Up-Regulated Expression of MIF by Interfacial Membrane Fibroblasts and Macrophages Around Aseptically Loosened Implants

BackgroundLocal chronic inflammatory reaction plays an important role in the process of aseptic loosening of implants after total joint replacement. In addition, macrophage migration inhibitory factor (MIF) is a key upstream regulator of inflammation, and it is a significant regulator of inflammatory diseases. The purpose of this study is to investigate if the fibroblasts and macrophages in the interfacial membranes overexpress MIF.Materials and MethodsThe 15 tissue samples of interfacial membranes were obtained from the tissues around the aseptically loosened femoral implants adjacent to osteolytic lesion in 15 patients. The 15 control synovial samples of hip joints were obtained from 15 patients who underwent primary hip arthroplasty because of the fresh fracture of the femoral neck. The levels of MIF protein and mRNA were evaluated by ELISA assay, immunofluorescence labeling, and real-time RT-PCR. Fibroblasts and macrophages were identified by immunofluorescence labeling.ResultsThe levels of MIF protein and mRNA were significantly increased, as well as the numbers of MIF+ fibroblasts and macrophages in the interfacial membranes compared with the control synovium.ConclusionNot only the macrophages, but also the fibroblasts in interfacial membranes overexpress MIF. MIF may play a significant role in the process of aseptic-loosening implants after total joint replacement.