The relationship between osteoclastogenic and anti-osteoclastogenic pro-inflammatory cytokines differs in human osteoporotic and osteoarthritic bone tissues

Causal relationship between circulating levels of cytokines and bone mineral density: A mendelian randomization study

BACKGROUND

Numerous studies have shown that various cytokines are important factors affecting bone mineral density (BMD), but the causality between the two remains uncertain.

METHODS

Genetic variants associated with 41 circulating cytokines from a genome-wide association study (GWAS) in 8,293 Finns were used as instrumental variables (IVs) for a two-sample Mendelian randomization (MR) analysis. Inverse variance weighting (IVW) was employed as the primary method to investigate whether the 41 cytokines were causally associated with BMD at five different sites [total body bone mineral density (TB-BMD), heel bone mineral density (HE-BMD), forearm bone mineral density (FA-BMD), femoral neck bone mineral density (FN-BMD), and lumbar spine bone mineral density (LS-BMD)]. Weighted median and MR-Egger were chosen to further confirm the robustness of the results. We performed MR pleiotropy residual sum and outlier test (MR-PRESSO), MR-Egger regression, and Cochran's Q test to detect pleiotropy and sensitivity testing.

RESULTS

After Bonferroni correction, two circulating cytokines had a strong causality with BMD at corresponding sites. Genetically predicted circulating hepatocyte growth factor (HGF) levels and HE-BMD were negatively correlated [β (95 % CI) -0.035(-0.055, -0.016), P=0.00038]. Circulating macrophage inflammatory protein-1α (MIP-1α) levels and TB-BMD were negatively correlated [β(95 %CI): -0.058(-0.092, -0.024), P=0.00074]. Weighted median and MR-Egger results were in line with the IVW results. We also found suggestive causal relationship (IVW P<0.05) between seven circulating cytokines and BMD at corresponding sites. No significant pleiotropy or heterogeneity was observed in our study.

CONCLUSION

Our MR analyses indicated a causal effect between two circulating cytokines and BMD at corresponding sites (HGF and HE-BMD, MIP-1α and TB-BMD), along with suggestive evidence of a potential causality between seven cytokines and BMD at the corresponding sites. These findings would provide insights into the prevention and treatment of osteoporosis, especially immunoporosis.

Evaluation of Functional Components of Lactobacillus plantarum AR495 on Ovariectomy-Induced Osteoporosis in Mice And RAW264.7 Cells

Osteoporosis is a disease characterized by abnormal bone metabolism, where bone resorption outpaces bone formation. In this study, we investigated the key functional components of Lactobacillus plantarum AR495 in mitigating ovariectomy (OVX)-induced osteoporosis in mice. The results indicated that both Lactobacillus plantarum AR495 and its fermentation broth significantly reduced urinary calcium and deoxypyridinoline (DPD) levels in the mice. These interventions inhibited bone resorption and improved trabecular bone architecture by modulating the nuclear factor κB (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) signaling pathway. Additionally, the L. plantarum AR495 and fermentation broth groups inhibited the RANKL/TRAF-6 and TLR4/MYD88 pathways, leading to enhanced bone metabolism, improved intestinal barrier function, and reduced intestinal inflammation. In vitro experiments revealed that AR495 fermentation supernatant fractions larger than 100 kDa and those between 50-100 kDa significantly decreased the activity of the osteoclast marker TRAP, regulated the expression of the TLR4/MYD88 pathway, and inhibited osteoclast formation, thereby alleviating the OVX-induced osteoporosis phenotype. These findings suggest that these components may be primary functional elements of L. plantarum AR495 in the treatment of osteoporosis.

Exploring the osteogenic potential of chitosan-quercetin bio-conjugate: In vitro and in vivo investigations in osteoporosis models

Anti-osteoporotic agents are clinically employed to improve bone health and prevent osteoporotic fractures. In the current study, we investigated the potential of chitosan-quercetin bio-conjugate as an anti-osteoporotic agent. The conjugate was prepared and characterized by FTIR and found notable interactions between chitosan and quercetin. Treating mouse MSCs with the bioconjugate in osteogenic conditions for a week led to elevated expression of differentiation markers Runx2, ALP, and Col-I, as determined by real-time PCR analysis. Evaluation at the cellular level using alizarin red staining demonstrated enhanced calcium deposition in MSCs following treatment with the bioconjugate. Likewise, ELISA analysis showed significantly elevated levels of secretory osteocalcin and osteonectin in groups treated with the conjugate. To broaden our comprehension, we utilized a zebrafish-based in vivo model of dexamethasone-induced osteoporosis to investigate bone regeneration. Toxicity profiling with zebrafish larvae confirmed the bio-conjugate's compatibility at a concentration of 25 μg/ml, underscoring the significance of finding the right dosage. Furthermore, in zebrafish models of osteoporosis, the bio-conjugate demonstrated significant potential for bone regeneration, as indicated by improved bone calcification, callus formation, and overall bone healing in a tail fin fracture model. Additionally, the study revealed that the bio-conjugate inhibited osteoclastic activity, leading to reduced TRAP activity and hydroxyproline release, suggesting its effectiveness in mitigating bone resorption. In conclusion, our research provides compelling evidence for the osteogenic capabilities of the chitosan-quercetin bio-conjugate, highlighting its promising applications in regenerative medicine and the treatment of conditions like osteoporosis.

Bone Marrow Adipose Tissue as a Critical Regulator of Postmenopausal Osteoporosis - A Concise Review

Postmenopausal osteoporosis (PMOP) is a major health problem affecting millions of women worldwide. PMOP patients are often accompanied by abnormal accumulation of bone marrow adipose tissue (BMAT). BMAT is a critical regulator of bone homeostasis, and an increasing BMAT volume is negatively associated with bone mass reduction or fracture. BMAT regulates bone metabolism via adipokines, cytokines and the immune system, but the specific mechanisms are largely unknown. This review emphasizes the impact of estrogen deficiency on bone homeostasis and BMAT expansion, and the mechanism by which BMAT regulates PMOP, providing a promising strategy for targeting BMAT in preventing and treating PMOP.

Analysis and validation of biomarkers of immune cell-related genes in postmenopausal osteoporosis: An observational study

Postmenopausal osteoporosis (PMOP) is a common metabolic inflammatory disease. In conditions of estrogen deficiency, chronic activation of the immune system leads to a hypo-inflammatory phenotype and alterations in its cytokine and immune cell profile, although immune cells play an important role in the pathology of osteoporosis, studies on this have been rare. Therefore, it is important to investigate the role of immune cell-related genes in PMOP. PMOP-related datasets were downloaded from the Gene Expression Omnibus database. Immune cells scores between high bone mineral density (BMD) and low BMD samples were assessed based on the single sample gene set enrichment analysis method. Subsequently, weighted gene co-expression network analysis was performed to identify modules highly associated with immune cells and obtain module genes. Differential analysis between high BMD and low BMD was also performed to obtain differentially expressed genes. Module genes are intersected with differentially expressed genes to obtain candidate genes, and functional enrichment analysis was performed. Machine learning methods were used to filter out the signature genes. The receiver operating characteristic (ROC) curves of the signature genes and the nomogram were plotted to determine whether the signature genes can be used as a molecular marker. Gene set enrichment analysis was also performed to explore the potential mechanism of the signature genes. Finally, RNA expression of signature genes was validated in blood samples from PMOP patients and normal control by real-time quantitative polymerase chain reaction. Our study of PMOP patients identified differences in immune cells (activated dendritic cell, CD56 bright natural killer cell, Central memory CD4 T cell, Effector memory CD4 T cell, Mast cell, Natural killer T cell, T follicular helper cell, Type 1 T-helper cell, and Type 17 T-helper cell) between high and low BMD patients. We obtained a total of 73 candidate genes based on modular genes and differential genes, and obtained 5 signature genes by least absolute shrinkage and selection operator and random forest model screening. ROC, principal component analysis, and t-distributed stochastic neighbor embedding down scaling analysis revealed that the 5 signature genes had good discriminatory ability between high and low BMD samples. A logistic regression model was constructed based on 5 signature genes, and both ROC and column line plots indicated that the model accuracy and applicability were good. Five signature genes were found to be associated with proteasome, mitochondria, and lysosome by gene set enrichment analysis. The real-time quantitative polymerase chain reaction results showed that the expression of the signature genes was significantly different between the 2 groups. HIST1H2AG, PYGM, NCKAP1, POMP, and LYPLA1 might play key roles in PMOP and be served as the biomarkers of PMOP.

