The immune system, bone and RANKL

COX-2 inhibition as a therapeutic strategy for bone loss in Staphylococcus aureus osteomyelitis

Bone loss in Staphylococcus aureus (S. aureus) osteomyelitis poses a serious challenge to orthopedic treatment, but the underlying mechanism of systemic osteoporosis caused by chronic infection is not completely clear. In this study, γ-irradiation-killed S. aureus (IKSA) was applied to simulate the inflammation and explore the mechanism of systemic bone loss caused by it. In this study, we found that the systemic application of IKSA caused bone loss in mice through increasing osteoclasts and decreasing osteoblasts. An immune response profile with up-regulated COX-2 is identified based on our transcriptional data from IKSA mice bone marrow cells. COX-2 expression is widely up-regulated in bone marrow immune cells, such as myeloid-derived suppressor cells (MDSCs), neutrophils and macrophages in the IKSA-treated mice. Mechanistically, COX-2 stimulated the increasing proportion of MDSCs and neutrophils and the inflammatory response of the bone marrow immune cells, that may regulate bone metabolism. Importantly, COX-2 inhibitor, celecoxib could rescue the bone loss induced by IKSA, which may reason from decrease of inflammatory gene expression in MDSCs, neutrophils and macrophages. Excitingly, COX-2 expression is also increased in bone marrow from mice and patients with S. aureus osteomyelitis. These findings suggested a therapeutic potential for inhibiting COX-2 in combating bone loss in S. aureus osteomyelitis.

Global trends in osteoimmunology and osteoporosis research: A bibliometric analysis from 2013 to 2022

BACKGROUND

A large number of studies have shown that osteoporosis is closely related to bone immunology. The purpose of this study is to conduct bibliometrics and visual analysis of the fields related to osteoimmunology and osteoporosis from 2013 to 2022 and to summarize the research hotspots and trends in this field.

METHODS

We searched the Web of Science core collection database for articles on osteoimmunology and osteoporosis published between 2013 and 2022. Vosviewer 1.6.18 and CiteSpace.6.2. R4 were used to analyze the retrieved data.

RESULTS

A total of 3218 articles on osteoimmunology and osteoporosis were included in this study. A total of 76 countries, 347 institutions, and 502 authors were included in the articles examined in this study. The main research countries were China, the United States, and South Korea. Shanghai Jiaotong University, Harvard University, and the University of California system were the main research institutions. The author who published the most papers was Xu, Jiake.

CONCLUSIONS

This study is the first to summarize the global research trends in the field of osteoimmunology and osteoporosis from 2013 to 2022. That helps researchers quickly understand the research hotspots and directions in this field.

Modulation of the hepatic RANK-RANKL-OPG axis by combined C5 and CD14 inhibition in a long-term polytrauma model

Background

Polytrauma and hemorrhagic shock can lead to direct and indirect liver damage involving intricate pathophysiologic mechanisms. While hepatic function has been frequently highlighted, there is minimal research on how the receptor activator of the NF-κB (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) system is regulated in the liver following trauma. Furthermore, cross-talking complement and toll-like-receptor (TLR) systems can contribute to the posttraumatic response. Therefore, we investigated the hepatic consequences of polytrauma focusing on the RANK-RANKL-OPG axis, and evaluated the effects of a dual blockade of complement factor C5 and TLR-cofactor CD14 on hepatic features.

Methods

The established pig model of polytrauma (PT) and hemorrhagic shock included pulmonary contusion, hepatic dissection, and bilateral femur fractures, surgically addressed either by external fixation (Fix ex) or intramedullary nailing (Nail). Four groups were investigated: 1) sham animals; 2) PT treated by Fix ex (Fix ex); 3) PT by Nail (Nail); or 4) PT by Nail plus combined C5/CD14 inhibition (Nail+Therapy). Serum samples were obtained between 0 - 72 h, and liver samples at 72 h after PT. Liver tissues were histologically scored and subjected to RT-qPCR-analyses, immunohistochemistry and ELISAs to evaluate the posttraumatic hepatic response with a focus on the RANK-RANKL-OPG system.

Results

Following PT, the liver injury score of the Nail+Therapy group was significantly lower than in the Fix ex or Nail group without immunomodulation (p<0.05). Similarly, the degree of necrosis, lobular stasis, and inflammation were significantly reduced when treated with C5/CD14-inhibitors. Compared to the Nail group, AST serum concentrations were significantly decreased in the Nail+Therapy group after 72 h (p<0.05). PCR analyses indicated that RANK, RANKL, and OPG levels in the liver were increased after PT in the Nail group compared to lower levels in the Nail+Therapy group. Furthermore, liver tissue analyses revealed increased RANK protein levels and cellular immunostaining for RANK in the Nail group, both of which were significantly reduced in the case of C5/CD14-inhibition (p<0.05).

Conclusion

Following experimental PT, dual inhibition of C5/CD14 resulted in altered, mainly reduced hepatic synthesis of proteins relevant to bone repair. However, a comprehensive investigation of the subsequent effects on the liver-bone axis are needed.

The complex association between the immune system and the skeletal system in osteoporosis: A study of single-cell RNA sequencing

OBJECTIVE

Osteoporosis (OP) is a disease characterized by decreased bone mass, deteriorated microstructure, and increased fragility and fracture risk. The diagnosis and prevention of OP and its complications have become major public health challenges. Therefore, exploring the complex ecological connections between the immune and skeletal systems may provide new insights for clinical prevention and treatment strategies.

METHODS

First, we performed single-cell RNA sequencing on human lumbar lamina tissue and conducted clustering and subgroup analysis of quality-controlled single-cell transcriptome data to identify target subgroups. Subsequently, enrichment analysis and pseudotime analysis were performed. In addition, we conducted in-depth studies on the gene regulatory network between different cell subgroups and the communication between bone immune cells.

RESULTS

In this study, we identified several cell subgroups that may be involved in the progression of OP. For example, the CCL4+ NKT and CXCL8+ neutrophils subgroups promote OP progression by mediating an inflammatory environment that disrupts bone homeostasis, and the MNDA+ Mac subgroup promotes osteoclast differentiation to promote OP. Moreover, the TNFAIP6+ Obl, NR4A2+ B and HMGN2+ erythrocyte subgroups promoted the balance of bone metabolism and suppressed OP. In the cell communication network, Obl closely interacts with immune cell subgroups through the CXCR4-CXCL12, CTGF-ITGB2, and TNFSF14-TNFRSF14 axes.

CONCLUSION

Our research revealed specific subgroups and intercellular interactions that play crucial roles in the pathogenesis of OP, providing potential new insights for more precise therapeutic interventions for OP.

A mechanistic study on the toluidine blue/ photodynamic therapy inhibition of lipopolysaccharide-induced inflammatory response in rat gingival fibroblasts

The purpose of this research was to investigate the effect of toluidine blue (TB) mediated photodynamic therapy (PDT) on the inhibition of lipopolysaccharide (LPS)-induced inflammation in rat gingival fibroblasts through in vitro experiments. Rat gingival fibroblasts were divided into five groups: (1) control, (2) LPS treatment, (3) laser treatment, (4) TB treatment (1.0 µg/mL), and (5) PDT treatment (TB plus laser irradiation at 320 mW/cm2 for 240 s). After 24 h, cell growth activity was measured using MTT assay. The levels of receptor activator for nuclear factor-κB ligand (RANKL) and osteoprotegerin (OPG) in the cell culture supernatant were measured using enzyme-linked immunosorbent assay (ELISA). Nuclear proteins were extracted and the phosphorylation levels of phosphorylated nuclear factor-κB/p65 (p-p65) and phosphorylated inhibitor of nuclear factor-κB (p-IκBα) were determined using Western Blot. MTT results showed no significant difference in cell viability between the groups (P > 0.05). After LPS induction, OPG expression decreased, RANKL expression increased, and the OPG/RANKL ratio decreased, which was different from the control group (P < 0.05). After PDT treatment, OPG expression increased, RANKL expression decreased (P < 0.05), and the OPG/RANKL ratio increased (P < 0.05). Compared to the control group, there was no significant difference in OPG and RANKL expression or the OPG/RANKL ratio (P > 0.05). The activation of NF-κB was closely related to the phosphorylation levels of p-p65 and p-IκBα. LPS significantly up-regulated p-p65 and p-IκBα expression (P < 0.05), while PDT treatment decreased their phosphorylation levels (P < 0.05). TB-PDT treatment can inhibit NF-κB signaling pathway activation, decrease RANKL and OPG expression, and reduce the OPG/RANKL ratio, thereby reducing inflammation and playing a role in periodontitis treatment.

