Estrogen Deficiency-Mediated M2 Macrophage Osteoclastogenesis Contributes to M1/M2 Ratio Alteration in Ovariectomized Osteoporotic Mice

Immune Cells as Mediators of Lipidome Influence on Osteoporosis: Evidence from a Mediation Analysis

Background: Although clinical studies have indicated a possible association between dyslipidemia and osteoporosis, the underlying genetic basis and mechanistic pathways remain insufficiently defined. Most prior research has concentrated on conventional lipid markers, which are prone to confounding and limit causal inference. Exploring lipidomic profiles offers a more comprehensive view of lipid metabolism and may reveal novel genetic links beyond traditional lipid traits. Additionally, alterations in immune cell function, often triggered by metabolic disturbances, may contribute to osteoporosis development; however, the potential mediating role of immune cells in the lipid-bone axis has not been systematically investigated. Methods: A total of 179 lipid species across 13 lipid classes were analyzed in 7174 Finnish individuals from the GeneRISK cohort. Genome-Wide Association Study (GWAS) summary statistics for osteoporosis and 731 immune cell immunophenotypes were sourced from the GWAS Catalog. A two-step, two-sample Mendelian randomization analysis, using inverse variance weighting (IVW), was conducted to explore the potential causal effects of lipids on osteoporosis and the mediating role of immune cells in the relationship between lipids and osteoporosis. Results: Mendelian randomization analysis indicated that triacylglycerol levels of 48:0 were possibly associated with an increased risk of osteoporosis (IVW: odds ratio [OR] 1.1320, 95% CI 1.0401-1.2321; p = 0.004), while triacylglycerol levels of 48:3 appeared to be associated with a reduced risk of osteoporosis (IVW: OR 0.9053, 95% CI 0.8364-0.9800; p = 0.014). Two statistically significant mediating effects were identified: First, IgD- CD38dim %B cells appeared to partially negatively mediate the association between triacylglycerol levels of 48:3 and osteoporosis, with a negative mediating effect of -0.00669 (95% CI: -0.0214, 0.00805), which accounted for 6.73% of the total effect. That is, the protective effect of triacylglycerol levels of 48:3 against osteoporosis was attenuated by IgD- CD38dim %B cells. Second, HLA DR++ monocytes% leukocytes also partially negatively mediated this relationship, with a mediating effect of -0.023 (95% CI: -0.0434, -0.00266), accounting for 23.2% of the total effect. This indicates that other immune cells, HLA DR++ monocytes %leukocytes, resisted the protective effect of triacylglycerol levels of 48:3 against osteoporosis, with a weakening effect stronger than that of IgD- CD38dim %B cells. Conclusions: Our findings contribute to the growing understanding of the potential causal relationships and shared pathogenic mechanisms between dyslipidemia and osteoporosis. The results suggest that the potential genetic effects of plasma lipid metabolites on osteoporosis may be partially down-regulated by specific kinds of immune cells.

Mechanistic Insights into Maltol-Mediated Reversal of Postmenopausal Osteoporosis via Regulation of CDK14 Ubiquitination in Macrophages

Maltol, primarily derived from Korean red ginseng, exhibits anti-inflammatory properties by modulating macrophage polarization and has potential therapeutic effects on postmenopausal osteoporosis, a condition linked to inflammation. This study explored the molecular mechanisms underlying maltol's ability to inhibit M1 macrophage polarization and regulate osteoblast differentiation via macrophage-mediated pathways. Using in vitro and in vivo models, we demonstrated that maltol upregulates RNF213, which inhibits the CDK14-Pdgfrβ signaling pathway, suppressing M1 polarization and reducing NFκB phosphorylation and pro-inflammatory cytokine production. Additionally, maltol decreases TNFSF12 secretion, mitigating estrogen deficiency-induced osteoblast apoptosis and promoting differentiation. These findings highlight maltol's potential in managing postmenopausal osteoporosis and other inflammatory diseases.

The Nexus Between Traditional Chinese Medicine and Immunoporosis: Implications in the Treatment and Management of Osteoporosis

Osteoporosis (OP) is a globally prevalent bone disease characterized by reduced bone mass and heightened fracture risk, posing a significant health and economic challenge to aging societies worldwide. Osteoimmunology-an emerging field of study-investigates the intricate relationship between the skeletal and the immune systems, providing insights into the immune system's impact on bone health and disease progression. Recent research has demonstrated the essential roles played by various immune cells (T cells, B cells, macrophages, dendritic cells, mast cells, granulocytes, and innate lymphoid cells) in regulating bone metabolism, homeostasis, formation, and remodeling through interactions with osteoclasts (OC) and osteoblasts (OB). These findings underscore that osteoimmunology provides an essential theoretical framework for understanding the pathogenesis of various skeletal disorders, including OP. Traditional Chinese medicine (TCM) and its active ingredients have significant clinical value in OP treatment. Unfortunately, despite their striking multieffect pathways in the pharmacological field, current research has not yet summarized them in a comprehensive and detailed manner with respect to their interventional roles in immune bone diseases, especially OP. Consequently, this review addresses recent studies on the mechanisms by which immune cells and their communication molecules contribute to OP development. Additionally, it explores the potential therapeutic benefits of TCM and its active components in treating OP from the perspective of osteoimmunology. The objective is to provide a comprehensive framework that enhances the understanding of the therapeutic mechanisms of TCM in treating immune-related bone diseases and to facilitate the development of novel therapeutic strategies.

Activated NETosis of bone marrow neutrophils up-regulates macrophage osteoclastogenesis via cGAS-STING/AKT2 pathway to promote osteoporosis

Bone marrow (BM) of postmenopausal osteoporosis has been found highly inflammatory, resulting from dysregulated immune cells induced by both estrogen efficiency and body aging. NETosis of neutrophils has been found aberrantly activated in age-related chronic inflammation, while their role in postmenopausal osteoporosis remains unclear. Here we found NETosis of BM neutrophils of OVX (ovariectomy) mice was significantly activated, and we verified NETs released by neutrophils induced M1 polarization and osteoclastogenesis of RAW264.7 macrophages. Further, we demonstrated effects of NETs on osteoclastogenesis was mediated by cGAS-STING/AKT2 pathway. Finally, we found in vivo NETs-clearance through GSK484 significantly inhibited osteoclastogenesis and attenuated osteoporosis of OVX mice. Our study highlights the role of neutrophil NETosis in activating osteoclastogenesis and bone resorption of postmenopausal osteoporosis, thereby providing novel targets for bone loss treatment.

Estrogen deficiency-mediated osteoimmunity in postmenopausal osteoporosis

Postmenopausal osteoporosis (PMO) is a common disease associated with aging, and estrogen deficiency is considered to be the main cause of PMO. Recently, however, osteoimmunology has been revealed to be closely related to PMO. On the one hand, estrogen deficiency directly affects the activity of bone cells (osteoblasts, osteoclasts, osteocytes). On the other hand, estrogen deficiency-mediated osteoimmunity also plays a crucial role in bone loss in PMO. In this review, we systematically describe the progress of the mechanisms of bone loss in PMO, estrogen deficiency-mediated osteoimmunity, the differences between PMO patients and postmenopausal populations without osteoporosis, and estrogen deficiency-mediated immune cells (T cells, B cells, macrophages, neutrophils, dendritic cells, and mast cells) activity. The comprehensive summary of this paper provides a clear knowledge context for future research on the mechanism of PMO bone loss.

Cystatin M/E Ameliorates Multiple Myeloma-Induced Hyper Osteolytic Bone Resorption

Multiple myeloma (MM) is a malignancy of terminally differentiated B-cells that is localized primarily in the bone marrow (BM) but also can be present in peripheral blood and tissue/organs [...].

hCeO2@CA-074Me Nanoparticles Alleviate Inflammation and Improve Osteogenic Microenvironment by Regulating the CTSB-NLRP3 Signaling Pathway

Background

It is well established that the interaction between osteogenesis and inflammation can impact bone tissue regeneration. The use of nanoparticles to treat and alleviate inflammation at the molecular level has the potential to improve the osteogenic microenvironment and serve as a therapeutic approach.

Methods

We have synthesized new hollow cerium oxide nanoparticles and doped with cathepsin B inhibitor (CA-074Me) to create novel hCeO2@CA-074Me NPs. We characterized the surface morphology and physicochemical properties of hCeO2@CA-074Me NPs. Macrophage RAW 264.7 was cultured with hCeO2@CA-074Me NPs using P. gingivalis-LPS (P.g-LPS) stimulation as a model of inflammation. RT-PCR and Western blot analysis was employed to evaluate the effects of hCeO2@CA-074Me NPs on macrophage phenotype and the CTSB-NLRP3 signaling pathway. To further investigate the inflammatory osteogenic microenvironment, MC3T3-E1 cells were cultured with P.g-LPS to create an in vitro osteogenic conditions under inflammation. The cells were then co-cultured with hCeO2@CA-074Me NPs for 7, 14, and 21 d. The osteogenic ability was evaluated using ALP staining, ALP quantitative analysis, alizarin red staining, and RT-PCR analysis.

