Search Results (403)

Purpose: Osteotoxicity is a well-recognized adverse effect of Methotrexate (MTX) therapy, primarily driven by oxidative stress and impaired bone remodeling. This study aimed to investigate the protective effects of Tempol, a membrane-permeable nitroxide antioxidant, against MTX-induced osteotoxicity, and to assess how these effects are influenced by ML210, a glutathione peroxidase 4 (GPX4) inhibitor. Methods: Murine osteocyte-like MLO-Y4 cells were treated with MTX alone, Tempol alone, or a combination of MTX with Tempol and ML210. Apoptotic markers (caspase-3, Bax, Bcl-2), MAPK signaling proteins (p-JNK, p-ERK), and oxidative stress parameters (TAS, TOS, SOD, GPx) were measured via ELISA to evaluate the redox and apoptotic responses. Results: MTX significantly induced apoptosis, as evidenced by increased caspase-3 activity and Bax expression, along with decreased Bcl-2 levels. MTX also activated the MAPK pathway by upregulating p-JNK and p-ERK. Furthermore, MTX decreased TAS, SOD, and GPx levels, while increasing TOS. Tempol treatment successfully reversed these effects, restoring apoptotic balance, inhibiting MAPK activation, and enhancing antioxidant capacity. However, co-treatment with ML210 markedly attenuated Tempol’s protective effects, resulting in sustained oxidative stress, elevated apoptotic markers, and persistent MAPK pathway activation. This suggests that Tempol’s cytoprotective actions are dependent on functional GPX4 activity. Conclusion: Tempol exhibits strong potential as an adjunctive antioxidant therapy to counteract MTX-induced osteotoxicity. Nevertheless, its efficacy is significantly influenced by the status of the endogenous antioxidant enzyme GPX4. These findings underscore the need for further investigation into Tempol’s mechanism of action in redox-dependent pathways and its suitability in clinical settings, especially where GPX4 function may be compromised. Full article

Diabetes mellitus disrupts bone homeostasis, inducing bone fragility, through mechanisms involving chronic inflammation and altered cellular signaling. Osteocytes, the primary mechanosensory cells in bone, play a pivotal role in regulating bone remodeling via the secretion of factors that influence both osteoclast and osteoblast activity. We investigated the impact of high glucose on osteocytic parathyroid hormone receptor type 1 (PTH1R) expression and its downstream effects on interleukin-6 (IL-6) secretion, macrophage polarization, and osteoclastogenesis. Using both in vitro and ex vivo bone models, we demonstrate that elevated glucose levels in static conditions without mechanical stimulation induce the overexpression of PTH1R in osteocytes. PTH1R upregulation in turn enhances osteocytic IL-6 secretion associated with the promotion of a pro-inflammatory macrophage M1 phenotype (increased tumor necrosis factor (TNF)-$\alpha$/CD206 and inducible nitric oxide synthase (iNOS)/CD206 ratios) and the upregulation of the pro-osteoclastogenic markers tartrate-resistant acid phosphatase (TRAP) and receptor activator of nuclear factor kappa-Β (RANK). Neutralization of IL-6 in the osteocytic secretome attenuated macrophage inflammatory gene overexpression, underscoring IL-6’s critical role in this regulatory axis. Our findings reveal that a high-glucose environment triggers osteocytic dysregulation of PTH1R-mediated signaling pathways, amplifying inflammatory and osteoclastogenic activity in bone via IL-6. This osteocyte–macrophage crosstalk may contribute to the increased bone resorption and impaired regeneration observed in diabetic bone disease. Targeting PTH1R upregulation and the IL-6 signaling pathway in osteocytes could represent a novel therapeutic approach to mitigating bone complications associated with diabetes. Full article

Advanced prostate cancer frequently metastasizes to bone, but no effective therapy exists. To seek a novel treatment option and identify a new drug target, we took an induced tumor-suppressing (iTS) cell-based approach and produced tumor-suppressing proteins and conditioned medium (CM). Notably, the overexpression of Lrp5 and β-catenin, as well as the pharmacological Wnt activator, converted osteocytes, Murine mesenchymal stem cells, mononuclear cells, and monocytes into iTS cells. While Lrp5 conditional knockout mice presented severe bone loss, Lrp5-overexpressing osteocyte-derived CM rescued tumor-induced bone damage. Whole-genome proteomics analysis revealed that Moesin (MSN), which acted as an oncogene in tumor cells, was enriched in CM as an extracellular tumor-suppressing protein. Its anti-tumor action was mediated primarily by the interaction with CD44. Consistently, FRET live-cell imaging demonstrated that extracellular MSN reduced Src tyrosine kinase activity and nuclear localization of β-catenin. Collectively, we demonstrated herein the iTS cell-based approach to protect bone from prostate cancer and showed MSN as a potent extracellular tumor-suppressing protein. Full article

