Figure legend
Figure 1 Study design and timeline. The rats were injected with monosodium iodoacetate to induce an osteoarthritis (OA) model. In experiment 1: The rats were randomly divided into a control group, an OA group and an OA+HIIT group (N= 12/group). Control rats received an intraarticular injection of an equal volume of normal saline. HIIT was conducted in the fourth week and consecutively exercised for six weeks. In experiment 2: OA rats were randomly divided into the OA group, OA+HIIT group, OA+ C-A1 group and OA+ C-A1+HIIT group (N= 12/group). In the third week of the OA model, rats were given an intraperitoneal injection of C-A1 to activate the Jak2/Stat3 pathway, followed by HIIT intervention in the fourth week.
Figure 2 Body weight and pain threshold of rats in each group. A: Changes in body weight after MIA injection into the right knee of control rats, OA rats, and OA+HIIT rats. N=6/ group, two-way repeated measures ANOVA with Tukey and Bonferroni tests as post hoc tests. B: The von Frey method measured the Mechanical withdrawal threshold (MWT). N=6/ group, repeated measures ANOVA with Tukey and Bonferroni tests as post hoc tests. **P < 0.01, ***P < 0.001. C: Changes in body weight after MIA injection into the right knee of OA rats, OA+HIIT rats, OA+ C-A1 rats, and OA+ C-A1+HIIT rats. N=6/ group, two-way repeated measures ANOVA with Tukey and Bonferroni tests as post hoc tests. D: The von Frey method measured the Mechanical withdrawal threshold (MWT). N=6/ group, repeated measures ANOVA with Tukey and Bonferroni tests as post hoc tests. *P < 0.05, ***P < 0.001.
Figure 3 HIIT reversed the osteoarthritis (OA)-induced inflammatory response. A: The content levels of SP and IL-6 in the serum of rats. N=6, one-way ANOVA, *P < 0.05, ***P < 0.001. B-C: Representative immunohistochemical images and quantitative analysis of MMP-13 and IL-6 in the extracellular matrix, blue is the nucleus, brown is target protein expression, scale =100 μm. One-way ANOVA, *P < 0.05, **P < 0.01, ***P < 0.001.
Figure 4 HIIT drove the pheno-typic transformations of microglia and down-regulated pain factors. A: The representative images of immunofluorescence in the microglia (blue is denoted for the nucleus and gold is for Tmem119 protein; scale bar = 100 µm) and quantitative analysis of Tmem119. N = 6 each group, ***P  < 0.001. B: Flow cytometry analysis and quantification of CD68 and CD163 in microglia. N= 6 each group, **P  < 0.01. C: Representative western blotting images of Glu, c-fos, SP, and IL-6, and quantification. N= 6 each group. One-way ANOVA, *P  < 0.05, **P  < 0.01, ***P  < 0.001.
Figure 5 The quantitative technique of protein mass spectrometry and KEGG pathway analysis. The protein sequencing approach was used to map the transcriptome of OA and OA+HIIT rats. (A) Heat map of the differentially expressed genes. (B) Protein-protein interaction (PPI) network shows the interactions among different proteins. (C-D) The top 20 KEGG pathways were enriched between OA and OA-HIIT groups. (E) The differentially expressed genes were shown in the volcano plot, with red denoted for up-regulation and blue for down-regulation. (F) The main proteins involved in Jak2/Stat3 signalling pathway were analyzed by qRT-PCR. N= 6 each group. *P  < 0.05 vs. OA.
Figure 6 HIIT promoted the pheno-typic transformations of microglia and relieved pain in OA rats through Jak2/STAT3 pathway. A-B: Flow cytometry analysis and quantification of CD68 and CD163 in microglia. N = 6 each group. ***P   < 0.001. C: Representative western blotting images of Glu, c-fos, SP, and IL-6, and quantification. N = 6 each group. *P   < 0.05, **P   < 0.01.