Osteoblast physiology in normal and pathological conditions

Manipulation of signaling pathways in bone tissue engineering and regenerative medicine: Current knowledge, novel strategies, and future directions

During osteogenesis, a large number of bioactive molecules, macromolecules, cells, and cellular signals are activated to induce bone growth and development. The activation of molecular pathways leads to the occurrence of cellular events, ultimately resulting in observable changes. Therefore, in the studies of bone tissue engineering and regenerative medicine, it is essential to target fundamental events to exploit the mechanisms involved in osteogenesis. In this context, signaling pathways are activated during osteogenesis and trigger the activation of numerous other processes involved in osteogenesis. Direct influence of signaling pathways should allow to manipulate the signaling pathways themselves and impact osteogenesis. A combination of sequential cascades takes place to drive the progression of osteogenesis. Also, the occurrence of these processes and, more generally, cellular and molecular processes related to osteogenesis necessitate the presence of transcription factors and their activity. The present review focuses on outlining several signaling pathways and transcription factors influencing the development of osteogenesis, and describes various methods of their manipulation to induce and enhance bone formation.

Ionic release from bioactive SiO2-CaOCME/poly(tetrahydrofuran)/poly(caprolactone) hybrids drives human-bone marrow stromal cell osteogenic differentiation

This study demonstrates that dissolution products of inorganic/organic SiO2-CaOCME/PTHF/PCL-diCOOH hybrid (70S30CCME-CL) drive human bone marrow stromal cells (h-BMSCs) down an osteogenic pathway with the production of mineralised matrix. We investigated osteogenesis through combined analyses of mRNA dynamics for key markers and targeted staining of mineralised matrix. We demonstrate that h-BMSCs undergo accelerated differentiation in vitro in response to the 70S30CCME-CL ionic milieu, as compared to incubation with osteogenic media. Extracts from 70S30CCME-CL promote osteogenesis by inducing changes in cellular metabolic activity, promoting changes in cell morphology consistent with the osteogenic lineage, and by enhancing mineralisation of hydroxyapatite in the extracellular matrix. Additionally, our results show that 70S30CCME-CL hybrids prove sustained functional resilience by maintaining osteostimulatory effects despite cumulated dissolution cycles. In co-differentiation medium, 70S30CCME-CL ionic release can modulate signalling pathways associated with non-osteogenic functions, further supporting their potential for bone regeneration applications. Overall, our study provides compelling experimental evidence that the 70S30CCME-CL hybrid is a promising biomaterial for bone tissue regeneration applications.

IGF signaling pathway in bone and cartilage development, homeostasis, and disease

The skeleton plays a fundamental role in the maintenance of organ function and daily activities. The insulin-like growth factor (IGF) family is a group of polypeptide substances with a pronounced role in osteoblast differentiation, bone development, and metabolism. Disturbance of the IGFs and the IGF signaling pathway is inextricably linked with assorted developmental defects, growth irregularities, and jeopardized skeletal structure. Recent findings have illustrated the significance of the action of the IGF signaling pathway via growth factors and receptors and its interactions with dissimilar signaling pathways (Wnt/β-catenin, BMP, TGF-β, and Hh/PTH signaling pathways) in promoting the growth, survival, and differentiation of osteoblasts. IGF signaling also exhibits profound influences on cartilage and bone development and skeletal homeostasis via versatile cell-cell interactions in an autocrine, paracrine, and endocrine manner systemically and locally. Our review summarizes the role and regulatory function as well as a potentially integrated gene network of the IGF signaling pathway with other signaling pathways in bone and cartilage development and skeletal homeostasis, which in turn provides an enlightening insight into visualizing bright molecular targets to be eligible for designing effective drugs to handle bone diseases and maladies, such as osteoporosis, osteoarthritis, and dwarfism.

Systematic transcriptome profiling of hPSC-derived osteoblasts unveils CORIN's mastery in governing osteogenesis through CEBPD modulation

The commitment of stem cells to differentiate into osteoblasts is a highly regulated and complex process that involves the coordination of extrinsic signals and intrinsic transcriptional machinery. While rodent osteoblastic differentiation has been extensively studied, research on human osteogenesis has been limited by cell sources and existing models. Here, we systematically dissect human pluripotent stem cell-derived osteoblasts to identify functional membrane proteins and their downstream transcriptional networks involved in human osteogenesis. Our results reveal an enrichment of type II transmembrane serine protease CORIN in humans but not rodent osteoblasts. Functional analyses demonstrated that CORIN depletion significantly impairs osteogenesis. Genome-wide chromatin immunoprecipitation enrichment and mechanistic studies show that p38 MAPK-mediated CCAAT enhancer binding protein delta (CEBPD) upregulation is required for CORIN-modulated osteogenesis. Contrastingly, the type I transmembrane heparan sulfate proteoglycan SDC1 enriched in mesenchymal stem cells exerts a negative regulatory effect on osteogenesis through a similar mechanism. Chromatin immunoprecipitation-seq, bulk and single-cell transcriptomes, and functional validations indicated that CEBPD plays a critical role in controlling osteogenesis. In summary, our findings uncover previously unrecognized CORIN-mediated CEBPD transcriptomic networks in driving human osteoblast lineage commitment.

The emerging role of the semaphorin family in cartilage and osteoarthritis

In the pathogenesis of osteoarthritis, various signaling pathways may influence the bone joint through a common terminal pathway, thereby contributing to the pathological remodeling of the joint. Semaphorins (SEMAs) are cell-surface proteins actively involved in and primarily responsible for regulating chondrocyte function in the pathophysiological process of osteoarthritis (OA). The significance of the SEMA family in OA is increasingly acknowledged as pivotal. This review aims to summarize the mechanisms through which different members of the SEMA family impact various structures within joints. The findings indicate that SEMA3A and SEMA4D are particularly relevant to OA, as they participate in cartilage injury, subchondral bone remodeling, or synovitis. Additionally, other elements such as SEMA4A and SEMA5A may also contribute to the onset and progression of OA by affecting different components of the bone and joint. The mentioned mechanisms demonstrate the indispensable role of SEMA family members in OA, although the detailed mechanisms still require further exploration.

Cationic Glucan Dendrimer Gel-Mediated Local Delivery of Anti-OC-STAMP-siRNA for Treatment of Pathogenic Bone Resorption

Osteoclast stimulatory transmembrane protein (OC-STAMP) plays a pivotal role in the promotion of cell fusion during osteoclast differentiation (osteoclastogenesis) in the context of pathogenic bone resorption. Thus, it is plausible that the suppression of OC-STAMP through a bioengineering approach could lead to the development of an effective treatment for inflammatory bone resorptive diseases with minimum side effects. Here, we synthesized two types of spermine-bearing (Spe) cationic glucan dendrimer (GD) gels (with or without C12) as carriers of short interfering RNA (siRNA) to silence OC-STAMP. The results showed that amphiphilic C12-GD-Spe gel was more efficient in silencing OC-STAMP than GD-Spe gel and that the mixture of anti-OC-STAMP siRNA/C12-GD-Spe significantly downregulated RANKL-induced osteoclastogenesis. Also, local injection of anti-OC-STAMP-siRNA/C12-GD-Spe could attenuate bone resorption induced in a mouse model of periodontitis. These results suggest that OC-STAMP is a promising target for the development of a novel bone regenerative therapy and that C12-GD-Spe gel provides a new nanocarrier platform of gene therapies for osteolytic disease.

