ED-71 Improves Bone Mass in Ovariectomized Rats by Inhibiting Osteoclastogenesis Through EphrinB2-EphB4-RANKL/OPG Axis.

Purpose: Estrogen deficiency is the main reason of postmenopausal osteoporosis. Eldecalcitol (ED-71) is a new active vitamin D analogue clinically used in the treatment of postmenopausal osteoporosis. We aimed to investigate whether EphrinB2-EphB4 and RANKL/RANK/OPG signaling cooperate in mediating the process of osteoporosis by ED-71. Methods: In vivo, the ovariectomized (OVX) rats were administered orally with 30 ng/kg ED-71 once a day for 8 weeks. HE staining, Masson staining and Immunofluorescence staining were used to evaluate bone mass, bone formation, osteoclastogenesis associated factors and the expression of EphrinB2, EphB4, RANKL and OPG. In vitro, H2O2 stimulation was used to simulate the cell environment in osteoporosis. Immunofluorescence, quantitative real time PCR (qRT-PCR), enzyme-linked immunosorbent assay (ELISA) and Western Blot were applied to detect the expression of EphrinB2, EphB4, RANKL and OPG. In osteoblasts, EphB4 was knocked down by EphB4 small-interfering RNA (siRNA) transfection. LY294002 (PI3K inhibitor) or ARQ092 (AKT inhibitor) was used to block PI3K/AKT pathway. An indirect co-culture system of osteoblasts and osteoclasts was established. The mRNA and protein expression of osteoclastogenes is associated factors were tested by qRT-PCR and Western Blot. Results: ED-71 increased bone mass and decreased the number of osteoclasts in OVX rats. Moreover, ED-71 promoted the expression of EphrinB2, EphB4, and decreased the RANKL/OPG ratio in osteoblasts. Osteoclastogenesis was restrained when osteoclasts were indirectly co-cultured with ED-71-treated osteoblasts. After silencing of EphB4 expression in osteoblasts, ED-71 inhibited the expression of P-PI3K and P-AKT and increased the ratio of RANKL/OPG. This reversed the inhibitory effect of ED-71 on osteoclastogenes. Therefore, in ED-71-inhibited osteoclastogenes, EphB4 is a key factor affecting the secretion of RANKL and OPG by osteoblasts. EphB4 suppressed the RANKL/OPG ratio through activating PI3K/AKT signaling in osteoblasts. Conclusion: ED-71 inhibits osteoclastogenesis through EphrinB2-EphB4-RANKL/OPG axis, improving bone mass in ovariectomized rats. PI3K/AKT pathway is involved this process.

Sorbitol Destroyed Intestinal Microfold Cells (M Cells) Development through Inhibition of PDE4-Mediated RANKL Expression.

Objective: Microfold cells (M cells) are specific intestinal epithelial cells for monitoring and transcytosis of antigens, microorganisms, and pathogens in the intestine. However, the mechanism for M-cell development remained elusive. Materials and Methods: Real-time polymerase chain reaction, immunofluorescence, and western blotting were performed to analyze the effect of sorbitol-regulated M-cell differentiation in vivo and in vitro, and luciferase and chromatin Immunoprecipitation were used to reveal the mechanism through which sorbitol-modulated M-cell differentiation. Results: Herein, in comparison to the mannitol group (control group), we found that intestinal M-cell development was inhibited in response to sorbitol treatment as evidenced by impaired enteroids accompanying with decreased early differentiation marker Annexin 5, Marcksl1, Spib, sox8, and mature M-cell marker glycoprotein 2 expression, which was attributed to downregulation of receptor activator of nuclear factor kappa-В ligand (RANKL) expression in vivo and in vitro. Mechanically, in the M-cell model, sorbitol stimulation caused a significant upregulation of phosphodiesterase 4 (PDE4) phosphorylation, leading to decreased protein kinase A (PKA)/cAMP-response element binding protein (CREB) activation, which further resulted in CREB retention in cytosolic and attenuated CREB binds to RANKL promoter to inhibit RANKL expression. Interestingly, endogenous PKA interacted with CREB, and this interaction was destroyed by sorbitol stimulation. Most importantly, inhibition of PDE4 by dipyridamole could rescue the inhibitory effect of sorbitol on intestinal enteroids and M-cell differentiation and mature in vivo and in vitro. Conclusion: These findings suggested that sorbitol suppressed intestinal enteroids and M-cell differentiation and matured through PDE4-mediated RANKL expression; targeting to inhibit PDE4 was sufficient to induce M-cell development.

