Particulate Joint Replacement Materials Induce Apoptosis of Rabbit Synoviocytes Cell Line HIG-82 through c-Jun N-Terminal Kinase (JNK) Pathway

Many studies have focused on the biological responses of macrophages, osteoblasts, and osteoclasts cells after knee joint replacements. However, synoviocytes are also in close contact with wear particles within the joint cavity; their responses would influence other cells, and they may serve as inflammatory cells around the knee joint. Therefore, in this study we have examined the affects of 1~2 Vm wear particles on synoviocytes (HIG-82 cell) through cell viability, apoptosis and immunoblotting assays. The results indicated that metal cobalt particles induced significant apoptosis and activated JNK (c-jun N-terminal kinase), in turn causing apoptosis of HIG-82 cells. In contrast to cobalt particles, titanium dioxide was not significant in causing apoptosis in HIG-82 cells. This study proposes a pathway of apoptosis involving JNK activation. It may be an important concept for the prevention of prosthesis loosening.