Osteoclast Formation Assay Research Articles

FRI0033 The inhibitory effects of the yersinia outer protein m (YOPM) on osteoclastogenesis and bone destruction

BackgroundThe severe bone destruction during rheumatoid arthritis (RA) is mainly mediated by osteoclasts and thus, reducing osteoclast number is a keystep in ameliorating the outcome of the disease. Yersinia strains...

FRI0024 Antagonizing endosomal toll-like receptors diminishes inflammatory arthritis

BackgroundRheumatoid arthritis (RA), the most common chronic inflammatory joint disease, has a definite autoimmune background. There is evidence that release of endogenous nucleic acids triggers autoimmune reactions important for the...

Endotoxins potentiate COX-2 and RANKL expression in compressed PDL cells

This study aims to demonstrate in vitro the synergistic effect of orthodontic forces and periodontal pathogens on cyclooxygenase-2 regulation and the subsequent receptor activator of nuclear factor kappa-B ligand (RANKL) production from periodontal ligament (PDL) cells. In comparison to a control group, three experimental groups were formed from human primary PDL cells stressed with compressive forces, bacterial endotoxins, or a combination of both. Gene expression of cyclooxygenase-2 and RANKL was analysed with RT real-time PCR. The prostaglandin E2 production was determined with ELISA. A co-culture of PDL cells and an osteoclast-progenitor cell line was used in order to demonstrate the osteoclast formation effect caused by the simultaneous combined stress. The simultaneous combined stress resulted in a 56-fold up-regulation of cyclooxygenase-2 gene expression with a subsequent noticeable rise in the prostaglandin E2 in the culture medium. The RANKL/osteoprotegerin gene expression ratio was 50-fold up-regulated and the osteoclast formation assay revealed 153.5 ± 15.7 tartrate-resistant acid phosphatase (TRAP)-positive cells per well compared with 42.3 ± 3.8 TRAP-positive cells per well of the control group. The synergistic action of periodontal pathogens and orthodontic forces leads to an increased expression of cyclooxygenase-2 from PDL cells that intensify the RANKL production which in turn induces osteoclast differentiation and subsequent osteoclastogenesis. The present study puts an emphasis on the detrimental effect of orthodontic forces on patients with an active periodontal disease by underlining the significance of cyclooxygenase-2 activity and RANKL binding on the osteoclastogenesis process.

The bacterial effector protein YopM reduces rheumatoid arthritis (RA) outcome by inhibiting inflammation and bone destruction

Osteoclasts mediate the degradation of bone during RA and are derived from macrophages. The yersinia outer protein M (YopM) is an effector protein of Yersinia species that is able to enter host cells by membrane penetration. In the cell YopM mediates down-regulation of inflammatory responses. We investigated whether YopM has the potential to act as a selfdelivering immune therapeutic agent by reducing the inflammation and joint destruction linked to RA. Using confocal laser scanning we analysed the penetration of recombinant YopM into bone marrow macrophages (BMMs). Furthermore we studied the effects of YopM on osteoclastogenesis using in vitro osteoclast formation assay. To unravel the signaling pathways of YopM, we tested for phosphorylation of MAP-kinases (ERK, AKT and p-38) and activation of NF-KB signaling by Western Blot analysis. With respect to a potential in vivo application of YopM, we injected YopM intra articular and intravenous in mice and monitored the distribution by fluorescence reflection imaging (FRI). We treated hTNFtg mice, as animal model for RA, with YopM and recorded clinical parameters (weight, grip strength and paw swelling). Finally we analysed the destruction of bone and cartilage histologically compared to untreated hTNFtg mice and wildtype mice. As seen in confocal scanning microscopy, YopM penetrated the cell membrane of BMMs and accumulated near the nucleus. Studying the signaling pathways affected by YopM, we found that YopM reduced the TNFa induced activation of NF-kB via reducing the phosphorylation of IkBa. TNFa mediated phosphorylation of MAP kinases were not altered by YopM. Most interestingly, we found a strong reduction of osteoclast formation by YopM. Incubation of BMMs with YopM led to a 90% reduction in osteoclasts precursors and osteoclasts. YopM-Cy5 injected into the hind paws of hTNFtg mice was detectable in the joint without a systemic distribution for 48 hours and elimination mediated through renal clearance. Analysing the clinical parameters of RA in hTNFtg mice, we observed a delay of onset of paw swelling in mice treated with YopM. At histological analysis of the hind paws, we found reduced bone destruction and decreased osteoclast formation, as well as less inflammation in YopM treated hTNFtg mice in comparison to untreated hTNFtg mice. These results suggest that YopM has the potential to reduce inflammation and bone destruction in vivo. For this reason YopM may constitute a novel therapeutic agent for the treatment of RA.

