Fig 2: S100B, FGF1 and FGFR1 expression levels are increased in OA model rabbits. (A) Increased expression levels of S100B, FGF1 and FGFR1 mRNA in OA rabbits compared with Control rabbits were determined by reverse transcription-quantitative polymerase chain reaction. (B) Increased protein expression levels of S100B, FGF1 and FGFR1 were determined by western blotting. (C) Immunohistochemical analysis demonstrated increased S100B-specific staining and decreased type II collagen staining in OA rabbits compared with Control rabbits. *P<0.05 vs. Control. FGF, fibroblast growth factor; FGFR, FGF receptor; OA, osteoarthritis.

Fig 3: BALBc mice showed increased levels of glial markers in the dorsal hippocampus. Brain specimens were collected from the dorsal hippocampus of B6N and BALBc mice at the end of Experiments 1 and 2 corresponding to an age of 3 vs. 12 months. Protein simple measurements revealed elevated levels of microglia (IBA-1) and astrocytic (S100B, GFAP) markers in BALBc compared to B6N. If possible, data were normalized to the mean of B6N. In some cases, the signal was too weak for quantification (n.q.) which precluded normalization. *p < 0.05, ****p < 0.0001 (t-test), ##p < 0.01 (Mann–Whitney U-test).

Fig 4: Axonal IFN? upregulates cGAS in the non-neuronal cells of the sciatic nerve to promote regeneration(A) Western blots of IFN? and cGAS in sciatic nerve lysate at different time points after injury.(B) Quantification of IFN? expression level in (A). ANOVA followed by Dunnett’s test, n = 3 mice.(C) Quantification of cGAS expression level in (A). n = 3 nerves. ANOVA followed by Dunnett’s test, n = 3 mice.(D) Sections of intact or 3 dpc sciatic nerves from WT animal, stained with cGAS (red) antibody. Asterisk labels the lesion site. Scale bars, 200 µm.(E) Section of a sciatic nerve from WT animal at 3 dpc was stained with Tuj1 (green) and cGAS (red). Arrowhead labels cGAS+/Tuj1— cells. Scale bars, 50 µm.(F) Section of a sciatic nerve from WT animal at 3 dpc was stained with CD45 (green) and cGAS (red). Arrow labels double-positive cells and arrowhead labels cGAS+/CD45— cells. Scale bars, 50 µm.(G) Section of a sciatic nerve from WT animal at 3 dpc was stained with S100b (green) and cGAS (red). Arrow labels double-positive cells and arrowhead labels cGAS+/ S100b— cells. Scale bars, 50 µm.(H) Western blots of cGAS in sciatic nerve lysate at 1 dpc. Ctrl, IFNAR1 or IFNGR1 neutralizing antibodies were injected into the sciatic nerve after injury.(I) Quantification of cGAS expression in (H). n = 3–4 nerves. ANOVA followed by Dunnett’s test.(J) A diagram shows the method of sciatic nerve injection of DMSO vehicle or RU.521.(K) Representative sections from sciatic nerves of WT animals with DMSO vehicle or RU.521 injection. Scale bars, 200 µm.(L) Quantification of sensory axon regeneration in (K). Student’s t test, n = 4–5 mice. Mean ± SEM; *p < 0.05, **p < 0.01. See also Figure S7.

Fig 5: FGFR1 mediates the inflammatory effects of S100B. (A) FGFR1 mRNA expression levels were increased or decreased in S100B-overexpressing and S100B-siRNA synovial fibroblasts, respectively, as measured by RT-qPCR. (B) FGFR1 protein expression levels were increased or decreased in S100B-overexpressing and S100B-siRNA synovial fibroblasts, respectively, as measured by western blotting. (C) Validation of the FGFR1 knockdown FGFR1, by RT-qPCR. (D) RT-qPCR and (E) western blotting were used to determine FGFR1 expression levels in LPS-simulated S100B overexpressed synovial fibroblasts. Increased FGFR1 expression induced by LPS and S100B overexpression was significantly attenuated by FGFR1 siRNA. (F) TNF-a expression levels were decreased following FGFR1 knockdown in LPS-simulated, S100B-overexpressing synovial fibroblasts. (G) IL-1ß expression levels were decreased following FGFR1 knockdown in LPS-simulated, S100B-overexpressing synovial fibroblasts. **P<0.01 vs. LPS + Empty vector or LPS + Scrambled siRNA; †P<0.05 vs. LPS + Empty vector; $P<0.05 vs. LPS + Scrambled siRNA; #P<0.05 vs. LPS + S100B + Scrambled siRNA. IL-1ß, interleukin 1ß; FGFR, fibroblast growth factor receptor; LPS, lipopolysaccharide; RT-qPCR, reverse transcription-quantitative polymerase chain reaction; siRNA, small interfering RNA; TNF-a, tumor necrosis factor.