Collagen Membrane and Immune Response in Guided Bone Regeneration: Recent Progress and Perspectives

Effects of interleukin-10 treated macrophages on bone marrow mesenchymal stem cells via signal transducer and activator of transcription 3 pathway

BACKGROUND

Alveolar bone defects caused by inflammation are an urgent issue in oral implant surgery that must be solved. Regulating the various phenotypes of macrophages to enhance the inflammatory environment can significantly affect the progression of diseases and tissue engineering repair process.

AIM

To assess the influence of interleukin-10 (IL-10) on the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) following their interaction with macrophages in an inflammatory environment.

METHODS

IL-10 modulates the differentiation of peritoneal macrophages in Wistar rats in an inflammatory environment. In this study, we investigated its impact on the proliferation, migration, and osteogenesis of BMSCs. The expression levels of signal transducer and activator of transcription 3 (STAT3) and its activated form, phosphorylated-STAT3, were examined in IL-10-stimulated macrophages. Subsequently, a specific STAT3 signaling inhibitor was used to impede STAT3 signal activation to further investigate the role of STAT3 signaling.

RESULTS

IL-10-stimulated macrophages underwent polarization to the M2 type through substitution, and these M2 macrophages actively facilitated the osteogenic differentiation of BMSCs. Mechanistically, STAT3 signaling plays a crucial role in the process by which IL-10 influences macrophages. Specifically, IL-10 stimulated the activation of the STAT3 signaling pathway and reduced the macrophage inflammatory response, as evidenced by its diminished impact on the osteogenic differentiation of BMSCs.

CONCLUSION

Stimulating macrophages with IL-10 proved effective in improving the inflammatory environment and promoting the osteogenic differentiation of BMSCs. The IL-10/STAT3 signaling pathway has emerged as a key regulator in the macrophage-mediated control of BMSCs' osteogenic differentiation.

Macrophages in guided bone regeneration: potential roles and future directions

Guided bone regeneration (GBR) is one of the most widely used and thoroughly documented alveolar bone augmentation surgeries. However, implanting GBR membranes inevitably triggers an immune response, which can lead to inflammation and failure of bone augmentation. It has been shown that GBR membranes may significantly improve in vivo outcomes as potent immunomodulators, rather than solely serving as traditional barriers. Macrophages play crucial roles in immune responses and participate in the entire process of bone injury repair. The significant diversity and high plasticity of macrophages complicate our understanding of the immunomodulatory mechanisms underlying GBR. This review provides a comprehensive summary of recent findings on the potential role of macrophages in GBR for bone defects in situ. Specifically, macrophages can promote osteogenesis or fibrous tissue formation in bone defects and degradation or fibrous encapsulation of membranes. Moreover, GBR membranes can influence the recruitment and polarization of macrophages. Therefore, immunomodulating GBR membranes are primarily developed by improving macrophage recruitment and aggregation as well as regulating macrophage polarization. However, certain challenges remain to be addressed in the future. For example, developing more rational and sophisticated sequential delivery systems for macrophage activation reagents; addressing the interference of bone graft materials and dental implants; and understanding the correlations among membrane degradation, macrophage responses, and bone regeneration.

3D-printed bredigite scaffolds with ordered arrangement structures promote bone regeneration by inducing macrophage polarization in onlay grafts

Bone tissue engineering scaffolds may provide a potential strategy for onlay bone grafts for oral implants. For determining the fate of scaffold biomaterials and osteogenesis effects, the host immune response is crucial. In the present study, bredigite (BRT) bioceramic scaffolds with an ordered arrangement structure (BRT-O) and a random morphology (BRT-R) were fabricated. The physicochemical properties of scaffolds were first characterized by scanning electron microscopy, mechanical test and micro-Fourier transform infrared spectroscopy. In addition, their osteogenic and immunomodulatory properties in an onlay grafting model were investigated. In vitro, the BRT-O scaffolds facilitated the macrophage polarization towards a pro-regenerative M2 phenotype, which subsequently facilitated the migration and osteogenic differentiation of bone marrow-derived mesenchymal stem cells. In vivo, an onlay grafting model was successfully established in the cranium of rabbits. In addition, the BRT-O scaffolds grafted on rabbit cranium promoted bone regeneration and CD68 + CD206 + M2 macrophage polarization. In conclusion, the 3D-printed BRT-O scaffold presents as a promising scaffold biomaterial for onlay grafts by regulating the local immune microenvironment.

Implications of graphene-based materials in dentistry: present and future

Since the advent of nanoscience, nanobiomaterials have been applied in the dental industry. Graphene and its derivatives have attracted the most interest of all of them due to their exceptional look, biocompatibility, multiplication differential, and antibacterial capabilities. We outlined the most recent developments about their applications to dentistry in our review. There is discussion of the synthesis processes, architectures, and characteristics of materials based on graphene. The implications of graphene and its counterparts are then meticulously gathered and described. Finally, in an effort to inspire more excellent research, this paper explores the obstacles and potential of graphene-based nanomaterials for dental aspects.

Barrier membranes for periodontal guided bone regeneration: a potential therapeutic strategy

Periodontal disease is one of the most common oral diseases with the highest incidence world-wide. In particular, the treatment of periodontal bone defects caused by periodontitis has attracted extensive attention. Guided bone regeneration (GBR) has been recognized as advanced treatment techniques for periodontal bone defects. GBR technique relies on the application of barrier membranes to protect the bone defects. The commonly used GBR membranes are resorbable and non-resorbable. Resorbable GBR membranes are divided into natural polymer resorbable membranes and synthetic polymer resorbable membranes. Each has its advantages and disadvantages. The current research focuses on exploring and improving its preparation and application. This review summarizes the recent literature on the application of GBR membranes to promote the regeneration of periodontal bone defects, elaborates on GBR development strategies, specific applications, and the progress of inducing periodontal bone regeneration to provide a theoretical basis and ideas for the future application of GBR membranes to promote the repair of periodontal bone defects.

Development, Characterization, and Antibacterial Analysis of the Selenium-Doped Bio-Glass-Collagen-Gelatin Composite Scaffold for Guided Bone Regeneration

Background Guided bone regeneration (GBR) is an often-used technique to aid the successful placement of dental implants in sites with deficient bone. The search for the ideal GBR membrane with bioactive components improving the regenerative outcomes is still on. In this study, a novel composite GBR membrane was developed using selenium-doped bio-glass, collagen, and gelatin. It was further characterized for surface, chemical, biocompatibility, and antibacterial properties. Methodology Selenium-doped bio-glass was prepared using the sol-gel method. The membrane was fabricated using an equal ratio of collagen and gelatin mixed with 1% selenium-doped bio-glass. The solution was poured to obtain a thin layer of the material which was lyophilized to obtain the final GBR membrane. The membrane was analyzed with scanning electron microscopy, energy dispersive X-ray (EDX) analysis, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), zebrafish cytotoxicity test, and antibacterial assay. Results The membrane revealed good surface roughness with lamellar and fibrillar arrangement with a minute granular surface ideal for cell attachment and proliferation. The EDX analysis revealed the presence of carbon, oxygen, and nitrogen as predominant components with trace amounts of calcium, phosphorus, silica, and selenium. Fourier transform infrared spectroscopy analysis also proved the presence of collagen, gelatin, and bio-glass. The membrane revealed excellent biocompatibility with zebrafish growth at a normal rate with 90% viability maintained at 48, 72, and 96 hours and 95% viability at 120 hours. It also exhibited excellent antibacterial activity against Staphylococcus aureus and Escherichia coli with minimal growth of bacterial colonies. Conclusion The developed novel selenium bio-glass collagen and gelatin composite scaffold has a good surface and antibacterial properties along with excellent biocompatibility. Further cell line and in vivo studies should be conducted to explore its role in bone regeneration.

Microenvironment-targeted strategy steers advanced bone regeneration

Treatment of large bone defects represents a great challenge in orthopedic and craniomaxillofacial surgery. Traditional strategies in bone tissue engineering have focused primarily on mimicking the extracellular matrix (ECM) of bone in terms of structure and composition. However, the synergistic effects of other cues from the microenvironment during bone regeneration are often neglected. The bone microenvironment is a sophisticated system that includes physiological (e.g., neighboring cells such as macrophages), chemical (e.g., oxygen, pH), and physical factors (e.g., mechanics, acoustics) that dynamically interact with each other. Microenvironment-targeted strategies are increasingly recognized as crucial for successful bone regeneration and offer promising solutions for advancing bone tissue engineering. This review provides a comprehensive overview of current microenvironment-targeted strategies and challenges for bone regeneration and further outlines prospective directions of the approaches in construction of bone organoids.

