New insights into and novel applications of release technology for periodontal reconstructive therapies

Insights into Intra Periodontal Pocket Pathogenesis, Treatment, In Vitro-In Vivo Models, Products and Patents, Challenges and Opportunity

Periodontal disease is a multifactorial pathogenic condition involving microbial infection, inflammation, and various systemic complications. Here, a systematic and comprehensive review discussing key-points such as the pros and cons of conventional methods, new advancements, challenges, patents and products, and future prospects is presented. A systematic review process was adopted here by using the following keywords: periodontal diseases, pathogenesis, models, patents, challenges, recent developments, and 3-D printing scaffolds. Search engines used were "google scholar", "web of science", "scopus", and "pubmed", along with textbooks published over the last few decades. A thorough study of the published data rendered an accurate and deep understanding of periodontal diseases, the gap of research so far, and future opportunities. Formulation scientists and doctors need to be interconnected for a better understanding of the disease to prescribe a quality product. Moreover, prime challenges (such as a lack of a vital testing model, scarcity of clinical and preclinical data, products allowing for high drug access to deeper tissue regions for prolonged residence, lack of an international monitoring body, lack of 4D or time controlled scaffolds, and lack of successful AI based tools) exist that must be addressed for designing new quality products. Generally, several products have been commercialized to treat periodontal diseases with certain limitations. Various strategic approaches have been attempted to target certain delivery regions, maximize residence time, improve efficacy, and reduce toxicity. Conclusively, the current review summarizes valuable information for researchers and healthcare professional to treat a wide range of periodontal diseases.

Unlocking nature's arsenal: Nanotechnology for targeted delivery of venom toxins in cancer therapy

AIM

The aim of the present review is to shed light on the nanotechnological approaches adopted to overcome the shortcomings associated with the delivery of venom peptides which possess inherent anti-cancer properties.

BACKGROUND

Venom peptides although have been reported to demonstrate anti-cancer effects, they suffer from several disadvantages such as in vivo instability, off-target adverse effects, limited drug loading and low bioavailability. This review presents a comprehensive compilation of different classes of nanocarriers while underscoring their advantages, disadvantages and potential to carry such peptide molecules for in vivo delivery. It also discusses various nanotechnological aspects such as methods of fabrication, analytical tools to assess these nanoparticulate formulations, modulation of nanocarrier polymer properties to enhance loading capacity, stability and improve their suitability to carry toxic peptide drugs.

CONCLUSION

Nanotechnological approaches bear great potential in delivering venom peptide-based molecules as anticancer agents by enhancing their bioavailability, stability, efficacy as well as offering a spatiotemporal delivery approach. However, the challenges associated with toxicity and biocompatibility of nanocarriers must be duly addressed.

PERSPECTIVES

The everlasting quest for new breakthroughs for safer delivery of venom peptides in human subjects is fuelled by unmet clinical needs in the current landscape of chemotherapy. In addition, exhaustive efforts are required in obtaining and purifying the venom peptides followed by designing and optimizing scale up technologies.

Flavonoid extract from propolis alleviates periodontitis by boosting periodontium regeneration and inflammation resolution via regulating TLR4/MyD88/NF-κB and RANK/NF-κB pathway

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional Chinese medicine, propolis has been used for treating oral diseases for centuries, widely. Flavonoid extract is the main active ingredient in propolis, which has attracted extensive attention in recent years.

AIM OF THE STUDY

The objective and novelty of the current study aims to identify the mechanism of total flavonoid extract of propolis (TFP) for the treatment of periodontitis, and evaluate the therapeutic effect of TFP-loaded liquid crystal hydrogel (TFP-LLC) in rats with periodontitis.

METHODS

In this study, we used lipopolysaccharide-stimulated periodontal ligament stem cells (PDLSCs) to construct in vitro inflammation model, and investigated the anti-inflammatory effect of TFP by expression levels of inflammatory factors. Osteogenic differentiation was assessed using alkaline phosphatase activity and alizarin red staining. Meanwhile, the expression of toll like receptor 4 (TLR4), myeloid differentiation primary response 88 (MyD88), nuclear factor-kappa B (NF-κB), receptor activator of NF-κB (RANK) etc, were quantitated to investigate the therapeutic mechanism of TFP. Finally, we constructed TFP-LLC using a self-emulsification method and administered it to rats with periodontitis via periodontal pocket injection to evaluate the therapeutic effects. The therapeutic index, microcomputed tomography (Micro-CT), H&E staining, TRAP staining, and Masson staining were used for this evaluation.

RESULTS

TFP reduced the expression of TLR4, MyD88, NF-κB and inflammatory factor in lipopolysaccharide-stimulated PDLSCs. Meanwhile, TFP simultaneously regulating alkaline phosphatase, RANK, runt-associated transcription factor-2 and matrix metalloproteinase production to accelerate osteogenic differentiation and collagen secretion. In addition, TFP-LLC can stably anchor to the periodontal lesion site and sustainably release TFP. After four weeks of treatment with TFP-LLC, we observed a decrease in the levels of NF-κB and interleukin-1β (IL-1β) in the periodontal tissues of rats, as well as a significant reduction in inflammation in HE staining. Similarly, Micro CT results showed that TFP-LLC could significantly inhibit alveolar bone resorption, increase bone mineral density (BMD) and reduce trabecular bone space (Tb.Sp) in rats with periodontitis.

