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Bone marrow adipose tissue (BMAT) accrues in osteoporosis, whereas its contribution to the progression of bone resorption remains insufficiently understood. To understand the mechanisms that promote BMAT expansion in osteoporosis, in the present study, we performed extensive analysis of the spatiotemporal pattern of BMAT expansion during the progression of bone resorption in TgRANKL transgenic mouse models of osteoporosis expressing human RANKL (receptor activator of nuclear factor‐κB ligand). Our results showed that TgRANKL mice of both sexes developed dramatically increased BMAT expansion compared to wild‐type (WT) littermates, that was analogous to the levels of RANKL expression and the severity of the bone loss phenotype. BMAT was formed at close proximity to areas undergoing active bone remodelling and bone resorption, whereas bone resorption preceded BMAT development. Expression analysis in bone fractions demonstrated that BMAT constitutes a major source for RANKL production. Ex vivo analysis of isolated bone marrow stromal cells from TgRANKL mice showed an increased adipogenic differentiation capacity compared to WT, while osteoclast supernatants further exaggerated adipogenesis, supporting a critical role of the osteoclast‐derived secretome in the differentiation of bone marrow adipocytes. Furthermore, the effectiveness of an antiosteoporosis treatment in BMAT development was investigated upon treatment of TgRANKL models with the bisphosphonate alendronate. Notably, alendronate effectively improved bone mass and attenuated BMAT expansion, indicating a possible involvement of osteoclasts and bone resorption in BMAT development. On the contrary, inhibition of BMAT with PPARγ antagonists (GW9662 or BADGE) effectively ameliorated BMAT expansion but failed to reverse the osteoporotic phenotype of TgRANKL mice. Overall, our data demonstrate that TgRANKL mice constitute unique genetic mouse models for investigating the pathogenic mechanisms that regulate the development and expansion of BMAT in osteolytic diseases. [ABSTRACT FROM AUTHOR]

Background: Root resorption consists of complex, multistep processes that involve cell signalling caused by inflammation and stromal cells, which promotes the secretion of receptor activator of nuclear factor κB ligand/ macrophage‐colony stimulating factor (RANKL/M‐CSF) resulting in a resorptive process. Objective: The aim of this narrative review was to analyse the literature related to root resorption resulting from microbial infection and to comparing it with non‐microbial infection. Methods: An electronic literature search was performed using the PubMed database and applying keywords of articles published in English. Eligible papers were reviewed to reveal the descriptions of bone and root resorption processes. The abstracts were searched manually to identify articles about infection‐stimulating bone and root resorption. Results: Three main types of root resorption were identified, two associated with primary bacterial infection and one secondary to bacterial infection. These include external inflammatory resorption, internal inflammatory resorption and external cervical (invasive) resorption. Discussion: The magnitude of cytokine involvement that promotes resorption and M‐CSF/RANKL production depends on multiple factors, including pathogen virulence, site of infection and host genetic factors that activate the inflammation at the infection site. Two mechanisms activate the resorption mechanisms—the canonical and non‐canonical pathways that can activate clastic cells independently of the RANKL/RANK canonical pathways. Conclusions: Two pathways of root resorption co‐exist in the body. When resorption is caused by infection, chronic inflammation due to bacterial infection prolongs the secretions of pro‐inflammatory cytokines that intensify root and bone resorption. The second pathway is bacterial independent of the non‐infection root resorption that is part of the wound healing process, which is limited in time due to its innate ability. [ABSTRACT FROM AUTHOR]

Background: This study aimed to investigate the effect of erbium, chromium doped:yttrium,scandium,gallium,garnet (Er,Cr:YSGG) laser application combined with non‐surgical mechanical debridement (MD) on clinical parameters and peri‐implant crevicular fluid receptor activator of nuclear factor‐kappa B ligand (RANKL) and osteoprotegerin (OPG) levels in the treatment of peri‐implantitis. Methods: A total of 49 patients who underwent non‐surgical treatment of peri‐implantitis were randomly divided into two groups. The control group (n = 26) received MD alone, while the laser group (n = 23) received MD+Er,Cr:YSGG. The clinical parameters (bleeding on probing [BoP], gingival index [GI], plaque index [PI], probing depth [PD]), marginal bone loss (MBL), and biochemical parameters (RANKL and OPG) were measured at baseline (T0) and 6 months after treatment (T1). Results: There was a statistically significant decrease in all the clinical parameters in both groups at T1 compared to T0 (p < 0.05). The BoP, PD, MBL, and RANKL reductions were significantly higher in the laser group than in the control group (p = 0.046, p = 0.014, p = 0.047, p = 0.045, respectively). The OPG levels significantly increased at T1 in the laser group (p = 0.01). The OPG/RANKL ratio increased significantly in both groups at T1, which favored the laser group (p = 0.034). Conclusions: Although both treatment methods were influential in treating peri‐implantitis, the laser group (MD+Er,Cr:YSGG) yielded more favorable results by reducing clinical inflammation and improving biochemical parameters. Based on these findings, Er,Cr:YSGG laser may be a beneficial adjunctive treatment in this patient group. [ABSTRACT FROM AUTHOR]

Background and Aim: Bone as an endocrine organ regulates metabolic processes independently of mineral metabolism through the production/release of proteins collectively named 'osteokines'. Relevant connections were reported between the insulin/glucose system, calcification of the atherosclerotic plaque, and several osteokines. We aimed to test the hypothesis that the osteokine network could be involved in beta‐cell function, insulin sensitivity, and vascular damage in a cohort of people with newly diagnosed type 2 diabetes (T2D). Subjects and Methods: In 794 drug‐naive, GADA‐negative, newly‐diagnosed T2D patients (mean ± SD age: 59 ± 9.8 years; BMI: 29.3 ± 5.3 kg/m2; HbA1c: 6.6 ± 1.3%) we assessed: plasma concentration of osteocalcin (OCN), osteopontin (OPN), RANKL, and its putative decoy receptor osteoprotegerin (OPG); insulin sensitivity (SI) by hyperinsulinemic euglycemic clamp; beta cell function (BCF), estimated by OGTT minimal modelling and expressed as derivative (DC) and proportional (PC) control. Echo‐doppler of carotid and lower limb arteries were also performed in 708 and 701 subjects, respectively. Results: OCN, RANKL and OPG were significantly associated with PC (p < 0.02); OCN was positively related to DC (p = 0.018). OPG was associated with lower IS (p < 0.001). Finally, the higher RANKL levels, the greater was the severity of atherosclerosis in common carotid artery (p < 0.001). Increased OPG and OPN concentrations were related to subclinical atherosclerosis in peripheral arteries of lower limbs (p = 0.023 and p = 0.047, respectively). Conclusion: These data suggest that, in patients with newly diagnosed T2D, the osteokine network crosstalks with the glucose/insulin system and may play a role in modulating the atherosclerotic process. [ABSTRACT FROM AUTHOR]

Background and Objectives: The alveolar bone remodelling promoted by reasonable mechanical force triggers orthodontic tooth movement (OTM). The generation of osteoclasts is essential in this process. However, the mechanism of mechanical force mediating osteoclast differentiation remains elusive. Small nucleolar RNA host gene 5 (SNHG5), which was reported to mediate the osteogenic differentiation of bone marrow mesenchymal stem cells in our previous study, was downregulated in human periodontal ligament cells (hPDLCs) under mechanical force. At the same time, the RANKL/OPG ratio increased. Based on this, we probed into the role of SNHG5 in osteoclast formation during OTM and the relevant mechanism. Materials and Methods: SNHG5 and the RANKL/OPG ratio under different compressive forces were detected by western blotting (WB) and qRT‐PCR. Impact of overexpression or knockdown of SNHG5 on osteoclast differentiation was detected by qRT‐PCR, WB and transwell experiments. The combination of SNHG5 and C/EBPβ was verified by RNA immunoprecipitation and RNA pull‐down assays. The expression of SNHG5 and osteoclast markers in gingiva were analysed by qRT‐PCR and the paraffin sections of periodontal tissues were used for histological analysis. Results: Compressive force downregulated SNHG5 and upregulated the RANKL/OPG ratio in hPDLCs. Overexpression of SNHG5 inhibited RANKL's expression and osteoclast differentiation. SNHG5 combined with C/EBPβ, a regulator of osteoclast. The expression of SNHG5 in periodontal tissue decreased during OTM. Conclusion: SNHG5 inhibited osteoclast differentiation during OTM, achieved by affecting RANKL secretion, which may provide a new idea to interfere with bone resorption during orthodontic treatment. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of photobiomodulation therapy (PBMT) using 660 and 808 nm diode lasers (individual and in combination) on periodontal ligament mesenchymal stem cells (PDLSCs) in the presence of zoledronic acid (ZA). PDLSCs were cultured for 48 h in DMEM complete medium containing 5 μM ZA. PBMT was done three times with a 24‐h interval in groups 1 (660 nm, 5 J/cm2), 2 (880 nm, 3 J/cm2), and 3 (660 + 808 nm) either in normal or ZA‐treated culture medium. Control groups did not receive PBMT. Twenty‐four hours post‐irradiation, cell proliferation and expression of RANKL and OPG were assessed using MTT and real‐time PCR tests, respectively. The results showed a significant decrease in cell viability in ZA‐treated cells (p < 0.001). Additionally, ZA induced the expression of OPG (p = 0.03) while reducing RANKL (p < 0.001). Cell proliferation was significantly increased in 808 and 660 + 808 nm groups. Moreover, all PBMT groups could significantly increase and decrease the RANKL and OPG, respectively, in the presence of ZA (all p < 0.001). A combination of 660 + 808 nm showed the highest effects on both genes. In conclusion, it seems that PBMT can modulate the effects of ZA by inducing PDLSC proliferation and increasing RANKL‐to‐OPG gene expression ratio. [ABSTRACT FROM AUTHOR]

