Beta-tricalcium Phosphate Scaffolds Research Articles

Reinforcing β-tricalcium phosphate scaffolds for potential applications in bone tissue engineering: impact of functionalized multi-walled carbon nanotubes

Beta-tricalcium phosphate (β-TCP) scaffolds manufactured through the foam replication method are widely employed in bone tissue regeneration. The mechanical strength of these scaffolds is a significant challenge, partly due to the rheological properties of the original suspension. Various strategies have been explored to enhance the mechanical properties. In this research, β-TCP scaffolds containing varying concentrations (0.25–1.00 wt%) of multi-walled carbon nanotubes (MWCNT) were developed. The findings indicate that the addition of MWCNTs led to a concentration-dependent improvement in the viscosity of β-TCP suspensions. All the prepared slurries exhibited viscoelastic behavior, with the storage modulus surpassing the loss modulus. The three time interval tests revealed that MWCNT-incorporated β-TCP suspensions exhibited faster structural recovery compared to pure β-TCP slurries. Introducing MWCNT modified compressive strength, and the optimal improvement was obtained using 0.75 wt% MWCNT. The in vitro degradation of β-TCP was also reduced by incorporating MWCNT. While the inclusion of carbon nanotubes had a marginal negative impact on the viability and attachment of MC3T3-E1 cells, the number of viable cells remained above 70% of the control group. Additionally, the results demonstrated that the scaffold increased the expression level of osteocalcin, osteoponthin, and alkaline phosphatase genes of adiposed-derived stem cells; however, higher levels of gene expersion were obtained by using MWCNT. The suitability of MWCNT-modified β-TCP suspensions for the foam replication method can be assessed by evaluating their rheological behavior, aiding in determining the critical additive concentration necessary for a successful coating process.

3D printing of multi-scale porous β-tricalcium phosphate scaffolds: Mechanical properties and degradation

Processing-structure-property relationships of 3D-printed multi-scale porous ceramics were investigated. Direct ink writing (DIW) of oil-templated colloidal pastes produced hierarchically porous beta-tricalcium phosphate (TCP) scaffolds. Print architecture and microporosity within filaments were varied, mimicking bone structure. The scaffolds exhibited 60–70 % porosity with interconnected macropores 300–700 μm and microporosity within the filaments at the 10 micron-scale. Varying surfactant and oil concentrations created two micro-pore morphologies – bubble-like pores (emulsion) and channel-like pores (capillary suspension). Emulsion scaffolds were stronger, stiffer and more reliable than capillary suspension scaffolds under both compression and bending. Reducing nozzle diameter and inter-filament distance improved strength and stiffness, at lower density. Immersed at physiological pH, the hierarchically porous TCP scaffolds' strength and modulus degraded at a moderate rate suitable for bone tissue engineering (BTE). Mechanical behavior can be controlled by manipulating process parameters which influence the material's structure. These properties were comparable with trabecular bone, promising for BTE.

Design, In Vitro Evaluation and In Vivo Biocompatibility of Additive Manufacturing Three-Dimensional Printing of β beta-Tricalcium Phosphate Scaffolds for Bone Regeneration

The reconstruction of bone deficiencies remains a challenge due to the limitations of autologous bone grafting. The objective of this study is to evaluate the bone regeneration efficacy of additive manufacturing of tricalcium phosphate (TCP) implants using lithography-based ceramic manufacturing (LCM). LCM uses LithaBone TCP 300 slurry for 3D printing, producing cylindrical scaffolds. Four models of internal scaffold geometry were developed and compared. The in vitro studies included cell culture, differentiation, seeding, morphological studies and detection of early osteogenesis. The in vivo studies involved 42 Wistar rats divided into four groups (control, membrane, scaffold (TCP) and membrane with TCP). In each animal, unilateral right mandibular defects with a total thickness of 5 mm were surgically performed. The animals were sacrificed 3 and 6 months after surgery. Bone neoformation was evaluated by conventional histology, radiology, and micro-CT. Model A (spheres with intersecting and aligned arrays) showed higher penetration and interconnection. Histological and radiological analysis by micro-CT revealed increased bone formation in the grafted groups, especially when combined with a membrane. Our innovative 3D printing technology, combined with precise scaffold design and efficient cleaning, shows potential for bone regeneration. However, further refinement of the technique and long-term clinical studies are crucial to establish the safety and efficacy of these advanced 3D printed scaffolds in human patients.

