Cytokine-scavenging nanodecoys reconstruct osteoclast/osteoblast balance toward the treatment of postmenopausal osteoporosis

Harnessing innovation in microneedle technology for Women's healthcare

Women's health management plays a crucial role in modern healthcare, encompassing the prevention, detection, and treatment of female diseases. However, existing technologies often face challenges, such as the invasiveness and discomfort associated with serological testing and injection-based therapies. Microneedles, as an emerging technology in biomedical engineering, demonstrate significant advantages. These micron-sized transdermal devices are applicable in a range of applications, from drug delivery to interstitial fluid sampling, and their painless, minimally invasive nature significantly enhances medication compliance. In recent years, microneedles have been widely utilized in women's health management, showing promising results in early disease prevention and subsequent treatment. Although there are reviews about microneedles applied in disease treatment management, few of them focus on the application of microneedles in the prevention and early detection of women's disease. Herein, we present a comprehensive overview of the current application status of microneedles in women's health management, with a special emphasis on their design and mechanism for disease prevention, and treatment in women. Finally, we discuss the advantages and limitations of microneedles in women's health management, and propose suggestions for future research direction.

Engineered Macrophage Membrane-Coated Nanoparticles for Hepatic Ischemia-Reperfusion Injury Therapeutics

Hepatic ischemia-reperfusion injury (HIRI) is a common perioperative complication occurring after liver transplantation and can lead to further problems such as early allograft dysfunction (EAD). Currently, the treatment options for HIRI are extremely limited. In this study, we used bioinformatics analysis to elucidate the critical role of neutrophil chemokines (CXC chemokines) in HIRI. By analyzing sequencing data from the hepatic tissue of posttransplant patients with EAD and the reperfused animal model, we discovered that hepatocytes and macrophages are the primary cells secreting CXC chemokines, and the activation of the nuclear factor kappa B (NF-κB) signaling pathway is the main driver of their secretion. Melatonin (MT) can protect cells from oxidative harm while also inhibiting NF-κB signaling, suggesting its potential to ameliorate HIRI. Accordingly, we designed a nanoparticle platform coated with genetically engineered macrophage membranes-called CXCR2-MM@PLGA/MT-to target the cells secreting CXC chemokines. CXCR2 overexpression on the macrophage membranes not only enhanced the targeting capacity of the nanoparticles but also prevented neutrophil infiltration via the scavenging of CXC chemokines. Meanwhile, the MT delivered to the site of injury successfully attenuated CXC chemokine release after macrophage polarization and hepatocyte necrosis by inhibiting NF-κB phosphorylation and inducing antioxidant effects. Through the synergistic effects of MT and the CXCL/CXCR axis-blocking function of the engineered nanoparticles, CXCR2-MM@PLGA/MT attenuated the aggregation of neutrophils at the site of injury, markedly reducing local inflammation and cellular damage following HIRI. This engineered cellular nanoparticle-based therapy could thus serve as a safe, effective, and cost-efficient strategy for treating HIRI.

Efficacy and safety of acupuncture as an adjuvant therapy for osteoporosis: a systematic review and meta-analysis of randomized controlled trials

Objective

To systematically evaluate the efficacy and safety of acupuncture as an adjuvant therapy for osteoporosis (OP) through a comprehensive synthesis of recent randomized controlled trial (RCT) evidence.

Methods

A systematic literature search was conducted across PubMed, Web of Science, CNKI, and Wanfang databases (2014 - 2024) to identify RCTs investigating acupuncture combined with conventional therapy for OP. Study quality was appraised using the Cochrane Risk of Bias tool, and meta-analyses were performed using RevMan 5.4 and Stata 15.0, with subgroup analyses stratified by intervention type, population characteristics, and treatment duration.

Results

28 RCTs (n=2,758) were included. Meta-analysis revealed acupuncture significantly enhanced bone mineral density (BMD) versus controls: total (SMD = 0.47, p = 0.03), femoral neck (MD = 0.05, p = 0.01), lumbar spine (SMD = 0.40, p < 0.001), Ward's triangle (MD = 0.07, p = 0.02), and hip (SMD = 0.55, p < 0.001), with particularly marked improvements in the postmenopausal osteoporosis subgroup. Acupuncture demonstrated significant improvements in treatment efficacy, biochemical markers, pain scores, and symptom assessments, while reducing adverse events. Warm needle moxibustion outperformed controls in femoral neck (MD = 0.07, p = 0.002) and hip BMD (SMD = 0.87, p < 0.001), while electroacupuncture significantly elevated serum calcium (MD = 0.18, p = 0.02). Short-term interventions (≤ 3 months) demonstrated optimal efficacy.

Conclusion

Acupuncture demonstrates efficacy and safety as an OP adjuvant therapy. Current evidence is limited by regional bias and methodological heterogeneity. Multicenter, large-sample RCTs are needed to standardize protocols and validate long-term therapeutic efficacy.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42024499354.

Re-engineering bone: pathogenesis, diagnosis and emerging therapies for osteoporosis

Osteoporosis, a multifaceted metabolic bone disease, is becoming increasingly prevalent and poses a significant burden on global healthcare systems. Given the limitations of traditional treatments such as pharmacotherapy, tissue engineering has emerged as a promising alternative for osteoporosis management. This review begins by exploring the pathogenesis of osteoporosis, with a focus on the abnormal metabolic, cellular, and molecular signalling microenvironments that drive the disease. We also examine commonly used clinical diagnostic techniques, discussing their strengths and limitations. Notably, this review evaluates various advanced tissue engineering strategies for osteoporosis treatment. Delivery systems, including injectable hydrogels and nanomaterials, are detailed alongside bone tissue engineering materials such as bioactive ceramics, bone cements, and polymers. Additionally, biologically active substances, including exosomes and cytokines, and emerging therapies that leverage small-molecule drugs are explored. Through a comprehensive analysis of the advantages and limitations of current biomaterials and therapeutic approaches, this review provides insights into future directions for tissue engineering-based solutions. By synthesizing current advancements, it aims to inspire innovative perspectives for the clinical management of osteoporosis.

Integrative genomic analysis and diagnostic modeling of osteoporosis: unraveling the interplay of autophagy, osteogenesis, adipogenesis, and immune infiltration

Background

Osteoporosis (OP), marked by reduced bone density and structural decay, poses a heightened risk of fractures. Our study formulates a predictive diagnostic model for OP by analyzing differential gene expression, thereby improving early diagnosis and therapeutic approaches.

Methods

Using GSE62402, GSE56815, and GSE35958 datasets from the Gene Expression Omnibus (GEO) database, we identified differentially expressed genes (DEGs) via R packages, and evaluated the underlying molecular mechanisms by network analysis. Immune checkpoint and drug sensitivity were analyzed to construct and validate diagnostic models. The single-sample gene-set enrichment analysis (ssGSEA) was used to assess immune cell infiltration; the CIBERSORT algorithm was used to evaluate immune cells within the different subtypes of OP.

Results

The study identified 1,297 DEGs, with 14 DEGs related to autophagy, osteogenesis, and adipogenesis (AP&OG&AGRDEGs) showing significant expression differences between OP and control groups, including seven upregulated and seven downregulated genes (p-value < 0.05). The analysis results from gene ontology (GO), gene set enrichment analysis (GSEA), and the Kyoto encyclopedia of genes and genomes (KEGG) indicated that oxidative stress and inflammation-related signaling pathways are closely connected to OP. Immune checkpoint analysis identified differential expression of eight genes between OP patients and controls (p-value < 0.05). The ssGSEA findings showed significant variations in immune cell infiltration levels, particularly of natural killer cells, Th2 cells, mast cells, and plasmacytoid dendritic cells (p-value < 0.05). The diagnostic model, developed utilizing logistic regression, support vector machine (SVM), and the least absolute shrinkage and selection operator (LASSO), pinpointed nine pivotal genes-AKT1, NFKB1, TNF, CTNNB1, LMNA, BHLHE40, BMP4, WNT1, and COPS3-and confirmed their diagnostic efficacy through validation. In further subgroup analysis, eight types of immune cells were found to be differentially expressed across various risk groups. Subtype analysis based on ConsensusClusterPlus revealed differential expression of six key genes in distinct subtypes of OP.

Conclusion

This comprehensive study established a network of OP-associated genes, and provides insights into the molecular mechanisms involving immune responses in OP. It identified key diagnostic genes and analyzed immune cell infiltration to better understand OP pathogenesis. The study underscores the importance of personalized treatment and the potential role of immune modulation in managing OP.

