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Osteoclast Precursors (osteoclast + precursor)
Terms modified by Osteoclast Precursors Selected AbstractsRANK Expression as a Cell Surface Marker of Human Osteoclast Precursors in Peripheral Blood, Bone Marrow, and Giant Cell Tumors of BoneJOURNAL OF BONE AND MINERAL RESEARCH, Issue 9 2006Gerald J Atkins Abstract RANK expression in vivo on hematopoietic subsets including pre-osteoclasts, identified by monoclonal antibodies, has not been described. We describe the lineages that express RANK in bone marrow, peripheral blood, and GCTs. We show that CD14+RANKhigh cells constitute a circulating pre-osteoclast pool. Introduction: The expression of RANK by subsets of hematopoietic cells has not been adequately studied in humans. While attributed to the monocytoid lineage, the phenotype of the pre-osteoclast (pre-OC) with respect to RANK expression in vivo remains unclear. We tested monoclonal antibodies (MAbs) raised against the extracellular domain of recombinant human RANK for reactivity with normal peripheral blood (PB) and bone marrow (BM) mononuclear cells (PBMNCs and BMMNCs, respectively). We also tested reactivity with giant cell tumor cells (GCT), a confirmed source of pre-OC and mature OCs. Materials and Methods: Human PBMNCs, BMMNCs, and GCT cells were analyzed for reactivity with anti-RANK MAbs by flow cytometry in combination with hematopoietic lineage restricted markers. GCTs were also analyzed by immunofluorescence. CD14+ monocytoid cells were sorted by fluorescence-activated cell sorting (FACS) based on their relative RANK expression and cultured under OC-forming conditions. Results: RANK+ cells were detected similarly by three independent anti-RANK MAbs. One MAb (80736) immunoprecipitated RANK,RANKL complexes from surface-biotinylated GCT lysates. Using dual-color flow cytometry, RANK was detected on CD14+ (monocytoid), CD19+ (B-lymphoid), CD56+ (NK cell), and glycophorin A+ erythroid progenitors. Minor populations of both CD3+ T lymphocytes and BM CD34+ hematopoietic progenitors also expressed cell surface RANK. In GCTs, RANK expression was identified on mononuclear CD45+CD14+,V,3+c-Fms+ cells, likely to be committed pre-OC, and on multinucleated CD45+,V,3+TRACP+ OCs. Importantly, sorted CD14+RANKhigh PBMNCs treated with recombinant RANKL and macrophage-colony stimulating factor (M-CSF) gave rise to approximately twice the number of osteoclasts than RANKmid or RANKlow cells. Conclusions: These results suggest that committed monocytoid RANK+ pre-OCs are represented in the marrow and circulate in the periphery, forming a pool of cells capable of responding rapidly to RANKL. The ability to reliably detect committed pre-OC in peripheral blood could have important clinical applications in the management of diseases characterized by abnormal osteoclastic activity. [source] Differential Contribution of Osteoclast- and Osteoblast-Lineage Cells to CpG-Oligodeoxynucleotide (CpG-ODN) Modulation of Osteoclastogenesis,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 9 2005Alla Amcheslavsky Abstract CpG-ODNs modulate osteoclast differentiation through Toll-like receptor 9 (TLR9). Using TLR9-deficient mice, we found that activation of TLR9 on both osteoclast precursors and osteoblasts mediate the osteoclastogenic effect of CpG-ODN. Osteoclastic TLR9 is more important for this activity. Introduction: Bacterial infections cause pathological bone loss by accelerating differentiation and activation of the osteoclast. A variety of bacteria-derived molecules have been shown to enhance osteoclast differentiation through activation of Toll-like receptors (TLRs). We have shown that CpG-oligodeoxynucleotides (CpG-ODNs), mimicking bacterial DNA and exerting their cellular activities through TLR9, modulate osteoclast differentiation in a complex manner: the ODNs inhibit the activity of the physiological osteoclast differentiation factor RANKL in early osteoclast precursors (OCPs) but markedly stimulate osteoclastogenesis in cells primed by RANKL. Materials and Methods: Osteoclast precursors and osteoblasts from TLR9-deficient (TLR9,/,) and wildtype (TLR9+/+) mice were used for in vitro analyses of osteoclast differentiation and modulation of signal transduction