Bone Substitute Options for Spine Fusion in Patients With Spine Trauma-Part II: The Role of rhBMP.

In Part II, we focus on an important aspect of spine fusion in patients with spine trauma: the pivotal role of recombinant human bone morphogenetic protein-2 (rhBMP-2). Despite the influx of diverse techniques facilitated by technological advancements in spinal surgery, spinal fusion surgery remains widely used globally. The persistent challenge of spinal pseudarthrosis has driven extensive efforts to achieve clinically favorable fusion outcomes, with particular emphasis on the evolution of bone graft substitutes. Part II of this review aims to build upon the foundation laid out in Part I by providing a comprehensive summary of commonly utilized bone graft substitutes for spinal fusion in patients with spinal trauma. Additionally, it will delve into the latest advancements and insights regarding the application of rhBMP-2, offering an updated perspective on its role in enhancing the success of spinal fusion procedures.

Engineering Large-Scale Self-Mineralizing Bone Organoids with Bone Matrix-Inspired Hydroxyapatite Hybrid Bioinks.

Addressing large bone defects remains a significant challenge owing to the inherent limitations in self-healing capabilities, resulting in prolonged recovery and suboptimal regeneration. Although current clinical solutions are available, they have notable shortcomings, necessitating more efficacious approaches to bone regeneration. Organoids derived from stem cells show great potential in this field; however, the development of bone organoids has been hindered by specific demands, including the need for robust mechanical support provided by scaffolds and hybrid extracellular matrices (ECM). In this context, bioprinting technologies have emerged as powerful means of replicating the complex architecture of bone tissue. Our research focused on the fabrication of a highly intricate bone ECM analog using a novel bioink composed of GelMA/AlgMA/hydroxyapatite. Bioprinted scaffolds facilitate the long-term cultivation and progressive maturation of extensive bioprinted bone organoids, foster multicellular differentiation, and offer valuable insights into the initial stages of bone formation. The intrinsic self-mineralizing quality of our bioink closely emulates the properties of natural bone, empowering organoids with enhanced bone repair for both in vitro and in vivo applications. This trailblazing investigation propels the field of bone tissue engineering and holds significant promise for its translation into practical applications. This article is protected by copyright. All rights reserved.

Multi-scale cortical bone traits vary in females and males from two mouse models of genetic diversity.

Understanding the genetic basis of cortical bone traits can allow for the discovery of novel genes or biological pathways regulating bone health. Mice are the most widely used mammalian model for skeletal biology and allow for the quantification of traits that cannot easily be evaluated in humans, such as osteocyte lacunar morphology. The goal of our study was to investigate the effect of genetic diversity on multi-scale cortical bone traits of 3 long bones in skeletally-mature mice. We measured bone morphology, mechanical properties, material properties, lacunar morphology, and mineral composition of mouse bones from 2 populations of genetic diversity. Additionally, we compared how intrabone relationships varied in the 2 populations. Our first population of genetic diversity included 72 females and 72 males from the 8 inbred founder strains used to create the Diversity Outbred (DO) population. These 8 strains together span almost 90% of the genetic diversity found in mice (Mus musculus). Our second population of genetic diversity included 25 genetically unique, outbred females and 25 males from the DO population. We show that multi-scale cortical bone traits vary significantly with genetic background; heritability values range from 21% to 99% indicating genetic control of bone traits across length scales. We show for the first time that lacunar shape and number are highly heritable. Comparing the 2 populations of genetic diversity, we show that each DO mouse does not resemble a single inbred founder, but instead the outbred mice display hybrid phenotypes with the elimination of extreme values. Additionally, intrabone relationships (eg, ultimate force vs. cortical area) were mainly conserved in our 2 populations. Overall, this work supports future use of these genetically diverse populations to discover novel genes contributing to cortical bone traits, especially at the lacunar length scale.

Variability of BMP-2 content in DBM products derived from different long bone.