Exercise and osteoimmunology in bone remodeling

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

Agomelatine alleviates steroid-induced osteoporosis by targeting SIRT1/RANKL/FOXO1/OPG signalling in rats

One of the major contributors to secondary osteoporosis is long-term glucocorticoid usage. Clinically used antidepressant agomelatine also has anti-inflammatory properties. Our research aimed to inspect the probable defensive effect of agomelatine against steroid-promoted osteoporosis. There were four groups of rats; group I had saline as a negative control; rats of group II had dexamethasone (0.6 mg/kg, s.c.), twice weekly for 12 weeks; rats of group III had agomelatine (40 mg/kg/day, orally), as a positive control, daily for 12 weeks; and rats of group IV had dexamethasone + agomelatine in the same previous doses combined for 12 weeks. Finally, biochemical as well as histopathological changes were evaluated and dexamethasone treatment caused osteoporosis, as evidenced by discontinuous thin cancellous bone trabeculae, minor fissures and fractures, irregular eroded endosteal surface with elevated alkaline phosphate, tartarate resistant acid phosphate (TRACP) and osteocalcin levels. Osteoprotegerin (OPG), calcium, and phosphorus levels decreased with disturbed receptor activator of nuclear factor κ B ligand (RANKL), forkhead box O1 (FOXO1), and silent information regulator 1 (SIRT1) protein expression. However, treatment with agomelatine restored the normal levels of biochemical parameters to a great extent, supported by SIRT activation with an improvement in histopathological changes. Here, we concluded that agomelatine ameliorates steroid-induced osteoporosis through a SIRT1/RANKL/FOXO1/OPG-dependent pathway.

Periodontal ligament cells-derived exosomes promote osteoclast differentiation via modulating macrophage polarization

Several studies have demonstrated that exosomes (Exos) are involved in the regulation of macrophage polarization and osteoclast differentiation. However, the characteristics as well as roles of exosomes from human periodontal ligament cells (hPDLCs-Exos) in M1/M2 macrophage polarization and osteoclast differentiation remain unclear. Here, periodontal ligament cells were successfully extracted by method of improved Type-I collagen enzyme digestion. hPDLCs-Exos were extracted by ultracentrifugation. hPDLCs-Exos were identified by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA) and western blotting (WB). Osteoclast differentiation was evaluated by real-time quantitative polymerase chain reaction (RT-qPCR), WB and tartrate-resistant acid phosphatase (TRAP) staining. M1/M2 macrophage polarization were evaluated by RT-qPCR and WB. The results showed hPDLCs-Exos promoted osteoclast differentiation and M2 macrophage polarization, but inhibited M1 macrophage polarization. Moreover, M1 macrophages inhibited osteoclast differentiation, whereas M2 macrophages promoted osteoclast differentiation. It has shown that hPDLCs-Exos promoted osteoclast differentiation by inhibiting M1 and promoting M2 macrophage polarization.

Immune Dysfunction in Medication-Related Osteonecrosis of the Jaw

The pathogenesis of medication-related osteonecrosis of the jaw (MRONJ) is multifactorial and there is a substantial consensus on the role of antiresorptive drugs (ARDs), including bisphosphonates (BPs) and denosumab (Dmab), as one of the main determinants. The time exposure, cumulative dose and administration intensity of these drugs are critical parameters to be considered in the treatment of patients, as cancer patients show the highest incidence of MRONJ. BPs and Dmab have distinct mechanisms of action on bone, but they also exert different effects on immune subsets which interact with bone cells, thus contributing to the onset of MRONJ. Here, we summarized the main effects of ARDs on the different immune cell subsets, which consequently affect bone cells, particularly osteoclasts and osteoblasts. Data from animal models and MRONJ patients showed a deep interference of ARDs in modulating immune cells, even though a large part of the literature concerns the effects of BPs and there is a lack of data on Dmab, demonstrating the need to further studies.

The Genetics of Primary Biliary Cholangitis: A GWAS and Post-GWAS Update

Primary biliary cholangitis (PBC) is a chronic, progressive cholestatic liver disease in which the small intrahepatic bile ducts are destroyed by autoimmune reactions. Among autoimmune diseases, which are polygenic complex traits caused by the combined contribution of genetic and environmental factors, PBC exhibits the strongest involvement of genetic heritability in disease development. As at December 2022, genome-wide association studies (GWASs) and associated meta-analyses identified approximately 70 PBC susceptibility gene loci in various populations, including those of European and East Asian descent. However, the molecular mechanisms through which these susceptibility loci affect the pathogenesis of PBC are not fully understood. This study provides an overview of current data regarding the genetic factors of PBC as well as post-GWAS approaches to identifying primary functional variants and effector genes in disease-susceptibility loci. Possible mechanisms of these genetic factors in the development of PBC are also discussed, focusing on four major disease pathways identified by in silico gene set analyses, namely, (1) antigen presentation by human leukocyte antigens, (2) interleukin-12-related pathways, (3) cellular responses to tumor necrosis factor, and (4) B cell activation, maturation, and differentiation pathways.

The Role of Prunes in Modulating Inflammatory Pathways to Improve Bone Health in Postmenopausal Women

The prevalence of osteoporosis among women aged 50 y and older is expected to reach 13.6 million by 2030. Alternative nonpharmaceutical agents for osteoporosis, including nutritional interventions, are becoming increasingly popular. Prunes (dried plums; Prunus domestica L.) have been studied as a potential whole-food dietary intervention to mitigate bone loss in preclinical models of osteoporosis and in osteopenic postmenopausal women. Sixteen preclinical studies using in vivo rodent models of osteopenia or osteoporosis have established that dietary supplementation with prunes confers osteoprotective effects both by preventing and reversing bone loss. Increasing evidence from 10 studies suggests that, in addition to antiresorptive effects, prunes exert anti-inflammatory and antioxidant effects. Ten preclinical studies have found that prunes and/or their polyphenol extracts decrease malondialdehyde and NO secretion, increase antioxidant enzyme expression, or suppress NF-κB activation and proinflammatory cytokine production. Two clinical trials have investigated the impact of dried plum consumption (50-100 g/d for 6-12 mo) on bone health in postmenopausal women and demonstrated promising effects on bone mineral density and bone biomarkers. However, less is known about the impact of prune consumption on oxidative stress and inflammatory mediators in humans and their possible role in modulating bone outcomes. In this review, the current state of knowledge on the relation between inflammation and bone health is outlined. Findings from preclinical and clinical studies that have assessed the effect of prunes on oxidative stress, inflammatory mediators, and bone outcomes are summarized, and evidence supporting a potential role of prunes in modulating inflammatory and immune pathways is highlighted. Key future directions to bridge the knowledge gap in the field are proposed.

The Impact of COVID-19 in Bone Metabolism: Basic and Clinical Aspects

The use of standard procedures for the diagnosis of osteoporosis and assessment of fracture risk significantly decreased during the COVID-19 pandemic, while the incidence of fragility fractures was mostly unaltered. Both COVID-19 per se and its treatments are associated with a negative impact on bone health. Preclinical models show that mice infected with SARS-CoV2 even without symptoms display loss of trabecular bone mass two weeks post infection, due to increased numbers of osteoclasts. Osteoporosis medications do not aggravate the clinical course of COVID-19, while preclinical data suggests possible beneficial effects of some therapies. While vitamin D deficiency is clearly associated with a worse clinical course of COVID-19, evidence of improved patient outcome with vitamin D supplementation is lacking. Osteoporosis treatment should not be generally discontinued, and recommendations for substituting therapies are available. Osteoporosis therapies do not interfere with the efficacy or side-effect profiles of COVID-19 vaccines and should not be stopped or indefinitely delayed because of vaccination.

Neuroendocrine-Immune Regulatory Network of Eucommia ulmoides Oliver

Eucommia ulmoides Oliver (E. ulmoides) is a popular medicinal herb and health supplement in China, Japan, and Korea, and has a variety of pharmaceutical properties. The neuroendocrine-immune (NEI) network is crucial in maintaining homeostasis and physical or psychological functions at a holistic level, consistent with the regulatory theory of natural medicine. This review aims to systematically summarize the chemical compositions, biological roles, and pharmacological properties of E. ulmoides to build a bridge between it and NEI-associated diseases and to provide a perspective for the development of its new clinical applications. After a review of the literature, we found that E. ulmoides has effects on NEI-related diseases including cancer, neurodegenerative disease, hyperlipidemia, osteoporosis, insomnia, hypertension, diabetes mellitus, and obesity. However, clinical studies on E. ulmoides were scarce. In addition, E. ulmoides derivatives are diverse in China, and they are mainly used to enhance immunity, improve hepatic damage, strengthen bones, and lower blood pressure. Through network pharmacological analysis, we uncovered the possibility that E. ulmoides is involved in functional interactions with cancer development, insulin resistance, NAFLD, and various inflammatory pathways associated with NEI diseases. Overall, this review suggests that E. ulmoides has a wide range of applications for NEI-related diseases and provides a direction for its future research and development.