Results

Findings clearly demonstrated that hCeO2@CA-074Me NPs could effectively reduce the production of ROS and inhibited CTSB-NLRP3 signal pathway, thereby significantly attenuating the damage caused by the cellular inflammatory response. hCeO2@CA-074Me NPs could also induce the polarization of macrophages towards anti-inflammatory M2 phenotype. Additionally, results confirmed that hCeO2@CA-074Me NPs could inhibit inflammation and ameliorate osteogenic microenvironment, thus promoting the osteogenesis of MC3T3-E1 cells.

Conclusion

The synthetic hCeO2@CA-074Me NPs could able to modify the osteogenic microenvironment under inflammatory conditions by simultaneously inhibiting the CTSB-NLRP3 signaling pathway and regulating the macrophage phenotype through their ability to scavenge ROS. Based on these findings, our study may offer a promising approach for managing inflammatory bone damage.

Contribution of macrophage polarization in bone metabolism: A literature review

Macrophage polarization divides macrophages into two main cell subpopulations, classically and alternatively activated macrophages (M1 and M2, respectively). M1 polarization promotes osteoclastogenesis, while M2 polarization promotes osteogenesis. The physiological homeostasis of bone metabolism involves a high dynamic balance between osteoclastic-mediated bone resorption and formation. Reportedly, M1/M2 imbalance causes the onset and persistence of inflammation-related bone diseases. Therefore, understanding the research advances in functions and roles of macrophages in such diseases will provide substantial guidance for improved treatment of bone diseases. In this review, we underscore and summarize the research advances in macrophage polarization, and bone-related diseases, such as rheumatoid arthritis, osteoarthritis, and osteoporosis, over the last 5 years. Our findings showed that targeting macrophages and balancing macrophage polarization can effectively reduce inflammation and decrease bone destruction while promoting bone formation and vascular repair. These results indicate that regulating macrophage and macrophage polarization to restore homeostasis is a prospective approach for curing bone-related diseases.

Promotion of mandibular distraction osteogenesis by parathyroid hormone via macrophage polarization induced through iNOS downregulation

Objective

To investigate whether Parathyroid hormone (PTH) can promote mandibular distraction osteogenesis by regulating macrophage polarization and the underlying mechanisms of this phenomenon.

Methods

Forty-eight Rabbits were used to establish the mandibular distraction osteogenesis experimental model, randomly divided into 2 groups. Intermittent post-operative injections of 20 μg/kg PTH and normal saline were administered to the experimental and control groups, respectively. Regenerated new bone was examined using HE staining, osteoclast numbers were determined through tartrate-resistant acid phosphatase (TRAP) staining, and macrophage polarization markers arginase 1 (Arg1) and inducible nitric oxide synthase (iNOS) expressions were elucidated using immunohistochemistry (IHC), the mRNA expression of CD206, CD11C, Arg1 and iNOS were detected using qPCR.

Results

The bone trabeculae in the experimental group were thicker, with a more homogeneous structure and more new osteoid than in the control group. In the area of distraction osteogenesis, the osteoclast count in the experimental group was higher than in the control group (P < 0.05). IHC results indicated differential expressions of Arg1 and iNOS in the experimental group compared to the control group (P < 0.05). Relative mRNA expressions of CD11c and iNOS were lower in the experimental group than in the control group (P < 0.05), whereas the expressions of CD206 and Arg1 mRNA were higher in the experimental group compared to the control group (P < 0.05).

Conclusion

Intermittent PTH injections increased macrophage quantity in the mandible generated by distraction osteogenesis, downregulated iNOS, upregulated Arg1, and promoted macrophage polarization from M1 to M2 phenotype, thereby promoting mandibular distraction osteogenesis.

Beyond resorption: osteoclasts as drivers of bone formation

Emerging evidence illustrates that osteoclasts (OCs) play diverse roles beyond bone resorption, contributing significantly to bone formation and regeneration. Despite this, OCs remain mysterious cells, with aspects of their lifespan-from origin, fusion, alterations in cellular characteristics, to functions-remaining incompletely understood. Recent studies have identified that embryonic osteoclastogenesis is primarily driven by osteoclast precursors (OCPs) derived from erythromyeloid progenitors (EMPs). These precursor cells subsequently fuse into OCs essential for normal bone development and repair. Postnatally, hematopoietic stem cells (HSCs) become the primary source of OCs, gradually replacing EMP-derived OCs and assuming functional roles in adulthood. The absence of OCs during bone development results in bone structure malformation, including abnormal bone marrow cavity formation and shorter long bones. Additionally, OCs are reported to have intimate interactions with blood vessels, influencing bone formation and repair through angiogenesis regulation. Upon biomaterial implantation, activation of the innate immune system ensues immediately. OCs, originating from macrophages, closely interact with the immune system. Furthermore, evidence from material-induced bone formation events suggests that OCs are pivotal in these de novo bone formation processes. Nevertheless, achieving a pure OC culture remains challenging, and interpreting OC functions in vivo faces difficulties due to the presence of other multinucleated cells around bone-forming biomaterials. We here describe the fusion characteristics of OCPs and summarize reliable markers and morphological changes in OCs during their fusion process, providing guidance for researchers in identifying OCs both in vitro and in vivo. This review focuses on OC formation, characterization, and the roles of OCs beyond resorption in various bone pathophysiological processes. Finally, therapeutic strategies targeting OCs are discussed.

Europium-Containing Nanospheres for Treating Ovariectomy-Induced Osteoporosis: Targeted Bone Remodeling and Macrophage Polarization Modulation

Purpose

Osteoporosis, characterized by reduced bone mass and structural deterioration, poses a significant healthcare challenge. Traditional treatments, while effective in reducing fracture risks, are often limited by side effects. This study introduces a novel nanocomplex, europium (Eu) ions-doped superparamagnetic iron oxide (SPIO) nanocrystals encapsulated in poly(lactic-co-glycolic acid) (PLGA) nanospheres, abbreviated as SPIO:Eu@PLGA nanospheres, as a potential therapeutic agent for osteoporosis by modulating macrophage polarization, enhancing osteoblast differentiation and inhibiting osteoclastogenesis.

Methods

SPIO and SPIO:Eu nanocrystals were synthesized through pyrolysis and encapsulated in PLGA using an emulsification method. To evaluate the impact of SPIO:Eu@PLGA nanospheres on macrophage reprogramming and reactive oxygen species (ROS) production, flow cytometry analysis was conducted. Furthermore, an ovariectomized (OVX) rat model was employed to assess the therapeutic efficacy of SPIO:Eu@PLGA nanospheres in preventing the deterioration of osteoporosis.

Results

In vitro, SPIO:Eu@PLGA nanospheres significantly attenuated M1 macrophage activation induced by lipopolysaccharides, promoting a shift towards the M2 phenotype. This action is linked to the modulation of ROS and the NF-κB pathway. Unlike free Eu ions, which do not achieve similar results when not incorporated into the SPIO nanocrystals. SPIO:Eu@PLGA nanospheres enhanced osteoblast differentiation and matrix mineralization while inhibiting RANKL-induced osteoclastogenesis. In vivo studies demonstrated that SPIO:Eu@PLGA nanospheres effectively targeted trabecular bone surfaces in OVX rats under magnetic guidance, preserving their structure and repairing trabecular bone loss by modulating macrophage polarization, thus restoring bone remodeling homeostasis. The study underscores the critical role of Eu doping in boosting the anti-osteoporotic effects of SPIO:Eu@PLGA nanospheres, evident at both cellular and tissue levels in vitro and in vivo.

Conclusion

The inclusion of Eu into SPIO matrix suggests a novel approach for developing more effective osteoporosis treatments, particularly for conditions induced by OVX. This research provides essential insights into SPIO:Eu@PLGA nanospheres as an innovative osteoporosis treatment, addressing the limitations of conventional therapies through targeted delivery and macrophage polarization modulation.

Knowledge Mapping of Macrophages in Osteoporosis: A Bibliometric Analysis (1999-2023)

BACKGROUND

Osteoporosis is a common metabolic disorder that significantly impacts quality of life in the elderly population. Macrophages play a crucial role in the development of osteoporosis by regulating bone metabolism through cytokine secretion. However, there is a lack of scholarly literature in the field of bibliometrics on this topic.

OBJECTIVE

This study provides a detailed analysis of the research focus and knowledge structure of macrophage studies in osteoporosis using bibliometrics.

METHODS

The scientific literature on macrophage research in the context of osteoporosis, retrieved from the Web of Science Core Collection (WoSCC) database spanning from January 1999 to December 2023, has been incorporated for bibliometric examination. The data is methodically analyzed and visually represented using analytical and visualization tools including VOSviewer, CiteSpace, Scimago Graphica, the Bibliometrix R package, and Pajek.

