Fig. 4

Mer modulated microglial/macrophage M1/M2 polarization after TBI. a Representative images of immunofluorescent staining for Mer (red), CD16/32 (green), and DAPI (blue) showing Mer was expressed in CD16/32-positive cells in the perilesional area of cortex at 3 days post-TBI. Scale bar = 10 μm. b Representative images of immunofluorescent staining for Mer (red), CD206 (green), and DAPI (blue) showing Mer was expressed in CD206-positive cells in the perilesional area of cortex at 3 days post-TBI. Scale bar = 10  μm. c Representative images of immunofluorescent staining for CD16/32 (red), Iba-1 (green), and DAPI (blue) in the ipsilateral cortex at 3 days post-TBI. Scale bar = 50 μm. d Quantification showing the percentage of CD16/32 and Iba-1 double-positive cells was significantly increased in the cortex on day 3 after TBI, which was further elevated in the Mer siRNA group. n = 6 mice per group. e Representative images of immunofluorescent staining for Mer (red), CD206 (green), and DAPI (blue) in the ipsilateral cortex at 3 days post-TBI. Scale bar = 50 μm. f Quantification showing the percentage of CD206 and Iba-1 double-positive cells increased significantly in the ipsilateral cortex on day 3 after TBI; however, it significantly decreased following Mer siRNA administration. g The ratio between CD16/32⁺ Iba-1⁺ M1-like cells and CD206⁺ Iba-1⁺ M2-like cells nearly doubled after Mer siRNA administration. In d, f, and g, data are presented as mean ± SD; #, p < 0.05; ***, p < 0.001; ns, nonsignificant, p > 0.05. One-way ANOVA followed by Bonferroni’s post hoc tests