Demineralized bone matrix (DBM) has been regarded as an ideal bone substitute as a native carrier of bone morphogenetic proteins (BMPs) and other growth factors. However, the osteoinductive properties diverse in different DBM products. We speculate that the harvest origin further contributing to variability of BMPs contents in DBM products besides the process technology. In the study, the cortical bone of femur, tibia, humerus, and ulna from a signal donor were prepared and followed demineralizd into DBM products. Proteins in bone martix were extracted using guanidine-HCl and collagenase, respectively, and BMP-2 content was detected by sandwich enzyme-linked immunosorbent assay (ELISA). Variability of BMP-2 content was found in 4 different DBM products. By guanidine-HCl extraction, the average concentration in DBMs harvested from ulna, humerus, tibia, and femur were 0.613 ± 0.053, 0.848 ± 0.051, 3.293 ± 0.268, and 21.763 ± 0.344, respectively (p < 0.05), while using collagenase, the levels were 0.089 ± 0.004, 0.097 ± 0.004, 0.330 ± 0.012, and 1.562 ± 0.008, respectively (p < 0.05). In general, the content of BMP-2 in long bones of Lower limb was higher than that in long bones of upper limb, and GuHCl had remarkably superior extracted efficiency for BMP-2 compared to collagenase. The results suggest that the origin of cortical bones harvested to fabricate DBM products contribute to the variability of native BMP-2 content, while the protein extracted method only changes the measured values of BMP-2.

Quantitative 1H Magnetic Resonance Imaging on Normal and Pathologic Rat Bones by Solid-State 1H ZTE Sequence with Water and Fat Suppression.

BACKGROUND: Osteoporosis (OP) and osteomalacia (OM) are metabolic bone diseases characterized by mineral and matrix density changes. Quantitative bone matrix density differentiates OM from OP. MRI is a noninvasive and nonionizing imaging technique that can measure bone matrix density quantitatively in ex vivo and in vivo. PURPOSE: To demonstrate water + fat suppressed 1H MRI to compute bone matrix density in ex vivo rat femurs in the preclinical model. STUDY TYPE: Prospective. ANIMAL MODEL: Fifteen skeletally mature female Sprague-Dawley rats, five per group (normal, ovariectomized (OVX), partially nephrectomized/vitamin D (Vit-D) deficient), 250-275 g, ∼15 weeks old. FIELD STRENGTH/SEQUENCE: 7T, zero echo time sequence with water + fat (VAPOR) suppression capability, µCT imaging, and gravimetric measurements. ASSESSMENT: Cortical and trabecular bone segments from normal and disease models were scanned in the same coil along with a dual calibration phantom for quantitative assessment of bone matrix density. STATISTICAL TESTS: ANOVA and linear regression were used for data analysis, with P-values <0.05 statistically significant. RESULTS: The MRI-derived three-density PEG pellet densities have a strong linear relationship with physical density measures (r2 = 0.99). The Vit-D group had the lowest bone matrix density for cortical bone (0.47 ± 0.16 g cm-3), whereas the OVX had the lowest bone matrix density for trabecular bone (0.26 ± 0.04 g cm-3). Gravimetry results confirmed these MRI-based observations for Vit-D cortical (0.51 ± 0.07 g cm-3) and OVX trabecular (0.26 ± 0.03 g cm-3) bone groups. DATA CONCLUSION: Rat femur images were obtained using a modified pulse sequence and a custom-designed double-tuned (1H/31P) transmit-receive solenoid-coil on a 7T preclinical MRI scanner. Phantom experiments confirmed a strong linear relation between MRI-derived and physical density measures and quantitative bone matrix densities in rat femurs from normal, OVX, and Vit-D deficient/partially nephrectomized animals were computed. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY: Stage 2.

Demineralized bone matrix for repair and regeneration of maxillofacial defects: A narrative review.