Patient-specific beta-tricalcium phosphate scaffold for customized alveolar ridge augmentation: a case report

BackgroundBeta-tricalcium phosphate (β-TCP) is a biocompatible ceramic material widely used in the field of oral regeneration. Due to its excellent biological and mechanical properties, it is increasingly utilized for alveolar ridge augmentation or guided bone regeneration (GBR). With recent advances in computer-aided design and manufacturing (CAD/CAM), β-TCP can now be used in the form of digitally designed patient-specific scaffolds for customized bone regeneration (CBR) of advanced defects in a two-stage implant therapy concept. In this case report following the CARE case report guidelines, we present a novel application of a patient-specific β-TCP scaffold in pre-implant mandibular alveolar ridge augmentation.Case presentationA 63-year-old female patient with significant horizontal bone loss in the posterior mandible was treated with a custom β-TCP scaffold in the context of a two-stage backward-planned implant therapy. Cone-beam computed tomography nine months after augmentation showed successful integration of the scaffold into the surrounding bone, allowing implant placement. Follow-up until two years after initial surgery showed excellent oral and peri-implant health.ConclusionsThis case highlights the potential of patient-specific β-TCP scaffolds for alveolar ridge augmentation and their advantage over traditional techniques, including avoidance of xeno-, allo-, and autografts. The results provide encouraging evidence for their use in clinical practice. Patient-specific β-TCP scaffolds may be a promising alternative for clinicians seeking to provide their patients with safe, predictable, and effective alveolar ridge augmentation results in customized bone regeneration procedures.

Evaluation of bone regeneration using human derived-gingival mesenchymal stem cells loaded on beta tricalcium phosphate and hyaluronic acid: an experimental study

Background Healing of critical-sized bone defects (CSDs) is a challenging problem in both clinical and research settings. Aim The present study aimed to assess the regenerative capacity of human gingival-derived mesenchymal stem cells (hGMSCs) loaded on beta-tricalcium phosphate scaffold (β-TCP) and hyaluronic acid (HA) gel in surgically created standardized CSDs in rabbit’s femurs. Materials and methods To achieve this aim, CSDs of 6 mm diameter each, were unilaterally created in femur of adult New Zeeland male white rabbits (n = 18). The rabbits were then divided randomly into three groups and received the following treatment modalities: group A (study group): six defects were treated with hGMSCs loaded on β-TCP scaffold combined with HA gel; group B (positive control group): six defects (n = 6 rabbits) were treated with β-TCP combined with HA gel; group C (negative control group): three defects were left without intervention. Two rabbits from groups A, B and one rabbit from group C were sacrificed at 6 weeks, femurs were dissected out to evaluate bone healing histologically and histomorphometrically. Results The findings of this study indicate that, hGMSCs exhibited fibroblast like morphology and expressed phenotypic MSCs markers (positive for cluster of differentiation CD105 and negative for CD34). Histologically, local application of hGMSCs loaded on β-TCP scaffold with HA gel showed enhanced pattern of bone regeneration as compared to the unloaded scaffold. Histomorphometrically, there was a statistically significant difference in the newly formed bone between the bony defects treated with hGMSCs and control groups. Conclusion GMSCs can be considered as a dependent source of MSCs with bone tissue regenerative capacity.

