EVect of osteoprotegerin and osteoprotegerin ligand on osteoclast formation by arthroplasty membrane derived macrophages

Objective—Osteoprotegerin ligand (OPGL) is a newly discovered molecule, which is expressed by osteoblasts/bone stromal cells. This ligand and M-CSF are now known to be essential for osteoclast diVerentiation from marrow and circulating precursors. This study examined whether OPGL and its soluble receptor osteoprotegerin (OPG), influenced osteoclast formation from human arthroplasty derived macrophages, to determine if the eVects of OPGL and OPG on these cells could contribute to the osteolysis of aseptic loosening. Methods—OPGL (± dexamethasone/MCSF) was added to cultures of macrophages isolated from the pseudomembrane of loosened hip arthroplasties incubated on glass coverslips and dentine slices. OPG was added to cocultures of arthroplasty derived macrophages and UMR106 osteoblast-like cells. Osteoclast diVerentiation in long term cultures was assessed by expression of macrophage (CD14) and osteoclast markers (tartrate resistant acid phosphatase (TRAP), vitronectin receptor (VNR) and lacunar