Craniomaxillofacial Bone Research Articles

Inflammatory Licensed hMSCs Exhibit Enhanced Immunomodulatory Capacity in a Biomaterial Mediated Manner.

Craniomaxillofacial (CMF) bone injuries represent particularly challenging environments for regenerative healing due to their large sizes, irregular and unique defect shapes, angiogenic requirements, and mechanical stabilization needs. These defects also exhibit a heightened inflammatory environment that can complicate the healing process. This study investigates the influence of the initial inflammatory stance of human mesenchymal stem cells (hMSCs) on key osteogenic, angiogenic, and immunomodulatory criteria when cultured in a class of mineralized collagen scaffolds under development for CMF bone repair. We previously showed that changes in scaffold pore anisotropy and glycosaminoglycan content can significantly alter the regenerative activity of both MSCs and macrophages. While MSCs are known to adopt an immunomodulatory phenotype in response to inflammatory stimuli, here, we define the nature and persistence of MSC osteogenic, angiogenic, and immunomodulatory phenotypes in a 3D mineralized collagen environment, and further, whether changes to scaffold architecture and organic composition can blunt or accentuate this response as a function of inflammatory licensing. Notably, we found that a one-time licensing treatment of MSCs induced higher immunomodulatory potential compared to basal MSCs as observed by sustained immunomodulatory gene expression throughout the first 7 days as well as an increase in immunomodulatory cytokine (PGE2 and IL-6) expression throughout a 21-day culture period. Further, heparin scaffolds facilitated higher osteogenic cytokine secretion but lower immunomodulatory cytokine secretion compared to chondroitin-6-sulfate scaffolds. Anisotropic scaffolds facilitated higher secretion of both osteogenic protein OPG and immunomodulatory cytokines (PGE2 and IL-6) compared to isotropic scaffolds. These results highlight the importance of scaffold properties on the sustained kinetics of cell response to an inflammatory stimulus. The development of a biomaterial scaffold capable of interfacing with hMSCs to facilitate both immunomodulatory and osteogenic responses is an essential next step to determining the quality and kinetics of craniofacial bone repair.

Is three-point fixation needed to mechanically stabilize zygomaticomaxillary complex fractures?

Fixation is critical in zygomaticomaxillary complex (ZMC) fractures to avoid malunion; however, controversy exists as to how much hardware is required to achieve adequate stability. Current fixation regimens may not represent the minimum stabilization needed for uneventful healing. Craniomaxillofacial (CMF) computational models have shown limited load transmission through the infraorbital rim (IOR), and a previous experimental study of ZMC fractures has suggested that IOR plating does not alter CMF bone strain patterns. This study aimed to measure the impact of stabilization on fracture site displacement under muscle loading, testing the hypothesis that three-point fixation is not critical for ZMC fracture stability. Four ZMC complex fractures were simulated on two cadaveric samples and stabilized with three-point plating. Displacements simulating mouth openings of 20mm and 30mm were applied to the mandible using a custom apparatus. Fracture gap displacement under load was measured at multiple points along each fracture line, and bone strain was captured using a combination of uniaxial and rosette gauges. Data capture was repeated with the IOR plate removed (two-point fixation) and with the zygomaticomaxillary plate removed (one-point fixation). Fracture displacement under muscle loading was consistent, with gaps of less than 1mm in 95% of cases (range 0.05-1.44mm), reflecting clinical stability. Large variabilities were observed in the strain measurements, which may reflect the complexity of CMFS load patterns and the sensitivity of strain values to gauge placement. This study supports the concept of hardware reduction, suggesting that two-point (or even one-point) fixation may provide sufficient stability for a ZMC fracture under applied muscle loading.

