Osteoprotegerin ligand is a cytokine that regulates osteoclast differentiation and activation

Denosumab for giant cell tumors of bone from 2010 to 2022: a bibliometric analysis

Giant cell tumors of the bone (GCTB) are considered moderately malignant bone tumors. Denosumab, as a neoadjuvant therapy, provides new possibilities for treating GCTB. However, even after multiple studies and long-term clinical trials, there are limitations in the treatment process. Research data and Medical Subject Headings terms related to denosumab and GCTB were collected from January 2010 to October 2022 using the Web of Science and MeSH ( https://meshb.nlm.nih.gov ) browsers. These data were imported into CiteSpace and VOSviewer softwares for bibliometric analysis. Overall, 445 publications on denosumab and GCTB were identified. Over the last 12 years, the growth rate of the total number of publications has remained relatively stable. The USA published the highest number of articles (83) and had the highest centrality (0.42). Amgen Inc. and Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) First Ortoped Rizzoli were identified as the most influential institutions. Many authors have made outstanding contributions to this field. Lancet Oncology had the highest journal impact factor (54.433). Local recurrence and drug dosage are current research hotspots, and future development trends will mainly focus on prognostic markers of GCTB and the development of new therapies. Further research is required to analyze denosumab's safety and efficacy and understand its local recurrence of GCTB, to identify the optimal dose. Future progress in this field will likely focus on exploring new diagnostic and recurrence markers to monitor disease progression and examine new therapeutic targets and treatment strategies.

Essentiality of Nfatc1 short isoform in osteoclast differentiation and its self-regulation

During osteoclast differentiation, the expression of the transcription factor nuclear factor of activated T cell 1 (Nfatc1) increases in an autoproliferative manner. Nfatc1 isoforms are of three sizes, and only the short isoform increases during osteoclast differentiation. Genetic ablation of the whole Nfatc1 gene demonstrated that it is essential for osteoclastogenesis; however, the specific role of the Nfatc1 short form (Nfatc1/αA) remains unknown. In this study, we engineered Nfatc1 short form-specific knockout mice and found that these mice died in utero by day 13.5. We developed a novel osteoclast culture system in which hematopoietic stem cells were cultured, proliferated, and then differentiated into osteoclasts in vitro. Using this system, we show that the Nfatc1/αA isoform is essential for osteoclastogenesis and is responsible for the expression of various osteoclast markers, the Nfatc1 short form itself, and Nfatc1 regulators.

Time of day of exercise does not affect the beneficial effect of exercise on bone structure in older female rats

Background: Circadian clock genes are expressed in bone and biomarkers of bone resorption and formation exhibit diurnal patterns in animals and humans. Disruption of the diurnal rhythms may affect the balance of bone turnover and compromise the beneficial effects of exercise on bone. Objective: This study investigated whether the time of day of exercise alters bone metabolism in a rodent model. We hypothesized that exercise during the active phase results in greater bone mass than exercise during the rest phase in older female rats. Methods: Fifty-five, female 12-month-old Sprague Dawley rats were randomly assigned to four treatment groups (n = 13-14/group). Rats were subjected to no exercise or 2 h of involuntary exercise at 9 m/min and 5 days/wk for 15 weeks using motor-driven running wheels at Zeitgeber time (ZT) 4-6 (rest phase), 12-14 (early active phase), or 22-24 (late active phase). ZT 0 is defined as light on, the start of the rest phase. A red lamp was used at minimal intensity during the active, dark phase exercise period, i.e., ZT 12-14 and 22-24. Bone structure, body composition, and bone-related cytokines in serum and gene expression in bone were measured. Data were analyzed using one-way ANOVA followed by Tukey-Kramer post hoc contrasts. Results: Exercise at different ZT did not affect body weight, fat mass, lean mass, the serum bone biomarkers, bone structural or mechanical parameters, or expression of circadian genes. Exercise pooled exercise data from different ZT were compared to the No-Exercise data (a priori contrast) increased serum IGF-1 and irisin concentrations, compared to No-Exercise. Exercise increased tibial bone volume/total volume (p = 0.01), connectivity density (p = 0.04), and decreased structural model index (p = 0.02). Exercise did not affect expression of circadian genes. Conclusion: These data indicate that exercise is beneficial to bone structure and that the time of day of exercise does not alter the beneficial effect of exercise on bone in older female rats.

Age-associated spinal stenosis in the turquoise killifish

Aging triggers spinal degeneration, including common spinal stenosis, which causes back and leg pain in older individuals, significantly impacting their quality of life. Here, we explored aging traits in turquoise killifish spines, potentially offering a model for age-linked spinal stenosis in humans. Aged turquoise killifish exhibited body shape deformation and increased vertebral collapse, which was further accelerated by spawning. High-resolution CT scans revealed suppressed cortical bone thickness and hemal arch area in vertebrae due to spawning, and osteophyte formation was observed in both aged and breeding fish populations. Scale mineralization mirrored these changes, increasing with age but being suppressed by spawning. The expression of sp7, sox9b, axin1, and wnt4a/b genes can be utilized to monitor age- and reproduction-dependent spine deformation. This study demonstrates that turquoise killifish and humans share certain phenotypes of age-related vertebral abnormalities, suggesting that turquoise killifish could serve as a potential model for studying human spinal stenosis.

RANK ligand converts the NCoR/HDAC3 co-repressor to a PGC1β- and RNA-dependent co-activator of osteoclast gene expression

The nuclear receptor co-repressor (NCoR) complex mediates transcriptional repression dependent on histone deacetylation by histone deacetylase 3 (HDAC3) as a component of the complex. Unexpectedly, we found that signaling by the receptor activator of nuclear factor κB (RANK) converts the NCoR/HDAC3 co-repressor complex to a co-activator of AP-1 and NF-κB target genes that are required for mouse osteoclast differentiation. Accordingly, the dominant function of NCoR/HDAC3 complexes in response to RANK signaling is to activate, rather than repress, gene expression. Mechanistically, RANK signaling promotes RNA-dependent interaction of the transcriptional co-activator PGC1β with the NCoR/HDAC3 complex, resulting in the activation of PGC1β and inhibition of HDAC3 activity for acetylated histone H3. Non-coding RNAs Dancr and Rnu12, which are associated with altered human bone homeostasis, promote NCoR/HDAC3 complex assembly and are necessary for RANKL-induced osteoclast differentiation in vitro. These findings may be prototypic for signal-dependent functions of NCoR in other biological contexts.

Mechanism of regulating macrophages/osteoclasts in attenuating wear particle-induced aseptic osteolysis

Joint replacement surgery is the most effective treatment for end-stage arthritis. Aseptic loosening caused by periprosthetic osteolysis is a common complication after joint replacement. Inflammation induced by wear particles derived from prosthetic biomaterials is a major cause of osteolysis. We emphasize that bone marrow-derived macrophages and their fusion-derived osteoclasts play a key role in this pathological process. Researchers have developed multiple intervention approaches to regulate macrophage/osteoclast activation. Aiming at wear particle-induced periprosthetic aseptic osteolysis, this review separately discusses the molecular mechanism of regulation of ROS formation and inflammatory response through intervention of macrophage/osteoclast RANKL-MAPKs-NF-κB pathway. These molecular mechanisms regulate osteoclast activation in different ways, but they are not isolated from each other. There is also a lot of crosstalk among the different mechanisms. In addition, other bone and joint diseases related to osteoclast activation are also briefly introduced. Therefore, we discuss these new findings in the context of existing work with a view to developing new strategies for wear particle-associated osteolysis based on the regulation of macrophages/osteoclasts.

Nuclear Factor-Kappa B Regulation of Osteoclastogenesis and Osteoblastogenesis

Maintenance of skeletal integrity requires the coordinated activity of multinucleated bone-resorbing osteoclasts and bone-forming osteoblasts. Osteoclasts form resorption lacunae on bone surfaces in response to cytokines by fusion of precursor cells. Osteoblasts are derived from mesenchymal precursors and lay down new bone in resorption lacunae during bone remodeling. Nuclear factorkappa B (NF-κB) signaling regulates osteoclast and osteoblast formation and is activated in osteoclast precursors in response to the essential osteoclastogenic cytokine, receptor activator of NF-κB ligand (RANKL), which can also control osteoblast formation through RANK-RANKL reverse signaling in osteoblast precursors. RANKL and some pro-inflammatory cytokines, including tumor necrosis factor (TNF), activate NF-κB signaling to positively regulate osteoclast formation and functions. However, these cytokines also limit osteoclast and osteoblast formation through NF-κB signaling molecules, including TNF receptor-associated factors (TRAFs). TRAF6 mediates RANKL-induced osteoclast formation through canonical NF-κB signaling. In contrast, TRAF3 limits RANKL- and TNF-induced osteoclast formation, and it restricts transforming growth factor β (TGFβ)-induced inhibition of osteoblast formation in young and adult mice. During aging, neutrophils expressing TGFβ and C-C chemokine receptor type 5 (CCR5) increase in bone marrow of mice in response to increased NF-κB-induced CC motif chemokine ligand 5 (CCL5) expression by mesenchymal progenitor cells and injection of these neutrophils into young mice decreased bone mass. TGFβ causes degradation of TRAF3, resulting in decreased glycogen synthase kinase-3β/β-catenin-mediated osteoblast formation and age-related osteoporosis in mice. The CCR5 inhibitor, maraviroc, prevented accumulation of TGFβ+/CCR5+ neutrophils in bone marrow and increased bone mass by inhibiting bone resorption and increasing bone formation in aged mice. This paper updates current understanding of how NF-κB signaling is involved in the positive and negative regulation of cytokine-mediated osteoclast and osteoblast formation and activation with a focus on the role of TRAF3 signaling, which can be targeted therapeutically to enhance bone mass.

