Cerium Oxide Nanoparticles Regulate Osteoclast Differentiation Bidirectionally by Modulating the Cellular Production of Reactive Oxygen Species

Activating Macrophage Continual Efferocytosis via Microenvironment Biomimetic Short Fibers for Reversing Inflammation in Bone Repair

Efferocytosis-mediated inflammatory reversal plays a crucial role in bone repairing process. However, in refractory bone defects, the macrophage continual efferocytosis may be suppressed due to the disrupted microenvironment homeostasis, particularly the loss of apoptotic signals and overactivation of intracellular oxidative stress. In this study, a polydopamine-coated short fiber matrix containing biomimetic "apoptotic signals" to reconstruct the microenvironment and reactivate macrophage continual efferocytosis for inflammatory reversal and bone defect repair is presented. The "apoptotic signals" (AM/CeO2) are prepared using CeO2 nanoenzymes with apoptotic neutrophil membrane coating for macrophage recognition and oxidative stress regulation. Additionally, a short fiber "biomimetic matrix" is utilized for loading AM/CeO2 signals via abundant adhesion sites involving π-π stacking and hydrogen bonding interactions. Ultimately, the implantable apoptosis-mimetic nanoenzyme/short-fiber matrixes (PFS@AM/CeO2), integrating apoptotic signals and biomimetic matrixes, are constructed to facilitate inflammatory reversal and reestablish the pro-efferocytosis microenvironment. In vitro and in vivo data indicate that the microenvironment biomimetic short fibers can activate macrophage continual efferocytosis, leading to the suppression of overactivated inflammation. The enhanced repair of rat femoral defect further demonstrates the osteogenic potential of the pro-efferocytosis strategy. It is believed that the regulation of macrophage efferocytosis through microenvironment biomimetic materials can provide a new perspective for tissue repair.

Tailoring Biomaterials Ameliorate Inflammatory Bone Loss

Inflammatory diseases, such as rheumatoid arthritis, periodontitis, chronic obstructive pulmonary disease, and celiac disease, disrupt the delicate balance between bone resorption and formation, leading to inflammatory bone loss. Conventional approaches to tackle this issue encompass pharmaceutical interventions and surgical procedures. Nevertheless, pharmaceutical interventions exhibit limited efficacy, while surgical treatments impose trauma and significant financial burden upon patients. Biomaterials show outstanding spatiotemporal controllability, possess a remarkable specific surface area, and demonstrate exceptional reactivity. In the present era, the advancement of emerging biomaterials has bestowed upon more efficacious solutions for combatting the detrimental consequences of inflammatory bone loss. In this review, the advances of biomaterials for ameliorating inflammatory bone loss are listed. Additionally, the advantages and disadvantages of various biomaterials-mediated strategies are summarized. Finally, the challenges and perspectives of biomaterials are analyzed. This review aims to provide new possibilities for developing more advanced biomaterials toward inflammatory bone loss.

Systematic review of the osteogenic effect of rare earth nanomaterials and the underlying mechanisms

Rare earth nanomaterials (RE NMs), which are based on rare earth elements, have emerged as remarkable biomaterials for use in bone regeneration. The effects of RE NMs on osteogenesis, such as promoting the osteogenic differentiation of mesenchymal stem cells, have been investigated. However, the contributions of the properties of RE NMs to bone regeneration and their interactions with various cell types during osteogenesis have not been reviewed. Here, we review the crucial roles of the physicochemical and biological properties of RE NMs and focus on their osteogenic mechanisms. RE NMs directly promote the proliferation, adhesion, migration, and osteogenic differentiation of mesenchymal stem cells. They also increase collagen secretion and mineralization to accelerate osteogenesis. Furthermore, RE NMs inhibit osteoclast formation and regulate the immune environment by modulating macrophages and promote angiogenesis by inducing hypoxia in endothelial cells. These effects create a microenvironment that is conducive to bone formation. This review will help researchers overcome current limitations to take full advantage of the osteogenic benefits of RE NMs and will suggest a potential approach for further osteogenesis research.

Bacteroid cerium oxide particles promote macrophage polarization to achieve early vascularization and subsequent osseointegration around implants

The establishment of an osseointegration is crucial for the long-term stability and functionality of implant materials, and early angiogenesis is the key to successful osseointegration. However, the bioinertness of titanium implants affects osseointegration, limiting their clinical application. In this study, inspired by the rapid polarization of macrophages following the phagocytosis of bacteria, we developed bacteroid cerium oxide particles; these particles were composed of CeO2 and had a size similar to that of Bacillus (0.5 μ m). These particles were constructed on the implant surfaces using a hydrothermal method. In vitro experiments demonstrated that the particles effectively decreased the reactive oxygen species (ROS) levels in macrophages (RAW264.7). Furthermore, these particles exerted effects on M1 macrophage polarization, enhanced nitric oxide (NO) secretion to promote vascular regeneration, and facilitated rapid macrophage transition to the M2 phenotype. Subsequently, the particles facilitated human umbilical vein endothelial cell (HUVEC) migration. In vivo studies showed that these particles rapidly stimulated innate immune responses in animal models, leading to enhanced angiogenesis around the implant and improved osseointegration. In summary, the presence of bacteroid cerium oxide particles on the implant surface regulated and accelerated macrophage polarization, thereby enhancing angiogenesis during the immune response and improving peri-implant osseointegration.