Decellularized periosteum promotes guided bone regeneration via manipulation of macrophage polarization

Periosteum has shown potential as an effective barrier membrane for guided bone regeneration (GBR). However, if recognized as a "foreign body," insertion of a barrier membrane in GBR treatment will inevitably alter the local immune microenvironment and subsequently influence bone regeneration. The aim of this investigation was to fabricate decellularized periosteum (DP) and investigate its immunomodulatory properties in GBR. DP was successfully fabricated from periosteum from the mini-pig cranium. In vitro experiments indicated that the DP scaffold modulated macrophage polarization toward a pro-regenerative M2 phenotype, which in turn facilitated migration and osteogenic differentiation of bone marrow-derived mesenchymal stem cells. A rat GBR model with a cranial critical-size defect was established, and our in vivo experiment confirmed the beneficial effects of DP on the local immune microenvironment and bone regeneration. Collectively, the findings of this study indicate that the prepared DP possesses immunomodulatory properties and represents a promising barrier membrane for GBR procedures.

Bone regeneration in implant dentistry: Which are the factors affecting the clinical outcome?

The key factors that are needed for bone regeneration to take place include cells (osteoprogenitor and immune-inflammatory cells), a scaffold (blood clot) that facilitates the deposition of the bone matrix, signaling molecules, blood supply, and mechanical stability. However, even when these principles are met, the overall amount of regenerated bone, its stability over time and the incidence of complications may significantly vary. This manuscript provides a critical review on the main local and systemic factors that may have an impact on bone regeneration, trying to focus, whenever possible, on bone regeneration simultaneous to implant placement to treat bone dehiscence/fenestration defects or for bone contouring. In the future, it is likely that bone tissue engineering will change our approach to bone regeneration in implant dentistry by replacing the current biomaterials with osteoinductive scaffolds combined with cells and mechanical/soluble factors and by employing immunomodulatory materials that can both modulate the immune response and control other bone regeneration processes such as osteogenesis, osteoclastogenesis, or inflammation. However, there are currently important knowledge gaps on the biology of osseous formation and on the factors that can influence it that require further investigation. It is recommended that future studies should combine traditional clinical and radiographic assessments with non-invasive imaging and with patient-reported outcome measures. We also envisage that the integration of multi-omics approaches will help uncover the mechanisms responsible for the variability in regenerative outcomes observed in clinical practice.

Injectable Antibacterial Hydrogel with Asiaticoside-Loaded Liposomes and Ultrafine Silver Nanosilver Particles Promotes Healing of Burn-Infected Wounds

Post-injury infection and wound healing are recurrent daily life problems. Therefore, the necessity of developing a biomaterial with antibacterial and wound-healing properties is paramount. Based on the special porous structure of hydrogel, this work modifies recombinant collagen and quaternary ammonium chitosan and fused them with silver nanoparticles (Ag@mental-organic framework (Ag@MOF)) with antibacterial properties, and asiaticoside-loaded liposomes (Lip@AS) with anti-inflammatory/vascularization effects to form the rColMA/QCSG/LIP@AS/Ag@MOF (RQLAg) hydrogel. The prepared hydrogel possesses good sustainable release capabilities of Ag+ and AS and exhibits concentration-dependent swelling properties, pore size, and compressive strength. Cellular experiments show that the hydrogel exhibits good cell compatibility and promote cell migration, angiogenesis, and M1 macrophage polarization. Additionally, the hydrogels exhibit excellent antibacterial activity against Escherichia coli and Staphylococcus aureus in vitro. In vivo, Sprague Dawley rats burn-wound infection model showed that the RQLAg hydrogel could efficiently promote wound healing and has stronger healing promoting abilities than those of Aquacel Ag. In summary, the RQLAg hydrogel is expected to be an excellent material for accelerating open wound healing and preventing bacterial infections.

Fabrication of ACP-CCS-PVA composite membrane for a potential application in guided bone regeneration

The barrier membranes of guided bone regeneration (GBR) have been widely used in clinical medicine to repair bone defects. However, the unmatched mechanical strength, unsuitable degradation rates, and insufficient regeneration potential limit the application of the current barrier membranes. Here, amorphous calcium phosphate-carboxylated chitosan-polyvinyl alcohol (ACP-CCS-PVA) composite membranes are fabricated by freeze-thaw cycles, in which the ATP-stabilized ACP nanoparticles are uniformly distributed throughout the membranes. The mechanical performance and osteogenic properties are significantly improved by the ACP incorporated into the CCS-PVA system, but excess ACP would suppress cell proliferation and osteogenic differentiation. Our work highlights the pivotal role of ACP in GBR and provides insight into the need for biomaterial fabrication to balance mechanical strength and mineral content.

Green biomanufacturing in recombinant collagen biosynthesis: trends and selection in various expression systems

Collagen, classically derived from animal tissue, is an all-important protein material widely used in biomedical materials, cosmetics, fodder, food, etc. The production of recombinant collagen through different biological expression systems using bioengineering techniques has attracted significant interest in consideration of increasing market demand and the process complexity of extraction. Green biomanufacturing of recombinant collagen has become one of the focus topics. While the bioproduction of recombinant collagens (type I, II, III, etc.) has been commercialized in recent years, the biosynthesis of recombinant collagen is extremely challenging due to protein immunogenicity, yield, degradation, and other issues. The rapid development of synthetic biology allows us to perform a heterologous expression of proteins in diverse expression systems, thus optimizing the production and bioactivities of recombinant collagen. This review describes the research progress in the bioproduction of recombinant collagen over the past two decades, focusing on different expression systems (prokaryotic organisms, yeasts, plants, insects, mammalian and human cells, etc.). We also discuss the challenges and future trends in developing market-competitive recombinant collagens.

Underestimated microbial infection of resorbable membranes on guided regeneration

Barrier membranes are critical in creating tissuecompartmentalization for guided tissue (GTR) and bone regeneration (GBR) therapies. More recently, resorbable membranes have been widely used for tissue and bone regeneration due to their improved properties and the dispensable re-entry surgery for membrane removal. However, in cases with membrane exposure, this may lead to microbial contamination that will compromise the integrity of the membrane, surrounding tissue, and bone regeneration, resulting in treatment failure. Although the microbial infection can negatively influence the clinical outcomes of regenerative therapy, such as GBR and GTR, there is a lack of clinical investigations in this field, especially concerning the microbial colonization of different types of membranes. Importantly, a deeper understanding of the mechanisms of biofilm growth and composition and pathogenesis on exposed membranes is still missing, explaining the mechanisms by which bone regeneration is reduced during membrane exposure. This scoping review comprehensively screened and discussed the current in vivo evidence and possible new perspectives on the microbial contamination of resorbable membranes. Results from eligible in vivo studies suggested that different bacterial species colonized exposed membranes according to their composition (collagen, expanded polytetrafluoroethylene (non-resorbable), and polylactic acid), but in all cases, it negatively affected the attachment level and amount of bone gain. However, limited models and techniques have evaluated the newly developed materials, and evidence is scarce. Finally, new approaches to enhance the antimicrobial effect should consider changing the membrane surface or incorporating long-term released antimicrobials in an effort to achieve better clinical success.

Optimization of stress distribution of bone-implant interface (BII)

Many studies have found that the threshold of occlusal force tolerated by titanium-based implants is significantly lower than that of natural teeth due to differences in biomechanical mechanisms. Therefore, implants are considered to be susceptible to occlusal trauma. In clinical practice, many implants have shown satisfactory biocompatibility, but the balance between biomechanics and biofunction remains a huge clinical challenge. This paper comprehensively analyzes and summarizes various stress distribution optimization methods to explore strategies for improving the resistance of the implants to adverse stress. Improving stress resistance reduces occlusal trauma and shortens the gap between implants and natural teeth in occlusal function. The study found that: 1) specific implant-abutment connection design can change the force transfer efficiency and force conduction direction of the load at the BII; 2) reasonable implant surface structure and morphological character design can promote osseointegration, maintain alveolar bone height, and reduce the maximum effective stress at the BII; and 3) the elastic modulus of implants matched to surrounding bone tissue can reduce the stress shielding, resulting in a more uniform stress distribution at the BII. This study concluded that the core BII stress distribution optimization lies in increasing the stress distribution area and reducing the local stress peak value at the BII. This improves the biomechanical adaptability of the implants, increasing their long-term survival rate.

