Experimental design
A total of 84 rats were included in the two experiments of this study. The experimental timeline and the sample size of rats are illustrated in Figure 1. Experiment 1 included 36 rats and were randomly divided into the control group, OA group and OA+HIIT group (N = 12/group). Experiment 2 included 48 OA rats and were randomly divided into the OA group, OA+HIIT group, OA+C-A1 group, and OA+C-A1+HIIT group (N= 12/group). Jak2/Stat3 pathway activator (C-A1, 100ug/kg/d, MedChemExpress, New Jersey, USA) was administered by intraperitoneal injection in the third week for 28 days [24]. HIIT treatments were conducted in the fourth week and continued for six weeks. After six weeks of exercise, the L3-L5 segments of the spinal cord tissue were harvested and analyzed by proteomics sequencing, quantitative real-time polymerase chain reaction (qRT-PCR), flow cytometry, Western blot (WB) and immunofluorescence (IF). Immunohistochemistry (IHC) was used to detect the matrix metalloproteinase 13 (MMP-13) and IL-6 in the extracellular matrix of articular cartilage.