Repair Of Segmental Bone Defects Research Articles

Gradient gyroid Ti6Al4V scaffolds with TiO2 surface modification: Promising approach for large bone defect repair

Large bone defects, particularly those exceeding the critical size, present a clinical challenge due to the limited regenerative capacity of bone tissue. Traditional treatments like autografts and allografts are constrained by donor availability, immune rejection, and mechanical performance. This study aimed to develop an effective solution by designing gradient gyroid scaffolds with titania (TiO2) surface modification for the repair of large segmental bone defects. The scaffolds were engineered to balance mechanical strength with the necessary internal space to promote new bone formation and nutrient exchange. A gradient design of the scaffold was optimized through Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD) simulations to enhance fluid flow and cell adhesion. In vivo studies in rabbits demonstrated that the G@TiO2 scaffold, featuring a gradient structure and TiO2 surface modification, exhibited superior healing capabilities compared to the homogeneous structure and TiO2 surface modification (H@TiO2) and gradient structure (G) scaffolds. At 12 weeks post-operation, in a bone defect representing nearly 30 % of the total length of the radius, the implantation of the G@TiO2 scaffold achieved a 27 % bone volume to tissue volume (BV/TV) ratio, demonstrating excellent osseointegration. The TiO2 surface modification provided photothermal antibacterial effects, enhancing the scaffold's biocompatibility and potential for infection prevention. These findings suggest that the gradient gyroid scaffold with TiO2 surface modification is a promising candidate for treating large segmental bone defects, offering a combination of mechanical strength, bioactivity, and infection resistance.

A mechanical-assisted post-bioprinting strategy for challenging bone defects repair

Bioprinting that can synchronously deposit cells and biomaterials has lent fresh impetus to the field of tissue regeneration. However, the unavoidable occurrence of cell damage during fabrication process and intrinsically poor mechanical stability of bioprinted cell-laden scaffolds severely restrict their utilization. As such, on basis of heart-inspired hollow hydrogel-based scaffolds (HHSs), a mechanical-assisted post-bioprinting strategy is proposed to load cells into HHSs in a rapid, uniform, precise and friendly manner. HHSs show mechanical responsiveness to load cells within 4 s, a 13-fold increase in cell number, and partitioned loading of two types of cells compared with those under static conditions. As a proof of concept, HHSs with the loading cells show an enhanced regenerative capability in repair of the critical-sized segmental and osteoporotic bone defects in vivo. We expect that this post-bioprinting strategy can provide a universal, efficient, and promising way to promote cell-based regenerative therapy.

Synergistic large segmental bone repair by 3D printed bionic scaffolds and engineered ADSC nanovesicles: Towards an optimized regenerative microenvironment

Achieving sufficient bone regeneration in large segmental defects is challenging, with the structure of bone repair scaffolds and their loaded bioactive substances crucial for modulating the local osteogenic microenvironment. This study utilized digital laser processing (DLP)-based 3D printing technology to successfully fabricate high-precision methacryloylated polycaprolactone (PCLMA) bionic bone scaffold structures. Adipose-derived stem cell-engineered nanovesicles (ADSC-ENs) were uniformly and stably modified onto the bionic scaffold surface using a perfusion device, constructing a conducive microenvironment for tissue regeneration and long bone defect repair through the scaffold's structural design and the vesicles' biological functions. Scanning electron microscopy (SEM) examination of the scaffold surface confirmed the efficient loading of ADSC-ENs. The material group loaded with vesicles (PCLMA-BAS-ENs) demonstrated good cell compatibility and osteogenic potential when analyzed for the adhesion and osteogenesis of primary rabbit bone marrow mesenchymal stem cells (BMSCs) on the material surface. Tested in a 15 mm critical rabbit radial defect model, the PCLMA-BAS-ENs scaffold facilitated near-complete bone defect repair after 12 weeks. Immunofluorescence and proteomic results indicated that the PCLMA-BAS-ENs scaffold significantly improved the osteogenic microenvironment at the defect site in vivo, promoted angiogenesis, and enhanced the polarization of macrophages towards M2 phenotype, and facilitated the recruitment of BMSCs. Thus, the PCLMA-BAS-ENs scaffold was proven to significantly promote the repair of large segmental bone defects. Overall, this strategy of combining engineered vesicles with highly biomimetic scaffolds to promote large-segment bone tissue regeneration holds great potential in orthopedic and other regenerative medicine applications.