Anti-Acidification and Immune Regulation by Nano-Ceria-Loaded Mg-Al Layered Double Hydroxide for Rheumatoid Arthritis Therapy

Rheumatoid arthritis (RA) is a chronic autoimmune disease featuring an abnormal immune microenvironment and resultant accumulation of hydrogen ions (H+ ) produced by activated osteoclasts (OCs). Currently, clinic RA therapy can hardly achieve sustained or efficient therapeutic outcomes due to the failures in generating sufficient immune modulation and manipulating the accumulation of H+ that deteriorates bone damage. Herein, a highly effective immune modulatory nanocatalytic platform, nanoceria-loaded magnesium aluminum layered double hydroxide (LDH-CeO2 ), is proposed for enhanced immune modulation based on acid neutralization and metal ion inherent bioactivity. Specifically, the mild alkaline LDH initiates significant M2 repolarization of macrophages triggered by the elevated antioxidation effect of CeO2 via neutralizing excessive H+ in RA microenvironment, thus resulting in the efficient recruitment of regulatory T cell (Treg) and suppressions on T helper 17 cell (Th 17) and plasma cells. Moreover, the osteogenic activity is stimulated by the Mg ion released from LDH, thereby promoting the damaged bone healing. The encouraging therapeutic outcomes in adjuvant-induced RA model mice demonstrate the high feasibility of such a therapeutic concept, which provides a novel and efficient RA therapeutic modality by the immune modulatory and bone-repairing effects of inorganic nanocatalytic material.

Mechanochemical synthesis of cerium chlorapatite from a mixture of cerium chloride heptahydrate, dicalcium phosphate dihydrate, and calcium hydroxide for biomedical application

BACKGROUND

Cerium ions promote osteoclastogenesis and activate bone metabolism, while cerium oxide nanoparticles exhibit potent anti-inflammatory properties, making them promising for biomedical applications.

OBJECTIVE

The purpose of this study was to develop and evaluate a synthesis method for sustained-release cerium-ion bioceramics containing apatite. Substituted apatite was found to be an effective biomaterial.

METHODS

Cerium-containing chlorapatite was synthesized using a mechanochemical method employing dicalcium phosphate, cerium chloride heptahydrate, and calcium hydroxide as raw materials. The synthesized samples were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Raman spectroscopy.

RESULTS

Cerium chlorapatite was successfully synthesized in the 10.1% and 20.1% samples. However, at Ce concentrations higher than 30.2%, the samples consisted of three or more phases, indicating the instability of a single phase.

CONCLUSION

The method used in this study was found to be more efficient and cost-effective than the precipitation method for producing substituted apatite and calcium phosphate-based biomaterials. This research contributes to the development of sustained-release cerium-ion bioceramics with potential applications in the field of biomedicine.

Nanozymes With Osteochondral Regenerative Effects: An Overview of Mechanisms and Recent Applications

With the discovery of the intrinsic enzyme-like activity of metal oxides, nanozymes garner significant attention due to their superior characteristics, such as low cost, high stability, multi-enzyme activity, and facile preparation. Notably, in the field of biomedicine, nanozymes primarily focus on disease detection, antibacterial properties, antitumor effects, and treatment of inflammatory conditions. However, the potential for application in regenerative medicine, which primarily addresses wound healing, nerve defect repair, bone regeneration, and cardiovascular disease treatment, is garnering interest as well. This review introduces nanozymes as an innovative strategy within the realm of bone regenerative medicine. The primary focus of this approach lies in the facilitation of osteochondral regeneration through the modulation of the pathological microenvironment. The catalytic mechanisms of four types of representative nanozymes are first discussed. The pathological microenvironment inhibiting osteochondral regeneration, followed by summarizing the therapy mechanism of nanozymes to osteochondral regeneration barriers is introduced. Further, the therapeutic potential of nanozymes for bone diseases is included. To improve the therapeutic efficiency of nanozymes and facilitate their clinical translation, future potential applications in osteochondral diseases are also discussed and some significant challenges addressed.

Recent Advances on Cerium Oxide-Based Biomaterials: Toward the Next Generation of Intelligent Theranostics Platforms

Disease or organ damage due to unhealthy living habits, or accidents, is inevitable. Discovering an efficient strategy to address these problems is urgently needed in the clinic. In recent years, the biological applications of nanotechnology have received extensive attention. Among them, as a widely used rare earth oxide, cerium oxide (CeO2 ) has shown good application prospects in biomedical fields due to its attractive physical and chemical properties. Here, the enzyme-like mechanism of CeO2 is elucidated, and the latest research progress in the biomedical field is reviewed. At the nanoscale, Ce ions in CeO2 can be reversibly converted between +3 and +4. The conversion process is accompanied by the generation and elimination of oxygen vacancies, which give CeO2 the performance of dual redox properties. This property facilitates nano-CeO2 to catalyze the scavenging of excess free radicals in organisms, hence providing a possibility for the treatment of oxidative stress diseases such as diabetic foot, arthritis, degenerative neurological diseases, and cancer. In addition, relying on its excellent catalytic properties, customizable life-signaling factor detectors based on electrochemical techniques are developed. At the end of this review, an outlook on the opportunities and challenges of CeO2 in various fields is provided.