and gene expression. Results: As expected CpG-ODN did not exert any activity in cells derived from TLR9,/,mice; these cells, however, responded in a normal manner to other stimuli. Using bone marrow/osteoblasts co-cultures from all possible combinations of TLR9,/, and TLR9+/+ mice-derived cells, we showed that TLR9 in the two lineages is required for CpG-ODN induction of osteoclastogenesis. Conclusions: CpG-ODN modulates osteoclastogenesis in a TLR9-dependent manner. Activation of TLR9 in bone marrow-derived osteoclasts precursors is more crucial to induction of osteoclastogenesis than activation of the osteoblastic TLR9. [source] Murine and Chicken Chondrocytes Regulate Osteoclastogenesis by Producing RANKL in Response to BMP2,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 3 2008Michihiko Usui Abstract Chondrocytes express RANKL, but their role in osteoclastogenesis is not clear. We report that hypertrophic chondrocytes induce osteoclast formation through RANKL production stimulated by BMP2 and Runx2/Smad1 and thus they may regulate resorption of calcified matrix by osteoclasts at growth plates. Introduction: Bone morphogenetic protein (BMP) signaling and Runx2 regulate chondrogenesis during bone development and fracture repair and RANKL expression by osteoblast/stromal cells. Chondrocytes express RANKL, and this expression is stimulated by vitamin D3, but it is not known if chondrocytes directly support osteoclast formation or if BMPs or Runx2 is involved in this potential regulation of osteoclastogenesis. Material and Methods: The chondrocyte cell line, ATDC5, primary mouse sternal chondrocytes, and chick sternal chondrocytes were used. Cells were treated with BMP2, and expression of RANKL and chondrocyte marker genes was determined by real-time RT-PCR and Western blot. Chondrocytes and spleen-derived osteoclast precursors ± BMP2 were co-cultured to examine the effect of chondrocyte-produced RANKL on osteoclast formation. A reporter assay was used to determine whether BMP2-induced RANKL production is through transcriptional regulation of the RANKL promoter and whether it is mediated by Runx2. Results: BMP2 significantly increased expression of RANKL mRNA and protein in all three types of chondrocytes, particularly by Col X-expressing and upper sternal chondrocytes. Chondrocytes constitutively induced osteoclast formation. This effect was increased significantly by BMP2 and prevented by RANK:Fc. BMP2 significantly increased luciferase activity of the RANKL-luc reporter, and Smad1 increased this effect. Deletion or mutation of Runx2 binding sites within the RANKL promoter or overexpression of a dominant negative Runx2 abolished BMP2- and Smad1-mediated activation of RANKL promoter activity. Conclusions: Hypertrophic chondrocytes may regulate osteoclastogenesis at growth plates to remove calcified matrix through BMP-induced RANKL expression. [source] Differential Contribution of Osteoclast- and Osteoblast-Lineage Cells to CpG-Oligodeoxynucleotide (CpG-ODN) Modulation of Osteoclastogenesis,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 9 2005Alla Amcheslavsky Abstract CpG-ODNs modulate osteoclast differentiation through Toll-like receptor 9 (TLR9). Using TLR9-deficient mice, we found that activation of TLR9 on both osteoclast precursors and osteoblasts mediate the osteoclastogenic effect of CpG-ODN. Osteoclastic TLR9 is more important for this activity. Introduction: Bacterial infections cause pathological bone loss by accelerating differentiation and activation of the osteoclast. A variety of bacteria-derived molecules have been shown to enhance osteoclast differentiation through activation of Toll-like receptors (TLRs). We have shown that CpG-oligodeoxynucleotides (CpG-ODNs), mimicking bacterial DNA and exerting their cellular activities through TLR9, modulate osteoclast differentiation in a complex manner: the ODNs inhibit the activity of the physiological osteoclast differentiation factor RANKL in early osteoclast precursors (OCPs) but markedly stimulate osteoclastogenesis in cells primed by RANKL. Materials and Methods: Osteoclast precursors and osteoblasts from TLR9-deficient (TLR9,/,) and wildtype (TLR9+/+) mice were used for in vitro analyses of osteoclast differentiation and modulation