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BACKGROUND: Upregulation of hedgehog protein signaling can increase the expression of osteoarthritis markers, Runx2, a disintegrin and metalloproteinase with thrombospondin motifs, collagen type X alpha 1, and matrix metalloproteinase 13, while inhibition of hedgehog proteins attenuates the severity of osteoarthritis. It is speculated that osteoarthritic chondrocytes can influence bone formation by affecting osteoblasts through the Indian hedgehog protein (IHH) signaling pathway. OBJECTIVE: To investigate the effect of human osteoarthritic chondrocytes on subchondral osteoblasts. METHODS: Tibial plateau specimens from patients with osteoarthritis were collected. Chondrocytes were extracted using enzymatic digestion, and osteoblasts were extracted using enzymatic pre-digestion + bone block method. Chondrocytes were identified by toluidine blue staining and immunofluorescence and osteoblasts were identified by alkaline phosphatase staining and immunofluorescence. Chondrocytes were cultured in sodium alginate beads to maintain chondrocyte phenotype and co-cultured with osteoblasts. The co-culture system was added with IHH signaling pathway inhibitor (cyclopamine, 10 nmol/L) and activator (purmorphamine, 10 nmol/L) separately. After 48 hours of co-culture, osteoblasts from each group were collected, mRNA expressions of Gli1, osteoprotegerin, Runx2, parathyroid hormone-related peptide, alkaline phosphatase, receptor activator of nuclear factor-kB ligand (RANKL) and osteocalcin were detected by qRT-PCR, and protein expressions of GLi1, oseoprotegerin and RANKL in osteoblasts were detected by western blot. RESULTS AND CONCLUSION: The mRNA expression levels of GLi1, osteoprotegerin and RUNX2 in osteoblasts were significantly increased, while the mRNA expression levels of parathyroid hormone-related peptide were decreased (P < 0.05) when co-cultured with human osteoarthritic chondrocytes. The mRNA and protein levels of Gli1 were significantly decreased after the addition of IHH signaling pathway inhibitor (cyclopamine) (P < 0.05), and the mRNA and protein levels of Gli1 were significantly increased after the addition of IHH signaling pathway activator (purmorphamine) (P < 0.05). Osteoprotegerin showed the same trend as Gli1 in the experiment. The osteoprotegerin/RANKL ratio followed the same trend as osteoprotegerin. To conclude, human osteoarthritic chondrocytes can promote the expression of Gli1, osteoprotegerin, Runx2 and other proteins in osteoblasts. The upregulation of osteoprotegerin is related to the IHH signaling pathway. Osteoarthritic chondrocytes can up-regulate the expression of osteoprotegerin in osteoblasts through the IHH signaling pathway and thus up-regulate the osteoprotegerin/RANKL ratio, which will contribute to bone formation in subchondral bone. [ABSTRACT FROM AUTHOR]

BACKGROUND: Osteoprotegerin (OPG)/receptor activator of nuclear factor-κB (RANK)/receptor activator of nuclear factor-κB ligand (RANKL) are important cytokines for coupling osteoclast and osteoblast differentiation and activation, and are key factors for regulating bone metabolism, which affect the immune system, bone regeneration and remodeling, and are closely related to the physiological and pathological remodeling of the alveolar bone. OBJECTIVE: To analyze the effects of the OPG/RANK/RANKL signaling pathway on alveolar bone remodeling and the progress in its targeted therapy application in the dental field. METHODS: We searched relevant articles included in CNKI and PubMed databases with the keywords of “OPG, anti-RANKL antibody, RANKL, periodontitis, orthodontic tooth movement, implant, tooth eruption, periapical lesion, alveolar bone resorption” in Chinese and English, respectively. A total of 63 articles were finally included for review. RESULTS AND CONCLUSION: Anti-RANKL therapy can treat oral diseases by targeting the inhibition of osteoclast formation and alveolar bone absorption. Local and systemic anti-RANKL therapy can inhibit the progression of periodontitis, peri-implantitis and periapical lesions, and it also plays an important role in preventing orthodontic relapse, strengthening orthodontic anchorage and implant osseointegration. RANKL therapy can treat oral diseases by promoting osteoclast differentiation and alveolar bone absorption. RANKL treatment can accelerate orthodontic tooth movement, shorten the treatment cycle and reduce the incidence of orthodontic complications. Although there are limitations in anti-RANKL therapy, they can be avoided by rational applications, such as excluding local and systemic risk factors before treatment, regular oral maintenance and avoiding traumatic alveolar surgery as much as possible during treatment. [ABSTRACT FROM AUTHOR]

Simple Summary: Advances in the treatment of acute lymphoblastic leukemia (ALL) have led to a marked improvement in the survival rate of patients. Nevertheless, these patients may develop adverse effects during and after treatment, such as bone abnormalities and vitamin D deficiency. Bone remodeling allows for bone volume and structure to be maintained, which is controlled by the receptor activator of the nuclear factor-kB (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) system-determining pathway in the balance between bone formation and resorption. Some reports have explored the role of corticosteroids in modulating the RANKL and OPG levels and RANKL/OPG ratio in pediatric patients. Nevertheless, studies evaluating the role of RANKL and OPG in the bone health of pediatric ALL patients during treatment are limited. During remission, we observed an increase in the RANKL/OPG ratio, increased RANKL levels, and decreased OPG levels in ALL patients. These changes may predispose such patients to the development of bone health disorders in their adult lives. Background: The receptor activator of the nuclear factor-kB (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) pathway is a determining pathway in the balance between bone formation and resorption, and disruptions in this complex can affect bone metabolism. Methods: This study analyzes the changes in RANKL, OPG, and 25(OH)D levels; the RANKL/OPG ratio; and other bone turnover markers (BTMs) from diagnosis to complete remission in children with acute lymphoblastic leukemia (ALL). This is a prospective observational cohort study, carried out at the Instituto Mexicano del Seguro Social, Mexico City, including 33 patients (4–17 years) with newly diagnosed B-cell ALL. The patients were treated with the HP09 chemotherapy protocol. Children who had previously been treated with corticosteroids were excluded. A peripheral blood sample at diagnosis and remission was collected to determine the 25(OH)D and BTM concentrations. Results: Increased RANKL (p = 0.001) and osteocalcin (p < 0.001) levels and RANKL/OPG ratio (<0.001) and a decreased OPG level (p = 0.005) were observed at remission, predominantly in the high-risk (HR) relapse and vitamin D deficiency groups. A negative association between RANKL and OPG (r = −0.454, p = 0.008) was observed. Conclusions: we suggest that the RANKL/OPG ratio could serve as a bone remodeling marker in ALL patients. [ABSTRACT FROM AUTHOR]

Despite their diverse physiologies and roles, the heart, skeletal muscles, and smooth muscles all derive from a common embryonic source as bones. Moreover, bone tissue, skeletal and smooth muscles, and the heart share conserved signaling pathways. The maintenance of skeletal health is precisely regulated by osteocytes, osteoblasts, and osteoclasts through coordinated secretion of bone‐derived factors known as osteokines. Increasing evidence suggests the involvement of osteokines in regulating atherosclerotic vascular disease. Therefore, this review aims to examine the evidence for the role of osteokines in atherosclerosis development and progression comprehensively. Specifically discussed are extensively studied osteokines in atherosclerosis such as osteocalcin, osteopontin, osteoprotegerin, and fibroblast growth factor 23. Additionally, we highlighted the effects of exercise on modulating these key regulators derived from bone tissue metabolism. We believe that gaining an enhanced understanding of how osteocalcin contributes to the process of atherosclerosis will enable us to develop targeted and comprehensive therapeutic strategies against diseases associated with its progression. Significance Statement: Bone is now recognized as an endocrine organ, with numerous studies demonstrating its direct effects on blood vessels and cells, as well as indirect impacts on the process of atherosclerosis. We believe that osteokines hold significant research potential in this area, and understanding their role in atherosclerosis and uncovering underlying mechanisms could lead to new therapeutic targets and improved treatment outcomes. In this review, we summarize four well‐established mechanisms through which osteokines contribute to atherosclerosis, providing valuable insights for future researchers. [ABSTRACT FROM AUTHOR]

Depression and osteoporosis are common diseases in dialysis patients. In addition, patients with osteoporosis are more susceptible to depression. Contrary to previous anti-osteoporosis agents, denosumab and romosozumab could be used in dialysis patients and have similar action mechanisms for blocking RANKL. RANKL causes bone resorption after binding RANKL, but binding with OPG leads to suppress of bone resorption. In recent mice study, inhibition of RANKL with denosumab improved depressive-like phenotype. Besides, it was found that OPG was associated with depression. Therefore, this study aimed to investigate the association of depressive symptoms with RANKL and OPG in hemodialysis patients. We conducted a cross-sectional study with a total of 172 hemodialysis patients. The participants were measured for plasma RANKL, OPG, MMP-2, and MMP-9 levels. Logistic regression analysis was performed to evaluate the effect of RANKL and OPG on the presence of depressive symptoms. The depressive symptoms were observed in 90 (52.3%) subjects. RANKL tertile 3 had negative association with BDI score (β − 4.527, 95% CI − 8.310 to − 0.743) in univariate analysis, and this association persisted even after multivariate adjustments (β − 5.603, 95% CI − 9.715 to −1.491) in linear regression. In logistic regression between RANKL tertiles and depressive symptoms, RANKL tertile 3 had significantly lower unadjusted OR (0.40, 95% CI 0.19–0.86), and multivariate-adjusted OR (0.31, 95% CI 0.12–0.82) for depressive symptoms. OPG was not significantly associated with depressive symptoms. Higher plasma RANKL concentrations were significantly associated with lower depressive symptoms in HD patients. Trial registration WHO registry, No. KCT0003281, date: January 12, 2017. [ABSTRACT FROM AUTHOR]

