Fig. 1: Damaged microglia rapidly produce IL-1α at the site of spinal cord contusion in mice.

a Representative confocal image showing IL-1α immunostaining (green) in the spinal cord of an injured Cx3cr1^Cre::Rosa26^TdT transgenic mouse, in which microglia express the fluorescent reporter Td-Tomato (TdT, red), at 4 h post-SCI. White arrowheads point to specific double-labeled cells. b–d Confocal immunofluorescence images showing expression of IL-1α (blue) in microglia (TdT, red), but not macrophages (LysM, green), in the spinal cord of an injured LysM-eGFP::Cx3cr1^CreER::R26-TdT mouse at 4 h post-SCI. e, f Quantification of IL-1α-positive (+) cells and IL-1α⁺TdT⁺ microglia at the lesion epicenter in untreated Cx3cr1^Cre::Rosa26^TdT mice (e n = 3 at 4 h, n = 9 at 24 h, n = 6 at 4 days, n = 3 at 7 days, n = 4 at 14 days, n = 3 at 35 days) and fluorescent reporter mice treated with PLX5622 or the control diet (f n = 3 control diet 4 h, n = 3 PLX diet 4 h, n = 4 control diet 24 h, n = 4 PLX diet 24 h, n = 3 control diet 4 days, n = 3 PLX diet 4 days) and killed at various time points post-SCI. g–r High magnification confocal images of IL-1α⁺ TdT⁺ microglia revealed that these cells often exhibit damaged cell bodies and processes (g–l) or have retracted, swollen processes, indicative of an activated status (m–r). White arrowheads point to relevant cell morphologies reminiscent of damaged (g–l) or activated (m–r) cells. Nuclear staining (DAPI) is shown in blue (i, l, o, r) in the merged images. Data are presented as mean values + /− SEM and statistical significance was determined by a one-way (e) or two-way (f) ANOVA with Bonferroni’s post-hoc test. Pairwise comparisons and p-values are indicated in the graphs. Scale bars: (a) 50 µm, (b–d, in d) 50 µm, (g–r, in r) 10 µm.