BIOMATERIAL PARTICLE PHAGOCYTOSIS BY BONE-RESORBING OSTEOCLASTS

Abundant implant-derived biomaterial wear particles are generated in a septic loosening and are deposited in periprosthetic tissues in which they are phagocytosed by mononuclear and multinucleated macrophage-lik e cells. It has been stated that the multinucleated cells which contai n wear particles are not bone-resorbing osteoclasts. To investigate th e validity of this claim we isolated human osteoclasts from giant-cell tumours of bone and rat osteoclasts from long bones. These were cultu red on glass coverslips and on cortical bone slices in the presence of particles of latex, PMMA and titanium. Osteoclast phagocytosis of the se particle types was shown by light microscopy, energy-dispersive X-r ay analysis and SEM. Giant cells containing phagocytosed particles wer e seen to be associated with the formation of resorption lacunae. Oste oclasts containing particles were also calcitonin-receptor-positive an d showed an inhibitory response to calcitonin. Our findings demonstrat e that osteoclasts are capable of phagocytosing particles of a wide ra nge of size, including particles of polymeric and metallic biomaterial s found in periprosthetic tissues, and that after particle phagocytosi s, they remain fully functional, hormone-responsive, bone-resorbing ce lls.