Bisphosphonate-incorporated coatings for orthopedic implants functionalization

Bisphosphonates (BPs), the stable analogs of pyrophosphate, are well-known inhibitors of osteoclastogenesis to prevent osteoporotic bone loss and improve implant osseointegration in patients suffering from osteoporosis. Compared to systemic administration, BPs-incorporated coatings enable the direct delivery of BPs to the local area, which will precisely enhance osseointegration and bone repair without the systemic side effects. However, an elaborate and comprehensive review of BP coatings of implants is lacking. Herein, the cellular level (e.g., osteoclasts, osteocytes, osteoblasts, osteoclast precursors, and bone mesenchymal stem cells) and molecular biological regulatory mechanism of BPs in regulating bone homeostasis are overviewed systematically. Moreover, the currently available methods (e.g., chemical reaction, porous carriers, and organic material films) of BP coatings construction are outlined and summarized in detail. As one of the key directions, the latest advances of BP-coated implants to enhance bone repair and osseointegration in basic experiments and clinical trials are presented and critically evaluated. Finally, the challenges and prospects of BP coatings are also purposed, and it will open a new chapter in clinical translation for BP-coated implants.

High systemic immune-inflammation index is relevant to osteoporosis among middle-aged and older people: A cross-sectional study

BACKGROUND

As one of novel inflammatory indexes proposed in recent years, systemic immune-inflammation index (SII) can comprehensively reflect the inflammatory and immune state of the body. This study aims to explore the relationship between SII and osteoporosis among middle-aged and older people.

MATERIALS AND METHODS

Our study includes 20,497 individuals from National Health and Nutrition Examination Survey (NHANES) 2005-2008, and target study population are confined to people aged 45 years and above. SII is calculated as platelet count × neutrophil count/lymphocyte count. Multivariate logistic regression analysis is used to explore the link between SII and osteoporosis, and receiver operating characteristics curve is used to screen optimal cut-off value of SII for indicating the occurrence of osteoporosis.

RESULTS

A total of 435 people with osteoporosis are screened among 4625 middle-aged and older people, and individuals in osteoporosis group have higher SII than those in nonosteoporosis group (p = .024). Logistic regression analysis indicates that with the enhancement of SII, prevalence of osteoporosis in each tertile category also increases (p < .001). This tendency is also not changed in univariate model (p < .001), as well as the adjustments for different parameters. Moreover, we also identify that SII of 530.09 is the optimal cut-off value for indicating the occurrence of osteoporosis among middle-aged and older people.

CONCLUSIONS

This present NHANES-based study noticed that higher SII is positively linked to osteoporosis among middle-aged and older people, and SII should not exceed 530.09 for them to obtain a potentially lower risk of osteoporosis.

Associations Between Inflammatory Mediators and Bone Outcomes in Postmenopausal Women: A Cross-Sectional Analysis of Baseline Data from the Prune Study

Purpose

Hypoestrogenism triggers increased production of inflammatory mediators, which contribute to bone loss during postmenopausal osteoporosis. This study aimed to investigate the association between circulating inflammatory markers and bone outcomes in postmenopausal women.

Materials and methods

We conducted a cross-sectional, secondary analysis of baseline data from participants who completed a 12-month randomized controlled trial, The Prune Study (NCT02822378), which included healthy postmenopausal women (n=183, 55-75 years old) with bone mineral density (BMD) T-score between 0.0 and -3.0 at any site. BMD was measured using dual-energy X-ray absorptiometry, and bone geometry and strength were measured using peripheral quantitative computed tomography. Blood was collected at baseline to measure (1) serum biomarkers of bone turnover, including procollagen type 1 N-terminal propeptide (P1NP) and C-terminal telopeptide and (2) inflammatory markers, including serum high-sensitivity C-reactive protein (hs-CRP) and plasma pro-inflammatory cytokines, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, IL-8, and monocyte chemoattractant protein (MCP)-1, using enzyme-linked immunosorbent assay. The associations between bone and inflammatory outcomes at baseline were analyzed using correlation and regression analyses.

Results

Serum hs-CRP negatively correlated with P1NP (r=-0.197, p=0.042). Plasma IL-1β, IL-6, IL-8, and TNF-α negatively correlated with trabecular bone score at the lumbar spine (all p<0.05). In normal-weight women, plasma IL-1β, IL-6, and IL-8 negatively correlated (p<0.05) with trabecular and cortical bone area, content, and density at various sites in the tibia and radius. Serum hs-CRP positively predicted lumbar spine BMD (β=0.078, p=0.028). Plasma IL-6 negatively predicted BMD at the total body (β=-0.131, p=0.027) and lumbar spine (β=-0.151, p=0.036), whereas plasma TNF-α negatively predicted total hip BMD (β=-0.114, p=0.028).

Conclusion

At baseline, inflammatory markers were inversely associated with various estimates of bone density, geometry, and strength in postmenopausal women. These findings suggest that inflammatory markers may be an important mediator for postmenopausal bone loss.

Mapping knowledge landscapes and emerging trends of the links between osteoarthritis and osteoporosis: A bibliometric analysis

Background

Osteoarthritis has the characteristics of degenerative changes in articular cartilage and secondary osteoporosis, and it is a common chronic irreversible joint disease. In addition to affecting articular cartilage, subchondral bone, joint capsule and synovial membrane also undergo pathological changes during the development of the disease. Multiple studies have revealed that patients with osteoarthritis were found to have a significantly increased risk of osteoporosis, which also contributes to the progression of osteoarthritis. However, in the current existing studies, we found that no scholars have used bibliometric analysis in the study of the relationship between osteoarthritis and osteoporosis. From the perspective of bibliometrics, this study summarizes in detail the degree of cooperation between countries, research institutions, authors, and related journals in the field of osteoarthritis and osteoporosis research and their respective influence. In this way, the evolution of knowledge structure, the change of research focus and the hot topics with research potential in the future can be further visualized and analyzed.

Methods

Search the Web of Science core collection in Science Citation Index Expanded for articles and reviews of research on osteoarthritis and osteoporosis from 1998 to 2021. Bibliometric tools such as VOSviewer, CiteSpace, were be frequently used in our study. They are mainly used to analyze collaborations between countries, research institutions, and publication authors. Meantime, co-citation analysis of journals, co-occurrence analysis of keywords and subject categories will also be reflected in the study.

Results

According to the search strategy, 1,078 publications were included during the period 1998-2021. And the number of annual publications on the relationship between osteoarthritis and osteoporosis is on the rise. The United States has achieved the most and contributed the most in this field and the Boston University was the most prolific institution. For the statistical analysis of published publications, Reginster JY had the highest number of publications, while Felson DT had the highest co-citation frequency. Respectively, Osteoarthritis And Cartilage was the most productive journal in this area of research. The keywords "inflammation," "expression," and "mesenchymal stem cells" may also be the development trend and research hotspot of the future research direction in this field.

Conclusions

In our study, the relationship between osteoarthritis and osteoporosis was analyzed by using literature measurement. These analysis results can lead researchers to learn more directly about the trend in this area and provide guidance for determining popular research directions.

Fecal microbiota transplantation ameliorates bone loss in mice with ovariectomy-induced osteoporosis via modulating gut microbiota and metabolic function

Background

Osteoporosis (OP) is a systemic metabolic bone disease characterized by decreased bone mass and destruction of bone microstructure, which tends to result in enhanced bone fragility and related fractures. The postmenopausal osteoporosis (PMOP) has a relatively high proportion, and numerous studies reveal that estrogen-deficiency is related to the imbalance of gut microbiota (GM), impaired intestinal mucosal barrier function and enhanced inflammatory reactivity. However, the underlying mechanisms remain unclear and the existing interventions are also scarce.

Methods

In this study, we established a mouse model induced by ovariectomy (OVX) and conducted fecal microbiota transplantation (FMT) by gavage every day for 8 weeks. Subsequently, the bone mass and microarchitecture of mice were evaluated by the micro computed tomography (Micro-CT). The intestinal permeability, pro-osteoclastogenic cytokines expression, osteogenic and osteoclastic activities were detected by the immunohistological analysis, histological examination, enzyme-linked immunosorbent assay (ELISA) and western blot analysis accordingly. Additionally, the composition and abundance of GM were assessed by 16S rRNA sequencing and the fecal short chain fatty acids (SCFAs) level was measured by metabolomics.

Results

Our results demonstrated that FMT inhibited the excessive osteoclastogenesis and prevented the OVX-induced bone loss. Specifically, compared with the OVX group, FMT enhanced the expressions of tight junction proteins (zonula occludens protein 1 (ZO-1) and Occludin) and suppressed the release of pro-osteoclastogenic cytokines (tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β)). Furthermore, FMT also optimized the composition and abundance of GM, and increased the fecal SCFAs level (mainly acetic acid and propionic acid).

Conclusions

Collectively, based on GM-bone axis, FMT prevented the OVX-induced bone loss by correcting the imbalance of GM, improving the SCFAs level, optimizing the intestinal permeability and suppressing the release of pro-osteoclastogenic cytokines, which may be an alternative option to serve as a promising candidate for the prevention and treatment of PMOP in the future.

The translational potential of this article

This study indicates the ingenious involvement of GM-bone axis in PMOP and the role of FMT in reshaping the status of GM and ameliorating the bone loss in OVX-induced mice. FMT might serve as a promising candidate for the prevention and treatment of PMOP in the future.