[Display omitted] • Osteoprotegerin (OPG) significantly upregulates during the development of obesity. • Hyperlipidaemia-induced Cbfa1 is responsible for OPG transactivation and overexpression. • Up-regulation of OPG is responsible for the adipocyte differentiation and lipid storage. • Targeting OPG by electroacupuncture improved obesity in mice. • Single blinded, randomized, sham-controlled clinical trials revealed that electroacupuncture improved obesity and suppressed OPG in patients. Adipogenesis, the process of white adipose tissue expansion, plays a critical role in the development of obesity. Osteoprotegerin (OPG), known for its role in bone metabolism regulation, emerges as a potential regulator in mediating adipogenesis during obesity onset. This study aims to elucidate the involvement of OPG in adipogenesis during the early phases of diet-induced obesity and explore its therapeutic potential in obesity management. Using a diet-induced obesity model, we investigated OPG expression patterns in adipocytes and explored the mechanisms underlying its involvement in adipogenesis. We also assessed the effects of targeted silencing of OPG and recombinant OPG administration on obesity progression and insulin resistance. Additionally, the impact of electroacupuncture treatment on OPG levels and obesity management was evaluated in both animal models and human participants. OPG expression was prominently activated in adipocytes of white adipose tissues during the early phase of diet-induced obesity. Hyperlipidemia induced Cbfa1-dependent OPG transcription, initiating and promoting adipogenesis, leading to cell-size expansion and lipid storage. Intracellular OPG physically bound to RAR and released the PPARɤ/RXR complex, activating adipogenesis-associated gene expression. Targeted silencing of OPG suppressed obesity development, while recombinant OPG administration promoted disease progression and insulin resistance in obese mice. Electroacupuncture treatment suppressed obesity development in an OPG-dependent manner and improved obesity parameters in obese human participants. OPG emerges as a key regulator in mediating adipogenesis during obesity development. Targeting OPG holds promise for the prevention and treatment of obesity, as evidenced by the efficacy of electroacupuncture treatment in modulating OPG levels and managing obesity-related outcomes. [ABSTRACT FROM AUTHOR]

Background/Aim. Chronic pulpitis (CP) is an inflammatory dental pulp disorder associated with various pathophysiological mechanisms in its origin. The aim of the study was to evaluate the changes in the pulp tissue of osteoprotegerin (OPG) and tumor necrosis factor (TNF)-α and establish their relationship with the histological changes of pulp tissue, as well as with the micromorphological changes, occurring in the mineralized tissue. Methods. The study examined the dental pulp of 41 patients with CP and 12 healthy individuals. The group of the diseased subjects was subdivided based on the presence of communication of the pulp with the oral cavity, i.e., open (n = 22) or closed (clausa) (n = 19) CP. Results. The levels of TNF-α were statistically significantly increased, while OPG levels were decreased in the pulp of patients with CP, compared to the control group. TNF-α levels were almost the same in the pulp of patients with closed CP and the control group, while values were significantly increased in those with open CP compared to control. Histopathological analysis showed a significant increase in the number of mononuclear inflammatory cells in the diseased pulp. Scanning electron microscopy showed distinct changes, which correlate with internal resorption. Conclusion. The results indicate a much greater and intensified process of root resorption in patients with closed CP, which is unassociated with dental pulp OPG and TNF-α level changes. [ABSTRACT FROM AUTHOR]

Background: Osteoprotegerin (OPG) is a secretory glycoprotein known for its involvement in bone metabolism and immune regulation. Research has extended OPG's significance in cardiovascular diseases (CVDs). Elevated OPG levels have been associated with increased cardiovascular risks, prompting interest in its role as a potential biomarker. Main Body: This study summarizes several studies that investigated the relationship between OPG levels and the incidence of CVD. The studies indicate that higher plasma levels of OPG are associated with an increased incidence of all‐cause death, cardiovascular death, and heart failure, even after adjusting for clinical confounders. Moreover, the findings suggest that OPG has the potential to serve as a predictive biomarker for adverse cardiovascular events in the patient population studied. The findings suggest that OPG could aid in risk stratification, allowing clinicians to identify high‐risk patients who might benefit from intensified preventive measures or tailored therapeutic interventions. Therefore, early identification of individuals at risk for adverse cardiovascular events could lead to improved patient outcomes and reduced disease burden. Conclusions: OPG's role in bone health and immune regulation has expanded to potential use as a biomarker for adverse cardiovascular events in stable coronary artery disease (CAD) patients. Despite limitations, its association with cardiovascular risks highlights its importance in risk assessment and personalized interventions. [ABSTRACT FROM AUTHOR]

Introduction: Adipogenesis, the process of white adipose tissue expansion, plays a critical role in the development of obesity. Osteoprotegerin (OPG), known for its role in bone metabolism regulation, emerges as a potential regulator in mediating adipogenesis during obesity onset. Objectives: This study aims to elucidate the involvement of OPG in adipogenesis during the early phases of diet-induced obesity and explore its therapeutic potential in obesity management. Methods: Using a diet-induced obesity model, we investigated OPG expression patterns in adipocytes and explored the mechanisms underlying its involvement in adipogenesis. We also assessed the effects of targeted silencing of OPG and recombinant OPG administration on obesity progression and insulin resistance. Additionally, the impact of electroacupuncture treatment on OPG levels and obesity management was evaluated in both animal models and human participants. Results: OPG expression was prominently activated in adipocytes of white adipose tissues during the early phase of diet-induced obesity. Hyperlipidemia induced Cbfa1-dependent OPG transcription, initiating and promoting adipogenesis, leading to cell-size expansion and lipid storage. Intracellular OPG physically bound to RAR and released the PPARɤ/RXR complex, activating adipogenesis-associated gene expression. Targeted silencing of OPG suppressed obesity development, while recombinant OPG administration promoted disease progression and insulin resistance in obese mice. Electroacupuncture treatment suppressed obesity development in an OPG-dependent manner and improved obesity parameters in obese human participants. Conclusion: OPG emerges as a key regulator in mediating adipogenesis during obesity development. Targeting OPG holds promise for the prevention and treatment of obesity, as evidenced by the efficacy of electroacupuncture treatment in modulating OPG levels and managing obesity-related outcomes.

BACKGROUND: Acupotomy is effective in the treatment of knee osteoarthritis, but its mechanism is not very clear. OBJECTIVE: To observe the effect of acupotomy on the apoptosis of knee chondrocytes in knee osteoarthritis rats based on osteoclast associated receptor (OSCAR)-tumor necrosis factor-associated apoptosis-inducing ligand (TRAIL)-osteoprotetin (OPG) pathway. METHODS: Twenty-seven Sprague-Dawley rats were randomly divided into normal group (n=9), model group (n=9) and acupotomy group (n=9). Rats in the normal group were routinely housed without any treatment. Animal models of knee osteoarthritis were established by knee injection of papain. Acupotomy intervention was performed 1 week after modeling, once a week for a total of three times. Relevant tests were performed at the end of the intervention. RESULTS AND CONCLUSION: The Lequesne MG behavioral scores of rats in the model group were elevated compared with the normal group (P < 0.01), while the Lequesne MG behavioral scores of rats in the acupotomy group were decreased compared with the model group (P < 0.01). Hematoxylin-eosin staining results showed that compared with the normal group, the cartilage surface of the rat’s knee joints in the model group was worn and uneven and the chondrocytes were swollen, ruptured, reduced in number, and arranged disorderly; while the cartilage surface of the rat’s knee joints in the acupotomy group was relatively smooth, and the chondrocytes were high in number and arranged in an orderly manner, with the structure basically clear. Immunohistochemical staining results showed that compared with the normal group, the positive expressions of OSCAR and TRAIL were increased in the model group (P < 0.01), while the positive expression of OPG was decreased (P < 0.01). Compared with the model group, the positive expressions of OSCAR and TRAIL in the acupotomy group were decreased (P < 0.01), while the positive expression of OPG was increased (P < 0.01). TUNEL staining results showed that compared with the normal group, the number of apoptotic cells in the model group were increased (P < 0.01); compared with the model group, the number of apoptotic cells in the acupotomy group decreased (P < 0.01). RT-qRCR and western blot results showed that compared with the normal group, the protein expressions of OSCAR, TRAIL and Bax in the model group were increased (P < 0.01), and the protein expressions of OPG and Bcl-2 were decreased (P < 0.01); compared with the model group, the protein expressions of OSCAR, TRAIL, and Bax in the acupotomy group were decreased (P < 0.01), and the protein expressions of OPG and Bcl-2 were increased (P < 0.01). To conclude, acupotomy can reduce cartilage injury of the knee joint in rats with knee osteoarthritis, which may be related to the blockage of mitochondrial pathway apoptotic signaling release by the OSCAR-TRAIL-OPG pathway. [ABSTRACT FROM AUTHOR]

