The Role of Inflammatory Cytokines, the RANKL/OPG Axis, and the Immunoskeletal Interface in Physiological Bone Turnover and Osteoporosis

A prospective study of vitamin D, proinflammatory cytokines, and risk of fragility fractures in women on aromatase inhibitors for breast cancer

BACKGROUND

Vitamin D is critical to bone health by regulating intestinal absorption of calcium, whereas proinflammatory cytokines, including IL-1, IL-6, IL-12, and TNF-α, are known to increase bone resorption. We hypothesized that vitamin D and these cytokines at the time of breast cancer diagnosis were predictive for fragility fractures in women receiving aromatase inhibitors (AIs).

METHODS

In a prospective cohort of 1,709 breast cancer patients treated with AIs, we measured the levels of 25-hydroxyvitamin D (25OHD), IL-1β, IL-6, IL-12, and TNF-α from baseline blood samples. The associations of these biomarkers were analyzed with bone turnover markers (BALP and TRACP), bone regulatory markers (OPG and RANKL), bone mineral density (BMD) close to cancer diagnosis, and risk of fragility fractures during a median of 7.5 years of follow up.

RESULTS

Compared to patients with vitamin D deficiency, patients with sufficient levels had higher bone turnover, lower BMD, and higher fracture risk; the latter became non-significant after controlling for covariates including BMD and no longer existed when patients taking vitamin D supplement or bisphosphonates or with history of fracture or osteoporosis were excluded. There was a non-significant trend of higher levels of IL-1β and TNF-α associated with higher risk of fracture (highest vs. lowest tertile, IL-1β: adjusted HR=1.37, 95% CI=0.94-1.99; TNF-α: adjusted HR=1.38, 95% CI=0.96-1.98).

CONCLUSIONS

Our results do not support proinflammatory cytokines or vitamin D levels as predictors for risk of fragility fractures in women receiving AIs for breast cancer.

Quercetin in Osteoporosis Treatment: A Comprehensive Review of Its Mechanisms and Therapeutic Potential

PURPOSE OF REVIEW

This review aims to provide a theoretical basis and insights for quercetin's clinical application in the prevention and treatment of osteoporosis (OP), analyzing its roles in bone formation promotion, bone resorption inhibition, anti-inflammation, antioxidant effects, and potential mechanisms.

RECENT FINDINGS

OP, a prevalent bone disorder, is marked by reduced bone mineral density and impaired bone architecture, elevating the risk of fractures in patients. The primary approach to OP management is pharmacotherapy, with quercetin, a phytochemical compound, emerging as a focus of recent interest. This natural flavonoid exerts regulatory effects on bone marrow mesenchymal stem cells, osteoblasts, and osteoclasts and promotes bone health and metabolic equilibrium via anti-inflammatory and antioxidative pathways. Although quercetin has demonstrated significant potential in regulating bone metabolism, there is a need for further high-quality clinical studies focused on medicinal quercetin.

Mitigation of inflammatory bowel disease-related osteoporosis by oxyberberine: Insights into the RANKL/NF-κB signaling pathway

Inflammatory bowel disease is linked to a higher occurrence of bone loss. Oxyberberine can effectively improve experimental inflammatory bowel disease. However, no study has shown the effect of oxyberberine on inflammatory bowel disease induced bone loss. The present study was performed to investigate the role of oxyberberine in inflammatory bowel disease induced osteoporosis in chronic inflammatory bowel disease mice model. The inflammatory bowel disease mice were orally given two doses of oxyberberine daily. Blood, colon, and bone specimens were collected for biomarker assessments and histological examinations. Bone biomechanical properties and key proteins and genes involved in the receptor activator of nuclear factor kappa-B ligand/nuclear factor kappa-B signaling pathway were evaluated. Additionally, the binding characteristics of oxyberberine and receptor activator of nuclear factor kappa-B ligand were evaluated by in silico simulation. Results indicated that oxyberberine treatment significantly attenuated the macroscopic damage, colonic shortening, and histological injury from the colon. Furthermore, oxyberberine decreased serum inflammatory cytokine levels. The intervention with oxyberberine significantly mitigated the deterioration of bone mass, biomechanical properties, and microstructural parameters. Moreover, the upregulated osteoclast formation factors in model mice were significantly abolished by oxyberberine. In silico simulation results also showed that oxyberberine was firmly bound with target protein. Hence, our findings indicated that oxyberberine had the potential to mitigate inflammatory bowel disease induced inflammation in bone, inhibit osteoclast formation through regulating the receptor activator of nuclear factor kappa-B ligand/nuclear factor kappa-B signaling pathway, and might be a valuable approach in preventing bone loss associated with inflammatory bowel disease.

The interplay of rheumatoid arthritis and osteoporosis: exploring the pathogenesis and pharmacological approaches

Rheumatoid arthritis (RA) and osteoporosis are two chronic disorders that are often seen together. RA is an autoimmune disorder that causes pain and inflammation in the joints, while osteoporosis is a disorder in which the bones become weak and fragile. Risk factors for bone loss in RA include disease activity, longer disease duration, erosive disease, autoantibody positivity, and joint damage leading to impaired physical activity. Recent research has shown that there is a complex interplay between immune cells, cytokines, and bone remodeling processes in both RA and osteoporosis. The bone remodeling process is regulated by cytokines and immune system signaling pathways, with osteoclasts activated through the RANK/RANKL/OPG pathway and the Wnt/DKK1/sclerostin pathway. Understanding these mechanisms can aid in developing targeted therapies for treatment of osteoporosis in RA patients. Current pharmacological approaches include anti-osteoporotic drugs such as bisphosphonates, denosumab, teriparatide, abaloparatide, raloxifene, and romosozumab. Conventional disease-modifying antirheumatic drugs such as methotrexate and biologicals including TNF inhibitors, IL-6 inhibitors, rituximab, and abatacept lower disease activity in RA and can improve bone metabolism by reducing inflammation but have limited impact on bone mineral density. This review will shed light on the relationship between osteoporosis and rheumatoid arthritis as well as the various factors that influence the onset of osteoporosis in RA patients. We also explore several treatment approaches to effectively managing osteoporosis in RA patients.

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.

Association of neutrophil to lymphocyte ratio with bone mineral density in post-menopausal women: a systematic review and meta-analysis

BACKGROUND

We conducted a systematic review and meta-analysis to compare the neutrophil lymphocyte ratio (NLR) levels between women with post-menopausal osteopenia or osteoporosis to those with normal bone mineral density (BMD).

METHODS

We used Web of Science, PubMed, and Scopus to conduct a systematic search for relevant publications published before June 19, 2022, only in English language. We reported standardized mean difference (SMD) with a 95% confidence interval (CI). Because a significant level of heterogeneity was found, we used the random-effects model to calculate pooled effects. We used the Newcastle-Ottawa scale for quality assessment.

RESULTS

Overall, eight articles were included in the analysis. Post-menopausal women with osteoporosis had elevated levels of NLR compared to those without osteoporosis (SMD = 1.03, 95% CI = 0.18 to 1.88, p = 0.017, I2 = 98%). In addition, there was no difference between post-menopausal women with osteopenia and those without osteopenia in neutrophil lymphocyte ratio (NLR) levels (SMD = 0.58, 95% CI=-0.08 to 1.25, p = 0.085, I2 = 96.8%). However, there was no difference between post-menopausal women with osteoporosis and those with osteopenia in NLR levels (SMD = 0.75, 95% CI=-0.01 to 1.51, p = 0.05, I2 = 97.5%, random-effect model).

CONCLUSION

The results of this study point to NLR as a potential biomarker that may be easily introduced into clinical settings to help predict and prevent post-menopausal osteoporosis.

In Vitro Insights into the Role of 7,8-Epoxy-11-Sinulariolide Acetate Isolated from Soft Coral Sinularia siaesensis in the Potential Attenuation of Inflammation and Osteoclastogenesis

The balance between bone-resorbing osteoclasts and bone-forming osteoblasts is essential for the process of bone remodeling. Excessive osteoclast differentiation plays a pivotal role in the pathogenesis of bone diseases such as rheumatoid arthritis and osteoporosis. In the present study, we examined whether 7,8-epoxy-11-sinulariolide acetate (Esa), a marine natural product present in soft coral Sinularia siaesensis, attenuates inflammation and osteoclastogenesis in vitro. The results indicated that Esa significantly inhibited lipopolysaccharide (LPS)-induced inflammation model of RAW264.7 cells and suppressed receptor activator for nuclear factor-κB ligand (RANKL)-triggered osteoclastogenesis. Esa significantly down-regulated the protein expression of iNOS, COX-2, and TNF-α by inhibiting the NF-κB/MAPK/PI3K pathways and reducing the release of reactive oxygen species (ROS) in RAW264.7 macrophages. Besides, Esa treatment significantly inhibited osteoclast differentiation and suppressed the expression of osteoclast-specific markers such as NFATC1, MMP-9, and CTSK proteins. These findings suggest that Esa may be a potential agent for the maintenance of bone homeostasis associated with inflammation.