Fabrication of bFGF/polydopamine-loaded PEEK implants for improving soft tissue integration by upregulating Wnt/β-catenin signaling

The difficulties associated with polyetheretherketone (PEEK) implants and soft tissue integration for craniomaxillofacial bone repair have led to a series of complications that limit the clinical benefits. In this study, 3D printed multi-stage microporous PEEK implants coated with bFGF via polydopamine were fabricated to enhance PEEK implant-soft tissue integration. Multistage microporous PEEK scaffolds prepared by sulfonation of concentrated sulfuric acid were coated with polydopamine, and then used as templates for electrophoretic deposition of bFGF bioactive factors. Achieving polydopamine and bFGF sustained release, the composite PEEK scaffolds possessed good mechanical properties, hydrophilicity, protein adhesion properties. The in vitro results indicated that bFGF/polydopamine-loaded PEEK exhibited good biocompatibility to rabbit embryonic fibroblasts (REF) by promoting cell proliferation, adhesion, and migration. Ribonucleic acid sequencing (RNA-seq) revealed that bFGF/polydopamine-loaded PEEK implants significantly upregulated the expression of genes and proteins associated with soft tissue integration and activated Wnt/β-catenin signaling in biological processes, but related expression of genes and proteins was significantly downregulated when the Wnt/β-catenin signaling was inhibited. Furthermore, in vivo bFGF/polydopamine-loaded PEEK implants exhibited excellent performance in improving the growth and adhesion of the surrounding soft tissue. In summary, bFGF/polydopamine-loaded PEEK implants possess soft tissue integration properties by activating the Wnt/β-catenin signaling, which have a potential translational clinical application in the future.

Wnt/β-Catenin Signaling in Craniomaxillofacial Osteocytes.

There is a growing appreciation within the scientific community that cells exhibit regional variation. Whether the variation is attributable to differences in embryonic origin or anatomical location and mechanical loading has not been elucidated; what is clear, however, is that adult cells carry positional information that ultimately affects their functions. The purpose of this review is to highlight the functions of osteocytes in the craniomaxillofacial (CMF) skeleton as opposed to elsewhere in the body, and in doing so gain mechanistic insights into genetic conditions and chemically-induced diseases that particularly affect this region of our anatomy. In the CMF skeleton, elevated Wnt/β-catenin signaling affects not only bone mass and volume, but also mineralization of the canalicular network and osteocyte lacunae. Aberrant elevation in the Wnt/β-catenin pathway can also produce micropetrosis and osteonecrosis of CMF bone, presumably due to a disruption in the signaling network that connects osteocytes to one another, and to osteoblasts on the bone surface.

Wnt7b: Is It an Important Factor in the Bone Formation Process after Calvarial Damage?

Previous studies found that Wnt7b played a unique and indispensable role in the process of osteoblast differentiation and could accelerate the repair of bone loss. However, what is the role of Wnt7B in osteogenesis? Is it possible to increase the expression of Wnt7b to promote the repair of skull defects? This study intends to provide the basic data for the application of Wnt7b in the treatment of craniomaxillofacial bone repair. A calvarial defect mouse model that could induce Wnt7b overexpression was established. Three days after the operation, the mice in each group were intraperitoneally injected with tamoxifen (TAM) or oil eight times every other day. There were three groups. The TAMc group (R26Wnt7b/Wnt7b) was injected with tamoxifen. The Oil group (3.2 kb Col1-Cre-ERT2; R26Wnt7b/Wnt7b) was injected with oil. The TAM group (3.2 kb Col1-Cre-ERT2; R26Wnt7b/Wnt7b) was injected with tamoxifen. Four weeks after the surgery, micro-CT scanning was utilized to observe new bone formation and compare the ability to form new bone around the defect area. Four weeks after the operation, bone healing conditions were measured by using micro-CT scanning. The defect area of the TAM group was smaller than that of the other groups. Similarly, the bone volume fraction (BV/TV) significantly increased (p < 0.05), the trabecular number (Tb.N) increased, and the trabecular separation (Tb.Sp) decreased. Wnt7b participates in the bone formation process after calvarial damage, indicating the important role of Wnt7b in osteogenesis.

Click-based injectable bioactive PEG-hydrogels guide rapid craniomaxillofacial bone regeneration by the spatiotemporal delivery of rhBMP-2.

