Skeletal muscle injury triggers inflammatory response, of which the accumulation of intramuscular monocytes/macrophages is a prominent feature. Macrophages in injured muscle comprise both blood monocytes-derived infiltrating macrophages, which are recruited through CCR2 signaling, and pre-existing muscle resident macrophages, which are established during embryogenesis and maintained until adulthood through self-renewal proliferation. During regenerative acute muscle injury, infiltrating monocytes/macrophages are heterogeneously activated in a temporal dynamic, responding to the changing microenvironment in injured muscle and contributing to the complete injury repair. Injury-associated monocytes/macrophages recede with the completion of muscle injury repair. In contrast, injury-associated monocytes/macrophages persist in dystrophic muscle of Duchenne muscular dystrophy (DMD), likely accounting for persistent inflammation and progressive fibrosis of DMD muscle. We review here the current knowledge on monocyte/macrophage infiltration and activation in both acutely injured skeletal muscle and dystrophic muscle with subsequent discussion of the potential therapeutic implication in treating muscular dystrophy.
Wang et al. (Thu,) studied this question.