The Role Of HIF-α/RANKL-OPG Pathway Induced By Ti Particles In Fibro-like Synoviocytes In Prosthetic Aseptic Loosening

Background:Wear-induced osteolysis is the main cause of aseptic loosening of joint prostheses.Cells involved in this complex biological effect include macrophages,osteoclasts,osteoblasts,fibro-like synoviocytes(FLSs),lymphocytes.Chronic inflammatory response caused by wear particles,leading to aggregation of macrophages around the prosthesis and the releasing of chemokines and cytokines,which than activing RANKL-OPG signaling pathway leading to osteoclast differentiation and maturation results in bone absorption is the consensus of the previous researches.The expression of HIF-1α is critical to the establishment of hypoxia tolerance in the preprosthesis tissues.Same studies have shown that the expression of HIF-1α plays an important role in promoting bone development and inducing vascular growth in fracture healing.We detected the expression of RANKL,OPG and HIF-1αa in the interfacial membrane by immunohistochemical staining,suggesting that HIF-1α interacts with RANKL-OPG signaling pathway and is closely related to the aseptic loosening of prosthesis.Objective:To explore the correlation between HIF-1α expression and RANKL/OPG pathway of Fibroblast-like synoviocytes(FLSs)induced by Ti particles in the vitro model of aseptic loosening interfacial membrane.Method:FLSs were extracted from the synovial tissue collected in surgery,authenticated by flow cytometry and then co-cultured with Ti particles.MTT assay was conducted to evaluate FLSs activity and proliferation.QRT-PCR and Western blotting were conducted to measure the mRNA and protein expression of RANKL、OPG and HIF-1α in FLSs co-cultured with Ti particles at different concentration and time.Result:Ti particles stimulated FLSs proliferation.Genes and proteins expression level of RANKL/OPG and HIF-1α were up-regulated with the increase of concentration of Ti particles.Expression of HIF-1α gene and protein increased time-dependently;RANKL/OPG increased firstly and then declined alongside the increase of HIF-1αexpression.Conclusion:Ti particles induced expression of HIF-1α and activated RANKL/OPG pathway.Up-regulation of HIF-1α may suppress the activation of RANKL/OPG pathway in FLSs of the interfacial membrane induced by Ti particles.