Calcitonin controls bone formation by inhibiting the release of sphingosine 1-phosphate from osteoclasts
ABSTRACT: The hormone calcitonin (CT) is primarily known for its pharmacologic action as an inhibitor of bone resorption, yet CT-deficient mice display increased bone formation. These findings raised the question about the underlying cellular and molecular mechanism of CT action. Here we show that either ubiquitous or osteoclast-specific inactivation of the murine CT receptor (CTR) causes increased bone formation. CT negatively regulates the osteoclast expression of Spns2 gene, which encodes a transporter for the signaling lipid sphingosine 1-phosphate (S1P). CTR-deficient mice show increased S1P levels, and their skeletal phenotype is normalized by deletion of the S1P receptor S1P3. Finally, pharmacologic treatment with the non-selective S1P receptor agonist FTY720 causes increased bone formation in wildtype, but not in S1P3-deficient mice. This study redefines the role of CT in skeletal biology, confirms that S1P acts as an osteoanabolic molecule in vivo, and provides evidence for a pharmacologically exploitable crosstalk between osteoclasts and osteoblasts. Osteoclasts of wildtype and Calcr-/- C57Bl/6 mice were treated with Calcitonin and compared to the non-treated osteoclasts of wildtype or Calcr-/- mice, respectively.
Project description:Genetic deletion of Nfatc1 in mice results in profound osteoclast-poor osteopetrosis, a high bone mass state caused by a lack of osteoclast activity. We hypothesized that the family of NFATc1 regulated transcripts in the osteoclast would be enriched for genes associated with osteoclast function. We used microarrays profile gene expression in wild-type and NFATc1-deficient osteoclasts generated in vitro to identify NFATc1-dependent transcripts in osteoclasts. Bone marrow macrophages from wild-type and mice with an induced deficiency of NFATc1 (NFATc1 fl/fl MxCre+ mice where NFATc1 excision was induced by polyIC treatment) were cultured ex vivo in MCSF and RANKL for 3 days. 2 biological replicates were assayed for each genotype.
Project description:Osteoclastogenesis is induced by the stimulation of RANKL. In the early stage of osteoclast differentiation, the osteoclast progenitor cells are primed by M-CSF, following a tightly controlled genetic program where specific sets of genes are up-regulated by RANKL. Some of them, for instance, control differentiation, cell-cell fusion and bone resorption. We used microarrays to detail the global program of gene expression underlying osteoclastogenesis and identified various up-regulated genes during this process. Macrophages and osteoclasts were cultured for RNA extraction and hybridization on Affymetrix microarrays. We sought to obtain homogeneous populations of macrophages and osteoclasts in order to increase the temporal resolution of expression profiles. To that end, mouse bone marrow cells were cultured in the presence of M-CSF for three days and harvested as macrophage and oseteoclast common progenitor cells. Then common progenitor cells were further cultured in the presence of M-CSF alone for macrophages and M-CSF plus RANKL for osteoclasts, respectively.
Project description:Bone remodeling is characterized by the sequential, local tethering of osteoclasts and osteoblasts, and is key to the maintenance of bone integrity. While bone matrix-mobilized growth factors, such as TGF-β, are proposed to regulate remodeling, no in vivo evidence exists that an osteoclast-produced molecule is the enigmatic coupling factor. We have identified Cthrc1, a protein secreted by mature bone-resorbing osteoclasts, that targets stromal cells so as to stimulate osteogenesis. The expression of Cthrc1 is robustly induced when mature osteoclasts are placed on dentin or hydroxyapatite, and also by increasing extracellular calcium. Cthrc1 expression in bone increases in a high turnover state, such as that which is induced by RANKL injections in vivo, whereas it decreases with aging or following alendronate treatment, conditions associated with suppressed bone turnover. The targeted deletion of the Cthrc1 gene eliminates Cthrc1 expression in bone, whereas its deficiency in osteoblasts does not exert any significant effect. Osteoclast-specific deletion of the Cthrc1 gene results in osteopenia due to reduced bone formation: it also impairs the coupling process following resorption induced by RANKL injections, with a resultant impairment of bone mass recovery. Thus, Cthrc1 is an osteoclast-secreted “coupling factor” that regulates bone remodeling and hence, skeletal integrity. Total bone marrow cells were prepared from the femurs and tibias of 8-10-week-old C57BL/6 mice and cultured in the presence of M-CSF (100ng/ml) for 3 days as described previously (Takeshita et al., 2000 JBMR 15:1477-1488). Cells were harvested with 0.02% EDTA/PBS and used as bone marrow macrophages (BMMs). These BMMs were cultured in the presence of M-CSF (100 ng/ml) and RANKL (100ng/ml) for 2 days. TRAP positive mononuclear cells were harvested and used as pre-osteoclasts (pOC). These pOC cells were further cultured in the presence of M-CSF and RANKL for 2 days in normal plastic plate or on dentin slices. After 2 days, multinucleated TRAP positive mature osteoclasts were generated as mature osteoclasts on plate (mOCp) and mature resorbing osteoclasts on dentin (mOCd), respectively. RNAs were extracted from four different stages of osteoclast lineage cells; BMMs, pOC, mOCp and mOCd, and used for microarray analysis.