of signal transduction and gene expression. Results: As expected CpG-ODN did not exert any activity in cells derived from TLR9,/,mice; these cells, however, responded in a normal manner to other stimuli. Using bone marrow/osteoblasts co-cultures from all possible combinations of TLR9,/, and TLR9+/+ mice-derived cells, we showed that TLR9 in the two lineages is required for CpG-ODN induction of osteoclastogenesis. Conclusions: CpG-ODN modulates osteoclastogenesis in a TLR9-dependent manner. Activation of TLR9 in bone marrow-derived osteoclasts precursors is more crucial to induction of osteoclastogenesis than activation of the osteoblastic TLR9. [source] NF-,B p50 and p52 Expression Is Not Required for RANK-Expressing Osteoclast Progenitor Formation but Is Essential for RANK- and Cytokine-Mediated Osteoclastogenesis,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 7 2002Lianping Xing Abstract Expression of RANKL by stromal cells and of RANK and both NF-,B p50 and p52 by osteoclast precursors is essential for osteoclast formation. To examine further the role of RANKL, RANK, and NF-,B signaling in this process, we used NF-,B p50,/,;p52,/, double knockout (dKO) and wild-type (WT) mice. Osteoclasts formed in cocultures of WT osteoblasts with splenocytes from WT mice but not from dKO mice, a finding unchanged by addition of RANKL and macrophage colony-stimulating factor (M-CSF). NF-,B dKO splenocytes formed more colony-forming unit granulocyte macrophage (CFU-GM) colonies than WT cells, but no osteoclasts were formed from dKO CFU-GM colonies. RANKL increased the number of CFU-GM colonies twofold in WT cultures but not in dKO cultures. Fluorescence-activated cell sorting (FACS) analysis of splenocytes from NF-,B dKO mice revealed a two-to threefold increase in the percentage of CD11b (Mac-1) and RANK double-positive cells compared with WT controls. Treatment of NF-,B dKO splenocytes with interleukin (IL)-1, TNF-,, M-CSF, GM-CSF, and IL-6 plus soluble IL-6 receptor did not rescue the osteoclast defect. No increase in apoptosis was observed in cells of the osteoclast lineage in NF-,B dKO or p50,/,;p52+/, (3/4KO) mice. Thus, NF-,B p50 and p52 expression is not required for formation of RANK-expressing osteoclast progenitors but is essential for RANK-expressing osteoclast precursors to differentiate into TRAP+ osteoclasts in response to RANKL and other osteoclastogenic cytokines. [source] Stimulatory Effect of Insulin-Like Growth Factor Binding Protein-5 on Mouse Osteoclast Formation and Osteoclastic Bone-Resorbing ActivityJOURNAL OF BONE AND MINERAL RESEARCH, Issue 5 2000Masanori Kanatani Abstract Insulin-like growth factor binding protein-5 (IGFBP-5) stimulates osteoblast proliferation directly or indirectly through IGF-I action, but its effects on osteoclast formation and osteoclastic activity are unknown. We tested the effects of IGFBP-5 on osteoclastic activity and osteoclast formation. IGFBP-5 significantly stimulated pit formation by pre-existent osteoclasts in mouse bone cell cultures and its stimulatory effect was completely blocked by IGF-I antibody (Ab). However, IGFBP-5 did not affect the bone-resorbing activity of isolated rabbit osteoclasts. When IGFBP-5 was added to unfractionated bone cells after degeneration of pre-existent osteoclasts, IGFBP-5 (77 pM,7.7 nM) dose-dependently stimulated osteoclast-like cell formation, irrespective of the presence of IGF-I Ab. Moreover, osteoclast-like cells newly formed by IGFBP-5 from unfractionated bone cells possessed the ability to form pits on dentine slices. We next examined the direct effect of IGFBP-5 on osteoclast precursors in the absence of stromal cells, using hemopoietic blast cells derived from spleen cells. IGFBP-5 dose-dependently stimulated osteoclast-like cell formation from osteoclast precursors, irrespective of the presence of IGF-I Ab. Growth hormone (GH) as well as IGF-I significantly stimulated bone resorption by pre-existent osteoclasts in mouse bone cell cultures and these stimulatory effects were completely blocked by IGF-I Ab. GH as well as IGF-I stimulated osteoclast-like cell formation from unfractionated bone cells and this stimulatory effect of GH was significantly but partially blocked by IGF-I Ab. The direct stimulatory