The maintenance of bone homeostasis requires the coordinated activity of specialized cells (osteoblasts, osteoclasts and osteocytes), soluble factors and hormones with regulatory functions. Disruption of this tightly controlled balance contributes to several skeletal pathological conditions, among which osteoporosis is one of the most prevalent. Iron, an essential element for the basic cellular functions of both osteoblasts and osteoclasts, plays a pivotal role in preserving bone homeostasis and skeletal integrity. Both iron deficiency and iron overload impair bone remodeling through distinct but converging mechanisms. Iron deficiency compromises collagen synthesis, alters hypoxia-dependent signaling, and may affect vitamin D metabolism, collectively predisposing the individual to reduced bone mineral density and increased fracture risk. Conversely, excess iron enhances oxidative stress, promotes osteoclastogenesis, and suppresses osteoblast differentiation and function, thereby favoring bone loss, particularly in the aging population and postmenopausal individuals. Hepcidin, the master regulator of systemic iron availability, has emerged as a key modulator of bone turnover, whereas the bone-derived hormone fibroblast growth factor 23 (FGF23) links iron imbalance to phosphate homeostasis, vitamin D metabolism, and inflammation. Beyond metabolic bone diseases, dysregulated iron handling is increasingly recognized as a hallmark of osteosarcoma biology, influencing tumor growth, metabolic reprogramming, and an individual’s susceptibility to ferroptosis. The emerging, albeit only preclinical, evidence of the roles of iron and ferroptosis in osteosarcoma is therefore also covered. This review summarizes the current understanding of the interactions between iron metabolism and bone biology and addresses how an imbalance in iron metabolism may lead to major skeletal disorders. Overall, iron homeostasis could represent a potential target for preventing and treating osteoporosis and for improving therapeutic strategies for osteosarcoma. Full article

Prolonged tooth loss causes alveolar ridge atrophy, complicating implantation, especially in patients with impaired mineral metabolism. This study aimed to develop a personalized titanium mesh for guided bone regeneration and qualitatively evaluate its local tissue response in a vitamin D3-deficient rabbit model. A titanium mesh design has been developed in the form of a plate-shaped profile frame of a truncated pyramid with a solid upper base and perforated side faces. For testing in a rabbit model with vitamin D3 deficiency, a bone defect was created and repaired in the mandible using hydroxyapatite, an individual titanium mesh and a collagen membrane. Histological analysis was performed in the Laboratory of Digital Microscopic Analysis. The optimized geometry and parameters of the mesh openings contributed to effective vascularization and osteogenesis. In the postoperative period (3, 5 and 7 days), moderate edema and hyperemia were noted with their complete leveling by the 7th day (p < 0.05). According to the histological examination, 3 months after the installation of the titanium mesh, the formation of dense connective tissue with signs of active osteogenesis was observed in the defect area, including zones of mineralized bone trabeculae, osteocytes and osteon elements. The findings of this study indicate acceptable biocompatibility of the developed titanium structure and suggest osteoconductive potential, which, however, needs to be confirmed in controlled, quantitatively powered studies. Full article

Orthodontic tooth movement (OTM), a complex biological process driven by orchestrated bone remodeling, involves osteoclastic bone resorption and osteoblastic bone formation in response to mechanical force. Traditionally, OTM-related cell death has been discussed in terms of apoptosis and necrosis. However, recent advances in cell death research have revealed various forms of regulated cell death (RCD) beyond these conventional categories. This review summarizes the current understanding of the diverse RCD pathways and their roles in various cell populations during OTM. It delineates the involvement of distinct RCD mechanisms, including apoptosis, autophagy, pyroptosis, ferroptosis, and necroptosis. On the compression side, these RCD pathways in periodontal ligament (PDL) cells, cementoblasts, cementocytes, and bone-related cells actively drive inflammatory responses, promote bone resorption, and contribute to root resorption. Conversely, on the tension side, specific RCD pathways, notably autophagy in the PDL and osteocytes, play crucial roles in promoting osteogenesis and tissue repair. Collectively, cell death is not merely a passive elimination of cells but actively functions as a critical switch for alveolar bone remodeling during OTM. Understanding these multifaceted RCD mechanisms provides novel insights into the biological regulation of tooth movement and identifies potential therapeutic targets for enhancing tooth movement efficiency and mitigating adverse effects. Full article

