Histological analysis
The mouse knee samples were fixed with 4% paraformaldehyde solution for 48 h and then decalcified with 0.5 M ethylenediaminetetraacetic acid (EDTA) until the tissues became soft. The samples were embedded in paraffin and cut into 5 mm sections by a microtome. The tissue sections were subsequently stained with safranin O and then observed by optical microscopy. The OARSI grading system (0–6) was used to evaluate the sections.