Role of Traditional Chinese Medicine in Bone Regeneration and Osteoporosis

According to World Health Organization (WHO), osteoporosis is a systematic bone disability marked by reduced bone mass and microarchitectural degeneration of osseous cells, which leads to increased bones feebleness and fractures vulnerability. It is a polygenetic, physiological bone deformity that frequently leads to osteoporotic fractures and raises the risk of fractures in minimal trauma. Additionally, the molecular changes that cause osteoporosis are linked to decreased fracture repair and delayed bone regeneration. Bones have the ability to regenerate as part of the healing mechanism after an accident or trauma, including musculoskeletal growth and ongoing remodeling throughout adulthood. The principal treatment approaches for bone loss illnesses, such as osteoporosis, are hormone replacement therapy (HRT) and bisphosphonates. In this review, we searched literature regarding the Traditional Chinese medicines (TCM) in osteoporosis and bone regeneration. The literature results are summarized in this review for osteoporosis and bone regeneration. Traditional Chinese medicines (TCM) have grown in popularity as a result of its success in curing ailments while causing minimal adverse effects. Natural Chinese medicine has already been utilized to cure various types of orthopedic illnesses, notably osteoporosis, bone fractures and rheumatism with great success. TCM is a discipline of conventional remedy that encompasses herbal medication, massage (tui na), acupuncture, food, and exercise (qigong) therapy. It is based on more than 2,500 years of Chinese healthcare profession. This article serves as a comprehensive review summarizing the osteoporosis, bone regeneration and the traditional Chinese medicines used since ancient times for the management of osteoporosis and bone regeneration.

Osteoporose-Management während der COVID-19 Pandemie

Aim The COVID-19 pandemic has influenced the management of many chronic conditions including osteoporosis as resources are re-allocated to urgent care.

Methods This mini-review summarizes the effects of COVID-19 on diagnosis and management of osteoporosis. Evidence regarding possible effects of osteoporosis medications on COVID-19 outcomes and the relationship of COVID-19 vaccination to osteoporosis care is reviewed. Finally, initiation and maintenance of osteoporosis treatment during the pandemic are highlighted.

Results The use of standard procedures for the diagnosis of osteoporosis and assessment of fracture risk significantly decreased during the COVID-19 pandemic, while the incidence of fragility fractures was mostly unaltered. Both COVID-19 per se and its treatments are associated with a negative impact on bone health. Osteoporosis medications do not aggravate the clinical course of COVID-19, while preclinical data suggests possible beneficial effects of some therapies. While vitamin D deficiency is clearly associated with a worse clinical course of COVID-19, evidence of outcome improvement through vitamin D supplementation is lacking. Osteoporosis treatment should not be generally discontinued, and recommendations for substituting therapies are available. Osteoporosis therapies do not interfere with the efficacy or side-effect profiles of COVID-19 vaccines and should not be stopped or indefinitely delayed because of vaccination.

Conclusion The diagnosis and management of osteoporosis are challenging during the COVID-19 pandemic. Osteoporosis medications are safe and effective and should be continued. Further studies will elucidate the impact of the COVID-19 pandemic on long-term bone health.

Understanding Gene Expression and Transcriptome Profiling of COVID-19: An Initiative Towards the Mapping of Protective Immunity Genes Against SARS-CoV-2 Infection

The COVID-19 pandemic has created an urgent situation throughout the globe. Therefore, it is necessary to identify the differentially expressed genes (DEGs) in COVID-19 patients to understand disease pathogenesis and the genetic factor(s) responsible for inter-individual variability. The DEGs will help understand the disease's potential underlying molecular mechanisms and genetic characteristics, including the regulatory genes associated with immune response elements and protective immunity. This study aimed to determine the DEGs in mild and severe COVID-19 patients versus healthy controls. The Agilent-085982 Arraystar human lncRNA V5 microarray GEO dataset (GSE164805 dataset) was used for this study. We used statistical tools to identify the DEGs. Our 15 human samples dataset was divided into three groups: mild, severe COVID-19 patients and healthy control volunteers. We compared our result with three other published gene expression studies of COVID-19 patients. Along with significant DEGs, we developed an interactome map, a protein-protein interaction (PPI) pattern, a cluster analysis of the PPI network, and pathway enrichment analysis. We also performed the same analyses with the top-ranked genes from the three other COVID-19 gene expression studies. We also identified differentially expressed lncRNA genes and constructed protein-coding DEG-lncRNA co-expression networks. We attempted to identify the regulatory genes related to immune response elements and protective immunity. We prioritized the most significant 29 protein-coding DEGs. Our analyses showed that several DEGs were involved in forming interactome maps, PPI networks, and cluster formation, similar to the results obtained using data from the protein-coding genes from other investigations. Interestingly we found six lncRNAs (TALAM1, DLEU2, and UICLM CASC18, SNHG20, and GNAS) involved in the protein-coding DEG-lncRNA network; which might be served as potential biomarkers for COVID-19 patients. We also identified three regulatory genes from our study and 44 regulatory genes from the other investigations related to immune response elements and protective immunity. We were able to map the regulatory genes associated with immune elements and identify the virogenomic responses involved in protective immunity against SARS-CoV-2 infection during COVID-19 development.

Advances in bone turnover markers

Bone fragility fractures remain an important worldwide health and economic problem due to increased morbidity and mortality. The current methods for predicting fractures are largely based on the measurement of bone mineral density and the utilization of mathematical risk calculators based on clinical risk factors for bone fragility. Despite these approaches, many bone fractures remain undiagnosed. Therefore, current research is focused on the identification of new factors such as bone turnover markers (BTM) for risk calculation. BTM are a group of proteins and peptides released during bone remodeling that can be found in serum or urine. They derive from bone resorptive and formative processes mediated by osteoclasts and osteoblasts, respectively. Potential use of BTM in monitoring these phenomenon and therefore bone fracture risk is limited by physiologic and pathophysiologic factors that influence BTM. These limitations in predicting fractures explain why their inclusion in clinical guidelines remains limited despite the large number of studies examining BTM.

Challenges and Opportunities for Osteoporosis Care During the COVID-19 Pandemic

PURPOSE

The coronavirus disease 2019 (COVID-19) has both directly and indirectly affected osteoporosis diagnosis and treatment throughout the world.

METHODS

This mini-review summarizes the available evidence regarding the effects of COVID-19, its treatment, and the consequences of the pandemic itself on bone health. Additionally, we review evidence and expert recommendations regarding putative effects of osteoporosis medications on COVID-19 outcomes and vaccine efficacy and summarize recommendations for continuation of osteoporosis treatment during the pandemic.

RESULTS

The use of standard screening procedures to assess for osteoporosis and fracture risk declined dramatically early in the pandemic, while rates of fragility fractures were largely unchanged. COVID-19, its treatments, and public health measures to prevent viral spread are each likely to negatively affect bone health. Osteoporosis treatments are not known to increase risk of adverse events from COVID-19, and preclinical data suggest possible beneficial effects of some therapies. Vitamin D deficiency is clearly associated with adverse outcomes from COVID-19, but it remains unclear whether vitamin D supplementation may improve outcomes. Osteoporosis treatment should be continued whenever possible, and recommendations for substituting therapies, if required, are available.

CONCLUSION

The COVID-19 pandemic has decreased screening and disrupted treatment for osteoporosis. Osteoporosis medications are safe and effective during the pandemic and should be continued whenever possible. Further studies are needed to fully understand the impact of the COVID-19 pandemic on long-term bone health.

