Figure 4.

CCR2 deficiency blocked MO/MP recruitment into injured muscle_.. A) Flow cytometry showed a markedly increased number of intramuscular macrophages in wild-type mice at d 3 and 7, with the peak at d 3 (a). The number of intramuscular macrophages in Ccr2^−/− mice was also increased after injury (a) but was significantly reduced at d 3 and 7 as compared with wild-type mice. The number of neutrophils in Ccr2^−/− mice was increased at d 3 as compared with wild-type mice (b). B) Flow cytometry at baseline showed that the percentage of 7/4⁺Ly-6G⁻ MOs/MPs (a) was increased in bone marrow but reduced in blood in Ccr2^−/− mice as compared with wild-type controls. At d 3 postinjury, the percentage of 7/4⁺Ly-6G⁻ MOs/MPs (d) was also increased in bone marrow and reduced in blood in Ccr2^−/− mice. The numbers of 7/4⁺Ly-6G⁻ MOs/MPs per femur were significantly higher in bone marrow (BM; b, e) but lower in blood (c, f) at baseline (b, c) and d 3 (e, f) in Ccr2^−/− mice than those in wild-type mice. Bone marrow monocyte transfer showed that the number of Ccr2^RFP/+ monocytes recruited into wild-type injured muscle at d 3 was significantly higher than that of Ccr2^RFP/RFP monocytes (lacking CCR2) (g, h). C) Flow cytometry at d 3 showed that the numbers of F4/80⁺ MOs/MPs were reduced in blood and in injured muscle of Ccr2^−/− mice (a), among which the Ly-6C⁺ but not the Ly-6C⁻ subset was significantly reduced in blood (b). However, both Ly-6C⁺ and Ly-6C⁻ subsets were significantly reduced in injured muscle of Ccr2^−/− mice (c). n = 5–7 mice/group/experiment. *P < 0.05; **P < 0.01; ***P < 0.001.