Functionalized TiCu/TiCuN coating promotes osteoporotic fracture healing by upregulating the Wnt/β-catenin pathway

USP2-induced upregulation of LEF1 through deubiquitination relieves osteoporosis development by promoting the osteogenic differentiation of bone marrow mesenchymal stem cells

BACKGROUND

Bone marrow mesenchymal stem cells (BMSCs) exhibit therapeutic potential for osteoporosis through their differentiation into osteoblasts. Here, we investigated the role and mechanism of lymphoid enhancer-binding factor 1 (LEF1) in regulating osteogenic differentiation of human BMSCs (hBMSCs).

METHODS

hBMSCs were exposed to the specific medium to induce their osteogenic differentiation. The ovariectomy (OVX)-induced osteoporotic mouse model was constructed. LEF1 and USP2 mRNA expression was analyzed by quantitative PCR, and protein levels were detected by immunohistochemistry and immunoblotting. Cell proliferation was assessed by CCK-8 assay. Alkaline phosphatase (ALP) expression and activity assay and Alizarin Red staining were used to evaluate osteogenic differentiation. LEF1 protein stability analysis and co-immunoprecipitation (Co-IP) assay were performed to test the USP2/LEF1 interaction.

RESULTS

During hBMSC osteogenic differentiation, LEF1 and USP2 levels were increased in hBMSCs. Inhibiting LEF1 or USP2 diminished the proliferation and osteogenic differentiation of hBMSCs in vitro. Mechanistically, USP2 stabilized LEF1 protein by mediating LEF1 deubiquitination. Increased expression of LEF1 reversed USP2 knockdown-imposed suppression on proliferation and osteogenic differentiation of hBMSCs. Moreover, increased USP2 expression reduced bone loss and enhanced osteogenic differentiation in OVX mice. Additionally, LEF1 and USP2 were downregulated in the bone marrow of patients with osteoporosis.

CONCLUSION

Our findings provide the first demonstration of the USP2/LEF1 cascade that enhances the osteogenic differentiation of hBMSCs, broadening the field for the development of BMSCs as effective agents in osteoporosis therapy.

Advances in copper-containing biomaterials for managing bone-related diseases

Bone-related diseases pose a major challenge in contemporary society, with significant implications for both health and economy. Copper, a vital trace metal in the human body, facilitates a wide range of physiological processes by being crucial for the function of proteins and enzymes. Numerous studies have validated copper's role in bone regeneration and protection, particularly in the development and expansion of bone collagen. Owing to copper's numerous biological advantages, an increasing number of scientists are endeavoring to fabricate novel, multifunctional copper-containing biomaterials as an effective treatment strategy for bone disorders. This review integrates the current understanding regarding the biological functions of copper from the molecular and cellular levels, highlighting its potential for bone regeneration and protection. It also reviews the novel fabrication techniques for developing copper-containing biomaterials, including copper-modified metals, calcium phosphate bioceramics, bioactive glasses, bone cements, hydrogels and biocomposites. The fabrication strategies and various applications of these biomaterials in addressing conditions such as fractures, bone tumors, osteomyelitis, osteoporosis, osteoarthritis and osteonecrosis are carefully elaborated. Moreover, the long-term safety and toxicity assessments of these biomaterials are also presented. Finally, the review addresses current challenges and future prospects, in particular the regulatory challenges and safety issues faced in clinical implementation, with the aim of guiding the strategic design of multifunctional copper-based biomaterials to effectively manage bone-related diseases.

Implant Design and Its Applications in the Fixation of Osteoporotic Bones: Newer Technologies in Nails, Plates and External Fixators

Background

Osteoporosis, characterised by decreased bone mass and degradation of bone tissue, poses a major global health concern, particularly for the ageing population. The traditional fixation techniques often fail in osteoporotic bones due to their diminished density and strength. Technological advancements in orthopaedic implants, specifically nails, plates, and external fixators, have emerged to address these challenges.

Materials and Methods

Improvements in implant design focus on material properties, surface modifications, and geometric advancements. Titanium and its alloys are favoured for their biomechanical properties such as lower elastic modulus and high strength-to-weight ratio. The biodegradable materials like polylactic acid and magnesium alloys offer the advantage of gradual resorption as bone heals. Surface modifications, such as coatings with bioactive materials and drug-eluting surfaces, promote osseointegration and enhance fixation strength.

Results and Discussion

Intramedullary (IM) nails have evolved to enhance stability and minimise complications associated with osteoporotic fractures. Third and fourth-generation nails incorporate surface treatments for better integration and healing. The advances in screw design, locking mechanisms, and flexible axial stimulation have improved fixation and allowed micromotion, which promotes fracture healing. The use of external fixators, particularly for complex fractures in osteoporotic bones, offers less invasive treatment options with adaptable stiffness for improved healing.

Conclusion

Technological innovations in implant materials, design, and surgical techniques have significantly improved the management of osteoporotic fractures. Newer technologies, including 3D printing, virtual and augmented reality, and artificial intelligence, show promise in enhancing implant customization, surgical planning, and postoperative outcomes. However, further clinical validation and research are needed to expand their clinical applications.