Structural and functional insights in polysaccharides coated cerium oxide nanoparticles and their potential biomedical applications: A review

Cerium oxide nanoparticles have now significant presence in biomedical fields due to their wide applications; however, challenges regarding their safety and biocompatibility persist. Polysaccharides based biopolymers have inherent hydroxyl and carboxyl groups, enabling them to govern the surface functionalization of cerium oxide nanoparticles, hence their chemical and physical characteristics. Because of this, polysaccharides such as dextran, alginate, pullulan, chitosan, polylactic acid, starch, and pectin are practical substitutes for the conventional coatings used to synthesize cerium oxide nanoparticles. This review discusses the effect of biopolymer coatings on the properties of cerium oxide nanoparticles, such as size, stability, aggregation, and biocompatibility. Additionally, it also summarises various biomedical applications of polysaccharides coated cerium oxide nanoparticles, such as in bone tissue regeneration, liver inflammation, wound healing, and antibacterial and anticancer activities. Biocompatible cerium oxide nanoparticles will surely improve their applications in the biomedical field.

Nacre-mimetic cerium-doped nano-hydroxyapatite/chitosan layered composite scaffolds regulate bone regeneration via OPG/RANKL signaling pathway

Autogenous bone grafting has long been considered the gold standard for treating critical bone defects. However, its use is plagued by numerous drawbacks, such as limited supply, donor site morbidity, and restricted use for giant-sized defects. For this reason, there is an increasing need for effective bone substitutes to treat these defects. Mollusk nacre is a natural structure with outstanding mechanical property due to its notable "brick-and-mortar" architecture. Inspired by the nacre architecture, our team designed and fabricated a nacre-mimetic cerium-doped layered nano-hydroxyapatite/chitosan layered composite scaffold (CeHA/CS). Hydroxyapatite can provide a certain strength to the material like a brick. And as a polymer material, chitosan can slow down the force when the material is impacted, like an adhesive. As seen in natural nacre, the combination of these inorganic and organic components results in remarkable tensile strength and fracture toughness. Cerium ions have been demonstrated exceptional anti-osteoclastogenesis capabilities. Our scaffold featured a distinct layered HA/CS composite structure with intervals ranging from 50 to 200 μm, which provided a conducive environment for human bone marrow mesenchymal stem cell (hBMSC) adhesion and proliferation, allowing for in situ growth of newly formed bone tissue. In vitro, Western-blot and qPCR analyses showed that the CeHA/CS layered composite scaffolds significantly promoted the osteogenic process by upregulating the expressions of osteogenic-related genes such as RUNX2, OCN, and COL1, while inhibiting osteoclast differentiation, as indicated by reduced TRAP-positive osteoclasts and decreased bone resorption. In vivo, calvarial defects in rats demonstrated that the layered CeHA/CS scaffolds significantly accelerated bone regeneration at the defect site, and immunofluorescence indicated a lowered RANKL/OPG ratio. Overall, our results demonstrate that CeHA/CS scaffolds offer a promising platform for bone regeneration in critical defect management, as they promote osteogenesis and inhibit osteoclast activation.

GC-MS Analysis, Antibacterial, and Anticancer Activities of Hibiscus sabdariffa L. Methanolic Extract: In Vitro and In Silico Studies

The emergence of bacteria that are resistant to several antibiotics has represented a serious hazard to human health globally. Bioactive metabolites from medicinal plants have a wide spectrum of therapeutic possibilities against resistant bacteria. Therefore, this study was performed to investigate the antibacterial efficacy of various extracts of three medicinal plants as Salvia officinalis L., Ziziphus spina-christi L., and Hibiscus sabdariffa L. against pathogenic Gram-negative Enterobacter cloacae (ATCC13047), Pseudomonas aeruginosa (RCMB008001), Escherichia coli (RCMB004001), and Gram-positive Staphylococcus aureus (ATCC 25923), bacteria using the agar-well diffusion method. Results revealed that, out of the three examined plant extracts, the methanol extract of H. sabdariffa L. was the most effective against all tested bacteria. The highest growth inhibition (39.6 ± 0.20 mm) was recorded against E. coli. Additionally, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of the methanol extract of H. sabdariffa were detected in the case of all tested bacteria. Moreover, an antibiotic susceptibility test revealed that all tested bacteria showed multidrug resistance (MDR). While 50% of tested bacteria were sensitive and 50% were intermediately sensitive to piperacillin/tazobactam (TZP) based on the inhibition zone but still less than the extract. Synergistic assay demonstrated the promising role of using a combination of H. sabdariffa L. and (TZP) against tested bacteria. A surface investigation using a scanning electron microscope of the E. coli treated with TZP, extract, or a combination of the two revealed extremely considerable bacterial cell death. In addition, H. sabdariffa L. has a promising anticancer role versus Caco-2 cells with IC₅₀ of 17.51 ± 0.07 µg/mL and minimal cytotoxicity upon testing versus Vero cells with CC₅₀ of 165.24 ± 0.89 µg/mL. Flow cytometric analysis confirmed that H. sabdariffa extract significantly increased the apoptotic rate of Caco-2-treated cells compared to the untreated group. Furthermore, GC-MS analysis confirmed the existence of various bioactive components in the methanol hibiscus extract. Utilizing molecular docking with the MOE-Dock tool, binding interactions between n-Hexadecanoic acid, hexadecanoic acid-methyl ester, and oleic acid, 3-hydroxypropyl ester were evaluated against the target crystal structures of E. coli (MenB) (PDB ID:3T88) and the structure of cyclophilin of a colon cancer cell line (PDB ID: 2HQ6). The observed results provide insight into how molecular modeling methods might inhibit the tested substances, which may have applications in the treatment of E. coli and colon cancer. Thus, H. sabdariffa methanol extract is a promising candidate to be further investigated for developing alternative natural therapies for infection treatment.