RESULTS AND CONCLUSIONS

In the last quarter-century, there has been a consistent rise in the quantity of scholarly publications focusing on the relationship between macrophages and osteoporosis, resulting in a total of 1499 research documents. These studies have originated from 45 different countries, with China, South Korea, and the United States being the most prominent contributors, and the United States having the highest frequency of citations. Noteworthy research institutions involved in this field include Shanghai Jiao Tong University, Wonkwang University, Huazhong University of Science and Technology, and Seoul National University. The Journal of Bone and Mineral Research is widely regarded as the premier and most frequently referenced publication in the field. These publications involve the collaboration of 8744 authors, with Lee Myeung Su contributing the most articles, and Takayanagi being the most co-cited author. Key emerging research focal points are encapsulated in keywords such as "mTOR," "BMSCs," "bone regeneration," and "exosome." The relationships between exosome from macrophage sources and those from BMSCs, along with the regulatory role of the mTOR signaling pathway on macrophages, represent crucial directions for future development in this field. This study represents the inaugural comprehensive bibliometric analysis detailing trends and advancements in macrophage research within the osteoporosis domain. It delineates recent frontiers and hotspots, providing valuable insights for researchers in this particular area of study.

Intelligent Supramolecular Modification for Implants: Endogenous Regulation of Bone Defect Repair in Osteoporosis

Addressing osteoporosis-related bone defects, a supramolecular strategy is innovated for modifying carbon fiber reinforced polyether ether ketone (CF/PEEK) composites. By covalently attaching intelligent macromolecules via in situ RAFT polymerization, leveraging the unique pathological microenvironment in patients with iron-overloaded osteoporosis, intelligent supramolecular modified implant surface possesses multiple endogenous modulation capabilities. After implantation, surface brush-like macromolecules initially resist macrophage adhesion, thereby reducing the level of immune inflammation. Over time, the molecular chains undergo conformational changes due to Fe (III) mediated supramolecular self-assembly, transforming into mechanistic signals. These signals are then specifically transmitted to pre-osteoblast cell through the binding capacity of the KRSR short peptide at the molecular terminus, induced their osteogenic differentiation via the YAP/β-catenin signaling axis. Furthermore, osteoblasts secrete alkaline phosphatase (ALP), which significantly hydrolyzes phosphate ester bonds in surface macromolecular side groups, resulting in the release of alendronate (ALN). This process further improves the local osteoporotic microenvironment. This intelligent surface modification tailors bone repair to individual conditions, automatically realize multiple endogenous regulation once implanted, and truly realize spontaneous activation of a series of responses conducive to bone repair in vivo. It is evidenced by improved bone regeneration in iron-overloaded osteoporotic rabbits and supported by in vitro validations.

Integrated single-cell and bulk RNA sequencing analysis reveal immune-related biomarkers in postmenopausal osteoporosis

Background

Postmenopausal osteoporosis (PMOP) represents as a significant health concern, particularly as the population ages. Currently, there is a paucity of comprehensive descriptions regarding the immunoregulatory mechanisms and early diagnostic biomarkers associated with PMOP. This study aims to examine immune-related differentially expressed genes (IR-DEGs) in the peripheral blood mononuclear cells of PMOP patients to identify immunological patterns and diagnostic biomarkers.

Methods

The GSE56815 dataset from the Gene Expression Omnibus (GEO) database was used as the training group, while the GSE2208 dataset served as the validation group. Initially, differential expression analysis was conducted after data integration to identify IR-DEGs in the peripheral blood mononuclear cells of PMOP. Subsequently, feature selection of these IR-DEGs was performed using RF, SVM-RFE, and LASSO regression models. Additionally, the expression of IR-DEGs in distinct bone marrow cell subtypes was analyzed using single-cell RNA sequencing (scRNA-seq) datasets, allowing the identification of cellular communication patterns within various cell subgroups. Finally, molecular subtypes and diagnostic models for PMOP were constructed based on these selected IR-DEGs. Furthermore, the expression levels of characteristic IR-DEGs were examined in rat osteoporosis (OP) models.

Results

Using machine learning, six IR-DEGs (JUN, HMOX1, CYSLTR2, TNFSF8, IL1R2, and SSTR5) were identified. Subsequently, two molecular subtypes of PMOP (subtype 1 and subtype 2) were established, with subtype 1 exhibiting a higher proportion of M1 macrophage infiltration. Analysis of the scRNA-seq dataset revealed 11 distinct cell clusters. It was noted that JUN was significantly overexpressed in M1 macrophages, while HMOX1 showed a marked elevation in endothelial cells and M2 macrophages. Cell communication results suggested that the PMOP microenvironment features increased interactions among M2 macrophages, CD8+ T cells, Tregs, and fibroblasts. The diagnostic model based on these six IR-DEGs demonstrated excellent diagnostic performance (AUC = 0.927). In the OP rat model, the expression of IL1R2 and TNFSF8 were significantly elevated.

Conclusion

JUN, HMOX1, CYSLTR2, TNFSF8, IL1R2, and SSTR5 may serve as promising molecular targets for diagnosing and subtyping patients with PMOP. These results offer novel perspectives on the early diagnosis of PMOP and the advancement of personalized immune-based therapies.

Metabolic Control During Macrophage Polarization by a Citrate-Functionalized Scaffold for Maintaining Bone Homeostasis

Metabolites, as markers of phenotype at the molecular level, can regulate the function of DNA, RNA, and proteins through chemical modifications or interactions with large molecules. Citrate is an important metabolite that affects macrophage polarization and osteoporotic bone function. Therefore, a better understanding of the precise effect of citrate on macrophage polarization may provide an effective alternative strategy to reverse osteoporotic bone metabolism. In this study, a citrate functional scaffold to control the metabolic pathway during macrophage polarization based on the metabolic differences between pro-inflammatory and anti-inflammatory phenotypes for maintaining bone homeostasis, is fabricated. Mechanistically, only outside M1 macrophages are accumulated high concentrations of citrate, in contrast, M2 macrophages consume massive citrate. Therefore, citrate-functionalized scaffolds exert more sensitive inhibitory effects on metabolic enzyme activity during M1 macrophage polarization than M2 macrophage polarization. Citrate can block glycolysis-related enzymes by occupying the binding-site and ensure sufficient metabolic flux in the TCA cycle, so as to turn the metabolism of macrophages to oxidative phosphorylation of M2 macrophage, largely maintaining bone homeostasis. These studies indicate that exogenous citrate can realize metabolic control of macrophage polarization for maintaining bone homeostasis in osteoporosis.

Unraveling the molecular and immunological landscape: Exploring signaling pathways in osteoporosis

Osteoporosis, characterized by compromised bone density and microarchitecture, represents a significant global health challenge, particularly in aging populations. This comprehensive review delves into the intricate signaling pathways implicated in the pathogenesis of osteoporosis, providing valuable insights into the pivotal role of signal transduction in maintaining bone homeostasis. The exploration encompasses cellular signaling pathways such as Wnt, Notch, JAK/STAT, NF-κB, and TGF-β, all of which play crucial roles in bone remodeling. The dysregulation of these pathways is a contributing factor to osteoporosis, necessitating a profound understanding of their complexities to unveil the molecular mechanisms underlying bone loss. The review highlights the pathological significance of disrupted signaling in osteoporosis, emphasizing how these deviations impact the functionality of osteoblasts and osteoclasts, ultimately resulting in heightened bone resorption and compromised bone formation. A nuanced analysis of the intricate crosstalk between these pathways is provided to underscore their relevance in the pathophysiology of osteoporosis. Furthermore, the study addresses some of the most crucial long non-coding RNAs (lncRNAs) associated with osteoporosis, adding an additional layer of academic depth to the exploration of immune system involvement in various types of osteoporosis. Finally, we propose that SKP1 can serve as a potential biomarker in osteoporosis.

Jaw osteoporosis: Challenges to oral health and emerging perspectives of treatment

Osteoporosis is a prevalent bone metabolic disease that poses a significant challenge to global human health. Jaw osteoporosis, characterized by microstructural damage of the jaw resulting from various factors, is one of the common manifestations of this condition. Recent studies have demonstrated that jaw osteoporosis has multifaceted effects on oral health and can negatively impact conditions such as periodontitis, oral implantation, orthodontic treatment, and wound healing. However, there are still some limitations in the conventional treatment of osteoporosis. For instance, while bisphosphonates can enhance bone quality, they may also lead to osteonecrosis of the jaw, which poses a potential safety hazard in oral diagnosis and treatment. In recent years, considerable attention has been focused on improving the pathological condition of jaw osteoporosis. Treatment strategies such as gut microbial regulation, extracellular vesicles, molecular targeted therapy, herbal medicine, mechanical stimulation are expected to enhance efficacy and minimize adverse reactions. Therefore, understanding these effects and exploring novel treatments for jaw osteoporosis may provide new insights for oral health maintenance and disease treatment. This article reviews the impact of jaw osteoporosis on oral health and describes the limitations associated with current methods. It also discusses emerging perspectives on treatment, offering a comprehensive overview of the challenges and future directions in managing jaw osteoporosis.

The Impact of Depression on Detrimental Changes in Bone Microstructure in Female Mice

Background

Several clinical studies have examined the connection between depression and bone loss, but the cause-and-effect relationship between the two conditions, especially in animal models, is not well-studied.

