Cell-to-cell communication in guided bone regeneration: molecular and cellular mechanisms

Does defect configuration affect the outcomes of alveolar ridge preservation? An experimental in vivo study

PURPOSE

The purpose of this study was to compare the bone healing potential of 1-, 2-, and 3-wall defects following alveolar ridge preservation (ARP) treatment, as well as to evaluate the efficacy of ARP as a treatment option for destructive sites.

METHODS

Three groups, characterized by 1-, 2-, and 3-wall defects, were randomly assigned to the maxillary second, third, and fourth premolars in each of 8 beagle dogs. Each defect was created at either the mesial or distal root site of the tooth, which was hemi-sectioned and extracted. The contralateral root was preserved to superimpose with the experimental site for histomorphometric analysis. For each site, either spontaneous healing (SH; control) or ARP (test intervention) was randomly applied. Each group was divided in half and underwent a healing period of either 4 or 12 weeks. The Mann-Whitney U test and Kruskal-Wallis test were used for histomorphometric analyses. Statistical significance was set at P<0.05.

RESULTS

Qualitative analysis revealed a higher percentage of new bone in the apical area compared to the coronal area, regardless of defect type and healing period. In quantitative analysis, the 3-wall defect exhibited a significantly higher percentage of mineralization in the ARP group after 12 weeks of healing (ARP: 61.73%±7.52%; SH: 48.84%±3.06%; P=0.029). An increased percentage of mineralization was observed with a greater number of remaining bony walls, although this finding did not reach statistical significance.

CONCLUSIONS

Within the limitations of this study, ARP treatment for compromised sockets appears to yield a higher percentage of mineralization compared to SH. Although the effectiveness of the remaining bony walls was limited, their presence appeared to improve the percentage of mineralization in ARP treatment.

Proteomic Analysis of Human Serum Proteins Adsorbed onto Collagen Barrier Membranes

Collagen barrier membranes are frequently used in guided tissue and bone regeneration. The aim of this study was to analyze the signature of human serum proteins adsorbed onto collagen membranes using a novel protein extraction method combined with mass spectrometry. Native porcine-derived collagen membranes (Geistlich Bio-Gide®, Wolhusen, Switzerland) were exposed to pooled human serum in vitro and, after thorough washing, subjected to protein extraction either in conjunction with protein enrichment or via a conventional surfactant-based method. The extracted proteins were analyzed via liquid chromatography with tandem mass spectrometry. Bioinformatic analysis of global profiling, gene ontology, and functional enrichment of the identified proteins was performed. Overall, a total of 326 adsorbed serum proteins were identified. The enrichment and conventional methods yielded similar numbers of total (315 vs. 309), exclusive (17 vs. 11), and major bone-related proteins (18 vs. 14). Most of the adsorbed proteins (n = 298) were common to both extraction groups and included several growth factors, extracellular matrix (ECM) proteins, cell adhesion molecules, and angiogenesis mediators involved in bone regeneration. Functional analyses revealed significant enrichment of ECM, exosomes, immune response, and cell growth components. Key proteins [transforming growth factor-beta 1 (TGFβ1), insulin-like growth factor binding proteins (IGFBP-5, -6, -7)] were exclusively detected with the enrichment-based method. In summary, native collagen membranes exhibited a high protein adsorption capacity in vitro. While both extraction methods were effective, the enrichment-based method showed distinct advantages in detecting specific bone-related proteins. Therefore, the use of multiple extraction methods is advisable in studies investigating protein adsorption on biomaterials.

Induction of human stem cells into ameloblasts by reaggregation strategy

BACKGROUND

Human epithelium-derived stem cells and induced pluripotent stem cells (hiPSCs) possess the capability to support tooth formation and differentiate into functional enamel-secreting ameloblasts, making them promising epithelial-component substitutes for future human tooth regeneration. However, current tissue recombination approaches are not only technically challenging, requiring precise induction procedures and sophisticated microsurgery, but also exhibit low success rates in achieving tooth formation and ameloblastic differentiation.

METHODS

Suspended human keratinocyte stem cells (hKSCs) or cells from three hiPSC lines were directly mixed with dissociated embryonic mouse dental mesenchymal cells (mDMCs) that possess odontogenic potential in different proportions and reaggregated them to construct bioengineered tooth germs. The success rates of tooth formation and ameloblastic differentiation were confirmed after subrenal culture. The sorting capability, sequential development, and ameloblastic differentiation of stem cells were examined via GFP tracing, RT-PCR, and histological analysis, respectively.

RESULTS

Our reaggregation approach achieved an impressive success rate of more than 90% in tooth formation and 100% in ameloblastic differentiation when the chimeric tooth germs contained 1%~10% hKSCs or 5% hiPSCs. In addition, we observed that hiPSCs, upon exposure to mDMCs, initially transformed into epidermal cells, as indicated by KRT14 and CD29 expression, before progressing into dental epithelial cells, as indicated by SP6 and SHH expression. We also found that epithelial-derived hiPSCs, when reaggregated with mDMCs, were more favorable for tooth formation than their mesenchymal-derived counterparts.

CONCLUSIONS

This study establishes a simplified yet highly effective cell-cell reaggregation strategy for inducing stem cells to support tooth formation and differentiate into functional ameloblasts, paving the way for novel approaches for the development of stem cell-based tooth organoids and bioengineered tooth germs in vitro.

