The cytotoxic effect of titanium particles phagocytosed by osteoblasts

The cytotoxic effect of different concentrations of titanium particles on o steoblasts was studied in vitro. It was found that the viability of the ost eoblasts was inversely proportional to the particle concentration. Phagocyt osis of particles by the osteoblasts was evident and was demonstrated to be responsible for cell necrosis. Moreover, during and after phagocytosis, th e osteoblasts released products that were cytotoxic for other osteoblasts, as established with a conditioned medium assay. The titanium particles thus had both a direct and an indirect effect on osteoblast viability. It also was observed that the titanium particles induced a process of programmed ce ll death (apoptosis) when co-cultured with osteoblasts. The results of this study suggest that not only is the amount of wear debris generated importa nt, but the local accumulation of the debris also may have a significant im pact on bone cell function. (C) 1999 John Wiley & Sons, Inc. J Biomed Mater Res, 46, 399-407, 1999.