Investigation for effects of iNOS on biological function of chondrocytes in rats with post-traumatic osteoarthritis.

OBJECTIVE: Inducible nitric oxide synthase (iNOS) is one rate-limiting enzyme in nitric oxide (NO) synthesis, and plays a role in mediating cell proliferation, apoptosis, and inflammation. Post-traumatic arthritis (PTA) is secondary after osteoarthritis (OA). This study thus established rat PTA model, on which the role of iNOS in PTA pathogenesis was investigated. MATERIALS AND METHODS: Chondrocytes and synovial fluids were collected for comparing NO content and iNOS activity. In vitro cultured PTA rat chondrocytes were tested for expression of iNOS, matrix metallopeptidase 13 (MMP-13), and alpha-1 chain of type II collagen (COL2A1) expression with or without Interleukin 1β (IL-1β) treatment. NO content and iNOS activity in the supernatant were measured, followed by flow cytometry for Ki-67 expression and apoptosis. IL-1β treated cells were transfected with small interfere iNOS (si-iNOS), followed by expressional assay of iNOS, MMP-13 and Col2A1, activity assay of NO and iNOS, plus Ki-67 level and apoptosis. RESULTS: Compared to Sham group, PTA model rats had higher iNOS expression, NO content, and iNOS activity. IL-1β treatment remarkably elevated iNOS and MMP-13 expression in chondrocytes, it decreased COL2A1 expression, increased NO content and iNOS activity, whilst suppressed cell proliferation to facilitate apoptosis. Silencing of iNOS expression decreased iNOS or MMP-13 expression, increased COL2A1 expression, suppressed NO or iNOS content, potentiated proliferation and decreased apoptosis. CONCLUSIONS: iNOS expression and NO content were elevated in PTA rat chondrocyte. iNOS and NO production can facilitate chondrocyte apoptosis and matrix degradation, and suppress chondrocyte proliferation, thus playing a role in PTA pathogenesis.