RANKL/RANK/OPG Pathway: A Mechanism Involved in Exercise-Induced Bone Remodeling

Development of a BMU-on-a-chip model based on spatiotemporal regulation of cellular interactions in the bone remodeling cycle

Bone remodeling is essential for maintaining bone homeostasis throughout life by replacing old bone with new tissue. This dynamic process occurs continuously within basic multicellular unit (BMU) through well-coordinated interactions among osteocytes, osteoblasts, and osteoclasts. However, a precise in vitro model that accurately replicates this mechanism has not yet been developed. In this study, we created a human in vitro BMU-modeling chip platform by tri-culturing cells within a chip unit integrated into a tissue culture well plate, enabling high-throughput three-dimensional (3D) cell culture. To establish the tri-culture, human osteoblasts were isolated from human surgical bone samples and differentiated into osteocytes within collagen gel inside the chip unit. Subsequently, osteoblasts and peripheral blood mononuclear cells (PBMCs) containing osteoclast precursors were added to the chip unit. To simulate each phase of the bone remodeling cycle, we optimized the tri-culture process by adjusting the timing and using two types of osteoblasts at different stages of differentiation. The completed tri-culture model successfully mimicked the bone formation phase. When receptor activators of nuclear factor kappa-Β (RANKL) and macrophage colony-stimulating factor (M-CSF) were introduced, the cells exhibited characteristics of the reversal phase, where osteogenic and osteoclastogenic environments coexist. Additionally, using more differentiated osteoblasts within the tri-culture platform induced osteoclast differentiation, resembling the bone resorption phase. Overall, our model effectively replicates each phase of the bone remodeling cycle in BMUs, both spatially and temporally. This advancement not only facilitates the study of the intricate mechanisms of bone remodeling and cellular function but also aids drug development by providing a robust bone model for testing target drugs.

The protective effects of tectoridin on bone fractures against oxidative stress via the inhibition of NF-κB and apoptotic pathways in ovariectomized rats

Oxidative stress and inflammation lead to high bone turnover, contributing to osteoporosis caused by estrogen deficiency in postmenopausal women. Tectoridin, an isoflavonoid with antioxidant and anti-inflammatory properties, was evaluated for its protective effects in ovariectomized (OVX) rats, a model of postmenopausal osteoporosis. Five groups of female rats (n = 6) were established: normal, OVX control, OVX treated with tectoridin at 10 and 20 mg/kg bw, and OVX treated with estrogen, over a four-week period. Tectoridin treatment resulted in reduced body weight and improved femur weight and thickness. Serum E2, calcium, and phosphate levels increased, while alkaline phosphatase (ALP) levels decreased after treatment. Additionally, tectoridin altered lipid profiles by decreasing total cholesterol (TC), triglycerides (TG), and low-density lipoprotein (LDL), while increasing high-density lipoprotein (HDL). The treatment elevated serum bone-specific alkaline phosphatase (BALP) and procollagen type I N-terminal propeptide (PINP) levels, and decreased levels of bone resorption markers CTX-1 and NTx. Tectoridin upregulated osteogenic markers Runx2, Osx, and BMP2, suggesting enhanced bone properties. Moreover, it reduced lipid peroxidation and increased superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities, indicating reduced oxidative stress. Tectoridin also inhibited inflammatory proteins and exhibited anti-apoptotic effects on Bax/Caspase3 and Bcl2 expression. This study highlights the potential of tectoridin in modulating oxidative stress, inflammation, and improving bone remodeling in OVX rats, making it a candidate for managing postmenopausal osteoporosis.

Risk assessment and drug interruption guidelines for dentoalveolar surgery in patients with osteoporosis receiving anti-resorptive therapy

Medication-related osteonecrosis of the jaw (MRONJ) is a rare and challenging complication of anti-resorptive therapy. This review addresses the critical issue of risk management in patients with osteoporosis who require dentoalveolar surgery while undergoing anti-resorptive therapy. Dental practitioners should be aware of these risks; however, they should not refuse treatment based solely on them. This review discusses the risks through five major factors: invasive dentoalveolar surgeries, concomitant oral infection, type of medication, duration of medication, and preoperative drug discontinuation. Additionally, we discussed the local factors associated with dental practices. Our review underscored the importance of personalized risk assessment, considering each patient's unique drug history and oral condition. Based on a comprehensive literature review and clinical evidence, we proposed specific guidelines for preoperative drug interruption tailored to different anti-resorptive agents. These recommendations aimed to balance osteoporosis management by minimizing the risk of MRONJ during oral surgical interventions and bridging the knowledge gap in managing patients with osteoporosis requiring dental care. This review will allow clinicians to improve their practice and optimize patient outcomes by providing evidence-based strategies.

Structural characterization and anti-weightless bone loss activity of an anionic polysaccharide from Dictyophora indusiata

This study explores the extraction and purification of polysaccharides from Dictyophora indusiata (D. indusiata) with its antioxidant and anti-weightlessness bone loss properties. An anionic polysaccharide (SADIP) with a molecular weight of 13.42 kDa was isolated and purified from D. indusiata. SADIP consists of a glucose-based sugar chain backbone. Its backbone consists of glycosidic linkages of →4)-α-D-Glcp-(1 → and →4)-β-D-Glcp-(1→, with sulfate groups attached at the O-6 position of →4)-β-D-Glcp-(1 → residues. Side chains were α-D-Glcp-(1 → 6)-α-D-Glcp-(1 → linked at C-6 position of →4,6)-α-D-Glcp-(1 → through O-6 bonds. In vitro, SADIP scavenged up to 99.32 ± 0.24 % of 2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) radicals and 76.72 ± 0.34 % of hydroxyl radicals. In vivo, SADIP reduced malondialdehyde (MDA) levels induced by weightlessness and increased low levels of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) caused by weightlessness. Additionally, three-point mechanical bending tests and Micro-CT analysis demonstrated that SADIP has ability to alleviate bone loss induced by weightlessness. This study provides a theoretical foundation for the rational developmation of D. indusiata resources.

Remineralization Rate of Lytic Lesions of the Spine in Multiple Myeloma Patients Undergoing Radiation Therapy

Study DesignRetrospective cohort study.ObjectiveIn general, Multiple Myeloma (MM) patients are treated with systemic therapy including chemotherapy. Radiation therapy can have an important supportive role in the palliative management of MM-related osteolytic lesions. Our study aims to investigate the degree of radiation-induced remineralization in MM patients to gain a better understanding of its potential impact on bone mineral density and, consequently, fracture prevention. Our primary outcome measure was percent change in bone mineral density measured in Hounsfield Units (Δ% HU) between pre- and post-radiation measurements, compared to non-targeted vertebrae.MethodsWe included 119 patients with MM who underwent radiotherapy of the spine between January 2010 and June 2021 and who had a CT scan of the spine at baseline and between 3-24 months after radiation. A linear mixed effect model tested any differences in remineralization rate per month (βdifference) between targeted and non-targeted vertebrae.ResultsAnalyses of CT scans yielded 565 unique vertebrae (366 targeted and 199 non-targeted vertebrae). In both targeted and non-targeted vertebrae, there was an increase in bone density per month (βoverall = .04; P = .002) with the largest effect being between 9-18 months post-radiation. Radiation did not cause a greater increase in bone density per month compared to non-targeted vertebrae (βdifference = .67; P = .118).ConclusionOur results demonstrate that following radiation, bone density increased over time for both targeted and non-targeted vertebrae. However, no conclusive evidence was found that targeted vertebrae have a higher remineralization rate than non-targeted vertebrae in patients with MM.

Aging: A struggle for beneficial to overcome negative factors made by muscle and bone

Musculoskeletal health is strongly influenced by regulatory interactions of bone and muscle. Recent discoveries have identified a number of key mechanisms through which soluble factors released during exercise by bone exert positive effects on muscle and by muscle on bone. Although exercise can delay the negative effects of aging, these beneficial effects are diminished with aging. The limited response of aged muscle and bone tissue to exercise are accompanied by a failure in bone and muscle communication. Here, we propose that exercise induced beneficial factors must battle changes in circulating endocrine and inflammatory factors that occur with aging. Furthermore, sedentary behavior results in the release of negative factors impacting the ability of bone and muscle to respond to physical activity especially with aging. In this review we report on exercise responsive factors and evidence of modification occurring with aging.

OPG/RANK/RANKL Single-Nucleotide Polymorphisms in Rheumatoid Arthritis: Associations with Disease Susceptibility, Bone Mineral Density, and Clinical Manifestations in a Chinese Han Population

Objective

The osteoprotegerin (OPG)/receptor activator of nuclear factor-κB (RANK)/receptor activator of nuclear factor-κB ligand (RANKL) system plays a pivotal role in the balance between osteoblasts and osteoclasts and is closely related to the pathogenesis of rheumatoid arthritis (RA). The present study aimed to clarify the associations of OPG/RANK/RANKL gene single-nucleotide polymorphisms (SNPs) with disease susceptibility, bone mineral density (BMD), and clinical manifestations in RA patients.