Nanocomposite hydrogels optimize the microenvironment by exterior/interior crosstalk for reprogramming osteoporotic homeostasis in bone defect healing

Discovering new tactics for healing bone defects becomes a worldwide challenge in osteoporosis patients. The disordered acidic microenvironment plays a pivotal role in driving the imbalance of bone homeostasis regulated by osteoblasts and osteoclasts. However, the scarcity of hydrogel materials developed to optimize local bone microenvironment has made osteoporotic defect healing more challenging. Herein, we present innovative nanocomposite hydrogels with precisely engineered microarchitectures designed to optimize the acidic microenvironment by facilitating crosstalk between exterior and interior spaces, aimed at enhancing the reconstruction of osteoporotic bone defects. The chlorogenic acid grafted chitosan as double-sided crosslinkers is specially designed to not only combine with acid-reversible Laponite® nanosheet via interfacial interactions but also integrate with gold nanorod (a typical photothermal agent) through catechol-Au bond. The supramolecular construction of nanocomposite hydrogels holds promise for achieving a highly continuous and homogeneous pore network microarchitecture. As expected, hydrogels display outstanding spatiotemporal local mild hyperthermia, which accelerates the neutralization reaction between OH- ions released from Laponite® and hydrogen ions (pH ∼ 4.0). The optimized microenvironment restores osteoclast/osteoblast homeostasis, resulting in the promotion of osteoblastogenesis and inhibition of osteoclastogenesis, thereby facilitating the healing of osteoporotic bone defects. This work is hoped to design versatile hydrogels for optimizing the microenvironment, displaying promising integrative substitute materials for clinically effective treatment of osteoporotic bone defects.

Engineered Cell Membrane Coating Technologies for Biomedical Applications: From Nanoscale to Macroscale

Cell membrane coating has emerged as a promising strategy for the surface modification of biomaterials with biological membranes, serving as a cloak that can carry more functions. The cloaked biomaterials inherit diverse intrinsic biofunctions derived from different cell sources, including enhanced biocompatibility, immunity evasion, specific targeting capacity, and immune regulation of the regenerative microenvironment. The intrinsic characteristics of biomimicry and biointerfacing have demonstrated the versatility of cell membrane coating technology on a variety of biomaterials, thus, furthering the research into a wide range of biomedical applications and clinical translation. Here, the preparation of cell membrane coatings is emphasized, and different sizes of coated biomaterials from nanoscale to macroscale as well as the engineering strategies to introduce additional biofunctions are summarized. Subsequently, the utilization of biomimetic membrane-cloaked biomaterials in biomedical applications is discussed, including drug delivery, imaging and phototherapy, cancer immunotherapy, anti-infection and detoxification, and implant modification. In conclusion, the latest advancements in clinical and preclinical studies, along with the multiple benefits of cell membrane-coated nanoparticles (NPs) in biomimetic systems, are elucidated.

Role of YAP/TAZ in bone diseases: A transductor from mechanics to biology

Wolff's Law and the Mechanostat Theory elucidate how bone tissues detect and convert mechanical stimuli into biological signals, crucial for maintaining bone equilibrium. Abnormal mechanics can lead to diseases such as osteoporosis, osteoarthritis, and nonunion fractures. However, the detailed molecular mechanisms by which mechanical cues are transformed into biological responses in bone remain underexplored. Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ), key regulators of bone homeostasis, are instrumental in this process. Emerging research highlights bone cells' ability to sense various mechanical stimuli and relay these signals intracellularly. YAP/TAZ are central in receiving these mechanical cues and converting them into signals that influence bone cell behavior. Abnormal YAP/TAZ activity is linked to several bone pathologies, positioning these proteins as promising targets for new treatments. Thus, this review aims to provide an in-depth examination of YAP/TAZ's critical role in the interpretation of mechanical stimuli to biological signals, with a special emphasis on their involvement in bone cell mechanosensing, mechanotransduction, and mechanoresponse. The translational potential of this article: Clinically, appropriate stress stimulation promotes fracture healing, while bed rest can lead to disuse osteoporosis and excessive stress can cause osteoarthritis or bone spurs. Recent advancements in the understanding of YAP/TAZ-mediated mechanobiological signal transduction in bone diseases have been significant, yet many aspects remain unknown. This systematic review summarizes current research progress, identifies unaddressed areas, and highlights potential future research directions. Advancements in this field facilitate a deeper understanding of the molecular mechanisms underlying bone mechanics regulation and underscore the potential of YAP/TAZ as therapeutic targets for bone diseases such as fractures, osteoporosis, and osteoarthritis.

Rectifying the Crosstalk between the Skeletal and Immune Systems Improves Osteoporosis Treatment by Core-Shell Nanocapsules

Contemporary osteoporosis treatment often neglects the intricate interactions among immune cells, signaling proteins, and cytokines within the osteoporotic microenvironment. Here, we developed core-shell nanocapsules composed of a cationized lactoferrin core and an alendronate polymer shell. By tuning the size of these nanocapsules and leveraging the alendronate shell, we enabled precise delivery of small interfering RNA targeting the Semaphorin 4D gene (siSema4D) to specific bone sites. This strategy integrates the antiresorptive drug alendronate with siSema4D, efficiently inhibiting osteoclast (OC) differentiation and bone resorption, while promoting osteogenesis to restore the balance between osteoblasts (OBs) and OCs. Moreover, encapsulating siSema4D within the nanocapsules helps to mitigate immunological cascades, thereby reversing the inflammatory microenvironment and restoring immune homeostasis and providing insights into the immunomodulatory effects of Sema4D in osteoporosis therapy. In both ovariectomized and senile osteoporotic mouse models, local intramuscular administration of core-shell nanocapsules effectively rectified the imbalance between the skeletal and immune systems, significantly enhancing the overall efficacy of osteoporosis treatment. Our findings underscore the therapeutic promise of addressing the multifaceted osteoporotic microenvironment through targeted interventions.

Synthetic nanoparticles functionalized with cell membrane-mimicking, bone-targeting, and ROS-controlled release agents for osteoporosis treatment

Postmenopausal osteoporosis is a common degenerative disease, with suboptimal clinical outcomes. The targets of current therapeutic agents are both nonspecific and diverse. We synthesized a novel nanoparticle (NP), ALN@BMSCM@PLGA-TK-PEG-SS31. After intravenous injection, the NP evaded immune phagocytosis, targeted bone tissue, and efficiently downregulated bone reactive oxygen species (ROS) generation. The core PLGA-TK-PEG-SS31 NP was ∼100 nm in diameter. The TK chemical bond breaks on exposure to ROS, releasing the novel mitochondrion-targeting peptide SS31. Outer bone marrow mesenchymal stem cell membranes (BMSCMs) were used to coat the NP with surface proteins to ensure membrane functionality. The circulation time was prolonged and immune phagocytosis was evaded. Embedding the DSPE-PEG-ALN lipid within the cell membrane enhanced the bone-targeting ability of the NP. Our results suggest that ALN@BMSCM@PLGA-TK-PEG-SS31 exerted dual effects on bone tissue in vitro, significantly inhibiting RANKL-induced osteoclastogenesis in the presence of H2O2 and promoting osteogenic differentiation in BMSCs. In a mouse model of ovariectomy-induced osteoporosis, ALN@BMSCM@PLGA-TK-PEG-SS31 significantly ameliorated oxidative stress and increased bone mass with no notable systemic side effects. These results suggest that ALN@BMSCM@PLGA-TK-PEG-SS31 is a promising treatment for osteoporosis.

Biomimetic Extracellular Vesicles Containing Biominerals for Targeted Osteoporosis Therapy

Osteoporosis (OP) is a systemic skeletal disorder characterized by decreased bone mineral density and a heightened risk of fractures. Therapies for OP have primarily focused on balancing bone formation and bone resorption, but enhancing the remineralization of osteoporotic bone is also a key strategy for effective repair. Recent insights into biomineralization mechanisms have highlighted the essential role of mineral-containing extracellular vesicles (EVs) secreted by osteoblasts in promoting bone marrow mesenchymal stromal/stem cell (BMSC) differentiation and initiating matrix mineralization. Drawing from these principles, we developed a biomimetic approach to replicate the structure and function of the osteoblast-derived EVs by engineering biomimetic mitochondrial minerals with bone marrow homing cell membranes (CMs). This bone-targeted biomimetic system exhibits excellent biocompatibility, enhancing osteogenic differentiation and stimulating angiogenesis by regulating cellular energy metabolism. Additionally, the CM-coated structure shows affinity for collagen fibrils, effectively enhancing intrafibrillar collagen mineralization, thereby facilitating osteoporotic bone repair. Overall, the biomimetic system offers a safe and efficient therapeutic alternative, positioning it as a platform for bone tissue engineering and regenerative medicine.

