Fluorinated hydroxyapatite conditions a favorable osteo-immune microenvironment via triggering metabolic shift from glycolysis to oxidative phosphorylation.

BACKGROUND: Biological-derived hydroxyapatite is widely used as a bone substitute for addressing bone defects, but its limited osteoconductive properties necessitate further improvement. The osteo-immunomodulatory properties hold crucial promise in maintaining bone homeostasis, and precise modulation of macrophage polarization is essential in this process. Metabolism serves as a guiding force for immunity, and fluoride modification represents a promising strategy for modulating the osteoimmunological environment by regulating immunometabolism. In this context, we synthesized fluorinated porcine hydroxyapatite (FPHA), and has demonstrated its enhanced biological properties and osteogenic capacity. However, it remains unknown whether and how FPHA affects the immune microenvironment of the bone defects. METHODS: FPHA was synthesized and its composition and structural properties were confirmed. Macrophages were cultured with FPHA extract to investigate the effects of FPHA on their polarization and the related osteo-immune microenvironment. Furthermore, total RNA of these macrophages was extracted, and RNA-seq analysis was performed to explore the underlying mechanisms associated with the observed changes in macrophages. The metabolic states were evaluated with a Seahorse analyzer. Additionally, immunohistochemical staining was performed to evaluate the macrophages response after implantation of the novel bone substitutes in critical size calvarial defects in SD rats. RESULTS: The incorporation of fluoride ions in FPHA was validated. FPHA promoted macrophage proliferation and enhanced the expression of M2 markers while suppressing the expression of M1 markers. Additionally, FPHA inhibited the expression of inflammatory factors and upregulated the expression of osteogenic factors, thereby enhancing the osteogenic differentiation capacity of the rBMSCs. RNA-seq analysis suggested that the polarization-regulating function of FPHA may be related to changes in cellular metabolism. Further experiments confirmed that FPHA enhanced mitochondrial function and promoted the metabolic shift of macrophages from glycolysis to oxidative phosphorylation. Moreover, in vivo experiments validated the above results in the calvarial defect model in SD rats. CONCLUSION: In summary, our study reveals that FPHA induces a metabolic shift in macrophages from glycolysis to oxidative phosphorylation. This shift leads to an increased tendency toward M2 polarization in macrophages, consequently creating a favorable osteo-immune microenvironment. These findings provide valuable insights into the impact of incorporating an appropriate concentration of fluoride on immunometabolism and macrophage mitochondrial function, which have important implications for the development of fluoride-modified immunometabolism-based bone regenerative biomaterials and the clinical application of FPHA or other fluoride-containing materials.

Mechanically robust and personalized silk fibroin-magnesium composite scaffolds with water-responsive shape-memory for irregular bone regeneration.

The regeneration of critical-size bone defects, especially those with irregular shapes, remains a clinical challenge. Various biomaterials have been developed to enhance bone regeneration, but the limitations on the shape-adaptive capacity, the complexity of clinical operation, and the unsatisfied osteogenic bioactivity have greatly restricted their clinical application. In this work, we construct a mechanically robust, tailorable and water-responsive shape-memory silk fibroin/magnesium (SF/MgO) composite scaffold, which is able to quickly match irregular defects by simple trimming, thus leading to good interface integration. We demonstrate that the SF/MgO scaffold exhibits excellent mechanical stability and structure retention during the degradative process with the potential for supporting ability in defective areas. This scaffold further promotes the proliferation, adhesion and migration of osteoblasts and the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) in vitro. With suitable MgO content, the scaffold exhibits good histocompatibility, low foreign-body reactions (FBRs), significant ectopic mineralisation and angiogenesis. Skull defect experiments on male rats demonstrate that the cell-free SF/MgO scaffold markedly enhances bone regeneration of cranial defects. Taken together, the mechanically robust, personalised and bioactive scaffold with water-responsive shape-memory may be a promising biomaterial for clinical-size and irregular bone defect regeneration.

