Scaffold-Free Spheroids with Two-Dimensional Heteronano-Layers (2DHNL) Enabling Stem Cell and Osteogenic Factor Codelivery for Bone Repair

Enhancing Bone Regeneration and Osteogenic Quality by n-HA Internalized Osteoblasts Synergized with ON Protein: Mechanistic Insights

Bone scaffolds offer hope for oral jawbone repair, yet improving their osteogenic performance remains a clinical challenge. This study investigates a novel approach to enhance early bone formation and osteogenic quality by coloading hydroxyapatite (HA)─internalized osteoblasts (OHA) and osteonectin (ON) onto various scaffolds. Our findings demonstrated that the OHA could effectively facilitate the early bone regeneration by providing rapid calcium and phosphorus ion release via lysosome-mediated HA degradation, while the ON protein helps in ion deposition, cell proliferation, and matrix mineralization. When the PHA (PCL+HA) scaffold was incorporated with both the OHA and ON, the scaffold exhibited superior pro-osteogenic performance, driven by synergistic effects of rapid ion release from the OHA, slow ion release from the PHA, and upregulation of osteogenesis-related genes. The analyses of mechanisms revealed that the OHA activated MAPK and PI3K-Akt pathways, while ON stimulated calcium and Wnt signaling, collectively promoting the osteogenic potential. The strategy presented in this study paves a promising way for the development of advanced bone scaffolds to improve the bone regeneration quality.

Bioactive peptides and proteins for tissue repair: microenvironment modulation, rational delivery, and clinical potential

Bioactive peptides and proteins (BAPPs) are promising therapeutic agents for tissue repair with considerable advantages, including multifunctionality, specificity, biocompatibility, and biodegradability. However, the high complexity of tissue microenvironments and their inherent deficiencies such as short half-live and susceptibility to enzymatic degradation, adversely affect their therapeutic efficacy and clinical applications. Investigating the fundamental mechanisms by which BAPPs modulate the microenvironment and developing rational delivery strategies are essential for optimizing their administration in distinct tissue repairs and facilitating clinical translation. This review initially focuses on the mechanisms through which BAPPs influence the microenvironment for tissue repair via reactive oxygen species, blood and lymphatic vessels, immune cells, and repair cells. Then, a variety of delivery platforms, including scaffolds and hydrogels, electrospun fibers, surface coatings, assisted particles, nanotubes, two-dimensional nanomaterials, and nanoparticles engineered cells, are summarized to incorporate BAPPs for effective tissue repair, modification strategies aimed at enhancing loading efficiencies and release kinetics are also reviewed. Additionally, the delivery of BAPPs can be precisely regulated by endogenous stimuli (glucose, reactive oxygen species, enzymes, pH) or exogenous stimuli (ultrasound, heat, light, magnetic field, and electric field) to achieve on-demand release tailored for specific tissue repair needs. Furthermore, this review focuses on the clinical potential of BAPPs in facilitating tissue repair across various types, including bone, cartilage, intervertebral discs, muscle, tendons, periodontal tissues, skin, myocardium, nervous system (encompassing brain, spinal cord, and peripheral nerve), endometrium, as well as ear and ocular tissue. Finally, current challenges and prospects are discussed.

Application of loaded graphene oxide biomaterials in the repair and treatment of bone defects

Addressing bone defects is a complex medical challenge that involves dealing with various skeletal conditions, including fractures, osteoporosis (OP), bone tumours, and bone infection defects. Despite the availability of multiple conventional treatments for these skeletal conditions, numerous limitations and unresolved issues persist. As a solution, advancements in biomedical materials have recently resulted in novel therapeutic concepts. As an emerging biomaterial for bone defect treatment, graphene oxide (GO) in particular has gained substantial attention from researchers due to its potential applications and prospects. In other words, GO scaffolds have demonstrated remarkable potential for bone defect treatment. Furthermore, GO-loaded biomaterials can promote osteoblast adhesion, proliferation, and differentiation while stimulating bone matrix deposition and formation. Given their favourable biocompatibility and osteoinductive capabilities, these materials offer a novel therapeutic avenue for bone tissue regeneration and repair. This comprehensive review systematically outlines GO scaffolds' diverse roles and potential applications in bone defect treatment.

Hierarchical Integration of Curcumin-Loaded CaCO3 Nanoparticles and Black Phosphorus Nanosheets in Core/Shell Nanofiber for Cranial Defect Repair

Reconstruction and healing of large craniofacial bone defects are major clinical challenges due to high risk of chronic inflammation and reduced cell mineralization levels. Herein, a core-shell nanofiber-based implant with significant pro-osteogenesis capability for treating skull defects is reported, which is hierarchically integrated with curcumin-loaded calcium carbonate nanoparticles (CaCO3@Cur NPs) in the outer layers and black phosphorus nanosheets (BPNSs) in the core compartments. The radical alignment of the integrated nanocomponents allows the sequential in situ release of the therapeutic agents in a controlled manner after implantation. Curcumin can repolarize M1 macrophages into M2 phenotypes for anti-inflammation purposes. Meanwhile, the released calcium and phosphate ions can promote the biomineralization of hydroxyapatite at the defect site and facilitate bone regeneration. Evaluations on cranial defect-bearing rat models demonstrated that the electrospun fibers in the present study substantially promoted restoration of the damaged skulls and inhibited inflammation in the wound bed. This strategy provides a new idea for the treatment of skull defects in the clinic.