Gene Expression Profiling of Markers of Inflammation, Angiogenesis, Coagulation and Fibrinolysis in Patients with Coronary Artery Disease with Very High Lipoprotein(a) Levels Treated with PCSK9 Inhibitors

Besides lipids, inflammation, angiogenesis, coagulation and fibrinolysis play very important roles in coronary artery disease (CAD). We measured gene expression of the inflammatory markers interleukin (IL)-1β (IL1B) and interferon (IFN)-γ (IFNG), vascular endothelial growth factor-A (VEGF-A) (VEGFA), and coagulation and fibrinolysis markers tissue factor (TF) (F3) and plasminogen activator inhibitor-1 (PAI-1) (SERPINE) in healthy controls and CAD patients with high lipoprotein(a) (Lp(a)). The aim of our study was to identify, first, if there is a difference in these markers between controls and patients; secondly, if these markers are associated with lipids; and third, what the influence of proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors is on these markers. We included 124 subjects, 27 controls and 97 patients with CAD (30 in placebo and 67 in the PCSK9 group). Blood samples were collected for lipid and gene measurement. The results showed higher expression of IL1B (p < 0.0001), VEGFA (p < 0.0001), and F3 (p = 0.018) in controls in comparison with patients. Significant correlations were observed between IL1B and lipids. Treatment with PCSK9 inhibitors increased VEGFA (p < 0.0001) and F3 (p = 0.001), and decreased SERPINE (p = 0.043). The results of our study underpin the importance of IL-1β, VEGF-A and TF in CAD as well as the effect of PCSK9 treatment on these markers.

microRNA-25-3p suppresses osteogenic differentiation of BMSCs in patients with osteoporosis by targeting ITGB3

This study was conducted to investigate the impact of the microRNA (miR)-25-3p/ITGB3 axis on the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) from patients with osteoporosis (OP). BMSCs isolated from the bone marrow of healthy controls and OP patients were identified by flow cytometry, in which ITGB3 mRNA and miR-25-3p expression was detected by RT-qPCR and ITGB3, Runx2, OPN, ALP, and OSX protein expression by western blot. The binding between ITGB3 and miR-25-3p was assessed by dual-luciferase reporter gene and Ago2-RIP assays. BMSC osteogenic differentiation was observed by alizarin red staining and ALP activity. The differentiation of BMSCs to adipocytes and chondrocytes was measured by oil red O staining and alcian blue staining, respectively. BMSCs were successfully isolated from the bone marrow of healthy controls (normal-BMSCs) and OP patients (OP-BMSCs). ITGB3, Runx2, OPN, ALP, and OSX expression was poorer and miR-25-3p expression was higher in OP-BMSCs than in normal-BMSCs. Mechanistically, ITGB3 was negatively targeted by miR-25-3p. After osteogenic, adipogenic, and chondrogenic differentiation of BMSCs were successfully induced, adipogenic differentiation increased and osteogenic and chondrogenic differentiation decreased in OP-BMSCs compared with normal-BMSCs. Overexpression of ITGB3 facilitated mineralized nodule formation and elevated ALP activity and Runx2, OPN, and ALP expression in OP-BMSCs. miR-25-3p upregulation diminished mineralized nodule formation, ALP activity, and Runx2, OPN, and ALP expression in OP-BMSCs and normal-BMSCs, which was annulled by additional ITGB3 overexpression. miR-25-3p targets ITGB3, thereby suppressing osteogenic differentiation of BMSCs from OP patients.

The regulative effect and repercussion of probiotics and prebiotics on osteoporosis: involvement of brain-gut-bone axis

Osteoporosis (OP) is a systemic disease characterized by decreased bone mass and degeneration of bone microstructure. In recent years, more and more researches have focused on the close relationship between gut microbiota (GM) and the occurrence and progression of OP, and the regulation of probiotics and prebiotics on bone metabolism has gradually become a research hotspot. Based on the influence of brain-gut-bone axis on bone metabolism, this review expounds the potential mechanisms of probiotics and prebiotics on OP from next perspectives: regulation of intestinal metabolites, regulation of intestinal epithelial barrier function, involvement of neuromodulation, involvement of immune regulation and involvement of endocrine regulation, so as to provide a novel and promising idea for the prevention and treatment of OP in the future.

Perspective of the GEMSTONE Consortium on Current and Future Approaches to Functional Validation for Skeletal Genetic Disease Using Cellular, Molecular and Animal-Modeling Techniques

The availability of large human datasets for genome-wide association studies (GWAS) and the advancement of sequencing technologies have boosted the identification of genetic variants in complex and rare diseases in the skeletal field. Yet, interpreting results from human association studies remains a challenge. To bridge the gap between genetic association and causality, a systematic functional investigation is necessary. Multiple unknowns exist for putative causal genes, including cellular localization of the molecular function. Intermediate traits ("endophenotypes"), e.g. molecular quantitative trait loci (molQTLs), are needed to identify mechanisms of underlying associations. Furthermore, index variants often reside in non-coding regions of the genome, therefore challenging for interpretation. Knowledge of non-coding variance (e.g. ncRNAs), repetitive sequences, and regulatory interactions between enhancers and their target genes is central for understanding causal genes in skeletal conditions. Animal models with deep skeletal phenotyping and cell culture models have already facilitated fine mapping of some association signals, elucidated gene mechanisms, and revealed disease-relevant biology. However, to accelerate research towards bridging the current gap between association and causality in skeletal diseases, alternative in vivo platforms need to be used and developed in parallel with the current -omics and traditional in vivo resources. Therefore, we argue that as a field we need to establish resource-sharing standards to collectively address complex research questions. These standards will promote data integration from various -omics technologies and functional dissection of human complex traits. In this mission statement, we review the current available resources and as a group propose a consensus to facilitate resource sharing using existing and future resources. Such coordination efforts will maximize the acquisition of knowledge from different approaches and thus reduce redundancy and duplication of resources. These measures will help to understand the pathogenesis of osteoporosis and other skeletal diseases towards defining new and more efficient therapeutic targets.

Euphoesulatin A prevents osteoclast differentiation and bone loss via inhibiting RANKL-induced ROS production and NF-κB and MAPK signal pathways

Euphoesulatin A (Eup A), a new jatrophane diterpenoid isolated from the Euphorbia esula L. (Euphorbiaceae), was reported to inhibit RANKL-induced osteoclastogenesis. However, the underlying mechanism and the effect in osteoporosis mouse model are still unclear. This study is the first to demonstrate that Eup A inhibits osteoclastogenesis in vitro and in vivo. Mechanistic analysis suggested that Eup A (3, 6, 12 μM) dose-dependently inhibited osteoclastogenesis by down-regulating the activation of NFATc1 and NF-κB and MAPKs signal pathways. Moreover, Eup A (10 mg/kg) significantly prevented bone loss in ovariectomized mice. This work provides in vitro and in vivo evidence that Eup A could be a potential candidate for the development of anti-osteoporosis agents.

G Protein-Coupled Receptors in Osteoarthritis: A Novel Perspective on Pathogenesis and Treatment

G protein-coupled receptors (GPCRs) are transmembrane receptor proteins that trigger numerous intracellular signaling pathways in response to the extracellular stimuli. The GPCRs superfamily contains enormous structural and functional diversity and mediates extensive biological processes. Until now, critical roles have been established in many diseases, including osteoarthritis (OA). Existing studies have shown that GPCRs play an important role in some OA-related pathogenesis, such as cartilage matrix degradation, synovitis, subchondral bone remodeling, and osteophyte formation. However, current pharmacological treatments are mostly symptomatic and there is a paucity of disease-modifying OA drugs so far. Targeting GPCRs is capable of inhibiting cartilage matrix degradation and synovitis and up-regulating cartilage matrix synthesis, providing a new therapeutic strategy for OA. In this review, we have comprehensively summarized the structures, biofunctions, and the novel roles of GPCRs in the pathogenesis and treatment of OA, which is expected to lay the foundation for the development of novel therapeutics against OA. Even though targeting GPCRs may ameliorate OA progression, many GPCRs-related therapeutic strategies are still in the pre-clinical stage and require further investigation.

Low bone mineral density is associated with severe periodontitis at the end of the second decade of life: A population-based study

AIM

To evaluate the association between low bone mineral density (BMD) and severe periodontitis at the end of the second decade of life.

MATERIALS AND METHODS

This population-based study analysed 2032 youngers (18-19 years old) of the RPS cohort. BMD of lumbar spine (BMD-LS) and of the whole body (BMD-WB) were assessed by dual x-ray emission densitometry. Low BMD-LS (Z-score ≤ -2) and low BMD-WB (Z-score ≤ -1.5) were correlated with severe periodontitis. The extent of periodontal disease was also evaluated as the following outcomes: proportions of teeth affected by clinical attachment loss ≥5 mm and probing depth ≥5 mm. Multivariate models by sex, education, family income, risk of alcohol dependence, smoking, plaque, bleeding index, and body mass index were estimated through logistic regression (binary outcomes) and Poisson regression (continuous outcomes).

