Inflammation in Muscle Repair, Aging, and Myopathies

Numerous recent studies have expanded our knowledge on the complexity of the immune system and its contribution to skeletal muscle repair, aging, and myopathies. Indeed, it is becoming clear that a precisely regulated cross talk between muscle and immune cells, involving endocrine/paracrine and cell-cell contact interactions, is required for muscle repair and maintenance of muscle homeostasis. Alterations of these mechanisms lead to unsuccessful repair in response to direct mechanical trauma (acute injury) or following secondary damage as a consequence of aging or genetic neuromuscular defects. In fact, though the capacity of muscle to regenerate relies primarily on a specific population of muscle stem cells, named satellite cells, the inflammatory cells that infiltrate the injured muscle appear to be as critical for successful regeneration. Conversely, if damage persists, as in chronic myopathies, inflammatory cell infiltration is perpetuated and leads to progressive muscle fibrosis, thus exacerbating disease severity.