Injectable nanofiber-reinforced bone cement with controlled biodegradability for minimally-invasive bone regeneration

3D Printed Multifunctional Biomimetic Bone Scaffold Combined with TP-Mg Nanoparticles for the Infectious Bone Defects Repair

Infected bone defects are one of the most challenging problems in the treatment of bone defects due to the high antibiotic failure rate and the lack of ideal bone grafts. In this paper, inspired by clinical bone cement filling treatment, α-c phosphate (α-TCP) with self-curing properties is composited with β-tricalcium phosphate (β-TCP) and constructed a bionic cancellous bone scaffolding system α/β-tricalcium phosphate (α/β-TCP) by low-temperature 3D printing, and gelatin is preserved inside the scaffolds as an organic phase, and later loaded with a metal-polyphenol network structure of tea polyphenol-magnesium (TP-Mg) nanoparticles. The scaffolds mimic the structure and components of cancellous bone with high mechanical strength (>100 MPa) based on α-TCP self-curing properties through low-temperature 3D printing. Meanwhile, the scaffolds loaded with TP-Mg exhibit significant inhibition of Staphylococcus aureus (S.aureus) and promote the transition of macrophages from M1 pro-inflammatory to M2 anti-inflammatory phenotype. In addition, the composite scaffold also exhibits excellent bone-enhancing effects based on the synergistic effect of Mg2+ and Ca2+. In this study, a multifunctional ceramic scaffold (α/β-TCP@TP-Mg) that integrates anti-inflammatory, antibacterial, and osteoinduction is constructed, which promotes late bone regenerative healing while modulating the early microenvironment of infected bone defects, has a promising application in the treatment of infected bone defects.

Multifunctional Bone Regeneration Membrane with Flexibility, Electrical Stimulation Activity and Osteoinductive Activity

The use of membrane-based guided bone regeneration techniques has great potential for single-stage reconstruction of critical-sized bone defects. Here, a multifunctional bone regeneration membrane combining flexible elasticity, electrical stimulation (ES) and osteoinductive activity is developed by in situ doping of MXene 2D nanomaterials with conductive functionality and β-TCP particles into a Poly(lactic acid-carbonate (PDT) composite nano-absorbable membrane (P/T/MXene) via electrostatic spinning technique. The composite membrane has good feasibility due to its temperature sensitivity, elastic memory capacity, coordinated degradation profile and easy preparation process. In vitro experiments showed the P/T/MXene membrane effectively promoted the recruitment and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) under ES and enhanced the angiogenic capacity of endothelial cells, which synergistically promoted bone regeneration through neovascularization. In addition, an in vivo rat model of cranial bone defects further confirmed the bone regeneration efficacy of the P/T/MXene membrane. In conclusion, the developed P/T/MXene membrane can effectively promote bone regeneration through their synergistic multifunctional effects, suggesting the membranes have great potential for guiding tissue regeneration and providing guidance for the biomaterials design.

Picein alleviates oxidative stress and promotes bone regeneration in osteoporotic bone defect by inhibiting ferroptosis via Nrf2/HO-1/GPX4 pathway