A dual functional Ti-Ga alloy: inhibiting biofilm formation and osteoclastogenesis differentiation via disturbing iron metabolism

BACKGROUND

Although biomedical implants have been widely used in orthopedic treatments, two major clinical challenges remain to be solved, one is the bacterial infection resulting in biofilm formation, and the other is aseptic loosening during implantation due to over-activated osteoclastogenesis. These factors can cause many clinical issues and even lead to implant failure. Thus, it is necessary to endow implants with antibiofilm and aseptic loosening-prevention properties, to facilitate the integration between implants and bone tissues for successful implantation. To achieve this goal, this study aimed to develop a biocompatible titanium alloy with antibiofilm and anti-aseptic loosening dual function by utilizing gallium (Ga) as a component.

METHODS

A series of Ti-Ga alloys were prepared. We examined the Ga content, Ga distribution, hardness, tensile strength, biocompatibility, and anti-biofilm performance in vitro and in vivo. We also explored how Ga³⁺ ions inhibited the biofilm formation of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) and osteoclast differentiation.

RESULTS

The alloy exhibited outstanding antibiofilm properties against both S. aureus and E. coli in vitro and decent antibiofilm performance against S. aureus in vivo. The proteomics results demonstrated that Ga³⁺ ions could disturb the bacterial Fe metabolism of both S. aureus and E. coli, inhibiting bacterial biofilm formation. In addition, Ti-Ga alloys could inhibit receptor activator of nuclear factor-κB ligand (RANKL)-dependent osteoclast differentiation and function by targeting iron metabolism, then suppressing the activation of the NF-κB signaling pathway, thus, showing their potential to prevent aseptic loosening.

CONCLUSION

This study provides an advanced Ti-Ga alloy that can be used as a promising orthopedic implant raw material for various clinical scenarios. This work also revealed that iron metabolism is the common target of Ga³⁺ ions to inhibit biofilm formation and osteoclast differentiation.

Cerium Oxide Nanoparticles Promote Osteoplastic Precursor Differentiation by Activating the Wnt Pathway

Osteoplastic precursors are critical for fracture repair and bone homeostasis maintenance. Cerium oxide nanoparticles (CeO₂ NPs) can promote the osteogenic differentiation of mesenchymal stem cells and secrete vascular endothelial growth factors. However, little is known about its role in precursor osteoblasts; therefore, we further investigated the effect and mechanism of CeO₂ NPs in precursor osteoblasts. Cell counting kit-8 analysis was utilized to detect the toxicity of CeO₂ NPs on MC3T3-E1 mouse osteogenic precursor cells. Then, alizarin red S staining was employed to assess the degree of extracellular matrix mineralization, and quantitative real-time polymerase chain reaction analysis was performed to measure the levels of osteogenesis-related genes. To identify differentially expressed genes, mRNA-sequencing was performed. Subsequently, GO and KEGG analyses were deployed to identify the major downstream pathways, whereas Western blot was used for verification. CeO₂ NPs significantly enhanced the ability of MC3T3-E1 precursor osteoblasts to enhance matrix mineralization and increased the expression of osteogenic genes such as runt-related transcription factor 2, collagen Iα1, and osteocalcin. Pathway analysis revealed that CeO₂ NPs enhanced the nuclear translocation of β-catenin and activated the Wnt pathway by promoting family with sequence similarity 53 member B/simplet expression, while Western blot analysis indicated the same results. After using a Wnt pathway inhibitor (KYA1797K), the simulative effect of CeO₂ NPs was abolished. This study revealed that CeO₂ NPs promoted MC3T3-E1 precursor osteoblast differentiation by activating the Wnt pathway.