Dihydrotanshinone I attenuates estrogen-deficiency bone loss through RANKL-stimulated NF-κB, ERK and NFATc1 signaling pathways

Postmenopausal osteoporosis, a chronic condition that predominantly affects postmenopausal women, presents a significant impediment to their overall well-being. The condition arises from estrogen deficiency, leading to enhanced osteoclast activity. Salvia miltiorrhiza, a well-established Chinese herbal medicine with a history of clinical use for osteoporosis treatment, contains diverse active constituents that have shown inhibitory effects on osteoclast formation and bone loss. Dihydrotanshinone I (DTI), a phenanthrenonequinone compound derived from the root of Salvia miltiorrhiza, has been identified as a potential therapeutic agent, although its mechanism of action on osteoclasts remains elusive. In this study, we aimed to elucidate the inhibitory potential of DTI on RANKL-induced osteoclastogenesis. We observed the ability of DTI to effectively impede the expression of key osteoclast-specific genes and proteins, as assessed by Real-time PCR and Western Blotting analyses. Mechanistically, DTI exerted its inhibitory effects on osteoclast formation by modulating critical signaling pathways including NF-κB, ERK, and calcium ion signaling. Notably, DTI intervention disrupted the nuclear translocation and subsequent transcriptional activity of the NFATc1, thus providing mechanistic insights into its inhibitory role in osteoclastogenesis. To further assess the therapeutic potential of DTI, we employed an ovariectomized osteoporosis animal model to examine its impact on bone loss. Encouragingly, DTI demonstrated efficacy in mitigating bone loss induced by estrogen deficiency. In conclusion, our investigation elucidates the ability of DTI to regulate multiple signaling pathways activated by RANKL, leading to the inhibition of osteoclast formation and prevention of estrogen-deficiency osteoporosis. Consequently, DTI emerges as a promising candidate for the treatment of osteoporosis.

The RANK-RANKL-OPG System: A Multifaceted Regulator of Homeostasis, Immunity, and Cancer

The RANK-RANKL-OPG system is a complex signaling pathway that plays a critical role in bone metabolism, mammary epithelial cell development, immune function, and cancer. RANKL is a ligand that binds to RANK, a receptor expressed on osteoclasts, dendritic cells, T cells, and other cells. RANKL signaling promotes osteoclast differentiation and activation, which leads to bone resorption. OPG is a decoy receptor that binds to RANKL and inhibits its signaling. In cancer cells, RANKL expression is often increased, which can lead to increased bone resorption and the development of bone metastases. RANKL-neutralizing antibodies, such as denosumab, have been shown to be effective in the treatment of skeletal-related events, including osteoporosis or bone metastases, and cancer. This review will provide a comprehensive overview of the functions of the RANK-RANKL-OPG system in bone metabolism, mammary epithelial cells, immune function, and cancer, together with the potential therapeutic implications of the RANK-RANKL pathway for cancer management.

Phase I, Randomized, Placebo-Controlled, Dose-Escalation Study of GB223, a Fully-Humanized Monoclonal Antibody to RANKL, in Healthy Chinese Adults

BACKGROUND

GB223 is a novel, fully-humanized monoclonal antibody against the receptor activator of nuclear factor-kappa B ligand (RANKL). In this phase I study, the safety, tolerability, pharmacokinetics, pharmacodynamics, and immunogenicity of GB223 were investigated.

PATIENTS AND METHODS

This was a randomized, double-blinded, placebo-controlled, single-dose escalation study conducted in 44 healthy Chinese adults. Participants were randomly assigned to receive a single subcutaneous injection dose of 7, 21, 63, 119, or 140 mg of GB223 (n = 34) or placebo (n = 10) and were followed up for 140-252 days.

RESULTS

The results of noncompartmental analysis showed that GB223 was slowly absorbed after dosing, with a time to reach maximum concentration (Tmax) ranging from 5 to 11 days. Serum GB223 concentrations decreased slowly, with a long half-life ranging from 7.91 to 19.60 days. A two-compartment Michaelis-Menten model was found to best describe the pharmacokinetics of GB223, and the absorption rate of GB223 differed between males (0.0146 h-1) and females (0.0081 h-1). Serum C-terminal telopeptide of type I collagen decreased significantly postdose, and the inhibition lasted 42-168 days. No deaths or drug-related serious adverse events occurred. The most frequent adverse events were blood parathyroid hormone increased (94.1%), blood phosphorus decreased (67.6%) and blood calcium decreased (58.8%). In the GB223 group, 44.1% (15/34) of subjects were antidrug antibody positive after dosing.

CONCLUSION

In this study, we demonstrated for the first time that a single subcutaneous injection of GB223, from 7 to 140 mg, is safe and well tolerated in healthy Chinese subjects. GB223 has a nonlinear pharmacokinetic profile, and sex was a potential covariate that may affect the absorption rate of GB223.

CLINICAL TRIAL REGISTRATION

NCT04178044 and ChiCTR1800020338.

Multiple Factors Involved in Bone Damage Caused by Chikungunya Virus Infection

Chronic cases of chikungunya fever represent a public health problem in countries where the virus circulates. The disease is prolonged, in some cases, for years, resulting in disabling pain and bone erosion among other bone and joint problems. As time progresses, tissue damage is persistent, although the virus has not been found in blood or joints. The pathogenesis of these conditions has not been fully explained. Additionally, it has been considered that there are multiple factors that might intervene in the viral pathogenesis of the different conditions that develop. Other mechanisms involved in osteoarthritic diseases of non-viral origin could help explain how damage is produced in chronic conditions. The aim of this review is to analyze the molecular and cellular factors that could be involved in the tissue damage generated by different infectious conditions of the chikungunya virus.

Case Report: Unresectable pulmonary metastases of a giant cell tumor of bone treated with denosumab: a case report and review of literature

Giant cell tumors of bone (GCTB) sometimes metastasize to distant organs. In this case report, we present pulmonary metastases of GCTB mimicking malignancies. A 49-year-old man underwent two surgical treatments for a GCTB of the right proximal radius. At the time of the second surgery, no lesions were observed on chest radiography. Three years after surgery, the patient presented with cough and dyspnea, and chest radiography and computed tomography (CT) revealed multiple lung nodules. Positron emission tomography/CT revealed a high accumulation of 18F-fluoro-2-deoxy-D-glucose (18F-FDG) in multiple lesions. Based on the rapid growth and accumulation of 18F-FDG, a metastatic malignant tumor was suspected. CT-guided needle biopsy was performed, and the histology showed proliferation of spindle cells and multinuclear giant cells without malignant changes. Denosumab was administered because multiple lung lesions were unresectable. One month after denosumab treatment, CT showed marked shrinkage of the lesions, and the symptoms significantly improved. Eighteen months after the initial treatment with denosumab, the patient had no symptoms or tumor growth. Although its long-term efficacy and safety remain unclear, denosumab may be a treatment option for patients with unresectable pulmonary GCTB.

Different concentrations of fetal bovine serum affect cytokine modulation in Lipopolysaccharide-activated apical papilla cells in vitro

BACKGROUND

Fetal bovine serum (FBS) is the most used supplement in culture media; however, it may interfere with in vitro assays via effects on cell proliferation and cytokine production. The ideal FBS concentration for assays using apical papilla cells (APCs) remains unknown. Therefore, this study aimed to evaluate the effects of FBS on APC activation, cell viability/proliferation, and cytokine production.