Methods

A total of 32 female mice were, randomly divided into control group (CON, n=19) and depression group (DEP, n=13). The mice in the DEP group were subjected to 21 consecutive days of restraint stress, following depressive-like behaviors were assessment. The femurs were collected using Micro-Computed Tomography (μCT) and histochemical staining. In parallel, levels of serotonin-related proteins in the brain were measured using Western blot analysis, and sex hormone profiles were determined through liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS).

Results

The mice in the DEP group exhibited clear signs of depressive-like behaviors and an increase in serotonin transporter levels (t=-2.435, P< 0.05). In comparison to the CON mice, the DEP mice showed a decrease in bone mineral density (t =3.741, P< 0.05), bone surface area density (t =8.009, P<0.01), percent bone volume (t =4.293, P< 0.05), trabecular number (t =5.844, P<0.01), and connected density (t =11.000, P< 0.05). Additionally, there was an increase in trabecular separation (t =-7.436, P<0.01) in DEP mice. Furthermore, the DEP mice displayed a significant reduction in serum estrogen levels (t =4.340, P< 0.05) and changes in its metabolite (t =-3.325, P< 0.05), while the levels of androgens remained unchanged.

Conclusion

The restraint stress not only led to the development of depressive-like behaviors but also disrupted the estrogen metabolism pathway, resulting in damage to bone mass and microstructure in female mice. These findings suggest that stress-induced depression may pose a risk for bone loss in female mice by altering estrogen metabolism pathways.

Rapid Selenoprotein Activation by Selenium Nanoparticles to Suppresses Osteoclastogenesis and Pathological Bone Loss

Osteoclast hyperactivation stands as a significant pathological factor contributing to the emergence of bone disorders driven by heightened oxidative stress levels. The modulation of the redox balance to scavenge reactive oxygen species emerges as a viable approach to addressing this concern. Selenoproteins, characterized by selenocysteine (SeCys2) as the active center, are crucial for selenium-based antioxidative stress therapy for inflammatory diseases. This study reveals that surface-active elemental selenium (Se) nanoparticles, particularly lentinan-Se (LNT-Se), exhibit enhanced cellular accumulation and accelerated metabolism to SeCys2, the primary active Se form in biological systems. Consequently, LNT-Se demonstrates significant inhibition of osteoclastogenesis. Furthermore, in vivo studies underscore the superior therapeutic efficacy of LNT-Se over SeCys2, potentially attributable to the enhanced stability and safety profile of LNT-Se. Specifically, LNT-Se effectively modulates the expression of the selenoprotein GPx1, thereby exerting regulatory control over osteoclastogenesis inhibition, and the prevention of osteolysis. In summary, these results suggest that the prompt activation of selenoproteins by Se nanoparticles serves to suppress osteoclastogenesis and pathological bone loss by upregulating GPx1. Moreover, the utilization of bioactive Se species presents a promising avenue for effectively managing bone disorders.

The emerging role of tranexamic acid and its principal target, plasminogen, in skeletal health

The worldwide burden of skeletal diseases such as osteoporosis, degenerative joint disease and impaired fracture healing is steadily increasing. Tranexamic acid (TXA), a plasminogen inhibitor and anti-fibrinolytic agent, is used to reduce bleeding with high effectiveness and safety in major surgical procedures. With its widespread clinical application, the effects of TXA beyond anti-fibrinolysis have been noticed and prompted renewed interest in its use. Some clinical trials have characterized the effects of TXA on reducing postoperative infection rates and regulating immune responses in patients undergoing surgery. Also, several animal studies suggest potential therapeutic effects of TXA on skeletal diseases such as osteoporosis and fracture healing. Although a direct effect of TXA on the differentiation and function of bone cells in vitro was shown, few mechanisms of action have been reported. Here, we summarize recent findings of the effects of TXA on skeletal diseases and discuss the underlying plasminogen-dependent and -independent mechanisms related to bone metabolism and the immune response. We furthermore discuss potential novel indications for TXA application as a treatment strategy for skeletal diseases.

Targeting SAT1 prevents osteoporosis through promoting osteoclast apoptosis

Osteoporosis is a systemic bone disease characterized by decreased bone mass that is tightly regulated by the coordinated actions of osteoclasts and osteoblasts. Apoptosis as a precise programmed cell death involves a cascade of gene expression events which are mechanistically linked to the regulation of bone metabolism. Nevertheless, the critical biomolecules involved in regulating cell apoptosis in osteoporosis remain unknown. To gain a deeper insight into the relationship between apoptosis and osteoporosis, this study integrated the sequencing results of human samples and using a machine learning workflow to overcome the limitations of a single study. Among all immune cell populations, we assessed the apoptotic level and portrayed the distinct subtypes and lineage differentiation of monocytic cells in osteoporotic tissues. Osteoclasts expressed a higher level of Spermidine/spermine-N1-Acetyltransferase1 (SAT1) during osteoclastogenesis which prevented osteoclasts apoptosis and facilitate osteoporosis progression. In addition, Berenil, one potent SAT1 inhibitor, increased osteoclast apoptosis and reversed the bone loss in the femurs of a murine ovariectomy model. In summary, Berenil promotes osteoclast apoptosis, inhibits the bone resorption and improves the abnormal bone structure in vitro and in vivo models by targeting SAT1, demonstrating its potential as a precise therapeutic strategy for clinical osteoporosis treatment.

The immune cells in modulating osteoclast formation and bone metabolism

Osteoclasts are pivotal in regulating bone metabolism, with immune cells significantly influencing both physiological and pathological processes by modulating osteoclast functions. This is particularly evident in conditions of inflammatory bone resorption, such as rheumatoid arthritis and periodontitis. This review summarizes and comprehensively analyzes the research progress on the regulation of osteoclast formation by immune cells, aiming to unveil the underlying mechanisms and pathways through which diseases, such as rheumatoid arthritis and periodontitis, impact bone metabolism.

Inhibition of NF-κB and ERK signaling pathways in osteoclasts and M1 macrophage polarization: Mechanistic insights into the anti-osteoporotic effects of Pseudolaric acid B

Osteoporosis, characterized by bone metabolism disruption leading to gradual bone loss and increased fracture susceptibility, is linked to the excessive activation of osteoclasts. Pseudolaric acid B (PAB), identified as an NF-κB signaling inhibitor crucial for osteoclastogenesis, is explored here for its protective effects in osteoporosis. Noncytotoxic PAB's impact on osteoclast differentiation was assessed through cell viability and osteoclast formation assays, with subsequent testing of osteoclast function via bone resorption assays. Quantitative real-time polymerase chain reaction evaluated PAB's genetic-level impact on osteoclastogenesis. Network pharmacology, western blot, and luciferase reporter gene assays were employed to elucidate PAB's regulatory mechanism. In an in vivo model of osteoporosis induced by ovariectomy (OVX) in mice, micro-CT, H&E staining, and TRAP staining facilitated histomorphometry analysis, while flow cytometry verified macrophage polarization. PAB demonstrated inhibitory effects on osteoclast formation and bone resorption in BMM and RAW264.7 cells, suppressing osteoclast-specific genes. Bioinformatic analysis, western blot, and luciferase assay results indicated PAB's inhibition of IκBα phosphorylation in the NF-κB signaling pathway and ERK in MAPKs, elucidating its mechanism. In vivo experiments confirmed PAB's attenuation of osteoporosis by reducing osteoclast formation in OVX mice. PAB further facilitated macrophage conversion from M1 to M2 and suppressed IL-1β, TNF-α, and IL-6 synthesis. In conclusion, PAB prevents osteoporosis by inhibiting RANKL-induced osteoclastogenesis through NF-κB and ERK signaling pathway suppression, coupled with macrophage polarization. These findings indicate the potential therapeutic role of PAB in osteoporosis.

Effects of circulating inflammatory proteins on osteoporosis and fractures: evidence from genetic correlation and Mendelian randomization study

Objective

There is a controversy in studies of circulating inflammatory proteins (CIPs) in association with osteoporosis (OP) and fractures, and it is unclear if these two conditions are causally related. This study used MR analyses to investigate the causal associations between 91 CIPs and OP and 9 types of fractures.

Methods

Genetic variants data for CIPs, OP, and fractures were obtained from the publicly available genome-wide association studies (GWAS) database. We used inverse variance weighted (IVW) as the primary analysis, pleiotropy, and heterogeneity tests to analyze the validity and robustness of causality and reverse MR analysis to test for reverse causality.