OBJECTIVES: Demineralized bone matrix (DBM) is a well-established bone graft material widely accepted by dentists and the public for its favorable osteoconductivity and osteoinductive potential. This article aimed to provide a narrative review of the current therapeutic applications and limitations of DBM in maxillofacial bone defects. STUDY SELECTION, DATA, AND SOURCES: Randomized controlled trials, prospective or retrospective clinical studies, case series and reports, and systematic reviews. MEDLINE, PubMed, and Google Scholar were searched using keywords. CONCLUSIONS: Some evidence supported the therapeutic application of DBM in periodontal intrabony defects, maxillary sinus lifts, ridge preservation, ridge augmentation, alveolar cleft repair, orthognathic surgery, and other regional maxillofacial bone defects. However, the limitations of DBM should be considered when using it, including potential low immunogenicity, instability of osteoinductive potential, handling of the graft material, and patient acceptance. CLINICAL SIGNIFICANCE: With the increasing demand for the treatment of maxillofacial bone defects, DBM is likely to play a greater role as a promising bone graft material. Safe and effective combination treatment strategies and how to maintain a stable osteoinductive potential will be the future challenges of DBM research.

Bone quality in zebrafish vertebrae improves after alendronate administration in a glucocorticoid-induced osteoporosis model.

Glucocorticoid-induced osteoporosis (GIOP) changes the microarchitecture of bones and often leads to the reduction of bone-mineral density (BMD) and increased fracture rates. Zebrafish has been used as an alternative model for GIOP, however, the interaction of GIOP, and its treatment, with zebrafish bone morphometrics and mechanical properties, remains a challenge. Thus, this study aimed to evaluate the effects of prednisolone and alendronate on the properties of zebrafish vertebrae. Adult 7-month-old zebrafish were distributed into four groups: control (CTRL), prednisolone-only (PN), alendronate-only (ALN), and the sequential use of both medicines (PN + ALN). Fish skeletons were scanned via micro-tomography (n = 3) to obtain vertebra morphometrics (e.g., BMD). Bone morphology was assessed using scanning electron microscopy (n = 4) and the biomechanical behaviour with nanoindentation technique (n = 3). The BMD decreased in PN (426.08 ± 18.58 mg/cm3) and ALN (398.23 ± 10.20 mg/cm3) groups compared to the CTRL (490.43 ± 41.96 mg/cm3) (p < 0.001); however, administering the medicines in sequence recovered the values to healthy levels (495.43 ± 22.06 mg/cm3) (p > 0.05). The bone layered structures remain preserved in all groups. The vertebrae of the groups that received ALN and PN + ALN, displayed higher modulus of elasticity (27.27 ± 1.59 GPa and 25.68 ± 2.07 GPa, respectively) than the CTRL (22.74 ± 1.60 GP) (p < 0.001). ALN alone increased the hardness of zebrafish vertebrae to the highest value among the treatments (1.32 ± 0.13 GPa) (p < 0.001). Conversely, PN + ALN (1.25 ± 0.11 GPa) showed unaltered hardness from the CTRL (1.18 ± 0.13 GPa), but significantly higher than the PN group (1.08 ± 0.12 GPa) (p < 0.001). ALN administered after GIOP development, rescued osteoporotic condition by recovering the BMD and bone hardness in zebrafish vertebrae.

Preparation of black phosphorus@sodium alginate microspheres with bone matrix vesicle structure via electrospraying for bone regeneration.