Comparative bone healing with induced membrane technique (IMT) versus empty defects in septic and aseptic conditions in a novel rabbit humerus model

BackgroundLong bone defects resulting from primary trauma or secondary to debridement of fracture-related infection (FRI) remain a major clinical challenge. One approach often used is the induced membrane technique (IMT). The effectiveness of the IMT in infected versus non-infected settings remains to be definitively established. In this study we present a new rabbit humerus model and compare the IMT approach between animals with prior infection and non-infected equivalents.MethodsA 5 mm defect was created in the humerus of New Zealand White rabbits (n = 53) and fixed with a 2.5 mm stainless steel plate. In the non-infected groups, the defect was either left empty (n = 6) or treated using the IMT procedure (PMMA spacer for 3 weeks, n = 6). Additionally, both approaches were applied in animals that were inoculated with Staphylococcus aureus 4 weeks prior to defect creation (n = 5 and n = 6, respectively). At the first and second revision surgeries, infected and necrotic tissues were debrided and processed for bacteriological quantification. In the IMT groups, the PMMA spacer was removed 3 weeks post implantation and replaced with a beta-tricalcium phosphate scaffold and bone healing observed for a further 10 weeks. Infected groups also received systemic antibiotic therapy. The differences in bone healing between the groups were evaluated radiographically using a modification of the radiographic union score for tibial fractures (RUST) and by semiquantitative histopathology on Giemsa-Eosin-stained sections.ResultsThe presence of S. aureus infection at revision surgery was required for inclusion to the second stage. At the second revision surgery all collected samples were culture negative confirming successful treatment. In the empty defect group, bone healing was increased in the previously infected animals compared with non-infected controls as revealed by radiography with significantly higher RUST values at 6 weeks (p = 0.0281) and at the end of the study (p = 0.0411) and by histopathology with increased cortical bridging (80% and 100% in cis and trans cortical bridging in infected animals compared to 17% and 67% in the non-infected animals). With the IMT approach, both infected and non-infected animals had positive healing assessments.ConclusionWe successfully developed an in vivo model of bone defect healing with IMT with and without infection. Bone defects can heal after an infection with even better outcomes compared to the non-infected setting, although in both cases, the IMT achieved better healing.

BONE DEFECT HEALING USING THE INDUCED MEMBRANE TECHNIQUE AFTER CHRONICALLY INFECTED NONUNION IN A NOVEL RABBIT MODEL

In chronically infected fracture non-unions, treatment requires extensive debridement to remove necrotic and infected bone, often resulting in large defects requiring elaborate and prolonged bone reconstruction. One approach includes the induced membrane technique (IMT), although the differences in outcome between infected and non-infectious aetiologies remain unclear. Here we present a new rabbit humerus model for IMT secondary to infection, and, furthermore, we compare bone healing in rabbits with a chronically infected non-union compared to non-infected equivalents.A 5 mm defect was created in the humerus and filled with a polymethylmethacrylate (PMMA) spacer or left empty (n=6 per group). After 3 weeks, the PMMA spacer was replaced with a beta-tricalcium phosphate (chronOs, Synthes) scaffold, which was placed within the induced membrane and observed for a further 10 weeks. The same protocol was followed for the infected group, except that four week prior to treatment, the wound was inoculated with Staphylococcus aureus (4×106 CFU/animal) and the PMMA spacer was loaded with gentamicin, and systemic therapy was applied for 4 weeks prior to chronOs application.All the animals from the infected group were culture positive during the first revision surgery (mean 3×105 CFU/animal, n= 12), while at the second revision, after antibiotic therapy, all the animals were culture negative. The differences in bone healing between the non-infected and infected groups were evaluated by radiography and histology. The initially infected animals showed impaired bone healing at euthanasia, and some remnants of bacteria in histology. The non-infected animals reached bone bridging in both empty and chronOs conditions.We developed a preclinical in vivo model to investigate how bacterial infection influence bone healing in large defects with the future aim to explore new treatment concepts of infected non-union.