Sophoraflavanone G Inhibits RANKL-Induced Osteoclastogenesis via MAPK/NF-κB Signaling Pathway

Osteoporosis is a common chronic bone metabolism disorder characterized by decreased bone mass and reduced bone density in the bone tissue. Osteoporosis can lead to increased fragility of the skeleton, making it prone to brittle fractures. Osteoclasts are macrophage-like cells derived from hematopoietic stem cells, and their excessive activity in bone resorption leads to lower bone formation than absorption during bone remodeling, which is one of the important factors inducing osteoporosis. Therefore, how to inhibit osteoclast formation and reducing bone loss is an important direction for treating osteoporosis. Sophoraflavanone G, derived from Sophora flavescens Alt and Rhizoma Drynariae, is a flavonoid compound with various biological activities. However, there have been few studies on osteoporosis and osteoclasts so far. Therefore, we hypothesize that genistein G can inhibit osteoclast differentiation, alleviate bone loss phenomenon, and conduct in vitro and in vivo experiments for research and verification purposes.

A facile strategy for tuning the density of surface-grafted biomolecules for melt extrusion-based additive manufacturing applications

Melt extrusion-based additive manufacturing (ME-AM) is a promising technique to fabricate porous scaffolds for tissue engineering applications. However, most synthetic semicrystalline polymers do not possess the intrinsic biological activity required to control cell fate. Grafting of biomolecules on polymeric surfaces of AM scaffolds enhances the bioactivity of a construct; however, there are limited strategies available to control the surface density. Here, we report a strategy to tune the surface density of bioactive groups by blending a low molecular weight poly(ε-caprolactone)5k (PCL5k) containing orthogonally reactive azide groups with an unfunctionalized high molecular weight PCL75k at different ratios. Stable porous three-dimensional (3D) scaffolds were then fabricated using a high weight percentage (75 wt.%) of the low molecular weight PCL5k. As a proof-of-concept test, we prepared films of three different mass ratios of low and high molecular weight polymers with a thermopress and reacted with an alkynated fluorescent model compound on the surface, yielding a density of 201-561 pmol/cm2. Subsequently, a bone morphogenetic protein 2 (BMP-2)-derived peptide was grafted onto the films comprising different blend compositions, and the effect of peptide surface density on the osteogenic differentiation of human mesenchymal stromal cells (hMSCs) was assessed. After two weeks of culturing in a basic medium, cells expressed higher levels of BMP receptor II (BMPRII) on films with the conjugated peptide. In addition, we found that alkaline phosphatase activity was only significantly enhanced on films containing the highest peptide density (i.e., 561 pmol/cm2), indicating the importance of the surface density. Taken together, these results emphasize that the density of surface peptides on cell differentiation must be considered at the cell-material interface. Moreover, we have presented a viable strategy for ME-AM community that desires to tune the bulk and surface functionality via blending of (modified) polymers. Furthermore, the use of alkyne-azide "click" chemistry enables spatial control over bioconjugation of many tissue-specific moieties, making this approach a versatile strategy for tissue engineering applications.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s42242-024-00286-2.

ß-Hydroxy-ß-methylbutyrate: A feed supplement influencing performance, bone metabolism, intestinal morphology, and muscle quality of laying hens: a preliminary one-point study

Laying hens, selectively bred for high egg production, often suffer from bone fragility and fractures, impacting their welfare and causing economic losses. Additionally, gut health and muscle quality are crucial for overall health and productivity. This study aimed to evaluate the effects of ß-Hydroxy-ß-methylbutyrate (HMB) supplementation on performance, bone metabolism, intestinal morphology, and muscle quality in laying hens. Forty-eight Bovans Brown hens were divided into a control group and an HMB-supplemented group (0.02% HMB in diet). The study spanned from the 31st to the 60th wk of age. Assessments included bone mechanical testing, serum hormonal analysis, histological analysis of bone and intestine, and muscle quality analysis. The HMB supplementation led to decreased feed intake without affecting body weight or laying rate in laying hens. It caused an increase in both mean daily and total egg weight, indicating improved feed utilization, without influencing the feed intake to egg weight ratio. Enhanced bone formation markers and altered intestinal morphometric parameters were observed, along with improved trabecular bone structure. However, no changes in measured other bone quality indices, including geometric, densitometric, or mechanical properties were observed. Muscle analysis revealed no significant changes in overall meat quality, except for a decrease in cholesterol content and alterations in the fatty acid profile, notably a reduction in total n-3 polyunsaturated and total polyunsaturated fatty acids (PUFA). In conclusion, although not all effects of HMB supplementation were unequivocally beneficial, the positive changes in performance data and trabecular bone microarchitecture support further research into various doses and durations of supplementation. Such studies are necessary to fully understand and optimize the benefits of HMB for enhancing the health and productivity of laying hens.

Forkhead box O proteins: steering the course of stem cell fate

Stem cells are pivotal players in the intricate dance of embryonic development, tissue maintenance, and regeneration. Their behavior is delicately balanced between maintaining their pluripotency and differentiating as needed. Disruptions in this balance can lead to a spectrum of diseases, underscoring the importance of unraveling the complex molecular mechanisms that govern stem cell fate. Forkhead box O (FOXO) proteins, a family of transcription factors, are at the heart of this intricate regulation, influencing a myriad of cellular processes such as survival, metabolism, and DNA repair. Their multifaceted role in steering the destiny of stem cells is evident, as they wield influence over self-renewal, quiescence, and lineage-specific differentiation in both embryonic and adult stem cells. This review delves into the structural and regulatory intricacies of FOXO transcription factors, shedding light on their pivotal roles in shaping the fate of stem cells. By providing insights into the specific functions of FOXO in determining stem cell fate, this review aims to pave the way for targeted interventions that could modulate stem cell behavior and potentially revolutionize the treatment and prevention of diseases.

Connective tissue growth factor enhances TGF-β1-induced osteogenic differentiation via activation of p38 MAPK in mesenchymal stem cells

OBJECTIVES

Cellular differentiation is based on the effects of various growth factors. Transforming growth factor (TGF)-β1 plays a pivotal role in inducing osteogenic differentiation of mesenchymal stem cells (MSCs). In this study, we investigated the influence of connective tissue growth factor (CTGF), known to function synergistically with TGF-β1, on osteogenic differentiation in MSCs.

METHODS

UE7T-13 cells were treated with TGF-β1 and/or CTGF. Subsequently, protein levels of intracellular signaling pathway molecules were determined through western blot analysis. The mRNA expression levels of osteogenic differentiation markers were investigated using reverse transcription-quantitative polymerase chain reaction. Bone matrix mineralization was evaluated through alizarin red staining.

RESULTS

Co-treatment with TGF-β1 and CTGF resulted in the suppression of TGF-β1-induced phosphorylation of extracellular signal-regulated kinase 1/2, an intracellular signaling pathway molecule in MSCs, while significantly enhancing the phosphorylation of p38 mitogen-activated protein kinase (MAPK). In MSCs, co-treatment with CTGF and TGF-β1 led to increased expression levels of alkaline phosphatase and type I collagen, markers of osteogenic differentiation induced by TGF-β1. Osteopontin expression was observed only after TGF-β1 and CTGF co-treatment. Notably, bone sialoprotein and osteocalcin were significantly upregulated by treatment with CTGF alone. Furthermore, CTGF enhanced the TGF-β1-induced mineralization in MSCs, with complete suppression observed after treatment with a p38 MAPK inhibitor.

CONCLUSIONS

CTGF enhances TGF-β1-induced osteogenic differentiation and subsequent mineralization in MSCs by predominantly activating the p38 MAPK-dependent pathway.

Brucella Spondylitis: Current Knowledge and Recent Advances

The most prevalent zoonotic disease is brucellosis, which poses a significant threat for worldwide public health. Particularly in endemic areas, spinal involvement is a major source of morbidity and mortality and can complicate the course of the disease. The diagnosis of Brucella spondylitis is challenging and should be suspected in the appropriate epidemiological and clinical context, in correlation with microbiological and radiological findings. Treatment depends largely on the affected parts of the body. Available treatment options include antibiotic administration for an adequate period of time and, when appropriate, surgical intervention. In this article, we examined the most recent data on the pathophysiology, clinical manifestation, diagnosis, and management of spinal brucellosis in adults.

