Melt electrowriting scaffolds with fibre-guiding features for periodontal attachment.

Periodontal regeneration requires the re-attachment of oblique and perpendicular periodontal ligament (PDL) fibres to newly formed cementum and alveolar bone, which has proven elusive with existing approaches. In this study, multiple fibre-guiding biphasic tissue engineered constructs were fabricated by melt electrowriting. The biphasic scaffolds were 95 % porous and consisted of a pore size gradient bone compartment and periodontal compartment made of fibre-guiding channels with micro-architectural features ranging from 100 to 60 µm aimed to direct PDL fibre alignment and attachment. In vitro evaluations over 3 and 7 days demonstrated a marked improvement in collagen fibre orientation (over 60 % fully aligned) for scaffolds with micro-architecture ≤100 µm. The biphasic scaffolds were placed on a dentine slice and implanted ectopically, and this demonstrated that all micro-channels groups facilitated oblique and perpendicular alignment and attachment on the dentine with a mean nuclei angle and mean collagen fibre angle of approximately 60° resembling the native periodontal ligament attachment. A further in vivo testing using a surgically created rodent periodontal model highlighted the 80 µm micro-channel group's effectiveness, showing a significant increase in oblique PDL fibre attachment (72 %) and periodontal regeneration (56 %) when compared to all other groups onto the tooth root compared to control groups. Further to this, immunohistochemistry demonstrated the presence of periostin in the newly formed ligament indicating that functional regeneration occurred These findings suggest that scaffold micro-architectures of 100 µm or below can play a crucial role in directing periodontal tissue regeneration, potentially addressing a critical gap in periodontal therapy. STATEMENT OF SIGNIFICANCE: Periodontal regeneration remains a significant clinical challenge. Essential to restoring dental health and function is the proper attachment of the periodontal ligament, which is functionally oriented, to regenerated bone and cementum. Our research presents an innovative biphasic scaffold, utilizing Melt Electrowriting to systematically guide tissue growth. Distinct from existing methods, our scaffold is highly porous, adaptable, and precisely guides periodontal ligament fibre attachment to the opposing tooth root and alveolar bone interfaces, a critical step for achieving periodontal functional regeneration. Our findings not only bridge a significant gap in biomaterial driven tissue guidance but also promise more predictable outcomes for patients, marking a transformative advancement in the field.

BMP2 and GDF5 for Compartmentalized Regeneration of the Scapholunate Ligament.

Background Chronic injuries to the scapholunate ligament (SLIL) alter carpal kinematics and may progress to early degenerative osteoarthritis. To date, there is no consensus for the best method for SLIL reconstruction. This study aims to assess the use of growth factors (bone morphogenetic protein [BMP]2 and growth and differentiation factor 5 [GDF5]) for compartmentalized regeneration of bone and ligament in this multiphasic scaffold in a rabbit knee model. Case Description A total of 100 µg of BMP2 and 30 µg of GDF5 were encapsulated into a heparinized gelatin-hyaluronic acid hydrogel and loaded into the appropriate compartment of the multiphasic scaffold. The multiphasic scaffold was implanted to replace the native rabbit medial collateral ligament ( n = 16). The rabbits were randomly assigned to two different treatment groups. The first group was immobilized postoperatively with the knee pinned in flexion with K-wires for 4 weeks ( n = 8) prior to sacrifice. The second group was immobilized for 4 weeks, had the K-wires removed followed by a further 4 weeks of mobilization prior to sample harvesting. Literature Review Heterotopic ossification as early as 4 weeks was noted on gross dissection and confirmed by microcomputed tomography and histological staining. This analysis revealed formation of a bony bridge located within and over the ligament compartment in the intra-articular region. Biomechanical testing showed increased ultimate force of the ligament compartment at 4 weeks postimplantation consistent with the presence of bone formation and higher numbers of scaffold failures at the bone-tendon junction. This study has demonstrated that the addition of BMP2 and GDF5 in the bone-ligament-bone (BLB) scaffold resulted in heterotopic bone formation and failure of the ligament compartment. Clinical Relevance The implantation of a three-dimensional-printed BLB scaffold alone demonstrated superior biomechanical and histological results, and further investigation is needed as a possible clinical reconstruction for the SLIL.

Hydrogel based soft tissue expanders for orodental reconstruction.