An "All-in-One" Strategy to Reconstruct Temporomandibular Joint Osteoarthritic Microenvironment Using γ-Fe2O3@TA@ALN Nanoparticles

Current clinical strategies for the treatment of temporomandibular joint osteoarthritis (TMJOA) primarily target cartilage biology, overlooking the synergetic effect of various cells and inorganic components in shaping the arthritic microenvironment, thereby impeding the effectiveness of existing therapeutic options for TMJOA. Here, γ-Fe2O3@TA@ALN magnetic nanoparticles (γ-Fe2O3@TA@ALN MNPs) composed of γ-Fe2O3, tannic acid (TA), and alendronate sodium (ALN) are engineered to reconstruct the osteoarthritic microenvironment and mitigate TMJOA progression. γ-Fe2O3@TA@ALN MNPs can promote chondrocytes' proliferation, facilitate chondrogenesis and anisotropic organization, enhance lubrication and reduce cartilage wear, and encourage cell movement. Magnetic-responsive γ-Fe2O3@TA@ALN MNPs also exhibit pH sensitivity, which undergoes decomposition within acidic environment to release ALN on demand. Under a 0.2 T static magnetic field, γ-Fe2O3@TA@ALN MNPs accelerate the synthesis of cartilage-specific proteins, and suppress catabolic-related genes expression and reactive oxygen species generation, affording additional protection to TMJ cartilage. In TMJOA mouse models, articular injection of γ-Fe2O3@TA@ALN MNPs effectively alleviates cartilage degeneration and subchondral bone loss in short and long terms, offering promising avenues for the development of therapeutic interventions for TMJOA.

Receptor Activator of Nuclear Factor Kappa-B-Expressing Mesenchymal Stem Cells-Derived Extracellular Vesicles for Osteoporosis Therapy

The dynamic balance between bone resorption and formation is critical for maintaining healthy bone homeostasis. However, the receptor activator of the nuclear factor B ligand (RANKL) primarily stimulates mature osteoclasts to resorb bone, and its upregulation leads to osteoporosis in patients. Here, we designed RANK-expressing extracellular vesicles (EVs) derived from mesenchymal stem cells to maintain bone homeostasis in mice. This engineered EV (EV@R) effectively neutralizes excess RANKL in bone tissue due to the RANK-RANKL interaction, thereby attenuating osteoclast differentiation. Additionally, we found that miRNA-21a-5p in EV@R contributes to restoring bone metabolic homeostasis. We demonstrate the protective and therapeutic efficacy of EV@R against osteoporosis in the ovariectomy-induced osteoporosis mouse model with a lasting effect and minimal side effects. Our study provides an alternative way to use engineered EVs for bone homeostasis treatment.

MOF-Based Guided Bone Regeneration Membrane for Promoting Osteogenesis by Regulating Bone Microenvironment through Cascade Effects

Regulation of bone microenvironment (BME) including innate pH values and metal ions affects cellular functions and activities of osteoblasts and osteoclasts, thereby significantly influencing the process of bone regeneration. How to achieve multiple effective regulations of the BME through cascade effects via facile material design and fabrication to significantly facilitate osteogenesis remains a challenge. Herein, a facilely-designed resorbable guided bone regeneration membrane (PCL/DEX@Ca-Zol) based on a drug-loaded metal-organic framework is reported. Thereinto, calcium ions, zoledronic acid, and dexamethasone embedded in the membrane can be responsively released specifically inside bone defect in an acid-triggered manner to synergistically regulate BME by neutralization of pH value, enhancement of osteogenic differentiation and mineralization, and inhibition of osteoclasts in one-go. Along with polycaprolactone as a structural support in the membrane for bone regeneration with fully utilized components of the composite membrane material, enhances bone regeneration with minimized side effects is accordingly achieved with the assistance of effective modulation of BME through multiple cascade effects.

3D-printed bone regeneration scaffolds modulate bone metabolic homeostasis through vascularization for osteoporotic bone defects

The treatment of osteoporotic bone defects poses a challenge due to the degradation of the skeletal vascular system and the disruption of local bone metabolism within the osteoporotic microenvironment. However, it is feasible to modulate the disrupted local bone metabolism imbalance through enhanced vascularization, a theory termed "vascularization-bone metabolic balance". This study developed a 3D-printed polycaprolactone (PCL) scaffold modified with EPLQLKM and SVVYGLR peptides (PCL-SE). The EPLQLKM peptide attracts bone marrow-derived mesenchymal stem cells (BMSCs), while the SVVYGLR peptide enhances endothelial progenitor cells (EPCs) vascular differentiation, thus regulating bone metabolism and fostering bone regeneration through the paracrine effects of EPCs. Further mechanistic research demonstrated that PCL-SE promoted the vascularization of EPCs, activating the Notch signaling pathway in BMSCs, leading to the upregulation of osteogenesis-related genes and the downregulation of osteoclast-related genes, thereby restoring bone metabolic balance. Furthermore, PCL-SE facilitated the differentiation of EPCs into "H"-type vessels and the recruitment of BMSCs to synergistically enhance osteogenesis, resulting in the regeneration of normal microvessels and bone tissues in cases of femoral condylar bone defects in osteoporotic SD rats. This study suggests that PCL-SE supports in-situ vascularization, remodels bone metabolic translational balance, and offers a promising therapeutic regimen for osteoporotic bone defects.

Non-diabetic elderly populations: SIRI as a risk factor and PIV as a protective factor against bone abnormalities

Objective

The prevalence of osteoporosis and its resultant healthcare challenges are escalating, posing significant burdens on public health systems. Studies have introduced immunoinflammatory indices, which are recognized for effectively reflecting the systemic immunoinflammatory status. Despite their potential, the exploration of these indices in the context of osteoporosis remains limited. The study sought to explore the relationship between immune inflammation-related indices and osteoporosis in non-diabetic elderly populations.

Methods

The clinical data of 438 non-diabetic elderly subjects were retrospectively analyzed and all statistical analyses were performed using SPSS 27.0.

Results

Differences were observed between the osteoporosis group and the normal bone density group in terms of age, neutrophil, lymphocyte, monocyte, hemoglobin, and platelet. A review of prior studies revealed a close association between osteoporosis and chronic inflammation. Immunological indices such as Platelet to Lymphocyte Ratio (PLR), Neutrophil to Lymphocyte Ratio (NLR), Monocyte to Lymphocyte Ratio (MLR), Systemic Immuno-Inflammatory Index (SII), Systemic Inflammatory Response Index (SIRI) and Peripheral Immunity Index (PIV) were calculated. The analysis indicated significant differences in MLR, SII, SIRI and PIV. A multifactorial binary logistic regression model was established, incorporating age, MLR, SII, SIRI, and PIV as variables. The results identified age and SIRI as independent risk factors for bone abnormalities in non-diabetic elderly populations, while PIV served as an independent protective factor. Receiver operating characteristic analysis demonstrated that SIRI and PIV predicted osteoporosis with areas under the curve (AUC) of 0.609 and 0.620, respectively. The diagnostic value was enhanced when combined with age, yielding AUC values of 0.725 for PIV combined with age. PIV combined with age was particularly effective as a biomarker for bone abnormalities in this population. The optimal Youden's index was calculated to be 0.367, corresponding to a sensitivity of 63.8% and a specificity of 72.9%.

Conclusions

For non-diabetic elderly populations, SIRI is a risk factor, while PIV serves as a protective factor against bone abnormalities. Combined with previous studies, we suggest that people at high risk of osteoporosis should avoid or minimize the intake of pro-inflammatory dietary patterns. Meanwhile, research from an immune perspective is expected to open new avenues for osteoporosis treatment.

Inflammation-Responsive Polyion Complex Vesicles for Autoimmune Disease Therapy via Cell-Free DNA Scavenging and Inflammatory Microenvironment Modulation

Cell-free DNA (cfDNA) scavenging represents a promising anti-inflammatory modality for autoimmune disease (AID) treatment. However, it remains challenging for existing systems to achieve inflammation-targeted cfDNA scavenging and the management of cfDNA-unrelated inflammatory pathways. Herein, inflammation-responsive polyion complex vesicles (PICsomes) are developed, bridging inflammation-instructed cfDNA scavenging, and methotrexate (MTX) delivery for AID management. A positively charged, PEGylated polypeptide with guanidine side chains (PEG-PG) is developed, which self-assembles with a negatively charged, cis-aconitic anhydride-modified poly-L-lysine (PC) to form the PICsomes and encapsulate MTX disodium salt. The neutrally charged PICsomes feature prolonged blood circulation after systemic administration, allowing for passive accumulation to the inflamed tissues. In the slightly acidic inflammatory microenvironment, PC transforms from negatively charged to positively charged, thereby disintegrating the PICsomes and liberating the PEG-PG and MTX. Consequently, PEG-PG-mediated cfDNA scavenging and MTX-mediated immunosuppression cooperate to inhibit inflammation and ameliorate the inflammatory microenvironment, promoting tissue repair in AID mouse models including collagen-induced arthritis and 2,4,6-trinitrobenzenesulfonic acid-induced colitis.