Alginate/Gelatin Hydrogel Scaffold Containing nCeO2 as a Potential Osteogenic Nanomaterial for Bone Tissue Engineering

Background

Clinicians frequently face difficulties when trying to fix bone abnormalities. Gelatin-Alginate (GA) is frequently employed as a carrier because it is non-toxic, biodegradable, and has a three-dimensional network structure. Meanwhile, cerium oxide nanoparticles (nCeO₂) demonstrated high antioxidant enzyme simulation activity. Therefore, in order to develop a porous hydrogel scaffold for the application of bone tissue engineering, an appropriate-type GA-nCeO₂ hydrogel scaffold was developed and evaluated.

Methods

 GA-nCeO₂ hydrogel scaffold was prepared by the lyophilized method and characterized. The surface morphology and cell adhesion of the scaffold were observed by the scanning electron microscope. CCK8 and live-dead staining methods were used to evaluate its biological safety and cell proliferation. Then the osteogenic differentiation in early and late stages was discussed. The expression of osteogenic genes was also detected by RT-PCR. Finally, a bone defect model was made in SD rats, and bone formation in vivo was detected.

Results

 The results showed that GA-nCeO₂ hydrogel scaffold exhibited a typical three-dimensional porous structure with a mean pore ratio of 70.61 ± 1.94%. The GA-nCeO₂ hydrogel was successfully endowed with simulated enzyme activity including superoxide dismutase (SOD) and catalase (CAT) after the addition of nCeO₂. Osteoblasts demonstrated superior cell proliferation and adhesion on composite scaffolds, and both mineralization test and gene expression demonstrated the strong osteogenic potential of GA-nCeO₂ hydrogel. The outcomes of hematoxylin and eosin (H&E) staining and Masson trichrome staining in the femoral defect model of SD rats further supported the scaffold's favorable biocompatibility and bone-promoting capacity.

Conclusion

Due to its favorable safety, degradability, and bone formation property, GA-nCeO₂ hydrogel was anticipated to be used as a potential bone defect healing material.

Metal Oxide Nanoparticles: Review of Synthesis, Characterization and Biological Effects

In the last few years, the progress made in the field of nanotechnology has allowed researchers to develop and synthesize nanosized materials with unique physicochemical characteristics, suitable for various biomedical applications. Amongst these nanomaterials, metal oxide nanoparticles (MONPs) have gained increasing interest due to their excellent properties, which to a great extent differ from their bulk counterpart. However, despite such positive advantages, a substantial body of literature reports on their cytotoxic effects, which are directly correlated to the nanoparticles' physicochemical properties, therefore, better control over the synthetic parameters will not only lead to favorable surface characteristics but may also increase biocompatibility and consequently lower cytotoxicity. Taking into consideration the enormous biomedical potential of MONPs, the present review will discuss the most recent developments in this field referring mainly to synthesis methods, physical and chemical characterization and biological effects, including the pro-regenerative and antitumor potentials as well as antibacterial activity. Moreover, the last section of the review will tackle the pressing issue of the toxic effects of MONPs on various tissues/organs and cell lines.

ROS-responsive resveratrol-loaded cyclodextrin nanomicelles reduce inflammatory osteolysis

Bone loss in inflammatory disorders such as osteomyelitis, septic arthritis, and periodontitis is caused by excessive osteoclastic activity. Meanwhile, reactive oxygen species (ROS) have been identified as contributors to osteoclast differentiation, and the application of ROS scavengers has emerged as a promising strategy to protect against bone loss. Recently, resveratrol (RSV), a polyphenolic phytoalexin, has been demonstrated to inhibit osteoclastogenesis by scavenging ROS; however, the application of RSV as an antioxidant is limited by its low water solubility, structural instability, and short elimination half-life. In this study, we developed a PEGylated cyclodextrin (CD)-based nanoplatform (PCP) for local delivery of RSV as nanomicelles (RSV-NMs). In addition, polymer functionalization with phenylboronic acid ester in RSV-NMs successfully achieved ROS-responsive release of RSV. The RSV-NMs in a well-dispersed state possessed good biocompatibility as well as improved solubility and stability compared with RSV compound. In vitro, RSV-NMs significantly inhibited the formation of tartrate-resistant acid phosphatase (TRAP)-positive multinuclear cells and suppressed F-actin (filamentous actin) ring formation. Additionally, the mRNA expressions of osteoclastic marker genes, including matrix metalloprotein-9 (MMP-9), nuclear factor of activated T cells 1 (NFATc1), TRAP, and cathepsin K, were consequently downregulated in the presence of RSV-NMs. In vivo, RSV-NMs provided protection against LPS-induced bone destruction, as evidenced by a decreased number of osteoclasts, increased bone density, and reduced area of bone resorption. Taken together, these results indicate that our ROS-responsive RSV-NMs can be employed as a potential therapeutic agent for the treatment of inflammatory osteolysis.