3D-Cultured MC3T3-E1-Derived Exosomes Promote Endothelial Cell Biological Function under the Effect of LIPUS

Porous Ti-6Al-4V scaffold materials can be used to heal massive bone defects because they can provide space for vascularisation and bone formation. During new bone tissue development, rapid vascular ingrowth into scaffold materials is very important. Osteoblast-derived exosomes are capable of facilitating angiogenesis-osteogenesis coupling. Low-intensity pulsed ultrasound (LIPUS) is a physical therapy modality widely utilised in the field of bone regeneration and has been proven to enhance the production and functionality of exosomes on two-dimensional surfaces. The impact of LIPUS on exosomes derived from osteoblasts cultured in three dimensions remains to be elucidated. In this study, exosomes produced by osteoblasts on porous Ti-6Al-4V scaffold materials under LIPUS and non-ultrasound stimulated conditions were co-cultured with endothelial cells. The findings indicated that the exosomes were consistently and stably taken up by the endothelial cells. Compared to the non-ultrasound group, the LIPUS group facilitated endothelial cell proliferation and angiogenesis. After 24 h of co-culture, the migration ability of endothelial cells in the LIPUS group was 17.30% higher relative to the non-ultrasound group. LIPUS may represent a potentially viable strategy to promote the efficacy of osteoblast-derived exosomes to enhance the angiogenesis of porous Ti-6Al-4V scaffold materials.

Zinc based biodegradable metals for bone repair and regeneration: Bioactivity and molecular mechanisms

Bone fractures and critical-size bone defects are significant public health issues, and clinical treatment outcomes are closely related to the intrinsic properties of the utilized implant materials. Zinc (Zn)-based biodegradable metals (BMs) have emerged as promising bioactive materials because of their exceptional biocompatibility, appropriate mechanical properties, and controllable biodegradation. This review summarizes the state of the art in terms of Zn-based metals for bone repair and regeneration, focusing on bridging the gap between biological mechanism and required bioactivity. The molecular mechanism underlying the release of Zn ions from Zn-based BMs in the improvement of bone repair and regeneration is elucidated. By integrating clinical considerations and the specific bioactivity required for implant materials, this review summarizes the current research status of Zn-based internal fixation materials for promoting fracture healing, Zn-based scaffolds for regenerating critical-size bone defects, and Zn-based barrier membranes for reconstituting alveolar bone defects. Considering the significant progress made in the research on Zn-based BMs for potential clinical applications, the challenges and promising research directions are proposed and discussed.

Emerging factors affecting peri-implant bone metabolism

Implant dentistry has evolved to the point that standard implant osseointegration is predictable. This is attributed in part to the advancements in material sciences that have led toward improvements in implant surface technology and characteristics. Nonetheless, there remain several cases where implant therapy fails (specifically at early time points), most commonly attributed to factors affecting bone metabolism. Among these patients, smokers are known to have impaired bone metabolism and thus be subject to higher risks of early implant failure and/or late complications related to the stability of the peri-implant bone and mucosal tissues. Notably, however, emerging data have unveiled other critical factors affecting osseointegration, namely, those related to the metabolism of bone tissues. The aim of this review is to shed light on the effects of implant-related factors, like implant surface or titanium particle release; surgical-related factors, like osseodensification or implanted biomaterials; various drugs, like selective serotonin reuptake inhibitors, proton pump inhibitors, anti-hypertensives, nonsteroidal anti-inflammatory medication, and statins, and host-related factors, like smoking, diet, and metabolic syndrome on bone metabolism, and aseptic peri-implant bone loss. Despite the infectious nature of peri-implant biological complications, these factors must be surveyed for the effective prevention and management of peri-implantitis.

Micro finite element analysis of continuously loaded mini-implants - A micro-CT study in the rat tail model

Implant migration has been described as a minor displacement of orthodontic mini-implants (OMIs) when subjected to constant forces. Aim of this study was to evaluate the impact of local stresses on implant migration and bone remodelling around constantly loaded OMIs. Two mini-implants were placed in one caudal vertebra of 61 rats, connected by a nickel‑titanium contraction spring, and loaded with different forces (0.0, 0.5, 1.0, 1.5 N). In vivo micro-CT scans were taken immediately and 1, 2 (n = 61), 4, 6 and 8 (n = 31) weeks post-op. Nine volumes of interest (VOIs) around each implant were defined. To analyse stress values, micro-finite element models were created. Bone remodelling was analysed by calculating the bone volume change between scans performed at consecutive time points. Statistical analysis was performed using a linear mixed model and likelihood-ratio-tests, followed by Tuckey post hoc tests when indicated. The highest stresses were observed in the proximal top VOI. In all VOIs, stress values tended to reach their maximum after two weeks and decreased thereafter. Bone remodelling analysis revealed initial bone loss within the first two weeks and bone gain up to week eight, which was noted especially in the highest loading group. The magnitude of local stresses influenced bone remodelling and it can be speculated that the stress related bone resorption favoured implant migration. After a first healing phase with a high degree of bone resorption, net bone gain representing consolidation was observed.

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.