Craniomaxillofacial bone defects result in physical and psychological dual injuries making the promotion or acceleration of bone regeneration imperative. In this work, a fully biodegradable hydrogel is facilely prepared via thiol-ene "click" reactions under human physiological conditions using multifunctional poly(ethylene glycol) (PEG) derivatives as precursors. This hydrogel shows excellent biological compatibility, enough mechanical strength, a low swelling rate and an appropriate degradation rate. Rat bone marrow mesenchymal stem cells (rBMSCs) can survive and proliferate on/in the PEG hydrogel and differentiate into osteogenic cells. The PEG hydrogel can also effectively load rhBMP-2 through the above "click" reaction. Under the physical barrier of the chemically crosslinked hydrogel network, the spatiotemporal release of rhBMP-2 effectively promotes the proliferation and osteogenic differentiation of rBMSCs at a loading concentration of 1 μg ml-1. Finally, based on a rat calvarial critical-size defect model, the rhBMP-2 immobilized hydrogel loaded with rBMSCs basically accomplishes the repair and regeneration within 4 weeks featured by remarkably enhanced osteogenesis and angiogenesis. The click-based injectable bioactive PEG hydrogel developed in the present study is a new type of bone substitute with great expectations in future clinical applications.

Functional Hydrogels and Their Applications in Craniomaxillofacial Bone Regeneration.

Craniomaxillofacial bone defects are characterized by an irregular shape, bacterial and inflammatory environment, aesthetic requirements, and the need for the functional recovery of oral-maxillofacial areas. Conventional clinical treatments are currently unable to achieve high-quality craniomaxillofacial bone regeneration. Hydrogels are a class of multifunctional platforms made of polymers cross-linked with high water content, good biocompatibility, and adjustable physicochemical properties for the intelligent delivery of goods. These characteristics make hydrogel systems a bright prospect for clinical applications in craniomaxillofacial bone. In this review, we briefly demonstrate the properties of hydrogel systems that can come into effect in the field of bone regeneration. In addition, we summarize the hydrogel systems that have been developed for craniomaxillofacial bone regeneration in recent years. Finally, we also discuss the prospects in the field of craniomaxillofacial bone tissue engineering; these discussions can serve as an inspiration for future hydrogel design.

Preliminary Application Research of 3D Bioprinting in Craniofacial Reconstruction.

In recent years, 3-dimensional (3D) printing has been widely used in regenerative medicine research and other fields because of its ability to customize macroscopic morphology and precisely control microstructure. Polymer scaffolds are 1 of the commonly used 3D bioprinting materials for defect repair and have recently been a research focus. Our article explored the bone-formation accelerating effect of 3D-printed porous scaffold Poly(glycerol sebacate) [PGS] in the critical bone defect of an enhancing rabbit mandibular model. Also, we overview and summarize the classification of 3D bioprinting materials and prospects for their various application scenarios in craniofacial reconstruction surgery. A PGS elastomer scaffold was prepared by polymerizing equimolar amounts of sebacic acid and glycerol using a biological 3D printer. Six male New Zealand white rabbits were prepared (3 for the control group and 3 for the PGS group), each weighing 3kg. Osteotomy was performed at the anterior edge of the ascending ramus of the mandible with a bone saw to open the 8mm defect. Defects of the control group were empty, and defects of the PGS group were put into 8mm-wide PGS elastomer scaffolds. The rabbits were euthanized 6 weeks after the operation, and the postoperative mandibles were collected. Information (presence or absence of pus from infection, nonunion, degree of macroscopic bone healing) was recorded, and the skeletal tissue was fixed in a paraformaldehyde solution. The mandible on the enhanced side was significantly longer than that on the opposite side, and the contralateral incisor was hyperplasia. The mandibles of rabbits in each group healed well, and there was no obvious local infection and purulence. The gross specimen appearance showed that both ends of the defect were connected. When comparing the reconstructed mandibles of the two groups, it is apparent that the width and thickness of the new bone in the PGS group were significantly better than that in the control group. This article verifies the effect of 3D polypore PGS scaffolds in animal craniomaxillofacial bone defects and introduces various application scenarios of 3D printing materials in craniomaxillofacial reconstruction surgery. There are quite good application prospects for 3D bioprinting in animal experiments and even clinical treatment of craniofacial defects.

Amnion and chorion matrix maintain hMSC osteogenic response and enhance immunomodulatory and angiogenic potential in a mineralized collagen scaffold.