Methods

A case-control study including 319 RA patients and 330 healthy controls was conducted. All subjects were genotyped for rs4355801 and rs1023968 in OPG, rs10805033 in RANK, and rs9533155 and rs875625 in RANKL. BMD and clinical manifestations were recorded.

Results

An association was found between OPG rs4355801 and risk of RA. In recessive models, the GG genotype of rs4355801 was associated with an increased risk of RA compared with the AA/AG genotypes (OR=1.679, 95% CI: 1.062-2.655, p=0.025). A correlation between RANKL rs9533155 and BMD was found in RA patients. Patients with the GG genotype (n=108) in RANKL rs9533155 had the more decreased BMD values at lumbar level 2 (t=3.424, p=0.009), lumbar level 3 (t=3.171, p=0.019), lumbar level 4 (t=4.187, p=0.001), and total lumbar levels 2-4 (t=2.989, p=0.021) compared with CC+GC genotypes. No associations were found between the OPG, RANK, and RANKL SNPs and clinical manifestations of RA (all p>0.05). Logistic regression analysis indicated that older age (OR=1.057, 95% CI: 1.017-1.099, p=0.005), higher HAQ (OR=2.786, 95% CI: 1.329-5.841, p=0.007), and GG genotype of rs9533155 (OR=3.242, 95% CI: 1.254-8.376, p=0.015) were risk factors of lumbar osteoporosis onset in RA patients.

Conclusion

In summary, OPG rs4355801 is associated with susceptibility to RA and RANKL rs9533155 GG genotype potentially contributes to decreased BMD in RA. Studies with larger sample sizes are needed to confirm the present findings.

Aerobic exercise prevents renal osteodystrophy via irisin-activated osteoblasts

Renal osteodystrophy is commonly seen in patients with chronic kidney disease (CKD) due to disrupted mineral homeostasis. Given the impaired renal function in these patients, common antiresorptive agents, including bisphosphonates, must be used with caution or even contraindicated. Therefore, an alternative therapy without renal burden to combat renal osteodystrophy is urgently needed. Here, we report that clinically relevant aerobic exercise significantly prevents high-turnover renal osteodystrophy in CKD mice and patients with CKD without compromising renal function. Mechanistically, 4-week aerobic exercise in CKD mice increased expression of skeletal muscle PPARγ coactivator-1α (PGC-1α) and circulating irisin. Both exercise and irisin administration significantly activated osteoblasts, but not osteoclasts, via integrin αvβ5, thereby conferring bone quality benefits. Removal of irisin-influenced thermogenic adipose tissues or genetic ablation of uncoupling protein 1 did not alter the irisin-conferred antiosteodystrophy effect. Importantly, in a pilot clinical study, 12-week aerobic exercise in patients with high-grade CKD significantly increased circulating irisin and prevented osteodystrophy progression, without detectable renal burden. The combination of irisin and current antiresorptive agents effectively rescued renal osteodystrophy in mice. Our work provides mechanistic insights into the role of exercise and irisin in renal osteodystrophy, and it highlights a clinically relevant, low-cost, kidney-friendly therapy for patients with this devastating disease.

Exploring the Potential of Moringa oleifera in Managing Bone Loss: Insights from Preclinical Studies

Moringa oleifera (MO) is renowned for its remarkable medicinal uses, supported by claims across various cultures and growing scientific evidence. Preclinical experimental evidence indicated that MO may effectively reduce bone loss and promote bone remodelling through its effects on osteoclasts and osteoblasts. In vivo studies demonstrated that MO enhances critical aspects of bone health, such as bone volume, trabecular thickness and overall bone density. Furthermore, MO positively influenced bone biomarkers including alkaline phosphatase and procollagen type 1 N-terminal propeptide, reflecting improved bone formation. Additionally, in vitro and ex vivo studies revealed that MO boosted bone regeneration, stimulated osteoblast activity and reduced inflammation. In terms of mechanisms, MO may modulate signalling pathways related to bone metabolism, such as BMP2, PI3K/Akt/FOXO1, p38α/MAPK14 and RANKL/RANK//OPG pathways. This evidence provides a strong foundation for future clinical research and potential therapeutic applications in managing and preventing bone loss conditions.

Review of osteokines in spinal cord injury: potential biomarkers during rehabilitation

After spinal cord injury (SCI), mechanical unloading, denervation, as well as negative changes in blood supply, inflammation state, and hormone levels produce significant negative effects on bone density, leading to a high prevalence of osteoporosis after SCI. It has been recently discovered that skeletal bone also has endocrine functions. Osteokines, secreted from bone tissue, could play multiple roles in regulating bone density, muscle mass, glucose metabolism, and functions of the central nervous system-changes in the osteokine levels after SCI have been detected. Therefore, bone density and osteokine levels should be stressed in clinical settings. Clinical treatment measures for bone loss after SCI include exercise training, physical agent therapy, acupuncture, and so on. According to previous studies, these treatments could affect the expression levels of osteokines. In conclusion, bone loss and changes in osteokines after SCI are worthy of great attention during the rehabilitation of SCI. Osteokines could become biomarkers during SCI rehabilitation, reflecting both bone density and systemic functions. This review summarized recent findings regarding bone loss after SCI, changes in osteokines, and the effect of rehabilitation therapies, with a particular emphasis on the local and systemic regulatory roles of osteokines, as well as their potential as biomarkers during SCI rehabilitation.

The antiosteoporotic effect of oxymatrine compared to testosterone in orchiectomized rats

BACKGROUND

Castration of adult male rats led to the development of osteoporosis. Oxidative stress and inflammatory factors have been identified as potential causative factors. Notably, oxymatrine (OMT) possesses potent anti-inflammatory and antioxidant activities. This study aims to elucidate the antiosteoporotic effects of OMT compared to testosterone in an orchiectomized (ORX) rat model of osteoporosis.

METHODS

A total of 60 Wistar male rats were divided into the following groups: control (CTRL), surgery + no orchiectomy (SHAM), ORX, ORX + testosterone, and ORX + OMT. Urinary deoxypyridinoline (DPD), calcium (Ca), and phosphorus (P), as well as serum testosterone, parathormone (PTH), alkaline phosphatase (ALP), osteocalcin, N-telopeptide of type I collagen (NTX I), tartrate resistance acid phosphatase (TRAP), and total Ca and P levels were evaluated. Bone was assessed for malondialdehyde (MDA), reduced glutathione (GSH), interleukin 6 (IL-6), Kelch-like ECH-associated protein 1 (Keap1), nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase 1 (HO-1) expression, and receptor activator of nuclear factor κB ligand/ osteoprotegerin (RANKL/OPG) ratio. Bone dual-energy X-ray absorptiometry (DEXA) scan and histological and immunohistochemical studies were performed.

RESULTS

Testosterone or OMT treatment ameliorated the reduced bone mineral density (BMD) and bone mineral content (BMC) in the DEXA scan and the changes in PTH and Ca levels. Compared to the ORX group, bone formation, and turnover markers were also significantly reversed in the treatment groups. Treatment with testosterone or OMT significantly reduced bone MDA, IL-6, Keap1, RANKL, and RANKL/OPG ratio, and significantly elevated bone GSH, Nrf2, and HO-1. Moreover, testosterone or OMT treatment has restored cortical bone thickness and osteocyte number and reduced bone levels of TNF-α in ORX rats. Consequently, treatment with either testosterone or OMT exhibited nearly equal therapeutic efficacy; however, neither of them could normalize the measured parameters.

CONCLUSION

OMT treatment showed equal efficacy compared to testosterone in ameliorating osteoporosis in ORX rats, possibly by improving some inflammatory and oxidative stress parameters.

Unraveling the Intricacies of OPG/RANKL/RANK Biology and Its Implications in Neurological Disorders-A Comprehensive Literature Review

The OPG/RANKL/RANK framework, along with its specific receptors, plays a crucial role in bone remodeling and the functioning of the central nervous system (CNS) and associated disorders. Recent research and investigations provide evidence that the components of osteoprotegerin (OPG), receptor activator of NF-kB ligand (RANKL), and receptor activator of NF-kB (RANK) are expressed in the CNS. The CNS structure encompasses cells involved in neuroinflammation, including local macrophages, inflammatory cells, and microglia that cross the blood-brain barrier. The OPG/RANKL/RANK trio modulates the neuroinflammatory response based on the molecular context. The levels of OPG/RANKL/RANK components can serve as biomarkers in the blood and cerebrospinal fluid. They act as neuroprotectants following brain injuries and also participate in the regulation of body weight, internal body temperature, brain ischemia, autoimmune encephalopathy, and energy metabolism. Although the OPG/RANKL/RANK system is primarily known for its role in bone remodeling, further exploring deeper into its multifunctional nature can uncover new functions and novel drug targets for diseases not previously associated with OPG/RANKL/RANK signaling.