Abstract Introduction Takayasu’s arteritis (TAK) patients are at an elevated risk of metabolic syndrome and cardiovascular diseases (CVD). Currently, there are no well-validated biomarkers to assess this risk in this population. Previous research in different cohorts has linked serum levels of osteoprotegerin (OPG) and its polymorphisms to accelerated atherosclerosis and a marker of poor prognosis in CVD. Thus, we assessed this protein as a potential biomarker of CVD in TAK patients. Objectives To evaluate the serum levels of OPG and its SNPs (single nucleotide polymorphisms) in TAK patients and healthy controls, and to associate these parameters with clinical data. Methods This bicentric cross-sectional study included TAK patients who were compared with healthy individuals (control group). The serum levels of OPG and the frequency of OPG SNPs [1181G > C (rs2073618), 245 A > C (rs3134069), 163T > C (rs3102735), and 209 C > T (rs3134070)] were compared between the both groups and associated with clinical data. Results In total, 101 TAK patients and 93 controls were included in the study. The serum levels of OPG (3.8 ± 1.9 vs. 4.3 ± 1.8pmol/L, respectively; P = 0.059), and its four polymorphisms were comparable between both groups. In an additional analysis of only TAK patients, serum OPG levels and its four genes were not associated with any CVD parameters, except for higher OPG levels among patients without dyslipidemia. Conclusion No significant differences were observed in serum OPG levels or in the genotype frequencies of OPG SNPs between the patient and control groups. Similarly, no correlation was found between laboratory parameters and clinical data on CVD risk in TAK patients.

Opinions on the effects of osteoprotegerin (OPG) have evolved over the years from a protein protecting the vasculature from calcification to a cardiovascular risk factor contributing to inflammation within the vascular wall. Nowadays, the link between OPG and angiotensin II (Ang II) appears to be particularly important. In this study, the endothelial function was investigated in OPG-knockout mice (B6.129.S4-OPG, OPG−) and wild-type (C57BL/6J, OPG+) mice under basic conditions and after Ang II exposure by assessing the endothelium-dependent diastolic response of aortic rings to acetylcholine in vitro. A further aim of the study was to compare the effect of Ang II on the expression of cytokines in the aortic wall of both groups of mice. Our study shows that rings from OPG− mice had their normal endothelial function preserved after incubation with Ang II, whereas those from OPG+ mice showed significant endothelial dysfunction. We conclude that the absence of OPG, although associated with a pro-inflammatory cytokine profile in the vascular wall, simultaneously protects against Ang II-induced increases in pro-inflammatory cytokines in the murine vascular wall. Our study also demonstrates that the absence of OPG can result in a decrease in the concentration of pro-inflammatory cytokines in the vascular wall after Ang II exposure. The presence of OPG is therefore crucial for the development of Ang II-induced inflammation in the vascular wall and for the development of Ang II-induced endothelial dysfunction. [ABSTRACT FROM AUTHOR]

This study aimed to determine the contribution of titanium prepared platelet-rich fibrin (T-PRF) with open flap debridement (OFD) on clinical, biochemical and radiographic measurements of periodontal regeneration. Twenty periodontitis patients with bilateral intrabony defects and stage III grade A periodontitis were included in the study. A total of 40 defects were randomly selected for OFD alone (control group, n = 20) or combined OFD+ T-PRF (test group, n = 20). Clinical and radiographic parameters (at baseline and nine months after surgery), and growth factor levels in gingival crevicular fluid (at baseline and at two, four, six, and twelve weeks after surgical treatment) were also evaluated. Considering the clinical parameters, alterations in probing pocket depth, gingival marginal level and clinical endpoint in the test regions treated with T-PRF significantly improved (P<0.05). Fibroblast growth factor-2 and platelet-derived growth factor-BB levels between the two groups in the second and fourth weeks were also significantly different (P<0.05). Furthermore, the receptor activator of nuclear factor κB ligand/osteoprotegerin ratio between the groups was significantly different in the second, fourth, sixth, and twelfth weeks (P<0.05). The bone-filling rate was also significantly greater in the test group than in the control group (P <0.001). Compared with OFD alone, combining T-PRF with the procedure was more successful with regards to clinical, radiographic, and biochemical measurements of periodontal regeneration. [ABSTRACT FROM AUTHOR]

Evidence is accumulating that osteal macrophages, in addition to bone‐resorbing osteoclasts and bone‐forming osteoblasts, participate vitally in bone remodeling process. Oncostatin M (OSM), an inflammatory cytokine belonging to interleukin‐6 superfamily, is recognized as an essential factor secreted by osteal macrophages to orchestrate bone remodeling. Osteoprotegerin (OPG) produced by osteoblasts regulates osteoclastogenesis. We have reported that bone morphogenetic protein‐4 (BMP‐4) stimulates OPG synthesis in MC3T3‐E1 osteoblast‐like cells, and that SMAD1/5/8(9), p38 mitogen‐activated protein kinase (MAPK), and p70 S6 kinase are involved in the OPG synthesis. The present study aims to investigate the effect of OSM on the synthesis of OPG stimulated by BMP‐4 in osteoblasts. OSM suppressed the release and the mRNA expression of OPG upregulated by BMP‐4 in MC3T3‐E1 cells. Neither the BMP‐4‐induced phosphorylation of SMAD1/5/9 nor that of p38 MAPK was affected by OSM. On the other hand, the phosphorylation of p70 S6 kinase stimulated by BMP‐4 was considerably suppressed by OSM. These results strongly suggest that OSM suppresses the BMP‐4‐stimulated OPG synthesis via inhibition of the p70 S6 kinase‐mediated pathway in osteoblast‐like cells. Significance Statement: Oncostatin M (OSM), a cytokine of the interleukin‐6 superfamily, modulates bone remodeling. Osteoprotegerin (OPG) secreted from osteoblasts regulates osteoclastogenesis. We previously showed that bone morphogenetic protein‐4 (BMP‐4) activates SMAD1/5/8(9), p38 mitogen‐activated protein kinase, and p70 S6 kinase, resulting in OPG synthesis in osteoblast‐like MC3T3‐E1 cells. In the present study, we investigated the effects of OSM on the BMP‐4‐induced synthesis of OPG in these cells. Our results strongly suggest that OSM suppresses OPG synthesis by inhibiting the p70 S6 kinase‐mediated pathway in osteoblasts. [ABSTRACT FROM AUTHOR]

For humans to explore and colonize the universe, both engineering and physiological obstacles must be successfully addressed. A major physiological problem is that humans lose bone rapidly in microgravity. Understanding the underlying mechanisms for this bone loss is crucial for designing strategies to ameliorate these effects. Because bone physiology is entangled with other organ systems, and bone loss is a component of human adaptation to microgravity, strategies to reduce bone loss must also account for potential effects on other systems. Here, we consider the receptors involved in normal bone remodeling and how this regulation is altered in low-gravity environments. We examine how single cells, tissues and organs, and humans as a whole are affected by low gravity, and the role of receptors that have been implicated in responses leading to bone loss. These include receptors linking cells to the extracellular matrix and to each other, alterations in the extracellular matrix associated with changes in gravity, and changes in fluid distribution and fluid behavior due to lack of gravity that may have effects on receptor-based signaling shared by bone and other regulatory systems. Inflammatory responses associated with the environment in space, which include microgravity and radiation, can also potentially trigger bone loss. [ABSTRACT FROM AUTHOR]

Background: Lung fibrosis is a chronic lung disease with a high mortality rate with only two approved drugs (pirfenidone and nintedanib) to attenuate its progression. To date, there are no reliable biomarkers to assess fibrosis development and/or treatment effects for these two drugs. Osteoprotegerin (OPG) is used as a serum marker to diagnose liver fibrosis and we have previously shown it associates with lung fibrosis as well. Methods: Here we used murine and human precision-cut lung slices to investigate the regulation of OPG in lung tissue to elucidate whether it tracks with (early) fibrosis development and responds to antifibrotic treatment to assess its potential use as a biomarker. Results: OPG mRNA expression in murine lung slices was higher after treatment with profibrotic cytokines TGFβ1 or IL13, and closely correlated with Fn and PAI1 mRNA expression. More OPG protein was released from fibrotic human lung slices than from the control human slices and from TGFβ1 and IL13-stimulated murine lung slices compared to control murine slices. This OPG release was inhibited when murine slices were treated with pirfenidone or nintedanib. OPG release from human fibrotic lung slices was inhibited by pirfenidone treatment. Conclusion: OPG can already be detected during the early stages of fibrosis development and responds, both in early- and late-stage fibrosis, to treatment with antifibrotic drugs currently on the market for lung fibrosis. Therefore, OPG should be further investigated as a potential biomarker for lung fibrosis and a potential surrogate marker for treatment effect. [ABSTRACT FROM AUTHOR]