Background: Diabetes mellitus (DM)‐associated hyperinflammatory host response significantly provokes periodontal tissue destruction. In this context, the support of nonsurgical periodontal therapy in diabetics with host modulation agents is a current field of study. This clinical study aims to investigate the clinical efficacy of melatonin supplementation and discuss its possible biological mechanisms in nonsurgical periodontal treatment in patients with DM and periodontitis through some fundamental markers. Methods: In this randomized controlled and single‐blind study, 27 of 55 diabetic patients with periodontitis (stage III/IV and grade C) underwent full‐mouth scaling and root planing (fmSRP) alone and 28 patients underwent melatonin administration (6 mg daily, 30 days) in addition to fmSRP (full‐mouth scaling and root planing plus melatonin, fmSRP‐mel). The potential therapeutic contribution of melatonin was evaluated clinically and biochemically (gingival crevicular fluid RANKL, OPG, MMP‐8, and serum IL‐1β levels) at 3rd and 6th months. Results: Melatonin (tablet, 6 mg daily, 30 days) did not cause any local or systemic side effects. fmSRP alone resulted in significant reduction in serum IL‐1β levels, pocket depths, gingival inflammation, and gingival crevicular fluid RANKL and MMP‐8 levels (p < 0.05). Moreover, melatonin supplementation resulted in a more significant decrease in bleeding and pocket depth scores at probing, especially at 3 months (p < 0.05). Furthermore, RANKL and MMP‐8 levels were significantly lower at 3 months and IL‐1β levels at 6 months compared to the control group (p < 0.05). However, OPG levels were not affected significantly by the treatments (p > 0.05). Conclusion: Melatonin, as a host modulation agent, significantly increases the clinical efficacy of fmSRP. The reduction in periodontal inflammation and pocket depths may be a result of marked suppression of RANKL‐associated osteoclastogenesis and extracellular matrix damage by melatonin. [ABSTRACT FROM AUTHOR]

In recent times, there has been growing attention towards exploring the nutritional and functional aspects of potato protein, along with its diverse applications. In the present study, we examined the anti‐osteoclast properties of potato protein hydrolysate (PP902) in vitro. Murine macrophages (RAW264.7) were differentiated into osteoclasts by receptor activator of nuclear factor‐κB ligand (RANKL), and PP902 was examined for its inhibitory effect. Initially, treatment with PP902 was found to significantly prevent RANKL‐induced morphological changes in macrophage cells, as determined by tartrate‐resistant acid phosphatase (TRAP) staining analysis. This notion was further supported by F‐actin analysis using a confocal microscope. Furthermore, PP902 treatment effectively and dose‐dependently down‐regulated the expression of RANKL‐induced osteoclastogenic marker genes, including TRAP, CTR, RANK, NFATc1, OC‐STAMP, and c‐Fos. These inhibitory effects were associated with suppressing NF‐κB transcriptional activation and subsequent reduced nuclear translocation. The decrease in NF‐κB activity resulted from reduced activation of its upstream kinases, including I‐κBα and IKKα. Moreover, PP902 significantly inhibited RANKL‐induced p38MAPK and ERK1/2 activities. Nevertheless, PP902 treatment prevents RANKL‐induced intracellular reactive oxygen species generation via increased HO‐1 activity. The combined antioxidant and anti‐inflammatory effects of PP902 resulted in significant suppression of osteoclastogenesis, suggesting its potential as an adjuvant therapy for osteoclast‐related diseases. [ABSTRACT FROM AUTHOR]

Background and Objective: Periodontitis is an inflammatory disease that destroys periodontal tissues. Interleukin‐20 (IL‐20), on the other hand, is known as a potent angiogenic, chemotactic, and pro‐inflammatory cytokine associated with various chronic inflammatory disorders. IL‐20 has a significant role in the regulation of osteoclastogenesis and osteoblastogenesis. This study aimed to evaluate the effect of IL‐20 on periodontal destruction. Methods: In this study, a total of 60 participants were included, 30 of whom were systemically and periodontally healthy (control group), and 30 were systemically healthy but had periodontitis (periodontitis group). Gingival crevicular fluid (GCF) and serum samples were collected from the participants for biochemical analysis. Enzyme‐linked immunosorbent assay was used to determine the levels of IL‐20, tumor necrosis factor (TNF)‐α, IL1β/IL‐10, RANKL/osteoprotegerin (OPG), and matrix metalloproteinase‐8 (MMP8). For statistical analysis, the independent t‐test, Pearson correlation coefficients, and the Chi‐square test were used. Results: GCF IL‐20, RANKL, RANKL/OPG, serum IL‐20, RANKL, RANKL/OPG, MMP‐8, TNF‐α, IL‐1B, and IL‐1β/IL‐10 values were found to be statistically significantly higher in the periodontitis group than in the control group. GCF OPG and serum IL‐10 values were found to be statistically significantly higher in the control group than in the periodontitis group. No statistically significant difference was observed between the groups in serum OPG values. A statistically significantly positive correlation was observed between serum IL‐20 value and serum RANKL, RANKL/OPG, MMP‐8, TNF‐α, IL‐1β values, and periodontal clinical parameters. The ROC curves showed: AUC = 0.788 for GCF IL‐20, and AUC = 1.000 for serum IL‐20. Conclusion: According to the results of the study, IL‐20 was found to be associated with periodontitis. The role of IL‐20 in periodontal pathogenesis is related to osteoclastogenesis and collagen degradation. It is conceivable that IL‐20 may increase bone destruction by both affecting the RANKL/OPG ratio and proinflammatory cytokines. [ABSTRACT FROM AUTHOR]

Background: Bone tissue homeostasis relies on the coordinated activity of the bone‐forming osteoblasts and bone‐resorbing osteoclasts. Osteomesopyknosis is considered a distinctive rare sclerosing skeletal disorder of unelucidated pathophysiology and presumably autosomal dominant transmission. However, the causal genes are unknown. Methods: We present a case report encompassing clinical assessments, imaging studies, and whole‐exome sequencing analysis, complemented by functional in vitro experiments. Results: This new case of osteomesopyknosis was associated with a missense ALOX5 variant predicted to induce protein misfolding and proteasomal degradation. Transfection experiments demonstrated that the variant was associated with reduced protein levels restored by proteasomal inhibition with bortezomib. Likewise, gene expression analysis showed that the mutated gene was associated with a decreased RANKL/OPG ratio, which is a critical driver of osteoclast precursor differentiation. Conclusion: Our data indicate impaired bone resorption as the underlying mechanism of this rare osteosclerosis, implicating ALOX5 pathogenic variants as potential etiological factors. [ABSTRACT FROM AUTHOR]

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disorder involving scarring of pulmonary tissue and a subsequent decrease in respiratory capacity, ultimately resulting in death. Tartrate resistant acid phosphatase 5 (ACP5) plays a role in IPF but the exact mechanisms are yet to be elucidated. In this study, we have utilized various perturbations of the bleomycin mouse model of IPF including genetic knockout, RANKL inhibition, and macrophage adoptive transfer to further understand ACP5's role in pulmonary fibrosis. Genetic ablation of Acp5 decreased immune cell recruitment to the lungs and reduced the levels of hydroxyproline (reflecting extracellular matrix‐production) as well as histological damage. Additionally, gene expression profiling of murine lung tissue revealed downregulation of genes including Ccl13, Mmp13, and Il‐1α that encodes proteins specifically related to immune cell recruitment and macrophage/fibroblast interactions. Furthermore, antibody‐based neutralization of RANKL, an important inducer of Acp5 expression, reduced immune cell recruitment but did not decrease fibrotic lung development. Adoptive transfer of Acp5−/− bone marrow‐derived monocyte (BMDM) macrophages 7 or 14 days after bleomycin administration resulted in reductions of cytokine production and decreased levels of lung damage, compared to adoptive transfer of WT control macrophages. Taken together, the data presented in this study suggest that macrophage derived ACP5 plays an important role in development of pulmonary fibrosis and could present a tractable target for therapeutic intervention in IPF. [ABSTRACT FROM AUTHOR]

The Coronavirus Disease 2019 (COVID‐19) pandemic has resulted in the loss of millions of lives, although a majority of those infected have managed to survive. Consequently, a set of outcomes, identified as long COVID, is now emerging. While the primary target of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is the respiratory system, the impact of COVID‐19 extends to various body parts, including the bone. This study aims to investigate the effects of acute SARS‐CoV‐2 infection on osteoclastogenesis, utilizing both ancestral and Omicron viral strains. Monocyte‐derived macrophages, which serve as precursors to osteoclasts, were exposed to both viral variants. However, the infection proved abortive, even though ACE2 receptor expression increased postinfection, with no significant impact on cellular viability and redox balance. Both SARS‐CoV‐2 strains heightened osteoclast formation in a dose‐dependent manner, as well as CD51/61 expression and bone resorptive ability. Notably, SARS‐CoV‐2 induced early pro‐inflammatory M1 macrophage polarization, shifting toward an M2‐like profile. Osteoclastogenesis‐related genes (RANK, NFATc1, DC‐STAMP, MMP9) were upregulated, and surprisingly, SARS‐CoV‐2 variants promoted RANKL‐independent osteoclast formation. This thorough investigation illuminates the intricate interplay between SARS‐CoV‐2 and osteoclast precursors, suggesting potential implications for bone homeostasis and opening new avenues for therapeutic exploration in COVID‐19. [ABSTRACT FROM AUTHOR]

