Background: The repair of osteoporotic bone defects remains challenging due to excessive reactive oxygen species (ROS), persistent inflammation, and an imbalance between osteogenesis and osteoclastogenesis. Methods: Here, an injectable H2-releasing hydrogel (magnesium@polyethylene glycol-poly(lactic-co-glycolic acid), Mg@PEG-PLGA) was developed to remodel the challenging bone environment and accelerate the repair of osteoporotic bone defects. Results: This Mg@PEG-PLGA gel shows excellent injectability, shape adaptability, and phase-transition ability, can fill irregular bone defect areas via minimally invasive injection, and can transform into a porous scaffold in situ to provide mechanical support. With the appropriate release of H2 and magnesium ions, the 2Mg@PEG-PLGA gel (loaded with 2 mg of Mg) displayed significant immunomodulatory effects through reducing intracellular ROS, guiding macrophage polarization toward the M2 phenotype, and inhibiting the IκB/NF-κB signaling pathway. Moreover, in vitro experiments showed that the 2Mg@PEG-PLGA gel inhibited osteoclastogenesis while promoting osteogenesis. Most notably, in animal experiments, the 2Mg@PEG-PLGA gel significantly promoted the repair of osteoporotic bone defects in vivo by scavenging ROS and inhibiting inflammation and osteoclastogenesis. Conclusions: Overall, our study provides critical insight into the design and development of H2-releasing magnesium-based hydrogels as potential implants for repairing osteoporotic bone defects.

Hydroxyapatite (HAp) coatings currently have limited therapeutic applications because they lack anti-infection, osteoinductivity, and poor mechanical characteristics. On the titanium substrate, electrochemical deposition (ECD) was used to construct the strontium (Sr)-featuring hydroxyapatite (HAp)/graphene oxides (GO)/linezolid (LZ) nanomaterial coated with antibacterial and drug delivery properties. The newly fabricated nanomaterials were confirmed by X-ray diffraction analysis (XRD), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analysis and morphological features were examined by scanning electron microscope (SEM) analysis. The results reveal multiple nucleation sites for SrHAp/GO/LZ composite coatings due to oxygen-comprising moieties on the 2D surface of GO. It was shown to be favorable for osteoblast proliferation and differentiation. The elastic modulus and hardness of LZ nanocomposite with SrHAp/GO/LZ coatings were increased by 67 % and 121 %, respectively. An initial 5 h burst of LZ release from the SrHAp/GO/LZ coating was followed by 14 h of gradual release, owing to LZ\'s physical and chemical adsorption. The SrHAp/GO/LZ coating effectively inhibited both S. epidermidis and S. aureus, and the inhibition lasted for three days, as demonstrated by the inhibition zone and colony count assays. When MG-63 cells are coated with SrHAp/GO/LZ composite coating, their adhesion, proliferation, and differentiation greatly improve when coated with pure titanium. A novel surface engineering nanomaterial for treating and preventing osteoporotic bone defects, SrHAp/GO/LZ, was shown to have high mechanical characteristics, superior antibacterial abilities, and osteoinductivity.

