IHC
After rats were euthanized, cartilage was harvested, and the articular part of the right knee of rats was isolated and then dehydrated, decalcified, and embedded in paraffin. The knee articular tissue was placed in EDTA decalcification (Servicebio, Wuhan, China) solution and shaken at 120 rpm at a constant temperature (25 ℃ ~ 30 ℃). Longitudinal-oriented sections (3 µm) of the knee joint were cut using a paraffin microtome (RM2265, Leica, Germany). The primary antibodies used were anti-IL-6 (1:500, Sigma-Aldrich) and anti-MMP-13 (1:50, Absin, Shanghai, China). IHC labelling was applied as routine technology. In brief, after being blocked with 10% goat serum for 20 min at room temperature, sections were incubated with primary antibodies for 1 h at 37 ℃ . Horseradish peroxidase-labelled secondary antibodies were added and stood at room temperature for 1 h. The nucleus was then stained by mounting medium with DAPI and observed with a digital pathology image scanner (version 12.3.3.5048, Leica, Wetzlar, Germany).