Project description:Objective: To study the effects of Short Chain Fatty Acids (SCFAs) on arthritic bone remodeling. Methods: We treated a recently described preclinical murine model of psoriatic arthritis (PsA), R26STAT3Cstopfl/fl CD4Cre mice, with SCFA supplemented water. We also performed in vitro osteoclast differentiation assays in the presence of serum-level SCFAs to evaluate the direct impact of these microbial metabolites on maturation and function of osteoclasts. We further characterized the molecular mechanism of SCFAs by bulk transcriptomics analysis. Results: The osteoporosis condition in R26STAT3Cstopfl/fl CD4Cre animals is attributed primarily to an expansion of osteoclast progenitor cells (OCPs), leading to robust osteoclast differentiation. We show that SCFA supplementation can rescue the osteoporosis phenotype in this model of PsA. Our in vitro experiments revealed an inhibitory effect of the SCFAs on osteoclast differentiation, even at very low serum concentrations. This suppression of osteoclast differentiation enabled SCFAs to impede osteoporosis development in R26STAT3Cstopfl/fl CD4Cre mice. Further interrogation revealed that bone marrow derived OCPs from diseased mice expressed a higher level of SCFA receptors than that of control mice and that the progenitor cells in the bone marrow of SCFA-treated mice presented a modified transcriptomic landscape, suggesting a direct impact by SCFAs on osteoclast progenitors. Conclusion: We demonstrated how gut microbiota-derived SCFAs can regulate distal pathology, i.e., osteoporosis, and identified a potential therapeutic option for restoring bone density in rheumatic disease, further highlighting the critical role of the gut-bone axis in these disorders.
Project description:Osteoclast differentiation is crucial for bone absorption and osteoclast is involved in bone destruction in rheumatoid arthritis. The aim of this study was to investigate the inhibitory effect of MJ2 on osteoclast differentiation and to elucidate its mechanism. Murine macrophage cell line, Raw 264.7 cells and collagen-induced arthritis mouse model were used for in vitro and in vivo study, respectively. MJ2-treated cells significantly inhibited osteoclast differentiation and decreased arthritic score. Surface proteins (SP) extracted from MJ2 also showed inhibitory effect on osteoclast differentiation by upregulating lipocalin 2 (lcn2) expression. Specifically, heat shock protein 60 (hsp60) in SP was revealed as an active component of MJ2. Hsp60 inhibited binding of receptor activator of nuclear factor-κB ligand (RANKL) to receptor activator of nuclear factor κB (RANK). In conclusion, MJ2 inhibited osteoclast formation and differentiation through lcn2 and RANKL-binding property and the effective component of MJ2 might be hsp60 present in surface layer.
Project description:We used microarrays to understand the effect miR-155 has on osteoclast differentiation. RAW264.7 cells were grown in a-MEM supplemented with 10% FBS and antibiotics. mRNA extracted from wild-type RAW264.7 cells and miR-155 mis-expressing cells either before or after 72 hr of stimulation with 20ng/ml RANKL and M-CSF to induce osteoclast differentiation.
Project description:Intercellular communication is essential in bone remodelling to ensure that new bone is formed with only temporary bone loss. Monocytes and osteoclasts actively take part in controlling bone remodelling by providing signals that promote osteogenic differentiation of mesenchymal stem/stromal cells (MSCs). Extracellular vesicles (EVs) have attracted attention as regulators of bone remodelling. EVs facilitate intercellular communication by transferring a complex cargo of biologically active molecules to target cells. In the present study, we evaluated the potency of EVs from monocytes and osteoclasts to induce a lineage-specific response in MSCs. We analysed gene expression and protein secretion by both adipose tissue-derived MSCs and bone marrow-derived MSCs after stimulation with EVs from lipopolysaccharide-activated primary human monocytes and (mineral-resorbing) osteoclasts. Isolated EVs were enriched in exosomes (EVs of endosomal origin) and were free of cell debris. Monocyte- and osteoclast-derived EVs were taken up by adipose tissue-derived MSCs. EVs from activated monocytespromoted the secretion of cytokines by MSCs, which may represent an immunomodulatory mechanism. Monocyte-derived EVs also upregulated the expression of genes encoding for matrix metalloproteinases. Therefore, we hypothesize that monocytes facilitate tissue remodelling through EV-mediated signalling. We did not observe a significant effect of osteoclast-derived EVs on gene expression or protein secretion in MSCs. EV-mediated signalling might represent an additional mode of cell-cell signalling during the transition from injury and inflammation to bone regeneration and play an important role in the coupling between bone resorption and bone formation. This article is protected by copyright. All rights reserved.
