Receptor Activator Of Nuclear Factor kappa-B Ligand Research Articles

RANKL regulates differentially breast cancer stem cell properties through its RANK and LGR4 receptors.

Breast cancer stem cells (BCSC) are a subpopulation responsible for cancer resistance and relapse. The receptor activator of nuclear factor kappa-Β ligand (RANKL) is a cytokine capable of activating RANK and LGR4 receptors. RANKL/RANK signaling maintains the self-renewal of BCSCs, however, the effect of RANKL via LGR4 remains unclear. Evidence from osteoclasts suggests that RANKL/LGR4 axis disrupts RANK signaling, leading to opposing cellular responses. Anti-RANKL inhibitors are potential agents for eradicating CSCs, but their effect on RANKL/LGR4 signal has not been demonstrated. This project aimed to elucidate the role of RANKL in regulating stemness depending on the expression of its receptors. We use in vitro and in vivo approaches to evaluate the effects of RANKL inhibition in stemness in low or high-LGR4 expressing cells. Furthermore, we analyze the effects of RANKL stimulation on the stemness of LGR4 or RANK overexpressing cells. Additionally, we evaluated the impact of RANKL/LGR4 signaling in the activity of Wnt/β-catenin and NF-κB signaling pathways. Our findings indicated that elevated RANKL expression is related to a favorable prognosis in patients with high LGR4 levels. Furthermore, RANKL inhibition decreased BCSC properties in LGR4-low cell lines, while it promoted migration in LGR4-high cells. Additionally, the RANKL/RANK axis activated NF-κB signaling and enhanced BCSCs in RANK-overexpressing cells. In contrast, in LGR4-overexpressing cells, RANKL failed to activate NF-κB but instead inhibited the Wnt/β-catenin pathway, leading to a reduction in BCSCs. Our findings suggest that RANKL exerts different responses according to the expression of its receptors.

Unraveling the impact of blood RANKL and OPG levels on Alzheimer's disease: Independent of bone mineral density and inflammation.

Observational studies have revealed a close relationship between reduced bone mineral density (BMD) and Alzheimer's disease (AD) risk. The receptor activator of nuclear factor kappa-B ligand (RANKL) and osteoprotegerin (OPG) system, pivotal in regulating bone metabolism, has been implicated in brain function, but the causal impact on AD risk remains unclear. We employed bi-directional Mendelian randomization (MR) and multivariable MR (MVMR) approaches to elucidate the effect of blood soluble RANKL (sRANKL) and OPG levels on AD, assessing whether this influence was independent of BMD and inflammation. Three distinct AD genome-wide association study (GWAS) data sets from the International Genomics of Alzheimer's Project (IGAP), UK Biobank (UKB), and FinnGen were utilized. Summary-level data on blood sRANKL and OPG were sourced from deCODE Genetics. Genetically predicted per standard deviation (SD) increase in blood sRANKL levels was significantly associated with a reduced risk of AD across all three AD GWAS data sets (IGAP: odds ratio [OR]=0.82, 95% confidence interval [CI]=0.72-0.94, p=0.004; UKB: OR=0.85, 95% CI=0.78-0.91, p < 0.001; FinnGen: OR=0.83, 95% CI = 0.73-0.94, p=0.004). No significant causal relationship was observed between OPG levels and AD. In addition, there was no causal impact of AD on the blood levels of sRANKL and OPG. MVMR results showed that the inverse association between sRANKL and AD risk persisted after adjusting for BMD and interleukin-1α and chemoattractant protein-1. Our study provides evidence that elevated sRANKL levels are causally linked to a reduced risk of AD, independent of BMD and inflammation. These findings enhance our understanding of the complex interactions between bone metabolism and AD. Blood soluble receptor activator of nuclear factor kappa-B ligand (sRANKL) levels are linked to a reduced risk of Alzheimer's disease (AD).The association between sRANKL levels and AD is independent of bone mineral density (BMD) and inflammation.No causal link exists between blood osteoprotegerin levels and AD.AD does not affect blood levels of sRANKL or osteoprotegerin.

The absence of IRG1 exacerbates bone loss in a mouse model of ovariectomy-induced osteoporosis by increasing osteoclastogenesis through the potentiation of NLRP3 inflammasome activation.