CONCLUSION

Collectively, we have firstly verified the therapeutic effects and mechanisms of TFP in PDLSCs for periodontitis treatment. Our results indicate that TFP perform anti-inflammatory and tissue repair activities through TLR4/MyD88/NF-κB and RANK/NF-κB pathways in PDLSCs. Meanwhile, for the first time, we employed LLC delivery system to load TFP for periodontitis treatment. The results showed that TFP-LLC could be effectively retained in the periodontal pocket and exerted a crucial role in inflammation resolution and periodontal tissue regeneration.

Research progress of vascularization strategies of tissue-engineered bone

The bone defect caused by fracture, bone tumor, infection, and other causes is not only a problematic point in clinical treatment but also one of the hot issues in current research. The development of bone tissue engineering provides a new way to repair bone defects. Many animal experimental and rising clinical application studies have shown their excellent application prospects. The construction of rapid vascularization of tissue-engineered bone is the main bottleneck and critical factor in repairing bone defects. The rapid establishment of vascular networks early after biomaterial implantation can provide sufficient nutrients and transport metabolites. If the slow formation of the local vascular network results in a lack of blood supply, the osteogenesis process will be delayed or even unable to form new bone. The researchers modified the scaffold material by changing the physical and chemical properties of the scaffold material, loading the growth factor sustained release system, and combining it with trace elements so that it can promote early angiogenesis in the process of induced bone regeneration, which is beneficial to the whole process of bone regeneration. This article reviews the local vascular microenvironment in the process of bone defect repair and the current methods of improving scaffold materials and promoting vascularization.

Dual Photo-Enhanced Interpenetrating Network Hydrogel with Biophysical and Biochemical Signals for Infected Bone Defect Healing

The healing of infected bone defects (IBD) is a complex physiological process involving a series of spatially and temporally overlapping events, including pathogen clearance, immunological modulation, vascularization, and osteogenesis. Based on the theory that bone healing is regulated by both biochemical and biophysical signals, in this study, a copper doped bioglass (CuBGs)/methacryloyl-modified gelatin nanoparticle (MA-GNPs)/methacrylated silk fibroin (SilMA) hybrid hydrogel is developed to promote IBD healing. This hybrid hydrogel demonstrates a dual-photocrosslinked interpenetrating network mechanism, wherein the photocrosslinked SilMA as the main network ensures structural integrity, and the photocrosslinked MA-GNPs colloidal network increases strength and dissipates loading forces. In an IBD model, the hydrogel exhibits excellent biophysical characteristics, such as adhesion, adaptation to irregular defect shapes, and in situ physical reinforcement. At the same time, by sequentially releasing bioactive ions such as Cu2+ , Ca2+ , and Si2+ ions from CuBGs on demand, the hydrogel spatiotemporally coordinates antibacterial, immunomodulatory and bone remodeling events, efficiently removing infection and accelerating bone repair without the use of antibiotics or exogenous recombinant proteins. Therefore, the hybrid hydrogel can be used as a simple and effective method for the treatment of IBD.

Impact of local drug delivery and natural agents as new target strategies against periodontitis: new challenges for personalized therapeutic approach

Periodontitis is a persistent inflammation of the soft tissue around the teeth that affects 60% of the population in the globe. The self-maintenance of the inflammatory process can cause periodontal damage from the alveolar bone resorption to tooth loss in order to contrast the effects of periodontitis, the main therapy used is scaling and root planing (SRP). At the same time, studying the physiopathology of periodontitis has shown the possibility of using a local drug delivery system as an adjunctive therapy. Using local drug delivery devices in conjunction with SRP therapy for periodontitis is a potential tool since it increases drug efficacy and minimizes negative effects by managing drug release. This review emphasized how the use of local drug delivery agents and natural agents could be promising adjuvants for the treatment of periodontitis patients affected or not by cardiovascular disease, diabetes, and other system problems. Moreover, the review evidences the current issues and new ideas that can inspire potential later study for both basic research and clinical practice for a tailored approach.

Evaluation of Osteogenic Potential of Fucoidan Containing Chitosan Hydrogel in the Treatment of Periodontal Intra-Bony Defects-A Randomized Clinical Trial

Periodontal diseases significantly impact about half of the global population, and their treatment often encompasses relieving symptoms as well as regenerating the destroyed tissues. Revolutionary research in the management of periodontal disease includes biomaterials, a boon to re-generative dentistry owing to their excellent biological properties: non-toxicity, anti-inflammatory, biocompatibility, biodegradability, and adhesion. This study aimed to fabricate an injectable fucoidan containing chitosan hydrogel and prove its effectiveness in periodontal bone regeneration. The injectable hydrogel was prepared using the sol-gel method and was subjected to various physical, chemical, and biological characterizations to understand its efficacy in formation of new bone. The effectiveness of the developed hydrogel was assessed in periodontal bony defects to study the soft and hard tissue changes. A total of 40 periodontitis patients with bony defects were recruited and randomized into two groups to receive fucoidan-chitosan hydrogel and concentrated growth factor, respectively. Customized acrylic stents were used to guide the hydrogel placement into the defect site. Post-surgical changes in clinical parameters were assessed at 3, 6, and 9 months to appreciate the soft and hard tissue changes using repeated measures analysis of variance and Bonferroni's post hoc test. Significance was kept at 5%. The porosity, water uptake of the prepared hydrogel showed good efficacy, with particle size of the fucoidan containing chitosan hydrogel of 6.000 nm. The MG-63 osteoblasts cell line revealed biocompatibility, biodegradability and showed slow and sustained drug release, increased cell proliferation, and enhanced alkaline phosphatase secretion. Mineralization assay was greatest in the fucoidan containing chitosan hydrogel. Clinically, it exhibited significantly lower probing depth values and a higher mean improvement in clinical attachment level as compared to the concentrated growth factor (CGF) group at the end of 3 and 6 months (p < 0.05). The mean of the defect fills in the fucoidan containing chitosan group was 1.20 at the end of 9 months (p < 0.001) as compared with defect fills observed in the CGF group. The presence of fucoidan in the hydrogel significantly contributed to bone regeneration in humans, thus strengthening its potential in tissue engineering. Fucoidan-chitosan will be a promising biomaterial for bone tissue regeneration.