Background and Aim: Osteoporosis, a systemic metabolic bone disease, is characterized by the decline of bone mass and quality due to excessive osteoclast activity. Currently, drug‐targeting osteoclasts show promising therapy for osteoporosis. In this study, we investigated the effect of cichoric acid (CA) on receptor activator of nuclear kappa‐B ligand (RANKL)‐induced osteoclastogenesis and the bone loss induced by ovariectomy in mice. Experimental Procedure: Molecular docking technologies were employed to examine the interaction between CA and RANKL. CCK8 assay was used to evaluate the cell viability under CA treatment. TRAcP staining, podosome belt staining, and bone resorption assays were used to test the effect of CA on osteoclastogenesis and osteoclast function. Further, an OVX‐induced osteoporosis mice model was employed to identify the effect of CA on bone loss using micro‐CT scanning and histological examination. To investigate underlying mechanisms, network pharmacology was applied to predict the downstream signaling pathways, which were verified by Western blot and immunofluorescence staining. Key Results: The molecular docking analysis revealed that CA exhibited a specific binding affinity to RANKL, engaging multiple binding sites. CA inhibited RANKL‐induced osteoclastogenesis and bone resorption without cytotoxic effects. Mechanistically, CA suppressed RANKL‐induced intracellular reactive oxygen species, nuclear factor‐kappa B, and mitogen‐activated protein kinase pathways, followed by abrogated nuclear factor activated T‐cells 1 activity. Consistent with this finding, CA attenuated post‐ovariectomy‐induced osteoporosis by ameliorating osteoclastogenesis. Conclusions and Implications: CA inhibited osteoclast activity and bone loss by targeting RANKL. CA might represent a promising candidate for treating osteoclast‐related diseases, such as osteoporosis. [ABSTRACT FROM AUTHOR]

Background: The regulation of inflammatory mediators in the degenerating intervertebral disc (IVD) and corresponding ligamentum flavum (LF) is a topic of emerging interest. The study aimed to investigate the expression of a broad array of inflammatory mediators in the degenerated LF and IVD using a dog model of spontaneous degenerative disc disease (DDD) to determine potential treatment targets. Methods: LF and IVD tissues were collected from 22 normal dogs (Pfirrmann grades I and II) and 18 dogs affected by DDD (Pfirrmann grades III and IV). A qPCR gene array was used to investigate the expression of 80 inflammatory genes for LF and IVD tissues, whereafter targets of interest were investigated in additional tissue samples using qPCR, western blot (WB), and immunohistochemistry. Results: Tumor necrosis factor superfamily (TNFSF) signaling was identified as a regulated pathway in DDD, based on the significant regulation (n‐fold ± SD) of various TNFSF members in the degenerated IVD, including nerve growth factor (NGF; −8 ± 10), CD40LG (464 ± 442), CD70 (341 ± 336), TNFSF Ligand 10 (9 ± 8), and RANKL/TNFSF Ligand 11 (85 ± 74). In contrast, TNFSF genes were not significantly affected in the degenerated LF compared to the control LF. Protein expression of NGF (WB) was significantly upregulated in both the degenerated LF (4.4 ± 0.5) and IVD (11.3 ± 5.6) compared to the control group. RANKL immunopositivity was significantly upregulated in advanced stages of degeneration (Thompson grades IV and V) in the nucleus pulposus and annulus fibrosus of the IVD, but not in the LF. Conclusions: DDD involves a significant upregulation of various TNFSF members, with tissue‐specific expression profiles in LF and IVD tissues. The differential involvement of TNFSF members within multiple spinal tissues from the same individual provides new insights into the inflammatory processes involved in DDD and may provide a basis to formulate hypotheses for the determination of potential treatment targets. [ABSTRACT FROM AUTHOR]

One of the major contributors to secondary osteoporosis is long‐term glucocorticoid usage. Clinically used antidepressant agomelatine also has anti‐inflammatory properties. Our research aimed to inspect the probable defensive effect of agomelatine against steroid‐promoted osteoporosis. There were four groups of rats; group I had saline as a negative control; rats of group II had dexamethasone (0.6 mg/kg, s.c.), twice weekly for 12 weeks; rats of group III had agomelatine (40 mg/kg/day, orally), as a positive control, daily for 12 weeks; and rats of group IV had dexamethasone + agomelatine in the same previous doses combined for 12 weeks. Finally, biochemical as well as histopathological changes were evaluated and dexamethasone treatment caused osteoporosis, as evidenced by discontinuous thin cancellous bone trabeculae, minor fissures and fractures, irregular eroded endosteal surface with elevated alkaline phosphate, tartarate resistant acid phosphate (TRACP) and osteocalcin levels. Osteoprotegerin (OPG), calcium, and phosphorus levels decreased with disturbed receptor activator of nuclear factor κ B ligand (RANKL), forkhead box O1 (FOXO1), and silent information regulator 1 (SIRT1) protein expression. However, treatment with agomelatine restored the normal levels of biochemical parameters to a great extent, supported by SIRT activation with an improvement in histopathological changes. Here, we concluded that agomelatine ameliorates steroid‐induced osteoporosis through a SIRT1/RANKL/FOXO1/OPG‐dependent pathway. [ABSTRACT FROM AUTHOR]

Osteoclasts overactivity plays a critical role in the progress of inflammatory bone loss. In addition, ROS can facilitate the formation and function of osteoclasts. Silver nanoparticles (Ag NPs) with ROS scavenging activity are potential candidates for inflammatory bone loss. In this regard, the biosynthetic Ag NPs with low toxicity and high stability by using Flos Sophorae Immaturus extract as the reducing and capping agents are reported. The inflammatory bone loss model is established by injecting LPS. Quantitative reverse transcription‐polymerase chain reaction and Western Blot are utilized to determine the expression level of target biomarkers related to osteoclast formation. Ag NPs can significantly reduce the number of TRAP‐positive (TRAP+) cells. In addition, Ag NPs down‐regulate the expression of biomarkers relevant to osteoclast formation. Interestingly, Ag NPs can effectively suppress osteoclast formation via down‐regulating ROS‐mediated phosphorylation of NF‐κB pathways. The in vivo study shows that Ag NPs can ameliorate bone density and decrease osteoclast number. Due to these benefits, the constructed Ag NPs can delay the progression of inflammatory bone loss. These findings suggest that Ag NPs are a potential therapeutic agent in the treatment of inflammatory bone loss. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to monitor changes in Osteoprotegerin (OPG) and receptor activator of nuclear factor‐kappa ligand (RANKL) levels in the saliva during orthodontic tooth movement (OTM). Materials and Methods: Nine healthy females (15–20 y of age) with four pre‐molar extractions and fixed appliance were included. In total, 134 stimulated and 134 unstimulated saliva samples were collected: at baseline and then every 6–8 weeks at follow‐up appointments during the whole orthodontic treatment. Twelve age‐matched females with no active orthodontic treatment served as a control group. Saliva samples were analysed by enzyme‐linked immunosorbent assay (Elisa). The mean levels of OPG and RANKL were calculated according to the different orthodontic treatment stages: alignment, space closure and finishing. A mixed model analysis was used to compare the means of treatment stages. Baseline OPG levels were compared with the control group using an independent t‐test. OPG levels were measured in stimulated saliva due to low levels in unstimulated saliva. Results: No significant difference was observed between baseline OPG values and the control group. OPG increased significantly at all treatment stages: alignment, space closure and finishing compared with baseline (P = 0.002, P = 0.039, P ≤ 0.001, respectively). The salivary levels of OPG increased gradually, except during space closure, reaching peak levels at finishing. RANKL was undetectable in stimulated and unstimulated saliva by sandwich Elisa during OTM. Conclusions: This novel approach shows the changes in the levels of OPG in OTM and indicates how and when to sample saliva during orthodontic treatment to analyse bone remodelling. [ABSTRACT FROM AUTHOR]

Objective: Advanced lung cancers carrying Kirsten rat sarcoma viral oncogene homolog (KRAS) mutation remain a group that lacks effective treatments. Receptor activator of nuclear factorκB ligand (RANKL) has been demonstrated to drive malignant phenotypes in lung cancer; however, its role in KRAS‐mutant (mt) lung adenocarcinoma (LUAD) is not yet fully elucidated. Materials and methods: The data used to explore expression and prognosis were obtained from The Cancer Genome Atlas, Genotype‐Tissue Expression databases, and from our hospital. The proliferation, invasion, and migration capacities of KRAS‐mt LUAD cells were evaluated. The prediction model was established via Lasso regression method. Results: RANKL is strongly expressed in advanced KRAS‐mt LUAD, and significantly distinct association exists between high RANKL expression and poor survival. The enriched expression of RANKL in advanced KRAS‐mt LUAD was confirmed by specimens from our hospital. Further, although not statistically significant, our clinical cohort (n = 57) revealed a longer median progression‐free survival in advanced KRAS‐mt LUAD patients treated with RANKL inhibitor than those without (300 vs. 133 days, p = 0.210), but not in KRAS‐wt ones (208 vs. 250 days, p = 0.334). Decrease of KRAS‐mt LUAD cells' capacity for proliferation, invasion, and migration was observed when RANKL was knocked down. Enrichment analysis suggested distinct roles of RANKL between KRAS‐mt and KRAS‐wt LUAD, with adhesion‐related pathways and molecules significantly downregulated in the KRAS‐mt RANKL‐high tumors. Finally, a model for predicting overall survival of KRAS‐wt LUAD was established according to four related key genes (BCAM, ICAM5, ITGA3, and LAMA3), which had good performance in prediction concordance. Conclusions: RANKL acts as an unfavorable prognostic biomarker for patients with advanced KRAS‐mt LUAD. Inhibition of RANKL may be a feasible strategy for this subset of patients. [ABSTRACT FROM AUTHOR]

