormant preceding division and differentiation is known as “niche.” The niche consists of myofibers, which are believed to modulate the active/inactive state of the stem cells, extracellular matrix, neural networks, blood vessels, and a multitude of soluble molecules. It was observed that changes in the composition of the niche have an impact on the stem cell functions and hierarchy. Furthermore, it seems that its layout is variable throughout the entire life, translating into a decrease in the regenerative capacity of satellite cells in aged tissues. The scope of this chapter is to provide a detailed view of the changes that occur in the skeletal stem cell niche during life and to analyze their implications on tissue regeneration. Future studies should focus on developing new therapeutic tools for diseases involving muscle atrophy