Influence of Bone Substitutes on Mesenchymal Stromal Cells in an Inflammatory Microenvironment

Bone regeneration is driven by mesenchymal stromal cells (MSCs) via their interactions with immune cells, such as macrophages (MPs). Bone substitutes, e.g., bi-calcium phosphates (BCPs), are commonly used to treat bone defects. However, little research has focused on MSC responses to BCPs in the context of inflammation. The objective of this study was to investigate whether BCPs influence MSC responses and MSC-MP interactions, at the gene and protein levels, in an inflammatory microenvironment. In setup A, human bone marrow MSCs combined with two different BCP granules (BCP 60/40 or BCP 20/80) were cultured with or without cytokine stimulation (IL1β + TNFα) to mimic acute inflammation. In setup B, U937 cell-line-derived MPs were introduced via transwell cocultures to setup A. Monolayer MSCs with and without cytokine stimulation served as controls. After 72 h, the expressions of genes related to osteogenesis, healing, inflammation and remodeling were assessed in the MSCs via quantitative polymerase chain reactions. Additionally, MSC-secreted cytokines related to healing, inflammation and chemotaxis were assessed via multiplex immunoassays. Overall, the results indicate that, under both inflammatory and non-inflammatory conditions, the BCP granules significantly regulated the MSC gene expressions towards a pro-healing genotype but had relatively little effect on the MSC secretory profiles. In the presence of the MPs (coculture), the BCPs positively regulated both the gene expression and cytokine secretion of the MSCs. Overall, similar trends in MSC responses were observed with BCP 60/40 and BCP 20/80. In summary, within the limits of in vitro models, these findings suggest that the presence of BCP granules at a surgical site may not necessarily have a detrimental effect on MSC-mediated wound healing, even in the event of inflammation.

Histological and Immunohistochemical Analysis of the Effects of Topical Melatonin Treatment Associated with Collagen Sponge and rhBMP-2 Protein on Bone Remodeling

Extensive bone defect healing is an important health issue not yet completely resolved. Different alternative treatments have been proposed but, in face of a critical bone defect, it is still very difficult to reach a complete regeneration, with the new-formed bone presenting all morphological and physiological characteristics of a normal, preinjury bone. Topical melatonin use has shown as a promising adjuvant for bone regeneration due to its positive effects on bone metabolism. Thus, to search for new, safe, biological techniques that promote bone repair and favor defect healing, we hypothesized that there is a synergistic effect of melatonin treatment associated with rhBMP-2 to guide bone regeneration. This study aimed to investigate bone repair effects of topical melatonin administration in different concentrations (1, 10, and 100 µg), associated or not with rhBMP-2. Surgical-induced bone defect healing was qualitatively evaluated through histopathological analysis by light microscopy. Additionally, quantitative stereology was performed in immunohistochemistry-prepared tissue to identify angiogenic, osteogenic, and osteoclastogenic factors. Quantification data were compared between groups by the ANOVA/Tukey test and differences were considered significant when p < 0.05. Our results showed that the presence of the scaffold in the bone defect hindered the process of bone repair because in the group treated with "blood clot + scaffold" the results of bone formation and immunolabeling were reduced in comparison with all other groups (treated with melatonin alone or in association with rhBMP-2). Statistical analysis revealed a significant difference between the control group (bone defect + blood clot), and groups treated with different concentrations of melatonin in association with rhBMP-2, indicating a positive effect of the association for bone repair. This treatment is promising once it becomes a new safe alternative technique for the clinical treatment of fractures, bone defects, and bone grafts. Our results support the hypothesis of the safe use of the association of melatonin and rhBMP-2 and have established a safe and effective dose for this experimental treatment.

Dynamic transcriptome analysis of NFAT family in guided bone regeneration with occlusive periosteum in swine model

OBJECTIVE

To investigate the dynamic expression of NFAT family of periosteum in guided bone regeneration process.

MATERIAL AND METHODS

The swine ribs on one side were used as the trauma group and the contralateral side as the control group. After rib segment was removed, periosteum was sutured to form a closed cavity mimicking guided bone regeneration. The periosteum and regenerated bone tissue were collected at nine time points for gene sequencing and hematoxylin-eosin staining. The expression data of each member were extracted for analysis. Expression correlations among various members were analyzed.

RESULTS

Staining showed the guided bone regeneration was almost completed 1 month after the operation with later stage for bone remodeling. The expression levels of each member in both groups changed greatly, especially within postoperative 1.5 months. The expression of NFATc1 and NFATC2IP in trauma group was significantly correlated with those of control group. The foldchange of each member also had large fluctuations especially within 1.5 months. In the trauma group, NFATc2 and NFATc4 were significantly upregulated, and there was a significant aggregation correlation of NFAT family expression between the various time points within one month, similar to the "pattern-block" phenomenon.

CONCLUSION

This study revealed the dynamic expression of NFAT family in guided bone regeneration, and provided a reference for the specific mechanism. The first 1.5 months is a critical period and should be paid attention to. The significant high-expression of NFATc2 and NFATc4 may role importantly in this process, which needs further research to verify it.

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.

Healing complications and their detrimental effects on bone gain in vertical-guided bone regeneration: A systematic review and meta-analysis

PURPOSE

Guided bone regeneration (GBR) utilizes a barrier membrane to allow osteogenic cells to populate a space by excluding epithelial and connective tissue cells. The purpose of this systematic review was to investigate the ratio of means (RoM) of vertical bone gained (Outcome) in vertical GBR procedures with healing complications (Intervention) and in vertical GBR procedures without healing complications (Comparison) in patients with vertically resorbed edentulous ridges that require dental implant placement (Population). A further aim was to investigate the incidence of complications after vertical GBR, and the influence of the timing of implant placement and regenerative devices on complications.

MATERIALS AND METHODS

MEDLINE (through PubMed), EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL) were searched in duplicate up to, and including, November 2020 for randomized and controlled clinical trials and prospective and retrospective case series. Outcomes included patient-level and site-level RoM of vertical bone gain between healing complications and uneventful healing, and incidences of complications that occurred after vertical GBR. Random-effects and fixed-effects meta-analyses were performed where appropriate. This study was registered on PROSPERO (CRD42021226432).