Oroxylin A inhibits inflammatory cytokines in periodontitis via HO­1.

Periodontal disease is a common infectious disease that can lead to the loss of teeth. Hower how to effectively suppress the inflammation with medication is unclear. The aim of the present study was to investigate the anti­inflammatory effect of Oroxylin A in periodontitis and its potential role through heme oxygenase­1 (HO­1). Primary rat gingival fibroblasts (RGFs) were cultured using the tissue block method and identified by immunofluorescence. Following lipopolysaccharide (LPS) stimulation of RGFs, Oroxylin A was administered at 50, 100, 200 or 400 µg/ml. Reverse transcription­quantitative PCR was used to assess mRNA expression of cyclooxygenase (COX)­2, TNF­α, RANKL and osteoprotegerin (OPG). Western blotting was used to detect protein expression levels of COX ­2, TNF­α, RANKL and OPG. Following HO­1 knockdown, the same treatment was performed. The expression of COX­2 in rat gingival tissue was observed by immunohistochemistry. One­way analysis of variance and Student's t test were used for statistical analysis. Oroxylin A downregulated mRNA expression of COX­2, TNF­α, RANKL and OPG in LPS­induced RGFs. With increase of Oroxylin A dose, the expression of HO­1 was gradually upregulated. When HO­1 was knocked down, Oroxylin A did not downregulate the expression of COX­2, TNF­α, RANKL and OPG in LPS­induced RGFs. Immunohistochemical results showed that expression of COX­2 was downregulated by Oroxylin A, and the expression of TNF­α, RANKL and OPG were also downregulated. Oroxylin A decreased expression of inflammatory cytokines in LPS­induced RGFs and had a good inhibitory effect on periodontitis in rats.

Synthesis of Heterocyclic Ring-Fused Bisnoralcohol Derivatives as Novel Small-Molecule Antiosteoporosis Agents.

A series of heterocyclic ring-fused derivatives of bisnoralcohol (BA) were synthesized and evaluated for their inhibitory effects on RANKL-induced osteoclastogenesis. Most of these derivatives possessed potent antiosteoporosis activities in a dose-dependent manner. Among these compounds, 31 (SH442, IC50 = 0.052 µM) exhibited the highest potency, displaying 100% inhibition at 1.0 µM and 82.8% inhibition at an even lower concentration of 0.1 µM, which was much more potent than the lead compound BA (IC50 = 2.325 µM). Cytotoxicity tests suggested that the inhibitory effect of these compounds on RANKL-induced osteoclast differentiation did not result from their cytotoxicity. Mechanistic studies revealed that SH442 inhibited the expression of osteoclastogenesis-related marker genes and proteins, including TRAP, TRAF6, c-Fos, CTSK, and MMP9. Especially, SH442 could significantly attenuate bone loss of ovariectomy mouse in vivo. Therefore, these BA derivatives could be used as promising leads for the development of a new type of antiosteoporosis agent.

Pleurotus sajor-caju (Fr.) Singer ß-1,3-Glucanoligosaccharide (Ps-GOS) Suppresses RANKL-Induced Osteoclast Differentiation and Function in Pre-Osteoclastic RAW 264.7 Cells by Inhibiting the RANK/NFκB/cFOS/NFATc1 Signalling Pathway.

