Fig. 2

Chemokine receptor CXCR4 and its ligand CXCL12 are expressed by astrocytes. a–d Double labeling of CXCR4 and GFAP on spinal cord cross sections of castrated males at 30 dpl. Cell nuclei were counterstained in blue with DAPI. Within the LPC lesion, delimited by the dotted line, CXCR4 and GFAP staining were very low in males receiving an empty implant (LPC), but high levels of CXCR4 and GFAP colocalized in males receiving an implant filled with T (LPC + T) (a, b, d). a′ represents the enlargement of CXCR4/GFAP colabeling under the LPC + T condition. AMD3100 blocked the T-dependent appearance and colocalization of CXCR4 and GFAP inside the lesion. The arrival of CXCR4⁺ astrocytes in the lesion coincided with their reduction at the borders (c, e). f–i, Double labeling of CXCL12 and GFAP on spinal cord cross sections of castrated males at 30 dpl. CXCL12 and GFAP staining were very low in control males (LPC), but elevated in males receiving an implant filled with T (LPC + T). f′ represents the enlargement of CXCL12/GFAP colabeling under the LPC + T condition. AMD3100 blocked the T-dependent appearance and colocalization of CXCL12 and GFAP inside the lesion. The arrival of CXCL12⁺ astrocytes in the lesion was not accompanied by a reduction in CXCL12 staining at the borders (h). Arrows indicate no overlapping of CXCR4 and GFAP expression in a′ and expression of CXCL12 in GFAP⁺ cells bodies in f′. Arrow heads indicate no expression of CXCR4 (a′) and CXCL12 (f′) in the whole astrocyte branching. Data are presented as means ± S.E.M. (one-way ANOVA with Tukey's multiple comparisons tests). Asterisks mark significant differences. ***P < 0.001, *P < 0.05. Scale bars: 20 µm in a and f and 10 µm in a′ and f′