Modulation of the effects of osteoprotegerin (OPG) ligand in a human leukemic cell line by OPG and calcitonin

The discovery of osteoprotegerin (OPG), osteoprotegerin ligand (OPGL), and RANK has elucidated the mechanism by which osteoblasts and stromal cells re gulate osteoclastic differentiation and function and mediate the effects ex erted by other hormones and cytokines. We have investigated the effects of these novel cytokines on the preosteoclastic cell line FLG 29.1. We show th at OPGL alone and in combination with macrophage colony-stimulating factor (CSF-1) dramatically reduced replication and increased tartrate-resistant a cid phosphatase activity. However, although FLG29.1 cells appear to adhere to the bone surface, they are not able to form resorption lacunae. OPG and calcitonin completely abolished the differentiation induced by OPGL. RANK w as detectable in FLG 29.1 and the number of positive cells was increased by OPGL/CSF-1 treatment while reduced by calcitonin. We propose that calciton in could interact with the OPG/OPGL, and its effects on RANK may explain in part the action of this hormone in suppressing bone resorption. (C) 2000 A cademic Press.