Effect of osteopontin on TIMP-1 and TIMP-2 mRNA in chondrocytes of human knee osteoarthritis in vitro

Tissue inhibitors of metalloproteinases (TIMPs) regulate the activity of matrix metalloproteinases (MMPs) and enzymes from the a disintegrin and metalloproteinase domain with thrombospondin motifs family in osteoarthritis (OA). Elevated osteopontin (OPN) levels in plasma, synovial fluid and articular cartilage are associated with progressive OA joint damage; however, the role of OPN in the pathological changes of knee OA remains undetermined. The present study was undertaken to examine the effect of OPN on the expression of TIMP-1 and TIMP-2 mRNA in chondrocytes from 16 patients with knee OA. In this study, following the stimulation of human chondrocytes with recombinant human OPN (rhOPN; 100 ng/ml and 1 μg/ml, respectively) for 48 h, MTT assay was used to determine cell viability while the quantitative polymerase chain reaction (PCR) was used to detect the alterations in TIMP-1 and TIMP-2 levels. The results illustrated that neither 100 ng/ml nor 1 μg/ml rhOPN caused cytotoxicity or apoptosis of chondrocytes and that the relative mRNA expression of TIMP-1 and TIMP-2 was significantly increased in the 1 μg/ml rhOPN group compared with that in the control group (P=0.022 and P=0.003, respectively). However, no significant difference in expression was revealed between the 100 ng/ml rhOPN and control groups (P=0.998 and P=0.209, respectively). In conclusion, OPN may have a protective effect against pathological changes in advanced-stage OA.