Cell-based mechanisms and strategies of co-culture system both in vivo and vitro for bone tissue engineering

The lack of a functional vascular supply has been identified as a major challenge limiting the clinical introduction of stem cell-based bone tissue engineering (BTE) for the repair of large-volume bone defects (LVBD). Various approaches have been explored to improve the vascular supply in tissue-engineered constructs, and the development of strategies that could effectively induce the establishment of a functional vascular supply has become a major goal of BTE research. One of the state-of-the-art methods is to incorporate both angiogenic and osteogenic cells in co-culture systems. This review clarifies the key concepts involved, summarises the cell types and models used to date, and systematically evaluates their performance. We also discuss the cell-to-cell communication between these two cell types and the strategies explored in BTE constructs with angiogenic and osteogenic cells to optimise their functions. In addition, we outline unresolved issues and remaining obstacles that need to be overcome for further development in this field and eventual successful repair of LVBD.

P7C3 Ameliorates Bone Loss by Inhibiting Osteoclast Differentiation and Promoting Osteogenesis

Bone homeostasis, the equilibrium between bone resorption and formation, is essential for maintaining healthy bone tissue in adult humans. Disruptions of this process can lead to pathological conditions such as osteoporosis. Dual-targeted agents, capable of inhibiting excessive bone resorption and stimulating bone formation, are being explored as a promising strategy for developing new treatments to address osteoporosis. In this study, we investigated the effects of P7C3 on bone remodeling and its potential therapeutic role in osteoporosis treatment in mice. Specifically, P7C3 can remarkably suppress receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclast differentiation in bone marrow macrophages via the Akt-NF-κB-NFATc1 signaling pathway. Additionally, RNA sequencing (RNAseq) analysis revealed that P7C3 promoted osteoblast differentiation and function through the Wnt/β-catenin signaling pathway, thereby enhancing bone formation. Furthermore, μCT analysis and histological examination of bone tissues from P7C3-treated mice showed attenuation of both Ti-induced bone erosion and ovariectomy (OVX)-induced bone loss. These findings suggest that P7C3 may have a novel function in bone remodeling and may be a promising therapeutic agent for the treatment of osteoporosis. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Hypermethylated CDO1 and CELF4 in cytological specimens as triage strategy biomarkers in endometrial malignant lesions

Objective

Developing a non-invasive and reliable triage test for endometrial malignant lesions is an important goal, as it could help to reduce the number of invasive diagnostic procedures required and improve patient survival. We aimed to estimate the diagnostic value of DNA methylation levels in cervical cytological samples of endometrial cancer (EC) and endometrial atypical hyperplasia (AH).

Methods

A total of 607 women who had indications for endometrial biopsy in the Department of Obstetrics and Gynecology of Cangzhou Central Hospital from October 2022 to April 2023 were enrolled in this study. The cervical exfoliated cells were collected for gene methylation before endometrial biopsy. Clinical information, tumor biomarkers, and endometrial thickness (ET) of transvaginal ultrasonography (TVS) were also collected. With endometrial histopathology as the gold standard, multivariate unconditional logistic regression was applied to analyze the risk factors of endometrial malignant lesions. The role of cysteine dioxygenase type 1 (CDO1) and CUGBP Elav-like family member 4 (CELF4) gene methylation as a triage strategy biomarker in endometrial malignant lesions was specifically explored.

Results

Multivariate logistic regression analysis showed that premenopausal ET ≥ 11 mm or postmenopausal ET ≥ 5 mm, CDO1 ΔCt ≤ 8.4, or CELF4 ΔCt ≤ 8.8 were the risk factors for AH and EC, with odds ratios (ORs) (95%CI) of 5.03 (1.83-13.82) and 6.92 (1.10-43.44), respectively (p-values < 0.05). The sensitivity and specificity of CDO1/CELF4 dual-gene methylation assay for AH and EC reached 84.9% (95%CI: 75.3%-94.5%) and 86.6% (95%CI: 83.8%-89.5%), respectively. ET combined with DNA methylation detection further improved the specificity to (94.9%, 95%CI: 93.1%-96.8%).

Conclusion

The accuracy of cervical cytology DNA methylation is superior to that of other clinical indicators in the non-invasive examination of endometrial malignant lesions. DNA methylation combined with TVS can further improve the specificity and is a promising biomarker triage strategy in women with suspected endometrial lesions.

The effect of coenzyme Q10 supplementation on liver enzymes: A systematic review and meta-analysis of randomized clinical trials

Coenzyme Q10 is a potent antioxidant and is necessary for energy production in mitochondria. Clinical data have suggested that coenzyme Q10 (CoQ10) has some beneficial effects on liver function. However, these results are equivocal. This systematic review and meta-analysis aimed to clarify the effect of coenzyme Q10 supplementation on the serum concentration of liver function enzymes. We searched the online databases using relevant keywords up to April 2022. Randomized clinical trials (RCTs) investigating the effect of CoQ10, compared with a control group, on serum concentrations of liver enzymes were included. We found a significant reduction following supplementation with CoQ10 on serum concentrations of alanine aminotransferase (ALT) based on 15 effect sizes from 13 RCTs (weighted mean difference [WMD] = -5.33 IU/L; 95% CI: -10.63, -0.03; p = .04), aspartate aminotransferase (AST) based on 15 effect sizes from 13 RCTs (WMD = -4.91 IU/L; 95% CI: -9.35, -0.47; p = .03) and gamma-glutamyl transferase (GGT) based on eight effect sizes from six RCTs (WMD = -8.07 IU/L; 95% CI: -12.82, -3.32; p = .001; I 2 = 91.6%). However, we found no significant effects of CoQ10 supplementation on alkaline phosphatase concentration (WMD = 1.10 IU/L; 95% CI: -5.98, 8.18; p = .76). CoQ10 supplementation significantly improves circulating ALT, AST, and GGT levels; therefore, it might positively affect liver function. Further high-quality RCTs with more extended intervention periods and larger sample sizes are recommended to confirm our results.

Effectiveness of the production of tissue-engineered living bone graft: a comparative study using perfusion and rotating bioreactor systems

Bioreactor systems are very precious tools to generate living bone grafts in vitro. The aim of this study was to compare the effectiveness of rotating and perfusion bioreactor in the production of a living bone construct. Human bone marrow-derived mesenchymal stem cells (BMDSCs) were seeded on the surfaces of hydroxyapatite-based scaffolds and cultured for 21 days in three different conditions: (1) static 3D culture, (2) 3D culture in a perfusion bioreactor, and (3) dynamic 3D culture in a rotating bioreactor. Quantitative evaluation of cell number showed that cultivation in the perfusion bioreactor significantly reduced cell proliferation compared to the rotating bioreactor and static culture. Osteogenic differentiation test demonstrated that BMDSCs cultured in the rotating bioreactor produced significantly greater amount of osteopontin compared to the cells cultured in the perfusion bioreactor. Moreover, Raman spectroscopy showed that cultivation of BMDSCs in the rotating bioreactor enhanced extracellular matrix (ECM) mineralization that was characterized by B-type carbonated substitution of hydroxyapatite (associated with PO43- groups) and higher mineral-to-matrix ratio compared to the ECM of cells cultured in the perfusion system. Thus, it was concluded that the rotating bioreactor was much more effective than the perfusion one in the generation of bone tissue construct in vitro.

