A review of denosumab for the treatment of osteoporosis

Unraveling the intricacies of osteoclast differentiation and maturation: insight into novel therapeutic strategies for bone-destructive diseases

Osteoclasts are the principal cells that efficiently resorb bone. Numerous studies have attempted to reveal the molecular pathways leading to the differentiation and activation of osteoclasts to improve the treatment and prevention of osteoporosis and other bone-destructive diseases. While the cumulative knowledge of osteoclast regulatory molecules, such as receptor activator of nuclear factor-kB ligand (RANKL) and nuclear factor of activated T cells 1 (NFATc1), contributes to the understanding of the developmental progression of osteoclasts, little is known about how the discrete steps of osteoclastogenesis modify osteoclast status but not the absolute number of osteoclasts. The regulatory mechanisms involved in osteoclast maturation but not those involved in differentiation deserve special attention due to their potential use in establishing a more effective treatment strategy: targeting late-phase differentiation while preserving coupled bone formation. Recent studies have shed light on the molecules that govern late-phase osteoclast differentiation and maturation, as well as the metabolic changes needed to adapt to shifting metabolic demands. This review outlines the current understanding of the regulation of osteoclast differentiation, as well as osteoclast metabolic adaptation as a differentiation control mechanism. Additionally, this review introduces molecules that regulate the late-phase osteoclast differentiation and thus minimally impact coupled bone formation.

Smart Strategies to Overcome Drug Delivery Challenges in the Musculoskeletal System

The musculoskeletal system (MSKS) is composed of specialized connective tissues including bone, muscle, cartilage, tendon, ligament, and their subtypes. The primary function of the MSKS is to provide protection, structure, mobility, and mechanical properties to the body. In the process of fulfilling these functions, the MSKS is subject to wear and tear during aging and after injury and requires subsequent repair. MSKS diseases are a growing burden due to the increasing population age. The World Health Organization estimates that 1.71 billon people suffer from MSKS diseases worldwide. MSKS diseases usually involve various dysfunctions in bones, muscles, and joints, which often result in pain, disability, and a decrease in quality of life. The most common MSKS diseases are osteoporosis (loss of bone), osteoarthritis (loss of cartilage), and sarcopenia (loss of skeletal muscle). Because of the disease burden and the need for treatment, regenerative drug therapies for MSKS disorders are increasingly in demand. However, the difficulty of effective drug delivery in the MSKS has become a bottleneck for developing MSKS therapeutics. The abundance of extracellular matrix and its small pore size in the MSKS present a formidable barrier to drug delivery. Differences of vascularity among various MSKS tissues pose complications for drug delivery. Novel strategies are necessary to achieve successful drug delivery in different tissues composing the MSKS. Those considerations include the route of administration, mechanics of surrounding fluids, and biomolecular interactions, such as the size and charge of the particles and targeting motifs. This review focuses on recent advances in challenges to deliver drugs to each tissue of the MSKS, current strategies of drug delivery, and future ideas of how to overcome drug delivery challenges in the MSKS.

RANK is a poor prognosis marker and a therapeutic target in ER-negative postmenopausal breast cancer

Despite strong preclinical data, the therapeutic benefit of the RANKL inhibitor, denosumab, in breast cancer patients, beyond the bone, is unclear. Aiming to select patients who may benefit from denosumab, we hereby analyzed RANK and RANKL protein expression in more than 2,000 breast tumors (777 estrogen receptor-negative, ER- ) from four independent cohorts. RANK protein expression was more frequent in ER- tumors, where it associated with poor outcome and poor response to chemotherapy. In ER- breast cancer patient-derived orthoxenografts (PDXs), RANKL inhibition reduced tumor cell proliferation and stemness, regulated tumor immunity and metabolism, and improved response to chemotherapy. Intriguingly, tumor RANK protein expression associated with poor prognosis in postmenopausal breast cancer patients, activation of NFKB signaling, and modulation of immune and metabolic pathways, suggesting that RANK signaling increases after menopause. Our results demonstrate that RANK protein expression is an independent biomarker of poor prognosis in postmenopausal and ER- breast cancer patients and support the therapeutic benefit of RANK pathway inhibitors, such as denosumab, in breast cancer patients with RANK+ ER- tumors after menopause.

Physiological functions of podosomes: From structure and function to therapy implications in osteoclast biology of bone resorption

With increasing age, bone tissue undergoes significant alterations in composition, architecture, and metabolic functions, probably causing senile osteoporosis. Osteoporosis possess the vast majority of bone disease and associates with a reduction in bone mass and increased fracture risk. Bone loss is on account of the disorder in osteoblast-induced bone formation and osteoclast-induced bone resorption. As a unique bone resorptive cell type, mature bone-resorbing osteoclasts exhibit dynamic actin-based cytoskeletal structures called podosomes that participate in cell-matrix adhesions specialized in the degradation of mineralized bone matrix. Podosomes share many of the same molecular constitutions as focal adhesions, but they have a unique structural organization, with a central core abundant in F-actin and encircled by scaffolding proteins, kinases and integrins. Here, we conclude recent advancements in our knowledge of the architecture and the functions of podosomes. We also discuss the regulatory pathways in osteoclast podosomes, providing a reference for future research on the podosomes of osteoclasts and considering podosomes as a therapeutic target for inhibiting bone resorption.

Tetrandrine inhibits RANKL-induced osteoclastogenesis by promoting the degradation of TRAIL

Background

Tetrandrine, a bisbenzylisoquinoline (BBI) alkaloid extracted from Stephania tetrandra (S. Moore), and is widely used in several diseases such as tuberculosis, hyperglycemia, malaria, and tumors. Tetrandrine was recently shown to prevent bone loss in ovariectomized mice. However, the specific mechanism underlying osteoclastogenesis inhibition remains unclear.

Methods

Tetrandrine’s cytotoxicity to cells was determined using the Cell Counting Kit-8 assay. Tartrate-resistant acid phosphatase staining, immunofluorescence and bone resorption assay were performed to evaluate osteoclasts’ differentiation and absorption capacity. The bone-forming capacity was assessed using alkaline phosphatase and Alizarin red S staining. qPCR and Western blotting were applied to assess the related genes and protein expression. Tetrandrine’s impact on TRAIL was demonstrated through a co-immunoprecipitation assay. Animal experiments were performed for the detection of the therapeutic effect of Tetrandrine on osteoporosis.

Results

Tetrandrine attenuated RANKL-induced osteoclastogenesis and decreased the related gene expression. The co-immunoprecipitation assay revealed that Tetrandrine administration accelerated the ubiquitination of TNF-related apoptosis-inducing ligand (TRAIL), which was subsequently degraded. Moreover, TRAIL overexpression was found to partially reverse the Tetrandrine-induced inhibition of osteoclastogenesis. Meanwhile, Tetrandrine significantly inhibited the phosphorylation of p38, p65, JNK, IKBα and IKKα/β, while the TRAIL overexpression weakened this effect. In addition, Tetrandrine promoted osteogenesis and inhibited the TRAIL expression in osteoblasts. Tetrandrine consistently improved bone destruction by stimulating bone formation and inhibiting bone resorption in an OVX-induced mouse model.

Conclusion

Tetrandrine inhibits RANKL-induced osteoclastogenesis by promoting TRAIL degradation and promotes osteoblast differentiation, suggesting its potential in antiosteopenia pharmacotherapy.

Cost-effectiveness of Denosumab for the Treatment of Postmenopausal Osteoporosis in Malaysia

From the perspective of Malaysian health care providers, denosumab was cost-effective in the treatment of postmenopausal osteoporosis, with an optimal outcome starting at age 60 years. Our results provide important insights into the value for money of anti-osteoporotic agents that can serve as a reference for other countries with comparable epidemiological data.

INTRODUCTION

The study aimed to compare the cost-effectiveness of denosumab with alendronate and no treatment in the management of postmenopausal osteoporosis among the Malaysian population.