MiR-199a-5P promotes osteogenic differentiation of human stem cells from apical papilla via targeting IFIT2 in apical periodontitis.

Periapical alveolar bone loss is the common consequence of apical periodontitis (AP) caused by persistent local inflammation around the apical area. Human stem cells from apical papilla (hSCAPs) play a crucial role in the restoration of bone lesions during AP. Studies have recently identified the critical role of microRNAs (miRNAs) involved in AP pathogenesis, but little is known about their function and potential molecular mechanism, especially in the osteogenesis of hSCAPs during AP. Here, we investigated the role of clinical sample-based specific miRNAs in the osteogenesis of hSCAPs. Differential expression of miRNAs were detected in the periapical tissues of normal and patients with AP via transcriptomic analysis, and the expression of miR-199a-5p was confirmed by qRT-PCR. Treatment of hSCAPs with miR-199a-5p mimics while loaded onto beta-tricalcium phosphate (β-TCP) ceramic particle scaffold to explore its effect on osteogenesis in vivo. RNA binding protein immunoprecipitation (RIP) and Luciferase reporter assay were conducted to identify the target gene of miR-199a-5p. The expression of miR-199a-5p was decreased in the periapical tissues of AP patients, and miR-199a-5p mimics markedly enhanced cell proliferation and osteogenic differentiation of hSCAPs, while miR-199a-5p antagomir dramatically attenuated hSCAPs osteogenesis. Moreover, we identified and confirmed Interferon Induced Protein with Tetratricopeptide Repeats 2 (IFIT2) as a specific target of miR-199a-5p, and silencing endogenous IFIT2 expression alleviated the inhibitory effect of miR-199a-5p antagomir on the osteogenic differentiation of hSCAPs. Furthermore, miR-199a-5p mimics transfected hSCAPs loaded onto beta-tricalcium phosphate (β-TCP) scaffolds induced robust subcutaneous ectopic bone formation in vivo. These results strengthen our understanding of predictors and facilitators of the key AP miRNAs (miR-199a-5p) in bone lesion repair under periapical inflammatory conditions. And the regulatory networks will be instrumental in exploring the underlying mechanisms of AP and lay the foundation for future regenerative medicine based on dental mesenchymal stem cells.

Metal-Organic Framework Functionalized Bioceramic Scaffolds with Antioxidative Activity for Enhanced Osteochondral Regeneration.

Osteoarthritis (OA) is a degenerative disease that often causes cartilage lesions and even osteochondral damage. Osteochondral defects induced by OA are accompanied by an inflammatory arthrosis microenvironment with overproduced reactive oxygen species (ROS), resulting in the exacerbation of defects and difficulty regenerating osteochondral tissues. Therefore, it is urgently needed to develop osteochondral scaffolds that can not only promote the integrated regeneration of cartilage and subchondral bone, but also possess ROS-scavenging ability to protect tissues from oxidative stress. Herein, zinc-cobalt bimetallic organic framework (Zn/Co-MOF) functionalized bioceramic scaffolds are designed for repairing osteochondral defects under OA environment. By functionalizing Zn/Co-MOF on the 3D-printed beta-tricalcium phosphate (β-TCP) scaffolds, the Zn/Co-MOF functionalized β-TCP (MOF-TCP) scaffolds with broad-spectrum ROS-scavenging ability are successfully developed. Benefiting from its catalytic active sites and degradation products, Zn/Co-MOF endows the scaffolds with excellent antioxidative and anti-inflammatory properties to protect cells from ROS invasion, as well as dual-bioactivities of simultaneously inducing osteogenic and chondrogenic differentiation in vitro. Furthermore, in vivo results confirm that MOF-TCP scaffolds accelerate the integrated regeneration of cartilage and subchondral bone in severe osteochondral defects. This study offers a promising strategy for treating defects induced by OA as well as other inflammatory diseases.

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.