Biofunctionalized hydrogel composed of genipin-crosslinked gelatin/hyaluronic acid incorporated with lyophilized platelet-rich fibrin for segmental bone defect repair

Segmental bone defects can arise from trauma, infection, metabolic bone disorders, or tumor removal. Hydrogels have gained attention in the field of bone regeneration due to their unique hydrophilic properties and the ability to customize their physical and chemical characteristics to serve as scaffolds and carriers for growth factors. However, the limited mechanical strength of hydrogels and the rapid release of active substances have hindered their clinical utility and therapeutic effectiveness. With ongoing advancements in material science, the development of injectable and biofunctionalized hydrogels holds great promise for addressing the challenges associated with segmental bone defects.In this study, we incorporated lyophilized platelet-rich fibrin (LPRF), which contains a multitude of growth factors, into a genipin-crosslinked gelatin/hyaluronic acid (GLT/HA-0.5 % GP) hydrogel to create an injectable and biofunctionalized composite material. Our findings demonstrate that this biofunctionalized hydrogel possesses optimal attributes for bone tissue engineering.Furthermore, results obtained from rabbit model with segmental tibial bone defects, indicate that the treatment with this biofunctionalized hydrogel resulted in increased new bone formation, as confirmed by imaging and histological analysis. From a translational perspective, this biofunctionalized hydrogel provides innovative and bioinspired capabilities that have the potential to enhance bone repair and regeneration in future clinical applications.

Dual-functional 3D-printed porous bioactive scaffold enhanced bone repair by promoting osteogenesis and angiogenesis

The treatment of bone defects is a difficult problem in orthopedics. The excessive destruction of local bone tissue at defect sites destroys blood supply and renders bone regeneration insufficient, which further leads to delayed union or even nonunion. To solve this problem, in this study, we incorporated icariin into alginate/mineralized collagen (AMC) hydrogel and then placed the drug-loaded hydrogel into the pores of a 3D-printed porous titanium alloy (AMCI/PTi) scaffold to prepare a bioactive scaffold with the dual functions of promoting angiogenesis and bone regeneration. The experimental results showed that the ACMI/PTi scaffold had suitable mechanical properties, sustained drug release function, and excellent biocompatibility. The released icariin and mineralized collagen (MC) synergistically promoted angiogenesis and osteogenic differentiation in vitro. After implantation into a rabbit radius defect, the composite scaffold showed a satisfactory effect in promoting bone repair. Therefore, this composite dual-functional scaffold could meet the requirements of bone defect treatment and provide a promising strategy for the repair of large segmental bone defects in clinic.

NR4A1 PROMOTES OSTEOGENIC DIFFERENTIATION OF MESENCHYMAL STEM CELLS AND IMPROVES INFLAMMATION-INHIBITED BONE REGENERATION

Stem cell therapy is an effective means to address the repair of large segmental bone defects. However, the intense inflammatory response triggered by the implants severely impairs stem cell differentiation and tissue regeneration. High-dose transforming growth factor β1 (TGF-β1), the most locally expressed cytokine in implants, inhibits osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and promotes tissue fibrosis, severely compromising the efficacy of stem cell therapy. Small molecule inhibitors of TGF-β1 can be used to ameliorate the osteogenic disorders caused by high concentrations of TGF-β1, but systemic inhibition of TGF-β1 function will cause strong adverse effects. How to find safe and reliable molecular targets to antagonize TGF-β1 remains to be elucidated. Orphan nuclear receptor Nr4a1, an endogenous inhibitory molecule of TGF-β1, suppresses tissue fibrosis, but its role in BMSC osteogenesis is unclear. We found that TGF-β1 inhibited Nr4a1 expression through HDAC4. Overexpression of Nr4a1 in BMSCs reversed osteogenic differentiation inhibited by high levels of TGF- β1. Mechanistically, RNA sequencing showed that Nr4a1 activated the ECM-receptor interaction and Hippo signaling pathway, which in turn promoted BMSC osteogenesis. In bone defect repair and fracture healing models, transplantation of Nr4a1-overexpressing BMSCs into C57BL/6J mice or treatment with the Nr4a1 agonist Csn-B significantly ameliorated inflammation-induced bone regeneration disorders. In summary, our findings confirm the endogenous inhibitory effect of Nr4a1 on TGF- β1 and uncover the effectiveness of Nr4a1 agonists as a therapeutic tool to improve bone regeneration, which provides a new solution strategy for the treatment of clinical bone defects and inflammatory skeletal diseases.