RESULTS

The prevalence of severe periodontitis was 10.97%. Low BMD-LS (odds ratio [OR] = 2.08, confidence interval [CI] = 1.12-3.85, p = .01) and low BMD-WB (OR = 1.34, CI = 1.001-1.81, p = .04) were associated with severe periodontitis in the final multivariate models. Low BMD-LS and BMD-WB were also associated with a greater extent of periodontitis (p < .05).

CONCLUSIONS

Low BMD was found to be associated with the severity and extent of periodontitis in adolescents. Adolescents at peak bone mass age presenting low BMD are more likely to be affected by severe periodontitis.

Interaction between bone and immune cells: Implications for postmenopausal osteoporosis

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

Systematic review of ratios between disease /health periodontitis modulators and meta-analysis of their levels in gingival tissue and biological fluids

OBJECTIVE

The ratio between molecules which acts towards the diseased or healthy phenotype determine whether the periodontitis lesions will progress or stabilize. Considering gingival tissue and biofluids, we aimed to present a systematic review (qualitative analysis) on the ratios between disease/health periodontitis modulators, and a meta-analysis (quantitative analysis) of their levels in individuals with periodontitis compared to controls.

DESIGN

Electronic searches of the PubMed, Scopus, EMBASE and Web of Science databases were conducted for publications up to May 2020.

RESULTS

A total of 53 publications were included in the systematic review, being 22 of them focusing on the ratios between Interleukin [IL]-1/IL-10, IL-6/IL-10, IL-1/IL-1RA and RANKL/OPG. Twenty-one publications were eligible for meta-analyses. The ratios of IL-1, IL-6 and RANKL mRNA levels were significantly higher in diseased gingival tissue, as well as their protein levels in gingival crevicular fluid (GCF) of periodontitis individuals. Considering the saliva levels, the RANKL/OPG ratio was higher in periodontitis subjects in comparison to controls. Meta-analyses showed higher IL-1β, IL-1α, IL-6 and IL-10 gene expressions in gingival tissue and protein levels in GCF, while RANKL was higher in GCF of periodontitis individuals in comparison to controls.

CONCLUSIONS

Both the ratios and meta-analyses showed higher levels of modulators in gingival tissue and GCF of diseased individuals.

Inhibitory Effects of Gold and Silver Nanoparticles on the Differentiation into Osteoclasts In Vitro

Gold nanoparticles (GNPs) have been widely studied to inhibit differentiation into osteoclasts. However, reports of the inhibitory effects of silver nanoparticles (SNPs) during the process of differentiation into osteoclasts are rare. We compared the inhibitory effect of GNPs and SNPs during the process of differentiation into osteoclasts. Bone marrow-derived cells were differentiated into osteoclasts by the receptor activator of the nuclear factor-kappa-Β ligand (RANKL). The inhibitory effect of GNPs or SNPs during the process of differentiation into osteoclasts was investigated using tartrate-resistant acid phosphatase (TRAP) and actin ring staining. The formation of TRAP positive ⁽⁺⁾ multinuclear cells (MNCs) with the actin ring structure was most inhibited in the SNP group. In addition, the expression of specific genes related to the differentiation into osteoclasts, such as c-Fos, the nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1), TRAP, and Cathepsin K (CTSK) were also inhibited in the SNP groups. As a result, the levels related to differentiation into osteoclasts were consistently lower in the SNP groups than in the GNP groups. Our study suggests that SNPs can be a useful material for inhibiting differentiation into osteoclasts and they can be applied to treatments for osteoporosis patients.

The Inhibitory Role of Rab11b in Osteoclastogenesis through Triggering Lysosome-Induced Degradation of c-Fms and RANK Surface Receptors

Rab11b, abundantly enriched in endocytic recycling compartments, is required for the establishment of the machinery of vesicle trafficking. Yet, no report has so far characterized the biological function of Rab11b in osteoclastogenesis. Using in vitro model of osteoclasts differentiated from murine macrophages like RAW-D cells or bone marrow-derived macrophages, we elucidated that Rab11b served as an inhibitory regulator of osteoclast differentiation sequentially via (i) abolishing surface abundance of RANK and c-Fms receptors; and (ii) attenuating nuclear factor of activated T-cells c1 (NFATc-1) upstream signaling cascades, following RANKL stimulation. Rab11b was localized in early and late endosomes, Golgi complex, and endoplasmic reticulum; moreover, its overexpression enlarged early and late endosomes. Upon inhibition of lysosomal function by a specific blocker, chloroquine (CLQ), we comprehensively clarified a novel function of lysosomes on mediating proteolytic degradation of c-Fms and RANK surface receptors, drastically ameliorated by Rab11b overexpression in RAW-D cell-derived osteoclasts. These findings highlight the key role of Rab11b as an inhibitor of osteoclastogenesis by directing the transport of c-Fms and RANK surface receptors to lysosomes for degradation via the axis of early endosomes-late endosomes-lysosomes, thereby contributing towards the systemic equilibrium of the bone resorption phase.

Pathogenic Mechanisms of Myeloma Bone Disease and Possible Roles for NRF2

Osteolytic bone lesions are one of the central features of multiple myeloma (MM) and lead to bone pain, fractures, decreased quality of life, and decreased survival. Dysfunction of the osteoclast (OC)/osteoblast (OB) axis plays a key role in the development of myeloma-associated osteolytic lesions. Many signaling pathways and factors are associated with myeloma bone diseases (MBDs), including the RANKL/OPG and NF-κB pathways. NRF2, a master regulator of inflammatory signaling, might play a role in the regulation of bone metabolism via anti-inflammatory signaling and decreased reactive oxygen species (ROS) levels. The loss of NRF2 expression in OCs reduced bone mass via the RANK/RANKL pathway and other downstream signaling pathways that affect osteoclastogenesis. The NRF2 level in OBs could interfere with interleukin (IL)-6 expression, which is associated with bone metabolism and myeloma cells. In addition to direct impact on OCs and OBs, the activity of NRF2 on myeloma cells and mesenchymal stromal cells influences the inflammatory stress/ROS level in these cells, which has an impact on OCs, OBs, and osteocytes. The interaction between these cells and OCs affects the osteoclastogenesis of myeloma bone lesions associated with NRF2. Therefore, we have reviewed the effects of NRF2 on OCs and OBs in MBDs.

IL-33/IL-31 Axis in Osteoporosis

The study of the immunoskeletal interface has led to the discovery of numerous cytokines involved in the regulation of bone remodeling, providing valuable information on the pathogenesis of osteoporosis. The role of inflammatory cytokines of the Th1 and Th17 profile in osteoporosis is well known. Here we focus on two newly discovered Th2 cytokines, IL-31 and IL-33, whose implications in osteoporosis are recently emerging. Clinical and experimental observations suggest an important role of the IL-33/IL-31 axis in osteoporosis. IL-33 induces IL-31 secretion by Th2 cells and inhibits RANKL-dependent osteoclastogenesis, thus counteracting bone loss. IL-31 influences Th1/Th17 osteoclastogenetic inflammation and limits Th2 osteoprotective processes, thus favoring osteoporosis. Better knowledge of the role of IL-31 and IL-33 and their receptor complexes in osteoporosis could provide an interesting perspective for the development of new and more effective therapies, possibly with less side effects.

The role of GPCRs in bone diseases and dysfunctions

The superfamily of G protein-coupled receptors (GPCRs) contains immense structural and functional diversity and mediates a myriad of biological processes upon activation by various extracellular signals. Critical roles of GPCRs have been established in bone development, remodeling, and disease. Multiple human GPCR mutations impair bone development or metabolism, resulting in osteopathologies. Here we summarize the disease phenotypes and dysfunctions caused by GPCR gene mutations in humans as well as by deletion in animals. To date, 92 receptors (5 glutamate family, 67 rhodopsin family, 5 adhesion, 4 frizzled/taste2 family, 5 secretin family, and 6 other 7TM receptors) have been associated with bone diseases and dysfunctions (36 in humans and 72 in animals). By analyzing data from these 92 GPCRs, we found that mutation or deletion of different individual GPCRs could induce similar bone diseases or dysfunctions, and the same individual GPCR mutation or deletion could induce different bone diseases or dysfunctions in different populations or animal models. Data from human diseases or dysfunctions identified 19 genes whose mutation was associated with human BMD: 9 genes each for human height and osteoporosis; 4 genes each for human osteoarthritis (OA) and fracture risk; and 2 genes each for adolescent idiopathic scoliosis (AIS), periodontitis, osteosarcoma growth, and tooth development. Reports from gene knockout animals found 40 GPCRs whose deficiency reduced bone mass, while deficiency of 22 GPCRs increased bone mass and BMD; deficiency of 8 GPCRs reduced body length, while 5 mice had reduced femur size upon GPCR deletion. Furthermore, deficiency in 6 GPCRs induced osteoporosis; 4 induced osteoarthritis; 3 delayed fracture healing; 3 reduced arthritis severity; and reduced bone strength, increased bone strength, and increased cortical thickness were each observed in 2 GPCR-deficiency models. The ever-expanding number of GPCR mutation-associated diseases warrants accelerated molecular analysis, population studies, and investigation of phenotype correlation with SNPs to elucidate GPCR function in human diseases.

