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BACKGROUND: Carnosic acid, a bioactive compound found in rosemary, has been shown to reduce inflammation and reactive oxygen species (ROS). However, its mechanism of action in osteoclast differentiation remains unclear. OBJECTIVE: To investigate the effects of carnosic acid on osteoclast activation, ROS production, and mitochondrial function. METHODS: Primary bone marrow-derived macrophages from mice were extracted and cultured in vitro. Different concentrations of carnosic acid (0, 10, 15, 20, 25 and 30 μmol/L) were tested for their effects on bone marrow-derived macrophage proliferation and toxicity using the cell counting kit-8 cell viability assay to determine a safe concentration. Bone marrow-derived macrophages were cultured in graded concentrations and induced by receptor activator of nuclear factor-κB ligand for osteoclast differentiation for 5-7 days. The effects of carnosic acid on osteoclast differentiation and function were then observed through tartrate-resistant acid phosphatase staining, F-actin staining, H2DCFDA probe and mitochondrial ROS, and Mito-Tracker fluorescence detection. Western blot and RT-PCR assays were subsequently conducted to examine the effects of carnosic acid on the upstream and downstream proteins of the receptor activator of nuclear factor-κB ligand-induced MAPK signaling pathway. RESULTS AND CONCLUSION: Tartrate-resistant acid phosphatase staining and F-actin staining showed that carnosic acid dose-dependently inhibited in vitro osteoclast differentiation and actin ring formation in the cell cytoskeleton, with the highest inhibitory effect observed in the high concentration group (30 μmol/L). Carnosic acid exhibited the most significant inhibitory effect during the early stages (days 1-3) of osteoclast differentiation compared to other intervention periods. Fluorescence imaging using the H2DCFDA probe, mitochondrial ROS, and Mito-Tracker demonstrated that carnosic acid inhibited cellular and mitochondrial ROS production while reducing mitochondrial membrane potential, thereby influencing mitochondrial function. The results of western blot and RT-PCR revealed that carnosic acid could suppress the expression of NFATc1, CTSK, MMP9, and C-fos proteins associated with osteoclast differentiation, and downregulate the expression of NFATc1, Atp6vod2, ACP5, CTSK, and C-fos genes related to osteoclast differentiation. Furthermore, carnosic acid enhanced the expression of antioxidant enzyme proteins and reduced the generation of ROS during the process of osteoclast differentiation. Overall, carnosic acid exerts its inhibitory effects on osteoclast differentiation by inhibiting the phosphorylation modification of the P38/ERK/JNK protein and activating the MAPK signaling pathway in bone marrow-derived macrophages. [ABSTRACT FROM AUTHOR]

Visfatin, an adipokine secreted by various cell types, plays multifaceted pathophysiological roles in inflammatory conditions, including obesity, which is closely associated with osteoclastogenesis, a key process underlying bone loss and increased osteoporosis (OP) risk. However, the role of visfatin in osteoclastogenesis remains controversial. This study was conducted to investigate the effects of visfatin on receptor activator of nuclear factor kappa-B ligand (RANKL)-induced osteoclast differentiation from precursor cells in vitro. Our results demonstrated that although visfatin exhibited a modest osteoclast-inductive effect relative to that of RANKL, co-stimulation of bone marrow-derived macrophages (BMDMs) with visfatin and RANKL led to significantly enhanced osteoclast differentiation and activation compared to individual stimulation. Neutralization of visfatin activity using blocking antibodies before differentiation markedly suppressed RANKL-induced osteoclastogenesis, as evidenced by a near-complete absence of tartrate-resistant acid phosphatase-positive multinucleated osteoclasts, decreased levels of nuclear factor of activated T cells cytoplasmic 1 and osteoclast-specific proteins, inhibition of nuclear factor-κB and mitogen-activated protein kinase signaling pathways, and a decrease in resorption pit formation. Our findings underscore the critical role of visfatin in RANKL-induced osteoclastogenesis in vitro and highlight the RANKL/visfatin signaling axis as a potential therapeutic target for destructive bone loss-related diseases. [ABSTRACT FROM AUTHOR]

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]

Bone regeneration is a highly dynamic and complex process that involves hematopoietic stem cells and mesenchymal cells, collagen fibers, non-collagenous proteins and biomolecules from extracellular matrices, and different cytokines and immune cells, as well as growth factors and hormones. Some phytochemicals due to antioxidant and anti-inflammatory effects can modulate the bone signaling pathways and improve bone healing and thus can be a good candidate for osteoregeneration. The aim of this study was to analyze the impact of Juglans regia L. extract compared to ellagic acid on bone neoformation in rats. The animals with a 5 mm calvaria defect were divided into four groups (n = 10): group 1 was treated with ellagic acid 1% (EA), group 2 was treated with Juglans regia L. extract 10% (JR), group 3 was treated with a biphasic mix of hydroxyapatite and tricalcium phosphate (Ceraform), and group 4 was treated with vehicle inert gel with carboxymethylcellulose (CMC). After 3 weeks of treatment, blood samples were collected for oxidative stress and inflammation assessment. Additionally, the receptor activator of nuclear factor kappa-Β ligand (RANKL) and hydroxyproline levels were quantified in blood. The skull samples were analyzed by scanning electron microscopy in order to detect the modifications in the four groups. The results suggested that JR extract had relevant anti-oxidant effect and bone protective activity and generated the accumulation of Ca and P, demonstrating the potential therapeutic abilities in bone regeneration. [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]

Platelet-rich plasma (PRP) is utilized as an autologous blood product to encourage bone regeneration. The receptor activator of nuclear factor-NB ligand (RANKL) is a key and central regulator of osteoclast homeostasis. A rat model of experimentally generated periodontitis was used to assess the impact of PRP preparation on the expression of the osteoclastogenic and pro-inflammatory markers respectively; RANKL and IL-1β. To induce periodontitis by silk ligature, thirty-six adult male Sprague Dawleys rats were used and they were allocated into three equal groups (n = 12): group I consisted of intact periodontal tissue, group II; rat-induced periodontitis without treatment by PRP, and group III of periodontitis + 10 µL PRP injection. The rats were sacrificed after both experiment durations (7 and 30 days), and the incisor teeth were fixed and decalcified in HCl for a day and in 10 % EDTA solution for eight weeks at room temperature then samples were processed for H&E stain for bone healing scores and bone cells counting, and the samples were utilized by IHC for detection of both RANKL and IL-1β expression. The PRP enhanced the process of healing on days 7 and 30 showed (Score 10) vs. the control positive group that had a delay in alveolar bone regarded as (Score 4) significantly (P ≤ 0.05). The PRP group attenuated significantly (P ≤ 0.05) the alveolar bone loss by increasing the number of osteoblasts and declining the proliferation of osteoclast vs. the control positive group that revealed bone destruction due to rising osteoclast proliferation and decreasing the osteoblast proliferation significantly (P ≤ 0.05). PRP inhibited the IL-1β expression (score = 0) vs. the control positive group that showed moderate staining of positive cells detected in both inflammatory cells and endothelium (score = 4). Regarding the RANKL expression, the PRP reduced its expression in vs. the control positive group (score = 4 vs. 12 respectively). PRP is an anabolic agent that enhances proliferation of osteoblast and inhibit the osteoclast differentiation by downregulation of IL-1β and RANKL. [ABSTRACT FROM AUTHOR]

