Bioaggregate Inhibits Osteoclast Differentiation, Fusion, and Bone Resorption In Vitro

Nanoparticulate bioceramic putty suppresses osteoclastogenesis and inflammatory bone loss in mice via inhibition of TRAF6-mediated signalling pathways: A laboratory investigation

AIM

This study aimed to determine the effects of iRoot BP Plus on receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis in vitro and inflammation-mediated bone resorption in vivo and investigated the underlying molecular mechanisms.

METHODOLOGY

CCK-8 was performed to test cell viability in RANKL-induced RAW 264.7 cells and BMDMs in response to iRoot BP Plus. The effect of iRoot BP Plus on osteoclastogenesis was determined using TRAP staining and phalloidin staining, respectively. Pit formation assay was conducted to measure osteoclast resorptive capacity. Western blot and qPCR were performed to examine osteoclast-related proteins and gene expression, respectively. Western blot was also used to investigate the signalling pathways involved. For in vivo experiments, an LPS-induced mouse calvarial bone resorption model was established to analyse the effect of iRoot BP Plus on bone resorption (n = 6 per group). At 7 days, mouse calvaria were collected and prepared for histological analysis.

RESULTS

We identified that iRoot BP Plus extracts significantly attenuated RANKL-induced osteoclastogenesis, reduced sealing zone formation, restrained osteolytic capacity and decreased osteoclast-specific gene expression (p < .01). Mechanistically, iRoot BP Plus extracts reduced TRAF6 via proteasomal degradation, then suppressed the phosphorylation of mitogen-activated protein kinases (MAPKs), blocked the nuclear translocation of c-Fos and diminished nuclear factor-κB (NF-κB) p65 and NFATc1 accumulation. Consistent with the in vitro results, iRoot BP Plus extracts attenuated osteoclast activity thus protecting against inflammatory bone resorption in vivo (p < .05), which was accompanied by a suppression of TRAF6, c-Fos, NFATc1 and cathepsin K expression.

CONCLUSION

These findings provide valuable insights into the signalling mechanisms underlying nanoparticulate bioceramic putty-mediated bone homeostasis.

Bioceramics in Endodontics: Updates and Future Perspectives

Bioceramics, with excellent bioactivity and biocompatibility, have been widely used in dentistry, particularly in endodontics. Mineral trioxide aggregate (MTA) is the most widely used bioceramic in endodontics. Recently, many new bioceramics have been developed, showing good potential for the treatment of endodontic diseases. This paper reviews the characteristics of bioceramics and their applications in various clinical endodontic situations, including root-end filling, root canal therapy, vital pulp therapy, apexification/regenerative endodontic treatment, perforation repair, and root defect repair. Relevant literature published from 1993 to 2023 was searched by keywords in PubMed and Web of Science. Current evidence supports the predictable outcome of MTA in the treatment of endodontic diseases. Although novel bioceramics such as Biodentine, EndoSequence, and calcium-enriched mixtures have shown promising clinical outcomes, more well-controlled clinical trials are still needed to provide high-level evidence for their application in endodontics. In addition, to better tackle the clinical challenges in endodontics, efforts are needed to improve the bioactivity of bioceramics, particularly to enhance their antimicrobial activity and mechanical properties and reduce their setting time and solubility.

Small extracellular vesicles derived from hypoxic preconditioned dental pulp stem cells ameliorate inflammatory osteolysis by modulating macrophage polarization and osteoclastogenesis

Extensive macrophage inflammatory responses and osteoclast formation are predominant during inflammatory or infective osteolysis. Mesenchymal stem cell (MSC)-derived small extracellular vesicles (MSC-sEV) have been shown to exert therapeutic effects on bone defects. However, cultured MSCs are typically exposed to normoxia (21% O₂) in vitro, which differs largely from the oxygen concentration in vivo under hypoxic conditions. It is largely unknown whether sEV derived from dental pulp stem cells (DPSCs) cultured under hypoxic conditions (Hypo-sEV) exert better therapeutic effects on lipopolysaccharide (LPS)-induced inflammatory osteolysis than those cultured under normoxic conditions (Nor-sEV) by simultaneously inhibiting the macrophage inflammatory response and osteoclastogenesis. In this study, we show that hypoxia significantly induces the release of sEV from DPSCs. Moreover, Hypo-sEV exhibit significantly improved efficacy in promoting M2 macrophage polarization and suppressing osteoclast formation to alleviate LPS-induced inflammatory calvarial bone loss compared with Nor-sEV. Mechanistically, hypoxia preconditioning markedly alters the miRNA profiles of DPSC-sEV. MiR-210-3p is enriched in Hypo-sEV, and can simultaneously induce M2 macrophage generation and inhibit osteoclastogenesis by targeting NF-κB1 p105, which attenuates osteolysis. Our study suggests a promising potential for hypoxia-induced DPSC-sEV to treat inflammatory or infective osteolysis and identifies a novel role of miR-210-3p in concurrently hindering osteoclastogenesis and macrophage inflammatory response by inhibiting NF-kB1 expression.