effect of GH on osteoclast-like cell formation from hemopoietic blast cells was not affected by IGF-I Ab. The present data indicate that IGFBP-5 stimulates bone resorption both by stimulation of osteoclast formation in an IGF-I,independent fashion and by IGF-I,dependent activation of mature osteoclasts, possibly via osteoblasts, in vitro. (J Bone Miner Res 2000;15:902,910) [source] The Roles of Osteoprotegerin and Osteoprotegerin Ligand in the Paracrine Regulation of Bone ResorptionJOURNAL OF BONE AND MINERAL RESEARCH, Issue 1 2000Lorenz C. Hofbauer Abstract Although multiple hormones and cytokines regulate various aspects of osteoclast formation, the final two effectors are osteoprotegerin ligand (OPG-L)/osteoclast differentiation factor (ODF), a recently cloned member of the tumor necrosis factor superfamily, and macrophage colony,stimulating factor. OPG-L/ODF is produced by osteoblast lineage cells and exerts its biological effects through binding to its receptor, osteoclast differentiation and activation receptor (ODAR)/receptor activator of NF-,B (RANK), on osteoclast lineage cells, in either a soluble or a membrane-bound form, the latter of which requires cell-to-cell contact. Binding results in rapid differentiation of osteoclast precursors in bone marrow to mature osteoclasts and, at higher concentrations, in increased functional activity and reduced apoptosis of mature osteoclasts. The biological activity of OPG-L/ODF is neutralized by binding to osteoprotegerin (OPG)/osteoclastogenesis inhibitory factor (OCIF), a member of the TNF-receptor superfamily that also is secreted by osteoblast lineage cells. The biological importance of this system is underscored by the induction in mice of severe osteoporosis by targeted ablation of OPG/OCIF and by the induction of osteopetrosis by targeted ablation of OPG-L/ODF or overexpression of OPG/OCIF. Thus, osteoclast formation may be determined principally by the relative ratio of OPG-L/ODF to OPG/OCIF in the bone marrow microenvironment, and alterations in this ratio may be a major cause of bone loss in many metabolic disorders, including estrogen deficiency and glucocorticoid excess. That changes in but two downstream cytokines mediate the effects of large numbers of upstream hormones and cytokines suggests a regulatory mechanism for osteoclastogenesis of great efficiency and elegance. [source] TNF receptor type 1 regulates RANK ligand expression by stromal cells and modulates osteoclastogenesisJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 5 2004Yousef Abu-Amer Abstract TNF, is a major osteoclastogenic cytokine and a primary mediator of inflammatory osteoclastogenesis. We have previously shown that this cytokine directly targets osteoclasts and their precursors and that deletion of its type-1 receptor (TNFr1) lessens osteoclastogenesis and impacts RANK signaling molecules. Osteoclastogenesis is primarily a RANK/RANKL-dependent event and occurs in an environment governed by both hematopoietic and mesenchymal compartments. Thus, we reasoned that TNF/TNFr1 may regulate RANKL and possibly RANK expression by stromal cells and osteoclast precursors (OCPs), respectively. RT-PCR experiments reveal that levels of RANKL mRNA in WT stromal cells are increased following treatment with 1,25-VD3 compared to low levels in TNFr1-null cells. Expression levels of OPG, the RANKL decoy protein, were largely unchanged, thus supporting a RANKL/OPG positive ratio favoring WT cells. RANK protein expression by OCPs was lower in TNFr1-null cells despite only subtle differences in mRNA expression in both cell types. Mix and match experiments of different cell populations from the two mice phenotypes show that WT stromal cells significantly, but not entirely, restore osteoclastogenesis by TNFr1-null OCPs. Similar results were obtained when the latter cells were cultured in the presence of exogenous RANKL. Altogether, these findings indicate that in the absence of TNFr1 both cell compartments are impaired. This was further confirmed by gain of function experiments using TNFr1- null cultures of both cell types at which exogenous TNFr1 cDNA was virally expressed. Thus, restoration of TNFr1 expression in OCPs and stromal cells was sufficient to reinstate osteoclastogenesis and