Interplay between myofibers and pro-inflammatory macrophages controls muscle damage in mdx mice

Abstract

Duchenne Muscular Dystrophy is a genetic muscle disease characterized by chronic inflammation and fibrosis, mediated by a pro-fibrotic macrophage population expressing pro-inflammatory markers. Our aim was to characterize cellular events leading to the alteration of macrophage properties, and to modulate macrophage inflammatory status using the gaseous mediator H2S. Using co-culture experiments, we first showed that myofibers derived from mdx mice strongly skewed the polarization of resting macrophages towards a pro-inflammatory phenotype. Treatment of mdx mice with NaHS, an H2S donor, reduced the number of pro-inflammatory macrophages in skeletal muscle, which was associated with a decreased number of nuclei per fiber, together with a reduced myofiber branching and fibrosis. Finally, we established the metabolic sensor AMPK as a critical NaHS target in muscle macrophages. These results identify an interplay between myofibers and macrophages where dystrophic myofibers contribute to the maintenance of a highly inflammatory environment sustaining a pro-inflammatory macrophage status, in turn favoring myofiber damage, myofiber branching and fibrosis establishment. They also identify H2S donors as a potential therapeutic strategy to improve dystrophic muscle phenotype by dampening chronic inflammation.

Duchenne muscular dystrophy trajectory in R-DMDdel52 preclinical rat model identifies COMP as biomarker of fibrosis

“…Although the primary cellular cause of DMD is myonecrosis caused by rupture of the sarcolemma, it becomes more and more obvious that other cell types largely contribute to disease severity and progression, such as macrophages [ 37 , 42 , 52 , 65 ] and FAPs [ 26 , 32 , 44 , 64 ]. To identify the skeletal muscle cellular and transcriptional modification in DMD, we performed a comparative scRNAseq analysis on diaphragms of R-DMDdel52 and their WT littermates aged 12 months.…”

Temporal regulation of TAK1 to counteract muscular dystrophy

“…macrophages, which play a critical role in skeletal muscle degeneration and regeneration (44,45). CD11c + proinflammatory M1 macrophages infiltrate the dystrophic muscle and contributes to myolysis whereas during the regenerative phase, a shift towards CD206-expressing antiinflammatory M2 macrophages facilitates repair (45)(46)(47). We found a significant reduction in the relative mRNA levels of F4/80, CD11c, and CD206 in the GA muscle of 8-week-old mdx;Tak1 mKO mice compared to littermate mdx;Tak1 fl/fl mice (Fig.…”

Benefits and pathologies associated with the inflammatory response

“…Overexpression of the Klotho protein in macrophages also improves the mdx dystrophic phenotype, through an increase of MuSC proliferation via TNF [72]. In the other way around, is was recently shown that isolated mdx myofibers induce the expression of proinflammatory markers by macrophages in vitro, suggesting that damaged myofibers sustain the inflammation in DMD [73]. Since macrophages are involved in fibrosis in other tissues, this axis has been investigated in muscular dystrophies.…”

“…Treatment of mdx mice with eicosapentaenoic acid (EPA), which is metabolized in resolvins (described above as beneficial for accelerating muscle regeneration in an acute injury context), shifts macrophages towards a recovery macrophage status and improves myogenesis [95,96]. In the same vein, treating mdx mice with NaHS, a donor of the gaseous mediator hydrogen sulfide (H2S) reduces the number of pro-inflammatory macrophages in skeletal muscle, which was associated with a decreased number of nuclei per fiber, as well as reduced myofiber branching and fibrosis [73]. Similarly, targeting AMPK, which activation is required for macrophage inflammatory shift during acute post-injury muscle regeneration, is also an efficient way to improve the dystrophic muscle.…”