A 3D-printed molybdenum-containing scaffold exerts dual pro-osteogenic and anti-osteoclastogenic effects to facilitate alveolar bone repair

The positive regulation of bone-forming osteoblast activity and the negative feedback regulation of osteoclastic activity are equally important in strategies to achieve successful alveolar bone regeneration. Here, a molybdenum (Mo)-containing bioactive glass ceramic scaffold with solid-strut-packed structures (Mo-scaffold) was printed, and its ability to regulate pro-osteogenic and anti-osteoclastogenic cellular responses was evaluated in vitro and in vivo. We found that extracts derived from Mo-scaffold (Mo-extracts) strongly stimulated osteogenic differentiation of bone marrow mesenchymal stem cells and inhibited differentiation of osteoclast progenitors. The identified comodulatory effect was further demonstrated to arise from Mo ions in the Mo-extract, wherein Mo ions suppressed osteoclastic differentiation by scavenging reactive oxygen species (ROS) and inhibiting mitochondrial biogenesis in osteoclasts. Consistent with the in vitro findings, the Mo-scaffold was found to significantly promote osteoblast-mediated bone formation and inhibit osteoclast-mediated bone resorption throughout the bone healing process, leading to enhanced bone regeneration. In combination with our previous finding that Mo ions participate in material-mediated immunomodulation, this study offers the new insight that Mo ions facilitate bone repair by comodulating the balance between bone formation and resorption. Our findings suggest that Mo ions are multifunctional cellular modulators that can potentially be used in biomaterial design and bone tissue engineering.

Immunomodulation in the Treatment of Periodontitis: Progress and Perspectives

Periodontitis is one of the most common dental diseases. Compared with healthy periodontal tissues, the immune microenvironment plays the key role in periodontitis by allowing the invasion of pathogens. It is possible that modulating the immune microenvironment can supplement traditional treatments and may even promote periodontal regeneration by using stem cells, bacteria, etc. New anti-inflammatory therapies can enhance the generation of a viable local immune microenvironment and promote cell homing and tissue formation, thereby achieving higher levels of immune regulation and tissue repair. We screened recent studies to summarize the advances of the immunomodulatory treatments for periodontitis in the aspects of drug therapy, microbial therapy, stem cell therapy, gene therapy and other therapies. In addition, we included the changes of immune cells and cytokines in the immune microenvironment of periodontitis in the section of drug therapy so as to make it clearer how the treatments took effects accordingly. In the future, more research needs to be done to improve immunotherapy methods and understand the risks and long-term efficacy of these methods in periodontitis.

Characterization and Therapeutic Use of Extracellular Vesicles Derived from Platelets

Autologous blood products, such as platelet-rich plasma (PRP), are gaining increasing interest in different fields of regenerative medicine. Although growth factors, the main components of PRP, are thought to stimulate reparation processes, the exact mechanism of action and main effectors of PRP are not fully understood. Plasma contains a high amount of extracellular vesicles (EVs) produced by different cells, including anucleated platelets. Platelet-derived EVs (PL-EVs) are the most abundant type of EVs in circulation. Numerous advantages of PL-EVs, including their ability to be released locally, their ease of travel through the body, their low immunogenicity and tumourigenicity, the modulation of signal transduction as well as the ease with which they can be obtained, has attracted increased attention n. This review focuses briefly on the biological characteristics and isolation methods of PL-EVs, including exosomes derived from platelets (PL-EXOs), and their involvement in the pathology of diseases. Evidence that shows how PL-EVs can be used as a novel tool in medicine, particularly in therapeutic and regenerative medicine, is also discussed in this review.

Hard Dental Tissues Regeneration-Approaches and Challenges

With the development of the modern concept of tissue engineering approach and the discovery of the potential of stem cells in dentistry, the regeneration of hard dental tissues has become a reality and a priority of modern dentistry. The present review reports the recent advances on stem-cell based regeneration strategies for hard dental tissues and analyze the feasibility of stem cells and of growth factors in scaffolds-based or scaffold-free approaches in inducing the regeneration of either the whole tooth or only of its component structures.

The Effects of Platelet-Rich and Platelet-Poor Plasma on Biological Characteristics of BM-MSCs In Vitro

Platelet-rich plasma (PRP) and its byproduct platelet-poor plasma (PPP) are rich sources of cytokines in tissue damage repair. Bone marrow-derived mesenchymal stem cells (BM-MSCs) have received more and more attention for their ability to treat multiple diseases. The purpose of our study was to investigate the biologic action of PPP and PRP on BM-MSCs. The adipogenic potential of BM-MSCs revealed no obvious change, but the osteogenic ability of BM-MSCs was enhanced after treated with PRP. CCK8 assays and cell colony formation assays showed that PRP promoted cell proliferation, while this effect of PPP was not obvious. No obvious difference was found in cell cycle and apoptosis of BM-MSCs between PRP and PPP treatment. Expression of β-galactosidase, a biological marker of senescence, was decreased upon PRP treatment which indicated that PRP provided significant protection against cellular senescence. The migratory capacity of BM-MSCs was detected by scratch and transwell assays. The results indicated that PRP could affect the migration ability of BM-MSCs. From immunofluorescence detection and western blot, we demonstrated that the level of epithelial-mesenchymal transition-related proteins was changed and several pluripotency marker genes, including Sox2, Sall4, Oct4, and Nanog, were increased. Finally, the expression of the key signal pathway such as PI3K/AKT was examined. Our findings suggested that PRP promoted cell migration of BM-MSCs via stimulating the signaling pathway of PI3K/AKT.