RESULTS

A total of 31 publications were selected for the qualitative and quantitative analyses. The RoM of vertical bone gained was 0.65 [95% CI = 0.47, 0.91] and 0.62 [95% CI = 0.45, 0.85] when membrane exposure without suppuration and abscess formation without membrane exposure occurred respectively, in comparison to uneventful healing. The overall incidence proportion of healing complications occurring at the augmented site at a site- and patient-level was 11.0% [95% CI = 7.0, 15.6] and 10.8% [95% CI = 6.6, 15.7]. At a patient-level, there were no significant differences between a simultaneous or staged approach, or with the regenerative device used. The site-level incidence proportion of membrane exposure without suppuration, membrane exposure with suppuration, and with abscess formation without membrane exposure was 8.7% [95% CI = 4.2, 14.2], 0.7% [95% CI = 0.0, 2.9], and 0.5% [95% CI = 0.0, 1.7], respectively. The site-level weighted mean incidence proportion of neurologic complications occurring at the donor site was 0.8% [95% CI = 0.0, 5.3].

CONCLUSIONS

There is a significant reduction in bone gain when healing complications occur. However, healing complications are relatively uncommon surgical complications after vertical GBR.

Different angiogenic response and bone regeneration following the use of various types of collagen membranes - in vivo histomorphometric study in rabbit calvarial critical-size defects

Introduction/Objective. Success of guided bone regeneration depends on the size and morphology of defect, characteristics of barrier membranes and adequate angiogenesis. The aim of the study was to reveal impact of three different collagen membranes on angiogenesis and bone production in critical-size defects. Methods. Defects were created in rabbit calvarias, filled with bovine bone graft and randomly covered with one of three investigated collagen membranes (Biogide ? BG, Heart ? PC, Mucograft ? MG) or left without a membrane for the control group (C). After two and four weeks of healing, a total of 10 animals were sacrificed for histological and histomorphometric analysis of angiogenesis, bone regeneration, and inflammatory response. Results. In the early healing phase, the highest values of trabecular thickness and trabecular area were recorded with PC and BG membranes, respectively. After four weeks, significantly improved bone healing was noted in the MG group, as well as significantly pronounced inflammation. Initially, vessel density was significantly higher in the C group compared to all three membranes. After four weeks, significantly better results were observed in the MG compared to the other groups, BG compared to the rest of groups, and between PC and C groups. Conclusion. The use of collagen membranes significantly affects angiogenesis, reducing it in the early and enhancing it at the later healing phase. All three tested membranes in combination with bone graft significantly improved the amount of regenerated bone. Among the investigated groups, MG favored more pronounced angiogenic, osteogenic, and inflammatory response in the observation period of four weeks.

Novel Histomorphometrical Approach to Evaluate the Integration Pattern and Functionality of Barrier Membranes

GBR (guided bone regeneration) is a standard procedure for building up bony defects in the jaw. In this procedure, resorbable membranes made of bovine and porcine collagen are increasingly being used, which, in addition to many possible advantages, could have the potential disadvantage of a shorter barrier functionality, especially when augmenting large-volume defects. Thus, it is of importance to evaluate the integration behavior and especially the standing time of barrier membranes using specialized methods to predict its respective biocompatibility. This study is intended to establish a new histomorphometrical analysis method to quantify the integration rate of collagen-based barrier membranes. Three commercially available barrier membranes, i.e., non-crosslinked membranes (BioGide^® and Jason^® membrane), a ribose-crosslinked membrane (Ossix^® Plus), and a newly developed collagen–hyaluronic acid-based (Coll-HA) barrier membrane were implanted in the subcutaneous tissue of 48 6–8-week-old Wistar rats. The explants, after three timepoints (10, 30, and 60 days), were processed and prepared into histological sections for histopathological (host tissue response) and histomorphometrical (cellular invasion) analyses. 10 days after implantation, fragmentation was not evident in any of the study groups. The sections of the Coll-HA, Jason^® and BioGide^® membranes showed a similar mild inflammatory reaction within the surrounding tissue and an initial superficial cell immigration. Only in the Ossix^® Plus group very little inflammation and no cell invasion was detected. While the results of the three commercially available membranes remained intact in the further course of the study, only fragments of the Coll-HA membrane were found 30 and 60 days after implantation. Histomorphometrically, it can be described that although initially (at 10 days post-implantation) similar results were found in all study groups, after 30 days post-implantation the cellular penetration depth of the hyaluronic acid-collagen membrane was significantly increased with time (**** p < 0.0001). Similarly, the percentage of cellular invasion per membrane thickness was also significantly higher in the Coll-HA group at all timepoints, compared to the other membranes (**** p < 0.0001). Altogether, these results show that the histomorphometrical analysis of the cellular migration can act as an indicator of integration and duration of barrier functionality. Via this approach, it was possible to semi-quantify the different levels of cellular penetration of GBR membranes that were only qualitatively analyzed through histopathological approaches before. Additionally, the results of the histopathological and histomorphometrical analyses revealed that hyaluronic acid addition to collagen does not lead to a prolonged standing time, but an increased integration of a collagen-based biomaterial. Therefore, it can only partially be used in the dental field for indications that require fast resorbed membranes and a fast cell or tissue influx such as periodontal regeneration processes.