Osteoporosis (OP) can result in slower bone regeneration than the normal condition due to abnormal oxidative stress and high levels of reactive oxygen species (ROS), a condition detrimental for bone formation, making the OP-related bone healing a significant clinical challenge. As the osteogenic differentiation ability of bone marrow mesenchymal stem cells (BMSCs) is closely related to bone regeneration; currently, this study assessed the effects of Picein on BMSCs in vitro and bone regeneration in osteoporotic bone defect in vivo. Cell viability was determined by CCK-8 assay. The production of (ROS), malonaldehyde, superoxide dismutase activities, and glutathione was evaluated by using commercially available kits, and a flow cytometry analysis was adopted to detect macrophage polarization. Osteogenic capacity of BMSCs was evaluated by alkaline phosphatase (ALP) activity, ALP staining, and Alizarin red S staining. The expression of osteogenic-related proteins (OPN, Runx-2, OCN) and osteogenic-related genes (ALP, BMP-4, COL-1, and Osterix) were evaluated by Western blotting and real-time PCR (RT-PCR). In addition, proliferation, migration ability, and angiogenic capacity of human umbilical vein endothelial cells (HUVECs) were evaluated by EdU staining, scratch test, transwell assay, and tube formation assay, respectively. Angiogenic-related genes (VEGF, vWF, CD31) were also evaluated by RT-PCR. Results showed that Picein alleviated erastin-induced oxidative stress, enhanced osteogenic differentiation capacity of BMSCs, angiogenesis of HUVECs, and protects cells against ferroptosis through Nrf2/HO-1/GPX4 axis. Moreover, Picein regulate immune microenvironment by promoting the polarization of M2 macrophages in vitro. In addition, Picein also reduce the inflammation levels and promotes bone regeneration in osteoporotic bone defect in OP rat models in vivo. Altogether, these results suggested that Picein can promote bone regeneration and alleviate oxidative stress via Nrf2/HO-1/GPX4 pathway, offering Picein as a novel antioxidant agent for treating osteoporotic bone defect.

Nanofiber-induced hierarchically-porous magnesium phosphate bone cements accelerate bone regeneration by inhibiting Notch signaling

Magnesium phosphate bone cements (MPC) have been recognized as a viable alternative for bone defect repair due to their high mechanical strength and biodegradability. However, their poor porosity and permeability limit osteogenic cell ingrowth and vascularization, which is critical for bone regeneration. In the current study, we constructed a novel hierarchically-porous magnesium phosphate bone cement by incorporating extracellular matrix (ECM)-mimicking electrospun silk fibroin (SF) nanofibers. The SF-embedded MPC (SM) exhibited a heterogeneous and hierarchical structure, which effectively facilitated the rapid infiltration of oxygen and nutrients as well as cell ingrowth. Besides, the SF fibers improved the mechanical properties of MPC and neutralized the highly alkaline environment caused by excess magnesium oxide. Bone marrow stem cells (BMSCs) adhered excellently on SM, as illustrated by formation of more pseudopodia. CCK8 assay showed that SM promoted early proliferation of BMSCs. Our study also verified that SM increased the expression of OPN, RUNX2 and BMP2, suggesting enhanced osteogenic differentiation of BMSCs. We screened for osteogenesis-related pathways, including FAK signaing, Wnt signaling and Notch signaling, and found that SM aided in the process of bone regeneration by suppressing the Notch signaling pathway, proved by the downregulation of NICD1, Hes1 and Hey2. In addition, using a bone defect model of rat calvaria, the study revealed that SM exhibited enhanced osteogenesis, bone ingrowth and vascularization compared with MPC alone. No adverse effect was found after implantation of SM in vivo. Overall, our novel SM exhibited promising prospects for the treatment of critical-sized bone defects.

Magnesium malate-modified calcium phosphate bone cement promotes the repair of vertebral bone defects in minipigs via regulating CGRP

Active artificial bone substitutes are crucial in bone repair and reconstruction. Calcium phosphate bone cement (CPC) is known for its biocompatibility, degradability, and ability to fill various shaped bone defects. However, its low osteoinductive capacity limits bone regeneration applications. Effectively integrating osteoinductive magnesium ions with CPC remains a challenge. Herein, we developed magnesium malate-modified CPC (MCPC). Incorporating 5% magnesium malate significantly enhances the compressive strength of CPC to (6.18 ± 0.49) MPa, reduces setting time and improves disintegration resistance. In vitro, MCPC steadily releases magnesium ions, promoting the proliferation of MC3T3-E1 cells without causing significant apoptosis, proving its biocompatibility. Molecularly, magnesium malate prompts macrophages to release prostaglandin E2 (PGE2) and synergistically stimulates dorsal root ganglion (DRG) neurons to synthesize and release calcitonin gene-related peptide (CGRP). The CGRP released by DRG neurons enhances the expression of the key osteogenic transcription factor Runt-related transcription factor-2 (RUNX2) in MC3T3-E1 cells, promoting osteogenesis. In vivo experiments using minipig vertebral bone defect model showed MCPC significantly increases the bone volume fraction, bone density, new bone formation, and proportion of mature bone in the defect area compared to CPC. Additionally, MCPC group exhibited significantly higher levels of osteogenesis and angiogenesis markers compared to CPC group, with no inflammation or necrosis observed in the hearts, livers, or kidneys, indicating its good biocompatibility. In conclusion, MCPC participates in the repair of bone defects in the complex post-fracture microenvironment through interactions among macrophages, DRG neurons, and osteoblasts. This demonstrates its significant potential for clinical application in bone defect repair.

