Correlation between sintering temperature of hydroxyapatite particles and the production of inflammatory cytokines by human monocytes

Osteolysis remains the most important problem in orthopaedic implant failure. Wear debris from the implant contains hydroxyapatite particles which have show to activate monocyte cells. Although the response of monoccytes has been observed to be influenced by size and shape of the hydroxyapatite particles, little is known on the effect of surface properties on inflammatory cytokines production. In this study, human monocytes have been exposed to hydroxyapatite particles sintered at different temperatures (not sintered, sintered at 600 and 1180°C. We show that the sintering temperature modifies the crystal size and the pH of zero charge of the particles. Moreover, interleukin 1-beta, tumor necrosis factor-alpha and interleukin-6 secretion were evaluated as a function of the sintering temperature because they play a key role in the osteoclast cells differentiation. The level of secretion was small compared to the production induced by zymosan particles. But we demonstrate in the present paper that the particles sintered at the highest temperature induced the most important production of the cytokines studied