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Hypoxia promotes the release of sEV from DPSCs.

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Hypoxia-induced DPSC-sEV (Hypo-sEV) show increased potential to inhibit inflammatory osteolysis.

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The miR-210-3p enriched in Hypo-sEV contributes to therapeutic effects of Hypo-sEV.

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MiR-210-3p concurrently induces M2 macrophage generation and inhibits osteoclastogenesis by targeting NF-κB1.

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Hypoxia-induced DPSC-sEV represent a promising therapy for inflammatory osteolysis.

Trends of calcium silicate biomaterials in medical research and applications: A bibliometric analysis from 1990 to 2020

Background: Calcium silicate biomaterials (CSB) have witnessed rapid development in the past 30 years. This study aimed to accomplish a comprehensive bibliometric analysis of the published research literature on CSB for biomedical applications and explore the research hotspot and current status.

Methods: Articles related to CSB published in the last three decades (1990–2020) were retrieved from Web of Science Core Collection. The R bibliometrix package and VOSviewer were used to construct publication outputs and collaborative networking among authors, their institutes, countries, journals’ matrices and keywords plus.

Results: A total of 872 publications fulfilling the search criteria were included. CSB is mainly reported for bone tissues and dental applications. Among researchers, Chang J from Chinese Academy of Sciences and Gandolfi MG from the University of Bologna are the most productive author in these two fields, respectively. China was the leading contributor to the research on CSB in the medical field. A total of 130 keywords appeared more ten or more times were identified. The term “mineral trioxide aggregate” ranked first with 268 occurrences. The co-occurrence analysis identified three major clusters: CSB in dentistry, bone tissue and vitro bioactivity.

Conclusion: Calcium silicate biomaterials have a promising scope for various biomedical applications ranging from regeneration of hard tissues (bone and teeth) to skin, tumor, cardiac muscle and other soft tissues. This study may help researchers further understand the frontiers of the field.

Physicochemical properties and osteoclastogenesis for three premixed calcium silicate-based sealers post set

Solubility, pH, ion release, cytotoxicity, and osteoclastogenesis inhibition in bone marrow-derived monocyte macrophages (BMMs) were evaluated in EndoSequence BC Sealer (END), Bio-C Sealer (BC), and Sealer Plus BC (SPBC). pH was determined after immersion of the sealers in deionized water (DW) and Minimum Essential Medium Alpha (α-MEM). Solubility was obtained by mass loss. Ion release was measured by using X-ray fluorescence spectroscopy (XRF). Cytotoxicity was evaluated by MTT assay. Inhibition of osteoclastogenesis was evaluated by tartrate-resistant acid phosphatase (TRAP). Data were analyzed using the t-test, ANOVA and Tukey/Dunnett's post-hoc tests (α = 0.05). END had the highest pH in DW (p < 0.05), and BC, in α-MEM (p < 0.05). Solubility in DW was the lowest for SPBC (p < 0.005). The highest calcium release was observed for BC in DW at 12 h (p < 0.05), and in α-MEM at 12 and 24 h (p < 0.05). The lowest toxicity was detected for END (p < 0.05). BC had the highest inhibitory effect on osteoclasts (p < 0.05). Overall, the highest solubility and pH values were found in DW. However, the calcium silicate-based sealer showed higher solubility than the ISO standards. Calcium release was the highest for BC. END showed the highest cell viability, and BC, the highest osteoclast inhibition.

In vitro biocompatibility and bioactivity of calcium silicate‑based bioceramics in endodontics (Review)

Calcium silicate-based bioceramics have been applied in endodontics as advantageous materials for years. In addition to excellent physical and chemical properties, the biocompatibility and bioactivity of calcium silicate-based bioceramics also serve an important role in endodontics according to previous research reports. Firstly, bioceramics affect cellular behavior of cells such as stem cells, osteoblasts, osteoclasts, fibroblasts and immune cells. On the other hand, cell reaction to bioceramics determines the effect of wound healing and tissue repair following bioceramics implantation. The aim of the present review was to provide an overview of calcium silicate-based bioceramics currently applied in endodontics, including mineral trioxide aggregate, Bioaggregate, Biodentine and iRoot, focusing on their in vitro biocompatibility and bioactivity. Understanding their underlying mechanism may help to ensure these materials are applied appropriately in endodontics.

