Objective       To determine the change of matrix metalloproteinases 13 (MMP-13) expression in the articular cartilage of osteoarthritis mice and investigate its correlation with articular injury.       Methods       Murine articular chondrocytes were isolated from neonatal mice and cultured primarily

and then treated with 10 ng/mL interleukin-1β (IL-1β) for 24 h. The mRNA expression of MMP-13 was detected by quantitative real-time reverse transcriptase-polymerase chain reaction. A total of 30 C57BL/6J mice were randomly divided into 3 groups

normal control (n=10)

osteoarthritis group 1 (n=10) and osteoarthritis group 2 (n=10). The osteoarthritis model was induced by surgical destabilization of the medial meniscus (DMM). Ten mice of the model group 1 were killed in 5 weeks after surgery

while the other 10 of group 2 were in 10 weeks. The articular cartilage was observed histologically

and the expression level of MMP-13 in impaired articular cartilage was measured by immunohistochemical assay.        Results        IL-1β induced increased mRNA expression of MMP-13 in primary cultured murine articular chondrocytes. Articular cartilage in mice with DMM surgery exhibited features of osteoarthritis

and the injury became more severe with the time elapsing. Immunohistochemical assay showed that the expression of MMP-13 was enhanced in 5 weeks after DMM surgery

and continually increased in 10 weeks post-operatively.       Conclusion       MMP-13

as a chondro-destructive marker

is of high expression in the articular cartilage

and plays an essential role in the process of osteoarthritis.