Increasing evidence suggests a common physiological process for bone and coronary artery calcification (CAC), implying the role of bone metabolism markers in subclinical atherosclerosis development. However, the association between bone turnover markers and the development of CAC has remained controversial, as seen in various studies. Because CAC measurement has both financial burden and radiation exposure risk in individuals with suspected cardiovascular disease (CVD), applying the diagnostic role of osteogenic markers in predicting abnormal CAC would improve treatment adherence and reduce the rate of CVD mortality. In this review, we begin by describing the current understanding of the molecular mechanisms of bone markers in the etiology of CAC. Furthermore, we summarize bone-associated regulatory factors at the molecular level as novel therapeutic targets for CAC. In addition, we focused on the current results on the prognostic role of novel mediators of osteogenic activity in determining the risk of CAC as a preclinical factor of atherosclerotic CVD. Accumulating evidence suggests the role of bone marker-mediated pathways in the progression of CAC, which may lead to early diagnosis of CVD complications and the establishment of innovative targets for pharmacological therapy. Indeed, miRNAs and lncRNAs, as novel therapeutic interventions, can be a research priority in regulating bone metabolism at the gene expression level to attenuate high CAC and improve CVD outcomes. [ABSTRACT FROM AUTHOR]

Background: There is an increasing occurrence of periodontitis and metabolic syndrome (MetS), which is resulting in a decline in the overall quality of life. Both disorders can occur together since they are both linked to insulin resistance and systemic inflammation. However, evidence for a role of interleukin (IL)-20 in this comorbidity is very limited. This cross-sectional study aimed to comprehensively investigate, for the first time, the levels of RANKL/OPG, MMP-8 and OSI as well as the role of IL-20 in patients with MetS and periodontitis. Methods: The study included a total of 80 individuals, divided into four groups: 20 individuals who were healthy both systemically and periodontally, 20 individuals who were systemically healthy but had periodontitis, 20 individuals who had MetS but were periodontally healthy, and 20 individuals who had both MetS and periodontitis. Periodontal clinical parameters (plaque index, gingival index, bleeding on probing, clinical attachment loss, probing pocket depth) were evaluated. Gingival crevicular fluid (GGF) and serum samples were collected and used for biochemical assays. Enzyme-linked immunosorbent assay was used to determine the levels of IL-20, receptor activator of nuclear factor kappa B ligand (RANKL)/osteoprotegerin (OPG), matrix metalloproteinase-8 (MMP-8) and oxidative stress index (OSI). Results: IL-20 levels measured in serum and GCF were statistically significantly highest in patients with MetS and periodontitis (p = 0.001). Significant positive correlation was observed between serum and GCF IL-20 values and periodontal parameters (p < 0.05). There was a positive correlation between RANKL and RANKL/OPG levels and IL-20 and clinical parameters (p < 0.05). OSI values were found to be increased in the presence of both periodontitis and MetS (p = 0.001) and were positively correlated with serum and GCF IL-20 (p < 0.05). Conclusions: These data from the study suggest a correlation between IL-20 and both MetS and periodontitis. IL-20 may potentially worsen the condition of periodontal tissue by increasing both the oxidative stress levels, periodontal collagen degredation and the ratio of RANKL to OPG. Trial registration: This study was registered on ClinicTrials.gov (NCT06092853), 2023-10-10, retrospectively registered. [ABSTRACT FROM AUTHOR]

Background: Platelet-rich plasma (PRP) is utilized as an autologous blood product to encourage bone regeneration. The receptor activator of nuclear factor-NB ligand (RANKL) is a key and central regulator of osteoclast homeostasis. A rat model of experimentally generated periodontitis was used to assess the impact of PRP preparation on the expression of the osteoclastogenic and pro-inflammatory markers respectively; RANKL and IL-1β. Material and Methods: To induce periodontitis by silk ligature, thirty-six adult male Sprague Dawleys rats were used and they were allocated into three equal groups (n = 12): group I consisted of intact periodontal tissue, group II; rat-induced periodontitis without treatment by PRP, and group III of periodontitis + 10 µL PRP injection. The rats were sacrificed after both experiment durations (7 and 30 days), and the incisor teeth were fixed and decalcified in HCl for a day and in 10 % EDTA solution for eight weeks at room temperature then samples were processed for H&E stain for bone healing scores and bone cells counting, and the samples were utilized by IHC for detection of both RANKL and IL-1β expression. Results: The PRP enhanced the process of healing on days 7 and 30 showed (Score 10) vs. the control positive group that had a delay in alveolar bone regarded as (Score 4) significantly (P ≤ 0.05). The PRP group attenuated significantly (P ≤ 0.05) the alveolar bone loss by increasing the number of osteoblasts and declining the proliferation of osteoclast vs. the control positive group that revealed bone destruction due to rising osteoclast proliferation and decreasing the osteoblast proliferation significantly (P ≤ 0.05). PRP inhibited the IL-1β expression (score = 0) vs. the control positive group that showed moderate staining of positive cells detected in both inflammatory cells and endothelium (score = 4). Regarding the RANKL expression, the PRP reduced its expression in vs. the control positive group (score = 4 vs. 12 respectively). Conclusion: PRP is an anabolic agent that enhances proliferation of osteoblast and inhibit the osteoclast differentiation by downregulation of IL-1β and RANKL.

Increasing evidence suggests a common physiological process for bone and coronary artery calcification (CAC), implying the role of bone metabolism markers in subclinical atherosclerosis development. However, the association between bone turnover markers and the development of CAC has remained controversial, as seen in various studies. Because CAC measurement has both financial burden and radiation exposure risk in individuals with suspected cardiovascular disease (CVD), applying the diagnostic role of osteogenic markers in predicting abnormal CAC would improve treatment adherence and reduce the rate of CVD mortality. In this review, we begin by describing the current understanding of the molecular mechanisms of bone markers in the etiology of CAC. Furthermore, we summarize bone-associated regulatory factors at the molecular level as novel therapeutic targets for CAC. In addition, we focused on the current results on the prognostic role of novel mediators of osteogenic activity in determining the risk of CAC as a preclinical factor of atherosclerotic CVD. Accumulating evidence suggests the role of bone marker-mediated pathways in the progression of CAC, which may lead to early diagnosis of CVD complications and the establishment of innovative targets for pharmacological therapy. Indeed, miRNAs and lncRNAs, as novel therapeutic interventions, can be a research priority in regulating bone metabolism at the gene expression level to attenuate high CAC and improve CVD outcomes.

Abstract Background There is an increasing occurrence of periodontitis and metabolic syndrome (MetS), which is resulting in a decline in the overall quality of life. Both disorders can occur together since they are both linked to insulin resistance and systemic inflammation. However, evidence for a role of interleukin (IL)-20 in this comorbidity is very limited. This cross-sectional study aimed to comprehensively investigate, for the first time, the levels of RANKL/OPG, MMP-8 and OSI as well as the role of IL-20 in patients with MetS and periodontitis. Methods The study included a total of 80 individuals, divided into four groups: 20 individuals who were healthy both systemically and periodontally, 20 individuals who were systemically healthy but had periodontitis, 20 individuals who had MetS but were periodontally healthy, and 20 individuals who had both MetS and periodontitis. Periodontal clinical parameters (plaque index, gingival index, bleeding on probing, clinical attachment loss, probing pocket depth) were evaluated. Gingival crevicular fluid (GGF) and serum samples were collected and used for biochemical assays. Enzyme-linked immunosorbent assay was used to determine the levels of IL-20, receptor activator of nuclear factor kappa B ligand (RANKL)/osteoprotegerin (OPG), matrix metalloproteinase-8 (MMP-8) and oxidative stress index (OSI). Results IL-20 levels measured in serum and GCF were statistically significantly highest in patients with MetS and periodontitis (p = 0.001). Significant positive correlation was observed between serum and GCF IL-20 values and periodontal parameters (p