METHODS

A well-validated Markov model was used to estimate the cost-effectiveness of denosumab in a hypothetical cohort of postmenopausal osteoporotic women between 50 and 80 years old who had no history of fractures. A 10-year time horizon from the perspective of Malaysian health care providers was used in this analysis. The model parameters, including transition probabilities and costs, were based on Malaysian sources. Treatment efficacy data were obtained from a network meta-analysis. The study outcomes were presented as incremental cost per quality-adjusted life-year (QALY) gained. Sensitivity analyses were performed to ensure the robustness of the results. A cost-effectiveness threshold was set at MYR 21,438 (USD 5175) per QALY.

RESULTS

Denosumab was found to be a cost-effective option for postmenopausal osteoporotic women aged 60 and older. The incremental cost-effectiveness ratios (ICERs) for denosumab versus alendronate ranged from MYR 16,955 (USD 4093) per QALY at age 60 to MYR 4380 (USD 1057) per QALY at age 80. The cost-effectiveness of denosumab improved monotonically with increasing age. Denosumab was 72.8-92.7% likely to be cost-effective at the cost-effectiveness threshold. Sensitivity analyses demonstrated that the results were robust across all parameter variations, with the annual cost of denosumab being the most sensitive.

CONCLUSIONS

From the perspective of the Malaysian health care provider, denosumab appears to be a cost-effective treatment choice for postmenopausal osteoporotic women over 60 years of age.

Periapical status in patients affected by osteoporosis: A retrospective clinical study

Objectives

To assess the periapical status in patients with osteoporosis (OP) treated with denosumab (D), bisphosphonates (BPs), or not on medication, and to understand if these conditions influence the prevalence and the progression of apical periodontitis (AP).

Material and Methods

Seventy‐six patients with OP alone or treated with D, or BPs, formed the study group (O), and those from 76 patients matched for age and sex, without diseases, and not taking medications, constituted the control (C) in this retrospective case−control study. The data from the complete clinical and radiographic examination, medical history, decayed, missing, and filled teeth (DMFT), and periapical index score (PAI) were recorded for each patient. Wilcoxon rank test, χ², and Student's t test were used as appropriate.

Results

The prevalence of AP was similar in O and C. Furthermore, AP was significantly more frequent in root canal‐treated teeth in O patients (p = .03).

Conclusions

OP does not appear to be associated with the development of AP. Moreover, the increased prevalence of AP in root canal‐treated teeth in O patients highlights a possible relationship between the healing dynamics of the disease post‐therapy and the patients' medication. A larger sample is needed to confirm these findings.

Celastrol Attenuates RANKL-Induced Osteoclastogenesis in vitro and Reduces Titanium Particle-Induced Osteolysis and Ovariectomy-Induced Bone Loss in vivo

Excessive bone resorption by osteoclasts contributes significantly to osteoclast-related diseases such as periprosthetic osteolysis and osteoporosis. Osteolysis in a titanium particle-induced calvarial model and bone loss in an ovariectomized mice model occurred similarly to those in humans; thus, these models can be used to evaluate potential therapies for aseptic prosthetic loosening and osteoporosis. Celastrol, which is extracted from the seeds of the genus Tripterygium, has been thoroughly investigated for its anti-inflammatory and anti-cancer pharmacological effects. However, the mechanisms involving bone metabolism by which celastrol inhibits osteoclastogenesis are not yet fully understood. We demonstrated that celastrol inhibited the receptor activator of nuclear factor κB ligand-induced osteoclastogenesis and the bone resorptive function of osteoclasts in vitro by inhibiting the activation of transforming growth factor β-activated kinase 1-mediated NF-κB and mitogen-activated protein kinase signaling pathways and downregulating osteoclastogenesis marker-related genes. Furthermore, celastrol was also shown to be beneficial in both the titanium particle-induced osteolysis calvarial and the murine ovariectomy-induced bone loss. Collectively, our results suggested that celastrol is promising for the prevention of aseptic prosthetic loosening and osteoporosis in the treatment of osteolytic diseases induced by disrupted osteoclast formation and function.

Celastrol Attenuates RANKL-Induced Osteoclastogenesis in vitro and Reduces Titanium Particle-Induced Osteolysis and Ovariectomy-Induced Bone Loss in vivo

Excessive bone resorption by osteoclasts contributes significantly to osteoclast-related diseases such as periprosthetic osteolysis and osteoporosis. Osteolysis in a titanium particle-induced calvarial model and bone loss in an ovariectomized mice model occurred similarly to those in humans; thus, these models can be used to evaluate potential therapies for aseptic prosthetic loosening and osteoporosis. Celastrol, which is extracted from the seeds of the genus Tripterygium, has been thoroughly investigated for its anti-inflammatory and anti-cancer pharmacological effects. However, the mechanisms involving bone metabolism by which celastrol inhibits osteoclastogenesis are not yet fully understood. We demonstrated that celastrol inhibited the receptor activator of nuclear factor κB ligand-induced osteoclastogenesis and the bone resorptive function of osteoclasts in vitro by inhibiting the activation of transforming growth factor β-activated kinase 1-mediated NF-κB and mitogen-activated protein kinase signaling pathways and downregulating osteoclastogenesis marker-related genes. Furthermore, celastrol was also shown to be beneficial in both the titanium particle-induced osteolysis calvarial and the murine ovariectomy-induced bone loss. Collectively, our results suggested that celastrol is promising for the prevention of aseptic prosthetic loosening and osteoporosis in the treatment of osteolytic diseases induced by disrupted osteoclast formation and function.

Atherosclerosis and Bone Loss in Humans-Results From Deceased Donors and From Patients Submitted to Carotid Endarterectomy

Background and Aims: Atherosclerosis and osteoporosis share common risk factors, as well as inflammatory mechanisms. Our aim was to understand how atherosclerotic lesions are related with disturbances in bone.

Methods: Gene expression of pro-inflammatory and bone metabolism related proteins (IL-1β, IL-6, IL-17A, TNF, RANKL, OPG, COL1, CTSK, OCL, TRAP, CBFA1, DKK1, SOST, ADIPOQ, and ADIPOR1) were analyzed in arteries and bones from 45 deceased donors and adipose tissue was used as control. Additionally, in 139 patients with advanced atherosclerosis submitted to carotid endarterectomy we compared calcium content (Alizarin red) and plaque inflammatory scores (CD3⁺, CD68⁺, and adiponectin) of patients with normal bone mineral density (BMD) with those with low BMD and explored the associations between gene expression in atherosclerotic plaques and BMD. Serum levels of pro-inflammatory and bone related proteins were measured both in donors and patients. Associations were investigated by the Pearson or Spearman correlation tests, and multivariate regression analyzes were performed when justified.

Results: Gene expression of bone remodeling and pro-inflammatory proteins correlated positively in bone and aorta, independently of age and sex of donors, but not in adipose tissue. The expression of bone formation genes was significantly higher in atheroma plaques from endarterectomized patients with normal vs. low BMD as well as inflammatory CD68⁺ scores, regardless of patients' age and sex, but not of body mass index. No relationship was observed between serum levels and gene expression levels of pro-inflammatory or bone remodeling proteins.

Conclusions: Our results suggest that the relationship between bones and vessels in the context of atherosclerotic disease and osteoporosis may rely on the intrinsic connection between the tissues involved, independently of disease stage. Serum measurements of pro-inflammatory and bone-remodeling proteins do not accurately translate tissue pathologic processes.

Inhibitory Effect of LGS and ODE Isolated from the Twigs of Syringa oblata subsp. dilatata on RANKL-Induced Osteoclastogenesis in Macrophage Cells

Osteoblasts and osteoclasts play a pivotal role in maintaining bone homeostasis, of which excessive bone resorption by osteoclasts can cause osteoporosis and various bone diseases. However, current osteoporosis treatments have many side effects, and research on new treatments that can replace these treatments is ongoing. Therefore, in this study, the roles of ligustroside (LGS) and oleoside dimethylester (ODE), a natural product-derived compound isolated from Syringa oblata subsp. dilatata as a novel, natural product-derived osteoporosis treatments were investigated. In the results of this study, LGS and ODE inhibited the differentiation of receptor activator of nuclear factor kappa-Β ligand (RANKL)-induced RAW264.7 cells into osteoclasts without cytotoxicity, and down-regulated the activity of TRAP, a specific biomarker of osteoclasts. In addition, it inhibited bone resorption and actin ring formation, which are important functions and features of osteoclasts. Also, the effects of LGS and ODE on the mitogen-activated protein kinase (MAPK) and nuclear factor kappa-light-chain-enhancer of activated B (NF-κB) and phosphoinositide 3-kinases (PI3K)/ protein kinase B (Akt)/mechanistic target of rapamycin (mTOR) signaling pathways that play important roles in osteoclast differentiation were evaluated. In the results, LGS and ODE downregulated the phosphorylation of RANKL-induced MAPK and PI3K/Akt/mTOR proteins in a concentration-dependent manner, translocation of NF-κB into the nucleus was inhibited. As a result, the compounds LGS and ODE isolated from S. oblate subsp. dilatata effectively regulated the differentiation of RANKL-induced osteoclasts and inhibited the phosphorylation of signaling pathways that play a pivotal role in osteoclast differentiation. Therefore, these results suggest the possibility of LGS and ODE as new natural product treatments for bone diseases caused by excessive osteoclasts.