METHODOLOGY

Human APCs were cultured, plated, and maintained in media containing increasing concentrations of FBS for 24 h, 48 h, 72 h, 7 days, and 14 days in the presence of Lipopolysaccharide (LPS - 1 µg/mL). At each time point, the cells were subjected to the MTT assay. The cytokines transforming growth factor (TGF)-β1, osteoprotegerin (OPG), and interleukin (IL)-6, along with the chemokine CCL2, were quantified using the enzyme-linked immunosorbent assay at the 24-h time-point. Statistical analysis was performed using two-way analysis of variance (ANOVA) followed by Tukey's post-hoc test (p<0.05).

RESULTS

In general, APCs exhibited increasing metabolic activity in an FBS concentration-dependent fashion, regardless of the presence of LPS. In contrast, FBS interfered with the production of all the cytokines evaluated in this study, affecting the response induced by the presence of LPS.

CONCLUSION

FBS increased APC metabolism in a concentration-dependent manner and differentially affected the production of TGF-β1, OPG, IL-6, and CCL2 by APCs in vitro.

Structure-Based Discovery of Receptor Activator of Nuclear Factor-κB Ligand (RANKL)-Induced Osteoclastogenesis Inhibitors

Receptor activator of nuclear factor-κB ligand (RANKL) has been actively pursued as a therapeutic target for osteoporosis, given that RANKL is the master mediator of bone resorption as it promotes osteoclast differentiation, activity and survival. We employed a structure-based virtual screening approach comprising two stages of experimental evaluation and identified 11 commercially available compounds that displayed dose-dependent inhibition of osteoclastogenesis. Their inhibitory effects were quantified through TRAP activity at the low micromolar range (IC₅₀ < 5 μΜ), but more importantly, 3 compounds displayed very low toxicity (LC₅₀ > 100 μΜ). We also assessed the potential of an N-(1-aryl-1H-indol-5-yl)aryl-sulfonamide scaffold that was based on the structure of a hit compound, through synthesis of 30 derivatives. Their evaluation revealed 4 additional hits that inhibited osteoclastogenesis at low micromolar concentrations; however, cellular toxicity concerns preclude their further development. Taken together with the structure-activity relationships provided by the hit compounds, our study revealed potent inhibitors of RANKL-induced osteoclastogenesis of high therapeutic index, which bear diverse scaffolds that can be employed in hit-to-lead optimization for the development of therapeutics against osteolytic diseases.

Pro- and anti-inflammatory cytokines and osteoclastogenesis-related factors in peri-implant diseases: systematic review and meta-analysis

BACKGROUND

Pro- and anti-inflammatory cytokines are acknowledged, during inflammatory bone destruction, as key regulators of osteoclast and osteoblast differentiation and activity. However, evidence regarding the exact role of pro- and anti-inflammatory cytokines and osteoclastogenesis-related factors in peri-implant diseases is unclear. We aimed to execute a systematic review and meta-analysis about the pro- and anti-inflammatory cytokines and osteoclastogenesis-related factors levels in peri-implant diseases.

METHODS

The focused question was elaborated to summarize the levels of pro-and anti-inflammatory cytokines and osteoclastogenesis-related factors in tissue samples (mRNA) and biofluids (protein levels) of patients with/without peri-implant diseases. Electronic searches of the PubMed, Cochrane Controlled Trials Registry, Web of Science, EMBASE, Scopus and Google scholar databases were conducted for publications up to March 2023. Meta-analysis evaluating the mediator´s levels (protein levels by ELISA) in peri-implant crevicular fluid (PICF) were made. The effect size was estimated and reported as the mean difference. The 95% confidence interval was estimated for each mediator, and the pooled effect was determined significant if two-sided p-values < 0.05 were obtained.

RESULTS

Twenty-two publications were included in the systematic review (qualitative analysis), with nine of these subjected to meta-analyses (quantitative analysis). In the qualitative analysis, higher pro-inflammatory cytokines [Interleukin (IL)-1β, IL-6] and pro-osteoclastogenic mediator [Receptor Activator of Nuclear Factor-Kappa B ligand (RANKL)] levels were observed in PICF of individuals with peri-implant diseases in comparison to healthy individuals. Higher RANKL/osteoprotegerin (OPG) ratios were observed in PICF from individuals with peri-implant diseases in comparison to healthy individuals. Meta-analysis showed higher RANKL levels in diseased groups compared to controls.

CONCLUSIONS

The results showed that the levels of IL-1β, IL-6, IL-10, and RANKL/OPG are not balanced in peri-implant disease, suggesting that these mediators are involved in the host osteo-immunoinflammatory response related to peri-implantitis.

Macrophages-bone marrow mesenchymal stem cells crosstalk in bone healing

Bone healing is associated with many orthopedic conditions, including fractures and osteonecrosis, arthritis, metabolic bone disease, tumors and periprosthetic particle-associated osteolysis. How to effectively promote bone healing has become a keen topic for researchers. The role of macrophages and bone marrow mesenchymal stem cells (BMSCs) in bone healing has gradually come to light with the development of the concept of osteoimmunity. Their interaction regulates the balance between inflammation and regeneration, and when the inflammatory response is over-excited, attenuated, or disturbed, it results in the failure of bone healing. Therefore, an in-depth understanding of the function of macrophages and bone marrow mesenchymal stem cells in bone regeneration and the relationship between the two could provide new directions to promote bone healing. This paper reviews the role of macrophages and bone marrow mesenchymal stem cells in bone healing and the mechanism and significance of their interaction. Several new therapeutic ideas for regulating the inflammatory response in bone healing by targeting macrophages and bone marrow mesenchymal stem cells crosstalk are also discussed.

Integrating the autoimmune connective tissue diseases for the medical student: A classification proposal based on pathogenesis and clinical phenotype

It is hard for medical students to recognize and understand the clinical presentation of systemic connective tissue diseases (SCTDs). In this study, we aimed to review the immune mechanisms of the main SCTDs and to propose a classification system focused on the student and based on each immune dysfunction's clinical phenotype. The search involved the MEDLINE database and included the terms "systemic lupus erythematosus," "antiphospholipid syndrome," "inflammatory myopathies," "rheumatoid arthritis," "Sjögren's syndrome" or "systemic sclerosis" and "pathogenesis," and "immunology" or "mechanism of disease." Systemic lupus erythematosus (SLE) is a prototypic immune-complex disease with a tendency toward vascular injury. Antiphospholipid syndrome (APS) is a diffuse immune-mediated thrombotic vasculopathy. In inflammatory myopathies (IMs), muscle inflammation leading to muscle weakness is the cardinal manifestation. Rheumatoid arthritis (RA) is a unique form of erosive and destructive polyarthritis. Sjögren's syndrome (SS) causes sicca symptoms due to infiltration of the exocrine glands. Disseminated fibrosis in systemic sclerosis (SSc) is caused by vascular injury with excessive fibroblast activation. After the review, we created a focus group involving all the authors to group the diseases according to their pathogenesis and clinical phenotype. Our group agreed that SCTDs can be divided in 3 groups based on the preferential clinical presentation and immune dysfunction: 1) vasculopathic features (SLE and APS), 2) tissue inflammation (IMs, RA, and SS), and 3) tissue fibrosis (SSc). In synthesis, we suggest that clustering SCTDs in groups based on clinical phenotype and presumptive immune dysfunction instead of ordering autoantibodies randomly can help students understand the diseases.

Tracking Targets of Dynamic Super-Enhancers in Vitro to Better Characterize Osteoclastogenesis and to Evaluate the Effect of Diuron on the Maturation of Human Bone Cells

BACKGROUND

Osteoclasts are major actors in the maintenance of bone homeostasis. The full functional maturation of osteoclasts from monocyte lineage cells is essential for the degradation of old/damaged bone matrix. Diuron is one of the most frequently encountered herbicides, particularly in water sources. However, despite a reported delayed ossification in vivo, its impact on bone cells remains largely unknown.

OBJECTIVES

The objectives of this study were to first better characterize osteoclastogenesis by identifying genes that drive the differentiation of CD14+ monocyte progenitors into osteoclasts and to evaluate the toxicity of diuron on osteoblastic and osteoclastic differentiation in vitro.

METHODS

We performed chromatin immunoprecipitation (ChIP) against H3K27ac followed by ChIP-sequencing (ChIP-Seq) and RNA-sequencing (RNA-Seq) at different stages of differentiation of CD14+ monocytes into active osteoclasts. Differentially activated super-enhancers and their potential target genes were identified. Then to evaluate the toxicity of diuron on osteoblasts and osteoclasts, we performed RNA-Seq and functional tests during in vitro osteoblastic and osteoclastic differentiation by exposing cells to different concentrations of diuron.