provides direct evidence that TNFr1 integrity is required for optimal RANK-mediated osteoclastogenesis. © 2004 Wiley-Liss, Inc. [source] Platelet-rich plasma impairs osteoclast generation from human precursors of peripheral bloodJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 6 2010Elisabetta Cenni Abstract Platelet-rich plasma is used to accelerate bone repair for the release of osteogenic growth factors from activated platelets. To date, the effects on osteoclasts have been only scarcely investigated, even though these cells are crucial for bone remodeling. The aim of this research was the evaluation of the effects of thrombin-activated platelets (PRP) on osteoclastogenesis from human blood precursors. We evaluated both the ability to influence osteoclast differentiation induced by the receptor activator of nuclear factor-kappaB ligand (RANKL), and the ability to induce osteoclast differentiation without RANKL. In both assays, the incubation with PRP supernatant at 10% did not significantly affect the formation of tartrate-resistant acid phosphatase (TRACP)-positive multinucleated cells that were able to form the F-actin ring. However, when PRP at 25 and 50% was added to the medium without RANKL, the generation of TRACP-positive multinucleated cells was inhibited. PRP, even at 10%, reduced the osteoclast-mediated bone collagen degradation, suggesting inhibition of osteoclast activation. Similarly, after incubation with PRP supernatant, calcitonin receptor mRNA was lower than the untreated samples. In conclusion, PRP at 10% interfered with the complete differentiation process of human osteoclast precursors. At higher concentration it impaired osteoclast formation also at an early stage of differentiation. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:792,797, 2010 [source] Expression profiling reveals alternative macrophage activation and impaired osteogenesis in periprosthetic osteolysisJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 1 2008Panagiotis Koulouvaris Abstract Interactions between periprosthetic cells and prosthetic wear debris have been recognized as an important event in the development of osteolysis and aseptic loosening. Although the ability of wear debris to activate pro-inflammatory macrophage signaling has been documented, the full repertoire of macrophage responses to wear particles has not been established. Here, we examined the involvement of alternative macrophage activation and defective osteogenic signaling in osteolysis. Using real-time RT-PCR analysis of periprosthetic soft tissue from osteolysis patients, we detected elevated levels of expression of alternative macrophage activation markers (CHIT1, CCL18), chemokines (IL8, MIP1 ,) and markers of osteoclast precursor cell differentiation and multinucleation (Cathepsin K, TRAP, DC-STAMP) relative to osteoarthritis controls. The presence of cathepsin K positive multinuclear cells was confirmed by immunohistochemistry. Reduced expression levels of the osteogenic signaling components BMP4 and FGF18 were detected. Expression levels of TNF-,, IL-6, and RANKL were unchanged, while the anti-osteoclastogenic cytokine OPG was reduced in osteolysis patients, resulting in elevated RANKL:OPG ratios. In vitro studies confirmed the role of particulate debris in alternative macrophage activation and inhibition of osteogenic signaling. Taken together, these results suggest involvement in osteolysis of alternative macrophage activation, accompanied by elevated levels of various chemokines. Increased recruitment and maturation of osteoclast precursors is also observed, as is reduced osteogenesis. These findings provide new insights into the molecular pathogenesis of osteolysis, and identify new potential candidate markers for disease progression and therapeutic targeting. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:106,116, 2008 [source] Tumor necrosis factor-, mediates polymethylmethacrylate particle-induced NF-,B activation in osteoclast precursor cellsJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2002John C. Clohisy Tumor necrosis factor-, (TNF) is a potent osteoclastogenic cytokine that has a fundamental role in the pathogenesis of implant particle-induced osteolysis. The nuclear transcription factor NF-,B mediates TNF signaling and this transcription complex is necessary for osteoclastogenesis. Because polymethylmethacrylate (PMMA) particles cause osteolysis, we reasoned the PMMA would induce NF-,B activation. In fact, we find that exposure of osteoclast precursors, in the form of colony stimulating factor-1 (CSF-1) dependent murine bone marrow macrophages, to PMMA particles prompts nuclear translocation and activation of NF-,B. Supershift assays confirm the presence of the p50 and p65 NF-,B subunits in the activated transcription factor. Particle-induced NF-,B activation is equal in both wild type and LPS- hyporesponsive cells indicating that the phenomenon does not represent endotoxin contamination. A soluble, competitive inhibitor of TNF (huTNF:Fc) dampens particle-directed NF-,B activation and this response is also abrogated in TNF,/, osteoclast precursors. Thus, PMMA particle activation of NF-,B is a secondary event resulting from enhanced TNF expression and is independent of LPS contamination. © 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] The role of osteoclast differentiation in aseptic loosening,JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 1 2002Edward M. Greenfields The major cause of orthopaedic implant loosening is thought to be accelerated osteoclastic bone resorption due to the action of cytokines produced in response to phagocytosis of implant-derived wear particles. This accelerated osteoclastic bone resorption could be due to increases in any of the following processes: recruitment of osteoclast precursors to the local microenvironment, differentiation of precursors into mature multinucleated osteoclasts, activation of mature osteoclasts, and/or survival of osteoclasts. Our studies have focused on differentiation and survival to complement work by others who have focused on recruitment of precursors and activation. Taken together, our studies and those of other investigators provide strong evidence that increased recruitment of osteoclast precursors and their subsequent differentiation play major roles in wear particle-induced osteolysis. In contrast, increased osteoclast activation and survival appear to play minor roles. These studies suggest that development of therapeutic interventions that reduce either recruitment or differentiation of osteoclast precursors would improve the performance of orthopaedic implants. © 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] Antiinflammatory effects of tumor necrosis factor on hematopoietic cells in a murine model of erosive arthritisARTHRITIS & RHEUMATISM, Issue 6 2010Stephan Blüml Objective To investigate the mechanisms leading to the influx of inflammatory hematopoietic cells into the synovial membrane and the role of tumor necrosis factor receptor I (TNFRI) and TNFRII in this process in an animal model of rheumatoid arthritis (RA). Methods We performed bone marrow transplantations in human TNF,transgenic mice using hematopoietic cells from wild-type, TNFRI,/,, TNFRII,/,, and TNFRI/II,/, mice as donors and assessed the severity of arthritis histologically. Generation of osteoclasts from the different genotypes was analyzed in vitro and in vivo. Apoptosis was analyzed using annexin V staining as well as TUNEL assays. Results Despite lacking responsiveness to TNF in their hematopoietic compartment, mice not only developed full-blown erosive arthritis but even showed increased joint destruction when compared with mice with a TNF-responsive hematopoietic compartment. We demonstrated different roles of the 2 different TNFRs in the regulation of these processes. The absence of TNFRI on hematopoietic cells did not affect joint inflammation but markedly attenuated erosive bone destruction via reduced synovial accumulation of osteoclast precursors. In contrast, the absence of TNFRII on hematopoietic cells increased joint inflammation as well as erosive bone destruction via the regulation of osteoclast precursor apoptosis. Conclusion Our findings indicate that selective blockade of TNFRI, leaving the antiinflammatory effects of TNFRII unaltered instead of unselectively blocking TNF, might be advantageous in patients with RA. [source] Mediation of nonerosive arthritis in a mouse model of lupus by interferon-,,stimulated monocyte