Sclareol inhibits RANKL-induced osteoclastogenesis and promotes osteoblastogenesis through promoting CCN1 expression via repressing the MAPK pathway

Osteoclasts are crucial cellular components of bone and are the cause of various bone problems like osteoporosis. Various biological activities such as anti-tumorous, anti-inflammatory, antibacterial, and immunomodulatory function are influenced by Sclareol, as a natural diterpene compound. However, studies on the effect and mechanism of Sclareol on osteoporosis are rare. In the current research, the influence of Sclareol on osteoclastogenesis and osteoblastogenesis was targeted to be discovered in ovariectomy (OVX)-induced animal models and in vitro. The expression levels of osteoclast-related genes such as c-Fos, NFATc1, and CTSK were detected by RT-qPCR and western blotting to understand the inhibition of Sclareol on the creation of osteoclast. The influence of Sclareol on osteoblastogenesis and the expression of osteoblastogenic markers were also examined. Sclareol inhibited the osteoclastogenesis caused by receptor activator of nuclear factor-κB ligand (RANKL) which promoted osteoblastogenesis through upregulating the expression of cysteine-rich protein 61 (CYR61/CCN1), which is a matricellular protein of the CCN family. The p-ERK and p-P38 protein expression levels were considerably downregulated by Sclareol. Furthermore, CCN1 overexpression partially mimicked the inhibitory effect of Sclareol, while the opposite results were obtained after CCN1 silencing. Additionally, Sclareol protected against loss of bones in an osteoporosis mouse model generated by OVX. The acquired results indicated that Sclareol represses RANKL-induced osteoclastogenesis and promotes osteoblastogenesis via promoting the expression of CCN1 by constraining the mitogen-activated protein kinase (MAPK) pathway. Our findings proposed that for the avoidance and treatment of osteoclast-linked disorders, Sclareol is a potentially effective drug. A proposed model for mediated regulation of osteoclastogenesis and osteoblastogenesis by Sclareol. The basic model of the process by which Sclareol prevents osteoclastogenesis and promotes osteoblastogenesis. Sclareol may increase the expression of CCN1 through inhibiting the MAPK pathway, thereby inhibiting osteoclast differentiation and attenuating bone resorption. Sclareol represses the expression of c-Fos, which stimulates the formation of osteoclast. In contrast, Sclareol promotes osteoblast differentiation by upregulating Runx2 expression, thereby improving the formation of bones. Consequently, Sclareol protects against loss of bones by regulating the stability of bone makeover via inhibition of bone formation and stimulation of bone resorption. Graphical Headlights 1. Sclareol represses RANKL-induced osteoclastogenesis. 2. Sclareol promotes osteoblast differentiation. 3. Sclareol inhibits the MAPK pathway through induction of CCN1. 4. Sclareol protects against bone loss by regulating the balance of bone remodeling via inhibition of bone formation and stimulation of bone resorption.

Advances in genetic selection and breeder practice improve commercial layer hen welfare

Modern commercial layer breeds represent the culmination of ~7000 years of natural genetic selection. This selection was driven in former times by a combination of genetic-shift and -drift events, that led to chickens being favoured as domesticated species for meat and egg production. More recently, in the early 20th century, the concept of hybrid vigour was discovered and accelerated the natural breeding progress that delivered new genetic lines and more favourable production traits. In the mid-20th century, the broiler-type and egg layer-type lines diverged and, in the 21st century, genetic analysis has further accelerated the progress made towards extended primary breeding characteristics such as egg quality, production and feed-intake traits, together with secondary breeding characteristics such as behavioural traits that have improved robustness in different housing systems, climates and feed types, which together have significantly improved welfare traits. Most recently, there has been the adoption of higher-powered computational analytics together with quantitative trait loci and single-nucleotide polymorphism assessment, which have further improved the uniformity of production traits within breeds. Most importantly, this has provided the primary breeding companies with improved and broader basis of selection of the modern commercial layer breeds, which also improved the alignment of layer strains with market requirements, and diverse variations in housing, nutritional and environmental conditions. This is also testament to the speed with which the commercial layer geneticists can respond to changing welfare policy on factors such as stocking density and beak treatment. The present paper reviews the modern approaches to genetic selection, including considerations of and benefits to the welfare state of commercial layers.

Tocilizumab, a Potent Interleukin-6 Receptor Inhibitor, Decreases Bone Resorption and Increases the Rate of Bacterial Infection After Tooth Extraction in Rats

PURPOSE

Our objective was to evaluate the influence of pretreatment with tocilizumab (TCZ) in bone healing after tooth extraction in rats.

METHODS

Wistar male rats were equally divided into sham (ie, nonoperated), saline (both treated with 0.1 ml/kg saline), and six TCZ groups treated with 1, 2, 4, 8, 16, and 32 mg/kg TCZ (TCZ1 to TCZ32, respectively). Twenty-four hours after administration of vehicle or TCZ, exodontia of the first lower left molar was performed, and the animals were euthanized three days later for hematological analysis and organ (liver, spleen, and kidney mass indexes, and histological evaluation), gingiva (myeloperoxidase [MPO] assay), and mandible (radiographic, histomorphometric analysis, and IL-6 immunostaining) evaluation. Analysis of variance/Bonferroni test (statistical significance, P < .05) was performed using GraphPad Prism version 5.0 (GraphPad Inc, San Diego, CA, USA).

RESULTS

There was no difference in radiographic results; however, leukopenia (P = .039) and neutropenia (P < .001) were statistically significant in the TCZ16 and TCZ32 groups. Weight loss (P < .001) and reduced liver index (P = .001) were significantly dose-dependent; however, no histological alterations were observed in the other organs. Osteoclast counts were reduced in groups TCZ4 to TCZ32 (P < .001), and IL-6 immunostaining increased in the TCZ8 to TCZ32 groups (P < .001). Alveolar infection rates increased in groups TCZ4 to TCZ32 (P < .001), and MPO had a biphasic response, exhibiting a reduction in groups TCZ2 and TCZ4, and an increase in group TCZ32 (P = .004).

CONCLUSION

TCZ-induced immunosuppression led to a reduction in osteoclast function, an increase in alveolar infection, and compensatory neutrophil infiltration.

Protocadherin-7 contributes to maintenance of bone homeostasis through regulation of osteoclast multinucleation

Osteoclasts are hematopoietic-derived cells that resorb bone. They are required to maintain proper bone homeostasis and skeletal strength. Although osteoclast differentiation depends on receptor activator of NFκB ligand (RANKL) stimulation, additional molecules further contribute to osteoclast maturation. Here, we demonstrate that protocadherin-7 (Pcdh7) regulates formation of multinucleated osteoclasts and contributes to maintenance of bone homeostasis. We found that Pcdh7 expression is induced by RANKL stimulation, and that RNAi-mediated knockdown of Pcdh7 resulted in impaired formation of osteoclasts. We generated Pcdh7-deficient mice and found increased bone mass due to decreased bone resorption but without any defect in bone formation. Using an in vitro culture system, it was revealed that formation of multinucleated osteoclasts is impaired in Pcdh7-deficient cultures, while no apparent defects were observed in differentiation and function of Pcdh7-deficient osteoblasts. Taken together, these results reveal an osteoclast cell-intrinsic role for Pcdh7 in maintaining bone homeostasis.