Bone matrix vesicles are commonly acknowledged as the primary site of biomineralization in human skeletal tissue. Black phosphorus has exhibited favorable properties across various chemical and physical domains. In this investigation, a novel composite microsphere was synthesized through the amalgamation of sodium alginate (ALG) with black phosphorus nanosheets (BP) utilizing the electrospray (ES) technique. These microspheres were tailored to mimic the regulatory function of matrix vesicles (MV) upon exposure to a biomimetic mineralization fluid (SBF) during the biomineralization process. Results revealed that black phosphorus nanosheets facilitated the generation of hydroxyapatite (HA) on the microsphere surface. Live-dead assays and cell proliferation experiments showcased a cell survival rate exceeding 85 %. Moreover, wound healing assessments unveiled that M-ALG-BP microspheres exhibited superior migration capacity, with a migration rate surpassing 50 %. Furthermore, after 7 days of osteogenic induction, M-ALG-BP microspheres notably stimulated osteoblast differentiation. Particularly noteworthy, M-ALG-BP microspheres significantly enhanced osteogenic differentiation of osteoblasts and induced collagen production in vitro. Additionally, experiments involving microsphere implantation into mouse skeletal muscle demonstrated the potential for ectopic mineralization by ALG-BP microspheres. This investigation underscores the outstanding mineralization properties of ALG-BP microspheres and their promising clinical prospects in bone tissue engineering.

3D-printed polycaprolactone/tricalcium silicate scaffolds modified with decellularized bone ECM-oxidized alginate for bone tissue engineering.

The treatment of large craniofacial bone defects requires more advanced and effective strategies than bone grafts since such defects are challenging and cannot heal without intervention. In this regard, 3D printing offers promising solutions through the fabrication of scaffolds with the required shape, porosity, and various biomaterials suitable for specific tissues. In this study, 3D-printed polycaprolactone (PCL)-based scaffolds containing up to 30 % tricalcium silicate (TCS) were fabricated and then modified by incorporation of decellularized bone matrix- oxidized sodium alginate (DBM-OA). The results showed that the addition of 20 % TCS increased compressive modulus by 4.5-fold, yield strength by 12-fold, and toughness by 15-fold compared to pure PCL. In addition, the samples containing TCS revealed the formation of crystalline phases with a Ca/P ratio near that of hydroxyapatite (1.67). Cellular experiment results demonstrated that TCS have improved the biocompatibility of PCL-based scaffolds. On day 7, the scaffolds modified with DBM and 20 % TCS exhibited 8-fold enhancement of ALP activity of placenta-derived mesenchymal stem/stromal cells (P-MSCs) compared to pure PCL scaffolds. The present study's results suggest that the incorporation of TCS and DBM-OA into the PCL-based scaffold improves its mechanical behavior, bioactivity, biocompatibility, and promotes mineralization and early osteogenic activity.

Treatment of a Large Tibial Non-Union Bone Defect in a Cat Using Xenograft with Canine-Derived Cancellous Bone, Demineralized Bone Matrix, and Autograft.

A 17-month-old domestic short-hair cat was referred due to a non-union in the left tibia. The initial repair, conducted 3 months prior at another animal hospital, involved an intramedullary (IM) pin and wire to address a comminuted fracture. Unfortunately, the wire knot caused a skin tract, resulting in osteomyelitis. Although the wire knot was removed at that hospital, the draining tract persisted, continuously discharging exudate. Upon evaluation, the first surgery was reassessed and revised, involving the removal of the IM pin and the application of external skeletal fixation alongside an antibiotic susceptibility test. After 118 days post-revision surgery, while some cortical continuity was observed, a significant bone defect persisted, posing a substantial risk of refracture should the implant be removed. A second revision surgery was performed, utilizing a bone plate combined with cancellous bone autograft, recombinant human bone morphogenetic protein-2, and xenograft featuring a canine-derived cancellous chip mixed with demineralized bone matrix. Remarkably, the bone completed its healing within 105 days following the subsequent surgery. Radiography demonstrated successful management of the large bone defect up to the 2-year postoperative check-up. During telephone follow-ups for 3.5 years after surgery, no complications were identified, and the subject maintained a favorable gait.

Comparison of Fusion Rates among Various Demineralized Bone Matrices in Posterior Lumbar Interbody Fusion.