Role of denosumab in bone erosions in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by systemic inflammation and synovitis which evolve into joint destruction and deformity. Bone abnormalities are represented by marginal bone erosions and iuxta-articular and generalized osteoporosis. Overactivation of osteoclasts along with dysregulation of osteoblasts are the key events. Bone resorption is mediated by the receptor activator of nuclear factor (NF)-κB (RANK) ligand (RANK-L), responsible for the differentiation, proliferation, and activation of osteoclasts. RANK-L binds its receptor RANK, localized on the surface of preosteoclasts and mature osteoclasts promoting osteoclastogenesis. High levels of RANK-L were demonstrated in active RA patients. Denosumab, a fully human monoclonal antibody, binds RANK-L and suppresses the RANK-RANK-L signaling pathway leading to the inhibition of osteoclastogenesis. A retrospective analysis of published studies such as clinical trials evidenced the efficacy of denosumab in preventing bone erosion progression in RA patients. Key messages Key questions to answer in future include the following: Could denosumab be associated with other biologic therapies in RA patients? Could denosumab block the progression of bone damage in RA? Could denosumab be used for the prevention of bone erosion in RA?

Policosanol Stimulates Osteoblast Differentiation via Adenosine Monophosphate-Activated Protein Kinase-Mediated Expression of Insulin-Induced Genes 1 and 2

Policosanol is known as a hypocholesterolemic compound and is derived from plants such as sugar cane and corn. Policosanol can lower blood pressure or inhibit adipogenesis, but its effect on osteogenic differentiation and the molecular mechanism is unclear. This study aims to investigate the effect of policosanol on osteogenic differentiation in MC3T3-E1 cells and zebrafish models. Administration of policosanol into MC3T3-E1 induced the expression of the osteogenic genes such as distal-less homeobox 5 (Dlx5) and runt-related transcription factor 2 (Runx2). Alkaline phosphatase activity and extracellular mineralization also increased. Policosanol promoted activation of adenosine monophosphate-activated protein kinase (AMPK) and insulin-induced genes (INSIGs) expression and regulation of INSIGs modulated osteoblast differentiation. AMPK activation through transfection of the constitutively active form of AMPK (CA-AMPK) increased INSIGs expression, whereas policosanol-induced INSIGs expression was suppressed by inhibitor of AMPK (Com. C). Furthermore, the osteogenic effects of policosanol were verified in zebrafish. Amputated caudal fin rays were regenerated by policosanol treatment. Taken together, these results show that policosanol increases osteogenic differentiation and contributes to fin regeneration in zebrafish via AMPK-mediated INSIGs expression, suggesting that policosanol has potential as an osteogenic agent.

Effect of Fermented Rapeseed Meal in Feeds for Growing Piglets on Bone Morphological Traits, Mechanical Properties, and Bone Metabolism

Quality feed is essential for correct bone development and proper functioning of animals. Post-weaned piglets experience a radical change in eating behaviour that can influence their feed intake. For this reason, functional feed additives and ingredients that can be used in post-weaning feeds are needed. The objective of this study was to evaluate the effects of partially replacing wheat with rapeseed meal fermented using Bacillus subtilis strain 87Y on overall bone quality and bone metabolism in weaner piglets. From the 28th day of life, barrows were fed either a standard wheat-based diet or a diet containing 8% fermented rapeseed meal (FRSM) with or without a feed additive containing enzymes, antioxidants, probiotics, and prebiotics. The experimental period lasted 60 days, after which femur quality indices were assessed. Differences in bone length and weight were observed, but there were no changes in bone mineralization or bone mid-diaphysis morphometrical traits between treatments. FRSM inclusion reduced bone mid-diaphysis biomechanical properties, but these changes were dependent on feed-additive supplementation. Analysis of the levels of serum bone turnover markers suggests the intensification of bone resorption in FRSM-fed groups as deoxypyridinoline levels increase. The results obtained warrant further research on what the disturbances in bone mechanical properties and metabolism observed in FRSM-fed weaners means for the subsequent fattening period.

Bioglass obtained via one-pot synthesis as osseointegrative drug delivery system

Osseointegration is a fundamental process during which implantable biomaterial integrates with host bone tissue. The surgical procedure of biomaterial implantation is highly associated with the risk of bacterial infection. Thus, the research continues for biodegradable bone void fillers which are able to stimulate the bone tissue regeneration and locally deliver the antibacterial agent. Herein, we obtained bifunctional bioglass (BG) using novel, preoptimized, rapid one-pot synthesis. Following the ISO Standards, the influence of the obtained BG on osteoblast-mediated phenomena, such as osteoconduction and osteoinduction was assessed and compared to two commercial materials: bioactive glass powder 45S and bioactive glass powder 85S. Direct-contact tests revealed osteoblast adhesion to BG particles; whereas, tests on extracts confirmed high viability of cells incubated with BG extract. Analyses of gene expression, alkaline phosphatase activity, and calcium phosphates deposition confirmed the stimulation of early and late stages of osteoblast differentiation and mineralization. Additionally, an extended evaluation of intracellular calcium fluctuations revealed a possible correlation between osteoblast calcium uptake and extracellular matrix mineralization. Moreover, proposed bioglass exhibited satisfactory doxycycline adsorption capacity and release profile. The obtained results confirmed the bifunctionality of the proposed BG and indicated its potential as osseointegrative bone drug delivery system.

Synthesis, Characterization, In Vitro Cytological Responses, and In Vivo Bone Regeneration Effects of Low-Crystalline Nanocarbonated Hydroxyapatite

Hydroxyapatite (HA) has been commonly used as an alternative bone substitute. But it has drawbacks, such as poor degradation and limited osteogenesis. Low-crystalline carbonated hydroxyapatite (L-CHA), which has greater biodegradability than HA, is suggested as one of the main components of bone minerals, but the exact mechanism behind the roles of carbonate substituted in biological behaviors of low-crystalline HA is still a mystery. In this study, L-CHAs with different carbonate contents were prepared, and the effects of the content on the physicochemical properties, in vitro cytological responses, and in vivo bone defects repair effects of L-CHAs were investigated. The results demonstrated that CO₃^2- had successfully entered the lattice structure of L-CHAs with a maximum content of 9.2 wt %. Both low-crystalline undoped HA (L-HA) and L-CHAs were nanocrystalline (20-30 nm) with significantly higher specific surface areas, protein adsorption capacities, and biodegradability compared to high-crystalline HA (H-HA) with submicron crystalline size (200-400 nm). Besides, the amounts of the adsorbed protein and released Ca²⁺ ions increased in a carbonate-content-dependent manner. Compared to L-HA and H-HA, L-CHAs promoted the adhesion and proliferation of bone marrow mesenchymal stem cells and significantly upregulated the levels of alkaline phosphatase (ALP) activity and the expression of osteogenesis-related genes. In addition, L-CHA-9 not only showed a faster biodegradation rate but also effectively promoted bone regeneration when implanted in the critical-sized bone defects of rabbit femora. This study provided evidence for the development of L-CHA as a promising biodegradable and bioactive material with great osteoconductivity and osteogenic capability with respect to conventional HA.

Human umbilical cord mesenchymal stem cells induction in peri-implantitis Rattus norvegicus accelerates and enhances osteogenesis activity and implant osseointegration

Peri-implantitis additional treatment generally aims to repair damaged tissue through a regenerative approach. Human umbilical cord mesenchymal stem cells (hUCMSCs) produce a high osteogenic effect and are capable of modulating the immune system by suppressing inflammatory response, modulating bone resorption, and inducing endogenous osteogenesis.

AIM

This study was intended to discover the effect of hUCMSCs on an implant osseointegration process in peri-implantitis rat subjects as assessed by several markers including interleukin-10 (IL-10), transforming growth factor-β (TGF-β), receptor activator of nuclear factor kappa- β ligand (RANKL), bone morphogenic protein (BMP-2), osterix (Osx), and osteoprotegerin (OPG).

MATERIAL AND METHODS

The research design implemented during this study represented a true experimental design incorporating the use of Rattus norvegicus (Wistar strain) as subjects.