The immune-responsive gene 1 (IRG1) protein plays a role in various pathological processes by connecting cellular metabolism to a range of cellular activities through the production of itaconate. Recent studies have highlighted the significance of IRG1 and itaconate in bone metabolism and homeostasis. However, the precise role of IRG1 in osteoporosis remains inadequately documented. This study aimed to determine the role of IRG1 in osteoporosis through the utilization of IRG1 knockout (KO) mice and a model of ovariectomy (OVX)-induced osteoporosis. The expression of IRG1 was found to be higher in the bone tissues of postmenopausal osteoporotic mice induced by OVX in comparison to sham control mice. When compared to wild type (WT) mice, OVX-induced bone loss was significantly worse in IRG1 KO mice, and this was accompanied by an increase in osteoclastogenesis and bone resorption. However, the loss of bone and the process of osteoclastogenesis and bone resorption were effectively reversed when the IRG1 KO mice were replenished with itaconate. The osteoclastogenesis induced by receptor activator of nuclear factor kappa-Β ligand (RANKL) in bone marrow-derived macrophages (BMMs) was found to be enhanced by IRG1 deficiency, which could be reversed through the replenishment of itaconate. Further investigation revealed that IRG1 deficiency potentiated the activation of NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome. The inhibition of NLRP3 inflammasome using a targeted inhibitor significantly ameliorated RANKL-induced osteoclastogenesis in IRG1 KO BMMs. Overall, this study highlights the significance of IRG1 in regulating osteoclastogenesis and proposes it as a potential target for osteoporosis treatment.

Evaluation of the effects of obesity on orthodontic tooth movement.

This study aimed to evaluate bone remodeling in gingival crevicular fluid (GCF) during canine distalization in obese individuals and compare it to that in normal-weight individuals. Additionally, the orthodontic tooth movement rates of obese individuals were measured and compared with those of normal-weight individuals. Thirty-six patients (18 obese and 18 normal-weight) aged 12-18 years who were candidates for maxillary first premolar extraction for Angle Class II malocclusion were included in the study. The two groups were formed according to World Health Organization guidelines. A normal-weight group (body mass index [BMI] 16-85%) and an obese group (BMI ≥ 95%). Gingival crevicular fluid samples were collected before, 24 hours after, and on the 7th, 14th, and 21st days after the application of the distalization force. Enzyme-linked immunosorbent assay was used to measure leptin, receptor activator of nuclear factor kappa-Β ligand (RANKL), osteoprotegerin (OPG) and interleukin-6 (IL-6) levels in GCF samples. In addition to the recorded GCF sampling times, the amount of canine tooth movement was calculated using digital models obtained on the 28th day and 3rd month. Leptin, RANKL, OPG, and IL-6 levels were significantly higher in the obese group (P < 0.05). The digital model measurements displayed high rates of repeatability (ICC 0.990). The difference in the amount of tooth movement between groups was not statistically significant (P > 0.05). Although obese and normal-weight individuals showed different biomarker levels during tooth movement, there were no significant differences in the amount of movement.

Lutein and inflammation: a comprehensive review of its mechanisms of action

Lutein, a natural dihydroxy carotenoid and a member of the non-vitamin A carotenoids family, is abundant in yellow-colored fruits and green leafy vegetables such as spinach and lettuce. As the second most common type of carotenoid found in human serum, lutein offers a plethora of medicinal benefits, including anti-cancer, anti-inflammatory, and anti-oxidative properties. It is well-absorbed and systemically localized to the liver, lung, and retina, where it can cross the blood-retina barrier and accumulate in the macular pigment. Due to its anti-oxidative and singlet oxygen quenching properties, lutein is reported to reduce the risk of age-related macular degeneration (AMD). Higher concentrations of fasting plasma carotenoids and enhanced skin yellowing after lutein consumption indicate its presence in various regions of the human body, including the skin, breast, brain, and cervix. Lutein has remarkable benefits for neurodegenerative diseases, cardiovascular health, liver protection, and bone disease prevention. In the central nervous system (CNS), lutein supports brain homeostasis through its antioxidant and anti-inflammatory properties, increasing interleukin-10 (IL-10) and reducing tumor necrosis factor-α (TNF-α). It reduces the risk of coronary artery disease and exerts anti-inflammatory effects on peripheral blood mononuclear cells (PBMCs). Lutein protects against alcohol-induced liver damage by modulating the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling pathway. Additionally, lutein promotes bone health by enhancing mineralized bone nodule development and inhibiting osteoclast production, reducing bone resorption, and suppressing soluble receptor activator of nuclear factor kappa B ligand (RANKL). These multifaceted benefits make lutein a valuable agent in disease prevention and health promotion. This review discusses the comprehensive profile of lutein as a phytochemical activity, including anti-inflammatory, antioxidant, anti-cancer, hepatoprotective, neurological, and cardioprotective effects. Additionally, it discusses lutein’s beneficial impact on macular degeneration and eye diseases, showcasing its potential as a natural, plant-based therapeutic agent.