Impact of Fluid Dynamics on the Viability and Differentiation Capacity of 3D-Cultured Jaw Periosteal Cells

Perfused bioreactor systems are considered to be a promising approach for the 3D culturing of stem cells by improving the quality of the tissue-engineered grafts in terms of better cell proliferation and deeper penetration of used scaffold materials. Our study aims to establish an optimal perfusion culture system for jaw periosteal cell (JPC)-seeded scaffolds. For this purpose, we used beta-tricalcium phosphate (β-TCP) scaffolds as a three-dimensional structure for cell growth and osteogenic differentiation. Experimental set-ups of tangential and sigmoidal fluid configurations with medium flow rates of 100 and 200 µL/min were applied within the perfusion system. Cell metabolic activities of 3D-cultured JPCs under dynamic conditions with flow rates of 100 and 200 µL/min were increased in the tendency after 1, and 3 days of culture, and were significantly increased after 5 days. Significantly higher cell densities were detected under the four perfused conditions compared to the static condition at day 5. However, cell metabolic and proliferation activity under dynamic conditions showed flow rate independency in our study. In this study, dynamic conditions increased the expression of osteogenic markers (ALPL, COL1A1, RUNX2, and OCN) compared to static conditions and the tangential configuration showed a stronger osteogenic effect than the sigmoidal flow configuration.

Multiple channels with interconnected pores in a bioceramic scaffold promote bone tissue formation

Insufficient nutrition exchange and limited transportation of blood supply in a porous only scaffold often hinder bone formation, even though the porous scaffold is loaded with cells or growth factors. To overcome these issues, we developed a cell- and growth factor-free approach to induce bone formation in a critical-size bone defect by using an interconnected porous beta-tricalcium phosphate (β-TCP) scaffold with multiple channels. In vitro cell experimental results showed that multiple channels significantly promoted cell attachment and proliferation of human bone marrow mesenchymal stem cells, stimulated their alkaline phosphatase activity, and up-regulated the osteogenic gene expression. Multiple channels also considerably stimulated the expression of various mechanosensing markers of the cells, such as focal adhesion kinase, filamentous actin, and Yes-associated protein-1 at both static and dynamic culturing conditions. The in vivo bone defect implantation results demonstrated more bone formation inside multiple-channeled scaffolds compared to non-channeled scaffolds. Multiple channels prominently accelerated collagen type I, bone sialoprotein and osteocalcin protein expression. Fluorochrome images and angiogenic marker CD31 staining exhibited more mineral deposition and longer vasculature structures in multiple-channeled scaffolds, compared to non-channeled scaffolds. All the findings suggested that the creation of interconnected multiple channels in the porous β-TCP scaffold is a very promising approach to promote bone tissue regeneration.

4: Bone Tissue Engineering in the Growing Skull: A Short-term Study Using Dipyridamole-loaded 3D-printed Beta-tricalcium Phosphate Scaffolds to Repair Critically Sized Calvarial Defects in a Translational Animal Model