Bone Destruction-Chemotactic Osteoprogenitor Cells Deliver Liposome Nanomedicines for the Treatment of Osteosarcoma and Osteoporosis

Therapeutic efficacy of skeletal diseases is usually limited by unfavorable drug delivery due to incapable bone targeting and low bone affinity of conventional drug carriers, as well as relatively reduced vascularization and dense structure of bone tissues. Due to CXC chemokine receptor 4 (CXCR4)/CXC chemokine ligand 12 (CXCL12) signal axis-guided recruitment, osteoprogenitor cells (OPCs) can actively migrate to bone disease nidus. Here, drugs-loaded nanoliposomes are prepared and decorated onto OPCs by biotin-streptavidin linkage for precise bone disease targeting and effective drug delivery. In mouse models of tibia defect and orthotopic osteosarcoma, superior targeting property of OPCs-based drug delivery systems toward diseased bone niduses is verified. By encapsulating antitumor and antiosteoporosis drugs into nanoliposomes, OPCs-based drug delivery systems effectively inhibit disease development and restore bone destruction in mouse models of orthotopic osteosarcoma and ovariectomized osteoporosis. This study reveals a cell-based drug delivery system for precise bone disease targeting and highly effective drug delivery, which will find great potential as a universal drug delivery platform for targeting treatment of various bone diseases.

Unleashing the Potential of Electroactive Hybrid Biomaterials and Self-Powered Systems for Bone Therapeutics

The incidence of large bone defects caused by traumatic injury is increasing worldwide, and the tissue regeneration process requires a long recovery time due to limited self-healing capability. Endogenous bioelectrical phenomena have been well recognized as critical biophysical factors in bone remodeling and regeneration. Inspired by bioelectricity, electrical stimulation has been widely considered an external intervention to induce the osteogenic lineage of cells and enhance the synthesis of the extracellular matrix, thereby accelerating bone regeneration. With ongoing advances in biomaterials and energy-harvesting techniques, electroactive biomaterials and self-powered systems have been considered biomimetic approaches to ensure functional recovery by recapitulating the natural electrophysiological microenvironment of healthy bone tissue. In this review, we first introduce the role of bioelectricity and the endogenous electric field in bone tissue and summarize different techniques to electrically stimulate cells and tissue. Next, we highlight the latest progress in exploring electroactive hybrid biomaterials as well as self-powered systems such as triboelectric and piezoelectric-based nanogenerators and photovoltaic cell-based devices and their implementation in bone tissue engineering. Finally, we emphasize the significance of simulating the target tissue's electrophysiological microenvironment and propose the opportunities and challenges faced by electroactive hybrid biomaterials and self-powered bioelectronics for bone repair strategies.

Single-cell sequencing reveals that specnuezhenide protects against osteoporosis via activation of METTL3 in LEPR+ BMSCs

BACKGROUND

Osteoporosis (OP) has garnered significant attention due to its substantial morbidity and mortality rates, imposing considerable health burdens on societies worldwide. However, the molecular mechanisms underlying osteoporosis pathogenesis remain largely elusive, and the available therapeutic interventions are limited. Therefore, there is an urgent need for innovative strategies in the treatment of osteoporosis.

PURPOSE

The primary objective of this study was to elucidate the molecular mechanisms underlying osteoporosis pathogenesis using single-cell RNA sequencing (scRNA-seq), thereby proposing novel therapeutic agents.

METHODS

The mice osteoporosis model was established through bilateral ovariectomy. Micro-computed tomography (μCT) and hematoxylin and eosin (H&E) staining were employed to assess the pathogenesis of osteoporosis. scRNA-seq was utilized to identify and analyze distinct molecular mechanisms and sub-clusters. Gradient dilution analysis was used to obtain specific sub-clusters, which were further validated by immunofluorescence staining and flow cytometry analysis. Molecular docking and cellular thermal shift assay (CETSA) were applied for screening potential agents in the TCMSPs database. Alkaline phosphatase (ALP) activity and alizarin red S (ARS) staining were performed to evaluate the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Osteogenic organoids analysis was employed to assess the proliferation and sphere-forming ability of BMSCs. Quantitative real-time PCR (qRT-PCR) and western blot analysis were conducted to investigate signaling pathways. Wound healing assay and tube formation analysis were employed to evaluate the angiogenesis of endothelial cells.

RESULTS

The scRNA-seq analysis revealed the crucial role of LEPR+ BMSCs in the pathogenesis of osteoporosis, which was confirmed by immunofluorescence staining of the epiphysis. Subsequently, the LEPR+ BMSCs were obtained by gradient dilution analysis and identified by immunofluorescence staining and flow cytometry. Accordingly, specnuezhenide (Spe) was screened and identified as a potential compound targeting METTL3 from the TCMSPs database. Spe promoted bone formation as evidenced by μ-CT, and H&E analysis. Additionally, Spe enhanced the osteogenic capacity of LEPR+ BMSCs through ALP and ARS assay. Notably, METTL3 pharmacological inhibitors S-Adenosylhomocysteine (SAH) attenuated the aforementioned osteo-protective effects of Spe. Particularly, Spe enhanced the LEPR+ BMSCs-dependent angiogenesis through the secretion of SLIT3, which was abolished by SAH in LEPR+ BMSCs.

CONCLUSION

Collectively, these findings suggest that Spe could enhance the osteogenic potential of LEPR+ BMSCs and promote LEPR+ BMSCs-dependent angiogenesis by activating METTL3 in LEPR+ BMSCs, indicating its potential as an ideal therapeutic agent for clinical treatment of osteoporosis.

In Vitro and In Vivo Evaluation of Toxicity of Structurally Different Diamond-Like Carbon Wear Debris in Joint Replacements

Diamond-like carbon (DLC) wear debris, which is often composed of different types of structures, is generated from DLC-modified artificial joints in the human body, and its biocompatibility evaluation is especially important to prevent wear-debris-induced implant failure. Here, RAW 264.7 macrophages (inflammatory-reaction assay) and primary mouse osteoblasts (osteoblastogenesis assay) were employed to investigate the toxicity of DLC wear particles (DWPs) by evaluation of cell viability and morphology, enzyme-linked immunosorbent assays, and quantitative reverse-transcription polymerase chain reaction (PCR). Relevant histopathological analysis of rat joints was also performed in vivo. We found that DWPs with a relatively high sp2/sp3 ratio (graphite-phase tendency) manifested a higher cytotoxicity and significant inhibition of osteoblastogenesis. DWPs with a relatively low sp2/sp3 ratio (diamond-phase tendency) showed good biocompatibility in vivo. The DWPs exhibiting a low sp2/sp3 ratio demonstrated reduced secretion of TNF-α and IL-6, along with increased secretion of TIMP-1, resulting in the downregulation of MMP-2 and MMP-9 and upregulation of interleukin-10 (IL-10), thereby attenuating the inflammatory response. Moreover, coculturing osteoblasts with DWPs exhibiting a low sp2/sp3 ratio resulted in an elevated OPG/RANKL ratio and increased expression of OPG mRNA. Because of the absence of electrostatic repulsion, DWPs with a relatively low sp2/sp3 ratio enhanced bovine serum albumin adsorption, which favored cellular activities. Cytotoxicity assessment of DWPs can help establish an evaluation system for particle-related joint disease and can facilitate the clinical application of DLC-coated prostheses.

Two-pronged anti-cancer nanovaccines enpowered by exogenous/endogenous tumor-associated antigens

Cancer vaccines based on single-source (exogenous or endogenous) tumor-associated antigens (TAAs) are often challenged by the insufficient T cell response and the immunosuppressive tumor microenvironment (TME). Herein, a dual TAAs-boosted nanovaccine based on cancer cell (4T1) membrane-cloaked, CO-immobilized Prussian blue nanoparticles (4T1-PB-CO NPs) is developed and coupled with anti-interleukin (IL)-10 therapy to maximize the efficacy of antitumor immunotherapy. 4T1 cell membrane not only endows NPs with tumor targeting ability, but also serves as exogenous TAAs to trigger CD4+ T cell response and M1-phenotype polarization of tumor-associated macrophages. Under near-infrared light irradiation, 4T1-PB-CO NPs release CO to induce immunogenic cell death (ICD) of tumor cells, thus generating endogenous TAAs to activate CD8+ T cell response. Meanwhile, ICD triggers release of damage-associated molecular patterns, which can promote DC maturation to amplify the antitumor T cell response. When combined with anti-IL-10 that reverses the immunosuppressive TME, 4T1-PB-CO NPs efficiently suppress the primary tumors and produce an abscopal effect to inhibit distant tumors in a breast tumor-bearing mouse model. Such a two-pronged cancer vaccine represents a promising paradigm for robust antitumor immunotherapy.