Tension-free flap closure to prevent soft tissue dehiscence is a prerequisite for successful bone augmentation in orodental reconstructive surgery. Since soft tissue contour follows the underlying jaw bony architecture, resorption of alveolar (jaw) bone limits the availability of soft tissue for wound closure following major bone reconstruction, required to facilitate oral rehabilitation with endosseous dental implants following tooth loss. Although there are several clinical procedures to increase soft tissue volume, these techniques are complicated and technically demanding. Soft tissue expansion, an established technique in reconstructive surgery, is an ideal alternative to generate surplus soft tissue prior to bone augmentation and dental implant placement. Increase in tissue volume can be achieved by using soft tissue expanders (STEs). Contemporary STEs have evolved from silicone balloons to osmotically inflating hydrogel-based systems. Here, we provide an overview of STEs in clinical oral surgery, outline the current research in STEs, and an update on recent clinical trials as well as the associated complications. Also, the mechanism governing soft tissue expansion and the critical factors that control the expansion process are covered. Design considerations for STEs for intraoral applications are given particular attention. Finally, we present our perspectives on utilization of minimally invasive methods to administer STEs for orodental applications. STATEMENT OF SIGNIFICANCE: Soft tissue expansion is required for a range of reconstructive applications and more notably in regenerative dentistry for vertical bone augmentation. This review describes the commercially available soft tissue expanders along with the latest systems being currently developed. This review insightfully discusses the biological and physical mechanisms leading to soft tissue expansion and critically assesses the design criteria of soft tissue expanders. A particular focus is given on the development of a new generation of hydrogel-based soft tissue expanders; their chemistry and required physical properties for tissue expansion is described and the obstacles towards clinical translations are identified. Finally, the review elaborates on promising minimally invasive injectable hydrogel-based tissue expanders and highlights the beneficial features of these systems.

3D printing for bone regeneration: challenges and opportunities for achieving predictability.

3D printing offers attractive opportunities for large-volume bone regeneration in the oro-dental and craniofacial regions. This is enabled by the development of CAD-CAM technologies that support the design and manufacturing of anatomically accurate meshes and scaffolds. This review describes the main 3D-printing technologies utilized for the fabrication of these patient-matched devices, and reports on their pre-clinical and clinical performance including the occurrence of complications for vertical bone augmentation and craniofacial applications. Furthermore, the regulatory pathway for approval of these devices is discussed, highlighting the main hurdles and obstacles. Finally, the review elaborates on a variety of strategies for increasing bone regeneration capacity and explores the future of 4D bioprinting and biodegradable metal 3D printing.

Harnessing the Native Extracellular Matrix for Periodontal Regeneration Using a Melt Electrowritten Biphasic Scaffold.

Scaffolds have been used to promote periodontal regeneration by providing control over the spacio-temporal healing of the periodontium (cementum, periodontal ligament (PDL) and alveolar bone). This study proposes to enhance the biofunctionality of a biphasic scaffold for periodontal regeneration by means of cell-laid extracellular matrix (ECM) decoration. To this end, a melt electrowritten scaffold was cultured with human osteoblasts for the deposition of bone-specific ECM. In parallel, periodontal ligament cells were used to form a cell sheet, which was later combined with the bone ECM scaffold to form a biphasic PDL-bone construct. The resulting biphasic construct was decellularised to remove all cellular components while preserving the deposited matrix. Decellularisation efficacy was confirmed in vitro, before the regenerative performance of freshly decellularised constructs was compared to that of 3-months stored freeze-dried scaffolds in a rodent periodontal defect model. Four weeks post-surgery, microCT revealed similar bone formation in all groups. Histology showed higher amounts of newly formed cementum and periodontal attachment in the fresh and freeze-dried ECM functionalised scaffolds, although it did not reach statistical significance. This study demonstrated that the positive effect of ECM decoration was preserved after freeze-drying and storing the construct for 3 months, which has important implications for clinical translation.

Effect of In Vitro Culture Length on the Bone-Forming Capacity of Osteoblast-Derived Decellularized Extracellular Matrix Melt Electrowritten Scaffolds.