Mechanically strong porous bioceramic tubes facilitate large segmental bone defect repair by providing long-term structurally stability and promoting osteogenesis

Mechanically strong magnesium-doped Ca-silicate bioceramic scaffolds have many advantages in repairing large segmental bone defects. Herein we combine β-TCP with 6 mol% magnesium-doped calcium silicate (Mg6) at three different ratios (TCP, TCP+15 %Mg6, TCP+85 %Mg6) to find an appropriate ratio which can exert considerable influence on bone regeneration. In this study, the bioceramic scaffolds were assessed for mechanical strength, bioactive ion release, biocompatibility, and osteogenic capacity through in vitro testing. Additionally, the potential for promoting bone regeneration was investigated through in vivo implantation of porous tube-like scaffolds. The results showed that the compressive strength increased with the augmentation of Mg6 component. Especially the compressive strength of the TCP+85 %Mg6 group reached 38.1 ± 3.8 MPa, three times that of the other two groups. Furthermore, extensive in vivo investigations revealed that the TCP+85 %Mg6 bioceramic scaffolds were particularly beneficial for the osteogenic capacity of critical-sized femoral defects (20 mm in length). Altogether, magnesium doping in bioceramic implants is a promising strategy to provide stronger mechanical support and enhance osteogenesis to accelerate the repair of large defects.

Engineered periosteum-diaphysis substitutes with biomimetic structure and composition promote the repair of large segmental bone defects

The repair of large segmental bone defects remains a big challenge due to limited self-healing capacity of bone. Digging into the structure and composition of natural long bone let us realize that the periosteum cambium on the surface of diaphysis plays a crucial role in bone repair. In this study, we explored the feasibility of using a tissue-engineered periosteum-diaphysis substitute to repair the large segmental bone defects. To create an artificial periosteum cambium, bone marrow mesenchymal stem cells (BMSCs) and endothelial progenitor cells (EPCs) were co-cultured on electrospun silk fibroin (SF) fibrous membranes for mimicking the cellular composition and microstructure of cambium layer of the native periosteum. These SF membranes supported the adhesion and proliferation of both BMSCs and EPCs. In addition, we found that a 1:1 ratio of BMSCs and EPCs supported osteogenesis and angiogenesis optimally. This biomimetic periosteum layer was integrated with artificial diaphysis made of tubular SF scaffolds to construct a biomimetic periosteum-diaphysis substitute. Animal studies confirmed that the biomimetic periosteum-diaphysis substitutes promoted the repair of critical-size bone defects of rabbit radius. Furthermore, the transplanted biomimetic periosteum-diaphysis substitute could prevent the growth of fibrous tissues in the bone defect, and thus reduce the occurrence of nonunion. This study described a promising tissue engineering strategy for the repair of large segmental bone defects.

Construction of Vascularized Tissue Engineered Bone with nHA-Coated BCP Bioceramics Loaded with Peripheral Blood-Derived MSC and EPC to Repair Large Segmental Femoral Bone Defect

The regenerative repair of segmental bone defect (SBD) is an urgent problem in the field of orthopedics. Rapid induction of angiogenesis and osteoinductivity after implantation of scaffold is critical. In this study, a unique tissue engineering strategy with mixture of peripheral blood-derived mesenchymal stem cells (PBMSC) and endothelial progenitor cells (PBEPC) was applied in a 3D-printed biphasic calcium phosphate (BCP) scaffold with highly bioactive nano hydroxyapatite (nHA) coating (nHA/BCP) to construct a novel vascularized tissue engineered bone (VTEB) for rabbit femoral SBD repair. The 2D coculture of PBMSC and PBEPC showed that they could promote the osteogenic or angiogenic differentiation of the cells from each other, especially in the group of PBEPC/PBMSC = 75:25. Besides, the 3D coculture results exhibited that the nHA coating could further promote PBEPC/PBMSC adhesion, proliferation, and osteogenic and angiogenic differentiation on the BCP scaffold. In vivo experiments showed that among the four groups (BCP, BCP-PBEPC/PBMSC, nHA/BCP, and nHA/BCP-PBEPC/PBMSC), the nHA/BCP-PBEPC/PBMSC group induced the best formation of blood vessels and new bone and, thus, the good repair of SBD. It revealed the synergistic effect of nHA and PBEPC/PBMSC on the angiogenesis and osteogenesis of the BCP scaffold. Therefore, the construction of VTEB in this study could provide a possibility for the regenerative repair of SBD.