Results

The IVW results with Bonferroni correction indicated that CXCL11 (OR = 1.2049; 95% CI: 1.0308-1.4083; P = 0.0192) can increase the risk of OP; IL-4 (OR = 1.2877; 95% CI: 1.1003-1.5070; P = 0.0016), IL-7 (OR = 1.2572; 95% CI: 1.0401-1.5196; P = 0.0180), IL-15RA (OR = 1.1346; 95% CI: 1.0163-1.2668; P = 0.0246), IL-17C (OR = 1.1353; 95% CI: 1.0272-1.2547; P = 0.0129), CXCL10 (OR = 1.2479; 95% CI: 1.0832-1.4377; P = 0.0022), eotaxin/CCL11 (OR = 1.1552; 95% CI: 1.0525-1.2678; P = 0.0024), and FGF23 (OR = 1.9437; 95% CI: 1.1875-3.1816; P = 0.0082) can increase the risk of fractures; whereas IL-10RB (OR = 0.9006; 95% CI: 0.8335-0.9730; P = 0.0080), CCL4 (OR = 0.9101; 95% CI: 0.8385-0.9878; P = 0.0242), MCP-3/CCL7 (OR = 0.8579; 95% CI: 0.7506-0.9806; P = 0.0246), IFN-γ [shoulder and upper arm (OR = 0.7832; 95% CI: 0.6605-0.9287; P = 0.0049); rib(s), sternum and thoracic spine (OR = 0.7228; 95% CI: 0.5681-0.9197; P = 0.0083)], β-NGF (OR = 0.8384; 95% CI: 0.7473-0.9407; P = 0.0027), and SIRT2 (OR = 0.5167; 95% CI: 0.3296-0.8100; P = 0.0040) can decrease fractures risk.

Conclusion

Mendelian randomization (MR) analyses indicated the causal associations between multiple genetically predicted CIPs and the risk of OP and fractures.

Smart osteoclasts targeted nanomedicine based on amorphous CaCO3 for effective osteoporosis reversal

BACKGROUND

Osteoporosis is characterized by an imbalance in bone homeostasis, resulting in the excessive dissolution of bone minerals due to the acidified microenvironment mediated by overactive osteoclasts. Oroxylin A (ORO), a natural flavonoid, has shown potential in reversing osteoporosis by inhibiting osteoclast-mediated bone resorption. The limited water solubility and lack of targeting specificity hinder the effective accumulation of Oroxylin A within the pathological environment of osteoporosis.

RESULTS

Osteoclasts' microenvironment-responsive nanoparticles are prepared by incorporating Oroxylin A with amorphous calcium carbonate (ACC) and coated with glutamic acid hexapeptide-modified phospholipids, aiming at reinforcing the drug delivery efficiency as well as therapeutic effect. The obtained smart nanoparticles, coined as OAPLG, could instantly neutralize acid and release Oroxylin A in the extracellular microenvironment of osteoclasts. The combination of Oroxylin A and ACC synergistically inhibits osteoclast formation and activity, leading to a significant reversal of systemic bone loss in the ovariectomized mice model.

CONCLUSION

The work highlights an intelligent nanoplatform based on ACC for spatiotemporally controlled release of lipophilic drugs, and illustrates prominent therapeutic promise against osteoporosis.

Gut microbially produced tryptophan metabolite melatonin ameliorates osteoporosis via modulating SCFA and TMAO metabolism

Osteoporosis (OP) is a severe global health issue that has significant implications for productivity and human lifespan. Gut microbiota dysbiosis has been demonstrated to be closely associated with OP progression. Melatonin (MLT) is an important endogenous hormone that modulates bone metabolism, maintains bone homeostasis, and improves OP progression. Multiple studies indicated that MLT participates in the regulation of intestinal microbiota and gut barrier function. However, the promising effects of gut microbiota-derived MLT in OP remain unclear. Here, we found that OP resulted in intestinal tryptophan disorder and decreased the production of gut microbiota-derived MLT, while administration with MLT could mitigate OP-related clinical symptoms and reverse gut microbiota dysbiosis, including the diversity of intestinal microbiota, the relative abundance of many probiotics such as Allobaculum and Parasutterella, and metabolic function of intestinal flora such as amino acid metabolism, nucleotide metabolism, and energy metabolism. Notably, MLT significantly increased the production of short-chain fatty acids and decreased trimethylamine N-oxide-related metabolites. Importantly, MLT could modulate the dynamic balance of M1/M2 macrophages, reduce the serum levels of pro-inflammatory cytokines, and restore gut-barrier function. Taken together, our results highlighted the important roles of gut microbially derived MLT in OP progression via the "gut-bone" axis associated with SCFA metabolism, which may provide novel insight into the development of MLT as a promising drug for treating OP.

A novel mechanism of Vildagliptin in regulating bone metabolism and mitigating osteoporosis

Osteoporosis has become a global social problem with the tendency toward the aging population. The challenge in managing osteoporosis is to develop new anti-osteoporosis drugs that target bone anabolism. The purpose of this study was to uncover the novel mechanism of Vildagliptin on bone metabolism. We revealed that Vildagliptin significantly promoted osteogenic differentiation of precursor osteoblasts and bone marrow mesenchymal stem cells (BMSCs). At the same time, it significantly enhanced the polarization of RAW264.7 macrophages to the M2 type and the secretion of osteogenic factors BMP2 and TGF-β1. This was confirmed by the increased osteogenic differentiation observed in the osteoblast-RAW264.7 co-culture system. Moreover, Vildagliptin significantly enhanced the transformation of BMSCs into the osteogenic morphology in the osteoblast-BMSC co-culture system. Finally, Vildagliptin also inhibited osteoclastic differentiation of RAW 264.7 cells. The potential mechanism underlying these effects involved targeting the GAS6/AXL/ERK5 pathway. In the in vivo study, Vildagliptin significantly alleviated postmenopausal osteoporosis in ovariectomized mice. These findings represent the first comprehensive revelation of the regulatory effect of Vildagliptin on bone metabolism. Specifically, Vildagliptin demonstrates the ability to promote bone anabolism and inhibit bone resorption by simultaneously targeting osteoblasts, BMSCs, and osteoclasts. The bone-protective effects of Vildagliptin were further confirmed in a postmenopausal osteoporosis model. The clinical significance of this study lies in laying a theoretical foundation for bone protection therapy in type-2 diabetes patients with compromised bone conditions or postmenopausal osteoporosis.

Use of oxygen-loaded nanobubbles to improve tissue oxygenation: Bone-relevant mechanisms of action and effects on osteoclast differentiation

Gas-loaded nanobubbles have potential as a method of oxygen delivery to increase tumour oxygenation and therapeutically alleviate tumour hypoxia. However, the mechanism(s) whereby oxygen-loaded nanobubbles increase tumour oxygenation are unknown; with their calculated oxygen-carrying capacity being insufficient to explain this effect. Intra-tumoural hypoxia is a prime therapeutic target, at least partly due to hypoxia-dependent stimulation of the formation and function of bone-resorbing osteoclasts which establish metastatic cells in bone. This study aims to investigate potential mechanism(s) of oxygen delivery and in particular the possible use of oxygen-loaded nanobubbles in preventing bone metastasis via effects on osteoclasts. Lecithin-based nanobubbles preferentially interacted with phagocytic cells (monocytes, osteoclasts) via a combination of lipid transfer, clathrin-dependent endocytosis and phagocytosis. This interaction caused general suppression of osteoclast differentiation via inhibition of cell fusion. Additionally, repeat exposure to oxygen-loaded nanobubbles inhibited osteoclast formation to a greater extent than nitrogen-loaded nanobubbles. This gas-dependent effect was driven by differential effects on the fusion of mononuclear precursor cells to form pre-osteoclasts, partly due to elevated potentiation of RANKL-induced ROS by nitrogen-loaded nanobubbles. Our findings suggest that oxygen-loaded nanobubbles could represent a promising therapeutic strategy for cancer therapy; reducing osteoclast formation and therefore bone metastasis via preferential interaction with monocytes/macrophages within the tumour and bone microenvironment, in addition to known effects of directly improving tumour oxygenation.

Temporal dynamics of immune-stromal cell interactions in fracture healing

Bone fracture repair is a complex, multi-step process that involves communication between immune and stromal cells to coordinate the repair and regeneration of damaged tissue. In the US, 10% of all bone fractures do not heal properly without intervention, resulting in non-union. Complications from non-union fractures are physically and financially debilitating. We now appreciate the important role that immune cells play in tissue repair, and the necessity of the inflammatory response in initiating healing after skeletal trauma. The temporal dynamics of immune and stromal cell populations have been well characterized across the stages of fracture healing. Recent studies have begun to untangle the intricate mechanisms driving the immune response during normal or atypical, delayed healing. Various in vivo models of fracture healing, including genetic knockouts, as well as in vitro models of the fracture callus, have been implemented to enable experimental manipulation of the heterogeneous cellular environment. The goals of this review are to (1): summarize our current understanding of immune cell involvement in fracture healing (2); describe state-of-the art approaches to study inflammatory cells in fracture healing, including computational and in vitro models; and (3) identify gaps in our knowledge concerning immune-stromal crosstalk during bone healing.