Dual delivery of platelet-derived growth factor and bone morphogenetic factor-6 on titanium surface to enhance the early period of implant osseointegration

OBJECTIVE

To test the surface properties and in vitro effects of a new sequential release system on MC3T3-E1 cells for improved osseointegration.

BACKGROUND

BMP6-loaded anodized titanium coated with PDGF containing silk fibroin (SF) may improve osseointegration.

METHODS

Titanium surfaces were electrochemically anodized, and SF layer was covered via electrospinning. Five experimental groups (unanodized Ti (Ti), anodized Ti (AnTi), anodized + BMP6-loaded Ti (AnTi-BMP6), anodized + BMP6 loaded + silk fibroin-coated Ti (AnTi-BMP6-SF), and anodized + BMP6-loaded + silk fibroin with PDGF-coated Ti (AnTi-BMP6-PDGF-SF)) were tested. After SEM characterization, contact angle analysis, and FTIR analysis, the amount of released PDGF and BMP6 was detected using ELISA. Cell proliferation (XTT), mineralization, and gene expression (RUNX2 and ALPL) were also evaluated.

RESULTS

After successful anodization and loading of PDGF and BMP6, contact angle measurements showed hydrophobicity for TiO₂ and hydrophilicity for protein-adsorbed surfaces. In FTIR, protein-containing surfaces exhibited amide-I, amide-II, and amide-III bands at 1600 cm^-1 -1700 cm^-1 , 1520 cm^-1 -1540 cm^-1 , and 1220 cm^-1 -1300 cm^-1 spectrum levels with a significant peak in BMP6- and/or SF-loaded groups at 1100 cm^-1 . PDGF release and BMP6 release were delayed, and relatively slower release was detected in SF-coated surfaces. Higher MC3T3-E1 proliferation and mineralization and lower gene expression of RUNX2 and ALPL were detected in AnTi-BMP6-PDGF-SF toward day 28.

CONCLUSION

The new system revealed a high potential for an improved early osseointegration period by means of a better factor release curve and contribution to the osteoblastic cell proliferation, mineralization, and associated gene expression.

Recent advances in periodontal regeneration: A biomaterial perspective

Periodontal disease (PD) is one of the most common inflammatory oral diseases, affecting approximately 47% of adults aged 30 years or older in the United States. If not treated properly, PD leads to degradation of periodontal tissues, causing tooth movement, and eventually tooth loss. Conventional clinical therapy for PD aims at eliminating infectious sources, and reducing inflammation to arrest disease progression, which cannot achieve the regeneration of lost periodontal tissues. Over the past two decades, various regenerative periodontal therapies, such as guided tissue regeneration (GTR), enamel matrix derivative, bone grafts, growth factor delivery, and the combination of cells and growth factors with matrix-based scaffolds have been developed to target the restoration of lost tooth-supporting tissues, including periodontal ligament, alveolar bone, and cementum. This review discusses recent progresses of periodontal regeneration using tissue-engineering and regenerative medicine approaches. Specifically, we focus on the advances of biomaterials and controlled drug delivery for periodontal regeneration in recent years. Special attention is given to the development of advanced bio-inspired scaffolding biomaterials and temporospatial control of multi-drug delivery for the regeneration of cementum-periodontal ligament-alveolar bone complex. Challenges and future perspectives are presented to provide inspiration for the design and development of innovative biomaterials and delivery system for new regenerative periodontal therapy.

Evaluation of New Bone Formation Using Autogenous Tooth Bone Graft Combined with Platelet-Rich Fibrin in Calvarial Defects

The purpose of the present study was to evaluate the contributions of autogenous tooth bone graft (ATBG) combined with platelet-rich fibrin (PRF) on new bone formation and bone morphogenetic protein (BMP)-2 in rabbit calvarial defects. Twelve male New Zealand rabbits were used in this study. Three circular bone defects were prepared in each rabbit with a drill. These defects were divided into 3 groups: control, treated with ATBG, and treated with ATBG+PRF. The animals were sacrificed at 28 days. Samples were evaluated by histomorphometric analyses and total augmented area, new bone area and bone density were calculated. In addition, expression of BMP-2 was determined by immunohistochemical staining. The total augmented area, new bone area and bone density were significantly greater in the ATBG group than in the control group (P <0.05). Also, these values were significantly higher in the ATBG+PRF group than the ATBG group (P <0.05). Test groups demonstrated significantly increased BMP-2 levels compared with the control group (P <0.05). The present study suggested that ATBG combined with PRF significantly increased the new bone formation and enhanced bone healing in cranial defects.