Transient receptor potential canonical channel 1 dependent pathways are required for osteoclast fusion and mediate osteoporotic bone loss

The formation of osteoclasts involves a sequence of cellular events including monocyte migration towards each other, cell-cell contacts and fusion to multinucleated cells. Given that TRPC1has a pivotal role in...

The Yersinia outer protein M inhibits osteoclastogenesis in vitro and reduces bone destruction in hTNFtg mice in vivo

BackgroundOne main phenomenon in rheumatoid arthritis (RA) is severe bone destruction, mainly mediated by osteoclasts in the arthritic joints. YopM is the outer protein M of Yersinia species. It has...

L-type Ca 2+ channel agonist inhibits RANKL-induced osteoclast formation via NFATc1 down-regulation

Aims BayK 8644 is an L-type Ca 2+ channel agonist that enhances Ca 2+ influx and elevates cytosolic Ca 2+. As intracellular calcium plays a key role in osteoclast formation, we investigated the effects of BayK 8644 in cultures of bone marrow-derived precursor cells with macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor kappaB ligand (RANKL). Main methods We performed an osteoclast formation assay, a pit formation assay, real-time PCR, and Western blot analysis. Key findings BayK 8644 concentration-dependently suppressed osteoclastogenesis, as well as the expression of osteoclastic marker genes. It also decreased osteoclastic bone resorption on a dentine slice. While the RANKL-stimulated induction of IL-1β and IL-6 was not affected, TNF-α induction was reduced by BayK 8644 treatment. In addition, BayK 8644 blocked IκB degradation and the induction of nuclear factor of activated T cells c1 (NFATc1), the master regulator of osteoclast differentiation, following RANKL stimulation. Finally, forced expression of NFATc1 reversed the inhibitory effect of BayK 8644 on osteoclastogenesis, suggesting that NFATc1 is a downstream target for the anti-osteoclastogenic action of BayK 8644. Taken together, our data suggest that BayK 8644 has an anti-osteoclastogenic effect by inhibiting RANKL-induced activation of NF-κB pathways, thereby suppressing the gene expression of NFATc1 in osteoclast precursors. Significance Our results provide a molecular understanding of the inhibitory effect of the L-type Ca 2+ channel agonist, BayK 8644, on osteoclastogenesis.

Brain‐derived neurotrophic factor is a potential osteoclast stimulating factor in multiple myeloma

Multiple myeloma (MM) is characterized by accumulation of monoclonal plasma cells in the bone marrow and progression of lytic bone lesions. The mechanisms of enhanced bone resorption in patients with myeloma are not fully defined. We have previously identified the role of brain-derived neurotrophic factor (BDNF) in proliferation and migration of MM cells. In our study, we investigated whether BDNF was possibly involved in MM cell-induced osteolysis. We showed that BDNF was elevated in MM patients and the bone marrow plasma levels of BDNF positively correlated with extent of bone disease. In osteoclast formation assay, bone marrow plasma from patients with MM increased osteoclast formation and the effect was significantly blocked by neutralizing antibody to BDNF, suggesting a critical role for BDNF in osteoclast activation. Furthermore, the direct effects of recombinant BDNF on osteoclast formation and bone resorption support the potential role of BDNF in the MM bone disease. BDNF receptor TrkB was expressed by human osteoclast precursors and a Trk inhibitor K252a markedly inhibited osteoclast formation stimulated with BDNF, demonstrating that BDNF used TrkB for its effects on osteoclast. Finally, bone marrow plasma BDNF level positively correlated with macrophage inflammatory protein-1α and receptor activator of nuclear factor-κB ligand, two major osteoclast stimulatory factors in MM. These results support an important role for BDNF in the development of myeloma bone disease.