Craniomaxillofacial (CMF) bone injuries present a major surgical challenge and cannot heal naturally due to their large size and complex topography. We are developing a mineralized collagen scaffold that mimics extracellular matrix (ECM) features of bone. These scaffolds induce in vitro human mesenchymal stem cell (hMSC) osteogenic differentiation and in vivo bone formation without the need for exogenous osteogenic supplements. Here, we seek to enhance pro-regenerative potential via inclusion of placental-derived products in the scaffold architecture. The amnion and chorion membranes are distinct components of the placenta that each have displayed anti-inflammatory, immunomodulatory, and osteogenic properties. While potentially a powerful modification to our mineralized collagen scaffolds, the route of inclusion (matrix-immobilized or soluble) is not well understood. Here we compare the effect of introducing amnion and chorion membrane matrix versus soluble extracts derived from these membranes into the collagen scaffolds on scaffold biophysical features and resultant hMSC osteogenic activity. While inclusion of amnion and chorion matrix into the scaffold microarchitecture during fabrication does not influence their porosity, it does influence compression properties. Incorporating soluble extracts from the amnion membrane into the scaffold post-fabrication induces the highest levels of hMSC metabolic activity and equivalent mineral deposition and elution of the osteoclast inhibitor osteoprotegerin (OPG) compared to the conventional mineralized collagen scaffolds. Mineralized collagen-amnion composite scaffolds elicited enhanced early stage osteogenic gene expression (BGLAP, BMP2), increased immunomodulatory gene expression (CCL2, HGF, and MCSF) and increased angiogenic gene expression (ANGPT1, VEGFA) in hMSCs. Mineralized collagen-chorion composite scaffolds promoted immunomodulatory gene expression in hMSCs (CCL2, HGF, and IL6) while unaffecting osteogenic gene expression. Together, these findings suggest that mineralized collagen scaffolds modified using matrix derived from amnion and chorion membranes represent a promising environment conducive to craniomaxillofacial bone repair.

ETV2 promotes osteogenic differentiation of human dental pulp stem cells through the ERK/MAPK and PI3K-Akt signaling pathways

BackgroundThe repair of cranio-maxillofacial bone defects remains a formidable clinical challenge. The Ets variant 2 (ETV2) transcription factor, which belongs to the E26 transformation-specific (ETS) family, has been reported to play a key role in neovascularization. However, the role of ETV2 in the osteogenesis of human dental pulp stem cells (hDPSCs) remains unexplored.MethodsTransgenic overexpression of ETV2 was achieved using a lentiviral vector, based on a Dox-inducible system. The effects of Dox-induced overexpression of ETV2 on the osteogenesis of hDPSCs were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR), western blot, immunofluorescence staining, alkaline phosphatase (ALP) staining, and Alizarin Red S (ARS) staining. Additionally, RNA-sequencing (RNA-Seq) analysis was performed to analyze the underlying mechanisms of ETV2-induced osteogenesis. Additionally, the role of ETV2 overexpression in bone formation in vivo was validated by animal studies with a rat calvarial defect model and a nude mice model.ResultsOur results demonstrated that ETV2 overexpression significantly upregulated the mRNA and protein expression levels of osteogenic markers, markedly enhanced ALP activity, and promoted matrix mineralization of hDPSCs. Moreover, the results of RNA-Seq analysis and western blot showed that the ERK/MAPK and PI3K-Akt signaling pathways were activated upon transgenic overexpression of ETV2. The enhanced osteogenic differentiation of hDPSCs due to ETV2 overexpression was partially reversed by treatment with inhibitors of ERK/MAPK or PI3K-AKT signaling. Furthermore, the results of in vivo studies demonstrated that ETV2 overexpression improved bone healing in a rat calvarial defect model and increased ectopic bone formation in nude mice.ConclusionsCollectively, our results indicated that ETV2 overexpression exerted positive effects on the osteogenesis of hDPSCs, at least partially via the ERK/MAPK and PI3K/AKT signaling pathways.

AN INTRAOPERATIVE CORRECTION METHOD OF MAXILLOFACIAL SURGERY BASED ON LASER SCANNER

The oral craniomaxillofacial region is adjacent to the cranium with complex anatomical structures. Therefore, precise and minimally invasive surgeries are essential for preserving its function and reconstructing its appearance. The most commonly used method is optical surgical navigation technology. Compared with preoperative computed tomography image registration, the accuracy of intraoperative navigation can be calculated to help surgeons judge the effect of surgery. This study aimed to introduce laser scanning in craniomaxillofacial bone surgery, so as to create a new method of navigation accuracy verification, and compare the image with the preoperative plan. The experimental results of this study showed that the average accuracy of point verification calculation was greater than 3[Formula: see text]mm, which was much greater than the average accuracy of laser scanning plane verification based on mixed Student [Formula: see text] distribution (less than 1[Formula: see text]mm), and a statistically significant difference was found between them. It was demonstrated that relying solely on individual points to depict the operation of the entire bone surface was insufficient in navigation surgery.