SARS-CoV-2 Impairs Osteoblast Differentiation Through Spike Glycoprotein and Cytokine Dysregulation

Pulmonary and extrapulmonary manifestations have been reported following infection with SARS-CoV-2, the causative agent of COVID-19. The virus persists in multiple organs due to its tropism for various tissues, including the skeletal system. This study investigates the effects of SARS-CoV-2 infection, including both ancestral and Omicron viral strains, on differentiating mesenchymal stem cells (MSCs), the precursor cells, into osteoblasts. Although both viral strains can productively infect osteoblasts, precursor cell infection remained abortive. Viral exposure during osteoblast differentiation demonstrates that both variants inhibit mineral and organic matrix deposition. This is accompanied by reduced expression of runt-related transcription factor 2 (RUNX2) and increased levels of interleukin-6 (IL-6), a cytokine that negatively regulates osteoblast differentiation. Furthermore, the upregulation of receptor activator of nuclear factor kappa B ligand (RANKL) strongly suggests that the ancestral and Omicron variants may disrupt bone homeostasis by promoting osteoclast differentiation, ultimately leading to the formation of bone-resorbing cells. This process is dependent of spike glycoprotein since its neutralization significantly reduced the effect of infective SARS-CoV-2 and UV-C inactivated virus. This study underscores the capacity of ancestral and Omicron SARS-CoV-2 variants to disrupt osteoblast differentiation, a process essential for preserving the homeostasis and functionality of bone tissue.

Factors secreted from the stem cells of human exfoliated deciduous teeth inhibit osteoclastogenesis through the activation of the endogenous antioxidant system.

Systemic administration of conditioned medium (CM) from stem cells derived from human exfoliated deciduous teeth (SHED-CM) in mouse models of rheumatoid arthritis, osteoporosis, and osteoarthritis suppresses excessive osteoclast activity and restores bone integrity. However, the mechanism through which SHED-CM regulates osteoclastogenesis remains largely unknown. In the present study, we examined the anti-osteoclastogenic mechanism of SHED-CM in vitro. Bone marrow macrophages and RAW264.7 cells were treated with receptor activator of nuclear factor kappa-Β ligand (RANKL) in the presence of SHED-CM or CM from bone marrow mesenchymal stem cells (BMSC-CM). Osteoclast differentiation was assessed using tartrate-resistant acid phosphatase staining, actin ring formation, and expression of osteoclast-specific markers. RANKL-induced reactive oxygen species (ROS) production was analyzed as a critical mediator of osteoclastogenesis. The activation of endogenous antioxidant gene expression was examined using reverse transcription quantitative PCR. Liquid chromatography with tandem mass spectrometry (LC-MS) was used to identify proteins enriched in SHED-CM, and neutralizing antibodies were used to evaluate their functional roles. Compared to BMSC-CM, SHED-CM effectively inhibited RANKL-induced early osteoclast differentiation and late maturation. Notably, SHED-CM but not BMSC-CM suppressed RANKL-induced ROS production. SHED-CM increased the expression of genes encoding antioxidant enzymes. The LC-MS analysis identified seven proteins uniquely enriched in SHED-CM that activated the endogenous antioxidant system. Neutralizing antibodies against some of these proteins restore RANKL-induced ROS production and osteoclast differentiation. SHED-CM inhibited osteoclastogenesis, partially through the activation of multiple antioxidant enzymes in osteoclast precursors, highlighting its potential for treating bone-destructive diseases.

Acute Extrinsic Activation of the RANKL Pathway Decreases Wound Healing and Functional Recovery After Spinal Cord Injury in Mice.

Manipulating wound healing-associated signaling after SCI presents a promising avenue for increasing the recovery of function after injury. This study explores the potential of targeting molecular regulators of wound healing, initially identified in nonneural tissues, to enhance outcomes after SCI. Astrocytes, pivotal in central nervous system wound healing, play a crucial role in tissue remodeling and recovery. However, the optimal manipulation of astrogliosis for beneficial outcomes remains elusive. Previous research demonstrated a transcriptional response in astrocytes resembling epithelial-to-mesenchymal transitions (EMTs) after CNS injury. Here, we investigate the extrinsic manipulation of wound healing through the Receptor Activator of Nuclear-factor Kappa-Β (RANK) pathway, known for its involvement in nonneural tissue remodeling and linked to EMT pathway. Using a severe thoracic spinal cord contusion mouse model, we demonstrate that acute activation of the RANK pathway with RANK ligand (RANKL) adversely affects tissue remodeling, resulting in larger lesion volumes and delayed recovery of posture and locomotion. These findings suggest that early perturbations in the tight molecular regulation of tissue remodeling negatively impact the wound-healing process after SCI. The study provides a proof-of-concept demonstration that exogenous nonneural remodeling ligands can modify astrocyte responses and functional recovery after SCI, raising questions about the optimal time frame for beneficial remodeling interventions during injury progression. These insights open new avenues for therapeutic strategies aimed at improving functional outcomes following SCI.