Bovine Colostrum Supplementation Improves Bone Metabolism in an Osteoporosis-Induced Animal Model

Osteoporosis is characterized by bone loss. The present study aims to investigate the effects of bovine colostrum (BC) on bone metabolism using ovariectomized (OVX) and orchidectomized (ORX) rat models. Twenty-seven-week-old Wistar Han rats were randomly assigned as: (1) placebo control, (2) BC supplementation dose 1 (BC1: 0.5 g/day/OVX, 1 g/day/ORX), (3) BC supplementation dose 2 (BC2: 1 g/day/OVX, 1.5 g/day/ORX) and (4) BC supplementation dose 3 (BC3: 1.5 g/day/OVX, 2 g/day/ORX). Bone microarchitecture, strength, gene expression of VEGFA, FGF2, RANKL, RANK and OPG, and bone resorption/formation markers were assessed after four months of BC supplementation. Compared to the placebo, OVX rats in the BC1 group exhibited significantly higher cortical bone mineral content and trabecular bone mineral content (p < 0.01), while OVX rats in the BC3 group showed significantly higher trabecular bone mineral content (p < 0.05). ORX rats receiving BC dose 2 demonstrated significantly higher levels of trabecular bone mineral content (p < 0.05). Serum osteocalcin in the ORX was pointedly higher in all BC supplementation groups than the placebo (BC1: p < 0.05; BC2, BC3: p < 0.001). Higher doses of BC induced significantly higher relative mRNA expression of OPG, VEGFA, FGF2 and RANKL (p < 0.05). BC supplementation improves bone metabolism of OVX and ORX rats, which might be associated with the activation of the VEGFA, FGF2 and RANKL/RANK/OPG pathways.

Fc Gamma Receptors as Regulators of Bone Destruction in Inflammatory Arthritis

Bone erosion is one of the primary features of inflammatory arthritis and is caused by excessive differentiation and activation of osteoclasts. Fc gamma receptors (FcγRs) have been implicated in osteoclastogenesis. Our recent studies demonstrate that joint-deposited lupus IgG inhibited RANKL-induced osteoclastogenesis. FcγRI is required for RANKL-induced osteoclastogenesis and lupus IgG-induced signaling transduction. We reviewed the results of studies that analyzed the association between FcγRs and bone erosion in inflammatory arthritis. The analysis revealed the dual roles of FcγRs in bone destruction in inflammatory arthritis. Thus, IgG/FcγR signaling molecules may serve as potential therapeutic targets against bone erosion.

An Up-Date of the Muscle Strengthening Exercise Effectiveness in Postmenopausal Women with Osteoporosis: A Qualitative Systematic Review

BACKGROUND

Osteoporosis (OP) is a systemic disease that is characterized by decreased bone density and quality. Purpose: The purpose of this systematic review was to determine the effects of muscle strengthening exercise in postmenopausal women with OP. Methods: A literature search was conducted systematically in MEDLINE, CINAHL, EMBASE databases for human studies up to 31 March 2021. Two researchers screened the articles against predefined inclusion criteria; a third resolved discrepancies. Articles were included if they assessed the effects of muscle strengthening exercise in postmenopausal women with OP. The protocol for this systematic review was registered on PROSPERO (CRD42021207917) and a qualitative systematic review was carried out following the PRISMA statement. Methodological quality was evaluated through the scientific validity scales PEDro. Finally, RTCs and NRCTs risk of bias was assessed with the Cochrane risk of bias tool (Risk of Bias-ROB 2.0) and ROBINS-1, respectively. Results: A total of 16 studies (1028 subjects) that met the different eligibility criteria previously established were selected. There is evidence of good methodological quality and a low to moderate risk of bias that supports that muscle strengthening exercise alone or in combination with other therapeutic modalities improves BMD (9, n = 401) in proximal femur and lumbar vertebra body, muscle strength (10, n = 558), balance (4, n = 159), functionality (7, n = 617), and quality of life (5, n = 291).

CONCLUSIONS

Exercise programs focused on muscle strengthening have benefits for all variables studied in postmenopausal women with OP.

Age-related trabecular bone loss is associated with a decline in serum Galectin-1 level

BACKGROUND

Senile osteoporosis with age-related bone loss is diagnosed depending on radiographic changes of bone and bone mineral density (BMD) measurement. However, radiographic alterations are usually signs of medium-late stage osteoporosis. Therefore, biomarkers have been proposed as indicators of bone loss. In the current study, Galectin-1 (Gal-1) showed age-related decline in mice serum. The role of Gal-1 in osteoporosis has not been investigated so far. Hence, the current study illustrated the relationship of serum Gal-1 level with bone loss.

METHODS

We employed 6- and 18-month-old mice to establish an animal model of age-related trabecular bone loss, whose bone density and microstructure were investigated by micro-CT. ELISA was used to measure the levels of Gal-1 in serum. The correlation analysis was performed to illustrate the relationship between serum Gal-1 levels and trabecular bone loss. In addition, immunohistochemistry was used to investigate the abundance of Gal-1 in bone marrow of mice. ELISA and western blot were performed to measure the secretion ability and protein expression of Gal-1 in bone marrow stromal cells (BMSC), hematopoietic stem cells (HSC) and myeloid progenitor (MP) respectively. Flow cytometry was used to measure BMSC number in bone marrow. Finally, male volunteers with age-related BMD decrease were recruited and the relationship between serum Gal-1 and BMD was analyzed.

RESULTS

Gal-1 showed age-related decline in mice serum. Serum Gal-1 was positively associated with BV/TV of femur, tibia and L1 vertebrae in mice. BMSC secreted more Gal-1 compared with HSC and MP. BMSC number in bone marrow was significantly lower in aged mice compared with young mice. Significant attenuation of Gal-1 protein expression was observed in BMSC and HSC from aged mice compared with young mice. Further, we found a decline in serum Gal-1 levels in men with age-related BMD decrease. There was positive correlation between BMD and serum Gal-1 levels in these men.

CONCLUSIONS

Age-related trabecular bone loss is associated with a decline in serum Gal-1 level in mice and men. Our study suggested Gal-1 had great potential to be a biomarker for discovering BMSC senescence, diagnosing early osteoporosis and monitoring trabecular bone loss.

Infectious Osteomyelitis: Marrying Bone Biology and Microbiology to Shed New Light on a Persistent Clinical Challenge

Infections of bone occur in a variety of clinical settings, ranging from spontaneous isolated infections arising from presumed hematogenous spread to those associated with skin and soft tissue wounds or medical implants. The majority are caused by the ubiquitous bacterium Staphyloccocus (S.) aureus, which can exist as a commensal organism on human skin as well as an invasive pathogen, but a multitude of other microbes are also capable of establishing bone infections. While studies of clinical isolates and small animal models have advanced our understanding of the role of various pathogen and host factors in infectious osteomyelitis (iOM), many questions remain unaddressed. Thus, there are many opportunities to elucidate host-pathogen interactions that may be leveraged toward treatment or prevention of this troublesome problem. Herein, we combine perspectives from bone biology and microbiology and suggest that interdisciplinary approaches will bring new insights to the field. © 2021 American Society for Bone and Mineral Research (ASBMR).

Influence of photodynamic therapy on the periodontitis-induced bone resorption in rat

This study aimed to evaluate the effects of toluidine blue-mediated photodynamic therapy (TB-PDT) on the periodontitis-induced bone resorption in periodontitis in rats. Periodontal disease was induced by cotton ligature around the right second maxillary molar in 64 rats. After 4 weeks, the rats were randomly divided into four groups: sterile saline solution (control group); laser therapy (laser group); TB (100 μg/mL); TB plus laser (0.15 W/cm2) irradiation every other day for 240 s (PDT group). All rats were euthanized at 15 days postoperatively. Eight gingival tissue samples were collected from each group. The expressions of receptor activator of nuclear factor kappa-Β ligand (RANKL) and osteoprotegerin (OPG) in gingival tissue samples were detected by real-time quantitative polymerase chain reaction (RT-qPCR). The maxillae from the rest of the rats were taken for histological examination. In the PDT group, the analysis revealed less bone loss than in the control treatment (P < 0.05). No significant difference was found among the control group, TB group, and laser group (P > 0.05). Significantly higher and lower expressions of RANKL and OPG were revealed in the PDT group than that in control group, respectively (P < 0.01). When compared with the control group, the expression of RANKL was significantly reduced by 40.0% in periodontitis in rats treated with TB-PDT for 15 days (P < 0.01). The expression of OPG was increased in the PDT group with TB-PDT for 15 days, when compared with the control group (P < 0.05). TB-PDT treatment significantly reverses the abnormal expression of RANKL and OPG in periodontitis in rats.

Administration of zoledronic acid alleviates osteoporosis in HIV patients by suppressing osteoclastogenesis via regulating RANKL expression

Background

Osteoporosis is a common phenomenon in HIV patients on tenofovir treatment, but its underlying mechanisms remain to be explored.