Injectable and high-strength PLGA/CPC loaded ALN/MgO bone cement for bone regeneration by facilitating osteogenesis and inhibiting osteoclastogenesis in osteoporotic bone defects

Osteoporosis (OP) can result in slower bone regeneration than the normal condition due to the imbalance between osteogenesis and osteoclastogenesis, making osteoporotic bone defects healing a significant clinical challenge. Calcium phosphate cement (CPC) is a promising bone substitute material due to its good osteoinductive activity, however, the drawbacks such as fragility, slow degradation rate and incapability to control bone loss restrict its application in osteoporotic bone defects treatment. Currently, we developed the PLGA electrospun nanofiber sheets to carry alendronate (ALN) and magnesium oxide nanoparticle (nMgO) into CPC, therefore, to obtain a high-strength bone cement (C/AM-PL/C). The C/AM-PL/C bone cement had high mechanical strength, anti-washout ability, good injection performance and drug sustained release capacity. More importantly, the C/AM-PL/C cement promoted the osteogenic differentiation of bone marrow mesenchymal stem cells and neovascularization via the release of Mg2+ (from nMgO) and Ca2+ (during the degradation of CPC), and inhibited osteoclastogenesis via the release of ALN in vitro. Moreover, the injection of C/AM-PL/C cement significantly improved bone healing in an OP model with femur condyle defects in vivo. Altogether, the injectable C/AM-PL/C cement could facilitate osteoporotic bone regeneration, demonstrating its capacity as a promising candidate for treatment of osteoporotic bone defects.

Injectable, anti-collapse, adhesive, plastic and bioactive bone graft substitute promotes bone regeneration by moderating oxidative stress in osteoporotic bone defect

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.

Absorbable calcium and phosphorus bioactive membranes promote bone marrow mesenchymal stem cells osteogenic differentiation for bone regeneration

Large segmental bone defects are commonly operated with autologous bone grafting, which has limited bone sources and poses additional surgical risks. In this study, we fabricated poly(lactide-co-glycolic acid) (PLGA)/β-tricalcium phosphate (β-TCP) composite membranes by electrostatic spinning and further promoted osteogenesis by regulating the release of β-TCP in the hope of replacing autologous bone grafts in the clinical practice. The addition of β-TCP improved the mechanical strength of PLGA by 2.55 times. Moreover, β-TCP could accelerate the degradation of PLGA and neutralize the negative effects of acidification of the microenvironment caused by PLGA degradation. In vitro experiments revealed that PLGA/TCP10 membranes are biocompatible and the released β-TCP can modulate the activity of osteoblasts by enhancing the calcium ions concentration in the damaged area and regulating the pH of the local microenvironment. Simultaneously, an increase in β-TCP can moderate the lactate content of the local microenvironment, synergistically enhancing osteogenesis by promoting the tube-forming effect of human umbilical vein endothelial cells. Therefore, it is potential to utilize PLGA/TCP bioactive membranes to modulate the microenvironment at the site of bone defects to promote bone regeneration.