RESULTS

The combinatorial study of the epigenetic and transcriptional remodeling taking place during differentiation has revealed a very dynamic epigenetic profile that supports the expression of genes vital for osteoclast differentiation and function. In total, we identified 122 genes induced by dynamic super-enhancers at late days. Our data suggest that high concentration of diuron (50μM) affects viability of mesenchymal stem cells (MSCs) in vitro associated with a decrease of bone mineralization. At a lower concentration (1μM), an inhibitory effect was observed in vitro on the number of osteoclasts derived from CD14+ monocytes without affecting cell viability. Among the diuron-affected genes, our analysis suggests a significant enrichment of genes targeted by pro-differentiation super-enhancers, with an odds ratio of 5.12 (ρ=2.59×10-5).

DISCUSSION

Exposure to high concentrations of diuron decreased the viability of MSCs and could therefore affect osteoblastic differentiation and bone mineralization. This pesticide also disrupted osteoclasts maturation by impairing the expression of cell-identity determining genes. Indeed, at sublethal concentrations, differences in the expression of these key genes were mild during the course of in vitro osteoclast differentiation. Taken together our results suggest that high exposure levels of diuron could have an effect on bone homeostasis. https://doi.org/10.1289/EHP11690.

Comparative Analysis of TNF-alpha, TNF-R1, and TNF-R2 in Patients with Low-impact Fractures Due to Osteoporosis

Objective  To analyze the serum levels of TNF-alpha and its TNF-R1 and TNF-R2 receptors in the blood of patients with low-impact fractures due to osteoporosis, comparing between genders and with healthy patients. Methods  The present study was conducted with a blood sample of 62 patients, divided into patients with osteoporosis and healthy patients. The results were obtained using the ELISA method. Cytokine concentrations were determined based on the absorbance values obtained. Results  Serum TNF-alpha levels were undetectable in female patients, while in males they were found only in one patient, with no significant difference. Similar results were found in the analyses of TNF-R1 and TNF-R2 levels, a significant increase in levels of TNF-alpha receptors in the groups of patients with osteoporosis compared with the control group in both sexes. There was no significant difference between the sexes in the dosage of both receptors within the group with osteoporosis. There was also a positive and significant correlation in the levels of TNF-R1 and TNF-R2 only in women. Conclusion The significant increase in TNF-R1 and TNF-R2 levels in women with osteoporosis suggest that the release and expression of these receptors may be contributing differently to the development of osteoporosis in men and women.

Denosumab use in osteogenesis imperfecta: an update on therapeutic approaches

Osteogenesis imperfecta (OI) is an inherited skeletal disorder that leads to bone fragility and multiple fractures. Given advances in the genetic understanding of existing phenotypes and newly discovered mutations, therapeutic management of OI has become challenging. Denosumab, a monoclonal antibody that inhibits the interaction between the receptor activator of nuclear factor kappa B ligand (RANKL) and its receptor RANK, has been approved to treat postmenopausal osteoporosis and emerged as an important therapy for malignancies and other skeletal disorders, including pediatric skeletal conditions such as OI. This review summarizes information about denosumab therapy in OI by exploring its mechanisms of action, main indications, and safety and efficacy. Several case reports and small series have been published about the short-term use of denosumab in children with OI. Denosumab was considered a strong drug candidate for OI patients with bone fragility and a high risk of fracture, particularly for patients with the bisphosphonate (BP)-unresponsive OI-VI subtype. The evidence for denosumab's effects in children with OI indicates that it effectively improves bone mineral density but not fracture rates. A decrease in bone resorption markers was observed after each treatment. Safety was assessed by tracking the effects on calcium homeostasis and reporting side effects. No severe adverse effects were reported. Hypercalciuria and moderate hypercalcemia were reported, suggesting that BPs be used to prevent the bone rebound effect. In other words, denosumab can be used as a targeted intervention in children with OI. The posology and administration protocol require more investigation to achieve secure efficiency.

Denosumab treatment and infection risks in patients with osteoporosis: propensity score matching analysis of a national-wide population-based cohort study

Introduction

Denosumab demonstrates efficacy in reducing the incidence of hip, vertebral, and nonvertebral fractures in postmenopausal women with osteoporosis. We present a population-based national cohort study to evaluate the infection risks in patients with osteoporosis after long-term denosumab therapy.

Methods

We used the Taiwan National Health Insurance Research Database (NHIRD) to identify patients with osteoporosis. The case cohort comprised patients treated with denosumab. Propensity score (PS) matching was used to select denosumab nonusers for the control cohort. The study period was between August 2011 and December 2017. Our study comprised 30,106 pairs of case and control patients.

Results

Patients receiving denosumab therapy had high risks of the following infections: pneumonia and influenza (adjusted hazard ratio [aHR]: 1.33; 95% confidence interval [CI]: 1.27 -1.39), urinary tract infection (aHR: 1.36; 95% CI:1.32 -1.40), tuberculosis (aHR: 1.60; 95% CI: 1.36 -1.87), fungal infection (aHR: 1.67; 95% CI:1.46 -1.90), candidiasis (aHR: 1.68; 95% CI: 1.47 -1.93), herpes zoster infection (aHR: 1.27; 95% CI: 1.19 -1.35), sepsis (aHR: 1.54; 95% CI:1.43 -1.66), and death (aHR: 1.26; 95% CI: 1.20 -1.32). However, the longer the duration of denosumab treatment, the lower the risk patients had of developing infections.

Discussion

Denosumab therapy is associated with a higher infection risk at the early periods of treatment. Nevertheless, the risk attenuates significantly after the 2nd year of therapy. Clinicians should closely monitor infection status in patients with osteoporosis during the initial stages of denosumab therapy.

Biomarkers of aging

Aging biomarkers are a combination of biological parameters to (i) assess age-related changes, (ii) track the physiological aging process, and (iii) predict the transition into a pathological status. Although a broad spectrum of aging biomarkers has been developed, their potential uses and limitations remain poorly characterized. An immediate goal of biomarkers is to help us answer the following three fundamental questions in aging research: How old are we? Why do we get old? And how can we age slower? This review aims to address this need. Here, we summarize our current knowledge of biomarkers developed for cellular, organ, and organismal levels of aging, comprising six pillars: physiological characteristics, medical imaging, histological features, cellular alterations, molecular changes, and secretory factors. To fulfill all these requisites, we propose that aging biomarkers should qualify for being specific, systemic, and clinically relevant.

Functional Role of Phospholipase D in Bone Metabolism

Phospholipase D (PLD) proteins are major enzymes that regulate various cellular functions, such as cell growth, cell migration, membrane trafficking, and cytoskeletal dynamics. As they are responsible for such important biological functions, PLD proteins have been considered promising therapeutic targets for various diseases, including cancer and vascular and neurological diseases. Intriguingly, emerging evidence indicates that PLD1 and PLD2, 2 major mammalian PLD isoenzymes, are the key regulators of bone remodeling; this suggests that these isozymes could be used as potential therapeutic targets for bone diseases, such as osteoporosis and rheumatoid arthritis. PLD1 or PLD2 deficiency in mice can lead to decreased bone mass and dysregulated bone homeostasis. Although both mutant mice exhibit similar skeletal phenotypes, PLD1 and PLD2 play distinct and nonredundant roles in bone cell function. This review summarizes the physiological roles of PLD1 and PLD2 in bone metabolism, focusing on recent findings of the biological functions and action mechanisms of PLD1 and PLD2 in bone cells.

The anaphylatoxin C5a: Structure, function, signaling, physiology, disease, and therapeutics

The complement system is one of the oldest known tightly regulated host defense systems evolved for efficiently functioning cell-based immune systems and antibodies. Essentially, the complement system acts as a pivot between the innate and adaptive arms of the immune system. The complement system collectively represents a cocktail of ∼50 cell-bound/soluble glycoproteins directly involved in controlling infection and inflammation. Activation of the complement cascade generates complement fragments like C3a, C4a, and C5a as anaphylatoxins. C5a is the most potent proinflammatory anaphylatoxin, which is involved in inflammatory signaling in a myriad of tissues. This review provides a comprehensive overview of human C5a in the context of its structure and signaling under several pathophysiological conditions, including the current and future therapeutic applications targeting C5a.

Molecular events in the jaw vascular unit: A traditional review of the mechanisms involved in inflammatory jaw bone diseases

Inflammatory jaw bone diseases are common in stomatology, including periodontitis, peri-implantitis, medication-related osteonecrosis of the jaw, radiation osteomyelitis of the jaw, age-related osteoporosis, and other specific infections. These diseases may lead to tooth loss and maxillofacial deformities, severely affecting patients' quality of life. Over the years, the reconstruction of jaw bone deficiency caused by inflammatory diseases has emerged as a medical and socioeconomic challenge. Therefore, exploring the pathogenesis of inflammatory diseases associated with jaw bones is crucial for improving prognosis and developing new targeted therapies. Accumulating evidence indicates that the integrated bone formation and dysfunction arise from complex interactions among a network of multiple cell types, including osteoblast-associated cells, immune cells, blood vessels, and lymphatic vessels. However, the role of these different cells in the inflammatory process and the 'rules' with which they interact are still not fully understood. Although many investigations have focused on specific pathological processes and molecular events in inflammatory jaw diseases, few articles offer a perspective of integration. Here, we review the changes and mechanisms of various cell types in inflammatory jaw diseases, with the hope of providing insights to drive future research in this field.

