Hydroxyapatite-induced Phagocytic Activity by Murine Macrophages in vitro

The aim of the present study was to assess phagocytic activities of murine macrophages (RAW264.7 cell line) to hydroxyapatite (HA) particles. Transmission electron microscope (TEM) was used to assess localization of HA particles in the cells at 7, 15, 30 and 60 min. The HA particles and latex beads, as a control, were also incubated with the cells pretreated with various concentration of cytochalasin B or colchicine. Phagocytic index (PI) was used to determine the phagocytic activity at one hr of incubation. TEM analysis showed that HA particles were in direct contact with the cells at 7 min with a few particles located within cell vacuoles. The cells increasingly phagocytosed the particles up to 60 min. Cytochalasin B or colchicine significantly inhibited phagocytic activity of the cells to both HA particles and latex beads in a dose-dependent fashion. Therefore, the results of the present study suggest that HA particles may induce phagocytic activity of RAW264.7cells in an actin and microtubule polymerization-dependent mechanism.