Project description:Osteoclasts are multinucleated cells specialized in degrading the mineralized bone matrix. Osteoclast differentiation and function are tightly regulated, to prevent excessive or insufficient bone resorption. Several control mechanisms participate in modulating osteoclastogenesis, and an increasing number of reports describe the role of microRNAs (miRNAs) in this process. Disrupting the expression of specific miRNAs can result in alterations of osteoclast formation and bone homeostasis. We and others have previously characterized 9 miRNAs whose levels change during osteoclast differentiation, and identified some of the target genes that mediate their function. However, little is known about changes in the miRNA expression profile during osteoclastogenesis. In this study, we isolated a murine primary bone marrow population enriched for osteoclast precursors, and used the Agilent microarray platform to analyze the expression of mature miRNAs after 1, 3, and 5 days of RANKL-driven differentiation. 93 miRNAs showed greater than 2 fold-change during these early, middle, and late stages of osteoclastogenesis. Many of these miRNAs were detected for the first time in osteoclasts, and we validated the expression of selected miRNAs by quantitative RT-PCR. We identified clusters of differentially expressed miRNAs, and performed computational analyses to predict functional pathways that may be regulated by these miRNAs. Several miRNAs were predicted to regulate genes involved in cytoskeletal remodeling, a crucial mechanism for the migration of osteoclast precursors, their maturation, and bone resorbing activity. Our results suggest that clusters of miRNAs differentially expressed during the course of osteoclastogenesis converge on the regulation of several key functional pathways. Overall, this study identified miRNAs expressed during early, middle and late osteoclastogenesis, contributing to understanding the molecular mechanisms regulating this complex differentiation process. Mouse primary bone marrow cultures were enriched for osteoclast precursors by depletion of B220/CD45R+ and CD3+ cells (B and T lymphocytes, respectively). Cells were differentiated with M-CSF and RANKL, and miRNA expression was analyzed at days 1, 3, and 5. Four biological replicates for each time point were used.
Project description:Epigenetic regulation is a fundamental mechanism mediating various cellular processes. However, epigenetic mechanisms in osteoclastogenesis remain to be elucidated. We performed microarray analysis to investigate gene expression in osteoclasts derived from wild-type and Dnmt3aknockout mice. In vitro osteoclast culture were performed using wild-type control and Dnmt3a knockout bone marrow-derived monocyte/macrophage precursor cells.
Project description:Paget’s disease of bone (PDB) is a chronic focal skeletal disorder that affects 2-3% of the population over the age of 60. PDB is inherited as an autosomal dominant trait with genetic heterogeneity. SQSTM1/p62 UBA domain mutation (p62P392L) is widely identified in PDB and has been shown to increase osteoclastogenesis. Further, environmental factors such as paramyxovirus are implicated in PDB and MVNP has been shown to induce Pagetic phenotype in osteoclasts. However, the molecular mechanisms underlying p62P392L and MVNP stimulation of osteoclast differentiation in PDB are unclear. We therefore determined p62P392L regulated gene expression profiling during osteoclast differentiation. We identified 9.7% genes were upregulated (> 4-fold) in p62P392L transduced cells. P62P392L mutant increased Integrin β3 (185 fold), integrin β5 (26 fold), IL-1α (11 fold), IL-6R (8 fold), CXCL-2 (7.5 fold), CXCL-3 (5 fold) compared to p62WT transduced cells. Furthermore, bone marrow mononuclear cells derived from patients with PDB showed high levels of SIRPβ1 mRNA expression compared to normal subjects. Thus, p62P392L mutant regulated gene expression profiling during osteoclast differentiation provides new insights into molecular mechanisms and therapeutic targets to control elevated osteoclast activity in PDB. Total RNA isolated from normal human bone marrow mononuclear cells transduced with p62EV, p62WT, p62P392L retroviral expression vectors and stimulated with M-CSF and RANKL for 48 h were subjected to Agilent microarray (~26,000 genes) analysis. One replicate per treatment was hybridized.