Recent advancements in decellularization have seen the development of extracellular matrix (ECM)-decorated scaffolds for bone regeneration; however, little is understood of the impact of in vitro culture prior to decellularization on the performances of these constructs. Therefore, this study investigated the effect of in vitro culture on ECM-decorated melt electrowritten polycaprolactone scaffold bioactivity. The scaffolds were seeded with osteoblasts and cultured for 1, 2, or 4 weeks to facilitate bone-specific ECM deposition and subsequently decellularized to form an acellular ECM-decorated scaffold. The utilization of mild chemicals and DNase was highly efficient in removing DNA while preserving ECM structure and composition. ECM decoration of the melt electrowritten fibers was observed within the first week of culture, with increased ECM at 2 and 4 week culture periods. Infiltration of re-seeded cells as well as overall bone regeneration in a rodent calvarial model was impeded by a longer culture period. Thus, it was demonstrated that the length of culture has a key influence on the osteogenic properties of decellularized ECM-decorated scaffolds, with long-term culture (2+ weeks) causing pore obstruction and creating a physical barrier which interfered with bone formation. These findings have important implications for the development of effective ECM-decorated scaffolds for bone regeneration.

Additively manufactured polyethylene terephthalate scaffolds for scapholunate interosseous ligament reconstruction.

The regeneration of the ruptured scapholunate interosseous ligament (SLIL) represents a clinical challenge. Here, we propose the use of a Bone-Ligament-Bone (BLB) 3D-printed polyethylene terephthalate (PET) scaffold for achieving mechanical stabilisation of the scaphoid and lunate following SLIL rupture. The BLB scaffold featured two bone compartments bridged by aligned fibres (ligament compartment) mimicking the architecture of the native tissue. The scaffold presented tensile stiffness in the range of 260 ± 38 N/mm and ultimate load of 113 ± 13 N, which would support physiological loading. A finite element analysis (FEA), using inverse finite element analysis (iFEA) for material property identification, showed an adequate fit between simulation and experimental data. The scaffold was then biofunctionalized using two different methods: injected with a Gelatin Methacryloyl solution containing human mesenchymal stem cell spheroids (hMSC) or seeded with tendon-derived stem cells (TDSC) and placed in a bioreactor to undergo cyclic deformation. The first approach demonstrated high cell viability, as cells migrated out of the spheroid and colonised the interstitial space of the scaffold. These cells adopted an elongated morphology suggesting the internal architecture of the scaffold exerted topographical guidance. The second method demonstrated the high resilience of the scaffold to cyclic deformation and the secretion of a fibroblastic related protein was enhanced by the mechanical stimulation. This process promoted the expression of relevant proteins, such as Tenomodulin (TNMD), indicating mechanical stimulation may enhance cell differentiation and be useful prior to surgical implantation. In conclusion, the PET scaffold presented several promising characteristics for the immediate mechanical stabilisation of disassociated scaphoid and lunate and, in the longer-term, the regeneration of the ruptured SLIL.

Fabrication and Characterization of Decellularized Periodontal Ligament Cell Sheet Constructs.

Decellularized tissue engineered constructs have the potential to promote regeneration by providing a biomimetic extracellular matrix that directs tissue specific regeneration when implanted in situ. Recently, the use of cell sheets has shown promising results in promoting periodontal regeneration. Here, we describe the fabrication of decellularized periodontal cell sheets with intact extracellular matrix structural and biological properties. Melt electro-spun polycaprolactone (PCL) scaffolds are used as a carrier for the inherently fragile cell sheets, in order to provide support during the processes of decellularization. An optimized decellularization method is outlined using perfusion with a combination of NH4OH and Triton X-100 together with a DNase treatment step for DNA removal. The maintenance of extracellular matrix structural and biological integrity is important, and here, we describe the assessment of these properties using immunostaining for extracellular matrix proteins and ELISA for growth factor quantification.

Cell Seeding on 3D Scaffolds for Tissue Engineering and Disease Modeling Applications.

Scaffold cell seeding is a crucial step for the standardization and homogeneous maturation of tissue engineered constructs. This is particularly critical in the context of additively manufactured scaffolds whereby large pore size and high porosity usually impedes the retention of the seeding solution resulting in poor seeding efficacy and heterogeneous cell distribution. To circumvent this limitation, a simple yet efficient cell seeding technique is described in this chapter consisting of preincubating the scaffold in 100% serum for 1 h leading to reproducible seeding. A proof of concept is demonstrated using highly porous melt electrowritten polycaprolactone scaffolds as the cell carrier. As cell density, cell distribution, and differentiation within the scaffold are important parameters, various assays are proposed to validate the seeding and perform quality control of the cellularized construct using techniques such as alizarin red, Sirius red, and immunostaining.