Sensing the future: A review on emerging technologies for assessing and monitoring bone health

Bone health is crucial at all stages of life. Several medical conditions and changes in lifestyle affect the growth, structure, and functions of bones. This may lead to the development of bone degenerative disorders, such as osteoporosis, osteoarthritis, rheumatoid arthritis, etc., which are major public health concerns worldwide. Accurate and reliable measurement and monitoring of bone health are important aspects for early diagnosis and interventions to prevent such disorders. Significant progress has recently been made in developing new sensing technologies that offer non-invasive, low-cost, and accurate measurements of bone health. In this review, we have described bone remodeling processes and common bone disorders. We have also compiled information on the bone turnover markers for their use as biomarkers in biosensing devices to monitor bone health. Second, this review details biosensing technology for bone health assessment, including the latest developments in various non-invasive techniques, including dual-energy X-ray absorptiometry, magnetic resonance imaging, computed tomography, and biosensors. Further, we have also discussed the potential of emerging technologies, such as biosensors based on nano- and micro-electromechanical systems and application of artificial intelligence in non-invasive techniques for improving bone health assessment. Finally, we have summarized the advantages and limitations of each technology and described clinical applications for detecting bone disorders and monitoring treatment outcomes. Overall, this review highlights the potential of emerging technologies for improving bone health assessment with the potential to revolutionize clinical practice and improve patient outcomes. The review highlights key challenges and future directions for biosensor research that pave the way for continued innovations to improve diagnosis, monitoring, and treatment of bone-related diseases.

Biocompatibility and dimensional stability through the use of 3D-printed scaffolds made by polycaprolactone and bioglass-7: An in vitro and in vivo study

PURPOSE

This experiment aimed to observe the differences in biological properties by producing BGS-7 + PCL scaffolds with different weight fractions of BGS-7 through 3D printing and to confirm whether using the scaffold for vertical bone augmentation is effective.

MATERIALS AND METHODS

Cube-shaped bioglass (BGS-7) and polycaprolactone (PCL) scaffolds with different weight fractions (PCL alone, PCL with 15% and 30% BGS-7) are produced using 3D printing. The surface hydroxyapatite (HA) apposition, the pH change, proliferation and attachment assays, and various gene expression levels are assessed. After a 7-mm implant was inserted 3 mm into the rabbit calvaria, vertical bone augmentation is performed around the implant and inside the scaffold in four ways: scaffold only, scaffold+bone graft, bone graft only, and no graft. Sacrifice is performed at 6, 12, and 24 weeks, and the various parameters are compared radiographically and histologically.

RESULTS

HA apposition, cell proliferation, cell attachment, and expression of osteogenic genes increase as the proportion of BGS-7 increase. In the in vivo test, a higher bone-implant contact ratio, bone volume ratio, bone mineral density, and new bone area are observed when the scaffold and bone grafts were used together.

CONCLUSION

The 3D-printed scaffold, a mixture of BGS-7 and PCL, exhibit higher biological compatibility as the proportion of BGS-7 increase. Additionally, the use of scaffold is effective for vertical bone augmentation.

Molecular mechanism of bone metastasis in breast cancer

Bone metastasis is a debilitating complication that frequently occurs in the advanced stages of breast cancer. However, the underlying molecular and cellular mechanisms of the bone metastasis remain unclear. Here, we elucidate how bone metastasis arises from tumor cells that detach from the primary lesions and infiltrate into the surrounding tissue, as well as how these cells disseminate to distant sites. Specifically, we elaborate how tumor cells preferentially grow within the bone micro-environment and interact with bone cells to facilitate bone destruction, characterized as osteoclastic bone metastasis, as well as new bone matrix deposition, characterized as osteoblastic bone metastasis. We also updated the current understanding of the molecular mechanisms underlying bone metastasis and reasons for relapse in breast cancer, and also opportunities of developing novel diagnostic approaches and treatment.

Effects of COVID-19 on bone fragility: a new perspective from osteoimmunological biomarkers

Introduction

While there is an increasing understanding of COVID-19's effect on different organs, little is known about the effect of the disease on bone turnover and remodeling so far. Osteoimmunological biomarkers have been described as potential indicators of bone remodeling in inflammatory conditions, but their potential role in evaluating the effect of COVID-19 on bone fragility has not been explored so far.

Methods

The present study aims to measure the osteoimmunological biomarkers in elderly patients undergoing orthopedic surgery, to evaluate the potential effect of COVID-19 on the bone response to the surgery.

Results

In our patients, the RANKL/OPG ratio indicated an increase of bone resorption in COVID-19-positive patients, confirming a strong diagnostic and prognostic value. RANKL/OPG displays a good correlation with the bone fragility maker FGF23, indicating that this parameter is a reliable maker of bone fragility in COVID-19 patients and could provide useful and comprehensive information about inflammation-induced bone loss. Consistently, the RANKL/OPG ratio showed a good correlation also with the two inflammatory markers IL-6 and sRAGE.

Discussion

Taken together these results indicate that the use of an osteoimmunological biomarker like the RANKL/OPG ratio could provide a significant improvement in the clinical evaluation of the COVID-19 effect on bone loss. This aspect is extremely important in elderly patients undergoing orthopedic surgery, which can manifest more severe effects of COVID-19 and present an increased level of age-induced bone fragility.

Porous metal materials for applications in orthopedic field: A review on mechanisms in bone healing

Background

Porous metal materials have been widely studied for applications in orthopedic field, owing to their excellent features and properties in bone healing. Porous metal materials with different compositions, manufacturing methods, and porosities have been developed. Whereas, the systematic mechanisms on how porous metal materials promote bone healing still remain unclear.

Methods

This review is concerned on the porous metal materials from three aspects with accounts of specific mechanisms, inflammatory regulation, angiogenesis and osteogenesis. We place great emphasis on different cells regulated by porous metal materials, including mesenchymal stem cells (MSCs), macrophages, endothelial cells (ECs), etc.

Result

The design of porous metal materials is diversified, with its varying pore sizes, porosity material types, modification methods and coatings help researchers create the most experimentally suitable and clinically effective scaffolds. Related signal pathways presented from different functions showed that porous metal materials could change the behavior of cells and the amount of cytokines, achieving good influence on osteogenesis.

Conclusion

This article summarizes the current progress achieved in the mechanism of porous metal materials promoting bone healing. By modulating the cellular behavior and physiological status of a spectrum of cellular constituents, such as macrophages, osteoblasts, and osteoclasts, porous metal materials are capable of activating different pathways and releasing regulatory factors, thus exerting pivotal influence on improving the bone healing effect.

The translational potential of this article

Porous metal materials play a vital role in the treatment of bone defects. Unfortunately, although an increasing number of studies have been concentrated on the effect of porous metal materials on osteogenesis-related cells, the comprehensive regulation of porous metal materials on the host cell functions during bone regeneration and the related intrinsic mechanisms remain unclear. This review summarizes different design methods for porous metal materials to fabricate the most suitable scaffolds for bone remodeling, and systematically reviews the corresponding mechanisms on inflammation, angiogenesis and osteogenesis of porous metal materials. This review can provide more theoretical framework and innovative optimization for the application of porous metal materials in orthopedics, dentistry, and other areas, thereby advancing their clinical utility and efficacy.

Emerging role and function of Hippo-YAP/TAZ signaling pathway in musculoskeletal disorders

Hippo pathway is an evolutionarily conservative key pathway that regulates organ size and tissue regeneration by regulating cell proliferation, differentiation and apoptosis. Yes-associated protein 1 (YAP)/ WW domain-containing transcription regulator 1 (TAZ) serves as a pivotal transcription factor within the Hippo signaling pathway, which undergoes negative regulation by the Hippo pathway. The expression of YAP/TAZ affects various biological processes, including differentiation of osteoblasts (OB) and osteoclasts (OC), cartilage homeostasis, skeletal muscle development, regeneration and quality maintenance. At the same time, the dysregulation of the Hippo pathway can concurrently contribute to the development of various musculoskeletal disorders, including bone tumors, osteoporosis (OP), osteoarthritis (OA), intervertebral disc degeneration (IDD), muscular dystrophy, and rhabdomyosarcoma (RMS). Therefore, targeting the Hippo pathway has emerged as a promising therapeutic strategy for the treatment of musculoskeletal disorders. The focus of this review is to elucidate the mechanisms by which the Hippo pathway maintains homeostasis in bone, cartilage, and skeletal muscle, while also providing a comprehensive summary of the pivotal role played by core components of this pathway in musculoskeletal diseases. The efficacy and feasibility of Hippo pathway-related drugs for targeted therapy of musculoskeletal diseases are also discussed in our study. These endeavors offer novel insights into the application of Hippo signaling in musculoskeletal disorders, providing effective therapeutic targets and potential drug candidates for treating such conditions.