An inducible explant model of osteoclast-osteoprogenitor coordination in exacerbated osteoclastogenesis

Elucidating a basic blueprint of osteoclast-osteoblast coordination in skeletal remodeling and understanding how this coordination breaks down with age and disease is essential for addressing the growing skeletal health problem in our aging population. The paucity of simple, activatable, biologically relevant models of osteoclast-osteoblast coordination has hindered our understanding of how skeletal remolding is regulated. Here, we describe an inducible ex vivo model of osteoclast-osteoblast progenitor coordination. Induction activates the release of osteoclastogenic factors from osteoprogenitors, which elicits the differentiation and fusion of neighboring preosteoclasts. In turn, multinucleated osteoclasts release soluble coupling factors, RANK⁺ extracellular vesicles and promote osteoprogenitor proliferation, recapitulating aspects of perturbed coordination in diseases underpinned by excessive osteoclast formation. We expect this model to expedite the investigation of cell-cell fusion, osteoclast-osteoblast progenitor coordination, and extracellular vesicle signaling during bone remodeling and offer a powerful tool for evaluating signaling cascades and novel therapeutic interventions in osteoclast-linked skeletal disease.

Histochemical assessment of osteoclast-like giant cells in Rankl-/- mice

OBJECTIVES

We examined mice with gene deletion of Receptor activator of nuclear factor-κB (Rank) ligand (Rankl) to histologically clarify whether they contained progenitor cells committed to osteoclastic differentiation up to the stage requiring RANK/RANKL signaling.

METHODS

The tibiae and femora of ten-week-old male wild-type, c-fos^-/-, and Rankl^-/- mice were used for immunohistochemistry and transmission electron microscopy (TEM).

RESULTS

In Rankl^-/- mice, we observed osteoclast-like giant cells, albeit in low numbers, with single or two nuclei, engulfing the mineralized extracellular matrix. TEM revealed that these giant cells contained large numbers of mitochondria, vesicles/vacuoles, and clear zone-like structures but no ruffled borders. They often engulfed fragmented bony/cartilaginous components of the extracellular matrix that had been degraded. Additionally, osteoclast-like giant cells exhibited immunoreactivity for vacuolar H⁺-ATPase, galectin-3, and siglec-15 but not for tartrate-resistant acid phosphatase, cathepsin K, or MMP-9, all of which are classical hallmarks of osteoclasts. Furthermore, osteoclast-like giant cells were ephrinB2-positive as they were near EphB4-positive osteoblasts that are also positive for alkaline phosphatase and Runx2 in Rankl^-/- mice. Unlike Rankl^-/- mice, c-fos^-/- mice lacking osteoclast progenitors and mature osteoclasts had no ephrinB2-positive osteoclast-like cells or alkaline phosphatase-positive/Runx2-reactive osteoblasts. This suggests that similar to authentic osteoclasts, osteoclast-like giant cells might have the potential to activate osteoblasts in Rankl^-/- mice.

CONCLUSIONS

It seems plausible that osteoclast-like giant cells may have acquired some osteoclastic traits and the ability to resorb mineralized matrices even when the absence of RANK/RANKL signaling halted the osteoclastic differentiation cascade.

Histochemical assessment on osteoclasts in long bones of toll-like receptor 2 (TLR2) deficient mice

OBJECTIVE

Toll-like receptor 2 (TLR2), recognizes a wide variety of pathogen-associated molecular patterns such as lipopolysaccharides, peptidoglycans, and lipopeptides, and is generally believed to be present in monocytes, macrophages, dendritic cells, and vascular endothelial cells. However, no histological examination of osteoclasts, which differentiate from precursors common to macrophages/monocytes, has been performed in a non-infected state of TLR2 deficiency. The objective of this study was to examine the histological properties and function of osteoclasts in the long bones of 8-week-old male TLR2 deficient (TLR2^-/-) mice to gain insight into TLR2 function in biological circumstances without microbial infection.

METHODS

Eight-week-old male wild-type and TLR2^-/- mice were fixed with paraformaldehyde solution, and their tibiae and femora were used for micro-CT analysis, immunohistochemistry, transmission electron microscopy, and real-time PCR analysis.

RESULTS

TLR2^-/- tibiae and femora exhibited increased bone volume of metaphyseal trabeculae and elevated numbers of TRAP-positive osteoclasts. However, the number of multinucleated TRAP-positive osteoclasts was reduced, whereas mononuclear TRAP-positive cells increased, despite the high expression levels of Dc-Stamp and Oc-Stamp. Although TRAP-positive multinucleated and mononuclear osteoclasts showed the immunoreactivity and elevated expression of RANK and siglec-15, they revealed weak cathepsin K-positivity and less incorporation of the mineralized bone matrix, and often missing ruffled borders. It seemed likely that, despite the increased numbers, TLR2^-/- osteoclasts reduced cell fusion and bone resorption activity.

CONCLUSION

It seems likely that even without bacterial infection, TLR2 might participate in cell fusion and subsequent bone resorption of osteoclasts.

Abnormal kynurenine level contributes to the pathological bone features of ankylosing spondylitis

OBJECTIVE

Ankylosing spondylitis (AS) exhibits paradoxical bone features typically characterized by new bone formation and systemic bone loss. Although abnormal kynurenine (Kyn), a tryptophan metabolite, has been closely linked to the disease activity of AS, the distinct role of its pathological bone features remains unknown.

METHODS

Kynurenine sera level was collected from healthy control (HC; n = 22) and AS (n = 87) patients and measured by ELISA. In the AS group, we analyzed and compared the Kyn level based on the modified stoke ankylosing spondylitis spinal score (mSASSS), MMP13, and OCN. Under osteoblast differentiation, the treatment with Kyn in AS-osteoprogenitors conducted cell proliferation, alkaline phosphatase activity, bone mineralization-related alizarin red s (ARS), von kossa (VON), hydroxyapatite (HA) staining, and mRNA expression markers (ALP, RUNX2, OCN, and OPG) for bone formation. TRAP and F-actin staining was used for osteoclast formation of mouse osteoclast precursors.

RESULTS

Kyn sera level was significantly elevated in the AS group compared to the HC. In addition, Kyn sera level was correlated with mSASSS (r = 0.03888, p = 0.067), MMP13 (r = 0.0327, p = 0.093), and OCN (r = 0.0436, p = 0.052). During osteoblast differentiation, treatment with Kyn exhibited no difference in cell proliferation and alkaline phosphate (ALP) activity for bone matrix maturation but promoted ARS, VON, and HA staining for bone mineralization. Interestingly, osteoprotegerin (OPG) and OCN expressions of AS-osteoprogenitors were augmented in the Kyn treatment during differentiation. In growth medium, Kyn treatment of AS-osteoprogenitors resulted in induction of OPG mRNA, protein expression, and Kyn-response genes (AhRR, CYP1b1, and TIPARP). Secreted OPG proteins were observed in the supernatant of AS-osteoprogenitors treated with Kyn. Notably, the supernatant of Kyn-treated AS-osteoprogenitors interrupted the RANKL-mediated osteoclastogenesis of mouse osteoclast precursor such as TRAP-positive osteoclast formation, NFATc1 expression, and osteoclast differentiation markers.

CONCLUSION

Our results revealed that elevated Kyn level increased the bone mineralization of osteoblast differentiation in AS and decreased RANKL-mediated osteoclast differentiation by inducing OPG expression. Out study have implication for potential coupling factors linking osteoclast and osteoblast where abnormal Kyn level could be involved in pathological bone features of AS.