Preliminary studies on the anti-osteoporosis activity of Baohuoside I

The aim of the present study was to investigate the anti-osteoporotic activity of Baohuoside I, an active component of Herba Epimedii. Effects of Baohuoside I on the differentiation of BMSCs and the formation of adipocytes were evaluated using alkaline phosphatase staining and methylene blue staining method, respectively. Osteoporosis model was established in ovariectomized rats prior to the measurement of the serum SOD and MDA levels as well as the expression of inflammatory cytokines protein in the rats' tissues after treatment with Baohuoside I using ELISA assay kits. The estrogen-like effect of Baohuoside I was also measured on HeLa cells. The positive rates of ALP staining in Baohuoside I groups were significantly higher (p < 0.01) compared with the normal group, with no obvious adipocyte formation observed in the groups that received Baohuoside I treatments. The levels of inflammatory markers (IL-1β, TNF-α, IL-6 and IL-8) in the treated groups were significantly lower (p < 0.05) than in the model group. Likewise, the treated groups exhibited a significantly higher (p < 0.05) serum levels of MDA compared with the model group, while SOD levels were markedly lower (p < 0.05) in a dose-dependent fashion. Baohuoside I showed no estrogen-like effect on HeLa cells upon treatment with the drug. Collectively, these results indicated that the anti-osteoporotic activity of Baohuoside I could be related to the induction of BMSCs differentiation into osteoblasts coupled with the inhibition of adipocyte formation, regulation of immune functions, and antioxidant activity.

Association between occurrence of ossicular chain defect and osteoprotegerin gene expression in patients with chronic otitis media

OBJECTIVE

Chronic otitis media (COM) is an important debilitating public problem causing hearing loss due to irreversible resorption of the ossicular chain. Activation of osteoprotegerin (OPG) during an acute attack of COM prevents bone resorption.The aim of the study was to investigate the role of OPG gene expression level on ossicular chain resorption in chronic otitis media.

MATERIALS AND METHODS

Fifty operated COM patients were included in the study. While 20 patients underwent ossiculoplasty, 30 patients underwent type 1 tympanoplasty. For RNA isolation and OPG gene expression analysis, middle ear swabs were taken from nasopharynx in the ostium of the Eustachian tube. RNA was isolated with mRNA easy kit and kept at - 85 °C till the cDNA and expression analysis. Expression levels were analyzed with real-time quantitative PCR in comparison with PDGB gene expression level as an internal control.

RESULTS

Sample Cq measurements of type 1 tympanoplasty group were higher than Cq measurements of the internal control group (p = 0.027; p < 0.05). In contrast, there was no statistically significant difference between sample Cq measurements of ossiculoplasty group and Cq measurements of the internal control group (p = 0.293; p > 0.05).

CONCLUSION

Since OPG gene expression level was significantly higher in type 1 tympanoplasty group, OPG gene regulation system may have an effect on ossicular chain destruction in COM.

Dihydromyricetin Protects against Bone Loss in Ovariectomized Mice by Suppressing Osteoclast Activity

Dihydromyricetin (DMY), the main flavonoid component of Ampelopsis grossedentata, possesses pharmacological activities useful for treatment of diseases associated with inflammation and oxidative damage. Because osteoclasts are often involved in chronic low-grade systemic inflammation and oxidative damage, we hypothesized that DMY may be an effective treatment for osteoclast-related diseases. The effects of DMY on osteoclast formation and activity were examined in vitro. Female C57BL/6 mice were ovariectomized to mimic menopause-induced bone loss and treated with DMY, and femur samples were subjected to bone structure and histological analysis, serum biochemical indicators were also measured. DMY suppressed the activation of nuclear factor-κB, c-Fos and mitogen-activated protein kinase, and prevented production of reactive oxygen species. DMY decreased expression of osteoclast-specific genes, including Trap, Mmp-9, Cathepsin K, C-Fos, Nfatc1, and Rank. In addition, DMY prevented bone loss and decreased serum levels of tumor necrosis factor-α, interleukin-1β, and interleukin-6, and with a decrease in the ratio between receptor activator of nuclear factor-κB (RANK) ligand (RANKL) and osteoprotegerin (OPG) in vivo. These findings demonstrate that DMY attenuates bone loss and inhibits osteoclast formation and activity through modulation of multiple pathways both upstream and downstream of RANKL signaling. DMY may thus be a useful option for treatment of osteoclast-related diseases such as rheumatoid arthritis and osteoporosis.

Omics analysis of human bone to identify genes and molecular networks regulating skeletal remodeling in health and disease

The skeleton is a metabolically active organ throughout life where specific bone cell activity and paracrine/endocrine factors regulate its morphogenesis and remodeling. In recent years, an increasing number of reports have used multi-omics technologies to characterize subsets of bone biological molecular networks. The skeleton is affected by primary and secondary disease, lifestyle and many drugs. Therefore, to obtain relevant and reliable data from well characterized patient and control cohorts are vital. Here we provide a brief overview of omics studies performed on human bone, of which our own studies performed on trans-iliacal bone biopsies from postmenopausal women with osteoporosis (OP) and healthy controls are among the first and largest. Most other studies have been performed on smaller groups of patients, undergoing hip replacement for osteoarthritis (OA) or fracture, and without healthy controls. The major findings emerging from the combined studies are: 1. Unstressed and stressed bone show profoundly different gene expression reflecting differences in bone turnover and remodeling and 2. Omics analyses comparing healthy/OP and control/OA cohorts reveal characteristic changes in transcriptomics, epigenomics (DNA methylation), proteomics and metabolomics. These studies, together with genome-wide association studies, in vitro observations and transgenic animal models have identified a number of genes and gene products that act via Wnt and other signaling systems and are highly associated to bone density and fracture. Future challenge is to understand the functional interactions between bone-related molecular networks and their significance in OP and OA pathogenesis, and also how the genomic architecture is affected in health and disease.

Effects of osteoprotegerin, RANK and RANKL on bone destruction and collapse in avascular necrosis femoral head

Avascular necrosis of femoral head (AVFH) is a clinically recalcitrant disease of hip that leads to joint destruction. Osteoprotegerin (OPG), receptor activator of nuclear factor kappa-B (RANK) and RANK ligand (RANKL) regulates the balance, maturation and function of osteoclast and bone remodeling. This study aims to investigate molecular pathways which leads to AVN by studying expression profile of OPG, RANK and RANKL genes. Quantitative Real Time-PCR is used to evaluate mRNA expression of OPG, RANK and RANKL. mRNA and protein level in normal and necrotic tissue from 42 samples of ANFH specimens were analyzed. OPG and RANKL protein levels are estimated by western blotting. The results indicated that OPG mRNA levels are higher but not significantly different in necrotic tissue than that in normal tissue (P>0.05). Although expression of RANK and RANKL is significantly lower than that of OPG, RANK and RANKL mRNA levels are higher in necrotic tissue than normal tissue (P<0.05). Protein levels of OPG and RANKL show no significant difference. In conclusion, OPG, RANK and RANKL play important role in progress of bone remodeling in necrotic area and in disturbance of bone homeostasis, which might have an effect on bone destruction and subsequent collapse of hip joint.

Osteoporosis and polymorphisms of osteoprotegerin gene in postmenopausal women - a pilot study

Objectives

Osteoprotegerin (OPG) has an important role in bone remodeling, and it has been proposed that the OPG gene might be a candidate gene for osteoporosis predisposition. Several studies have already assessed the connection between OPG gene polymorphism and bone mineral density (BMD). In this study we wanted to analyze the association of two polymorphisms in the OPG gene with BMD and bone turnover markers in women with and without osteoporosis.

Material and methods

In 22 postmenopausal women with osteoporosis (aged 65.6 ±12.6) and 59 women without osteoporosis (aged 60.8 ±8.7) we analyzed the association of two polymorphisms in the OPG gene with BMD, measured by dual energy absorptiometry and with bone turnover markers (crosslaps and osteoprotegerin). A163G, G209A, T245G and G1181C polymorphisms were determined.

Results

No significant differences in age, anthropometry, number of fractures, osteocalcin and cross-laps were found between women with and without osteoporosis. Women with osteoporosis were significantly longer in postmenopause. Significantly more women with osteoporosis had AG polymorphism (p = 0.038) compared to women without osteoporosis, while no significant difference was found in prevalence of TT and GG polymorphism between patients with and without osteoporosis. No relationship was found between investigated polymorphism and bone turnover markers. A significant negative correlation between total hip BMD and crosslaps (p = 0.046) as well as between total hip T score and crosslaps (p = 0.044) was found in women without osteoporosis

Conclusions

Postmenopausal women with osteoporosis had AG polymorphism more frequently than women without osteoporosis. Our results indicate that A163G polymorphism could have an impact on higher bone loss in postmenopausal women.