differentiation that is nonpermissive of osteoclastogenesisARTHRITIS & RHEUMATISM, Issue 4 2010Kofi A. Mensah Objective In contrast to rheumatoid arthritis (RA), the joint inflammation referred to as Jaccoud's arthritis that occurs in systemic lupus erythematosus (SLE) is nonerosive. Although the mechanism responsible is unknown, the antiosteoclastogenic cytokine interferon-, (IFN,), whose transcriptome is present in SLE monocytes, may be responsible. This study was undertaken to examine the effects of IFN, and lupus on osteoclasts and erosion in the (NZB × NZW)F1 mouse model of SLE with K/BxN serum,induced arthritis. Methods Systemic IFN, levels in (NZB × NZW)F1 mice were elevated by administration of AdIFN,. SLE disease was marked by anti,double-stranded DNA (anti-dsDNA) antibody titer and proteinuria, and Ifi202 and Mx1 expression represented the IFN, transcriptome. Microfocal computed tomography was used to evaluate bone erosions. Flow cytometry for CD11b and CD11c was used to evaluate the frequency of circulating osteoclast precursors (OCPs) and myeloid dendritic cells (DCs) in blood. Results Administration of AdIFN, to (NZB × NZW)F1 mice induced osteopetrosis. (NZB × NZW)F1 mice without autoimmune disease were fully susceptible to focal erosions in the setting of serum-induced arthritis. However, (NZB × NZW)F1 mice with high anti-dsDNA antibody titers and the IFN, transcriptome were protected against bone erosions. AdIFN, pretreatment of NZW mice before K/BxN serum administration also resulted in protection against bone erosion (r2 = 0.4720, P < 0.01), which was associated with a decrease in the frequency of circulating CD11b+CD11c, OCPs and a concomitant increase in the percentage of CD11b+CD11c+ cells (r2 = 0.6330, P < 0.05), which are phenotypic of myeloid DCs. Conclusion These findings suggest that IFN, in SLE shifts monocyte development toward myeloid DCs at the expense of osteoclastogenesis, thereby resulting in decreased bone erosion. [source] Interleukin-27 inhibits human osteoclastogenesis by abrogating RANKL-mediated induction of nuclear factor of activated T cells c1 and suppressing proximal RANK signalingARTHRITIS & RHEUMATISM, Issue 2 2010George D. Kalliolias Objective Interleukin-27 (IL-27) has stimulatory and regulatory immune functions and is expressed in rheumatoid arthritis (RA) synovium. This study was undertaken to investigate the effects of IL-27 on human osteoclastogenesis, to determine whether IL-27 can stimulate or attenuate the osteoclast-mediated bone resorption that is a hallmark of RA. Methods Osteoclasts were generated from blood-derived human CD14+ cells. The effects of IL-27 on osteoclast formation were evaluated by counting the number of tartrate-resistant acid phosphatase,positive multinucleated cells and measuring the expression of osteoclast-related genes. The induction of nuclear factor of activated T cells c1 (NFATc1) and the activation of signaling pathways downstream of RANK were measured by immunoblotting. The expression of key molecules implicated in osteoclastogenesis (NFATc1, RANK, costimulatory receptors, and immunoreceptor tyrosine,based activation motif,harboring adaptor proteins) was measured by real-time reverse transcription,polymerase chain reaction. Murine osteoclast precursors obtained from mouse bone marrow and synovial fluid macrophages derived from RA patients were also tested for their responsiveness to IL-27. Results IL-27 inhibited human osteoclastogenesis, suppressed the induction of NFATc1, down-regulated the expression of RANK and triggering receptor expressed on myeloid cells 2 (TREM-2), and inhibited RANKL-mediated activation of ERK, p38, and NF-,B in osteoclast precursors. Synovial fluid macrophages from RA patients were refractory to the effects of IL-27. In contrast to the findings in humans, IL-27 only moderately suppressed murine osteoclastogenesis, and this was likely attributable to low expression of the IL-27 receptor subunit WSX-1 on murine osteoclast precursors. Conclusion IL-27 inhibits human osteoclastogenesis by a direct mechanism that suppresses the responses of osteoclast precursors to RANKL. These findings suggest that, in addition to its well-known antiinflammatory effects, IL-27 plays a homeostatic role in restraining