Protocadherin-7 contributes to maintenance of bone homeostasis through regulation of osteoclast multinucleation

Osteoclasts are hematopoietic-derived cells that resorb bone. They are required to maintain proper bone homeostasis and skeletal strength. Although osteoclast differentiation depends on receptor activator of NF-κB ligand (RANKL) stimulation, additional molecules further contribute to osteoclast maturation. Here, we demonstrate that protocadherin-7 (Pcdh7) regulates formation of multinucleated osteoclasts and contributes to maintenance of bone homeostasis. We found that Pcdh7 expression is induced by RANKL stimulation, and that RNAi-mediated knockdown of Pcdh7 resulted in impaired formation of osteoclasts. We generated Pcdh7-deficient mice and found increased bone mass due to decreased bone resorption but without any defect in bone formation. Using an in vitro culture system, it was revealed that formation of multinucleated osteoclasts is impaired in Pcdh7-deficient cultures, while no apparent defects were observed in differentiation and function of Pcdh7-deficient osteoblasts. Taken together, these results reveal an osteoclast cell-intrinsic role for Pcdh7 in maintaining bone homeostasis. [BMB Reports 2020; 53(9): 472-477].

Group 2 innate lymphoid cells in nasal polyposis

OBJECTIVE

Chronic rhinosinusitis with nasal polyps (CRSwNP) is characterized by a chronic type 2 inflammatory response in the paranasal sinuses. Group 2 innate lymphoid cells (ILC2s) are potent innate immune cells that contribute to type 2 inflammation by producing cytokines such as interleukin (IL)-4, IL-5, and IL-13. There is increasing evidence suggesting that ILC2s play an important role in the CRSwNP pathogenesis.

DATA SOURCES

We reviewed published literature obtained through PubMed inquiries.

STUDY SELECTIONS

Studies relevant to the presence, function, and activation of ILC2s in CRSwNP were included.

RESULTS

Nasal polyps (NPs) are one of the first tissues in which human ILC2s were discovered, and many groups have since reported that these cells are highly elevated in NPs. ILC2s in NPs are also highly activated and produce type 2 cytokines in vivo. Mediators known to activate ILC2s, including receptor activator of nuclear factor kappa-Β ligand, thymic stromal lymphopoietin, various lipid mediators (including prostaglandin D₂ and cysteinyl leukotrienes), IL-4, and IL-13 have also been shown to be elevated in NPs compared with healthy sinonasal tissue. Other well-known ILC2 activators, IL-25 and IL-33, are sometimes elevated in NPs in some countries. Furthermore, activation of ILC2s by means of 4 distinct transcriptional pathways (nuclear factor kappa-light-chain-enhancer of activated B cells, nuclear factor of activated T cells, signal transducer and activator of transcription 5, and signal transducer and activator of transcription 6) is needed for the most robust generation of type 2 cytokines.

CONCLUSION

ILC2-mediated type 2 inflammation plays a crucial role in the pathogenesis of CRSwNP. Targeting the upstream mediators responsible for activating ILC2s and the downstream products that these cells release may play an important role in modifying the inflammatory response and improving clinical outcomes in CRSwNP.

Clinical effects of switching from minodronate to denosumab treatment in patients with postmenopausal osteoporosis: a retrospective study

Background

Denosumab is a major treatment option for patients with postmenopausal osteoporosis; however, the evidence for its use is lacking. Therefore, in this 24-month retrospective study, we aimed to evaluate the effects of switching from minodronate (MIN) to denosumab in these patients.

Methods

Patients with postmenopausal osteoporosis either switched from MIN to denosumab (Group 1; n = 32) or continued MIN treatment (Group 2; n = 24). Bone mineral density (BMD) of the lumbar spine (L2–L4) and femoral neck was assessed at baseline and every 6 months for 24 months. Serum bone-specific alkaline phosphatase (BAP) and N-terminal telopeptide were measured at baseline, 12 months, and 24 months.

Results

Twenty-nine of the 32 patients (90.6%) in group 1 and all patients (24/24) in group 2 completed the 24-month follow-up. Switching from MIN to denosumab (Group 1) significantly increased lumbar BMD at 12, 18, and 24 months (6.1, 7.4, and 9.6%, respectively) and femoral neck BMD at 12, 18, and 24 months (2.8, 3.2, and 3.4%, respectively), whereas MIN continuous treatment (Group 2) showed no significant difference from baseline. Switching therapy also showed a significant decrease in serum BAP from baseline to 12 and 24 months (− 19.3 and − 26.5%, respectively) and serum NTX from baseline to 12 months (− 13.1%), whereas continuous MIN treatment failed to show any significant differences from baseline.

Conclusion

Switching from MIN to denosumab in patients with postmenopausal osteoporosis showed clinical benefits with regard to BMD and bone turnover markers in comparison with continuous MIN treatment. It may therefore be a valid treatment option in the clinical setting.

IgSF11 regulates osteoclast differentiation through association with the scaffold protein PSD-95

Osteoclasts are multinucleated, giant cells derived from myeloid progenitors. While receptor activator of NF-κB ligand (RANKL) stimulation is the primary driver of osteoclast differentiation, additional signaling further contributes to osteoclast maturation. Here, we demonstrate that immunoglobulin superfamily member 11 (IgSF11), whose expression increases during osteoclast differentiation, regulates osteoclast differentiation through interaction with postsynaptic density protein 95 (PSD-95), a scaffold protein with multiple protein interaction domains. IgSF11 deficiency in vivo results in impaired osteoclast differentiation and bone resorption but no observed defect in bone formation. Consequently, IgSF11-deficient mice exhibit increased bone mass. Using in vitro osteoclast culture systems, we show that IgSF11 functions through homophilic interactions. Additionally, we demonstrate that impaired osteoclast differentiation in IgSF11-deficient cells is rescued by full-length IgSF11 and that the IgSF11-PSD-95 interaction requires the 75 C-terminal amino acids of IgSF11. Our findings reveal a critical role for IgSF11 during osteoclast differentiation and suggest a role for IgSF11 in a receptor- and signal transduction molecule-containing protein complex.

The PPAR-γ antagonist T007 inhibits RANKL-induced osteoclastogenesis and counteracts OVX-induced bone loss in mice

Background

Osteoclasts are key determinant cellular components implicated in the development and progression of disorders driven by bone damage. Herein, we studied the upshot of T007, an antagonist of peroxisome proliferator-activated receptor-gamma (PPARγ), on osteoclastogenesis using cell and animal models.

Results

The in vitro assays revealed that T007 hindered the osteoclastogenesis caused by the treatment with the receptor activator of nuclear factor-κB ligand (RANKL) through inhibiting the levels of PPARγ in cells. The PPARγ siRNA partially reproduced the inhibitory action of T007. The opposite findings were produced after PPARγ overexpression. Furthermore, T007 prevented from bone loss in a mouse model of osteoporosis induced by ovariectomy (OVX). These findings implied that T007 is a potential efficient drug for the prophylaxis and cure of osteoclast-related disorders.

Conclusions

Taken together, our findings demonstrated that T007 impedes osteoclastogenesis and will be useful for the therapy of bone related diseases, essentially osteoporosis.

Flrt2 is involved in fine-tuning of osteoclast multinucleation

Osteoclasts are multinucleated giant cells derived from myeloid progenitors. Excessive bone resorption by osteoclasts can result in serious clinical outcomes for which better treatment options are needed. Here, we identified fibronectin leucine-rich transmembrane protein 2 (Flrt2), a ligand of the Unc5 receptor family for neurons, as a novel target associated with the late/maturation stage of osteoclast differentiation. Flrt2 expression is induced by stimulation with receptor activator of nuclear factor-kB ligand (RANKL). Flrt2 deficiency in osteoclasts results in reduced hyper-multinucleation, which could be restored by RNAi-mediated knockdown of Unc5b. Treatment with Netrin1, another ligand of Unc5b which negatively controls osteoclast multinucleation through down regulation of RANKL-induced Rac1 activation, showed no inhibitory effects on Flrt2-deficient cells. In addition, RANKL-induced Rac1 activation was attenuated in Flrt2-deficient cells. Taken together, these results suggest that Flrt2 regulates osteoclast multinucleation by interfering with Netrin 1-Unc5b interaction and may be a suitable therapeutic target for diseases associated with bone remodeling.