Brain-Derived Neurotrophic Factor Is a Potential Osteoclast Stimulatory Factor In Multiple Myeloma

AbstractAbstract 1917 Background and Objective:Multiple myeloma (MM) is characterized by accumulation of monoclonal plasma cells in the bone marrow and progression of lytic bone lesions. The mechanisms of enhanced bone resorption in patients with myeloma are not fully defined. We have previously identified the role of brain-derived neurotrophic factor (BDNF) in proliferation and migration of MM cells. In the present study, we investigated whether BDNF was present in marrow from patients with MM and possibly involved in MM cell-induced osteolysis. Methods and Results:Levels of bone marrow plasma BDNF was measured by ELISA in a cohort of individuals with MM and controls. The concentration of BDNF was found to be significantly elevated in patients with MM (879 ± 93) pg/ml when compared with bone marrow plasma derived from normal control subjects (186 ± 52) pg/ml (p < 0.001). Moreover, bone marrow plasma levels of BDNF positively correlated with plasma cell burden and extent of bone disease in MM patients. In osteoclast formation assay, bone marrow plasma from 31 of 37 patients with MM tested significantly stimulated the formation of osteoclast when compared to controls (61.8 ± 7 [mean ± SEM for the 31 patients] versus 25.2 ± 6 TRAP+ multinucleated cells/well [mean ± SEM for the 12 controls]; p < 0.01). The effect was significantly blocked by a neutralizing antibody to BDNF (p < 0.05), suggesting a critical role for BDNF in osteoclast activation. Furthermore, BDNF was found to dose-dependently increased the formation of multinucleated, TRAP+ osteoclast. The direct effects of recombinant BDNF on osteoclast formation and bone resorption support the potential role of BDNF in the MM bone disease. Using reverse-transcriptase polymerase chain reaction analysis and western blotting assay, we demonstrated that BDNF receptor TrkB was expressed by human osteoclast precursors and a Trk inhibitor K252a markedly inhibited osteoclast formation stimulated with BDNF. These data suggested that TrkB is the functional receptor mediating BDNF's effect on osteoclast formation. Finally, bone marrow plasma BDNF level positively correlated with macrophage inflammatory protein (MIP)-1α (r = 0.45, p < 0.005) and receptor activator of nuclear factor-κB ligand (RANKL) (r = 0.68, p < 0.0001), two major osteoclast stimulatory factors in MM. Conclusion:Taken together, our results demonstrate the ability of MM cells to secret BDNF correlates with the severity of osteoclastic bone resorption, and provide evidence that BDNF play a causal role in the development of MM bone lesions through TrkB receptor. Disclosures:No relevant conflicts of interest to declare.

Fc-Engineered RANK-Fc Fusion Proteins for Neutralization of Soluble RANKL and Induction of Antibody-Dependent Cellular Cytotoxicity (ADCC) Against Multiple Myeloma

AbstractAbstract 3039Bone resorption is commonly associated with aging, but also with certain cancers. Recent studies identified Receptor Activator of NF-κB (RANK) ligand (RANKL) and its receptors RANK and osteoprotegerin as key regulators of bone remodelling. Multiple myeloma (MM) disrupts the balance within this molecule system towards osteoclastogenesis and bone destruction. Neutralization of RANKL by the monoclonal antibody Denosumab (AMG162) is presently being evaluated for treatment of both non-malignant and malignant osteolysis. We found, in line with previously published data, that primary MM cells (9 of 10) express substantial levels of RANKL at the cell surface and that MM cells directly release RANKL in soluble form (sRANKL). Next we evaluated the possibility to combine neutralization of sRANKL with targeting of MM cells for antibody-dependent cellular cytotoxicity (ADCC) of NK cells utilizing RANK-Ig fusion proteins with modified Fc portions. Compared to wildtype RANK-Fc, our mutants (S239D/I332E and E233P/L234V/L235A/DG236/A327G/A330S) displayed highly enhanced (RANK-Fc-ADCC) and abrogated (RANK-Fc-KO) affinity, respectively, to the NK cell FcγRIIIa, but comparable capacity to neutralize RANKL in binding competition and osteoclast formation assays. Analyses with RANKL transfectants and RANKL-negative controls confirmed the high and lacking potential of the RANK-Fc-ADCC and the RANK-Fc-KO to induce NK ADCC, respectively, and ascertained that the RANK-Fc-ADCC specifically induced NK cell lysis of RANKL-expressing but not RANKL-negative target cells. Most notably, in cultures of NK cells with RANKL-expressing primary MM cells RANK-Fc-ADCC potently enhanced NK cell degranulation, cytokine release and MM cells lysis due to enhanced NK reactivity. Thus, our Fc-engineered RANK-Fc-ADCC fusion protein may both neutralize detrimental effects of sRANKL and enhance NK anti-tumor reactivity by targeting RANKL-expressing malignant cells thereby constituting an attractive immunotherapeutic means for treatment of MM. Disclosures:No relevant conflicts of interest to declare.