Enhanced vascularization and osseointegration under osteoporotic conditions through functional peptide coating on implant surfaces

Patients with osteoporosis face challenges such as decreased bone density, a sparse trabecular structure, weakened osteogenic ability, and impaired angiogenesis, leading to poor osseointegration and implant failure. Surface modification of implants with biologically active molecules possessing various functions is an effective strategy to improve osseointegration. In this study, we constructed a simple multifunctional coating interface that significantly improves osseointegration. In brief, a multifunctional coating interface was constructed by coupling the Rgd adhesive peptide, Ogp osteogenic peptide, and Ang angiogenic peptide to Lys6 (k6), which self-assembled layer by layer with TA to form the (TA-Rgd@ogp@ang)n composite membrane. This study characterized the surface morphology and biomechanical properties of the coating under both gas and liquid phases and monitored the deposition process and reaction rate of the two peptides with TA using a quartz crystal microbalance. Moreover, (TA-Rgd@ogp@ang)n exhibited a triple synergistic effect on cell migration and adhesion, osteogenic differentiation, and angiogenesis. It also ameliorated the high ROS environment characteristic of osteoporosis pathology, promoted angiogenic bone defect regeneration in osteoporosis, thereby avoiding poor osseointegration. This work provides a new approach for the prevention of implant failure in pathological environments by constructing multifunctional coatings on implants, with tremendous potential applications in the fields of orthopedics and dentistry.

Macrophage membrane-reversibly camouflaged nanotherapeutics accelerate fracture healing by fostering MSCs recruitment and osteogenic differentiation

The fracture healing outcome is largely dependent on the quantities as well as osteogenic differentiation capacities of mesenchymal stem cells (MSCs) at the lesion site. Herein, macrophage membrane (MM)-reversibly cloaked nanocomplexes (NCs) are engineered for the lesion-targeted and hierarchical co-delivery of short stromal derived factor-1α peptide (sSDF-1α) and Ckip-1 small interfering RNA (Ckip-1 siRNA, siCkip-1) to promote bone repair by concurrently fostering recruitment and osteogenic differentiation of endogenous MSCs. To construct the NCs, a membrane-penetrating α-helical polypeptide first assembles with siCkip-1, and the cationic NCs are sequentially coated with catalase and an outer shell of sSDF-1α-anchored MM. Due to MM-assisted inflammation homing, intravenously injected NCs could efficiently accumulate at the fractured femur, where catalase decomposes the local hydrogen peroxide to generate oxygen bubbles that drives the shedding of sSDF-1α-anchored MM in the extracellular compartment. The exposed, cationic inner core thus enables robust trans-membrane delivery into MSCs to induce Ckip-1 silencing. Consequently, sSDF-1α-guided MSCs recruitment cooperates with siCkip-1-mediated osteogenic differentiation to facilitate bone formation and accelerate bone fracture healing. This study provides an enlightened strategy for the hierarchical co-delivery of macromolecular drugs into different cellular compartments, and it also renders a promising modality for the management of fracture healing.

Macrophage-Biomimetic Nanoplatform-Based Therapy for Inflammation-Associated Diseases

Inflammation-associated diseases are very common clinically with a high incidence; however, there is still a lack of effective treatments. Cell-biomimetic nanoplatforms have led to many breakthroughs in the field of biomedicine, significantly improving the efficiency of drug delivery and its therapeutic implications especially for inflammation-associated diseases. Macrophages are an important component of immune cells and play a critical role in the occurrence and progression of inflammation-associated diseases while simultaneously maintaining homeostasis and modulating immune responses. Therefore, macrophage-biomimetic nanoplatforms not only inherit the functions of macrophages including the inflammation tropism effect for targeted delivery of drugs and the neutralization effect of pro-inflammatory cytokines and toxins via membrane surface receptors or proteins, but also maintain the functions of the inner nanoparticles. Macrophage-biomimetic nanoplatforms are shown to have remarkable therapeutic efficacy and excellent application potential in inflammation-associated diseases. In this review, inflammation-associated diseases, the physiological functions of macrophages, and the classification and construction of macrophage-biomimetic nanoplatforms are first introduced. Next, the latest applications of different macrophage-biomimetic nanoplatforms for the treatment of inflammation-associated diseases are summarized. Finally, challenges and opportunities for future biomedical applications are discussed. It is hoped that the review will provide new ideas for the further development of macrophage-biomimetic nanoplatforms.

Inflammatory microenvironment regulation and osteogenesis promotion by bone-targeting calcium and magnesium repletion nanoplatform for osteoporosis therapy

Osteoporosis is the most common bone metabolic disease that affects the health of middle-aged and elderly people, which is hallmarked by imbalanced bone remodeling and a deteriorating immune microenvironment. Magnesium and calcium are pivotal matrix components that participate in the bone formation process, especially in the immune microenvironment regulation and bone remodeling stages. Nevertheless, how to potently deliver magnesium and calcium to bone tissue remains a challenge. Here, we have constructed a multifunctional nanoplatform composed of calcium-based upconversion nanoparticles and magnesium organic frameworks (CM-NH2-PAA-Ald, denoted as CMPA), which features bone-targeting and pH-responsive properties, effectively regulating the inflammatory microenvironment and promoting the coordination of osteogenic functions for treating osteoporosis. The nanoplatform can efficaciously target bone tissue and gradually degrade in response to the acidic microenvironment of osteoporosis to release magnesium and calcium ions. This study validates that CMPA possessing favorable biocompatibility can suppress inflammation and facilitate osteogenesis to treat osteoporosis. Importantly, high-throughput sequencing results demonstrate that the nanoplatform exerts a good inflammatory regulation effect through inhibition of the nuclear factor kappa-B signaling pathway, thereby normalizing the osteoporotic microenvironment. This collaborative therapeutic strategy that focuses on improving bone microenvironment and promoting osteogenesis provides new insight for the treatment of metabolic diseases such as osteoporosis.

Biomimetic Nano-Degrader Based CD47-SIRPα Immune Checkpoint Inhibition Promotes Macrophage Efferocytosis for Cardiac Repair

CD47-SIRPα axis is an immunotherapeutic target in tumor therapy. However, current monoclonal antibody targeting CD47-SIRPα axis is associated with on-target off-tumor and antigen sink effects, which significantly limit its potential clinical application. Herein, a biomimetic nano-degrader is developed to inhibit CD47-SIRPα axis in a site-specific manner through SIRPα degradation, and its efficacy in acute myocardial infarction (AMI) is evaluated. The nano-degrader is constructed by hybridizing liposome with red blood cell (RBC) membrane (RLP), which mimics the CD47 density of senescent RBCs and possesses a natural high-affinity binding capability to SIRPα on macrophages without signaling capacity. RLP would bind with SIRPα and induce its lysosomal degradation through receptor-mediated endocytosis. To enhance its tissue specificity, Ly6G antibody conjugation (aRLP) is applied, enabling its attachment to neutrophils and accumulation within inflammatory sites. In the myocardial infarction model, aRLP accumulated in the infarcted myocardium blocks CD47-SIRPα axis and subsequently promoted the efferocytosis of apoptotic cardiomyocytes by macrophage, improved heart repair. This nano-degrader efficiently degraded SIRPα in lysosomes, providing a new strategy for immunotherapy with great clinical transformation potential.

Harnessing extracellular vesicle membrane for gene therapy: EVs-biomimetic nanoparticles

One of the main concerns in oligonucleotide-based therapeutics is achieving a successful cell targeting while avoiding drug degradation and clearance. Nanoparticulated drug delivery systems have emerged as a way of overcoming these issues. Among them, membrane-coated nanoparticles are of increasing relevance mainly due to their enhanced cellular uptake, immune evasion and biocompatibility. In this study, we designed and elaborated a simple and highly tuneable biomimetic drug delivery nanosystem based on a polymeric core surrounded by extracellular vesicles (EVs)-derived membranes. This strategy should allow the nanosystems to benefit from the properties conferred by the membrane proteins present in EVs membrane, key paracrine mediators. The developed systems were able to successfully encapsulate the required oligonucleotides. Also, their characterisation through already well standardised methods (dynamic light scattering, transmission electron microscopy and nanoparticle tracking analysis) and by fluorescence cross-correlation spectroscopy (FCCS) showed the desired core-shell structure. The cellular uptake using different cell types further confirmed the coating though an enhancement in cell internalisation of the developed biomimetic nanoparticles. This study brings up new possibilities for GapmeR delivery as it might be a base for the development of new delivery systems for gene therapy.