In vivo prevascularization strategy enhances neovascularization of β-tricalcium phosphate scaffolds in bone regeneration

BackgroundNeovascularization is critical for bone regeneration. Numerous studies have explored prevascularization preimplant strategies, ranging from calcium phosphate cement (CPC) scaffolds to co-culturing CPCs with stem cells. The aim of the present study was to evaluate an alternative in vivo prevascularization approach, using preimplant-prepared macroporous beta-tricalcium phosphate (β-TCP) scaffolds and subsequent transplantation in bone defect model.MethodsThe morphology of β-TCPs was characterized by scanning electron microscopy. After 3 weeks of prevascularization within a muscle pouch at the lateral size of rat tibia, we transplanted prevascularized macroporous β-TCPs in segmental tibia defects, using blank β-TCPs as a control. Extent of neovascularization was determined by angiography and immunohistochemical (IHC) evaluations. Tibia samples were collected at different time points for biomechanical, radiological, and histological analyses. RT-PCR and western blotting were used to evaluate angio- and osteo-specific markers.ResultsWith macroporous β-TCPs, we documented more vascular and supporting tissue invasion in the macroporous β-TCPs with prior in vivo prevascularization. Radiography, biomechanical, IHC, and histological analyses revealed considerably more vascularity and bone consolidation in β-TCP scaffolds that had undergone the prevascularization step compared to the blank β-TCP scaffolds. Moreover, the prevascularization treatment remarkably upregulated mRNA and protein expression of BMP2 and vascular endothelial growth factor (VEGF) during bone regeneration.ConclusionThis novel in vivo prevascularization strategy successfully accelerated vascular formation to bone regeneration. Our findings indicate that prevascularized tissue-engineered bone grafts have promising potential in clinical applications.The translational potential of this articleThis study indicates a novel in vivo prevascularization strategy for growing vasculature on β-TCP scaffolds to be used for repair of large segmental bone defects, might serve as a promising tissue-engineered bone grafts in the future.

Decellularized xenogenic bone graft for repair of segmental bone defect in rabbits.

Bone grafting is a preferred treatment option for the healing of large diaphyseal bone defects and is useful in the management of nonunion, delayed union, and tumor resection. To investigate a decellularization protocol of bovine cancellous bone for xenogenic implantation in radial bone defects in rabbits. Bovine bone scaffolds fabricated with various decellularization protocols viz phosphate buffer saline (PBS), 1% sodium dodecyl sulfate (SDS), and rapid freeze and thaw technique. The manufactured scaffolds were characterized by biomechanical testing, histological staining, and scanning electron microscopy. A 10 mm rabbit radius bone defect was repaired with autograft and SDS treated and rapid freeze and thaw in groups A, B, and C respectively. Healing was evaluated by radiography and histopathology at 0, 30, 60, and 90 days. The grafts were also checked for host tissue reaction and incorporation into the defect. The freeze and thaw group showed complete elimination of all cellular nuclei, regular arrangement of collagen fiber, and no significant difference in tensile strength compared to 1% SDS treated and native groups. The in vivo radiographic and histopathological study showed that the rapid freeze and thaw group had complete bridging of the bone gap defect with new bone formation and they were immunologically less reactive compared to group B. The in vitro and in vivo evaluation of the grafts suggested that freeze and thaw technique was most superior to all other techniques for effective decellularization and augmentation of bone healing with better integration of the graft into the host.

Biomimetic Methacrylated Gelatin Hydrogel Loaded With Bone Marrow Mesenchymal Stem Cells for Bone Tissue Regeneration.