RESULTS

Data analysed by means of a Brown Forsythe test indicated differences between the increase in BMP-2 expression (p < 0.000) and Osx expression (p < 0.001) and between RANKL expression (p < 0.001, Tukey HSD) and OPG expression (p < 0.000, Games Howell).

CONCLUSION

According to the findings of this research, hUCMSCs induction is successful in accelerating and enhancing osteogenic activity and implant osseointegration in peri-implantitis rat subjects.

Resveratrol Modulates Bone Mineral Density and Bone Mineral Content in A Rat Model of Male Hypogonadism

OBJECTIVE

To determine whether resveratrol (Res) can correct osteoporosis induced in a rat model of male hypogonadism.

METHODS

Thirty-two rats were randomly divided into 4 groups, 8 in each group; 1) a control sham group: underwent a similar surgical procedure for induction of orchiectomy (ORCD) without ligation of any arteries or veins or removal of the testis and epididymis; 2) a control + Res-treated group (Con+Res): underwent sham surgery similar to the control, but was then treated with Res, as described below; 3) an ORCD-induced group: bilateral ORCD surgery as described above, and 4) a ORCD+Res-treated group: bilateral ORCD surgery followed by Res treatment. Res treatment began 4 weeks after ORCD and continued for 12 weeks. After 12 weeks, bone mineral density (BMD) and bone mineral content (BMC) were measured in the tibia and femur of each rat's right hind leg. Blood levels of bone turnover indicators such as deoxypyridinoline (Dpd), N-telopeptide of type I collagen (NTX I), alkaline phosphatase (ALP), and osteocalcin (OC), as well as receptor activator of nuclear factor kappa B (RANK) and osteoprotegerin (OPG) were assessed.

RESULTS

ORCD significantly decreased BMD (P<0.01) and significantly increased bone resorption, manifested by increased RANK. In addition, it inhibited serum levels of OPG and OC. Res treatment after ORCD effectively increased serum levels of bone formation markers such as OPG and OC, compared with testisectomized rats (P<0.05).

CONCLUSION

Res could ameliorate bone loss induced by male hypogonadism, possible via restoration of the normal balance between RANK and OPG.

Polysaccharides from aloe vera target the Wnt/β-catenin pathway to impact the tooth density of pulpitis rats

PURPOSE

To investigate the mechanism of polysaccharides from aloe vera (PAV), a main active ingredient of Aloe vera, treatment in pulpitis rats.

METHODS

Pulpitis were modeled by drilling the occlusal central fossa with Sprague Dawley rats. Next, the rats were treated with 20, 40, and 80 mg/kg PAV for three weeks, respectively. Computed tomography scanning assay, hematoxylin and eosin staining, and tartrate-resistant acid phosphatase staining were used to detect the pathology change. Then, levels of tumor necrosis factor-α, interleukin-1β, prostaglandin E2, and ciclooxigenase 2 were detected by enzyme-linked immunosorbent assay. The expressions of bone morphogenetic protein 2 human (BMP-2), osteocalcin, osterix, and runt-related transcription factor 2 (Runx2) were quantified by quantitative real-time polymerase chain reaction and Western blotting (WB). Finally, Wnt3a expression, p-GSK3β/GSK3β and p-β-catenin/β-catenin ratio were analyzed by WB.

RESULTS

PAV up regulated the bone mineral density, and reduced the breakage of the crown and cervical structures, and the necrosis of the crown and root pulp of pulpitis rats. In addition, results indicated that PAV could inhibit osteoblast formation. While osteoblasts' number was decreased, proteins of BMP-2, osteocalcin, osterix, and Runx2 were up-regulated by PAV. Furthermore, PAV increased the Wnt3a expression and the p-β-catenin/β-catenin ratio, and decreased p-GSK3β/GSK3β ratio. Interestingly, these effects were all in dose dependence.

CONCLUSIONS

PAV could inhibit pulp inflammation and promote osteoblasts differentiation via suppressing the activation of the Wnt/β-catenin signaling, enhancing the dental bone density.

Increased Sparc release from subchondral osteoblasts promotes articular chondrocyte degeneration under estrogen withdrawal

OBJECTIVE

The incidence of osteoarthritis (OA) in menopausal women is significantly higher than in same-aged men. Investigating the role of subchondral osteoblasts in estrogen deficiency-induced OA may help elucidate the pathological mechanism, providing new insights for the diagnosis and treatment of menopausal OA.

METHODS

A classical ovariectomy-induced OA (OVX-OA) rat model was utilized to isolate primary articular chondrocytes and subchondral osteoblasts, which were identified and then cocultured in Transwell. The expression of chondrocyte anabolic and catabolic indicators was evaluated. The differentially expressed proteins in the conditioned medium (CM) of osteoblasts were identified by Liquid Chromatograph-Mass Spectrometer (LC-MS/MS). Normal chondrocytes were treated with osteoblast CM, and then RNA sequencing was performed on the treated chondrocytes. KEGG was used to identify significant enrichment of signaling pathways, and Simple Western was used to verify the expression of related proteins in the signaling pathways.

RESULTS

Coculture of OVX-OA subchondral osteoblasts with chondrocytes significantly downregulated the expression of the anabolic indicators and upregulated the expression of the catabolic indicators in chondrocytes. 1,601 proteins were identified in both normal and OVX osteoblast culture supernatants. Protein-protein interaction network analysis revealed that Sparc was one of the hub proteins. The AMPK/Foxo3a signaling pathway of chondrocytes was downregulated by OVX-OA osteoblasts CM. AICAR, the AMPK agonist, partially reversed the catabolic effect of OVX-OA osteoblasts on chondrocytes.

CONCLUSIONS

Sparc secreted by OVX-OA subchondral osteoblasts can downregulate the AMPK/Foxo3a signaling pathway of chondrocytes, thereby promoting chondrocyte degeneration.

The effect of long non-coding RNAs in joint destruction of rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease accompanied with joint destruction. Serious joint destruction will eventually lead to disability and the decline of life quality in RA patients. At present, the therapeutic effect of drugs to alleviate joint destruction in RA is limited. Recently, accumulating evidences have shown that long non-coding RNAs (lncRNAs) play an important role in the pathogenesis of joint diseases. Therefore, this paper reviews the expression change and the action mechanism of lncRNAs in joint destruction of RA in recent years. A more comprehensive understanding of the role of lncRNAs in joint destruction will help the treatment of RA.

Surface Free Energy Dominates the Biological Interactions of Postprocessed Additively Manufactured Ti-6Al-4V

Additive manufacturing (AM) has emerged as a disruptive technique within healthcare because of its ability to provide personalized devices; however, printed metal parts still present surface and microstructural defects, which may compromise mechanical and biological interactions. This has made physical and/or chemical postprocessing techniques essential for metal AM devices, although limited fundamental knowledge is available on how alterations in physicochemical properties influence AM biological outcomes. For this purpose, herein, powder bed fusion Ti-6Al-4V samples were postprocessed with three industrially relevant techniques: polishing, passivation, and vibratory finishing. These surfaces were thoroughly characterized in terms of roughness, chemistry, wettability, surface free energy, and surface ζ-potential. A significant increase in Staphylococcus epidermidis colonization was observed on both polished and passivated samples, which was linked to high surface free energy donor γ^– values in the acid–base, γ^AB component. Early osteoblast attachment and proliferation (24 h) were not influenced by these properties, although increased mineralization was observed for both these samples. In contrast, osteoblast differentiation on stainless steel was driven by a combination of roughness and chemistry. Collectively, this study highlights that surface free energy is a key driver between AM surfaces and cell interactions. In particular, while low acid–base components resulted in a desired reduction in S. epidermidis colonization, this was followed by reduced mineralization. Thus, while surface free energy can be used as a guide to AM device development, optimization of bacterial and mammalian cell interactions should be attained through a combination of different postprocessing techniques.