From Genomics to Metabolomics: Molecular Insights into Osteoporosis for Enhanced Diagnostic and Therapeutic Approaches

Osteoporosis (OP) is a prevalent skeletal disorder characterized by decreased bone mineral density (BMD) and increased fracture risk. The advancements in omics technologies-genomics, transcriptomics, proteomics, and metabolomics-have provided significant insights into the molecular mechanisms driving OP. These technologies offer critical perspectives on genetic predispositions, gene expression regulation, protein signatures, and metabolic alterations, enabling the identification of novel biomarkers for diagnosis and therapeutic targets. This review underscores the potential of these multi-omics approaches to bridge the gap between basic research and clinical applications, paving the way for precision medicine in OP management. By integrating these technologies, researchers can contribute to improved diagnostics, preventative strategies, and treatments for patients suffering from OP and related conditions.

Molecular Signaling Pathways and MicroRNAs in Bone Remodeling: A Narrative Review

Bone remodeling is an intricate process executed throughout one's whole life via the cross-talk of several cellular events, progenitor cells and signaling pathways. It is an imperative mechanism for regaining bone loss, recovering damaged tissue and repairing fractures. To achieve this, molecular signaling pathways play a central role in regulating pathological and causal mechanisms in different diseases. Similarly, microRNAs (miRNAs) have shown promising results in disease management by mediating mRNA targeted gene expression and post-transcriptional gene function. However, the role and relevance of these miRNAs in signaling processes, which regulate the delicate balance between bone formation and bone resorption, are unclear. This review aims to summarize current knowledge of bone remodeling from two perspectives: firstly, we outline the modus operandi of five major molecular signaling pathways, i.e.,the receptor activator of nuclear factor kappa-B (RANK)-osteoprotegrin (OPG) and RANK ligand (RANK-OPG-RANKL), macrophage colony-stimulating factor (M-CSF), Wnt/β-catenin, Jagged/Notch and bone morphogenetic protein (BMP) pathways in regards to bone cell formation and function; and secondly, the miRNAs that participate in these pathways are introduced. Probing the miRNA-mediated regulation of these pathways may help in preparing the foundation for developing targeted strategies in bone remodeling, repair and regeneration.

The Pathogenetic Role of RANK/RANKL/OPG Signaling in Osteoarthritis and Related Targeted Therapies

Background: Osteoarthritis (OA) is the most common degenerative joint disease and affects millions of people worldwide, particularly the elderly population. The pathophysiology of OA is complex and involves multiple factors. Methods: Several studies have emphasized the crucial role of inflammation in this process. The receptor activator of NF-κB ligand (RANKL), the receptor activator of NF-κB (RANK), and osteoprotegerin (OPG) trigger a signaling cascade that leads to the excessive production of RANKL in the serum. Conclusions: The aim of this narrative review is (i) to assess the role of the RANK/RANKL/OPG signaling pathway in the context of OA progression, focusing especially on the physiopathology and on all the mechanisms leading to the activation of the inflammatory cascade, and (ii) to evaluate all the potential therapeutic strategies currently available that restore balance to bone formation and resorption, reducing structural abnormalities and relieving pain in patients with OA.

In Vivo Effects of Biosilica and Spongin-Like Collagen Scaffolds on the Healing Process in Osteoporotic Rats

Due to bioactive properties, introducing spongin-like collagen (SPG) into the biosilica (BS) extracted from marine sponges would present an enhanced biological material for improving osteoporotic fracture healing by increasing bone formation rate. Our aim was to characterize the morphology of the BS/SPG scaffolds by scanning electron microscopy (SEM), the chemical bonds of the material by Fourier transform infrared spectroscopy (FTIR), and evaluating the orthotopic in vivo response of BS/SPG scaffolds in tibial defects of osteoporotic fractures in rats (histology, histomorphometry, and immunohistochemistry) in two experimental periods (15 and 30 days). SEM showed that scaffolds were porous, showing the spicules of BS and fibrous aspect of SPG. FTIR showed characteristic peaks of BS and SPG. For the in vivo studies, after 30 days, BS and BS/SPG showed a higher amount of newly formed bone compared to the first experimental period, observed both in the periphery and in the central region of the bone defect. For histomorphometry, BS/SPG presented higher %BV/TV compared to the other experimental groups. After 15 days, BS presented higher volumes of collagen type I. After 30 days, all groups demonstrated higher volumes of collagen type III compared to volumes at 15 days. After 30 days, BS/SPG presented higher immunostaining of osteoprotegerin compared to the other experimental groups at the same experimental period. The results showed that BS and BS/SPG scaffolds were able to improve bone healing. Future research should focus on the effects of BS/SPG on longer periods in vivo studies.

Donor Sex and Passage Conditions Influence MSC Osteogenic Response in Mineralized Collagen Scaffolds

Contemporary tissue engineering efforts often seek to use mesenchymal stem cells (MSCs) due to their multi-potent potential and ability to generate a pro-regenerative secretome. While many have reported the influence of matrix environment on MSC osteogenic response, few have investigated the effects of donor and sex. Here, a well-defined mineralized collagen scaffold is used to study the influence of passage number and donor-reported sex on MSC proliferation and osteogenic potential. A library of bone marrow and adipose tissue-derived stem cells from eight donors to examine donor viability in osteogenic capacity in mineralized collagen scaffolds is obtained. MSCs displayed reduced proliferative capacity as a function of passage duration. Further, MSCs showed significant sex-associated variability in osteogenic capacity. Notably, MSCs from male donors displayed significantly higher cell proliferation while MSCs from female donors displayed significantly higher osteogenic response via increased alkaline phosphate activity, osteoprotegerin release, and mineral formation in vitro. The study highlights the essentiality of including donor-reported sex as an experimental variable and reporting culture expansion in future studies of biomaterial regenerative potential.

Effects and Mechanisms of Polyunsaturated Fatty Acids on Age-Related Musculoskeletal Diseases: Sarcopenia, Osteoporosis, and Osteoarthritis-A Narrative Review

Background: The process of the globally aging population has been accelerating, leading to an increasing social burden. As people age, the musculoskeletal system will gradually go through a series of degenerative and loss of function and eventually develop age-related musculoskeletal diseases, like sarcopenia, osteoporosis, and osteoarthritis. On the other hand, several studies have shown that polyunsaturated fatty acids (PUFAs) possess various important physiological functions on the health of muscles, bones, and joints. Objective: This narrative review paper provides a summary of the literature about the effects and mechanisms of PUFAs on age-related musculoskeletal diseases for the prevention and management of these diseases. Methods: Web of Science, PubMed, Science Direct, and Scopus databases have been searched to select the relevant literature on epidemiological, cellular, and animal experiments and clinical evidence in recent decades with keywords "polyunsaturated fatty acids", "PUFAs", "omega-3", "omega-6", "musculoskeletal diseases", "sarcopenia", "osteoporosis", "osteoarthritis", and so on. Results: PUFAs could prevent and treat age-related musculoskeletal diseases (sarcopenia, osteoporosis, and osteoarthritis) by reducing oxidative stress and inflammation and controlling the growth, differentiation, apoptosis, and autophagy of cells. This review paper provides comprehensive evidence of PUFAs on age-related musculoskeletal diseases, which will be helpful for exploitation into functional foods and drugs for their prevention and treatment. Conclusions: PUFAs could play an important role in the prevention and treatment of sarcopenia, osteoporosis, and osteoarthritis.

Morinda officinalis polysaccharide boosts osteogenic differentiation of bone marrow mesenchymal stem cells by Wnt/β-catenin signaling

OBJECTIVES

To investigate the role of Morinda officinalis polysaccharide (MOP) in the protein expression of the Wnt/β-catenin signaling cascade during the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), and to elucidate the mechanisms by which MOP enhances osteogenic differentiation at the cellular level.

METHODS

BMSCs were isolated and cultured using the whole bone marrow adherence method, followed by flow cytometry for the detection of BMSC marker antigens. Two groups were prepared: a low-dose MOP (L-MOP, 10 µg/mL) group and a high-dose MOP (H-MOP, 40 µg/mL) group. MTT assays and cell clone formation assays were performed to evaluate the effects of different MOP doses on BMSC proliferation. Alizarin red staining (ARS) and alkaline phosphatase (ALP) staining were conducted to assess the impact of varying MOP doses on nodule calcification and ALP activity in BMSCs. Additionally, western blot assays were carried out to determine the effects of different MOP concentrations on the expression levels of osteogenesis-related factors and Wnt/β-catenin pathway proteins in BMSCs.