Trimethylamine-N-Oxide Promotes Osteoclast Differentiation and Bone Loss via Activating ROS-Dependent NF-κB Signaling Pathway

Trimethylamine-N-oxide (TMAO), an important gut microbiota (GM)-derived metabolite, has been shown to be abnormally increased in osteoporosis. However, the role and underlying mechanism of TMAO in regulating bone loss during osteoporosis have not been fully investigated. In the current study, we found that 100–400 μM TMAO dose-dependently enhanced TRAP-positive osteoclasts, F-actin ring formation, and resorption area on bovine bone slices and up-regulated osteoclast-related gene expression (Calcr, Traf6, Dcstamp, Acp5, C-Fos, and NFATc1). Western blotting validated that TMAO not only activated NF-κB signaling pathway but also stimulated c-Fos and NFATc1 protein expression in a dose-dependent manner. Furthermore, BAY 11-7082, an NF-κB inhibitor, pretreatment markedly suppressed TRAP-positive osteoclast formation and osteoclast-related genes under TMAO treatment. BAY 11-7082 also inhibited p-p65/p65, c-Fos, and NFATc1 protein expression promoted by TMAO. Moreover, TMAO significantly increased ROS production, which was inhibited by N-acetylcysteine (NAC), an ROS antagonist. In addition, we proved that NAC pretreatment could inhibit TMAO-promoted NF-κB activation. NAC also suppressed TRAP-positive osteoclast formation, osteoclast-related gene expression, and protein expression of c-Fos and NFATc1 under TMAO treatment. In vivo studies showed significantly decreased bone mass and increased TRAP-positive osteoclasts in TMAO-treated C57BL/6 mice. Moreover, western-blotting and immunohistochemical staining showed that TMAO administration markedly stimulated NF-κB p65 expression. Additionally, TMAO administration significantly promoted the gene and protein expression of C-Fos and NFATc1. In conclusion, TMAO could promote osteoclast differentiation and induce bone loss in mice by activating the ROS-dependent NF-κB signaling pathway.

A novel approach for the prevention of ionizing radiation-induced bone loss using a designer multifunctional cerium oxide nanozyme

The disability, mortality and costs due to ionizing radiation (IR)-induced osteoporotic bone fractures are substantial and no effective therapy exists. Ionizing radiation increases cellular oxidative damage, causing an imbalance in bone turnover that is primarily driven via heightened activity of the bone-resorbing osteoclast. We demonstrate that rats exposed to sublethal levels of IR develop fragile, osteoporotic bone. At reactive surface sites, cerium ions have the ability to easily undergo redox cycling: drastically adjusting their electronic configurations and versatile catalytic activities. These properties make cerium oxide nanomaterials fascinating. We show that an engineered artificial nanozyme composed of cerium oxide, and designed to possess a higher fraction of trivalent (Ce³⁺) surface sites, mitigates the IR-induced loss in bone area, bone architecture, and strength. These investigations also demonstrate that our nanozyme furnishes several mechanistic avenues of protection and selectively targets highly damaging reactive oxygen species, protecting the rats against IR-induced DNA damage, cellular senescence, and elevated osteoclastic activity in vitro and in vivo. Further, we reveal that our nanozyme is a previously unreported key regulator of osteoclast formation derived from macrophages while also directly targeting bone progenitor cells, favoring new bone formation despite its exposure to harmful levels of IR in vitro. These findings open a new approach for the specific prevention of IR-induced bone loss using synthesis-mediated designer multifunctional nanomaterials.

Determination of Therapeutic and Safety Effects of Zygophyllum coccineum Extract in Induced Inflammation in Rats

Background

Z. coccineum is a facultative plant with many medicinal applications. This study examined the anti-inflammatory activity of Zygophyllum coccineum (Z. coccineum) in an arthritis animal model.

Materials and Methods

Seventy-Six Wistar Albino rats of either sex randomly divided into six groups (12/each). The inflammation model was done using Complete Freund's Adjuvant in albino rats. The anti-inflammatory activities of the extract were estimated at different dose levels (15.6, 31, and 60 mg/kg) as well as upon using methotrexate (MTX) as a standard drug (0.3 mg/kg). Paw volume and arthritis index scores have been tested in all examined animals' treatments. Histological examination of joints was also performed. Flow cytometric studies were done to isolated osteoclasts. Cytokines assay as well as biochemical testing was done in the examined samples. Results. In vitro studies reported an IC₅₀ of 15.6 μg/ml for Z. coccineum extract in lipoxygenase inhibition assay (L.O.X.). Moreover, it could be noticed that isorhamnetin-3-O-glucoside, tribuloside, and 7-acetoxy-4-methyl coumarin were the most common compounds in Z. coccineum extract separated using L.C.–ESI-TOF–M.S. (liquid chromatography-electrospray ionization ion-trap time-of-flight mass spectrometry). Microscopic examinations of synovial tissue and hind limb muscles revealed the effect of different doses of Z. coccineum extract on restoring chondrocytes and muscles structures. Osteoclast size and apoptotic rate examinations revealed the protective effect of Z. coccineum extract on osteoclast. The results upon induction of animals and upon treatment using of MTX significantly increased apoptotic rate of osteoclast compared to control, while using of 15.6 μg/ml. for Z. coccineum extract lead to recover regular apoptotic rate demonstrating the protective effect of the extract. Z. coccineum extract regulated the secretion of proinflammatory and anti-inflammatory cytokines. Biochemical tests indicated the safety of Z. coccineum extract on kidney and liver functions. Conclusion. Z. coccineum extract has efficient and safe anti-inflammatory potential in an induced rat model.