Edible grey oyster mushroom, Pleurotus sajor-caju, ß (1,3), (1,6) glucan possesses a wide range of biological activities, including anti-inflammation, anti-microorganism and antioxidant. However, its biological activity is limited by low water solubility resulting from its high molecular weight. Our previous study demonstrated that enzymatic hydrolysis of grey oyster mushroom ß-glucan using Hevea ß-1,3-glucanase isozymes obtains a lower molecular weight and higher water solubility, Pleurotus sajor-caju glucanoligosaccharide (Ps-GOS). Additionally, Ps-GOS potentially reduces osteoporosis by enhancing osteoblast-bone formation, whereas its effect on osteoclast-bone resorption remains unknown. Therefore, our study investigated the modulatory activities and underlying mechanism of Ps-GOS on Receptor activator of nuclear factor kappa-Β ligand (RANKL) -induced osteoclastogenesis in pre-osteoclastic RAW 264.7 cells. Cell cytotoxicity of Ps-GOS on RAW 264.7 cells was determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay and its effect on osteoclast differentiation was determined by tartrate-resistant acid phosphatase (TRAP) staining. Additionally, its effect on osteoclast bone-resorptive ability was detected by pit formation assay. The osteoclastogenic-related factors were assessed by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), Western blot and immunofluorescence. The results revealed that Ps-GOS was non-toxic and significantly suppressed the formation of mature osteoclast multinucleated cells and their resorption activity by reducing the number of TRAP-positive cells and pit formation areas in a dose-dependent manner. Additionally, Ps-GOS attenuated the nuclear factor kappa light chain-enhancer of activated B cells' P65 (NFκB-P65) expression and their subsequent master osteoclast modulators, including nuclear factor of activated T cell c1 (NFATc1) and Fos proto-oncogene (cFOS) via the NF-κB pathway. Furthermore, Ps-GOS markedly inhibited RANK expression, which serves as an initial transmitter of many osteoclastogenesis-related cascades and inhibited proteolytic enzymes, including TRAP, matrix metallopeptidase 9 (MMP-9) and cathepsin K (CTK). These findings indicate that Ps-GOS could potentially be beneficial as an effective natural agent for bone metabolic disease.

Therapeutic avenues in bone repair: Harnessing an anabolic osteopeptide, PEPITEM, to boost bone growth and prevent bone loss.

The existing suite of therapies for bone diseases largely act to prevent further bone loss but fail to stimulate healthy bone formation and repair. We describe an endogenous osteopeptide (PEPITEM) with anabolic osteogenic activity, regulating bone remodeling in health and disease. PEPITEM acts directly on osteoblasts through NCAM-1 signaling to promote their maturation and formation of new bone, leading to enhanced trabecular bone growth and strength. Simultaneously, PEPITEM stimulates an inhibitory paracrine loop: promoting osteoblast release of the decoy receptor osteoprotegerin, which sequesters RANKL, thereby limiting osteoclast activity and bone resorption. In disease models, PEPITEM therapy halts osteoporosis-induced bone loss and arthritis-induced bone damage in mice and stimulates new bone formation in osteoblasts derived from patient samples. Thus, PEPITEM offers an alternative therapeutic option in the management of diseases with excessive bone loss, promoting an endogenous anabolic pathway to induce bone remodeling and redress the imbalance in bone turnover.

Repurposing the multiple sclerosis drug Siponimod for osteoporosis treatment.

Osteoporosis is the most common bone disorder, in which an imbalance between osteoclastic bone resorption and osteoblastic bone formation disrupts bone homeostasis. Osteoporosis management using anti-osteoclastic agents is a promising strategy; however, this remains an unmet need. Sphingosine-1-phosphate (S1P) and its receptors (S1PRs) are essential for maintaining bone homeostasis. Here, we identified that Siponimod, a Food and Drug Administration-approved S1PR antagonist for the treatment of multiple sclerosis, shows promising therapeutic effects against osteoporosis by inhibiting osteoclast formation and function. We found that Siponimod inhibited osteoclast formation in a dose-dependent manner without causing cytotoxicity. Podosome belt staining and bone resorption assays indicated that Siponimod treatment impaired osteoclast function. Western blot and qPCR assays demonstrated that Siponimod suppressed the expression of osteoclast-specific markers, including C-Fos, Nftac1, and Ctsk. Mechanistically, we validated that Siponimod downregulated receptor activator of nuclear factor kappa B ligand (RANKL)-induced Mitogen-activated protein kinases (MAPKs) and nuclear factor kappa B (NF-κB) signaling pathways during osteoclastogenesis. Moreover, in a preclinical mouse model, Siponimod prevented ovariectomy-induced bone loss by suppressing osteoclast activity in vivo. Collectively, these results suggest that Siponimod could serve as an alternative therapeutic agent for the treatment of osteoporosis.

Coenzyme Q10 prevents RANKL-induced osteoclastogenesis by promoting autophagy via inactivation of the PI3K/AKT/mTOR and MAPK pathways.