The effects of exenatide and insulin glargine treatments on bone turnover markers and bone mineral density in postmenopausal patients with type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) related bone fracture. The effects of glucagon-like peptide-1 receptor analogs for the treatment of T2DM on bone are controversial in human studies. This study aimed to compare the effects of GLP-1 receptor analogs exenatide and insulin glargine treatment on bone turnover marker levels and bone mineral density (BMD) in postmenopausal female patients with T2DM. Thirty female patients with T2DM who were naive to insulin and incretin-based treatments, with spontaneous postmenopause, were randomized to exenatide or insulin glargine arms and were followed up for 24 weeks. BMD was evaluated using dual-energy X-ray absorptiometry and bone turnover markers by serum enzyme-linked immunosorbent assay. The body mass index significantly decreased in the exenatide group compared to the glargine group (P < .001). Receptor activator of nuclear factor kappa-B (RANK) and RANK ligand (RANKL) levels were significantly decreased with exenatide treatment (P = .009 and P = .015, respectively). Osteoprotegerin (OPG) level significantly increased with exenatide treatment (P = .02). OPG, RANK, RANKL levels did not change with insulin glargine treatment. No statistically significant difference was found between the pre- and posttreatment BMD, alkaline phosphatase, bone-specific alkaline phosphatase, and type 1 crosslinked N-telopeptide levels in both treatment arms. Despite significant weight loss with exenatide treatment, BMD did not decrease, OPG increased, and the resorption markers of RANK and RANKL decreased, which may reflect early antiresorptive effects of exenatide via the OPG/RANK/RANKL pathway.

Clinical and immunologic implication of neo-osteogenesis in chronic rhinosinusitis

INTRODUCTION

Chronic rhinosinusitis (CRS) is a multifactorial disease characterized by long-term inflammation of the nasal and sinus passages. Neo-osteogenesis which is a major finding of recalcitrant CRS is clinically related to the disease severity and surgical outcomes of CRS.

AREAS COVERED

The immunological and molecular mechanisms underlying neo-osteogenesis of CRS remain unclear, and many recent studies have suggested the importance of inflammatory mediators secreted by immune cells. This paper provides a broader understanding of neo-osteogenesis in CRS by reviewing recent updates and evidence of the association between CRS pathophysiology and neo-osteogenesis.

EXPERT OPINION

Crosstalk between the bone and mucosa eventually results in refractory CRS. In addition, both eosinophilic and non-eosinophilic CRS cytokines can play a role in neo-osteogenesis and trigger an enhanced CRS-associated immune response. The significance of predicting neo-osteogenesis in advance or during postoperative care could be essential for effectively managing refractory CRS and enhancing the prognosis of CRS patients.

The Inflammatory Contribution of B-Lymphocytes and Neutrophils in Progression to Osteoporosis

Osteoporosis is a bone disease characterized by structural deterioration and low bone mass, leading to fractures and significant health complications. In this review, we summarize the mechanisms by which B-lymphocytes and neutrophils contribute to the development of osteoporosis and potential therapeutics targeting these immune mediators to reduce the proinflammatory milieu. B-lymphocytes-typically appreciated for their canonical role in adaptive, humoral immunity-have emerged as critical regulators of bone remodeling. B-lymphocytes communicate with osteoclasts and osteoblasts through various cytokines, including IL-7, RANK, and OPG. In inflammatory conditions, B-lymphocytes promote osteoclast activation and differentiation. However, B-lymphocytes also possess immunomodulatory properties, with regulatory B-lymphocytes (Bregs) secreting TGF-β1 to restrain pathogenic osteoclastogenesis. Neutrophils, the body's most prevalent leukocyte, also contribute to the proinflammatory environment that leads to osteoporotic bone remodeling. In aged individuals, neutrophils display reduced chemotaxis, phagocytosis, and apoptosis. Understanding the delicate interplay between B-lymphocytes and neutrophils in the context of impaired bone metabolism is crucial for targeted therapies for osteoporosis.

Eplerenone modulates the inflammatory response in monosodium iodoacetate-induced knee osteoarthritis in rats: Involvement of RANKL/OPG axis

AIMS

Osteoarthritis (OA) is a multifactorial degenerative disease marked by the progressive deterioration of articular cartilage with inflammation of the synovium. OA's main symptoms include pain and function loss. Monosodium Iodoacetate (MIA) experimental model is widely-used for OS induction since it produces symptoms comparable to those occurring in humans.

MATERIALS AND METHODS

Thirty-two rats were divided into four groups (n = 8). The 1st group received saline and included the normal-control rats. Groups 2-4 received intra-articular injections of MIA (3 mg/50 μL) in the rats' knee joints to induce OA. Group 2 included the MIA-control rats. Groups 3 and 4 received intra-articular MIA followed by a 14-day oral eplerenone (50 and 100 mg/kg); respectively.

KEY FINDINGS

Intra-articular injection of MIA in rats' knee joints caused significant inflammation and pain, elevation of Akt and ERK gene expression in knee joints along with significant alterations in the histological pictures of knee joints and OARSI scores. RANKL/OPG Axis was significantly disrupted.

SIGNIFICANCE

Eplerenone treatment produced a significant improvement in motor coordination and spontaneous locomotor activity in rats and modulated the key inflammatory mediators in OA (TNF-α, NF-κβ, and IL-6). Eplerenone also suppressed the qRT-PCR gene expression of Akt and ERK in knee joint tissues and improved the histological pictures and OARSI scores of knee joints of treated rats. Eplerenone caused a decline in RANKL concentration accompanied by a rise in OPG concentration thus modulating the RANKL/OPG Axis. Consequently, eplerenone is a candidate for OA therapy due to its potential anti-inflammatory effects.

Differential regulation of skeletal stem/progenitor cells in distinct skeletal compartments

Skeletal stem/progenitor cells (SSPCs), characterized by self-renewal and multipotency, are essential for skeletal development, bone remodeling, and bone repair. These cells have traditionally been known to reside within the bone marrow, but recent studies have identified the presence of distinct SSPC populations in other skeletal compartments such as the growth plate, periosteum, and calvarial sutures. Differences in the cellular and matrix environment of distinct SSPC populations are believed to regulate their stemness and to direct their roles at different stages of development, homeostasis, and regeneration; differences in embryonic origin and adjacent tissue structures also affect SSPC regulation. As these SSPC niches are dynamic and highly specialized, changes under stress conditions and with aging can alter the cellular composition and molecular mechanisms in place, contributing to the dysregulation of local SSPCs and their activity in bone regeneration. Therefore, a better understanding of the different regulatory mechanisms for the distinct SSPCs in each skeletal compartment, and in different conditions, could provide answers to the existing knowledge gap and the impetus for realizing their potential in this biological and medical space. Here, we summarize the current scientific advances made in the study of the differential regulation pathways for distinct SSPCs in different bone compartments. We also discuss the physical, biological, and molecular factors that affect each skeletal compartment niche. Lastly, we look into how aging influences the regenerative capacity of SSPCs. Understanding these regulatory differences can open new avenues for the discovery of novel treatment approaches for calvarial or long bone repair.

Bisphosphonates for osteoporosis in people with cystic fibrosis

BACKGROUND

Osteoporosis is a disorder of bone mineralisation occurring in about one third of adults with cystic fibrosis. Bisphosphonates can increase bone mineral density and decrease the risk of new fractures in post-menopausal women and people receiving long-term oral corticosteroids. This is an updated version of a previous review.

OBJECTIVES

To assess the effects of bisphosphonates on the frequency of fractures, bone mineral density, quality of life, adverse events, trial withdrawals, and survival in people with cystic fibrosis.

SEARCH METHODS

We searched the Cystic Fibrosis and Genetic Disorders Group's Trials Register of references (identified from electronic database searches and hand searches of journals and abstract books) on 5 May 2022. We performed additional searches of PubMed, clinicaltrials.gov and the WHO ICTRP (International Clinical Trials Registry Platform) on 5 May 2022.

SELECTION CRITERIA

Randomised controlled trials of at least six months duration studying bisphosphonates in people with cystic fibrosis.

DATA COLLECTION AND ANALYSIS

Authors independently selected trials, extracted data and assessed risk of bias in included studies. Trial investigators were contacted to obtain missing data. We judged the certainty of the evidence using GRADE.