Leonurus sibiricus L. ethanol extract promotes osteoblast differentiation and inhibits osteoclast formation

Leonurus sibiricus L. (LS) is a medicinal plant used in East Asia, Europe and the USA. LS is primarily used in the treatment of gynecological diseases, and recent studies have demonstrated that it exerts anti-inflammatory and antioxidant effects. To the best of our knowledge, the present study demonstrated for the first time that LS may promote osteoblast differentiation and suppress osteoclast differentiation in vitro, and that it inhibited lipopolysaccharide (LPS)-induced bone loss in a mouse model. LS was observed to promote the osteoblast differentiation of MC3T3-E1 cells and upregulate the expression of runt-related transcription factor 2 (RUNX2), a key gene involved in osteoblast differentiation. This resulted in the induction of the expression of various osteogenic genes, including alkaline phosphatase (ALP), osteonectin (OSN), osteopontin (OPN), type I collagen (COL1) and bone sialoprotein (BSP). LS was also observed to inhibit osteoclast differentiation and bone resorption. The expression levels of nuclear factor of activated T-cells 1 (NFATc1) and c-Fos were inhibited following LS treatment. NFATc1 and c-Fos are key markers of osteoclast differentiation that inhibit receptor activator of nuclear factor-κB ligand (RANKL)-induced mitogen-activated protein kinase (MAPKs) and nuclear factor (NF)-κB. As a result, LS suppressed the expression of osteoclast-associated genes, such as matrix metallopeptidase-9 (MMP-9), cathepsin K (Ctsk), tartrate-resistant acid phosphatase (TRAP), osteoclast-associated immunoglobulin-like receptor (OSCAR), c-src, c-myc, osteoclast stimulatory transmembrane protein (OC-STAMP) and ATPase H+ transporting V0 subunit d2 (ATP6v0d2). Consistent with the in vitro results, LS inhibited the reduction in bone mineral density and the bone volume/total volume ratio in a mouse model of LPS-induced osteoporosis. These results suggest that LS may be a valuable agent for the treatment of osteoporosis and additional bone metabolic diseases.

Building for better bones: evaluation of a clinical pathway in the secondary prevention of osteoporotic fractures

Objective

Osteoporosis is a common disease that is underdiagnosed and undertreated. A multidisciplinary intervention may improve the identification and treatment of osteoporosis and may consequently prevent secondary fractures.

Method

Retrospective, single-centre study comparing attitude to screening and treatment of patients admitted to the orthopaedic unit of the general hospital AZ Sint-Jan Brugge-Oostende AV (Belgium) before and after the implementation of a clinical pathway.

Results

A total of 172 patients (86 before and 86 after) were included in this study. The implementation of the pathway resulted in an increase in bone mineral density tests performed, an increment in the number of referrals to a specialist in the field of osteoporosis, and an increase in prevention and treatment of osteoporosis.

Conclusion

The implementation of a clinical pathway coordinated and evaluated by a clinical pharmacist improved the identification, referral and treatment of osteoporosis in patients hospitalised due to low-impact fractures.

Inhibition of Osteoclastogenesis by Thioredoxin-Interacting Protein-Derived Peptide (TN13)

Overactivated osteoclasts lead to many bone diseases, including osteoporosis and rheumatoid arthritis. The p38 MAPK (p38) is an essential regulator of the receptor activator of nuclear factor-κB ligand (RANKL)-mediated osteoclastogenesis and bone loss. We previously reported TAT conjugated thioredoxin-interacting protein-derived peptide (TAT-TN13) as an inhibitor of p38 in hematopoietic stem cells (HSCs). Here, we examined the role of TAT-TN13 in the differentiation and function of osteoclasts. TAT-TN13 significantly suppressed RANKL-mediated differentiation of RAW 264.7 cells and bone marrow macrophages (BMMs) into osteoclasts. TAT-TN13 also inhibited the RANKL-induced activation of NF-κB and nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), leading to the decreased expression of osteoclast-specific genes, including tartrate-resistant acid phosphatase (TRAP) and Cathepsin K. Additionally, TAT-TN13 treatment protected bone loss in ovariectomized (OVX) mice. Taken together, these results suggest that TAT-TN13 inhibits osteoclast differentiation by regulating the p38 and NF-κB signaling pathway; thus, it may be a useful agent for preventing or treating osteoporosis.

Non-Viral Delivery System and Targeted Bone Disease Therapy

Skeletal systems provide support, movement, and protection to the human body. It can be affected by several life suffering bone disorders such as osteoporosis, osteoarthritis, and bone cancers. It is not an easy job to treat bone disorders because of avascular cartilage regions. Treatment with non-specific drug delivery must utilize high doses of systemic administration, which may result in toxicities in non-skeletal tissues and low therapeutic efficacy. Therefore, in order to overcome such limitations, developments in targeted delivery systems are urgently needed. Although the idea of a general targeted delivery system using bone targeting moieties like bisphosphonates, tetracycline, and calcium phosphates emerged a few decades ago, identification of carrier systems like viral and non-viral vectors is a recent approach. Viral vectors have high transfection efficiency but are limited by inducing immunogenicity and oncogenicity. Although non-viral vectors possess low transfection efficiency they are comparatively safe. A number of non-viral vectors including cationic lipids, cationic polymers, and cationic peptides have been developed and used for targeted delivery of DNA, RNA, and drugs to bone tissues or cells with successful consequences. Here we mainly discuss such various non-viral delivery systems with respect to their mechanisms and applications in the specific targeting of bone tissues or cells. Moreover, we discuss possible therapeutic agents that can be delivered against various bone related disorders.

Extracellular vesicles in bone: "dogrobbers" in the "eternal battle field"

Throughout human life, bone is constantly in a delicate dynamic equilibrium of synthesis and resorption, hosting finely-tuned bone mineral metabolic processes for bone homeostasis by collaboration or symphony among several cell types including osteoclasts (OCs), osteoblasts (OBs), osteocytes (OYs), vascular endothelial cells (ECs) and their precursors. Beyond these connections, a substantial level of communication seems to occur between bone and other tissues, and together, they form an organic unit linked to human health and disease. However, the current hypothesis, which includes growth factors, hormones and specific protein secretion, incompletely explains the close connections among bone cells or between bone and other tissues. Extracellular vesicles (EVs) are widely-distributed membrane structures consisting of lipid bilayers, membrane proteins and intravesicular cargo (including proteins and nucleic acids), ranging from 30 nm to 1000 nm in diameter, and their characters have been highly conserved throughout evolution. EVs have targeting abilities and the potential to transmit multidimensional, abundant and complicated information, as powerful and substantial "dogrobbers" mediating intercellular communications. As research has progressed, EVs have gradually become thought of as "dogrobbers" in bone tissue-the "eternal battle field" -in a delicate dynamic balance of destruction and reconstruction. In the current review, we give a brief description of the major constituent cells in bone tissues and explore the progress of current research on bone-derived EVs. In addition, this review also discusses in depth not only potential directions for future research to breakthrough in this area but also problems existing in current research that need to be solved for a better understanding of bone tissues.

Effects of Long-Term Denosumab on Bone Histomorphometry and Mineralization in Women With Postmenopausal Osteoporosis

CONTEXT

Denosumab is a potent antiresorptive agent that reduces fractures in postmenopausal women with osteoporosis.

OBJECTIVE

Determine effects of up to 10 years of denosumab on bone histology, remodeling, and matrix mineralization characteristics.

DESIGN AND SETTING

International, multicenter, randomized, double-blind trial [Fracture Reduction Evaluation of Denosumab in Osteoporosis Every 6 Months (FREEDOM)] with a long-term open-label extension.

PATIENTS

Postmenopausal women with osteoporosis (92 women in FREEDOM, 46 in extension) who provided iliac bone biopsies, including 11 who provided biopsies at multiple time points.

INTERVENTIONS

FREEDOM subjects were randomized 1:1 to subcutaneous denosumab 60 mg or placebo every 6 months for 3 years. Long-term extension subjects continued receiving denosumab, open-label, for 7 additional years.