Methods

Quantitative real-time PCR was performed to analyze the expression of miR-302, miR-101, miR-145 and osteoclast-specific genes in the serum of HIV patients treated with tenofovir and ZOL. ELISA was used to evaluate the expression of RANKL, SMAD3 and PRKACB in the serum of these patients. Luciferase assay was carried out to explore the inhibitory effects of miR-302, miR-101 and miR-145 on the expression of PRKACB, RANKL and SMAD3, respectively. Western blot was used to examine the expression of genes involved in NF‑κB and JNK signaling pathways.

Results

ZOL treatment significantly suppressed the expression of CTx and osteocalcin in HIV patients treated with tenofovir. The BMD loss of HIV patients treated with tenofovir was effectively hindered by ZOL treatment. Mechanistically, the expression of miR-302, miR-101, miR-145, RANKL, SMAD3 and PRKACB in the serum was remarkably activated by ZOL treatment. Luciferase assays showed that miR-302, miR-101 and miR-145 effectively suppressed the expression of PRKACB, RANKL and SMAD3, respectively, through binding to their 3′ UTR. Furthermore, ZOL treatment notably restored the normal expression of osteoclast‑specific genes while activating NF‑κB and JNK signaling pathways.

Conclusion

The findings of this study demonstrated that administration of ZOL suppressed the expression of RANKL via modulating signaling pathways of miR-101-3p/RANKL, miR-302/PRKACB/RANKL and miR-145/SMAD3/RANKL. Furthermore, down-regulated expression of RANKL by ZOL treatment alleviated osteoporosis in HIV-positive subjects treated with tenofovir.

Osteonecrosis of the jaw induced by treatment with anti-PD-1 immunotherapy: a case report

Recognizing rare but clinically significant toxicity of immunotherapy is critical. Here we describe the first detailed case of severe osteonecrosis of the jaw due to anti-PD-1. A 75-year-old man with metastatic melanoma, with no prior radiation or treatment with bone-targeting agents, experienced jaw pain 1 week after his first dose of nivolumab. Imaging studies were negative, and treatment was resumed after pain was controlled. 4 months later, the patient experienced acute exacerbation of pain and malocclusion of the jaw. Imaging showed bilateral fractures of the angle of mandible with extensive disruption of the normal trabecular architecture, requiring total mandibulectomy. The patient's metastatic melanoma responded to treatment and remains controlled >20 months after treatment cessation without further therapy.

Lactobacillus plantarum GKM3 and Lactobacillus paracasei GKS6 Supplementation Ameliorates Bone Loss in Ovariectomized Mice by Promoting Osteoblast Differentiation and Inhibiting Osteoclast Formation

Osteoporosis, an imbalance in the bone-forming process mediated by osteoblasts and the bone-resorbing function mediated by osteoclasts, is a bone degenerative disease prevalent among the aged population. Due to deleterious side effects of currently available medications, probiotics as a potential treatment of osteoporosis is an appealing approach. Hence, this study aims to evaluate the beneficial effects of two novel Lactobacilli strain probiotics on bone health in ovariectomized (OVX) induced osteoporotic mice model and its underlying mechanisms. Forty-five 9-week-old Institute of Cancer Research (ICR) mice underwent either a sham-operation (n = 9) or OVX (n = 36). Four days after the operation, OVX mice were further divided into four groups and received either saline alone, Lactobacillus plantarum GKM3, Lactobacillus paracasei GKS6 or alendronate per day for 28 days. After sacrifice by decapitation, right distal femur diaphysis was imaged via micro-computed tomography (MCT) and parameters including bone volume/tissue volume ratio (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular separation (Tb.Sp), and bone mineral density (BMD) were measured. Moreover, GKM3 and GKS6 on RANKL-induced osteoclast formation and osteoblast differentiation using in vitro cultures were also investigated. The results showed that both probiotics strains inhibited osteoporosis in the OVX mice model, with L. paracasei GKS6 outperforming L. plantarum GKM3. Besides this, both GKS6 and GKM3 promoted osteoblast differentiation and inhibited RANKL-induced osteoclast differentiation via the Bone Morphogenetic Proteins (BMP) and RANKL pathways, respectively. These findings suggested that both strains of Lactobacilli may be pursued as potential candidates for the treatment and management of osteoporosis, particularly in postmenopausal osteoporosis.

Protein array test detected three osteoporosis related plasma inflammatory cytokines in Chinese postmenopausal women

Inflammatory cytokines were involved in pathological conditions of osteoporosis (OP). However, the specific OP-associated inflammatory cytokines are still awaiting to be detected by using a systemic method. Herein, we adopted an extreme sampling scheme and examined inflammatory cytokines between subjects with low and high bone mineral density (BMD) through protein microarray. First, 8 candidate cytokines including B lymphocyte chemoattractant (BLC), osteopontin (OPN) and insulin-like growth factor-binding protein 4 (IGFBP4) were identified in the discovery extreme sampling subgroup. Then, the different expressions for BLC, OPN and IGFBP4 were validated and replicated in two independent extreme sampling subgroups. Further functional experiments showed that the cytokine BLC was involved in bone metabolism by inhibiting bone formation and promoting bone resorption. Together, this study further revealed that inflammatory cytokines were closely related with OP, and that they highlighted critical roles of BLC in the pathogenesis of OP.

RANK Ligand Helps Immunity to Leishmania major by Skewing M2-Like Into M1 Macrophages

Macrophages host Leishmania major infection, which causes cutaneous Leishmaniasis in humans. In the murine model, resistance to infection depends on the host immunity mediated by CD4 T-cell cytokines and macrophages. In association to other stimuli, the Th1 cytokine IFN-γ induces NO-mediated microbial killing by M1/classically-activated macrophages. By contrast, the Th2 cytokine IL-4 promotes M2/alternatively activated macrophages, which express arginase-1 and shelter infection. Other cytokines, such as RANKL, might also participate in the crosstalk between T cells and macrophages to restrict parasite infection. RANKL and its receptor RANK are known to play an essential role in bone remodeling, by inducing osteoclatogenesis. It has also been shown that RANKL stimulates antigen-presenting cells, such as DCs and macrophages, to enhance T cell responses. Here we investigated how RANKL directly modulates the effector macrophage phenotypes and immunity to L. major parasites. We found that inflammatory peritoneal macrophages from B6 mice express RANK and M2 features, such as CD301 (MGL) and CD206 (mannose receptor). Nonetheless, treatment with RANKL or IFN-γ induced macrophage differentiation into more mature F40/80^hi macrophages able to produce IL-12 and TNF-α. In parallel, macrophages treated with RANKL, IFN-γ, or RANKL along with IFN-γ progressively downregulated the expression of the M2 hallmarks MGL, arginase-1, and CCL17. Moreover, a synergism between IFN-γ and RANKL enhanced inducible NO synthase (iNOS) expression and NO production by macrophages. These results are consistent with the idea that RANKL helps IFN-γ to induce a M2-like to M1 phenotype shift. Accordingly, concomitant treatment with RANKL and IFN-γ promoted macrophage-mediated immunity to L. major, by inducing NO and ROS-dependent parasite killing. Furthermore, by cooperating with IFN-γ, endogenous RANKL engages CD4 T-cell help toward L. major-infected macrophages to upregulate M1 and Th1 cytokine responses. Therefore, RANKL, in combination with IFN-γ, is a potential local therapeutic tool to improve immune responses in Leishmaniasis, by skewing M2-like into effector M1 macrophages.

[Basic Studies on the Mechanism, Prevention, and Treatment of Osteonecrosis of the Jaw Induced by Bisphosphonates]

Since the first report in 2003, bisphosphonate-related osteonecrosis of the jaw (BRONJ) has been increasing, without effective clinical strategies. Osteoporosis is common in elderly women, and bisphosphonates (BPs) are typical and widely used anti-osteoporotic or anti-bone-resorptive drugs. BRONJ is now a serious concern in dentistry. As BPs are pyrophosphate analogues and bind strongly to bone hydroxyapatite, and the P-C-P structure of BPs is non-hydrolysable, they accumulate in bones upon repeated administration. During bone-resorption, BPs are taken into osteoclasts and exhibit cytotoxicity, producing a long-lasting anti-bone-resorptive effect. BPs are divided into nitrogen-containing BPs (N-BPs) and non-nitrogen-containing BPs (non-N-BPs). N-BPs have far stronger anti-bone-resorptive effects than non-N-BPs, and BRONJ is caused by N-BPs. Our murine experiments have revealed the following. N-BPs, but not non-N-BPs, exhibit direct and potent inflammatory/necrotic effects on soft-tissues. These effects are augmented by lipopolysaccharide (the inflammatory component of bacterial cell-walls) and the accumulation of N-BPs in jawbones is augmented by inflammation. N-BPs are taken into soft-tissue cells via phosphate-transporters, while the non-N-BPs etidronate and clodronate inhibit this transportation. Etidronate, but not clodronate, has the effect of expelling N-BPs that have accumulated in bones. Moreover, etidronate and clodronate each have an analgesic effect, while clodronate has an anti-inflammatory effect via inhibition of phosphate-transporters. These findings suggest that BRONJ may be induced by phosphate-transporter-mediated and infection-promoted mechanisms, and that etidronate and clodronate may be useful for preventing and treating BRONJ. Our clinical trials support etidronate being useful for treating BRONJ, although additional clinical trials of etidronate and clodronate are needed.