PREFACE: A SPECIAL SELECTION ON EMERGING TECHNIQUES FOR BIOMECHANICS–PART II

PREFACE: A SPECIAL SELECTION ON EMERGING TECHNIQUES FOR BIOMECHANICS–PART II

A Bilayer Membrane Doped with Struvite Nanowires for Guided Bone Regeneration.

Guided bone regeneration (GBR) therapy demonstrates a prominent curative effect on the management of craniomaxillofacial (CMF) bone defects. In this study, a GBR membrane consisting of a microporous layer and a struvite-nanowire-doped fibrous layer is constructed via non-solvent induced phase separation, followed by an electrospinning procedure to treat critical-sized calvarial defects. The microporous layer shows selective permeability for excluding the rapid-growing non-osteogenic tissues and potential wound stabilization. The nanowire-like struvite is synthesized as the deliverable therapeutic agent within the fibrous layer to facilitate bone regeneration. Such a membrane displays a well-developed heterogeneous architecture, satisfactory mechanical performance, and long-lasting characteristics. The in vitro biological evaluation reveals that apart from being a strong barrier, the bilayer struvite-laden membrane can actively promote cellular adhesion, proliferation, and osteogenic differentiation. Consequently, the multifunctional struvite-doped membranes are applied to treat 5mm-sized bilateral calvarial defects in rats, resulting in overall improved healing outcomes compared with the untreated or the struvite-free membrane-treated group, which is characterized by enhanced osteogenesis and significantly increased new bone formation. The encouraging preclinical results reveal the great potential of the bilayer struvite-doped membrane as a clinical GBR device for augmenting large-area CMF bone reconstruction.

Small extracellular vesicles derived from hypoxic mesenchymal stem cells promote vascularized bone regeneration through the miR-210-3p/EFNA3/PI3K pathway

Angiogenesis is closely coupled with osteogenesis and has equal importance. Thus, promoting angiogenesis during the bone repair process is vital for ideal bone regeneration. As important mediators of cell-cell communication and biological homeostasis, mesenchymal stem cell-derived small extracellular vesicles (MSC-sEVs) have been proved to be highly involved in bone and vascular regeneration. Because hypoxia microenvironment promotes the proangiogenic activity of MSCs, in the present study, we investigate the effect and underlying molecular mechanisms of sEVs from hypoxia-preconditioned MSCs (hypo-sEVs) on angiogenesis and develop an effective strategy to promote vascularized bone regeneration. Compared to sEVs from normoxia MSCs (nor-sEVs), hypo-sEVs promoted the proliferation, migration, and angiogenesis of HUVECs and ultimately enhanced bone regeneration and new blood vessel reconstruction in a critical-size calvarial bone defect model. miRNA sequence and the verified results showed that miR-210-3p in hypo-sEVs was increased via HIF-1α under hypoxia. The upregulated miR-210-3p in hypo-sEVs promoted angiogenesis by downregulating EFNA3 expression and enhancing the phosphorylation of the PI3K/AKT pathway. Thus, this study suggests a successful strategy to enhance vascularized bone regeneration by utilizing hypo-sEVs via the miR-210-3p/EFNA3/PI3K/AKT pathway. Statement of significanceConsidering the significance of vascularization in ideal bone regeneration, strategies to promote angiogenesis during bone repair are required. Hypoxia microenvironment can promote the proangiogenic potential of mesenchymal stem cells (MSCs). Nonetheless, the therapeutic effect of small extracellular vesicles (sEVs) from hypoxia-preconditioned MSCs on cranio-maxillofacial bone defect remains unknown, and the underlying mechanism is poorly understood. This study shows that hypo-sEVs significantly enhance the proliferation, migration, and angiogenesis of HUVECs as well as promote vascularized bone formation. Moreover, this work indicates that HIF-1α can induce overexpression of miR-210-3p under hypoxia, and miR-210-3p can hinder EFNA3 expression and subsequently activate the PI3K/AKT pathway. The application of hypo-sEVs provides a facile and promising strategy to promote vascularized bone regeneration in a critical-size bone defect model.