Cell membrane coated nanoparticles: cutting-edge drug delivery systems for osteoporosis therapy

Osteoporosis, characterized by a reduction in bone mineral density, represents a prevalent skeletal disorder with substantial global health implications. Conventional therapeutic strategies, exemplified by bisphosphonates and hormone replacement regimens, though effective, encounter inherent limitations and challenges. Recent years have witnessed the surge of cell-membrane-coated nanoparticles (CMNPs) as a promising intervention for osteoporosis, leveraging their distinct attributes including refined biocompatibility, heightened pharmaceutical payload capacity, as well as targeted drug release kinetics. However, a comprehensive review consolidating the application of CMNPs-based therapy for osteoporosis remains absent within the existing literature. In this review, we provide a concise overview of the distinctive pathogenesis associated with osteoporosis, alongside an in-depth exploration of the physicochemical attributes intrinsic to CMNPs derived from varied cellular sources. Subsequently, we explore the potential utility of CMNPs, elucidating emerging trends in their deployment for osteoporosis treatment through multifaceted therapeutic approaches. By linking the notable attributes of CMNPs with their roles in mitigating osteoporosis, this review serves as a catalyst for further advances in the design of advanced CMNPs tailored for osteoporosis management. Ultimately, such progress is promising for enhancing outcomes in anti-bone loss interventions, paving the way for clinical translation in the near future.

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.

Immunomodulatory nanomedicine for osteoporosis: Current practices and emerging prospects

Osteoporosis results from the disruption of the balance between bone resorption and bone formation. However, classical anti-osteoporosis drugs exhibit several limitations in clinical applications, such as multiple adverse reactions and poor therapeutic effects. Therefore, there is an urgent need for alternative treatment strategies. With the evolution of immunomodulatory nanomedicine, a variety of nanomaterials have been designed for anti-osteoporosis treatment, offering prospects of minimal adverse reactions, enhanced bone induction, and high osteogenic activity. This review initially provides a brief overview of the fundamental principles of bone reconstruction, current osteogenic clinical methods in osteoporosis treatment, and the significance of osteogenic-angiogenic coupling, laying the groundwork for understanding the pathophysiology and therapeutics of osteoporosis. Subsequently, the article emphasizes the relationship between bone immunity and osteogenesis-angiogenesis coupling and provides a detailed analysis of the application of immunomodulatory nanomedicines in the treatment of osteoporosis, including various types of nanomaterials and their integration with carrier biomaterials. Importantly, we discuss the potential of some emerging strategies in immunomodulatory nanomedicine for osteoporosis treatment. This review introduces the innovative applications of immunomodulatory nanomedicine in the treatment of osteoporosis, aiming to serve as a reference for the application of immunomodulatory nanomedicine strategies in osteoporosis treatment. STATEMENT OF SIGNIFICANCE: Osteoporosis, as one of the most prevalent skeletal disorders, poses a significant threat to public health. To date, conventional anti-osteoporosis strategies have been limited in efficacy and plagued with numerous side effects. Fortunately, with the advancement of research in osteoimmunology and nanomedicine, strategies integrating these two fields show great promise in combating osteoporosis. Nanomedicine with immunomodulatory properties exhibits enhanced efficiency, prolonged effectiveness, and increased safety. However, as of now, there exists no comprehensive review amalgamating immunomodulation with nanomedicine to delineate the progress of immunomodulatory nanomedicine in osteoporosis treatment, as well as the future direction of this strategy.

Smart osteoclasts targeted nanomedicine based on amorphous CaCO3 for effective osteoporosis reversal

BACKGROUND

Osteoporosis is characterized by an imbalance in bone homeostasis, resulting in the excessive dissolution of bone minerals due to the acidified microenvironment mediated by overactive osteoclasts. Oroxylin A (ORO), a natural flavonoid, has shown potential in reversing osteoporosis by inhibiting osteoclast-mediated bone resorption. The limited water solubility and lack of targeting specificity hinder the effective accumulation of Oroxylin A within the pathological environment of osteoporosis.

RESULTS

Osteoclasts' microenvironment-responsive nanoparticles are prepared by incorporating Oroxylin A with amorphous calcium carbonate (ACC) and coated with glutamic acid hexapeptide-modified phospholipids, aiming at reinforcing the drug delivery efficiency as well as therapeutic effect. The obtained smart nanoparticles, coined as OAPLG, could instantly neutralize acid and release Oroxylin A in the extracellular microenvironment of osteoclasts. The combination of Oroxylin A and ACC synergistically inhibits osteoclast formation and activity, leading to a significant reversal of systemic bone loss in the ovariectomized mice model.

CONCLUSION

The work highlights an intelligent nanoplatform based on ACC for spatiotemporally controlled release of lipophilic drugs, and illustrates prominent therapeutic promise against osteoporosis.

Synthetic biology-based bacterial extracellular vesicles displaying BMP-2 and CXCR4 to ameliorate osteoporosis

Osteoporosis (OP) is a systematic bone disease characterized by low bone mass and fragile bone microarchitecture. Conventional treatment for OP has limited efficacy and long-term toxicity. Synthetic biology makes bacterial extracellular vesicle (BEVs)-based therapeutic strategies a promising alternative for the treatment of OP. Here, we constructed a recombinant probiotics Escherichia coli Nissle 1917-pET28a-ClyA-BMP-2-CXCR4 (ECN-pClyA-BMP-2-CXCR4), in which BMP-2 and CXCR4 were overexpressed in fusion with BEVs surface protein ClyA. Subsequently, we isolated engineered BEVs-BMP-2-CXCR4 (BEVs-BC) for OP therapy. The engineered BEVs-BC exhibited great bone targeting in vivo. In addition, BEVs-BC had good biocompatibility and remarkable ability to promote osteogenic differentiation of BMSCs. Finally, the synthetic biology-based BEVs-BC significantly prevented the OP in an ovariectomized (OVX) mouse model. In conclusion, we constructed BEVs-BC with both bone-targeting and bone-forming in one-step using synthetic biology, which provides an effective strategy for OP and has great potential for industrialization.

Macrophage membrane-camouflaged biomimetic nanovesicles for targeted treatment of arthritis

Arthritis has become the most common joint disease globally. Current attention has shifted towards preventing the disease and exploring pharmaceutical and surgical treatments for early-stage arthritis. M2 macrophages are known for their anti-inflammatory properties and their ability to support cartilage repair, offering relief from arthritis. Whereas, it remains a great challenge to promote the beneficial secretion of M2 macrophages to prevent the progression of arthritis. Therefore, it is warranted to investigate new strategies that could use the functions of M2 macrophages and enhance its therapeutic effects. This review aims to explore the macrophage cell membrane-coated biomimetic nanovesicles for targeted treatment of arthritis such as osteoarthritis (OA), rheumatoid arthritis (RA), and gouty arthritis (GA). Cell membrane-camouflaged biomimetic nanovesicle has attracted increasing attention, which successfully combine the advantages and properties of both cell membrane and delivered drug. We discuss the roles of macrophages in the pathophysiology and therapeutic targets of arthritis. Then, the common preparation strategies of macrophage membrane-coated nanovesicles are concluded. Moreover, we investigate the applications of macrophage cell membrane-camouflaged nanovesicles for arthritis, such as OA, RA, and GA. Taken together, macrophage cell membrane-camouflaged nanovesicles hold the tremendous prospect for biomedical applications in the targeted treatment of arthritis.

Chondrocyte membrane-coated nanoparticles promote drug retention and halt cartilage damage in rat and canine osteoarthritis

Osteoarthritis (OA) is a chronic joint disease characterized by progressive degeneration of articular cartilage. A challenge in the development of disease-modifying drugs is effective delivery to chondrocytes. The unique structure of the joint promotes rapid clearance of drugs through synovial fluid, and the dense and avascular cartilage extracellular matrix (ECM) limits drug penetration. Here, we show that poly(lactide-co-glycolic acid) nanoparticles coated in chondrocyte membranes (CM-NPs) were preferentially taken up by rat chondrocytes ex vivo compared with uncoated nanoparticles. Internalization of the CM-NPs was mediated primarily by E-cadherin, clathrin-mediated endocytosis, and micropinocytosis. These CM-NPs adhered to the cartilage ECM in rat knee joints in vivo and penetrated deeply into the cartilage matrix with a residence time of more than 34 days. Simulated synovial fluid clearance studies showed that CM-NPs loaded with a Wnt pathway inhibitor, adavivint (CM-NPs-Ada), delayed the catabolic metabolism of rat and human chondrocytes and cartilage explants under inflammatory conditions. In a surgical model of rat OA, drug-loaded CM-NPs effectively restored gait, attenuated periarticular bone remodeling, and provided chondroprotection against cartilage degeneration. OA progression was also mitigated by CM-NPs-Ada in a canine model of anterior cruciate ligament transection. These results demonstrate the feasibility of using chondrocyte membrane-coated nanoparticles to improve the pharmacokinetics and efficacy of anti-OA drugs.

