THE EXPRESSION OF OSTEOCLAST MARKERS ON FOREIGN-BODY GIANT-CELLS

The expression of some candidate osteoclast markers, tartrate-resistan t acid phosphatase (TRAP), macrophage associated antigens (M Phi Ag), and vitronectin receptor (VNR) on foreign body giant cells (FBGCs) was investigated in peri-implant tissues of loosened total joint arthropl asties. Osteoclasts showed distinct staining characteristics. They wer e strongly TRAP-positive at tartrate concentrations of 50-200 mM and e xpressed VNR and a restricted range of M Phi Ag. In contrast, FBGCs we re shown to be significantly heterogeneous. Significant numbers of FBG Cs were TRAP-positive at a 100 mM tartrate concentration and some were more intense than osteoclasts. A population of FBGCs did not express M Phi Ag such as CD11b, but expressed VNR. It was demonstrated that th ese candidate osteoclast markers were also positive on FBGCs. These re sults have highlighted the difficulty in distinguishing these two cell lineages and suggested that there might be some uncertainty in defini ng osteoclast-like cells in culture studies.