Cytological properties of stromal cells derived from giant cell tumor of bone (GCTSC) which can induce osteoclast formation of human blood monocytes without cell to cell contact

When human blood monocytes were cocultured with stromal cells derived from human giant cell tumor of bone (GCTSC) and a Millipore filter (0.4 μm) was interposed between monocytes and GCTSC, multinucleated giant cell formation of monocytes was induced. The multinucleated giant cells have characters as osteoclast-like cells, indicating that a soluble osteoclast-inducing factor(s) is secreted from GCTSC expressing RANK, RANKL/ODF/OPGL and TACE mRNA. Furthermore, OCIF/OPG inhibited GCTSC-induced osteoclastogenesis, showing that the RANK-RANKL system is involved in GCTSC-induced osteoclastogenesis and that soluble form of ODF/RANKL induces osteoclasts from monocytes. GCTSC expressed the cytokine mRNAs such as M-CSF, GM-CSF, IL-3, IL-4, IL-6, and IFN-γ mRNAs. None of IL-1rα, IL-1α, IL-1β, IL-2, IL-4, IL-10, IL-18, TNF-α, G-CSF and IFN-γ could be detected in all culture media. A significant amount of IL-6 could be detected in the culture media of all GCTSC. IL-8 was found in the culture media of two GCTSC and two osteosarcoma-derived cells. M-CSF was detected in all culture media. GCTSC express CaSR, and stimulation of GCTSC with either extracellular Ca2+ or neomycin, agonist of CaSR, augumented the expression of RANKL. Some lines of GCTSC expressed alkaline phosphatase, osteocalcin and Cbfa1, suggesting that GCTSC are intimately related to osteoblastic lineage.