Optimizing the biodegradability and osteogenesis of biogenic collagen membrane via fluoride-modified polymer-induced liquid precursor process

Biogenic collagen membranes (BCM) have been widely used in guided bone regeneration (GBR) owing to their biodegradability during tissue integration. However, their relatively high degradation rate and lack of pro-osteogenic properties limit their clinical outcomes. It is of great importance to endow BCM with tailored degradation as well as pro-osteogenic properties. In this study, a fluoride-modified polymer-induced liquid precursor (PILP) based biomineralization strategy was used to convert the collagen membrane from an organic phase to an apatite-based inorganic phase, thus achieving enhanced anti-degradation performance as well as osteogenesis. As a result, three phases of collagen membranes were prepared. The original BCM in the organic phase induced the mildest inflammatory response and was mostly degraded after 4 weeks. The organic-inorganic mixture phase of the collagen membrane evoked a prominent inflammatory response owing to the fluoride-containing amorphous calcium phosphate (F-ACP) nanoparticles, resulting in active angiogenesis and fibrous encapsulation, whereas the inorganic phase induced a mild inflammatory response and degraded the least owing to the transition of F-ACP particles into calcium phosphate with high crystallinity. Effective control of ACP is key to building novel apatite-based barrier membranes. The current results may pave the way for the development of advanced apatite-based membranes with enhanced barrier performances.

Immunomodulatory Biomaterials and Emerging Analytical Techniques for Probing the Immune Micro-Environment

After implantation of a biomaterial, both the host immune system and properties of the material determine the local immune response. Through triggering or modulating the local immune response, materials can be designed towards a desired direction of promoting tissue repair or regeneration. High-throughput sequencing technologies such as single-cell RNA sequencing (scRNA-seq) emerging as a powerful tool for dissecting the immune micro-environment around biomaterials, have not been fully utilized in the field of soft tissue regeneration. In this review, we first discussed the procedures of foreign body reaction in brief. Then, we summarized the influences that physical and chemical modulation of biomaterials have on cell behaviors in the micro-environment. Finally, we discussed the application of scRNA-seq in probing the scaffold immune micro-environment and provided some reference to designing immunomodulatory biomaterials. The foreign body response consists of a series of biological reactions. Immunomodulatory materials regulate immune cell activation and polarization, mediate divergent local immune micro-environments and possess different tissue engineering functions. The manipulation of physical and chemical properties of scaffolds can modulate local immune responses, resulting in different outcomes of fibrosis or tissue regeneration. With the advancement of technology, emerging techniques such as scRNA-seq provide an unprecedented understanding of immune cell heterogeneity and plasticity in a scaffold-induced immune micro-environment at high resolution. The in-depth understanding of the interaction between scaffolds and the host immune system helps to provide clues for the design of biomaterials to optimize regeneration and promote a pro-regenerative local immune micro-environment.

Application of decellularized vascular matrix in small-diameter vascular grafts

Coronary artery bypass grafting (CABG) remains the most common procedure used in cardiovascular surgery for the treatment of severe coronary atherosclerotic heart disease. In coronary artery bypass grafting, small-diameter vascular grafts can potentially replace the vessels of the patient. The complete retention of the extracellular matrix, superior biocompatibility, and non-immunogenicity of the decellularized vascular matrix are unique advantages of small-diameter tissue-engineered vascular grafts. However, after vascular implantation, the decellularized vascular matrix is also subject to thrombosis and neoplastic endothelial hyperplasia, the two major problems that hinder its clinical application. The keys to improving the long-term patency of the decellularized matrix as vascular grafts include facilitating early endothelialization and avoiding intravascular thrombosis. This review article sequentially introduces six aspects of the decellularized vascular matrix as follows: design criteria of vascular grafts, components of the decellularized vascular matrix, the changing sources of the decellularized vascular matrix, the advantages and shortcomings of decellularization technologies, modification methods and the commercialization progress as well as the application prospects in small-diameter vascular grafts.

Gene-activated titanium implants for gene delivery to enhance osseointegration

Osseointegration is the direct and intimate contact between mineralized tissue and titanium implant at the bone-implant interface. Early establishment and stable maintenance of osseointegration is the key to long-term implant success. However, in patients with compromised conditions such as osteoporosis and patients beginning early load-bearing activities such as walking, lower osseointegration around titanium implants is often observed, which might result in implant early failure. Gene-activated implants show an exciting prospect of combining gene delivery and biomedical implants to solve the problems of poor osseointegration formation, overcoming the shortcomings of protein therapy, including rapid degradation and overdose adverse effects. The conception of gene-activated titanium implants is based on "gene-activated matrix" (GAM), which means scaffolds using non-viral vectors for in situ gene delivery to achieve a long-term and efficient transfection of target cells. Current preclinical studies in animal models have shown that plasmid DNA (pDNA), microRNA (miRNA), and small interference RNA (siRNA) functionalized titanium implants can enhance osseointegration with safety and efficiency, leading to the expectation of applying this technique in dental and orthopedic clinical scenarios. This review aims to comprehensively summarize fabrication strategies, current applications, and futural outlooks of gene-activated implants, emphasizing nucleic acid targets, non-viral vectors, implant surface modification techniques, nucleic acid/vector complexes loading strategies.

Barrier Membranes for Guided Bone Regeneration (GBR): A Focus on Recent Advances in Collagen Membranes

Guided bone regeneration (GBR) has become a clinically standard modality for the treatment of localized jawbone defects. Barrier membranes play an important role in this process by preventing soft tissue invasion outgoing from the mucosa and creating an underlying space to support bone growth. Different membrane types provide different biological mechanisms due to their different origins, preparation methods and structures. Among them, collagen membranes have attracted great interest due to their excellent biological properties and desired bone regeneration results to non-absorbable membranes even without a second surgery for removal. This work provides a comparative summary of common barrier membranes used in GBR, focusing on recent advances in collagen membranes and their biological mechanisms. In conclusion, the review article highlights the biological and regenerative properties of currently available barrier membranes with a particular focus on bioresorbable collagen-based materials. In addition, the advantages and disadvantages of these biomaterials are highlighted, and possible improvements for future material developments are summarized.

Regulating Macrophages through Immunomodulatory Biomaterials Is a Promising Strategy for Promoting Tendon-Bone Healing

The tendon-to-bone interface is a special structure connecting the tendon and bone and is crucial for mechanical load transfer between dissimilar tissues. After an injury, fibrous scar tissues replace the native tendon-to-bone interface, creating a weak spot that needs to endure extra loading, significantly decreasing the mechanical properties of the motor system. Macrophages play a critical role in tendon-bone healing and can be divided into various phenotypes, according to their inducing stimuli and function. During the early stages of tendon-bone healing, M1 macrophages are predominant, while during the later stages, M2 macrophages replace the M1 macrophages. The two macrophage phenotypes play a significant, yet distinct, role in tendon-bone healing. Growing evidence shows that regulating the macrophage phenotypes is able to promote tendon-bone healing. This review aims to summarize the impact of different macrophages on tendon-bone healing and the current immunomodulatory biomaterials for regulating macrophages, which are used to promote tendon-bone healing. Although macrophages are a promising target for tendon-bone healing, the challenges and limitations of macrophages in tendon-bone healing research are discussed, along with directions for further research.

Three-dimensional (3D) scaffolds as powerful weapons for tumor immunotherapy

Though increasing understanding and remarkable clinical successes have been made, enormous challenges remain to be solved in the field of cancer immunotherapy. In this context, biomaterial-based immunomodulatory strategies are being developed to boost antitumor immunity. For the local immunotherapy, macroscale biomaterial scaffolds with 3D network structures show great superiority in the following aspects: facilitating the encapsulation, localized delivery, and controlled release of immunotherapeutic agents and even immunocytes for more efficient immunomodulation. The concentrating immunomodulation in situ could minimize systemic toxicities, but still exert abscopal effects to harness the power of overall anticancer immune response for eradicating malignancy. To promote such promising immunotherapies, the design requirements of macroscale 3D scaffolds should comprehensively consider their physicochemical and biological properties, such as porosity, stiffness, surface modification, cargo release kinetics, biocompatibility, biodegradability, and delivery modes. To date, increasing studies have focused on the relationships between these parameters and the biosystems which will guide/assist the 3D biomaterial scaffolds to achieve the desired immunotherapeutic outcomes. In this review, by highlighting some recent achievements, we summarized the latest advances in the development of various 3D scaffolds as niches for cancer immunotherapy. We also discussed opportunities, challenges, current trends, and future perspectives in 3D macroscale biomaterial scaffold-assisted local treatment strategies. More importantly, this review put more efforts to illustrate how the 3D biomaterial systems affect to modulate antitumor immune activities, where we discussed how significant the roles and behaviours of 3D macroscale scaffolds towards in situ cancer immunotherapy in order to direct the design of 3D immunotherapeutic.

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Macroscale biomaterial scaffolds with 3D network structures show great superiority for enhanced tumor immunotherapy.

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More focuses have been put on the relationships between the properties of 3D scaffolds and the biosystem when immunotherapy.

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The most recent remarkable 3D cancer immunotherapeutic platforms are summarized for future clinical transformation.

