Protection against titanium particle induced osteolysis by cannabinoid receptor 2 selective antagonist

Osteolysis and subsequent aseptic loosening are the most common causes of failure of total joint arthroplasty. Osteolysis is initiated by inflammatory response to wear debris, resulting in localized, osteoclastic peri-implant bone loss. However, there were no effective measures for prevention and treatment of periprosthetic osteolysis. The aim of the current study was to determine whether CB2 selective antagonist (AM630) inhibits wear debris-induced osteolysis in a murine osteolysis model. Titanium (Ti) particles were introduced into established air pouches on BALB/c mice, followed by implantation of calvaria bone from syngeneic littermates. AM630 was given to mice intraperitoneally 2 days before Ti particles introduction and maintained until the sacrifice of the mice. Mice without drug treatment, as well as mice injected with saline alone, were included. Each group contains 10 mice. Pouch tissues were harvested 14 days after bone implantation for histological and molecular analysis. Ti particles stimulation significantly increased CB2 expression. However, less CB2 was observed in AM630 treatment group. AM630 inhibited Ti particle-induced osteolysis associated gene activity of RANK, RANKL and CPK, and diminished RANKL expression in Ti particle stimulated pouches. AM630 markedly reduced the number of TRAP+ cells in pouch tissues. In conclusion, this study provides the evidence that blockage of CB2 with AM630 can markedly reduce Ti particle induced osteolysis in a murine air pouch model. This finding points to the possibility that CB2 selective antagonists like AM630 may have potential value for prevention and treatment of wear particle induced osteolysis.