PI3Kγ Deletion Reduces Variability in the In Vivo Osteolytic Response Induced by Orthopaedic Wear Particles

Orthopedic wear particles activate a number of intracellular signaling pathways associated with inflammation in macrophages and we have previously shown that the phosphoinositol-3-kinase (PI3K)/Akt pathway is one of the signal transduction pathways that mediates the in vitro activation of macrophages by orthopedic wear particles. Since PI3K gamma is primarily responsible for PI3K activity during inflammation, we hypothesized that PI3K gamma mediates particle-induced osteolysis in vivo. Our results do not strongly support the hypothesis that PI3K gamma regulates the overall amount of particle-induced osteolysis in the murine calvarial model. However, our results strongly support the conclusion that variability in the amount of particle-induced osteolysis between individual mice is reduced in the PI3K gamma(-/-) mice. These results suggest that PI3K gamma contributes to osteolysis to different degrees in individual mice and that the mice, and patients, that are most susceptible to osteolysis may be so, in part, due to an increased contribution from PI3K gamma. (C) 2011 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29: 1649-1653, 2011