Bone-Targeted Biomimetic Nanogels Re-Establish Osteoblast/Osteoclast Balance to Treat Postmenopausal Osteoporosis

Insufficient bone formation and excessive bone resorption caused by estrogen deficiency are the major factors resulting in the incidence of postmenopausal osteoporosis (PMOP). The existing drugs usually fail to re-establish the osteoblast/osteoclast balance from both sides and generate side-effects owing to the lack of bone-targeting ability. Here, engineered cell-membrane-coated nanogels PNG@mR&C capable of scavenging receptor activator of nuclear factor-κB ligand (RANKL) and responsively releasing therapeutic PTH 1-34 in the bone microenvironment are prepared from RANK and CXCR4 overexpressed bone mesenchymal stem cell (BMSC) membrane-coated chitosan biopolymers. The CXCR4 on the coated-membranes confer bone-targeting ability, and abundant RANK effectively absorb RANKL to inhibit osteoclastogenesis. Meanwhile, the release of PTH 1-34 triggered by osteoclast-mediated acid microenvironment promote osteogenesis. In addition, the dose and frequency are greatly reduced due to the smart release property, prolonged circulation time, and bone-specific accumulation. Thus, PNG@mR&C exhibits satisfactory therapeutic effects in the ovariectomized (OVX) mouse model. This study provides a new paradigm re-establishing the bone metabolic homeostasis from multitargets and shows great promise for the treatment of PMOP.

A Glutathione Peroxidase-Mimicking Nanozyme Precisely Alleviates Reactive Oxygen Species and Promotes Periodontal Bone Regeneration

The use of oxidoreductase nanozymes to regulate reactive oxygen species (ROS) has gradually emerged in periodontology treatments. However, current nanozymes for treating periodontitis eliminate ROS extensively and non-specifically, ignoring the physiological functions of ROS under normal conditions, which may result in uncontrolled side effects. Herein, using the MIL-47(V)-F (MVF) nanozyme, which mimics the function of glutathione peroxidase (GPx), it is proposed that ROS can be properly regulated by specifically eliminating H2 O2 , the most prominent ROS. Through H2 O2 elimination, MVF contributes to limiting inflammation, regulating immune microenvironment, and promoting periodontal regeneration. Moreover, MVF stimulates osteogenic differentiation of periodontal stem cells directly, further promoting regeneration due to the vanadium in MVF. Mechanistically, MVF regulates ROS by activating the nuclear factor erythroid 2-related factor 2/heme oxygenase 1 (Nrf2/HO-1) pathway and promotes osteogenic differentiation directly through the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathway. A promising periodontitis therapy strategy is presented using GPx-mimicking nanozymes through their triple effects of antioxidation, immunomodulation, and bone remodeling regulation, making nanozymes an excellent tool for developing precision medicine.

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.

Structure and function of the membrane microdomains in osteoclasts

The cell membrane structure is closely related to the occurrence and progression of many metabolic bone diseases observed in the clinic and is an important target to the development of therapeutic strategies for these diseases. Strong experimental evidence supports the existence of membrane microdomains in osteoclasts (OCs). However, the potential membrane microdomains and the crucial mechanisms underlying their roles in OCs have not been fully characterized. Membrane microdomain components, such as scaffolding proteins and the actin cytoskeleton, as well as the roles of individual membrane proteins, need to be elucidated. In this review, we discuss the compositions and critical functions of membrane microdomains that determine the biological behavior of OCs through the three main stages of the OC life cycle.

Genetically Engineered Biomimetic Nanoparticles for Targeted Delivery of mRNA to Treat Rheumatoid Arthritis

In addition to inhibiting persistent inflammation, phosphatase and tensin homolog deleted from chromosome 10 (PTEN) is known as an important therapeutic target for alleviating rheumatoid arthritis (RA) symptoms. Modulation of PTEN gene expression in synovial tissue using messenger RNA (mRNA) is a promising approach to combat RA. However, mRNA therapeutics are often hampered by unsatisfactory stability and inefficient localization in synovial tissue. In this study, a genetically engineered biomimetic membrane-coated mRNA (MR@P-mPTEN) carrier that effectively delivers mRNA-PTEN (mPTEN) directly to the RA joint is presented. By overexpressing tumor necrosis factor (TNF-α) receptors on macrophage biomimetic membranes via plasmid transfection, decoys that reduce inflammatory pathway activation are prepared for TNF-α. The resulting construct, MR@P-mPTEN, shows good stability and RA targeting based on in vivo fluorescence imaging. It is also found that MR@P-mPTEN competitively binds TNF-α and activates the PTEN pathway in vitro and in vivo, thereby inhibiting synovitis and joint damage. Clinical micro-computed tomography and histological analyses confirm the treatment effects. These results suggest that the genetically engineered biomimetic therapeutic platform MR@P-mPTEN both inhibits pro-inflammatory cytokines and upregulates PTEN protein expression to alleviate RA damage, providing a new a new combination strategy for RA treatment.

Macrophage Membrane-Reversibly Cloaked Nanotherapeutics for the Anti-Inflammatory and Antioxidant Treatment of Rheumatoid Arthritis

During rheumatoid arthritis (RA) development, over-produced proinflammatory cytokines represented by tumor necrosis factor-α (TNF-α) and reactive oxygen species (ROS) represented by H2 O2 form a self-promoted cycle to exacerbate the synovial inflammation and tissue damage. Herein, biomimetic nanocomplexes (NCs) reversibly cloaked with macrophage membrane (RM) are developed for effective RA management via dual scavenging of TNF-α and ROS. To construct the NCs, membrane-penetrating, helical polypeptide first condenses TNF-α siRNA (siTNF-α) and forms the cationic inner core, which further adsorbs catalase (CAT) via electrostatic interaction followed by surface coating with RM. The membrane-coated NCs enable prolonged blood circulation and active joint accumulation after systemic administration in Zymosan A-induced arthritis mice. In the oxidative microenvironment of joints, CAT degrades H2 O2 to produce O2 bubbles, which shed off the outer membrane layer to expose the positively charged inner core, thus facilitating effective intracellular delivery into macrophages. siRNA-mediated TNF-α silencing and CAT-mediated H2 O2 scavenging then cooperate to inhibit inflammation and alleviate oxidative stress, remodeling the osteomicroenvironment and fostering tissue repair. This study provides an enlightened strategy to resolve the blood circulation/cell internalization dilemma of cell membrane-coated nanosystems, and it renders a promising modality for RA treatment.

Cell unit-inspired natural nano-based biomaterials as versatile building blocks for bone/cartilage regeneration

The regeneration of weight-bearing bone defects and critical-sized cartilage defects remains a significant challenge. A wide range of nano-biomaterials are available for the treatment of bone/cartilage defects. However, their poor compatibility and biodegradability pose challenges to the practical applications of these nano-based biomaterials. Natural biomaterials inspired by the cell units (e.g., nucleic acids and proteins), have gained increasing attention in recent decades due to their versatile functionality, compatibility, biodegradability, and great potential for modification, combination, and hybridization. In the field of bone/cartilage regeneration, natural nano-based biomaterials have presented an unparalleled role in providing optimal cues and microenvironments for cell growth and differentiation. In this review, we systematically summarize the versatile building blocks inspired by the cell unit used as natural nano-based biomaterials in bone/cartilage regeneration, including nucleic acids, proteins, carbohydrates, lipids, and membranes. In addition, the opportunities and challenges of natural nano-based biomaterials for the future use of bone/cartilage regeneration are discussed.

Metal-polyDNA nanoparticles reconstruct osteoporotic microenvironment for enhanced osteoporosis treatment

Current clinical approaches to osteoporosis primarily target osteoclast biology, overlooking the synergistic role of bone cells, immune cells, cytokines, and inorganic components in creating an abnormal osteoporotic microenvironment. Here, metal-polyDNA nanoparticles (Ca-polyCpG MDNs) composed of Ca2+ and ultralong single-stranded CpG sequences were developed to reconstruct the osteoporotic microenvironment and suppress osteoporosis. Ca-polyCpG MDNs can neutralize osteoclast-secreted hydrogen ions, provide calcium repletion, promote remineralization, and repair bone defects. Besides, the immune-adjuvant polyCpG in MDNs could induce the secretion of osteoclastogenesis inhibitor interleukin-12 and reduce the expression of osteoclast function effector protein to inhibit osteoclast differentiation, further reducing osteoclast-mediated bone resorption. PPi4- generated during the rolling circle amplification reaction acts as bisphosphonate analog and enhances bone targeting of Ca-polyCpG MDNs. In ovariectomized mouse and rabbit models, Ca-polyCpG MDNs prevented bone resorption and promoted bone repair by restoring the osteoporotic microenvironment, providing valuable insights into osteoporosis therapy.