Background and Objectives: Posterior lumbar interbody fusion (PLIF) plays a crucial role in addressing various spinal disorders. The success of PLIF is contingent upon achieving bone fusion, as failure can lead to adverse clinical outcomes. Demineralized bone matrix (DBM) has emerged as a promising solution for promoting fusion due to its unique combination of osteoinductive and osteoconductive properties. This study aims to compare the effectiveness of three distinct DBMs (Exfuse®, Bongener®, and Bonfuse®) in achieving fusion rates in PLIF surgery. Materials and Methods: A retrospective review was conducted on 236 consecutive patients undergoing PLIF between September 2016 and February 2019. Patients over 50 years old with degenerative lumbar disease, receiving DBM, and following up for more than 12 months after surgery were included. Fusion was evaluated using the Bridwell grading system. Bridwell grades 1 and 2 were defined as 'fusion', while grades 3 and 4 were considered 'non-fusion.' Clinical outcomes were assessed using visual analog scale (VAS) scores for pain, the Oswestry disability index (ODI), and the European quality of life-5 (EQ-5D). Results: Fusion rates were 88.3% for Exfuse, 94.3% for Bongener, and 87.7% for Bonfuse, with no significant differences. All groups exhibited significant improvement in clinical outcomes at 12 months after surgery, but no significant differences were observed among the three groups. Conclusions: There were no significant differences in fusion rates and clinical outcomes among Exfuse, Bongener, and Bonfuse in PLIF surgery.

Composite Remineralization of Bone-Collagen Matrices by Low-Temperature Ceramics and Serum Albumin: A New Approach to the Creation of Highly Effective Osteoplastic Materials.

This study examined the effectiveness of coating demineralized bone matrix (DBM) with amorphous calcium phosphate (DBM + CaP), as well as a composite of DBM, calcium phosphate, and serum albumin (DBM + CaP + BSA). The intact structure of DBM promotes the transformation of amorphous calcium phosphate (CaP) into dicalcium phosphate dihydrate (DCPD) with a characteristic plate shape and particle size of 5-35 µm. The inclusion of BSA in the coating resulted in a better and more uniform distribution of CaP on the surface of DBM trabeculae. MG63 cells showed that both the obtained forms of CaP and its complex with BSA did not exhibit cytotoxicity up to a concentration of 10 mg/mL in vitro. Ectopic (subcutaneous) implantation in rats revealed pronounced biocompatibility, as well as strong osteoconductive, osteoinductive, and osteogenic effects for both DBM + CaP and DBM + CaP + BSA, but more pronounced effects for DBM + CaP + BSA. In addition, for the DBM + CaP + BSA samples, there was a pronounced full physiological intrafibrillar biomineralization and proangiogenic effect with the formation of bone-morrow-like niches, accompanied by pronounced processes of intramedullary hematopoiesis, indicating a powerful osteogenic effect of this composite.

A physicochemical evaluation of ossein-hydroxyapatite within the bovine bone matrix revealed demineralization and making type I collagen available as a result of processing and solubilization by acids.

Bovine bone is an animal-origin matrix rich in type I collagen (COL I) and it necessitates prior demineralization and makes COL I available. This study investigated the ossein-hydroxyapatite physicochemical properties evaluation as a result of processing and solubilization by acids and revealed the bone matrix demineralization and making COL I available. The tibia residue from bovine sources was processed, ground, and transformed into bone matrix powder. The bone matrix was solubilized in acetic acid followed by lactic acid. The bone matrix was evaluated as a result of processing and solubilization by acids: ossein and hydroxyapatite percentages by nitrogen and ash content, mineral content, particle size distribution, Fourier-transformation infrared spectroscopy, x-ray diffraction, and scanning electron microscope. For the obtained residual extracts, pH and mineral content were evaluated. The solubilization by acids affected the ossein-hydroxyapatite physicochemical properties, and the bone matrix solubilized by acetic and lactic acid showed the preservation of the ossein alongside the loss of hydroxyapatite. The processing and the solubilization by acids were revealed to be a  alternative to bone matrix demineralization and enabling the accessibility of bone COL I. PRACTICAL APPLICATION: Bovine bone is an abundant type I collagen source, but processing maneuvers and demineralization effect present limitations due to the rigidity of the structural components. Exploring methodologies to process and demineralize will allow type I collagen to be obtained from the bone source, and direct and amplify the potentialities in the chemical and food industries. The research focused on bone sources and collagen availability holds paramount significance, and promotes repurposing agribusiness residues and development of protein-base products.