Gain-of-function mutation in FGFR3 in mice leads to decreased bone mass by affecting both osteoblastogenesis and osteoclastogenesis

Achondroplasia (ACH) is a short-limbed dwarfism resulting from gain-of-function mutations in fibroblast growth factor receptor 3 (FGFR3). Previous studies have shown that ACH patients have impaired chondrogenesis, but the effects of FGFR3 on bone formation and bone remodeling at adult stages of ACH have not been fully investigated. Using micro-computed tomography and histomorphometric analyses, we found that 2-month-old Fgfr3(G369C/+) mice (mouse model mimicking human ACH) showed decreased bone mass due to reduced trabecular bone volume and bone mineral density, defect in bone mineralization and increased osteoclast numbers and activity. Compared with primary cultures of bone marrow stromal cells (BMSCs) from wild-type mice, Fgfr3(G369C/+) cultures showed decreased cell proliferation, increased osteogenic differentiation including up-regulation of alkaline phosphatase activity and expressions of osteoblast marker genes, and reduced bone matrix mineralization. Furthermore, our studies also suggest that decreased cell proliferation and enhanced osteogenic differentiation observed in Fgfr3(G369C/+) BMSCs are caused by up-regulation of p38 phosphorylation and that enhanced Erk1/2 activity is responsible for the impaired bone matrix mineralization. In addition, in vitro osteoclast formation and bone resorption assays demonstrated that osteoclast numbers and bone resorption area were increased in cultured bone marrow cells derived from Fgfr3(G369C/+) mice. These findings demonstrate that gain-of-function mutation in FGFR3 leads to decreased bone mass by regulating both osteoblast and osteoclast activities. Our studies provide new insight into the mechanism underlying the development of ACH.

Correlation of COX2 expression with tumor-induced osteoclastic lesions in breast cancer bone metastasis

1116 Background: Metastatic dissemination is complicated and depends largely on the interaction of primary tumors and the local host environment. In this study we have established a new mouse model to mimic the process of tumor metastasis in breast cancer patients and revealed the enhancing influence of COX2 expression on bone metastases in breast cancer. Methods: TM40D-MB mouse mammary tumor cells were transplanted to the mammary glands of syngeneic mice, causing a local tumor and were metastatic to bone. We compared the expression profile of high (TM40D-MB) versus low metastatic (TM40D) tumor cells using the Affymetrix microarray platform. Differentially expressed genes were confirmed by Northern-blot analysis. The COX2 gene was selected for further functional studies. TM40D-COX2 and TM40D-C controle cells were injected to mouse femur and the effect was analysed by microcomputed tomography (μCT) scanning for trabecular bone volume. Shown effects were challenged by selective COX2 inhibition (NS-398) in an osteoclast formation assay. Results: Mammary tumors developed in the glands in situ and were metastatic to bone with over 53% efficiency. Microarray analysis revealed a list of genes that were consistently up-/down-regulated in TM40D-MB tumor cells. Various differentially expressed genes (e.g. PTX3, FGF7, COX2) were confirmed using Northern-blot analysis. Injection of TM40D-COX2 cells to mouse femur caused a significant increase in bone destruction compared to TM40D-C as measured by the micro-computed tomography. In vitro assays showed that COX2 significantly increased the rate of osteoclast formation, and this effect was reversible by the specific COX2 inhibitor. Conclusions: These data indicate that COX2 expression can influence bone metastasis in this new breast cancer model. The availability of this mouse model and the comparative study of gene expression signatures between TM40D and other bone metastasis models will likely generate important information about common pathways for breast cancer bone metastasis. Further functional studies of metastasis signature genes should help to develop means to curb the metastasis process. Clinical evaluation of specific COX2 inhibitors will clarify the use of these drugs in adjuvant and advanced disease treatment. No significant financial relationships to disclose.