[Biocompatibility and effect on bone formation of a native acellular porcine pericardium: Results of in vitro and in vivo]

OBJECTIVE

To examine the morphology and biocompatibility of a native acellular porcine pericardium (APP) in vitro and to evaluate its barrier function and effects on osteogenesis when used in guided bone regeneration (GBR) in vivo.

METHODS

First, the morphology of APP (BonanGen^Ⓡ) was detected using a scanning electron microscope (SEM). Next, for biocompatibility test, proliferation of human bone marrow mesenchymal stem cells (hBMSCs) were determined using cell counting kit-8 (CCK-8) after being seeded 1, 3 and 7 days. Meanwhile, the cells stained with phalloidine and 4, 6-diamidino-2-phenylindole (DAPI) were observed using a confocal laser scanning microscopy (CLSM) to view the morphology of cell adhesion and pattern of cell proliferation on day 5. A 3-Beagle dog model with 18 teeth extraction sockets was used for the further research in vivo. These sites were randomly treated by 3 patterns below: filled with Bio-Oss^Ⓡand coverd by APP membrane (APP group), filled with Bio-Oss^Ⓡand covered by Bio-Gide^Ⓡmembrane (BG group) and natural healing (blank group). Micro-CT and hematoxylin-eosin (HE) were performed after 4 and 12 weeks.

RESULTS

A bilayer and three-dimensional porous ultrastructure was identified for APP through SEM. In vitro, APP facilitated proliferation and adhesion of hBMSCs, especially after 7 days (P < 0.05). In vivo, for the analysis of the whole socket healing, no distinct difference of new bone ratio was found between all the three groups after 4 weeks (P>0.05), however significantly more new bone regeneration was detected in APP group and BG group in comparison to blank group after 12 weeks (P < 0.05). The radio of bone formation below the membrane was significantly higher in APP group and BG group than blank group after 4 and 12 weeks (P < 0.05), however, the difference between APP group and BG group was merely significant in 12 weeks (P < 0.05). Besides, less resorption of buccal crest after 4 weeks and 12 weeks was observed in APP group of a significant difference compared in blank group (P < 0.05). The resorption in BG group was slightly lower than blank group (P>0.05).

CONCLUSION

APP showed considerable biocompatibility and three-dimentional structure. Performing well as a barrier membrane in the dog alveolar ridge preservation model, APP significantly promoted bone regeneration below it and reduced buccal crest resorption. On the basis of this study, APP is a potential osteoconductive and osteoinductive biomaterial.

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.

Technology-enhanced learning: a role for video animation

The last 20 years has seen a shift in medical education from printed analogue formats of knowledge transfer to digital knowledge transfer via media platforms and virtual learning environments. Traditional university medical teaching was characterised by lectures and printed textbooks, which to a degree still have an important role to play in knowledge acquisition, but which in isolation do not engage the modern learner, who has become reliant on digital platforms and 'soundbite' learning. Recently, however, traditional methods of teaching and learning have been augmented by, and indeed sometimes replaced by, the alternative learning methods such as: problem-based learning; a greater integration of basic science and clinical considerations; smaller teaching groups; the 'flipped classroom' concept; and various technological tools which promote an interactive learning style. The aim of these new teaching methods is to overcome the well-documented limitations of traditional lectures and printed material in the transfer of knowledge from expert to student, by better engaging the minds of more visual learners and encouraging the use of diverse resources for lifelong learning. In this commentary paper, we share the concept of video animation as an additional educational tool, and one that can help to integrate molecular, cellular and clinical processes that underpin our understanding of biology and pathology in modern education. Importantly, while they can provide focused and attractive formats for 'soundbite' learning, their aim as a tool within the broader educational toolbox is to direct the interested reader towards more traditional formats of learning, which permit a deeper dive into a particular field or concept. In this manner, carefully constructed video animations can serve to provide a broad overview of a particular field or concept and to facilitate deeper learning when desired by the student.

Teaching the knowledge explosion is a challenge.

Video animation plays a future role in teaching complex biological concepts and processes.

Video animation helps in educating professionals and the public.

Synthesis and Characterization of Melatonin-Loaded Chitosan Microparticles Promote Differentiation and Mineralization in Preosteoblastic Cells

In terms of a novel scaffold with well good osteoinductive and osteoconductive capacity, melatonin (Mel) possesses positive effects on chemical linkage in scaffold structures, which may allow osteogenic differentiation. The aim of this study is to fabricate Mel-loaded chitosan (CS) microparticles (MPs) as a novel bone substitute through generating a Mel sustained release system from Mel-loaded CS MPs and evaluating its effect on the osteogenic capacity of MC3T3-E1 in vitro. The physical-chemical characteristics of the prepared CS MPs were examined by both Fourier transform infrared spectroscopy and scanning electron microscopy. The released profile and kinetics of Mel from MPs were quantified, and the bioactivity of the released Mel on preosteoblastic MC3T3-E1 cells was characterized in vitro. An in vitro drug release assay has shown high encapsulation efficiency and sustained release of Mel over the investigation period. In an osteogenesis assay, Mel-loaded CS MPs have significantly enhanced alkaline phosphatase (ALP) mRNA expression and ALP activity compared with the control group. Meanwhile, the osteoblast-specific differentiation genes, including runt related transcription factor 2 (Runx2), bone morphogentic protein-2 (Bmp2), collagen I (Col I), and osteocalcin (Ocn), were also significantly upregulated. Furthermore, quantificational alizarin red-based assay demonstrated that Mel-loaded CS MPs notably enhanced the calcium deposit of MC3T3-E1 compared with controls. In essence, Mel-loaded CS MPs can control the release of Mel for a period of time to accelerate osteogenic differentiation of preosteoblast cells in vitro.

