Polyethylene particles stimulate expression of ITAM-related molecules in peri-implant tissues and when stimulating osteoclastogenesis in vitro

Wear particle-induced orthopaedic prosthesis loosening is associated with elevated osteoclast activity. The immunoreceptor tyrosine-based activation motif (ITAM)-related molecules OSCAR, FcR gamma, TREM2 and DAP12 are important for osteoclast formation. The aim of this study was to determine if these molecules are involved in pen-implant loosening by investigating their expression in pen-implant tissues obtained at revision of joint replacement components containing polyethylene (PE) wear particles, and in osteoclasts formed in vitro in the presence of PE particles. The results showed that there was a marked and statistically significant increase in protein levels of the ITAM-related molecules in the revision tissues. The levels of OSCAR, FcR gamma, TREM2 and DAP12 mRNA in the revision tissues were also increased. In vitro PE particles stimulated osteoclast resorption in the presence of 50 ng ml(-1) receptor activator NF kappa B (RANKL) and significantly elevated the expression of OSCAR, FcR gamma, TREM2 and DAP12 during osteoclast formation. These findings suggest that the ITAM signalling molecules and their co-receptors have a role in pathogenic bone loss associated with implant PE wear. (c) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.