RESULTS

Highly purified BMSCs were successfully extracted. Subsequent assays demonstrated that BMSCs exhibited enhanced proliferation at all MOP doses, particularly at the H-MOP dose, compared to the control group. Both L-MOP and H-MOP increased calcium content and ALP activity in BMSCs, as well as elevated the expression of osteogenic factors and Wnt/β-catenin pathway proteins compared to the blank control group. However, the addition of Dickkopf-1 (DKK1) significantly reduced BMSC proliferation and osteogenic differentiation compared to the H-MOP group.

CONCLUSIONS

MOP can enhance BMSC proliferation and osteogenic differentiation by activating the Wnt/β-catenin signaling pathway.

Biological Functions of Macromolecular Protein Hydrogels in Constructing Osteogenic Microenvironment

Irreversible bone defects resulting from trauma, infection, and degenerative illnesses have emerged as a significant health concern. Structurally and functionally controllable hydrogels made by bone tissue engineering (BTE) have become promising biomaterials. Natural proteins are able to establish connections with autologous proteins through unique biologically active regions. Hydrogels based on proteins can simulate the bone microenvironment and regulate the biological behavior of stem cells in the tissue niche, making them candidates for research related to bone regeneration. This article reviews the biological functions of various natural macromolecular proteins (such as collagen, gelatin, fibrin, and silk fibroin) and highlights their special advantages as hydrogels. Then the latest research trends on cross-linking modified macromolecular protein hydrogels with improved mechanical properties and composite hydrogels loaded with exogenous micromolecular proteins have been discussed. Finally, the applications of protein hydrogels, such as 3D printed hydrogels, microspheres, and injectable hydrogels, were introduced, aiming to provide a reference for the repair of clinical bone defects.

Does Physical Exercise Ameliorate Chronic Kidney Disease-Related Complications? The Case of Anaemia and Chronic Kidney Disease-Mineral Bone Disorder

BACKGROUND

Physical exercise (PE) can regulate inflammation, cardiovascular health, sarcopenia, anaemia, and bone health in the chronic kidney disease (CKD) population. Experimental and clinical studies both help us better understand the mechanisms that underlie the beneficial effects of the exercise, especially in renal anaemia and CKD-mineral bone disorders (CKD-MBDs). Here, we summarize this evidence, exploring the biological pathways involved, locally released substances, and crosstalk between tissues, but also the shortcomings of current knowledge.

SUMMARY

Anaemia: Both in healthy and CKD subjects, PE may mimic hypoxia, inhibiting PHDs; so hydroxylate HIF-α subunits may be translocated into the nucleus, resulting in dimerization of HIF-1α and HIF-1β, recruitment of p300 and CBP, and ultimately, binding to HREs at target genes to cause activation. However, in CKD subjects acute PE causes higher levels of lactate, leading to iron restriction by upregulating hepatic hepcidin expression, while chronic PE allows an increased lactate clearance and HIF-α and VEGFα levels, stimulating both erythropoiesis and angiogenesis.

CKD-MBD

PE may improve bone health decreasing bone resorption and increasing bone formation throughout at least three main pathways: (a) increasing osteoprotegerin and decreasing RANKL system; (b) decreasing cytokine levels; and (c) stimulating production of myokines and adipokines.

KEY MESSAGES

Future research needs to be defined to develop evidence-based exercise guidance to provide optimal benefit for CKD using exercise interventions as adjuvant therapy for CKD-related complications such as anaemia and CKD-MBD.

High-intensity interval training mitigates the progression of periodontitis and improves behavioural aspects in rats

AIM

To investigate the effects of high-intensity interval training (HIIT) on periodontitis (PD) progression and behavioural outcomes.

MATERIALS AND METHODS

Forty-eight Wistar rats were divided into four groups: non-trained (NT); non-trained with PD; HIIT with PD; and HIIT. The HIIT protocol, involving daily treadmill sessions, spanned 8 weeks, with PD induced by ligature after the 6th week. Behavioural tests were conducted to assess anxiety and memory. Post euthanasia, we evaluated the systemic inflammatory profile and oxidative stress markers in the hippocampus and amygdala. A morphological evaluation and elemental composition analysis of the mandibular alveolar bone were performed.

RESULTS

PD exacerbated alveolar bone level, bone surface damage and alterations in calcium and phosphorus percentages on the bone surface (p < .05), while HIIT attenuated these changes (p < .05). HIIT improved systemic inflammatory markers altered by PD (tumour necrosis factor [TNF]-α, interleukin [IL]-10, TNF-α/IL-10 and IL-1β/IL-10 ratios, p < .05). PD animals exhibited lower total antioxidant capacity and levels of thiobarbituric acid reactive substances in the amygdala and hippocampus, respectively (p < .05). HIIT maintained these parameters at levels similar to those in NT animals. HIIT improved anxiety and memory outcomes altered by PD (p < .05).

CONCLUSIONS

HIIT attenuates systemic inflammation, anxiety and memory outcomes promoted by PD.

Local and Systemic Peptide Therapies for Soft Tissue Regeneration: A Narrative Review

Background: The musculoskeletal system, due to inherent structure and function, lends itself to contributing toward joint pain, whether from inflammatory disorders such as rheumatoid arthritis, degenerative diseases such as osteoarthritis, or trauma causing soft tissue injury. Administration of peptides for treatment of joint pain or inflammation is an emerging line of therapy that seeks to offer therapeutic benefits while remaining safe and relatively non-invasive. Purpose: The purpose of this study is to review the current literature on existing oral peptide agents, intra-articular peptide agents, and new developments in human trials to assess route of administration (RoA) for drug delivery in terms of soft tissue regeneration. Study Design: Narrative Review. Methods: A comprehensive literature search was conducted using the PubMed database. The search included medical subject headings (MeSH) terms related to peptide therapy, soft tissue regeneration, and RoA. Inclusion criteria comprised articles focusing on the mechanisms of action of peptides, clinical or biochemical outcomes, and review articles. Exclusion criteria included insufficient literature or studies not meeting the set evidence level. Conclusion: The review identified various peptides demonstrating efficacy in soft tissue repair. Oral and intra-articular peptides showed distinct advantages in soft tissue regeneration, with intra-articular routes providing localized effects and oral routes offering systemic benefits. However, both routes have limitations in bioavailability and absorption. Still in their infancy, further inquiries/research into the properties and efficacy of emerging peptides will be necessary before widespread use. As a viable alternative prior to surgical intervention, peptide treatments present as promising candidates for positive outcomes in soft tissue regeneration.

Consumption of Phytoestrogens Affects Bone Health by Regulating Estrogen Metabolism

Osteoporosis is a significant concern in bone health, and understanding its pathomechanism is crucial for developing effective prevention and treatment strategies. This article delves into the relationship between estrogen metabolism and bone mineralization, shedding light on how phytoestrogens can influence this intricate process. Estrogen, a hormone primarily associated with reproductive health, plays a pivotal role in maintaining bone density and structure. The article explores the positive effects of estrogen on bone mineralization, highlighting its importance in preventing conditions like osteoporosis. Phytoestrogens, naturally occurring compounds found in certain plant-based foods, are the focal point of the discussion. These compounds have the remarkable ability to mimic estrogen's actions in the body. The article investigates how phytoestrogens can modulate the activity of estrogen, thereby impacting bone health. Furthermore, the article explores the direct effects of phytoestrogens on bone mineralization and structure. By regulating estrogen metabolism, phytoestrogens can contribute to enhanced bone density and reduced risk of osteoporosis. Finally, the article emphasizes the role of plant-based diets as a source of phytoestrogens. By incorporating foods rich in phytoestrogens into one's diet, individuals may potentially bolster their bone health, adding a valuable dimension to the ongoing discourse on osteoporosis prevention. In conclusion, this article offers a comprehensive overview of 137 positions of literature on the intricate interplay between phytoestrogens, estrogen metabolism, and bone health, shedding light on their potential significance in preventing osteoporosis and promoting overall well-being.

The effect of cannabinoids on single-level lumbar arthrodesis outcomes in a rat model

BACKGROUND CONTEXT

The opioid epidemic is a public health crisis affecting spine care and pain management. Medical marijuana is a potential nonopioid analgesic yet to be studied in the surgical setting since its effects on bone healing are not fully understood. Studies have demonstrated analgesic and potentially osteoinductive properties of cannabinoids with endocannabinoid receptor expression in bone tissue.

