Enhancing Mechanical Properties and Biological Performances of Injectable Bioactive Glass by Gelatin and Chitosan for Bone Small Defect Repair

Antioxidant flavonoid-loaded nano-bioactive glass bone paste: in vitro apatite formation and flow behavior

Non-cement pastes in the form of injectable materials have gained considerable attention in non-invasive regenerative medicine. Different osteoconductive bioceramics have been used as the solid phase of these bone pastes. Mesoporous bioactive glass can be used as an alternative bioceramic for paste preparation because of its osteogenic qualities. Plant-derived osteogenic agents can also be used in paste formulation to improve osteogenesis; however, their side effects on physical and physicochemical properties should be investigated. In this study, nano-bioactive glass powder was synthesized by a sol-gel method, loaded with different amounts of quercetin (0, 100, 150, and 200 μM), an antioxidant flavonoid with osteogenesis capacity. The loaded powder was then homogenized with a mixture of hyaluronic acid and sodium alginate solution to form a paste. We subsequently evaluated the rheological behavior, injectability, washout resistance, and in vitro bioactivity of the quercetin-loaded pastes. The washout resistance was found to be more than 96% after 14 days of immersion in simulated body fluid (SBF) as well as tris-buffered and citric acid-buffered solutions at 25 °C and 37 °C. All pastes exhibited viscoelastic behavior, in which the elastic modulus exceeded the viscous modulus. The pastes displayed shear-thinning behavior, in which viscosity was more influenced by angular frequency when the quercetin content increased. Results indicated that injectability was much improved using quercetin and the injection force was in the range 20-150 N. Following 14 days of SBF soaking, the formation of a nano-structured apatite phase on the surfaces of quercetin-loaded pastes was confirmed through scanning electron microscopy, X-ray diffractometry, and Fourier-transform infrared spectroscopy. Overall, quercetin, an antioxidant flavonoid osteogenic agent, can be loaded onto the nano-bioactive glass/hyaluronic acid/sodium alginate paste system to enhance injectability, rheological properties, and bioactivity.

An injectable pH neutral bioactive glass-based bone cement with suitable bone regeneration ability

Background

As a class of promising bone augmentation materials, bone cements have attracted particular attention. Due to various limitations, the current bone cements are still imperfect. In this study, an injectable pH neutral bioactive bone cement (PSC/CSC) was developed by mixing phosphosilicate bioactive glass (PSC) and α-calcium sulfate hemihydrate (CSH), with the goal of optimizing bone defects repairs.

Methods

A range of compositions (PSC/CSC: 10P/90C, 30P/70C, 50P/50C) were developed and their physicochemical properties evaluated. Their bone regeneration ability was compared to those of two widely used bone cements as controls (calcium phosphate cement (CPC) and Genex®) in rabbit femoral condyle bone defect models for 4, 8 and 12 weeks. Based on physicochemical properties and in vivo bone regeneration ability, the PSC/CSC exhibited the best outcomes was selected. Then, in vitro, the effects of selected PSC/CSC, CPC and Genex® extracts on MC3T3-E1 cell proliferation, migration and osteogenesis as well as angiogenesis of HUVECs were examined.

Results

Based on physicochemical properties, the 30P/70C formula exhibited suitable operability and compressive strength (3.5 ± 0.3 MPa), which fulfilled the requirements for cancellous bone substitutes. In vivo, findings from micro-CT and histological analyses showed that the 30P/70C formula better promoted bone regeneration, compared to 10P/90C, 50P/50C, CPC and Genex®. Hence, 30P/70C was selected as the ideal PSC-based cement. In vitro, the 30P/70C extracts showed better promotion of cell viability, alkaline phosphatase (ALP) activity, calcium mineral deposition, mRNA and protein expression levels of osteogenesis in MC3T3-E1 cells, further supporting its superiority. Meanwhile, the 30P/70C extracts also showed better stimulation of HUVECs proliferation and angiogenesis.

Conclusion

The new composite cement, 30P/70C, is a favorable bioactive glass-based bone cement with suitable operability, compressive strength and bone regeneration ability.

The translational potential of this article

Clinically, treatment of large bone defects is still a major challenge for orthopaedic trauma. We showed that 30P/70C has the potential to be clinically used as an injectable cement for rapid bone repairs and reconstruction of critical sized bone defects.