BACKGROUND: Liuwei Dihuang Wan takes “three tonifying and three reducing effects” as its compatibility feature to nourish yin and tonify the kidneys, while Zuogui Wan takes “seeking yin in yang” as its compatibility feature to nourish yin and tonify the kidneys by promoting yang. Both of them belong to the same method of nourishing yin and tonifying the kidneys, and have better curative effects at the symptomatic and cellular molecular levels. OBJECTIVE: To observe the effects of Liuwei Dihuang Wan and Zuogui Wan in bone metabolism, and to explore their mechanism of action in the osteoprotegerin (OPG)/receptor activator of nuclear factor-κB ligand (RANKL) osteoblastic pathway. METHODS: Thirty-two Sprague-Dawley rats were randomized into model, Liuwei Dihuang Wan, Zuogui Wan, and sham operation group, with eight rats in each group. Osteoporosis models were prepared using removal of both ovaries in the first three groups. Starting at 30 days postoperatively, rats in the Liuwei Dihuang Wan group were gavaged with Liuwei Dihuang Wan 1.125 g/kg/d; rats in the Zuoqui Wan group were gavaged with Zuogui Wan 2.25 g/kg/d; and rats in the sham operation group and the model group were gavaged with saline 10 mL/kg/d. After 12 weeks of gavage, the rat tibia was taken to measure bone mineral density. The serum levels of estrogen, bone alkaline phosphatase, and cAMP/cGMP were measured using ELISA, and the expression of OPG/RANKL in the femur was detected using western blot. RESULTS AND CONCLUSION: Compared with the sham operation group, the model group showed a decrease in bone mineral density and levels of estrogen and bone alkaline phosphatase (P < 0.05) and an increase in cAMP/cGMP level (P < 0.05). Compared with the model group, the Liuwei Dihuang Wan group and the Zuogui Wan group significantly increased bone mineral density (P < 0.05) and bone alkaline phosphatase levels (P < 0.05); the Zuogui Wan group significantly decreased cAMP/cGMP levels (P < 0.05) and upregulated OPG expression (P < 0.05); the Liuwei Dihuang Wan group upregulated OPG expression and downregulated RANKL expression (P < 0.05); and both groups were unable to significantly increase estrogen levels (P > 0.05). To conclude, Zuogui Wan, which seeks yin from yang, can effectively increase the expression of OPG but cannot downregulate the expression of RANKL. However, Liuwei Dihuang Wan, which has three tonifying and three reducing effects, can bidirectionally regulate the expression of OPG and RANKL. This result suggests that Liuwei Dihuang Wan can significantly inhibit osteoclastic function compared with Zuogui Wan, and further research is needed to verify this conclusion. [ABSTRACT FROM AUTHOR]

BACKGROUND: Cistanoside A has the effects of anti-inflammation, antioxidation, antioxidation, reducing renal damage and anti-osteoporosis, but its effect on osteoclast differentiation, function and its underlying molecular mechanisms remain unclear. OBJECTIVE: To investigate the effect of Cistanoside A on osteoclast differentiation and bone resorption induced by receptor activator of nuclear factor kappa-B ligand (RANKL) in vitro and its mechanism. METHODS: Bone marrow macrophages were obtained from the femur and tibia of 4-6-week-old C57BL/6 mice. The cytotoxic effect of Cistanoside A (5, 10, 20, 40, 80, and 160 μmol/L) on bone marrow macrophage viability was examined using the cell counting kit-8 assay kit. Tartrate-resistant acid phosphatase staining was performed to observe the effect of different concentrations of Cistanoside A on osteoblast differentiation and its effective intervention concentration was determined. There was positive control group, Cistanoside A low, medium, and high dose groups (40, 80, and 160 μmol/L). After cell attachment, 50 ng/mL RANKL was added to induce osteoblast differentiation, and the corresponding dose of Cistanoside A was added to the Cistanoside A low, medium, and high dose groups, respectively. F-actin ring and 2-(4-Amidinophenyl)-6-indolecarbamidine dihydrochloride staining were performed to detect the effects of Cistanoside A on the formation of osteoclasts. Toluidine blue staining of bone abrasion slices was used to observe the effects of Cistanoside A on bone resorption function of osteoclasts. The expression of upstream and downstream proteins of the JNK/MAPK pathway was detected by Western blot. The expression of genes related to osteoclast differentiation and bone resorption function such as tartrate-resistant acid phosphatase, DC-STAMP, Nfatc-1, Ctsk and c-Fos was detected by RTqPCR. RESULTS AND CONCLUSION: Tartrate-resistant acid phosphatase staining, F-actin ring staining and resorption pit assay showed that Cistanoside A significantly inhibited RANKL-induced osteoclast differentiation and bone resorption in a dose-dependent manner compared with the positive control group. The results of RT-qPCR showed that compared with the positive control group, both high and low dose groups of Cistanoside A could significantly downregulate the mRNA expression of tartrate-resistant acid phosphatase, DC-STAMP, Nfatc-1, Ctsk and c-Fos in a dosedependent manner. The results of western blot assay showed that the high dose group of Cistanoside A significantly inhibited the expression of p-JNK protein at 10, 20, 30 and 60 minutes of intervention; compared with the positive control group, Cistanoside A significantly inhibited the expression of Nfatc1 and c-Fos proteins in a dose-dependent manner. To conclude, Cistanoside A could inhibit the formation and bone resorption of osteoclasts by reducing the level of p-JNK protein, inhibiting the activation of MAPK pathway and the expression of key genes in osteoclasts. [ABSTRACT FROM AUTHOR]

Background/purpose: Cementum shares many properties with bone; however, in contrast to bone, it is not innervated or vascularized and has a limited capacity for remodeling. Osteocytes located in the lacunae-canalicular system of bone tissue play a central role in bone remodeling by communicating with osteoblasts and osteoclasts. Although cementocytes are present in cellular cementum and are morphologically similar to osteocytes, it remains unclear whether they are involved in the dynamic functional regulation of metabolism in cementum. The present study focused on the extracellular vesicles (EVs) secreted by cementocytes and examined their effects on osteoclasts and osteoblasts. Materials and methods: EVs were extracted from the mouse cementocyte cell line, IDG-CM6. The effects of EVs on recombinant RANKL-induced osteoclastogenesis and recombinant Bone morphogenetic protein (BMP)-2-mediated osteoblastogenesis were investigated using the mouse osteoclast progenitor cell line, RAW264.7 and mouse pre-osteoblast cell line, MC3T3-E1, respectively. Results: EVs enhanced the formation of tartrate-resistant acid phosphatase activity-positive cells. Real-time PCR revealed that EVs up-regulated the expression of osteoclast-related genes. On the other hand, the cell culture supernatant of cementocytes significantly inhibited the differentiation of osteoclasts. Regarding osteoblastogenesis, EVs suppressed the expression of alkaline phosphatase, bone sialoprotein, and osteocalcin induced by recombinant BMP-2 at the gene and protein levels. Conclusion: A network of cementocytes, osteoblasts, and osteoclasts may exist in cellular cementum, which suggests the involvement of cementocytes in dynamic metabolism of cementum through EVs.