Complications With Demineralized Bone Matrix, Hydroxyapatite and Beta-Tricalcium Phosphate in Single and Two-Level Anterior Cervical Discectomy and Fusion Surgery.

STUDY DESIGN: Systematic literature review. OBJECTIVES: To analyze the evidence available reporting complications in single or two-level anterior cervical discectomy and fusion (ACDF) using a demineralized bone matrix (DBM), hydroxyapatite (HA), or beta-tricalcium phosphate (ß-TCP). METHODS: A systematic review of the literature using PubMed, EMBASE, Cochrane Library, and ClinicalTrials.gov databases was performed in August 2020 to identify studies reporting complications in one or two-level ACDF surgery using DBM, HA, or ß-TCP. The study was reported following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. RESULTS: A total of 1857 patients were included, 981 male and 876 female, across 17 articles; 5 prospective, and 12 retrospectives. We noted heterogeneity among the included studies concerning the study design and combination of graft materials utilized in them. However, we noted a higher incidence of adjacent segment disease (17.7%) and pseudoarthrosis (9.3%) in fusion constructs using DBM. Studies using ß-TCP reported a higher incidence of pseudoarthrosis (28.2%) and implant failures (17.9%). CONCLUSIONS: Degenerative cervical conditions treated with one or two-level ACDF surgery using DBM, HA, or ß-TCP with or without cervical plating are associated with complications such as adjacent segment disease, dysphagia, and pseudarthrosis. However, consequent to the study designs and clinical heterogeneity of the studies, it is not possible to correlate these complications accurately with any specific graft material employed. Further well-designed prospective studies are needed to correctly know the related morbidity of each graft used for achieving fusion in ACDF.

The Use of Osteobiologics in Single versus Multi-Level Anterior Cervical Discectomy and Fusion: A Systematic Review.

STUDY DESIGN: Systematic literature review. OBJECTIVES: In this study we assessed evidence for the use of osteobiologics in single vs multi-level anterior cervical discectomy and fusion (ACDF) in patients with cervical spine degeneration. The primary objective was to compare fusion rates after single and multi-level surgery with different osteobiologics. Secondary objectives were to compare differences in patient reported outcome measures (PROMs) and complications. METHODS: After a global team of reviewers was selected, a systematic review using different repositories was performed, confirming to PRISMA and GRADE guidelines. In total 1206 articles were identified and after applying inclusion and exclusion criteria, 11 articles were eligible for analysis. Extracted data included fusion rates, definition of fusion, patient reported outcome measures, types of osteobiologics used, complications, adverse events and revisions. RESULTS: Fusion rates ranged from 87.7% to 100% for bone morphogenetic protein 2 (BMP-2) and 88.6% to 94.7% for demineralized bone matrix, while fusion rates reported for other osteobiologics were lower. All included studies showed PROMs improved significantly for each osteobiologic. However, no differences were reported when comparing osteobiologics, or when comparing single vs multi-level surgery specifically. CONCLUSION: The highest fusion rates after 2-level ACDF for cervical spine degeneration were reported when BMP-2 was used. However, PROMs did not differ between the different osteobiologics. Further blinded randomized trials should be performed to compare the use of BMP-2 in single vs multi-level ACDF specifically.