bone erosion. This homeostatic function is compromised under conditions of chronic inflammation such as in RA synovitis. [source] Peripheral blood T lymphocytes from patients with early rheumatoid arthritis express RANKL and interleukin-15 on the cell surface and promote osteoclastogenesis in autologous monocytesARTHRITIS & RHEUMATISM, Issue 4 2006María-Eugenia Miranda-Carús Objective To investigate the osteoclastogenic potential of T cells from the peripheral blood (PB) and synovial fluid (SF) of patients with rheumatoid arthritis (RA) on autologous monocytes, and to study the cytokines implicated in this process. Methods T cells and monocytes were isolated from the PB of 20 healthy subjects and 20 patients with early RA, and from the SF of 20 patients with established RA. Autologous T cell/monocyte cocultures were established in the absence of exogenous cytokines or growth factors in order to examine spontaneous ex vivo osteoclast differentiation by tartrate-resistant acid phosphatase staining and calcified matrix resorption activity. Results Surface RANKL was expressed on freshly isolated T cells from the PB of patients with early RA and the SF of patients with established RA. In addition, surface interleukin-15 (IL-15) was detected on freshly isolated T cells and monocytes from the PB of patients with early RA and the SF of patients with established RA. Autologous T cell/monocyte cocultures derived from the SF of patients with established RA and from the PB of patients with early RA, but not from the PB of healthy controls, resulted in osteoclast differentiation that was significantly inhibited by osteoprotegerin (OPG) and by neutralizing monoclonal antibodies to IL-15, IL-17, tumor necrosis factor , (TNF,), and IL-1,. OPG, anti-TNF,, and anti,IL-1, demonstrated a cooperative inhibitory effect. At 1-year followup, surface RANKL and IL-15 and ex vivo osteoclastogenesis were no longer observed on PB T cells or monocytes from patients with early RA in whom clinical remission had been achieved with treatment. Conclusion T cells are important contributors to the pathogenesis of bone erosions in RA through interaction with osteoclast precursors of the monocyte/macrophage lineage. [source] Differential Contribution of Osteoclast- and Osteoblast-Lineage Cells to CpG-Oligodeoxynucleotide (CpG-ODN) Modulation of Osteoclastogenesis,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 9 2005Alla Amcheslavsky Abstract CpG-ODNs modulate osteoclast differentiation through Toll-like receptor 9 (TLR9). Using TLR9-deficient mice, we found that activation of TLR9 on both osteoclast precursors and osteoblasts mediate the osteoclastogenic effect of CpG-ODN. Osteoclastic TLR9 is more important for this activity. Introduction: Bacterial infections cause pathological bone loss by accelerating differentiation and activation of the osteoclast. A variety of bacteria-derived molecules have been shown to enhance osteoclast differentiation through activation of Toll-like receptors (TLRs). We have shown that CpG-oligodeoxynucleotides (CpG-ODNs), mimicking bacterial DNA and exerting their cellular activities through TLR9, modulate osteoclast differentiation in a complex manner: the ODNs inhibit the activity of the physiological osteoclast differentiation factor RANKL in early osteoclast precursors (OCPs) but markedly stimulate osteoclastogenesis in cells primed by RANKL. Materials and Methods: Osteoclast precursors and osteoblasts from TLR9-deficient (TLR9,/,) and wildtype (TLR9+/+) mice were used for in vitro analyses of osteoclast differentiation and modulation of signal transduction and gene expression. Results: As expected CpG-ODN did not exert any activity in cells derived from TLR9,/,mice; these cells, however, responded in a normal manner to other stimuli. Using bone marrow/osteoblasts co-cultures from all possible combinations of TLR9,/, and TLR9+/+ mice-derived cells, we showed that TLR9 in the two lineages is required for CpG-ODN induction of osteoclastogenesis. Conclusions: CpG-ODN modulates osteoclastogenesis in a TLR9-dependent manner. Activation of TLR9 in bone marrow-derived osteoclasts precursors is more crucial to induction of osteoclastogenesis than activation of the osteoblastic TLR9. [source] | |||||||||||||