The use of endosseous dental implants may become unfeasible in the presence of significant maxillary bone atrophy; thus, surgical techniques have been proposed to promote bone regeneration in such cases. However, such techniques are complex and may expose the patient to complications. Subperiosteal implants, being placed between the periosteum and the residual alveolar bone, are largely independent of bone thickness. Such devices had been abandoned due to the complexity of positioning and adaptation to the recipient bone site, but are nowadays witnessing an era of revival following the introduction of new acquisition procedures, new materials, and innovative manufacturing methods. We have analyzed the changes induced in gene and protein expression in C-12720 human osteoblasts by differently surface-modified TiO2 materials to verify their ability to promote bone formation. The TiO2 materials tested were (i) raw machined, (ii) electropolished with acid mixture, (iii) sand-blasted + acid-etched, (iv) AlTiColorTM surface, and (v) anodized. All five surfaces efficiently stimulated the expression of markers of osteoblastic differentiation, adhesion, and osteogenesis, such as RUNX2, osteocalcin, osterix, N-cadherin, β-catenin, and osteoprotegerin, while cell viability/proliferation was unaffected. Collectively, our observations document that presently available TiO2 materials are well suited for the manufacturing of modern subperiosteal implants. [ABSTRACT FROM AUTHOR]

Background: Osteoprotegerin (OPG) is supposed to participate in the development of atherosclerosis and cardio-cerebrovascular disease. However, the results of research on relationship between OPG and ischemic stroke (IS) are controversial. Therefore, we carried out the first systematic review and meta-analysis to evaluate prognostic effect of osteoprotegerin in patients with IS. Methods: We comprehensively searched databases of PubMed, Embase, and the Cochrane Library through 21 August 2023 to identify observational studies that evaluated effect of OPG on poor functional outcome (modified Rankin Scale [mRS] Score of 3–6) and mortality in patients with IS. Adjusted odds ratios (aOR) with a 95% confidence interval (CI) of each included study were used as much as possible to assess the pooled effect. Results: Five studies that enrolled 4,506 patients in total fulfilled our inclusion criteria. Three studies were included in the pooled analysis for each endpoint since one of the included studies had provided data on poor functional outcome as well as mortality. OPG was neither associated with poor functional outcome (aOR 1.29, 95% CI 0.90–1.85) nor with mortality (aOR 1.57, 95% CI 0.90–2.74) in patients with IS. Conclusions: There is insufficient evidence to demonstrate the correlation between OPG and mortality or poor functional outcome in IS patients. OPG cannot be applied to predict worse neurological function in IS patients based on the current evidence. [ABSTRACT FROM AUTHOR]

BACKGROUND: Osteoporosis is a disease in which bone density and structure are destroyed and fractures are caused by increased bone fragility, leading to high clinical disability and mortality rates. OBJECTIVE: To review the research progress in the role of bone immunity in physiological and pathological processes related to bone metabolism, providing ideas for the research and clinical application of bone immunity in bone diseases. METHODS: The first author searched PubMed and CNKI databases in November 2022 for relevant literature using the keywords of “osteoimmunology, immuno-skeletal interface, bone metabolism, skeletal metabolism, lymphocyte, immune factor” in English and Chinese, respectively. The time range of retrieval was mainly from January 2010 to November 2022, and a small number of classical long-term literatures were included. After reading the topic and abstract for preliminary screening and excluding repetitive studies, low-quality journals and unrelated literature, 81 documents were finally included for review. RESULTS AND CONCLUSION: Osteoimmunology refers to that bone and immune cells share the same microenvironment and interact with each other to jointly perform the “bone immune system,” which includes all cells in the bone marrow. Immuno-skeletal interface has protective effects on bone under physiological conditions, but it may lead to bone destruction under pathological conditions. Osteoprotegerin is mainly derived from B cells and can inhibit osteoclast metabolism. However, when the body is in an inflammatory state, T cells and B cells work together to promote bone resorption. In addition, interleukin-1, interleukin-6 and tumor necrosis factor-α regulate the expression of receptor activator of nuclear factor-κB ligand in vivo and affect bone metabolism. In most clinical diseases (such as rheumatoid arthritis, estrogen deficiency, HIV infection, and hyperparathyroidism), the immuno-skeletal interface interacts with the bone immune system, resulting in the regulation of bone metabolism. In terms of clinical prospect, the interaction between bone immunity and bone metabolism should be studied in order to propose new strategies for therapeutic intervention to reduce the risk of fracture. [ABSTRACT FROM AUTHOR]

Biofunctionalized hydrogels are widely used in tissue engineering for bone repair. This study examines the bone regenerative effect of the blood-derived growth factor preparation of Hypoxia Preconditioned Serum (HPS) and its fibrin-hydrogel formulation (HPS-F) on drilled defects in embryonic day 19 chick femurs. Measurements of bone-related growth factors in HPS reveal significant elevations of Osteopontin, Osteoprotegerin, and soluble-RANKL compared with normal serum (NS) but no detection of BMP-2/7 or Osteocalcin. Growth factor releases from HPS-F are measurable for at least 7 days. Culturing drilled femurs organotypically on a liquid/gas interface with HPS media supplementation for 10 days demonstrates a 34.6% increase in bone volume and a 52.02% increase in bone mineral density (BMD) within the defect area, which are significantly higher than NS and a basal-media-control, as determined by microcomputed tomography. HPS-F-injected femur defects implanted on a chorioallantoic membrane (CAM) for 7 days exhibit an increase in bone mass of 123.5% and an increase in BMD of 215.2%, which are significantly higher than normal-serum-fibrin (NS-F) and no treatment. Histology reveals calcification, proteoglycan, and collagen fiber deposition in the defect area of HPS-F-treated femurs. Therefore, HPS-F may offer a promising and accessible therapeutic approach to accelerating bone regeneration by a single injection into the bone defect site. [ABSTRACT FROM AUTHOR]

Background: Bone tissue homeostasis relies on the coordinated activity of the bone‐forming osteoblasts and bone‐resorbing osteoclasts. Osteomesopyknosis is considered a distinctive rare sclerosing skeletal disorder of unelucidated pathophysiology and presumably autosomal dominant transmission. However, the causal genes are unknown. Methods: We present a case report encompassing clinical assessments, imaging studies, and whole‐exome sequencing analysis, complemented by functional in vitro experiments. Results: This new case of osteomesopyknosis was associated with a missense ALOX5 variant predicted to induce protein misfolding and proteasomal degradation. Transfection experiments demonstrated that the variant was associated with reduced protein levels restored by proteasomal inhibition with bortezomib. Likewise, gene expression analysis showed that the mutated gene was associated with a decreased RANKL/OPG ratio, which is a critical driver of osteoclast precursor differentiation. Conclusion: Our data indicate impaired bone resorption as the underlying mechanism of this rare osteosclerosis, implicating ALOX5 pathogenic variants as potential etiological factors. [ABSTRACT FROM AUTHOR]

Objectives: Osteoprotegerin (OPG) is a member of the tumor necrosis factor receptor family involved in processes in many inflammatory states. OPG concentration is enhanced in the majority of chronic kidney disease (CKD) patients and those undergoing renal replacement therapy. The aim of the study was to assess the relation of OPG and chronic inflammation in peritoneal dialysis (PD) patients and to evaluate whether OPG concentrations in plasma and dialysate were related to plasma and dialysate levels of proinflammatory mediators (interleukin 6 (IL-6), high-sensitivity C-reactive protein (hsCRP), interleukin 33 (IL-33) and interleukin 1 receptor-like 1IL-1RL1 (IL-1RL1, sST2)). Methods: The study included 37 patients of the Peritoneal Dialysis Center, Department of Nephrology, Transplantology and Internal Medicine, Szczecin, Poland, 4–6 weeks after the onset of peritoneal dialysis therapy. During a peritoneal equilibration test, plasma (at 2 h) and dialysate (at 4 h) OPG, IL-33, 1IL-1RL1 (sST2), IL-6 and hsCRP concentrations were determined. Results: Plasma concentration of OPG did not correlate with dialysate OPG level (Rs = 0.04, p = 0.8). There was a strong positive correlation between plasma OPG concentrations and plasma IL-1RL1 (sST2) (Rs = 0.41; p = 0.01), plasma IL-6 (Rs = 0.38; p = 0.01) and plasma hsCRP (Rs = 0.35; p = 0.02). Dialysate OPG concentrations were positively associated with dialysate IL-1RL1 (sST2) (Rs = 0.37; p = 0.02) and dialysate IL-6 levels (Rs = 0.44; p = 0.005). Multivariate analysis showed that higher IL-1RL1 (sST2) (ß = +0.38, p = 0.006), higher plasma hsCRP (ß = +0.32, p = 0.02) and older age (ß = +0.35, p = 0.01) were independent determinants of higher plasma OPG concentration and that higher concentrations of dialysate IL-6 (ß = +0.37, p = 0.02) were independent determinants of higher dialysate OPG concentration. Conclusions: Both plasma and dialysate OPG levels are associated with the severity of systemic and local inflammation illustrated by the plasma and dialysate concentrations of IL-1RL1 (sST2), hsCRP and IL-6, suggesting that OPG might have a pivotal role in explaining the milieu of systemic and intraperitoneal inflammation. [ABSTRACT FROM AUTHOR]