Investigation of the preventive effect of methylsulfonylmethane on alveolar bone loss and oxidative stress in a rat model of periodontitis

BackgroundTo investigate the preventive efficacy of methylsulfonylmethane (MSM) on alveolar bone destruction in rats with periodontitis.MethodsTwenty-four male Sprague-Dawley rats were randomly divided into three groups: control, experimental periodontitis (Ep), and Ep-MSM. Periodontitis was induced by placing 4.0 silk sutures in the subparamarginal position on the necks of the mandibular first molars and applying the suture for 5 weeks. The Ep-MSM group was given 500 mg/body weight/day MSM intraperitoneally for 35 days. At the end of the study, bilateral mandibular samples were taken. Periodontal bone loss was measured through histologic sections. Histomorphometric and immunohistochemical (receptor activator of nuclear factor kappa B ligand (RANKL), osteoprotegerin (OPG)) evaluations were performed on right mandibular tissue samples, and biochemical (interleukin (IL)-1 beta (β)/IL-10, malondialdehyde (MDA), glutathione (GSH), oxidative stress index (OSI)) evaluations were performed on left mandibular tissue samples.ResultsNo significant difference was found between the groups in IL-1β and IL-1β/IL-10 values ​​(p > 0.05). A significant decrease in IL-10 levels was observed in the Ep-MSM and Ep groups compared with the control group (p < 0.05). MDA levels significantly increased in the Ep and Ep-MSM groups compared with the control group, and GSH levels significantly decreased in the Ep group compared with the other groups (p < 0.05). OSI values ​​were significantly higher only in the Ep group (p < 0.05). RANKL levels showed a significant increase in the Ep group compared with the other groups. OPG levels were significantly increased only in the Ep-MSM group (p < 0.05).ConclusionsThe results of this study may suggest that MSM has preventive effects on alveolar bone loss and oxidative stress.

Inhibition of osteocyte apoptosis does not prevent iron overload-induced bone resorption and bone loss.

Iron overload leads to apoptosis and increased expression of receptor activator of nuclear factor kappa-Β ligand (RANKL) in osteocytes, which in turn accelerates osteoclastogenesis. Since osteocytes are the main RANKL producers, we hypothesized that apoptotic osteocytes increase RANKL expression in osteocytes, which in turn stimulates osteoclastogenesis and bone resorption. In this study, alendronate or IG9402, a bisphosphonate (BP) analog which does not inhibit bone resorption, inhibited iron overload-induced osteocyte apoptosis and increased RANKL expression. Both BPs also prevented osteoblast apoptosis but did not inhibit the increase in osteoblastic RANKL. Alendronate, but not IG9402, prevented the increase in osteoclastogenesis and serum levels of the bone resorption marker C-telopeptide of type I collagen (CTX) in iron-overloaded mice. Alendronate also prevented the iron overload-induced reduction in femoral bone mineral density, disruption of bone microstructure, and weakness of bone strength. Although IG9402 did not prevent bone loss due to iron overload, it partially prevented reduction of strength, suggesting that osteocyte viability contributes to the maintenance of bone strength. In conclusion, although osteocyte apoptosis in the presence of iron overload leads to an increase in osteocytic RANKL production. However, blocking these events was not sufficient to inhibit iron overload-induced osteoclastogenesis and bone loss.

PTH-dependent stabilization of RANKL mRNA is associated with increased phosphorylation of the KH-Type Splicing Regulatory Protein

Parathyroid hormone (PTH) receptor agonists promote bone formation but also increase osteoclastogenesis, in part by increasing expression of the receptor activator of nuclear factor kappa-Β ligand (RANKL). In addition to activation of transcription, regulation of mRNA stability is another important molecular mechanism controlling mRNA abundance. PTH treatment for 6 hrs. resulted in a 7.4-fold elevation in RANKL mRNA expression in UAMS-32P cells, despite prior inhibition of cellular transcription by thiophosphoryl (TPL). RANKL mRNA, like other TNF family members, contains AU-Rich Elements (AREs) in the 3’ UTR. AU-Rich Element Binding Proteins (ABPs including KSRP, TTP, AUF1 and HuR) bind to AREs and regulate mRNA stability. There was significantly more KSRP bound to RANKL mRNA than any of the other ABPs. PTH did not increase the amount of ABPs bound to the RANKL transcript. However, the level of cellular phosphorylated KSRP was significantly increased in UAMS-32P cells pre-treated with TPL followed by PTH exposure, compared to cells treated with vehicle following TPL. The extent of phosphorylation of cellular AUF1, HuR, and TTP did not increase with PTH treatment. There were no significant changes in the cellular content of total Pin1 and phospho-Pin1 protein with PTH treatment. We conclude that increases in cellular phospho-KSRP following PTH treatment, together with fact that the total amount of the KSRP bound to the RANKL mRNA did not change with PTH-treatment, may indicate that phospho-KSRP plays some role in stabilizing the RANKL transcript.