Abstract Background Nitrogen-containing bisphosphonate(N-BP)had been found to inhibit the osteogenic differentiation and calcification in vascular smooth muscle cells (VSMCs), but the mechanism is not clear. We intend to verify that N-BP induces enhancement of OPG expression and inhibition of RANKL expression via inhibition of farnesyl pyrophosphate synthase(FPPS) to inhibit the osteogenic differentiation and calcification in VSMCs. Methods β-glycerophosphate (β-GP) was used to induce the osteogenic differentiation and calcification in VSMCs. VSMCs were treated with N-BP or pretreated with downstream products of farnesyl pyrophosphate synthase(FPPS) in mevalonate pathway, such as farnesol (FOH) or geranylgeraniol (GGOH). Alizarin red S staining and determination of calcium content were used to detect calcium deposition.Western Blotting were used to detect expressions of proteins(OPG and RANKL ) and osteogenic marker proteins (Runx2 and OPN). Results β-GP induced the osteogenic differentiation and calcification in VSMCs, increased RANKL protein expression and had no significant effect on OPG protein expression. With the treatment of N-BP, the expression of OPG protein was increased and expression of RANKL protein was decreased in VSMCs undergoing osteogenic differentiation and calcification. In addition, N-BP reduced the osteogenic marker proteins (Runx2 and OPN) expression and calcium deposition in VSMCs undergoing osteogenic differentiation and calcification. These effects of N-BP on the osteogenic differentiation and calcification in VSMCs were concentration-dependent, which could be reversed by the downstream products of FPPS, such as FOH or GGOH. Conclusion N-BP increases OPG expression and decreases RANKL expression via inhibition of FPPS to inhibit the osteogenic differentiation and calcification in VSMCs.

Abstract Introduction Osteoporosis, a systemic skeletal disease, is characterized by a quantitative and qualitative, and progressive decrease in bone mass, which is related to inflammation. Since a cytokine storm is triggered in Coronavirus disease 2019 (COVID-19), this study aims to evaluate pro-inflammatory cytokines (TNF-α, IL-1β), Receptor activator of nuclear factor-κB ligand (RANKL)/serum osteoprotegerin (OPG) ratio, and their relationship in mild and severe COVID-19. Methods This study was performed on 48 adult patients (18 mild, 18 severe COVID-19, and 12 healthy subjects as a control group). Serum OPG, RANKL, TNF-α, IL-1β, 25-OH vitamin D, and ALKp were measured by ELISA and colorimetric assay. Results COVID-19 patients had a significant increase in RANKL, and RANKL/OPG in mild and severe form (p

In this study, we investigated the inhibitory effects of radiofrequency exposure on RANKL-induced osteoclast differentiation in RAW264.7 cells, along with the underlying mechanisms. RAW264.7 cells were subjected to radiofrequency exposure at three distinct power densities: 50 µW/cm2, 150 µW/cm2, and 450 µW/cm2. The results showed that, among the three dosage levels, exposure to 150 µW/cm2 of radiofrequency radiation significantly reduced the proliferation capacity of RAW264.7 cells. RF exposure at three power densities resulted in significant increases in the level of osteoclast apoptosis and notable decreases in osteoclast differentiation. Notably, the most pronounced effects on apoptosis, differentiation in RAW 264.7 cells were observed at the 150 µW/cm2 power density. These effects were accompanied by concurrent decreases in mRNA and protein levels of osteoclast-specific genes, including RANK, NFATc1, and TRACP. Furthermore, radiofrequency exposure at power density of 150 µW/cm2 induced a significant decrease in cytoplasmic NF-κB protein levels while increasing its nuclear fraction, thereby counteracting the effects of RANKL-induced NF-κB activation. These data suggest that radiofrequency exerts inhibitory properties on RANKL-induced NF-κB transcriptional activity, subsequently indirectly suppressing the expression of downstream NF-κB target genes, such as NFATc1 and TRACP. In conclusion, our study demonstrates that radiofrequency radiation effectively inhibits osteoclast differentiation by modulating the NF-κB signaling pathway. These findings have important implications for potential therapeutic interventions in osteoporosis. Plain Language Summary: Osteoporosis is a common bone disease where bones become weak and brittle, often leading to fractures. It frequently occurs in older adults, especially postmenopausal women, due to low estrogen levels and inadequate calcium intake. This causes increased activity of bone cells called osteoclasts which break down bone tissue, resulting in severe bone loss. Currently, the primary treatment is long-term use of medications like bisphosphonates. However, these drugs can have side effects. The main adverse reactions include fever, vomiting, rash, diarrhea, dizziness, abdominal pain, musculoskeletal pain, headache, allergic-like reactions, indigestion, edema, and ocular symptoms. This study explored using radiofrequency (RF) radiation as a safe, non-invasive alternative therapy for osteoporosis. RF radiation is a type of energy used in communications like cell phones and WiFi. We tested whether exposure to 900MHz RF radiation could inhibit the formation and activity of osteoclasts to prevent excessive bone breakdown. We treated osteoclast precursor cells with RANKL, a protein that stimulates osteoclast formation. Cells were then exposed to RF radiation at various intensities. The results showed that medium-level RF radiation (150 μW/cm2) significantly suppressed RANKL-induced osteoclast differentiation and bone resorption capacity. This effect was like the osteoclast inhibition seen with estrogen treatment. Further analysis revealed that RF radiation blocks the activation of NF-κB, a key signaling molecule that promotes osteoclast formation when RANKL is present. This in turn reduced production of downstream signals like NFATc1 and TRACP which are essential for osteoclast differentiation. In summary, this study demonstrates that medium-intensity RF radiation could potentially prevent excessive osteoclastic bone resorption in osteoporosis patients by interfering with NF-κB signaling cascade. The research highlights RF radiation's promise as a novel, non-invasive osteoporosis therapy. [ABSTRACT FROM AUTHOR]

Purpose: Chordomas are malignant tumors that destroy bones, compress surrounding nerve tissues and exhibit phenotypes that recapitulate notochordal differentiation in the axial skeleton. Chordomas recur frequently, as they resist radio-chemotherapy and are difficult to completely resect, leading to repeated bone destruction and local expansion via unknown mechanisms. Here, using chordoma specimens and JHC7 chordoma cells, we asked whether chordoma cells possess bone-dissolving activity. Methods: CT imaging and histological analysis were performed to evaluate the structure and mineral density of chordoma-invaded bone and osteolytic marker expression. JHC7 cells were subjected to immunocytochemistry, imaging of cell fusion, calcium dynamics and acidic vacuoles, and bone lysis assays. Results: In patients, we found that the skull base invaded by chordoma was highly porous, showed low mineral density and contained brachyury-positive chordoma cells and conventional osteoclasts both expressing the osteolytic markers tartrate-resistant acid phosphatase (TRAP) and collagenases. JHC7 cells expressed TRAP and cathepsin K, became multinucleated via cell-cell fusion, showed spontaneous calcium oscillation, and were partly responsive to the osteoclastogenic cytokine RANKL. JHC7 cells exhibited large acidic vacuoles, and nonregulatory bone degradation without forming actin rings. Finally, bone-derived factors, calcium ions, TGF-β1, and IGF-1 enhanced JHC7 cell proliferation. Conclusion: In chordoma, we propose that in addition to conventional bone resorption by osteoclasts, chordoma cells possess bone-dissolving activity at the tumor-bone boundary. Furthermore, bone destruction and tumor expansion may occur in a positive feedback loop. [ABSTRACT FROM AUTHOR]