Exosomes from conditioned media of bone marrow-derived mesenchymal stem cells promote bone regeneration by enhancing angiogenesis

Growth factors in serum-free conditioned media from human bone marrow-derived mesenchymal stem cells (MSC-CM) are known to be effective in bone regeneration. However, the secretomes in MSC-CM that act as active ingredients for bone regeneration, as well as their mechanisms, remains unclear. Exosomes, components of MSC-CM, provide the recipient cells with genetic information and enhance the recipient cellular paracrine stimulation, which contributes to tissue regeneration. We hypothesized that MSC-CM-derived exosomes (MSC-Exo) promoted bone regeneration, and that angiogenesis was a key step. Here, we prepared an MSC-Exo group, MSC-CM group, and Exo-antiVEGF group (MSC-Exo with angiogenesis inhibitor), and examined the osteogenic and angiogenic potential in MSCs. Furthermore, we used a rat model of calvaria bone defect and implanted each sample to evaluate bone formation weekly, until week 4 after treatment. Results showed that MSC-Exo enhanced cellular migration and osteogenic and angiogenic gene expression in MSCs compared to that in other groups. In vivo, early bone formation by MSC-Exo was also confirmed. Two weeks after implantation, the newly formed bone area was 31.5 ± 6.5% in the MSC-Exo group while those in the control and Exo-antiVEGF groups were 15.4 ± 4.4% and 8.7 ± 1.1%, respectively. Four weeks after implantation, differences in the area between the MSC-Exo group and the Exo-antiVEGF or control groups were further broadened. Histologically, notable accumulation of osteoblast-like cells and vascular endothelial cells was observed in the MSC-Exo group; however, fewer cells were found in the Exo-antiVEGF and control groups.

In conclusion, MSC-Exo promoted bone regeneration during early stages, as well as enhanced angiogenesis. Considering the tissue regeneration with transplanted cells and their secretomes, this study suggests that exosomes might play an important role, especially in angiogenesis.

Boosting mesenchymal stem cells regenerative activities on biopolymers-calcium phosphate functionalized collagen membrane

The regeneration of bone-soft tissue interface, using functional membranes, remains challenging and can be promoted by improving mesenchymal stem cells (MSCs) paracrine function. Herein, a collagen membrane, used as guided bone regeneration membrane, was functionalized by calcium phosphate, chitosan and hyaluronic acid hybrid coating by simultaneous spray of interacting species process. Composed of brushite, octacalcium phosphate and hydroxyapatite, the hybrid coating increased the membrane stiffness by 50%. After 7 days of MSCs culture on the hybrid coated polymeric membrane, biological studies were marked by a lack of osteoblastic commitment. However, MSCs showed an enhanced proliferation along with the secretion of cytokines and growth factors that could block bone resorption and favour endothelial cell recruitment without exacerbating polynuclear neutrophils infiltration. These data shed light on the great potential of inorganic/organic coated collagen membranes as an alternative bioactive factor-like platform to improve MSCs regenerative capacity, in particular to support bone tissue vascularization and to modulate inflammatory infiltrates.

Pedicle Periosteum as a Barrier for Guided Bone Regeneration in the Rabbit Frontal Bone

BACKGROUND/AIM

For alveolar ridge reconstruction prior to dental implant placement, a barrier membrane is placed to create space over the bone defect. Although periosteum possesses osteogenic capacity, direct contact between defects and periosteum has been avoided. The present study aimed to investigate whether pedicle periosteum could be used as a barrier membrane.

MATERIALS AND METHODS

Twelve rabbits were used. A U-shaped incision was made in the frontal bone, and the skin-periosteum over the frontal bone was stripped. Two trephine-drilled holes with a diameter of 5 mm were prepared in the frontal bone. One hole was covered with pedicle periosteum (periosteum side), and the periosteum was secured to the contralateral side. The other defect was covered with an occlusive membrane (membrane side).

RESULTS

The histological observation showed that both defects, which were covered either by the periosteum or by the membrane, were closed almost completely after 12 weeks of healing. No statistically significant difference was observed in the bone defect closure rates between the two sides at 4 and 12 weeks.

CONCLUSION

This study demonstrated that the pedicle periosteum possesses regenerative effects equivalent to those of occlusive membrane. The periosteum contributes to new bone formation by acting as a mechanical barrier and a source of osteogenic components.

TGF-β activity in acid bone lysate adsorbs to titanium surface

Objectives

Osteoblasts lay down new bone on implant surfaces. The underlying cellular mechanism and the spatio‐temporal mode of action, however, remain unclear. It can be proposed that growth factors released upon acidification by osteoclasts adsorb to the implant surface and control the early stages of osseointegration.

Methods

To simulate bone lysis by osteoclasts, titanium discs were exposed to acid bone lysate (ABL) followed by vigorous washing and seeding of oral fibroblasts. The expression of TGF‐β target genes interleukin 11 (IL11) and NADPH oxidase 4 (NOX4) was evaluated by reverse transcriptase polymerase chain reaction and IL11 ELISA. TGF‐β signaling activation was assessed via Smad2/3 immunofluorescence. The impact of ABL on osteogenic differentiation was determined with murine ST2 mesenchymal stromal cells.

