BONE-MARROW CELLS ARE TARGETS FOR THE ANABOLIC ACTIONS OF PROSTAGLANDIN E(2) ON BONE - INDUCTION OF A TRANSITION FROM NONADHERENT TO ADHERENT OSTEOBLAST PRECURSORS

Although prostaglandin E(2) (PGE(2)) is known to stimulate bone format ion in vivo, its mechanism of action is not well understood, Circumsta ntial evidence suggests that bone marrow cells (BMC) may well be invol ved in this, and in order to investigate this further we have studied the effect of PGE(2) on proliferation and matrix synthesis in high-den sity BMC cultures and on colony-forming unit (CFU-f) formation efficie ncy by BMC in vitro, High-density cultures of BMC formed a collagenous , calcified matrix, synthesized osteocalcin and expressed alkaline pho sphatase activity, The addition of PGE(2) caused a concentration-depen dent increase in total (but not specific) APase activity, cell number, and collagen accumulation, It was found that PGE(2) need only be pres ent during the first 48 hours of the culture period and that longer ex posure had no additional effect, PGE(2) also caused a concentration-de pendent increase in CFU-f formation, and it was found that this was du e to the recruitment of new mesenchymal precursor cells from the nonad herent fraction of the BMC. Once again, the presence of PGE(2) for onl y the first 48 hours of the culture period was enough to precipitate a maximal response, We conclude that one mechanism for the anabolic act ions of PGE(2) may be the recruitment of OB precursors from a populati on of nonadherent mesenchymal precursor cells present in the bone marr ow.