An automated 3D-printed perfusion bioreactor combinable with pulsed electromagnetic field stimulators for bone tissue investigations

In bone tissue engineering research, bioreactors designed for replicating the main features of the complex native environment represent powerful investigation tools. Moreover, when equipped with automation, their use allows reducing user intervention and dependence, increasing reproducibility and the overall quality of the culture process. In this study, an automated uni-/bi-directional perfusion bioreactor combinable with pulsed electromagnetic field (PEMF) stimulation for culturing 3D bone tissue models is proposed. A user-friendly control unit automates the perfusion, minimizing the user dependency. Computational fluid dynamics simulations supported the culture chamber design and allowed the estimation of the shear stress values within the construct. Electromagnetic field simulations demonstrated that, in case of combination with a PEMF stimulator, the construct can be exposed to uniform magnetic fields. Preliminary biological tests on 3D bone tissue models showed that perfusion promotes the release of the early differentiation marker alkaline phosphatase. The histological analysis confirmed that perfusion favors cells to deposit more extracellular matrix (ECM) with respect to the static culture and revealed that bi-directional perfusion better promotes ECM deposition across the construct with respect to uni-directional perfusion. Lastly, the Real-time PCR results of 3D bone tissue models cultured under bi-directional perfusion without and with PEMF stimulation revealed that the only perfusion induced a ~ 40-fold up-regulation of the expression of the osteogenic gene collagen type I with respect to the static control, while a ~ 80-fold up-regulation was measured when perfusion was combined with PEMF stimulation, indicating a positive synergic pro-osteogenic effect of combined physical stimulations.

Clumps of mesenchymal stem cells/extracellular matrix complexes directly reconstruct the functional periodontal tissue in a rat periodontal defect model

Periodontitis is an inflammatory disease characterized by tooth-supporting periodontal tissue destruction, including the cementum, periodontal ligament, and alveolar bone. To regenerate the damaged periodontal tissue, mesenchymal stem cells (MSCs) have attracted much scientific and medical attention. Recently, we generated clumps of MSCs/extracellular matrix (ECM) complexes (C-MSCs), which consist of cells and self-produced ECM. C-MSCs can be transplanted into lesion areas without artificial scaffold to induce tissue regeneration. To develop reliable scaffold-free periodontal tissue regenerative cell therapy by C-MSCs, this study investigated the periodontal tissue regenerative capacity of C-MSCs and the behavior of the transplanted cells. Rat bone marrow-derived MSCs were isolated from rat femur. Confluent cells were scratched using a micropipette tip and then torn off. The sheet was rolled to make a three-dimensional round clump of cells, C-MSCs. Then, ten C-MSCs were grafted into a rat periodontal fenestration defect model. To trace the grafted cells in the defect, PKH26-labeled cells were also employed. Micro-CT and histological analyses demonstrated that transplantation of C-MSCs induced successful periodontal tissue regeneration in the rat periodontal defect model. Interestingly, the majority of the cells in the reconstructed tissue, including cementum, periodontal ligaments, and alveolar bone, were PKH26 positive donor cells, suggesting the direct tissue formation by MSCs. This study demonstrates a promising scaffold-free MSCs transplantation strategy for periodontal disease using C-MSCs and offers the significance of multipotency of MSCs to induce successful periodontal tissue regeneration.

Assessment of the Toxicity of Biocompatible Materials Supporting Bone Regeneration: Impact of the Type of Assay and Used Controls

Assessing the toxicity of new biomaterials dedicated to bone regeneration can be difficult. Many reports focus only on a single toxicity parameter, which may be insufficient for a detailed evaluation of the new material. Moreover, published data frequently do not include control cells exposed to the environment without composite or its extract. Here we present the results of two assays used in the toxicological assessment of materials’ extracts (the integrity of the cellular membrane and the mitochondrial activity/proliferation), and the influence of different types of controls used on the obtained results. Results obtained in the cellular membrane integrity assay showed a lack of toxic effects of all tested extracts, and no statistical differences between them were present. Control cells, cells incubated with chitosan extract or chitosan-bioglass extract were used as a reference in proliferation calculations to highlight the impact of controls used on the result of the experiment. The use of different baseline controls caused variability between obtained proliferation results, and influenced the outcome of statistical analysis. Our findings confirm the thesis that the type of control used in an experiment can change the final results, and it may affect the toxicological assessment of biomaterial.

The Effectiveness of Compartmentalized Bone Graft Sponges Made Using Complementary Bone Graft Materials and Succinylated Chitosan Hydrogels

Bone defects can occur from many causes, including disease or trauma. Bone graft materials (BGMs) have been used to fill damaged areas for the reconstruction of diseased bone tissues since they are cost effective and readily available. However, BGMs quickly disperse around the tissue area, which ultimately leads to it migrating away from the defect after transplantation. We tested chitosan hydrogels as a useful carrier to hold BGMs in the transplantation area. In this study, we synthesized succinylated chitosan (SCS)-based hydrogels with a high decomposition rate and excellent biocompatibility. We confirmed that BGMs were well distributed inside the SCS hydrogel. The SCS-B hydrogel showed a decrease in mechanical properties, such as compressive strength and Young’s modulus, as the succinylation rate increased. SCS-B hydrogels also exhibited a high cell growth rate and bone differentiation rate. Moreover, the in vivo results showed that the SCS hydrogel resorbed into the surrounding tissues while maintaining the BGMs in the transplantation area for up to 6 weeks. These data support the idea that SCS hydrogel can be useful as a bioactive drug carrier for a broad range of biomedical applications.