Graphene Oxide Quantum Dots-Preactivated Dental Pulp Stem Cells/GelMA Facilitates Mitophagy-Regulated Bone Regeneration

Background

In bone tissue engineering (BTE), cell-laden scaffolds offer a promising strategy for repairing bone defects, particularly when host cell regeneration is insufficient due to age or disease. Exogenous stem cell-based BTE requires bioactive factors to activate these cells. Graphene oxide quantum dots (GOQDs), zero-dimensional derivatives of graphene oxide, have emerged as potential osteogenic nanomedicines. However, constructing biological scaffolds with GOQDs and elucidating their biological mechanisms remain critical challenges.

Methods

We utilized GOQDs with a particle size of 10 nm, characterized by a surface rich in C-O-H and C-O-C functional groups. We developed a gelatin methacryloyl (GelMA) hydrogel incorporated with GOQDs-treated dental pulp stem cells (DPSCs). These constructs were transplanted into rat calvarial bone defects to estimate the effectiveness of GOQDs-induced DPSCs in repairing bone defects while also investigating the molecular mechanism underlying GOQDs-induced osteogenesis in DPSCs.

Results

GOQDs at 5 μg/mL significantly enhanced the osteogenic differentiation of DPSCs without toxicity. The GOQDs-induced DPSCs showed active osteogenic potential in three-dimensional cell culture system. In vivo, transplantation of GOQDs-preactivated DPSCs/GelMA composite effectively facilitated calvarial bone regeneration. Mechanistically, GOQDs stimulated mitophagy flux through the phosphatase-and-tensin homolog-induced putative kinase 1 (PINK1)/Parkin E3 ubiquitin ligase (PRKN) pathway. Notably, inhibiting mitophagy with cyclosporin A prevented the osteogenic activity of GOQDs.

Conclusion

This research presents a well-designed bionic GOQDs/DPSCs/GelMA composite scaffold and demonstrated its ability to promote bone regeneration by enhancing mitophagy. These findings highlight the significant potential of this composite for application in BTE and underscore the crucial role of mitophagy in promoting the osteogenic differentiation of GOQDs-induced stem cells.

Copper ion-doped multifunctional hydrogel with mild photothermal enhancement promotes vascularized bone regeneration

The design and construction of a new and excellent synthetic graft is of great significance in the field of bone defect repair and reconstruction. In this study, a dopamine modified chitosan hydrogel doped with Cu ions with a mild photothermal effect was designed to provide a better microenvironment to advance the bone repair via promote the angiogenesis and osteogenesis. Characterizations showed the successful synthesis of the material while it also presented excellent biocompatibility and mild photothermal effect under the irradiation of near-infrared light. Further, it could enhance the angiogenesis of HUVECs cells through promoting the ability of migration and tube formation and enhance the osteogenic differentiation of MC3T3-E1 cells via increasing the content of vital osteogenic factors including Runx2, Col-1, OPN, OCN, OSX, etc. The in vivo experiment also testified that it could promote the bone defect repair in rat models. These results indicate the multifunctional hydrogel is an ideal material for the treatment of bone defects and has good clinical application potential.

Injectable bioactive poly(propylene fumarate) and polycaprolactone based click chemistry bone cement for spinal fusion in rabbits

Degenerative spinal pathology is a widespread medical issue, and spine fusion surgeries are frequently performed. In this study, we fabricated an injectable bioactive click chemistry polymer cement for use in spinal fusion and bone regrowth. Taking advantages of the bioorthogonal click reaction, this cement can be crosslinked by itself eliminating the addition of a toxic initiator or catalyst, nor any external energy sources like UV light or heat. Furthermore, nano-hydroxyapatite (nHA) and microspheres carrying recombinant human bone morphogenetic protein-2 (rhBMP-2) and recombinant human vascular endothelial growth factor (rhVEGF) were used to make the cement bioactive for vascular induction and osteointegration. After implantation into a rabbit posterolateral spinal fusion (PLF) model, the cement showed excellent induction of new bone formation and bridging bone, achieving results comparable to autograft control. This is largely due to the osteogenic properties of nano-hydroxyapatite (nHA) and the released rhBMP-2 and rhVEGF growth factors. Since the availability of autograft sources is limited in clinical settings, this injectable bioactive click chemistry cement may be a promising alternative for spine fusion applications in addressing various spinal conditions.