CREM deficiency in mice alters the response of bone to intermittent parathyroid hormone treatment

CREM belongs to the ATF/CREB family of basic leucine zipper transcription factors. We previously showed that PTH induces ICER (inducible cAMP early repressor) in osteoblasts. ICER proteins, which are transcribed from the P2 promoter of the Crem gene, act as transcriptional attenuators. The objective of this study was to determine whether the Crem gene plays a role in the response of bone to intermittent PTH. Adult Crem knockout (KO) and wild type (WT) male mice were given daily subcutaneous injections of vehicle or hPTH(1–34) (160 μg/kg) for 10 days. Bone mineral content and density (BMC and BMD, respectively) were measured in femur and tibia by dual energy X-ray absorptiometry (DEXA). Bone morphometry was analyzed by X-ray computed microtomography (microCT) and histomorphometry. Serum bone turnover markers were measured. In vitro osteoclast formation assays were performed in bone marrow cultures treated with PTH or the combination of RANKL and M-CSF. KO mice had slightly higher basal bone mass than wild type mice. PTH treatment increased tibial BMC and BMD to a greater extent in WT mice compared to KO mice. PTH increased both cortical area and trabecular bone area in WT but not in KO femurs. PTH increased the bone formation rate and percent osteoblast surface to the same extent in femurs of WT and KO mice but increased osteoclast parameters and calvarial porosity to a greater extent in KO mice. PTH increased serum osteocalcin levels to the same extent in WT and KO mice. PTH-induced osteoclast formation was 2-fold greater in bone marrow cultures from KO mice. Collectively, our data suggest that the CREM deficiency in mice alters the response of bone to intermittent PTH treatment such that osteoclastogenesis is increased. Crem gene may specify the anabolic response to intermittent PTH treatment by restraining PTH-induced osteoclastogenesis.

Negative Regulation of Osteoclastogenesis by Ectodomain Shedding of Receptor Activator of NF-κB Ligand

Receptor activator of NF-kappaB ligand (RANKL) is a transmembrane glycoprotein that has an essential role in the development of osteoclasts. The extracellular portion of RANKL is cleaved proteolytically to produce soluble RANKL, but definite RANKL sheddase(s) and the physiologic function of RANKL shedding have not yet been determined. In the present study, we found that matrix metalloproteinase (MMP) 14 and a disintegrin and metalloproteinase (ADAM) 10 have strong RANKL shedding activity. In Western blot analysis, soluble RANKL was detected as two different molecular weight products, and RNA interference of MMP14 and ADAM10 resulted in a reduction of both the lower and higher molecular weight products. Suppression of MMP14 in primary osteoblasts increased membrane-bound RANKL and promoted osteoclastogenesis in cocultures with macrophages. Soluble RANKL produced by osteoblasts from MMP14-deficient mice was markedly reduced, and their osteoclastogenic activity was promoted, consistent with the findings of increased osteoclastogenesis in vivo. RANKL shedding is an important process that down-regulates local osteoclastogenesis.

Characterization of Sugar Binding by Osteoclast Inhibitory Lectin

Osteoclast inhibitory lectin (OCIL) is a membrane-bound C-type lectin that blocks osteoclast differentiation and, via binding to its cognate receptor NKRP1D, inhibits natural killer cell-mediated cytotoxicity. OCIL is a member of the natural killer cell receptor C-type lectin group that includes CD69 and NKRP1D. We investigated carbohydrate binding of soluble recombinant human and mouse OCIL in enzyme-linked immunosorbent assay-based assays. OCIL bound immobilized high molecular weight sulfated glycosaminoglycans, including fucoidan, lambda-carrageenan, and dextran sulfate, but not unsulfated dextran or sialated hyaluronic acid. Carbohydrate binding was Ca(2+)-independent. Binding of immobilized low molecular weight glycosaminoglycans, including chondroitin sulfate (A, B, and C forms) and heparin, was not observed. However, the soluble forms of these low molecular weight glycosaminoglycans competed for OCIL binding of immobilized fucoidan (as did soluble fucoidan, dextran sulfate, and lambda-carrageenan), indicating that OCIL does recognize these carbohydrates. Inhibition constants for chondroitin sulfate A and heparin binding were 380 and 5 nm, respectively. Immobilized and soluble monosaccharides did not bind OCIL. The presence of saturating levels of fucoidan, dextran sulfate, and lambda-carrageenan did not affect OCIL inhibition of osteoclast formation. The fucoidan-binding lectins Ulex europaeus agglutinin I and Anguilla anguilla agglutinin did not block osteoclast formation or affect the inhibitory action of OCIL. Although the osteoclast inhibitory action of OCIL is independent of sugar recognition, we have found that OCIL, a lectin widely distributed, but notably localized in bone, skin, and other connective tissues, binds a range of physiologically important glycosaminoglycans, and this property may modulate OCIL actions upon other cells.