Gradient fluid shear stress regulates migration of osteoclast precursors

Cell migration is highly sensitive to fluid shear stress (FSS) in blood flow or interstitial fluid flow. However, whether the FSS gradient can regulate the migration of cells remains unclear. In this work, we constructed a parallel-plate flow chamber with different FSS gradients and verified the gradient flow field by particle image velocimetry measurements and finite element analyses. We then investigated the effect of FSS magnitudes and gradients on the migration of osteoclast precursor RAW264.7 cells. Results showed that the cells sensed the FSS gradient and migrated toward the low-FSS region. This FSS gradient-induced migration tended to occur in low-FSS magnitudes and high gradients, e.g., the migration angle relative to flow direction was approximately 90° for 0.1 Pa FSS and 0.2 Pa mm⁻¹ FSS gradient. When chemically inhibiting the calcium signaling pathways of the mechanosensitive cation channel, endoplasmic reticulum, phospholipase C, and extracellular calcium, the cell migration toward the low-FSS region was significantly reduced. This study may provide insights into the mechanism of the recruitment of osteoclast precursors at the site of bone resorption and of mechanical stimulation-induced bone remodeling.

Enterococcus faecalis immunoregulates osteoclastogenesis of macrophages

Persistent apical periodontitis (PAP) is characterized by refractory inflammation and progressive bone destruction. Enterococcus faecalis infection is considered an important etiological factor for the development of PAP, although the exact mechanisms remain unknown. This study aimed at investigating the role of E. faecalis in cell proliferation, inflammatory reactions and osteoclast differentiation of macrophages using an in vitro infection model of osteoclast precursor RAW264.7 cells. A cell viability assay of cultured RAW264.7 cells exposed to live E. faecalis at a multiplicity of infection of 100 for 2h, indicated that the infection exhibited no cytotoxic effect. Transmission electron microscopy images revealed no apoptotic changes but a rise of metabolic activity and phagocytic features in the infected RAW264.7 cells. Confocal laser scanning microscopic and flow cytometric analysis indicated that the phagocytosis of RAW264.7 cells was activated by E. faecalis infection. Furthermore, quantitative real-time PCR assays demonstrated that the expression of inflammatory cytokines was remarkably elevated in infected RAW264.7 cells. Differentiation of infected RAW264.7 cells into osteoclasts was remarkably attenuated, and expression of osteoclast marker genes as well as fusogenic genes significantly dropped. In summary, E. faecalis appears to attenuate osteoclastic differentiation of RAW264.7 precursor cells, rather stimulates them to function as macrophages.

Dose effects of beta-tricalcium phosphate nanoparticles on biocompatibility and bone conductive ability of three-dimensional collagen scaffolds

Three-dimensional collagen scaffolds coated with beta-tricalcium phosphate (β-TCP) nanoparticles reportedly exhibit good bioactivity and biodegradability. Dose effects of β-TCP nanoparticles on biocompatibility and bone forming ability were then examined. Collagen scaffold was applied with 1, 5, 10, and 25 wt% β-TCP nanoparticle dispersion and designated TCP1, TCP5, TCP10, and TCP25, respectively. Compressive strength, calcium ion release and enzyme resistance of scaffolds with β-TCP nanoparticles applied increased with β-TCP dose. TCP5 showed excellent cell-ingrowth behavior in rat subcutaneous tissue. When TCP10 was applied, osteoblastic cell proliferation and rat cranial bone augmentation were greater than for any other scaffold. The bone area of TCP10 was 7.7-fold greater than that of non-treated scaffold. In contrast, TCP25 consistently exhibited adverse biological effects. These results suggest that the application dose of β-TCP nanoparticles affects the scaffold bioproperties; consequently, the bone conductive ability of TCP10 was remarkable.

Ion Release, Microstructural, and Biological Properties of iRoot BP Plus and ProRoot MTA Exposed to an Acidic Environment

INTRODUCTION

This study evaluated how exposing the novel calcium silicate nanoparticulate bioceramic iRoot BP Plus (Innovative Bioceramix, Vancouver, Canada) to an acidic environment affects ion release from this material and alters MC3T3-E1 preosteoblast viability on and attachment to this material. These factors were compared against those of ProRoot MTA under similar conditions.

METHODS

Each material was exposed to phosphate-buffered saline (pH = 7.4) or butyric acid (pH = 5.4) for 5 days. Trace metal elements within the 2 materials and released ions were identified using inductively coupled plasma optical emission spectroscopy. The microstructures and elemental compositions of MTA and iRoot BP Plus after treatment with butyric acid were determined using scanning electron microscopy with an energy-dispersive X-ray spectrometer. Furthermore, the viability of MC3T3-E1 cells on and their levels of attachment to the materials after the butyric acid treatment were compared.

RESULTS

iRoot BP Plus contained fewer toxic metal elements than MTA. Under acidic conditions, both materials displayed similar ion release abilities, with increased release of Si and Ca ions. Substantial changes in microstructure, including reduced apatite formation, were observed for both materials after exposure to acidic pH. Furthermore, exposing iRoot BP Plus and MTA to an acidic environment increased and decreased MC3T3-E1 cell viability on these materials, respectively. MC3T3-E1 cell attachment to both materials was not significantly affected by acidic pH.

CONCLUSIONS

iRoot BP Plus seems more biologically appropriate for application in an inflamed acidic environment than ProRoot MTA.