The STING inhibitor C-176 attenuates osteoclast-related osteolytic diseases by inhibiting osteoclast differentiation

Inflammatory osteolysis occurs primarily in the context of osteoarthritis, aseptic inflammation, prosthesis loosening, and other conditions. An excessive immune inflammatory response causes excessive activation of osteoclasts, leading to bone loss and bone destruction. The signaling protein stimulator of interferon gene (STING) can regulate the immune response of osteoclasts. C-176 is a furan derivative that can inhibit activation of the STING pathway and exert anti-inflammatory effects. The effect of C-176 on osteoclast differentiation is not yet clear. In this study, we found that C-176 could inhibit STING activation in osteoclast precursor cells and inhibit osteoclast activation induced by nuclear factor κB ligand receptor activator in a dose-dependent manner. After treatment with C-176, the expression of the osteoclast differentiation marker genes nuclear factor of activated T-cells c1(NFATc1), cathepsin K, calcitonin receptor, and V-ATPase a3 decreased. In addition, C-176 reduced actin loop formation and bone resorption capacity. The WB results showed that C-176 downregulated the expression of the osteoclast marker protein NFATc1 and inhibited activation of the STING-mediated NF-κB pathway. We also found that C-176 could inhibit the phosphorylation of mitogen-activated protein kinase signaling pathway factors induced by RANKL. Moreover, we verified that C-176 could reduce LPS-induced bone absorption in mice, reduce joint destruction in knee arthritis induced by meniscal instability, and protect against cartilage matrix loss in ankle arthritis induced by collagen immunity. In summary, our findings demonstrated that C-176 could inhibit the formation and activation of osteoclasts and could be used as a potential therapeutic agent for inflammatory osteolytic diseases.

Effects of anti-RANKL antibodies administered to pregnant mice on bone and tooth development in neonates

OBJECTIVES

This study examined how the anti-bone resorptive agent denosumab, which comprises anti-receptor activator of nuclear factor kappa B ligand (anti-RANKL) monoclonal antibodies, administered during pregnancy affected neonatal development. Anti-RANKL antibodies, which are known to bind to mouse RANKL and inhibit osteoclast formation, were administered to pregnant mice. Following this, the survival, growth, bone mineralization, and tooth development of their neonates were analyzed.

METHODS

Anti-RANKL antibodies (5 mg/kg) were injected into pregnant mice on day 17 of gestation. After parturition, their neonatal offspring underwent microcomputed tomography at 24 h and at 2, 4, and 6 weeks after birth. Three-dimensional bone and teeth images were subjected to histological analysis.

RESULTS

Approximately 70% of the neonatal mice born to mice who received anti-RANKL antibodies died within 6 weeks after birth. These mice had a significantly lower body weight and significantly higher bone mass compared with the control group. Furthermore, delayed tooth eruption and abnormal tooth morphology (eruption length, enamel surface, and cusps) were observed. Conversely, while the tooth germ shape and mothers against decapentaplegic homolog 1/5/8 expression remained unchanged at 24 h after birth in the neonatal mice born to mice that received anti-RANKL antibodies, osteoclasts were not formed.

CONCLUSIONS

These results suggest that anti-RANKL antibodies administered to mice in the late stage of pregnancy results in adverse events in their neonatal offspring. Thus, it is speculated that administering denosumab to pregnant humans will affect fetal development and growth after birth.

New Insights into the Role of Synovial Fibroblasts Leading to Joint Destruction in Rheumatoid Arthritis

Rheumatoid arthritis (RA), one of the most common autoimmune diseases, is characterized by multiple-joint synovitis with subsequent destruction of bone and cartilage. The excessive autoimmune responses cause an imbalance in bone metabolism, promoting bone resorption and inhibiting bone formation. Preliminary studies have revealed that receptor activator of NF-κB ligand (RANKL)-mediated osteoclast induction is an important component of bone destruction in RA. Synovial fibroblasts are the crucial producers of RANKL in the RA synovium; novel analytical techniques, primarily, single-cell RNA sequencing, have confirmed that synovial fibroblasts include heterogeneous subsets of both pro-inflammatory and tissue-destructive cell types. The heterogeneity of immune cells in the RA synovium and the interaction of synovial fibroblasts with immune cells have recently received considerable attention. The current review focused on the latest findings regarding the crosstalk between synovial fibroblasts and immune cells, and the pivotal role played by synovial fibroblasts in joint destruction in RA.

Osteoclastogenesis of human peripheral blood, bone marrow, and cord blood monocytes

Osteoclasts are multinucleated bone resorbing cells that can be differentiated from human monocytes in vitro. There are few studies comparing osteoclastogenesis of different monocyte sources. We compared monocytes from human bone marrow (BM), peripheral blood (PB), and umbilical cord blood (CB) and their osteoclastogenic potential by culturing them with RANKL (20 and 80 ng/ml) and M-CSF (10 ng/ml) for 14 days. We also cultured cells without growth factors, as umbilical cord blood monocytes have been reported to be able to fuse spontaneously into osteoclasts. The data was analysed on d4, d8, d11, and d14. After culture with RANKL and M-CSF, all types of cell cultures developed TRACP -positive multinuclear cells that were able to form resorption pits on human bone slices. Only occasional multinuclear cells and small infrequent resorbed areas could be found in PB and CB-derived cultures without growth factors. BM-derived cells formed greater resorption areas than PB- and CB-derived monocytes. The greatest monocyte population in BM samples were intermediate (CD14⁺⁺CD16⁺) and in PB and CB classical monocytes (76.3% and 54.4%, respectively). In conclusion, our data demonstrates that bone resorbing osteoclasts can be differentiated from BM, PB and CB. However, the osteoclast precursor origin can affect the osteoclast properties and function.

Long-term effect of denosumab on bone microarchitecture as assessed by tissue thickness-adjusted trabecular bone score in postmenopausal women with osteoporosis: results from FREEDOM and its open-label extension

In postmenopausal women with osteoporosis, up to 10 years of denosumab treatment significantly and continuously improved bone microarchitecture assessed by tissue thickness-adjusted trabecular bone score, independently of bone mineral density. Long-term denosumab treatment decreased the number of high fracture-risk patients and shifted more patients to lower fracture-risk categories.

PURPOSE

To investigate the long-term effect of denosumab on bone microarchitecture assessed by tissue thickness-adjusted trabecular bone score (TBS_TT) in post-hoc subgroup analysis of FREEDOM and open-label extension (OLE).

METHODS

Postmenopausal women with lumbar spine (LS) or total hip BMD T-score <-2.5 and ≥-4.0 who completed the FREEDOM DXA substudy and continued in OLE were included. Patients received either denosumab 60 mg subcutaneously every 6 months for 3 years and same-dose open-label denosumab for 7 years (long-term denosumab; n=150) or placebo for 3 years and open-label denosumab for 7 years (crossover denosumab; n=129). BMD and TBS_TT were assessed on LS DXA scans at FREEDOM baseline, month 1, and years 1-6, 8, and 10.

RESULTS

In long-term denosumab group, continued increases from baseline to years 4, 5, 6, 8, and 10 in BMD (11.6%, 13.7%, 15.5%, 18.5%, and 22.4%) and TBS_TT (3.2%, 2.9%, 4.1%, 3.6%, and 4.7%) were observed (all P < 0.0001). Long-term denosumab treatment decreased the proportion of patients at high fracture-risk (according to TBS_TT and BMD T-score) from baseline up to year 10 (93.7 to 40.4%), resulting in increases in the proportions at medium-risk (6.3 to 53.9%) and low-risk (0 to 5.7%) (P < 0.0001). Similar responses were observed in crossover denosumab group. Changes in BMD and TBS_TT were poorly correlated during denosumab treatment.

CONCLUSION

In postmenopausal women with osteoporosis, up to 10 years of denosumab significantly and continuously improved bone microarchitecture assessed by TBS_TT, independently of BMD, and shifted more patients to lower fracture-risk categories.

Bone Metastases and Health in Prostate Cancer: From Pathophysiology to Clinical Implications

Clinically relevant bone metastases are a major cause of morbidity and mortality for prostate cancer patients. Distinct phenotypes are described: osteoblastic, the more common osteolytic and mixed. A molecular classification has been also proposed. Bone metastases start with the tropism of cancer cells to the bone through different multi-step tumor-host interactions, as described by the "metastatic cascade" model. Understanding these mechanisms, although far from being fully elucidated, could offer several potential targets for prevention and therapy. Moreover, the prognosis of patients is markedly influenced by skeletal-related events. They can be correlated not only with bone metastases, but also with "bad" bone health. There is a close correlation between osteoporosis-a skeletal disorder with decreased bone mass and qualitative alterations-and prostate cancer, in particular when treated with androgen deprivation therapy, a milestone in its treatment. Systemic treatments for prostate cancer, especially with the newest options, have improved the survival and quality of life of patients with respect to skeletal-related events; however, all patients should be evaluated for "bone health" and osteoporotic risk, both in the presence and in the absence of bone metastases. Treatment with bone-targeted therapies should be evaluated even in the absence of bone metastases, as described in special guidelines and according to a multidisciplinary evaluation.

Bacteria associated with apical periodontitis promotes in vitro the differentiation of macrophages to osteoclasts

OBJECTIVE

To analyze the possible in vitro effect of the cytokine RANKL and bacteria involved in apical periodontitis on the differentiation of macrophages into osteoclasts.