Bone tissue is a common metastatic site of lung cancer, and bone metastasis is characterized by abnormal differentiation and malfunction of osteoclast, and the roles of exosomes derived from lung cancer have attracted much attention. In our study, we found that the level of HOTAIR expression in A549 and H1299 exosomes was higher than those of normal lung fibrocytes. Overexpression of HOTAIR in A549 and H1299 exosomes promoted osteoclast differentiation. Furthermore, A549‐Exos and H1299‐Exos targeted bone tissues, and bone formation was significantly inhibited in vivo. Mechanistically, exosomal lncRNA HOTAIR promoted bone resorption by targeting TGF‐β/PTHrP/RANKL pathway. [ABSTRACT FROM AUTHOR]

Background and Aims: Limitations of the conventional diagnostic techniques urged researchers to seek novel methods to predict, diagnose, and monitor periodontal disease. Use of the biomarkers available in oral fluids could be a revolutionary surrogate for the manual probing/diagnostic radiograph. Several salivary biomarkers have the potential to accurately discriminate periodontal health and disease. This study aimed to determine the diagnostic sensitivity and specificity of salivary interleukin (IL)‐17, receptor activator of nuclear factor‐κB ligand (RANKL), osteoprotegerin (OPG), RANKL/OPG for differentiating (1) periodontal health from disease and (2) stable and unstable periodontitis. Methods: Participants with periodontitis (n = 50) and gingivitis (n = 25), both diseases represented the cases, and subjects with healthy periodontium (n = 15) as a control were recruited for this study. Periodontitis cases were further equally subdivided into stable and unstable. Whole unstimulated salivary sample were collected from all participants. Periodontal parameters including bleeding on probing, probing pocket depth, clinical attachment loss, and number of missing teeth were recorded. The protein levels of salivary IL‐17, RANKL, and OPG were determined by using enzyme‐linked immunosorbent assays technique. Results: Salivary IL‐17, OPG, RANKL, and RANKL/OPG showed high sensitivity and specificity to differentiate periodontal health from gingivitis and periodontitis. Similar pattern was observed in discriminating stable and unstable periodontitis. Salivary IL‐17 and RANKL showed a good accuracy to differentiate gingivitis from periodontitis. However, OPG and RANKL/OPG did not exhibit enough sensitivity and specificity to differentiate the latter conditions. Conclusion: Salivary IL‐17, RANKL, OPG, and RANKL/OPG system are potential candidates for differentiating periodontal health and disease and discriminate stable and unstable periodontitis. [ABSTRACT FROM AUTHOR]

Background and Objectives: The potential role of the transcription factor Differentiated embryo‐chondrocyte 2 (Dec2) in the progression of inflammatory diseases such as periodontitis has been unclear. Here, the effect of Dec2 on the expression of RANKL and on osteoclastogenesis was determined. Material and Methods: Wild‐type (WT) and Dec2 knockout (KO) mice as a model for periodontitis were used to assess alveolar bone resorption by microcomputed tomography (CT). Western blot, flow cytometry, quantitative real‐time PCR, and immunohistochemical analyses were utilized to detect inflammation and osteoclasts. Luciferase reporter and Chromatin immunoprecipitation (ChIP) assays examined the interaction between Dec2 and RANKL. Results: Micro‐CT showed that the alveolar bone resorption of Dec2KO mice was more severe than WT mice after treatment with P. gingivalis. Immunohistochemistry and Tartrate‐resistant acid phosphatase staining showed active osteoclast differentiation in Dec2KO mice. There was an increase in CD11b+F4/80+ and CD4+RANKL+ T cells in Dec2KO mice treated with P. gingivalis. Moreover, inflammatory and immune markers were expressed at significantly higher levels in gingival mononuclear cells in Dec2KO mice. Furthermore, luciferase reporter and ChIP assays confirmed the direct binding of Dec2 protein to the RANKL gene. Conclusion: Dec2 has an immune regulation ability that modulates P. gingivalis‐induced periodontitis via RANKL. [ABSTRACT FROM AUTHOR]

Ganoderma mushrooms have been used to treat rheumatoid arthritis (RA) in East Asia. Whether Ganoderic acid A (GAA), the natural product extracted from Ganoderma, could be utilized to alleviate osteoarthritis (OA) is investigated in this study. Destabilization of the medial meniscus (DMM) model was constructed to reveal the in vivo effect of GAA. We found that GAA could significantly alleviate the pathology of DMM, as confirmed by the diminished maximum histologic scores. On the contrary, GAA could down‐regulate the relative expression of osteoprotegerin (OPG) and up‐regulate the relative expression of nuclear factor kappa‐B ligand (RANKL) in DMM cartilage and human articular chondrocytes (HC‐A) cells with diminished matrix metallopeptidase 13 (MMP‐13) secretion in the synovial fluid. It was further demonstrated that the serum concentration of OPG was correlated with the severity of osteoarthritis. All these data reveal that GAA could improve OA by regulating the RANKL/OPG ratio to inhibit the secretion of MMP‐13. [ABSTRACT FROM AUTHOR]

Background: Glucose metabolism plays a pivotal role in sustaining the inflammatory response to microbial stimulation by providing sufficient energy in immune cells. The main purpose of our study was to explore whether hexokinase 2 (HK2)-mediated glycolysis affected the expression of receptor activator of NF-κB Ligand (RANKL) in Porphyromonas gingivalis lipopolysaccharide (P. gingivalis-LPS)-treated osteoblasts and evaluate the potential involvement of the AKT/PI3K pathway activation during HK2-mediated glycolysis.Methods: Primary mice osteoblasts were treated with P. gingivalis-LPS, whereas the HK2 inhibitor (Lonidamine, LND) and small interference RNA were used to restrain HK2 expression. Conditioned medium from osteoblasts was utilized for culturing osteoclast precursors. The mRNA and protein levels of genes involved in glycolysis and bone metabolism including RANKL and osteoprotegerin (OPG) were detected by real-time PCR and western blotting. HK2 and lactate levels were detected by ELISA. Tartrate-resistant acid phosphatase (TRAP) staining was utilized to assess osteoclast formation. The involvement of the AKT/PI3K pathway in osteoblasts was explored by Western blotting.Results: P. gingivalis-LPS enhanced HK2 expression along with rising glycolysis in osteoblasts. LND and HK2-knockdown decreased RANKL expression and the RANKL/OPG ratio in osteoblasts, leading to less osteoclast formation from osteoclast precursors as evidenced by TRAP staining, while the osteogenic potential and proliferation of osteoblasts were not affected by HK2-knockdown. Moreover, P. gingivalis-LPS activated the AKT/PI3K pathway, which could regulate HK2 and RANKL expression in osteoblasts.Conclusions: HK2-mediated glycolysis promoted RANKL in osteoblasts and enhanced osteoclast differentiation. Targeting glycolysis may provide novel therapeutic methods for reducing alveolar bone loss. [ABSTRACT FROM AUTHOR]

Osteoporosis is a bone disease that is caused by disorder of the skeletal microenvironment, and it characterized by a high disability rate and the occurrence of low energy fractures. Studies on osteoporosis and related treatment options have always been hot spots in the field of bone biology. In the past, the understanding of osteoporosis has been rather limited; research has only shown that osteoporosis involves the imbalance of bone resorption and bone formation, and recent studies have not provided cutting‐edge theories of the basic understanding of osteoporosis. Recent studies have shown crosstalk between bone and immune responses. RANKL, an essential factor for osteoclasts (OCs), is associated with the immune system. T helper (Th17)/regulatory T (Treg) cells are two different kinds of T cells that can self‐interact and regulate the differentiation and formation of OCs. Therefore, understanding the correlation between the skeletal and immune systems and further revealing the roles and the cooperation between RANKL and the Th17/Treg balance will help to provide new insights for the treatment of osteoporosis. [ABSTRACT FROM AUTHOR]

The fibroblast growth factor (FGF)/FGF receptor (FGFR) signaling pathway plays important roles in the development and growth of the skeleton. Apert syndrome caused by gain‐of‐function mutations of FGFR2 results in aberrant phenotypes of the skull, midface, and limbs. Although short limbs are representative features in patients with Apert syndrome, the causative mechanism for this limb defect has not been elucidated. Here we quantitatively confirmed decreases in the bone length, bone mineral density, and bone thickness in the Apert syndrome model of gene knock‐in Fgfr2S252W/+ (EIIA‐Fgfr2S252W/+) mice. Interestingly, despite these bone defects, histological analysis showed that the endochondral ossification process in the mutant mice was similar to that in wild‐type mice. Tartrate‐resistant acid phosphatase staining revealed that trabecular bone loss in mutant mice was associated with excessive osteoclast activity despite accelerated osteogenic differentiation. We investigated the osteoblast–osteoclast interaction and found that the increase in osteoclast activity was due to an increase in the Rankl level of osteoblasts in mutant mice and not enhanced osteoclastogenesis driven by the activation of FGFR2 signaling in bone marrow‐derived macrophages. Consistently, Col1a1‐Fgfr2S252W/+ mice, which had osteoblast‐specific expression of Fgfr2 S252W, showed significant bone loss with a reduction of the bone length and excessive activity of osteoclasts was observed in the mutant mice. Taken together, the present study demonstrates that the imbalance in osteoblast and osteoclast coupling by abnormally increased Rankl expression in Fgfr2S252W/+ mutant osteoblasts is a major causative mechanism for bone loss and short long bones in Fgfr2S252W/+ mice. [ABSTRACT FROM AUTHOR]