Immobilization of BMP-2, BMP-7 and alendronic acid on titanium surfaces: Adhesion, proliferation and differentiation of bone marrow-derived stem cells

This study analyzed the influence of titanium (TiO₂ ) surface modifications with two osteogenic proteins (BMP-2, BMP-7) and an anti-osteoclastic drug (alendronic acid [AA]) on sandblasted/acid-etched (SLA) and plain TiO₂ (PT) on cell adhesion, proliferation and differentiation (alkaline phosphatase [AP] and osteocalcin [OC]) of bone-marrow derived stem cells (BMSCs) after 1, 3 and 7 days in-vitro. Initially, AA surfaces showed the highest cell number and surface coverage. At day 3 and 7, BMP and AA-modified surfaces exhibited a significantly enhanced cell growth. For proliferation, at days 3 and 7, an enhancement on BMP-2, BMP-7 and AA-surfaces was seen. At day 7, SLA also showed a higher proliferation when compared to PT. Initially, AP expression was elevated on SLA and AA surfaces. At days 3 and 7, a significant increased AP expression was seen for SLA, BMP-2, BMP-7 and AA discs. For OC, SLA and AA surfaces had the highest expression after 1 day whereas after 3 and 7 days a significant difference was recorded for SLA, BMP-2, BMP-7 and AA. In conclusion, a beneficial biological effect of a chemical immobilization method of BMP-2, BMP-7 and alendronate onto titanium surfaces on BMSCs was proven.

Gene Delivery Therapeutics in the Treatment of Periodontitis and Peri-Implantitis: A State of the Art Review

BACKGROUND

Periodontal disease is a chronic inflammatory condition that affects supporting tissues around teeth, resulting in periodontal tissue breakdown. If left untreated, periodontal disease could have serious consequences; this condition is in fact considered as the primary cause of tooth loss. Being highly prevalent among adults, periodontal disease treatment is receiving increased attention from researchers and clinicians. When this condition occurs around dental implants, the disease is termed peri-implantitis. Periodontal regeneration aims at restoring the destroyed attachment apparatus, in order to improve tooth stability and thus reduce disease progression and subsequent periodontal tissue breakdown. Although many biomaterials have been developed to promote periodontal regeneration, they still have their own set of disadvantages. As a result, regenerative medicine has been employed in the periodontal field, not only to overcome the drawbacks of the conventional biomaterials but also to ensure more predictable regenerative outcomes with minimal complications. Regenerative medicine is considered a part of the research field called tissue engineering/regenerative medicine (TE/RM), a translational field combining cell therapy, biomaterial, biomedical engineering and genetics all with the aim to replace and restore tissues or organs to their normal function using in vitro models for in vivo regeneration. In a tissue, cells are responding to different micro-environmental cues and signaling molecules, these biological factors influence cell differentiation, migration and cell responses. A central part of TE/RM therapy is introducing drugs, genetic materials or proteins to induce specific cellular responses in the cells at the site of tissue repair in order to enhance and improve tissue regeneration. In this review, we present the state of art of gene therapy in the applications of periodontal tissue and peri-implant regeneration.

PURPOSE

We aim herein to review the currently available methods for gene therapy, which include the utilization of viral/non-viral vectors and how they might serve as therapeutic potentials in regenerative medicine for periodontal and peri-implant tissues.

Building capacity for macrophage modulation and stem cell recruitment in high-stiffness hydrogels for complex periodontal regeneration: Experimental studies in vitro and in rats

Recently, we found that although high-stiffness matrices stimulated osteogenic differentiation of bone marrow-derived stromal cells (BMSCs), the macrophages (Mφs) in high-stiffness transglutaminase crosslinked gelatins (TG-gels) tended to undergo M1 polarization and hence compromised cell osteogenesis. In this study, we hypothesized that the copresentation of interleukin (IL)-4 and stromal cell-derived factor (SDF)-1α in high-stiffness TG-gels may enhance periodontal regeneration by modulating Mφ polarization and promoting endogenous stem cell recruitment. We found that Mφs were more likely to polarize toward an immunomodulatory M2 state in the presence of IL-4 and hence positively influence the osteogenic differentiation of BMSCs when these cells coexisted in either indirect or direct co-culture systems. In cell migration assays, BMSCs exhibited an enhanced capability to move toward gels containing SDF-1α, and more cells could be recruited into the three-dimensional matrix of TG-gels. When TG-gels containing IL-4 and/or SDF-1α were used to repair periodontal defects, more new bone (MicroCT) was formed in animals that received the dual cytokine-loaded transplants at 4 weeks postsurgery. Mφs were recruited to all the transplanted gels, and after one week, more M1-phenotype cells were found in the groups without IL-4, while the presence of IL-4 was more likely to result in M2 polarization (immunofluorescence staining). When the tissue biopsies were histologically examined, the TG-gels containing both IL-4 and SDF-1α led to a generally satisfactory regeneration with respect to attachment recovery (epithelial and connective tissue) and hybrid tissue regeneration (bone, periodontal ligament and cementum). Our data suggest that the incorporation of IL-4 into high-stiffness TG-gels may promote the M2 polarization of Mφs and that SDF-1α can be applied to guide endogenous cell homing. Overall, building capacity for Mφ modulation and cell recruitment in high-stiffness hydrogels represents a simple and effective strategy that can support high levels of periodontal tissue regeneration. STATEMENT OF SIGNIFICANCE: The development of hydrogel-based regenerative therapies centered on the mobilization and stimulation of native cells for therapeutics opens a window toward realizing periodontal endogenous regeneration. In the present study, the parallel use of immunomodulatory and homing factors in high-stiffness hydrogel materials is shown to induce stem cell homing, modulate cell differentiation and indeed induce regrowth of the periodontium. We found that incorporation of interleukin (IL)-4 in high-stiffness TG-gels coaxed macrophages to polarize into M2 phenotypes, and stromal cell-derived factor (SDF)-1α could be applied to direct endogenous cell homing. Hence, we present for the first time a clinically relevant strategy based on macrophage modulation and host cell recruitment that can support high levels of periodontal tissue regeneration.

