PROSTAGLANDIN E(2) STIMULATES PREOSTEOBLAST REPLICATION - AN AUTORADIOGRAPHIC STUDY IN CULTURED FETAL-RAT CALVARIAE

To determine the mechanism for the anabolic effect of prostaglandins ( PGs) on bone, [H-3]thymidine(TdR) autoradiography was performed to loc alize the cells that replicate and to determine the fate of these labe led cells over time in cultured 20-day fetal rat calvariae. Treatment of bone organ cultures for 24 or 96 h with cortisol significantly decr eased the number of [H-3]TdR-labeled osteoblasts and periosteal cells. Treatment of bones with 0.1 or 1 mu M PGE(2) alone had no effect on [ H-3]TdR labeling of the osteoblast layer but doubled the number of lab eled periosteal cells compared to control bones at 24 h. However, when both cortisol and PGE(2) were added together, the number of labeled o steoblasts and periosteal cells increased. This effect was dependent o n the concentration of PGE(2). In bones treated with 0.1 mu M PGE(2) a nd 0.1 mu M cortisol for 24 h, [H-3]TdR labeling of periosteal cells w as 5.5 times the labeling in bones treated with cortisol alone and ost eoblast labeling increased 4.1-fold. Similar results in [H-3]TdR label ing of osteoblasts and periosteal cells were found with 6-day neonatal mouse calvaria treated with PGE(2) and cortisol. These data demonstra te that PGE(2) in the presence of cortisol increases periosteal cell r eplication, which leads to an increased number of osteoblasts and incr eased bone formation. (C) 1994 Academic Press, Inc.