OUTCOMES

Bone histology, histomorphometry, matrix mineralization.

RESULTS

Ten-year denosumab biopsies showed normal histology. Bone histomorphometry indicated normal bone structure and reduced bone remodeling after 10 years of denosumab, similar to levels after 2 and/or 3 and 5 years of denosumab. The degree of mineralization of bone was increased and mineralization heterogeneity was reduced in the denosumab years 2/3 group vs placebo. Changes in these mineralization variables progressed from years 2/3 to year 5 of denosumab, but not thereafter.

CONCLUSIONS

Denosumab for 2/3, 5, and 10 years was associated with normal histology, low bone remodeling rate, increased matrix mineralization, and lower mineralization heterogeneity compared with placebo. These variables were unchanged from year 5 to year 10. These data, in combination with the maintenance of low fracture rates for up to 10 years as previously reported with denosumab therapy, suggest that strong, prolonged remodeling inhibition does not impair bone strength.

The role of OPG/RANKL in the pathogenesis of diabetic cardiovascular disease

Cardiovascular (CV) disease is the leading cause of mortality in patients with type 2 diabetes mellitus. A major factor in the pathogenesis of CV disease is vascular calcification (VC), which is accelerated in type 2 diabetes mellitus. Calcification of the vessel wall contributes to vascular stiffness and left ventricular hypertrophy whereas intimal calcification may predispose to plaque rupture and CV death. The pathogenesis of VC is complex but appears to be regulated by the osteoprotegerin (OPG)/receptor activator of nuclear factor-κB ligand (RANKL) signaling pathway, which is involved in bone remodeling. Within the bone, OPG prevents RANKL from binding to receptor activator of nuclear factor-κB and inhibiting bone resorption. Outside of the bone, the clinical significance of OPG blocking RANKL is not well understood, but OPG knockout mice that lack OPG develop early and severe VC. This minireview outlines some of the research on OPG/RANKL in the pathogenesis of VC and discusses potential therapies, which may reduce VC and CV burden in humans.

Tanshinone‑IIA attenuates the deleterious effects of oxidative stress in osteoporosis through the NF‑κB signaling pathway

Osteoclasts are responsible for bone resorption caused by bone microstructural damage and bone-related disorders. Evidence shows that tanshinone IIA (Tan‑IIA), a traditional Chinese medicine, is used clinically as a drug for the treatment of cardiovascular and cerebrovascular diseases. However, the efficacy and mechanism underlying the effect of Tan‑IIA on the viability of osteoclasts remain to be fully elucidated. The present study investigated the therapeutic effects of Tan‑IIA on osteoblast differentiation and oxidative stress in vitro and in vivo. Cell viability was analyzed and oxidative stress was examined in the osteoblasts. Wnt1sw/sw mice were used to investigate the therapeutic effects of Tan‑IIA on spontaneous tibia fractures and severe osteopenia. The bone strength, collagen and mineral were examined in the tibia. Osteoblast activity was also analyzed in the experimental mice. The Tan‑IIA‑induced differentiation of osteoclasts and the mechanism of action were investigated in osteocytes. The data showed that Tan‑IIA treatment improved cell viability. The data also demonstrated that Tan‑IIA decreased the levels of H2O2, accumulation of reactive oxygen species and apoptosis of osteoblasts. Tan‑IIA inhibited the deleterious outcomes triggered by oxidative stress. In addition, Tan‑IIA inhibited the activation of nuclear factor (NF)‑κB and its target genes, tumor necrosis factor (TNF)‑α, inducible nitric oxide synthase and cyclooxygenase 2, and increased the levels of TNF receptor‑associated factor 1 and inhibitor of apoptosis protein‑1/2 in the osteocytes. Furthermore, it was shown that Tan‑IIA reduced the propensity to fractures and severe osteopenia in mice with osteoporosis. Tan‑IIA also exhibited improved bone strength, mineral and collagen in the bone matrix of the experimental mice. It was found that the Tan‑IIA‑mediated benefits on osteoblast activity and function were through the NF‑κB signaling pathway. Taken together, the data obtained in the present study suggested that Tan‑IIA had protective effects against oxidative stress in osteoblastic differentiation in mice with osteoporosis by regulating the NF‑κB signaling pathway.

The relationship between osteoporosis and body composition in pre- and postmenopausal women from different ethnic groups in China

OBJECTIVE

To investigate the ethnic differences in osteoporosis (OP) and body composition (BC) and their relationship in the Maonan, Mulam, Hmong, and Yao minorities in China.

DESIGN

A total of 860 Maonan, Mulam, Hmong, and Yao women were included in this cross-sectional study. Demographic, health history, and lifestyle information was collected using questionnaires. BC was measured through bioelectrical impedance analysis, and bone mineral density (BMD) was assessed via calcaneal quantitative ultrasound.

RESULTS

Compared with premenopausal women, postmenopausal women exhibited a lower fat-free mass (FFM), muscle mass (MM), limb muscle mass, and T-score but a higher waist-to-hip ratio and prevalence of OP in each minority (p < .05). After adjustment for age, Hmong women displayed the highest body mass index, fat mass, percentage of body fat, visceral fat, and subcutaneous fat contents, while Yao women presented the highest T-scores and lowest prevalence of OP among the four minorities (p < .05). Having a greater number of children and an older age were significant risk factors for OP in all ethnic groups (p < .05, OR > 1). In addition, our results revealed that FFM and MM exhibited exactly the same weak positive relationship with the T-score (r = 0.081, p < .05) after adjusting for menopausal status and age in all of the participants. Furthermore, significant ethnic differences in the relationship between BC and the T-score existed in the four minorities studied here.

CONCLUSIONS

BC and OP prevalence varied by menopausal status and ethnic group, and ethnic-specific relationships between BC and BMD were present in the four minorities. More research is needed to further investigate the ethnic differences in BC, OP, and risk factors for lower BMD to develop targeted prevention strategies to reduce the burden of OP across different ethnic groups in China.

Genetic architecture of bone quality variation in layer chickens revealed by a genome-wide association study

Skeletal problems in layer chickens are gaining attention due to animal welfare and economic losses in the egg industry. The genetic improvement of bone traits has been proposed as a potential solution to these issues; however, genetic architecture is not well understood. We conducted a genome-wide association study (GWAS) on bone quality using a sample of 1534 hens genotyped with a 600 K Chicken Genotyping Array. Using a linear mixed model approach, a novel locus close to GSG1L, associated with femur bone mineral density (BMD), was uncovered in this study. In addition, nine SNPs in genes were associated with bone quality. Three of these genes, RANKL, ADAMTS and SOST, were known to be associated with osteoporosis in humans, which makes them good candidate genes for osteoporosis in chickens. Genomic partitioning analysis supports the fact that common variants contribute to the variations of bone quality. We have identified several strong candidate genes and genomic regions associated with bone traits measured in end-of-lay cage layers, which accounted for 1.3–7.7% of the phenotypic variance. These SNPs could provide the relevant information to help elucidate which genes affect bone quality in chicken.

The purinergic receptor P2X5 regulates inflammasome activity and hyper-multinucleation of murine osteoclasts

Excessive bone resorption by osteoclasts (OCs) can result in serious clinical outcomes, including bone loss that may weaken skeletal or periodontal strength. Proper bone homeostasis and skeletal strength are maintained by balancing OC function with the bone-forming function of osteoblasts. Unfortunately, current treatments that broadly inhibit OC differentiation or function may also interfere with coupled bone formation. We therefore identified a factor, the purinergic receptor P2X5 that is highly expressed during the OC maturation phase, and which we show here plays no apparent role in early bone development and homeostasis, but which is required for osteoclast-mediated inflammatory bone loss and hyper-multinucleation of OCs. We further demonstrate that P2X5 is required for ATP-mediated inflammasome activation and IL-1β production by OCs, and that P2X5-deficient OC maturation is rescued in vitro by addition of exogenous IL-1β. These findings identify a mechanism by which OCs react to inflammatory stimuli, and may identify purinergic signaling as a therapeutic target for bone loss-related inflammatory conditions.