Objectives: Sickle bone disease (SBD) is a chronic complication of sickle cell disease (SCD) whose pathogenesis is not completely understood. Chronic inflammation associated with SCD could alter bone remodeling. Our aim was to analyze the serum levels of bone remodeling markers in a group of SCD children to evaluate their involvement in the SBD. Methods: We enrolled 26 SCD subjects and 26 age‐matched controls, who lived in the same geographic area. DKK‐1, sclerostin, RANKL, and OPG serum levels were evaluated. Neutrophil‐lymphocyte ratio (NLR) was also evaluated as a marker of inflammation. Results: The analysis of bone remodeling markers did not show any significant difference between the two groups except for DKK‐1 levels that were significantly higher in the patients than controls (p <.05). A significant direct correlation between NLR and DKK‐1 (p =.004) was found. An inverse correlation between NLR and osteocalcin (p =.01) has also been observed. Conclusions: The chronic inflammation, which represents a peculiar characteristic in SCD patients, would represent the primary causal agent of the activation of osteoblastogenesis inhibitors responsible of bone impairment in these subjects. Further studies will be needed to better explain the role of these inhibitors in SCD, to prevent or treat bone damage in this population. [ABSTRACT FROM AUTHOR]

Periodontopathic bacteria constantly stimulate the host, which causes an immune response, leading to host‐induced periodontal tissue damage. The complex interaction and imbalance between Th17 and Treg cells may be critical in the pathogenesis of periodontitis. Furthermore, the RANKL/RANK/OPG system plays a significant role in periodontitis bone metabolism, and its relationship with the Th17/Treg cell imbalance may be a bridge between periodontal bone metabolism and the immune system. This article reviews the literature related to the Th17/Treg cell imbalance mediated by pathogenic periodontal microbes, and its mechanism involving RANKL/RANK/OPG in periodontitis bone metabolism, in an effort to provide new ideas for the study of the immunopathological mechanism of periodontitis. [ABSTRACT FROM AUTHOR]

Excessive activity of osteoclasts contributes to skeletal diseases such as osteoporosis and osteolysis. However, current drugs targeting osteoclast have various deficiencies, placing natural compounds as substitutions of great potential. Roburic acid (RA) is a triterpenoid exacted from Radix Gentianae Macrophyllae, which exhibits inhibitory effects on inflammation and oxidation. By employing an in vitro osteoclastogenesis model, this study investigates the effects and mechanisms of RA on intracellular signaling induced by receptor activator of nuclear factor‐κB ligand (RANKL). As expected, RA at a concentration scope from 1 to 10 μM dampened the osteoclast differentiation of bone marrow macrophages (BMMs) but without cell toxicity. Interestingly, RA showed no effect on osteoblastogenesis in vitro. Furthermore, RA mitigated F‐actin ring formation, hydroxyapatite resorption, and gene expression in osteoclasts. Mechanistically, RA suppressed TNF receptor‐associated factor 6 (TRAF6), the crucial adaptor protein following RANKL‐RANK binding. On the one hand, RA downregulated the nuclear factor‐κB (NF‐κB) activity, extracellular regulated protein kinases (ERK) phosphorylation, and calcium oscillations. On the other hand, RA upregulated the antioxidative response element (ARE) response and the protein expression of heme oxygenase (HO)‐1. These upstream alterations eventually led to the suppression of the nuclear factor of activated T cells 1 (NFATc1) activity and the expression of proteins involved in osteoclastogenesis and bone resorption. Furthermore, by using an ovariectomized (OVX) mice model, RA was found to have therapeutic effects against bone loss. On account of these findings, RA could be used to restrain osteoclasts for treating osteoporosis and other osteolytic diseases. [ABSTRACT FROM AUTHOR]

Methionine adenosyltransferase II alpha (MAT2A) is the key enzyme to transform methionine and adenosine‐triphosphate (ATP) to S‐adenosylmethionine (SAM), a general methyl‐group donor in vitro. MAT2A has been reported to participate in the NF‐κB pathway and maintain the methylated modification, which also affects osteoclastogenesis. In this study, we found the expression of MAT2A was increased upon RANKL stimulation. Pharmacological inhibition of MAT2A by its selective inhibitor AG‐270 or genetic silencing by MAT2A‐shRNA suppressed osteoclast formation and function in vitro. In vivo treatment with the inhibitor AG‐270 also prevented OVX‐induced bone loss. Further study revealed that the inhibition of MAT2A affected osteoclast differentiation mainly by suppressing crucial transcription factors and reactive oxygen species induced by RANKL. A quasi‐targeted metabolomics assay performed by LC‐MS/MS indicated that SAM was reduced by MAT2A knockdown, and the administration of SAM partly rescued the effects of MAT2A inhibition on osteoclastogenesis. These findings revealed that MAT2A is crucial for osteoclastogenesis and might be a potential target for the treatment of osteoporosis attributed to osteoclast dysfunction. [ABSTRACT FROM AUTHOR]

Background: Glucose and lipid abnormalities, oxidative stress (OXS) and reduced brain‐derived neurotrophic factor (BDNF) are involved in cognitive dysfunction in diabetes. Glucagon like peptide 1 (GLP1) receptors modulate glucose and lipid metabolism, cognitive function and serum osteocalcin. On the other hand, osteocalcin modulates cognitive function and glucose and lipid metabolism. This study investigated whether the GLP 1 agonist liraglutide improves cognitive function via modulation of serum osteocalcin and glucose and lipid metabolism. Methods: Effects of 4 weeks liraglutide treatment (100 µg/Kg/d and 300 µg/Kg/d) on changes in cognitive function and bone homeostasis, induced by high fat diet/low‐dose streptozotocin (HFD‐STZ), were determined in rats. Cognitive function was assessed using Morris water maze (MWM) test. Serum and bone biochemical parameters were determined. Results: Liraglutide dose‐dependently improved cognitive function in diabetic rats (reduced escape latency, and increased time spent in target quadrant in MWM test, compared to diabetic control). Glucose and lipid abnormalities and the associated changes in serum BDNF and oxidative stress makers were improved. Serum BDNF and glutathione were significantly increased, whereas malondialdehyde level was reduced. Serum osteocalcin was significantly increased and correlated with improvement in cognitive dysfunction. Serum and bone receptor activator of nuclear factor κB ligand (RANKL)/osteoprotegerin ratios were significantly reduced by liraglutide treatment. Conclusion: Improvement of cognitive dysfunction by liraglutide involves modulation of glucose and lipid metabolism and serum osteocalcin. GLP1 agonists may provide an alternative metabolic approach for cognitive dysfunction in diabetes. [ABSTRACT FROM AUTHOR]

Receptor activator of nuclear factor kappa‐B ligand (RANKL) is one of the key factors regulating the maturation of osteoclasts and an important target for osteoporosis treatment. A monoclonal antibody against RANKL showed effective therapeutic activity against osteoporosis by inhibiting bone resorption by osteoclasts. However, being an exogenous protein, its efficacy decreases after long‐term use, and its discontinuation increases the risk of vertebral fractures. Here, we aimed to design an active immunotherapeutic agent to induce a T‐cell dependent primary response. The agent, a mutant RANKL vaccine (mRv), was produced by cross‐linking mutant RANKL, lacking the ability to stimulate osteoclast maturation, with the carrier protein keyhole limpet hemocyanin, a neo‐antigen with a large molecular mass. Subcutaneous injection of mRv stimulated rats with ovariectomy‐induced osteoporosis to produce high titers of anti‐RANKL antibodies. The mutant RANKL vaccine decreased serum CTX‐1 and BALP levels and inhibited the microstructural degeneration of trabecular bone in osteoporotic rats. mRv overcame immune system tolerance, stimulated rats to produce therapeutic antibodies, stabilized bone metabolism, and inhibited trabecular microstructural degeneration. These findings confirm the potential of the mutant RANKL vaccine to be developed into an effective preventive and therapeutic agent for osteoporosis. [ABSTRACT FROM AUTHOR]

Experimental and clinical studies suggest a positive impact of anthocyanins on bone health; however, the mechanisms of anthocyanins altering the differentiation and function of osteoblasts and osteoclasts are not fully understood. This work demonstrates that dietary anthocyanins and resveratrol increased proliferation of cultured human hFOB 1.19 osteoblasts. In addition, treatment of serum starvation of hFOB osteoblasts with anthocyanins and resveratrol at 1.0 μg/ml reduced apoptosis, the Bax/Bcl‐2 ratio, p53, and HDAC1 expression, but increased SIRT1/3 and PGC1α mRNA expression, suggesting mitochondrial and epigenetic regulation. In Sp7/osterix:mCherry transgenic medaka, peonidin‐3‐O‐glucoside and resveratrol increased osteoblast differentiation and increased the expression of Sp7/osterix. Cyanidin, peonidin‐3‐O‐glucoside, and resveratrol also reduced RANKL‐induced ectopic osteoclast formation and bone resorption in col10α1:nlGFP/rankl:HSE:CFP medaka in doses of 1–4 μg/ml. The results indicate that both cyanidin and peonidin‐3‐O‐glucoside have anabolic effects on bone, increasing osteoblast proliferation and differentiation, mitochondrial biogenesis, and by altering the osteoblast epigenome. Cyanidin and peonidin‐3‐O‐glucoside also reduced RANKL‐induced bone resorption in a transgenic medaka model of bone resorption. Thus, peonidin‐3‐O‐glucoside and cyanidin appear to both increase bone formation and reduce bone loss, suggesting that they be further investigated as potential treatments for osteoporosis and osteomalacia. [ABSTRACT FROM AUTHOR]