Purpose:The repair of bony defects remains a challenge to reconstructive surgeons due to limitations of current bone replacement techniques. Previous studies have shown that dipyridamole-loaded 3D-printed bioceramic (DIPY-3DPBC) scaffolds composed of 100% beta-tricalcium phosphate regenerate bone across critically sized defects in multiple in vivo models. However, a critical step to translating this bone tissue engineering construct to bedside is its successful application in a pre-clinical translational model that mimics biologic similarities to humans. Pigs are considered to be an excellent species for bone tissue engineering studies due to their similarities to humans both in bone biology and wound healing. In this short-term study, our group implanted DIPY-3DPBC scaffolds in an effort to repair critically sized bony defects in a translational, skeletally immature, growing craniofacial pig model. The purpose was to evaluate the performance of these 3D-printed constructs in terms of bone growth and scaffold absorption.Methods:Unilateral calvarial defects were created in six-week-old Göttingen minipigs (n=12). Four defects were left empty to serve as negative controls, four defects were filled with a 1000μM DIPY-3DPBC scaffold with a closed scaffold design (contains a solid barrier on the ectocortical side of the scaffold to prevent soft tissue infiltration), and four defects were filled with a 1000μM DIPY-3DPBC scaffold with an open design (no solid barrier on the ectocortical side). Animals were euthanized at 12-weeks post-operatively. Calvaria were subjected to micro-computed tomography (CT) for volumetric (3D) analysis. 3D reconstruction was performed using Amira software to quantitatively assess percent bone volume occupying the defect space (bone volume/total volume x 100%) and percent scaffold volume occupying the defect space (scaffold volume/total volume x 100%). A generalized linear mixed model (GLMM) was used to determine significance between groups. Results are presented using means with corresponding 95% confidence intervals and p-values.Results:Significantly higher mean (± 95% CI) percent bone volume was observed in calvarial defects treated with the scaffolds compared to negative controls (42.6% ± 8.6% vs 4.6% ± 12.1%, p≤0.001). Defects that were filled with closed cap scaffolds had a significantly greater mean percent bone volume compared to defects filled with the open scaffolds (52.9% ± 12.1% vs 32.3% ± 12.1%, p=0.024). No significant difference was detected between percent scaffold volume between closed and open scaffolds (4.4% ± 1.6% vs 3.7% ± 1.6%, p=0.493).Conclusions:The results from this work indicate an effective bone tissue engineering scaffold design that is able to regenerate bone across critically sized calvarial defects in a short-term skeletally immature, growing translational pig model.

Local administration of HMGB-1 promotes bone regeneration on the critical-sized mandibular defects in rabbits

Reconstruction of a critical-sized osseous defect is challenging in maxillofacial surgery. Despite novel treatments and advances in supportive therapies, severe complications including infection, nonunion, and malunion can still occur. Here, we aimed to assess the use of a beta-tricalcium phosphate (β-TCP) scaffold loaded with high mobility group box-1 protein (HMGB-1) as a novel critical-sized bone defect treatment in rabbits. The study was performed on 15 specific pathogen-free New Zealand rabbits divided into three groups: Group A had an osseous defect filled with a β-TCP scaffold loaded with phosphate-buffered saline (PBS) (100 µL/scaffold), the defect in group B was filled with recombinant human bone morphogenetic protein 2 (rhBMP-2) (10 µg/100 µL), and the defect in group C was loaded with HMGB-1 (10 µg/100 µL). Micro-computed tomography (CT) examination demonstrated that group C (HMGB-1) showed the highest new bone volume ratio, with a mean value of 66.5%, followed by the group B (rhBMP-2) (31.0%), and group A (Control) (7.1%). Histological examination of the HMGB-1 treated group showed a vast area covered by lamellar and woven bone surrounding the β-TCP granule remnants. These results suggest that HMGB-1 could be an effective alternative molecule for bone regeneration in critical-sized mandibular bone defects.

Biocompatibility of a HA/β-TCP/C Scaffold as a Pulp-Capping Agent for Vital Pulp Treatment: An In Vivo Study in Rat Molars

Bioceramic materials possess desirable biological properties, highlighting their non-reactivity and osteoconductivity. Their use has been extended in vital pulp treatment. The purpose of this study was to evaluate and compare the effects of beta-tricalcium phosphate (β-TCP), hydroxyapatite (HA), and collagen (C) scaffold with mineral trioxide aggregate (MTA) on the vital pulp of rat molars. Thirty-two molars of Sprague–Dawley rats underwent direct pulp capping with β-TCP/HA/C (n = 16) and MTA (n = 16). After 30 days, the following parameters were evaluated in the tested samples: the degree of pulp inflammation and pulp vitality, the presence of reparative dentin, the homogeneity of the odontoblastic layer, and the presence of pulp fibrosis. No statistically significant differences were observed between HA/β-TCP/C and MTA in terms of the degree of inflammation (p = 0.124). Significant differences were found in reparative dentin formation between the treatment groups (p = 0.0005). Dentin bridge formation was observed in the MTA-treated group. The local action of HA/β-TCP/C is similar to that of MTA when used as an agent for pulp vital treatment in terms of absence of inflammation and maintenance of pulp vitality, although there are significant differences between both materials regarding the formation of dentin bridges.