Tolerant and Rapid Endochondral Bone Regeneration Using Framework-Enhanced 3D Biomineralized Matrix Hydrogels

Tissue-engineered bone has emerged as a promising alternative for bone defect repair due to the advantages of regenerative bone healing and physiological functional reconstruction. However, there is very limited breakthrough in achieving favorable bone regeneration due to the harsh osteogenic microenvironment after bone injury, especially the avascular and hypoxic conditions. Inspired by the bone developmental mode of endochondral ossification, a novel strategy is proposed for tolerant and rapid endochondral bone regeneration using framework-enhanced 3D biomineralized matrix hydrogels. First, it is meticulously designed 3D biomimetic hydrogels with both hypoxic and osteoinductive microenvironment, and then integrated 3D-printed polycaprolactone framework to improve their mechanical strength and structural fidelity. The inherent hypoxic 3D matrix microenvironment effectively activates bone marrow mesenchymal stem cells self-regulation for early-stage chondrogenesis via TGFβ/Smad signaling pathway due to the obstacle of aerobic respiration. Meanwhile, the strong biomineralized microenvironment, created by a hybrid formulation of native-constitute osteogenic inorganic salts, can synergistically regulate both bone mineralization and osteoclastic differentiation, and thus accelerate the late-stage bone maturation. Furthermore, both in vivo ectopic osteogenesis and in situ skull defect repair successfully verified the high efficiency and mechanical maintenance of endochondral bone regeneration mode, which offers a promising treatment for craniofacial bone defect repair.

Biodegradable Nanoflowers with Abaloparatide Spatiotemporal Management of Functional Alveolar Bone Regeneration

Post-extraction alveolar bone atrophy greatly hinders the subsequent orthodontic tooth movement (OTM) or implant placement. In this study, we synthesized biodegradable bifunctional bioactive calcium phosphorus nanoflowers (NFs) loaded with abaloparatide (ABL), namely ABL@NFs, to achieve spatiotemporal management for alveolar bone regeneration. The NFs exhibited a porous hierarchical structure, high drug encapsulation efficacy, and desirable biocompatibility. ABL was initially released to recruit stem cells, followed by sustained release of Ca2+ and PO43- for in situ interface mineralization, establishing an osteogenic "biomineralized environment". ABL@NFs successfully restored morphologically and functionally active alveolar bone without affecting OTM. In conclusion, the ABL@NFs demonstrated promising outcomes for bone regeneration under orthodontic condition, which might provide a desirable reference of man-made "bone powder" in the hard tissue regeneration field.

Preferentially Biodegradable Gypsum Fibers Endowing Invisible Microporous Structures and Enhancing Osteogenic Capability of Calcium Phosphate Cements

It is known that hydroxyapatite-type calcium phosphate cement (CPC) shows appreciable self-curing properties, but the phase transformation products often lead to slow biodegradation and disappointing osteogenic responses. Herein, we developed an innovative strategy to endow invisible micropore networks, which could tune the microstructures and biodegradation of α-tricalcium phosphate (α-TCP)-based CPC by gypsum fibers, and the osteogenic capability of the composite cements could be enhanced in vivo. The gypsum fibers were prepared via extruding the gypsum powder/carboxylated chitosan (CC) slurry through a 22G nozzle (410 μm in diameter) and collecting with a calcium salt solution. Then, the CPCs were prepared by mixing the α-TCP powder with gypsum fibers (0-24 wt %) and an aqueous solution to form self-curing cements. The physicochemical characterizations showed that injectability was decreased with an increase in the fiber contents. The μCT reconstruction demonstrated that the gypsum fiber could be distributed in the CPC substrate and produce long-range micropore architectures. In particular, incorporation of gypsum fibers would tune the ion release, produce tunnel-like pore networks in vitro, and promote new bone tissue regeneration in rabbit femoral bone defects in vivo. Appropriate gypsum fibers (16 and 24 wt %) could enhance bone defect repair and cement biodegradation. These results demonstrate that the highly biodegradable cement fibers could mediate the microstructures of conventional CPC biomaterials, and such a bicomponent composite strategy may be beneficial for expanding clinical CPC-based applications.