MATERIAL AND METHODS

Bacteria were isolated (mainly E. faecium and E. faecalis) from the root canal of fifty patients with apical periodontitis, the possible effect of these bacteria on the phagocytic activity of the monocyte cell line THP-1 was analyzed by flow cytometry. Furthermore, the effect of these bacteria (alone or in combination with the cytokine RANKL) on the differentiation of THP-1 macrophages into osteoclasts was analyzed through the expression of the receptor RANK and the tartrate-resistant acid phosphatase TRAP. Finally, the release of different cytokines (IL-1β, TNF-α, IL-6, IL-8, IL-10, and IL-12p70) by THP-1 cells induced to differentiate into osteoclasts was also analyzed.

RESULTS

We observed a significant proportion of THP-1 cells were able to internalize E. faecium and E. faecalis. Furthermore, these bacteria were able to induce (alone or in combination with RANKL) a significant expression of RANK by THP-1 macrophages; accordingly, E. faecium and E. faecalis induced very significant levels of TRAP in these cells. Finally, during the differentiation of THP-1 macrophages induced by RANKL or bacteria, a significant release of the pro-inflammatory cytokines IL-6 and TNF-α was observed.

CONCLUSIONS AND CLINICAL RELEVANCE

Our data suggest that the causative agents of apical periodontitis can induce the differentiation of osteoclasts as well as the release of pro-inflammatory cytokines, phenomena that may have an important role in the bone damage observed in this condition.

Crosstalk within a brain-breast-bone axis regulates mineral and skeletal metabolism during lactation

To support the increased calcium demands for milk production during lactation, a dramatic and reversible physiological response occurs to alter bone and mineral metabolism. This coordinated process involves a brain-breast-bone axis that integrates hormonal signals that allow for adequate calcium delivery to milk yet also protects the maternal skeletal from excessive bone loss or decreases in bone quality or function. Here, we review the current knowledge on the crosstalk between the hypothalamus, mammary gland, and skeleton during lactation. We discuss the rare entity of pregnancy and lactation associated osteoporosis and consider how the physiology of bone turnover in lactation may impact the pathophysiology of postmenopausal osteoporosis. Further understanding of the regulators of bone loss during lactation, particularly in humans, may provide insights into new therapies for osteoporosis and other diseases of excess bone loss.

Nitric oxide scavengers based on o-phenylenediamine for the treatment of rheumatoid arthritis

Nitric oxide (NO) plays various physiologically favorable roles in the body. However, excessive production of NO causes inflammation and leads to various chronic inflammatory diseases. A typical NO-related disease is rheumatoid arthritis (RA), and it is well known that NO is a critical molecule for inflammation in the pathophysiology of RA. Therefore, depletion of NO can be an attractive treatment option for RA. In this study, we proposed a new method to discover effective NO scavengers in the form of small molecules. o-Phenylenediamine (o-PD), the core structure of the NO scavenger, is a diamino-aromatic compound that irreversibly reacts with NO through nucleophilic substitution of amine. Inspired by the nucleophilicity, we attempted to find new scavenger candidates by searching for conditions that increase the nucleophilicity of the amine moieties. Candidates were classified into the basic form o-PD, monoamine aniline, o-PD substituted with a nitro group, carboxyl group, and three methyl groups. The NO-scavenging ability of these candidates was demonstrated using the DAF-2 assay. N-Methyl-o-PD (N-Me) in the methyl (-CH₃) group had the highest reactivity with NO among the candidates, and the efficiency of NO scavengers was confirmed in vitro and in vivo. Depleted levels of NO and reduced levels of pro-inflammatory cytokines by N-Me demonstrated remarkable therapeutic efficacy against joint damage and delayed severity in a collagen-induced arthritis (CIA) model. Therefore, our findings suggest that N-Me is a new NO scavenger with great potential for RA treatment and further clinical drug development.

Osteoclast-derived extracellular miR-106a-5p promotes osteogenic differentiation and facilitates bone defect healing

Small extracellular vesicles (sEVs) are considered to play critical roles in intercellular communications during normal and pathological processes since they are enriched with miRNAs and other signal molecules. In bone remodeling, osteoclasts generate large amounts of sEVs. However, there is very few research studying whether and how osteoclast-derived sEVs (OC-sEVs) affect surrounding cells. In our study, microarray analysis identified miR-106a-5p as highly enriched in OC-sEV. Further experiments confirmed that OC-sEVs inhibited Fam134a through miR-106a-5p and significantly promoted bone mesenchymal stem cell (BMSC) osteogenic mineralization in vitro. Next, we prepared an sEV-modified demineralized bone matrix (DBM) as scaffold treating calvarial defect mouse model to evaluate the pro-osteogenic activities of the scaffold. In vivo results indicated that DBM modified with miR-106a-5p-sEVs showed an enhanced capacity for bone regeneration. This important finding further emphasizes that sEV-mediated miR-106a-5p transfer plays a critical role in osteogenesis and indicates a novel communication mode between osteoclasts and BMSCs.

Osteoclasts, Master Sculptors of Bone

Osteoclasts are multinucleated cells with the unique ability to resorb bone matrix. Excessive production or activation of osteoclasts leads to skeletal pathologies that affect a significant portion of the population. Although therapies that effectively target osteoclasts have been developed, they are associated with sometimes severe side effects, and a fuller understanding of osteoclast biology may lead to more specific treatments. Along those lines, a rich body of work has defined essential signaling pathways required for osteoclast formation, function, and survival. Nonetheless, recent studies have cast new light on long-held views regarding the origin of these cells during development and homeostasis, their life span, and the cellular sources of factors that drive their production and activity during homeostasis and disease. In this review, we discuss these new findings in the context of existing work and highlight areas of ongoing and future investigation.

Applications of Gene Therapy in Dentistry: A Review Article

Gene therapy promises to possess a good prospect in bridging the gap between dental applications and medicine. The dynamic therapeutic modalities of gene therapy have been advancing rapidly. Conventional approaches are being revamped to be more comprehensive and pre-emptive, which could do away with the need for surgery and medicine altogether. The complementary base sequences known as genes convey the instructions required to manufacture proteins. The oral cavity is one of the most accessible locations for the therapeutic intervention of gene therapy for several oral tissues. In 1990, the first significant trial of gene therapy was overseen to alleviate adenosine deaminase deficiency. The notion of genetic engineering has become increasingly appealing as a reflection of its benefits over conventional treatment modalities. An example of how this technology may alter dentistry is the implementation of gene therapy for dental and oral ailments. The objective of this article is to examine the effects of gene therapy on the field of dentistry, periodontology and implantology. Furthermore, the therapeutic factors of disease therapy, minimal invasion, and appropriate outcome have indeed been taken into consideration.

Bone circuitry and interorgan skeletal crosstalk

The past decade has seen significant advances in our understanding of skeletal homeostasis and the mechanisms that mediate the loss of bone integrity in disease. Recent breakthroughs have arisen mainly from identifying disease-causing mutations and modeling human bone disease in rodents, in essence, highlighting the integrative nature of skeletal physiology. It has become increasingly clear that bone cells, osteoblasts, osteoclasts, and osteocytes, communicate and regulate the fate of each other through RANK/RANKL/OPG, liver X receptors (LXRs), EphirinB2-EphB4 signaling, sphingolipids, and other membrane-associated proteins, such as semaphorins. Mounting evidence also showed that critical developmental pathways, namely, bone morphogenetic protein (BMP), NOTCH, and WNT, interact each other and play an important role in postnatal bone remodeling. The skeleton communicates not only with closely situated organs, such as bone marrow, muscle, and fat, but also with remote vital organs, such as the kidney, liver, and brain. The metabolic effect of bone-derived osteocalcin highlights a possible role of skeleton in energy homeostasis. Furthermore, studies using genetically modified rodent models disrupting the reciprocal relationship with tropic pituitary hormone and effector hormone have unraveled an independent role of pituitary hormone in skeletal remodeling beyond the role of regulating target endocrine glands. The cytokine-mediated skeletal actions and the evidence of local production of certain pituitary hormones by bone marrow-derived cells displays a unique endocrine-immune-skeletal connection. Here, we discuss recently elucidated mechanisms controlling the remodeling of bone, communication of bone cells with cells of other lineages, crosstalk between bone and vital organs, as well as opportunities for treating diseases of the skeleton.