The treatment of osteoporotic bone defect remains a big clinical challenge because osteoporosis (OP) is associated with oxidative stress and high levels of reactive oxygen species (ROS), a condition detrimental for bone formation. Anti-oxidative nanomaterials such as selenium nanoparticles (SeNPs) have positive effect on osteogenesis owing to their pleiotropic pharmacological activity which can exert anti-oxidative stress functions to prevent bone loss and facilitate bone regeneration in OP. In the current study a strategy of one-pot method by introducing Poly (lactic acid-carbonate) (PDT) and β-Tricalcium Phosphate (β-TCP) with SeNPs, is developed to prepare an injectable, anti-collapse, shape-adaptive and adhesive bone graft substitute material (PDT-TCP-SE). The PDT-TCP-SE bone graft substitute exhibits sufficient adhesion in biological microenvironments and osteoinductive activity, angiogenic effect and anti-inflammatory as well as anti-oxidative effect in vitro and in vivo. Moreover, the PDT-TCP-SE can protect BMSCs from erastin-induced ferroptosis through the Sirt1/Nrf2/GPX4 antioxidant pathway, which, in together, demonstrated the bone graft substitute material as an emerging biomaterial with potential clinical application for the future treatment of osteoporotic bone defect. STATEMENT OF SIGNIFICANCE: Injectable, anti-collapse, adhesive, plastic and bioactive bone graft substitute was successfully synthesized. Incorporation of SeNPs with PDT into β-TCP regenerated new bone in-situ by moderating oxidative stress in osteoporotic bone defects area. The PDT-TCP-SE bone graft substitute reduced high ROS levels in osteoporotic bone defect microenvironment. The bone graft substitute could also moderate oxidative stress and inhibit ferroptosis via Sirt1/Nrf2/GPX4 pathway in vitro. Moreover, the PDT-TCP-SE bone graft substitute could alleviate the inflammatory environment and promote bone regeneration in osteoporotic bone defect in vivo. This biomaterial has the advantages of simple synthesis, biocompatibility, anti-collapse, injectable, and regulation of oxidative stress level, which has potential application value in bone tissue engineering.

Osteoporosis, characterized by an imbalance in bone homeostasis, is a global health concern. Bone defects are difficult to heal in patients with osteoporosis. Classical drug treatments for osteoporotic bone defects have unsatisfactory efficacy owing to side effects and imprecise delivery problems. In this study, a magnetic aggregation-induced bone-targeting poly(lactic-co-glycolic acid, PLGA)-based nanocarrier (ZOL-PLGA@Yoda1/SPIO) is synthesized to realize dual-targeted delivery and precise Piezo1-activated therapy for osteoporotic bone defects. Piezo1 is an important mechanotransducer that plays a key role in regulating bone homeostasis. To achieve dual-targeting properties, ZOL-PLGA@Yoda1/SPIO is fabricated using zoledronate (ZOL)-decorated PLGA, superparamagnetic iron oxide (SPIO), and Piezo1-activated molecule Yoda1 via the emulsion solvent diffusion method. Bone-targeting molecular mediation and magnetic aggregation-induced properties can jointly and effectively achieve precise delivery to localized bone defects. Moreover, Yoda1 loading enables targeted and efficient mimicking of mechanical signals and activation of Piezo1. Experiments in vivo and in vitro demonstrate that ZOL-PLGA@Yoda1/SPIO can activate Piezo1 in bone defect areas of osteoporotic mice, improve osteogenesis through YAP/β-catenin signaling axis, promote a well-coordinated osteogenesis-angiogenesis coupling, and significantly accelerate bone reconstruction within the defects without noticeable side effects. Overall, this novel dual-targeting nanocarrier provides a potentially effective strategy for the clinical treatment of osteoporotic bone defects.

Bone defects in osteoporosis usually present excessive reactive oxygen species (ROS), abnormal inflammation levels, irregular shapes and impaired bone regeneration ability; therefore, osteoporotic bone defects are difficult to repair. In this study, an injectable thermosensitive hydrogel poly (D, L-lactide)-poly (ethylene glycol)- poly (D, L-lactide) (PLEL) system containing resveratrol (Res) and dexamethasone (DEX) is designed to create a microenvironment conducive to osteogenesis in osteoporotic bone defects. This PLEL hydrogel is injected and filled irregular defect areas and achieving a rapid sol-gel transition in situ. Res has a strong anti-inflammatory effects that can effectively remove excess free radicals at the damaged site, guide macrophage polarization to the M2 phenotype, and regulate immune responses. Additionally, DEX can promote osteogenic differentiation. In vitro experiments showed that the hydrogel effectively promoted osteogenic differentiation of mesenchymal stem cells, removed excess intracellular ROS, and regulated macrophage polarization to reduce inflammatory responses. In vivo experiments showed that the hydrogel promoted osteoporotic bone defect regeneration and modulated immune responses. Overall, this study confirmed that the hydrogel can treat osteoporotic bone defects by synergistically modulating bone damage microenvironment, alleviating inflammatory responses, and promoting osteogenesis; thus, it represents a promising drug delivery strategy to repair osteoporotic bone defects.