Investigating the Effects of Sex Hormones on Macrophage Polarization

Sex differences in the development and progression of cardiovascular disease are well established, but the effects of sex hormones on macrophage polarization and pro-atherogenic functions are not well described. We hypothesize that sex hormones directly modulate macrophage polarization, and thereby regulate the progression of atherosclerosis. Bone marrow-derived monocytes from adult male and female C57BL/6 mice were differentiated into macrophages using macrophage colony-stimulating factor (20 ng/mL) and pre-treated with either 17β-estradiol (100 nM), testosterone (100 nM), or a vehicle control for 24 h. Macrophages were polarized into pro- or anti-inflammatory phenotypes and the effects of sex hormone supplementation on the gene expression of macrophage phenotypic markers were assessed using RT-qPCR. Inflammatory markers, including IL-1β, were quantified using an addressable laser bead immunoassay. A transwell migration assay was used to determine changes in macrophage migration. Sex differences were observed in macrophage polarization, inflammatory responses, and migration. Pre-treatment with 17β-estradiol significantly impaired the gene expression of inflammatory markers and the production of IL-1β in inflammatory macrophages. In anti-inflammatory macrophages, 17β-estradiol significantly upregulated the expression of anti-inflammatory markers and enhanced migration. Pre-treatment with testosterone enhanced anti-inflammatory mRNA expression and impaired the production of IL-1β. Our observations suggest a protective role of 17β-estradiol in atherogenesis that may contribute to the sexual dimorphisms in cardiovascular disease observed in human patients.

The Role of TAM Receptors in Bone

The TAM (TYRO3, MERTK, and AXL) family of receptor tyrosine kinases are pleiotropic regulators of adult tissue homeostasis maintaining organ integrity and self-renewal. Disruption of their homeostatic balance fosters pathological conditions like autoinflammatory or degenerative diseases including rheumatoid arthritis, lupus erythematodes, or liver fibrosis. Moreover, TAM receptors exhibit prominent cell-transforming properties, promoting tumor progression, metastasis, and therapy resistance in various cancer entities. Emerging evidence shows that TAM receptors are involved in bone homeostasis by regulating osteoblastic bone formation and osteoclastic bone resorption. Therefore, TAM receptors emerge as new key players of the regulatory cytokine network of osteoblasts and osteoclasts and represent accessible targets for pharmacologic therapy for a broad set of different bone diseases, including primary and metastatic bone tumors, rheumatoid arthritis, or osteoporosis.

Immune homeostasis modulation by hydrogel-guided delivery systems: a tool for accelerated bone regeneration

Immune homeostasis is delicately mediated by the dynamic balance between effector immune cells and regulatory immune cells. Local deviations from immune homeostasis in the microenvironment of bone fractures, caused by an increased ratio of effector to regulatory cues, can lead to excessive inflammatory conditions and hinder bone regeneration. Therefore, achieving effective and localized immunomodulation of bone fractures is crucial for successful bone regeneration. Recent research has focused on developing localized and specific immunomodulatory strategies using local hydrogel-based delivery systems. In this review, we aim to emphasize the significant role of immune homeostasis in bone regeneration, explore local hydrogel-based delivery systems, discuss emerging trends in immunomodulation for enhancing bone regeneration, and address the limitations of current delivery strategies along with the challenges of clinical translation.

Macrophage Polarization and the Regulation of Bone Immunity in Bone Homeostasis

Bone homeostasis is a dynamic equilibrium state of bone formation and absorption, ensuring skeletal development and repair. Bone immunity encompasses all aspects of the intersection between the skeletal and immune systems, including various signaling pathways, cytokines, and the crosstalk between immune cells and bone cells under both homeostatic and pathological conditions. Therefore, as key cell types in bone immunity, macrophages can polarize into classical pro-inflammatory M1 macrophages and alternative anti-inflammatory M2 macrophages under the influence of the body environment, participating in the regulation of bone metabolism and playing various roles in bone homeostasis. M1 macrophages can not only act as precursors of osteoclasts (OCs), differentiate into mature OCs, but also secrete pro-inflammatory cytokines to promote bone resorption; while M2 macrophages secrete osteogenic factors, stimulating the differentiation and mineralization of osteoblast precursors and mesenchymal stem cells (MSCs), and subsequently increase bone formation. Once the polarization of macrophages is imbalanced, the resulting immune dysregulation will cause inflammatory stimulation, and release a large amount of inflammatory factors affecting bone metabolism, leading to pathological conditions such as osteoporosis (OP), rheumatoid arthritis (RA), and steroid-induced femoral head necrosis (SANFH). In this review, we introduce the signaling pathways and related factors of macrophage polarization, as well as their relationships with immune factors, OB, OC, and MSC. We also discuss the roles of macrophage polarization and bone immunity in various diseases of bone homeostasis imbalance, as well as the factors regulating them, which may help to develop new methods for treating bone metabolic disorders.

Targeting different phenotypes of macrophages: A potential strategy for natural products to treat inflammatory bone and joint diseases

BACKGROUND

Macrophages, a key class of immune cells, have a dual role in inflammatory responses, switching between anti-inflammatory M2 and pro-inflammatory M1 subtypes depending on the specific environment. Greater numbers of M1 macrophages correlate with increased production of inflammatory chemicals, decreased osteogenic potential, and eventually bone and joint disorders. Therefore, reversing M1 macrophages polarization is advantageous for lowering inflammatory factors. To better treat inflammatory bone disorders in the future, it may be helpful to gain insight into the specific mechanisms and natural products that modulate macrophage polarization.

OBJECTIVE

This review examines the impact of programmed cell death and different cells in the bone microenvironment on macrophage polarization, as well as the effects of natural products on the various phenotypes of macrophages, in order to suggest some possibilities for the treatment of inflammatory osteoarthritic disorders.

METHODS

Using 'macrophage polarization,' 'M1 macrophage' 'M2 macrophage' 'osteoporosis,' 'osteonecrosis of femoral head,' 'osteolysis,' 'gouty arthritis,' 'collagen-induced arthritis,' 'freund's adjuvant-induced arthritis,' 'adjuvant arthritis,' and 'rheumatoid arthritis' as search terms, the relevant literature was searched using the PubMed, the Cochrane Library and Web of Science databases.

RESULTS

Targeting macrophages through different signaling pathways has become a key mechanism for the treatment of inflammatory bone and joint diseases, including HIF-1α, NF-κB, AKT/mTOR, JAK1/2-STAT1, NF-κB, JNK, ERK, p-38α/β, p38/MAPK, PI3K/AKT, AMPK, AMPK/Sirt1, STAT TLR4/NF-κB, TLR4/NLRP3, NAMPT pathway, as well as the programmed cell death autophagy, pyroptosis and ERS.

CONCLUSION

As a result of a search of databases, we have summarized the available experimental and clinical evidence supporting herbal products as potential treatment agents for inflammatory osteoarthropathy. In this paper, we outline the various modulatory effects of natural substances targeting macrophages in various diseases, which may provide insight into drug options and directions for future clinical trials. In spite of this, more mechanistic studies on natural substances, as well as pharmacological, toxicological, and clinical studies are required.

Identification of key immune genes of osteoporosis based on bioinformatics and machine learning

Introduction

Immunity is involved in a variety of bone metabolic processes, especially osteoporosis. The aim of this study is to explore new bone immune-related markers by bioinformatics method and evaluate their ability to predict osteoporosis.

Methods

The mRNA expression profiles were obtained from GSE7158 in Gene expression Omnibus (GEO), and immune-related genes were obtained from ImmPort database (https://www.immport.org/shared/). immune genes related to bone mineral density(BMD) were screened out for differential analysis. protein-protein interaction (PPIs) networks were used to analyze the interrelationships between different immune-related genes (DIRGs). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of DIRGs function were performed. A least absolute shrinkage and selection operation (LASSO) regression model and multiple Support Vector Machine-Recursive Feature Elimination (mSVM-RFE) model were constructed to identify the candidate genes for osteoporosis prediction The receiver operator characteristic (ROC) curves were used to validate the performances of predictive models and candidate genes in GEO database (GSE7158,GSE13850).Through the RT - qPCR verify the key genes differentially expressed in peripheral blood mononuclear cells Finally, we constructed a nomogram model for predicting osteoporosis based on five immune-related genes. CIBERSORT algorithm was used to calculate the relative proportion of 22 immune cells.

Results

A total of 1158 DEGs and 66 DIRGs were identified between high-BMD and low-BMD women. These DIRGs were mainly enriched in cytokine-mediated signaling pathway, positive regulation of response to external stimulus and the cellular components of genes are mostly localized to external side of plasma membrane. And the KEGG enrichment analysis were mainly involved in Cytokine-cytokine receptor interaction, PI3K-Akt signaling pathway, Neuroactive ligand-receptor interaction,Natural killer cell mediated cytotoxicity. Then five key genes (CCR5, IAPP, IFNA4, IGHV3-73 and PTGER1) were identified and used as features to construct a predictive prognostic model for osteoporosis using the GSE7158 dataset.

Conclusion

Immunity plays an important role in the development of osteoporosis.CCR5, IAPP, IFNA4, IGHV3-73 and PTGER1were play an important role in the occurrences and diagnosis of OP.