The Modulatory Effects of Mesenchymal Stem Cells on Osteoclastogenesis

The effect of mesenchymal stem cells (MSCs) on bone formation has been extensively demonstrated through several in vitro and in vivo studies. However, few studies addressed the effect of MSCs on osteoclastogenesis and bone resorption. Under physiological conditions, MSCs support osteoclastogenesis through producing the main osteoclastogenic cytokines, RANKL and M-CSF. However, during inflammation, MSCs suppress osteoclast formation and activity, partly via secretion of the key anti-osteoclastogenic factor, osteoprotegerin (OPG). In vitro, co-culture of MSCs with osteoclasts in the presence of high concentrations of osteoclast-inducing factors might reflect the in vivo inflammatory pathology and prompt MSCs to exert an osteoclastogenic suppressive effect. MSCs thus seem to have a dual effect, by stimulating or inhibiting osteoclastogenesis, depending on the inflammatory milieu. This effect of MSCs on osteoclast formation seems to mirror the effect of MSCs on other immune cells, and may be exploited for the therapeutic potential of MSCs in bone loss associated inflammatory diseases.

Molecular mechanisms of osteoporotic hip fractures in elderly women

A common manifestation of age-related bone loss and resultant osteoporosis are fractures of the hip. Age-related osteoporosis is thought to be determined by a number of intrinsic factors including genetics, hormonal changes, changes in levels of oxidative stress, or an inflammatory status associated with the aging process. The aim of this study was to investigate gene expression and bone architecture in bone samples derived from elderly osteoporotic women with hip fractures (OP) in comparison to bone samples from age matched women with osteoarthritis of the hip (OA). Femoral heads and adjacent neck tissue were collected from 10 women with low-trauma hip fractures (mean age 83±6) and consecutive surgical hip replacement. Ten bone samples from patients undergoing hip replacement due to osteoarthritis (mean age 80±5) served as controls. One half of each bone sample was subjected to gene expression analysis. The second half of each bone sample was analyzed by microcomputed tomography. From each half, samples from four different regions, the central and subcortical region of the femoral head and neck, were analyzed. We could show a significantly decreased expression of the osteoblast related genes RUNX2, Osterix, Sclerostin, WNT10B, and Osteocalcin, a significantly increased ratio of RANKL to Osteoprotegerin, and a significantly increased expression of the enzymes superoxide dismutase 2 (SOD2) and glutathione peroxidase GPX3, and of the inflammatory cytokine IL6 in bone samples from hip fracture patients compared to controls. Major microstructural changes in OP bone were seen in the neck and were characterized by a significant decrease of bone volume, trabecular number, and connectivity density and a significant increase of trabecular separation. In conclusion, our data give evidence for a decreased expression of osteoblast related genes and increased expression of osteoclast related genes. Furthermore, increased expression of SOD2 and GPX3 suggest increased antioxidative activity in bone samples from elderly osteoporotic women with hip fractures.

Expression of osteoprotegerin, RNAK and RANKL genes in femoral head avascular necrosis and related signaling pathway

Femoral head avascular necrosis (AVN) causes the damage of hip joint and related dysfunctions, thus consisting of a clinical challenge. Osteoprotegerin (OPG), receptor activator of nuclear factor κB (RANK) and its ligand (RANKL) all regulate the formation of bones via gene transcriptional regulation for the balance between osteoblasts and osteoclasts. This study thus investigated the expressional profiles of OPG, RANK and RANKL genes in AVN patients, and explored related molecular mediating pathways. Real-time qPCR was used to measure the gene expression of OPG, RANK and RANKL genes in AVN femoral head tissue samples from 42 patients, along with normal tissues. Western blotting analysis was performed to quantify protein levels of OPG and RANKL. There was a trend but not statistically significant elevation of mRNA levels of OPG in femoral head AVN tissues compared to normal tissues (P>0.05). The expression of RNAK and RNAKL, however, was significantly elevated in necrotic tissues (P<0.05). No significant difference in protein levels of OPG or RANKL between groups. The expression of OPG, RANK and RANKL genes exert a crucial role in the progression of AVN, suggesting their roles in mediating bone homeostasis and potential effects on bone destruction.

Identifying genes related with rheumatoid arthritis via system biology analysis

Rheumatoid arthritis (RA) is a chronic, inflammatory joint disease that mainly attacks synovial joints. However, the underlying systematic relationship among different genes and biological processes involved in the pathogenesis are still unclear. By analyzing and comparing the transcriptional profiles from RA, OA (osteoarthritis) patients as well as ND (normal donors) with bioinformatics methods, we tend to uncover the potential molecular networks and critical genes which play important roles in RA and OA development. Initially, hierarchical clustering was performed to classify the overall transcriptional profiles. Differentially expressed genes (DEGs) between ND and RA and OA patients were identified. Furthermore, PPI networks were constructed, functional modules were extracted, and functional annotation was also applied. Our functional analysis identifies 22 biological processes and 2 KEGG pathways enriched in the commonly-regulated gene set. However, we found that number of set of genes differentially expressed genes only between RA and ND reaches up to 244, indicating this gene set may specifically accounts for processing to disease of RA. Additionally, 142 biological processes and 19 KEGG pathways are over-represented by these 244 genes. Meanwhile, although another 21 genes were differentially expressed only in OA and ND, no biological process nor pathway is over-represented by them.

Bone resorption during the first year after implantation of a single-segment dynamic interspinous stabilization device and its risk factors

Background

Dynamic interspinous stabilization devices generally provide satisfactory results, but can result in recurrent lumbar disc herniation, spinous process fracture, or bone resorption of the spinous process. The purpose of this study was to investigate if the Wallis dynamic stabilization device is associated with bone resorption.

Methods

Patients who underwent single-segment posterior lumbar decompression and implantation of a Wallis dynamic interspinous stabilization device at the L4/5 level between January 1, 2009 and October 1, 2011 were included. Bone resorption rate, Oswestry Disability Index (ODI), Japanese Orthopedic Association (JOA) score, and visual analogue scale (VAS) pain score were measured. Patient baseline and 1-year follow-up data were collected and analyzed. The bone resorption rate of the L4 and L5 spinous processes was calculated.

Results

Twenty four males and 20 females with a mean age of 42.7 ± 14.7 years were included. Twenty nine patients had significant bone resorption (bone resorption rate > 20%) and 15 had no bone resorption (bone resorption rate ≤ 20%) at 1 year after surgery. Lumbar lordosis ≥ 50° was associated with a lower bone resorption than lumbar lordosis < 50° and increasing BMI was associated with increased bone resorption. There were no significant differences between the bone resorption and no bone resorption groups in the improvement rate of VAS pain score, ODI, and JOA score at 1 year after surgery.

Conclusions

Significant bone resorption occurs within 1 year after implantation of the Wallis device in more than 50% of patients. However, it does not affect short-term functional results.

ADRA2A is involved in neuro-endocrine regulation of bone resorption

Adrenergic stimulation is important for osteoclast differentiation and bone resorption. Previous research shows that this happens through β2-adrenergic receptor (AR), but there are conflicting evidence on presence and role of α2A-AR in bone. The aim of this study was to investigate the presence of α2A-AR and its involvement in neuro-endocrine signalling of bone remodelling in humans. Real-time polymerase chain reaction (PCR) and immunohistochemistry were used to investigate α2A-AR receptor presence and localization in bone cells. Functionality of rs553668 and rs1800544 single nucleotide polymorphism SNPs located in α2A-AR gene was analysed by qPCR expression on bone samples and luciferase reporter assay in human osteosarcoma HOS cells. Using real-time PCR, genetic association study between rs553668 A>G and rs1800544 C>G SNPs and major bone markers was performed on 661 Slovenian patients with osteoporosis. α2A-AR is expressed in osteoblasts and lining cells but not in osteocytes. SNP rs553668 has a significant influence on α2A-AR mRNA level in human bone samples through the stability of mRNA. α2A-AR gene locus associates with important bone remodelling markers (BMD, CTX, Cathepsin K and pOC). The results of this study are providing comprehensive new evidence that α2A-AR is involved in neuro-endocrine signalling of bone turnover and development of osteoporosis. As shown by our results the neurological signalling is mediated through osteoblasts and result in bone resorption. Genetic study showed association of SNPs in α2A-AR gene locus with bone remodelling markers, identifying the individuals with higher risk of development of osteoporosis.