Introduction: Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disease with poorly understood pathophysiology. Recent studies have highlighted systemic inflammation, especially the role of circulating inflammatory proteins, in ALS. Methods: This study investigates the potential causal link between these proteins and ALS. We employed a two-sample Mendelian Randomization(MR) approach, analyzing data from large-scale genome-wide association studies to explore the relationship between 91 circulating inflammatory proteins and ALS. This included various MR methods like MR Egger, weighted median, and inversevariance weighted, complemented by sensitivity analyses for robust results. Results: Significant associations were observed between levels of inflammatory proteins, including Adenosine Deaminase, Interleukin-17C, Oncostatin-M, Leukemia Inhibitory Factor Receptor, and Osteoprotegerin, and ALS risk. Consistencies were noted across different P-value thresholds. Bidirectional MR suggested that ALS risk might influence levels of certain inflammatory proteins. Discussion: Our findings, via MR analysis, indicate a potential causal relationship between circulating inflammatory proteins and ALS. This sheds new light on ALS pathophysiology and suggests possible therapeutic targets. Further research is required to confirm these results and understand the specific roles of these proteins in ALS. [ABSTRACT FROM AUTHOR]

Objective: Osteoprotegerin is a member of the tumor necrosis factor receptor superfamily. The study aimed to assess serum osteoprotegerin and endothelial dysfunction relationship in obese non-diabetic subjects. Elucidating the association linking serum osteoprotegerin level to obesity and insulin resistance. Materials and methods: Sixty obese non-diabetic subjects attending the outpatient endocrine clinic were compared with 20 controls. All subjects went through history taking, clinical examination, and anthropometric measuring. Laboratory tests included fasting blood glucose, HbA1c, HOMA-IR, lipid profile, and serum osteoprotegerin level—assessment of endothelial dysfunction measured by carotid intimal thickening and flow meter dilatation. Results: Obese subjects had significantly higher rates of insulin resistance and dyslipidemia compared with controls (P = 0.017 and 0.002, respectively). Serum osteoprotegerin levels were significantly lower in obese subjects compared with controls (P = 0.011). In obese subjects, there was a significant positive correlation between osteoprotegerin and HOMA-IR (r = 0.272; P = 0.035), whereas there was no significant correlation between OPG and endothelial dysfunction. Conclusion: The study showed that osteoprotegerin significantly decreased in obese non-diabetic individuals in comparison with control subjects. A significant positive correlation between osteoprotegerin and HOMA-IR has been reported in obese non-diabetic subjects. OPG can be considered a serum biomarker to predict insulin resistance in obese individuals. [ABSTRACT FROM AUTHOR]

Objective To study the effect of different masticatory pressures on alveolar bone remodeling in rats with orthodontic moving teeth. Methods Forty-five male SD rats aged 8 weeks were randomly divided into 3 groups: the baseline group (n=5), the soft diet group (n=20) and the hard diet group (n=20). Rats in the baseline group were sacrificed at the beginning of the experiment. The experimental rat models of right upper first molar movement were established in the soft diet group and the hard diet group. Left side of the maxillary was used as the control group. Each group was fed with corresponding diet. Five rats were sacrificed in each group on the day 3, day 5, day 7 and day 14 after orthodontic treatment respectively. Micro CT was used to measure the mesial movement distance of molar, bone volume/tissue volume (BV/TV), trabecular separation (Tb. Sp) and trabecular thickness (Tb. Th) of the alveolar bone on the pressure side. The number of osteoclasts in alveolar bone was counted after TRAP staining. In situ hybridization was used to detect the expression of RANKL and OPG. Results The amount of tooth movement was smaller on day 14 in the soft diet group than that of the hard diet group (P＜0.05). There were no significant differences in BV/TV, Tb.SP and Tb.Th between the soft diet group and the hard diet group. TRAP staining and in situ hybridization showed that the number of osteoclasts and the RANKL/OPG ratio on day 5 and day 7 were lower in the soft diet group than those of the hard diet group (P＜0.05). Conclusion The osteoclast activity in the alveolar bone on the pressure side of the orthodontic tooth is decreased and the tooth movement is inhibited under lower masticatory pressure. [ABSTRACT FROM AUTHOR]

Osteopontin (OPN) and osteoprotegerin (OPG) are glycoproteins that participate in the regulation of tissue biomineralization. The aim of the project is to verify the hypothesis that the content of OPN and OPG in the aorta walls increases with the development of atherosclerosis and that these proteins are quantitatively related to the main proteins in the extracellular arteries matrix. Quantitative and qualitative analyses of the OPN and OPG content in 101 aorta sections have been conducted. Additionally, an enzyme-linked immunosorbent assay (ELISA) test has been performed to determine the collagen types I–IV and elastin content in the tissues. Correlations between the biochemical data and patients' age/sex, atherosclerosis stages, and calcification occurrences in the tissue have been established. We are the first to report correlations between OPN or OPG and various types of collagen and elastin content (OPG/type I collagen correlation: r = 0.37, p = 0.004; OPG/type II collagen: r = 0.34, p = 0.007; OPG/type III collagen: r = 0.39, p = 0.002, OPG/type IV collagen: r = 0.27, p = 0.03; OPG/elastin: r = 0.42, p = 0.001; OPN/collagen type I: r = 0.34, p = 0.007; OPN/collagen type II: r = 0.52, p = 0.000; OPN/elastin: r = 0.61, p = 0.001). OPN overexpression accompanies calcium deposit (CA) formation with the protein localized in the calcium deposit, whereas OPG is located outside the CA. Although OPN and OPG seem to play a similar function (inhibiting calcification), these glycoproteins have different tissue localizations and independent expression regulation. The independent expression regulation presumably depends on the factors responsible for stimulating the synthesis of collagens and elastin. [ABSTRACT FROM AUTHOR]

Custom synthesis of extracellular matrix (ECM)-inspired materials for condition-specific reconstruction has emerged as a potentially translatable regenerative strategy. In skull defect reconstruction, nanoparticulate mineralized collagen glycosaminoglycan scaffolds (MC-GAG) have demonstrated osteogenic and anti-osteoclastogenic properties, culminating in the ability to partially heal in vivo skull defects without the addition of exogenous growth factors or progenitor cell loading. In an effort to reduce catabolism during early skull regeneration, we fabricated a composite material (MCGO) of MC-GAG and recombinant osteoprotegerin (OPG), an endogenous anti-osteoclastogenic decoy receptor. In the presence of differentiating osteoprogenitors, MCGO demonstrated an additive effect with endogenous OPG limited to the first 14 days of culture with total eluted and scaffold-bound OPG exceeding that of MC-GAG. Functionally, MCGO exhibited similar osteogenic properties as MC-GAG, however, MCGO significantly reduced maturation and resorptive activities of primary human osteoclasts. In a rabbit skull defect model, MCGO scaffold-reconstructed defects displayed higher mineralization as well as increased hardness and microfracture resistance compared to non-OPG functionalized MC-GAG scaffolds. The current work suggests that MCGO is a development in the goal of reaching a materials-based strategy for skull regeneration.

Abstract Background First-degree relatives (FDRs) of rheumatoid arthritis (RA) patients are known to have increased risk of developing the disease. The detection of altered bone metabolism in FDRs could be a predictor of the disease. Musculoskeletal ultrasound (MSUS) is known for its ability to detect subclinical joint inflammation in RA, but changes in FDRs are not yet described. We aimed to study serum Osteopontin (OPN) and Osteoprotegerin (OPG) levels in FDRs of RA patients as markers of altered bone metabolism in relation to clinical, laboratory and musculoskeletal ultrasound (MSUS) findings. Methods Fifty-five individuals were included, 20 had definite RA, 25 were first degree relatives (FDRs) of RA patients, and 10 healthy controls. Clinical evaluation for joint swelling/tenderness was performed for all. ESR, CRP, rheumatoid factor (RF), anti-citrullinated antibodies (ACPA), OPN, OPG, and Musculoskeletal ultrasound (MSUS) by the US7 score were evaluated. Results Osteoprotegerin was significantly higher in RA (143.89 pg/ml ± 365.47) than in FDRs (22.23 pg/ml ± 65.73; p = 0.009) and controls (6.20 pg/ml ± 12.43; p = 0.003). OPN was also higher in RA (3.66 ng/ml ± 4.20) than in FDRs (1.97 ng/ml ± 1.04) and controls (2.81 ng/ml ± 1.31), though not significant (p = 0.102). Eight of 25 FDRs (32%) had arthralgia without clinical arthritis and 17/25 (68%) were asymptomatic. FDRs with arthralgia had significantly higher ESR and CRP levels than asymptomatic FDRs (9.82 mm/h ± 4.13; p = 0.003, and 3.93 mg/l ± 3.58; p = 0.003). Osteoprotegerin was higher in FDRs than in controls, and also in those with arthralgia (51.55 pg/ml ± 114.68) than in those without (8.44 pg/ml ± 9.67), though without significant difference. OPN was higher in FDRs with arthralgia (2.09 ng/ml ± 1.19) than in asymptomatic (1.70 ng/ml ± 0.55), also without significant difference. Pathologic findings by US7 were detected in 10/25 (40%) FDRs, of which three (12%) had arthralgia and seven (28%) were asymptomatic. Conclusions The raised OPG and lower OPN in FDRs than in controls reflect an altered bone metabolism which could precede clinical disease phase. OPN and OPG could serve as markers of altered preclinical bone metabolism in FDRs of RA. US7 score might be a useful screening tool to identify ‘at-risk’ individuals.