Coenzyme Q10 (CoQ10) is a potent antioxidant that is implicated in the inhibition of osteoclastogenesis, but the underlying mechanism has not been determined. We explored the underlying molecular mechanisms involved in this process. RAW264.7 cells received receptor activator of NF-κB ligand (RANKL) and CoQ10, after which the differentiation and viability of osteoclasts were assessed. After the cells were treated with CoQ10 and/or H2O2 and RANKL, the levels of reactive oxygen species (ROS) and proteins involved in the PI3K/AKT/mTOR and MAPK pathways and autophagy were tested. Moreover, after the cells were pretreated with or without inhibitors of the two pathways or with the mitophagy agonist, the levels of autophagy-related proteins and osteoclast markers were measured. CoQ10 significantly decreased the number of TRAP-positive cells and the level of ROS but had no significant impact on cell viability. The relative phosphorylation levels of PI3K, AKT, mTOR, ERK, and p38 were significantly reduced, but the levels of FOXO3/LC3/Beclin1 were significantly augmented. Moreover, the levels of FOXO3/LC3/Beclin1 were significantly increased by the inhibitors and mitophagy agonist, while the levels of osteoclast markers showed the opposite results. Our data showed that CoQ10 prevented RANKL-induced osteoclastogenesis by promoting autophagy via inactivation of the PI3K/AKT/mTOR and MAPK pathways in RAW264.7 cells.

Accumulation of γδT cells in the decidua is promoted by RANKL which upregulates ICAM-1 via NF-κB.

In brief: The mechanism underlying the accumulation of γδT cells in the decidua, which helps maintain maternal-fetal immunotolerance in early pregnancy, is unknown. This study reveals that DSC-derived RANKL upregulates ICAM-1 expression via the NF-κB pathway to enable γδT cell accumulation in the early decidua. Abstract: Decidual γδT (dγδT) cells help maintain maternal-fetal immunotolerance in early pregnancy. However, the mechanism underlying the accumulation of γδT cells in the decidua is unknown. Previous work showed that RANKL upregulated intercellular adhesion molecule 1 (ICAM-1) in decidual stromal cells (DSCs), and Rankl knockout mice had limited dγδT cell populations. In this study, we measured the expression levels of RANKL/RANK and ICAM-1 in DSCs, in addition to the integrins of ICAM-1 on dγδT cells, and the number of dγδT cells from patients with recurrent spontaneous abortion (RSA) and normal pregnant women in the first trimester. RSA patients showed significantly decreased RANKL/RANK and ICAM-1/CD11a signaling in decidua, and a decreased percentage of dγδT cells, which was positively correlated with DSC-derived RANKL and ICAM-1. Next, an in vitro adhesion experiment showed that the enhanced attraction of human DSCs to dγδT cells after RANKL overexpression was almost completely aborted by anti-ICAM-1. Furthermore, Rankl knockout mice showed a significant reduction in NF-κB activity compared with wild-type controls. Finally, we applied a selective NF-κB inhibitor named PDTC to validate the role of NF-κB in RANKL-mediated ICAM-1 upregulation. Taken together, our data show that DSC-derived RANKL upregulates ICAM-1 expression via the NF-κB pathway to enable γδT cell accumulation in the early decidua. A reduction in RANKL/ICAM-1 signaling in DSCs may result in insufficient accumulation of γδT cells in decidua and, in turn, RSA.

[The relationship between the expression of PGE2 and COX-2 and the osteogenic activity and oxygen level of alveolar bone].

PURPOSE: To study the relationship between the expression of prostaglandin E2 (PGE2) and cyclooxygenase-2 (COX-2) and the osteogenic activity and oxygen level of alveolar bone. METHODS: The alveolar bones of 56 patients with chronic periodontitis who received dental treatment from March 2021 to March 2023 were collected as the experimental (periodontitis) group, and the healthy alveolar bones of 53 patients who received dental treatment during the same period were selected as the control group. The osteoblasts were cultured by tissue block culture, and modified Kaplow's alkaline phosphatase (ALP) staining was used to identify the cells. COX-2, PGE2 and osteoclastogenesis inhibitory factor (OPG) receptor activator of nuclear factor-κb ligand (RANKL) and other indicators were determined by ELISA. PGE2, COX-2, OPG, internal oxygen level, ALP, RANKL and their correlation were compared between the two groups. Statistical analysis was performed with SPSS 27.0 software package. RESULTS: PGE2, COX-2 and RANKL in periodontitis group were significantly higher than those in the control group, but OPG, internal oxygen level and ALP were significantly lower than those in the control group (P＜0.05). PGE2 and COX2 were highly positively correlated with OPG, internal oxygen level and ALP, but were highly positively correlated with RANKL(P＜0.05). CONCLUSIONS: The expression of PGE2 and COX-2 is highly negatively correlated with ALP and oxygen levels. Clinical treatment may consider increasing oxygen levels, increasing oxygen partial pressure, and regulating ALP levels by drugs, so as to change the inflammatory condition of periodontitis or other dental diseases.