MAIN RESULTS

We included nine trials with a total of 385 participants (272 adults and 113 children (aged five to 18 years)). Trial durations ranged from six months to two years. Only two of the studies were considered to have a low risk of bias for all the domains.  Bisphosphonates compared to control in people with cystic fibrosis who have not had a lung transplant Seven trials included only adult participants without lung transplants, one trial included both adults and children without lung transplantation (total of 238 adults and 113 children). We analysed adults (n = 238) and children (n = 113) separately. Adults Three trials assessed intravenous bisphosphonates (one assessed pamidronate and two assessed zoledronate) and five trials assessed oral bisphosphonates (one assessed risedronate and four assessed alendronate). Bisphosphonates were compared to either placebo or calcium (with or without additional vitamin D). Data showed no difference between treatment or control groups in new vertebral fractures at 12 months (odds ratio (OR) 0.22, 95% confidence interval (CI) 0.02 to 2.09; 5 trials, 142 participants; very low-certainty evidence) and two trials (44 participants) reported no vertebral fractures at 24 months. There was no difference in non-vertebral fractures at 12 months (OR 2.11, 95% CI 0.18 to 25.35; 4 trials, 95 participants; very low-certainty evidence) and again two trials (44 participants) reported no non-vertebral fractures at 24 months. There was no difference in total fractures between groups at 12 months (OR 0.57, 95% CI 0.13 to 2.50; 5 trials, 142 participants) and no fractures were reported in two trials (44 participants) at 24 months. At 12 months, bisphosphonates may increase bone mineral density at the lumbar spine (mean difference (MD) 6.31, 95% CI 5.39 to 7.22; 6 trials, 171 participants; low-certainty evidence) and at the hip or femur (MD 4.41, 95% 3.44 to 5.37; 5 trials, 155 participants; low-certainty evidence). There was no clear difference in quality of life scores at 12 months (1 trial, 47 participants; low-certainty evidence), but bisphosphonates probably led to more adverse events (bone pain) at 12 months (OR 8.49, 95% CI 3.20 to 22.56; 7 trials, 206 participants; moderate-certainty evidence). Children The single trial in 113 children compared oral alendronate to placebo. We graded all evidence as low certainty. At 12 months we found no difference between treatment and placebo in new vertebral fractures (OR 0.32, 95% CI 0.03 to 3.13; 1 trial, 113 participants) and non-vertebral fractures (OR 0.19, 95% CI 0.01 to 4.04; 1 trial, 113 participants). There was also no difference in total fractures (OR 0.18, 95% CI 0.02 to 1.61; 1 trial, 113 participants). Bisphosphonates may increase bone mineral density at the lumbar spine at 12 months (MD 14.50, 95% CI 12.91 to 16.09). There was no difference in bone or muscle pain (MD 3.00, 95% CI 0.12 to 75.22), fever (MD 3.00, 95% CI 0.12 to 75.22) or gastrointestinal adverse events (OR 0.67, 95% CI 0.20 to 2.26). The trial did not measure bone mineral density at the hip/femur or report on quality of life.  Bisphosphonates compared to control in people with cystic fibrosis who have had a lung transplant One trial of 34 adults who had undergone lung transplantation compared intravenous pamidronate to no bisphosphonate treatment. It did not report at 12 months and we report the 24-month data (not assessed by GRADE). There was no difference in the number of fractures, either vertebral or non-vertebral. However, bone mineral density increased with treatment at the lumbar spine (MD 6.20, 95% CI 4.28 to 8.12) and femur (MD 7.90, 95% CI 5.78 to 10.02). No participants in either group reported either bone pain or fever. The trial did not measure quality of life.

AUTHORS' CONCLUSIONS

Oral and intravenous bisphosphonates may increase bone mineral density in people with cystic fibrosis, but there are insufficient data to determine whether treatment reduces fractures. Severe bone pain and flu-like symptoms may occur with intravenous bisphosphonates. Before any firm conclusions can be drawn, trials in larger populations, including children, and of longer duration are needed to determine effects on fracture rate and survival. Additional trials are needed to determine if bone pain is more common or severe (or both) with the more potent zoledronate and if corticosteroids can ameliorate or prevent these adverse events. Future trials should also assess gastrointestinal adverse effects associated with oral bisphosphonates.

The Ethanol Extracts of Osmanthus fragrans Leaves Ameliorate the Bone Loss via the Inhibition of Osteoclastogenesis in Osteoporosis

The aim of this study was to evaluate the anti-osteoporosis effects of Osmanthus fragrans leaf ethanol extract (OFLEE) in bone marrow-derived macrophages (BMM) and animals with osteoporosis. OFLEE not only suppressed tartrate-resistant acid phosphatase (TRAP)-positive cells with multiple nuclei but also decreased TRAP activity in BMM treated with macrophage colony stimulating factor (M-CSF) and receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL). The formation of F-actin rings and the expression and activation of matrix metalloproteinases were decreased by OFLEE in BMM treated with M-CSF and RANKL. OFLEE suppressed M-CSF- and RANKL-induced osteoclastogenesis by inhibiting NF-κB phosphorylation, tumor necrosis factor receptor-associated factor 6, c-fos, the nuclear factor of activated T-cells, cytoplasmic 1, and cathepsin K in BMM. OFLEE downregulated reactive oxygen species, cyclooxygenase-2, inducible nitric oxide synthase, prostaglandin E₂, tumor necrosis factor α, interleukin (IL)-1β, IL-6, IL-17, and RANKL in BMM treated with M-CSF and RANKL. Oral administration of OFLEE suppressed osteoporotic bone loss without hepatotoxicity in ovariectomy-induced osteoporosis animals. Our findings suggest that OFLEE, with anti-inflammatory effects, prevents osteoporotic bone loss through the suppression of osteoclastic differentiation in BMM and animals with osteoporosis.

Simultaneous neutralization of TGF-β and IL-6 attenuates Staphylococcus aureus-induced arthritic inflammation through differential modulation of splenic and synovial macrophages

Septic arthritis is a joint disease caused by Staphylococcus aureus. Different macrophage populations contribute in various ways to control blood-borne infections and induce inflammatory responses. Macrophage tissue-resident niche is necessary for the suppression of chronic inflammation and may contribute to the pathogenesis of septic arthritis. Thus, to obtain a resolution of the disease and restoration of synovial homeostasis, it needs the activation of macrophages that further regulate the inflammatory consequences. The aim of this study was to find out the mechanism by which neutralization of transforming growth factor-beta (TGF-β) and/or interleukin (IL)-6 after induction of septic arthritis could alter the specific macrophage responses in spleen and synovial joints via different cytokines (osteoprotegerin (OPG), osteopontin (OPN), IL-10, IL-12 and CXCL8) cross-talking, and how the response could be modulated by reactive oxygen species vs antioxidant enzyme activities. Dual neutralization of TGF-β and IL-6 is notably effective in eliciting splenic and synovial tissue-resident macrophage responses. Synovial macrophage-derived IL-10 can elicit protection against septic arthritis via regulating receptor-activated nuclear factor Kappa-B ligand (RANKL)/OPG interaction. They also reduced oxidative stress by increasing the activity of antioxidant enzymes including SOD and catalase. Histopathological analysis revealed that dual neutralization of TGF-β and IL-6 prevented bone destruction and osteoclastic activity in septic arthritis by promoting the differential functional response of the splenic and synovial macrophages. Additionally, the macrophage-derived IL-10 can elicit protection against S. aureus-induced septic arthritis via regulating RANKL/OPG interaction. Further studies on STAT3 and STAT4 are needed for the understanding of such cross-talking in resident macrophages of arthritic mice.

Positive Effects of Biologics on Osteoporosis in Rheumatoid Arthritis

Osteoporosis is a systemic skeletal disorder that causes vulnerability of bones to fracture owing to reduction in bone density and deterioration of the bone tissue microstructure. The prevalence of osteoporosis is higher in patients with autoimmune inflammatory rheumatic diseases, including rheumatoid arthritis (RA), than in those of the general population. In this autoimmune inflammatory rheumatic disease, in addition to known risk factors for osteoporosis, various factors such as chronic inflammation, autoantibodies, metabolic disorders, drugs, and decreased physical activity contribute to additional risk. In RA, disease-related inflammation plays an important role in local or systemic bone loss, and active treatment for inflammation can help prevent osteoporosis. In addition to conventional synthetic disease-modifying anti-rheumatic drugs that have been traditionally used for treatment of RA, biologic DMARDs and targeted synthetic DMARDs have been widely used. These agents can be employed more selectively and precisely based on disease pathogenesis. It has been reported that these drugs can inhibit bone loss by not only reducing inflammation in RA, but also by inhibiting bone resorption and promoting bone formation. In this review, the pathogenesis and research results of the increase in osteoporosis in RA are reviewed, and the effects of biological agents on osteoporosis are discussed.

Advances in Diagnosis and Management of Childhood Osteoporosis

Childhood osteoporosis leads to increased propensity to fracture, and thus is an important cause of morbidity, pain and healthcare utilisation. Osteoporosis in children may be caused by a primary bone defect or secondary to an underlying medical condition and/or its treatment. Primary osteoporosis is rare, but there is an increasing number of children with risk factors for secondary osteoporosis. Therefore it is imperative that all paediatricians are aware of the diagnostic criteria and baseline investigations for childhood osteoporosis to enable timely referral to a specialist in paediatric bone health. This review will discuss the approach to diagnosis, investigation and management of childhood osteoporosis, with particular consideration to advances in molecular diagnosis of primary bone disorders, and current and emerging therapies for fracture reduction.

Risk association of RANKL and OPG gene polymorphism with breast cancer to bone metastasis in Pashtun population of Khyber Pakhtunkhwa, Pakistan

Introduction

The receptor activator NF-κB ligand (RANKL) and Osteoprotegrin (OPG) single nucleotide polymorphisms (SNPs) have been associated with the risk of breast cancer to bone metastasis. This study was designed to investigate the association of RANKL and OPG gene polymorphisms with breast to bone metastasis in Pashtun population of Khyber Pakhtunkhwa, Pakistan.

Materials and methods

A total of 215 participants were enrolled containing 106 breast cancer patients, 58 breast to bone metastasis and 51 age and gender matched healthy controls. RANKL (rs9533156) and OPG (rs2073618, rs3102735) polymorphisms were genotyped in genomic DNA, using Tetra-ARMS PCR protocol. The results were analyzed among the three groups and P-value less then 0.05 were considered statistically significant.

Results

Our results displayed significant association of OPG (rs3102735) risk allele and corresponding genotypes in breast cancer vs healthy controls, bone metastasis vs healthy controls and breast cancer vs breast to bone metastasis as a disease risk. However, there was no association observed for OPG (rs2073618) risk allele and corresponding genotypes with the diseases risk. Similarly, RANKL (rs9533156) risk allele and corresponding genotypes in breast cancer vs healthy controls, bone metastasis vs healthy controls and breast cancer vs breast to bone metastasis exhibited significant association except for the risk allele carrying genotypes in breast to bone metastasis.

Conclusion

OPG (rs3102735) and RANKL (rs9533156) exhibited significant association with breast to bone metastasis while OPG (rs2073618) didn’t show significant association with breast to bone metastasis in Pashtun population of Pakistan. However, this study unlocks more questions to investigate the exact scenario of genetic predisposition of breast to bone metastasis.

Changes in bone turnover markers in patients without bone metastases receiving immune checkpoint inhibitors: An exploratory analysis

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Immune checkpoint inhibitors (ICIs) are correlated with immune-related adverse events (irAEs) that may potentially affect all host tissues.

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The effects of ICIs on the skeleton are poorly investigated, thus we evaluated the changes of specific markers of bone resorption and formation.

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We found an increase of type I collagen C-terminal telopeptide (CTX-I) levels after 3 months of ICIs treatment with a concomitant reduction of N-terminal propeptide of type I procollagen (PINP) levels with a trend toward statistical significance.

•

CTX-I increase was also associated with poor prognosis in terms of treatment response and survival.

Immune checkpoint inhibitors (ICIs) has revolutionized the treatment of different advanced solid tumors, but most patients develop severe immune-related adverse events (irAEs). Although a bi-directional crosstalk between bone and immune systems is widely described, the effect of ICIs on the skeleton is poorly investigated. Here, we analyze the changes in plasma levels of type I collagen C-terminal telopeptide (CTX-I) and N-terminal propeptide of type I procollagen (PINP), reference makers of bone turnover, in patients treated with ICIs and their association with clinical outcome.

A series of 44 patients affected by advanced non-small cell lung cancer or renal cell carcinoma, without bone metastases, and treated with ICIs as monotherapy were enrolled. CTX-I and PINP plasma levels were assessed at baseline and after 3 months of ICIs treatment by ELISA kits.

A significant increase of CTX-I with a concomitant decreasing trend towards the reduction of PINP was observed after 3 months of treatment. Intriguingly, CTX-I increase was associated with poor prognosis in terms of treatment response and survival. These data suggest a direct relationship between ICIs treatment, increased osteoclast activity and potential fracture risk.

Overall, this study reveals that ICIs may act as triggers for skeletal events, and if confirmed in larger prospective studies, it would identify a new class of skeletal-related irAEs.

Effect of Taraxaci Herba on Bone Loss in an OVX-Induced Model through the Regulation of Osteoclast Differentiation

Bone is a dynamic tissue that maintains homeostasis with a balance of osteoclasts for bone resorption and osteoblasts for bone formation. Women are deficient in estrogen after menopause, which promotes bone resorption due to excessive activity of osteoclasts, leading to osteoporosis. TH (also known as dandelion) is native to warm regions and has traditionally been used to treat gynecological diseases and inflammation. Menopause is a major cause of osteoporosis as it causes abnormal activity of osteoclasts, and various studies have shown that anti-inflammatory drugs have the potential to treat osteoporosis. We analyzed the effect of TH on osteoclast differentiation and the relevant mechanisms using RANKL. After administration of TH in a menopause-like rat model in which ovariectomy of the was rats carried out, changes in bone microstructure were analyzed via micro-CT, and the antiosteoporosis effect of TH was verified by a histological analysis. In addition, the pharmacological effects of TH in an animal model of osteoporosis were compared and analyzed with osteoporosis medications (17β-estradiol (E₂) and alendronate (ALN)). TH significantly inhibited the initial osteoclast differentiation via the NFATc1/c-Fos mechanism. In addition, bone density in the femur of osteoporotic rats was increased, and the expression of osteoclast-related factors in the serum and tissues was controlled. The results of this study provide objective evidence of the inhibitory effect of TH on osteoclastogenesis and OVX-induced bone loss.

Shilajit extract reduces oxidative stress, inflammation, and bone loss to dose-dependently preserve bone mineral density in postmenopausal women with osteopenia: A randomized, double-blind, placebo-controlled trial

BACKGROUND

Accelerated bone loss associated with aging and estrogen withdrawal is mediated in part by increased oxidative stress and inflammation.

OBJECTIVE

Investigate dietary supplementation with a standardized aqueous extract of shilajit with clinically demonstrated antioxidant, anti-inflammatory, and collagen-promoting activity on attenuating bone loss in postmenopausal women with osteopenia.

DESIGN

Sixty postmenopausal women aged 45 - 65 years with osteopenia were randomized to receive 1 of 3 treatments daily for 48 weeks: (1) placebo, (2) 250 mg shilajit extract, or (3) 500 mg shilajit extract. Bone mineral density (BMD) of the lumbar spine (LS) and femoral neck (FN) were measured at weeks 0, 24, and 48, and circulating markers of bone turnover (CTX-1, BALP, RANKL, OPG), oxidative stress (MDA, GSH), and inflammation (hsCRP) at weeks 0, 12, 24, and 48.

RESULTS

BMD of both the LS and FN progressively decreased in women receiving placebo but was dose-dependently attenuated with shilajit extract supplementation, resulting in significantly increased percentage changes from baseline in BMD at 24- and 48-weeks in both supplemented groups compared to placebo (p < 0.001). CTX-1, BALP, and RANKL decreased, whereas OPG increased, in both groups supplemented with the shilajit extract, but not in the placebo group, resulting in significantly decreased or increased percentage changes from baseline, respectively. MDA was significantly decreased (p < 0.001) and GSH was significantly increased (p < 0.001) in both supplemented groups compared to placebo from week 12 for the duration of the study. Progressive reductions in hsCRP were observed in both supplemented groups, resulting in significantly decreased percentage changes from baseline in supplemented women compared to placebo (p < 0.001).

CONCLUSION

Daily supplementation with this shilajit extract supports BMD in postmenopausal women with osteopenia in part by attenuating the increased bone turnover, inflammation and oxidative stress that coincides with estrogen deficiency in this population at increased risk for osteoporosis and bone fractures.

Bone matrix quality in a developing high-fat diet mouse model is altered by RAGE deletion

Overweightness and obesity in adolescents are epidemics linked to chronic low-grade inflammation and elevated fracture risk. The increased fracture risk observed in overweight/obese adolescence contrasts the traditional concept that high body mass is protective against fracture, and thus highlights the need to determine why weight gain becomes detrimental to fracture during growth and maturity. The Receptor for Advanced Glycation End products (RAGE) is a central inflammatory regulator that can influence bone metabolism. It remains unknown how RAGE removal impacts skeletal fragility in overweightness/obesity, and whether increased fracture risk in adolescents could result from low-grade inflammation deteriorating bone quality. We characterized the multiscale structural, mechanical, and chemical properties of tibiae extracted from adolescent C57BL/6J (WT) and RAGE null (KO) mice fed either low-fat (LF) or high-fat (HF) diet for 12 weeks starting at 6 weeks of age using micro-computed tomography, strength, Raman spectroscopy, and nanoindentation. Overweight/obese WT HF mice possessed degraded mineral-crystal quality and increased matrix glycoxidation in the form of pentosidine and carboxymethyl-lysine, with HF diet in females only showing reduced cortical surface expansion and TMD independently of RAGE ablation. Furthermore, in contrast to males, HF diet in females led to more material damage and plastic deformation. RAGE KO mitigated glycoxidative matrix accumulation, preserved mineral quantity, and led to increased E/H ratio in females. Taken together, these results highlight the complex, multi-scale and sex-dependent relationships between bone quality and function under overweightness, and identifies RAGE-controlled glycoxidation as a target to potentially preserve matrix quality and mechanical integrity.

Associations of Bone Mineral Density with RANKL and Osteoprotegerin in Arab Postmenopausal Women: A Cross-Sectional Study

Background and objective: There is limited information as to the association of several key bone markers with bone mineral density (BMD) in understudied ethnic groups. This study investigated the relationship between circulating levels of osteoprotegerin (OPG) and receptor activator of nuclear factor kappa-Β ligand (RANKL) with BMD in Arab postmenopausal women. Materials and methods: In this cross-sectional study, a total of 617 Saudi postmenopausal women from the Osteoporosis Registry of the Chair for Biomarkers of Chronic Diseases were included. Anthropometric data, BMD, and biochemical data were retrieved from the registry. Participants were stratified into three groups based on T-score; n = 169 with osteoporosis, n = 282 with osteopenia, and n = 166 normal. Analysis of bone markers including RANKL, OPG, osteocalcin, and N-terminal telopeptide (NTx) was completed using commercially available bioassays. Results: The results suggested that OPG was significantly and positively correlated with age in the osteoporosis group (r = 0.29, p < 0.05), while it was inversely correlated with BMD femoral neck left (r = −0.56, p < 0.001) and BMD femoral neck right (r = −0.37, p < 0.05) in the same group. Moreover, RANKL showed a significant inverse correlation with NTx in the osteopenia group (r = −0.37, p < 0.05). Furthermore, the RANKL/OPG ratio had a positive and significant correlation with BMI (r = 0.34, p < 0.05), BMD femoral neck left (r = 0.36, p < 0.05) and BMD femoral neck right (r = 0.35, p < 0.05) in the osteopenia group. By contrast, it showed a significant inverse correlation with waist to hip ratio in the osteoporosis group (r = −0.38, p < 0.05). Multiple regression analysis showed that OPG contributes to BMD variations in the osteopenia group (p = 0.03). Conclusions: In conclusion, changes in circulating levels of RANKL and OPG might be a protective mechanism contrary to the increased bone loss in postmenopausal women.