Sec-O-Glucosylhamaudol Inhibits RANKL-Induced Osteoclastogenesis by Repressing 5-LO and AKT/GSK3β Signaling

Sec-O-glucosylhamaudol (SOG), an active flavonoid compound derived from the root of Saposhnikovia divaricata (Turcz. ex Ledeb.) Schischk., exhibits analgesic, anti-inflammatory, and high 5-lipoxygenase (5-LO) inhibitory effects. However, its effect on osteoclastogenesis was unclear. We demonstrated that SOG markedly attenuated RANKL-induced osteoclast formation, F-actin ring formation, and mineral resorption by reducing the induction of key transcription factors NFATc1, c-Fos, and their target genes such as TRAP, CTSK, and DC-STAMP during osteoclastogenesis. Western blotting showed that SOG significantly inhibited the phosphorylation of AKT and GSK3β at the middle–late stage of osteoclastogenesis without altering calcineurin catalytic subunit protein phosphatase-2β-Aα expression. Moreover, GSK3β inhibitor SB415286 partially reversed SOG-induced inhibition of osteoclastogenesis, suggesting that SOG inhibits RANKL-induced osteoclastogenesis by activating GSK3β, at least in part. 5-LO gene silencing by small interfering RNA in mouse bone marrow macrophages markedly reduced RANKL-induced osteoclastogenesis by inhibiting NFATc1. However, it did not affect the phosphorylation of AKT or GSK3β, indicating that SOG exerts its inhibitory effects on osteoclastogenesis by suppressing both the independent 5-LO pathway and AKT-mediated GSK3β inactivation. In support of this, SOG significantly improved bone destruction in a lipopolysaccharide-induced mouse model of bone loss. Taken together, these results suggest a potential therapeutic effect for SOG on osteoclast-related bone lysis disease.

ROS-Mediated Anti-Angiogenic Activity of Cerium Oxide Nanoparticles in Melanoma Cells

Angiogenesis plays a key role in cancer progression, including transition to the metastatic phase via reactive oxygen species (ROS)-dependent pathways, among others. Antivascular endothelial growth factor (VEGF) antibodies have been trialed as an anti-angiogenic therapy for cancer but are associated with high cost, limited efficacy, and side effects. Cerium oxide nanoparticles (nanoceria) are promising nanomaterials for biomedical applications due to their ability to modulate intracellular ROS. Nanoceria can be produced by a range of synthesis methods, with chemical precipitation as the most widely explored. It has been reported that chemical precipitation can fine-tune primary particle size where a limited number of synthesis parameters were varied. Here, we explore the effect of temperature, precipitating agent concentration and rate of addition, stirring rate, and surfactant concentration on nanoceria primary particle size using a fractional factorial experimental design approach. We establish a robust synthesis method for faceted nanoceria with primary particle diameters of 5-6 nm. The nanoceria are not cytotoxic to a human melanoma cell line (Mel1007) at doses up to 400 μg/mL and are dose-dependently internalized by the cells. The intracellular ROS level for some cells that internalized the nanoceria is reduced, which correlates with a dose-dependent reduction in angiogenic gene expression including VEGF. These findings contribute to our knowledge of the anti-angiogenic effects of nanoceria and help to develop our understanding of potentially new anti-angiogenic agents for combination cancer therapies.

Ceria nanoparticles ameliorate renal fibrosis by modulating the balance between oxidative phosphorylation and aerobic glycolysis

Background and aims

Renal fibrosis is the common outcome in all progressive forms of chronic kidney disease. Unfortunately, the pathogenesis of renal fibrosis remains largely unexplored, among which metabolic reprogramming plays an extremely crucial role in the evolution of renal fibrosis. Ceria nanoparticles (CeNP-PEG) with strong ROS scavenging and anti-inflammatory activities have been applied for mitochondrial oxidative stress and inflammatory diseases. The present study aims to determine whether CeNP-PEG has therapeutic value for renal fibrosis.

Methods

The unilateral ureteral obstructive fibrosis model was used to assess the therapeutic effects in vivo. Transforming growth factor beta1-induced epithelial-to-mesenchymal transition in HK-2 cells was used as the in vitro cell model. The seahorse bioscience X96 extracellular flux analyzer was used to measure the oxygen consumption rate and extracellular acidification rate.

Results

In the present study, CeNP-PEG treatment significantly ameliorated renal fibrosis by increased E-cadherin protein expression, and decreased α-SMA, Vimentin and Fibronectin expression both in vitro and in vivo. Additionally, CeNP-PEG significantly reduced the ROS formation and improved the levels of mitochondrial ATP. The seahorse analyzer assay demonstrated that the extracellular acidification rate markedly decreased, whereas the oxygen consumption rate markedly increased, in the presence of CeNP-PEG. Furthermore, the mitochondrial membrane potential markedly enhanced, hexokinase 1 and hexokinase 2 expression significantly decreased after treatment with CeNP-PEG.

Conclusions

CeNP-PEG can block the dysregulated metabolic status and exert protective function on renal fibrosis. This may provide another therapeutic option for renal fibrosis.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01122-w.

