Objective  The objective of this study is to explore the mechanism of macrophage chemotaxis during the repair process following contusion of skeletal muscle.

  Methods  66 ICR male mice were randomly divided into control group(C group, n=11) and muscle contusion group(S group, n=55).Their gastrocnemius muscles were harvested at the time points of 12 h, 1 d, 5 d, 10 d and 15 d post-injury. The changes in skeletal muscle morphology were assessed by HE staining. The gene expression of macrophage and chemokines was analyzed by real-time PCR.

  Results  ① On 12 h post-injury, cross sections of gastrocnemius muscles showed substantial fiber damage and inflammatory infiltrate.On day 5 post-injury, a small quantity of centronucleated myofibers were observed.On day 10 post-injury, central nucleation phenomenon became more pronounced.On day 15 post-injury, central nucleation almost disappeared.② The molecule marker of M1 macrophages(CD68) increased significantly post-injury, and the molecule marker of M2 macrophages(CD206 and CD163) increased significantly later.③ MCP-1 and CCR2 mRNA increased significantly post-injury(P < 0.01).SDF-1 mRNA increased significantly at 12 h, 10 d and 15 d (P < 0.01).However, CXCR4 mRNA did not change significantly post injury.④ The results showed that there was significant correlation between MCP-1 and CD68, and CCR2.In addition, there was significant correlation between SDF-1 and CXCR4.

  Conclusion  MCP-1/CCR2 may be involved in the chemotaxis of M1 macrophages during skeletal muscle regeneration post-injury.