title: Macrophage colony-stimulating factor-induced macrophage differentiation promotes regrowth in atrophied skeletal muscles and C2C12 myotubes.
abstract: Skeletal muscle injury and regeneration are closely associated with an inflammatory reaction that is usually characterized by sequential recruitment of neutrophils and monocytes or macrophages. Selective macrophage depletion models have shown that macrophages are essential for complete regeneration of muscle fibers after freeze injuries, toxin injuries, ischemia-reperfusion, and hindlimb unloading and reloading. Although there is growing evidence that macrophages possess major myogenic capacities, it is not known whether the positive effects of macrophages can be optimized to stimulate muscle regrowth. We used in vivo and in vitro mouse models of atrophy to investigate the effects of stimulating macrophages with macrophage colony-stimulating factor (M-CSF) on muscle regrowth. When atrophied soleus muscles were injected intramuscularly with M-CSF, we observed a 1.6-fold increase in macrophage density and a faster recovery in muscle force (20%), combined with an increase in muscle fiber diameter (10%), after 7 days of reloading, compared with PBS-injected soleus muscles. Furthermore, coculture of atrophied myotubes with or without bone marrow-derived macrophages (BMDM) and/or M-CSF revealed that the combination of BMDMs and M-CSF was required to promote myotube growth (15%). More specifically, M-CSF promoted the anti-inflammatory macrophage phenotype, which in turn decreased protein degradation and MuRF-1 expression by 25% in growing myotubes. These results indicate that specific macrophage subsets can be stimulated to promote muscle cell regrowth after atrophy.
authors.affiliation: Centre de Recherche du CHU de Québec CHUL, Université Laval, Quebec City, Quebec, Canada.
authors.forename: Nicolas A
authors.initials: NA
authors.lastname: Dumont
authors.forename: Jérôme
authors.initials: J
authors.lastname: Frenette
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000187:drug effects / Q000473:pathology; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D018920:Coculture Techniques; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000473:pathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D023421:Models, Animal; D009119:Muscle Contraction / Q000187:drug effects; D024510:Muscle Development / Q000187:drug effects; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000473:pathology*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000473:pathology* / Q000503:physiopathology; D009133:Muscular Atrophy / Q000473:pathology* / Q000503:physiopathology; D009504:Neutrophils / Q000187:drug effects / Q000473:pathology; D010641:Phenotype; D014176:Protein Biosynthesis / Q000187:drug effects; D059748:Proteolysis / Q000187:drug effects
chemical_list: D016173:Macrophage Colony-Stimulating Factor