PURPOSE

We hypothesize that tetrahydrocannabinol (THC) and cannabidiol (CBD) will not decrease bone healing in spinal fusion.

STUDY DESIGN

Seventy-eight adult Sprague-Dawley rats were used for this study. Utilizing allogenic bone grafts (6 donor rats), posterolateral inter-transverse lumbar fusion at the L4-L5 level was performed. The animals were equally divided into four treatment groups, each receiving 0.1 ml intraperitoneal injections weekly as follows: placebo (saline), 5 mg/kg THC, 5 mg/kg CBD, and a combination of 5 mg/kg THC and 5mg/kg CBD (Combo).

METHODS

Callus tissue was harvested 2- and 8-weeks postsurgery for qPCR assessment to quantify changes in the expression of osteogenic genes. Manual palpation was done to assess the strength of the L4-L5 arthrodesis on all rats. μCT image-based callus analysis and histology were performed. One-way ANOVA followed by post hoc comparisons was performed.

RESULTS

μCT demonstrated no significant differences. Treatment groups had slightly increased bone volume and density compared to control. qPCR at 2 weeks indicated downregulated RANKL/OPG ratios skewing towards osteogenesis in the CBD group, with the THC and CBD+THC groups demonstrating a downward trend (p>.05). ALPL, BMP4, and SOST were significantly higher in the CBD group, with CTNNB1 and RUNX2 also showing an upregulating trend. The CBD group showed elevation in Col1A1 and MMP13. Data at eight weeks showed ALPL, RUNX2, BMP4, and SOST were downregulated for all treatment groups. In the CBD+THC group, RANK, RANKL, and OPG were downregulated. OPG downregulation reached significance for the THC and CBD+THC group compared to saline. Interestingly, the RANKL/OPG ratio showed upregulation in the CBD and CBD+THC groups. RANKL showed upregulation in the CBD group. At 2 and 8 weeks, the CBD treatment group showed superior histological progression, increasing between time points.

CONCLUSION

This study demonstrates that CBD and THC have no adverse effect on bone healing and the rate of spinal fusion in rats. Osteogenic factors were upregulated in the CBD-treated groups at 2 weeks, which indicates a potential for bone regeneration. In this group, compared to control, the RANKL/OPG ratio at the early healing phase demonstrates the inhibition of osteoclast differentiation, enhancing bone formation. Interestingly, it shows promoted osteoclast differentiation at the later healing phase, enhancing bone remodeling. This aligns with the physiological expectation of a lower ratio in the early phases and a higher ratio in the later remodeling phases.

CLINICAL SIGNIFICANCE

CBD and THC showed no inhibitory effects on bone healing in a spinal fusion model. Moreover, histologic and gene expression analysis demonstrated that CBD may, in fact, enhance bone healing. Further research is needed to confirm the safe usage of THC and CBD in the postoperative setting following spinal fusions.

Role of osteokines in atherosclerosis

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.

Irisin as an agent for protecting against osteoporosis: A review of the current mechanisms and pathways

BACKGROUND

Osteoporosis is recognized as a skeletal disorder characterized by diminished bone tissue quality and density. Regular physical exercise is widely acknowledged to preserve and enhance bone health, but the detailed molecular mechanisms involved remain unclear. Irisin, a factor derived from muscle during exercise, influences bone and muscle. Since its discovery in 2012, irisin has been found to promote bone growth and reduce bone resorption, establishing a tangible link between muscle exertion and bone health. Consequently, the mechanism by which irisin prevents osteoporosis have attracted significant scientific interest.

AIM OF THE REVIEW

This study aims to elucidate the multifaceted relationship between exercise, irisin, and bone health. Focusing on irisin, a muscle-derived factor released during exercise, we seek to understand its role in promoting bone growth and inhibiting resorption. Through a review of current research article on irisin in osteoporosis, Our review provides a deep dive into existing research on influence of irisin in osteoporosis, exploring its interaction with pivotal signaling pathways and its impact on various cell death mechanisms and inflammation. We aim to uncover the molecular underpinnings of how irisin, secreted during exercise, can serve as a therapeutic strategy for osteoporosis.

KEY SCIENTIFIC CONCEPTS OF THE REVIEW

Irisin, secreted during exercise, plays a vital role in bridging muscle function to bone health. It not only promotes bone growth but also inhibits bone resorption. Specifically, Irisin fosters osteoblast proliferation, differentiation, and mineralization predominantly through the ERK, p38, and AMPK signaling pathways. Concurrently, it regulates osteoclast differentiation and maturation via the JNK, Wnt/β-catenin and RANKL/RANK/OPG signaling pathways. This review further delves into the profound significance of irisin in osteoporosis and its involvement in diverse cellular death mechanisms, including apoptosis, autophagy, ferroptosis, and pyroptosis.

Applications of Bioactive Strontium Compounds in Dentistry

Divalent cations have captured the interest of researchers in biomedical and dental fields due to their beneficial effects on bone formation. These metallic elements are similar to trace elements found in human bone. Strontium is a divalent cation commonly found in various biomaterials. Since strontium has a radius similar to calcium, it has been used to replace calcium in many calcium-containing biomaterials. Strontium has the ability to inhibit bone resorption and increase bone deposition, making it useful in the treatment of osteoporosis. Strontium has also been used as a radiopacifier in dentistry and has been incorporated into a variety of dental materials to improve their radiopacity. Furthermore, strontium has been shown to improve the antimicrobial and mechanical properties of dental materials, promote enamel remineralization, alleviate dentin hypersensitivity, and enhance dentin regeneration. The objective of this review is to provide a comprehensive review of the applications of strontium in dentistry.

Converging Mechanisms of Vascular and Cartilaginous Calcification

Physiological calcification occurs in bones and epiphyseal cartilage as they grow, whereas ectopic calcification occurs in blood vessels, cartilage, and soft tissues. Although it was formerly thought to be a passive and degenerative process associated with aging, ectopic calcification has been identified as an active cell-mediated process resembling osteogenesis, and an increasing number of studies have provided evidence for this paradigm shift. A significant association between vascular calcification and cardiovascular risk has been demonstrated by various studies, which have shown that arterial calcification has predictive value for future coronary events. With respect to cartilaginous calcification, calcium phosphate or hydroxyapatite crystals can form asymptomatic deposits in joints or periarticular tissues, contributing to the pathophysiology of osteoarthritis, rheumatoid arthritis, ankylosing spondylitis, tendinitis, and bursitis. The risk factors and sequence of events that initiate ectopic calcification, as well as the mechanisms that prevent the development of this pathology, are still topics of debate. Consequently, in this review, we focus on the nexus of the mechanisms underlying vascular and cartilaginous calcifications, trying to circumscribe the similarities and disparities between them to provide more clarity in this regard.

Investigating the Effects and Mechanisms of Combined Vitamin D and K Supplementation in Postmenopausal Women: An Up-to-Date Comprehensive Review of Clinical Studies

Aging is a complex process and a significant risk factor for chronic diseases. Menopause, a component of aging in women, is associated with several important cardiometabolic conditions including metabolic syndrome, osteoporosis, and cardiovascular diseases. Menopausal women could benefit from preventative strategies that may decrease morbidity and mortality and improve their quality of life. Vitamins D and K are essential nutrients required for bone health, immune function, and reducing cardiovascular risks, yet their synergistic effect is less understood in aging women. This is the first comprehensive review to summarize the evidence found in randomized clinical trials of the beneficial effects of vitamin D and K co-treatment in postmenopausal women. In our literature search across key electronic databases such as Cochrane, PubMed, and Ovid, we identified 31 pertinent studies. Overall, significant findings indicate that the combined intake of vitamins D and K may positively affect cardiovascular and bone health in postmenopausal women, emphasizing the importance of maintaining a healthy diet rich in vegetables and fermented dairy products. Given the challenges in obtaining all necessary nutrients solely through the diet, vitamin D and K supplements are recommended for postmenopausal women to promote healthy aging and well-being.

PM2.5 exposure inhibits osteoblast differentiation by increasing the ubiquitination and degradation of Smad4

Increasing epidemiological evidence has shown that PM2.5 exposure is significantly associated with the occurrence of osteoporosis. It has been well demonstrated that PM2.5 exposure enhanced the differentiation and function of osteoclasts by indirectly causing chronic inflammation, while the mechanism in osteoblasts remains unclear. In our study, toxic effects were evaluated by direct exposure of 20-80 μg/ml PM2.5 to MC3T3-E1 cells and BMSCs. The results showed that PM2.5 exposure did not affect cell viability via proliferation and apoptosis, but significantly inhibited osteoblast differentiation in a dose-dependent manner. Osteogenic transcription factors Runx2 and Sp7 and other biomarkers Alp and Ocn decreased after PM2.5 exposure. RNA-seq revealed TGF-β signaling was involved in PM2.5 exposure inhibited osteoblast differentiation, which led to P-Smad1/5 and P-Smad2 reduction in the nucleus by increasing the ubiquitination and degradation of Smad4. At last, the inflammation response increased in MC3T3-E1 cells with PM2.5 exposure. Moreover, the mRNA levels of Mmp9 increased in bone marrow-derived macrophage cells treated with the conditional medium collected from MC3T3-E1 cells exposed to PM2.5. Overall, these results indicated that PM2.5 exposure inhibits osteoblast differentiation and concurrently increases the maturation of osteoclasts. Our study provides in-depth mechanistic insights into the direct impact of PM2.5 exposure on osteoblast, which would indicate the unrecognized role of PM2.5 on osteoporosis.