Significant Inverse Correlation of Serum Levels of Osteoprotegerin (OPG) and Transferrin Saturation in Thalassemia Dependent Transfusion (TDT) Patients.

BACKGROUND: Osteoporosis is a major problem in transfusion-dependent thalassemia patients (TDT) patients. Osteoprotegerin (OPG) is one of several bone markers that are closely associated with osteoporosis in TDT patients. OPG is a glycoprotein that functions as a feedback receptor for the Receptor Activator of Nuclear Factor kappa B Ligand (RANKL), which is an alpha tumor necrosis factor receptor. One of the causes of decreased bone mass density is iron toxicity, which can be identified by showing elevated transferrin saturation. Bone mass dual X-ray absorptiometry (DEXA) is a gold standard for the diagnosis of osteoporosis, these procedures are not commonly available in Indonesia. This study was conducted to analyze the correlation between serum levels of OPG and transferrin saturation in TDT patients. METHODS: A correlational study with a cross-sectional approach analyzed data from TDT patients at Hemato-Oncology Medic Outpatient Clinic, Hasan Sadikin General Hospital, Bandung, Indonesia. Primary data were obtained through blood sampling and anthropometry measurement while secondary data were obtained from the patient's medical records. OPG and transferrin saturation levels were assessed using the ELISA method. Research data were analyzed using the rank Spearman correlation test. RESULTS: Data were collected from 51 research subjects (30 women dan 21 men). The median OPG level was 380 (170-1230) pg/mL and the median transferrin saturation level was 89.4 (66.7 - 96.2)%. Analysis of correlation showed a significant correlation between and transferrin saturation level with a coefficient value of r -0.539 and p-value <0.001. CONCLUSION: There was a significant inverse correlation between OPG with transferrin saturation in TDT patients.

Osteoprotegerin and receptor activator of the nuclear factor kappa B ligand (RANKL) in healthy pubertal girls - relationships with physical growth and classical bone turnover markers.

Osteoprotegerin (OPG) is a trap receptor for the receptor activator of the nuclear factor kappa B ligand (RANKL). We aimed to determine the OPG and free soluble RANKL (sRANKL) concentrations in girls during puberty and their relationships with pubertal stage, growth rate and serum concentrations of estradiol, as well as classical bone formation (N-terminal propeptide of type I collagen (PINP), bone-specific alkaline phosphatase (BALP), osteocalcin (OC)) and bone resorption (C-terminal telopeptide of type I collagen (CTX)) markers. The semi-longitudinal study involved 88 healthy girls, aged 11.8-13.2 years. Their weight and height were measured twice at one-year intervals. Pubertal stages were assessed using the Tanner (T) scale. Blood samples were taken at the first examination. Serum concentrations of OPG, sRANKL, CTX and BALP were determined by enzyme-linked immunosorbent assay, estradiol and PINP by radioimmunoassay and osteocalcin by immunoradiometric assay. The one-year increase in height and weight of girls in the T2 and T3 pubertal stages was greater than that of girls in the T4 stage (p=0.000, p<0.03). OPG concentrations (T2: 4.04±0.62; T3: 4.31±0.79; T4: 4.46±0.84 pmol/L) sRANKL concentrations (T2: 0.22 (IQR 0.09-0.54); T3: 0.42 (IQR 0.22-0.79); T4: 0.35 (IQR 0.16-1.04) pmol/L) and sRANKL/OPG ratios (T2: 0.05 (IQR 0.03-0.13); T3: 0.11 (IQR 0.05-0.19); T4: 0.09 (IQR 0.05-0.19) did not differ significantly between pubertal stages. Concentrations of PINP, CTX, BALP and OC were higher in girls at T3 stage than at the T4 stage (p=0.000, p=0.001, p=0.046, p=0.038; respectively). Concentrations of sRANKL and OPG did not correlate with body weight, height, growth rate, or concentrations of estradiol, PINP, CTX, BALP and OC. There were correlations between the increase in height over one year and the concentrations of PINP (r=0.499, p=0.000), CTX (r=0.311, p=0.003) and BALP (r=0.224, p=0.036), as well as of estradiol (r=-0.473, p=0.000). Unlike PINP, OC, BALP, CTX or estradiol concentrations, sRANKL and OPG concentrations do not change in girls during puberty. Neither OPG nor sRANKL concentrations correlate with somatic characteristics and classical bone turnover markers concentrations.