The local application of drug-loaded bioactive scaffold materials is one of the important directions to solve the clinical problem of osteoporotic (OP) bone defects. This study retains the advantages of drug loading and mechanical properties of natural 3D bioactive scaffolds. The scaffolds are functionally modified through chemical and self-assembly approaches with application of polydopamine (PDA) nanoparticles and parathyroid hormone-related peptide-1 (PTHrP-1) for efficient local drug loading. This study investigates the effects of the novel bioactive scaffolds on ossification, osteoclastogenesis, and macrophage polarization. This work elucidates the effects of the scaffolds in regulating osteoclastic activity and new bone formation in vitro. Further studies on the establishment and repair of OP bone defects in small animals are conducted, and the potential of natural bioactive porous scaffold materials to promote the repair of OP bone defects is initially verified. The preparation of safe and economical anti-OP bone repair material provides a theoretical basis for clinical translational applications.

Bone disease and disorder treatment might be difficult because of its complicated nature. Millions of patients each year need bone substitutes that may help them recover quickly from a variety of illnesses. Synthetic bone replacements that mirror the structural, chemical, and biological features of bone matrix structure will be very helpful and in high demand. In this research, the inorganic bioactive glass nanoparticles matrixed with organic collagen and silk fibroin structure (COL/SF/CaO-SiO2) were used to create multifunctional bone-like fibers in this study, which we describe here. The fiber structure is organized in a layered fashion comparable to the sequence in which apatite and neo tissue are formed. The amino groups in COL and SF combined with CaO-SiO2 to stabilize the resulting composite nanofiber. Morphological and functional studies confirmed that crystalline CaO-SiO2 nanoparticles with average sizes of 20 ± 5 nm are anchored on a 115 ± 10 nm COL/SF nanofiber matrix. X-ray photoelectron spectroscopic (XPS) results confirmed the presence of C, N, O, Ca, and Si in the composite fiber with an atomic percentage of 59.46, 3.30, 20.25, 3.38 and 13.61%. respectively. The biocompatibility examination with osteoblast cells (Saos-2) revealed that the CAL/SF/CaO-SiO2 composite nanofiber had enhanced osteogenic activity. Finally, when the CAL/SF/CaO-SiO2 composite nanofiber scaffolds were used to treat an osteoporotic bone defect in a rat model, the composite nanofiber scaffolds significantly promoted bone regeneration and vascularization. This novel fibrous scaffold class represents a potential breakthrough in the design of advanced materials for complicated bone regeneration.

Oxidative stress is an important contributor to the development of osteoporosis. Melatonin, an indoleamine secreted by the pineal gland, has antioxidant properties. This study aims to explore whether melatonin can promote bone formation and elucidate the mechanisms underlying this process. In this study, we used an in vitro hydrogen peroxide (H2O2)-induced oxidative stress model in MC3T3-E1 cells and an in vivo ovariectomized osteoporotic bone defect model in rats to explore the protective effects of melatonin against osteoporotic bone defects along with the mechanism underlying these effects. We found that melatonin significantly increased alkaline phosphatase activity, mineralization capacity, and the expression of BMP2, RUNX2, and OPN in MC3T3-E1 cells treated with H2O2. Furthermore, melatonin was found to activate SIRT1, SIRT3 and inhibit p66Shc, reduce the intracellular reactive oxygen species levels, stabilize mitochondria, reduce malondialdehyde levels, increase superoxide dismutase activity, and reduce apoptosis in MC3T3-E1 cells treated with H2O2. Intriguingly, these effects could be reversed by the SIRT1 inhibitor EX527. In vivo experiments confirmed that melatonin improves the microstructure and bone mineral density of the distal femoral bone trabecula and promotes bone formation. Meanwhile, melatonin activated SIRT1, inhibited p66Shc and increased SIRT3 expression. Taken together, our findings showed that melatonin can restrain oxidative damage in MC3T3-E1 cells and promote osteogenesis by activating SIRT1 which regulate the activity of SIRT3 and inhibit the expression of p66Shc, suggesting that melatonin could be a potential therapeutic agent for osteoporosis-related bone metabolic diseases.