The Involvement of Neutrophils in the Pathophysiology and Treatment of Osteoarthritis

Osteoarthritis (OA) is a chronic disability that significantly impairs quality of life. OA is one of the most prevalent joint pathologies in the world, characterized by joint pain and stiffness due to the degeneration of articular cartilage and the remodeling of subchondral bone. OA pathogenesis is unique in that it involves simultaneous reparative and degradative mechanisms. Low-grade inflammation as opposed to high-grade allows for this coexistence. Previously, macrophages and T cells have been identified as playing major roles in the inflammation and destruction of OA joints, but recent studies have demonstrated that neutrophils also contribute to the pathogenesis. Neutrophils are the first immune cells to enter the synovium after joint injury, and neutrophilic activity is indispensably a requisite for the progression of OA. Neutrophils act through multiple mechanisms including tissue degeneration via neutrophil elastase (NE), osteophyte development, and the release of inflammatory cytokines and chemokines. As the actions of neutrophils in OA are discovered, the potential for novel therapeutic targets as well as diagnostic methods are revealed. The use of chondrogenic progenitor cells (CPCs), microRNAs, and exosomes are among the newest therapeutic advances in OA treatment, and this review reveals how they can be used to mitigate destructive neutrophil activity.

Multi-omics molecular biomarkers and database of osteoarthritis

Osteoarthritis (OA) is the most common form of arthritis in the adult population and is a leading cause of disability. OA-related genetic loci may play an important role in clinical diagnosis and disease progression. With the rapid development of diverse technologies and omics methods, many OA-related public data sets have been accumulated. Here, we retrieved a diverse set of omics experimental results from 159 publications, including genome-wide association study, differentially expressed genes and differential methylation regions, and 2405 classified OA-related gene markers. Meanwhile, based on recent single-cell RNA-seq data from different joints, 5459 cell-type gene markers of joints were collected. The information has been integrated into an online database named OAomics and molecular biomarkers (OAOB). The database (http://ibi.zju.edu.cn/oaobdb/) provides a web server for OA marker genes, omics features and so on. To our knowledge, this is the first database of molecular biomarkers for OA.

Application and pharmacological mechanism of methotrexate in rheumatoid arthritis

Methotrexate (MTX) has been used for the treatment of rheumatoid arthritis (RA) for about forty years and to date MTX remains the part of global standard of treatment for RA. The efficacy of MTX in RA is the result of multiple mechanisms of action. In order to summarize the possible pharmacological mechanisms of MTX in the treatment of RA, this review will elaborate on folate antagonism, promotion of adenosine accumulation, regulation of inflammatory signaling pathways, bone protection and maintenance of immune system function.

Mesh Ti6Al4V Material Manufactured by Selective Laser Melting (SLM) as a Promising Intervertebral Fusion Cage

Intervertebral cages made of Ti6Al4V alloy show excellent osteoconductivity, but also higher stiffness, compared to commonly used polyether-ether-ketone (PEEK) materials, that may lead to a stress-shielding effect and implant subsidence. In this study, a metallic intervertebral fusion cage, with improved mechanical behavior, was manufactured by the introduction of a three-dimensional (3D) mesh structure to Ti6Al4V material, using an additive manufacturing method. Then, the mechanical and biological properties of the following were compared: (1) PEEK, with a solid structure, (2) 3D-printed Ti6Al4V, with a solid structure, and (3) 3D-printed Ti6Al4V, with a mesh structure. A load-induced subsidence test demonstrated that the 3D-printed mesh Ti6Al4V cage had significantly lower tendency (by 15%) to subside compared to the PEEK implant. Biological assessment of the samples proved that all tested materials were biocompatible. However, both titanium samples (solid and mesh) were characterized by significantly higher bioactivity, osteoconductivity, and mineralization ability, compared to PEEK. Moreover, osteoblasts revealed stronger adhesion to the surface of the Ti6Al4V samples compared to PEEK material. Thus, it was clearly shown that the 3D-printed mesh Ti6Al4V cage possesses all the features for optimal spinal implant, since it carries low risk of implant subsidence and provides good osseointegration at the bone-implant interface.

Molecular Mechanisms Involved in Hypoxia-Induced Alterations in Bone Remodeling

Bone is crucial for the support of muscles and the protection of vital organs, and as a reservoir of calcium and phosphorus. Bone is one of the most metabolically active tissues and is continuously renewed to adapt to the changes required for healthy functioning. To maintain normal cellular and physiological bone functions sufficient oxygen is required, as evidence has shown that hypoxia may influence bone health. In this scenario, this review aimed to analyze the molecular mechanisms involved in hypoxia-induced bone remodeling alterations and their possible clinical consequences. Hypoxia has been associated with reduced bone formation and reduced osteoblast matrix mineralization due to the hypoxia environment inhibiting osteoblast differentiation. A hypoxic environment is involved with increased osteoclastogenesis and increased bone resorptive capacity of the osteoclasts. Clinical studies, although with contradictory results, have shown that hypoxia can modify bone remodeling.

Advances in pathogenesis and therapeutic strategies for osteoporosis

Osteoporosis, is the most common bone disorder worldwide characterized by low bone mineral density, leaving affected bones vulnerable to fracture. Bone homeostasis depends on the precise balance between bone resorption by osteoclasts and bone matrix formation by mesenchymal lineage osteoblasts, and involves a series of complex and highly regulated steps. Bone homeostasis will be disrupted when the speed of bone resorption is faster than bone formation. Based on various regulatory mechanisms of bone homeostasis, a series of drugs targeting osteoporosis have emerged in clinical practice, including bisphosphonates, selective estrogen receptor modulators, calcitonin, molecular-targeted drugs and so on. However, many drugs have major adverse effects or are unsuitable for long-term use. Therefore, it is very urgent to find more effective therapeutic drugs based on the new pathogenesis of osteoporosis. In this review, we summarize novel mechanisms involved in the pathological process of osteoporosis, including the roles of gut microbiome, autophagy, iron balance and cellular senescence. Based on the above pathological mechanism, we found promising drugs for osteoporosis treatment, such as: probiotics, alpha-ketoglutarate, senolytics and hydrogen sulfide. This new finding may provide an important basis for elucidating the complex pathological mechanisms of osteoporosis and provide promising drugs for clinical osteoporosis treatment.

Dickkopf‑3 and β‑catenin play opposite roles in the Wnt/β‑catenin pathway during the abnormal subchondral bone formation of human knee osteoarthritis

Osteoarthritis (OA) is condition which poses a main concern to the aging population and its severity is expected to increase with the increasing life expectancy. In the future, several possible targets for OA treatment need to be defined. Dickkopf-related protein 3 (DKK3) is an atypical member of the Wnt-antagonistic dickkopf-related protein (DKK) family. The availability of research into the role of DKK3 in the abnormal remodeling of subchondral bone in human knee joints is currently limited. Thus, the aim of the present study was the evaluation of DKK3 expression in the abnormal bone remodeling of subchondral bone in human knee OA in order to clarify the role of DKK3 in subchondral bone remodeling and to acknowledge its potential relevance to β-catenin. In total, 38 specimens were collected from osteotomies of the medial tibial plateau of the human knee. The patient samples were then divided into the normal, mild, moderate and severe symptom groups, according to the Osteoarthritis Research Society International (OARSI) score. Following hematoxylin and eosin (H&E) and Safranin O-fast green staining for alkaline phosphatase (AZO method), changes in the distribution and number of osteocytes in the subchondral bone and the degree of sclerosis of the subchondral bone were observed. Immunohistochemical staining, immunofluorescence, western blot analysis and reverse-transcription quantitative PCR (RT-qPCR) were used for the detection of DKK3 and β-catenin expression level changes in osteoblasts in the subchondral bone of the medial tibial plateau. H&E and alkaline phosphatase staining revealed that the total number of osteocytes in the subchondral bone increased with the severity of the disease. The samples were also evaluated using Safranin O-Fast Green staining and were attributed a score according to the OARSI scoring system: The scoring number and cartilage damage increased along with OA severity. Immunohistochemistry and immunofluorescence assays demonstrated that β-catenin expression in osteocytes increased from mild to moderate, whereas DKK3 expression decreased with the development of arthritis from normal, mild to moderate. According to the results of western blot analysis, β-catenin expression was higher in moderate OA and then decreased in severe OA. On the other hand, the DKK3 levels decreased along with the progression from normal, mild to moderate OA. The results of RT-qPCR demonstrated that β-catenin and DKK3 gene expression differed with the degree of OA. On the whole, the present study demonstrates that DKK3 and β-catenin may play opposite roles in OA subchondral bone remodeling.