Clumps of Mesenchymal Stem Cells/Extracellular Matrix Complexes Generated with Xeno-Free Chondro-Inductive Medium Induce Bone Regeneration via Endochondral Ossification

Three-dimensional clumps of mesenchymal stem cells (MSCs)/extracellular matrix (ECM) complexes (C-MSCs) can be transplanted into tissue defect site with no artificial scaffold. Importantly, most bone formation in the developing process or fracture healing proceeds via endochondral ossification. Accordingly, this present study investigated whether C-MSCs generated with chondro-inductive medium (CIM) can induce successful bone regeneration and assessed its healing process. Human bone marrow-derived MSCs were cultured with xeno-free/serum-free (XF) growth medium. To obtain C-MSCs, confluent cells that had formed on the cellular sheet were scratched using a micropipette tip and then torn off. The sheet was rolled to make a round clump of cells. The cell clumps, i.e., C-MSCs, were maintained in XF-CIM. C-MSCs generated with XF-CIM showed enlarged round cells, cartilage matrix, and hypertrophic chondrocytes genes elevation in vitro. Transplantation of C-MSCs generated with XF-CIM induced successful bone regeneration in the SCID mouse calvaria defect model. Immunofluorescence staining for human-specific vimentin demonstrated that donor human and host mouse cells cooperatively contributed the bone formation. Besides, the replacement of the cartilage matrix into bone was observed in the early period. These findings suggested that cartilaginous C-MSCs generated with XF-CIM can induce bone regeneration via endochondral ossification.

Therapeutic Effects of the Addition of Fibroblast Growth Factor-2 to Biodegradable Gelatin/Magnesium-Doped Calcium Silicate Hybrid 3D-Printed Scaffold with Enhanced Osteogenic Capabilities for Critical Bone Defect Restoration

Worldwide, the number of bone fractures due to traumatic and accidental injuries is increasing exponentially. In fact, repairing critical large bone defects remains challenging due to a high risk of delayed union or even nonunion. Among the many bioceramics available for clinical use, calcium silicate-based (CS) bioceramics have gained popularity due to their good bioactivity and ability to stimulate cell behavior. In order to improve the shortcomings of 3D-printed ceramic scaffolds, which do not easily carry growth factors and do not provide good tissue regeneration effects, the aim of this study was to use a gelatin-coated 3D-printed magnesium-doped calcium silicate (MgCS) scaffold with genipin cross-linking for regulating degradation, improving mechanical properties, and enhancing osteogenesis behavior. In addition, we consider the effects of fibroblast growth factor-2 (FGF-2) loaded into an MgCS scaffold with and without gelatin coating. Furthermore, we cultured the human Wharton jelly-derived mesenchymal stem cells (WJMSC) on the scaffolds and observed the biocompatibility, alkaline phosphatase activity, and osteogenic-related markers. Finally, the in vivo performance was assessed using micro-CT and histological data that revealed that the hybrid bioscaffolds were able to further achieve more effective bone tissue regeneration than has been the case in the past. The above results demonstrated that this type of processing had great potential for future clinical applications and studies and can be used as a potential alternative for future bone tissue engineering research, as well as having good potential for clinical applications.

In-vitro cellular and in-vivo investigation of ascorbic acid and β-glycerophosphate loaded gelatin/sodium alginate injectable hydrogels for urinary incontinence treatment

Urinary incontinence is one of the most common disorders especially in adult women. In this study, cellular and in-vivo analyses were performed on (3-glycidyloxypropyl) trimethoxysilane (GPTMS) and CaCl2 cross-linked alginate and gelatin hydrogels containing β-glycerophosphate and ascorbic acid to evaluate the regenerative potential as injectable compression agents for the treatment of urinary incontinence. The hydrogels were prepared with different percentages of components and were named as GA1 (7.2% w/v gelatin, 6% w/v sodium alginate, 0.5:1w/w GPTMS, CaCl2 1% (wt) sodium alginate, 50 μg/mL ascorbic acid, 1.5 mg/mL β-glycerophosphate), GA2 (10% w/v gelatin, 8.5% w/v sodium alginate, 0.5:1 w/w GPTMS, CaCl2 1% (wt) sodium alginate, 50 μg/mL ascorbic acid, 1.5 mg/mL β-glycerophosphate), and GA3 (10% (w/v) gelatin, 8.5% w/v sodium alginate, 1:1 w/w GPTMS, CaCl2 1% (wt) sodium alginate, 50 μg/mL ascorbic acid, 1.5 mg/mL β-glycerophosphate) hydrogels. The results of cell studies showed that although all three samples supported cell adhesion and survival, the cellular behavior of the GA2 sample was better than the other samples. Animal tests were performed on the optimal GA2 sample, which showed that this hydrogel repaired the misfunction tissue in a rat model within 4 weeks and the molecular layer thickness was reached the normal tissue after this duration. It seems that these hydrogels, especially GA2 sample containing 10% (w/v) gelatin, 8.5% (w/v) sodium alginate, 0.5:1 (w/w) GPTMS, CaCl2 1% (wt) sodium alginate, 50 μg/mL ascorbic acid, and 1.5 mg/mL β-glycerophosphate, can act as an injetable hydrogel for urinary incontinence treatment without the need for repeating the injection.