Cementum shares many properties with bone; however, in contrast to bone, it is not innervated or vascularized and has a limited capacity for remodeling. Osteocytes located in the lacunae-canalicular system of bone tissue play a central role in bone remodeling by communicating with osteoblasts and osteoclasts. Although cementocytes are present in cellular cementum and are morphologically similar to osteocytes, it remains unclear whether they are involved in the dynamic functional regulation of metabolism in cementum. The present study focused on the extracellular vesicles (EVs) secreted by cementocytes and examined their effects on osteoclasts and osteoblasts. EVs were extracted from the mouse cementocyte cell line, IDG-CM6. The effects of EVs on recombinant RANKL-induced osteoclastogenesis and recombinant Bone morphogenetic protein (BMP)-2-mediated osteoblastogenesis were investigated using the mouse osteoclast progenitor cell line, RAW264.7 and mouse pre-osteoblast cell line, MC3T3-E1, respectively. EVs enhanced the formation of tartrate-resistant acid phosphatase activity-positive cells. Real-time PCR revealed that EVs up-regulated the expression of osteoclast-related genes. On the other hand, the cell culture supernatant of cementocytes significantly inhibited the differentiation of osteoclasts. Regarding osteoblastogenesis, EVs suppressed the expression of alkaline phosphatase, bone sialoprotein, and osteocalcin induced by recombinant BMP-2 at the gene and protein levels. A network of cementocytes, osteoblasts, and osteoclasts may exist in cellular cementum, which suggests the involvement of cementocytes in dynamic metabolism of cementum through EVs. [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: Osteoarthritis (OA) is the most common degenerative joint disease and affects millions of people worldwide, particularly the elderly population. The pathophysiology of OA is complex and involves multiple factors. Methods: Several studies have emphasized the crucial role of inflammation in this process. The receptor activator of NF-κB ligand (RANKL), the receptor activator of NF-κB (RANK), and osteoprotegerin (OPG) trigger a signaling cascade that leads to the excessive production of RANKL in the serum. Conclusions: The aim of this narrative review is (i) to assess the role of the RANK/RANKL/OPG signaling pathway in the context of OA progression, focusing especially on the physiopathology and on all the mechanisms leading to the activation of the inflammatory cascade, and (ii) to evaluate all the potential therapeutic strategies currently available that restore balance to bone formation and resorption, reducing structural abnormalities and relieving pain in patients with OA. [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]

Background: Osteoporosis (OP) is a chronic disease characterized by decreased bone mass, loss of skeletal structural integrity and increased susceptibility to fracture. Available studies have shown that the pyruvate dehydrogenase kinase (PDK) family is associated with osteoclastogenesis and bone loss, but the specific role of Pdk3 in bone pathology has not been systematically investigated. Methods: A cell OP model was established in receptor activator for nuclear factor-κB Ligand (RANKL)-induced bone marrow macrophages (BMMs). Hereafter, the expression levels of Pdk3 and osteoclastogenesis feature genes including nuclear factor of activated T cells 1 (Nfatc1), Cathepsin K (Ctsk), osteoclast associated Ig-like receptor (Oscar) in BMMs-derived osteoclasts were examined based on real-time quantitative PCR and western blotting methods. Further, the phosphorylation of ERK, P65 and JAK/STAT and their correlation was Pdk3 was gauged. In particular, changes in the activity of these signaling pathways were observed by silencing experiments of the Pdk3 gene (using small interfering RNA). Finally, the effects of Pdk3 gene silencing on signaling pathway activity, osteoclastogenesis, and related inflammatory and apoptotic indicators were observed by transfection with PDK3-specific siRNA. Results: Following RANKL exposure, the levels of Pdk3 and osteoclastogenesis feature genes were all elevated, and a positive correlation between Pdk3 and osteoclastogenesis feature genes was seen. Meanwhile, ERK, P65 and JAK/STAT phosphorylation was increased by RANKL, and Pdk3 was confirmed to be positively correlated with the phosphorylation of ERK, P65 and JAK/STAT. Additionally, in RANKL-exposed osteoclasts, Pdk3 knockdown diminished the phosphorylation of ERK, P65 and JAK/STAT, reduced the expressions of osteoclastogenesis feature genes. Importantly, knockdown of Pdk3 also reduced the expression of inflammatory cytokines and resulted in elevated levels of Bax and Casp3 expression, as well as downregulation of Bcl2 expression. Conclusion: This study reveals for the first time the role of Pdk3 in RANKL-induced osteoclastogenesis and OP. These findings provide a foundation for future studies on the role of Pdk3 in other bone diseases and provide new ideas for the development of OP therapeutics targeting Pdk3. [ABSTRACT FROM AUTHOR]

Chronic apical periodontitis (CAP) is characterized by inflammation and destruction of the apical periodontium that is of pulpal origin, appearing as an apical radiolucent area, and does not produce clinical symptoms. Little is known about whether the PD-1/PD-L1 ratio is associated with the balance between RANKL and OPG in CAP. The relationship between PD-1/PD-L1 and RANKL/OPG in CAP is investigated in this study. A CAP rat model was established using Sprague-Dawley rats. The pulp chambers were exposed to the oral cavity to allow bacterial contamination. The apical tissues of the bilateral mandibular first molars were analyzed for histological morphology using hematoxylin and eosin (H&E) staining. Immunohistochemistry and qRT-PCR were used to determine the expression of PD-1, PD-L1, OPG, and RANKL mRNA and proteins in periapical tissues and mandibular samples, respectively. The radiological images indicated a poorly defined low-density shadow and alveolar bone resorption after periodontitis induction. Histological analysis revealed an infiltration of inflammatory cells and alveolar bone resorption in the periapical tissues. Mandibular mRNA and periapical protein expression of PD-1, PD-L1, and RANKL was upregulated 7–28 days after periodontitis induction, while the expression of OPG was downregulated. No significant relationship was observed between PD-1/PD-L1 and RANKL/OPG at either mRNA or protein levels in CAP. There is an increased expression of PD-1, PD-L1, and RANKL and a decreased expression of OPG, indicating progression of CAP. [ABSTRACT FROM AUTHOR]

Objective: To investigate the relationship between circulating receptor activator of nuclear factor-kappa B ligand (RANKL) levels and marrow adipose tissue in postmenopausal females. Methods: A total of 164 postmenopausal females were included in the study. Serum levels of osteoprotegerin (OPG) and RANKL were measured using ELISA kits. Body composition and bone mineral density (BMD) were assessed using dual-energy X-ray absorptiometry. Complex-based chemical shift imagingbased MRI was employed to evaluate the vertebral marrow proton density fat fraction (PDFF). A multivariate linear regression model was utilized to analyze the predictive effects of PDFF and BMD on circulating levels of OPG and RANKL. Results: Simple regression analysis showed significant associations among the marrow PDFF, BMD at either site, serum RANKL, and the RANKL/OPG ratio. In multivariate linear regression models, marrow PDFF was found to have a positive correlation (b = 3.15, 95% CI 2.60 to 3.70) and BMD had negative correlations (b = -0.200, 95% CI -0.348 to -0.051 for vertebral BMD; b = -0.383, 95% CI -0.589 to -0.177 for total hip BMD; and b =-0.393, 95% CI -0.598 to -0.188 for femoral neck BMD, all p < 0.01) with circulating soluble RANKL levels after adjusting for age, body mass index, physical activity, total fat mass, android/gynoid ratio, and lean mass. Similar results were observed for the RANKL/OPG ratio. Additionally, multivariate linear regression analyses revealed that marrow PDFF was a significant independent contributor of circulating soluble RANKL (b = 1.34, 95% CI 1.10 to 1.58, p < 0.001) after further controlling for BMD. However, marrow PDFF or BMD had no associations with circulating levels of OPG after adjusting for all potential confounders mentioned above. Conclusions: Vertebral marrow fat fraction is independently associated with circulating soluble RANKL levels in postmenopausal females. [ABSTRACT FROM AUTHOR]