Sex-Specific Effects of THRβ Signaling on Metabolic Responses to High Fat Diet in Mice

Thyroid hormone (TH) plays a crucial role in regulating the functions of both bone and adipose tissue. Given that TH exerts its cholesterol-lowering effects in hepatic tissue through the TH receptor-β (TRβ), we hypothesized that TRβ agonist therapy using MGL3196 (MGL) would be effective in treating increased adiposity and bone loss in response to a 12-week high-fat diet (HFD) in adult C57BL/6J mice. Transcriptional and serum profiling revealed that HFD-induced leptin promoted weight gain in both males and females, but MGL only suppressed leptin induction and weight gain in males. In vitro studies suggest that estrogen suppresses MGL activity in adipocytes, indicating that estrogen might interfere with MGL-TRβ function. Compared to systemic adiposity, HFD reduced bone mass in male but not female mice. Paradoxically, MGL treatment reversed macroscopic bone mineral density loss in appendicular bones, but micro-CT revealed that MGL exacerbated HFD-induced trabecular bone loss, and reduced bone strength. In studies on the mechanisms for HFD effects on bone, we found that HFD induced Rankl expression in male femurs that was blocked by MGL. By ex vivo assays, we found that RANKL indirectly represses osteoblast lineage allocation of osteoprogenitors by induction of inflammatory cytokines TNFα, IL-1β, and CCL2. Finally, we found that MGL functions in both systemic adiposity and bone by nongenomic TRβ signaling, as HFD-mediated phenotypes were not rescued in TRβ147F knockout mice with normal genomic but defective nongenomic TRβ signaling. Our findings demonstrate that the negative effects of HFD on body fat and bone phenotypes are impacted by MGL in a gender-specific manner.

NOX4 and its association with myeloperoxidase and osteopontin in regulating endochondral ossification

IMPORTANCE

Endochondral ossification plays an important role in skeletal development. Recent studies have suggested a link between increased intracellular reactive oxygen species (ROS) and skeletal disorders. Moreover, previous studies have revealed that increasing the levels of myeloperoxidase (MPO) and osteopontin (OPN) while inhibiting NADPH oxidase 4 (NOX4) can enhance bone growth. This investigation provides further evidence by showing a direct link between NOX4 and MPO, OPN in bone function.

OBJECTIVE

This study investigates NOX4, an enzyme producing hydrogen peroxide, in endochondral ossification and bone remodeling. NOX4's role in osteoblast formation and osteogenic signaling pathways is explored.

METHODS

Using NOX4-deficient (NOX4-/-) and ovariectomized (OVX) mice, we identify NOX4's potential mediators in bone maturation.

RESULTS

NOX4-/- mice displayed significant differences in bone mass and structure. Compared to the normal Control and OVX groups. Hematoxylin and eosin staining showed NOX4-/- mice had the highest trabecular bone volume, while OVX had the lowest. Proteomic analysis revealed significantly elevated MPO and OPN levels in bone marrow-derived cells in NOX4-/- mice. Immunohistochemistry confirmed increased MPO, OPN, and collagen II (COLII) near the epiphyseal plate. Collagen and chondrogenesis analysis supported enhanced bone development in NOX4-/- mice.

CONCLUSIONS AND RELEVANCE

Our results emphasize NOX4's significance in bone morphology, mesenchymal stem cell proteomics, immunohistochemistry, collagen levels, and chondrogenesis. NOX4 deficiency enhances bone development and endochondral ossification, potentially through increased MPO, OPN, and COLII expression. These findings suggest therapeutic implications for skeletal disorders.

Inflammation-Responsive Mesoporous Silica Nanoparticles with Synergistic Anti-inflammatory and Joint Protection Effects for Rheumatoid Arthritis Treatment

PURPOSE

Joint destruction is a major burden and an unsolved problem in rheumatoid arthritis (RA) patients. We designed an intra-articular mesoporous silica nanosystem (MSN-TP@PDA-GlcN) with anti-inflammatory and joint protection effects. The nanosystem was synthesized by encapsulating triptolide (TP) in mesoporous silica nanoparticles and coating it with pH-sensitive polydopamine (PDA) and glucosamine (GlcN) grafting on the PDA. The nano-drug delivery system with anti-inflammatory and joint protection effects should have good potency against RA.

METHODS

A template method was used to synthesize mesoporous silica (MSN). MSN-TP@PDA-GlcN was synthesized via MSN loading with TP, coating with PDA and grafting of GlcN on PDA. The drug release behavior was tested. A cellular inflammatory model and a rat RA model were used to evaluate the effects on RA. In vivo imaging and microdialysis (MD) system were used to analyze the sustained release and pharmacokinetics in RA rats.

RESULTS

TMSN-TP@PDA-GlcN was stable, had good biocompatibility, and exhibited sustained release of drugs in acidic environments. It had excellent anti-inflammatory effects in vitro and in vivo. It also effectively repaired joint destruction in vivo without causing any tissue toxicity. In vivo imaging and pharmacokinetics experiments showed that the nanosystem prolonged the residence time, lowered the Cmax value and enhanced the relative bioavailability of TP.

CONCLUSIONS

These results demonstrated that MSN-TP@PDA-GlcN sustained the release of drugs in inflammatory joints and produced effective anti-inflammatory and joint protection effects on RA. This study provides a new strategy for the treatment of RA.

Comparative Analysis of Myokines and Bone Metabolism Markers in Prepubertal Vegetarian and Omnivorous Children

The role of bone and muscle as endocrine organs may be important contributing factors for children's growth and development. Myokines, secreted by muscle cells, play a role in regulating bone metabolism, either directly or indirectly. Conversely, markers of bone metabolism, reflecting the balance between bone formation and bone resorption, can also influence myokine secretion. This study investigated a panel of serum myokines and their relationships with bone metabolism markers in children following vegetarian and omnivorous diets. A cohort of sixty-eight healthy prepubertal children, comprising 44 vegetarians and 24 omnivores, participated in this study. Anthropometric measurements, dietary assessments, and biochemical analyses were conducted. To evaluate the serum concentrations of bone markers and myokines, an enzyme-linked immunosorbent assay (ELISA) was used. The studied children did not differ regarding their serum myokine levels, except for a higher concentration of decorin in the vegetarian group (p = 0.020). The vegetarians demonstrated distinct pattern of bone metabolism markers compared to the omnivores, with lower levels of N-terminal propeptide of type I procollagen (P1NP) (p = 0.001) and elevated levels of C-terminal telopeptide of type I collagen (CTX-I) (p = 0.018). Consequently, the P1NP/CTX-I ratio was significantly decreased in the vegetarians. The children following a vegetarian diet showed impaired bone metabolism with reduced bone formation and increased bone resorption. Higher levels of decorin, a myokine involved in collagen fibrillogenesis and essential for tissue structure and function, may suggest a potential compensatory mechanism contributing to maintaining bone homeostasis in vegetarians. The observed significant positive correlations between myostatin and bone metabolism markers, including P1NP and soluble receptor activator of nuclear factor kappa-B ligand (sRANKL), suggest an interplay between muscle and bone metabolism, potentially through the RANK/RANKL/OPG signaling pathway.

Comprehensive Insights into Chondroblastoma Metastasis: Metastatic Patterns and Therapeutic Approaches

Chondroblastoma metastasis, though rare, represents a clinically significant and notably important aspect of bone tumors. Understanding its epidemiological characteristics, pathological features, and treatment modalities, despite its infrequency, is imperative for comprehensive patient management. This review aims to elucidate the epidemiology, molecular mechanisms, diagnostic challenges, and therapeutic strategies associated with chondroblastoma metastasis. The patterns, prognostic factors, and treatment outcomes were explored through an analysis of case studies and clinical reports. Notably, we highlighted emerging therapeutic perspectives aimed at improving patient outcomes. To the best of our knowledge, there has been no previous review addressing these matters cumulatively, highlighting a significant gap in the existing scholarly literature. By shedding light on the nuances of chondroblastoma metastasis, this review contributes to the advancement of knowledge in this field and informs clinical decision-making for improved patient care.