Enhanced osteogenic and ROS-scavenging MXene nanosheets incorporated gelatin-based nanocomposite hydrogels for critical-sized calvarial defect repair.

The healing of critical-sized bone defects is a major challenge in the field of bone tissue engineering. Gelatin-related hydrogels have emerged as a potential solution due to their desirable properties. However, their limited osteogenic, mechanical, and reactive oxygen species (ROS)-scavenging capabilities have hindered their clinical application. To overcome this issue, we developed a biofunctional gelatin-Mxene nanocomposite hydrogel. Firstly, we prepared two-dimensional (2D) Ti3C2 MXene nanosheets using a layer delamination method. Secondly, these nanosheets were incorporated into a transglutaminase (TG) enzyme-containing gallic acid-imbedded gelatin (GGA) pre-gel solution to create an injectable GGA-MXene (GM) nanocomposite hydrogel. The GM hydrogels exhibited superior compressive strength (44-75.6 kPa) and modulus (24-44.5 kPa) compared to the GGA hydrogels. Additionally, the GM hydrogel demonstrated the ability to scavenge reactive oxygen species (OH- and DPPH radicals), protecting MC3T3-E1 cells from oxidative stress. GM hydrogels were non-toxic to MC3T3-E1 cells, increased alkaline phosphatase secretion, calcium nodule formation, and upregulated osteogenic gene expressions (ALP, OCN, and RUNX2). The GM400 hydrogel was implanted in critical-sized calvarial defects in rats. Remarkably, it exhibited significant potential for promoting new bone formation. These findings indicated that GM hydrogel could be a viable candidate for future clinical applications in the treatment of critical-sized bone defects.

A Janus, robust, biodegradable bacterial cellulose/Ti3C2Tx MXene bilayer membranes for guided bone regeneration.

Guided bone regeneration (GBR) stands as an essential modality for craniomaxillofacial bone defect repair, yet challenges like mechanical weakness, inappropriate degradability, limited bioactivity, and intricate manufacturing of GBR membranes hindered the clinical efficacy. Herein, we developed a Janus bacterial cellulose(BC)/MXene membrane through a facile vacuum filtration and etching strategy. This Janus membrane displayed an asymmetric bilayer structure with interfacial compatibility, where the dense layer impeded cell invasion and the porous layer maintained stable space for osteogenesis. Incorporating BC with Ti3C2Tx MXene significantly enhanced the mechanical robustness and flexibility of the material, enabling clinical operability and lasting GBR membrane supports. It also contributed to a suitable biodegradation rate, which aligned with the long-term bone repair period. After demonstrating the desirable biocompatibility, barrier role, and osteogenic capability in vitro, the membrane's regenerative potential was also confirmed in a rat cranial defect model. The excellent bone repair performance could be attributed to the osteogenic capability of MXene nanosheets, the morphological cues of the porous layer, as well as the long-lasting, stable regeneration space provided by the GBR membrane. Thus, our work presented a facile, robust, long-lasting, and biodegradable BC/MXene GBR membrane, offering a practical solution to craniomaxillofacial bone defect repair.

Mussel-inspired antimicrobial hydrogel with cellulose nanocrystals/tannic acid modified silver nanoparticles for enhanced calvarial bone regeneration.

Bacterial infection is a serious challenge in the treatment of open bone defects, and reliance on antibiotic therapy may contribute to the emergence of drug-resistant bacteria. To solve this problem, this study developed a mineralized hydrogel (PVA-Ag-PHA) with excellent antibacterial properties and osteogenic capabilities. Silver nanoparticles (CNC/TA@AgNPs) were greenly synthesized using natural macromolecular cellulose nanocrystals (CNC) and plant polyphenolic tannins (TA) as stabilizers and reducing agents respectively, and then introduced into polyvinyl alcohol (PVA) and polydopamine-modified hydroxyapatite (PDA@HAP) hydrogel. The experimental results indicate that the PVA-Ag-PHA hydrogel, benefiting from the excellent antibacterial properties of CNC/TA@AgNPs, can not only eliminate Staphylococcus aureus and Escherichia coli, but also maintain a sustained sterile environment. At the same time, the HAP modified by PDA is uniformly dispersed within the hydrogel, thus releasing and maintaining stable concentrations of Ca2+ and PO43- ions in the local environment. The porous structure of the hydrogel with excellent biocompatibility creates a suitable bioactive environment that facilitates cell adhesion and bone regeneration. The experimental results in the rat critical-sized calvarial defect model indicate that the PVA-Ag-PHA hydrogel can effectively accelerate the bone healing process. Thus, this mussel-inspired hydrogel with antibacterial properties provides a feasible solution for the repair of open bone defects, demonstrating the considerable potential for diverse applications in bone repair.

Evaluation of new bone formation in critical-sized rat calvarial defect using 3D printed polycaprolactone/tragacanth gum-bioactive glass composite scaffolds.

Critical-sized bone defects are a major challenge in reconstructive bone surgery and usually fail to be treated due to limited remaining bone quality and extensive healing time. The combination of 3D-printed scaffolds and bioactive materials is a promising approach for bone tissue regeneration. In this study, 3D-printed alkaline-treated polycaprolactone scaffolds (M-PCL) were fabricated and integrated with tragacanth gum- 45S5 bioactive glass (TG-BG) to treat critical-sized calvarial bone defects in female adult Wistar rats. After a healing period of four and eight weeks, the new bone of blank, M-PCL, and M-PCL/TG-BG groups were harvested and assessed. Micro-computed tomography, histological, biochemical, and biomechanical analyses, gene expression, and bone matrix formation were used to assess bone regeneration. The micro-computed tomography results showed that the M-PCL/TG-BG scaffolds not only induced bone tissue formation within the bone defect but also increased BMD and BV/TV compared to blank and M-PCL groups. According to the histological analysis, there was no evidence of bony union in the calvarial defect regions of blank groups, while in M-PCL/TG-BG groups bony integration and repair were observed. The M-PCL/TG-BG scaffolds promoted the Runx2 and collagen type I expression as compared with blank and M-PCL groups. Besides, the bone regeneration in M-PCL/TG-BG groups correlated with TG-BG incorporation. Moreover, the use of M-PCL/TG-BG scaffolds promoted the biomechanical properties in the bone remodeling process. These data demonstrated that the M-PCL/TG-BG scaffolds serve as a highly promising platform for the development of bone grafts, supporting bone regeneration with bone matrix formation, and osteogenic features. Our results exhibited that the 3D-printed M-PCL/TG-BG scaffolds are a promising strategy for successful bone regeneration.

An injectable bone paste of poly (lactic acid)/zinc-doped nano hydroxyapatite composite microspheres for skull repair.

In this study, poly (lactic acid)/zinc-doped nano hydroxyapatite (PLA/nano-ZnHA) composite microspheres were prepared and formed into injectable bone paste with sodium alginate (SA) and polyvinyl alcohol (PVA) for bone defect repair. The effect of component of bone paste on injectability and zinc doping content related biological properties were mainly discussed. An injectable bone paste of PLA/nano-ZnHA composite microspheres (CM) was formed in mass ratio of (2.5-25):(0.25-4): (0-2.5):(20-65) of CM, SA, PVA and water with the favorable injectability (average force:4.46±1.72 N). In vitro 5%-10% zinc doping content displayed significantly higher promotion on cell proliferation and osteogenic differentiation than 15%-20% zinc doping content. Furthermore, in vivo the significant promoting effect of 0-5% zinc doping in ZnHA on bone repair was observed. Although 5% zinc doping content did not show a significant enhancement in bone volume/tissue volume (BV/TV), it has the ability to improve the bone mineral density (BMD) in early stage of bone repair compared with the 0% zinc doping content. The PLA/nano-ZnHA composite microsphere injectable paste with convenient surgical operation and well filling ability has the potential to become a competitive tissue repair material.

A Zn2+ cross-linked sodium alginate/epigallocatechin gallate hydrogel scaffold for promoting skull repair.

The optimal material for repairing skull defects should exhibit outstanding biocompatibility and mechanical properties. Specifically, hydrogel scaffolds that emulate the microenvironment of the native bone extracellular matrix play a vital role in promoting osteoblast adhesion, proliferation, and differentiation, thereby yielding superior outcomes in skull reconstruction. In this study, a composite network hydrogel comprising sodium alginate (SA), epigallocatechin gallate (EGCG), and zinc ions (Zn2+) was developed to establish an ideal osteogenic microenvironment for bone regeneration. Initially, physical entanglement and hydrogen bonding between SA and EGCG resulted in the formation of a primary network hydrogel known as SA-EGCG. Subsequently, the inclusion of Zn2+ facilitated the creation of a composite network hydrogels named SA-EGCG-Zn2+ via dynamic coordination bonds with SA and EGCG. The engineered SA-EGCG2 %-Zn2+ hydrogels offered an environment mimicking the native extracellular matrix (ECM). Moreover, the sustained release of Zn2+ from the hydrogel effectively enhanced cell adhesion, promoted proliferation, and stimulated osteoblast differentiation. In vitro experiments have shown that SA-EGCG2 %-Zn2+ hydrogels greatly enhance the attachment and growth of osteoblast precursor cells (MC3T3-E1), while also increasing the expression of genes related to osteogenesis in these cells. Additionally, in vivo studies have confirmed that SA-EGCG2 %-Zn2+ hydrogels promote new bone formation and accelerate the regeneration of bone in situ, indicating promising applications in the realm of bone tissue engineering.

Hydrogel loaded with thiolated chitosan modified taxifolin liposome promotes osteoblast proliferation and regulates Wnt signaling pathway to repair rat skull defects.

To alleviate skull defects and enhance the biological activity of taxifolin, this study utilized the thin-film dispersion method to prepare paclitaxel liposomes (TL). Thiolated chitosan (CSSH)-modified TL (CTL) was synthesized through charge interactions. Injectable hydrogels (BLG) were then prepared as hydrogel scaffolds loaded with TAX (TG), TL (TLG), and CTL (CTLG) using a Schiff base reaction involving oxidized dextran and carboxymethyl chitosan. The study investigated the bone reparative properties of CTLG through molecular docking, western blot techniques, and transcriptome analysis. The particle sizes of CTL were measured at 248.90 ± 14.03 nm, respectively, with zeta potentials of +36.68 ± 5.43 mV, respectively. CTLG showed excellent antioxidant capacity in vitro. It also has a good inhibitory effect on Escherichia coli and Staphylococcus aureus, with inhibition rates of 93.88 ± 1.59 % and 88.56 ± 2.83 % respectively. The results of 5-ethynyl-2 '-deoxyuridine staining, alkaline phosphatase staining and alizarin red staining showed that CTLG also had the potential to promote the proliferation and differentiation of mouse embryonic osteoblasts (MC3T3-E1). The study revealed that CTLG enhances the expression of osteogenic proteins by regulating the Wnt signaling pathway, shedding light on the potential application of TAX and bone regeneration mechanisms.

The effects of keratin-coated titanium on osteoblast function and bone regeneration.

Wool derived keratin, due to its demonstrated ability to promote bone formation, has been suggested as a potential bioactive material for implant surfaces. The aim of this study was to assess the effects of keratin-coated titanium on osteoblast functionin vitroand bone healingin vivo. Keratin-coated titanium surfaces were fabricated via solvent casting and molecular grafting. The effect of these surfaces on the attachment, osteogenic gene, and osteogenic protein expression of MG-63 osteoblast-like cells were quantifiedin vitro. The effect of these keratin-modified surfaces on bone healing over three weeks using an intraosseous calvaria defect was assessed in rodents. Keratin coating did not affect MG-63 proliferation or viability, but enhanced osteopontin, osteocalcin and bone morphogenetic expressionin vitro. Histological analysis of recovered calvaria specimens showed osseous defects covered with keratin-coated titanium had a higher percentage of new bone area two weeks after implantation compared to that in defects covered with titanium alone. The keratin-coated surfaces were biocompatible and stimulated osteogenic expression in adherent MG-63 osteoblasts. Furthermore, a pilot preclinical study in rodents suggested keratin may stimulate earlier intraosseous calvaria bone healing.

The potential bone regeneration effects of leptin- and osteolectin-coated 3D-printed PCL scaffolds: anin vivostudy.

This study investigated the effectiveness of bone regeneration upon the application of leptin and osteolectin to a three-dimensional (3D) printed poly(ϵ-caprolactone) (PCL) scaffold. A fused deposition modeling 3D bioprinter was used to fabricate scaffolds with a diameter of 4.5 mm, a height of 0.5 mm, and a pore size of 420-520 nm using PCL (molecular weight: 43 000). After amination of the scaffold surface for leptin and osteolectin adhesion, the experimental groups were divided into the PCL scaffold (control), the aminated PCL (PCL/Amine) scaffold, the leptin-coated PCL (PCL/Leptin) scaffold, and the osteolectin-coated PCL (PCL/Osteo) scaffold. Next, the water-soluble tetrazolium salt-1 (WST-1) assay was used to assess cell viability. All groups exhibited cell viability rates of >100%. Female 7-week-old Sprague-Dawley rats were used forin vivoexperiments. Calvarial defects were introduced on the rats' skulls using a 5.5 mm trephine bur. The rats were divided into the PCL (control), PCL/Leptin, and PCL/Osteo scaffold groups. The scaffolds were then inserted into the calvarial defect areas, and the rats were sacrificed after 8-weeks to analyze the defect area. Micro-CT analysis indicated that the leptin- and osteolectin-coated scaffolds exhibited significantly higher bone regeneration. Histological analysis revealed new bone and blood vessels in the calvarial defect area. These findings indicate that the 3D-printed PCL scaffold allows for patient-customized fabrication as well as the easy application of proteins like leptin and osteolectin. Moreover, leptin and osteolectin did not show cytotoxicity and exhibited higher bone regeneration potential than the existing scaffold.

Senolytics ameliorate the failure of bone regeneration through the cell senescence-related inflammatory signalling pathway.

Stress-induced premature senescent (SIPS) cells induced by various stresses deteriorate cell functions. Dasatinib and quercetin senolytics (DQ) can alleviate several diseases by eliminating senescent cells. α-tricalcium phosphate (α-TCP) is a widely used therapeutic approach for bone restoration but induces bone formation for a comparatively long time. Furthermore, bone infection exacerbates the detrimental prognosis of bone formation during material implant surgery due to oral cavity bacteria and unintentional contamination. It is essential to mitigate the inhibitory effects on bone formation during surgical procedures. Little is known that DQ improves bone formation in Lipopolysaccharide (LPS)-contaminated implants and its intrinsic mechanisms in the study of maxillofacial bone defects. This study aims to investigate whether the administration of DQ ameliorates the impairments on bone repair inflammation and contamination by eliminating SIPS cells. α-TCP and LPS-contaminated α-TCP were implanted into Sprague-Dawley rat calvaria bone defects. Simultaneously, bone formation in the bone defects was investigated with or without the oral administration of DQ. Micro-computed tomography and hematoxylin-eosin staining showed that senolytics significantly enhanced bone formation at the defect site. Histology and immunofluorescence staining revealed that the levels of p21- and p16-positive senescent cells, inflammation, macrophages, reactive oxygen species, and tartrate-resistant acid phosphatase-positive cells declined after administering DQ. DQ could partially alleviate the production of senescent markers and senescence-associated secretory phenotypes in vitro. This study indicates that LPS-contaminated α-TCP-based biomaterials can induce cellular senescence and hamper bone regeneration. Senolytics have significant therapeutic potential in reducing the adverse osteogenic effects of biomaterial-related infections and improving bone formation capacity.

A facile and smart strategy to enhance bone regeneration with efficient vitamin D3 delivery through sterosome technology.

The spontaneous healing of critical-sized bone defects is often limited, posing an increased risk of complications and suboptimal outcomes. Osteogenesis, a complex process central to bone formation, relies significantly on the pivotal role of osteoblasts. Despite the well-established osteogenic properties of vitamin D3 (VD3), its lipophilic nature confines administration to oral or muscle injection routes. Therefore, a strategic therapeutic approach involves designing a multifunctional carrier to enhance efficacy, potentially incorporating it into the delivery system. Here, we introduce an innovative sterosome-based delivery system, utilizing palmitic acid (PA) and VD3, aimed at promoting osteogenic differentiation and facilitating post-defect bone regeneration. The delivery system exhibited robust physical characteristics, including excellent stability, loading efficiency, sustained drug release and high cellular uptake efficiency. Furthermore, comprehensive investigations demonstrated outstanding biocompatibility and osteogenic potential in both 2D and 3D in vitro settings. A critical-sized calvarial defect model in mice recapitulated the notable osteogenic effects of the sterosomes in vivo. Collectively, our research proposes a clinically applicable strategy for bone healing, leveraging PA/VD3 sterosomes as an efficient carrier to deliver VD3 and enhance bone regenerative effects.

Enhancing calvarial defects repair with PDGF-BB mimetic peptide hydrogels.

Addressing bone defects represents a significant challenge to public health. Localized delivery of growth factor has emerged as promising approach for bone regeneration. However, the clinical application of Platelet-Derived Growth Factor (PDGF) is hindered by its high cost and short half-life. In this work, we introduce the application of PDGF-mimicking peptide (PMP1) hydrogels for calvarial defect restoration, showcasing their remarkable effectiveness. Through osteogenic differentiation assays and q-PCR analyses, we demonstrate PMP1's substantial capacity to enhance osteogenic differentiation of bone marrow mesenchymal stem cell (BMSC), leading to increased expression of crucial osteogenic genes. Further molecular mechanistic investigations reveal PMP1's activation of the PI3K-AKT-mTOR signaling pathway, a key element of its osteogenic effect. In vivo experiments utilizing a rat calvaria critical-sized defect model underscore the hydrogels' exceptional ability to accelerate new bone formation, thereby significantly advancing the restoration of calvaria defects. This research provides a promising bioactive material for bone tissue regeneration.

Magnesium-oxide-enhanced bone regeneration: 3D-printing of gelatin-coated composite scaffolds with sustained Rosuvastatin release.

Critical-size bone defects are one of the main challenges in bone tissue regeneration that determines the need to use angiogenic and osteogenic agents. Rosuvastatin (RSV) is a class of cholesterol-lowering drugs with osteogenic potential. Magnesium oxide (MgO) is an angiogenesis component affecting apatite formation. This study aims to evaluate 3D-printed Polycaprolactone/ß-tricalcium phosphate/nano-hydroxyapatite/ MgO (PCL/ß-TCP/nHA/MgO) scaffolds as a carrier for MgO and RSV in bone regeneration. For this purpose, PCL/ß-TCP/nHA/MgO scaffolds were fabricated with a 3D-printing method and coated with gelatin and RSV. The biocompatibility and osteogenicity of scaffolds were examined with MTT, ALP, and Alizarin red staining. Finally, the scaffolds were implanted in a bone defect of rat's calvaria, and tissue regeneration was investigated after 3 months. Our results showed that the simultaneous presence of RSV and MgO improved biocompatibility, wettability, degradation rate, and ALP activity but decreased mechanical strength. PCL/ß-TCP/nHA/MgO/gelatin-RSV scaffolds produced sustained release of MgO and RSV within 30 days. CT images showed that PCL/ß-TCP/nHA/MgO/gelatin-RSV scaffolds filled approximately 86.83 + 4.9 % of the defects within 3 months and improved angiogenesis, woven bone, and osteogenic genes expression. These results indicate the potential of PCL/ß-TCP/nHA/MgO/gelatin-RSV scaffolds as a promising tool for bone regeneration and clinical trials.

BMSCs-driven graphite oxide-grafted-carbon fibers reinforced polyetheretherketone composites as functional implants: in vivo biosafety and osteogenesis.

Mesenchymal stem cells (MSCs) are increasingly becoming a potential treatment approach for bone injuries due to the multi-lineage differentiation potential, ability to recognize damaged tissue sites and secrete bioactive factors that can enhance tissue repair. The aim of this work was to improve osteogenesis of carbon fibers reinforced polyetheretherketone (CF/PEEK) implants through bone marrow mesenchymal stem cells (BMSCs)-based therapy. Moreover, bioactive graphene oxide (GO) was introduced into CF/PEEK by grafting GO onto CF to boost the osteogenic efficiency of BMSCs. Subsequently, CF/PEEK was implanted into the symmetrical skull defect models of SD rats. Then in vivo biosafety and osteogenesis were evaluated. The results indicated that surface wettability of CF/PEEK was effectively improved by GO, which was beneficial for the adhesion of BMSCs. The pathological tissue sections stained with H&E showed no significant pathological change in the main organs including heart, liver, spleen, lung and kidney, which indicated no acute systemic toxicity. Furthermore, bone mineralization deposition rate of CF/PEEK containing GO was 2.2 times that of pure CF/PEEK. The X-ray test showed that the surface of CF/PEEK containing GO was obviously covered by more newly formed bone tissue than pure CF/PEEK after 8 weeks of implantation. This work demonstrated that GO effectively enhanced surface bioactivity of CF/PEEK and assisted BMSCs in accelerating differentiation into bone tissue, providing a feasible strategy for improving osteogenesis of PEEK and CF/PEEK.

Electrospun Biomimetic Periosteum Capable of Controlled Release of Multiple Agents for Programmed Promoting Bone Regeneration.

The effective repair of large bone defects remains a major challenge due to its limited self-healing capacity. Inspired by the structure and function of the natural periosteum, an electrospun biomimetic periosteum is constructed to programmatically promote bone regeneration using natural bone healing mechanisms. The biomimetic periosteum is composed of a bilayer with an asymmetric structure in which an aligned electrospun poly(ε-caprolactone)/gelatin/deferoxamine (PCL/GEL/DFO) layer mimics the outer fibrous layer of the periosteum, while a random coaxial electrospun PCL/GEL/aspirin (ASP) shell and PCL/silicon nanoparticles (SiNPs) core layer mimics the inner cambial layer. The bilayer controls the release of ASP, DFO, and SiNPs to precisely regulate the inflammatory, angiogenic, and osteogenic phases of bone repair. The random coaxial inner layer can effectively antioxidize, promoting cell recruitment, proliferation, differentiation, and mineralization, while the aligned outer layer can promote angiogenesis and prevent fibroblast infiltration. In particular, different stages of bone repair are modulated in a rat skull defect model to achieve faster and better bone regeneration. The proposed biomimetic periosteum is expected to be a promising candidate for bone defect healing.

Ligand-Selective Targeting of Macrophage Hydrogel Elicits Bone Immune-Stem Cell Endogenous Self-Healing Program to Promote Bone Regeneration.

Targeting macrophages can facilitate the site-specific repair of critical bone defects. Herein, a composite hydrogel, gelatin-Bletilla striata polysaccharide-mesoporous bioactive glass hydrogel (GBMgel), is constructed via the self-assembly of mesoporous bioactive glass on polysaccharide structures, through the Schiff base reaction. GBMgel can efficiently capture macrophages and drive the recruitment of seed stem cells and vascular budding required for regeneration in the early stages of bone injury, and the observed sustained release of inorganic silicon ions further enhances bone matrix deposition, mineralization, and vascular maturation. Moreover, the use of macrophage-depleted rat calvarial defect models further confirms that GBMgel, with ligand-selective macrophage targeting, increases the bone regeneration area and the proportion of mature bone. Mechanistic studies reveal that GBMgel upregulates the TLR4/NF-κB and MAPK macrophage pathways in the early stages and the JAK/STAT3 pathway in the later stages; thus initiating macrophage polarization at different time points. In conclusion, this study is based on the endogenous self-healing properties of bone macrophages, which enhances stem cell homing, and provides a research and theoretical basis upon which bone tissue can be reshaped and regenerated using the body's immune power, providing a new strategy for the treatment of critical bone defects.

Mechanical Properties of Human Concentrated Growth Factor (CGF) Membrane and the CGF Graft with Bone Morphogenetic Protein-2 (BMP-2) onto Periosteum of the Skull of Nude Mice.

Concentrated growth factor (CGF) is 100% blood-derived, cross-linked fibrin glue with platelets and growth factors. Human CGF clot is transformed into membrane by a compression device, which has been widely used clinically. However, the mechanical properties of the CGF membranes have not been well characterized. The aims of this study were to measure the tensile strength of human CGF membrane and observe its behavior as a scaffold of BMP-2 in ectopic site over the skull. The tensile test of the full length was performed at the speed of 2mm/min. The CGF membrane (5 × 5 × 2 mm3) or the CGF/BMP-2 (1.0 µg) membrane was grafted onto the skull periosteum of nude mice (5-week-old, male), and harvested at 14 days after the graft. The appearance and size of the CGF membranes were almost same for 7 days by soaking at 4 °C in saline. The average values of the tensile strength at 0 day and 7 days were 0.24 MPa and 0.26 MPa, respectively. No significant differences of both the tensile strength and the elastic modulus were found among 0, 1, 3, and 7 days. Supra-periosteal bone induction was found at 14 days in the CGF/BMP-2, while the CGF alone did not induce bone. These results demonstrated that human CGF membrane could become a short-term, sticky fibrin scaffold for BMP-2, and might be preserved as auto-membranes for wound protection after the surgery.

Craniofacial Bone Tissue Engineering: Current Approaches and Potential Therapy.

Craniofacial bone defects can result from various disorders, including congenital malformations, tumor resection, infection, severe trauma, and accidents. Successfully regenerating cranial defects is an integral step to restore craniofacial function. However, challenges managing and controlling new bone tissue formation remain. Current advances in tissue engineering and regenerative medicine use innovative techniques to address these challenges. The use of biomaterials, stromal cells, and growth factors have demonstrated promising outcomes in vitro and in vivo. Natural and synthetic bone grafts combined with Mesenchymal Stromal Cells (MSCs) and growth factors have shown encouraging results in regenerating critical-size cranial defects. One of prevalent growth factors is Bone Morphogenetic Protein-2 (BMP-2). BMP-2 is defined as a gold standard growth factor that enhances new bone formation in vitro and in vivo. Recently, emerging evidence suggested that Megakaryocytes (MKs), induced by Thrombopoietin (TPO), show an increase in osteoblast proliferation in vitro and bone mass in vivo. Furthermore, a co-culture study shows mature MKs enhance MSC survival rate while maintaining their phenotype. Therefore, MKs can provide an insight as a potential therapy offering a safe and effective approach to regenerating critical-size cranial defects.