Erythromycin inhibits wear debris-induced osteoclastogenesis by modulation of murine macrophage NF-κB activity

Activation of nuclear factor kappa B (NF-κB) signaling in response to cell stimulation by wear debris may be critical in the pathogenesis of aseptic loosening. Erythromycin (EM), a macrolide antibiotic, has been shown to effectively suppress some types of inflammatory reactions. In this study, we examined the effect of EM on wear debris-induced osteoclastic bone resorption in vitro. EM inhibited Ca + release from neonatal calvaria co-cultured with conditioned medium from mouse RAW264.7 macrophages activated by wear debris. Inhibition of Ca + release was associated with a decreased number of tartrate-resistant acid phosphatase (TRAP)-positive cells in cultured bones. To investigate the mechanism whereby EM inhibits bone-resorption, RAW cells were incubated with wear debris in the presence EM. Real time RT-CR analysis revealed that EM (5 μg/ml) significantly inhibited mRNA expression of NF-κB, cathepsin K (CPK), IL-1β and TNFα, but not RANK in RAW cells stimulated with wear debris. Furthermore, electrophoretic mobility-shift assay showed that EM (0.2 μg–5 μg/ml) could reduce DNA-binding activity of NF-κB in RAW cells stimulated with wear debris. The inhibition of inflammatory osteoclastogenesis by EM treatment was further confirmed by an osteoclast (OC) formation assay using primary cultures of mouse bone marrow progenitor cells stimulated with macrophage colony-stimulating factor and RANK ligand (RANKL). EM treatment (5 μg/ml) resulted in more than 70% reduction in multinucleated OC formation and 50% reduction of TRAP + cells by bone marrow progenitor cells. Our findings support that EM suppresses wear debris-induced osteoclastic bone resorption by, at least, down-regulation of NF-κB signaling pathway. It appears that EM represents a potential therapeutic candidate for the treatment and prevention of aseptic loosening.

A Novel Osteoblast-derived C-type Lectin That Inhibits Osteoclast Formation

We have cloned and expressed murine osteoclast inhibitory lectin (mOCIL), a 207-amino acid type II transmembrane C-type lectin. In osteoclast formation assays of primary murine calvarial osteoblasts with bone marrow cells, antisense oligonucleotides for mOCIL increased tartrate-resistant acid phosphatase-positive mononucleate cell formation by 3-5-fold, whereas control oligonucleotides had no effect. The extracellular domain of mOCIL, expressed as a recombinant protein in Escherichia coli, dose-dependently inhibited multinucleate osteoclast formation in murine osteoblast and spleen cell co-cultures as well as in spleen cell cultures treated with RANKL and macrophage colony-stimulating factor. Furthermore, mOCIL acted directly on macrophage/monocyte cells as evidenced by its inhibitory action on adherent spleen cell cultures, which were depleted of stromal and lymphocytic cells. mOCIL completely inhibited osteoclast formation during the proliferative phase of osteoclast formation and resulted in 70% inhibition during the differentiation phase. Osteoblast OCIL mRNA expression was enhanced by parathyroid hormone, calcitriol, interleukin-1alpha and -11, and retinoic acid. In rodent tissues, Northern blotting, in situ hybridization, and immunohistochemistry demonstrated OCIL expression in osteoblasts and chondrocytes as well as in a variety of extraskeletal tissues. The overlapping tissue distribution of OCIL mRNA and protein with that of RANKL strongly suggests an interaction between these molecules in the skeleton and in extraskeletal tissues.