Immunology of osteoporosis: relevance of inflammatory targets for the development of novel interventions

Osteoporosis is recognized as low bone mass and deteriorated bone microarchitecture. It is the leading cause of fractures and consequent morbidity globally. The established pathophysiological evidence favors the endocrine factors for osteoporosis and the role of the immune system on the skeletal system has been recently identified. Due to the common developmental niche bone and immune system interactions have led to the emergence of osteoimmunology. Immune dysregulation can initiate inflammatory conditions that adversely affect bone integrity. The role of immune cells, such as T-lymphocytes subsets (Th17), cannot be neglected in the pathogenesis of osteoporosis. Local inflammation within the bone from any cause attracts immune cells that participate in the activation of osteoclasts. This work summarizes the present knowledge of osteoimmunology in reference to osteoporosis and identifies novel targets for immunotherapy of osteoporosis.

Effects of Drugs and Chemotherapeutic Agents on Dental Implant Osseointegration: Narrative Review

BACKGROUND

Dental implants have been one of the most popular treatments for rehabilitating individuals with single missing teeth or fully edentulous jaws since their introduction. As more implant patients are well-aged and take several medications due to various systemic conditions, clinicians should be mindful of possible drug implications on bone remodeling and osseointegration.

OBJECTIVE

The present study aims to study and review some desirable and some unwelcomed implications of medicine on osseointegration.

METHODS

A broad search for proper relevant studies were conducted in four databases, including Web of Science, Pubmed, Scopus, and Google Scholar.

RESULTS

Some commonly prescribed medicines such as nonsteroidal anti-inflammatory drugs (NSAIDs), glucocorticoids, proton pump inhibitors (PPIs), selective serotonin reuptake inhibitors (SSRIs), anticoagulants, metformin, and chemotherapeutic agents may jeopardize osseointegration. On the contrary, some therapeutic agents such as anabolic, anti-catabolic, or dual anabolic and anti-catabolic agents may enhance osseointegration and increase the treatment's success rate.

CONCLUSION

Systemic medications that enhance osseointegration include mineralization promoters and bone resorption inhibitors. On the other hand, medications often given to the elderly with systemic problems might interfere with osseointegration, leading to implant failure. However, to validate the provided research, more human studies with a higher level of evidence are required.

Associations of IL-18 with Altered Cardiovascular Risk Profile in Psoriatic Arthritis and Ankylosing Spondylitis

Objective: To investigate the associations of IL-18 serum levels with serum lipids, cardiovascular risk, and disease activity in patients with ankylosing spondylitis (AS) and psoriatic arthritis (PsA) with axial (axPsA) and peripheral (perPsA) joint involvement. Methods: 155 adult patients (PsA 61/AS 94) were enrolled in the study. Standard disease activity indices, BASDAI, and ASDAS, were calculated for AS and PsA and DAPSA for PsA. Sera from peripheral blood samples were obtained after night fasting. Serum concentrations of cytokines (IL-18, IL-17) were measured by ELISA, while lipid profile with total cholesterol (TC), triglycerides (TG), low-density cholesterol-(LDL), high-density cholesterol (HDL), and C-reactive protein (CRP) concentrations were determined using routine procedures. The atherogenic index was calculated using the standard formula AI = TC/HDL. Results: Patients with PsA and peripheral joint involvement (perPsA) had significantly higher IL-18 serum levels than axial PsA and AS patients (medians 160 vs. 116 vs. 80 pg/mL). In patients with PsA and in the subgroup with PsA+ ischemic heart disease (IHD), IL-18 positively correlated with atherogenic index (AI) (rho = 0.46 and rho = 0.67, respectively) and TG serum concentrations (rho = 0.4 and rho = 0.675), while negatively with HDL levels (rho = −0.37 and rho = −0.608). In PsA + IHD subgroup IL-18 serum levels correlated positively also with disease activity (DAPSA) (rho = 0.613). Importantly, in patients with perPsA, characterized by the highest IL-18 serum levels, cardiovascular risk, and frequency of both hypertriglyceridemia and IHD, positive correlations between IL-18 and IL-17 (rho = 0.47, p = 0.002), TG (rho = 0.45 p = 0.01) levels and AI (rho = 0.63 p = 0.021) were found. Whereas linear regression models revealed that IL-17, TG concentrations and the tender joint count had an impact on IL-18 Conclusions: We confirmed that patients with perPsA are characterized by a more pronounced proinflammatory and proatherogenic cardiovascular risk profile than patients with axPsA and AS. Importantly our study indicates that in PsA, but not in AS, elevated serum concentration of IL-18 is associated with higher disease activity and proatherogenic lipid profile, leading to a higher cardiovascular risk. Thus, our results point out IL-18 as a critical contributor in these pathological processes and possible therapeutic targets.

Effect of inflammation on bones in diabetic patients with periodontitis via RANKL/OPG system-A review

Purpose

Diabetes mellitus and periodontitis are inflammatory diseases, the severity of inflammation results in the progression and persistence of both the disorders and affects bones. Diabetic complications aggravate in diabetic subjects having periodontitis; similarly, diabetic patients are more prone to developing gingivitis and periodontitis. Periodontal and diabetic inflammation disturbs bone homeostasis, which possibly involves both innate and adaptive immune responses. The pathogenic processes that link the two diseases are the focus of much research and it is likely that upregulated inflammation arising from each condition adversely affects the other. RANKL/OPG pathway plays a prominent role in periodontal and diabetic inflammation and bone resorption.

Method

This review article summarises the literature on the link between inflammatory cytokines and the prevalence of disturbed bone homeostasis in diabetic patients with periodontitis. An extensive search was done in PubMed, Scopus, Medline and Google Scholar databases between April 2003 and May 2021.

Result

A total of 27 articles, including pilot studies, case-control studies, cross-sectional studies, cohort studies, randomized control trials, longitudinal studies, descriptive studies and experimental studies, were included in our literature review.

Conclusion

Since RANKL/OPG are cytokines and have immune responses, regulating these cytokines expression will help control diabetes, periodontitis and bone homeostasis. The growing evidence of bone loss and increased fracture risk in diabetic patients with periodontitis makes it imperative that health professionals carry out planned treatment focusing on monitoring oral health in diabetic patients; bone markers should also be evaluated in patients with chronic periodontitis with an impaired glycemic state.

Inflammatory conversion of quiescent osteoblasts by metastatic breast cancer cells through pERK1/2 aggravates cancer-induced bone destruction

Disruption of bone homeostasis caused by metastatic osteolytic breast cancer cells increases inflammatory osteolysis and decreases bone formation, thereby predisposing patients to pathological fracture and cancer growth. Alteration of osteoblast function induces skeletal diseases due to the disruption of bone homeostasis. We observed increased activation of pERK1/2 in osteolytic breast cancer cells and osteoblasts in human pathological specimens with aggressive osteolytic breast cancer metastases. We confirmed that osteolytic breast cancers with high expression of pERK1/2 disrupt bone homeostasis via osteoblastic ERK1/2 activation at the bone-breast cancer interface. The process of inflammatory osteolysis modulates ERK1/2 activation in osteoblasts and breast cancer cells through dominant-negative MEK1 expression and constitutively active MEK1 expression to promote cancer growth within bone. Trametinib, an FDA-approved MEK inhibitor, not only reduced breast cancer-induced bone destruction but also dramatically reduced cancer growth in bone by inhibiting the inflammatory skeletal microenvironment. Taken together, these findings suggest that ERK1/2 activation in both breast cancer cells and osteoblasts is required for osteolytic breast cancer-induced inflammatory osteolysis and that ERK1/2 pathway inhibitors may represent a promising adjuvant therapy for patients with aggressive osteolytic breast cancers by altering the shared cancer and bone microenvironment.

Probiotics Stimulate Bone Formation in Obese Mice via Histone Methylations

Rationale: Manipulation of the gut microbiome can prevent pathologic bone loss. However, the effects of probiotics on mitochondrial epigenetic remodeling and skeletal homeostasis in the high-fat diet (HFD)-linked obesity remains to be explored. Here, we examined the impact of probiotics supplementation on mitochondrial biogenesis and bone homeostasis through the histone methylation mechanism in HFD fed obese mice.

Methods: 16S rRNA gene sequencing was performed to study the microbiota composition in the gut and microbial dysbiosis in obese mouse model. High resolution (microPET/CT) imaging was performed to demonstrate the obese associated colonic inflammation. Obese-associated upregulation of target miRNA in osteoblast was investigated using a microRNA qPCR array. Osteoblastic mitochondrial mass was evaluated using confocal imaging. Overexpression of mitochondrial transcription factor (Tfam) was used to investigate the glycolysis and mitochondrial bioenergetic metabolism using Tfam-transgenic (Tg) mice fed on HFD. The bone formation and mechanical strength was evaluated by microCT analysis and three-point bending analysis.

