European Cells & Materials (Nov 2024)
Mechanical load rescues injury-induced skeletal muscle fibrosis through macrophage polarization
Abstract
Background: Current therapeutic approaches for skeletal muscle fibrosis are insufficient. We hypothesize that mechanical load (ML) could mitigate muscle fibrosis by suppressing inflammation. Methods: We utilized ML to treat cardiotoxin (CTX) injury-induced skeletal muscle fibrosis in C57BL6/J mice. We analyzed the underlying mechanism by integrating single-cell RNA sequencing (scRNA-seq) with molecular techniques. Hematoxylin and eosin staining and Masson’s trichrome staining were used to assess skeletal muscle fibrosis. An enzyme-linked immunosorbent assay was used to detect inflammatory cytokine levels in serum. scRNA-seq, immunofluorescence, and Western blot were performed to determine cellular and molecular outcome changes. Results: After seven days of ML intervention, compared with CTX injury-induced fibrosis mice, ML significantly reduced pro-inflammatory cytokines interleukin (IL)-1β and IL-6 expression and increased anti-inflammatory cytokines transform growth factor (TGF)-β and IL-10 expression levels (all p < 0.05). Meanwhile, ML inhibited the expression of the fibrosis signaling pathway TGF-β1/Smad3 and decreased hyperplasia of fibrosis tissue in skeletal muscle (all p < 0.05). Next, scRNA-seq detected that M1 macrophage numbers, activity, and communication capacity are maximum increased in fibrotic skeletal muscle among B cells, endothelial cells, fast muscle cells, fibroblasts, skeletal muscle satellite cells, neutrophils, and T cells. However, ML significantly suppresses the expression of CD68+ M1 macrophage and p65 in the nuclear factor kappa-B (NF-κB) pathway and promotes the CD206+ M2 macrophage and peroxisome proliferator-activated receptor (PPAR)-γ expression levels in fibrotic skeletal muscle (all p < 0.05). Conclusion: ML can attenuate fibrosis in the injured skeletal muscle of mice by prompt polarization of M1 macrophages into M2 macrophages.
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