Large-segment bone defect caused by trauma or tumor is one of the most challenging problems in orthopedic clinics. Biomimetic materials for bone tissue engineering have developed dramatically in the past few decades. The organic combination of biomimetic materials and stem cells offers new strategies for tissue repair, and the fate of stem cells is closely related to their extracellular matrix (ECM) properties. In this study, a photocrosslinked biomimetic methacrylated gelatin (Bio-GelMA) hydrogel scaffold was prepared to simulate the physical structure and chemical composition of the natural bone extracellular matrix, providing a three-dimensional (3D) template and extracellular matrix microenvironment. Bone marrow mesenchymal stem cells (BMSCS) were encapsulated in Bio-GelMA scaffolds to examine the therapeutic effects of ECM-loaded cells in a 3D environment simulated for segmental bone defects. In vitro results showed that Bio-GelMA had good biocompatibility and sufficient mechanical properties (14.22kPa). A rat segmental bone defect model was constructed in vivo. The GelMA-BMSC suspension was added into the PDMS mold with the size of the bone defect and photocured as a scaffold. BMSC-loaded Bio-GelMA resulted in maximum and robust new bone formation compared with hydrogels alone and stem cell group. In conclusion, the bio-GelMA scaffold can be used as a cell carrier of BMSC to promote the repair of segmental bone defects and has great potential in future clinical applications.

Optimal regenerative repair of large segmental bone defect in a goat model with osteoinductive calcium phosphate bioceramic implants

So far, how to achieve the optimal regenerative repair of large load-bearing bone defects using artificial bone grafts is a huge challenge in clinic. In this study, a strategy of combining osteoinductive biphasic calcium phosphate (BCP) bioceramic scaffolds with intramedullary nail fixation for creating stable osteogenic microenvironment was applied to repair large segmental bone defects (3.0 cm in length) in goat femur model. The material characterization results showed that the BCP scaffold had the initial compressive strength of over 2.0 MPa, and total porosity of 84%. The cell culture experiments demonstrated that the scaffold had the excellent ability to promote the proliferation and osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells (BMSCs). The in vivo results showed that the intramedullary nail fixation maintained the initial stability and structural integrity of the implants at early stage, promoting the osteogenic process both guided and induced by the BCP scaffolds. At 9 months postoperatively, good integration between the implants and host bone was observed, and a large amount of newborn bones formed, accompanying with the degradation of the material. At 18 months postoperatively, almost the complete new bone substitution in the defect area was achieved. The maximum bending strength of the repaired bone defects reached to the 100% of normal femur at 18 months post-surgery. Our results demonstrated the good potential of osteoinductive BCP bioceramics in the regenerative repair of large load-bearing bone defects. The current study could provide an effective method to treat the clinical large segmental bone defects.

Investigation of a Prevascularized Bone Graft for Large Defects in the Ovine Tibia

In vivo bioreactors are a promising approach for engineering vascularized autologous bone grafts to repair large bone defects. In this pilot parametric study, we first developed a three-dimensional (3D) printed scaffold uniquely designed to accommodate inclusion of a vascular bundle and facilitate growth factor delivery for accelerated vascular invasion and ectopic bone formation. Second, we established a new sheep deep circumflex iliac artery (DCIA) model as an in vivo bioreactor for engineering a vascularized bone graft and evaluated the effect of implantation duration on ectopic bone formation. Third, after 8 weeks of implantation around the DCIA, we transplanted the prevascularized bone graft to a 5 cm segmental bone defect in the sheep tibia, using the custom 3D printed bone morphogenic protein 2 (BMP-2) loaded scaffold without prior in vivo bioreactor maturation as a control. Analysis by micro-computed tomography and histomorphometry found ectopic bone formation in BMP-2 loaded scaffolds implanted for 8 and 12 weeks in the iliac pouch, with greater bone formation occurring after 12 weeks. Grafts transplanted to the tibial defect supported bone growth, mainly on the periphery of the graft, but greater bone growth and less soft tissue invasion was observed in the avascular BMP-2 loaded scaffold implanted directly into the tibia without prior in vivo maturation. Histopathological evaluation noted considerably greater vascularity in the bone grafts that underwent in vivo maturation with an inserted vascular bundle compared with the avascular BMP-2 loaded graft. Our findings indicate that the use of an initial DCIA in vivo bioreactor maturation step is a promising approach to developing vascularized autologous bone grafts, although scaffolds with greater osteoinductivity should be further studied. Impact statement This translational pilot study aims at combining a tissue engineering scaffold strategy, in vivo prevascularization, and a modified transplantation technique to accelerate large segmental bone defect repair. First, we three-dimensional (3D) printed a 5 cm scaffold with a unique design to facilitate vascular bundle inclusion and osteoinductive growth factor delivery. Second, we established a new sheep deep circumflex iliac artery model as an in vivo bioreactor for prevascularizing the novel 3D printed osteoinductive scaffold. Subsequently, we transplanted the prevascularized bone graft to a clinically relevant 5 cm segmental bone defect in the sheep tibia for bone regeneration.