Novel Bioactive and Therapeutic Dental Polymeric Materials to Inhibit Periodontal Pathogens and Biofilms

Periodontitis is a common infectious disease characterized by loss of tooth-supporting structures, which eventually leads to tooth loss. The heavy burden of periodontal disease and its negative consequence on the patient's quality of life indicate a strong need for developing effective therapies. According to the World Health Organization, 10⁻15% of the global population suffers from severe periodontitis. Advances in understanding the etiology, epidemiology and microbiology of periodontal pocket flora have called for antibacterial therapeutic strategies for periodontitis treatment. Currently, antimicrobial strategies combining with polymer science have attracted tremendous interest in the last decade. This review focuses on the state of the art of antibacterial polymer application against periodontal pathogens and biofilms. The first part focuses on the different polymeric materials serving as antibacterial agents, drug carriers and periodontal barrier membranes to inhibit periodontal pathogens. The second part reviews cutting-edge research on the synthesis and evaluation of a new generation of bioactive dental polymers for Class-V restorations with therapeutic effects. They possess antibacterial, acid-reduction, protein-repellent, and remineralization capabilities. In addition, the antibacterial photodynamic therapy with polymeric materials against periodontal pathogens and biofilms is also briefly described in the third part. These novel bioactive and therapeutic polymeric materials and treatment methods have great potential to inhibit periodontitis and protect tooth structures.

Synergistic effects of dual growth factor delivery from composite hydrogels incorporating 2-N,6-O-sulphated chitosan on bone regeneration

A promising strategy to accelerate bone generation is to deliver a combination of certain growth factors to the integration site via a controlled spatial and temporal delivery mode. Here, a composite hydrogel incorporating poly(lactide-co-glycolide) (PLGA) microspheres was accordingly prepared to load and deliver the osteogenic rhBMP-2 and angiogenic rhVEGF₁₆₅ in the required manner. In addition, 2-N,6-O-sulphated chitosan (26SCS), which is a synergetic factor of growth factors, was incorporated in the composite hydrogel as well. The system showed a similar release behaviour of the two growth factors regardless of 26SCS inclusion. RhBMP-2 loaded in PLGA microspheres showed a sustained release over a period of 2 weeks, whereas rhVEGF₁₆₅ loaded in hydrogel eluted almost completely from the hydrogel over the first 16 days. Both growth factors retained their efficacy, as quantified with relevant in vitro assays. Moreover, an enhanced cell response was achieved upon the delivery of dual growth factors, compared to that obtained with a single factor. Furthermore, in the presence of 26SCS, the system revealed significantly upregulated alkaline phosphatase activity, human umbilical vein endothelial cell proliferation, sprouting, nitric oxide secretion, and angiogenic gene expression. This study highlighted that the composite hydrogel incorporated with 26SCS appears to constitute a promising approach to deliver multiple growth factors. From our findings, we could also conclude that rhBMP-2 can promote angiogenesis and that the mechanism is worthy of further study in subsequent research.

Exendin-4 relieves the inhibitory effects of high glucose on the proliferation and osteoblastic differentiation of periodontal ligament stem cells

BACKGROUND

With the impaired regenerative potential in patients with diabetes mellitus (DM), Periodontal ligament stem cells (PDLSCs) are regarded as an attractive source of stem cells for periodontal cytotherapy. Recent studies have shown that Exendin-4 (Ex-4) exerts cell-protective effects and bone remodeling ability on many types of cells. The aim of this study was to investigate whether Ex-4 alleviates the inhibition of high glucose on the proliferation and osteogenic differentiation of PDLSCs.

METHODS

PDLSCs were incubated in medium supplemented with 5.5 mM d-glucose (NG), 30 mM d-glucose (HG), NG plus Ex-4, and HG plus different concentration (1, 10, 20, 100 nM) of Ex-4 respectively. Cell proliferation was detected by CCK-8 assay and cell cycle analysis. Osteogenesis was assessed by Alizarin Red S staining and evaluation of the mRNA expression of Runx2, ALP and Osx at day 7, 14 and 21. Intracellular level of reactive oxygen species (ROS) was detected using 5-(and-6)-chloromethyl-2',7'-dichlorodihydro-fluorescein diacetate (CMH2DCF-DA).

RESULTS

The proliferation ability, mineralized nodules forming capacity and the mRNA expression of Runx2, ALP and Osx of PDLSCs in HG group were decreased, the ROS level was increased compared to NG group. With the treatment of Ex-4, the HG-inhibited proliferation ability and osteogenic differentiation ability of PDLSCs were significantly reversed, the HG-increased ROS level could be down-regulated. Moreover, Ex-4 enhanced the osteogenic differentiation of normal PDLSCs.

CONCLUSIONS

Ex-4 alleviates the inhibitory effect of HG on the proliferation and osteoblastic differentiation of PDLSCs, and has a significant enhance in the osteoblastic differentiation of normal PDLSCs, giving new insights into the possible therapeutic method of diabetic periodontitis.

Blood derivatives awaken in regenerative medicine strategies to modulate wound healing

Blood components play key roles in the modulation of the wound healing process and, together with the provisional fibrin matrix ability to selectively bind bioactive molecules and control its spatial-temporal presentation, define the complex microenvironment that characterize this biological process. As a biomimetic approach, the use of blood derivatives in regenerative strategies has awakened as a source of multiple therapeutic biomolecules. Nevertheless, and despite their clinical relevance, blood derivatives have been showing inconsistent therapeutic results due to several factors, including proper control over their delivery mechanisms. Herein, we highlight recent trends on the use biomaterials to protect, sequester and deliver these pools of biomolecules in tissue engineering and regenerative medicine approaches. Particular emphasis is given to strategies that enable to control their spatiotemporal delivery and improve the selectivity of presentation profiles of the biomolecules derived from blood derivatives rich in platelets. Finally, we discussed possible directions for biomaterials design to potentiate the aimed regenerative effects of blood derivatives and achieve efficient therapies.