Workflow for Fabricating 3D-Printed Resorbable Personalized Porous Scaffolds for Orofacial Bone Regeneration.

Resorption of alveolar bone following tooth extraction is a physiological process that can often prevent the placement of dental implants due to the limited bone remaining. In severe cases, vertical bone augmentation, which aims to restore bone in an extraskeletal dimension (outside of the skeletal envelope), is required prior to implant placement. While current treatment strategies rely on autologous grafts, or "Guided Bone Regeneration" involving the placement of particulate bone grafting biomaterials under a protective membrane, the field is shifting to patient-matched solutions. Herein, we describe the various steps required for modeling the patient data, creating the patient-matched scaffold geometry and 3D-printing using the biodegradable polymer polycaprolactone for application in the oro-dental and craniofacial areas.

Tissue integration and biodegradation of soft tissue substitutes with and without compression: an experimental study in the rat.

OBJECTIVES: To analyze the influence of compression on tissue integration and degradation of soft tissue substitutes. MATERIAL AND METHODS: Six subcutaneous pouches in twenty-eight rats were prepared and boxes made of Al2O3 were implanted and used as carriers for soft tissue substitutes: a collagen matrix (MG), two volume-stable collagen matrices (FG/MGA), and a polycaprolactone scaffold(E). The volume-stable materials (FG/MGA/E) were further implanted with a twofold (2) and a fourfold (4) compression, created by the stacking of additional layers of the substitute materials. The samples were retrieved at 1, 2, and 12 weeks (10 groups, 3 time points, n = 5 per time point and group, overall, 150 samples). The area fraction of infiltrated fibroblasts and inflammatory cells was evaluated histologically. Due to within-subject comparisons, mixed models were conducted for the primary outcome. The level of significance was set at 5%. RESULTS: The area fraction of fibroblasts increased in all groups over time. At 12 weeks, the densely compressed materials FG4 (1.1%), MGA4 (1.7%), and MGA2 (2.5%) obtained lower values as compared to the other groups, ranging between 4.7 (E2) and 6.5% (MG). Statistically significant differences (p ≤ 0.05) were observed between groups FG4 vs MG/FG2/E/E4 as well as between MGA4 vs MG/FG2/E/E4 and E vs MGA2. CONCLUSIONS: Higher levels of compression led to delayed tissue integration. The effect of different compression levels was more distinct when compared to the differences between the materials. CLINICAL RELEVANCE: All biomaterials demonstrated tissue integration and a minimal concomitant inflammatory reaction. Clinically, it might be more favorable to obtain a sufficient flap release or to reduce the material size to improve the tissue integration processes.

The effect of culture conditions on the bone regeneration potential of osteoblast-laden 3D bioprinted constructs.

Three Dimensional (3D) bioprinting is one of the most recent additive manufacturing technologies and enables the direct incorporation of cells within a highly porous 3D-bioprinted construct. While the field has mainly focused on developing methods for enhancing printing resolution and shape fidelity, little is understood about the biological impact of bioprinting on cells. To address this shortcoming, this study investigated the in vitro and in vivo response of human osteoblasts subsequent to bioprinting using gelatin methacryloyl (GelMA) as the hydrogel precursor. First, bioprinted and two-dimensional (2D) cultured osteoblasts were compared, demonstrating that the 3D microenvironment from bioprinting enhanced bone-related gene expression. Second, differentiation regimens of 2-week osteogenic pre-induction in 2D before bioprinting and/or 3-week post-printing osteogenic differentiation were assessed for their capacity to increase the bioprinted construct's biofunctionality towards bone regeneration. The combination of pre-and post-induction regimens showed superior osteogenic gene expression and mineralisation in vitro. Moreover, a rat calvarial model using microtomography and histology demonstrated bone regeneration potential for the pre-and post-differentiation procedure. This study shows the positive impact of bioprinting on cells for osteogenic differentiation and the increased in vivo osteogenic potential of bioprinted constructs via a pre-induction method. STATEMENT OF SIGNIFICANCE: 3D bioprinting, one of the most recent technologies for tissue engineering has mostly focussed on developing methods for enhancing printing properties, little is understood on the biological impact of bioprinting and /or subsequent in vitro maturation methods on cells. Therefore, we addressed these fundamental questions by investigating osteoblast gene expression in bioprinted construct and assessed the efficacy of several induction regimen towards osteogenic differentiation in vitro and in vivo. Osteogenic induction of cells prior to seeding in scaffolds used in conventional tissue engineering applications has been demonstrated to increase the osteogenic potential of the resulting construct. However, to the best of our knowledge, pre-induction methods have not been investigated in 3D bioprinting.