Role of Mast-Cell-Derived RANKL in Ovariectomy-Induced Bone Loss in Mice

Mast cells may contribute to osteoporosis development, because patients with age-related or post-menopausal osteoporosis exhibit more mast cells in the bone marrow, and mastocytosis patients frequently suffer from osteopenia. We previously showed that mast cells crucially regulated osteoclastogenesis and bone loss in ovariectomized, estrogen-depleted mice in a preclinical model for post-menopausal osteoporosis and found that granular mast cell mediators were responsible for these estrogen-dependent effects. However, the role of the key regulator of osteoclastogenesis, namely, receptor activator of NFκB ligand (RANKL), which is secreted by mast cells, in osteoporosis development has, to date, not been defined. Here, we investigated whether mast-cell-derived RANKL participates in ovariectomy (OVX)-induced bone loss by using female mice with a conditional Rankl deletion. We found that this deletion in mast cells did not influence physiological bone turnover and failed to protect against OVX-induced bone resorption in vivo, although we demonstrated that RANKL secretion was significantly reduced in estrogen-treated mast cell cultures. Furthermore, Rankl deletion in mast cells did not influence the immune phenotype in non-ovariectomized or ovariectomized mice. Therefore, other osteoclastogenic factors released by mast cells might be responsible for the onset of OVX-induced bone loss.

Impact of T helper cells on bone metabolism in systemic lupus erythematosus

Systemic lupus erythematosus (SLE), an autoimmune disease affecting multiple organs and tissues, is often complicated by musculoskeletal diseases. T helper cells (Th) play an important role in mediating lupus. With the rise of osteoimmunology, more studies have shown shared molecules and interactions between the immune system and bones. Th cells are vital in the regulation of bone metabolism by directly or indirectly regulating bone health by secreting various cytokines. Therefore, by describing the regulation of Th cells (including Th1, Th2, Th9, Th17, Th22, regulatory T cells (Treg), and follicular T helper cells (Tfh) in bone metabolism in SLE, this paper offers certain theoretical support for abnormal bone metabolism in SLE and provides new prospects for future drug development.

Autoimmunity and Carcinogenesis: Their Relationship under the Umbrella of Autophagy

The immune system and autophagy share a functional relationship. Both innate and adaptive immune responses involve autophagy and, depending on the disease's origin and pathophysiology, it may have a detrimental or positive role on autoimmune disorders. As a "double-edged sword" in tumors, autophagy can either facilitate or impede tumor growth. The autophagy regulatory network that influences tumor progression and treatment resistance is dependent on cell and tissue types and tumor stages. The connection between autoimmunity and carcinogenesis has not been sufficiently explored in past studies. As a crucial mechanism between the two phenomena, autophagy may play a substantial role, though the specifics remain unclear. Several autophagy modifiers have demonstrated beneficial effects in models of autoimmune disease, emphasizing their therapeutic potential as treatments for autoimmune disorders. The function of autophagy in the tumor microenvironment and immune cells is the subject of intensive study. The objective of this review is to investigate the role of autophagy in the simultaneous genesis of autoimmunity and malignancy, shedding light on both sides of the issue. We believe our work will assist in the organization of current understanding in the field and promote additional research on this urgent and crucial topic.

Oxidative Stress and Inflammation in Osteoporosis: Molecular Mechanisms Involved and the Relationship with microRNAs

Osteoporosis is characterized by the alteration of bone homeostasis due to an imbalance between osteoclastic bone resorption and osteoblastic bone formation. Estrogen deficiency causes bone loss and postmenopausal osteoporosis, the pathogenesis of which also involves oxidative stress, inflammatory processes, and the dysregulation of the expression of microRNAs (miRNAs) that control gene expression at post-transcriptional levels. Oxidative stress, due to an increase in reactive oxygen species (ROS), proinflammatory mediators and altered levels of miRNAs enhance osteoclastogenesis and reduce osteoblastogenesis through mechanisms involving the activation of MAPK and transcription factors. The present review summarizes the principal molecular mechanisms involved in the role of ROS and proinflammatory cytokines on osteoporosis. Moreover, it highlights the interplay among altered miRNA levels, oxidative stress, and an inflammatory state. In fact, ROS, by activating the transcriptional factors, can affect miRNA expression, and miRNAs can regulate ROS production and inflammatory processes. Therefore, the present review should help in identifying targets for the development of new therapeutic approaches to osteoporotic treatment and improve the quality of life of patients.

Nanowhiskers Orchestrate Bone Formation and Bone Defect Repair by Modulating Immune Cell Behavior

Immunomodulatory biomaterials have emerged as promising treatment agents for bone defects. However, it is unclear how such biomaterials control immune cell behaviors to facilitate large-segment bone defect repair. Herein, we fabricated biphasic calcium phosphate ceramics with nanowhisker structures to explore the immunoregulation features and influence on large-segment bone defect repair. We found that the nanowhisker structures markedly facilitated large-segment bone defect repair by promoting bone regeneration and scaffold resorption. Our in vitro experiment and transcriptomic analysis showed that mechanical stress derived from nanowhisker structures may activate the transcription of Egr-1 to induce early switch of macrophage phenotype to M2, which could not only facilitate osteogenic differentiation of BMSCs but also enhance the expression of osteoclast differentiation-regulating genes of M2 macrophage. In vivo study showed that the nanowhisker structures relieved local inflammatory responses by inducing early switch of macrophage phenotype from M1 to M2, which resulted in accelerated osteoclastogenesis for biomaterial resorption and osteogenesis for ectopic bone formation. Hence, we presume that nanowhisker structures may orchestrate bone formation and material resorption coupling to facilitate large-segment bone defect repair by controlling the switch of macrophage phenotype. This study provides new insight into the designing of immunomodulatory tissue engineering biomaterials for treating large-segment bone defects.

Mechanisms by which kidney-tonifying Chinese herbs inhibit osteoclastogenesis: Emphasis on immune cells

The immune system plays a crucial role in regulating osteoclast formation and function and has significance for the occurrence and development of immune-mediated bone diseases. Kidney-tonifying Chinese herbs, based on the theory of traditional Chinese medicine (TCM) to unify the kidney and strengthen the bone, have been widely used in the prevention and treatment of bone diseases. The common botanical drugs are tonifying kidney-yang and nourishing kidney-yin herbs, which are divided into two parts: one is the compound prescription of TCM, and the other is the single preparation of TCM and its active ingredients. These botanical drugs regulate osteoclastogenesis directly and indirectly by immune cells, however, we have limited information on the differences between the two botanical drugs in osteoimmunology. In this review, the mechanism by which kidney-tonifying Chinese herbs inhibiting osteoclastogenesis was investigated, emphasizing the immune response. The differences in the mechanism of action between tonifying kidney-yang herbs and nourishing kidney-yin herbs were analysed, and the therapeutic value for immune-mediated bone diseases was evaluated.

Mesenchymal stem cell-derived extracellular vesicles, osteoimmunology and orthopedic diseases

Mesenchymal stem cells (MSCs) play an important role in tissue healing and regenerative medicine due to their self-renewal and multi-directional differentiation properties. MSCs exert their therapeutic effects mainly via the paracrine pathway, which involves the secretion of extracellular vesicles (EVs). EVs have a high drug loading capacity and can transport various molecules, such as proteins, nucleic acids, and lipids, that can modify the course of diverse diseases. Due to their ability to maintain the therapeutic effects of their parent cells, MSC-derived EVs have emerged as a promising, safe cell-free treatment approach for tissue regeneration. With advances in inflammation research and emergence of the field of osteoimmunology, evidence has accumulated pointing to the role of inflammatory and osteoimmunological processes in the occurrence and progression of orthopedic diseases. Several studies have shown that MSC-derived EVs participate in bone regeneration and the pathophysiology of orthopedic diseases by regulating the inflammatory environment, enhancing angiogenesis, and promoting the differentiation and proliferation of osteoblasts and osteoclasts. In this review, we summarize recent advances in the application and functions of MSC-derived EVs as potential therapies against orthopedic diseases, including osteoarthritis, intervertebral disc degeneration, osteoporosis and osteonecrosis.

Moxibustion as adjuvant therapy for preventing bone loss in postmenopausal women: protocol for a randomised controlled trial

INTRODUCTION

Postmenopausal osteoporosis, caused by ageing and oestrogen deficiency, seriously threatens women's physical and mental health. Postmenopausal osteopenia is the transition from healthy bone to osteoporosis, and it may be the key period for preventing bone loss. Moxibustion, a physical therapy of Traditional Chinese Medicine, has potential benefits for osteoporosis treatment and prevention, but it has not been adequately studied. This study aims to explore the clinical effects and safety of moxibustion in delaying bone loss in postmenopausal women.

METHODS AND ANALYSIS

In this parallel-design, randomised, patient-blind and assessor-blind, controlled clinical study, 150 women with osteopenia at low fracture risk will be randomly assigned to a moxibustion treatment (MT) group or a placebo-moxibustion control (PMC) group in a 1:1 ratio. In addition to the fundamental measures (vitamin D3 and calcium) as recommended by the guidelines, participants of the two groups will receive MT or PMC treatment for 42 sessions over 12 months. The primary outcome will be the bone mineral density (BMD) of the lumbar spine at the end of the 12-month treatment, and secondary outcomes will be the BMD of the femoral neck and total hip, T-scores, bone turnover markers, serum calcium levels, serum magnesium levels, serum phosphorus levels, serum parathyroid hormone levels and 25-hydroxyvitamin D levels, intensity of bone pain, quality of life, incidence of osteoporosis and fractures, usage of emergency drugs or surgery, participant self-evaluation of therapeutic effects and the rate of adverse events. All statistical analyses will be performed based on the intention-to-treat and per-protocol principle.

