Biphasic influence of PGE2 on the resorption activity of osteoclast-like cells derived from human peripheral blood monocytes and mouse RAW264.7 cells

Osteoclasts are large bone-resorbing cells of hematopoietic origin. Their main function is to dissolve the inorganic component hydroxyapatite and to degrade the organic bone matrix. Prostaglandin E-2 (PGE(2)) indirectly affects osteoclasts by stimulating osteoblasts to release factors that influence osteoclast activity. The direct effect of PGE(2) on osteoclasts is still controversial. To study the influence of PGE(2) on osteoclast activity, human peripheral blood monocytes (hPBMC) and mouse RAW264.7 cells were cultured on osteoblast-derived extracellular matrix. hPBMC and RAW264.7 cells were differentiated by the addition of macrophage colony-stimulation factor and receptor activator of NF kappa B ligand and treated with PGE(2) before and after differentiation induction. The pit area, an indicator of resorption activity, and the activity of tartrate-resistant acid phosphatase were dose-dependently inhibited when PG(E)2 was present ab initio, whereas the resorption activity remained unchanged when the cells were exposed to PGE(2) from day 4 of culture. These results lead to the conclusion that PGE(2) treatment inhibits only the differentiation of precursor osteoclasts whereas differentiated osteoclasts are not affected. (C) 2016 Elsevier Ltd. All rights reserved.