In vitro evaluation of porous poly(hydroxybutyrate-co-hydroxyvalerate)/akermanite composite scaffolds manufactured using selective laser sintering.

Incorporation of a bioactive mineral filler in a biodegradable polyester scaffold is a promising strategy for scaffold assisted bone tissue engineering (TE). The current study evaluates the in vitro behavior of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV)/Akermanite (AKM) composite scaffolds manufactured using selective laser sintering (SLS). Exposure of the mineral filler on the surface of the scaffold skeleton was evident from in vitro mineralization in PBS. PHBV scaffolds and solvent cast films served as control samples and all materials showed preferential adsorption of fibronectin compared to serum albumin as well as non-cytotoxic response in human osteoblasts (hOB) at 24 h. hOB culture for up to 21 days revealed that the metabolic activity in PHBV films and scaffolds was significantly higher than that of PHBV/AKM scaffolds within the first two weeks of incubation. Afterwards, the metabolic activity in PHBV/AKM scaffolds exceeded that of the control samples. Confocal imaging showed cell penetration into the porous scaffolds. Significantly higher ALP activity was observed in PHBV/AKM scaffolds at all time points in both basal and osteogenic media. Mineralization during cell culture was observed on all samples with PHBV/AKM scaffolds exhibiting distinctly different mineral morphology. This study has demonstrated that the bioactivity of PHBV SLS scaffolds can be enhanced by incorporating AKM, making this an attractive candidate for bone TE application.

Fibre-guiding biphasic scaffold for perpendicular periodontal ligament attachment.

Periodontal regeneration is characterized by the attachment of oblique periodontal ligament fibres on the tooth root surface. To facilitate periodontal ligament attachment, a fibre-guiding tissue engineered biphasic construct was manufactured by melt electrowriting (MEW) for influencing reproducible cell guidance and tissue orientation. The biphasic scaffold contained fibre-guiding features in the periodontal ligament component comprising of 100 µm spaced channels (100CH), a pore size gradient in the bone component and maintained a highly porous and fully interconnected interface between the compartments. The efficacy of the fibre-guiding channels was assessed in an ectopic periodontal attachment model in immunocompromised rats. This demonstrated an unprecedented and systematic tissue alignment perpendicular to the dentin in the 100CH group, resulting in the close mimicry of native periodontal ligament architecture. In addition, the histology revealed high levels of tissue integration between the two compartments as observed by the perpendicular collagen attachment on the dentin surface, which also extended and infiltrated the scaffold's bone compartment. In conclusion, the 100 µm fibre-guiding scaffold induced a systematic tissue orientation at the dentin-ligament interface, resembling the native periodontium and thus resulting in enhanced alignment mimicking periodontal ligament regeneration. STATEMENT OF SIGNIFICANCE: Periodontitis is a prevalent inflammatory disease affecting a large portion of the adult population and leading to the destruction of the tooth-supporting structures (alveolar bone, periodontal ligament, and cementum). Current surgical treatments are unpredictable and generally result in repair rather than functional regeneration. A key feature of functional regeneration is the re-insertion of the oblique or perpendicularly orientated periodontal ligament fibre in both the alveolar bone and root surface. This study demonstrates that a highly porous scaffold featuring 100 µm width channels manufactured by the stacking of melt electrospun fibres, induced perpendicular alignment and attachment of the neo-ligament onto a dentine surface. The fibre guiding micro-architecture may pave the way for enhanced and more functional regeneration of the periodontium.

Lymphocytes Are Not Required for Neurogenic Heterotopic Ossification Development after Spinal Cord Injury.