Effects of osteogenic ambulatory mechanical stimulation on early stages of BMP-2 mediated bone repair

ABSTRACT Purpose: Mechanical loading of bone defects through rehabilitation is a promising approach to stimulate repair and reduce nonunion risk; however, little is known about how therapeutic mechanical stimuli modulate early-stage repair before mineralized bone formation. The objective of this study was to investigate the early effects of osteogenic loading on cytokine expression and angiogenesis during the first 3 weeks of BMP-2 mediated segmental bone defect repair. Materials and Methods: A rat model of BMP-2 mediated bone defect repair was subjected to an osteogenic mechanical loading protocol using ambulatory rehabilitation and a compliant, load-sharing fixator with an integrated implantable strain sensor. The effect of fixator load-sharing on local tissue strain, angiogenesis, and cytokine expression was evaluated. Results: Using sensor readings for local measurements of boundary conditions, finite element simulations showed strain became amplified in remaining soft tissue regions between 1 and 3 weeks (Week 3: load-sharing: −1.89 ± 0.35% and load-shielded: −1.38 ± 0.35% vs. Week 1: load-sharing: −1.54 ± 0.17%; load-shielded: −0.76 ± 0.06%). Multivariate analysis of cytokine arrays revealed that load-sharing significantly altered expression profiles in the defect tissue at 2 weeks compared to load-shielded defects. Specifically, loading reduced VEGF (p = 0.052) and increased CXCL5 (LIX) levels. Subsequently, vascular volume in loaded defects was reduced relative to load-shielded defects but similar to intact bone at 3 weeks. Endochondral bone repair was also observed histologically in loaded defects at 3 weeks. Conclusions: Together, these results demonstrate that moderate ambulatory strains previously shown to stimulate bone regeneration significantly alter early angiogenic and cytokine signaling and may promote endochondral ossification.

Experimental study on repair of large segmental bone defects of goat femur by nano calcium-deficient hydroxyapatite-multi (amino acid) copolymer membrane tubes.

The purpose of this study was to observe feasibility of nano calcium-deficient hydroxyapatite-multi (amino acid) copolymer (n-CDHA-MAC) membrane tubes in repairing goat femurs' large defects. Twelve goats were divided into two groups, whose femurs were created 30 mm segmental bone defects and then implants were performed. In experimental group, the bone defect of right femur was reconstructed by n-CDHA-MAC membrane tube, while left side was reconstructed by allogenic bone tube in control group. Every three goats were sacrificed at 4, 8, 16, 24 weeks after operation respectively. General observation, X-ray analysis, histology, Scanning electron microscope (SEM) examination and protein level comparison of BMP-2 were conducted to evaluate the effects of repairing segmental bone defects. All goats recovered well from anesthesia and surgical interventions. The radiographic evaluations showed that periosteal reaction outside of the membrane tubes and allogenic bone tubes were observed 4 weeks after surgery. At 16 weeks, callus was continuously increased in experimental group, which was more obvious than control group. At 24 weeks, callus outside of the membrane tubes connected together. Histologic evaluation showed fibro-cartilage callus was evolved into bony callus in experimental group, which was more obvious than control group at 8 and 16 weeks. The protein expression level of BMP-2 increased at 4, 8 weeks and peaked at 16 weeks in experimental groups. There were statistical differences at 8 and 16 weeks (P < 0.05). At each time point in 8, 16, 24 weeks after surgery, the bending stiffness, torsional stiffness and compressive strength of the two groups were similar, and there was no significant difference (P > 0.05). This novel surface degradation n-CDHA-MAC membrane tube has good ability to maintain enough membrane space, which can provide long-term and stable biomechanical support for large bone defects and integrate well with the surrounding bone.