Abstract While the relationship between circulating osteoprotegerin (OPG) and cardiovascular events is well-established in the general population, its association with cardiovascular risks in chronic kidney disease (CKD) patients remains less robust. This study hypothesized that elevated circulating OPG levels might be associated with an increased risk of major adverse cardiac events (MACE) in CKD patients, a total of 2,109 patients with CKD stages 1 through pre-dialysis 5 from the KNOW-CKD cohort were categorized into quartiles based on serum OPG levels. The primary outcome of the study was 3-point MACE, defined as a composite of nonfatal myocardial infarction, nonfatal stroke, or cardiac death. The median follow-up duration was 7.9 years. The cumulative incidence of 3-point MACE significantly varied across serum OPG levels in Kaplan–Meier curve analysis (P

Background: First-degree relatives (FDRs) of rheumatoid arthritis (RA) patients are known to have increased risk of developing the disease. The detection of altered bone metabolism in FDRs could be a predictor of the disease. Musculoskeletal ultrasound (MSUS) is known for its ability to detect subclinical joint inflammation in RA, but changes in FDRs are not yet described. We aimed to study serum Osteopontin (OPN) and Osteoprotegerin (OPG) levels in FDRs of RA patients as markers of altered bone metabolism in relation to clinical, laboratory and musculoskeletal ultrasound (MSUS) findings. Methods: Fifty-five individuals were included, 20 had definite RA, 25 were first degree relatives (FDRs) of RA patients, and 10 healthy controls. Clinical evaluation for joint swelling/tenderness was performed for all. ESR, CRP, rheumatoid factor (RF), anti-citrullinated antibodies (ACPA), OPN, OPG, and Musculoskeletal ultrasound (MSUS) by the US7 score were evaluated. Results: Osteoprotegerin was significantly higher in RA (143.89 pg/ml ± 365.47) than in FDRs (22.23 pg/ml ± 65.73; p = 0.009) and controls (6.20 pg/ml ± 12.43; p = 0.003). OPN was also higher in RA (3.66 ng/ml ± 4.20) than in FDRs (1.97 ng/ml ± 1.04) and controls (2.81 ng/ml ± 1.31), though not significant (p = 0.102). Eight of 25 FDRs (32%) had arthralgia without clinical arthritis and 17/25 (68%) were asymptomatic. FDRs with arthralgia had significantly higher ESR and CRP levels than asymptomatic FDRs (9.82 mm/h ± 4.13; p = 0.003, and 3.93 mg/l ± 3.58; p = 0.003). Osteoprotegerin was higher in FDRs than in controls, and also in those with arthralgia (51.55 pg/ml ± 114.68) than in those without (8.44 pg/ml ± 9.67), though without significant difference. OPN was higher in FDRs with arthralgia (2.09 ng/ml ± 1.19) than in asymptomatic (1.70 ng/ml ± 0.55), also without significant difference. Pathologic findings by US7 were detected in 10/25 (40%) FDRs, of which three (12%) had arthralgia and seven (28%) were asymptomatic. Conclusions: The raised OPG and lower OPN in FDRs than in controls reflect an altered bone metabolism which could precede clinical disease phase. OPN and OPG could serve as markers of altered preclinical bone metabolism in FDRs of RA. US7 score might be a useful screening tool to identify 'at-risk' individuals. [ABSTRACT FROM AUTHOR]

Purpose: Previous evidence shows that lithium chloride (LiCl), a suppressor of glycogen synthase kinase-3β (GSK-3β), may enhance bone formation in several medical and dental conditions. Thus, the purpose of the current study was to assess the effects of LiCl on extraction socket repair in rats. Methods: Thirty rats were randomly assigned into a control group (administration of water; n = 15) or a LiCl group (administration of 150 mg/kg of LiCl; n = 15). LiCl and water were given every other day, starting at 7 days before the extraction of upper first molars until the end of each experiment period. Histological sections from five rats per group were obtained at 10, 20, and 30 days post-extractions. Histometrical analysis of newly formed bone (NB) and the levels of tartrate-resistant acid phosphatase (TRAP)-stained cells were evaluated at 10, 20, and 30 days post-extractions. Immunohistochemical staining for receptor activator of nuclear factor kappa-Β ligand (RANKL), osteoprotegerin (OPG), bone sialoprotein (BSP), osteocalcin (OCN), and osteopontin (OPN) was assessed at 10 days post-extractions. Results: The LiCl group had a greater proportion of NB than the control group at 20 days (P < 0.05). At 30 days, the rate of TRAP-stained cells was lower in the LiCl group than in the control group (P < 0.05). At 10 days, the LiCl group presented stronger staining for OPG, BSP, OPN, and OCN, when compared to the control group (P < 0.05). Conclusion: Systemic LiCl enhanced extraction socket repair, stimulated an overall increase in bone formation markers, and restricted the levels of TRAP in rats. [ABSTRACT FROM AUTHOR]

While the relationship between circulating osteoprotegerin (OPG) and cardiovascular events is well-established in the general population, its association with cardiovascular risks in chronic kidney disease (CKD) patients remains less robust. This study hypothesized that elevated circulating OPG levels might be associated with an increased risk of major adverse cardiac events (MACE) in CKD patients, a total of 2,109 patients with CKD stages 1 through pre-dialysis 5 from the KNOW-CKD cohort were categorized into quartiles based on serum OPG levels. The primary outcome of the study was 3-point MACE, defined as a composite of nonfatal myocardial infarction, nonfatal stroke, or cardiac death. The median follow-up duration was 7.9 years. The cumulative incidence of 3-point MACE significantly varied across serum OPG levels in Kaplan–Meier curve analysis (P < 0.001, log-rank test), with the highest incidence observed in the 4th quartile. Cox regression analysis indicated that, relative to the 1st quartile, the risk of 3-point MACE was significantly higher in the 3rd (adjusted hazard ratio 2.901, 95% confidence interval 1.009 to 8.341) and the 4th quartiles (adjusted hazard ratio 4.347, 95% confidence interval 1.410 to 13.395). In conclusion, elevated circulating OPG levels are associated with adverse cardiovascular outcomes in pre-dialysis CKD patients. [ABSTRACT FROM AUTHOR]

Background: Studies in many populations have reported associations between circulating cytokine levels and various physiological or pathological conditions. However, the reliability of cytokine measurements in population studies, which measure cytokines in multiple assays over a prolonged period, has not been adequately examined; nor has stability during sample storage or intra-individual variation been assessed. Methods: We assessed (1) analytical reliability in short- and long-term repeated measurements; (2) stability and analytical reliability during long-term sample storage, and (3) variability within individuals over seasons, of four cytokines—osteopontin (OPN), osteoprotegerin (OPG), vascular endothelial growth factor-A (VEGF-A), and interleukin-17A (IL-17A). Measurements in plasma or serum samples were made with commercial kits according to standard procedures. Estimation was performed by fitting a random or mixed effects linear model on the log scale. Results: In repeated assays over a short period, OPN, OPG, and VEGF-A had acceptable reliability, with intra- and inter-assay coefficients of variation (CV) less than 0.11. Reliability of IL-17A was poor, with inter- and intra-assay CV 0.85 and 0.43, respectively. During long-term storage, OPG significantly decayed (− 33% per year; 95% confidence interval [− 54, − 3.7]), but not OPN or VEGF-A (− 0.3% or − 6.3% per year, respectively). Intra- and inter-assay CV over a long period were comparable to that in a short period except for a slight increase in inter-assay CV of VEGF-A. Within-individual variation was small for OPN and VEGF-A, with intra-class correlations (ICC) 0.68 and 0.83, respectively, but large for OPG (ICC 0.11). Conclusions: We conclude that OPN and VEGF-A can be reliably measured in a large population, that IL-17A is suitable only for small experiments, and that OPG should be assessed with caution due to degradation during storage and intra-individual variation. The overall results of our study illustrate the need for validation under relevant conditions when measuring circulating cytokines in population studies. [ABSTRACT FROM AUTHOR]

