title: Divergent impact of Toll-like receptor 2 deficiency on repair mechanisms in healthy muscle versus Duchenne muscular dystrophy.
abstract: Injury to skeletal muscle, whether acute or chronic, triggers macrophage-mediated innate immunity in a manner which can be either beneficial or harmful for subsequent repair. Endogenous ligands for Toll-like receptor 2 (TLR2) are released by damaged tissues and might play an important role in activating the innate immune system following muscle injury. To test this hypothesis, we compared macrophage behaviour and muscle repair mechanisms in mice lacking TLR2 under conditions of either acute (cardiotoxin-induced) or chronic (mdx mouse genetic model of Duchenne muscular dystrophy; DMD) muscle damage. In previously healthy muscle subjected to acute damage, TLR2 deficiency reduced macrophage numbers in the muscle post-injury but did not alter the expression pattern of the prototypical macrophage polarization markers iNOS and CD206. In addition, there was abnormal persistence of necrotic fibres and impaired regeneration in TLR2-/- muscles after acute injury. In contrast, TLR2 ablation in chronically diseased muscles of mdx mice not only resulted in significantly reduced macrophage numbers but additionally modified their phenotype by shifting from inflammatory (iNOS(pos) CD206(neg) ) to more anti-inflammatory (iNOS(neg) CD206(pos) ) characteristics. This decrease in macrophage-mediated inflammation was associated with ameliorated muscle histopathology and improved force-generating capacity of the dystrophic muscle. Our results suggest that the role of TLR2 in macrophage function and skeletal muscle repair depends greatly upon the muscle injury context, and raise the possibility that inhibition of TLR2 could serve as a useful therapeutic measure in DMD.
authors.affiliation: Meakins-Christie Laboratories and Program for Translational Research in Respiratory Diseases, McGill University Health Centre Research Institute, Montreal, Quebec, Canada.
authors.forename: Kamalika
authors.initials: K
authors.lastname: Mojumdar
authors.affiliation: Meakins-Christie Laboratories and Program for Translational Research in Respiratory Diseases, McGill University Health Centre Research Institute, Montreal, Quebec, Canada.
authors.forename: Christian
authors.initials: C
authors.lastname: Giordano
authors.affiliation: Meakins-Christie Laboratories and Program for Translational Research in Respiratory Diseases, McGill University Health Centre Research Institute, Montreal, Quebec, Canada.
authors.forename: Christian
authors.initials: C
authors.lastname: Lemaire
authors.affiliation: Meakins-Christie Laboratories and Program for Translational Research in Respiratory Diseases, McGill University Health Centre Research Institute, Montreal, Quebec, Canada.
authors.forename: Feng
authors.initials: F
authors.lastname: Liang
authors.affiliation: Meakins-Christie Laboratories and Program for Translational Research in Respiratory Diseases, McGill University Health Centre Research Institute, Montreal, Quebec, Canada.
authors.forename: Maziar
authors.initials: M
authors.lastname: Divangahi
authors.affiliation: Meakins-Christie Laboratories and Program for Translational Research in Respiratory Diseases, McGill University Health Centre Research Institute, Montreal, Quebec, Canada.
authors.forename: Salman T
authors.initials: ST
authors.lastname: Qureshi
authors.affiliation: Meakins-Christie Laboratories and Program for Translational Research in Respiratory Diseases, McGill University Health Centre Research Institute, Montreal, Quebec, Canada.
authors.forename: Basil J
authors.initials: BJ
authors.lastname: Petrof
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D054715:Cardiotoxins / Q000633:toxicity; D002478:Cells, Cultured; D003964:Diaphragm / Q000502:physiology; D004195:Disease Models, Animal; D005260:Female; D037181:Lectins, C-Type / Q000378:metabolism; D008262:Macrophage Activation / Q000502:physiology; D008297:Male; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins / Q000378:metabolism; D018101:Mice, Inbred mdx; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000293:injuries* / Q000502:physiology; D009137:Muscular Dystrophy, Animal / Q000209:etiology*; D020388:Muscular Dystrophy, Duchenne / Q000209:etiology*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D051195:Toll-Like Receptor 2 / Q000172:deficiency*; D014945:Wound Healing / Q000502:physiology*
chemical_list: D054715:Cardiotoxins; D037181:Lectins, C-Type; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D011956:Receptors, Cell Surface; D051195:Toll-Like Receptor 2; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse
keywords: DAMPs; DMD; TLR2; macrophage polarization; macrophages; mdx mouse; muscle regeneration