Results

We report here that ABL‐conditioned titanium discs, independent of turned or rough surface, increased the expression of IL11 and NOX4. This increase was blocked by the TGF‐β receptor 1 antagonist SB431542. Further support for the TGF‐β signaling activation came from the translocation of Smad2/3 into the nucleus of oral fibroblasts. Moreover, titanium discs exposed to ABL decreased alkaline phosphatase and osteopontin in ST2 cells.

Conclusions

These in vitro findings suggest that titanium can adsorb TGF‐β from ABLs. The data provide a strong impetus for studies on the protein adsorption on implant surfaces in vitro and in vivo, specifically for growth factors including bone‐derived TGF‐β during successful and failed osseointegration.

Use of a Non-Crosslinked Collagen Membrane During Guided Bone Regeneration Does Not Interfere With the Bone Regenerative Capacity of the Periosteum

PURPOSE

To assess whether the use of a non-crosslinked porcine collagen type I and III bi-layered membrane inter-positioned between the periosteum and a bone defect would interfere with the bone regenerative capacity of the periosteum.

MATERIALS AND METHODS

Sixty rats, each with 1 critical-size calvarial defect (CSD; diameter, 5 mm) in the parietal bone, were randomly allocated to 1 of 3 equal-size groups after CSD creation: 1) the periosteum was excised and the flap was repositioned without interposition of a membrane (no-periosteum [NP] group); 2) the flap including the periosteum was repositioned (periosteum [P] group); and 3) a non-crosslinked collagen membrane was inter-positioned between the flap, including the periosteum, and the bone defect (membrane [M] group). Micro-computed tomography, qualitative histology, immunohistochemistry, and reverse transcription real-time quantitative polymerase chain reaction were performed at 3, 7, 15, and 30 days postoperatively.

RESULTS

A markedly increased radiographic residual defect length was observed in the NP group compared with the P group at 30 days. The NP group also presented a smaller radiographic bone fill area than the P group at 15 and 30 days and then the M group at 30 days. The P and M groups exhibited considerably greater expression of bone morphogenetic protein-2 and osteocalcin than the NP group at 7 days; expression of transforming growth factor-β1 was considerably greater in the NP group at 15 days. Further, the P group presented considerably higher gene expression levels of Runx2 and Jagged1 at 7 days and of alkaline phosphatase at 3 and 15 days compared with the M and NP groups.

CONCLUSION

Interposition of this specific non-crosslinked collagen membrane between the periosteum and the bone defect during guided bone regeneration interferes only slightly, if at all, with the bone regenerative capacity of the periosteum.

Pervasion of beta-tricalcium phosphate with nanodiamond particles yields efficient and safe bone replacement material amenable for biofunctionalization and application in large-size osseous defect healing

Biofunctionalization of scaffold materials can enable the healing of large bone defects. In case of minimally invasive guided-bone regeneration (GBR), limitations are however hard-to-control side effects related to the potential release of biofactors into the systemic environment. Biofactors can be stably bound to nanodiamond particles (ND) through physisorption. We therefore tested the biological and clinical effects of refining beta-tricalcium phosphate (βTCP) with ND in vitro and in vivo. In vitro, βTCP carrying 4% ND resulted in enhanced attachment of mesenchymal stem cells. When assessing GBR after lateral augmentation of the mandible in sheep showed that ND in βTCP resulted in a consistently steady bone formation when compared to pure βTCP, demonstrating the biological inert behavior and the potential clinical safety of ND.

Autologous liquid platelet rich fibrin: A novel drug delivery system

There is currently widespread interest within the biomaterial field to locally deliver biomolecules for bone and cartilage regeneration. Substantial work to date has focused on the potential role of these biomolecules during the healing process, and the carrier system utilized is a key factor in their effectiveness. Platelet rich fibrin (PRF) is a naturally derived fibrin scaffold that is easily obtained from peripheral blood following centrifugation. Slower centrifugation speeds have led to the commercialization of a liquid formulation (liquid-PRF) resulting in an upper plasma layer composed of liquid fibrinogen/thrombin prior to clot formation that remains in its liquid phase for approximately 15 min until injected into bodily tissues. Herein, we introduce the use of liquid PRF as an advanced local delivery system for small and large biomolecules. Potential target molecules including large (growth factors/cytokines and morphogenetic/angiogenic factors), as well as small (antibiotics, peptides, gene therapy and anti-osteoporotic) molecules are considered potential candidates for enhanced bone/cartilage tissue regeneration. Furthermore, liquid-PRF is introduced as a potential carrier system for various cell types and nano-sized particles that are capable of limiting/by-passing the immune system and minimizing potential foreign body reactions within host tissues following injection.

STATEMENT OF SIGNIFICANCE

There is currently widespread interest within the biomaterial field to locally deliver biomolecules for bone and cartilage regeneration. This review article focuses on the use of a liquid version of platelet rich fibrin (PRF) composed of liquid fibrinogen/thrombin as a drug delivery system. Herein, we introduce the use of liquid PRF as an advanced local delivery system for small and large biomolecules including growth factors, cytokines and morphogenetic/angiogenic factors, as well as antibiotics, peptides, gene therapy and anti-osteoporotic molecules as potential candidates for enhanced bone/cartilage tissue regeneration.

Contour changes after guided bone regeneration of large non-contained mandibular buccal bone defects using deproteinized bovine bone mineral and a porcine-derived collagen membrane: an experimental in vivo investigation

OBJECTIVE

The objective of this study was to evaluate soft tissue contour changes after three different regenerative therapies in chronic ridge defects.