ETHICS AND DISSEMINATION

Ethics approval has been obtained from the Ethics Committee on Biomedical Research, West China Hospital of Sichuan University (permission number: 2021-1243). The results are expected to be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ChiCTR2100053953.

Effects of whole-body vibration at different periods on lumbar vertebrae in female rats

The current study aimed to investigate the effects of whole-body vibration (WBV) before and after ovariectomy on lumbar vertebrae, and to observe whether the positive effects of WBV before and after ovariectomy on lumbar vertebrae in rats could be maintained after vibration stopped. Three-month-old female rats were divided into four groups (n = 45/group): control (CON), ovariectomy (OVA), WBV before ovariectomy (WBV-BO), and WBV after ovariectomy (WBV-AO) groups. For 1-8 weeks, WBV-BO group was subjected to vertical WBV. At the 9th week, the rats in WBV-BO, WBV-AO, and OVA groups were ovariectomized. During 11-18 weeks, WBV-AO group was subjected to vibration. For 19-26 weeks, no intervention was done for rats. The lumbar vertebrae were examined by Micro-CT, compressive test, creep test, and microindentation test. At the 8th week, the displacement of the L1-L2 annulus fibrosus in WBV-BO group was 18% smaller compared with CON group (p<0.05). At the 18th week, the elastic modulus of the L5 vertebral body in WBV-BO and WBV-AO groups was 53% and 57% higher than that in CON group, respectively (p<0.05); the displacement of the L1-L2 annulus fibrosus in WBV-BO group was 25% smaller than those in the other groups (p<0.05). At the 26th week, there was no significant difference in the displacement of the L1-L2 annulus fibrosus between WBV-BO group and other groups (p>0.05); the elastic modulus of the L5 vertebral body had no significant difference between WBV-AO group and CON group (p>0.05). Our results demonstrated that WBV before ovariectomy effectively prevented disc degeneration with significant effects up to 8 weeks after ovariectomy. The vertebral mechanical properties could be significantly improved by WBV after ovariectomy, but the residual effect did not maintain after WBV stopped.

Macrophages and glial cells: Innate immune drivers of inflammatory arthritic pain perception from peripheral joints to the central nervous system

Millions of people suffer from arthritis worldwide, consistently struggling with daily activities due to debilitating pain evoked by this disease. Perhaps the most intensively investigated type of inflammatory arthritis is rheumatoid arthritis (RA), where, despite considerable advances in research and clinical management, gaps regarding the neuroimmune interactions that guide inflammation and chronic pain in this disease remain to be clarified. The pain and inflammation associated with arthritis are not isolated to the joints, and inflammatory mechanisms induced by different immune and glial cells in other tissues may affect the development of chronic pain that results from the disease. This review aims to provide an overview of the state-of-the-art research on the roles that innate immune, and glial cells play in the onset and maintenance of arthritis-associated pain, reviewing nociceptive pathways from the joint through the dorsal root ganglion, spinal circuits, and different structures in the brain. We will focus on the cellular mechanisms related to neuroinflammation and pain, and treatments targeting these mechanisms from the periphery and the CNS. A comprehensive understanding of the role these cells play in peripheral inflammation and initiation of pain and the central pathways in the spinal cord and brain will facilitate identifying new targets and pathways to aide in developing therapeutic strategies to treat joint pain associated with RA.

Osteoporosis treatment by mesenchymal stromal/stem cells and their exosomes: Emphasis on signaling pathways and mechanisms

Osteoporosis is the loss of bone density, which is one of the main problems in developed and developing countries and is more common in the elderly. Because this disease is often not diagnosed until a bone fracture, it can become a life-threatening disease and cause hospitalization. With the increase of older people in a population, this disease's personal and social costs increase year by year and affect different communities. Most current treatments focus on pain relief and usually do not lead to bone tissue recovery and regeneration. But today, the use of stem cell therapy is recommended to treat and improve this disease recovery, which helps restore bone tissue by improving the imbalance in the osteoblast-osteoclast axis. Due to mesenchymal stromal/stem cells (MSCs) characteristics and their exosomes, these cells and vesicles are excellent sources for treating and preventing the progression and improvement of osteoporosis. Due to the ability of MSCs to differentiate into different cells and migrate to the site of injury, these cells are used in tissue regenerative medicine. Also, due to their contents, the exosomes of these cells help regenerate and treat various tissue injuries by affecting the injury site's cells. In this article, we attempted to review new studies in which MSCs and their exosomes were used to treat osteoporosis.

Sex differences in the therapeutic effect of unaltered versus NFκB sensing IL-4 over-expressing mesenchymal stromal cells in a murine model of chronic inflammatory bone loss

Wear particles from joint arthroplasties induce chronic inflammation associated with prolonged upregulation of nuclear factor kappa-B (NF-κB) signaling in macrophages and osteoclasts, which leads to osteolysis and implant loosening. Mesenchymal stromal cell (MSC)-based therapy showed great potential for immunomodulation and mitigation of osteolysis in vivo, especially in the chronic phase of inflammation. We previously generated genetically modified MSCs that secrete the anti-inflammatory cytokine interleukin 4 (IL-4) in response to NF-κB activation (NFκB-IL-4 MSCs). However, whether the impact of sexual difference in the internal environment can alter the therapeutic effects of IL-4 over-secreting MSCs that simultaneously mitigate prolonged inflammation and enhance bone formation remains unknown. This study investigated the therapeutic effects of unaltered MSCs versus NFκB-IL-4 MSCs in mitigating chronic inflammation and enhancing bone formation in male and female mice. The murine model was established by continuous infusion of polyethylene particles contaminated with lipopolysaccharide (cPE) into the medullary cavity of the distal femur for 6 weeks to induce chronic inflammation. Unaltered MSCs or NFκB-IL-4 MSCs were infused into the femoral intramedullary cavity in sex-matched groups beginning 3 weeks after primary surgery. Femurs were harvested at 6 weeks, and bone marrow density was measured with micro-computational tomography. Numbers of osteoclast-like cells, osteoblasts, and macrophages were evaluated with histochemical and immunofluorescence staining. cPE infusion resulted in severe bone loss at the surgery site, increased tartrate-resistant acid phosphatase positive osteoclasts and M1 pro-inflammatory macrophages, and decreased alkaline phosphatase expression. MSC-based therapy effectively decreased local bone loss and polarized M1 macrophages into an M2 anti-inflammatory phenotype. In females, unaltered MSCs demonstrated a larger impact in enhancing the osteogenesis, but they demonstrated similar anti-inflammatory effects compared to NFκB-IL-4 MSCs. These results demonstrated that local inflammatory bone loss can be effectively modulated via MSC-based treatments in a sexually dimorphic manner, which could be an efficacious therapeutic strategy for treatment of periprosthetic osteolysis in both genders.

Targeting chronic inflammation as a potential adjuvant therapy for osteoporosis

Systemic, chronic, low-grade inflammation (SCLGI) underlies the pathogenesis of various widespread diseases. It is often associated with bone loss, thus connecting chronic inflammation to the pathogenesis of osteoporosis. In postmenopausal women, osteoporosis is accompanied by SCLGI development, likely owing to estrogen deficiency. We propose that SCGLI persistence in osteoporosis results from failed inflammation resolution, which is mainly mediated by specialized, pro-resolving mediators (SPMs). In corroboration, SPMs demonstrate encouraging therapeutic effects in various preclinical models of inflammatory disorders, including bone pathology. Since numerous data implicate gut dysbiosis in osteoporosis-associated chronic inflammation, restoring balanced microbiota by supplementing probiotics and prebiotics could contribute to the efficient resolution of SCGLI. In the present review, we provide evidence for this hypothesis and argue that efficient SCGLI resolution may serve as a novel approach for treating osteoporosis, complementary to traditional anti-osteoporotic medications.

Harnessing redox signaling to overcome therapeutic-resistant cancer dormancy

Dormancy occurs when cells preserve viability but stop proliferating, which is considered an important cause of tumor relapse, which may occur many years after clinical remission. Since the life cycle of dormant cancer cells is affected by both intracellular and extracellular factors, gene mutation or epigenetic regulation of tumor cells may not fully explain the mechanisms involved. Recent studies have indicated that redox signaling regulates the formation, maintenance, and reactivation of dormant cancer cells by modulating intracellular signaling pathways and the extracellular environment, which provides a molecular explanation for the life cycle of dormant tumor cells. Indeed, redox signaling regulates the onset of dormancy by balancing the intrinsic pathways, the extrinsic environment, and the response to therapy. In addition, redox signaling sustains dormancy by managing stress homeostasis, maintaining stemness and immunogenic equilibrium. However, studies on dormancy reactivation are still limited, partly explained by redox-mediated activation of lipid metabolism and the transition from the tumor microenvironment to inflammation. Encouragingly, several drug combination strategies based on redox biology are currently under clinical evaluation. Continuing to gain an in-depth understanding of redox regulation and develop specific methods targeting redox modification holds the promise to accelerate the development of strategies to treat dormant tumors and benefit cancer patients.