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Objectives To investigate the expression of Sam68 in articular cartilage of knee osteoarthritis and the relationship between Sam68 and NF-κB activation and apoptosis signaling in OA articular chondrocytes. Methods:Safranin-O staining and the OARSI scores were performed to assay the glycosaminoglycan content and articular cartilage. Sam68 expression in normal and osteoarthritic cartilage was assessed by immunohistochemistry and RT-PCR on both meniscal/ligamentous injury (MLI)-induced OA rat model and the clinical human OA cartilage tissues. TNF-α was applied to create a cellular model of OA using SW1353 chondrocytes-like cells. Sam68 expression in OA chondrocytes was also assessed by immunoblot. Inhibiting Sam68 in OA chondrocytes was conducted using small interfering RNA and its influence on the expression of apoptotic marker (cleaved caspase-3 and cleaved PARP) and catabolic genes (MMP-13, ADAMTS-5, iNOS and IL-6) were examined by immunoblot. Co-immunoprecipitation and immunoblot were applied to analysis nuclear and cytoplasmic fractions of OA chondrocytes for p65, IκBα and Sam68. Results:Glycosaminoglycan content was decreased in the MLI injured rat and the OARSI scores in the MLI injured rats were significantly increased(P<0.05). The surface of articular cartilage were destroyed compared with the control rats. Sam68 expression was increased in OA cartilage tissues and OA chondrocytes. Inhibition of Sam68 by siRNA significantly decreased the expression of apoptotic markers (cleaved caspase-3 and cleaved PARP) in OA chondrocytes. Sam68 knockdown suppressed Iκ-B degradation and p65 nuclear transportation in OA chondrocytes, indicating a suppressed NF-κB activation. In OA chondrocytes, the nuclear transportation of Sam68 and its interaction with p65 was detected. Furthermore, Sam68 knockdown also alleviated catabolic marker (MMP13, ADAMTS5, iNOS and IL-6) expression in OA chondrocytes. Conclusions:Sam68 expression was increased in OA cartilage tissues. The highly expressed Sam68 promotes NF-κB signaling activation, catabolic gene expression and cellular apoptosis in OA chondrocytes, which may provide better insights into the pathophysiology of OA and a potential target for its treatment.