Wear debris from implant interfaces is the major factor leading to periprosthetic osteolysis. Fibroblast-like synoviocytes (FLSs) populate the intimal lining of the synovium and are in direct contact with wear debris. This study aimed to elucidate the effect of Ti particles as wear debris on human FLSs and the mechanism by which they might participate in the bone remodeling process during periprosthetic osteolysis. FLSs were isolated from synovial tissue from patients, and the condition medium (CM) was collected after treating FLSs with sterilized Ti particles. The effect of CM was analyzed for the induction of osteoclastogenesis or any effect on osteogenesis and signaling pathways. The results demonstrated that Ti particles could induce activation of the NFκB signaling pathway and induction of COX-2 and inflammatory cytokines in FLSs. The amount of RANL in the conditioned medium collected from Ti particle-stimulated FLSs (Ti CM) showed the ability to stimulate osteoclast formation. The Ti CM also suppressed the osteogenic initial and terminal differentiation markers for osteoprogenitors, such as alkaline phosphate activity, matrix mineralization, collagen synthesis, and expression levels of Osterix, Runx2, collagen 1α, and bone sialoprotein. Inhibition of the WNT and BMP signaling pathways was observed in osteoprogenitors after the treatment with the Ti CM. In the presence of the Ti CM, exogenous stimulation by WNT and BMP signaling pathways failed to stimulate osteogenic activity in osteoprogenitors. Induced expression of sclerostin (SOST: an antagonist of WNT and BMP signaling) in Ti particletreated FLSs and secretion of SOST in the Ti CM were detected. Neutralization of SOST in the Ti CM partially restored the suppressed WNT and BMP signaling activity as well as the osteogenic activity in osteoprogenitors. Our results reveal that wear debris-stimulated FLSs might affect bone loss by not only stimulating osteoclastogenesis but also suppressing the bone-forming ability of osteoprogenitors. In the clinical setting, targeting FLSs for the secretion of antagonists like SOST might be a novel therapeutic approach for preventing bone loss during inflammatory osteolysis.
The development of a representative human, A meta-analysis of OA synovial biomarkers was conducted, identifying up to thirteen relevant pathophysiology-related factors, including, amongst others, IL-13, IL-10, IL-6, PIICP, and HA, with PIICP demonstrating the largest effect (SMD 6.11 [3.50, 8.72], Healthy HFLS-derived and OA-HFLS-derived iPSC (UoS-B and UoS-C lines, respectively) were generated, indicating successful reprogramming. Morphological observations demonstrated typical iPSC appearance, and ICC confirmed presence of pluripotency markers Tra-1-60, Oct3/4 and Nanog. Expression of Oct3/4, Nanog and Sox2 were confirmed by RT-qPCR with OA-iPSC lines expressing higher levels of all markers compared to non-OA iPSC. In particular, expression of Oct3/4 and Sox2 was 3.5 fold and 4.6 fold higher ( The successfully obtained OA and non-OA iPSCs can be differentiated towards mesenchymal lineages, including chondrocyte and bone progenitor cells, enabling phenotypic comparison and biomarker analysis as identified in meta-analysis. Cell bank dissemination of these cell lines could deepen further
Rheumatoid arthritis (RA) is a systemic autoimmune disease affecting 350,000 people in the UK. Within synovial joints, synoviocytes form a destructive pannus that degrades articular cartilage and bone. Synovial fluid glutamate levels increase 54 fold in RA patients and are also elevated in animal models of inflammatory and osteoarthritis. To determine whether elevated glutamate levels contribute to RA pathology we investigated which synovial joint tissues express glutamate receptors and whether glutamate stimulation influences synovio-cyte phenotype. Various glutamate receptor mRNAs (NMDAR1, KA1, AMPAGluR2, AMPA GluR3, mGluR4) were expressed in tissues of the rat knee. All receptors were expressed in the patella. The fibrocartilagenous menis-cus and articular cartilage chondrocytes expressed mGluR4 and both AMPA receptor subunits. Human synoviocytes expressed NMDAR1 and KA1 mRNA. To determine whether glutamate receptors were functional in human synoviocytes, cells were preloaded with a fluorescent indicator of intracellular calcium (iCa 2+) and stimulated with glutamate or specific agonists (NMDA or kainate, 500mM). Glutamate stimulated release of iCa2+ in 25% of synoviocytes whereas NMDA and Kainate each stimulated 15% of cells. NMDA responses increased to 57% in the absence of Mg2+ consistent with the inhibitory effect of Mg2+ on this receptor. To determine whether activation of glutamate receptors can influence human synoviocyte phenotype, we cultured synoviocytes in various glutamate concentrations (50mM to 2mM) and measured effects of glutamate receptor antagonists on release of a proinflammatory cytokine (IL-6) and degradative enzymes (MMP2 and 9). In some RA patients, glutamate stimulation increased synoviocyte pro MMP-2 release. TIMP1 and TIMP2 release were not affected by glutamate stimulation or co-treatment with receptor antagonists. IL-6 expression varied greatly in human synoviocytes derived from different RA patients (0–120pg/ml media). However, the AMPA/KA receptor antagonist NBQX significantly reduced IL-6 release at all glutamate concentrations. This inhibition was greater than that by CFM2 (AMPAR antagonist), indicating that activation of kainate receptors in human synoviocytes may induce IL-6 release. We conclude that glutamate receptors are functional in human synoviocytes and regulate release of MMP-2 and IL-6 Thus glutamatergic signalling may contribute to RA pathology and represent a new therapeutic target.
Chemokines produced by synoviocytes of the subacromial bursa are up-regulated in subacromial inflammation (bursitis) and rotator cuff disease. SDF-1a is an important chemotactic factor in the subacromial bursa that stimulates recruitment of inflammatory cells; however, its mechanism of induction and regulation in the subacromial bursa is unknown. We hypothesised that SDF-1a production in bursal synoviocytes may be induced by local cytokines such as interleukin IL-1β and IL-6. Subacromial bursa specimens were obtained following an institutional review board-approved protocol from patients undergoing shoulder surgery. Bursal specimens were stained with anti-human antibodies to IL-1, IL-6 and SDF-1a by immunohistochemistry and compared to normal and rheumatoid controls. Bursal cells were also isolated from specimens and cultured. Cultured cells were labelled with fluorescent probes and analysed by flow cytometry to determine cell lineage. Early-passaged cells were then treated with cytokines IL-1β and IL-6 and SDF-1a production and expression were measured by ELISA and RT-PCR.Purpose
Methods
Rheumatoid arthritis (RA) is an autoimmune disease characterized by symmetrical and chronic polyarthritis. Fibroblast-like synoviocytes are mainly involved in joint inflammation and cartilage and bone destruction by inflammatory cytokines and matrix-degrading enzymes in RA. Approaches that induce various cellular growth alterations of synoviocytes are considered as potential strategies for treating RA. However, since synoviocytes play a critical role in RA, the mechanism and hyperplastic modulation of synoviocytes and their motility need to be addressed. In this review, we focus on the alteration of synoviocyte signalling and cell fate provided by signalling proteins, various antioxidant molecules, enzymes, compounds, clinical candidates, to understand the pathology of the synoviocytes, and finally to achieve developed therapeutic strategies of RA. Cite this article:
