The potential risks of denosumab on pediatric patients have raised concerns about its safety. This article aims to analyze the adverse effects of denosumab in minors, with a specific focus on hypercalcemia.

A case study involving a child was analyzed. The OpenVigil 2.1 was utilized to extract adverse event data from the FAERS database, focusing on denosumab as the primary suspect drug in pediatric patients. The study also reviewed published cases of children developing hypercalcemia after discontinuing denosumab.

The incidence of denosumab induced hypercalcemia in individuals under 18 years old is significantly higher than the overall incidence. The signal value for hypercalcemia was higher in the male group and was highest in the adolescent group. Hypercalcemia usually appeared approximately 4 months after denosumab discontinuation. Males had a higher peak blood calcium level. Patients aged 0-11 years had a higher average peak serum calcium compared to aged 12-17 years.

This study highlights the risk of hypercalcemia after discontinuation of denosumab in minors, with young age and male gender identified as potential high-risk factors. These findings offer valuable safety warnings and preventative measures for the secure administration of this drug in pediatric populations.

Osteoclast activity is regulated by extracellular pH, whereby bone resorption is near-maximally activated at pH 7.0 but limited at ≥pH 7.4. This study examined the effects of low pH on osteoclast fusion, multi-nucleation, resorption and cell transcriptome. Osteoclasts were cultured on dentine discs at pH 7.4 (control) or pH 7.0 (acidified) for 5-7 days. Osteoclast number and resorptive activity were 1.9-fold and 6.7-fold higher, respectively, in acidified cultures. However, acidified osteoclasts were smaller, with fewer nuclei than controls (53 μm diameter with 9 ± 1 nuclei/cell versus 100 μm with 24 ± 3 nuclei/cell). mRNA expression analysis revealed that osteoclast formation and resorption-associated genes were increased in acidified osteoclasts. Switching mature osteoclasts formed for 5 days at pH 7.4 to acidified conditions decreased cell size 30 % within 4 h, resulting in a 2-fold increase in osteoclast numbers after 24 h. Resorptive activity in cells switched to pH 7.0 was visible within 8 h, and by 24 h resorption area was comparable to continually acidified osteoclasts. MicroCT analysis of dentine discs revealed 24-fold and 6.4-fold increases in resorption pit number in pH-switched osteoclasts relative to control and acidified cultures, respectively. RNAseq showed changes in extracellular pH differentially regulated gene expression, particularly metabolic and cell cycle-associated genes. Our results reveal previously unknown effects of extracellular pH on osteoclasts. Specifically, they show pH is an important modulator of osteoclast fusion and size that regulates the transcriptome. Furthermore, small changes in pH can induce significant morphological changes in osteoclasts and act as on/off switch between formation and resorption in ≤4 h.

Medication-Related Osteonecrosis of the Jaw (MRONJ) is a condition marked by osteonecrosis of the jaw bone and other symptoms seen following invasive surgical procedures in patients administered bone-modifying agents. Once disease develops, a patient's ADL levels are significantly compromised. However, the pathogenesis of this disease is not clearly understood. Bisphosphonates (BPs) are bone resorption inhibitors commonly used to treat osteoporosis. Although not confirmed, it is generally believed that MRONJ risk is higher in the presence of injectable rather than oral formulations. Here, we assessed risk of developing ONJ in mice in the presence of 3 different BPs-zoledronate, ibandronate, or alendronate-that are administered clinically intravenously or via infusion.

Eight-week-old wild-type mice were administered zoledronate, alendronate, ibandronate or PBS vehicle subcutaneously once a week for 2 weeks. Then the right first molars in the mandible were extracted. Six-weeks later, osteonecrosis development was analyzed by histochemistry.

Among mice administered BPs, mice treated with zoledronate exhibited the highest frequency of osteocytes exhibiting osteonecrosis. Bone mineral density was higher in mice receiving zoledronate, alendronate, or ibandronate than in PBS control mice, but effects of the 3 drugs were comparable. Moreover, formation of multi-nuclear osteoclasts in vitro was most strongly inhibited by zoledronate, followed by alendronate and ibandronate.

Administration of BPs with high osteoclastogenesis inhibitory potential, such as zoledronate, increases risk of ONJ development after tooth extraction more than treatment with other agents tested, even at equivalent dosage.

Bone metastasis is the primary cause of mortality in breast cancer (BC) patients. This study elucidates the functional role of DEC1 (differentiated embryonic chondrocyte expressed gene 1) in promoting BC bone metastasis. Analysis of patient-derived samples and public databases revealed significant upregulation of DEC1 and CXCR4 in breast tumors compared to adjacent normal tissues, with elevated levels correlating with increased metastatic potential, suggesting their synergistic involvement in BC progression. Intracardiac injection experiments demonstrated that 4T1-WT cells induced more severe osteolysis and larger metastatic lesions than 4T1-DEC1-KD cells. In MDA-MB-231 cells, DEC1 overexpression (OE) upregulated CXCR4 and proliferation/migration-related genes, whereas DEC1 knockdown (KD) suppressed these effects. Notably, AMD3100 (a CXCR4 antagonist) partially reversed the DEC1-OE-induced upregulation of CXCR4 and associated pro-metastatic genes. Mechanistically, DEC1 was found to bind the CXCR4 promoter region (-230 to -326) and activate its transcription, corroborated by ChIP-seq data. Furthermore, pharmacological inhibition of AKT (LY294002) or JAK2 (AZD1480), but not ERK (PD98059), attenuated DEC1-mediated CXCR4 upregulation, although all three inhibitors mitigated DEC1-driven migration-related gene expression. Additionally, DEC1 enhanced CXCL12 secretion from mesenchymal stromal cells and osteoblasts, amplifying the CXCR4/CXCL12 axis within the bone microenvironment. Collectively, our findings demonstrate that DEC1 promotes breast cancer (BC) bone metastasis by directly transactivating CXCR4 expression, providing a molecular basis for targeting DEC1 to prevent and treat BC bone metastasis.

Osteoporosis, characterized by excessive osteoclast activation, is mediated through the RANKL/RANK/OPG signaling axis. While flavonoids from Eucommia ulmoides (EU) have demonstrated anti-osteoclastogenic activity, their atomic-level mechanisms remain elusive. Here, we investigated six EU-derived flavonoids (cyrtominetin, quercetin, syringetin, genistein, ombuin, and kaempferol) targeting RANKL using integrated computational approaches. Molecular docking revealed strong binding affinities (Total_Score > 4.0) for all compounds, with cyrtominetin exhibiting the highest affinity (-50.205 kJ/mol via MM-PBSA), primarily through hydrogen bonds with Gly178, His180, Lys181, and Asn295. Moreover, most flavonoids interacted with RANKL by forming strong hydrogen bonds with Gly178 and Asn295, exhibiting higher binding affinity that was identified as essential for the activity. All-atom molecular dynamics simulations (100 ns) confirmed complex stability, demonstrating: low RMSD fluctuations (< 4.0 Å) and compact Rg values (16.0-17.0 Å). Notably, binding free energy decomposition identified both electrostatic and van der Waals contributions as critical for stabilization. These results identify cyrtominetin as a promising lead compound for RANKL inhibition, providing structural insights for designing flavonoid-based therapeutics against osteoporosis.

Osteoporosis is a systemic metabolic degenerative bone disease characterised by decreased bone mass, impaired bone microstructure, weakened bone strength and susceptibility to fracture. In China, the prevention and treatment of osteoporosis is faced with a high disease prevalence rate but low awareness, diagnosis and treatment rates. Bone resorption inhibitors and bone formation promoters often dominate osteoporosis treatment. Although conventional drugs can alleviate symptoms and reduce fracture risk, they often come with musculoskeletal, allergic and digestive side effects. Natural traditional Chinese medicine (TCM) products, known for their multi-targeting, high safety, efficacy and low cost, have been widely used in the treatment and prevention of osteoporosis in recent years and have gradually been recognised by many experts locally and abroad. This paper summarises recent research progress on natural TCM products in preventing and treating osteoporosis and provides a theoretical and experimental basis for the development of new drugs and the improvement of osteoporosis management.

Helminth infections, particularly in developing countries, remain a notable health burden worldwide. Group 3 innate lymphoid cells (ILC3s) are enriched in the intestine and play a critical role in immunity against extracellular bacteria and fungi. However, whether ILC3s are involved in intestinal helminth infection is still unclear. Here, we report that helminth infection reprograms ILC3s, which, in turn, promote anthelmintic immunity. ILC3-derived RANKL [receptor activator of NF-κB (nuclear factor κB) ligand] synergizes with interleukin-13 (IL-13) to facilitate intestinal tuft cell expansion after helminth infection, which further activates the tuft cell-group 2 innate lymphoid cell (ILC2) circuit to control helminth infection. Deletion of RANKL in ILC3s or deletion of RANK or its downstream adaptor RelB in intestinal epithelial cells substantially diminishes tuft cell hyperplasia and dampens anthelmintic immunity. Thus, ILC3s play an indispensable role in protecting against helminth infection through the regulation of intestinal tuft cell hyperplasia and type 2 immunity.

This study aimed to investigate the impacts of prior anti-osteoporosis treatments on bone mineral density (BMD) changes in Chinese postmenopausal women with osteoporosis following 1-year Denosumab (Dmab) therapy.

This retrospective cohort study enrolled 381 postmenopausal women, all receiving a 1-year Dmab treatment. Participants were stratified into five groups based on prior anti-osteoporosis treatments: no treatment (NT), alendronate (ALN), zoledronic acid (ZOL), teriparatide (TPT), and raloxifene (RAL). Potential factors influencing BMD changes were screened using least absolute shrinkage and selection operator (LASSO). The selected variables were then incorporated into a multivariate regression model to identify independent risk factors. Finally, after adjusting for confounders, the impacts of prior anti-osteoporosis treatment on sequential Dmab responses were evaluated.

1) Further BMD increases were observed after sequential 1-year Dmab with prior use of other anti-osteoporosis drugs; 2) Compared to the NT group, ZOL significantly reduced BMD changes at the lumbar spine (LS), femoral neck (FN), and total hip (TH) (LS: β = -0.01, P = 0.016; FN: β = -0.01, P = 0.010; TH: β = -0.01, P = 0.011); Significant negative associations with FN BMD changes were observed for the ALN group (β = -0.01, P< 0.001), and the RAL group (β = -0.01, P = 0.010) compared to the NT group; TPT showed no significant differences with the NT group at all sites; 3) Multiple analysis revealed baseline BMD were independently associated with changes in BMD (LS: β = -0.04, P = 0.009; FN: β = -0.19, P <0.001; TH: β = -0.14, P <0.001).

These findings indicated that prior anti-osteoporosis treatments differentially influenced BMD responses to 1-year Dmab therapy. While patients who had previously been treated with ZOL had limited subsequent BMD improvement, patients who had previously used TPT and had lower baseline BMD benefited more.

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.

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.

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.

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.

Osteoporosis is a common metabolic bone disease that seriously affects the quality of life and health of patients. Traditional diagnostic methods, such as dual energy X-ray absorptiometry (DXA), have limitations in early detection and dynamic monitoring, making it difficult to meet clinical needs. This paper focuses on the potential of radionuclide imaging techniques, such as Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET), in the early diagnosis of osteoporosis. The paper further elaborates on the importance of radionuclides in evaluating the therapeutic effect of osteoporosis drugs. By summarizing current research findings, this paper aims to emphasize the core role of radionuclides in the management of osteoporosis, and provide theoretical basis and practical guidance for optimizing the diagnosis and treatment strategies of bone metabolism diseases in the future.

Bone is a highly mechanosensitive tissue, where mechanical signaling plays a central role in maintaining skeletal homeostasis. Mechanotransduction regulates the balance between bone formation and resorption through coordinated interactions among bone cells. Key mechanosensing structures-including the extracellular/pericellular matrix (ECM/PCM), integrins, ion channels, connexins, and primary cilia, translate mechanical cues into biochemical signals that drive bone adaptation. Disruptions in mechanotransduction are increasingly recognized as an important factor in osteoporosis. Under pathological conditions, impaired mechanical signaling reduces bone formation and accelerates bone resorption, leading to skeletal fragility. Defects in mechanotransduction disrupt key pathways involved in bone metabolism, further exacerbating bone loss. Therefore, targeting mechanotransduction presents a promising pharmacological strategy for osteoporosis treatment. Recent advances have focused on developing drugs that enhance bone mechanosensitivity by modulating key mechanotransduction pathways, including integrins, ion channels, connexins, and Wnt signaling. A deeper understanding of mechanosignaling mechanisms may pave the way for novel therapeutic approaches aimed at restoring bone mass, mechanical integrity, and mechanosensitive bone adaptation.

Lipopolysaccharide (LPS) of Gram-negative bacteria in oral plaque is the major cause of periodontal disease. It is involved in the induction of inflammation and alveolar bone resorption at least partly by directly reacting to Toll-like receptor (TLR) 4 on osteoblasts. LPS induces osteoblasts to express proinflammatory cytokines, chemokines, and prostaglandins, as well as macrophage colony-stimulating factor (M-CSF) and receptor activator of NF-κB ligand (RANKL), which directly activate adjacent osteoclasts toward bone resorption. However, the regulator mechanisms have not been fully revealed at the molecular level. Here, we have demonstrated that LPS rapidly induces expression of early growth response 1 (EGR1), a zinc-finger transcription factor, and analyzed its physiological functions in osteoblasts. In both primary osteoblasts and an osteoblast cell line, LPS induced expression of EGR1 mRNA and protein within 30 min and 60 min, respectively, which were relatively slower than in macrophages. Inhibition of EGR1 by siRNA significantly inhibited LPS-induced mRNA expression of the tumor necrosis factor (TNF), interleukin-6 (IL-6), chemokines, cyclooxygenase-2 (COX2), matrix metalloproteinase-13 (MMP13), M-CSF, and RANKL in osteoblasts. Moreover, forced overexpression of EGR1 by the inducible expression system was sufficient to increase mRNA expression levels of TNF, IL-6, COX2, MMP13, and RANKL without LPS stimulation. As for the intracellular signal transduction, LPS-induced EGR1 expression in osteoblasts was dependent on the unique c-Jun N-terminal kinase (JNK)-extracellular signal-regulated kinase (ERK) activation pathway. Our data suggest an essential role of EGR1 in osteoblast responses to LPS-inducing tissue inflammation and osteolysis, providing new insights into the pathogenesis of periodontal disease.

Osteoporosis, a common metabolic condition that affects the bones, increases the risk of fractures, thereby diminishing one's quality of life and, in severe cases, can even result in life-threatening conditions. Osteoporosis is becoming increasingly prevalent worldwide as the population ages. Previous research on osteoporosis has focused on skeletal cellular components such as osteoblasts and osteoclasts. The emerging field of "osteoimmunology" has recently been introduced through new research. The concept highlights the critical impact of bone-immune system interactions on osteoporosis progression. The pathogenesis of osteoporosis is significantly influenced by T cells, particularly cytotoxic and helper T cells, which modulate osteoclast differentiation and activity. A crucial aspect of understanding osteoporosis is how T lymphocytes interact with osteoclasts. However, the precise mechanisms underlying T cell-osteoclast crosstalk remain poorly understood. This review systematically examines T cell and osteoclast involvement in osteoimmunology, with a particular focus on their involvement in osteoporosis. It seeks to elucidate the immune mechanisms driving the progression of osteoporosis and identify key molecules involved in T cell-osteoclast interactions. This aims to discover novel molecular targets and intervention strategies to improve early diagnosis and management of osteoporosis. Furthermore, this article will explore the potential of intervening in T cell-osteoclast interactions using conventional therapies, traditional Chinese medicine, immunomodulatory agents, and nanomaterial-based treatments, providing new perspectives for future osteoporosis management.

The RANK/RANKL/OPG signaling pathway plays a crucial role in breast cancer progression and metastasis. However, its expression patterns and potential implications in breast cancer stem cells remain poorly understood. This study aimed to characterize the expression profile of this pathway in breast cancer stem cells isolated from two distinct breast cancer cell lines: MDA-MB-231 and MCF-7. Mammospheres (MS), representing breast cancer stem cells, were generated using agar-coated 6 well tissue culture plates in suitable mammospheres culture conditions. Flow cytometric analysis showed enrichment of the CD44+/CD24- subpopulations in the mammospheres cultures, with MDA-MB-231 exhibiting a higher percentage compared to MCF-7. The isolated MS from both cell lines showed upregulation of stemness markers OCT4 and SOX2, with MS. MDA-MB-231 demonstrating higher expression levels. Analysis of the RANK/RANKL/OPG axis revealed differential expression patterns between the two cell lines. RANK expression was significantly upregulated in MS. MDA-MB-231 but not in MS. MCF-7. Interestingly, while OPG mRNA levels were elevated in mammospheres from both cell lines, secreted OPG protein levels were paradoxically reduced in the mammospheres conditioned media. Additionally, RUNX2, an osteoblastic marker, and a downstream target of RANK signaling, showed a decreased expression in both mammospheres compared to adherent cells. These findings suggest a complex, context-dependent regulation of the RANK/RANKL/OPG pathway in breast cancer stem cells, potentially contributing to the aggressive nature and metastatic propensity of triple-negative breast cancer. This study provides novel insights into the molecular characteristics of breast cancer stem cells and underscores the complexity of OPG/RANK/RANKL axis expression in them; a role yet to be fully elucidated.

Spinal cord injury (SCI) is a neurodegenerative disease, with a high disability rate. According to the results of mRNA-seq, transcription factor AP-2 Beta (TFAP2B) is a potential target of repetitive Transspinal Magnetic Stimulation (rTSMS) in SCI treatment. Our results demonstrated that rTSMS significantly improved motor function and promoted neuronal survival post-SCI. The result showed that TFAP2B was downregulated following SCI, while significant upregulation after rTSMS treatment, suggesting its pivotal role in neuronal repair. Overexpression of TFAP2B improved Basso Beattie and Bresnahan (BBB) score and athletic ability, and decreased cell apoptosis in SCI rats. Additionally, overexpression of TFAP2B reduced the expression of Iba1 and GFAP in spinal cord, and the expression of PDGFrβ was also reduced in SCI rats after TFAP2B overexpression. Knockdown of TFAP2B reverses the effect of rTSMS treatment in SCI. We found that rTSMS alleviate osteoporosis caused by SCI, resulting in increased BMD, BV/TV, and Tb.Th. rTSMS treatment lowered the RANKL/OPG ratio. In all, our study illustrated TFAP2B is a downstream target of rTSMS for the treatment of SCI, and overexpression of TFAP2B enhanced the therapeutic effect of rTSMS.

Objectives: Bone mineral density (BMD) variation under vitamin D supplementation, determined using dual-energy X-ray absorptiometry (DXA), is the gold standard and the main tool used in most studies in this domain. However, the scientific literature is lacking with regard to the usefulness of REMS in BMD follow-up, especially the importance of the fragility score (FS). The main objective of this study was to determine whether FS follow-up is relevant in a group of patients with axial spondyloarthritis and whether REMS could have clinical applicability. Methods: Patients with a certain diagnosis of axial spondyloarthritis (AxSpA) were recruited from two medical healthcare centers and were scanned using Radiofrequency Echographic Multi-Spectrometry in order to obtain their fragility score (FS), an objective measurement of bone quality. The main group was randomized into a vitamin D supplementation branch and a non-supplementation branch and followed up every 6 months for 18 months in total. Comparisons between the branches were made using MiniTab v.20 statistical software. Results: Lower FS values were obtained in patients who initially had high scores, suggesting a positive impact of vitamin D on bone quality (p = 0.008). Muscle strength was evaluated through a visual analogue scale (VAS), with improvements being seen in the supplementation branch (p < 0.005). Furthermore, although some patients had experienced falls in previous years, during the study period, no new events were recorded in either group. Conclusions: The FS is a reliable tool for evaluating bone architecture and is useful in everyday practice for the management of patients taking vitamin D supplements.

People with HIV (PWH) have an increased risk of developing cardiovascular disease (CVD). Our recent data demonstrated that the multi-isoform proinflammatory cytokine IL-32 is upregulated in PWH and is associated with arterial stiffness and subclinical atherosclerosis. However, the mechanisms by which IL-32 contributes to the pathogenesis of these diseases remain unclear. Here, we show that while the less expressed IL-32α isoform induces the differentiation of human classical monocytes into the calcium-resorbing osteoclast cells, the dominantly expressed isoforms IL-32β and IL-32γ suppress this function through the inhibition of TGF-β and induce the differentiation of monocytes into the calcium-depositing osteocalcin+ osteoblasts. These results aligned with the increase in plasma levels of osteoprotegerin, a biomarker of vascular calcification, and its association with the presence of coronary artery subclinical atherosclerosis and calcium score in PWH. These findings support a novel role for the proinflammatory cytokine IL-32 in the pathophysiology of CVD by increasing vascular calcification in PWH.

Developmental endothelial locus-1 (DEL-1) has traditionally been characterized within the scientific community as having anti-inflammatory properties with potential inhibitory effects on osteoclast formation. Our investigation challenges this paradigm by examining Del-1 expression in RAW264.7 cells and bone marrow-derived macrophages (BMMs) during osteoclastogenesis, as well as its functional impact on osteoclast development and activity. Our experimental findings revealed that Del-1 mRNA levels were markedly elevated in cells stimulated by the receptor activator of the nuclear factor κB ligand compared to unstimulated precursors. When cultured with varying concentrations of recombinant DEL-1, osteoclast differentiation increased in a dose-dependent manner. Furthermore, BMMs isolated from ovariectomized mice exhibited significantly higher Del-1 mRNA expression than those from control animals. To confirm DEL-1's role, we employed RNA interference techniques, demonstrating that DEL-1 silencing in RAW264.7 cells substantially reduced osteoclast formation. These results suggest that DEL-1 plays a previously unrecognized role in promoting osteoclastogenesis and may contribute to bone metabolism imbalances in conditions like osteoporosis, highlighting its complex role in skeletal homeostasis and its potential as a therapeutic target.

Originally identified for its involvement in bone remodeling, accumulating data emerged in the past years indicating that receptor activator of nuclear factor κB ligand (RANKL) actually acts as a multifunctional soluble molecule that influences various physiological and pathological processes. Regarding its role in carcinogenesis, while direct effects on tumor cell behavior have been precisely characterized, the impact of the RANKL/RANK system (and its inhibition) on the intratumoral immune landscape remains unclear.

After various in silico/in situ/in vitro analyses, the immunotherapeutic efficacy of RANKL blockade (alone and in combination with immune checkpoint inhibitors (anti-programmed cell death protein-1 (PD-1)) or doxorubicin/paclitaxel-based chemotherapy) was investigated using different syngeneic mouse models of triple-negative breast cancer (4T1, 67NR and E0771). Isolated from retrieved tumors, 14 immune cell (sub)populations, along with the activation status of antigen-presenting cells, were thoroughly analyzed in each condition. Finally, the impact of RANKL on the functionality of both dendritic cells (DC) and plasmacytoid dendritic cells (pDC) was determined.

A drastic tumor growth inhibition was reproductively observed following RANKL inhibition. Strikingly, this antitumor activity was not detected in immunocompromised mice, demonstrating its dependence on the adaptive immune responses and justifying the diverse enriched signatures linked to immune cell regulation/differentiation detected in RANKLhigh-expressing human neoplasms. Interestingly, neoadjuvant chemotherapy (but not PD-1 checkpoint inhibition) potentiated the anticancer effects of RANKL blockade by priming effector T cells and increasing their infiltration within the tumor microenvironment. Mechanistically, we highlighted that RANKL indirectly promotes regulatory T cell differentiation and suppressive function by inhibiting the mTOR signaling pathway on antigen-presenting cells.

Taken together, this study provides insight into the role of RANKL/RANK axis in immune tolerance, demonstrates the significant impact of RANKL-dependent impairment of T cell-DC/pDC crosstalk on tumor development and, ultimately, supports that this ligand could be an interesting actionable target for cancer immunotherapy.

Protein disulfide isomerase (PDI) is an oxidoreductase responsible for the formation, reduction and isomerization of disulfide bonds of nascent proteins in endoplasmic reticulum (ER). So far, the role of PDI in bone biology has never been characterized using genetically-modified animal models. In this study we generated osteoblast- specific PDI-deficient mice by crossing PDI-floxed (PDIfl/fl) mice with Osx-Cre mice. Compared with their littermate control PDIfl/fl mice, homozygous osteoblast-knockout mice (Osx-Cre/PDIfl/fl) were embryonically lethal, but heterozygous knockout mice (Osx-Cre/PDIfl/wt) displayed significantly pronounced growth retardation and reduced bone length. Besides, the decreases in bone density, osteoblast and osteoclast numbers, collagen fiber content and bone formation rate were observed in Osx-Cre/PDIfl/wt mice. Osteoblast precursors isolated from PDIfl/fl mice were infected with Cre recombinant adenovirus to produce PDI-deficient osteoblasts, followed by induction of differentiation. Osteoblasts deficient of PDI had decreased alkaline phosphatase activity, mineralizing capacity, and differentiation. Quantitative protein mass spectrometry analysis and immunoblotting showed that PDI deficiency markedly decreased the expression of the α-subunits of collagen prolyl 4-hydroxylase (C-P4H), including P4HA1, P4HA2 and P4HA3. These results demonstrate that PDI plays an essential role in osteoblast differentiation and bone formation and is required for the expression of the α-subunit of C-P4H in osteoblasts.

Denosumab, a drug that inhibits RANKL to reduce bone resorption in osteoporotic postmenopausal women, has been shown to improve semen quality in a subgroup of infertile men. This study aimed to investigate the effects of denosumab on mineral homeostasis in young infertile men.

Secondary data from two clinical trials designed to test the effect on semen quality were used: (1) a pilot intervention study with 12 men receiving a single-dose of 60 mg denosumab and (2) a single-center, double-blinded, randomized clinical trial, where 100 infertile men were randomized 1:1 to receive denosumab 60 mg once sc. or placebo. A linear mixed model for repeated measures was employed to analyze data from follow-up samples.

In the pilot intervention study, denosumab treatment induced a decrease in ionized calcium 5, 20, 40, and 80 days after treatment compared with baseline (all p < 0.05). Serum phosphate decreased on all time points up to and including day 40 (all p < 0.05), while alkaline phosphatase was only lowered at 40 days and onwards (p = 0.014). Serum PTH increased significantly at all time points up to and including day 80 (p = 0.026). One hundred eighty days after treatment, all reported analyses were comparable to baseline levels. The observed temporal changes were confirmed in the RCT with differences in serum calcium (p < 0.001) and phosphate (p < 0.001) on day 14, PTH (p < 0.002), and alkaline phosphatase (p < 0.001) on days 80 and 160. Denosumab treatment had no significant effect on vitamin D status, renal function, or serum albumin concentration after 80 and 160 days.

Small but significant changes in mineral homeostasis and bone mineral content were observed but the changes were transient and normalized after treatment cessation. A single injection of denosumab in infertile men appears to have no major long-term impact on bone or mineral homeostasis.

ClinicalTrials.gov NCT03030196. Registered January 24, 2017.

RANKL and its receptor RANK play a vital role in osteoclastogenesis. RANK primarily recruits TRAFs to promote osteoclastogenesis but also contains an TRAF-independent motif (IVVY535-538), which mediates osteoclast lineage commitment in vitro. Here, we have developed knockin mice in which inactivating mutations are introduced in the IVVY motif (IVVY to IVAF). Homozygous knockin (RANKAF/AF) mice are viable and born at the expected Mendelian ratio. Micro-computed tomography (μCT) and histomorphometric analyses of femurs of wild type (RANK+/+) and RANKAF/AF mice reveal significant increases in trabecular bone mass in RANKAF/AF compared to age and sex matched RANK+/+ mice due to impaired osteoclastogenesis in vivo. Bone marrow macrophages (BMMs) from RANKAF/AF mice do not form osteoclasts in vitro upon M-CSF and RANKL treatment. RANKL-induced activation of NF-ĸB, ERK, p38 and JNK pathways in RANKAF/AF BMMs remains intact, but RANKL-induced expression of c-Fos and NFATc1 is impaired in RANKAF/AF BMMs. Consistent with the crucial role of the IVVY motif in priming BMMs into the osteoclast lineage, RANKL-primed RANKAF/AF BMMs do not form osteoclasts in response to subsequent Porphyromonas gingivalis (Pg)-stimulation, indicating that the IVVY Motif plays a role in Pg-induced osteoclastogenesis. Mechanistically, RANK IVVY motif mediates Pg-induced osteoclast gene expression by rendering NFATc1 and c-Fos genes responsive to Pg stimulation. Consistently, cell penetrating peptides fused to RANK segments containing the IVVY motif impair Pg-induced osteoclastogenesis by impairing RANKL-activated c-Fos and NFATc1 expression. In conclusion, the RANK IVVY motif plays crucial roles in osteoclastogenesis in vivo and modulates Pg-mediated osteoclast formation in vitro.

BTB domain and CNC homolog 1 (BACH1) belongs to the family of basic leucine zipper proteins and is expressed in most mammalian tissues. It can regulate its own expression and play a role in transcriptionally activating or inhibiting downstream target genes. It has a crucial role in various biological processes, such as oxidative stress, cell cycle, heme homeostasis, and immune regulation. Recent research highlights BACH1's significant regulatory roles in a series of conditions, including stem cell pluripotency maintenance and differentiation, growth, senescence, and apoptosis. BACH1 is closely associated with cardiovascular diseases and contributes to angiogenesis, atherosclerosis, restenosis, pathological cardiac hypertrophy, myocardial infarction, and ischemia/reperfusion (I/R) injury. BACH1 promotes tumor cell proliferation and metastasis by altering tumor metabolism and the epithelial-mesenchymal transition phenotype. Moreover, BACH1 appears to show an adverse role in diseases such as neurodegenerative diseases, gastrointestinal disorders, leukemia, pulmonary fibrosis, and skin diseases. Inhibiting BACH1 may be beneficial for treating these diseases. This review summarizes the role of BACH1 and its regulatory mechanism in different cell types and diseases, proposing that precise targeted intervention of BACH1 may provide new strategies for human disease prevention and treatment.

Orthopedic implants made of biodegradable magnesium (Mg) provide an alternative to nondegradable implants for fracture repair. Widely reported to be pro-osteogenic, Mg implants are also believed to be anti-inflammatory and anti-osteoclastic, but this is difficult to reconcile with the early clinical inflammation observed around these implants. Here, by surveying implant healing in a rat bone model, we determined the cellular responses and structural assembly of bone correlated with the surface changes of Mg implants inherent in degradation. We show that, compared to titanium, both high-purity (99.998 %) and clinical-grade, rare earth-alloyed (MgYREZr) Mg implants create an initial, transient proinflammatory environment that facilitates inducible nitric oxide synthase-mediated macrophage polarization, osteoclastogenesis, and neoangiogenesis programs. While this immunomodulation subsequently reinforces reparative osteogenesis at the surface of both Mg implants, the faster degradation of high-purity Mg implants, but not MgYREZr implants, elicits a compositional alteration in the interfacial bone and a previously unknown proadipogenic response with persistent low-grade inflammation in the surrounding bone marrow. Beyond the need for rigorous tailoring of Mg implants, these data highlight the need to closely monitor osseointegration not only at the immediate implant surface but also in the peri-implant bone and adjacent bone marrow.

Osteoclasts are specialized cells essential for bone resorption, a crucial process in bone remodeling, and dysregulation of osteoclastogenesis can lead to pathological bone loss such as osteoporosis and rheumatoid arthritis. Therefore, understanding the precise mechanisms governing osteoclast differentiation is crucial for developing effective therapies for skeletal diseases. In osteoclastogenesis, as well as other differentiated cells, it is well understood that cell cycle arrest is essential for terminal differentiation and is tightly regulated by CDK inhibitors such as Cip/Kip family and Ink4 family protein. In this manuscript, we identified p15Ink4b, a member of the Ink4 family, as a novel regulator of osteoclastogenesis by comprehensive single-cell RNA sequence data reanalyzing. Furthermore, histological analysis and in vitro osteoclast differentiation assay revealed that p15Ink4b functionally regulates osteoclastogenesis. Our findings may not only provide insights into the molecular mechanisms of osteoclast differentiation but also underscore the potential of harnessing cell cycle mechanisms to develop novel therapeutic strategies for bone diseases.

Osteoporosis is a chronic condition primarily affecting postmenopausal women, significantly impacting their well-being and quality of life. Traditional treatment approaches include medications, vitamins, and exercise, but there is a growing interest in alternative therapies that enhance bone health. This review was conducted by searching multiple databases, including PubMed, Medline, and Google Scholar, for studies related to osteoporosis treatment. Articles focusing on both traditional therapies such as bisphosphonates, calcium, and vitamin D supplementation, and newer advancements like vibration therapy and bone-building devices such as Osteoboost were included. Traditional treatments, such as vitamin supplementation, exercise, and bisphosphonates, remain foundational in osteoporosis management, helping to maintain bone density and reduce fracture risks. Recent developments, including vibration therapy and Osteoboost, show promising results in bone regeneration without the use of medication. While traditional therapies continue to play an essential role, advancements like vibration therapy present novel alternatives for managing osteoporosis. Further research is necessary to optimize these approaches, ensuring they maximize benefits while minimizing risks, ultimately improving patient outcomes and quality of life.

Osteoporosis is defined as a condition of increased risk of fracture due to decreased bone strength. In developed countries, the number of patients with osteoporosis and fragility fractures has been increasing in recent years due to the growing elderly population, posing a social challenge not only to fracture patients and their families but also to the social healthcare economy. Osteoporosis can be divided into two categories: primary osteoporosis caused by aging or menopause and secondary osteoporosis caused by metabolic or inflammatory diseases or drugs such as glucocorticoids. The majority of patients have primary osteoporosis, and the pathogenesis of postmenopausal osteoporosis and factors associated with fragility fractures in the elderly have been elucidated. On the other hand, rheumatoid arthritis (RA) is one of the causes of secondary osteoporosis. RA is a chronic inflammatory disease characterized by joint swelling and destruction. Most often, treatment focuses on suppressing these symptoms. However, physicians should be aware of the risk of osteoporosis in RA patients, because (1) RA is a chronic inflammatory disease, which itself can be a risk factor for osteoporosis; (2) glucocorticoids, which are sometimes administered to treat RA, can be a risk factor for osteoporosis; and (3) patients with RA are becoming older, and aging is an osteoporosis risk factor. A comprehensive understanding of the pathogenesis of osteoporosis and its fragility fractures requires elucidating the mechanisms underlying osteoclast activation, which drives their development. Furthermore, identifying the factors associated with fragility fractures is essential. This review summarizes the pathogenesis of osteoporosis, the factors associated with fragility fractures, and the associations between RA and osteoporosis development.

Phospholipase C β (PLCβ) is involved in diverse biological processes, including inflammatory responses and neurogenesis; however, its role in bone cell function is largely unknown. Among the PLCβ isoforms (β1-β4), we found that PLCβ4 was the most highly upregulated during osteoclastogenesis. Here we used global knockout and osteoclast lineage-specific PLCβ4 conditional knockout (LysM-PLCβ4-/-) mice as subjects and demonstrated that PLCβ4 is a crucial regulator of receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclast differentiation. The deletion of PLCβ4, both globally and in the osteoclast lineage, resulted in a significant reduction in osteoclast formation and the downregulation of osteoclast marker genes. Notably, male LysM-PLCβ4-/- mice presented greater bone mass and fewer osteoclasts in vivo than their wild-type littermates, without altered osteoblast function. Mechanistically, we found that PLCβ4 forms a complex with p38 mitogen-activated protein kinase (MAPK) and MAPK kinase 3 (MKK3) in response to RANKL-induced osteoclast differentiation, thereby modulating p38 activation. An immunofluorescence assay further confirmed the colocalization of PLCβ4 with p38 after RANKL exposure. Moreover, p38 activation rescued impaired osteoclast formation and restored the reduction in p38 phosphorylation caused by PLCβ4 deficiency. Thus, our findings reveal that PLCβ4 controls osteoclastogenesis via the RANKL-dependent MKK3-p38 MAPK pathway and that PLCβ4 may be a potential therapeutic candidate for bone diseases such as osteoporosis.

Bone is a unique organ crucial for locomotion, mineral metabolism, and hematopoiesis. It maintains homeostasis through a balance between bone formation by osteoblasts and bone resorption by osteoclasts, which is regulated by the basic multicellular unit (BMU). Abnormal bone metabolism arises from an imbalance in the BMU. Osteoclasts, derived from the monocyte-macrophage lineage, are regulated by the RANKL-RANK-OPG system, which is a key factor in osteoclast differentiation. RANKL activates osteoclasts through its receptor RANK, while OPG acts as a decoy receptor that inhibits RANKL. In trabecular bone, high turnover involves rapid bone formation and resorption, influenced by conditions such as malignancy and inflammatory cytokines that increase RANKL expression. Cortical bone remodeling, regulated by aged osteocytes expressing RANKL, is less understood, despite ongoing research into how Rett syndrome, characterized by MeCP2 abnormalities, affects RANKL expression. Balancing trabecular and cortical bone involves mechanisms that preserve cortical bone, despite overall bone mass reduction due to aging or oxidative stress. Research into genes like sFRP4, which modulates bone mass, highlights the complex regulation by BMUs. The roles of the RANKL-RANK-OPG system extend beyond bone, affecting processes such as aortic valve formation and temperature regulation, which highlight the interconnected nature of biological research.

Osteoporosis is a metabolic skeletal disease characterized by low bone mass and strength, and increased risk for fragility fractures. It is a major health issue in aging populations, due to fracture-associated increased disability and mortality. Antiresorptive treatments are first line choices in most of the cases.

Bone homeostasis is complicated, and multiple factors can compromise skeletal health. Bone turnover is a continuous process regulated by the coupled activities of bone cells that preserves skeletal strength and integrity. Imbalance between bone resorption and formation leads to bone loss and increased susceptibility to fractures. Antiresorptives prevent bone loss and reduce fracture risk, by targeting osteoclastogenesis and osteoclast function and survival. Their major drawback is the coupling of osteoclast and osteoblast activity, due to which any reduction in bone resorption is followed by suppression of bone formation.

During the last couple of decades significant progress has been made in understanding of the genetic and molecular basis of osteoporosis. Critical pathways and key molecules that mediate regulation of bone resorption have been identified. These factors may underpin novel therapeutic avenues for osteoporosis, but their potential for translation into clinical applications is yet to be tested.

Orthodontic tooth movement (OTM) is a complex process involving bone remodeling, and is regulated by various molecular factors, including microRNAs (miRNAs). These small, non-coding RNAs are critical in post-transcriptional gene regulation and have been implicated in the modulation of osteoclast and osteoblast activity during OTM. This study aimed to explore the expression profiles of salivary exosome-derived miRNAs during OTM to identify potential biomarkers that could provide insights into the biological processes involved in orthodontic tooth movement. Saliva samples were collected from 15 patients at three time points: before treatment (Day 0), 7 days after the treatment's onset (Day 7), and 40 days after the treatment's onset (Day 40). The exosomes were isolated, and the miRNAs were extracted and sequenced. A differential expression analysis and gene ontology (GO) enrichment were performed to identify the miRNAs involved in osteoblast and osteoclast differentiation. Out of the 1405 detected miRNAs, 185 were analyzed. Several miRNAs were associated with bone-remodeling processes. The statistically significant finding was the downregulation of hsa-miR-4634 after 40 days of treatment. These findings contribute to the understanding of miRNA regulation in orthodontics and may have broader implications for skeletal disorders, such as osteoporosis.

This study aimed to evaluate bone remodeling in gingival crevicular fluid (GCF) during canine distalization in obese individuals and compare it to that in normal-weight individuals. Additionally, the orthodontic tooth movement rates of obese individuals were measured and compared with those of normal-weight individuals.

Thirty-six patients (18 obese and 18 normal-weight) aged 12-18 years who were candidates for maxillary first premolar extraction for Angle Class II malocclusion were included in the study. The two groups were formed according to World Health Organization guidelines. A normal-weight group (body mass index [BMI] 16-85%) and an obese group (BMI ≥ 95%). Gingival crevicular fluid samples were collected before, 24 hours after, and on the 7th, 14th, and 21st days after the application of the distalization force. Enzyme-linked immunosorbent assay was used to measure leptin, receptor activator of nuclear factor kappa-Β ligand (RANKL), osteoprotegerin (OPG) and interleukin-6 (IL-6) levels in GCF samples. In addition to the recorded GCF sampling times, the amount of canine tooth movement was calculated using digital models obtained on the 28th day and 3rd month.