The inflammatory response to bone infection - a review based on animal models and human patients

Bone infections are difficult to diagnose and treat, especially when a prosthetic joint replacement or implant is involved. Bone loss is a major complication of osteomyelitis, but the mechanism behind has mainly been investigated in cell cultures and has not been confirmed in human settings. Inflammation is important in initiating an appropriate immune response to invading pathogens. However, many of the signaling molecules used by the immune system can also modulate bone remodeling and contribute to bone resorption during osteomyelitis. Our current knowledge of the inflammatory response relies heavily on animal models as research based on human samples is scarce. Staphylococcus aureus is one of the most common causes of bone infections and is the pathogen of choice in animal models. The regulation of inflammatory genes during prosthetic joint infections and implant-associated osteomyelitis has only been studied in rodent models. It is important to consider the validity of an animal model when results are extrapolated to humans, and both bone composition and the immune system of pigs has been shown to be more similar to humans, than to rodents. Here in vivo studies on the inflammatory response to prosthetic joint infections and implant-associated osteomyelitis are reviewed.

RANK/RANKL Acts as a Protective Factor by Targeting Cholangiocytes in Primary Biliary Cholangitis

BACKGROUND

Primary biliary cholangitis (PBC) is an autoimmune liver disease characterized by the highly selective autoimmune injury of small intrahepatic bile ducts. Studies reported that the cholangiocytes from PBC patients expressed significantly higher levels of both receptor activator of nuclear factor-kappa B (RANK) and its ligand RANKL. However, the accurate role of RANK/RANKL axis in PBC remains unclear.

METHODS

Forty patients with PBC were enrolled according to the inclusion criteria. The biochemical parameters (alkaline phosphatase, ALP; gamma-glutamyltransferase, GGT; alanine aminotransferase, ALT; aspartate transaminase, AST; total bilirubin, TB) were collected at baseline and followed-up after 6 months of treatment with ursodeoxycholic acid (UDCA, 15 mg/kg d). Stages of PBC were diagnosed based on liver biopsy histopathology according to Nakanuma's criteria. RANK expression in hepatic tissues was detected by immunohistochemistry. The cellular immunofluorescence method was used to locate the distribution of RANK in the human intrahepatic biliary epithelial cells (HIBECs) cultured in vitro. HIBECs were treated with RANKL at a concentration of 100 ng/ml or transfected with RANK-overexpressing lentivirus (LV-RANK). CCK-8 assay and cell cycle assay were used to detect the cell proliferation. Real-time PCR was used to detect the expression of IL-6, E-cadherin, VCAM, ICAM-1, TNF-α, and CD80.

RESULTS

RANK expression in liver biopsies from early PBC patients (stage I + stage II) was significantly lower than that from advanced PBC patients (stage III + stage IV) (1.7 ± 0.63 vs. 2.3 ± 0.45 scores, P < 0.05). High-RANK patients seemed to have better response to UDCA than low-RANK patients (88.9% vs. 40.9%, P < 0.05). The baseline biochemical parameters between the two groups were comparable. The decline percentages of ALP and GGT after UDCA treatment were more obvious in high-RANK patients than those in low-RANK patients (53.90% ± 9.82% vs. 23.93% ± 6.24%, P < 0.05; 74.11% ± 7.18% vs. 48.00% ± 8.17%, P < 0.05, respectively). HIBECs proliferation was significantly inhibited after treatment of RANKL or transfection with LV-RANK. Increased expression of IL-6 and E-cadherin was observed in HIBECs treated with RANKL or LV-RANK.

CONCLUSION

The overall hepatic RANK expression was associated with disease severity and biochemical response in PBC patients. Activation of RANK/RANKL signaling pathway inhibited cholangiocytes proliferation in vitro. Our study suggested that RANK/RANKL pathway might be a potential target of immunotherapy of PBC based on its involvement in the occurrence and development of the disease.

Fibroblast-secreted trophic factors contribute with ECM remodeling stimulus and upmodulate osteocyte gene markers in osteoblasts

As osteogenesis is a multifactorial mechanism, we wonder whether osteoblast-induced extracellular matrix (ECM) remodeling might be modulated by trophic factors released by fibroblasts in a paracrine signaling manner. To address this issue, fibroblasts were cultured for 72 h under conventional conditions when their conditioned medium was harvested and used to challenge pre-osteoblasts (MC3T3-E1 cells) for 14 days. Preliminarily, we validated the potential effect of fibroblasts in contributing to osteocyte phenotype, which specifically requires significant expression of Dentin Matrix Protein 1 (DMP1; about 10-fold changes) and Sclerostin (SOST; about 7-fold changes), both biomarkers of osteocyte. Fibroblasts also seem contributing to ECM remodeling in osteoblasts, because we detected a high level of both mRNA and enzyme activities of matrix metalloproteinase -9 (MMP-9) as well as a high level of reversion inducing cysteine rich protein with kazal motifs (RECK) transcripts (about 13-fold changes), a membrane-anchored MMP inhibitor, which seems to be a constitutive pathway in osteoblasts. Considering inflammatory panorama and using RTqPCR technology, both IL-13 (about 13-fold changes) and IL-33 (about 5-fold changes) genes were up-expressed in response to the fibroblast-secreted trophic factors, as were the receptor activator of NF-κB ligand (RANKL; about 8-fold changes) and osteoprotegerin (OPG; about 3-fold changes). Although preliminary, these data suggest a stimulus to finely control osteoclastogenesis, and this mechanism reinforces the role of fibroblasts in bone remodeling and homeostasis. Moreover, these results suggest an important crosstalk between fibroblast and osteoblast, when fibroblast-secreted trophic factors upmodulate osteocyte gene markers and contribute to ECM remodeling stimulus in osteoblast.

Bone Diseases in Patients with Chronic Liver Disease

Osteoporosis is a frequently observed complication in patients with chronic liver disease, particularly liver cirrhosis and cholestatic liver diseases. In addition, osteoporosis is critical in patients receiving a liver transplant. Nevertheless, few studies have evaluated bone diseases in patients with more frequently observed chronic liver disease, such as chronic viral hepatitis, nonalcoholic fatty liver disease and alcoholic liver disease. Osteoporosis is a disease caused by an imbalance in the activities of osteoblasts and osteoclasts. Over the last few decades, many advances have improved our knowledge of the pathogenesis of osteoporosis. Importantly, activated immune cells affect the progression of osteoporosis, and chronic inflammation may exert an additional effect on the existing pathophysiology of osteoporosis. The microbiota of the intestinal tract may also affect the progression of bone loss in patients with chronic liver disease. Recently, studies regarding the effects of chronic inflammation on dysbiosis in bone diseases have been conducted. However, mechanisms underlying osteoporosis in patients with chronic liver disease are complex and precise mechanisms remain unknown. The following special considerations in patients with chronic liver disease are reviewed: bone diseases in patients who underwent a liver transplant, the association between chronic hepatitis B virus infection treatment and bone diseases, the association between sarcopenia and bone diseases in patients with chronic liver disease, and the association between chronic liver disease and avascular necrosis of the hip. Few guidelines are currently available for the management of low bone mineral density or bone diseases in patients with chronic liver disease. Due to increased life expectancy and therapeutic advances in chronic liver disease, the importance of managing osteoporosis and other bone diseases in patients with chronic liver disease is expected to increase. Consequently, specific guidelines need to be established in the near future.

The Effect of Exercise on the Prevention of Osteoporosis and Bone Angiogenesis

Physical activity or appropriate exercise prevents the development of osteoporosis. However, the exact mechanism remains unclear although it is well accepted that exercise or mechanical loading regulates the hormones, cytokines, signaling pathways, and noncoding RNAs in bone. Accumulating evidence has shown that bone is a highly vascularized tissue, and dysregulation of vasculature is associated with many bone diseases such as osteoporosis or osteoarthritis. In addition, exercise or mechanical loading regulates bone vascularization in bone microenvironment via the modulation of angiogenic mediators, which play a crucial role in maintaining skeletal health. This review discusses the effects of exercise and its underlying mechanisms for osteoporosis prevention, as well as an angiogenic and osteogenic coupling in response to exercise.

