Fibroblasts Express RANKL and Support Osteoclastogenesis in a COX‐2‐Dependent Manner After Stimulation With Titanium Particles

摘要: Synovial fibroblasts are possible mediators of osteolysis. Fibroblasts respond directly to titanium particles and increase RANKL expression through a COX-2/PGE2/EP4/PKA signaling pathway. pretreated with or PGE2 stimulated osteoclast formation, showing the functional importance induction. their activation pathways potential targets prevent osteolysis. Introduction: Bone loss adjacent implant is major cause joint arthroplasty failure. Although cellular molecular response microscopic wear debris recognized as causative, little known concerning role synovial in these events. Materials Methods: Murine embryonic knee culture were examined by FACS, real time RT-PCR, Northern blot, Western blot for expressions vascular cell adhesion molecule (VCAM)1, RANKL, cyclooxygenase (COX)-1, COX-2, four prostaglandin E2 (PGE2) receptor isoforms. Experiments performed presence absence COX inhibitors, protein kinase A (PKA) C (PKC) various EP agonists. Osteoclast formation was co-cultures glutaraldehyde-fixed primary murine spleen cells treated macrophage-colony stimulating factor (M-CSF) 7-days. Results: TNF-α VCAM1 expression, consistent fibroblast phenotype. Titanium gene dose-dependent manner. Gene increased 5-fold 4 h, levels reached maximum after 48 h. Within 1 also induced COX-2 mRNA levels, whereas both indomethacin celecoxib blocked stimulation suggesting COX-2-mediated event. Furthermore, rescued titanium-treated cultures containing inhibitors. Fibroblast either enhanced indicating EP4 most abundant isoform, EP1 EP2 expressed at low EP3 absent. The selective agonist iloprost butaprost minimally RANKL. In contrast, misoprostol magnitude similar PGE2. Finally, PKA antagonism strongly repressed PGE2. Conclusion: Thus, important mediator osteolysis target therapeutic strategies.