TGF-β1 affinity peptides incorporated within a chitosan sponge scaffold can significantly enhance cartilage regeneration

Scaffold incorporated with affinity peptides can efficiently promote cartilage regeneration without exogenous addition of growth factors and cells.

Polymer coated mesoporous ceramic for drug delivery in bone tissue engineering

Treatment strategy for various bone fracture and defects the researchers are focusing to develop a new carrier for delivering the drug into injured area with controlled and sustained manner using biomaterials with dynamic architecture orientation. Ceramic materials are resembled with bone compositional architecture and better bioactivity, degradability as well as antimicrobial activity made its enormous application in bone tissue engineering (BTE). Current focus in regenerative medicine were orchestration of biomaterials with the capacity of loading the drugs, growth factors, ionic components to promote better healing of bone tissue. Mesoporous type materials owed a great look towards the delivery of drugs, growth factors, etc in BTE because of its unique geometry. So the guest molecules loaded with geometrically organized ceramics would deliver onto the site of injury in controlled manner also the guiding and regulation of delivery of molecules have been controlled with the polymers response to different stimulation or biochemical factors as either scaffold or encapsulated particles for bone regeneration. Hence the review aims to describing the recent progress in bone tissue engineering using the ceramic based mesoporous materials encapsulated with polymers respond to different physiochemical stimulation for the efficient and controlled delivery of drug/growth factors for better bone healing.

Administration of signalling molecules dictates stem cell homing for in situ regeneration

Ex vivo-expanded stem cells have long been a cornerstone of biotherapeutics and have attracted increasing attention for treating intractable diseases and improving tissue regeneration. However, using exogenous cellular materials to develop restorative treatments for large numbers of patients has become a major concern for both economic and safety reasons. Advances in cell biological research over the past two decades have expanded the potential for using endogenous stem cells during wound healing processes, and in particular, recent insight into stem cell movement and homing has prompted regenerative research and therapy based on recruiting endogenous cells. Inspired by the natural healing process, artificial administration of specific chemokines as signals systemically or at the injury site, typically using biomaterials as vehicles, is a state-of-the-art strategy that potentiates stem cell homing and recreates an anti-inflammatory and immunomodulatory microenvironment to enhance in situ tissue regeneration. However, pharmacologically coaxing endogenous stem cells to act as therapeutics in the field of biomedicine remains in the early stages; its efficacy is limited by the lack of innovative methodologies for chemokine presentation and release. This review describes how to direct the homing of endogenous stem cells via the administration of specific signals, with a particular emphasis on targeted signalling molecules that regulate this homing process, to enhance in situ tissue regeneration. We also provide an outlook on and critical considerations for future investigations to enhance stem cell recruitment and harness the reparative potential of these recruited cells as a clinically relevant cell therapy.

Human platelet lysate supports the formation of robust human periodontal ligament cell sheets

The use of stem cell-derived sheets has become increasingly common in a wide variety of biomedical applications. Although substantial evidence has demonstrated that human platelet lysate (PL) can be used for therapeutic cell expansion, either as a substitute for or as a supplement to xenogeneic fetal bovine serum (FBS), its impact on cell sheet production remains largely unexplored. In this study, we manufactured periodontal ligament stem cell (PDLSC) sheets in vitro by incubating PDLSCs in sheet-induction media supplemented with various ratios of PL and FBS, i.e. 10% PL without FBS, 7.5% PL + 2.5% FBS, 5% PL + 5% FBS, 2.5% PL + 7.5% FBS or 10% FBS without PL. Cultures with the addition of all the designed supplements led to successful cell sheet production. In addition, all the resultant cellular materials exhibited similar expression profiles of matrix-related genes and proteins, such as collagen I, fibronectin and integrin β1. Interestingly, the cell components within sheets generated by media containing both PL and FBS exhibited improved osteogenic potential. Following in vivo transplantation, all sheets supported significant new bone formation. Our data suggest that robust PDLSC sheets can be produced by applying PL as either an alternative or an adjuvant to FBS. Further examination of the relevant influences of human PL that benefit cell behaviour and matrix production will pave the way towards optimized and standardized conditions for cell sheet production.

Visualizing Angiogenesis by Multiphoton Microscopy In Vivo in Genetically Modified 3D-PLGA/nHAp Scaffold for Calvarial Critical Bone Defect Repair