Impaired Osteoclastogenesis in Medication-Related Osteonecrosis and Potential Clinical Management with BMP-2

Review Impaired Osteoclastogenesis in Medication-Related Osteonecrosis and Potential Clinical Management with BMP-2 Chunfeng Xu 1, Yin Xiao 2, Yiqun Wu 1, Astrid Bakker 3 and Yuelian Liu 3,* 1 Department of Second Dental Center, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, College of Stomatology, Shanghai Jiao Tong University, National Centre for Stomatology, National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology, Shanghai Research Institute of Stomatology, Shanghai 201900, China 2 School of Medicine and Dentistry &amp; Institute for Biomedicine and Glycomics, Griffith University, Gold Coast Campus, QC 4222, Australia 3 Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije Universiteit Amsterdam, 1081 LA Amsterdam, The Netherlands * Correspondence: y.liu@acta.nl; Tel.: +31-205980626 Received: 5 November 2024; Revised: 18 December 2024; Accepted: 19 December 2024; Published: 23 December 2024 Abstract: Medication-related osteonecrosis of the jaw (MRONJ) is a rare, but severe, complication of applying inhibitors of osteoclasts, specifically bisphosphonates and the monoclonal antibody of receptor activator of nuclear factor kappa-Β ligand (RANKL), inhibitors of angiogenesis, and some chemotherapeutics. MRONJ is painful for the patients, while current treatments are unsatisfactory. Thus, it is imperative to understand the etiology and pathogenesis of MRONJ to improve treatment options and enable prevention. Various hypotheses have been proposed over the years to elucidate the pathogenesis of MRONJ. Noticeably, impaired osteoclastogenesis shines some light on novel preventive and treatment strategies. In this review, we summarized the current understanding of the role of osteoclastogenesis in the development of MRONJ and have put forward a hypothesis concerning the application of BMP2 in the clinical management strategy for MRONJ.

Assessment of Osteoprotegerin and Receptor Activator of Nf-Κb Ligand in Malaysian Male Patients with Chronic Obstructive Pulmonary Disease: A Cross-Sectional Study.

Background: Limited information exists regarding the pathophysiological interactions between osteoporosis and chronic obstructive pulmonary disease (COPD). Objective: To study the association of Osteoprotegerin (OPG) and receptor activator of nuclear factor kappa-Β ligand (RANKL) in male COPD patients. Methods: An observational clinical study was conducted at Penang General Hospital in Malaysia. Participants were divided into three groups: COPD patients with osteoporosis, COPD patients without osteoporosis, and healthy participants of the same age groups. Serum OPG (sOPG) and RANKL (sRANKL) levels were investigated. Results: The mean age of COPD patients was 64.10 ± 10.04 years. COPD patients had lower body mass index (23.22 ± 6.43) than healthy participants (27.32 ± 6.80). The T-score was significantly lower among COPD patients than healthy participants (p = 0.018). The sOPG concentration among healthy participants was significantly higher (361.90 ± 29.10 pg/mL, p < 0.001) than in the other groups, while the sRANKL concentration was not significantly different. The serum OPG/RANKL concentration was markedly higher in the control group than in the COPD patient group (p < 0.05). The COPD patients with osteoporosis had significantly lower pulmonary parameters (forced expiratory volume in the first [FEV]1% and FEV1/[forced vital capacity] (FVC), p < 0.01) and more dyspnea (modified medical research council = 2.60 ± 0.78 versus 1.90 ± 0.70, p < 0.01) than did the patients without osteoporosis. Furthermore, patients with severe COPD had a 3 times greater risk of developing osteoporosis (OR = 2.997 [95% CI = 2.181, 4.118], p < 0.001), while spirometric parameters had a significant inverse relationship with osteoporosis (FEV1% OR = 0.970, [95% CI = 0.954, 0.986], p = 0.001; FEV1/FVC OR = 0.984, (95% CI = 0.970, 0.999], p = 0.035). Conclusion: The study concluded that COPD patients had lower sOPG levels, leading to decreased OPG/RANKL ratio and faster bone resorption. Low bone mineral density was associated with more severe COPD. (Rev Invest Clin. 2024;76(6):262-73).