Exercise and osteoimmunology in bone remodeling.

Bones can form the scaffolding of the body, support the organism, coordinate somatic movements, and control mineral homeostasis and hematopoiesis. The immune system plays immune supervisory, defensive, and regulatory roles in the organism, which mainly consists of immune organs (spleen, bone marrow, tonsils, lymph nodes, etc.), immune cells (granulocytes, platelets, lymphocytes, etc.), and immune molecules (immune factors, interferons, interleukins, tumor necrosis factors, etc.). Bone and the immune system have long been considered two distinct fields of study, and the bone marrow, as a shared microenvironment between the bone and the immune system, closely links the two. Osteoimmunology organically combines bone and the immune system, elucidates the role of the immune system in bone, and creatively emphasizes its interdisciplinary characteristics and the function of immune cells and factors in maintaining bone homeostasis, providing new perspectives for skeletal-related field research. In recent years, bone immunology has gradually become a hot spot in the study of bone-related diseases. As a new branch of immunology, bone immunology emphasizes that the immune system can directly or indirectly affect bones through the RANKL/RANK/OPG signaling pathway, IL family, TNF-α, TGF-ß, and IFN-γ. These effects are of great significance for understanding inflammatory bone loss caused by various autoimmune or infectious diseases. In addition, as an external environment that plays an important role in immunity and bone, this study pays attention to the role of exercise-mediated bone immunity in bone reconstruction.

Sciadonic acid attenuates high-fat diet-induced bone metabolism disorders in mice.

High-fat diet (HFD) has been associated with certain negative bone-related outcomes, such as bone metabolism disruption and bone loss. Sciadonic acid (SC), one of the main nutritional and functional components of Torreya grandis seed oil, is a unique Δ5-unsaturated-polymethylene-interrupted fatty acid (Δ5-UPIFA) that has been claimed to counteract such disorders owing to some of its physiological effects. However, the role of SC in ameliorating bone metabolism disorders due to HFD remains unclear. In the present investigation, we observed that SC modulates the OPG/RANKL/RANK signaling pathway by modifying the lipid metabolic state and decreasing inflammation in mice. In turn, it could balance bone resorption and formation as well as calcium and phosphorus levels, enhance bone strength and bone mineral density (BMD), and improve its microstructure. In addition, SC could inhibit fat vacuoles in bone, reverse the phenomenon of reduced numbers and poor continuity of bone trabeculae, and promote orderly arrangement of collagen fibers and cartilage repair. This study provides some theoretical basis for SC as a dietary intervention agent to enhance bone nutrition.

The effect of Schizophyllan on the differentiation of osteoclasts and osteoblasts.

Schizophyllan (SPG), a ß-glucan from Schizophyllum commune, is recognized for its antioxidant, immunoregulatory, and anticancer activities. In this study, its effects on bone cells, particularly osteoclasts and osteoblasts, were examined. We demonstrated that SPG dose-dependently inhibited osteoclastogenesis and reduced gene expression associated with osteoclast differentiation. SPG also decreased bone resorption and F-actin ring formation. This inhibition could have been due to the downregulation of transcription factors c-Fos and nuclear factor of activated T cells 1 (NFATc1) via the MAPKs (JNK and p38), IκBα, and PGC1ß/PPARγ pathways. In coculture, SPG lowered osteoclastogenic activity in calvaria-derived osteoblasts by reducing macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor-κB ligand (RANKL) expression. In addition, SPG slightly enhanced osteoblast differentiation, as evidenced by increased differentiation marker gene expression and alizarin red staining. It also exhibited antiresorptive effects in a lipopolysaccharide-induced calvarial bone loss model. These results indicated a dual role of SPG in bone cell regulation by suppressing osteoclastogenesis and promoting osteoblast differentiation. Thus, SPG could be a therapeutic agent for bone resorption-related diseases such as osteoporosis, rheumatoid arthritis, and periodontitis.