Results: High-resolution imaging (µ-CT) and mechanical testing revealed that probiotics induced a significant increase of trabecular bone volume and bone mechanical strength respectively in obese mice. Probiotics or Indole-3-propionic acid (IPA) treatment directly to obese mice, prevents gut inflammation, and improved osteoblast mineralization. Mechanistically, probiotics treatment increases mitochondrial transcription factor A (Tfam) expression in osteoblasts by promoting Kdm6b/Jmjd3 histone demethylase, which inhibits H3K27me3 epigenetic methylation at the Tfam promoter. Furthermore, Tfam-transgenic (Tg) mice, fed with HFD, did not experience obesity-linked reduction of glucose uptake, mitochondrial biogenesis and mineralization in osteoblasts.

Conclusions: These results suggest that the probiotics mediated changes in the gut microbiome and its derived metabolite, IPA are potentially be a novel agent for regulating bone anabolism via the gut-bone axis.

Diphlorethohydroxycamalol isolated from Ishige okamurae prevents H2O2-induced oxidative damage via BMP2/Runx2 signaling in osteoblastic MC3T3-E1 cells

Accumulating evidence has shown an association between osteoporosis and oxidative damage. In the present study, the protective effects of diphlorethohydroxycarmalol (DPHC) isolated from the brown algae Ishige okamurae against H2O2-induced oxidative damage via bone morphogenetic protein 2 (BMP2)/ runt-related transcription factor 2 (Runx2) signaling were investigated using MC3T3-E1 osteoblastic cells. DPHC counteracted the reduction in cell viability caused by H2O2 exposure and protected against H2O2-induced dysfunction, demonstrated by improved cellular alkaline phosphatase (ALP) activity and calcium deposition. In addition, treatment with 0.05-0.2 mM DPHC elevated the protein expression of osteoblast differentiation factors type 1 collagen, ALP, p-Smad1/5, Osterix, BMP2, and Runx2, in response to H2O2-induced oxidative damage. Importantly, DPHC decreased the expression levels of receptor activator of nuclear factor kappa-B ligand, which promotes bone resorption, and inhibited the H2O2-induced generation of reactive oxygen species. Taken together, the results suggest that DPHC counteracts the effects of oxidative stress in osteoblastic cells and has the potential to be effective in preventing and alleviating osteoporosis.

Interaction between bone and immune cells: Implications for postmenopausal osteoporosis

Postmenopausal osteoporosis is a systemic disease characterized by the loss of bone mass and increased bone fracture risk largely resulting from significantly reduced levels of the hormone estrogen after menopause. Besides the direct negative effects of estrogen-deficiency on bone, indirect effects of altered immune status in postmenopausal women might contribute to ongoing bone destruction, as postmenopausal women often display a chronic low-grade inflammatory phenotype with altered cytokine expression and immune cell profile. In this context, it was previously shown that various immune cells interact with osteoblasts and osteoclasts either via direct cell-cell contact, or more likely via paracrine mechanisms. For example, specific subtypes of T lymphocytes express TNFα, which was shown to increase osteoblast apoptosis and to indirectly stimulate osteoclastogenesis via B cell-produced receptor-activator of NF-κB ligand (RANKL), thereby triggering bone loss during postmenopausal osteoporosis. T_h17 cells release interleukin-17 (IL-17), which directs mesenchymal stem cell differentiation towards the osteogenic lineage, but also indirectly increases osteoclast differentiation. B lymphocytes are a major regulator of osteoclast formation via granulocyte colony-stimulating factor secretion and the RANKL/osteoprotegerin system under estrogen-deficient conditions. Macrophages might act differently on bone cells dependent on their polarization profile and their secreted paracrine factors, which might have implications for the development of postmenopausal osteoporosis, because macrophage polarization is altered during disease progression. Likewise, neutrophils play an important role during bone homeostasis, but their over-activation under estrogen-deficient conditions contributes to osteoblast apoptosis via the release of reactive oxygen species and increased osteoclastogenesis via RANKL signaling. Furthermore, mast cells might be involved in the development of postmenopausal osteoporosis, because they store high levels of osteoclastic mediators, including IL-6 and RANKL, in their granules and their numbers are greatly increased in osteoporotic bone. Additionally, bone fracture healing is altered under estrogen-deficient conditions with the increased presence of pro-inflammatory cytokines, including IL-6 and Midkine, which might contribute to healing disturbances. Consequently, in addition to the direct negative influence of estrogen-deficiency on bone, immune cell alterations contribute to the pathogenesis of postmenopausal osteoporosis.

TRAP5b and RANKL/OPG Predict Bone Pathology in Patients with Gaucher Disease

Background and objective: Bone involvement occurs in 75% of patients with Gaucher disease (GD), and comprises structural changes, debilitating pain, and bone density abnormalities. Osteoporosis is a silent manifestation of GD until a pathologic fracture occurs. Thus, early diagnosis is crucial for identifying high-risk patients in order to prevent irreversible complications. Methods: Thirty-three patients with GD were assessed prospectively to identify predictive markers associated with bone density abnormalities, osteopenia (OSN), and osteoporosis (OSR). Subjects were categorized into three cohorts based on T- or Z-scores of bone mineral density (BMD). The first GD cohort consisted of those with no bone complications (Z-score ≥ −0.9; T-scores ≥ −1), the second was the OSN group (−1.8 ≥ Z-score ≥ −1; −2.5 ≥ T-score ≥ −1), and the third was the OSR group (Z-score ≤ −1.9; T-scores ≤ −2.5). Serum levels of TRAP5b, RANKL, OPG, and RANK were quantified by enzyme-linked immunosorbent assays. Results: TRAP5b levels were increased in GD patients, and showed a positive correlation with GD biomarkers, including plasma glucosylsphingosine (lyso-Gb1) and macrophage activation markers CCL18 and chitotriosidase. The highest level of TRAP5b was measured in patients with osteoporosis. The elevation of RANKL and RANKL/OPG ratio correlated with osteopenia in GD. Conclusion: TRAP5b, RANKL, and RANKL/OPG elevation indicate osteoclast activation in GD. TRAP5b is a potential bone biomarker for GD with the ability to predict the progression of bone density abnormalities.

Extracellular Vesicle-Mediated Bone Remodeling and Bone Metastasis: Implications in Prostate Cancer

Bone metastasis is the tendency of certain primary tumors to spawn and dictate secondary neoplasia in the bone. The process of bone metastasis is regulated by the dynamic crosstalk between metastatic cancer cells, cellular components of the bone marrow microenvironment (osteoblasts, osteoclasts, and osteocytes), and the bone matrix. The feed-forward loop mechanisms governs the co-option of homeostatic bone remodeling by cancer cells in bone. Recent developments have highlighted the discovery of extracellular vesicles (EVs) and their diverse roles in distant outgrowths. Several studies have implicated EV-mediated interactions between cancer cells and the bone microenvironment in synergistically promoting pathological skeletal metabolism in the metastatic site. Nevertheless, the potential role that EVs serve in arbitrating intricate sequences of coordinated events within the bone microenvironment remains an emerging field. In this chapter, we review the role of cellular participants and molecular mechanisms in regulating normal bone physiology and explore the progress of current research into bone-derived EVs in directly triggering and coordinating the processes of physiological bone remodeling. In view of the emerging role of EVs in interorgan crosstalk, this review also highlights the multiple systemic pathophysiological processes orchestrated by the EVs to direct organotropism in bone in prostate cancer. Given the deleterious consequences of bone metastasis and its clinical importance, in-depth knowledge of the multifarious role of EVs in distant organ metastasis is expected to open new possibilities for prognostic evaluation and therapeutic intervention for advanced bone metastatic prostate cancer.

Targeting S1PRs as a Therapeutic Strategy for Inflammatory Bone Loss Diseases-Beyond Regulating S1P Signaling

As G protein coupled receptors, sphingosine-1-phosphate receptors (S1PRs) have recently gained attention for their role in modulating inflammatory bone loss diseases. Notably, in murine studies inhibiting S1PR2 by its specific inhibitor, JTE013, alleviated osteoporosis induced by RANKL and attenuated periodontal alveolar bone loss induced by oral bacterial inflammation. Treatment with a multiple S1PRs modulator, FTY720, also suppressed ovariectomy-induced osteoporosis, collagen or adjuvant-induced arthritis, and apical periodontitis in mice. However, most previous studies and reviews have focused mainly on how S1PRs manipulate S1P signaling pathways, subsequently affecting various diseases. In this review, we summarize the underlying mechanisms associated with JTE013 and FTY720 in modulating inflammatory cytokine release, cell chemotaxis, and osteoclastogenesis, subsequently influencing inflammatory bone loss diseases. Studies from our group and from other labs indicate that S1PRs not only control S1P signaling, they also regulate signaling pathways induced by other stimuli, including bacteria, lipopolysaccharide (LPS), bile acid, receptor activator of nuclear factor κB ligand (RANKL), IL-6, and vitamin D. JTE013 and FTY720 alleviate inflammatory bone loss by decreasing the production of inflammatory cytokines and chemokines, reducing chemotaxis of inflammatory cells from blood circulation to bone and soft tissues, and suppressing RANKL-induced osteoclast formation.