Circulating osteogenic progenitors and osteoclast precursors are associated with long-term glycemic control, sex steroids, and visceral adipose tissue in men with type 2 diabetes mellitus

INTRODUCTION

Type 2 diabetes mellitus (T2DM) is well-known to be associated with normal bone density but, concurrently, low bone turnover and increased risk for fracture. One of the proposed mechanisms is possible derangement in bone precursor cells, which could be represented by deficiencies in circulating osteogenic progenitor (COP) cells and osteoclast precursors (OCP). The objective of our study is to understand whether extent of glycemic control has an impact on these cells, and to identify other factors that may as well.

METHODS

This was a secondary analysis of baseline data from 51 male participants, aged 37-65 in an ongoing clinical trial at Michael E. DeBakey VA Medical Center, Houston, Texas, USA. At study entry serum Hemoglobin A1c was measured by high-performance liquid chromatography osteocalcin (OCN) and C-terminal telopeptide of type 1 collagen (CTx) were measured by ELISA, and testosterone and estradiol by liquid-chromatography/mass-spectrometry. Areal bone mineral density (BMD), trabecular bone score and body composition were measured by dual energy x-ray absorptiometry, while COP and OCP were measured by flow cytometry.

RESULTS

When adjusted for serum testosterone, parathyroid hormone, and 25-hydroxyvitamin D, those with poor long-term glycemic control had significantly higher percentage of COP (p = 0.04). COP correlated positively with visceral adipose tissue (VAT) volume (r = 0.37, p = 0.01) and negatively with free testosterone (r = -0.28, p = 0.05) and OCN (r = -0.28, p = 0.07), although only borderline for the latter. OCP correlated positively with age, FSH, lumbar spine BMD, and COP levels, and negatively with glucose, triglycerides, and free estradiol. Multivariable regression analyses revealed that, in addition to being predictors for each other, another independent predictor for COP was VAT volume while age, glucose, and vitamin D for OCP.

CONCLUSION

Our results suggest that high COP could be a marker of poor metabolic control. However, given the complex nature and the multitude of factors influencing osteoblastogenesis/adipogenesis, it is possible that the increase in COP is a physiologic response of the bone marrow to increased osteoblast apoptosis from poor glycemic control. Alternatively, it is also likely that a metabolically unhealthy profile may retard the development of osteogenic precursors to fully mature osteoblastic cells.

LIM Kinases in Osteosarcoma Development

Tumorigenesis is a long-term and multistage process that often leads to the formation of metastases. During this pathological course, two major events appear to be crucial: primary tumour growth and metastatic expansion. In this context, despite research and clinical advances during the past decades, bone cancers remain a leading cause of death worldwide among paediatric cancer patients. Osteosarcomas are the most common malignant bone tumours in children and adolescents. Notwithstanding advances in therapeutic treatments, many patients succumb to these diseases. In particular, less than 30% of patients who demonstrate metastases at diagnosis or are poor responders to chemotherapy survive 5 years after initial diagnosis. LIM kinases (LIMKs), comprising LIMK1 and LIMK2, are common downstream effectors of several signalization pathways, and function as a signalling node that controls cytoskeleton dynamics through the phosphorylation of the cofilin family proteins. In recent decades, several reports have indicated that the functions of LIMKs are mainly implicated in the regulation of actin microfilament and the control of microtubule dynamics. Previous studies have thus identified LIMKs as cancer-promoting regulators in multiple organ cancers, such as breast cancer or prostate cancer. This review updates the current understanding of LIMK involvement in osteosarcoma progression.

The role of forkhead box class O1 during implant osseointegration

FOXO1, a member of the forkhead family of transcription factors, plays a vital role in the osteogenic lineage commitment of mesenchymal stem cells, and affects multiple cellular functions of osteogenic cells. However, prior studies have focused on mesenchymal stem cells but not on differentiated osteoblasts. In addition, studies about the role of FOXO1 during osseointegration are lacking. In this present study, we constructed osteoblast conditional FOXO1 knock-out mice and lentivirus-mediated FoxO1 overexpression to investigate maxillary titanium implant osseointegration. After 4 wk post implant placement, micro-computed tomography, histomorphometric analyses, and RT-qPCR assays were performed. Results showed that compared with the control group, overexpression of FOXO1 significantly enhanced bone formation around implant and bone-implant contact ratio, while loss of FOXO1 impaired peri-implant osteogenesis and osseointegration. Moreover, overexpression of FoxO1 enhanced expression of osteogenesis-related genes, such as Runx2, Alp1, Col1a1, and Bglap. Whereas, knock-out of Foxo1 reduced the expression of osteogenesis-related genes. Taken together, our results suggested that FOXO1 in osteoblasts could enhance osteogenesis-related gene expression to improve osseointegration.

The Relationship Between Bone and Reproductive Hormones Beyond Estrogens and Androgens

Reproductive hormones play a crucial role in the growth and maintenance of the mammalian skeleton. Indeed, the biological significance for this hormonal regulation of skeletal homeostasis is best illustrated by common clinical reproductive disorders, such as primary ovarian insufficiency, hypothalamic amenorrhea, congenital hypogonadotropic hypogonadism, and early menopause, which contribute to the clinical burden of low bone mineral density and increased risk for fragility fracture. Emerging evidence relating to traditional reproductive hormones and the recent discovery of newer reproductive neuropeptides and hormones has deepened our understanding of the interaction between bone and the reproductive system. In this review, we provide a contemporary summary of the literature examining the relationship between bone biology and reproductive signals that extend beyond estrogens and androgens, and include kisspeptin, gonadotropin-releasing hormone, follicle-stimulating hormone, luteinizing hormone, prolactin, progesterone, inhibin, activin, and relaxin. A comprehensive and up-to-date review of the recent basic and clinical research advances is essential given the prevalence of clinical reproductive disorders, the emerging roles of upstream reproductive hormones in bone physiology, as well as the urgent need to develop novel safe and effective therapies for bone fragility in a rapidly aging population.

Benefits of the Phytoestrogen Resveratrol for Perimenopausal Women

Endometriosis, characterized by macroscopic lesions in the ovaries, is a serious problem for women who desire conception. Damage to the ovarian cortex is inevitable when lesions are removed via surgery, which finally decreases the ovarian reserve, thereby accelerating the transition to the menopausal state. Soon after cessation of ovarian function, in addition to climacteric symptoms, dyslipidemia and osteopenia are known to occur in women aged >50 years. Epidemiologically, there are sex-related differences in the frequencies of dyslipidemia, hypertension, and osteoporosis. Females are more susceptible to these diseases, prevention of which is important for healthy life expectancy. Dyslipidemia and hypertension are associated with the progression of arteriosclerosis, and arteriosclerotic changes in the large and middle blood vessels are one of the main causes of myocardial and cerebral infarctions. Osteoporosis is associated with aberrant fractures in the spine and hip, which may confine the patients to the bed for long durations. Bone resorption is accelerated by activated osteoclasts, and rapid bone remodeling reduces bone mineral density. Resveratrol, a plant-derived molecule that promotes the function and expression of the sirtuin, SIRT1, has been attracting attention, and many reports have shown that resveratrol might exert cardiovascular protective effects. Preclinical reports also indicate that it can prevent bone loss and endometriosis. In this review, I have described the possible protective effects of resveratrol against arteriosclerosis, osteoporosis, and endometriosis because of its wide-ranging functions, including anti-inflammatory and antioxidative stress functions. As ovarian function inevitably declines after 40 years, intake of resveratrol can be beneficial for women with endometriosis aged <40 years.