The role of the Piezo1 channel in osteoblasts under cyclic stretching: A study on osteogenic and osteoclast factors.

OBJECTIVES: Orthodontic tooth movement is a mechanobiological reaction induced by appropriate forces, including bone remodeling. The mechanosensitive Piezo channels have been shown to contribute to bone remodeling. However, information about the pathways through which Piezo channels affects osteoblasts remains limited. Thus, we aimed to investigate the influence of Piezo1 on the osteogenic and osteoclast factors in osteoblasts under mechanical load. MATERIALS AND METHODS: Cyclic stretch (CS) experiments on MC3T3-E1 were conducted using a BioDynamic mechanical stretching device. The Piezo1 channel blocker GsMTx4 and the Piezo1 channel agonist Yoda1 were used 12 h before the application of CS. MC3T3-E1 cells were then subjected to 15% CS, and the expression of Piezo1, Piezo2, BMP-2, OCN, Runx2, RANKL, p-p65/p65, and ALP was measured using quantitative real-time polymerase chain reaction, western blot, alkaline phosphatase staining, and immunofluorescence staining. RESULTS: CS of 15% induced the highest expression of Piezo channel and osteoblast factors. Yoda1 significantly increased the CS-upregulated expression of Piezo1 and ALP activity but not Piezo2 and RANKL. GsMTx4 downregulated the CS-upregulated expression of Piezo1, Piezo2, Runx2, OCN, p-65/65, and ALP activity but could not completely reduce CS-upregulated BMP-2. CONCLUSIONS: The appropriate force is more suitable for promoting osteogenic differentiation in MC3T3-E1. The Piezo1 channel participates in osteogenic differentiation of osteoblasts through its influence on the expression of osteogenic factors like BMP-2, Runx2, and OCN and is involved in regulating osteoclasts by influencing phosphorylated p65. These results provide a foundation for further exploration of osteoblast function in orthodontic tooth movement.

Epstein-barr virus infections induce aberrant osteoclastogenesis in immune system-humanized NOD/Shi-scid/IL-2RγCnull mice.

Epstein-Barr virus (EBV) and other viral infections are possible triggers of autoimmune diseases, such as rheumatoid arthritis (RA). To analyze the causative relationship between EBV infections and RA development, we performed experiment on humanized NOD/Shi-scid/IL-2RγCnull (hu-NOG) mice reconstituted human immune system components and infected with EBV. In EBV-infected hu-NOG mice, breakdown of knee joint bones was found to be accompanied by the accumulation of receptor activator of nuclear factor-κB (NF-κB) (RANK) ligand (RANKL), a key factor in osteoclastogenesis, human CD19 and EBV-encoded small RNA (EBER)-bearing cells. Accumulation of these cells expanded in the bone marrow adjacent to the bone breakage, showing a histological feature like to that in bone marrow edema. On the other hand, human RANK/human matrix metalloprotease-9 (MMP-9) positive, osteoclast-like cells were found at broken bone portion of EBV-infected mouse knee joint. In addition, human macrophage-colony stimulating factor (M-CSF), an essential factor in development of osteoclasts, evidently expressed in spleen and bone marrow of EBV-infected humanized mice. Furthermore, RANKL and M-CSF were identified at certain period of EBV-transformed B lymphoblastoid cells (BLBCs) derived from umbilical cord blood lymphocytes. Co-culturing bone marrow cells of hu-NOG mice with EBV-transformed BLBCs resulted in the induction of a multinucleated cell population positive for tartrate-resistant acid phosphatase and human MMP-9 which indicating human osteoclast-like cells. These findings suggest that EBV-infected BLBCs induce human aberrant osteoclastogenesis, which cause erosive arthritis in the joints.

Glycogen Synthase Kinase-3 Beta (GSK3ß) as a Potential Drug Target in Regulating Osteoclastogenesis: An Updated Review on Current Evidence.