A polygenic score method boosted by non-additive models

Dominance heritability in complex traits has received increasing recognition. However, most polygenic score (PGS) approaches do not incorporate non-additive effects. Here, we present GenoBoost, a flexible PGS modeling framework capable of considering both additive and non-additive effects, specifically focusing on genetic dominance. Building on statistical boosting theory, we derive provably optimal GenoBoost scores and provide its efficient implementation for analyzing large-scale cohorts. We benchmark it against seven commonly used PGS methods and demonstrate its competitive predictive performance. GenoBoost is ranked the best for four traits and second-best for three traits among twelve tested disease outcomes in UK Biobank. We reveal that GenoBoost improves prediction for autoimmune diseases by incorporating non-additive effects localized in the MHC locus and, more broadly, works best in less polygenic traits. We further demonstrate that GenoBoost can infer the mode of genetic inheritance without requiring prior knowledge. For example, GenoBoost finds non-zero genetic dominance effects for 602 of 900 selected genetic variants, resulting in 2.5% improvements in predicting psoriasis cases. Lastly, we show that GenoBoost can prioritize genetic loci with genetic dominance not previously reported in the GWAS catalog. Our results highlight the increased accuracy and biological insights from incorporating non-additive effects in PGS models.

Tumor growth for remodeling process: A 2D approach

This paper aims to present a comprehensive framework for coupling tumor-bone remodeling processes in a 2-dimensional geometry. This is achieved by introducing a bio-inspired damage that represents the growing tumor, which subsequently affects the main populations involved in the remodeling process, namely, osteoclasts, osteoblasts, and bone tissue. The model is constructed using a set of differential equations based on the Komarova's and Ayati's models, modified to incorporate the bio-inspired damage that may result in tumor mass formation. Three distinct models were developed. The first two models are based on the Komarova's governing equations, with one demonstrating an osteolytic behavior and the second one an osteoblastic model. The third model is a variation of Ayati's model, where the bio-inspired damage is induced through the paracrine and autocrine parameters, exhibiting an osteolytic behavior. The obtained results are consistent with existing literature, leading us to believe that our in-silico experiments will serve as a cornerstone for paving the way towards targeted interventions and personalized treatment strategies, ultimately improving the quality of life for those affected by these conditions.

mPPTMP195 nanoparticles enhance fracture recovery through HDAC4 nuclear translocation inhibition

Delayed repair of fractures seriously impacts patients' health and significantly increases financial burdens. Consequently, there is a growing clinical demand for effective fracture treatment. While current materials used for fracture repair have partially addressed bone integrity issues, they still possess limitations. These challenges include issues associated with autologous material donor sites, intricate preparation procedures for artificial biomaterials, suboptimal biocompatibility, and extended degradation cycles, all of which are detrimental to bone regeneration. Hence, there is an urgent need to design a novel material with a straightforward preparation method that can substantially enhance bone regeneration. In this context, we developed a novel nanoparticle, mPPTMP195, to enhance the bioavailability of TMP195 for fracture treatment. Our results demonstrate that mPPTMP195 effectively promotes the differentiation of bone marrow mesenchymal stem cells into osteoblasts while inhibiting the differentiation of bone marrow mononuclear macrophages into osteoclasts. Moreover, in a mouse femur fracture model, mPPTMP195 nanoparticles exhibited superior therapeutic effects compared to free TMP195. Ultimately, our study highlights that mPPTMP195 accelerates fracture repair by preventing HDAC4 translocation from the cytoplasm to the nucleus, thereby activating the NRF2/HO-1 signaling pathway. In conclusion, our study not only proposes a new strategy for fracture treatment but also provides an efficient nano-delivery system for the widespread application of TMP195 in various other diseases.

D-alanine suppressed osteoclastogenesis derived from bone marrow macrophages and downregulated ERK/p38 signalling pathways

OBJECTIVES

D-alanine is a residue of the backbone structure of Type Ⅰ Lipoteichoic acid (LTA), which is a virulence factor in inflammation caused by gram-positive bacteria. However, the role of D-alanine in infectious bone destruction has not been investigated. We aimed to explore the role of D-alanine in the proliferation, apoptosis, and differentiation of osteoclasts.

DESIGN

Mouse bone marrow-derived macrophages (BMMs) were isolated as osteoclast precursors and stimulated with D-alanine. Cell proliferation and apoptosis were detected using CCK-8 and flow cytometry, respectively. The formation of osteoclasts morphologically observed by tartrate-resistant acid phosphatase staining (TRAP) and immunofluorescence staining. The expressions of osteoclastogenic genes were measured by real-time RT-PCR. The protein expressions of osteoclastogenic markers, p38, and ERK1/2 MAPK signalling were measured by western blot. The expression level of soluble Sema4D was detected via enzyme-linked immunosorbent assay (ELISA).

RESULTS

The cell proliferation of BMMs was significantly inhibited by D-alanine in a dose-dependent manner. Apoptosis of BMMs was markedly activated with the stimulation of D-alanine. The differentiation of BMMs into osteoclasts was significantly inhibited by D-alanine, and the gene and protein expressions of NFATc1, c-Fos, and Blimp decreased. Western blot showed that D-alanine inhibited the phosphorylated p38 and ERK1/2 signalling pathways of BMMs. Moreover, the expression level of soluble Sema4D significantly decreased in the supernatant of BMMs due to the D-alanine intervention.

CONCLUSION

D-alanine plays a pivotal role in the inhibition of RANKL-induced osteoclastogenesis and might become a potential therapeutic drug for bone-resorptive diseases.

Glycogen Synthase Kinase-3 Beta (GSK3β) as a Potential Drug Target in Regulating Osteoclastogenesis: An Updated Review on Current Evidence

Glycogen synthase kinase 3-beta (GSK3β) is a highly conserved protein kinase originally involved in glucose metabolism, insulin activity, and energy homeostasis. Recent scientific evidence demonstrated the significant role of GSK3β in regulating bone remodelling through involvement in multiple signalling networks. Specifically, the inhibition of GSK3β enhances the conversion of osteoclast progenitors into mature osteoclasts. GSK3β is recognised as a pivotal regulator for the receptor activator of nuclear factor-kappa B (RANK)/receptor activator of nuclear factor-kappa B ligand (RANKL)/osteoprotegerin (OPG), phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT), nuclear factor-kappa B (NF-κB), nuclear factor-erythroid 2-related factor 2 (NRF2)/Kelch-like ECH-associated protein 1 (KEAP1), canonical Wnt/beta (β)-catenin, and protein kinase C (PKC) signalling pathways during osteoclastogenesis. Conversely, the inhibition of GSK3β has been shown to prevent bone loss in animal models with complex physiology, suggesting that the role of GSK3β may be more significant in bone formation than bone resorption. Divergent findings have been reported regarding the efficacy of GSK3β inhibitors as bone-protecting agents. Some studies demonstrated that GSK3β inhibitors reduced osteoclast formation, while one study indicated an increase in osteoclast formation in RANKL-stimulated bone marrow macrophages (BMMs). Given the discrepancies observed in the accumulated evidence, further research is warranted, particularly regarding the use of GSK3β silencing or overexpression models. Such efforts will provide valuable insights into the direct impact of GSK3β on osteoclastogenesis and bone resorption.

Exercise and osteoimmunology in bone remodeling

Bones can form the scaffolding of the body, support the organism, coordinate somatic movements, and control mineral homeostasis and hematopoiesis. The immune system plays immune supervisory, defensive, and regulatory roles in the organism, which mainly consists of immune organs (spleen, bone marrow, tonsils, lymph nodes, etc.), immune cells (granulocytes, platelets, lymphocytes, etc.), and immune molecules (immune factors, interferons, interleukins, tumor necrosis factors, etc.). Bone and the immune system have long been considered two distinct fields of study, and the bone marrow, as a shared microenvironment between the bone and the immune system, closely links the two. Osteoimmunology organically combines bone and the immune system, elucidates the role of the immune system in bone, and creatively emphasizes its interdisciplinary characteristics and the function of immune cells and factors in maintaining bone homeostasis, providing new perspectives for skeletal-related field research. In recent years, bone immunology has gradually become a hot spot in the study of bone-related diseases. As a new branch of immunology, bone immunology emphasizes that the immune system can directly or indirectly affect bones through the RANKL/RANK/OPG signaling pathway, IL family, TNF-α, TGF-β, and IFN-γ. These effects are of great significance for understanding inflammatory bone loss caused by various autoimmune or infectious diseases. In addition, as an external environment that plays an important role in immunity and bone, this study pays attention to the role of exercise-mediated bone immunity in bone reconstruction.