title: Osteopontin promotes fibrosis in dystrophic mouse muscle by modulating immune cell subsets and intramuscular TGF-beta.
abstract: Duchenne muscular dystrophy (DMD) is an X-linked, degenerative muscle disease that is exacerbated by secondary inflammation. Here, we characterized the immunological milieu of dystrophic muscle in mdx mice, a model of DMD, to identify potential therapeutic targets. We identified a specific subpopulation of cells expressing the Vbeta8.1/8.2 TCR that is predominant among TCR-beta+ T cells. These cells expressed high levels of osteopontin (OPN), a cytokine that promotes immune cell migration and survival. Elevated OPN levels correlated with the dystrophic process, since OPN was substantially elevated in the serum of mdx mice and muscle biopsies after disease onset. Muscle biopsies from individuals with DMD also had elevated OPN levels. To test the role of OPN in mdx muscle, mice lacking both OPN and dystrophin were generated and termed double-mutant mice (DMM mice). Reduced infiltration of NKT-like cells and neutrophils was observed in the muscle of DMM mice, supporting an immunomodulatory role for OPN in mdx muscle. Concomitantly, an increase in CD4+ and FoxP3+ Tregs was also observed in DMM muscle, which also showed reduced levels of TGF-beta, a known fibrosis mediator. These inflammatory changes correlated with increased strength and reduced diaphragm and cardiac fibrosis. These studies suggest that OPN may be a promising therapeutic target for reducing inflammation and fibrosis in individuals with DMD.
authors.affiliation: Department of Neurology, David Geffen School of Medicine, UCLA, Los Angeles, California 90095-7334, USA.
authors.forename: Sylvia A
authors.initials: SA
authors.lastname: Vetrone
authors.forename: Encarnacion
authors.initials: E
authors.lastname: Montecino-Rodriguez
authors.forename: Elena
authors.initials: E
authors.lastname: Kudryashova
authors.forename: Irina
authors.initials: I
authors.lastname: Kramerova
authors.forename: Eric P
authors.initials: EP
authors.lastname: Hoffman
authors.forename: Scot D
authors.initials: SD
authors.lastname: Liu
authors.forename: M Carrie
authors.initials: MC
authors.lastname: Miceli
authors.forename: Melissa J
authors.initials: MJ
authors.lastname: Spencer
mesh_terms: D000375:Aging / Q000502:physiology; D000818:Animals; D003964:Diaphragm / Q000378:metabolism / Q000473:pathology; D005355:Fibrosis / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation; D006331:Heart Diseases / Q000378:metabolism / Q000473:pathology; D006801:Humans; D055633:Immune System Phenomena / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009137:Muscular Dystrophy, Animal / Q000276:immunology* / Q000378:metabolism* / Q000473:pathology; D009154:Mutation / Q000235:genetics; D053495:Osteopontin / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology; D016212:Transforming Growth Factor beta / Q000276:immunology* / Q000378:metabolism*
chemical_list: D016693:Receptors, Antigen, T-Cell, alpha-beta; D016212:Transforming Growth Factor beta; D053495:Osteopontin