Project description:Enhanced osteoclastogenesis and osteoclast activity contribute to the development of osteoporosis, which is characterized by increased bone resorption and inadequate bone formation. As novel anti-osteoporotic therapeutics are needed, understanding the genetic regulation of human osteoclastogenesis could help identify potential treatment targets. This study aimed to provide an overview of the transcriptional reprogramming during human osteoclast differentiation. Osteoclasts were differentiated from CD14+-monocytes from eight female donors. RNA-sequencing during differentiation demonstrated 8980 differentially expressed genes grouped into eight temporal patterns conserved across donors. These patterns showed distinct molecular functions, associated with postmenopausal osteoporosis susceptibility genes based on RNA from iliac crest biopsies, and bone mineral density SNPs. Network analyses showed mutual dependencies between the temporal expression patterns and provides insight into subtype-specific transcriptional networks. Donor specific expression patterns identified genes at monocyte stage, such as filamin B (FLNB) and oxidized low density lipoprotein receptor 1 (OLR1, encoding LOX-1), that are predictive for the resorptive activity of mature osteoclasts. Differentially expressed G-protein coupled receptors showed strong expression during osteoclast differentiation and associated with bone mineral density SNPs, implying a pivotal role in osteoclast differentiation and activity. The regulatory effects of three differentially expressed G-protein coupled receptors were exemplified by in vitro pharmacological modulation of complement 5A receptor 1 (C5AR1), somatostatin receptor 2 (SSTR2), and free fatty acid receptor 4 (FFAR4/GPR120). Activating C5AR1 enhanced osteoclast formation, while activating SSTR2 decreased resorptive activity of mature osteoclasts, and activating FFAR4 decreased both number and resorptive activity of mature osteoclasts. In conclusion, we report the transcriptional reprogramming during human osteoclast differentiation and identified SSTR2 and FFAR4 as anti-resorptive G-protein coupled receptors as well as FLNB and LOX-1 as potential molecular markers of osteoclast activity. These data can help future investigations to identify molecular regulators of osteoclast differentiation and activity and provide the basis for novel anti-osteoporotic targets.
Project description:Embryonically established osteoclast precursors expressing tdTomato reporter gene were analyzed by single cell RNA-sequencing. Data showed that hematopoietic stem cell independent yolk-sac erythromyeloid progenitors produced embryonic osteoclast precursors.
Project description:The deubiquitinase activity of Bap1 modifies osteoclast function by metabolic reprogramming. Bap1 deficient osteoclast lineage cells upregulate the cystine transporter, Slc7a11, by enhanced H2Aub occupancy of its promoter. SLC7A11 controls cellular ROS levels and redirects the mitochondrial metabolites away from the TCA cycle, both of which are necessary for osteoclast function.
Project description:To survey the proteome of osteoclast secretory lysosomes, we used superparamagnetic iron oxide nanoparticles (SPIONs) to enrich for these endo-lysosomal-related organelles from murine osteoclast cultures. Briefly, large scale murine bone marrow monocyte (BMM)-derived osteoclast cultures were ‘pulsed’ with SPIONs to encourage uptake into endosomes and then ‘chased’ into secretory lysosomes upon the convergence of SPION-loaded endosomes with lysosomes and secretory pathways. Following the ‘pulse-chase’, osteoclasts were homogenized, SPION-loaded organelles captured-from post-nuclear supernatants using magnetic columns, and enriched organelles eluted and processed for 1D in-gel digestion and mass spectrometry.