Molecular mechanisms of EGCG-CSH/n-HA/CMC in promoting osteogenic differentiation and macrophage polarization

2. This research investigates the impact of the EGCG-CSH/n-HA/CMC composite material on bone defect repair, emphasizing its influence on macrophage polarization and osteogenic differentiation of BMSCs. Comprehensive evaluations of the composite's physical and chemical characteristics were performed. BMSC response to the material was tested in vitro for proliferation, migration, and osteogenic potential. An SD rat model was employed for in vivo assessments of bone repair efficacy. Both transcriptional and proteomic analyses were utilized to delineate the mechanisms influencing macrophage behavior and stem cell differentiation. The material maintained excellent structural integrity and significantly promoted BMSC functions critical to bone healing. In vivo results confirmed accelerated bone repair, and molecular analysis highlighted the role of macrophage M2 polarization, particularly through changes in the SIRPA gene and protein expression. EGCG-CSH/n-HA/CMC plays a significant role in enhancing bone repair, with implications for macrophage and BMSC function. Our findings suggest that targeting SIRPA may offer new therapeutic opportunities for bone regeneration.

Patterned PVA Hydrogels with 3D Petri Dish® Micro-Molds of Varying Topography for Spheroid Formation of HeLa Cancer Cells: In Vitro Assessment

Cell spheroids are an important three-dimensional (3D) model for in vitro testing and are gaining interest for their use in clinical applications. More natural 3D cell culture environments that support cell-cell interactions have been created for cancer drug discovery and therapy applications, such as the scaffold-free 3D Petri Dish® technology. This technology uses reusable and autoclavable silicone micro-molds with different topographies, and it conventionally uses gelled agarose for hydrogel formation to preserve the topography of the selected micro-mold. The present study investigated the feasibility of using a patterned Poly(vinyl alcohol) hydrogel using the circular topography 12-81 (9 × 9 wells) micro-mold to form HeLa cancer cell spheroids and compare them with the formed spheroids using agarose hydrogels. PVA hydrogels showed a slightly softer, springier, and stickier texture than agarose hydrogels. After preparation, Fourier transform infrared (FTIR) spectra showed chemical interactions through hydrogen bonding in the PVA and agarose hydrogels. Both types of hydrogels favor the formation of large HeLa spheroids with an average diameter of around 700-800 µm after 72 h. However, the PVA spheroids are more compact than those from agarose, suggesting a potential influence of micro-mold surface chemistry on cell behavior and spheroid formation. This was additionally confirmed by evaluating the spheroid size, morphology, integrity, as well as E-cadherin and Ki67 expression. The results suggest that PVA promotes stronger cell-to-cell interactions in the spheroids. Even the integrity of PVA spheroids was maintained after exposure to the drug cisplatin. In conclusion, the patterned PVA hydrogels were successfully prepared using the 3D Petri Dish® micro-molds, and they could be used as suitable platforms for studying cell-cell interactions in cancer drug therapy.

Hydroxyapatite Nanoparticles Promote the Development of Bone Microtissues for Accelerated Bone Regeneration by Activating the FAK/Akt Pathway

Scaffold-free bone microtissues differentiated from mesenchymal stem cell (MSC) spheroids offer great potential for bottom-up bone tissue engineering as a direct supply of cells and osteogenic signals. Many biomaterials or biomolecules have been incorporated into bone microtissues to enhance their osteogenic abilities, but these materials are far from clinical approval. Here, we aimed to incorporate hydroxyapatite (HAP) nanoparticles, an essential component of bone matrix, into MSC spheroids to instruct their osteogenic differentiation into bone microtissues and further self-organization into bone organoids with a trabecular structure. Furthermore, the biological interaction between HAP nanoparticles and MSCs and the potential molecular mechanisms in the bone development of MSC spheroids were investigated by both in vitro and in vivo studies. As a result, improved cell viability and osteogenic abilities were observed for the MSC spheroids incorporated with HAP nanoparticles at a concentration of 30 μg/mL. HAP nanoparticles could promote the sequential expression of osteogenic markers (Runx2, Osterix, Sclerostin), promote the expression of bone matrix proteins (OPN, OCN, and Collagen I), promote the mineralization of the bone matrix, and thus promote the bone development of MSC spheroids. The differentiated bone microtissues could further self-organize into linear, lamellar, and spatial bone organoids with trabecular structures. More importantly, adding FAK or Akt inhibitors could decrease the level of HAP-induced osteogenic differentiation of bone microtissues. Finally, excellent new bone regeneration was achieved after injecting bone microtissues into cranial bone defect models, which could also be eliminated by the Akt inhibitor. In conclusion, HAP nanoparticles could promote the development of bone microtissues by promoting the osteogenic differentiation of MSCs and the formation and mineralization of the bone matrix via the FAK/Akt pathway. The bone microtissues could act as individual ossification centers and self-organize into macroscale bone organoids, and in this meaning, the bone microtissues could be called microscale bone organoids. Furthermore, the bone microtissues revealed excellent clinical perspectives for injectable cellular therapies for bone defects.