Secretory Activity of Mesenchymal Stromal Cells with Different Degree of Commitment under Conditions of Simulated Microgravity

Microgravity negatively affects the bone tissue which manifested in a decrease in mineral density of the bones during long-term space flights. Impairments of bone homeostasis are determined among other things by changes in secretory activity of heterogeneous populations of low-committed precursors, such as mesenchymal stromal cells (MSC) and osteoblasts. We studied the effect of microgravity modeling during 10 days on paracrine activity of osteogenically committed and intact MSC. Cell response to simulated microgravity depended on the degree of commitment. The response of osteogenically committed MSC was less pronounced and manifested in increased production of sclerostin. In intact MSC, an increase in IL-8 and VEGF secretion and a decrease in osteoprotegerin level were detected. These changes can underlie the shift of bone homeostasis towards bone resorption.

Maintaining homeostatic control of periodontal bone tissue

Alveolar bone is a unique osseous tissue due to the proximity of dental plaque biofilms. Periodontal health and homeostasis are mediated by a balanced host immune response to these polymicrobial biofilms. Dysbiotic shifts within dental plaque biofilms can drive a proinflammatory immune response state in the periodontal epithelial and gingival connective tissues, which leads to paracrine signaling to subjacent bone cells. Sustained chronic periodontal inflammation disrupts "coupled" osteoclast-osteoblast actions, which ultimately result in alveolar bone destruction. This chapter will provide an overview of alveolar bone physiology and will highlight why the oral microbiota is a critical regulator of alveolar bone remodeling. The ecology of dental plaque biofilms will be discussed in the context that periodontitis is a polymicrobial disruption of host homeostasis. The pathogenesis of periodontal bone loss will be explained from both a historical and current perspective, providing the opportunity to revisit the role of fibrosis in alveolar bone destruction. Periodontal immune cell interactions with bone cells will be reviewed based on our current understanding of osteoimmunological mechanisms influencing alveolar bone remodeling. Lastly, probiotic and prebiotic interventions in the oral microbiota will be evaluated as potential noninvasive therapies to support alveolar bone homeostasis and prevent periodontal bone loss.

Bone loss markers in the earliest Pacific Islanders

Kingdom of Tonga in Polynesia is one of the most obese nations where metabolic conditions, sedentary lifestyles, and poor quality diet are widespread. These factors can lead to poor musculoskeletal health. However, whether metabolic abnormalities such as osteoporosis occurred in archaeological populations of Tonga is unknown. We employed a microscopic investigation of femur samples to establish whether bone loss afflicted humans in this Pacific region approximately 3000 years ago. Histology, laser confocal microscopy, and synchrotron Fourier-transform infrared microspectroscopy were used to measure bone vascular canal densities, bone porosity, and carbonate and phosphate content of bone composition in eight samples extracted from adult Talasiu males and females dated to 2650 BP. Compared to males, samples from females had fewer vascular canals, lower carbonate and phosphate content, and higher bone porosity. Although both sexes showed evidence of trabecularised cortical bone, it was more widespread in females (35.5%) than males (15.8%). Our data suggest experiences of advanced bone resorption, possibly as a result of osteoporosis. This provides first evidence for microscopic bone loss in a sample of archaeological humans from a Pacific population widely afflicted by metabolic conditions today.

Mechanobiological Principles Influence the Immune Response in Regeneration: Implications for Bone Healing

A misdirected or imbalanced local immune composition is often one of the reasons for unsuccessful regeneration resulting in scarring or fibrosis. Successful healing requires a balanced initiation and a timely down-regulation of the inflammation for the re-establishment of a biologically and mechanically homeostasis. While biomaterial-based approaches to control local immune responses are emerging as potential new treatment options, the extent to which biophysical material properties themselves play a role in modulating a local immune niche response has so far been considered only occasionally. The communication loop between extracellular matrix, non-hematopoietic cells, and immune cells seems to be specifically sensitive to mechanical cues and appears to play a role in the initiation and promotion of a local inflammatory setting. In this review, we focus on the crosstalk between ECM and its mechanical triggers and how they impact immune cells and non-hematopoietic cells and their crosstalk during tissue regeneration. We realized that especially mechanosensitive receptors such as TRPV4 and PIEZO1 and the mechanosensitive transcription factor YAP/TAZ are essential to regeneration in various organ settings. This indicates novel opportunities for therapeutic approaches to improve tissue regeneration, based on the immune-mechanical principles found in bone but also lung, heart, and skin.

The Effect of Inflammation on Bone

Bone remodeling is the continual process to renew the adult skeleton through the sequential action of osteoblasts and osteoclasts. Nuclear factor RANK, an osteoclast receptor, and its ligand RANKL, expressed on the surface of osteoblasts, result in coordinated control of bone remodeling. Inflammation, a feature of illness and injury, plays a distinct role in skewing this process toward resorption. It does so via the interaction of inflammatory mediators and their related peptides with osteoblasts and osteoclasts, as well as other immune cells, to alter the expression of RANK and RANKL. Such chemical mediators include TNFα, glucocorticoids, histamine, bradykinin, PGE2, systemic RANKL from immune cells, and interleukins 1 and 6. Conditions, such as periodontal disease and alveolar bone erosion, aseptic prosthetic loosening, rheumatoid arthritis, and some sports related injuries are characterized by the result of this process. A thorough understanding of bone response to injury and disease, and ability to detect such biomarkers, as well as imaging to identify early structural and mechanical property changes in bone architecture, is important in improving management and outcomes of bone related pathology. While gut health and vitamin and mineral availability appear vitally important, nutraceuticals also have an impact on bone health. To date most pharmaceutical intervention targets inflammatory cytokines, although strategies to favorably alter inflammation induced bone pathology are currently limited. Further research is required in this field to advance early detection and treatments.

New perspectives on traumatic bone infections

In this paper, we review the results of previous studies and summarize the effects of various factors on the regulation of bone metabolism in traumatic bone infections. Infection-related bone destruction incorporates pathogens and iatrogenic factors in the process of bone resorption dominated by the skeletal and immune systems. The development of bone immunology has established a bridge of communication between the skeletal system and the immune system. Exploring the effects of pathogens, skeletal systems, immune systems, and antibacterials on bone repair in infectious conditions can help improve the treatment of these diseases.

Can telomere length predict bone health? A review of current evidence

Telomeres are repetitive DNA sequences located at the end of chromosomes that serve as a protective barrier against chromosomal deterioration during cell division. Approximately 50–200 base pairs of nucleotides are lost per cell division, and new repetitive nucleotides are added by the enzyme telomerase, allowing telomere maintenance. Telomere shortening has been proposed as an indicator for biological aging, but its relationship with age-related osteoporosis is ambiguous. We summarize the current evidence on the relationship between telomere length and bone health in experimental and epidemiological studies, which serve as a scientific reference for the development of novel diagnostic markers of osteoporosis or novel therapeutics targeting telomere and telomerase of bone cells to treat osteoporosis.

Microtopography of Immune Cells in Osteoporosis and Bone Lesions by Endocrine Disruptors

Osteoporosis stems from an unbalance between bone mineral resorption and deposition. Among the numerous cellular players responsible for this unbalance bone marrow (BM) monocytes/macrophages, mast cells, T and B lymphocytes, and dendritic cells play a key role in regulating osteoclasts, osteoblasts, and their progenitor cells through interactions occurring in the context of the different bone compartments (cancellous and cortical). Therefore, the microtopography of immune cells inside trabecular and compact bone is expected to play a relevant role in setting initial sites of osteoporotic lesion. Indeed, in physiological conditions, each immune cell type preferentially occupies either endosteal, subendosteal, central, and/or perisinusoidal regions of the BM. However, in the presence of an activation, immune cells recirculate throughout these different microanatomical areas giving rise to a specific distribution. As a result, the trabeculae of the cancellous bone and endosteal free edge of the diaphyseal case emerge as the primary anatomical targets of their osteoporotic action. Immune cells may also transit from the BM to the depth of the compact bone, thanks to the efferent venous capillaries coursing in the Haversian and Volkmann canals. Consistently, the innermost parts of the osteons and the periosteum are later involved by their immunomodulatory action, becoming another site of mineral reabsorption in the course of an osteoporotic insult. The novelty of our updating is to highlight the microtopography of bone immune cells in the cancellous and cortical compartments in relation to the most consistent data on their action in bone remodeling, to offer a mechanist perspective useful to dissect their role in the osteoporotic process, including bone damage derived from the immunomodulatory effects of endocrine disrupting chemicals.

The Influence of Radiation on Bone and Bone Cells-Differential Effects on Osteoclasts and Osteoblasts

The bone is a complex organ that is dependent on a tight regulation between bone formation by osteoblasts (OBs) and bone resorption by osteoclasts (OCs). These processes can be influenced by environmental factors such as ionizing radiation (IR). In cancer therapy, IR is applied in high doses, leading to detrimental effects on bone, whereas radiation therapy with low doses of IR is applied for chronic degenerative and inflammatory diseases, with a positive impact especially on bone homeostasis. Moreover, the effects of IR are of particular interest in space travel, as astronauts suffer from bone loss due to space radiation and microgravity. This review summarizes the current state of knowledge on the effects of IR on bone with a special focus on the influence on OCs and OBs, as these cells are essential in bone remodeling. In addition, the influence of IR on the bone microenvironment is discussed. In summary, the effects of IR on bone and bone remodeling cells strongly depend on the applied radiation dose, as differential results are provided from in vivo as well as in vitro studies with varying doses of IR. Furthermore, the isolated effects of IR on a single cell type are difficult to determine, as the bone cells and bone microenvironment are building a tightly regulated network, influencing on one another. Therefore, future research is necessary in order to elucidate the influence of different bone cells on the overall radiation-induced effects on bone.