Fabrication of trabecular-like beta-tricalcium phosphate biomimetic scaffolds for bone tissue engineering

The introduction of 3D printing into the manufacturing of ceramic components offers new possibilities to fabricate porous bioceramic scaffold with biomimetic morphology, customized-designed shape and suitable mechanical property for bone tissue engineering. However, most of 3D printed porous ceramic scaffolds are prepared from the array of unit cells, which do not exploit the whole potential of additive manufacturing. In this paper, a novel biomimetic porous beta-tricalcium phosphate (β-TCP) scaffolds with trabecular-like morphology were obtained based on three dimension (3D) Voronoi tessellation method and generated design. This bionic pore structure is fabricated via photopolymer-based digital light processing (DLP) 3D printing technique, a suitable 30 wt% β-TCP ceramic slurry with the addition of adjuvants was prepared. After optimized debinding-sintering process according the TG-DSC analysis, the β-TCP scaffolds showed fully interconnected trabecular-like pore structure with tailorable pore size (360 μm–1200 μm) and porosity (45%–75%) and compact microstructure. Combining compressive tests and finite element analysis (FEA), the relationship between inputting parameters, pore structure and compressive strength is investigated. Thus, the mechanical strength of the trabecular-like β-TCP scaffolds could be predicted and tuned in the initial generated design stage. In addition, the shrinkage ratio and XRD pattern are also detected. The method proposed in this study may provide an efficient bionic design intended for tissue engineering applications.

A Multicenter, Retrospective, Case Series of Patients With Charcot Neuroarthropathy Deformities Undergoing Arthrodesis Utilizing Recombinant Human Platelet-derived Growth Factor With Beta-Tricalcium Phosphate

Charcot neuroarthropathy has traditionally been treated using both nonsurgical and surgical strategies. Recently, orthobiologics have been used to promote arthrodesis in Charcot reconstructions, obviating the need for bone graft in some cases. Recombinant human platelet-derived growth factor BB homodimer (rhPDGF-BB) in combination with beta-tricalcium phosphate scaffold (β-TCP) is a bone graft substitute shown to have comparable efficacy to autograft in incidence of foot and ankle fusion. This multicenter, consecutive case series analyzed patients undergoing Charcot reconstructions utilizing rhPDGF-BB/β-TCP for joint fusion. In this cohort, 98 patients (62.24% male) with a mean age of 62.82 ± 10.28 years (range 40-87) had a fusion incidence of 217 of 223 joints (97.31%) with a mean time to fusion of 13.09 ± 4.87 weeks (range 6-30). There were 6 nonunions in the patient population. Fusion was defined as ≥50% osseous bridging based on computed tomography and/or radiographic consolidation, in addition to clinical findings. With an overall complication rate of 26.53% (26/98), adverse events occurring in more than 1 patient limb included hardware failures (n = 7, 7.14%), infection (n = 4, 4.08%), wound dehiscence (n = 4, 4.08%), amputation (n = 3, 3.06%), and death (n = 2, 2.04%). There were no adverse events related to the grafting material. From this review, we found rhPDGF-BB/β-TCP to be a safe and effective graft material that can be considered a viable alternative to autograft, even in high-risk patients such as those with Charcot neuroarthropathy.