Mesenchymal Stem Cell Spheroids: A Promising Tool for Vascularized Tissue Regeneration

BACKGROUND

Mesenchymal stem cells (MSCs) are undifferentiated cells that can differentiate into specific cell lineages when exposed to the right conditions. The ability of MSCs to differentiate into particular cells is considered very important in biological research and clinical applications. MSC spheroids are clusters of MSCs cultured in three dimensions, which play an important role in enhancing the proliferation and differentiation of MSCs. MSCs can also participate in vascular formation by differentiating into endothelial cells and secreting paracrine factors. Vascularization ability is essential in impaired tissue repair and function recovery. Therefore, the vascularization ability of MSCs, which enhances angiogenesis and accelerates tissue healing has made MSCs a promising tool for tissue regeneration. However, MSC spheroids are a relatively new research field, and more research is needed to understand their full potential.

METHODS

In this review, we highlight the importance of MSC spheroids' vascularization ability in tissue engineering and regenerative medicine while providing the current status of studies on the MSC spheroids' vascularization and suggesting potential future research directions for MSC spheroids.

RESULTS

Studies both in vivo and in vitro have demonstrated MSC spheroids' capacity to develop into endothelial cells and stimulate vasculogenesis.

CONCLUSION

MSC spheroids show potential to enhance vascularization ability in tissue regeneration. Yet, further research is required to comprehensively understand the relationship between MSC spheroids and vascularization mechanisms.

3D Stem Cell Spheroids with 2D Hetero-Nanostructures for In Vivo Osteogenic and Immunologic Modulated Bone Repair

3D stem cell spheroids have immense potential for various tissue engineering applications. However, current spheroid fabrication techniques encounter cell viability issues due to limited oxygen access for cells trapped within the core, as well as nonspecific differentiation issues due to the complicated environment following transplantation. In this study, functional 3D spheroids are developed using mesenchymal stem cells with 2D hetero-nanostructures (HNSs) composed of single-stranded DNA (ssDNA) binding carbon nanotubes (sdCNTs) and gelatin-bind black phosphorus nanosheets (gBPNSs). An osteogenic molecule, dexamethasone (DEX), is further loaded to fabricate an sdCNTgBP-DEX HNS. This approach aims to establish a multifunctional cell-inductive 3D spheroid with improved oxygen transportation through hollow nanotubes, stimulated stem cell growth by phosphate ions supplied from BP oxidation, in situ immunoregulation, and osteogenesis induction by DEX molecules after implantation. Initial transplantation of the 3D spheroids in rat calvarial bone defect shows in vivo macrophage shifts to an M2 phenotype, leading to a pro-healing microenvironment for regeneration. Prolonged implantation demonstrates outstanding in vivo neovascularization, osteointegration, and new bone regeneration. Therefore, these engineered 3D spheroids hold great promise for bone repair as they allow for stem cell delivery and provide immunoregulative and osteogenic signals within an all-in-one construct.

Methacrylated gelatin and platelet-rich plasma based hydrogels promote regeneration of critical-sized bone defects

Physiological repair of large-sized bone defects requires instructive scaffolds with appropriate mechanical properties, biocompatibility, biodegradability, vasculogenic ability and osteo-inductivity. The objective of this study was to fabricate in situ injectable hydrogels using platelet-rich plasma (PRP)-loaded gelatin methacrylate (GM) and employ them for the regeneration of large-sized bone defects. We performed various biological assays as well as assessed the mechanical properties of GM@PRP hydrogels alongside evaluating the release kinetics of growth factors (GFs) from hydrogels. The GM@PRP hydrogels manifested sufficient mechanical properties to support the filling of the tissue defects. For biofunction assay, the GM@PRP hydrogels significantly improved cell migration and angiogenesis. Especially, transcriptome RNA sequencing of human umbilical vein endothelial cells and bone marrow-derived stem cells were performed to delineate vascularization and biomineralization abilities of GM@PRP hydrogels. The GM@PRP hydrogels were subcutaneously implanted in rats for up to 4 weeks for preliminary biocompatibility followed by their transplantation into a tibial defect model for up to 8 weeks in rats. Tibial defects treated with GM@PRP hydrogels manifested significant bone regeneration as well as angiogenesis, biomineralization, and collagen deposition. Based on the biocompatibility and biological function of GM@PRP hydrogels, a new strategy is provided for the regenerative repair of large-size bone defects.

Smart-Responsive Multifunctional Therapeutic System for Improved Regenerative Microenvironment and Accelerated Bone Regeneration via Mild Photothermal Therapy

The treatment of bone defects remains a substantial clinical challenge due to the lack of spatiotemporal management of the immune microenvironment, revascularization, and osteogenic differentiation. Herein, deferoxamine (DFO)-loaded black phosphorus nanosheets decorated by polydopamine layer are prepared (BPPD) and compounded into gelatin methacrylate/sodium alginate methacrylate (GA) hybrid hydrogel as a smart-responsive therapeutic system (GA/BPPD) for accelerated bone regeneration. The BPPD nanocomposites served as bioactive components and near-infrared (NIR) photothermal agents, which conferred the hydrogel with excellent NIR/pH dual-responsive properties, realizing the stimuli-responsive release of DFO and PO4 3 - during bone regeneration. Under the action of NIR-triggered mild photothermal therapy, the GA/BPPD hydrogel exhibited a positive effect on promoting osteogenesis and angiogenesis, eliminating excessive reactive oxygen species, and inducing macrophage polarization to the M2 phenotype. More significantly, through macrophage M2 polarization-induced osteoimmune microenvironment, this hydrogel platform could also drive functional cytokine secretion for enhanced angiogenesis and osteogenesis. In vivo experiments further demonstrated that the GA/BPPD system could facilitate bone healing by attenuating the local inflammatory response, increasing the secretion of pro-healing factors, stimulating endogenous cell recruitment, and accelerating revascularization. Collectively, the proposed intelligent photothermal hydrogel platform provides a promising strategy to reshape the damaged tissue microenvironment for augmented bone regeneration.

Progress in the application of graphene and its derivatives to osteogenesis

As bone and joint injuries from various causes become increasingly prominent, how to effectively reconstruct and repair bone defects presents a difficult problem for clinicians and researchers. In recent years, graphene and its derivatives have been the subject of growing body of research and have been found to promote the proliferation and osteogenic differentiation of stem cells. This provides a new idea for solving the clinical problem of bone defects. However, as as numerous articles address various aspects and have not been fully systematized, there is an urgent need to classify and summarize them. In this paper, for the first time, the effects of graphene and its derivatives on stem cells in solution, in 2D and 3D structures and in vivo and their possible mechanisms are reviewed, and the cytotoxic effects of graphene and its derivatives were summarized and analyzed. The toxicity of graphene and its derivatives is further reviewed. In addition, we suggest possible future development directions of graphene and its derivatives in bone tissue engineering applications to provide a reference for further clinical application.

Green synthesis of metal-organic framework loaded dexamethasone on wood aerogels for enhanced cranial bone regeneration

Bone defects have attracted increasing attention in clinical settings. To date, there have been no effective methods to repair defective bones. Balsa wood aerogels are considered as an excellent source of chemicals for chemical modification to facilitate the in situ immobilization of zeolitic imidazolate framework-8. Furthermore, dexamethasone has received considerable attention for bone tissue engineering. In this study, for the first time, a simple but effective one-pot method for developing a novel zeolitic imidazolate framework-8 with different concentrations of dexamethasone was developed. These findings illustrate that the novel scaffold has a significant positive impact on osteogenic differentiation in vitro and repairs defects in vivo, suggesting that it can be used in bone tissue engineering.

FePSe3 -Nanosheets-Integrated Cryogenic-3D-Printed Multifunctional Calcium Phosphate Scaffolds for Synergistic Therapy of Osteosarcoma

Clinical treatment of osteosarcoma encounters great challenges of postsurgical tumor recurrence and extensive bone defect. To develop an advanced artificial bone substitute that can achieve synergistic bone regeneration and tumor therapy for osteosarcoma treatment, a multifunctional calcium phosphate composite enabled by incorporation of bioactive FePSe3 -nanosheets within the cryogenic-3D-printed α-tricalcium phosphate scaffold (TCP-FePSe3 ) is explored. The TCP-FePSe3 scaffold exhibits remarkable tumor ablation ability due to the excellent NIR-II (1064 nm) photothermal property of FePSe3 -nanosheets. Moreover, the biodegradable TCP-FePSe3 scaffold can release selenium element to suppress tumor recurrence by activating of the caspase-dependent apoptosis pathway. In a subcutaneous tumor model, it is demonstrated that tumors can be efficiently eradicated via the combination treatment with local photothermal ablation and the antitumor effect of selenium element. Meanwhile, in a rat calvarial bone defect model, the superior angiogenesis and osteogenesis induced by TCP-FePSe3 scaffold have been observed in vivo. The TCP-FePSe3 scaffold possesses improved capability to promote the repair of bone defects via vascularized bone regeneration, which is induced by the bioactive ions of Fe, Ca, and P released during the biodegradation of the implanted scaffolds. The TCP-FePSe3 composite scaffolds fabricated by cryogenic-3D-printing illustrate a distinctive strategy to construct multifunctional platform for osteosarcoma treatment.

3D-printed scaffolds with 2D hetero-nanostructures and immunomodulatory cytokines provide pro-healing microenvironment for enhanced bone regeneration

Three-dimensional (3D) printing technology is driving forward the progresses of various engineering fields, including tissue engineering. However, the pristine 3D-printed scaffolds usually lack robust functions in stimulating desired activity for varied regeneration applications. In this study, we combined the two-dimensional (2D) hetero-nanostructures and immuno-regulative interleukin-4 (IL-4) cytokines for the functionalization of 3D-printed scaffolds to achieve a pro-healing immuno-microenvironment for optimized bone injury repair. The 2D hetero-nanostructure consists of graphene oxide (GO) layers, for improved cell adhesion, and black phosphorous (BP) nanosheets, for the continuous release of phosphate ions to stimulate cell growth and osteogenesis. In addition, the 2D hetero-nanolayers facilitated the adsorption of large content of immuno-regulative IL-4 cytokines, which modulated the polarization of macrophages into M2 phenotype. After in vivo implantation in rat, the immuno-functioned 3D-scaffolds achieved in vivo osteo-immunomodulation by building a pro-healing immunological microenvironment for better angiogenesis and osteogenesis in the defect area and thus facilitated bone regeneration. These results demonstrated that the immuno-functionalization of 3D-scaffolds with 2D hetero-nanostructures with secondary loading of immuno-regulative cytokines is an encouraging strategy for improving bone regeneration.

In vivo and In vitro properties evaluation of curcumin loaded MgO doped 3D printed TCP scaffolds

The lack of site-specific chemotherapeutic agents to treat bone malignancy throws a significant challenge in the design of a delivery vehicle. The major scientific question posed in this study is, can we utilize curcumin-loaded magnesium oxide (MgO) doped 3D printed tricalcium phosphate (TCP) bone grafts as a localized delivery system that improves early stage in vivo osseointegration and in vitro chemoprevention, antibacterial properties? We have utilized curcumin as an alternative natural chemopreventive agent for bone cancer-specific delivery after direct incorporation on the 3D printed tricalcium phosphate (TCP) bone grafts. The addition of MgO as a dopant to TCP leads to ∼1.3 times enhancement in compressive strength. The designed drug delivery system shows up to ∼22% curcumin release in a physiological pH of 7.4 after 30 days. The presence of curcumin leads to up to ∼8.5 times reduction in osteosarcoma viability. In vitro results indicate that these scaffolds significantly enhance bone-forming osteoblast cells while reducing the bone-resorbing osteoclast cells. The in vivo rat distal femur model surgery followed by histological assessment with H&E, vWF, and Movat pentachrome staining results show that the designed scaffolds lead to new bone formation (up to ∼2.5 times higher than the control) after successful implantation. The presence of MgO and curcumin results in up to ∼71% antibacterial efficacy against osteomyelitis causing S. aureus. These 3D printed osteogenic and chemopreventive scaffolds can be utilized in patient-specific low load-bearing defect sites.

Bioinspired Mild Photothermal Effect-Reinforced Multifunctional Fiber Scaffolds Promote Bone Regeneration

Bone fractures are often companied with poor bone healing and high rates of infection. Early recruitment of mesenchymal stem cells (MSCs) is critical for initiating efficient bone repair, and mild thermal stimulation can accelerate the recovery of chronic diseases. Here, a bioinspired, staged photothermal effect-reinforced multifunctional scaffold was fabricated for bone repair. Uniaxially aligned electrospun polycaprolactone nanofibers were doped with black phosphorus nanosheets (BP NSs) to endow the scaffold with excellent near-infrared (NIR) responsive capability. Apt19S was then decorated on the surface of the scaffold to selectively recruit MSCs toward the injured site. Afterward, microparticles of phase change materials loaded with antibacterial drugs were also deposited on the surface of the scaffold, which could undergo a solid-to-liquid phase transition above 39 °C, triggering the release of payload to eliminate bacteria and prevent infection. Under NIR irradiation, photothermal-mediated up-regulation of heat shock proteins and accelerated biodegradation of BP NSs could promote the osteogenic differentiation of MSCs and biomineralization. Overall, this strategy shows the ability of bacteria elimination, MSCs recruitment, and bone regeneration promotion with the assistance of photothermal effect in vitro and in vivo, which emphasizes the design of a bioinspired scaffold and its potential for a mild photothermal effect in bone tissue engineering.

Effect of spheroid size on gene expression profiles of a mouse mesenchymal stem cell line in spheroid culture

BACKGROUND

Mesenchymal stem cell (MSC)-based therapies offer potential for bone repair. MSC spheroid cultures may harbor enhanced therapeutic potential over MSC monolayers through increased secretion of trophic factors. However, the impact of spheroid size on trophic factor expression is unclear.

OBJECTIVE

We investigated the effect of spheroid size on trophic factor-related gene expression.

METHODS

KUM10, a murine MSC line was used. RNA-seq was used to screen the transcriptional profiles of MSC monolayer and spheroid cultures. Differentially expressed genes identified in RNA-seq were evaluated by q-PCR in cultures of 5 × 104 (S group), 5 × 105 (M group), 5 × 106 (L group) cells/well.

RESULTS

Comparison of expression levels between KUM10 monolayer and spheroid cultures identified 2140 differentially expressed genes, of which 1047 were upregulated and 1093 were downregulated in KUM10 spheroids. Among these, 12 upregulated genes (Bmp2, Fgf9, Fgf18, Ngf, Pdgfa, Pdgfb, Tgfb1, Vegfa, Vegfc, Wnt4, Wnt5a, Wnt10a) were associated with secretory growth factors. Of these, expression of Fgf9, Fgf18, Vegfa and Vegfc was elevated in the L group, and Pdgfb and Tgfb1 was elevated in the S group.

CONCLUSIONS

Spheroid size may impact trophic factor expression. Our results will be useful for future studies assessing the utility of MSC spheroids for treating bone injury.

Nanoceria-GO-intercalated multicellular spheroids revascularize and salvage critical ischemic limbs through anti-apoptotic and pro-angiogenic functions

Critical limb ischemia (CLI) is a serious form of peripheral arterial disease that involves severe blockage of blood flow in lower extremities, often leading to foot necrosis and limb loss. Lack of blood flow and high pro-inflammation with overproduced reactive oxygen species (ROS) in CLI aggravate the degenerative events. Among other therapies, cell delivery is considered potential for restoring regenerative capacity, and preservation of cell survival under high oxidative stress has been challenging and prerequisite to harness cellular functions. Here, we introduce a multicellular delivery system that is intercalated with nanoceria-decorated graphene oxide (CeGO), which is considered to have high ROS scavenging ability while providing cell-matrix interaction signals. The CeGO nano-microsheets (8-nm-nanoceria/0.9-μm-GO) incorporated in HUVEC/MSC (7/3) could form cell-material hybrid spheroids mediated by cellular contraction. Under in vitro oxidative-stress-challenge with H₂O₂, the CeGO-intercalation enhanced the survival and anti-apoptotic capacity of cellular spheroids. Pro-angiogenic events of cellular spheroids, including cell sprouting and expression of angiogenic markers (HIF1α, VEGF, FGF2, eNOS) were significantly enhanced by the CeGO-intercalation. Proteomics analysis also confirmed substantial up-regulation of a series of angiogenesis-related secretome molecules. Such pro-angiogenic events with CeGO-intercalation were proven to be mediated by the APE/Ref-1 signaling pathway. When delivered to ischemic hindlimb in mice, the CeGO-cell spheroids could inhibit the accumulation of in vivo ROS rapidly, preserving high cell survival rate (cells were more proliferative and less apoptotic vs. those in cell-only spheroids), and up-regulated angiogenic molecular expressions. Monitoring over 28 days revealed significantly enhanced blood reperfusion and tissue recovery, and an ultimate limb salvage with the CeGO-cell delivery (∼60% salvaged vs. ∼29% in cell-only delivery vs. 0% in ischemia control). Together, the CeGO intercalated in HUVEC/MSC delivery is considered a potential nano-microplatform for CLI treatment, by scavenging excessive ROS and enhancing transplanted cell survival, while stimulating angiogenic events, which collectively help revascularization and tissue recovery, salvaging critical ischemic limbs.

Assessment of the Impacts of Centipeda minima (L.) on Cell Viability, and Osteogenic Differentiation of Mesenchymal Stem Cell Spheroids

Background and Objectives: Centipeda minima (L.) is a well-known and traditional pharmaceutical that has been utilized to treat different conditions controlling rhinitis, soothe pain, and decrease swelling. We assessed the impacts of Centipeda minima (L.) extricates (CMTs) on the osteogenic differentiation of cell spheroids made of human-bone-marrow-derived mesenchymal stem cells. Materials and Methods: Mesenchymal stem cells (MSCs) in spheroid 3D culture were generated and propagated in the presence of CMTs ranging from 0 to 1 μg/mL. Cell morphology was measured on Days 1, 3, 5, and 7. The quantitative cellular viability was evaluated on Days 1, 3, 5, and 7. Alkaline phosphatase activity assays were designed to measure the osteogenic differentiation of mesenchymal stem cell spheroids on Day 7. Alizarin Red S staining was performed to investigate the mineralization of cell spheroids on Days 7 and 14. Real-time polymerase chain reactions were used to measure the expression levels of RUNX2 and COL1A1 on Day 14. Western blot techniques were performed to identify the protein expression of Runt-related transcription factor 2 and type I collagen. Results: The control group’s mesenchymal stem cells displayed a spheroid shape. There was no noticeable change in morphology with the addition of CMTs at final concentrations of 0.001, 0.01, 0.1, and 1 μg/mL compared with the untreated (control) group. The application of CMTs did not induce a significant change in cell viability. The relative alkaline phosphatase activity values in the 0.001, 0.01, 0.1, and 1 μg/mL CMT groups were 114.4% ± 8.2%, 130.6% ± 25.3%, 87.8% ± 3.4%, and 92.1% ± 6.8%, respectively, considering a control of 100% (100.0% ± 17.9%). On Day 14, calcium deposits were clearly observed in each group. The relative values of Alizarin Red S staining in the 0.001, 0.01, 0.1, and 1 μg/mL CMT groups were 100.1% ± 8.9%, 105.9% ± 0.0%, 109.7% ± 19.1%, and 87.0% ± 40.9%, respectively, considering a control of 100% (100.0% ± 28.7%). The addition of CMT significantly increased RUNX2 expression in the 0.01 μg/mL group and COL1A1 in the 0.001 and 0.01 μg/mL groups. Normalization of protein expression showed that the addition of CMTs significantly increased type I collagen expression in the 0.001, 0.01, and 1 μg/mL groups. Conclusions: In conclusion, CMTs influence the osteogenic differentiation of bone-marrow-derived mesenchymal stem cells and the use of CMTs may positively influence the osteogenic differentiation of cell spheroids.