Rare earth smart nanomaterials for bone tissue engineering and implantology: Advances, challenges, and prospects

Bone grafts or prosthetic implant designing for clinical application is challenging due to the complexity of integrated physiological processes. The revolutionary advances of nanotechnology in the biomaterial field expedite and endorse the current unresolved complexity in functional bone graft and implant design. Rare earth (RE) materials are emerging biomaterials in tissue engineering due to their unique biocompatibility, fluorescence upconversion, antimicrobial, antioxidants, and anti-inflammatory properties. Researchers have developed various RE smart nano-biomaterials for bone tissue engineering and implantology applications in the past two decades. Furthermore, researchers have explored the molecular mechanisms of RE material-mediated tissue regeneration. Recent advances in biomedical applications of micro or nano-scale RE materials have provided a foundation for developing novel, cost-effective bone tissue engineering strategies. This review attempted to provide an overview of RE nanomaterials' technological innovations in bone tissue engineering and implantology and summarized the osteogenic, angiogenic, immunomodulatory, antioxidant, in vivo bone tissue imaging, and antimicrobial properties of various RE nanomaterials, as well as the molecular mechanisms involved in these biological events. Further, we extend to discuss the challenges and prospects of RE smart nano-biomaterials in the field of bone tissue engineering and implantology.

Internalized Nanoceria Modify the Radiation-Sensitivity Profile of MDA MB231 Breast Carcinoma Cells

Owing to its unique redox properties, cerium oxide (nanoceria) nanoparticles have been shown to confer either radiosensitization or radioprotection to human cells. We investigated nanoceria's ability to modify cellular health and reactive oxygen species (ROS) at various absorbed doses (Gray) of ionizing radiation in MDA-MB231 breast carcinoma cells. We used transmission electron microscopy to visualize the uptake and compartmental localization of nanoceria within cells at various treatment concentrations. The effects on apoptosis and other cellular health parameters were assessed using confocal fluorescence imaging and flow cytometry without and with various absorbed doses of ionizing radiation, along with intracellular ROS levels. Our results showed that nanoceria were taken up into cells mainly by macropinocytosis and segregated into concentration-dependent large aggregates in macropinosomes. Confocal imaging and flow cytometry data showed an overall decrease in apoptotic cell populations in proportion to increasing nanoparticle concentrations. This increase in cellular health was observed with a corresponding reduction in ROS at all tested absorbed doses. Moreover, this effect appeared pronounced at lower doses compared to unirradiated or untreated populations. In conclusion, internalized nanoceria confers radioprotection with a corresponding decrease in ROS in MDA-MB231 cells, and this property confers significant perils and opportunities when utilized in the context of radiotherapy.

Incorporation of cerium oxide into zirconia toughened alumina ceramic promotes osteogenic differentiation and osseointegration

Due to its high wear resistance and good biocompatibility, zirconia toughened alumina (ZTA) is an ideal material used as load-bearing implant. However, ZTA needs to be modified to overcome its bio-inert and thus improve osseointegration. Cerium oxide, which has been proved to be a bone-friendly ceramic, might be a desired material to enhance the bioactivity of ZTA. In this study, ZTA and cerium oxide doped ZTA (ZTAC) were prepared via sintering method. The in vitro study showed that the addition of cerium oxide promoted MC3T3-E1 cell adhesion and spreading through upregulating ITG α5 and ITG β1. In addition, the incorporation of cerium oxide enhanced cell proliferation, ALP activity, and ECM mineralization capacity. Moreover, the incorporation of cerium oxide promoted the expressions of osteogenesis related genes, such as ALP, Col-I, and OCN. The in vivo implantation test via a SD rat model showed that the incorporation of cerium oxide promoted new bone formation and bone-implant integration. In summary, this study provided a new strategy to fabricate bioactive ZTA implant for potential application in orthopedics field.

Inhibitory Effects of Gold and Silver Nanoparticles on the Differentiation into Osteoclasts In Vitro

Gold nanoparticles (GNPs) have been widely studied to inhibit differentiation into osteoclasts. However, reports of the inhibitory effects of silver nanoparticles (SNPs) during the process of differentiation into osteoclasts are rare. We compared the inhibitory effect of GNPs and SNPs during the process of differentiation into osteoclasts. Bone marrow-derived cells were differentiated into osteoclasts by the receptor activator of the nuclear factor-kappa-Β ligand (RANKL). The inhibitory effect of GNPs or SNPs during the process of differentiation into osteoclasts was investigated using tartrate-resistant acid phosphatase (TRAP) and actin ring staining. The formation of TRAP positive ⁽⁺⁾ multinuclear cells (MNCs) with the actin ring structure was most inhibited in the SNP group. In addition, the expression of specific genes related to the differentiation into osteoclasts, such as c-Fos, the nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1), TRAP, and Cathepsin K (CTSK) were also inhibited in the SNP groups. As a result, the levels related to differentiation into osteoclasts were consistently lower in the SNP groups than in the GNP groups. Our study suggests that SNPs can be a useful material for inhibiting differentiation into osteoclasts and they can be applied to treatments for osteoporosis patients.