High molecular weight hyaluronic acid alleviates ovariectomy-induced bone loss in mice

BackgroundThe rapid decline in ovarian function associated with menopause promotes osteoclast differentiation and increases bone resorption, disrupting of bone homeostasis and increasing the risk of osteoporosis. Hyaluronic acid (HA) is a polysaccharide ubiquitously present in the connective tissues. Recent reports indicate that high-molecular-weight HA (HMW-HA) promotes osteoblast proliferation, enhances alkaline phosphatase activity and mineral deposition, and promotes the expression of bone differentiation markers, such as Runx2 and osteocalcin. HMW-HA also inhibits the expression of the receptor activator of nuclear factor kappa-B ligand (RANKL) in osteoblasts. These results suggest that HMW-HA may be an effective therapeutic agent against postmenopausal osteoporosis. Therefore, this study aimed to examine whether HMW-HA alleviates ovariectomy (OVX)-induced bone loss in mice.MethodsEight-week-old female C57BL/6 J mice were randomly divided into the following five groups: Group 1: Sham/saline, Group 2: OVX/saline, Group 3: OVX/HMW-HA [15 mg/kg]; Group 4: OVX/HMW-HA [30 mg/kg]; and Group 5: OVX/HMW-HA [60 mg/kg]. Mice were administered HMW-HA or saline subcutaneously starting from 1 week after OVX and changes in bone mass were analyzed at 5 weeks using three-dimensional micro-computed tomography (3D-μCT). In addition, changes in osteoclast parameters were analyzed histologically.ResultsThe reduction in trabecular bone volume and trabecular number was significantly ameliorated in the OVX/HMW-HA group compared with that observed in the OVX/saline group, along with a significant inhibition of the increase in trabecular spacing. In addition, the OVX/HMW-HA group exhibited a significant reduction in osteoclast surface area and number compared with the OVX/saline group, with no significant differences compared with the sham group. In vitro experiments revealed that depletion of HMW-HA from the culture medium by hyaluronidase treatment increased RANKL expression in the bone marrow stromal cell line ST2. These data suggest that HMW-HA alleviates OVX-induced bone loss by downregulating osteoclast formation and/or activity in mice.ConclusionHMW-HA is a potential novel therapeutic agent for osteoporosis.

Relationship between neutrophil-to-lymphocyte ratio, monocyte-to-lymphocyte ratio, platelet-to-lymphocyte ratio and osteoporosis in postmenopausal type 2 diabetic patients: A retrospective study.

Neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), platelet-to-lymphocyte ratio (PLR) are newly discovered inflammatory markers in recent years. To explore the relationship between NLR, MLR, PLR, and bone mineral density (BMD), as well as osteoporosis (OP), in postmenopausal patients with type 2 diabetes mellitus (T2DM). 320 postmenopausal patients with T2DM who were admitted to the Department of Endocrinology and Metabolic Diseases of our hospital from January 2022 to January 2024 for treatment were included in this retrospective study. The patients were divided into 3 groups according to the BMD: normal bone mass group (n = 109), osteopenia group (n = 99), and OP group (n = 112). Clinical data and blood laboratory parameters were collected from the patients. The NLR, MLR, and PLR were calculated. Statistically significant differences were found in the comparison of NLR, MLR, and PLR among the 3 groups of patients (P < .001). The OP group had higher NLR, MLR, and PLR than the normal bone mass group and the osteopenia group. NLR, MLR, and PLR were negatively correlated with BMD at the lumbar spine (L1-L4), left femoral neck, and left hip, respectively. Analysis revealed that elevated levels of NLR and PLR were independent risk factors for OP in postmenopausal patients. The results of the receiver operating characteristic curve analysis indicated that the area under the curve (AUC) for NLR was higher than that of PLR. Combined use of NLR and PLR resulting in an improved AUC of 0.904. Neutrophils produce mediators such as interferon-gamma (IFN-γ), interleukin-6 (IL-6), interleukin-1 (IL-1), and receptor activator of nuclear factor kappa-B ligand (RANKL), which increase the number and activity of osteoclasts. Peripheral blood monocytes play a vital role in osteoclastogenesis as osteoclast precursors. The BMD of postmenopausal T2DM patients is negatively correlated with NLR, MLR, and PLR. NLR and PLR can both serve as predictive indicators for the occurrence of OP in postmenopausal T2DM patients.

OPG promotes lung metastasis by reducing CXCL10 production of monocyte-derived macrophages and decreasing NK cell recruitment