Prolactin regulates RANKL expression via signal transducer and activator of transcription 5a signaling in mammary epithelial cells of dairy cows

Receptor of activated nuclear factor kappa B ligand (RANKL) is regulated by prolactin in the mammary gland. However, the intrinsic molecular mechanism is not well understood. Herein, mammary epithelial cells (MECs) of dairy cows were isolated to characterize the molecular mechanism of prolactin in vitro. We demonstrated that prolactin stimulation increased the expression of RANKL in MECs. Moreover, the expression of RANKL induced by prolactin was inhibited by the prolactin receptor or signal transducer and activator of transcription 5A (STAT5a) knockdown. Furthermore, prolactin markedly increased RANKL-Luciferase reporter activity in MECs. We identified a putative gamma-interferon activated site (GAS) in the region between residues -883 to -239 bp of the RANKL promoter. Subsequently, we found that the mutated GAS sequence failed to respond to prolactin stimulation. In addition, STAT5a knockdown markedly decreased prolactin-stimulated RANKL promoter activity. Western blot results revealed that RANKL overexpression markedly decreased the STAT5a phosphorylation level in MECs. These findings indicate that prolactin could regulate RANKL promoter activity via STAT5a, contributing to increased RANKL expression in MECs. RANKL may have a negative regulatory effect on STAT5a activity.

Avicularin Alleviates Osteoporosis in Ovariectomized Mice by Inhibiting Osteoclastogenesis through NF-κB Pathway Inhibition

Osteoporosis (OP) is mainly manifested by bone loss and bone degeneration. OP is considered a risk factor for pathological fractures, as well as impacts the health of middle-aged and elderly individuals. Drug therapy remains the main treatment scheme for OP; however, its efficacy is limited and has been associated with serious side effects. Therefore, it is important to develop new, effective, and safe treatment methods for OP. Avicularin (AL) is a flavonoid and quercetin derivative from various plants. Our study showed that AL disrupts osteoclast activation and resorptive function via inhibition of the RANKL-induced osteoclast differentiation together with the resorption capacity of bone marrow-derived macrophages (BMMs). Hence, AL prevents the activation and resorptive activity of osteoclasts. The results of qPCR showed that genes related to osteoclasts exhibited downregulated expression after AL treatment. Furthermore, AL inhibited RANKL-induced phosphorylation as well as degradation of the inhibitor IκBα of the NF-κB pathway, together with P65 phosphorylation in BMMs. We used an OP mouse model that was established by ovariectomy (OVX). Relative to untreated OP mice, mice that received AL treatment showed a significant increase in bone mineral density; however, the expression of TRAP, NFATC1, mmp9, and CTX-1 was significantly reduced. These results indicate that AL disrupts osteoclastogenesis via inhibition of the NF-κB pathway, which in turn improves OVX-induced OP.

Cathepsin K degrades osteoprotegerin to promote osteoclastogenesis in vitro

Osteoblasts produce the receptor activator of nuclear factor-kappa B ligand (RANKL) and osteoprotegerin, the inducer and the suppressor of osteoclast differentiation and activation. We previously proposed that the degradation of osteoprotegerin by lysine-specific gingipain of Porphyromonas gingivalis and neutrophil elastase is one of the mechanisms of bone resorption associated with infection and inflammation. In the present study, we found that cathepsin K (CTSK) also degraded osteoprotegerin in an acidic milieu and the buffer with a pH of 7.4. The 37 k fragment of osteoprotegerin produced by the reaction with CTSK was further degraded into low molecular weight fragments, including a 13 k fragment, depending on the reaction time. The N-terminal amino acid sequence of the 37 k fragment matched that of the intact osteoprotegerin, indicating that CTSK preferentially hydrolyzes the death domain-like region of osteoprotegerin, not its RANKL-binding region. The 13 k fragment of osteoprotegerin was the C-terminal 13 k portion within the RANKL-binding region of the 37 k fragment. Finally, CTSK restored RANKL-dependent osteoclast differentiation that was suppressed by the addition of osteoprotegerin. Collectively, CTSK is a possible positive regulator of osteoclastogenesis.

[Treatment options for external inflammatory root resorption]

THE AIM OF THE STUDY

Was to compare the efficacy of various treatment options for external inflammatory root resorption according to literature data.

MATERIALS AND METHODS

Literature was searched in electronic databases «eLibrary» and «PubMed» for key words «external inflammatory resorption treatment», «external inflammatory resorption management». Inclusion criteria comprised publications in Russian or English, clinical and experimental studies, full description of treatment protocol and obtained results. Studies with no full text, describing root resorption of orthodontic origin, clinical cases and clinical case series were excluded from the study.

RESULTS

The problem of external inflammatory root resorption is poorly described in the Russian scientific literature. There are no registered protocols for its prevention and treatment or therapeutic agents with proved efficacy available in Russia. The only accessible approach for external inflammatory root resorption remains timely pulp extirpation after dental trauma which importance is underlined by all authors involved in the field of dental trauma studies. MTA and calcium hydroxide being popular as intracanal medications still have significant inconveniences as they potentially provoke root dentine fractures or replacement resorption.

CONCLUSION

There is a need for elaboration and implementation of new prevention and treatment options for external inflammatory root resorption after dental trauma.

Pulsed electromagnetic fields as a promising therapy for glucocorticoid-induced osteoporosis

Glucocorticoid-induced osteoporosis (GIOP) is considered the third type of osteoporosis and is accompanied by high morbidity and mortality. Long-term usage of glucocorticoids (GCs) causes worsened bone quality and low bone mass via their effects on bone cells. Currently, there are various clinical pharmacological treatments to regulate bone mass and skeletal health. Pulsed electromagnetic fields (PEMFs) are applied to treat patients suffering from delayed fracture healing and non-unions. PEMFs may be considered a potential and side-effect-free therapy for GIOP. PEMFs inhibit osteoclastogenesis, stimulate osteoblastogenesis, and affect the activity of bone marrow mesenchymal stem cells (BMSCs), osteocytes and blood vessels, ultimately leading to the retention of bone mass and strength. However, the underlying signaling pathways via which PEMFs influence GIOP remain unclear. This review attempts to summarize the underlying cellular mechanisms of GIOP. Furthermore, recent advances showing that PEMFs affect bone cells are discussed. Finally, we discuss the possibility of using PEMFs as therapy for GIOP.

Effect of Bifidobacterium on osteoclasts: TNF-α/NF-κB inflammatory signal pathway-mediated mechanism

Osteoporosis is a systemic multifactorial bone disease characterized by low bone quality and density and bone microstructure damage, increasing bone fragility and fracture vulnerability. Increased osteoclast differentiation and activity are important factors contributing to bone loss, which is a common pathological manifestation of bone diseases such as osteoporosis. TNF-a/NF-κB is an inflammatory signaling pathway with a key regulatory role in regulating osteoclast formation, and the classical pathway RANKL/RANK/OPG assists osteoclast formation. Activation of this inflammatory pathway promotes the formation of osteoclasts and accelerates the process of osteoporosis. Recent studies and emerging evidence have consistently demonstrated the potential of probiotics to modulate bone health. Secretions of Bifidobacterium, a genus of probiotic bacteria in the phylum Actinobacteria, such as short-chain fatty acids, equol, and exopolysaccharides, have indicated beneficial effects on bone health. This review discusses the molecular mechanisms of the TNF-a/NF-κB inflammatory pathway in regulating osteoclast formation and describes the secretions produced by Bifidobacterium and their potential effects on bone health through this pathway, opening up new directions for future research.

The Role of procollagen type 1 amino-terminal propertied (P1NP) Cytochrome P450 (CYPs) and Osteoprotegerin (OPG) as Potential Bone function markers in Prostate Cancer Bone Metastasis

Background: Procollagen type I amino-terminal propeptide (PINP) is often present during osteoblast development and could be a biomarker of early bone development. Osteoprotegerin (OPG) may protect tumor cells from apoptosis. Cytochrome P450 enzymes help tumor development and treatment (CYPs). Cytochrome P450 activates and deactivates anticancer drugs and procarcinogens.

Objective: The study examined the amounts of a diagnostic marker of bone formation, the amino terminal propeptide of type I procollagen (PINP), Osteoprotegerin (OPG), and P450, in prostate cancer patients at different stages and its ability to detect osteoblastic metastases.

Methods: ELISA was used to measure PINP, OPG, and P450 levels in 30 prostate cancer patients. (n = 32) and healthy men’s serum (n = 36).

Results: Prostate cancer patients had higher blood levels of PINP, OPG, and P450 than healthy persons (301.3±134.9, 980±467.2, and 84.2±28.4 pg/mL, respectively). Compared to I+II prostate cancer patients, III+IV patients showed higher serum PINP, OPG, and P450 levels (P 0.001). OPG, P450, and PINP had statistically significant Area under the ROC curve (0.9467, P= 0.0001, 0.91, P= 0.0001, and 0.6977, P= 0.4035) in prostate cancer patients.

Conclusions: Metastatic prostate cancer patients had greater PINP, OPG, and P450 levels, according to our findings. PINP, OPG, and P450 levels may affect prostate cancer progression. These findings imply that serum PINP, OPG, and P450 levels may predict and diagnose prostate cancer.