Differential inflammatory landscape stimulus during titanium surfaces obtained osteogenic phenotype

Molecular mechanism governing inflammatory scenario in response to titanium (Ti)-nanotexturing surfaces needs to be better addressed. Thus, we subjected pre-osteoblast to different Ti-texturing surfaces, as follows: machined (Mac), double acid-etching (DAE), and nanoscaled hydroxyapatite-blasted titanium surface (nHA), considering the cells chronically responding either directly (when the cells were cultured onto the surfaces) or indirectly (when the cells were challenged with the conditioned medium by the surfaces), up to 10 days. Our results showed that there is a dynamic requirement of inflammatory-related genes activation in response to nHA by up expressing IL1ß, IL6, IL10, and IL33 (direct condition) and IL6, IL10, IL18 (indirect condition). Importantly, our data show that there is inflammasome involvement, once NLRP3, ASC1, and CASP1 genes were also required. As we found a strong signal of IL10, an anti-inflammatory cytokine, we further investigated Sonic Hedgehog (Shh) signaling cascade. Surprisingly, Shh ligand and Smoothened (Smo) genes were up-modulated in response to nHA, while Patched (Ptc) was down-modulated. Finally, an interactome was built using bioinformatics reinforcing Shh signaling cascade on modulating IL10 transcripts by Src mediating this process and this prevalence of anti-inflammatory picture might explain the low profile of RANKL transcripts in response to nHA, compromising the osteoclastogenesis surrounding the implants. Taking our results into account, our data show that the inflammatory landscape promoted by nHA is strictly modulated by Shh signaling promoted anti-inflammatory pathways. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1597-1604, 2019.

Macrophage Origin, Metabolic Reprogramming and IL-1 Signaling: Promises and Pitfalls in Lung Cancer

Macrophages are tissue-resident cells that act as immune sentinels to maintain tissue integrity, preserve self-tolerance and protect against invading pathogens. Lung macrophages within the distal airways face around 8000⁻9000 L of air every day and for that reason are continuously exposed to a variety of inhaled particles, allergens or airborne microbes. Chronic exposure to irritant particles can prime macrophages to mediate a smoldering inflammatory response creating a mutagenic environment and favoring cancer initiation. Tumor-associated macrophages (TAMs) represent the majority of the tumor stroma and maintain intricate interactions with malignant cells within the tumor microenvironment (TME) largely influencing the outcome of cancer growth and metastasis. A number of macrophage-centered approaches have been investigated as potential cancer therapy and include strategies to limit their infiltration or exploit their antitumor effector functions. Recently, strategies aimed at targeting IL-1 signaling pathway using a blocking antibody have unexpectedly shown great promise on incident lung cancer. Here, we review the current understanding of the bridge between TAM metabolism, IL-1 signaling, and effector functions in lung adenocarcinoma and address the challenges to successfully incorporating these pathways into current anticancer regimens.

Linear growth and bone metabolism in pediatric patients with inflammatory bowel disease

OBJECTIVE

To review the pathophysiology and evaluation methods of linear growth and bone mineral density in children and adolescents diagnosed with inflammatory bowel disease.

SOURCE OF DATA

Narrative review carried out in the PubMed and Scopus databases through an active search of the terms: inflammatory bowel disease, growth, failure to thrive, bone health, bone mineral density, and children and adolescents, related to the last ten years, searching in the title, abstract, or keyword fields.

SYNTHESIS OF FINDINGS

Inflammatory bowel diseases of childhood onset may present as part of the clinical picture of delayed linear growth in addition to low bone mineral density. The presence of a chronic inflammatory process with elevated serum levels of inflammatory cytokines negatively interferes with the growth rate and bone metabolism regulation, in addition to increasing energy expenditure, compromising nutrient absorption, and favoring intestinal protein losses. Another important factor is the chronic use of glucocorticoids, which decreases the secretion of growth hormone and the gonadotrophin pulses, causing pubertal and growth spurt delay. In addition to these effects, they inhibit the replication of osteoblastic lineage cells and stimulate osteoclastogenesis.

CONCLUSION

Insufficient growth and low bone mineral density in pediatric patients with inflammatory bowel disease are complex problems that result from multiple factors including chronic inflammation, malnutrition, decreased physical activity, late puberty, genetic susceptibility, and immunosuppressive therapies, such as glucocorticoids.

Hexane Fraction of Turbo brunneus Inhibits Intermediates of RANK-RANKL Signaling Pathway and Prevent Ovariectomy Induced Bone Loss

Osteoporosis is a "silent disease" characterized by fragile and impaired bone quality. Bone fracture results in increased mortality and poor quality of life in aged people particularly in postmenopausal women. Bone is maintained through the delicate balance between osteoclast-mediated bone resorption and osteoblast-mediated bone formation. The imbalance is caused most often by overly active osteoclasts due to estrogen deficiency. Natural products have long been used to prevent and treat osteoporosis since they have fewer side effects. The marine environment is a potential source of biologically and structurally novel biomolecules with promising biological activities but is less explored for the treatment of bone-related diseases. The present study aims to evaluate the antiosteoporotic effect of Hexane fraction of Turbo brunneus methanolic extract (HxTME) and to investigate its role in RANK-RANKL signaling pathway using in vitro osteoclasts cultures and in vivo ovariectomized (OVX) Swiss mice model. The present study demonstrated that the HxTME significantly inhibited RANKL induced osteoclast differentiation and maturation in vitro. HxTME completely downregulated the mRNA expression of key transcription factors such as NFATc1, c-FOS, and osteoclasts related genes involved in osteoclastogenesis. In vivo studies also depicted the effectiveness of HxTME in ovariectomized mice by preserving bone microarchitecture, mineral content, and inhibiting bone loss in treated mice as analyzed by Histomorphometry, MicroCT, and Raman spectroscopy. Oral administration of HxTME fraction resulted in the decreased percentage of F4/80⁺, CD11b⁺, and CD4⁺ RANKL⁺ T cells in OVX mice whereas pro-osteoclastic cytokine, IL6 was markedly reduced upon treatment with HxTME. On stimulation with PMA/Io and PHA, a significant decrease in proliferative response in the splenocytes of HxTME treated OVX mice was observed. Fatty acid profiling revealed that HxTME is rich in ω3 and ω6 polyunsaturated fatty acids (PUFAs), which have high nutraceutical properties and are known to play important role in growth, development and maintenance of health. Therefore, HxTME may be a good source of nutraceutical in the treatment of bone-related diseases particularly in postmenopausal osteoporosis and may be pursued as a potential candidate for treatment and management of osteoporosis.

Emerging role of circadian rhythm in bone remodeling

The 24-h rhythm of behavioral and physiological processes is a typical biological phenomenon regulated by a group of circadian rhythm genes. Dysfunction of the circadian rhythm can cause a wide range of problems, such as cancer and metabolic diseases. In recent decades, increased understanding of the roles of circadian rhythm genes in the bone remodeling process have been documented, including osteoblastic bone formation, osteoclastic bone resorption, and osteoblast/osteoclast communication. A timely review of the current findings may help to facilitate the new field of circadian rhythmic bone remodeling research. Targeted pharmacological modulation of circadian rhythm genes is a possible therapeutic approach through which to overcome bone remodeling problems in the future.

Improved RANKL expression and osteoclastogenesis induction of CD27+CD38- memory B cells: A link between B cells and alveolar bone damage in periodontitis

BACKGROUND AND OBJECTIVE

Periodontitis is a bacteria-induced disease that often leads to alveolar bone damage. Its mechanisms were considered to be complicated, involving an imbalance of the formation and resorption of bone. We sought to disclose the antibody-independent function of B cells during periodontitis.

MATERIAL AND METHODS

Production of receptor activator for nuclear factor-κB ligand (RANKL) by total lymphocytes or sorted B-cell subsets in gingiva from healthy or experimental periodontitis animals was examined by flow cytometry, real-time polymerase chain reaction, and enzyme-linked immunosorbent assay. To define the effects of lymphocytes or B-cell subsets on osteoclastogenesis induction, bone marrow mononuclear cells were culture in culture medium of lymphocytes or cocultured with B-cell subsets. Osteoclasts were enumerated by tartrate-resistant acid phosphatase staining. Constituent ratio of B-cell subsets in healthy or experimental periodontitis was also detected by flow cytometry.