Tunicate cellulose nanocrystals reinforced modified calcium sulfate bone cement with enhanced mechanical properties for bone repair

Considering the poor mechanical properties of bone cement, its practical application has always been limited. In this study, we introduced tunicate cellulose nanocrystals (TCNCs) into calcium sulfate bone cement for the first time, and multiple enhanced composite bone cement was prepared by the condensation reflux method. Firstly, high-strength modified calcium sulfate hemihydrate (CSH) bone cement was successfully prepared by using tartaric acid, a crystal modifier with a chiral structure. Secondly, the inclusion of TCNCs not only exhibited significant reinforcement and toughening effects but also stimulated the adhesion, proliferation, and differentiation of related osteoblasts. Furthermore, TCNCs encapsulated the CSH particles, overcoming the limitations of excessive degradation rates in bone cement and enabling sustained release of Ca2+, promoting the healing of bone defects. Overall, this study presents novel ideas and methodologies for designing bone cement with exceptional performance. It also provides a new platform for the development of bone tissue engineering and is expected to become a new type of bone regeneration material. The utilization of oceanic resources in this context holds high-value potential, alleviating environmental burdens and providing clinically applicable bone tissue repair materials with broad application prospects.

Study on the poly(methyl methacrylate-acrylic acid)/calcium phosphate cement composite bound by chelation with enhanced water absorption and biomechanical properties

Polymethylmethacrylate (PMMA) bone cement has been widely used as a critical material for fixing prostheses and filling bone defects. The shrinkage of PMMA bone cement was addressed by the additives, however, the uneven integral water absorption and expansion performance as well as the deteriorated mechanical properties of the modified bone cement after immersion in phosphate buffered saline (PBS) and simulation body fluid (SBF) affected the long-term stability after implantation. Calcium phosphate cement (CPC) is a biomaterial with promising applications in orthopedics, whose hydration reaction provides an important driving force for the transfer of water. Besides, the mechanical properties of CPC can be enhanced with the curing process. In this study, CPC was utilized to modify the poly(methyl methacrylate-acrylic acid) [P(MMA-AA)] bone cement. The results demonstrated the successful construction of interconnected CPC water delivery networks in the P(MMA-AA)/CPC composite, the water absorption ratio and expansion ratio of the composite were up to 131.18 ± 9.14% and 168.19 ± 5.44%, respectively. Meanwhile, the transformation of CPC water delivery networks into rigid mechanical support networks as well as the chelation interaction between organic-inorganic enhanced the mechanical properties of the composite after immersion, the compressive strength after immersion reached 62.97 ± 0.97 MPa, which was 27.65% higher than that before immersion. The degradation ratio of the composite was up to 13.76 ± 0.23% after 9 days of immersion, which was 16.4% higher than that of CPC. Furthermore, composites exhibited superior biocompatibility as the release of Ca2+. Therefore, P(MMA-AA)/CPC composite serves as a promising medical filling material for clinical use.

Biomechanical evaluation of different posterior fixation techniques for treating thoracolumbar burst fractures of osteoporosis old patients: a finite element analysis

Objective: To investigate the biomechanical characteristics of different posterior fixation techniques in treatment of osteoporotic thoracolumbar burst fractures by finite element analysis. Methods: The Dicom format images of T10-L5 segments were obtained from CT scanning of a volunteer, and transferred to the Geomagic Studio software, which was used to build digital models. L1 osteoporotic burst fracture and different posterior fixation techniques were simulated by SolidWorks software. The data of ROM, the maximum displacement of fixed segment, ROM of fractured L1 vertebrae, the stress on the screws and rods as well as on fractured L1 vertebrae under different movement conditions were collected and analysed by finite element analysis. Results: Among the four groups, the largest ROM of fixed segment, the maximum displacement of fixed segment and ROM of fractured vertebrae occurred in CBT, and the corresponding data was 1.3°, 2.57 mm and 1.37°, respectively. While the smallest ROM of fixed segment, the maximum displacement of fixed segment and ROM of fractured vertebrae was found in LSPS, and the corresponding data was 0.92°, 2.46 mm and 0.89°, respectively. The largest stress of screws was 390.97 Mpa, appeared in CBT, and the largest stress of rods was 84.68 MPa, appeared in LSPS. The stress concentrated at the junction area between the root screws and rods. The maximum stress on fractured vertebrae was 93.25 MPa, appeared in CBT and the minimum stress was 56.68 MPa, appeared in CAPS. And the stress of fractured vertebrae concentrated in the middle and posterior column of the fixed segment, especially in the posterior edge of the superior endplate. Conclusion: In this study, long-segment posterior fixation (LSPF) provided with the greatest stability of fixed segment after fixation, while cortical bone screw fixation (CBT) provided with the smallest stability. Cement-augmented pedicle screw-rod fixation (CAPS) and combined using cortical bone screw and pedicle screw fixation (CBT-PS) provided with the moderate stability. CBT-PS exhibited superiority in resistance of rotational torsion for using multiple connecting rods. CAPS and CBT-PS maybe biomechanically superior options for the surgical treatment of burst TL fractures in osteoporotic patients.