A cell-free difunctional demineralized bone matrix scaffold enhances the recruitment and osteogenesis of mesenchymal stem cells by promoting inflammation resolution

The dialogue between host macrophages (Mφs) and endogenous mesenchymal stem cells (MSCs) promotes M2 Mφs polarization to resolve early-stage inflammation, thereby effectively guiding in situ bone regeneration. Once inflammation is unresolved/incontrollable, it will induce the impediment of MSCs homing at bone defect site, implying the seasonable resolution of inflammation in balancing bone homeostasis. Repeatedly, evidence elucidated that specialized pro-resolving mediators (SPMs) could conduce to proper resolve inflammation and promote the repairing of bone defect. A difunctional demineralized bone matrix (DBM) scaffold co-modified by maresin 1 (MaR1) and aptamer 19S (Apt19S) was fabricated to facilitate the osteogenesis of MSCs. To confirm the osteogenesis and immunomodulatory role of the difunctional DBM scaffold, the proliferation, recruitment, and osteogenic differentiation of MSCs and the Mφs M2 subtype polarization were evaluated in vitro. Then, the DBM scaffolds were implanted into mice model with critical size calvarial defect to evaluate bone repair efficiency. Finally, the specific resolution mechanism in Mφs cultured on the difunctional DBM scaffold was further in-depth investigated. This difunctional DBM scaffold exhibited an enhanced function on the recruitment, proliferation, migration, osteogenesis of MSCs and the resolution of inflammation, finally improved bone-scaffold integration. At the same time, MaR1 modified on the difunctional DBM scaffold increased the biosynthesis of 12-lipoxygenase (12-LOX) and 12S-hydroxy-eicosatetraenoic acid (12S-HETE), and also directly stimulated lipid droplets (LDs) biogenesis in Mφs, which suggested that MaR1 regulated Mφ lipid metabolism at bone repair site. Findings based on this synergy strategy demonstrated that Mφ lipid metabolism was essential in bone homeostasis, which might provide a theoretical direction for the treatment-associated application of MaR1 in inflammatory bone disease.

Collagen Membrane Derived from Fish Scales for Application in Bone Tissue Engineering

Guided tissue/bone regeneration (GTR/GBR) is currently the main treatment for alveolar bone regeneration. The commonly used barrier membranes in GTR/GBR are collagen membranes from mammals such as porcine or cattle. Fish collagen is being explored as a potential substitute for mammalian collagen due to its low cost, no zoonotic risk, and lack of religious constraints. Fish scale is a multi-layer natural collagen composite with high mechanical strength, but its biomedical application is limited due to the low denaturation temperature of fish collagen. In this study, a fish scale collagen membrane with a high denaturation temperature of 79.5 °C was prepared using an improved method based on preserving the basic shape of fish scales. The fish scale collagen membrane was mainly composed of type I collagen and hydroxyapatite, in which the weight ratios of water, organic matter, and inorganic matter were 20.7%, 56.9%, and 22.4%, respectively. Compared to the Bio-Gide^® membrane (BG) commonly used in the GTR/GBR, fish scale collagen membrane showed good cytocompatibility and could promote late osteogenic differentiation of cells. In conclusion, the collagen membrane prepared from fish scales had good thermal stability, cytocompatibility, and osteogenic activity, which showed potential for bone tissue engineering applications.

Patient-reported outcome measures following surgeries in implant dentistry and associated factors: a cross-sectional study

OBJECTIVES

We aimed to evaluate the patient-reported outcome measures (PROMs) of dental implant surgeries and analyse the associated indicators.

DESIGN

A cross-sectional study design was used.

SETTING

Department of Oral Implantology, Hospital of Stomatology, Wuhan University (May 2020-April 2021).

PARTICIPANTS

Participants with missing teeth in need of implant-supported rehabilitation.

INTERVENTIONS

Dental implant placement and/or bone augmentation procedures.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome was discomfort on postoperative day 1, measured using a numerical rating scale (NRS). Secondary outcomes included pain and anxiety during surgery; discomfort on postoperative days 3, 7 and 14; and post-surgical complications.

RESULTS

A total of 366 participants were included, of which 288 (78.7%) and 328 (89.7%) reported no to mild pain and anxiety (NRS 0-3) during surgery, respectively. The proportion of patients reporting discomfort decreased from postoperative day 1 (57.7%) to day 3 (36.1%) and day 7 (17.5%). The most frequent postoperative adverse events were pain and swelling. Patient-related factors (age, sex, smoking, alcohol consumption, history of periodontitis, and pain and anxiety during surgery) and surgery-related factors (type and extent of surgical procedure) were analysed. The factors associated with the severity of discomfort after surgery included alcohol consumption, pain perception during surgery, bone augmentation procedures and age (p<0.05). Similarly, the factors associated with the duration of discomfort included alcohol consumption, pain perception during surgery and age (p<0.05).

CONCLUSIONS

PROMs related to dental implant surgeries can be predicted using certain risk indicators. Alcohol consumption, pain during surgery and age were associated with discomfort following dental implant surgery.

Interactions Between Immunomodulatory Biomaterials and Immune Microenvironment: Cues for Immunomodulation Strategies in Tissue Repair

The foreign body response (FBR) caused by biomaterials can essentially be understood as the interaction between the immune microenvironment and biomaterials, which has severely impeded the application of biomaterials in tissue repair. This concrete interaction occurs via cells and bioactive substances, such as proteins and nucleic acids. These cellular and molecular interactions provide important cues for determining which element to incorporate into immunomodulatory biomaterials (IMBs), and IMBs can thus be endowed with the ability to modulate the FBR and repair damaged tissue. In terms of cellular, IMBs are modified to modulate functions of immune cells, such as macrophages and mast cells. In terms of bioactive substances, proteins and nucleic acids are delivered to influence the immune microenvironment. Meanwhile, IMBs are designed with high affinity for spatial targets and the ability to self-adapt over time, which allows for more efficient and intelligent tissue repair. Hence, IMB may achieve the perfect functional integration in the host, representing a breakthrough in tissue repair and regeneration medicine.

Updates in immunocompatibility of biomaterials: applications for regenerative medicine

INTRODUCTION

Biomaterials, either metallic, ceramic, or polymeric, can be used in medicine as a part of the implants, dialysis membranes, bone scaffolds, or components of artificial organs. Polymeric biomaterials cover a vast range of biomedical applications. The biocompatibility and immunocompatibility of polymeric materials are of fundamental importance for their possible therapeutic uses, as the immune system can intervene in the materials' performance. Therefore, based on application, different routes can be utilized for immunoregulation.

AREAS COVERED

As different biomaterials can be modulated by different strategies, this study aims to summarize and evaluate the available methods for the immunocompatibility enhancement of more common polymeric biomaterials based on their nature. Different strategies such as surface modification, physical characterization, and drug incorporation are investigated for the immunomodulation of nanoparticles, hydrogels, sponges, and nanofibers.

EXPERT OPINION

Recently, strategies for triggering appropriate immune responses by functional biomaterials have been highlighted. As most strategies correspond to the physical and surface properties of biomaterials, specific modulation can be conducted for each biomaterial system. Besides, different applications require different modulations of the immune system. In the future, the selection of novel materials and immune regulators can play a role in tuning the immune system for regenerative medicine.

Optimizing the bio-degradability and biocompatibility of a biogenic collagen membrane through cross-linking and zinc-doped hydroxyapatite

Biogenic collagen membranes have been widely used as soft tissue barriers in guided bone regeneration (GBR) and guided tissue regeneration (GTR). Nevertheless, their clinical performance remains unsatisfactory because of their low mechanical strength and fast degradation rate in vivo. Although cross-linking with chemical agents is effective and reliable for prolonging the degradation time of collagen membranes, some adverse effects including potential cytotoxicity and undesirable tissue integration have been observed during this process. As a fundamental nutritional trace element, zinc plays an active role in promoting the growth of cells and regulating the degradation of the collagen matrix. Herein, a biogenic collagen membrane was cross-linked with glutaraldehyde-alendronate to prolong its degradation time. The physiochemical and biological properties were enhanced by the incorporation of zinc-doped nanohydroxyapatite (nZnHA), with the native structure of collagen preserved. Specifically, the cross-linking combined with the incorporation of 1% and 2% nZnHA seemed to endow the membrane with the most appropriate biocompatibility and tissue integration capability among the cross-linked membranes, as well as offering a degradation period of six weeks in a rat subcutaneous model. Thus, improving the clinical performance of biogenic collagen membranes by cross-linking together with the incorporation of nZnHA is a promising strategy for the improvement of biogenic collagen membranes. STATEMENT OF SIGNIFICANCE: The significance of this research includes.