Introduction: Osteoporosis, a systemic skeletal disease, is characterized by a quantitative and qualitative, and progressive decrease in bone mass, which is related to inflammation. Since a cytokine storm is triggered in Coronavirus disease 2019 (COVID-19), this study aims to evaluate pro-inflammatory cytokines (TNF-α, IL-1β), Receptor activator of nuclear factor-κB ligand (RANKL)/serum osteoprotegerin (OPG) ratio, and their relationship in mild and severe COVID-19. Methods: This study was performed on 48 adult patients (18 mild, 18 severe COVID-19, and 12 healthy subjects as a control group). Serum OPG, RANKL, TNF-α, IL-1β, 25-OH vitamin D, and ALKp were measured by ELISA and colorimetric assay. Results: COVID-19 patients had a significant increase in RANKL, and RANKL/OPG in mild and severe form (p < 0.001) while OPG decreased significantly in severe form compared to healthy controls (p < 0.05). Inflammatory cytokines (TNF-α and IL-1β) increased in both groups of patients whereas Alkaline phosphatase (ALKp) increased only in severe patients (p < 0.001). Both groups had 25-OH vitamin D deficiency in comparison to healthy ones (p < 0.001). Pearson's correlation coefficient was performed to determine the relationship between RANKL, OPG, ALKp, and 25-OH vitamin D with TNF-α and IL-1β in mild and severe COVID-19, which was statistically significant. Conclusion: Serum RANKL/OPG ratio was elevated in COVID-19 individuals and is assumed to be a risk factor for BMD reduction and osteoporosis in these patients. Correlations between IL-1β, TNF-α, ALKp, 25-OH vitamin D, OPG, RANKL, and RANKL/OPG ratio offered the potential role of these proinflammatory markers in the mechanism of osteoporosis in COVID-19 patients. Summary: Since cytokine storm, can stimulate osteoclastic activity, favoring bone resorption, in this study, we decided to evaluate its molecular mechanisms in COVID-19. We found an elevation of RANKL/OPG ratio with a positive correlation with inflammatory cytokines in COVID-19 which can be assumed as a risk factor for osteoporosis. [ABSTRACT FROM AUTHOR]

Background: Nitrogen-containing bisphosphonate(N-BP)had been found to inhibit the osteogenic differentiation and calcification in vascular smooth muscle cells (VSMCs), but the mechanism is not clear. We intend to verify that N-BP induces enhancement of OPG expression and inhibition of RANKL expression via inhibition of farnesyl pyrophosphate synthase(FPPS) to inhibit the osteogenic differentiation and calcification in VSMCs. Methods: β-glycerophosphate (β-GP) was used to induce the osteogenic differentiation and calcification in VSMCs. VSMCs were treated with N-BP or pretreated with downstream products of farnesyl pyrophosphate synthase(FPPS) in mevalonate pathway, such as farnesol (FOH) or geranylgeraniol (GGOH). Alizarin red S staining and determination of calcium content were used to detect calcium deposition.Western Blotting were used to detect expressions of proteins(OPG and RANKL) and osteogenic marker proteins (Runx2 and OPN). Results: β-GP induced the osteogenic differentiation and calcification in VSMCs, increased RANKL protein expression and had no significant effect on OPG protein expression. With the treatment of N-BP, the expression of OPG protein was increased and expression of RANKL protein was decreased in VSMCs undergoing osteogenic differentiation and calcification. In addition, N-BP reduced the osteogenic marker proteins (Runx2 and OPN) expression and calcium deposition in VSMCs undergoing osteogenic differentiation and calcification. These effects of N-BP on the osteogenic differentiation and calcification in VSMCs were concentration-dependent, which could be reversed by the downstream products of FPPS, such as FOH or GGOH. Conclusion: N-BP increases OPG expression and decreases RANKL expression via inhibition of FPPS to inhibit the osteogenic differentiation and calcification in VSMCs. [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]

Osteosarcopenia, which refers to the concomitant presence of osteoporosis and sarcopenia, is expected to increase in the rapidly progressive aging world, with serious clinical implications. However, the pathophysiology of osteosarcopenia has not been fully elucidated, and no optimal treatment specific to osteosarcopenia is available. The RANKL–RANK pathway is widely used as a therapeutic target for osteoporosis. Growing evidence supports the importance of the RANKL–RANK pathway, not only in bone, but also in muscle, and the therapeutic potential of targeting this pathway in muscle diseases has been noted. The muscles and bones closely communicate with each other through various secretory factors called myokines and osteokines. This review covers the roles of the RANKL– RANK pathway in the bone and muscle and their reciprocal interactions. Moreover, we will suggest future directions to move forward for the treatment of osteosarcopenia to prepare for an upcoming aging society. [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]

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Depression and osteoporosis are common diseases in dialysis patients. In addition, patients with osteoporosis are more susceptible to depression. Contrary to previous anti-osteoporosis agents, denosumab and romosozumab could be used in dialysis patients and have similar action mechanisms for blocking RANKL. RANKL causes bone resorption after binding RANKL, but binding with OPG leads to suppress of bone resorption. In recent mice study, inhibition of RANKL with denosumab improved depressive-like phenotype. Besides, it was found that OPG was associated with depression. Therefore, this study aimed to investigate the association of depressive symptoms with RANKL and OPG in hemodialysis patients. We conducted a cross-sectional study with a total of 172 hemodialysis patients. The participants were measured for plasma RANKL, OPG, MMP-2, and MMP-9 levels. Logistic regression analysis was performed to evaluate the effect of RANKL and OPG on the presence of depressive symptoms. The depressive symptoms were observed in 90 (52.3%) subjects. RANKL tertile 3 had negative association with BDI score (β − 4.527, 95% CI − 8.310 to − 0.743) in univariate analysis, and this association persisted even after multivariate adjustments (β − 5.603, 95% CI − 9.715 to −1.491) in linear regression. In logistic regression between RANKL tertiles and depressive symptoms, RANKL tertile 3 had significantly lower unadjusted OR (0.40, 95% CI 0.19–0.86), and multivariate-adjusted OR (0.31, 95% CI 0.12–0.82) for depressive symptoms. OPG was not significantly associated with depressive symptoms. Higher plasma RANKL concentrations were significantly associated with lower depressive symptoms in HD patients. Trial registration WHO registry, No. KCT0003281, date: January 12, 2017. [ABSTRACT FROM AUTHOR]

Periapical lesions are common pathologies affecting the alveolar bone, often initiated by intraradicular lesions resulting from microbial exposure to dental pulp. These microorganisms trigger inflammatory and immune responses. When endodontic treatment fails to eliminate the infection, periapical lesions persist, leading to bone loss. The RANK/RANKL/OPG pathway plays a crucial role in both the formation and the destruction of the bone. In this study, the objective was to inhibit the RANK/RANKL pathway in vitro within exposed Thp-1 macrophages to endodontic microorganisms, specifically Enterococcus faecalis, which was isolated from root canals of 20 patients with endodontic secondary/persistent infection, symptomatic and asymptomatic, and utilizing an α-IRAK-4 inhibitor, we introduced endodontic microorganisms and/or lipoteichoic acid from Streptococcus spp. to cellular cultures in a culture plate, containing thp-1 cells and/or PBMC from patients with apical periodontitis. Subsequently, we assessed the percentages of RANK+, RANKL+, and OPG+ cells through flow cytometry and measured the levels of several inflammatory cytokines (IL-1β, TNF-α, IL-6, IL-8, IL-10, and IL-12p70) in the cellular culture supernatant through a CBA kit and performed analysis by flow cytometry. A significant difference was observed in the percentages of RANK+RANKL+, OPG+ RANKL+ cells in thp-1 cells and PBMCs from patients with apical periodontitis. The findings revealed significant differences in the percentages of the evaluated cells, highlighting the novel role of the IRAK-4 inhibitor in addressing this oral pathology, apical periodontitis, where bone destruction is observed. [ABSTRACT FROM AUTHOR]