3D printed hydroxyapatite – Zn2+ functionalized starch composite bone grafts for orthopedic and dental applications

Hydroxyapatite (HA) – polymer composite based 3D printed bone grafts require extensive mechanical and biological property optimization for specific clinical needs. This fuels the need to develop innovative methods of optimization. Using an in-house extrusion-based 3D printer, we show the feasibility of fabricating hydroxyapatite- Zn2+ functionalized starch composites as artificial bone graft substitutes. The experimental procedure for this purpose is fortified with a univariate multi-objective optimization strategy to predict the best composition. The compressive strength of the grafts improves up to ∼ 4 folds by parametric optimization and Zn2+ functionalization, without any post-processing. These grafts maintain mechanical integrity and strength during 6 weeks of dissolution study in simulated body fluid (SBF), while the non -functionalized starch-HA grafts fully degrade within a week. The Zn2+ functionalization results in up to ∼ 79% antibacterial efficacy against S. aureus. Osteoblast cell viability increases ∼ 1.6 folds on these graft surfaces on day 11. Our innovative methods of optimization are expected to reduce the experiment time, cost, and chance of human error in 3D printing. This study redefines the importance of understanding composition and process dependence for making a functionalized 3D printed bone graft for repairing low load-bearing defects such as craniomaxillofacial bone.

Craniomaxillofacial derived bone marrow mesenchymal stem/stromal cells (BMSCs) for craniomaxillofacial bone tissue engineering: A literature review

Craniomaxillofacial bone defects seriously affect the appearance, function, and psychological status of patients. Traditional autologous bone grafting is very challenging due to the limited sources of bone tissue, excessive surgical trauma, and high incidence of related complications. Craniomaxillofacial bone tissue engineering (BTE) strategies based on bone marrow mesenchymal stem cells (BMSCs) are emerging as an alternative. Craniomaxillofacial BMSCs (C-BMSCs) are homologous to craniomaxillofacial bones, which develop from the mesoderm and neural crest. This article aims to compare the differences in osteogenesis, angiogenesis, and immune regulation of C-BMSCs and other sources of BMSCs, and propose ideas and strategies such as 3D printing and mechanotherapy to completely harness the characteristics of C-BMSCs. In conclusion, C-BSMCs are a promising source of stem cells for the repair and reconstruction of craniomaxillofacial bone defects, and more attention should be paid to accelerating their basic research and clinical practices.

Innovations in craniofacial bone and periodontal tissue engineering – from electrospinning to converged biofabrication

ABSTRACT From a materials perspective, the pillars for the development of clinically translatable scaffold-based strategies for craniomaxillofacial (CMF) bone and periodontal regeneration have included electrospinning and 3D printing (biofabrication) technologies. Here, we offer a detailed analysis of the latest innovations in 3D (bio)printing strategies for CMF bone and periodontal regeneration and provide future directions envisioning the development of advanced 3D architectures for successful clinical translation. First, the principles of electrospinning applied to the generation of biodegradable scaffolds are discussed. Next, we present on extrusion-based 3D printing technologies with a focus on creating scaffolds with improved regenerative capacity. In addition, we offer a critical appraisal on 3D (bio)printing and multitechnology convergence to enable the reconstruction of CMF bones and periodontal tissues. As a future outlook, we highlight future directions associated with the utilisation of complementary biomaterials and (bio)fabrication technologies for effective translation of personalised and functional scaffolds into the clinics.