Local application of lithium or aspirin with biological scaffold has been identified as a potent means to improve bone formation. In this study, lithium and aspirin modified calcium phosphate cement (Asp-Li/CPC) was prepared, and the feasibility of this biological scaffold in the treatment of osteoporotic bone defect was observed in vivo and in vitro. In vitro experiments confirmed that Asp-Li/CPC had better ability to promote MC3T3-E1 cells differentiation into osteoblasts, osteoblast mineralization and viability, and promote cell expression of ALP, OP, RUNX-2, OC and COL-1 protein than simple CPC or lithium modified CPC by MTT, Alizarin red staining and Western blot evaluation. In vivo experiments confirmed that Asp-Li/CPC presented the strongest effect on bone regeneration and bone mineralization through the comparison with CPC group and Li/CPC group with X-ray images, Micro-CT and Histological evaluation. RT-qPCR analysis showed that Asp-Li/CPC, Li/CPC group and CPC group demonstrated increased BMP2, Smad1, OPG than the OVX group (P<0.05), while Asp-Li/CPC exhibited decreased TNF-α, IFN-γ and RANKL than the OVX group (P<0.05). Experiments in vivo and in vitro show that Asp-Li/CPC is a scheme for rapid repair of femoral condylar defects, and these effects may be achieved by inhibiting local inflammation and through BMP-2/Smad1 and OPG/RANKL signaling pathway.

BACKGROUND: The use of antiepileptic drugs and estrogen deficiency put forward higher requirements for bone defect regeneration. The present study investigated the effects of alendronate (ALN) on femoral bone defect in ovariectomized (OVX) rats under the influence of carbamazepine (CBZ).
METHODS: One hundred female SD rats at 3 months of age were either sham-operated or OVX and divided into four groups: sham control (CON); OVX control (OVX); ovariectomized rats treated with CBZ via gavage (75 mg/kg/day; CBZ); ovariectomized rats treated with CBZ plus ALN (2 mg/kg/day; CBZ-ALN). A critical-sized femoral metaphyseal bone defect was established in all female SD rats. Animals from the CBZ and CBZ-ALN groups received drugs by gavage the day after bone defect surgery was performed. After the rats were sacrificed, the defected area located in the distal femur was harvested for evaluation by microcomputed tomography (micro-CT), hematoxylin and eosin (HE) staining, and Masson\'s trichrome staining. The samples were also analyzed by biomechanics and immunohistochemical evaluation (IHC). Besides, biochemical analysis evaluates all serum samples.
RESULTS: The present study showed that ovariectomy changed the microstructural parameters of bone. The use of CBZ further decreased femur bone mass while treatment with ALN prevented bone loss. Compared to OVX and CBZ groups, CBZ-ALN group promoted bone neoformation and enhanced the ultimate load of the femur bone. However, the group of CBZ-ALN did not return to normal levels compared with the CON group. Besides, we noticed that CBZ-ALN group reduced tartrate-resistant acid phosphatase-5b (Tracp-5b) expression and had no significant effect on the expression of osteocalcin (OCN) and type I collagen (Col-I) in IHC compared with CBZ group. Biochemical analysis results presented that systemic delivery of CBZ showed pernicious effects on bone formation and resorption in ovariectomized rats, with the worse effects on C-terminal crosslinked telopeptide of type I collagen (CTX-1). Besides, a significant decrease in CTX-1 levels was observed in CBZ-ALN group as compared to the group of CBZ.
CONCLUSIONS: These results demonstrated that ALN can effectively reverse the effects of CBZ on the microarchitectural properties of bone, and thus can have a positive effect on local bone neoformation in rats with osteoporosis.
CONCLUSIONS: The dose of 2 mg/kg ALN improves the negative effect of prescription of CBZ at 75 mg/kg and promotes bone neoformation of femoral bony deficits.