Advanced oxidation protein products decrease the expression of calcium transport channels in small intestinal epithelium via the p44/42 MAPK signaling pathway

Advanced oxidation protein products (AOPPs), novel protein markers of oxidative damage, accumulate in the plasma of patients with inflammatory bowel disease (IBD). Osteoporosis, which is closely related to the regulation of intestinal calcium transport channels (CTCs), is a prevalent extraintestinal complication of IBD and is associated with oxidative stress. However, the underlying mechanisms are unknown. The present study aimed to verify whether AOPPs inhibit CTCs in the small intestinal epithelium and to identify the underlying mechanisms that may contribute to IBD-associated osteoporosis. Normal Sprague-Dawley rats were treated with AOPP-modified rat serum albumin. The calcium ion level in serum was not significantly altered, while the duodenal expression of CTCs (e.g. transient receptor potential vanilloid [TRPV6], calbindin-D9k [CaBP-D9k], plasma membrane Ca(2+)-ATPase 1 [PMCA1], and Na(+)/Ca(2+) exchanger 1 [NCX1]) were decreased. In contrast, the levels of the related hormones that regulate calcium absorption including parathyroid hormone (PTH), 25-(OH)D₃, and 1,25-(OH)₂D₃ were increased, although the trend toward an increase in PTH levels was not significant. In order to further investigate the effects of AOPP exposure, we also evaluated the expression of CTCs (including the voltage-dependent L-type calcium channel [CaV1.3], TRPV6, CaBP-D9k, PMCA1, and NCX1) in cultured human colorectal adenocarcinoma cells (Caco-2). The expression levels of total CTC protein and mRNA, except for CaV1.3, were significantly down-regulated in a concentration- and time-dependent manner. Moreover, phosphorylation of p44/42 mitogen-activated protein kinase (MAPK) was observed in vivo and in vitro. The p44/42 inhibitor U0126 reversed the down-regulation of CTCs induced by AOPPs in the Caco-2 monolayer. Our results indicate that AOPPs down-regulate the expression of CTCs through p44/42 MAPK signaling mechanisms in the small intestinal epithelium. These data provide new insights regarding the molecular basis of AOPP-induced reductions in intestinal CTCs, and are relevant to understanding the mechanisms of IBD-associated osteoporosis. Further studies are needed to explore these mechanisms in greater detail.

Local drug delivery for enhancing fracture healing in osteoporotic bone

Fragility fractures can cause significant morbidity and mortality in patients with osteoporosis and inflict a considerable medical and socioeconomic burden. Moreover, treatment of an osteoporotic fracture is challenging due to the decreased strength of the surrounding bone and suboptimal healing capacity, predisposing both to fixation failure and non-union. Whereas a systemic osteoporosis treatment acts slowly, local release of osteogenic agents in osteoporotic fracture would act rapidly to increase bone strength and quality, as well as to reduce the bone healing period and prevent development of a problematic non-union. The identification of agents with potential to stimulate bone formation and improve implant fixation strength in osteoporotic bone has raised hope for the fast augmentation of osteoporotic fractures. Stimulation of bone formation by local delivery of growth factors is an approach already in clinical use for the treatment of non-unions, and could be utilized for osteoporotic fractures as well. Small molecules have also gained ground as stable and inexpensive compounds to enhance bone formation and tackle osteoporosis. The aim of this paper is to present the state of the art on local drug delivery in osteoporotic fractures. Advantages, disadvantages and underlying molecular mechanisms of different active species for local bone healing in osteoporotic bone are discussed. This review also identifies promising new candidate molecules and innovative approaches for the local drug delivery in osteoporotic bone.

Raloxifene modulates regulators of osteoclastogenesis and angiogenesis in an oestrogen deficiency periapical lesion model

AIM

To analyse the local regulatory mechanisms of osteoclastogenesis and angiogenesis during the progression of periapical lesions in female rats with oestrogen deficiency and treatment with raloxifene (RLX).

METHODOLOGY

Female Wistar rats were distributed into groups: SHAM-veh, subjected to sham surgery and treated with a vehicle; OVX-veh, subjected to ovary removal and treated with a vehicle; and OVX-RLX, subjected to ovary removal and treated with RLX. Vehicle or RLX was administered orally for 90 days. During treatment, the dental pulp of mandibular first molars was exposed to the oral environment for induction of periapical lesions, which were analysed after 7 and 30 days. After the experimental periods, blood samples were collected for measurement of oestradiol, calcium, phosphorus and alkaline phosphatase. The rats were euthanized and the mandibles removed and processed for immunohistochemical detection of receptor activator of nuclear factor kappa-B ligand (RANKL), osteoprotegerin (OPG), hypoxia-inducible factor-1 alpha (HIF-1α) and bone-specific alkaline phosphatase (BALP). Data were compared using Kruskal-Wallis followed by Dunn test (nonparametric values) and anova followed by the Tukey's test (parametric values).

RESULTS

The plasma concentration of oestradiol showed hypo-oestrogenism in the rats subjected to ovary removal. On day 7, alkaline phosphatase activity, calcium and phosphorus were higher in the OVX-RLX group than in the OVX-veh group (P < 0.001), but immunolabelling for RANKL and HIF-1α was lower in OVX-RLX group (P < 0.001). On day 30, the OVX-veh group had higher immunolabelling for RANKL than the OVX-RLX group (P < 0.05). There were no significant differences in the immunoreactivity of OPG and BALP between any groups at either time-point (P > 0.05).

CONCLUSION

RLX therapy reversed the increased levels of the local regulators of both osteoclastogenesis and angiogenesis induced by oestrogen deficiency.

Interferon gamma (IFN-γ)-mediated inflammation and the kynurenine pathway in relation to risk of hip fractures: the Hordaland Health Study

The cytokine interferon gamma (IFN-γ) stimulates neopterin release and tryptophan degradation into kynurenines through the kynurenine pathway. High levels of neopterin were associated with increased hip fracture risk, as were some of the kynurenines, suggesting a role of IFN-γ-mediated inflammation in the processes leading to hip fracture.

INTRODUCTION

Low-grade systemic inflammation has been associated with bone loss and risk of fractures. Interferon gamma (IFN-γ) initiates macrophage release of neopterin and also stimulates degradation of tryptophan along the kynurenine pathway as part of cell-mediated immune activation. Plasma neopterin and the kynurenine/tryptophan ratio (KTR) are thus markers of IFN-γ-mediated inflammation. Risk of hip fracture was investigated in relation to markers of inflammation and metabolites in the kynurenine pathway (kynurenines).

METHODS

Participants (71 to 74 years, N = 3,311) in the community-based Hordaland Health Study (HUSK) were followed for hip fractures from enrolment (1998-2000) until 31 December 2009. Plasma C-reactive protein (CRP), neopterin, KTR, and six kynurenines were investigated as predictors of hip fracture, using Cox proportional hazards regression analyses.

RESULTS

A hazard ratio (HR) of 1.9 (95% confidence interval (CI) 1.3-2.7) for hip fracture was found in the highest compared to the lowest quartile of neopterin (p trend across quartiles <0.001). CRP and KTR were not related to hip fracture risk. Among the kynurenines, a higher risk of fracture was found in the highest compared to the lowest quartiles of anthranilic acid and 3-hydroxykynurenine. For subjects in the highest quartiles of neopterin, CRP, and KTR compared to those in no top quartiles, HR was 2.5 (95% CI 1.6-4.0).

CONCLUSIONS

This may indicate a role for low-grade immune activation in the pathogenic processes leading to hip fracture.

In vitro isolation and cultivation of human chondrocytes for osteoarthritis renovation

The purpose of this study was to evaluate the repair effects of chondrocytes that were cultured in vitro on osteoarthritis (OA). Chondrocytes were isolated from fetal rabbits and cultured in Biosilon microcarriers. Sixty rabbits were randomly divided into three groups equally (blank group, model group, treatment group). The rabbit knee OA model was established by inducing papain. Rabbits in the treatment group were injected with the chondrocytes that were cultured in vitro. Hematoxylin-eosin (HE) staining and gross morphologic observation were conducted. Expression level of cytokines such as IL-1bβ, IL-6, and TNF-α in cartilage synovial cells was also analyzed by an ELISA assay. The cultured chondrocyte was validated by a positive stain of type II collagen and vimentin by immunofluorescence. Compared to the model group, the articular cartilage of the rabbit knee in the treatment group showed a normal color, smooth surface, and none of malacia and coloboma. HE staining indicated that the articular surface of the treatment group tended to be smooth and flat; the matrix stained tinge and the cartilage destruction and fiber hyperplasia of the synovia were lightened. The expression levels of IL-1bβ, IL-6, and TNF-α also declined in the treatment group. OA symptoms were improved by treating with chondrocytes. In summary, the animal experiment in the present study indicated that chondrocyte injection played an active effect on renovation of OA.

Interferon (IFN)-γ-mediated inflammation and the kynurenine pathway in relation to bone mineral density: the Hordaland Health Study

The risk of osteoporosis increases in inflammatory disorders. In cell-mediated immune activation, interferon (IFN)-γ stimulates macrophage release of neopterin and increases the activity of indoleamine 2,3-dioxygenase (IDO), thereby stimulating tryptophan degradation along the kynurenine pathway. Plasma levels of neopterin and the kynurenine/tryptophan ratio (KTR) are thus markers of IFN-γ-mediated inflammation. Several kynurenine pathway metabolites (kynurenines) possess immunomodulatory properties. The aim of this study was to investigate associations between markers of IFN-γ-mediated inflammation and kynurenines with bone mineral density (BMD). The community-based Hordaland Health Study (HUSK), with middle-aged (46–49 years) and older (71–74 years) participants, was conducted from 1998 to 2000 (n = 5312). Hip BMD in relation to neopterin, KTR and kynurenines were investigated, using linear and logistic regression analyses. In the oldest group, neopterin (P ≤ 0·019) and KTR (P ≤ 0·001) were associated inversely with BMD after multiple adjustment. Comparing the highest to the lowest quartiles, the odds ratios of low BMD (being in the lowest quintile of BMD) in the oldest cohort were for neopterin 2·01 among men and 2·34 among women (P ≤ 0·007) and for KTR 1·80 for men and 2·04 for women (P ≤ 0·022). Xanthurenic acid was associated positively with BMD in all sex and age groups while 3-hydroxyanthranilic acid was associated positively with BMD among women only (P ≤ 0·010). In conclusion, we found an inverse association between BMD and markers of IFN-γ-mediated inflammation in the oldest participants. BMD was also associated with two kynurenines in both age groups. These results may support a role of cell-mediated inflammation in bone metabolism.