RANKL (Receptor Activator of Nuclear Factor Kappa-B Ligand) is a cytokine that plays a crucial role in bone remodeling by regulating differentiation and activation of osteoclast, which breaks down old bone tissue. In this study, we attempted to produce human-derived RANKL using plant expression systems. The RANKL expressed in Nicotiana benthamiana leaves was designed to accumulate within the endoplasmic reticulum lumen. The purified RANKL from N. benthamiana induced the differentiation of bone marrow-derived macrophages to mature osteoclast, albeit modestly. In conclusion, human-derived RANKL could be produced using a plant expression system, but it requires further improvement. [ABSTRACT FROM AUTHOR]

Bone is one of the most prevalent sites of metastases in various epithelial malignancies, including breast cancer and this metastasis to bone often leads to severe skeletal complications in women due to its osteolytic nature. To address this, we devised a novel drug delivery approach using an Alendronate (ALN) functionalized self-assembled porous crystalsomes for concurrent targeting of Oleanolic acid (OA) and ALN (ALN + OA@NCs) to bone metastasis. Initially, the conjugation of both PEG-OA and OA-PEG-ALN with ALN and OA was achieved, and this conjugation was then self-assembled into porous crystalsomes (ALN + OA@NCs) by nanoemulsion crystallization. The reconstruction of a 3D single particle using transmission electron microscopy ensured the crystalline porous structure of ALN + OA@NCs, was well aligned with characteristic nanoparticle attributes including size distribution, polydispersity, and zeta potential. Further, ALN + OA@NCs showed enhanced efficacy in comparison to OA@NCs suggesting the cytotoxic roles of ALN towards cancer cells, followed by augmentation ROS generation (40.81%), mitochondrial membrane depolarization (57.20%), and induction of apoptosis (40.43%). We found that ALN + OA@NCs facilitated inhibiting osteoclastogenesis and bone resorption followed by inhibited osteolysis. In vivo activity of ALN + OA@NCs in the 4 T1 cell-induced tibia model rendered a reduced bone loss in the treated mice followed by restoring bone morphometric markers which were further corroborated bone–targeting effects of ALN + OA@NCs to reduce RANKL-stimulated osteoclastogenesis. Further, In vivo intravenous pharmacokinetics showed the improved therapeutic profile of the ALN + OA@NCs in comparison to the free drug, prolonging the levels of the drug in the systemic compartment by reducing the clearance culminating the higher accumulation at the tumor site. Our finding proposed that ALN + OA@NCs can effectively target and treat breast cancer metastasis to bone and its associated complications. [Display omitted] [ABSTRACT FROM AUTHOR]

Osteoporosis, a metabolic bone disorder characterized by decreased bone mass per unit volume, poses a significant global health burden due to its association with heightened fracture risk and adverse impacts on patients' quality of life. This review synthesizes the current understanding of the pathophysiological mechanisms underlying osteoporosis, with a focus on key regulatory pathways governing osteoblast and osteoclast activities. These pathways include RANK/RANKL/OPG, Wingless-int (Wnt)/β-catenin, and Jagged1/Notch1 signaling, alongside the involvement of parathyroid hormone (PTH) signaling, cytokine networks, and kynurenine in bone remodeling. Pharmacotherapeutic interventions targeting these pathways play a pivotal role in osteoporosis management. Anti-resorptive agents, such as bisphosphonates, estrogen replacement therapy/hormone replacement therapy (ERT/HRT), selective estrogen receptor modulators (SERMs), calcitonin, anti-RANKL antibodies, and cathepsin K inhibitors, aim to mitigate bone resorption. Conversely, anabolic agents, including PTH and anti-sclerostin drugs, stimulate bone formation. In addition to pharmacotherapy, nutritional supplementation with calcium, vitamin D, and vitamin K2 holds promise for osteoporosis prevention. However, despite the availability of therapeutic options, a substantial proportion of osteoporotic patients remain untreated, highlighting the need for improved clinical management strategies. This comprehensive review aims to provide clinicians and researchers with a mechanistic understanding of osteoporosis pathogenesis and the therapeutic mechanisms of existing medications. By elucidating these insights, this review seeks to inform evidence-based decision-making and optimize therapeutic outcomes for patients with osteoporosis. [ABSTRACT FROM AUTHOR]

Orthodontic relapse, the return to a pre-treatment position after orthodontic correction, is driven by the RANKL/TNF-α-mediated ROS/Keap1/Nrf2 signaling axis. This mechanism triggers aseptic inflammation and oxidative stress, influencing bone resorption and formation. Antioxidants can mitigate oxidative stress, potentially improving post-orthodontic outcomes. This study explores the efficacy of antioxidant compounds derived from green seaweed/algae in managing orthodontic relapse. Green seaweed/algae extracts were prepared via sonication, and bioactive compounds were identified using ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS) analysis. Compounds underwent bioactivity prediction, toxicity assessment, and drug-likeness evaluation, revealing significant therapeutic potential. Network pharmacology and molecular docking identified key proteins associated with orthodontic relapse, including IL-1β, STAT3, ESR1, MAPK1, JAK2, and HMOX1. Molecular docking simulations indicated favorable binding energies for green seaweed compounds, particularly the alkaloids adenosine (ΔG −6.9 to −7.3 kcal/mol) and lycopodine (ΔG −6.3 to −8.5 kcal/mol), against targeted proteins, matching or outperforming standard drugs such as s-ibuprofen (ΔG −6.7 kcal/mol). In vitro assays confirmed the antioxidant activity of these compounds, with EC50 dose of 52.2–54.2 μg/mL for ABTS radical scavenging capacities. Protein expression analysis in tibial-femoral bone marrow cells further demonstrated the potential of green seaweed/algae compounds to suppress osteoclastogenesis by modulating the RANKL/TNF-α-mediated ROS/Keap1/Nrf2 pathway. This research highlights the promise of green seaweed-derived antioxidants in reducing oxidative stress and managing orthodontic relapse, providing a foundation for future therapeutic developments.

Abstract Background Skeletal Stem Cells (SSCs) are required for skeletal development, homeostasis, and repair. The perspective of their wide application in regenerative medicine approaches has supported research in this field, even though so far results in the clinic have not reached expectations, possibly due also to partial knowledge of intrinsic, potentially actionable SSC regulatory factors. Among them, the pleiotropic cytokine RANKL, with essential roles also in bone biology, is a candidate deserving deep investigation. Methods To dissect the role of the RANKL cytokine in SSC biology, we performed ex vivo characterization of SSCs and downstream progenitors (SSPCs) in mice lacking Rankl (Rankl −/− ) by means of cytofluorimetric sorting and analysis of SSC populations from different skeletal compartments, gene expression analysis, and in vitro osteogenic differentiation. In addition, we assessed the effect of the pharmacological treatment with the anti-RANKL blocking antibody Denosumab (approved for therapy in patients with pathological bone loss) on the osteogenic potential of bone marrow-derived stromal cells from human healthy subjects (hBMSCs). Results We found that, regardless of the ossification type of bone, osteochondral SSCs had a higher frequency and impaired differentiation along the osteochondrogenic lineage in Rankl −/− mice as compared to wild-type. Rankl −/− mice also had increased frequency of committed osteochondrogenic and adipogenic progenitor cells deriving from perivascular SSCs. These changes were not due to the peculiar bone phenotype of increased density caused by lack of osteoclast resorption (defined osteopetrosis); indeed, they were not found in another osteopetrotic mouse model, i.e., the oc/oc mouse, and were therefore not due to osteopetrosis per se. In addition, Rankl −/− SSCs and primary osteoblasts showed reduced mineralization capacity. Of note, hBMSCs treated in vitro with Denosumab had reduced osteogenic capacity compared to control cultures. Conclusions We provide for the first time the characterization of SSPCs from mouse models of severe recessive osteopetrosis. We demonstrate that Rankl genetic deficiency in murine SSCs and functional blockade in hBMSCs reduce their osteogenic potential. Therefore, we propose that RANKL is an important regulatory factor of SSC features with translational relevance.