Digital light processing of β-tricalcium phosphate bioceramic scaffolds with controllable porous structures for patient specific craniomaxillofacial bone reconstruction

β-TCP scaffolds with four representative pore configurations are prepared for using digital light processing (DLP)-based additive manufacturing. The process optimization, pore design, mechanical properties, and microstructure of the fabricated scaffolds are investigated. The optimal slurry solid content, exposure intensity, slice thickness, and exposure time were found to be 60 wt%, 10 mW/cm2, 25 μm, and 4 s, respectively. The DLP-formed β-TCP bone scaffolds showed 3D interconnected and multilevel pores, achieving porosities of 49%–89% and strut diameters of 200–1000 μm. The primary pore size exceeded 100 μm, and the secondary pore size was less than 10 μm. The porosity significantly affected the mechanical properties of the scaffolds, whereas the pore configuration exerted a minor influence. The prepared scaffolds with a pore configuration of triply periodic minimal surface behaved the best mechanical properties. The compressive strength and elastic modulus of the scaffolds reached 20–30 MPa and 2–4 GPa, respectively. Based on patient’s medical imaging data, large-volume β-TCP scaffolds (∽70 × 40 × 15 mm and 40 × 40 × 4 mm, after sintering) with controlled biomimicking porous structures and anatomical shapes were successfully designed and fabricated by DLP for repair of massively damaged mandible and cranial defects.

A Mini-Pig Mandibular Defect Model for Evaluation of Craniomaxillofacial Bone Regeneration.

Craniomaxillofacial bone defects represent a clinical challenge in the fields of maxillofacial surgery and (implant) dentistry. Regeneration of these bone defects requires the application of bone graft materials that facilitate new bone formation in a safe, reliable, and predictive manner. In addition to autologous bone graft, several types of (synthetic) bone substitute materials have become clinically available, and still major efforts are focused on improving such bone substitute materials by optimizing their properties. Given the regulatory necessity to evaluate the performance of new bone substitute materials for craniomaxillofacial bone regeneration in a large animal model with similarity to human bone before clinical application, we here describe a mini-pig mandibular bone defect model that allows for the creation of multiple (critical-size) bone defects within the mandibular body of a single animal. As examples of bone substitute materials, we utilize both the clinically used BioOss granules and an experimental calcium phosphate cement for filling the created defects. Regarding the latter, its advantages are the injectable application within the defect site, in which the material rapidly sets, and the tailorable degradation properties via the inclusion of hydrolytically degrading polymeric particles. For both bone substitute materials, we show the suitability of the bone defect model to assess bone regeneration via histology and micro-computed tomography. Impact statement Given the regulatory necessity to evaluate the performance of new bone substitute materials for craniomaxillofacial bone regeneration in a large animal model with similarity to the human bone before clinical application, we here describe a mini-pig mandibular bone defect model that allows for the creation of multiple (critical-size) bone defects within the mandibular body of a single animal that can be used for the evaluation of the bone regenerative capacity of new bone grafting materials as well as tissue-engineered products for alveolar bone regeneration.

HIF-1α Regulates Osteogenesis of Periosteum-Derived Stem Cells Under Hypoxia Conditions via Modulating POSTN Expression.

Periosteum is indispensable in bone repair and is an important source of skeletal stem cells (SSCs) for endogenous bone regeneration. However, there are only a few studies about SSCs in periosteum. The craniomaxillofacial bone regeneration is done under the hypoxia microenvironment, in which HIF-1α plays an important role. The effect of HIF-1α on periosteum-derived stem cells (PDSCs) and the mechanisms of PDSCs activation under hypoxia conditions are unknown. In this study, the calvarial bone defect was established, with the periosteum removed or retained. Results show that the bone regeneration was severely impaired in the periosteum removed group. Moreover, pluripotent PDSCs isolated from the periosteum were positive for mesenchymal stem cell (MSC) markers. To determine the role of HIF-1α, the expression of HIF-1α was knocked down in vivo and in vitro, impairing the bone regeneration or osteogenesis of PDSCs. Furthermore, the knockdown of HIF-1α expression also reduced periostin (POSTN) expression, and recombinant POSTN addition partly rescued the osteogenic inhibition. Finally, to explore the mechanism under POSTN activation, the phosphorylation level of the PI3K/AKT pathway was assessed in transfected PDSCs. The phosphorylation level of PI3K and AKT was enhanced with HIF-1α overexpression and inhibited with HIF-1α knockdown, and the addition of PI3K activator or AKT activator could partly rescue POSTN expression. In conclusion, as a potential target to promote bone repair under the hypoxia microenvironment, HIF-1α can regulate the osteogenic differentiation of PDSCs via the PI3K/AKT/POSTN pathway, which lay a solid foundation for periosteum-based craniomaxillofacial bone regeneration.