Background: Charcot arthropathy (CA) is a progressive noninfectious inflammatory disease that causes irreversible destruction to pedal architecture in diabetic neuropathy (DN) patients. The debilitating prognosis demands early detection to prevent the development and progression of this disorder. Dysregulated and persistent production of inflammatory cytokines is reported as the key element in initiating osteoclastogenesis in CA. The study analyzed the potential association of markers of inflammation and bone turnover of prediagnostic serum samples on CA. Methods: Seventy-one type 2 severe DN patients were selected based on inclusion-exclusion criteria. Serum samples of interleukin 6 (IL-6), osteoprotegerin (OPG), bone alkaline phosphatase (BALP), and C-reactive protein (CRP) were analyzed. These patients were followed for the development of symptoms of CA for 12 months. In the year of monitoring, 7 patients developed CA (group 1), whereas the remaining 64 patients did not develop CA (group 2). Results: The rate of development of CA in patients with severe DN was 9.8%. In this group, significantly increased median values of HbA1c (group 2: 8.00 [7.00-9.00], group 1: 10.00 [9.25-11.50], P =.013); IL-6 (group 2: 1.21 [0.72-2.16], group 1: 11.08 [6.65-63.64], P =.008); and CRP (group 2: 1.25 [0.78-3.20], group 1: 3.31 [1.18-41.33], P =.041) were found. The receiver operating characteristic analysis showed that IL-6 was more strongly associated with the onset of CA (IL-6: area under the curve = 0.808; P =.008) than CRP. Cut-off values of ≥6.6 for IL-6 show potential to rule out CA in high-risk patients, with a positive predictive value of 26.1%, a negative predictive value of 97.9%, a sensitivity of 85.7%, and a specificity of 73.4%. Conclusion: In our study population, we found that an exacerbated inflammatory state, reflected by IL-6 values, generally occurred in DN patients before the clinical detection of CA. Level of Evidence: Level II, prospective comparative study. [ABSTRACT FROM AUTHOR]

Effects of pre/postnatal 2.45 GHz continuous wave (CW), Wireless-Fidelity (Wi-Fi) Microwave (MW) irradiation on bone have yet to be well defined. The present study used biochemical and histological methods to investigate effects on bone formation and resorption in the serum and the tibia bone tissues of growing rats exposed to MW irradiation during the pre/postnatal period. Six groups were created: one control group and five experimental groups subjected to low-level different electromagnetic fields (EMF) of growing male rats born from pregnant rats. During the experiment, the bodies of all five groups were exposed to 2.45 GHz CW-MW for one hour/day. EMF exposure started after fertilization in the experimental group. When the growing male rats were 45 days old in the postnatal period, the control and five experimental groups' growing male and maternal rats were sacrificed, and their tibia tissues were removed. Maternal rats were not included in the study. No differences were observed between the control and five experimental groups in Receptor Activator Nuclear factor-kB (RANK) biochemical results. In contrast, there was a statistically significant increase in soluble Receptor Activator of Nuclear factor-kB Ligand (sRANKL) and Osteoprotegerin (OPG) for 10 V/m and 15 V/m EMF values. Histologically, changes in the same groups supported biochemical results. These results indicate that pre/postnatal exposure to 2.45 GHz EMF at 10 and 15 V/m potentially affects bone development. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to monitor changes in Osteoprotegerin (OPG) and receptor activator of nuclear factor‐kappa ligand (RANKL) levels in the saliva during orthodontic tooth movement (OTM). Materials and Methods: Nine healthy females (15–20 y of age) with four pre‐molar extractions and fixed appliance were included. In total, 134 stimulated and 134 unstimulated saliva samples were collected: at baseline and then every 6–8 weeks at follow‐up appointments during the whole orthodontic treatment. Twelve age‐matched females with no active orthodontic treatment served as a control group. Saliva samples were analysed by enzyme‐linked immunosorbent assay (Elisa). The mean levels of OPG and RANKL were calculated according to the different orthodontic treatment stages: alignment, space closure and finishing. A mixed model analysis was used to compare the means of treatment stages. Baseline OPG levels were compared with the control group using an independent t‐test. OPG levels were measured in stimulated saliva due to low levels in unstimulated saliva. Results: No significant difference was observed between baseline OPG values and the control group. OPG increased significantly at all treatment stages: alignment, space closure and finishing compared with baseline (P = 0.002, P = 0.039, P ≤ 0.001, respectively). The salivary levels of OPG increased gradually, except during space closure, reaching peak levels at finishing. RANKL was undetectable in stimulated and unstimulated saliva by sandwich Elisa during OTM. Conclusions: This novel approach shows the changes in the levels of OPG in OTM and indicates how and when to sample saliva during orthodontic treatment to analyse bone remodelling. [ABSTRACT FROM AUTHOR]

Osteoprotegerin (OPG) is a trap receptor for the receptor activator of the nuclear factor kappa B ligand (RANKL). We aimed to determine the OPG and free soluble RANKL (sRANKL) concentrations in girls during puberty and their relationships with pubertal stage, growth rate and serum concentrations of estradiol, as well as classical bone formation (N-terminal propeptide of type I collagen (PINP), bone-specific alkaline phosphatase (BALP), osteocalcin (OC)) and bone resorption (C-terminal telopeptide of type I collagen (CTX)) markers. The semi-longitudinal study involved 88 healthy girls, aged 11.8-13.2 years. Their weight and height were measured twice at one-year intervals. Pubertal stages were assessed using the Tanner (T) scale. Blood samples were taken at the first examination. Serum concentrations of OPG, sRANKL, CTX and BALP were determined by enzyme-linked immunosorbent assay, estradiol and PINP by radioimmunoassay and osteocalcin by immunoradiometric assay. The one-year increase in height and weight of girls in the T2 and T3 pubertal stages was greater than that of girls in the T4 stage (p=0.000, p<0.03). OPG concentrations (T2: 4.04±0.62; T3: 4.31±0.79; T4: 4.46±0.84 pmol/L) sRANKL concentrations (T2: 0.22 (IQR 0.09-0.54); T3: 0.42 (IQR 0.22-0.79); T4: 0.35 (IQR 0.16-1.04) pmol/L) and sRANKL/OPG ratios (T2: 0.05 (IQR 0.03-0.13); T3: 0.11 (IQR 0.05-0.19); T4: 0.09 (IQR 0.05-0.19) did not differ significantly between pubertal stages. Concentrations of PINP, CTX, BALP and OC were higher in girls at T3 stage than at the T4 stage (p=0.000, p=0.001, p=0.046, p=0.038; respectively). Concentrations of sRANKL and OPG did not correlate with body weight, height, growth rate, or concentrations of estradiol, PINP, CTX, BALP and OC. There were correlations between the increase in height over one year and the concentrations of PINP (r=0.499, p=0.000), CTX (r=0.311, p=0.003) and BALP (r=0.224, p=0.036), as well as of estradiol (r=-0.473, p=0.000). Unlike PINP, OC, BALP, CTX or estradiol concentrations, sRANKL and OPG concentrations do not change in girls during puberty. Neither OPG nor sRANKL concentrations correlate with somatic characteristics and classical bone turnover markers concentrations. [ABSTRACT FROM AUTHOR]

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This study evaluated the effect of photobiomodulation therapy (PBMT) using 660 and 808 nm diode lasers (individual and in combination) on periodontal ligament mesenchymal stem cells (PDLSCs) in the presence of zoledronic acid (ZA). PDLSCs were cultured for 48 h in DMEM complete medium containing 5 μM ZA. PBMT was done three times with a 24‐h interval in groups 1 (660 nm, 5 J/cm2), 2 (880 nm, 3 J/cm2), and 3 (660 + 808 nm) either in normal or ZA‐treated culture medium. Control groups did not receive PBMT. Twenty‐four hours post‐irradiation, cell proliferation and expression of RANKL and OPG were assessed using MTT and real‐time PCR tests, respectively. The results showed a significant decrease in cell viability in ZA‐treated cells (p < 0.001). Additionally, ZA induced the expression of OPG (p = 0.03) while reducing RANKL (p < 0.001). Cell proliferation was significantly increased in 808 and 660 + 808 nm groups. Moreover, all PBMT groups could significantly increase and decrease the RANKL and OPG, respectively, in the presence of ZA (all p < 0.001). A combination of 660 + 808 nm showed the highest effects on both genes. In conclusion, it seems that PBMT can modulate the effects of ZA by inducing PDLSC proliferation and increasing RANKL‐to‐OPG gene expression ratio. [ABSTRACT FROM AUTHOR]

Introduction: Osteoprotegerin (OPG) has recently been suggested to be involved in the pathophysiology of Parkinson's disease (PD). Aim of the research: To compare serum OPG levels in PD patients versus controls with mild headache or back pain (CG1) and acute ischaemic stroke (CG2) and evaluate the relationship between serum OPG level and 1) PD duration, 2) parathyroid hormone (PTH), vitamin D [25(OH)D], total calcium and 3) serum total cholesterol (TC), high-density lipoprotein cholesterol, low-density lipoprotein cholesterol and triglyceride levels. Material and methods: In the included 45 PD patients - 20 with initial PD (iPD) and 25 with advanced PD (aPD) and 50 controls (20 CG1, 30 CG2) - we measured serum OPG levels using a sandwich enzyme-linked immunosorbent assay and analysed data applying Student's t, Mann-Whitney, c2 tests, Pearson's correlation and linear regression analysis. Results: OPG serum level was lower in iPD compared to CG2 subjects (p = 0.026). OPG level depended on the duration of PD (p < 0.01) and TC level (p < 0.03) in PD patients, on 25(OH)D level (p < 0.04) in CG1 and on TC (p < 0.05) and PTH (p < 0.01) levels in CG2. Conclusions: Our results indicate that serum OPG level increases with PD duration and is associated with serum TC level in PD and ischaemic stroke patients. [ABSTRACT FROM AUTHOR]