Enhanced osteogenicity of the demineralized bone-dermal matrix composite by the optimal partial demineralization for sustained release of bioactive molecules.

Allogenic demineralized bone matrix (DBM), processed to expose bioactive proteins imbedded by calcium salts, is widely used for bone repair and regeneration as an alternative to the autologous bone graft. However, demineralized bone matrices from tissue banks vary significantly in residual calcium content and osteogenicity for clinical bone regeneration. The present study produced DBM with various residual calcium contents by partial demineralization using ethylenediaminetetraacetic acid disodium (EDTA) and hydrochloric acid. Compositional analysis reveals that, as the percent weight loss of bone materials increases from 0% to 74.9% during demineralization, the residual calcium content of DBM decreases from 24.8% to 0.2% and collagen content increases from 29.7% to 92.6%. Calorimetrical analysis and Fourier transform infrared (FTIR) analysis demonstrated that demineralization to the residual calcium content of <4% enables the complete exposure and/or release of bone collagen fibers and other bioactive molecules. In order to evaluate the relationship between the extent of demineralization and the osteogenicity of DBM, DBM particles were fabricated with the aid of acellular dermal matrix (ADM) microfibers to form flexible foam-like DBM/ADM composites. Proteomic analysis identified various type collagens and bone formation-related bioactive molecules in both ADM and DBM. Using the rat bilateral Φ = 5 mm calvarium defect repair model, the study had shown that the DBM/ADM composite with ~20% DBM residual calcium (e.g., ~40% calcium being removed) maximized the osteogenicity for bone defect repair after 4 and 8 weeks. DBM with ~40% calcium removal had the maximal osteogenicity presumably through the sustained release of bioactive molecules during the process of bone regeneration.

[Translated article] Mechanical resistance of polylactic acid bone matrices developed by 3D printing for the reconstruction of bone defects.

INTRODUCTION: Bone defects are one of the main limitations in orthopaedic surgery and traumatology. For this reason, multiple bone replacement systems have been developed, either by prosthetic implant or by substitution with osteoforming substances, whose limitations are their survival and lack of structurality, respectively. The objective of this work is the generation of a new material for the creation of biologically active structures that have sufficient tensile strength to maintain the structure during remodelling. MATERIAL AND METHODS: A new filament based on the fusion of natural polylactide acid (PLA) powder was designed for the generation of pieces by means of fused deposition modelling (FDM) on which to carry out tensile mechanical tests of osteosynthesis material. A total of 13 groups with different cortical thickness, filling and layer height were carried out, with 10 tensile tests in each group, defining the tensile breaking limit for each group. The regression lines for each group and their mechanical resistance to traction on the filament used were determined. RESULTS: The filament ratio per contact surface unit with the osteosynthesis used was the main determinant of the mechanical resistance to traction, either at the expense of the increase in cortical thickness or by the increase in the percentage of cancellous bone filling. Layer height had a minor effect on tensile strength. The regression value was high for cortical thickness and cancellous filling, being elements with a predictable biomechanical behaviour. CONCLUSIONS: The new methodology allows the creation of personalised neutral and implantable PLA bone matrices for the reconstruction of large bone defects by means of 3D printing by FDM with a mechanical resistance to traction greater than that of current biological support structures.

Self-Assembled Nanocomposite Hydrogels as Carriers for Demineralized Bone Matrix Particles and Enhanced Bone Repair.