Collagen-Based Biomaterials in Periodontal Regeneration: Current Applications and Future Perspectives of Plant-Based Collagen

Collagen is the most widely distributed protein in human body. Within the field of tissue engineering and regenerative medical applications, collagen-based biomaterials have been extensively growing over the past decades. The focus of this review is mainly on periodontal regeneration. Currently, multiple innovations of collagen-based biomaterials have evolved, from hemostatic collagen sponges to bone/tissue regenerative scaffolds and injectable collagen matrices for gene or cell regenerative therapy. Collagen sources also differ from animal to marine and plant-extracted recombinant human type I collagen (rhCOL1). Animal-derived collagen has a number of substantiated concerns such as pathogenic contamination and transmission and immunogenicity, and rhCOL1 is a potential solution to those aforementioned issues. This review presents a brief overview of periodontal regeneration. Also, current applications of collagen-based biomaterials and their mechanisms for periodontal regeneration are provided. Finally, special attention is paid to mechanical, chemical, and biological properties of rhCOL1 in pre-clinical and clinical studies, and its future perspectives in periodontal regeneration are discussed.

Prodrug inspired bi-layered electrospun membrane with properties of enhanced tissue integration for guided tissue regeneration

Guided tissue regeneration (GTR) membranes play a vital role in periodontal surgery. Recently a series of composite electrospun membranes have been fabricated to improve the unexpected biodegradation of collagen-based GTR membranes. However, their tissue integrity needs to be studied in depth. In this study, a bi-layered electrospun membrane (BEM) inspired by "prodrug" was fabricated, which contained a dense-layer (BEM-DL) and a potential loose-layer (BEM-LL). The nanofibers of BEM-DL were composed of poly(l-lactic-co-glycolic acid) and tilapia skin collagen (TSC). Whereas the BEM-LL consisted of two types of nanofibers, one was the same as BEM-DL and the other was made from TSC. The morphology, degradation in vitro, cytocompatibility and biocompatibility in rats were investigated with a poly(lactic-co-glycolic acid) electrospun membrane (PLGA) as the negative control. The pore size of BEM-LL soaked for 7 days became larger than the original sample (164.8 ± 90.9 and 52.5 ± 21.0 μm² , respectively), which was significantly higher (p < .05) than that of BEM-DL and PLGA. The BEM-LL displayed a larger weight loss rate of 82.3 ± 3.6% than the BEM-DL of 46.0 ± 2.8% at day 7 because of the rapid degradation of TSC fibers. The cytocompatibility test demonstrated that L929 cells were only spread on the surface of the BEM-DL while MC3T3-E1 cells grew into the BEM-LL layer. The subcutaneous implantation test further proved that BEM-DL performed as a cellular barrier, whereas BEM-LL was conducive to cell infiltration as deep as 200 μm with reduced fibrous encapsulation. Herein, the BEM inspired by "prodrug" is a promising GTR membrane with a property of enhanced tissue integration.

Systemic and local innate immune responses to surgical co-transplantation of mesenchymal stromal cells and biphasic calcium phosphate for bone regeneration

Bone regeneration from mesenchymal stromal cells (MSC) is attributed to comprehensive immune modulation mediated by the MSC. However, the temporal and spatial regulation of these immune responses has not yet been described. The aim of the present study was to assess the local and systemic innate immune responses to implantation of biphasic calcium phosphate biomaterial (BCP) alone, or with bone marrow derived MSC (BCP+MSC), in critical-sized calvarial bone defects of Lewis rats. Four weeks after implantation, flow cytometry analysis of innate immune cells revealed increased numbers of circulating classical monocyte-macrophages (MM) and decreased non-classical MM in the BCP+MSC group. At week 8, this differential systemic MM response was associated with an increased presence of local tissue anti-inflammatory macrophages expressing CD68 and CD163 markers (M2-like). In the BCP group without MSC, NK cells increased at weeks 1 and 4, and neutrophils increased in circulation at weeks 2 and 8. At week 8, the increase in number of neutrophils in circulation was associated with decreased local tissue neutrophils, in the BCP+MSC group. Gene expression analysis of tissue biopsies from defects implanted with BCP+MSC, in comparison to BCP alone, revealed upregulated expression of early osteogenesis genes along with macrophage differentiation-related genes at weeks 1 and 8 and neutrophil chemotaxis-related genes at week 1. This study is the first to demonstrate that surgical implantation of BCP or BCP+MSC grafts differentially regulate both systemic and local tissue innate immune responses which enhance bone formation. The results provide new insights into immune mechanisms underlying MSC-mediated bone regeneration. STATEMENT OF SIGNIFICANCE: The suitability of biphasic calcium phosphate and mesenchymal stromal cell construct (BCP+MSC) transplantation is evident from their progress in clinical trials for treating challenging maxillofacial bone defects. But less is known about the overall immune response generated by this surgical process and how it later impacts the bone formation. To this end, it is crucial to understand for both clinicians and researchers, the systemic immune response to transplanting MSC in patients for ensuring both the safety and efficacy of cell therapies. In this study, we used rat calvarial bone defect model and showed that both systemic and local innate immunes responses (monocyte-macrophages and neutrophils) are favorably directed towards enhanced bone formation in BCP+MSC implanted defects, as compared to BCP alone.

Graphene-Based Nanomaterials for Dental Applications: Principles, Current Advances, and Future Outlook

With the development of nanotechnology, nanomaterials have been used in dental fields over the past years. Among them, graphene and its derivatives have attracted great attentions, owing to their excellent physicochemical property, morphology, biocompatibility, multi-differentiation activity, and antimicrobial activity. In our review, we summarized the recent progress about their applications on the dentistry. The synthesis methods, structures, and properties of graphene-based materials are discussed. Then, the dental applications of graphene-based materials are emphatically collected and described. Finally, the challenges and outlooks of graphene-based nanomaterials on the dental applications are discussed in this paper, aiming at inspiring more excellent studies.

Zein-induced immune response and modulation by size, pore structure and drug-loading: Application for sciatic nerve regeneration

Zein is a biodegradable material with great potential in biomedical applications. However, as a plant-derived protein material, body's immune response is the key factor to determine its clinical performance. Herein, for the first time, the zein-induced immune response is evaluated systemically and locally, comparing with typical materials including alginate (ALG), poly(lactic-co-glycolic) acid (PLGA) and polystyrene (PS). Zein triggers an early inflammatory response consistent with the non-degradable PS, but this response decreases to the same level of the biosafe ALG and PLGA with zein degradation. Changing sphere sizes, pore structure and encapsulating dexamethasone can effectively modulate the zein-induced immune response, especially the pore structure which also inhibits neutrophil recruitment and promotes macrophages polarizing towards M2 phenotype. Thus, porous zein conduits with high and low porosity are further fabricated for the 15 mm sciatic nerve defect repair in rats. The conduits with high porosity induce more M2 macrophages to accelerate nerve regeneration with shorter degradation period and better nerve repair efficacy. These findings suggest that the pore structure in zein materials can alleviate the zein-induced early inflammation and promote M2 macrophage polarization to accelerate nerve regeneration. STATEMENT OF SIGNIFICANCE: Zein is a biodegradable material with great potential in biomedical applications. However, as a plant protein, its possible immune response in vivo is always the key issue. Until now, the systemic study on the immune responses of zein in vivo is still very limited, especially as an implant. Herein, for the first time, the zein-induced immune response was evaluated systemically and locally, comparing with typical biomaterials including alginate, poly(lactic-co-glycolic) acid and polystyrene. Changing sphere sizes, pore structure and encapsulating dexamethasone could effectively modulate the zein-induced immune response, especially the pore structure which also inhibited neutrophil recruitment and promoted macrophages polarizing towards M2 phenotype. Furthermore, the pore structure in zein nerve conduits was proved to alleviate the early inflammation and promote M2 macrophage polarization to accelerate nerve regeneration.

A Hierarchical-Structured Mineralized Nanofiber Scaffold with Osteoimmunomodulatory and Osteoinductive Functions for Enhanced Alveolar Bone Regeneration

Alveolar bone resorption is a major cause of teeth loss and jeopardizes the osseointegration of dental implants, greatly affecting patient's quality of life and health. It is still a great challenge to completely regenerate the alveolar bone defect through traditional guided bone regeneration (GBR) membranes due to their limited bioactivity and regeneration potential. Herein, a new hierarchical-structured mineralized nanofiber (HMF) scaffold, which is combined with both anisotropic and isotropic nanofibrous surface topography and the mineralized particles, is fabricated via a simple template-assisted electrospinning technology and in situ mineralization method. This HMF scaffold can not only directly induce osteogenic differentiation of bone mesenchymal stem cells (osteoinduction), but also stimulate macrophage toward pro-healing (M2) phenotype-polarization with an elevated secretion of the pro-healing cytokines, eventually enhancing the osteogenesis (osteoimmunomodulation). The results of in vivo rat alveolar bone defect repair experiments demonstrate that as compared with the combination of commercial Bio-Gide and Bio-Oss, the single HMF scaffold shows comparable or even superior bone repair effect, with better tissue-integration and more suitable degradation time and accompanied by a simplified operation.