Background: Sclerostin, an osteocyte-derived glycoprotein, plays a key role in bone metabolism by inhibiting the Wnt/β-catenin signaling pathway. While it is a recognized therapeutic target in osteoporosis, its relationship with sarcopenia remains unclear. This study aimed to investigate the associations between serum sclerostin levels, sarcopenia, and osteoporosis in older women. Methods: We conducted a cross-sectional study of 79 postmenopausal women aged ≥65 years. Sarcopenia was defined based on grip strength and appendicular skeletal muscle mass (ASM), osteoporosis was diagnosed according to femoral T-scores, and serum sclerostin levels were measured using ELISA. Associations with clinical variables and bone mineral density (BMD) were evaluated using correlation and logistic regression analyses. Results: Sclerostin levels were significantly higher in women with sarcopenia (p = 0.036) and exhibited a negative correlation with grip strength (r = −0.298, p = 0.008) but not with ASM. Positive correlations were found between sclerostin and multiple femoral BMD parameters. In a logistic regression analysis, sclerostin was modestly associated with sarcopenia (p = 0.045); however, no significant association was observed with osteoporosis (p = 0.257). Conclusions: Elevated sclerostin levels are associated with reduced muscle strength and sarcopenia in older women, independent of muscle mass, indicating that sclerostin may reflect a functional decline in musculoskeletal health. Muscle strength should therefore be considered when interpreting sclerostin’s clinical implications in aging populations. Full article

Bone metastasis in breast cancer remains a major therapeutic challenge because current osteoclast-targeted therapies do not fully disrupt the tumor–bone vicious cycle. Osteocytes, the most abundant bone cells, are increasingly recognized as key regulators of bone–tumor crosstalk. Previous work has shown that osteocyte-specific overexpression of the Wnt co-receptor LRP5 inhibits breast cancer-induced osteolysis and generates conditioned medium (CM) with tumor-suppressive activity. Proteomic analysis identified LIM domain and actin-binding protein 1 (LIMA1) as a central mediator that interacts with Myosin Vb (MYO5B), suggesting the role of the LIMA1/MYO5B regulatory axis. This study demonstrates that CM derived from LRP5-overexpressing osteocytes suppresses EO771 breast cancer cell proliferation, migration, and invasion, and downregulates tumor-promoting proteins, including MMP9, Snail, IL-6, and TGF-β1, while upregulating the apoptosis-related protein cleaved caspase-3. These effects were largely reversed by knockdown of LIMA1 or MYO5B. In syngeneic mouse models of mammary tumors and bone metastasis, systemic administration of LRP5-overexpressing osteocyte-derived CM reduced tumor burden and osteolytic bone destruction, whereas genetic knockdown of LIMA1 in osteocytes or MYO5B in tumor cells abrogated these protective effects. Collectively, these findings indicate that LRP5 activation in osteocytes engages the LIMA1/MYO5B signaling axis that inhibits breast cancer progression and osteolysis, disrupts tumor–stromal interactions, and restores bone–tumor homeostasis, thereby providing a potential therapeutic strategy to break the vicious cycle of bone metastasis in breast cancer. Full article

Background/Objectives: Autologous dentin matrix (ADM) has been suggested as a biologically plausible biomaterial for alveolar bone regeneration after tooth extraction. However, clinical evidence regarding its biological activity and early healing outcomes is limited. This exploratory, randomized controlled pilot study aimed to descriptively assess early alveolar healing patterns and bone morphogenetic protein 4 (BMP4) expression following tooth extraction using ADM compared with other grafting approaches. Methods: Patients requiring tooth extraction were allocated to one of four groups: ADM, xenograft, ADM combined with platelet-rich fibrin, and a graft-free control group. Histological and immunohistochemical analyses were performed four months after extraction to descriptively assess cellular features of healing and BMP4 expression. The trial was registered at the Brazilian Registry of Clinical Trials (ReBEC; RBR-24mdgrf) and conducted under prior ethics committee approval. Results: BMP4 expression was detected in 67.9% of the analyzed histological fields, predominantly localized in osteocytic, osteoblastic, and medullary areas. Although descriptive differences in BMP4-positive fields were observed among the groups, no statistically significant differences were identified between the groups. Histological evaluation revealed an active cellular environment across all treatment modalities, consistent with early post-extraction healing. No adverse events related to surgical procedures or grafting materials were reported during the study period. Conclusions: Within the limitations of this pilot randomized clinical trial, ADM exhibited consistent biological behavior during early post-extraction alveolar healing. The observed BMP4 expression likely reflects a general physiological healing response rather than a material-specific effect. This finding supports the biological plausibility of dentin-derived grafts as osteoconductive biomaterials. These findings are hypothesis-generating, and larger, adequately powered randomized clinical trials with standardized molecular and histological assessments are required to determine their clinical relevance. Full article