Advances in materials used for minimally invasive treatment of vertebral compression fractures

Vertebral compression fractures are becoming increasingly common with aging of the population; minimally invasive materials play an essential role in treating these fractures. However, the unacceptable processing-performance relationships of materials and their poor osteoinductive performance have limited their clinical application. In this review, we describe the advances in materials used for minimally invasive treatment of vertebral compression fractures and enumerate the types of bone cement commonly used in current practice. We also discuss the limitations of the materials themselves, and summarize the approaches for improving the characteristics of bone cement. Finally, we review the types and clinical efficacy of new vertebral implants. This review may provide valuable insights into newer strategies and methods for future research; it may also improve understanding on the application of minimally invasive materials for the treatment of vertebral compression fractures.

Punicalagin attenuates TNF-α-induced oxidative damage and promotes osteogenic differentiation of bone mesenchymal stem cells by activating the Nrf2/HO-1 pathway

Oxidative stress is one of the most important factors in changing bone homeostasis. Redox homeostasis plays a key role in the osteogenic differentiation of bone mesenchymal stem cells (BMSCs) and the angiogenesis ability of human umbilical vein endothelial cells (HUVECs) for bone regeneration. Currently, this study assessed the effects of punicalagin (PUN) on BMSCs and HUVECs. Cell viability was determined by CCK-8 assay. A flow cytometry analysis was adopted to detect macrophage polarization. The production of reactive oxygen stress (ROS), glutathione (GSH), malonaldehyde (MDA) and superoxide dismutase (SOD) activities were evaluated by using commercially-available kits. Osteogenic capacity of BMSCs was evaluated by ALP activity, ALP staining and ARS staining. The expression of osteogenic-related proteins (OCN, Runx-2, OPN) and Nrf/HO-1 levles were evaluated by Western blotting. Osteogenic-related genes (Osterix, COL-1, BMP-4, ALP) were evaluated by RT-PCR. Migration ability and invasion ability of HUVECs were evaluated by wound healing assay and Transwell assay. Angiogenic ability was detected by tube formation assay and the expression of angiogenic-related genes (VEGF, vWF, CD31) were evaluated by RT-PCR. Results showed that PUN alleviated oxidative stress by TNF-α, enhanced osteogenic differentiation in BMSCs and angiogenesis in HUVECs. Moreover, PUN regulate immune microenvironment by promoting the polarization of M2 macrophages and reduce the oxidative stress related products by activating Nrf2/HO-1 pathway. Altogether, these results suggested that PUN can promote osteogenic capacity of BMSCs, angiogenesis of HUVECs, alleviate oxidative stress via Nrf2/HO-1 pathway, offering PUN as a novel antioxidant agent for treating bone loss diseases.

