Adenovrius-mediated Sirna Targeting CXCR2 Attenuates Titanium Particle-induced Osteolysis By Suppressing Osteoclast Formation

Background:Total joint arthroplasty(TJA) is the gold standard treatment for osteoarthritis, rheumatoid arthritis and elderly hip fracture,can significantly improve patient movement function and quality of life. Wear particle-induced peri-implant loosening is the single most common complication affecting long-term outcomes in patients who have undergone total joint arthroplasty. Wear particles and by-products from joint replacements may cause chronic local inflammation and foreign body reactions, which can in turn lead to osteolysis. Studies showed that IL-8 could promote osteoblast-mediated osteoclast maturation. Thus, inhibiting the formation and activity of osteoclasts may improve the functionality and long-term success of total joint arthroplasty. The aim of this study was to interfere with CXC chemokine receptor type 2(CXCR2) to explore its role in wear particle-induced osteolysis.A mouse calvarial osteolysis model was established to measure the osteolysis-suppressing effects of si CXCR2 in vivo. In vitro, the objective of the current study was to investigate the effects of IL8/CXCR2 signaling on wear particle-induced osteoclast formation, which are mediated by osteoclast directly, as well as by altered the balance between RANKL and OPG in osteoblast indirectly.Methods:Experiment in vitro(1) In the RAW264.7 cell culture system. The expression of CXCR2 in RANKL-induced osteoclastogenesis was determined by flow cytometry.(2)In primary osteoclast culture system. osteoclastogenesis in vitro were determined by western blotting, real-time PCR, TRAP staining and so on.(2)In primary osteoblast culture system, to test whether the si CXCR2 can changed the protein and gene expression of OPG and RANKL by real-time PCR, Western blot.Experiment in vivoFirstly, a mouse calvarial osteolysis model was established, then to measure the effects of siCXCR2 on pathological osteolysis on by TRAP, bone resorption pit assay and micro-CT, to observe whether the si CXCR2 can inhibit titanium particle-induced osteolysis. Objective:1. CXCR2 was upregulated in osteoclast formation in vitro.2. siCXCR2 suppressed osteoclast formation both directly by acting on osteoclasts themselves and indirectly by altering RANKL and OPG expression in osteoblasts in vitro.3. The current results demonstrate that silencing CXCR2 signaling inhibits osteoclast formation titanium-induced osteolysis in a mouse calvarial model in vivoConclusion:CXCR2 plays a critical role in particle-induced osteolysis. Local injection with adenovirus-mediated siRNA targeting CXCR2 inhibited titanium-induced osteolysis in vivo. Furthermore, siCXCR2 suppressed osteoclast formation both directly by acting on osteoclasts themselves and indirectly by altering RANKL and OPG expression in osteoblasts in vitro, and siCXCR2 may be a novel treatment for aseptic loosening.