Purpose (6)-Shogaol is the most prevalent bioactive compound in ginger. The aim of this study was to examine both the prophylactic and therapeutic effects of (6)-shogaol in an experimental periodontitis model. Materials and Methods Thirty-five male Wistar albino rats were divided into four groups. In the healthy group (n=5), no intervention was undertaken. In the periodontitis group (n=10), periodontitis was induced by ligature placement for 14 days. In the prophylaxis group (n=10), periodontitis was induced with ligature placement for 14 days, and during this time, 20 mg/kg/day of (6)-shogaol was administered via oral gavage. In the therapeutic group (n=10), periodontitis was induced with ligature placement for 14 days, and following the removal of the ligature, 20 mg/kg/day of (6)-shogaol was administered via oral gavage for 14 days. Alveolar bone loss was histometrically measured, and malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GP), nuclear factor kappa B (NF-κB), receptor activator of nuclear factor kappa B ligand (RANKL), and osteoprotegerin (OPG) were immunohistochemically analyzed. Results Alveolar bone loss was significantly lower in the healthy group than in the remaining groups, as well as in the therapeutic group than in the periodontitis group (p<0.001). RANKL/OPG was significantly higher in the periodontitis group compared to the remaining groups and in the prophylaxis group compared to the therapeutic group (p<0.001). MDA was significantly lower in the healthy group than in the remaining groups (p<0.001). SOD was significantly lower in the periodontitis group than in the prophylaxis and therapeutic groups (p=0.039 and p=0.042, respectively). GP was significantly lower in the healthy group than in the prophylaxis and therapeutic groups (p=0.031 and p=0.002, respectively). Conclusion The administration of (6)-shogaol modulated the RANKL/OPG balance and antioxidant status in rats with ligature-induced periodontitis. [ABSTRACT FROM AUTHOR]

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In this study, it was aimed to assess effects of subclinical hyperthyroidism (SH) on bone metabolism using osteoprotegerin (OPG), sclerostin, Dickkopf-1 (DKK1) and biochemical parameters. This cross-sectional prospective study included 40 patients with SH and 40 euthyroid controls. Serum OPG, sclerostin, DKK-1, type-1 procollagen, C-terminal polypeptide (CTx) and 24-hours urine N-terminal telopeptide (NTx) were measures using ELISA kit. Bone mineral density measurements were performed using dual energy X-ray absorptiometry (DEXA). Risk for 10-years hip and major fracture was estimated by Turkish version of FRAX. No significant difference was detected in age, gender, body mass index, smoking and menopause rates between SH and control groups. The risk for 10-years hip fracture and major osteoporotic fracture were estimated as 4.45% and 0.55% in SH group, respectively. The OPG levels were significantly lower in patients with SH than controls (P = 0.017). No significant difference was detected in other bone formation and degradation parameters. No significant correlation was detected between OPG level and risk for major osteoporotic fracture (P > 0.05); however, a negative correlation was detected between OPG level and risk for hip fracture (rho = 0.233; P = 0.038). Serum OPG is markedly affected in patients with SH. In addition, OPG seemed to be associated with osteoporotic fracture risk. Available data show that SH is significantly associated with risk for fracture; thus, it is important to assess risk for fracture in patients with SH. [ABSTRACT FROM AUTHOR]

Abstract Background Bone tissue homeostasis relies on the coordinated activity of the bone‐forming osteoblasts and bone‐resorbing osteoclasts. Osteomesopyknosis is considered a distinctive rare sclerosing skeletal disorder of unelucidated pathophysiology and presumably autosomal dominant transmission. However, the causal genes are unknown. Methods We present a case report encompassing clinical assessments, imaging studies, and whole‐exome sequencing analysis, complemented by functional in vitro experiments. Results This new case of osteomesopyknosis was associated with a missense ALOX5 variant predicted to induce protein misfolding and proteasomal degradation. Transfection experiments demonstrated that the variant was associated with reduced protein levels restored by proteasomal inhibition with bortezomib. Likewise, gene expression analysis showed that the mutated gene was associated with a decreased RANKL/OPG ratio, which is a critical driver of osteoclast precursor differentiation. Conclusion Our data indicate impaired bone resorption as the underlying mechanism of this rare osteosclerosis, implicating ALOX5 pathogenic variants as potential etiological factors.

Background: Osteoprotegerin (OPG) plays a role in preventing osteoclast formation and osteoclastic bone resorption by inhibiting the receptor activator nuclear factor-β and its ligand (RANK–RANKL) interaction that causes bone resorption. Pangasius djambal gelatin contains essential amino acids that may stimulate bone remodeling. Purpose: This study aimed to investigate the expressions of OPG, RANKL, and RANK following tooth extraction to ascertain whether OPG is associated with the RANKL and RANK ratios following gelatin induction. Methods: This study was a true experimental study with a simple, randomized post-test only control group design. Twenty-four albino rats (Rattus norvegicus) were divided into two groups (n = 4). The treatment group was treated with P. djambal gelatin following tooth extraction, while the control group was left untreated. Animal models undergoing tooth extraction were anesthetized intraperitoneally with ketamine (1,000 mg/10 ml up to 0.2 ml). The tooth was then extracted slowly so as not to break it. P. djambal gelatin was dripped (0.1 ml) into the socket after the extraction procedure. The association of OPG with RANKL and RANK immunohistochemistry expressions was evaluated after three, five, and seven days. Results: There was a significant increase in OPG expression on day 7 (P < 0.05) and a significant decrease in the expression of RANKL and RANK (P < 0.05) in the treatment group. Conclusion: The application of P. djambal gelatin could increase OPG expression, decrease RANKL and RANK expression in the socket following tooth extraction, and might be associated with the inhibition of bone resorption.

Abstract Objectives The OPG/RANKL signal pathway was important regulation mechanism of bone remodeling cycle, but the effect of osteoprotegerin (OPG) and RANKL in osteoporosis was uncertain. We did a systematic review with meta-analysis to assess the association between serum OPG/RANKL and osteoporosis. Methods The systematic search, data extraction, critical appraisal, and meta-analysis were performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Randomized controlled studies were searched in PubMed, OvidMedline, Embase (1946 to present). Standard mean difference (SMD), and associated credible interval (CI) were calculated using RevMan statistical software to assess the continuous data. Heterogeneity in studies was measured by I 2 values. Subgroup analysis was performed based on different bone turnover. Results A total of 5 randomized controlled studies met the inclusion criteria. Both OPG and RANKL had no significant differences between the osteoporosis and control group, and the statistical heterogeneity was high in meta-analysis. However, RANKL had significant differences between the osteoporosis group with low bone turnover and control group (SMD = − 1.17; 95% CI − 1.77 to 0.57; P value

Peroxisome proliferator-activated receptor gamma (PPAR-γ) modifies many cellular processes that contribute to atherosclerosis. The increased concentrations of osteoprotegerin (OPG) are related with coronary artery disease, calcification in vascular tissue, advanced atherosclerosis, and diabetic complications has been informed. The aim of our study was to define the relation among PPAR-γ Pro12Ala and, OPG and PPAR-γ in Peripheral Vascular Disease (PVD) and hypertension (HT). Also, it was aim to investigate the relationship between flow-mediated dilatation (FMD) in HT and ankle brachial index (ABI) in PVD in terms of endothelial dysfunction (ED).

Aims: Osteoporosis is characterized by decreased trabecular bone volume, and microarchitectural deterioration in the medullary cavity. Interleukin-19 (IL-19), a member of the IL-10 family, is an anti-inflammatory cytokine produced primarily by macrophages. The aim of our study was to investigate the effect of IL-19 on osteoporosis. Methods: Blood and femoral bone marrow suspension IL-19 levels were first measured in the lipopolysaccharide (LPS)-induced bone loss model. Small interfering RNA (siRNA) was applied to knock down IL-19 for further validation. Thereafter, osteoclast production was stimulated with IL-19 in combination with mouse macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor-κB ligand (RANKL). The effect of IL-19 was subsequently evaluated using tartrate-resistant acid phosphatase (TRAP) staining and quantitative real-time polymerase chain reaction (RT-qPCR). The effect of IL-19 on osteoprotegerin (OPG) was then assessed using in vitro recombinant IL-19 treatment of primary osteoblasts and MLO-Y4 osteoblast cell line. Finally, transient transfection experiments and chromatin immunoprecipitation (ChIP) experiments were used to examine the exact mechanism of action. Results: In the LPS-induced bone loss mouse model, the levels of IL-19 in peripheral blood serum and femoral bone marrow suspension were significantly increased. The in vivo results indicated that global IL-19 deletion had no significant effect on RANKL content in the serum and bone marrow, but could increase the content of OPG in serum and femoral bone marrow, suggesting that IL-19 inhibits OPG expression in bone marrow mesenchymal stem cells (BMSCs) and thus increases bone resorption. Conclusion: IL-19 promotes bone resorption by suppressing OPG expression in BMSCs in a LPS-induced bone loss mouse model, which highlights the potential benefits and side effects of IL-19 for future clinical applications. Cite this article: Bone Joint Res 2023;12(11):691–701.