Tough, Injectable Calcium Phosphate Cement Based Composite Hydrogels to Promote Osteogenesis

Osteoporosis is one of the most disabling consequences of aging, and osteoporotic fractures and a higher risk of subsequent fractures lead to substantial disability and deaths, indicating that both local fracture healing and early anti-osteoporosis therapy are of great significance. However, combining simple clinically approved materials to achieve good injection and subsequent molding and provide good mechanical support remains a challenge. To meet this challenge, bioinspired by natural bone components, we develop appropriate interactions between inorganic biological scaffolds and organic osteogenic molecules, achieving a tough hydrogel that is both firmly loaded with calcium phosphate cement (CPC) and injectable. Here, the inorganic component CPC composed of biomimetic bone composition and the organic precursor, incorporating gelatin methacryloyl (GelMA) and N-Hydroxyethyl acrylamide (HEAA), endow the system with fast polymerization and crosslinking through ultraviolet (UV) photo-initiation. The GelMA-poly (N-Hydroxyethyl acrylamide) (GelMA-PHEAA) chemical and physical network formed in situ enhances the mechanical performances and maintains the bioactive characteristics of CPC. This tough biomimetic hydrogel combined with bioactive CPC is a new promising candidate for a commercial clinical material to help patients to survive osteoporotic fracture.

Reinforcement of Calcium Phosphate Cement with Hybrid Silk Fibroin/Kappa-Carrageenan Nanofibers

Calcium phosphate cements (CPCs) offer a promising solution for treating bone defects due to their osteoconductive, injectable, biocompatible, and bone replacement properties. However, their brittle nature restricts their utilization to non-load-bearing applications. In this study, the impact of hybrid silk fibroin (SF) and kappa-carrageenan (k-CG) nanofibers as reinforcements in CPC was investigated. The CPC composite was fabricated by incorporating electrospun nanofibers in 1, 3, and 5% volume fractions. The morphology, mineralization, mechanical properties, setting time, injectability, cell adhesion, and mineralization of the CPC composites were analyzed. The results demonstrated that the addition of the nanofibers improved the CPC mixture, leading to an increase in compressive strength (14.8 ± 0.3 MPa compared to 8.1 ± 0.4 MPa of the unreinforced CPC). Similar improvements were seen in the bending strength and work fracture (WOF). The MC3T3-E1 cell culture experiments indicated that cells attached well to the surfaces of all cement samples and tended to join their adjacent cells. Additionally, the CPC composites showed higher cell mineralization after a culture period of 14 days, indicating that the SF/k-CG combination has potential for applications as a CPC reinforcement and bone cell regeneration promoter.

Engeletin alleviates erastin-induced oxidative stress and protects against ferroptosis via Nrf2/Keap1 pathway in bone marrow mesenchymal stem cells

Ferroptosis is a novel form of cell death, which is a unique modality of cell death and closely associated with iron concentrations, generation of reactive oxygen species (ROS), and accumulation of the lipid reactive oxygen species. In the present study, the anti-ferroptosis effects of Engeletin was studied in erastin-induced bone marrow mesenchymal stem cells (BMSCs). After treatment with Engeletin, cell viability was determined by CCK-8 assay. The production of ROS, malonaldehyde (MDA), Superoxide dismutase (SOD) activities and glutathione peroxidase (GSH) were detected by using commercially-available kits. Ferroptosis-related proteins (GPX4, SLC7A11, TFR1, FPN1, Nrf2, Keap1) were evaluated by Western blotting. Osteogenic capacity was evaluated by ALP staining and ARS staining. The expression of osteogenic-related proteins (OPN, Runx2, OCN) were evaluated by Western blotting and changes in mRNA (ALP, BMP-2, COL-1, Osterix) were evaluated by RT-PCR. Consistent improvements in angiogenesis are observed with Engeletin in the presence of erastin. Engeletin significantly alleviated erastin-induced oxidative damage and protected against ferroptosis in BMSCs. Ferroptosis was inhibited by Engeletin, leading to decreasing reducing accumulation of ROS and lipid peroxidation products. Moreover, Engeletin promoted osteogenic differentiation in BMSCs and angiogenesis in human umbilical vein endothelial cells (HUVECs). Taken together, these findings indicate that Engeletin can protect BMSCs from erastin-induced ferroptosis through the Nrf2/Keap1 antioxidant pathway and identify Engeletin as a novel ferroptosis inhibitor, suggesting that Engeletin may promote resistance to ferroptosis and enable osteogenic function of BMSCs.