The roles of bone-derived exosomes and exosomal microRNAs in regulating bone remodelling

Pathological destructive bone diseases are primarily caused by the failure of a lifelong self-renewal process of the skeletal system called bone remodelling. The mechanisms underlying this process include enhanced osteoclast activity and decreased generation of the osteoblast lineage. Intercellular interaction and crosstalk among these cell types are crucial for the maintenance of bone remodelling, either through the secretion of growth factors or direct cell-cell physical engagement. Recent studies have revealed that exosomes derived from bone cells, including osteoclasts, osteoblasts and their precursors, play pivotal roles on bone remodelling by transferring biologically active molecules to target cells, especially in the processes of osteoclast and osteoblast differentiation. Here, we review the contents of bone-derived exosomes and their functions in the regulatory processes of differentiation and communication of osteoclasts and osteoblasts. In addition, we highlight the characteristics of microRNAs of bone-derived exosomes involved in the regulation of bone remodelling, as well as the potential clinical applications of bone-derived exosomes in bone remodelling disorders.

Elevated serum osteoprotegerin levels in women: friend or foe?

INTRODUCTION

osteoprotegerin has emerged as a new candidate for the treatment of osteoporosis. However, high levels of osteoprotegerin have been linked to vascular calcification, an independent and well-defined risk factor for cardiovascular disease (CVD) and mortality. Thus, the action of osteoprotegerin in these situations has been questioned.

OBJECTIVE

to evaluate the effect of osteoprotegerin (OPG) on the human body, especially in bone tissue and in vascular diseases.

METHODS

the scientific databases consulted were PubMed-Medline and Cochrane, using keywords (MeSH terms) grouped into the following syntaxes: (Osteoprotegerin OR Osteoclastogenesis Inhibitory Factor OR Receptors, Tumor Necrosis Factor, Member 11b OR Tumor Necrosis Factor Receptor Superfamily, Member 11b OR FDCR-1 Protein OR FDCR 1 Protein OR OCIF Protein OR Follicular Dendritic Cell-Derived Receptor-1) AND (Bones AND Bone OR Bones AND Bone Tissue OR Bones OR Bone Tissue OR Cardiovascular Diseases).

RESULTS

Osteoprotegerin is present in various organs and binds to two ligands: nuclear factor kB (RANKL) related to the differentiation of osteoclasts, and tumor necrosis factor related to the apoptosis-inducing ligand (TRAIL). OPG inhibits the regulation effects of nuclear factor kB on inflammation and on the skeletal and vascular systems, preventing the apoptosis induced by TRAIL, being related to the preservation of bone tissue.

CONCLUSION

a deeper knowledge of the mechanisms involved in the association between OPG serum levels, bone integrity and cardiovascular disease can provide important data for future therapeutic interventions.

The effects of strength training and raloxifene on bone health in aging ovariectomized rats

The aim of this study was to investigate the effects of strength training (ST) and raloxifene (Ral), alone or in combination, on the prevention of bone loss in an aging estrogen-deficient rat model. Aging Wistar female rats were ovariectomized at 14months and allocated to four groups: (1) non-trained and treated with vehicle, NT-Veh; (2) strength training and treated with vehicle, ST-Veh; (3) non-trained and treated with raloxifene, NT-Ral; and (4) strength training and treated with raloxifene, ST-Ral. ST was performed on a ladder three times per week and Ral was administered daily by gavage (1mg/kg/day), both for 120days. Areal bone mineral density (aBMD), strength, microarchitecture, and biomarkers (osteocalcin, OCN; osteoprotegerin, OPG; and tartrate-resistant acid phosphatase, TRAP) were assessed. Immunohistochemistry was performed for runt-related transcription factor 2 (RUNX2), osterix (OSX), OCN, OPG, TRAP, and receptor activator of nuclear factor kappa-B ligand (RANKL). The rats that performed ST (ST-Veh) or were treated with Ral (NT-Ral) showed significant improvements in aBMD (p=0.001 and 0.004), bone strength (p=0.001), and bone microarchitecture, such as BV/TV (%) (p=0.001), BS/TV (mm(2)/mm(3)) (p=0.023 and 0.002), Conn.Dn (1/mm(3)) (p=0.001), Tb.N (1/mm) (p=0.012 and 0.011), Tb.Th (1/mm) (p=0.001), SMI (p=0.001 and 0.002), Tb.Sp (p=0.001), and DA (p=0.002 and 0.007); there was also a significant decrease in plasma levels of OCN (p=0.001 and 0.002) and OPG (p=0.003 and 0.014), compared with animals in the NT-Veh group. Ral, with or without ST, promoted an increased immunolabeling pattern for RUNX2 (p=0.0105 and p=0.0006) and OSX (p=0.0105), but a reduced immunolabeling pattern for TRAP (p=0.0056) and RANKL (p=0.033 and 0.004). ST increased the immunolabeling pattern for RUNX2 (p=0.0105), and association with Ral resulted in an increased immunolabeling pattern for OPG (p=0.0034) and OCN (p=0.0024). In summary, ST and Ral administration in aged, estrogen-deficient Wistar female rats is associated with a decrease in bone turnover marker plasma levels, increased activity of cells that promote osteoblastogenesis, and decreased activity of cells that promote osteoclastogenesis; these are correlated with higher aBMD, bone strength, and bone microarchitecture at the femoral neck. The results indicate that strength training and Ral are potential tools to reduce the risk of fractures at clinically relevant sites.

Anti-osteoclastogenic activity of isoliquiritigenin via inhibition of NF-κB-dependent autophagic pathway

Previous studies, including those from our laboratory, have demonstrated that the natural flavonoid isoliquiritigenin (ISL) is a promising agent for bone destructive diseases. However, the mechanisms underlying its anti-osteoclastogenic effects are still far from clear. Here, we evaluated the potential alterations of autophagy and nuclear factor-κB (NF-κB) during anti-osteoclastogenic effects by ISL in vitro and in vivo. We observed that ISL inhibited the receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis and suppressed autophagic microtubule-associated protein light chain 3 (LC3)-II and Beclin 1 accumulation. ISL treatment resulted in the interruption of several specific features for autophagy in osteoclast precursors, including acidic vesicular organelle formation, LC3-II accumulation, and appearance of autophagic vacuoles. The RANKL-stimulated expression levels of autophagy-related genes and proteins also diminished in ISL-treated osteoclast precursors. The reactivation of autophagy by rapamycin almost reversed the ISL-elicited anti-osteoclastogenic effects. Interestingly, ISL inhibited the RANKL-stimulated NF-κB expression and nuclear translocation, whereas the NF-κB inhibitor Bay 11-7082 markedly suppressed the RANKL-induced autophagic activation. Consistent with the in vitro results, the administration of ISL could attenuate osteoclastogenic cathepsin K, autophagic LC3, and NF-κB expression to protect against inflammatory calvarial bone erosion in vivo. Our findings highlight the inhibition of NF-κB-dependent autophagy as an important mechanism of ISL-mediated anti-osteoclastogenic activity.

Bone morphogenetic protein signaling in bone homeostasis

Bone morphogenetic proteins (BMPs) are cytokines belonging to the transforming growth factor-β (TGF-β) superfamily. They play multiple functions during development and tissue homeostasis, including regulation of the bone homeostasis. The BMP signaling pathway consists in a well-orchestrated manner of ligands, membrane receptors, co-receptors and intracellular mediators, that regulate the expression of genes controlling the normal functioning of the bone tissues. Interestingly, BMP signaling perturbation is associated to a variety of low and high bone mass diseases, including osteoporosis, bone fracture disorders and heterotopic ossification. Consistent with these findings, in vitro and in vivo studies have shown that BMPs have potent effects on the activity of cells regulating bone function, suggesting that manipulation of the BMP signaling pathway may be employed as a therapeutic approach to treat bone diseases. Here we review the recent advances on BMP signaling and bone homeostasis, and how this knowledge may be used towards improved diagnosis and development of novel treatment modalities. This article is part of a Special Issue entitled "Muscle Bone Interactions".