Cellular alterations and crosstalk in the osteochondral joint in osteoarthritis and promising therapeutic strategies

Osteoarthritis (OA) is a joint disorder involving cartilage degeneration and subchondral bone sclerosis. The bone-cartilage interface is implicated in OA pathogenesis due to its susceptibility to mechanical and biological factors. The crosstalk between cartilage and the underlying subchondral bone is elevated in OA due to multiple factors, such as increased vascularization, porosity, microcracks and fissures. Changes in the osteochondral joint are traceable to alterations in chondrocytes and bone cells (osteoblasts, osteocytes and osteoclasts). The phenotypes of these cells can change with the progression of OA. Aberrant intercellular communications among bone cell-bone cell and bone cell-chondrocyte are of great importance and might be the factors promoting OA development. An appreciation of cellular phenotypic changes in OA and the mechanisms by which these cells communicate would be expected to lead to the development of targeted drugs with fewer side effects.

The Role of Osteokines in Sarcopenia: Therapeutic Directions and Application Prospects

Sarcopenia is an age-related disease in which muscle mass, strength and function may decline with age or can be secondary to cachexia or malnutrition and can lead to weakness, falls and even death. With the increase in life expectancy, sarcopenia has become a major threat to the health of the elderly. Currently, our understanding of bone-muscle interactions is not limited to their mechanical coupling. Bone and muscle have been identified as secretory endocrine organs, and their interaction may affect the function of each. Both muscle-derived factors and osteokines can play a role in regulating muscle and bone metabolism via autocrine, paracrine and endocrine mechanisms. Herein, we comprehensively summarize the latest research progress on the effects of the osteokines FGF-23, IGF-1, RANKL and osteocalcin on muscle to explore whether these cytokines can be utilized to treat and prevent sarcopenia.

Patient-specific effects of soluble factors from Staphylococcus aureus and Staphylococcus epidermidis biofilms on osteogenic differentiation of primary human osteoblasts

Due to the frequency of biofilm-forming Staphylococcus aureus and Staphylococcus epidermidis in orthopedics, it is crucial to understand the interaction between the soluble factors produced by prokaryotes and their effects on eukaryotes. Our knowledge concerning the effect of soluble biofilm factors (SBF) and their virulence potential on osteogenic differentiation is limited to few studies, particularly when there is no direct contact between prokaryotic and eukaryotic cells. SBF were produced by incubating biofilm from S. aureus and S. epidermidis in osteogenic media. Osteoblasts of seven donors were included in this study. Our results demonstrate that the detrimental effects of these pathogens do not require direct contact between prokaryotic and eukaryotic cells. SBF produced by S. aureus and S. epidermidis affect the metabolic activity of osteoblasts. However, the effect of SBF derived from S. aureus seems to be more pronounced compared to that of S. epidermidis. The influence of SBF of S. aureus and S. epidermidis on gene expression of COL1A1, ALPL, BGLAP, SPP1, RUNX2 is bacteria-, patient-, concentration-, and incubation time dependent. Mineralization was monitored by staining the calcium and phosphate deposition and revealed that the SBF of S. epidermidis markedly inhibits calcium deposition; however, S. aureus shows a less inhibitory effect. Therefore, these new findings support the hypotheses that soluble biofilm factors affect the osteogenic processes substantially, particularly when there is no direct interaction between bacteria and osteoblast.

A systematic dissection of human primary osteoblasts in vivo at single-cell resolution

Human osteoblasts are multifunctional bone cells, which play essential roles in bone formation, angiogenesis regulation, as well as maintenance of hematopoiesis. However, the categorization of primary osteoblast subtypes in vivo in humans has not yet been achieved. Here, we used single-cell RNA sequencing (scRNA-seq) to perform a systematic cellular taxonomy dissection of freshly isolated human osteoblasts from one 31-year-old male with osteoarthritis and osteopenia after hip replacement. Based on the gene expression patterns and cell lineage reconstruction, we identified three distinct cell clusters including preosteoblasts, mature osteoblasts, and an undetermined rare osteoblast subpopulation. This novel subtype was found to be the major source of the nuclear receptor subfamily 4 group A member 1 and 2 (NR4A1 and NR4A2) in primary osteoblasts, and the expression of NR4A1 was confirmed by immunofluorescence staining on mouse osteoblasts in vivo. Trajectory inference analysis suggested that the undetermined cluster, together with the preosteoblasts, are involved in the regulation of osteoblastogenesis and also give rise to mature osteoblasts. Investigation of the biological processes and signaling pathways enriched in each subpopulation revealed that in addition to bone formation, preosteoblasts and undetermined osteoblasts may also regulate both angiogenesis and hemopoiesis. Finally, we demonstrated that there are systematic differences between the transcriptional profiles of human and mouse osteoblasts, highlighting the necessity for studying bone physiological processes in humans rather than solely relying on mouse models. Our findings provide novel insights into the cellular heterogeneity and potential biological functions of human primary osteoblasts at the single-cell level.

Bioengineered Fluorescent Nanoprobe Conjugates for Tracking Human Bone Cells: In Vitro Biocompatibility Analysis

Herein, we validated novel functionalized hybrid semiconductor bioconjugates made of fluorescent quantum dots (QD) with the surface capped by chitosan (polysaccharide) and chemically modified with O-phospho-L-serine (OPS) that are biocompatible with different human cell sources. The conjugation with a directing signaling molecule (OPS) allows preferential accumulation in human bone mesenchymal stromal cells (HBMSC). The chitosan (Chi) shell with the fluorescent CdS core was characterized by spectroscopical (UV spectrophotometry and photoluminescence), by morphological techniques (Transmission Electron Microscopy (TEM)) and showed small size (ø 2.3 nm) and a stable photoluminescence emission band. The in vitro biocompatibility results were not dependent on the polysaccharide chain length (Chi with higher and lower molecular weight) but were remarkably affected by the surface modification (Chi or Chi-OPS). In addition, the efficiency of nanoparticles uptake by the cells was dependent on cells nature (human primary cells or cell lines) and tissue source (bone or skin) in the presence or absence of the OPS modification. The complex cellular uptake pathways involved in the cell labeling with the nanoparticles do not interfere on the normal cellular biology (adhesion and proliferation), osteogenic differentiation, and gene expression. The bone cells particles uptake evaluation showed a possible pathway by Caveolin-1 that regulates cell transduction in the membrane’s Caveolae. Caveolae mediates non-specific endocytosis, and it is upregulated in HBMSC. The OPS-modified nanoparticles promoted an intense intracellular trafficking by the HBMSCs that showed late-osteoblast phenotype with an increase of extracellular matrix (ECM) mineralization (Alizarin red and Von Kossa staining for calcium phosphate crystals). In this work, the OPS modified bioconjugated QD proved to be a reliable and stable fluorescent bioprobe for cell imaging and targeting research that could also help in clarifying some cellular mechanisms of particles intracellular traffic through the cytoplasmic membrane and osteogenic differentiation induction. The in vitro HBMSC’s biocompatibility responses indicated that the OPS-modified chitosan QDs have a prospective future in laboratory and pre-clinical applications such as bioimaging analysis and for ex-vivo cellular evaluation of biomedical implants.