Neurogenic heterotopic ossifications (NHOs) are incapacitating complications of traumatic brain and spinal cord injuries (SCI) that manifest as abnormal bone formation in periarticular muscles. Using a unique model of NHO after SCI in genetically unmodified mice, we have previously established that the innate immune system plays a key driving role in NHO pathogenesis. The role of adaptive immune cells in NHO pathogenesis, however, remains unexplored in this model. Here we established that B lymphocytes were reduced in the spleen and blood after SCI and increased in muscles of mice in which NHO develops, whereas minimal changes in T cell frequencies were noted. Interestingly, Rag1 -/- mice lacking mature T and B lymphocytes, developed NHO, similar to wild-type mice. Finally, mice that underwent splenectomy before SCI and muscle damage also developed NHO to the same extent as non-splenectomized SCI controls. Overall, our findings show that functional T and B lymphocytes have minimal influence or dispensable contributions to NHO development after experimental SCI in mice.

Interleukin-1 Is Overexpressed in Injured Muscles Following Spinal Cord Injury and Promotes Neurogenic Heterotopic Ossification.

Neurogenic heterotopic ossifications (NHOs) form in periarticular muscles after severe spinal cord (SCI) and traumatic brain injuries. The pathogenesis of NHO is poorly understood with no effective preventive treatment. The only curative treatment remains surgical resection of pathological NHOs. In a mouse model of SCI-induced NHO that involves a transection of the spinal cord combined with a muscle injury, a differential gene expression analysis revealed that genes involved in inflammation such as interleukin-1ß (IL-1ß) were overexpressed in muscles developing NHO. Using mice knocked-out for the gene encoding IL-1 receptor (IL1R1) and neutralizing antibodies for IL-1α and IL-1ß, we show that IL-1 signaling contributes to NHO development after SCI in mice. Interestingly, other proteins involved in inflammation that were also overexpressed in muscles developing NHO, such as colony-stimulating factor-1, tumor necrosis factor, or C-C chemokine ligand-2, did not promote NHO development. Finally, using NHO biopsies from SCI and TBI patients, we show that IL-1ß is expressed by CD68+ macrophages. IL-1α and IL-1ß produced by activated human monocytes promote calcium mineralization and RUNX2 expression in fibro-adipogenic progenitors isolated from muscles surrounding NHOs. Altogether, these data suggest that interleukin-1 promotes NHO development in both humans and mice. © 2021 American Society for Bone and Mineral Research (ASBMR).

The utilisation of resolvins in medicine and tissue engineering.

Recent advances in the field of regenerative medicine and biomaterial science have highlighted the importance of controlling immune cell phenotypes at the biomaterial interface. These studies have clearly indicated that a rapid resolution of the inflammatory process, mediated by a switch in the macrophage population towards a reparative phenotype, is essential for tissue regeneration to occur. While various biomaterial surfaces have been developed in order to impart immunomodulatory properties to the resulting constructs, an alternative strategy involving the use of reparative biological cues, known as resolvins, is emerging in regenerative medicine. This review reports on the mechanisms via which resolvins participate in the resolution of inflammation and describes their current utilisation in pre-clinical and clinical settings, along with their effectiveness when combined with biomaterial constructs in tissue engineering applications. STATEMENT OF SIGNIFICANCE: The resolution of the inflammatory process is necessary for achieving tissue healing and regeneration. Resolvins are lipid mediators and play a key role in the resolution of the inflammatory response and can be used in as biological cues to promote tissue regeneration. This review describes the various biological inflammatory mechanisms and pathways involving resolvins and how their action results in a pro-healing response. The use of these molecules in the clinical setting is then summarised for various applications along with their limitations. Lastly, the review focuses on the emergence resolvins in tissue engineering products including the use of a more stable form which holds greater prospect for regenerative purposes.

Iron accumulation is associated with periodontal destruction in a mouse model of HFE-related haemochromatosis.