RESULT

Gingiva B cells produce more RANKL and support more osteoclastogenesis than T and other lymphocytes, and this potential improved in periodontitis. Memory B cells (CD27+CD38-) decreased their percentage in periodontitis. Memory B cells have the highest propensity for RANKL production. Remarkably, memory B cells from periodontitis animals expressed significantly more RANKL compared to healthy controls. Memory B cells supported osteoclast differentiation in vitro in a RANKL-dependent manner, and the number of osteoclasts was higher in cultures with memory B cells from periodontitis animals than in those derived from healthy ones. Other B-cell subsets have limited impact on osteoclast formation.

CONCLUSION

Findings of this study further disclose the roles of B cells engaged in periodontal immunomodulation and reveal the considerable importance of memory B cells in alveolar bone homeostasis and their likely contribution to alveolar bone destruction in periodontitis.

Paeonol attenuates ligation-induced periodontitis in rats by inhibiting osteoclastogenesis via regulating Nrf2/NF-κB/NFATc1 signaling pathway

Paeonol is a natural phenolic compound in Moutan Cortex with multiple biological functions, such as anti-inflammatory and anti-oxidant activity. Recent evidence has proven that persistent inflammation, oxidative stress, along with nuclear factor E2-related factor 2 (Nrf2) signaling dysfunction in periodontium are the possible causes of alveolar bone resorption, and ultimately lead to periodontitis. The present study was designed to explore the protective effects of paeonol on ligation-induced periodontitis in rats, and investigate the possible mechanism. We found that treatment with paeonol (40, 80 mg/kg, intraperitoneal injection) for 7 days remarkably decreased the expression of receptor activator of nuclear factor kappa-B ligand increased the expression of osteoprotegrin and inhibited the formation of osteoclasts. This function of paeonol might be correlated with its ability to reduce inflammatory factors (IL-1β, IL-6 and TNF-α) and alleviate oxidative stress (SOD, MDA, GSH and ROS) in gingival tissues. Besides, paeonol increased Nrf2 activity. Silence of Nrf2 using specific siRNA diminished the inhibitory effect of paeonol on NF-κB p65 activation and downstream expression, suggesting that Nrf2 was essential for protective effect of paeonol. These results showed that paeonol protected against periodontitis-aggravated osteoclastogenesis and alveolar bone lesion via regulating Nrf2/NF-κB/NFATc1 signaling pathway.

Bone metabolism in Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a rare disease of not well-defined etiology that involves immune cell activation and frequently affects the skeleton. Bone involvement in LCH usually presents in the form of osteolytic lesions along with low bone mineral density. Various molecules involved in bone metabolism are implicated in the pathogenesis of LCH or may be affected during the course of the disease, including interleukins (ILs), tumor necrosis factor α, receptor activator of NF-κB (RANK) and its soluble ligand RANKL, osteoprotegerin (OPG), periostin and sclerostin. Among them IL-17A, periostin and RANKL have been proposed as potential serum biomarkers for LCH, particularly as the interaction between RANK, RANKL and OPG not only regulates bone homeostasis through its effects on the osteoclasts but also affects the activation and survival of immune cells. Significant changes in circulating and lesional RANKL levels have been observed in LCH patients irrespective of bone involvement. Standard LCH management includes local or systematic administration of corticosteroids and chemotherapy. Given the implication of RANK, RANKL and OPG in the pathogenesis of the disease and the osteolytic nature of bone lesions, agents aiming at inhibiting the RANKL pathway and/or osteoclastic activation, such as bisphosphonates and denosumab, may have a role in the therapeutic approach of LCH although further clinical investigation is warranted.

RANKL Triggers Treg-Mediated Immunoregulation in Inflammatory Osteolysis

The chronic inflammatory immune response triggered by the infection of the tooth root canal system results in the local upregulation of RANKL, resulting in periapical bone loss. While RANKL has a well-characterized role in the control of bone homeostasis/pathology, it can play important roles in the regulation of the immune system, although its possible immunoregulatory role in infectious inflammatory osteolytic conditions remains largely unknown. Here, we used a mouse model of infectious inflammatory periapical lesions subjected to continuous or transitory anti-RANKL inhibition, followed by the analysis of lesion outcome and multiple host response parameters. Anti-RANKL administration resulted in arrest of bone loss but interfered in the natural immunoregulation of the lesions observed in the untreated group. RANKL inhibition resulted in an unremitting proinflammatory response, persistent high proinflammatory and effector CD4 response, decreased regulatory T-cell (Treg) migration, and lower levels of Treg-related cytokines IL-10 and TGFb. Anti-RANKL blockade impaired the immunoregulatory process only in early disease stages, while the late administration of anti-RANKL did not interfere with the stablished immunoregulation. The impaired immunoregulation due to RANKL inhibition is characterized by increased delayed-type hypersensitivity in vivo and T-cell proliferation in vitro to the infecting bacteria, which mimic the effects of Treg inhibition, reinforcing a possible influence of RANKL on Treg-mediated suppressive response. The adoptive transfer of CD4+FOXp3+ Tregs to mice receiving anti-RANKL therapy restored the immunoregulatory capacity, attenuating the inflammatory response in the lesions, reestablishing normal T-cell response in vivo and in vitro, and preventing lesion relapse upon anti-RANKL therapy cessation. Therefore, while RANKL inhibition efficiently limited the periapical bone loss, it promoted an unremitting host inflammatory response by interfering with Treg activity, suggesting that this classic osteoclastogenic mediator plays a role in immunoregulation.

Underlying Mechanisms and Therapeutic Strategies for Bisphosphonate-Related Osteonecrosis of the Jaw (BRONJ)

Bisphosphonates (BPs), with a non-hydrolysable P-C-P structure, are cytotoxic analogues of pyrophosphate, bind strongly to bone, are taken into osteoclasts during bone-resorption and exhibit long-acting anti-bone-resorptive effects. Among the BPs, nitrogen-containing BPs (N-BPs) have far stronger anti-bone-resorptive effects than non-N-BPs. In addition to their pyrogenic and digestive-organ-injuring side effects, BP-related osteonecrosis of jaws (BRONJ), mostly caused by N-BPs, has been a serious concern since 2003. The mechanism underlying BRONJ has proved difficult to unravel, and there are no solid strategies for treating and/or preventing BRONJ. Our mouse experiments have yielded the following results. (a) N-BPs, but not non-N-BPs, exhibit direct inflammatory and/or necrotic effects on soft tissues. (b) These effects are augmented by lipopolysaccharide, a bacterial-cell-wall component. (c) N-BPs are transported into cells via phosphate transporters. (d) The non-N-BPs etidronate (Eti) and clodronate (Clo) competitively inhibit this transportation (potencies, Clo>Eti) and reduce and/or prevent the N-BP-induced inflammation and/or necrosis. (e) Eti, but not Clo, can expel N-BPs that have accumulated within bones. (f) Eti and Clo each have an analgesic effect (potencies, Clo>Eti) via inhibition of phosphate transporters involved in pain transmission. From these findings, we propose that phosphate-transporter-mediated and inflammation/infection-promoted mechanisms underlie BRONJ. To treat and/or prevent BRONJ, we propose (i) Eti as a substitution drug for N-BPs and (ii) Clo as a combination drug with N-BPs while retaining their anti-bone-resorptive effects. Our clinical trials support this role for Eti (we cannot perform such trials using Clo because Clo is not clinically approved in Japan).

Prevention and Treatment of Osteoporosis Using Chinese Medicinal Plants: Special Emphasis on Mechanisms of Immune Modulation

Numerous studies have examined the pathogenesis of osteoporosis. The causes of osteoporosis include endocrine factors, nutritional status, genetic factors, physical factors, and immune factors. Recent osteoimmunology studies demonstrated that the immune system and immune factors play important regulatory roles in the occurrence of osteoporosis, and people should pay more attention to the relationship between immunity and osteoporosis. Immune and bone cells are located in the bone marrow and share numerous regulatory molecules, signaling molecules, and transcription factors. Abnormal activation of the immune system alters the balance between osteoblasts and osteoclasts, which results in an imbalance of bone remodeling and osteoporosis. The incidence of osteoporosis is also increasing with the aging of China's population, and traditional Chinese medicine has played a vital role in the prevention and treatment of osteoporosis for centuries. Chinese medicinal plants possess unique advantages in the regulation of the immune system and the relationships between osteoporosis and the immune system. In this review, we provide a general overview of Chinese medicinal plants in the prevention and treatment of osteoporosis, focusing on immunological aspects.