Project description:Conversion of monocytes to osteoclasts is a unique terminal differentiation process within the hematopoietic system involving differentiation and massive cell fusion. Here we focused on DNA methylation changes during osteoclastogenesis. Hypermethylation and hypomethylation changes took place in several thousand genes, including all relevant functional categories in osteoclast differentiation and function. Comparison between the DNA methylation levels of CD14+ monocytes and derived osteoclast from 3 female donors. Bisulphite converted DNA from the 6 samples was hybridised to the Illumina Infinium 450k Human Methylation Beadchip
Project description:Paget’s disease of bone (PDB) is a chronic focal skeletal disorder that affects 2-3% of the population over the age of 60. PDB is inherited as an autosomal dominant trait with genetic heterogeneity. SQSTM1/p62 UBA domain mutation (p62P392L) is widely identified in PDB and has been shown to increase osteoclastogenesis. Further, environmental factors such as paramyxovirus are implicated in PDB and MVNP has been shown to induce Pagetic phenotype in osteoclasts. However, the molecular mechanisms underlying p62P392L and MVNP stimulation of osteoclast differentiation in PDB are unclear. We therefore determined MVNP regulated gene expression profiling during osteoclast differentiation. We identified 8.4% of genes were upregulated (> 4-fold) in MVNP transduced cells. MVNP increased integrin β3 (63 fold), NFAT activating protein (6.5 fold), OSCAR (5.5 fold), TRAF5 (8.5 fold) mRNA expression compared to empty vector (EV) transduced cells. MVNP also elevated gene expression of cytokines/growth factors such as IL-17 (18 fold), IL-1F7 (10 fold), IL-17R (4.5 fold) and IL-11 (7 fold). Interestingly, MVNP transduced cells demonstrated high level expression of signal regulatory protein beta 1 (SIRPβ1) (353 fold). SIRPβ1 has been shown to interact with DAP 12, an ITAM containing adaptor protein which plays an important role in osteoclast differentiation. Real-time PCR analysis of total RNA isolated from normal human peripheral blood monocytes transduced with MVNP confirmed upregulation of SIRPβ1 mRNA expression in the absence of RANKL stimulation. In contrast, RANKL stimulation did not alter SIRPβ1 expression in these cells. Furthermore, bone marrow mononuclear cells derived from patients with PDB showed high levels of SIRPβ1 mRNA expression compared to normal subjects. Thus, MVNP regulated gene expression profiling during osteoclast differentiation provides new insights into molecular mechanisms and therapeutic targets to control elevated osteoclast activity in PDB. Total RNA isolated from normal human bone marrow mononuclear cells transduced with EV, MVNP retroviral expression vectors and stimulated with M-CSF and RANKL for 48 h were subjected to Agilent microarray (~26,000 genes) analysis. One replicate per treatment was hybridized.
Project description:This experiment aimed to investigate the differential gene expression during differentiation of primary mouse bone marrow stem cells into osteoclasts. We treated primary mouse bone marrow stem cells with Receptor activator of nuclear factor kappa B ligand (RANKL) and DMSO (control) or RANKL and Oleg Federov (compound no. 1) (OF-1) and isolated the cells for RNA extraction at 24 h, 48 h, 72 h after treatment. We profiled genome-wide RNA expression with Illumina MouseWG-6 v2.0 Expression BeadChips.
Project description:Comparison of gene expression of the osteoclast precursor myeloid blast seeded on plastic and on bone, primed with M-CSF for 4 days and culture with M-CSF and RANKL for 1 day. Osteoclasts and macrophages share progenitors that must receive decisive lineage signals driving them into their respective differentiation routes. Macrophage colony stimulation factor M-CSF is a common factor; bone is likely the stimulus for osteoclast differentiation. To elucidate the effect of both, shared mouse bone marrow precursor myeloid blast was pre-cultured with M-CSF on plastic and on bone. M-CSF priming prior to stimulation with M-CSF and osteoclast differentiation factor RANKL resulted in a complete loss of osteoclastogenic potential without bone. This coincided with a steeply decreased expression of osteoclast genes TRACP and DC-STAMP, but an increased expression of the macrophage markers F4/80 and CD11b. Compellingly, M-CSF priming on bone accelerated the osteoclastogenic potential: M-CSF primed cells that had received only one day M-CSF and RANKL and were grown on bone already expressed an array of genes that are associated with osteoclast differentiation and these cells differentiated into osteoclasts within 2 days. This implies that adhesion to bone dictates the fate of osteoclast precursors. Common macrophage-osteoclast precursors may become insensitive to differentiate into osteoclasts and regain osteoclastogenesis when bound to bone or when in the vicinity of bone. Two conditions: Osteoclast precursors on plastic and on bone, n=4, dye swap