OBJECTIVE: To investigate the effect of Hfe gene mutation on the distribution of iron and periodontal bone loss in periodontal tissues. BACKGROUND DATA: It remains unclear how tissue iron loading affects the periodontium architectures in a genetic animal model of hereditary haemochromatosis (HH). METHODS: Male C57BL/6 Hfe -/- (8 weeks old) and wild-type (WT) mice were utilized to examine the iron distribution in periodontal tissues, as well as periodontal tissues changes using micro-computed tomography and histomorphometric analysis. Furthermore, tissue inflammatory mediators, bone markers and periodontal pathogens were carried out in PFA-fixed paraffin-embedded tissues using ELISA, RT-qPCR and genomic DNA qPCR, respectively. RESULTS: Excessive iron deposition was found in the periodontal ligament, gingiva and alveolar bone in Hfe -/- mice relative to their WT counterparts. This, in turn, was associated with significant periodontal bone loss, increased cemento-enamel junction-alveolar bone crest distance and decreased expression of molecules involved in bone development and turnover. Furthermore, the pro-inflammatory cytokine - interleukin 6 and periodontal bacteria - Campylobacter rectus were significantly increased in Hfe -/- mice compared with WT controls. CONCLUSION: Our results suggest that the iron loading in a mouse model of HH decreases alveolar bone formation and leads to alterations in the inflammatory state in the periodontium. Periodontal health should be assessed during the clinical assessment of HFE-HH patients.

Local delivery of hydrogel encapsulated vascular endothelial growth factor for the prevention of medication-related osteonecrosis of the jaw.

The anti-angiogenic effects of bisphosphonates have been hypothesized as one of the major etiologic factors in the development of medication-related osteonecrosis of the jaw (MRONJ), a severe debilitating condition with limited treatment options. This study evaluated the potential of a gelatine-hyaluronic acid hydrogel loaded with the angiogenic growth factor, vascular endothelial growth factor (VEGF), as a local delivery system to aid in maintaining vascularization in a bisphosphonate-treated (Zoledronic Acid) rodent maxillary extraction defect. Healing was assessed four weeks after implantation of the VEGF-hydrogel into extraction sockets. Gross examination and histological assessment showed that total osteonecrosis and inflammatory infiltrate was significantly reduced in the presence of VEGF. Also, total vascularity and specifically neovascularization, was significantly improved in animals that received VEGF hydrogel. Gene expression of vascular, inflammatory and bone specific markers within the defect area were also significantly altered in the presence of VEGF. Furthermore, plasma cytokine levels were assessed to determine the systemic effect of locally delivered VEGF and showed similar outcomes. In conclusion, the use of locally delivered VEGF within healing extraction sockets assists bone healing and prevents MRONJ via a pro-angiogenic and immunomodulatory mechanism.

Finite element analysis of the performance of additively manufactured scaffolds for scapholunate ligament reconstruction.

Rupture of the scapholunate interosseous ligament can cause the dissociation of scaphoid and lunate bones, resulting in impaired wrist function. Current treatments (e.g., tendon-based surgical reconstruction, screw-based fixation, fusion, or carpectomy) may restore wrist stability, but do not address regeneration of the ruptured ligament, and may result in wrist functional limitations and osteoarthritis. Recently a novel multiphasic bone-ligament-bone scaffold was proposed, which aims to reconstruct the ruptured ligament, and which can be 3D-printed using medical-grade polycaprolactone. This scaffold is composed of a central ligament-scaffold section and features a bone attachment terminal at either end. Since the ligament-scaffold is the primary load bearing structure during physiological wrist motion, its geometry, mechanical properties, and the surgical placement of the scaffold are critical for performance optimisation. This study presents a patient-specific computational biomechanical evaluation of the effect of scaffold length, and positioning of the bone attachment sites. Through segmentation and image processing of medical image data for natural wrist motion, detailed 3D geometries as well as patient-specific physiological wrist motion could be derived. This data formed the input for detailed finite element analysis, enabling computational of scaffold stress and strain distributions, which are key predictors of scaffold structural integrity. The computational analysis demonstrated that longer scaffolds present reduced peak scaffold stresses and a more homogeneous stress state compared to shorter scaffolds. Furthermore, it was found that scaffolds attached at proximal sites experience lower stresses than those attached at distal sites. However, scaffold length, rather than bone terminal location, most strongly influences peak stress. For each scaffold terminal placement configuration, a basic metric was computed indicative of bone fracture risk. This metric was the minimum distance from the bone surface to the internal scaffold bone terminal. Analysis of this minimum bone thickness data confirmed further optimisation of terminal locations is warranted.