Lung metastasis is a critical and often fatal progression in cancer patients, with monocyte-derived macrophages (Mo-macs) playing multifaceted roles in this process. Despite the recognized importance of Mac-macs, most studies focus on these cells themselves, while the precise mechanisms through which tumor cells manipulate Mo-macs to promote metastasis remain poorly understood. We developed an invivo CRISPR screening system to identify genes involved in macrophage-dependent metastasis by depleting Mo-macs. Osteoprotegerin (OPG) was identified as the factor significantly enhances lung metastasis. We validated its function in lung metastasis by modulating the expression of OPG in an array of cell lines and performed spontaneous and experimental lung metastasis assays. Genetically engineered mice were utilized to confirm the role of RANKL-RANK signaling in OPG-mediated metastasis. Additionally, we employed different neutralizing antibodies to elucidate the roles of Mo-macs and NK cells and inhibitor to clarify the role of CXCL10 signaling. Employing invivo screening techniques, we elucidate the role of OPG, a protein secreted by cancer cells, in driving lung metastasis, contingent upon regulating Mo-mac activity. OPG blocks the signaling cascade between receptor activator of nuclear factor kappa-B ligand (RANKL) and its receptor RANK on Mo-macs, thereby hindering Mo-macs from secreting CXCL10, a chemokine crucial for recruiting natural killer (NK) cells that help control lung metastasis. Moreover, we observe an enrichment of OPG amplifications in metastatic cancer patients, and elevated levels of OPG expression in lung metastatic sites compared to paired primary breast cancer samples. Our work revealed that OPG works as a lung metastasis promoting factor by blocking the RANKL-RANK-CXCL10 axis to drive the paucity of NK cells, which could be a therapeutic target for lung metastatic cancer patients. The full list of funding supporting this study can be found in the Acknowledgements section.

Elevated IL-6 Expression in Autologous Adipose-Derived Stem Cells Regulates RANKL Mediated Inflammation in Osteoarthritis.

Interleukin-6 (IL-6) expression in mesenchymal stem cells (MSCs) has been shown to play a pivotal role in modulating cartilage regeneration and immune responses, particularly in the context of diseases that involve both degenerative processes and inflammation, such as osteoarthritis (OA). However, the precise mechanism through which IL-6 and other immune-regulatory factors influence the therapeutic efficacy of autologous adipose-derived stem cells (ASCs) transplantation in OA treatment remains to be fully elucidated. This study aims to investigate the relationship between IL-6 expression in autologous ASCs isolated from OA patients and their impact on immune modulation, particularly focusing on the regulation of Receptor Activator of Nuclear factor Kappa-Β Ligand (RANKL), a key mediator of immune-driven cartilage degradation in OA. Autologous ASCs were isolated from the stromal vascular fraction (SVF) of adipose tissue obtained from 22 OA patients. The isolated ASCs were cultured and characterized using reverse transcription polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), and flow cytometry to the phenotype and immune regulatory factors of MSCs. Based on IL-6 expression levels, ASCs were divided into high and low IL-6 expression groups. These groups were then co-cultured with activated peripheral blood mononuclear cells (PBMCs) to evaluate their immune-modulatory capacity, including the induction of regulatory T cells, inhibition of immune cell proliferation, and regulation of key cytokines, such as interferon-gamma (IFN-γ). Additionally, RANKL expression, a critical factor in osteoclastogenesis and cartilage degradation, was assessed in both ASC groups. High IL-6-expressing ASCs demonstrated a significantly greater capacity to inhibit immune cell proliferation and IFN-γ production compared to their low IL-6-expressing counterparts under co-culture conditions. Moreover, the group of ASCs with high IL-6 expression showed a marked reduction in RANKL expression, suggesting enhanced potential to control osteoclast activity and subsequent cartilage defect in OA. Conclusion: Autologous ASCs with elevated IL-6 expression exhibit enhanced immunomodulatory properties, particularly in regulating over-activated immune response and reducing osteoclastogenesis through RANKL suppression. These findings indicate that selecting ASCs based on IL-6 expression could enhance the therapeutic efficacy of ASC-based treatments for OA by mitigating immune-driven joint inflammation and cartilage degradation, potentially slowing disease progression.

The role of osteoprotegerin (OPG) in exercise-induced skeletal muscle adaptation

Abstract Objectives The purpose of this narrative review is to offer an updated perspective on the current research on the glycoprotein Osteoprotegerin (OPG), including its potential therapeutic impact and mechanisms of action, and interaction with bone and muscle tissues. Content As health and social care advances people are living longer, with projections suggesting that in 2050 there will be 2 billion people who are aged over 60 years. Yet musculoskeletal health still declines into older age and as a result there is an increase in the proportion of older populations that spend more time with persistent disabilities. Although physical exercise is repeatedly demonstrated to minimise detrimental effects of ageing, it is not always a feasible intervention, and other directions must be considered. Summary and outlook OPG, a glycoprotein decoy receptor for the receptor activator of nuclear factor kappa-β ligand (RANKL) is a key regulator of bone formation yet emerging evidence has presented its potential to offer positive outcomes in regard to the preservation of skeletal muscle mass and function. Animal models have shown that OPG levels increase during exercise, and independently acts to restore losses of muscle strength and reduce bone resorption. Interventions to increase circulating OPG alongside exercise may act as a therapeutic target to combat the decline in quality of life in older age in humans. Further research is needed on the mechanisms of its action and interaction in humans in combination with exercise.