Copper metabolism in osteoarthritis and its relation to oxidative stress and ferroptosis in chondrocytes

Ferroptosis, an iron-ion-dependent process of lipid peroxidation, damages the plasma membrane, leading to non-programmed cell death. Osteoarthritis (OA), a prevalent chronic degenerative joint disease among middle-aged and older adults, is characterized by chondrocyte damage or loss. Emerging evidence indicates that chondrocyte ferroptosis plays a role in OA development. However, most research has concentrated on ferroptosis regulation involving typical iron ions, potentially neglecting the significance of elevated copper ions in both serum and joint fluid of patients with OA. This review aims to fill this gap by systematically examining the interplay between copper metabolism, oxidative stress, ferroptosis, and copper-associated cell death in OA. It will provide a comprehensive overview of copper ions' role in regulating ferroptosis and their dual role in OA. This approach seeks to offer new insights for further research, prevention, and treatment of OA.

Fibrous topology promoted pBMP2-activated matrix on titanium implants boost osseointegration

Titanium (Ti) implants have been extensively used after surgical operations. Its surface bioactivity is of importance to facilitate integration with surrounding bone tissue, and ultimately ensure stability and long-term functionality of the implant. The plasmid DNA-activated matrix (DAM) coating on the surface could benefit osseointegration but is still trapped by poor transfection for further application, especially on the bone marrow mesenchymal stem cells (BMSCs) in vivo practical conditions. Herein, we constructed a DAM on the surface of fibrous-grained titanium (FG Ti) composed of phase-transition lysozyme (P) as adhesive, cationic arginine-rich lipid (RLS) as the transfection agent and plasmid DNA (pDNA) for bone morphology protein 2 (BMP2) expression. The cationic lipid RLS improved up to 30-fold higher transfection than that of commercial reagents (Lipofectamine 2000 and polyethyleneimine) on MSC. And importantly, Ti surface topology not only promotes the DAM to achieve high transfection efficiency (∼75.7% positive cells) on MSC due to the favorable combination but also reserves its contact induction effect for osteoblasts. Upon further exploration, the fibrous topology on FG Ti could boost pDNA uptake for gene transfection, and cell migration in MSC through cytoskeleton remodeling and induce contact guidance for enhanced osteointegration. At the same time, the cationic RLS together with adhesive P were both antibacterial, showing up to 90% inhibition rate against Escherichia coli and Staphylococcus aureus with reduced adherent microorganisms and disrupted bacteria. Finally, the FG Ti-P/pBMP2 implant achieved accelerated bone healing capacities through highly efficient gene delivery, aligned surface topological structure and increased antimicrobial properties in a rat femoral condylar defect model.

Carnosine, Zinc and Copper: A Menage a Trois in Bone and Cartilage Protection

Dysregulated metal homeostasis is associated with many pathological conditions, including arthritic diseases. Osteoarthritis and rheumatoid arthritis are the two most prevalent disorders that damage the joints and lead to cartilage and bone destruction. Recent studies show that the levels of zinc (Zn) and copper (Cu) are generally altered in the serum of arthritis patients. Therefore, metal dyshomeostasis may reflect the contribution of these trace elements to the disease's pathogenesis and manifestations, suggesting their potential for prognosis and treatment. Carnosine (Car) also emerged as a biomarker in arthritis and exerts protective and osteogenic effects in arthritic joints. Notably, its zinc(II) complex, polaprezinc, has been recently proposed as a drug-repurposing candidate for bone fracture healing. On these bases, this review article aims to provide an overview of the beneficial roles of Cu and Zn in bone and cartilage health and their potential application in tissue engineering. The effects of Car and polaprezinc in promoting cartilage and bone regeneration are also discussed. We hypothesize that polaprezinc could exchange Zn for Cu, present in the culture media, due to its higher sequestering ability towards Cu. However, future studies should unveil the potential contribution of Cu in the beneficial effects of polaprezinc.

Copper-containing chitosan-based hydrogels enabled 3D-printed scaffolds to accelerate bone repair and eliminate MRSA-related infection

Bone defect combined with drug-resistant bacteria-related infection is a thorny challenge in clinic. Herein, 3D-printed polyhydroxyalkanoates/β-tricalcium phosphate (PHA/β-TCP, PT) scaffolds were prepared by fused deposition modeling. Then copper-containing carboxymethyl chitosan/alginate (CA/Cu) hydrogels were integrated with the scaffolds via a facile and low-cost chemical crosslinking method. The resultant PT/CA/Cu scaffolds could not only promote proliferation but also osteogenic differentiation of preosteoblasts in vitro. Moreover, PT/CA/Cu scaffolds exhibited a strong antibacterial activity towards a broad-spectrum of bacteria including methicillin-resistant Staphylococcus aureus (MRSA) through inducing the intercellular generation of reactive oxygen species. In vivo experiments further demonstrated that PT/CA/Cu scaffolds significantly accelerated bone repair of cranial defects and efficiently eliminated MRSA-related infection, showing potential for application in infected bone defect therapy.