Abstract Background Postmenopausal osteoporosis is a chronic metabolic bone disease caused by excessive osteoclast formation and function. Targeting osteoclast differentiation and activity can modulate bone resorption and alleviate osteoporosis. Cirsilineol, an active constituent of Vestita Wall, has shown numerous biological activities and has been used to treat many metabolic diseases. However, whether cirsilineol inhibits osteoclast activity and prevents postmenopausal osteoporosis still remain unknown. Materials and methods Primary bone marrow macrophages (BMMs) and RAW264.7 cells were used. Osteoclast activity was measured by TRAP staining, F-actin staining, and bone resorption assay after BMMs were treated with cirsilineol at concentrations of 0, 1, 2.5 and 5 µM. RT-PCR and western blotting were performed to evaluate the expression of osteoclast-related genes. In addition, female C57BL/6 mice underwent OVX surgery and were treated with cirsilineol (20 mg/kg) to demonstrate the effect of cirsilineol on osteoporosis. Results Cirsilineol significantly inhibited receptor activator of nuclear factor-kappa B ligand (RANKL)-induced osteoclast differentiation in a concentration- and time-dependent manner, respectively. Additionally, cirsilineol inhibited F-actin ring formation, thus reducing the activation of bone resorption ability. Cirsilineol suppressed the expression of osteoclast-related genes and proteins via blocking nuclear factor (NF)-κb, ERK, and p38 signaling cascades. More importantly, cirsilineol treatment in mice with osteoporosis alleviated osteoclasts hyperactivation and bone mass loss caused by estrogen depletion. Conclusion In this study, the protective effect of cirsilineol on osteoporosis has been investigated for the first time. In conclusion, our findings prove the inhibitory effect of cirsilineol on osteoclast activity via NF-κb/ERK/p38 signaling pathways and strongapplication of cirsilineol can be proposed as a potential therapeutic strategy.

Introduction: Exercise training is likely to be a non-pharmacological intervention to improve bone health in children and the elderly. The aim of this study was to investigate the effect of resistance-aerobic training on RUX2, CTX, RANKL and ALP biomarkers in rats of different ages. Methods: In the present experimental study, 30 male Wistar rats were obtained from Instituto Pasteur of Iran and were divided into three groups according to their age: immature (2 weeks old), mature (6 weeks old) and elderly (96 weeks old). In each age group, the mice were randomly divided into two training (n=5) and control (n=5) groups. Six weeks of combined training included three sessions of aerobic training and three sessions of resistance training per week. Extracting genes by PCR method was used. One-way analysis of variance and Tukey's post hoc test and SPSS16 software were used. The significance level P≥0.05 was considered. Results: One-way analysis of variance showed that resistance-aerobic training has had a significant effect on RUNX2, RANKL and ALP variables of rats in different age groups (P < 0.05). This significance was not observed in CTX variable (P > 0.05). On the other hand, the results of Tukey's RUNX2 test were significantly different between the adult training and elderly training groups (p = 0.019) as well as between the elderly control groups (p = 0.01) and adult training (p = 0.002). Regarding the RANKL variable, it showed that there was a significant difference only between the adult exercise group and the elderly control group (p = 0.01). Conclusion: Resistance-endurance training probably increases absorption and reabsorption biomarkers such as RUX2, RANKL and ALP in immature, mature and elderly male rats.

Infection of ruminants such as cattle with Mycobacterium avium subsp. paratuberculosis (MAP) causes Johne's disease, a disease characterized by chronic inflammation of the small intestine and diarrhoea. Infection with MAP is acquired via the faecal-to-oral route and the pathogen initially invades the epithelial lining of the small intestine. In this study we used an in vitro 3D mouse enteroid model to determine the influence of M cells in infection of the gut epithelia by MAP, in comparison with another bacterial intestinal pathogen of veterinary importance, Salmonella enterica serovar Typhimurium. The differentiation of M cells in the enteroid cultures was induced by stimulation with the cytokine receptor activator of nuclear factor-βB ligand (RANKL), and the effects on MAP and Salmonella uptake and intracellular survival were determined. The presence of M cells in the cultures correlated with increased uptake and intracellular survival of Salmonella, but had no effect on MAP. Interestingly neither pathogen was observed to preferentially accumulate within GP2- positive M cells. [ABSTRACT FROM AUTHOR]

Background: Skeletal Stem Cells (SSCs) are required for skeletal development, homeostasis, and repair. The perspective of their wide application in regenerative medicine approaches has supported research in this field, even though so far results in the clinic have not reached expectations, possibly due also to partial knowledge of intrinsic, potentially actionable SSC regulatory factors. Among them, the pleiotropic cytokine RANKL, with essential roles also in bone biology, is a candidate deserving deep investigation. Methods: To dissect the role of the RANKL cytokine in SSC biology, we performed ex vivo characterization of SSCs and downstream progenitors (SSPCs) in mice lacking Rankl (Rankl−/−) by means of cytofluorimetric sorting and analysis of SSC populations from different skeletal compartments, gene expression analysis, and in vitro osteogenic differentiation. In addition, we assessed the effect of the pharmacological treatment with the anti-RANKL blocking antibody Denosumab (approved for therapy in patients with pathological bone loss) on the osteogenic potential of bone marrow-derived stromal cells from human healthy subjects (hBMSCs). Results: We found that, regardless of the ossification type of bone, osteochondral SSCs had a higher frequency and impaired differentiation along the osteochondrogenic lineage in Rankl−/− mice as compared to wild-type. Rankl−/− mice also had increased frequency of committed osteochondrogenic and adipogenic progenitor cells deriving from perivascular SSCs. These changes were not due to the peculiar bone phenotype of increased density caused by lack of osteoclast resorption (defined osteopetrosis); indeed, they were not found in another osteopetrotic mouse model, i.e., the oc/oc mouse, and were therefore not due to osteopetrosis per se. In addition, Rankl−/− SSCs and primary osteoblasts showed reduced mineralization capacity. Of note, hBMSCs treated in vitro with Denosumab had reduced osteogenic capacity compared to control cultures. Conclusions: We provide for the first time the characterization of SSPCs from mouse models of severe recessive osteopetrosis. We demonstrate that Rankl genetic deficiency in murine SSCs and functional blockade in hBMSCs reduce their osteogenic potential. Therefore, we propose that RANKL is an important regulatory factor of SSC features with translational relevance. [ABSTRACT FROM AUTHOR]

Bone functions not only as a critical element of the musculoskeletal system but also serves as the primary lymphoid organ harboring hematopoietic stem cells (HSCs) and immune progenitor cells. The interdisciplinary field of osteoimmunology has illuminated the dynamic interactions between the skeletal and immune systems, vital for the maintenance of skeletal tissue homeostasis and the pathogenesis of immune and skeletal diseases. Aberrant immune activation stimulates bone cells such as osteoclasts and osteoblasts, disturbing the bone remodeling and leading to skeletal disorders as seen in autoimmune diseases like rheumatoid arthritis. On the other hand, intricate multicellular network within the bone marrow creates a specialized microenvironment essential for the maintenance and differentiation of HSCs and the progeny. Dysregulation of immune–bone crosstalk in the bone marrow environment can trigger tumorigenesis and exacerbated inflammation. A comprehensive deciphering of the complex "immune–bone crosstalk" leads to a deeper understanding of the pathogenesis of immune diseases as well as skeletal diseases, and might provide insight into potential therapeutic approaches. [ABSTRACT FROM AUTHOR]