Hierarchical Intrafibrillarly Mineralized Collagen Membrane Promotes Guided Bone Regeneration and Regulates M2 Macrophage Polarization

Mineralized collagen has been introduced as a promising barrier membrane material for guided bone regeneration (GBR) due to its biomimetic nanostructure. Immune interaction between materials and host significantly influences the outcome of GBR. However, current barrier membranes are insufficient for clinical application due to limited mechanical or osteoimmunomodulatory properties. In this study, we fabricated hierarchical intrafibrillarly mineralized collagen (HIMC) membrane, comparing with collagen (COL) and extrafibrillarly mineralized collagen (EMC) membranes, HIMC membrane exhibited preferable physicochemical properties by mimicking the nanostructure of natural bone. Bone marrow mesenchymal stem cells (BMSCs) seeded on HIMC membrane showed superior proliferation, adhesion, and osteogenic differentiation capacity. HIMC membrane induced CD206+Arg-1+ M2 macrophage polarization, which in turn promoted more BMSCs migration. In rat skull defects, HIMC membrane promoted the regeneration of new bone with more bone mass and more mature bone architecture. The expression levels of Runx2 and osterix and CD68 + CD206 + M2 macrophage polarization were significantly enhanced. HIMC membrane provides an appropriate osteoimmune microenvironment to promote GBR and represents a promising material for further clinical application.

Chitosan-collagen-hydroxyapatite membranes for tissue engineering

Tissue engineering is growing in developing new technologies focused on providing effective solutions to degenerative pathologies that affect different types of connective tissues. The search for biocompatible, bioactive, biodegradable, and multifunctional materials has grown significantly in recent years. Chitosan, calcium phosphates collagen, and their combination as composite materials fulfill the required properties and could result in biostimulation for tissue regeneration. In the present work, the chitosan/collagen/hydroxyapatite membranes were prepared with different concentrations of collagen and hydroxyapatite. Cell adhesion was evaluated by MTS assay for two in vitro models. Additionally, cytotoxicity of the different membranes employing hemolysis of erythrocytes isolated from human blood was carried out. The structure of the membranes was analyzed by X-rays diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermal stability properties by thermogravimetric methods (TGA). The highest cell adhesion after 48 h was obtained for chitosan membranes with the highest hydroxyapatite and collagen content. All composite membranes showed good cell adhesion and low cytotoxicity, suggesting that these materials have a significant potential to be used as biomaterials for tissue engineering. Graphical abstract.

7-Hydroxycoumarin mitigates the severity of collagen-induced arthritis in rats by inhibiting proliferation and inducing apoptosis of fibroblast-like synoviocytes via suppression of Wnt/β-catenin signaling pathway

BACKGROUND

7-Hydroxycoumarin (7-HC) as a coumarin compound is widely found in Chinese herbs and exhibits diverse biological activities. Promoting cell apoptosis of fibroblast-like synoviocytes (FLS) is a meaningful strategy for rheumatoid arthritis (RA). Though the protective effect of 7-HC on RA experimental models has been reported, the specific mechanisms, especially the possible relationships of this effect to regulating FLS proliferation and apoptosis, still need clarification.

PURPOSE

This study clarified the therapeutic effects of 7-HC on collagen-induced arthritis (CIA) in rats and explored the underlying mechanisms.

METHODS

In vivo, 7-HC (15, 30 or 60 mg/kg) was intraperitoneally given to CIA rats, and its therapeutic effect and anti-inflammatory activity were evaluated. Ki67 immunohistochemistry, TUNEL assay and synovial proteins detection were conducted. In vitro, after treating with 7-HC (20, 40 or 80 μM) in TNF-α-stimulated RA FLS (MH7A cell line), cell proliferation and apoptosis were examined. The involvement of Wnt/β-catenin pathway was checked in vivo and in vitro.

RESULTS

7-HC attenuated the severity of rat CIA, evidenced by the reduction of paw swelling, arthritis index, joint damage, collagen type II antibody serum level, and IL-1β, IL-6, TNF-α production in serum and synovium. Particularly, 7-HC in vivo had anti-proliferative and pro-apoptotic effects on CIA rat synovial cells, indicated by reduced synovial Ki67 expression, raised synovial apoptosis index, decreased Bcl-2 protein level and increased level of Bax and cleaved caspase 3 protein. Further, 7-HC in vitro suppressed proliferation and promoted apoptosis of TNF-α-stimulated MH7A cells by regulating the mitochondrial pathway. Mechanistically, 7-HC treatment inhibited Wnt/β-catenin pathway, suggested by the reduction of pathway-related proteins (e.g. Wnt1, LRP6, p-GSK-3β (Ser9), β-catenin, cyclin D1 and c-Myc), the recovery of GSK-3β activity and the inhibition of β-catenin nuclear translocation. As expected, combined use of lithium chloride, an activator of Wnt/β-catenin signaling, reversed the anti-proliferative and pro-apoptotic effects of 7-HC in vitro.

CONCLUSION

7-HC relieved the severity of rat CIA by inhibiting cell proliferation and inducing apoptosis of rheumatoid FLS via inhibition of Wnt/β-catenin pathway.

Ultrastructural and Physicochemical Characterization of a Non-Crosslinked Type 1 Bovine Derived Collagen Membrane

In this work, in vitro testing was used to study the properties of non-crosslinked type 1 bovine derived collagen membranes used in bone regeneration surgery. Collagen membranes were prepared, their surface roughness was quantified by interferometry, their morphology was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), their wettability was measured by the contact angle technique, their mechanical properties were investigated by tensile testing, their phase transformation temperatures were measured by Differential Scanning Calorimetry (DSC), and their biocompatibility was evaluated by immunological testing. The calorimetry tests showed that the membrane is formed only by type 1 collagen. The SEM observations showed that the morphology consists of layers of highly organized collagen fibers and patterns of striated fibrils typical of type 1 collagen. The small contact angle showed that the membrane is hydrophilic, with the possibility of rapid absorption of body fluids. The tensile tests showed that the membrane has enough elasticity, ductility, and mechanical strength for use in tissue regeneration. With the immunostaining technique, it was possible to confirm the membrane biocompatibility.

In vitro Cell Proliferation Assay of Demineralized Dentin Material Membrane in Osteoblastic MC3T3-E1 Cells

Aim

Demineralized dentin material membrane (DDMM) is a novel bioresorbable guided bone regeneration (GBR) which is derived from the demineralization process of bovine dentin. This material/process could be an alternative to resolve musculoskeletal dysfunction that harms the quality of human life.

Purpose

To evaluate the cytotoxic effect of DDMM as GBR membrane on MC3T3-E1 osteoblast cell line.

Methods

Cytotoxic effect was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Osteoblast MC3T3-E1 cell culture was used as a parameter of cell viability after reacting with GBR materials. The absorbance values were examined at each treatment to determine the percentage of cell viability. There were four groups created in the present study: two treatment groups and two control groups. The treatment groups consisted of a DDMM group and a bovine pericardium collagen membrane (BPCM) group. The control groups comprised a group containing cell culture medium as a negative control group and another positive control group that contained cell cultures.

Results

The results revealed no significant difference in MC3T3-E1 cell viability between the treatment and control groups (p < 0.05). Moreover, as observed in the DDMM group, there was an increase in the number of osteoblast cells.

Conclusion

DDMM is a suitable alternative biomaterial for GBR as it is non-cytotoxic and could potentially increase the rate of repair of craniofacial defects.

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Classical Dichotomy of Macrophages and Alternative Activation Models Proposed with Technological Progress

Macrophages are important immune cells that participate in the regulation of inflammation in implant dentistry, and their activation/polarization state is considered to be the basis for their functions. The classic dichotomy activation model is commonly accepted, however, due to the discovery of macrophage heterogeneity and more functional and iconic exploration at different technologies; some studies have discovered the shortcomings of the dichotomy model and have put forward the concept of alternative activation models through the application of advanced technologies such as cytometry by time-of-flight (CyTOF), single-cell RNA-seq (scRNA-seq), and hyperspectral image (HSI). These alternative models have great potential to help macrophages divide phenotypes and functional genes.