Morin is a natural compound isolated from moraceae family members and has been reported to possess a range of pharmacological activities. However, the effects of morin on bone-associated disorders and the potential mechanism remain unknown. In this study, we investigated the anti-osteoclastogenic effect of morin in vitro and the potential therapeutic effects on ovariectomy (OVX)-induced osteoporosis in vivo. In vitro, by using a bone marrow macrophage-derived osteoclast culture system, we determined that morin attenuated receptor activator of nuclear factor (NF)-κB ligand (RANKL)-induced osteoclast formation via the inhibition of the mitogen-activated protein kinase (MAPK), NF-κB and calcium pathways. In addition, the subsequent expression of nuclear factor of activated T cells c1 (NFATc1) and c-fos was significantly suppressed by morin. In addition, NFATc1 downregulation led to the reduced expression of osteoclastogenesis-related marker genes, such as V-ATPase-d2 and Integrin β3. In vivo, results provided that morin could effectively attenuate OVX-induced bone loss in C57BL/6 mice. In conclusion, our results demonstrated that morin suppressed RANKL-induced osteoclastogenesis via the NF-κB, MAPK and calcium pathways, in addition, its function of preventing OVX-induced bone loss in vivo, which suggested that morin may be a potential therapeutic agent for postmenopausal osteoporosis treatment. [ABSTRACT FROM AUTHOR]

Breast cancer, a common malignancy for women, preferentially metastasizes to bone and obesity elevates the chance of its progression. While mechanical loading can suppress obesity and tumor‐driven osteolysis, its effect on bone‐metastasized obese mice has not been investigated. Here, we hypothesized that mechanical loading can lessen obesity‐associated bone degradation in tumor‐invaded bone by regulating the fate of bone marrow‐derived cells. In this study, the effects of mechanical loading in obese mice were evaluated through X‐ray imaging, histology, cytology, and molecular analyses. Tumor inoculation to the tibia elevated body fat composition, osteolytic lesions, and tibia destruction, and these pathologic changes were stimulated by the high‐fat diet (HFD). However, mechanical loading markedly reduced these changes. It suppressed osteoclastogenesis by downregulating receptor activator of nuclear factor Kappa‐B ligand and cathepsin K and promoted osteogenesis, which was associated with the upregulation of OPG and downregulation of C/enhancer‐binding protein alpha and proliferator‐activated receptor gamma for adipogenic differentiation. Furthermore, it decreased the levels of tumorigenic genes such as Rac1, MMP9, and interleukin 1β. In summary, this study demonstrates that although a HFD aggravates bone metastases associated with breast cancer, mechanical loading significantly protected tumor‐invaded bone by regulating the fate of bone marrow‐derived cells. The current study suggests that mechanical loading can provide a noninvasive, palliative option for alleviating breast cancer‐associated bone metastasis, in particular for obese patients. [ABSTRACT FROM AUTHOR]

Objective: The benefit of Se supplementation in rheumatoid arthritis (RA) has been tested in clinical trials, but results remain inconclusive. The objective of this study was to specifically investigate the potential benefit of supranutritional Se by examining human samples from an area with supranutritional Se intake and testing a mouse model of RA. Methods: Peripheral blood mononuclear cells (PBMCs) from RA patients (N = 57) and healthy controls (HC, N = 71) from an area of supranutritional Se intake (Enshi, Hubei, China) were analysed by flow cytometry. Serum cytokine and Se levels were measured by cytometric beads array (CBA) and inductively coupled plasma mass spectrometry (ICP‐MS), respectively. With sufficient or supranutritional selenium intake, mice were induced with collagen‐induced arthritis (CIA) and examined for disease activity and immunopathology. The influence of Se supplementation in the generation of RANKL‐expressing osteoclastogenic CD4+ T cells was investigated by in vitro assays. Results: In Enshi city, HC showed the above‐normal concentrations of serum Se concentrations while RA patients were enriched in the normal range (70–150 ng mL−1) or below. RA patients with higher Se levels demonstrated milder disease and lower levels of C‐reactive protein, IL‐6, RANKL and Th17 cells. In the mouse CIA model, supranutritional Se supplementation delayed disease onset, ameliorated joint pathology and reduced CD4+CD44+RANKL+ T cells. Se supplementation could suppress RANKL expression in cultured mouse Th17 cells. Conclusion: Supranutritional Se suppresses RANKL‐expressing osteoclastogenic CD4+ T cells and could be beneficial to RA, which warrants formal testing in randomised clinical trials. [ABSTRACT FROM AUTHOR]

Problem: During the first trimester, the accumulation of macrophages, which is the second largest decidual leukocyte population (~20%) at the maternal‐fetal interface, is quite vital for a successful pregnancy, including embryo implantation, trophoblast invasion, and vascular remodeling. The mechanism of the enrichment and redistribution of macrophages in the uterine decidua of early pregnancy is largely unclear. Method of study: A total of 37 women with normal early pregnancies were included. Primary decidual macrophages (dMφs) (n = 37) and primary decidual stromal cells (DSCs) (n = 37) were isolated, and the adhesion molecules were analyzed by flow cytometry (FCM). Adhesive experiment was carried out to evaluate the adhesion capacity by counting cell numbers of dMφs adhered to DSCs in a co‐culture system. Results: We found that RANK+ dMφs was the dominating subtype at the maternal‐fetal interface. The expression of adhesion molecules (eg, CD29, CD31, CD54, and CD62L) on the surface of RANK+ dMφs was higher than that of RANK− dMφs. After co‐culture with DSCs, the expression of adhesion molecules on dMφs was up‐regulated in a RANKL‐dependent manner. Meanwhile, dMφs promoted the releasing of RANKL on DSCs after co‐culture. Consistently, dMφs exhibited the lessoned capacity of adhesion to DSCs when blocking the crosstalk of RANKL‐RANK between the DSCs and dMφs in vitro. Conclusion: These results suggest that the interaction of RANKL‐RANK up‐regulates the expression of adhesion molecules on the surface of dMφs, contributing to the accumulation and residence of dMφs in human early pregnancy. [ABSTRACT FROM AUTHOR]

Background and objective: Root resorption is an unavoidable side effect of orthodontic tooth movement. The mechanism of root resorption is similar to bone resorption; the odontoclasts share similar characteristics with osteoclasts (OCs). MicroRNAs (miRNAs) such as miR‐155‐5p play an important role in OC differentiation, but the underlying molecular mechanism of miR‐155‐5p in this process is not fully understood. We found that the miR‐155‐5p seed sequences were complementary to a sequence conserved in the 3‐untranslated region of CXCR2 mRNA. In this study, we explored the molecular mechanism underlying the effect of miR‐155‐5p on OC differentiation by targeting CXCR2. Materials and methods: In this study, we divided the orthodontic patients into mild, moderate, and severe groups according to the severity of root resorption. The gingival crevicular fluid (GCF) of patients in different groups was collected, and the expression levels of dentin phosphoprotein (DPP) were detected by ELISA, and the expression levels of CXCR2 and miR‐155‐5p in GCF were detected by real‐time quantitative PCR (qRT‐PCR). The relationship between miR‐155‐5p and CXCR2 was verified by double luciferase. We analyzed changes of CXCR2 and miR‐155‐5p expression after transfection of miR‐155‐5p mimic and inhibitor into RAW264.7 cells induced by receptor activator of nuclear factor‐κB ligand (RANKL) through qRT‐PCR and western blotting. The effect of miR‐155‐5p on OC differentiation was evaluated by tartrate‐resistant acid phosphatase (TRAP) staining. QRT‐PCR and western blotting were used to analyze expression of the osteoclastic bone resorption‐related enzymes carbonic anhydrase 2 (CA II), matrix metalloproteinase‐9 (MMP‐9), and cathepsin K. To further confirm the direct targeting effect of CXCR2 by miR‐155‐5p, we blocked CXCR2 using si‐CXCR2 in RANKL‐induced RAW264.7 cells. Results: Dentin phosphoprotein levels were consistent with the trend of miR‐155‐5p changes, and the trend of CXCR2 expression was opposite to miR‐155‐5p changes. miR‐155‐5p can be directly targeted to act on CXCR2. The expression of miR‐155‐5p was significantly downregulated in differentiated OCs. MiR‐155‐5p inhibited OC differentiation, and downregulated CA II, MMP‐9, and cathepsin K expression at the protein and mRNA levels. Conclusions: In summary, the results of this study suggested that miR‐155‐5p inhibited OC differentiation by targeting CXCR2, thus reducing root resorption in orthodontics. MiR‐155‐5p can be used as an effective target for avoiding or reducing the degree of root resorption in orthodontic treatment. [ABSTRACT FROM AUTHOR]

Receptor activator of NF-κB ligand (RANKL) is essential for osteoclast formation and bone remodeling. Nevertheless, the cellular source of RANKL for osteoclastogenesis has not been fully uncovered. Different from peripheral adipose tissue, bone marrow (BM) adipose lineage cells originate from bone marrow mesenchymal stromal cells (BMSCs). Here, we demonstrate that adiponectin promoter-driven Cre expression (AdipoqCre) can target bone marrow adipose lineage cells. We cross the AdipoqCre mice with ranklfl/fl mice to conditionally delete RANKL from BM adipose lineage cells. Conditional deletion of RANKL increases cancellous bone mass of long bones in mice by reducing the formation of trabecular osteoclasts and inhibiting bone resorption but does not affect cortical bone thickness or resorption of calcified cartilage. AdipoqCre; ranklfl/fl mice exhibit resistance to estrogen deficiency and rosiglitazone (ROS)-induced trabecular bone loss but show bone loss induced by unloading. BM adipose lineage cells therefore represent an essential source of RANKL for the formation of trabecula osteoclasts and resorption of cancellous bone during remodeling under physiological and pathological conditions. Targeting bone marrow adiposity is a promising way of preventing pathological bone loss. [ABSTRACT FROM AUTHOR]