MATERIAL AND METHODS

Buccal bone defects were created in the mandible of nine beagle dogs. Augmentation procedures were performed 3 months later using a bone replacement graft (BRG), resorbable collagen membrane (MBG), or a combination of both procedures (CBG). Silicone impressions were taken before tooth extraction (T1), before the augmentation procedure (T2), and 3 months after the regenerative surgeries (T3). Casts were optically scanned and stereolithography files were superimposed to analyze the horizontal changes in ridge contours.

RESULTS

After defect creation, most part of the horizontal changes occurred 4 and 6 mm below the gingival margin. In the mesial defect (D1) at T3, the mean horizontal gain in MBG amounted to 0.47 ± 0.34 mm, 0.79 ± 0.67 mm in the BRG, and 0.87 ± 0.69 mm for the CBG. In the middle defect (D2), the mean changes for the MBG were 0.11 ± 0.31, 1.01 ± 0.91 for the BRG, and 0.98 ± 0.49 for the CBG. The mean changes in the distal defect (D3) amounted to 0.24 ± 0.72 for the MBG, 1.04 ± 0.92 for the BRG, and 0.86 ± 0.56 for the CBG. The differences reached significance in all defects for the comparison MBG-BRG and MBG-CBG, while similar parameters were observed for the comparison BRG-CBG.

CONCLUSION

BRG and CBG were equally effective and superior to MBG in increasing the horizontal tissue contours. The augmentation seldom reached the values before extraction.

CLINICAL RELEVANCE

Scaffolding materials are needed for contour augmentation when using resorbable collagen membranes.

Histomorphometric and immunohistochemical evaluation of collagen containing xenogeneic bone blocks used for lateral bone augmentation in staged implant placement

BACKGROUND

The osteoconductive properties of collagen containing xenogeneic bone blocks (CCXBB) remain unclear. The aim of this prospective single-arm clinical study was to assess the histological outcomes of CCXBB blocks used as bone replacement grafts for lateral bone augmentation procedures.

METHODS

In 15 patients with severe horizontal alveolar ridge resorption, lateral augmentation procedures were performed using CCXBB as bone replacement grafts. Twenty-six weeks postoperatively, a re-entry procedure was performed to evaluate the bone width for adequate implant placement and two histological specimens were retrieved from each patient, one being processed for ground sectioning and the other for decalcified paraffin-included sections. In non-decalcified sections, the relative proportions occupied by bone, biomaterials, and connective tissue present in the biopsies were identified. In de-calcified sections, structures and cells positive for osteopontin (OPN), tartrate-resistant acid phosphatase activity (TRAP), osteocalcin (OSC), and alkaline phosphatase (ALP) were assessed.

RESULTS

Soft tissue dehiscence occurred during the follow-up in 5 out of 15 patients (33.3%). The mean crest width at baseline was 2.78 mm (SD 0.57) and the mean crest width at re-entry was 6.90 mm (SD 1.22), with a mean ridge width increase of 4.12 mm (SD 1.32). Twenty-six bone biopsies were obtained from 13 patients. Histomorphometric analysis showed a mean of 26.90% (SD 12.21) of mineralized vital bone (MVB), 21.37% (SD 7.36) of residual CCXBB, 47.13% (SD 19.15) of non-mineralized tissue, and 0.92% of DBBM. The immunohistochemical analysis revealed a large number of OPN-positive cells 8.12% (SD 4.73), a lower proportion of TRAP positive multinuclear cells 5.09% (SD 4.91), OSC-positive cells 4.09% (SD 4.34), and a limited amount of ALP positive cells 1.63% (SD 2).

CONCLUSIONS

CCXBB achieved significant horizontal crestal width allowing for staged implant placement in most of the patients. In light of the histological outcomes and implant failures, special attention must be placed to prevent soft tissue dehiscence when CCXBB is used in severe atrophic alveolar crests.

Allograft Bone as Antibiotic Carrier

The treatment of chronic bone and joint infections is characterized by obstinate persistency of the causing microorganisms and resulting long term disability to patients, associated with remarkable costs for the health care system. Difficulties derive from biofilm formed on dead bone and eventual implants, with resistance against immunological defences and antimicrobial substances. Biofilm embedded bacteria require up to 1000 times the antibiotic concentration of planktonic bacteria for elimination. Systemic antibiotic treatment alone cannot provide the concentrations required and surgical intervention is always prerequisite for potentially providing a cure. A second issue is that osseous defects are almost always present after surgical debridement, and it is difficult to address their reconstruction. One option is to use bone grafts, either from the patient´s own body or from foreign donors (allografts). Grafts are usually unvascularized and are prone to colonization with bacteria. Loading of allografts with antibiotics may not only protect grafts from bacterial adhesion but, using appropriate processing methods, may also provide high local antibiotic concentrations that may eliminate remaining sessile pathogens. For efficient action as antibiotic carriers, the release of antibiotics should be above the minimum biofilm eradication concentration (MBEC) for a prolonged period of time. Cleaning the bone from bone marrow opens a large reservoir for storage of antimicrobial substances that, after implantation, may be released to the surrounding in a sustained mode, possibly eliminating remaining biofilm remnants. Removal of bone marrow, leaving a pure matrix, provides increased safety and improved revascularization of the graft. Local provision of antibiotic concentrations above the MBEC may enable simultaneous internal fixation with osteosynthetic material and single stage exchange of infected endoprostheses, resulting in shorter hospital stays with reduced pain and faster rehabilitation of patients.