M2 Macrophage Membrane-Mediated Biomimetic-Nanoparticle Carrying COX-siRNA Targeted Delivery for Prevention of Tendon Adhesions by Inhibiting Inflammation

Tendon adhesion is the most common outcome of tendon or tendon-to-bone healing after injury. Our group developed a hydrogel-nanoparticle sustained-release system previously to inhibit cyclooxygenases (COXs) expression and consequently prevent tendon adhesion and achieved satisfactory results. However, effective treatment of multiple tendon adhesions is always a challenge in research on the prevention of tendon adhesion. In the present study, an M2M@PLGA/COX-siRNA delivery system is successfully constructed using the cell membranes of M2 macrophages and poly (lactic-co-glycolic acid) (PLGA) nanoparticles. Targeting properties and therapeutic effects are observed in mice or rat models of flexor digitorum longus (FDL) tendon injury combined with rotator cuff injury. The results showed that the M2M@PLGA/COX-siRNA delivery system has low toxicity and remarkable targeting properties to the injured areas. Treatment with the M2M@PLGA/COX-siRNA delivery system reduced the inflammatory reaction and significantly improved tendon adhesion in both the FDL tendon and rotator cuff tissues. These findings indicate that the M2M@PLGA delivery system can provide an effective biological strategy for preventing multiple tendon adhesions.

siRNA Delivery against Myocardial Ischemia Reperfusion Injury Mediated by Reversibly Camouflaged Biomimetic Nanocomplexes

siRNA-mediated management of myocardial ischemia reperfusion (IR) injury is greatly hampered by the inefficient myocardial enrichment and cardiomyocyte transfection. Herein, nanocomplexes (NCs) reversibly camouflaged with a platelet-macrophage hybrid membrane (HM) are developed to efficiently deliver Sav1 siRNA (siSav1) into cardiomyocytes, suppressing the Hippo pathway and inducing cardiomyocyte regeneration. The biomimetic BSPC@HM NCs consist of a cationic nanocore assembled from a membrane-penetrating helical polypeptide (P-Ben) and siSav1, a charge-reversal intermediate layer of poly(l-lysine)-cis-aconitic acid (PC), and an outer shell of HM. Due to HM-mediated inflammation homing and microthrombus targeting, intravenously injected BSPC@HM NCs can efficiently accumulate in the IR-injured myocardium, where the acidic inflammatory microenvironment triggers charge reversal of PC to shed off both HM and PC layers and allow the penetration of the exposed P-Ben/siSav1 NCs into cardiomyocytes. In rats and pigs, BSPC@HM NCs remarkably downregulates Sav1 in IR-injured myocardium, promotes myocardium regeneration, suppresses myocardial apoptosis, and recovers cardiac functions. This study reports a bioinspired strategy to overcome the multiple systemic barriers against myocardial siRNA delivery, and holds profound potential for gene therapy against cardiac injuries.

Vesicular Antibodies: Shedding Light on Antibody Therapeutics with Cell Membrane Nanotechnology

The high stability of antibodies and their ability to precisely bind to antigens and endogenous immune receptors, as well as their susceptibility to protein engineering, enable antibody-based therapeutics to be widely applied in cancer, inflammation, infection, and other disorders. Nevertheless, the application of traditional antibody-based therapeutics has certain limitations, such as high price, limited permeability, and protein engineering complexity. Recent breakthroughs in cell membrane nanotechnology have deepened the understanding of the critical role of membrane protein receptors in disease treatment, enabling vesicular-antibody-based therapeutics. Here, the concept of vesicular antibodies that are obtained by modifying target antibodies onto cell membranes for biomedical applications is proposed. Given that an antibody is basically a protein, as an extension of this concept, vesicles or membrane-coated nanoparticles that use surface antibodies and protein receptors on cell membranes for biomedical applications as vesicular antibodies are defined. Furthermore, several engineering strategies for vesicular antibodies are summarized and how vesicular antibodies can be used in a variety of situations is highlighted. In addition, current challenges and future prospects of vesicular antibodies are also discussed. It is anticipated this perspective will provide new insights on the development of next-generation antibodies for enhanced therapeutics.

Advances in materials-based therapeutic strategies against osteoporosis

Osteoporosis is caused by the disruption in homeostasis between bone formation and bone resorption. Conventional management of osteoporosis involves systematic drug administration and hormonal therapy. These treatment strategies have limited curative efficacy and multiple adverse effects. Biomaterials-based therapeutic strategies have recently emerged as promising alternatives for the treatment of osteoporosis. The present review summarizes the current status of biomaterials designed for managing osteoporosis. The advantages of biomaterials-based strategies over conventional systematic drug treatment are presented. Different anti-osteoporotic delivery systems are concisely addressed. These materials include injectable hydrogels and nanoparticles, as well as anti-osteoporotic bone tissue engineering materials. Fabrication techniques such as 3D printing, electrostatic spinning and artificial intelligence are appraised in the context of how the use of these adjunctive techniques may improve treatment efficacy. The limitations of existing biomaterials are critically analyzed, together with deliberation of the future directions in biomaterials-based therapies. The latter include discussion on the use of combination strategies to enhance therapeutic efficacy in the osteoporosis niche.

The nanoformula of zoledronic acid and calcium carbonate targets osteoclasts and reverses osteoporosis

Osteoporosis is known as an imbalance in bone catabolism and anabolism. Overactive bone resorption causes bone mass loss and increased incidence of fragility fractures. Antiresorptive drugs are widely used for osteoporosis treatment, and their inhibitory effects on osteoclasts (OCs) have been well established. However, due to the lack of selectivity, their off-target and side effects often bring suffering to patients. Herein, an OCs' microenvironment-responsive nanoplatform HA-MC/CaCO₃/ZOL@PBAE-SA (HMCZP) is developed, consisting of succinic anhydride (SA)-modified poly(β-amino ester) (PBAE) micelle, calcium carbonate shell, minocycline-modified hyaluronic acid (HA-MC) and zoledronic acid (ZOL). Results indicate that HMCZP, as compared with the first-line therapy, could more effectively inhibit the activity of mature OCs and significantly reverse the systemic bone mass loss in ovariectomized mice. In addition, the OCs-targeted capacity of HMCZP makes it therapeutically efficient at sites of severe bone mass loss and allows it to reduce the adverse effects of ZOL, such as acute phase reaction. High-throughput RNA sequencing (RNA-seq) reveals that HMCZP could down-regulate a critical osteoporotic target, tartrate-resistant acid phosphatase (TRAP), as well as other potential therapeutical targets for osteoporosis. These results suggest that an intelligent nanoplatform targeting OCs is a promising strategy for osteoporosis therapy.

Optineurin regulates NRF2-mediated antioxidant response in a mouse model of Paget's disease of bone

Degenerative diseases affecting the nervous and skeletal systems affect the health of millions of elderly people. Optineurin (OPTN) has been associated with numerous neurodegenerative diseases and Paget's disease of bone (PDB), a degenerative bone disease initiated by hyperactive osteoclastogenesis. In this study, we found age-related increase in OPTN and nuclear factor E2-related factor 2 (NRF2) in vivo. At the molecular level, OPTN could directly interact with both NRF2 and its negative regulator Kelch-like ECH-associated protein 1 (KEAP1) for up-regulating antioxidant response. At the cellular level, deletion of OPTN resulted in increased intracellular reactive oxygen species and increased osteoclastogenic potential. At the tissue level, deletion of OPTN resulted in substantially increased oxidative stress derived from leukocytes that further stimulate osteoclastogenesis. Last, curcumin attenuated hyperactive osteoclastogenesis induced by OPTN deficiency in aged mice. Collectively, our findings reveal an OPTN-NRF2 axis maintaining bone homeostasis and suggest that antioxidants have therapeutic potential for PDB.

MOTS-c Functionally Prevents Metabolic Disorders

Mitochondrial-derived peptides are a family of peptides encoded by short open reading frames in the mitochondrial genome, which have regulatory effects on mitochondrial functions, gene expression, and metabolic homeostasis of the body. As a new member of the mitochondrial-derived peptide family, mitochondrial open reading frame of the 12S rRNA-c (MOTS-c) is regarding a peptide hormone that could reduce insulin resistance, prevent obesity, improve muscle function, promote bone metabolism, enhance immune regulation, and postpone aging. MOTS-c plays these physiological functions mainly through activating the AICAR-AMPK signaling pathways by disrupting the folate-methionine cycle in cells. Recent studies have shown that the above hormonal effect can be achieved through MOTS-c regulating the expression of genes such as GLUT4, STAT3, and IL-10. However, there is a lack of articles summarizing the genes and pathways involved in the physiological activity of MOTS-c. This article aims to summarize and interpret the interesting and updated findings of MOTS-c-associated genes and pathways involved in pathological metabolic processes. Finally, it is expected to develop novel diagnostic markers and treatment approaches with MOTS-c to prevent and treat metabolic disorders in the future.