Demineralized bone matrix (DBM) has been widely used as an allogeneic alternative to autologous bone graft for bone repair. However, more extensive use of DBM is limited due to its particulate nature after demineralization and rapid particle dispersion following irrigation, resulting in unpredictable osteoinductivity. Here, a new design of injectable hydrogel carriers for DBM that combine self-healing ability and osteogenic properties based on the self-assembly of guanidinylated hyaluronic acid and silica-rich nanoclays is reported. The nanoclays serve as reversible linkages to form a dynamic hydrogel network with the guanidine moieties on the polymer chains. Gelation kinetics and mechanical properties can be controlled by altering nanoclay content in the hydrogel. The resulting hydrogel exerts self-healing ability due to its dynamic crosslinks and well retains its overall performance with high DBM loading. The hydrogel exhibits great cytocompatibility and osteogenic effects mediated by the nanoclays. In vivo delivery of DBM using the nanocomposite hydrogel further demonstrates robust bone regeneration in a mouse calvarial defect model in comparison to DBM delivered with aqueous HA. This work suggests a promising hydrogel platform for many applications including therapeutic delivery and tissue engineering.

Augmented drug resistance of osteosarcoma cells within decalcified bone matrix scaffold: The role of glutamine metabolism.

Due to the lack of a precise in vitro model that can mimic the nature microenvironment in osteosarcoma, the understanding of its resistance to chemical drugs remains limited. Here, we report a novel three-dimensional model of osteosarcoma constructed by seeding tumor cells (MG-63 and MNNG/HOS Cl no. 5) within demineralized bone matrix scaffolds. Demineralized bone matrix scaffolds retain the original components of the natural bone matrix (hydroxyapatite and collagen type I), and possess good biocompatibility allowing osteosarcoma cells to proliferate and aggregate into clusters within the pores. Growing within the scaffold conferred elevated resistance to doxorubicin on MG-63 and MNNG/HOS Cl no. 5 cell lines as compared to two-dimensional cultures. Transcriptomic analysis showed an increased enrichment for drug resistance genes along with enhanced glutamine metabolism in osteosarcoma cells in demineralized bone matrix scaffolds. Inhibition of glutamine metabolism resulted in a decrease in drug resistance of osteosarcoma, which could be restored by α-ketoglutarate supplementation. Overall, our study suggests that microenvironmental cues in demineralized bone matrix scaffolds can enhance osteosarcoma drug responses and that targeting glutamine metabolism may be a strategy for treating osteosarcoma drug resistance.

Microbiome-induced Increases and Decreases in Bone Tissue Strength can be Initiated After Skeletal Maturity.

Recent studies in mice have indicated that the gut microbiome can regulate bone tissue strength. However, prior work involved modifications to the gut microbiome in growing animals and it is unclear if the same changes in the microbiome, applied later in life, would change matrix strength. Here we changed the composition of the gut microbiome before and/or after skeletal maturity (16 weeks of age) using oral antibiotics (ampicillin + neomycin). Male and female mice (n=143 total, n=12-17/group/sex) were allocated into five study groups:1) Unaltered, 2) Continuous (dosing 4-24 weeks of age), 3) Delayed (dosing only 16-24 weeks of age), 4) Initial (dosing 4-16 weeks of age, suspended at 16 weeks), and 5) Reconstituted (dosing from 4-16 weeks following by fecal microbiota transplant from Unaltered donors). Animals were euthanized at 24 weeks of age. In males, bone matrix strength in the femur was 25-35% less than expected from geometry in mice from the Continuous (p= 0.001), Delayed (p= 0.005), and Initial (p=0.040) groups as compared to Unaltered. Reconstitution of the gut microbiota, however, led to a bone matrix strength similar to Unaltered animals (p=0.929). In females, microbiome-induced changes in bone matrix strength followed the same trend as males but were not significantly different, demonstrating sex-related differences in the response of bone matrix to the gut microbiota. Minor differences in chemical composition of bone matrix were observed (Raman spectroscopy). Our findings indicate that microbiome-induced impairment of bone matrix in males can be initiated and/or reversed after skeletal maturity. The portion of the femoral cortical bone formed after skeletal maturity (16 weeks) is small; however, this suggests that microbiome-induced changes in bone matrix occur without osteoblast/osteoclast turnover using an, as of yet unidentified mechanism. These findings add to evidence that the mechanical properties of bone matrix can be altered in the adult skeleton.