Repair of segmental bone defect using tissue engineered heterogeneous deproteinized bone doped with lithium

Lithium have been shown to play an important role in improving the osteogenic properties of biomaterials. This study aims to explore the osteogenic improvement effect of tissue engineered heterogeneous deproteinized bone (HDPB) doped with lithium, and evaluate their effectiveness in the healing of bone defects. Bone marrow mesenchymal stem cells (BMSCs) were co-cultured with different concentration of lithium chloride. Cell proliferation in each group was analyzed by 3-(4, 5-dimetyl-2-thiazoly-2, 5-diphenyl-2-H-tetrazolium bromide (MTT) assay. BMSCs were then co-cultured in osteogenic induction medium with different concentration of lithium chloride, and the expression of related mRNA was detected. The role of lithium in promoting BMSCs osteogenic differentiation and inhibiting BMSCs lipogenic differentiation was also investigated. Biomechanical properties of the tibia were evaluated at 8 weeks after operation. The tibial specimens of each group were collected at 4 and 8 weeks after surgery for histological examination and histological analysis. Micro-computed tomography (CT) scanning and 3D reconstruction were performed at 8 weeks. The results demonstrate that lithium can induce the osteogenic differentiation inhibit of adipogenic differentiation of BMSCs by regulating the Wnt signaling pathway. The histological evaluation further certified that average bone formation area in the group of tissue engineered HDPB doped with lithium was also significantly better than that of HDPB alone group. Based on the above evaluation, tissue engineered HDPB doped with lithium can effectively promote the regeneration of segmental bone defect, which can be used as a tissue engineering scaffold for clinical trials.

Robotic in situ 3D bio-printing technology for repairing large segmental bone defects

IntroductionThe traditional clinical treatment of long segmental bone defects usually requires multiple operations and depends on donor availability. The 3D bio-printing technology constitutes a great potential therapeutic tool for such an injury. However, in situ 3D bio-printing remains a major challenge. ObjectivesIn this study, we report the repair of long segmental bone defects by in situ 3D bio-printing using a robotic manipulator 3D printer in a swine model. MethodsWe systematically optimized bio-ink gelation under physiological conditions to achieve desirable mechanical properties suitable for bone regeneration, and a D-H kinematic model was used to improve printing accuracy to 0.5 mm. ResultsThese technical improvements allowed the repair of long segmental defects generated on the right tibia of pigs using 3D bio-printing within 12 min. The 3D bio-printing group showed improved treatment effects after 3 months. ConclusionThese findings indicated that robotic in situ 3D bio-printing is promising for direct clinical application.

Periosteum Mimetic Coating on Structural Bone Allografts via Electrospray Deposition Enhances Repair and Reconstruction of Segmental Defects.

Structural bone allograft transplantation remains one of the common strategies for repair and reconstruction of large bone defects. Due to the loss of periosteum that covers the outer surface of the cortical bone, the healing and incorporation of allografts is extremely slow and limited. To enhance the biological performance of allografts, herein, we report a novel and simple approach for engineering a periosteum mimetic coating on the surface of structural bone allografts via polymer-mediated electrospray deposition. This approach enables the coating on allografts with precisely controlled composition and thickness. In addition, the periosteum mimetic coating can be tailored to achieve desired drug release profiles by making use of an appropriate biodegradable polymer or polymer blend. The efficacy study in a murine segmental femoral bone defect model demonstrates that the allograft coating composed of poly(lactic-co-glycolic acid) and bone morphogenetic protein-2 mimicking peptide significantly improves allograft healing as evidenced by decreased fibrotic tissue formation, increased periosteal bone formation, and enhanced osseointegration. Taken together, this study provides a platform technology for engineering a periosteum mimetic coating which can greatly promote bone allograft healing. This technology could eventually result in an off-the-shelf and multifunctional structural bone allograft for highly effective repair and reconstruction of large segmental bone defects. The technology can also be used to ameliorate the performance of other medical implants by modifying their surfaces.

Fabrication of piezoelectric porous BaTiO3 scaffold to repair large segmental bone defect in sheep.

Porous titanium scaffolds can provide sufficient mechanical support and bone growth space for large segmental bone defect repair. However, they fail to restore the physiological environment of bone tissue. Barium titanate (BaTiO3) is considered a smart material that can produce an electric field in response to dynamic force. Low-intensity pulsed ultrasound stimulation (LIPUS), as a kind of micromechanical wave, can not only promote bone repair but also induce BaTiO3 to generate an electric field. In our studies, BaTiO3 was coated on porous Ti6Al4V and LIPUS was externally applied to observe the influence of the piezoelectric effect on the repair of large bone defects in vitro and in vivo. The results show that the piezoelectric effect can effectively promote the osteogenic differentiation of bone marrow stromal cells (BMSCs) in vitro as well as bone formation and growth into implants in vivo. This study provides an optional alternative to the conventional porous Ti6Al4V scaffold with enhanced osteogenesis and osseointegration for the repair of large bone defects.