Glycogen synthase kinase 3-beta (GSK3ß) is a highly conserved protein kinase originally involved in glucose metabolism, insulin activity, and energy homeostasis. Recent scientific evidence demonstrated the significant role of GSK3ß in regulating bone remodelling through involvement in multiple signalling networks. Specifically, the inhibition of GSK3ß enhances the conversion of osteoclast progenitors into mature osteoclasts. GSK3ß is recognised as a pivotal regulator for the receptor activator of nuclear factor-kappa B (RANK)/receptor activator of nuclear factor-kappa B ligand (RANKL)/osteoprotegerin (OPG), phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT), nuclear factor-kappa B (NF-κB), nuclear factor-erythroid 2-related factor 2 (NRF2)/Kelch-like ECH-associated protein 1 (KEAP1), canonical Wnt/beta (ß)-catenin, and protein kinase C (PKC) signalling pathways during osteoclastogenesis. Conversely, the inhibition of GSK3ß has been shown to prevent bone loss in animal models with complex physiology, suggesting that the role of GSK3ß may be more significant in bone formation than bone resorption. Divergent findings have been reported regarding the efficacy of GSK3ß inhibitors as bone-protecting agents. Some studies demonstrated that GSK3ß inhibitors reduced osteoclast formation, while one study indicated an increase in osteoclast formation in RANKL-stimulated bone marrow macrophages (BMMs). Given the discrepancies observed in the accumulated evidence, further research is warranted, particularly regarding the use of GSK3ß silencing or overexpression models. Such efforts will provide valuable insights into the direct impact of GSK3ß on osteoclastogenesis and bone resorption.

Design, Synthesis, and Biological Evaluation of ß-Trifluoroethoxydimethyl Selenides as Potent Antiosteoporosis Agents.

An efficient protocol for the synthesis of ß-trifluoroethoxydimethyl selenides was achieved under mild reaction conditions, and 39 compounds were prepared. All compounds were evaluated for their abilities to inhibit RANKL-induced osteoclastogenesis, compound 4aa exhibited the most potent activity. Further investigations revealed that 4aa could inhibit F-actin ring generation, bone resorption, and osteoclast-specific gene expression in vitro. Western blot analyses demonstrated that compound 4aa abrogated the RANKL-induced mitogen-activated protein kinase and NF-kB-signaling pathways. In addition, 4aa also displayed a notable impact on the osteoblastogenesis of MC3T3-E1 preosteoblasts. In vivo experiments revealed that compound 4aa significantly ameliorated bone loss in an ovariectomized (OVX) mice model. Furthermore, the surface plasmon resonance experiment results revealed that 4aa probably bound to RANKL. Collectively, the above-mentioned findings suggested that compound 4aa as a potential RANKL inhibitor averted OVX-triggered osteoporosis by regulating the inhibition of osteoclast differentiation and stimulation of osteoblast differentiation.

Selenoprotein W engages in overactive osteoclast differentiation in multiple myeloma.

BACKGROUND: Patients with multiple myeloma exhibit malignant osteolytic bone disease due to excessive osteoclast formation and function. We recently identified that osteoclastogenic stimulator selenoprotein W (SELENOW) is upregulated via ERK signaling and downregulated via p38 signaling during receptor activator of nuclear factor (NF)-κΒ ligand (RANKL)-induced osteoclast differentiation. In the intrinsic physiological process, RANKL-induced downregulation of SELENOW maintains proper osteoclast differentiation; in contrast, forced overexpression of SELENOW leads to overactive osteoclast formation and function. METHODS AND RESULTS: We observed that SELENOW is highly expressed in multiple myeloma-derived peripheral blood mononuclear cells (PBMCs) and mature osteoclasts when compared to healthy controls. Also, the level of tumor necrosis factor alpha (TNFα), a pathological osteoclastogenic factor, is increased in the PBMCs and serum of patients with multiple myeloma. ERK activation by TNFα was more marked and sustained than that by RANKL, allowing SELENOW upregulation. Excessive expression of SELENOW in osteoclast progenitors and mature osteoclasts derived from multiple myeloma facilitated efficient nuclear translocation of osteoclastogenic transcription factors NF-κB and NFATc1, which are favorable for osteoclast formation. CONCLUSION: Our findings suggest a possibility that feedforward signaling of osteoclastogenic SELENOW by TNFα derived from multiple myeloma induces overactive osteoclast differentiation, leading to bone loss during multiple myeloma.