Bone‐modifying therapies are essential in the treatment of patients with multiple myeloma. Zoledronic acid is preferred over other bisphosphonates due to its superiority in reducing the incidence of skeletal‐related events and improving survival. The anti‐receptor activator of nuclear factor‐κΒ ligand (RANKL)‐targeted agent denosumab has shown its non‐inferiority compared to bisphosphonates in preventing skeletal‐related events among newly diagnosed patients with myeloma bone disease. Denosumab may confer a survival benefit in patients eligible for autologous transplantation. Denosumab may present a safer profile for patients with renal impairment. Discontinuation of bone‐directed therapies can be considered for patients with deep responses and after an adequate time period on treatment; however, a rebound effect may become evident especially in the case of denosumab. Three‐monthly infusions of zoledronic acid or at‐home denosumab administration should be considered during the coronavirus disease 2019 (COVID‐19) pandemic. Measures to prevent hypocalcaemia, renal toxicity and osteonecrosis of the jaw are important for all bone‐modifying agents. [ABSTRACT FROM AUTHOR]

Although document studies (including ours) have been reported the achieved in vitro osteoclastic cellular model establishment from the RAW264.7 cell lineage, there was no study directly reported that American Type Culture Collection (ATCC) cell bank has various RAW264.7 cell lineages. Besides that, for our knowledge there was only one study compared the two different RAW264.7TIB‐71 and RAW264.7CRL‐2278 cell lineages for their osteoclastic differentiation, and they concluded that the RAW264.7CRL‐2278 demonstrated to generate much osteoclast than RAW264.7TIB‐71. However, on the contrary to their results we noticed the fusion of RAW264.7TIB‐71 in our previous studies was much compromising. Therefore, we try to explore the two cell lineages for their properties in osteoclastic differentiation with an in‐depth cellular cytoskeletal study. Our current study has showed that comparing to the RAW264.7CRL‐2278, RAW264.7TIB‐71 demonstrated a much higher efficacies for RANKL‐stimulated osteoclastic differentiation. Besides that, in our depth cytoskeletal studies, we found that the RANKL‐induced RAW264.7TIB‐71 cells could finally differentiate into mature osteoclasts. However, regardless the various pre‐treatment conditions, there was no mature osteoclast formed in RANKL‐induced RAW264.7CRL‐2278 cell lineage. [ABSTRACT FROM AUTHOR]

Background and purpose: Osteoporosis is characterized by excessive bone resorption due to enhanced osteoclast activation. Stimulation of nuclear factor of activated T cells 1 (NFATc1) and accumulation of reactive oxygen species (ROS) are important mechanisms underlying osteoclastogenesis. Robinin (Rob) is a flavonoid glycoside that has shown anti‐inflammatory and antioxidative effects in previous studies, but little is known about its effects on bone homeostasis. The purpose of our research was to investigate whether Rob could prevent bone resorption in ovariectomized (OVX) mice by suppressing osteoclast production through its underlying mechanisms. Methods: The docking pose of Rob and RANKL was identified by protein‐ligand molecular docking. Rob was added to bone marrow macrophages (BMMs) stimulated by nuclear factor‐κB (NF‐κB) ligand (RANKL). The effects of Rob on osteoclastic activity were evaluated by positive tartrate resistant acid phosphatase (TRAcP) staining kit and hydroxyapatite resorption assay. RANKL‐induced ROS generation in osteoclasts was detected by H2DCFDA and MitoSox Red staining. The classic molecular cascades triggered by RANKL, such as NF‐κB, ROS, calcium oscillations, and NFATc1‐mediated signaling pathways, were investigated using Fluo4 staining, western blot, and quantitative real‐time polymerase chain reaction. In addition, an OVX mouse model mimicking estrogen‐deficient osteoporosis was created to evaluate the therapeutic effects of Rob in vivo. Results: Computational docking results showed that Rob could bind specifically to RANKL's predicted binding sites. In vitro, Rob inhibited RANKL‐mediated osteoclastogenesis dose‐dependently without obvious cytotoxicity at low concentrations. We also found that Rob attenuated RANKL‐induced mitochondrial ROS production or enhanced activities of ROS‐scavenging enzymes, and ultimately reduced intracellular ROS levels. Rob abrogated the RANKL‐induced mitogen‐activated protein kinase (MAPK) and NF‐κB signaling pathways, and subsequently blocked NFATc1 signaling and TRAcP expression. In addition, Rob inhibited osteoclast proliferation by downregulating the expression of osteoclast target genes (Acp5, Cathepsin K, Atp6v0d2, Nfact1, c‐Fos, and Mmp9) and reducing Ca2+ oscillations. Our in vivo results showed that Rob reduced bone resorption in OVX animal model by repressing osteoclast activity and function. Conclusions: Rob inhibits the activation of osteoclasts by targeting RANKL and is therefore a potential osteoporosis drug. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to determine the expression of distinct matrix metalloproteinases, cytokines, and bone resorptive factors in temporomandibular joint osteoarthritis (TMJ‐OA) patients and their association with joint pain, mouth opening, and subchondral bone degeneration. Materials and methods: Twelve patients affected with TMJ‐OA (n = 5), disk displacement without reduction (DDWoR) (n = 3), or disk displacement with reduction (DDWR) (n = 4) were selected. Joint pain was quantified by using visual analog scale, mouth opening was quantified at the maximum pain‐free aperture, and bone degeneration was quantified using joint imaging. Synovial fluid samples were collected and immediately processed for cell and synovial fluid recovering. From cells, the MMP‐1, MMP‐2, MMP‐8, MMP‐13, IL‐6, IL‐23, and TNF‐α expression was quantified by qPCR. From synovial fluid, the RANKL and OPG levels were quantified by ELISA. Results: Higher levels of MMP‐1, MMP‐8, MMP‐13, IL‐6, IL‐23, TNF‐α, and RANKL/OPG ratio were detected in TMJ‐OA compared with DDWoR and DDWR patients (p <.05). Joint pain significantly correlated with TNF‐α levels (r =.975, p =.029). Besides, imaging signs of bone degeneration significantly correlated with RANKL/OPG ratio (r =.949, p =.042). Conversely, mouth opening did not correlate with any of the analyzed mediators. Conclusion: During TMJ‐OA, a pathological response characterized by the overexpression of TNF‐α and RANKL/OPG could be involved in joint pain and subchondral bone degeneration. [ABSTRACT FROM AUTHOR]

Bisphosphonates (BPs), especially zoledronic acid (ZOL), are clinically used to treat osteolytic bone lesions. However, serious side‐effects may be also induced during the therapeutic process. To improve the BPs drugs, here, we investigated the effects of a series of ZOL derivatives with increasing number of methylene linker between the imidazole ring and the P–C–P backbone named IPrDP, IBDP, IPeDP, and IHDP on cell viability and receptor activator of nuclear factor‐κB ligand (RANKL)‐induced osteoclast differentiation, function and apoptosis induction in mouse bone marrow‐derived macrophages (BMMs). Our results suggested that IPeDP and IHDP, which contains 4 and 5 methylene linkers, respectively, exerted lower toxicity on BMMs compared with ZOL, IPrDP, and IBDP, which contains 1, 2, and 3 methylene linkers respectively. At concentrations below cytotoxicity threshold, IPeDP and IHDP possessed strong abilities of antiosteoclast formation, antibone absorption, and inducing osteoclast apoptosis, which were similar to ZOL and more powerful than IPrDP and IBDP. The mechanism behind these effects of IPeDP and IHDP might involve the interference of small GTPases prenylation through suppression of mevalonate pathway. The downregulation of JNK and Akt phosphorylation and subsequent inhibition of the expression of c‐Fos and NFATc1 might also be involved. Our results supported the potential usage of IPeDP and IHDP to treat bone‐related disorders involving increased osteoclastogenesis. Our attempt to extend the methylene linker between the imidazole ring and the P–C–P backbone of ZOL also reveals some regularities between the structure and properties of the BPs drugs. [ABSTRACT FROM AUTHOR]

Whether T cells promote bone loss following immobilization after spinal cord injury (SCI) remains undetermined. Therefore, wild‐type (WT) and T cell–deficient (Tcrb−/−) male mice underwent sham or contusion SCI to cause hindlimb paralysis. Femurs were isolated and distal and midshaft regions were evaluated by microcomputed tomography scanning. Bone marrow (BM) levels of bone turnover markers, as well as receptor activator of nuclear factor‐kappa B ligand (RANKL) and osteoprotegerin (OPG), were measured by ELISA. At 2 weeks post‐SCI, immobilization resulted in marked reduction in trabecular fractional bone volume (55%), thickness (40%), connectivity, and cortical thickness only in the Tcrb−/− animals (interaction with P < 0.05). BM analysis revealed lower bone formation (procollagen type 1 intact N‐terminal propeptide), higher bone resorption (tartrate‐resistant acid phosphatase‐5b), and a higher RANKL/OPG ratio in the Tcrb−/− SCI animals. At 5 weeks post‐SCI, while both WT and Tcrb−/− paralyzed animals showed deterioration of all indices of bone structure, they were more severe in Tcrb−/− animals. In summary, unlike other skeletal disorders, loss of αβ T cells compromises, rather than preserves, skeletal integrity under conditions of immobilization. [ABSTRACT FROM AUTHOR]