Molecular evidence of osteoblast dysfunction in elderly men with osteoporotic hip fractures

Osteoporosis is extremely frequent in post-menopausal women; nevertheless, osteoporosis in men is also a severe and frequently occurring but often underestimated disease. Increasing evidence links bone loss in male idiopathic osteoporosis and age related osteoporosis to osteoblast dysfunction rather than increased osteoclast activity as seen in postmenopausal osteoporosis. The aim of this study was to investigate gene expression of osteoblast related genes and of bone architecture in bone samples derived from elderly osteoporotic men with hip fractures (OP) in comparison to bone samples from age matched men with osteoarthritis of the hip (OA). Femoral heads and adjacent neck tissue were collected from 12 men with low-trauma hip fractures and consecutive surgical hip replacement. Bone samples of age matched patients undergoing hip replacement due to osteoarthritis served as controls. One half of the bone samples was subjected to RNA extraction, reverse transcription, and real-time polymerase chain reactions. The second half of the bone samples was analyzed by static histomorphometry. From each half samples from four different regions, the central and subcortical region of the femoral head and neck, were analyzed. OP patients displayed a significantly decreased RUNX2, Osterix and SOST expression compared to OA patients. Major microstructural changes in OP bone were seen in the subcortical region of the neck and were characterized by a significant decrease of bone volume, and a significant increase of trabecular separation. In conclusion, decreased local gene expression of RUNX2 and Osterix in men with hip fractures strongly supports the concept of osteoblast dysfunction in male osteoporosis. Major microstructural changes in the trabecular structure associated with osteoporotic hip fractures in men are localized in the subcortical region of the femoral neck.

Mediolateral subchondral tibial bone mineral density difference does not predict osteoarthritis progression

Data on the relationship between osteoporosis and osteoarthritis are conflicting. Most studies report "snapshot" prevalences, and there are few studies evaluating localized knee bone mineral density (BMD) measurements with respect to subsequent osteoarthritis progression. The authors hypothesize that increased mediolateral difference of the proximal tibial BMD may predict progression of knee osteoarthritis. In this study, 246 female volunteers were followed up prospectively over 2 years. Baseline BMD measurements of bilateral proximal (subchondral) tibiae were performed, and the mediolateral BMD ratio was calculated. Precision studies were performed on healthy volunteers to validate the technique. The patients were divided into osteoarthritis progressors and non-progressors based on Kellgren-Lawrence radiographic criteria at 2-year follow-up. Patients who were taking bisphosphonates or who had a history of inflammatory, infectious, or metabolic bone disease and previous hip and knee surgery were excluded. Demographic data, calcium supplementation, physical activity, baseline knee radiographs, and radiographs at 2-year follow-up were obtained. The study was adequately powered to detect an effect size of 0.4. There were 121 progressors and 125 non-progressors. Mean mediolateral BMD ratio was 1.02 among the progressors and 1.01 among the non-progressors (t=0.632, P=.528). Potential confounders were equally distributed among both groups. The data suggest that there is no link between proximal tibial BMD ratio and progression of knee osteoarthritis.

Osteoporosis and osteoarthritis, rheumatoid arthritis and spondylarthropathies

Osteoporosis (OP) commonly occurs in the setting of inflammatory arthritis, whereas there is an inverse relationship with osteoarthritis (OA). We review the recent updates in epidemiology and pathophysiology of OP relating to several arthridities. In ankylosing spondylitis, lateral lumbar spine dual x-ray absorptiometry is better at detecting osteoporosis compared with the AP view and patients receiving treatment with anti- tumor necrosis factor medications had lower levels of bone turnover markers. With regard to rheumatoid arthritis, anticitrullinated peptide positivity without clinical arthritis as well as higher levels of interleukin-6 is associated with decreased bone mineral density and polymorphisms in the vitamin D receptor in RA patients may predispose to OP. With regard to OA, results from the Global Longitudinal Study of Osteoporosis in Women study and several radiological studies suggest that differences in the distribution of bone mass at the femoral neck may account for the inverse relationship of OA and OP, and several studies suggest that OA and OP have opposing cytokine and bone metabolism marker profiles.

The role of T helper (TH)17 cells as a double-edged sword in the interplay of infection and autoimmunity with a focus on xenobiotic-induced immunomodulation

Extensive research in recent years suggests that exposure to xenobiotic stimuli plays a critical role in autoimmunity induction and severity and that the resulting response would be exacerbated in individuals with an infection-aroused immune system. In this context, heavy metals constitute a prominent category of xenobiotic substances, known to alter divergent immune cell responses in accidentally and occupationally exposed individuals, thereby increasing the susceptibility to autoimmunity and cancer, especially when accompanied by inflammation-triggered persistent sensitization. This perception is learned from experimental models of infection and epidemiologic studies and clearly underscores the interplay of exposure to such immunomodulatory elements with pre- or postexposure infectious events. Further, the T_H17 cell subset, known to be associated with a growing list of autoimmune manifestations, may be the “superstar” at the interface of xenobiotic exposure and autoimmunity. In this review, the most recently established links to this nomination are short-listed to create a framework to better understand new insights into T_H17's contributions to autoimmunity.

The effect of alpha-lipoic acid in ovariectomy and inflammation-mediated osteoporosis on the skeletal status of rat bone

Osteoporosis is a high mortality and morbidity ranged skeletal disease and results in high costs of medical care in the European Union. We evaluated the possible protective effect of alpha-lipoic acid (ALA) on rat bone metabolism in ovariectomy and inflammation-mediated osteoporosis models. Groups were designed as: (1) sham; (2) sham+inflammation; (3) ovariectomy (OVX); (4) ovariectomy+ALA-25mg/kg; (5) ovariectomy+ALA-50mg/kg; (6) ovariectomy+inflammation; (7) ovariectomy+inflammation+ALA-25mg/kg; and (8) ovariectomy+inflammation+ALA-50mg/kg groups. OVX groups were allowed to recover for two months. Then, inflammation was induced in inflammation groups by subcutaneous talc injection. ALA-25mg/kg and 50mg/kg were administered to drug groups chronically. The skeletal response was assessed by bone mineral density (BMD), osteopontin and osteocalcin measurements. Pro-inflammatory cytokine measurements (interleukin (IL)-1 beta, interleukin-6, and tumor necrosis factor-alpha) were performed to observe inflammatory process. In OVX, INF and OVX+INF groups, BMD levels were lowest and osteocalcin, osteopontin, IL-1 beta, IL-6, and TNF-alpha levels were highest when compared to sham group. ALA administration increased BMD levels and decreased osteocalcin, osteopontin, IL-1 beta, IL-6, and TNF-alpha levels versus OVX and OVX+INF control groups. Both in senile and postmenopausal osteoporosis, the balance in coupling were destroyed on behalf of bone resorption. ALA had a protective effect on both senile and postmenopausal osteoporosis. The positive effect of this drug in these osteoporosis models might originate from its positive effects on bone turnover markers and cytokine levels. From this perspective, ALA may be a candidate for radical osteoporosis treatment both in senile and postmenopausal types clinically at the end of advanced studies.

The role of cytokines in skin aging

Cutaneous aging is one of the major noticeable menopausal complications that most women want to fight in their quest for an eternally youthful skin appearance. It may contribute to some maladies that occur in aging which, despite not being life-threatening, affect the well-being, psychological state and quality of life of aged women. Skin aging is mainly affected by three factors: chronological aging, decreased levels of estrogen after menopause, and environmental factors. Aged skin is characterized by a decrease in collagen content and skin thickness which result in dry, wrinkled skin that is easily bruised and takes a longer time to heal. Cytokines play a crucial role in the manifestation of these features of old skin. The pro-inflammatory cytokine tumor necrosis factor-alpha inhibits collagen synthesis and enhances collagen degradation by increasing the production of MMP-9. It also lowers the skin immunity and thus increases the risk of cutaneous infections in old age. Deranged levels of several interleukins and interferons also affect the aging process. The high level of CCN1 protein in aged skin gives dermal fibroblasts an 'age-associated secretory phenotype' that causes abnormal homeostasis of skin collagen and leads to the loss of the function and integrity of skin. Further research is required especially to establish the role of cytokines in the treatment of cutaneous aging.