Light-induced dynamic RGD pattern for sequential modulation of macrophage phenotypes

Due to the critical roles of macrophage in immune response and tissue repair, harnessing macrophage phenotypes dynamically to match the tissue healing process on demand attracted many attentions. Although there have developed many advanced platforms with dynamic features for cell manipulation, few studies have designed a dynamic chemical pattern to sequentially polarize macrophage phenotypes and meet the immune requirements at various tissue repair stages. Here, we propose a novel strategy for spatiotemporal manipulation of macrophage phenotypes by a UV-induced dynamic Arg-Gly-Asp (RGD) pattern. By employing a photo-patterning technique and the specific interaction between cyclodextrin (CD) and azobenzene-RGD (Azo-RGD), we prepared a polyethylene glycol-dithiol/polyethylene glycol-norbornene (PEG-SH/PEG-Nor) hydrogel with dynamic RGD-patterned surface. After irradiation with 365-nm UV light, the homogeneous RGD surface was transformed to the RGD-patterned surface which induced morphological transformation of macrophages from round to elongated and subsequent phenotypic transition from pro-inflammation to anti-inflammation. The mechanism of phenotypic polarization induced by RGD pattern was proved to be related to Rho-associated protein kinase 2 (ROCK2). Sequential modulation of macrophage phenotypes by the dynamic RGD-patterned surface provides a remote and non-invasive strategy to manipulate immune reactions and achieve optimized healing outcomes.

Micromolar sodium fluoride promotes osteo/odontogenic differentiation in dental pulp stem cells by inhibiting PI3K/AKT pathway

OBJECTIVE

Sodium fluoride (NaF) plays an important role in preventing dental caries. However, the regulatory effect of NaF on the committed differentiation of DPSCs is not fully understood. In this study, we characterized the impact of micromolar levels of NaF on the osteo/odontogenic differentiation of DPSCs.

DESIGN

DPSCs were isolated from healthy human third molars and were cultured in conditioned media with different concentrations of NaF. RNA sequencing (RNA-seq) combined with Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis was used to assess the pathways regulated by NaF. Alkaline phosphatase activity, Alizarin red staining, Western blotting, and real-time qRT-PCR were used to determine the osteo/odontogenic differentiation in DPSCs treated with NaF.

RESULTS

NaF significantly promoted the osteo/odontogenic differentiation of DPSCs at micromolar levels. Furthermore, RNA-seq and KEGG pathway enrichment analysis indicated that the PI3K/AKT pathway was involved in the pro-osteoclastogenesis effect of NaF. Western blotting analysis exhibited that the phosphorylation of AKT was decreased in NaF-treated DPSCs. Chemical inhibition of the PI3K/AKT pathway abrogated the NaF-promoted DPSCs osteo/odontogenic differentiation.

CONCLUSION

Micromolar NaF can promote the osteo/odontogenic differentiation of DPSCs by inhibiting the PI3K/AKT pathway.

DATA AVAILABILITY

The data used to support the findings of this study are available from the corresponding author upon request.

Macrophage-derived oncostatin M/bone morphogenetic protein 6 in response to Mg-based materials influences pro-osteogenic activity of human umbilical cord perivascular cells

Macrophages are the central immune cell involved in the foreign body reaction to the implants. Furthermore, the magnesium-based materials could modulate macrophage functions, and subsequently influence bone formation via not clearly understood mechanisms. To analysis the roles of materials (magnesium and its gadolinium-based alloy; Mg and Mg-10Gd) on secretion of macrophages and their effects on pro-osteogenic activity, human mesenchymal stem cells (MSC) and macrophages were cocultured directly on the materials surface. Here, oncostatin M (OSM) - glycoprotein 130 (gp130) signaling complex as well as BMP6/SMAD were found to be involved in the Mg and Mg-10Gd multifactorial modulating osteogenic differentiation. Furthermore, materials upregulated the gene expression of bone morphogenetic protein 6 (BMP6) in macrophages, as well as its protein receptors and mothers against decapentaplegic homolog (SMAD) 1/4/5 in cocultured MSC. Besides, both materials could reduce the secretion of tumour necrosis factor alpha (TNFα) and interleukin 1 beta (IL1β) in macrophages and cocultures. These results collectively imply that Mg and Mg-10Gd could create a beneficial microenvironment for osteogenic differentiation and further support Mg-based biomaterial immunomodulatory properties by modulating the interactions of macrophages and MSC for bone regeneration. STATEMENT OF SIGNIFICANCE: Mg-activated macrophages could regulate the pro-osteogenic activity via OSM/gp130 and Smad-related signalling. The neutralisation assay was utilised to confirm the hypothesis of inductive osteoblastic differentiation of human MSC via OSM/gp130 signalling. Current study are essential to evidence that the coordinated communication between macrophages and MSC (OSM/gp130/BMP6/TNFα/IL1β), which could be utilised for improving magnesium-based bone biomaterials and therapeutic applications.

Interaction of epigallocatechin-gallate and chlorhexidine with Streptococcus mutans stimulated odontoblast-like cells: Cytotoxicity, Interleukin-1β and co-species proteomic analyses

OBJECTIVES

The dentin therapeutic agent chlorhexidine has inflammatory and cytotoxic characteristics urging investigation of alternatives like the natural compound epigallocatechin-gallate. The aim is to verify the effect of epigallocatechin-gallate and chlorhexidine on viability, interleukin-1β (IL-1β) and differential protein expression of MDPC-23 odontoblast-like cells stimulated by Streptococcus mutans.

DESIGN

Cells were stimulated with heat-killed S. mutans at multiplicity of infection (MOI) of 100-1000 and subsequently treated with 100-1 µM of epigallocatechin-gallate. Cells with no treatment or chlorhexidine were controls. Combined stimulated/treated cells were tested for cytotoxicity (Alamar-Blue, N = 3, n = 3), total protein (N = 3, n = 3), IL-1β (ELISA, N = 3, n = 3), and differential protein expression by liquid chromatography-tandem mass spectrometry (LC-MS/MS, n = 2).

RESULTS

Cells stimulated at MOI 100/1000 and treated with 10 µM epigallocatechin-gallate and chlorhexidine did not present cytotoxicity. IL-1β significantly increased in both un-stimulated and stimulated chlorhexidine 10 µM groups when compared to un-treated control (p < 0.05). MOI 100 chlorhexidine 10 µM group significantly increased IL-1β compared to un-stimulated chlorhexidine 10 µM and epigallocatechin-gallate 10 µM groups, as well as to MOI 100 epigallocatechin-gallate 10 µM group (p < 0.05). LC-MS/MS revealed S. mutans and mammalian proteins, with tooth-specific proteins exhibiting different abundance levels, depending on the tested condition.

CONCLUSIONS

Odontoblast-like cells stimulated with S. mutans at different MOI combined with epigallocatechin-gallate treatment did not cause cytotoxicity. S. mutans stimulation combined with chlorhexidine 100 µM treatment decreased cell viability, while treatment with chlorhexidine 10 µM concentration significantly increased IL-1β. S. mutans stimulation and treatment of cells resulted in varied protein expression.

Topological structure of electrospun membrane regulates immune response, angiogenesis and bone regeneration

The fate of biomaterials is orchestrated by biocompatibility and bioregulation characteristics, reported to be closely related to topographical structures. For the purpose to investigate the topography of fibrous membranes on the guided bone regeneration performance, we successfully fabricated poly (lactate-co-glycolate)/fish collagen/nano-hydroxyapatite (PFCH) fibrous membranes with random, aligned and latticed topography by electrospinning. The physical, chemical and biological properties of the three topographical PFCH membranes were systematically investigated by in vitro and in vivo experiments. The subcutaneous implantation of C57BL6 mice showed an acceptable mild foreign body reaction of all three topological membranes. Interestingly, the latticed PFCH membrane exhibited superior abilities to recruit macrophage/monocyte and induce angiogenesis. We further investigated the osteogenesis of the three topographical PFCH membranes via the critical-size calvarial bone defect model of rats and mice and the results suggested that latticed PFCH membrane manifested promising performance to promote angiogenesis through upregulation of the HIF-1α signaling pathway; thereby enhancing bone regeneration. Our research illustrated that the topological structure of fibrous membranes, as one of the characteristics of biomaterials, could regulate its biological functions, and the fibrous structure of latticed topography could serve as a favorable surface design of biomaterials for bone regeneration. STATEMENT OF SIGNIFICANCE: In material-mediated regeneration medicine, the interaction between the biomaterial and the host is key to successful tissue regeneration. The micro-and nano-structure becomes one of the most critical physical clues for designing biomaterials. In this study, we fabricated three topological electrospun membranes (Random, Aligned and Latticed) to understand how topological structural clues mediate bone tissue regeneration. Interestingly, we found that the Latticed topographical PFCH membrane promotes macrophage recruitment, angiogenesis, and osteogenesis in vivo, indicating the fibrous structure of latticed topography could serve as a favorable surface design of biomaterials for bone regeneration.

