Effects of prostaglandin E2 on macrophages and osteoclasts in cultured fetal long bones.

Bone cultures exposed to prostaglandin E2 (PGE2) and revealed an increase in 45Ca release from bone to medium and an increase in osteoclast number compared to control bones. In addition, PGE2-treated osteoclasts contained a more extensive ruffled border region than control osteoclasts. These data suggest that PGE2 activates existing osteoclasts and causes proliferation and differentiation of osteoclast precursor cells. The existence of macrophages in resorbing fetal bone explants was documented. These macrophages contain numerous phagolysosomes and lipid vacuoles and are often located adjacent ot osteoclasts or closely apposed to calcified tissue surfaces. PGE2 caused an early increase in the number of macrophages. It is postulated that fetal bone macrophages are primarily engaged in phagocytosis and digestion of cellular debris, but also play a role in the process of bone resorption.