Bone remodeling is maintained through the coordinated actions of osteoblasts, osteoclasts, and osteocytes, among which osteocytes serve as major regulators of osteoclast-mediated bone resorption through the receptor activator of the nuclear factor-κB ligand (RANKL)–osteoprotegerin (OPG) signaling axis. While molecular signals regulating osteocytic RANKL-OPG expression are fairly understood, how post-transcriptional mechanisms impact osteocyte function remains poorly defined. HuR (human antigen R) encoded by Elavl1 (embryonic lethal abnormal vision-like 1), a ubiquitously expressed RNA-binding protein, is known for stabilizing AU-rich element-containing transcripts involved in inflammatory and stress responses; however, its role in osteocyte-derived bone resorption is unknown. In this study, we examined the effect of HuR loss on osteocyte–osteoclastogenesis. Short hairpin RNA (shRNA)-mediated HuR knockdown in MLO-Y4 osteocyte-like cells resulted in a significant increase in OPG mRNA and its protein expression, whereas RANKL levels remained unchanged, leading to a significantly reduced RANKL/OPG ratio. Both co-culture and conditioned-medium assays demonstrated that HuR-deficient osteocytes produced a markedly diminished osteoclastogenic environment. Actinomycin D chase experiments showed no alteration in OPG mRNA decay kinetics, and RNA immunoprecipitation (RIP)-PCR failed to detect HuR–OPG interactions, indicating that HuR regulates OPG expression through indirect mechanisms rather than mRNA binding. These findings identify HuR as an indirect regulator of osteocyte-derived OPG expression that impacts osteoclast differentiation and reveal a previously unrecognized mechanism by which HuR contributes to bone remodeling. Full article

Background and Objectives: Reduced bone quality due to osteoporosis significantly complicates oral rehabilitation and bone regeneration therapies. While Vitamin D (Vit. D3) is crucial for osteogenesis, systemic administration often lacks local efficacy. This study aimed to evaluate the osteoregenerative potential of a novel Chitosan-based nanostructured scaffold (NS) loaded with Vit. D3, underlining its efficacy in vitro and in an ovariectomized (OVX) rat model of osteoporosis. Materials and Methods: Chitosan NSs were fabricated with varying Vit. D3 concentrations. In vitro assessments included cytotoxicity (MTT assay), cell viability (Alamar Blue), and mineralization (Alizarin Red) using human dental follicle stem cells. In vivo, 30 Wistar rats were ovariectomized to induce osteoporosis (confirmed by biomarkers Osteocalcin and β-CTX) and were divided into three groups (n = 10). Bilateral maxillary bone defects were treated with (1) a Control (clot only), (2) a Hemostatic Sponge with Vit. D3 (HS/Vit. D3), or (3) an NS loaded with Vit. D3 (NS/Vit. D3-6.25 ng/mL). Histological and morphometric analyses were performed at 4 and 8 weeks. Results: In vitro, the NS loaded with 6.25 ng/mL Vit. D3 demonstrated superior cytocompatibility, achieving a cell viability of 117.77% at 72 h and significantly enhanced calcium nodule deposition compared to controls. In vivo, a total of 44 defect sites were analyzed following the exclusion of compromised samples (Control: 16 sites; HS/Vit. D3: 16 sites; NS/Vit. D3: 12 sites). The NS/Vit. D3-6.25 ng/mL group exhibited the highest degree of mature bone formation and vascularization (p < 0.05) compared to the Control and HS/Vit. D3 groups. While cellular activity (osteoblasts/osteocytes) was initially higher in the HS/Vit. D3 group, the NS/Vit. D3-6.25 ng/mL group achieved superior structural integration and scaffold replacement by mature bone tissue over time. Conclusions: The novel Vit. D3-loaded Chitosan NS effectively promotes bone regeneration in osteoporotic conditions. It supports osteogenic differentiation in vitro and enhances bone matrix maturation in vivo, suggesting its potential as a bioactive scaffold for regenerative dentistry. Full article