A 3D-printed PRP-GelMA hydrogel promotes osteochondral regeneration through M2 macrophage polarization in a rabbit model

Osteochondral regeneration is an orchestrated process of inflammatory immunity, host cell response, and implant degradation in tissue engineering. Here, the effects of a platelet-rich plasma (PRP)-gelatin methacryloyl (GelMA) hydrogel scaffold fabricated using the digital micro-mirror device (DMD) technique for osteochondral repair were investigated in a rabbit model. GelMA hydrogels with different PRP concentrations were fabricated, and their roles in bone marrow mesenchymal stem cells (BMSCs) and macrophage polarization in vitro were investigated. The incorporation of 20% PRP into the hydrogel showed optimal effects on the proliferation, migration, and osteogenic and chondrogenic differentiation of BMSCs. The 20% PRP-GelMA (v/v) hydrogel also promoted M2 polarization with high expression of Arg1 and CD206. Compared to the 20% PRP group, the 50% PRP group showed similar biological roles in BMSCs but less extent of osteogenesis. In the vivo study, the 20% PRP-GelMA composite was used for osteochondral reconstruction and showed more cartilage and subchondral bone regeneration than that observed using the pure GelMA hydrogel. The PRP-GelMA group exhibited more M2 macrophage infiltration and less M1 macrophage presentation at three time points as compared to the nontreatment group. The expression of Arg1 in the PRP-GelMA group increased significantly at 6 weeks but decreased to a lower level at 12 weeks, while CD163 showed sustained high expression until 18 weeks. Our findings demonstrated that the 3D-printed PRP-GelMA composite could promote osteochondral repair through immune regulation by M2 polarization and could be a potential candidate for osteochondral tissue engineering. STATEMENT OF SIGNIFICANCE: PRP-GelMA hydrogels promoted the migration and osteogenic and chondrogenic differentiation of BMSCs. PRP-GelMA hydrogels participated in immune regulation and M1-to-M2 transition of macrophages. PRP-GelMA hydrogels coordinated and promoted several overlapping osteochondral repair events, including dynamic immune regulation, chemotaxis of MSCs, and osteochondral differentiation. PRP-GelMA hydrogels showed superior cartilage and subchondral bone repair properties.

Application of biomaterials in periodontal tissue repair and reconstruction in the presence of inflammation under periodontitis through the foreign body response: Recent progress and perspectives

Periodontitis would cause dental tissue damage locally. Biomaterials substantially affect the surrounding immune microenvironment through treatment-oriented local inflammatory remodeling in dental periodontitis. This remodeling process is conducive to wound healing and periodontal tissue regeneration. Recent progress in understanding the foreign body response (FBR) and immune regulation, including cell heterogeneity, and cell-cell and cell-material interactions, has provided new insights into the design criteria for biomaterials applied in treatment of periodontitis. This review discusses recent progress and perspectives in the immune regulation effects of biomaterials to augment or reconstruct soft and hard tissue in an inflammatory microenvironment of periodontitis.

Polybutylene-adipate-terephthalate and niobium-containing bioactive glasses composites: Development of barrier membranes with adjusted properties for guided bone regeneration

This study aimed to develop bioactive guided bone regeneration (GBR) membranes by manufacturing PBAT/BAGNb composites as casting films. Composites were produced by melt-extrusion, and BAGNb was added at 10 wt%, 20 wt%, and 30 wt% concentration. Pure PBAT membranes were used as a control (0wt%BAGNb). FTIR and thermogravimetric analysis characterized the composites. Barrier membranes were produced by solvent casting, and their mechanical and surface properties were assessed by tensile strength test and contact angle analysis, respectively. The ion release and cell behavior were evaluated by pH, cell proliferation, and mineralization. Composites were successfully produced, and the chemical structure showed no interference of BAGNb in the PBAT structure. The addition of BAGNb increased the stiffness of the membranes and reduced the contact angle, increasing the roughness in one side of the membrane. Sustained pH increment was observed for BAGNb-containing membranes with increased proliferation and mineralization as the concentration of BAGNb increases. The incorporation of up to 30 wt% of BAGNb into PBAT barrier membranes was able to maintain adequate chemical-mechanical properties leading to the production of materials with tailored surface properties and bioactivity. Finally, this biomaterial class showed outstanding potential and may contribute to bone formation in GBR procedures.

Biofabrication of Gingival Fibroblast Cell-Laden Collagen/Strontium-Doped Calcium Silicate 3D-Printed Bi-Layered Scaffold for Osteoporotic Periodontal Regeneration

Periodontal disease is a chronic disease that can lead to lose teeth and even tooth loss if left untreated. Osteoporosis and periodontal disease share similar characteristics and associated factors. Current regenerative techniques for periodontal diseases are ineffective in restoring complete function and structural integrity of periodontium due to unwanted migration of cells. In this study, we applied the concept of guided tissue regeneration (GTR) and 3D fabricated gingival fibroblast cell-laden collagen/strontium-doped calcium silicate (SrCS) bi-layer scaffold for periodontal regeneration. The results revealed that the bioactive SrCS had a hydroxyapatite formation on its surface after 14 days of immersion and that SrCS could release Sr and Si ions even after 6 months of immersion. In addition, in vitro results showed that the bi-layer scaffold enhanced secretion of FGF-2, BMP-2, and VEGF from human gingival fibroblasts and increased secretion of osteogenic-related proteins ALP, BSP, and OC from WJMSCs. In vivo studies using animal osteoporotic models showed that the 3D-printed cell-laden collagen/SrCS bi-layer scaffold was able to enhance osteoporotic bone regeneration, as seen from the increased Tb.Th and BV/TV ratio and the histological stains. In conclusion, it can be seen that the bi-layer scaffolds enhanced osteogenesis and further showed that guided periodontal regeneration could be achieved using collagen/SrCS scaffolds, thus making it a potential candidate for future clinical applications.

Matrix stiffening by self-mineralizable guided bone regeneration

Collagen membranes produced in vitro with different degrees of intrafibrillar mineralization are potentially useful for guided bone regeneration (GBR). However, highly-mineralized collagen membranes are brittle and difficult for clinical manipulation. The present study aimed at developing an intrafibrillar self-mineralization strategy for GBR membrane by covalently conjugating high-molecular weight polyacrylic acid (HPAA) on Bio-Gide® membranes (BG). The properties of the self-mineralizable membranes (HBG) and their potential to induce bone regeneration were investigated. The HBG underwent the progressive intrafibrillar mineralization as well as the increase in stiffness after immersed in supersaturated calcium phosphate solution, osteogenic medium, or after being implanted into a murine calvarial bone defect. The HBG promoted in-situ bone regeneration via stimulating osteogenic differentiation of mesenchymal stromal cells (MSCs). Hippo signaling was inhibited when MSCs were cultured on the self-mineralized HBG, and in HBG-promoted MSC osteogenesis during in-situ bone regeneration. This resulted in translocation of the transcription co-activators Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) into the nucleus to induce transcription of genes promoting osteogenic differentiation of MSCs. Taken together, these findings indicated that HBG possessed the ability to self-mineralize in situ via intrafibrillar mineralization. The increase in stiffness of the extracellular matrix expedited in-situ bone regeneration by inactivating the Hippo-YAP/TAZ signaling cascade. STATEMENT OF SIGNIFICANCE: Guided bone regeneration (GBR) membranes made of naturally derived collagen have been widely used in the bone defect restoration. However, application of collagen GBR membranes run into the bottleneck with the challenges like insufficient stress strength, relatively poor dimensional stability and unsatisfactory osteoinductivity. This study develops a modified GBR membrane that can undergo progressive self-mineralization and matrix stiffening in situ. Increase in extracellular matrix stiffness provides the mechanical cues required for MSCs differentiation and expedites in-situ bone regeneration by inactivating the Hippo-YAP/TAZ signaling cascade.

Covalent immobilization of the phytic acid-magnesium layer on titanium improves the osteogenic and antibacterial properties

In order to improve early osseointegration and long-term survival rate of implants, a multifunctional titanium surface that promotes osteogenesis and antibacterial properties is expected. Incorporation of bioactive trace elements such as magnesium ions was proved a promising method to improve osseointegration of titanium. Phytic acid has strong chelating ability with multivalent cations, which has been used in surface modification. Moreover, phytic acid was proved antibacterial potential. Herein, to improve the osteogenic and antibacterial properties, a phytic acid-magnesium (PA-Mg) layer was introduced on titanium using phytic acid as a cross-linker molecule. No obvious changes of the surface characterization were observed by scanning electron microscopy and atomic force microscopy. X-ray photoelectron spectroscopy confirmed that the PA-Mg layer covalently bond to the Ti surface, and the thickness of the PA-Mg layer was about 150 nm. Besides, improved hydrophilic and more protein adsorption were observed on Ti-PA-Mg. Notably, a relatively controlled magnesium release was also observed on Ti-PA-Mg. Human bone mesenchymal stem cells showed better adhesion, proliferation, and osteogenic differentiation on Ti-PA-Mg samples, indicating improved biocompatibility and osteoinductivity. Moreover, Ti-PA-Mg had better antibacterial properties against porphyromonas gingivalis than Ti. Overall, the PA-Mg layer on Ti surface improved the osteogenic and antibacterial properties, which may have promise for use in dental implantation.