Clinical Outcomes and Cytokine Profile of Standard and Short Implant-supported Prostheses in Diabetics Treated for Periodontal Disease: A 5-year Study.

The present cross-sectional study aimed to assess the clinico-radiographic parameters as well as salivary levels of receptor activator of nuclear factor kappa-Β ligand (RANKL), osteoprotegerin (OPG), interleukin (IL)-6, and tumor necrosis factor-alpha (TNF-α) around standard and short dental implants (SDIs)-supported fixed partial denture in partially dentate type-II diabetes mellitus (T2DM) patients treated for periodontitis. The study comprised 4 groups: group 1 included T2DM patients with standard implants (n = 20); group II included non-T2DM patients with standard implants (n = 20); group III included T2DM patients with SDIs (n = 20); and group IV included non-T2DM patients with SDIs (n = 20). Participants eligible for the study included medically diagnosed T2DM patients with glycated hemoglobin (HbA1c) levels ≥ 6.5%, and non-T2DM participants with HbA1c levels between 4.0% and 5.0%. All had undergone previous periodontal therapy and had at least one standard implant and one SDI in the posterior maxillary or mandibular region. Exclusions were subjects with systemic conditions other than T2DM, recent use of steroids or antimicrobials, pregnancy or lactation, edentulism, misaligned dentition, or alcohol/tobacco use. Treatment involved non-surgical periodontal therapy, implant placement, and prosthetic procedures, with assessments including clinical (plaque index [PI], bleeding on probing [BOP], probing depth [PD]), radiographic (crestal bone loss [CBL]) parameters, and salivary cytokine levels including RANKL, OPG, IL-6, and TNF-α. The study groups, each comprising 20 participants, showed no significant differences in demographics, restoration type, T2DM duration, family history, body mass index, or brushing routine (p>0.05). At baseline and 5-year follow-up, T2DM participants exhibited poorer periodontal parameters compared to non-T2DM, with higher PI (baseline: 62.2 ± 5.8% vs 29.6 ± 3.7%; 5-year follow-up: 69.2 ± 6.1% vs 32.8 ± 3.8%), BOP (baseline: 30.5 ± 3.2% vs 18.2 ± 2.6%; 5-year follow-up: 35.5 ± 3.9% vs 20.5 ± 2.5%), PD (baseline: 5.5 ± 1.1 mm vs 3.1 ± 0.9 mm; 5-year follow-up: 4.2 ± 0.8 mm vs 2.4 ± 0.7 mm), and CBL (baseline: 4.4 ± 0.4 mm vs 2.0 ± 0.2 mm; 5-yearfollow-up: 4.9 ± 0.5 mm vs 2.3 ± 0.3 mm), regardless of implant type. Salivary cytokine levels (RANKL, OPG, IL-6, TNF-α) were consistently higher in T2DM groups than non-T2DM across both implant types. Participants with SDIs showed comparable clinico-radiographic outcomes and salivary levels of cytokines to standard implants. The application of SDI-supported rehabilitation in T2DM and non-diabetics showed comparable clinico-radiographic outcomes and salivary levels of cytokines to standard dental implants. Furthermore, T2DM patients exhibit poorer periodontal health and elevated inflammatory markers in patients with standard implants and SDIs.

Templated Synthesis of Hollow RuO2 Nanospheres for Alleviating Metal Wear Particle-Induced Osteoclast Activation and Bone Loss.

Wear particulate debris-induced osteoclast over-activation is a major causative factor in periprosthetic osteolysis and aseptic loosening, resulting in the non-infectious failure of total joint arthroplasty. To mitigate such pathological bone loss, various therapeutic targets have been identified. Oxidative stress is one of the main contributing factors in the promotion of osteoclastogenesis. Herein, using a template-assisted approach, hollow ruthenium oxide (RuO2) nanospheres are synthesized as an effective antioxidant for the treatment of CoCrMo alloy particles-induced osteolysis. Hollow RuO2 significantly suppressed receptor activator of nuclear factor kappa-B ligand (RANKL)-induced osteoclastogenesis, bone resorption, and the expression of specific markers (including NFATc1, c-Fos, MMP9, CTSK, and DC-STAMP) of bone marrow-derived macrophages via inhibition of the nuclear factor kappa-B (NF-κB) and tumor necrosis factor (TNF)-α pathways. In mouse calvaria, hollow RuO2 nanozymes demonstrate an appreciable attenuation in osteoclast differentiation, bone loss, and soft tissue malformations induced by CoCrMo alloy particles. This study envisions that the antioxidant nanozymes may be further applied as a therapeutic entity in the prevention and treatment of other inflammatory and oxidative stress-related ailments.