Bioinspired scaffolds with hierarchical structures for tailored mechanical behaviour and cell migration

Replacement and regeneration of damaged bone, particularly for those defects with critical size, are still major challenges in orthopaedic surgery. The conventional bone implants, normally with poor internal architecture design, may cause significant issues owing to the mechanical and structural mismatches between target bone and the implants. In this work, as inspired by hierarchical natural bone, for the first time, we developed hydroxyapatite (HA) and beta-tricalcium phosphate (β-TCP) scaffolds with three-level hierarchical structures across macro to nano scale using combined 3D printing (3DP) and freeze casting routines. It is clear these hierarchical porous scaffolds significantly enhance cell penetration (over 7 times) while maintaining cell proliferation ability. With three levels of hierarchies, the overall mechanical behaviour of the scaffolds can be tailored to be comparable to general cancellous bone (ranging from 1 to 6 MPa), demonstrating great potential for practical applications. Additionally, the combination of nanoindentation and mechanics model makes it possible to predict the mechanical behaviour of scaffolds at micro and macro scales.

Jaw Periosteal Cells Seeded in Beta-Tricalcium Phosphate Inhibit Dendritic Cell Maturation.

Mesenchymal stem cells (MSCs) have gained attraction not only in the field of regenerative medicine but also in the field of autoimmune disease therapies or organ transplantation due to their immunoregulatory and/or immunosuppressive features. Dendritic cells (DCs) play a crucial role in initiating and regulating immune reactions by promoting antigen-specific T cell activation. In this study, we investigated the effect of human jaw periosteal progenitor cells (JPCs) seeded in beta-tricalcium phosphate (β-TCP) scaffolds on monocyte-derived DC differentiation. Significantly lower numbers of differentiated DCs were observed in the presence of normal (Co) and osteogenically induced (Ob) JPCs-seeded β-TCP constructs. Gene expression analysis revealed significantly lower interleukin-12 subunit p35 (IL-12p35) and interleukin-12 receptor beta 2 (IL-12Rβ2) and pro-inflammatory cytokine interferon-gamma (IFN-γ) levels in DCs under Ob conditions, while interleukin-8 (IL-8) gene levels were significantly increased. Furthermore, in the presence of JPCs-seeded β-TCP constructs, interleukin-10 (IL-10) gene expression was significantly induced in DCs, particularly under Ob conditions. Analysis of DC protein levels shows that granulocyte-colony stimulating factor (G-CSF) was significantly upregulated in coculture groups. Our results indicate that undifferentiated and osteogenically induced JPCs-seeded β-TCP constructs have an overall inhibitory effect on monocyte-derived DC maturation.

Effects of Cryopreservation on Cell Metabolic Activity and Function of Biofabricated Structures Laden with Osteoblasts.

Biofabrication and maturation of bone constructs is a long-term task that requires a high degree of specialization. This specialization falls onto the hierarchy complexity of the bone tissue that limits the transfer of this technology to the clinic. This work studied the effects of the short-term cryopreservation on biofabricated osteoblast-containing structures, with the final aim to make them steadily available in biobanks. The biological responses studied include the osteoblast post-thawing metabolic activity and the recovery of the osteoblastic function of 3D-bioprinted osteoblastic structures and beta tricalcium phosphate (β-TCP) scaffolds infiltrated with osteoblasts encapsulated in a hydrogel. The obtained structures were cryopreserved at −80 °C for 7 days using dimethyl sulfoxide (DMSO) as cryoprotectant additive. After thawing the structures were cultured up to 14 days. The results revealed fundamental biological aspects for the successful cryopreservation of osteoblast constructs. In summary, immature osteoblasts take longer to recover than mature osteoblasts. The pre-cryopreservation culture period had an important effect on the metabolic activity and function maintain, faster recovering normal values when cryopreserved after longer-term culture (7 days). The use of β-TCP scaffolds further improved the osteoblast survival after cryopreservation, resulting in similar levels of alkaline phosphatase activity in comparison with the non-preserved structures. These results contribute to the understanding of the biology of cryopreserved osteoblast constructs, approaching biofabrication to the clinical practice.