Fig. 7

Intraperitoneal injection of PD-1 inhibitor suppresses microglial proliferation and scar formation, hinders axon regeneration, and prevents locomotor function recovery after SCI in vivo. A The schedule described that the mice were treated with PD-1 inhibitor at 1 and 14 dpi via intraperitoneal (i. p.) injection and were sacrificed at 28 dpi. B Immunofluorescence staining of BrdU (magenta), CX3CR1 (green) in sagittal sections of the PBS (control) and PD-1 inhibitor groups at 7 dpi in vivo. Scale bar: 20 μm. C Quantification of the density of BrdU⁺CX3CR1⁺ cells in (B). All data are presented as the mean ± SEM, n = 3 mice per group, **p < 0.01. D Immunofluorescence staining of CX3CR1 (red) in control and PD-1 inhibitor groups at 28 dpi in vivo. Scale bar: 100 μm. E Quantification of the density of CX3CR1⁺ cells in (D). All data are presented as the mean ± SEM, n = 3 mice per group, **p < 0.01. F Images of astrocytes (GFAP⁺, green) stained with neurons (NeuN⁺, magenta) in Zone1-Zone3 (Z1_Z3) at 28 dpi in PD-1 inhibitor and control groups in vivo. Scale bar: 100 μm. G Quantification of NeuN⁺ neurons in three zones (Z1_Z3) in (F). All data are presented as the mean ± SEM, n = 3 mice per group, **p < 0.01. H Images of GFAP (green) co-stained with axons (5-HT, magenta) at 28 dpi in PD-1 inhibitor and control groups in vivo. Asterisks indicate the lesion site, scale bars: low magnification, 100 μm; high magnification, 20 μm. I Quantification of the percentage of 5-HT⁺ area in the area of the spinal cord segment penetrating into the lesion core at 28 dpi in (H). All data are presented as the mean ± SEM, n = 3 mice per group, **p < 0.01. J Locomotor function was evaluated by BMS at the indicated time points in PD-1 inhibitor and control groups. All data are presented as the mean ± SEM, n = 8 mice per group, *p < 0.05; ***p < 0.001; ****p < 0.0001. K Representative images of footprint analysis in PD-1 inhibitor and control groups at 28 dpi. L, N Quantification of the paw rotation, stride width and stride length at 28 dpi. All data are presented as the mean ± SEM, n = 8 mice per group, **p < 0.01; ****p < 0.0001