The Multiple Roles of Microrna-223 in Regulating Bone Metabolism

Bone metabolism is a lifelong process for maintaining skeletal system homeostasis, which is regulated by bone-resorbing osteoclasts and bone-forming osteoblasts. Aberrant differentiation of osteoclasts and osteoblasts leads to imbalanced bone metabolism, resulting in ossification and osteolysis diseases. MicroRNAs (miRNAs) are pivotal factors in regulating bone metabolism via post-transcriptional inhibition of target genes. Recent studies have revealed that miR-223 exerts multiple effects on bone metabolism, especially in the processes of osteoclast and osteoblasts differentiation. In this review, we highlight the roles of miR-223 during the processes of osteoclast and osteoblast differentiation, as well as the potential clinical applications of miR-223 in bone metabolism disorders.

Long-term warfarin therapy and biomarkers for osteoporosis and atherosclerosis

Background

Stroke prevention by warfarin, a vitamin K antagonist, has been an integral part in the management of atrial fibrillation. Vitamin K-dependent matrix Gla protein (MGP) has been known as a potent inhibitor of arterial calcification and osteoporosis. Therefore, we hypothesized that warfarin therapy affects bone mineral metabolism, vascular calcification, and vascular endothelial dysfunction.

Methods

We studied 42 atrial fibrillation patients at high-risk for atherosclerosis having one or more coronary risk factors. Twenty-four patients had been treated with warfarin for at least 12 months (WF group), and 18 patients without warfarin (non-WF group). Bone alkaline phosphatase (BAP) and under carboxylated osteocalcin (ucOC) and receptor activator of nuclear factor-kappa B ligand (RANKL) were measured as bone metabolism markers. Reactive hyperemia-peripheral arterial tonometry (RH-PAT) index measured by Endo-PAT2000 was used as an indicator of vascular endothelial function.

Results

There were no significant differences in patient background characteristics and other clinical indicators between the two groups. In WF group, the ucOC levels were significantly higher than those in the non-WF group (10.3 ± 0.8 vs. 3.4 ± 0.9 ng/mL; P < 0.01), similarly, the RANKL levels in the WF group were higher than those in the non-WF group (0.60 ± 0.06 vs. 0.37 ± 0.05 ng/mL; P = 0.007). Moreover, RH-PAT index was significantly lower in the WF group compared to those in the non-WF group (1.48 ± 0.11 vs. 1.88 ± 0.12; P = 0.017).

Conclusions

Long-term warfarin therapy may be associated with bone mineral loss and vascular calcification in 60–80 year old hypertensive patients.

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Stroke prevention by warfarin has been an integral part in the management of atrial fibrillation.

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Warfarin prevents the activation of vitamin K-dependent proteins, MGP and Gas-6.

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Long-term warfarin therapy increases the serum levels of ucOC and RANKL.

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Long-term warfarin therapy is associated with vascular endothelial dysfunction.

Lycorine suppresses RANKL-induced osteoclastogenesis in vitro and prevents ovariectomy-induced osteoporosis and titanium particle-induced osteolysis in vivo

Osteoclasts play an important role in diseases involving bone loss. In this study, we assessed the effect of a plant-derived natural alkaloid (lycorine, or LY) on osteoclastogenesis in vitro and in vivo. Our in vitro study showed that receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis could be inhibited by LY; this effect was due to inhibition of mitogen-activated protein kinase (MAPK) signalling via MAP kinase kinases (MKKs). The MAPK agonist anisomycin could partially rescue the inhibitory effect of LY. Furthermore, LY also played a protective role in both a murine ovariectomy (OVX)-induced osteoporosis model and a titanium particle-induced osteolysis model. These results confirmed that LY was effective in preventing osteoclast-related diseases in vivo. In conclusion, our results show that LY is effective in suppressing osteoclastogenesis and therefore could be used to treat OVX-induced osteoporosis and wear particle-induced osteolysis.

Osteoblastic NF-κB pathway is involved in 1α, 25(OH)2D3-induced osteoclast-like cells formation in vitro

1α, 25-dihydroxyvitamin D3 (1α, 25(OH)2D3) acts on the osteoblasts to enhance the expressions of receptor activator of nuclear factor κB ligand (RANKL) and macrophage-colony stimulating factor (M-CSF) and induce the formation of osteoclasts. However, the mechanism in osteoblasts by which 1α, 25(OH)2D3 promotes osteoclastogenesis has not yet been completely understood. This study aimed to select the first generation of murine osteoblasts to explore the underlying mechanism of 1α, 25(OH)2D3-induced osteoclastic formation from bone marrow mononuclear cells (BMMNCs). We discovered the activation of osteoblastic NF-κB pathway under 10(-8) mol/L 1α, 25(OH)2D3 treatment, as evidenced by the transfer of NF-κB p65 from cytoplasm to nuclei. Then, the NF-κB p65-siRNA was designed, constructed, and transfected into osteoblastic cells. Immunofluorescence assay confirmed the successfully silenced NF-κB p65 gene in osteoblasts. In the co-culture system of osteoblasts and BMMNCs with 1α, 25(OH)2D3 added, the multinucleated osteoclast-like cells containing 2-3 nuclei were observed in BMMNCs co-cultured with non-transfection osteoblasts, conversely, silencing osteoblastic NF-κB p65 resulted in failed differentiation of BMMNCs along with substantial vacuolar degeneration in cytoplasm. In addition, the expressions of RANKL and M-CSF were notably decreased in NF-κB p65-silenced osteoblasts. Taken together, our data indicated that osteoblastic NF-κB pathway was involved in 1α, 25(OH)2D3-induced osteoclast-like cells formation from BMMNCs through regulating the expression of RANKL and M-CSF. Therefore, our findings further identified the mechanism of 1α, 25(OH)2D3-induced osteoclastogenesis on the basis of prior studies.

Mitochondrial superoxide in osteocytes perturbs canalicular networks in the setting of age-related osteoporosis

Osteocytes are major bone cells that play a crucial role in maintaining the quality of and healing damage to bone tissue. The number of living osteocytes and canalicular networks declines in an age-dependent manner. However, the pathological effects of mitochondrial redox imbalances on osteocytes and bone metabolism have not been fully elucidated. We generated mice lacking mitochondrial superoxide dismutase 2 (Sod2) in osteocytes. Like an aged bone, Sod2 depletion in the osteocytes positively enhanced the production of cellular superoxide in vivo. A bone morphological analysis demonstrated that the Sod2-deficient femurs showed remarkable bone loss in an age-dependent manner. Interestingly, Sod2 loss induced markedly disorganized osteocytic canalicular networks and decreased the number of live osteocytes. Furthermore, Sod2 deficiency significantly suppressed bone formation and increased bone resorption concomitant with the upregulation of sclerostin and receptor activator of NF-κB ligand (RANKL). In vitro experiments also revealed that treatment with paraquat, a superoxide inducer in mitochondria, promoted the RANKL expression via, in part, ERK phosphorylation. These findings demonstrate that the mitochondrial superoxide induced in osteocytes by Sod2 ablation causes age-related bone loss due to the impairment of canalicular networks and bone metabolism via the deregulation of the sclerostin and RANKL expression.

Recent genetic discoveries in osteoporosis, sarcopenia and obesity

Osteoporosis is a skeletal disorder characterized by low bone mineral density (BMD) and an increased susceptibility to fractures. Evidence from genetic studies indicates that BMD, a complex quantitative trait with a normal distribution, is genetically controlled. Genome-wide association studies (GWAS) as well as studies using candidate gene approaches have identified single-nucleotide polymorphisms (SNPs) that are associated with BMD, osteoporosis and osteoporotic fractures. These SNPs have been mapped close to or within genes including those encoding WNT/β-catenin signaling proteins. Understanding the genetics of osteoporosis will help to identify novel candidates for diagnostic and therapeutic targets. Genetic factors are also important for the development of sarcopenia, which is characterized by a loss of lean body mass, and obesity, which is characterized by high fat mass. Hence, in this review, we discuss the genetic factors, identified by genetic studies, which regulate the body components related to osteoporosis, sarcopenia, and obesity.

WNT signaling in bone development and homeostasis

The balance between bone formation and bone resorption controls postnatal bone homeostasis. Research over the last decade has provided a vast amount of evidence that WNT signaling plays a pivotal role in regulating this balance. Therefore, understanding how the WNT signaling pathway regulates skeletal development and homeostasis is of great value for human skeletal health and disease.