Apolipoprotein D

ApoD is a 25 to 30 kDa glycosylated protein, member of the lipocalin superfamily. As a transporter of several small hydrophobic molecules, its known biological functions are mostly associated to lipid metabolism and neuroprotection. ApoD is a multi-ligand, multi-function protein that is involved lipid trafficking, food intake, inflammation, antioxidative response and development and in different types of cancers. An important aspect of ApoD's role in lipid metabolism appears to involve the transport of arachidonic acid, and the modulation of eicosanoid production and delivery in metabolic tissues. ApoD expression in metabolic tissues has been associated positively and negatively with insulin sensitivity and glucose homeostasis in a tissue dependent manner. ApoD levels rise considerably in association with aging and neuropathologies such as Alzheimer's disease, stroke, meningoencephalitis, moto-neuron disease, multiple sclerosis, schizophrenia and Parkinson's disease. ApoD is also modulated in several animal models of nervous system injury/pathology.

Bone mineral density and mortality in end-stage renal disease patients

Osteoporosis characterized by low bone mineral density (BMD) as assessed by dual-energy X-ray absorptiometry (DXA) is common among end-stage renal disease (ESRD) patients and associates with high fracture incidence and high all-cause mortality. This is because chronic kidney disease-mineral bone disorders (CKD-MBDs) promote not only bone disease (osteoporosis and renal dystrophy) but also vascular calcification and cardiovascular disease. The disturbed bone metabolism in ESRD leads to 'loss of cortical bone' with increased cortical porosity and thinning of cortical bone rather than to loss of trabecular bone. Low BMD, especially at cortical-rich bone sites, is closely linked to CKD-MBD, vascular calcification and poor cardiovascular outcomes. These effects appear to be largely mediated by shared mechanistic pathways via the 'bone-vascular axis' through which impaired bone status associates with changes in the vascular wall. Thus, bone is more than just the scaffolding that holds the body together and protects organs from external forces but is-in addition to its physical supportive function-also an active endocrine organ that interacts with the vasculature by paracrine and endocrine factors through pathways including Wnt signalling, osteoprotegerin (OPG)/receptor activator of nuclear factor-κB (RANK)/RANK ligand system and the Galectin-3/receptor of advanced glycation end products axis. The insight that osteogenesis and vascular calcification share many similarities-and the knowledge that vascular calcification is a cell-mediated active rather than a passive mineralization process-suggest that low BMD and vascular calcification ('vascular ossification') to a large extent represent two sides of the same coin. Here, we briefly review changes of BMD in ESRD as observed using different DXA methods (central and whole-body DXA) at different bone sites for BMD measurements, and summarize recent knowledge regarding the relationships between 'low BMD' and 'fracture incidence, vascular calcification and increased mortality' in ESRD patients, as well as potential 'molecular mechanisms' underlying these associations.

TLR4 mediates alveolar bone resorption in experimental peri-implantitis through regulation of CD45+ cell infiltration, RANKL/OPG ratio, and inflammatory cytokine production

BACKGROUND

The present study was to determine the role of Toll-like receptor 4 (TLR4) signaling in inflammation and alveolar bone resorption using a murine model of Porphyromonas gingivalis-associated ligature-induced peri-implantitis.

METHODS

Smooth surface titanium implants were placed in the left maxilla alveolar bone 6 weeks after extraction of first and second molars in Wild-type (WT) and TLR4^-/- (TLR4 KO) mice. Silk ligatures immersed with P. gingivalis were tied around the implants 4 weeks after the implant placement and confirmation of osteointegration. Two weeks after the ligation, bone resorption, osteoclastogenesis, cellular inflammatory responses, and gingival mRNA expression levels of cytokines were assessed by micro-computed tomography, tartrate-resistant acid phosphatase (TRAP) staining, immunobiological examination and Real-time quantitative polymerase chain reaction, respectively.

RESULTS

In both WT and TLR4 KO mice, the bone resorption around implants was significantly increased in the P. gingivalis/ligation group compared with control group. In P. gingivalis/ligation group, the levels of bone resorption, TRAP+ cell formation, and gingival CD3+ and CD45+ cell infiltration were significantly decreased in TLR4 KO mice compared with that in WT mice. Receptor activator of nuclear factor-kappa B ligand /osteoprotegerin (RANKL/OPG) ratio was significantly increased after P. gingivalis/ligation treatment in WT mice not in TLR4 KO mice. When comparing the P. gingivalis/ligation group with the respective control group, gingival mRNA expressions of IL-1β, IFN-γ, and 1L-17 were significantly increased in TLR4 KO mice.

CONCLUSION

This study suggests that TLR4 mediates alveolar bone resorption in P. gingivalis associated ligature-induced peri-implantitis through regulation of immune B cell infiltration, RANKL/OPG expression ratio, and differential inflammatory cytokine production.

RANKL blockade alleviates peri-implant bone loss and is enhanced by anti-inflammatory microRNA-146a through TLR2/4 signaling

BACKGROUND

The present study was to determine the effect of local anti-RANKL antibody administration in the presence or absence of microRNA-146a on ligature-induced peri-implant bone resorption, and the potential role of TLR2/4 signaling in such effect.

RESULTS

Titanium implants were placed in the left maxilla alveolar bone 6 weeks after extraction of first and second molars in C57/BL6 wild-type (WT) and TLR2-/- TLR4-/- (TLR2/4 KO) mice. Silk ligatures were tied around the implants 4 weeks after implantation. Anti-RANKL antibody (500 μg/mL) with or without microRNA 146a (miR-146a) (100 nM) was injected into palatal gingiva around implant on days 3, 6, and 9 during 2 weeks of ligation period. Bone resorption around the implants was assessed by 2D imaging using area measurement and 3D imaging using micro-computed tomography (μCT). Real-time quantitative PCR (RT-qPCR) was used to determine the peri-implant gingival mRNA expression levels of pro-inflammatory cytokines (TNF-α) and osteoclastogenesis-related cytokines (RANKL). In both WT and TLR2/4 KO mice, the bone resorption around implants was significantly increased in the ligation only group when compared to the non-ligation group, but TLR2/4 KO mice showed significantly less bone loss compared to WT mice after ligation. As expected, gingival injection of anti-RANKL antibody significantly reduced bone loss compared with the ligation only group in both WT and TLR2/4 KO mice. Moreover, injection of miR-146a in addition to anti-RANKL antibody significantly enhanced the inhibition of bone loss in WT mice but not in TLR2/4 KO mice. Gingival mRNA expressions of RANKL were significantly reduced by anti-RANKL antibody treatment in both WT and TLR2/4 KO mice but were not affected by the additional miR-146a treatment. Gingival mRNA expression of TNF-α was significantly reduced by miR-146a treatment in WT mice but not in TLR2/4 KO mice. The number of gingival inflammatory cell infiltration and peri-implant TRAP-positive cell formation was significantly reduced by the additional miR-146a treatment in WT mice but not in TLR2/4 KO mice.

CONCLUSIONS

This study suggests that anti-inflammatory miR-146a enhance anti-RANKL-induced inhibition of peri-implant bone resorption through the regulation of TLR2/4 signaling and inhibition of TNF-α expression.

The IMpact of Vertical HIV infection on child and Adolescent SKeletal development in Harare, Zimbabwe (IMVASK Study): a protocol for a prospective cohort study

INTRODUCTION

The scale-up of antiretroviral therapy (ART) across sub-Saharan Africa (SSA) has reduced mortality so that increasing numbers of children with HIV (CWH) are surviving to adolescence. However, they experience a range of morbidities due to chronic HIV infection and its treatment. Impaired linear growth (stunting) is a common manifestation, affecting up to 50% of children. However, the effect of HIV on bone and muscle development during adolescent growth is not well characterised. Given the close link between pubertal timing and musculoskeletal development, any impairments in adolescence are likely to impact on future adult musculoskeletal health. We hypothesise that bone and muscle mass accrual in CWH is reduced, putting them at risk of reduced bone mineral density (BMD) and muscle function and increasing fracture risk. This study aims to determine the impact of HIV on BMD and muscle function in peripubertal children on ART in Zimbabwe.

METHODS AND ANALYSIS

Children with (n=300) and without HIV (n=300), aged 8-16 years, established on ART, will be recruited into a frequency-matched prospective cohort study and compared. Musculoskeletal assessments including dual-energy X-ray absorptiometry, peripheral quantitative computed tomography, grip strength and standing long jump will be conducted at baseline and after 1 year. Linear regression will be used to estimate mean size-adjusted bone density and Z-scores by HIV status (ie, total-body less-head bone mineral content for lean mass adjusted for height and lumbar spine bone mineral apparent density. The prevalence of low size-adjusted BMD (ie, Z-scores <-2) will also be determined.

ETHICS AND DISSEMINATION

Ethical approval for this study has been granted by the Medical Research Council of Zimbabwe and the London School of Hygiene and Tropical Medicine Ethics Committee. Baseline and longitudinal analyses will be published in peer-reviewed journals and disseminated to research communities.