Dynamin‐related protein 1 (DRP1) is a mitochondrial membrane GTPase and regulates mitochondrial fission. In this study, we found that the cytokine RANKL increased the expression of DRP1 and its receptor proteins, Fis1, Mid49, and Mid 51, during osteoclast formation in mouse bone marrow‐derived macrophages. Inactivation of the kinase GSK3β appeared to induce DRP1 expression. DRP1 knockdown or the DRP1 inhibitor Mdivi1 suppressed osteoclast differentiation via downregulation of c‐Fos and NFATc1, the key transcription factor for osteoclast formation. Finally, the DRP1 inhibitor suppressed lipopolysaccharide‐induced osteoclast formation in a calvarial model and ovariectomy‐induced bone loss in vivo. Taken together, our data demonstrate that DRP1 positively contributes to RANKL‐induced osteoclast differentiation by regulating the c‐Fos–NFATc1 axis, suggesting the importance of mitochondrial DRP1 in osteoclastogenesis. [ABSTRACT FROM AUTHOR]

Bisphosphonates (BPs) have been commonly used in the treatment of osteolytic bone lesions, such as osteoporosis and osteogenesis imperfecta. However, serious side‐effects can occur during the therapy. To search for novel potent BPs with lower side‐effects, a series of imidazole‐containing BPs (zoledronic acid [ZOL]; ZOL derivatives by substitution of the hydrogen at the 2‐position on the imidazole ring with a methyl [MIDP], ethyl [EIDP], n‐propyl [PIDP], or n‐butyl group [BIDP]) were developed and the effects on receptor activator of nuclear factor‐κB ligand (RANKL)‐induced osteoclast differentiation were investigated using the murine macrophage RAW 264.7 cells at the protein, gene, and morphological and functional levels. Influences of these BPs on the cell growth and proliferation of RAW 264.7 were also studied in order to determine cytotoxicity. The results showed that PIDP significantly inhibited the RANKL‐induced osteoclast formation in a dose‐dependent fashion without inducing cytotoxicity under the concentration of 12.5 μM. It exerted remarkable suppressive effects on the development of actin rings, the bone resorption, and the expressions of osteoclastogenesis‐related gene and protein markers. The down‐regulation of c‐Jun N‐terminal kinase (JNK), protein kinase B (Akt), and inhibitor of nuclear factor kappa‐B (IκB) phosphorylation in the early signaling event and subsequent inhibition of the expression of c‐Fos and nuclear factor of activated T cells (NFATc1) might be involved in these effects. All these results indicated that PIDP might be a promising drug to treat bone‐related disorders. [ABSTRACT FROM AUTHOR]

Osteoporosis is a disease in which bone mineral density decreases due to abnormal activity of osteoclasts, and is commonly found in post‐menopausal women who have decreased levels of female hormones. Sphingosylphosphorylcholine (SPC) is an important biological lipid that can be converted to sphingosine‐1‐phosphate (S1P) by autotaxin. S1P is known to be involved in osteoclast activation by stimulating osteoblasts, but bone regulation by SPC is not well understood. In this study, we found that SPC strongly inhibits RANKL‐induced osteoclast differentiation. SPC‐induced inhibitory effects on osteoclast differentiation were not affected by several antagonists of S1P receptors or pertussis toxin, suggesting cell surface receptor independency. However, SPC inhibited RANKL‐induced calcineurin activation and subsequent NFATc1 activity, leading to decrease of the expression of Trap and Ctsk. Moreover, we found that bone loss in an experimental osteoporosis mouse model was recovered by SPC injection. SPC also blocked ovariectomy‐induced body weight increase and Nfatc1 gene expression in mice. We also found that SPC inhibits RANKL‐induced osteoclast differentiation in human macrophages. Since currently available treatments for osteoporosis, such as administration of female hormones or hormone receptor modulators, show serious side effects, SPC has potential as a new agent for osteoporosis treatment. [ABSTRACT FROM AUTHOR]

Osteoporotic fractures cause major morbidity and mortality in the aging population. Genome‐wide association studies (GWAS) have identified USF3 as the novel susceptibility gene of osteoporosis. However, the functional role in bone metabolism and the target gene of the basic helix‐loop‐helix transcription factor USF3 are unclear. Here, we show that USF3 enhances osteoblast differentiation and suppresses osteoclastogenesis in cultured human osteoblast‐like U‐2OS cells. Mechanistic studies revealed that transcription factor USF3 antagonistically interacts with anti‐osteogenic TWIST1/TCF12 heterodimer in the WNT16 and RUNX2 promoter, and counteracts CREB1 and JUN/FOS in the RANKL promoter. Importantly, the osteoporosis GWAS variant g.1744A>G (rs2908007A>G) located in the WNT16 promoter confers G‐allele‐specific transcriptional modulation by USF3, TWIST1/TCF12 and TBX5/TBX15, and USF3 transactivates the osteoclastogenesis suppressor WNT16 promoter activity and antagonizes the repression of WNT16 by TWIST1 and TCF12. The risk G allele of osteoporosis GWAS variant g.3260A>G (rs4531631A>G) in the RANKL promoter facilitates the binding of CREB1 and JUN/FOS and enhances transactivation of the osteoclastogenesis contributor RANKL that is inhibited by USF3. Our findings uncovered the functional mechanisms of osteoporosis novel GWAS‐associated gene USF3 and lead single nucleotide polymorphisms rs2908007 and rs4531631 in the regulation of bone formation and resorption. [ABSTRACT FROM AUTHOR]

publisher‐imprint‐name Springer volume‐issue‐count 1 issue‐article‐count 0 issue‐toc‐levels 0 issue‐pricelist‐year 2020 issue‐copyright‐holder The Author(s) issue‐copyright‐year 2020 article‐contains‐esm No article‐numbering‐style Unnumbered article‐registration‐date‐year 2019 article‐registration‐date‐month 12 article‐registration‐date‐day 13 article‐toc‐levels 0 toc‐levels 0 volume‐type Regular journal‐product ArchiveJournal numbering‐style Unnumbered article‐grants‐type OpenChoice metadata‐grant OpenAccess abstract‐grant OpenAccess bodypdf‐grant OpenAccess bodyhtml‐grant OpenAccess bibliography‐grant OpenAccess esm‐grant OpenAccess online‐first false pdf‐file‐reference BodyRef/PDF/40169_2019_Article_249.pdf pdf‐type Typeset target‐type OnlinePDF issue‐type Regular article‐type OriginalPaper journal‐subject‐primary Medicine & Public Health journal‐subject‐secondary Medicine/Public Health, general journal‐subject‐collection Medicine open‐access true --> Background: The incidence and mortality rates of gastric cancer (GC) rank in top five among all malignant tumors. Chemokines and their receptor‐signaling pathways reportedly play key roles in the metastasis of malignant tumor cells. Receptor activator of nuclear factor κB ligand (RANKL) is a member of the tumor necrosis factor family, with strong chemokine‐like effects. Some studies have pointed out that the RANKL/RANK pathway is vital for the metastasis of cancer cells, but the specific mechanisms in GC remain poorly understood. Results: This study reports original findings in cell culture models and in patients with GC. Flow cytometry and western blotting analyses showed that RANK was expressed in BGC‐823 and SGC‐7901 cells in particular. Chemotaxis experiments and wound healing assay suggested that RANKL spurred the migration of GC cells. This effect was offset by osteoprotegerin (OPG), a decoy receptor for RANKL. RANKL contributed to the activation of human epidermal growth factor receptor (HER) family pathways. The lipid raft core protein, caveolin 1 (Cav‐1), interacted with both RANK and human epidermal growth factor receptor‐1(EGFR). Knockdown of Cav‐1 blocked the activation of EGFR and cell migration induced by RANKL. Moreover, RANK‐positive GC patients who displayed higher levels of EGFR expression had poor overall survival. Conclusions: In summary, we confirmed that with the promotion of RANKL, RANK and EGFR can form complexes with the lipid raft core protein Cav‐1, which together promote GC cell migration. The formation of the RANK‐Cav‐1‐EGFR complex provides a novel mechanism for the metastasis of GC. These observations warrant confirmation in independent studies, in vitro and in vivo. They also inform future drug target discovery research and innovation in the treatment of GC progression. [ABSTRACT FROM AUTHOR]

Bone erosion is the major cause of deformities in autoimmune disease conditions such as osteoporosis and rheumatoid arthritis. Aberrant receptor activator of nuclear factor kappa B ligand (RANKL) secretion in bone disorders have been implicated to promote uncontrolled osteoclast differentiation through the regulation of nuclear factor of activated T cells 1 (NFATc1) transcription factor. This phenomenon is governed by several molecular factors including microRNAs, which are under‐expressed during disease progression. This report focuses on elucidating the molecular mechanism of miR‐506‐3p towards the RANKL/NFATc1 pathway. miR‐506‐3p showed high binding affinity towards NFATc1 (ΔG = −22.4 kcal/mol). Bone marrow‐derived macrophages (BMMs) isolated from rats stimulated with RANKL (100 ng/ml) showed active expression of NFATc1 which differentiated into mature osteoclasts. Moreover, NFATc1 activation resulted in downstream secretion of various bone resorptive enzymes (cathepsin K, carbonic anhydrase II, tartarate acid phosphatase, and matrix metalloproteinase 9) which lead to active bone resorption. However, transfection of miR‐506‐3p resulted in selective repression of NFATc1 inside the cells. This further resulted in the diminished release of bone resorptive enzymes that were essential for the degradation of the bone. Overall, we predict that miR‐506‐3p can be used as a molecular intervention for RANKL/NFATc1 mediated osteoclastogenesis. [ABSTRACT FROM AUTHOR]