Black phosphorous-based biomaterials for bone defect regeneration: a systematic review and meta-analysis

Critical-sized bone defects are always difficult to treat, and they are associated with a significant burden of disease in clinical practice. In recent decades, due to the fast development of biomaterials and tissue engineering, many bioinspired materials have been developed to treat large bone defects. Due to the excellent osteoblastic ability of black phosphorous (BP), many BP-based biomaterials have been developed to treat bone defects. Therefore, there are abundant studies as well as a tremendous amount of research data. It is urgent to conduct evidence-based research to translate these research data and results into validated scientific evidence. Therefore, in our present study, a qualitative systematic review and a quantitative meta-analysis were performed. Eighteen studies were included in a systematic review, while twelve studies were included in the meta-analysis. Our results showed that the overall quality of experimental methods and reports of biomaterials studies was still low, which needs to be improved in future studies. Besides, we also proved the excellent osteoblastic ability of BP-based biomaterials. But we did not find a significant effect of near-infrared (NIR) laser in BP-based biomaterials for treating bone defects. However, the quality of the evidence presented by included studies was very low. Therefore, to accelerate the clinical translation of BP-based biomaterials, it is urgent to improve the quality of the study method and reporting in future animal studies. More evidence-based studies should be conducted to enhance the quality and clinical translation of BP-based biomaterials.

Bioinspired sandwich-like hybrid surface functionalized scaffold capable of regulating osteogenesis, angiogenesis, and osteoclastogenesis for robust bone regeneration

Recently, strategies that focus on biofunctionalized implant surfaces to enhance bone defect healing through the synergistic regulation of osteogenesis, angiogenesis, and osteoclastogenesis have attracted increasing attention in the bone tissue engineering field. Studies have shown that the Wnt/β-catenin signaling pathway has an imperative effect of promoting osteogenesis and angiogenesis while reducing osteoclastogenesis. However, how to prepare biofunctionalized bone implants with balanced osteogenesis, angiogenesis, and osteoclastogenesis by activating the Wnt/β-catenin pathway has seldom been investigated. Herein, through a bioinspired dopamine chemistry and self-assembly method, BML-284 (BML), a potent and highly selective Wnt signaling activator, was loaded on a mussel-inspired polydopamine (PDA) layer that had been immobilized on the porous beta-tricalcium calcium phosphate (β-TCP) scaffold surface and subsequently modified by a biocompatible carboxymethyl chitosan hydrogel to form a sandwich-like hybrid surface. β-TCP provides a biomimetic three-dimensional porous microenvironment similar to that of natural cancellous bone, and the BML-loaded sandwich-like hybrid surface endows the scaffold with multifunctional properties for potential application in bone regeneration. The results show that the sustained release of BML from the sandwich-like hybrid surface significantly facilitates the adhesion, migration, proliferation, spreading, and osteogenic differentiation of MC3T3-E1 cells as well as the angiogenic activity of human umbilical vein endothelial cells. In addition to osteogenesis and angiogenesis, the hybrid surface also exerts critical roles in suppressing osteoclastic activity. Remarkably, in a critical-sized cranial defect model, the biofunctionalized β-TCP scaffold could potentially trigger a chain of biological events: stimulating the polarization of M2 macrophages, recruiting endogenous stem cells and endothelial cells at the injury site to enable a favorable microenvironment for greatly accelerating bone ingrowth and angiogenesis while compromising osteoclastogenesis, thereby promoting bone healing. Therefore, these surface-biofunctionalized β-TCP implants, which regulate the synergies of osteogenesis, angiogenesis, and anti-osteoclastogenesis, indicate strong potential for clinical application as advanced orthopedic implants.

Hope for bone regeneration: The versatility of iron oxide nanoparticles

Although bone tissue has the ability to heal itself, beyond a certain point, bone defects cannot rebuild themselves, and the challenge is how to promote bone tissue regeneration. Iron oxide nanoparticles (IONPs) are a magnetic material because of their excellent properties, which enable them to play an active role in bone regeneration. This paper reviews the application of IONPs in bone tissue regeneration in recent years, and outlines the mechanisms of IONPs in bone tissue regeneration in detail based on the physicochemical properties, structural characteristics and safety of IONPs. In addition, a bibliometric approach has been used to analyze the hot spots and trends in the field in order to identify future directions. The results demonstrate that IONPs are increasingly being investigated in bone regeneration, from the initial use as magnetic resonance imaging (MRI) contrast agents to later drug delivery vehicles, cell labeling, and now in combination with stem cells (SCs) composite scaffolds. In conclusion, based on the current research and development trends, it is more inclined to be used in bone tissue engineering, scaffolds, and composite scaffolds.