Leptin, RANKL, OPG, and IL-6 levels were significantly higher in the obese group (P < 0.05). The digital model measurements displayed high rates of repeatability (ICC 0.990). The difference in the amount of tooth movement between groups was not statistically significant (P > 0.05).

Although obese and normal-weight individuals showed different biomarker levels during tooth movement, there were no significant differences in the amount of movement.

Background/Objectives: This nationwide retrospective study evaluated the effects of anticancer therapy on osteoporosis in 126,132 Korean breast cancer survivors from 2002 to 2020. Methods: The Cox proportional hazards model assessed the effects of treatment on osteoporosis. To circumvent the guarantee-time bias for osteoporosis development, a landmark analysis was employed. A stabilized inverse probability of treatment weighting was performed to control any confounding bias. The propensity score was calculated using a multinomial logistic regression model with age, national health insurance, and the Charlson comorbidity index. Results: During a median follow-up of 4.22 years, 28,603 cases of osteoporosis were documented. Aromatase inhibitors (AIs) were associated with a higher risk of osteoporosis development in comparison to tamoxifen (TMX) or chemotherapy. Notably, AIs administered subsequent to a combination of chemotherapy and anti-HER2 therapy exhibited the highest risk of osteoporosis development. Subgroup analysis revealed that the mean interval from breast cancer diagnosis to osteoporosis development was 5.00 years for women diagnosed with cancer at age < 50 and 3.89 years for those diagnosed at age ≥ 60. TMX increased the risk of osteoporosis in women diagnosed with cancer at age < 50, whereas chemotherapy was not a significant risk factor for osteoporosis development in those diagnosed at age ≥ 60. The impact of anticancer therapy on osteoporosis development was more pronounced in women diagnosed with breast cancer at a younger age compared to those diagnosed at an older age. Conclusions: Effective prevention and active management strategies should be implemented to address bone loss in both younger and older breast cancer patients.

Objective: In developed countries, stroke is the fifth cause of death, with a high mortality rate, and with recovery to normal neurological function in one-third of survivors. Atherosclerotic occlusive disease of the extracranial part of the internal carotid artery and related embolic complications are common preventable causes of ischemic stroke (IS), attributable to 7-18% of all first-time cases. Osteoprotegerin (OPG), a soluble member of the tumor necrosis factor receptor (TNFR) superfamily, is considered a modulator of vascular calcification linked to vascular smooth muscle cell proliferation and collagen production in atherosclerotic plaques. Therefore, OPG emerges as a potential biomarker (BM) of calcified carotid plaques and carotid artery stenosis (CAS). Methods: We performed a literature search of PubMed on OPG in CAS and atherosclerosis published until 2024. Results: Increased levels of serum OPG were reported in both patients with symptomatic and asymptomatic CAS, and higher values were observed in those with unstable atherosclerotic plaques. Notably, increased OPG levels were observed regardless of the location of atherosclerosis, including coronary and other peripheral arteries. In addition, chronic kidney disease, the most significant confounder disturbing the association between vascular damage and circulating OPG levels, decreases the usefulness of OPG as a BM in CAS. Conclusions: Osteoprotegerin may be considered an emerging BM of global rather than cerebrovascular atherosclerosis. Its diagnostic significance in identifying patients with asymptomatic CAS and their monitoring is limited.

This study aimed to investigate the regulation and underlying mechanism of Cathepsin K (CTSK) in bone-invasive pituitary adenomas (BIPAs). A total of 1437 patients with pituitary adenomas were included and followed up. RNA sequencing, immunohistochemistry, and qRT-PCR were used to analyze CTSK expression. The effects of CTSK on cellular proliferation, bone matrix degradation, and osteoclast differentiation were determined by gain/loss of function experiments in vitro and in vivo. The exploration of signaling pathways was determined through molecular biology experiments. Here, we reported a significant fraction (∼10 %) of pituitary adenoma patients developed bone invasion, which was correlated with tumor recurrence. Patients with BIPAs had shorter recurrence-free survival. CTSK expression was increased in BIPA patients and was strongly associated with a worse prognosis. Increased CTSK expression enhanced pituitary adenoma cell proliferation through the activation of the mammalian target of rapamycin (mTOR) signaling pathway and promoted bone invasion by increasing osteoclast differentiation both in vitro and in vivo. Treatment with the CTSK inhibitor odanacatib effectively inhibited pituitary adenoma cell proliferation and bone invasion in these models. Additionally, CTSK facilitated osteoclast differentiation by promoting RANKL expression in MC3T3-E1 cells via interaction with TLR4. Based on these findings, we conclude that CTSK has the potential to become a novel predictive biomarker and therapeutic target for BIPAs.

During reproduction, multiple species such as insects and all mammals undergo extensive physiological and morphological adaptions to ensure health and survival of the mother and optimal development of the offspring. Here we report that the intestinal epithelium undergoes expansion during pregnancy and lactation in mammals. This enlargement of the intestinal surface area results in a novel geometry of expanded villi. Receptor activator of nuclear factor-κΒ (RANK, encoded by TNFRSF11A) and its ligand RANKL were identified as a molecular pathway involved in this villous expansion of the small intestine in vivo in mice and in intestinal mouse and human organoids. Mechanistically, RANK-RANKL protects gut epithelial cells from cell death and controls the intestinal stem cell niche through BMP receptor signalling, resulting in the elongation of villi and a prominent increase in the intestinal surface. As a transgenerational consequence, babies born to female mice that lack Rank in the intestinal epithelium show reduced weight and develop glucose intolerance after metabolic stress. Whereas gut epithelial remodelling in pregnancy/lactation is reversible, constitutive expression of an active form of RANK is sufficient to drive intestinal expansion followed by loss of villi and stem cells, and prevents the formation of Apcmin-driven small intestinal stem cell tumours. These data identify RANK-RANKL as a pathway that drives intestinal epithelial expansion in pregnancy/lactation, one of the most elusive and fundamental tissue remodelling events in mammalian life history and evolution.