Bone remodelling is a physiological process influenced by mechanical stimuli such as those generated during orthodontic treatment. Biochemical markers allow the phases of remodelling to be identified, its progression to be assessed, alterations to be detected and scaffold-based tissue regeneration to be evaluated. This study reviews the main markers involved in bone formation and resorption, highlighting their clinical relevance. A literature search was conducted in biomedical databases, selecting studies that analysed crevicular gingival fluid samples in areas of tension and compression. The markers were classified according to their function and location, and their baseline values, temporal variations and methods of analysis were compiled. Among the markers of bone formation, Osteoprotegerin (OPG), Transforming Growth factor β1 (TGF-β1) and Interleukin 27 (IL-27) stand out; while resorption markers include Receptor Activator of Nuclear Factor appa β Ligand (RANKL), Tumour Necrosis Factor (TNF-α) and Interleukin 1β (IL-1β). The results show different expression patterns depending on the type of force applied and the timing of the follow-up, allowing molecular profiles associated with each phase of remodelling to be established. This characterisation improves our understanding of tooth movement and provides a basis for the development of more precise scaffolds and functional biomaterials in orthodontics. Full article

Prostate cancer (PCa) exhibits a unique propensity to metastasize to bone, where it predominantly generates osteoblastic lesions. The formation of these lesions is a complex and dynamic process driven by reciprocal interactions between tumor cells and the bone microenvironment. Emerging evidence indicates that extracellular vesicles (EVs) play pivotal roles in the establishment of metastatic colonies and disease progression, as well as in local tumor–bone interactions. Through their diverse cargos, including proteins, lipids, and non-coding RNAs, EVs mediate bidirectional communication that regulates osteoclastogenesis, osteoblast activation, and osteocyte function, ultimately reshaping the bone niche to favor tumor growth. Importantly, EVs exhibit dual and context-dependent functions, acting either as promoters or suppressors of malignancy depending on the cellular source and microenvironmental context. These insights highlight EVs not only as mechanistic drivers of PCa bone metastases but also as promising therapeutic targets. Approaches aimed at modulating EV biogenesis, eliminating deleterious EVs, or harnessing EVs as drug delivery vehicles hold significant potential for advancing treatment strategies against PCa bone metastases. Full article

Bone is a dynamic tissue with ecological and evolutionary importance, as it can grow and remodel itself in response to mechanical stimuli. In mammals, osteocytes are widely recognised as the central regulators of bone formation and mechanotransduction. However, many advanced teleosts lack these cells yet still exhibit evidence of bone formation and remodelling. This challenges the prevailing view that osteocytes are indispensable for these processes. Notably, these anosteocytic teleosts exhibit clear responses to mechanical loading, suggesting alternative mechanisms at play. African cichlids, known for their remarkable ecological diversification, which occurs in craniofacial bone morphology. However, these differences are based on very few genetic changes, while including interspecific variation in bone remodeling capacities. Thus, cichlid, being anosteocytic, and variable in remodeling abilities based on very few genetic changes, represents an ideal model system for understanding the mechanisms underlying remodeling. This protocol outlines the development of primary cell cultures from cichlid jaw bones that can be applied across species, establishing a foundation for future research aimed at elucidating the cellular and molecular mechanisms underlying bone formation and remodelling in anosteocytic systems. Full article

To address the challenges of excessively fast degradation and relatively poor biocompatibility of biomedical magnesium alloys, in this study, Mg/HA magnesium alloy treated by different friction stir processing (FSP) techniques served as the substrate for fabricating a micro-arc oxidation (MAO) coating. SEM, EDS, XRD, and XPS were employed to characterize the coating’s microstructure, phase composition, and element distribution, while its comprehensive properties were evaluated via electrochemical tests, nanoindentation, friction–wear experiments, contact angle measurements, and antibacterial assays. Results indicate that MAO coatings on all substrates exhibit a dense, uniform grayish-white macroscopic morphology with 3–5 μm pores. Cross-sectional observations reveal a metallurgical bond between the coating and substrate, with minor blind pores and microcracks distributed in the coating, and different coatings show similar thickness and high density. The coatings mainly consist of Ca₃(PO₄)₂, CaCO₃, Mg, MgSiO₃, and MgO. HA powder is uniformly dispersed in the substrate treated by 1500-3 FSP passes, promoting more Ca²⁺ and PO₄³⁻ release during the MAO process. This yields the highest Ca/P ratio, endowing the coating with excellent biological performance to induce osteocyte growth. All coatings have good wear/corrosion resistance and a maximum adhesion of 14.485 N. Notably, MAO coatings on substrates with 1500-3 and 1700-3 FSP passes are moderately hydrophilic, facilitating cell adhesion/spreading and meeting biomedical implants’ short-term antibacterial rate requirements. Full article