The reconstruction of critically sized bone defects remains a serious clinical problem because of poor angiogenesis within tissue-engineered scaffolds during repair, which gives rise to a lack of sufficient blood supply and causes necrosis of the new tissues. Rapid vascularization is a vital prerequisite for new tissue survival and integration with existing host tissue. The de novo generation of vasculature in scaffolds is one of the most important steps in making bone regeneration more efficient, allowing repairing tissue to grow into a scaffold. To tackle this problem, the genetic modification of a biomaterial scaffold is used to accelerate angiogenesis and osteogenesis. However, visualizing and tracking in vivo blood vessel formation in real-time and in three-dimensional (3D) scaffolds or new bone tissue is still an obstacle for bone tissue engineering. Multiphoton microscopy (MPM) is a novel bio-imaging modality that can acquire volumetric data from biological structures in a high-resolution and minimally-invasive manner. The objective of this study was to visualize angiogenesis with multiphoton microscopy in vivo in a genetically modified 3D-PLGA/nHAp scaffold for calvarial critical bone defect repair. PLGA/nHAp scaffolds were functionalized for the sustained delivery of a growth factor pdgf-b gene carrying lentiviral vectors (LV-pdgfb) in order to facilitate angiogenesis and to enhance bone regeneration. In a scaffold-implanted calvarial critical bone defect mouse model, the blood vessel areas (BVAs) in PHp scaffolds were significantly higher than in PH scaffolds. Additionally, the expression of pdgf-b and angiogenesis-related genes, vWF and VEGFR2, increased correspondingly. MicroCT analysis indicated that the new bone formation in the PHp group dramatically improved compared to the other groups. To our knowledge, this is the first time multiphoton microscopy was used in bone tissue-engineering to investigate angiogenesis in a 3D bio-degradable scaffold in vivo and in real-time.

Advances and perspectives in tooth tissue engineering

Bio-engineered teeth that can grow and remodel in a manner similar to that of natural teeth have the potential to serve as permanent replacements to the currently used prosthetic teeth, such as dental implants. A major challenge in designing functional bio-engineered teeth is to mimic both the structural and anisotropic mechanical characteristics of the native tooth. Therefore, the field of dental and whole tooth regeneration has advanced towards the molecular and nanoscale design of bio-active, biomimetic systems, using biomaterials, drug delivery systems and stem cells. The focus of this review is to discuss recent advances in tooth tissue engineering, using biomimetic scaffolds that provide proper architectural cues, exhibit the capacity to support dental stem cell proliferation and differentiation and sequester and release bio-active agents, such as growth factors and nucleic acids, in a spatiotemporal controlled manner. Although many in vitro and in vivo studies on tooth regeneration appear promising, before tooth tissue engineering becomes a reality for humans, additional research is needed to perfect methods that use adult human dental stem cells, as opposed to embryonic dental stem cells, and to devise the means to generate bio-engineered teeth of predetermined size and shape. Copyright © 2016 John Wiley & Sons, Ltd.

Osthole improves function of periodontitis periodontal ligament stem cells via epigenetic modification in cell sheets engineering

Inflammatory microenvironment causes the change of epigenetic modification in periodontal ligament stem cells derived from periodontitis tissues (P-PDLSCs), which results in defective osteogenic differentiation compared to cells from healthy tissues. It’s urgent to explore therapeutic strategies aimed at epigenetic targets associated with the regenerative ability of PDLSCs. Osthole, a small-molecule compound extracted from Chinese herbs, has been documented to promote osteogenesis and cell sheets formation of healthy PDLSCs. However, whether osthole shows same effect on P-PDLSCs and the mechanism of promotive effect is still unknown. The purpose of this study was to determine whether Osthole could restore defective osteogenic differentiation of P-PDLSCs via epigenetic modification. We demonstrated that 10⁻⁷ Mol/L of Osthole was the best concentration for osteogenic differentiation and proliferation of P-PDLSCs. Mechanistically, we also found that Osthole upregulated MOZ and MORF, histone acetylases that specifically catalyze acetylation of Histone3 lisine9 (H3K9) and Histone3 lisine14 (H3K14), which are key regulators in osteogenic differentiation of P-PDLSCs. Furthermore, Osthole treatment improved cell sheet formation and enhanced the bone formation of PDLSC sheets in animal models of periodontitis. Our study suggests that Osthole is a promising drug to cure periodontitis via regulating epigenetic modification in cell sheets engineering.

Poly(Lactic-co-Glycolic Acid): Applications and Future Prospects for Periodontal Tissue Regeneration

Periodontal tissue regeneration is the ultimate goal of the treatment for periodontitis-affected teeth. The success of regenerative modalities relies heavily on the utilization of appropriate biomaterials with specific properties. Poly (lactic-co-glycolic acid) (PLGA), a synthetic aliphatic polyester, has been actively investigated for periodontal therapy due to its favorable mechanical properties, tunable degradation rates, and high biocompatibility. Despite the attractive characteristics, certain constraints associated with PLGA, in terms of its hydrophobicity and limited bioactivity, have led to the introduction of modification strategies that aimed to improve the biological performance of the polymer. Here, we summarize the features of the polymer and update views on progress of its applications as barrier membranes, bone grafts, and drug delivery carriers, which indicate that PLGA can be a good candidate material in the field of periodontal regenerative medicine.

Advantages of Autologous Platelet-Rich Fibrin Membrane on Gingival Crevicular Fluid Growth Factor Levels and Periodontal Healing: A Randomized Split-Mouth Clinical Study

BACKGROUND

This study evaluates contributions of platelet-rich fibrin (PRF) combined with conventional flap surgery on growth factor levels in gingival crevicular fluid (GCF) and periodontal healing.

METHODS

Twenty-six patients (52 sites) with chronic periodontitis were treated either with autologous PRF with open flap debridement (OFD+PRF) or OFD alone. Growth factor levels in GCF at baseline and 2, 4, and 6 weeks after surgery were analyzed, and clinical parameters such as probing depth (PD), relative clinical attachment level (rCAL), and gingival margin level (GML) at baseline and 9 months after surgery were measured.

RESULTS

Mean PD reduction and rCAL gain were significantly greater in OFD+PRF sites than in OFD sites. Mean GML change was -0.38 + 0.10 mm in OFD sites and 0.11 + 0.08 mm in the test group; difference between the two groups was statistically significant (P <0.05). Both groups demonstrated increased expression levels of fibroblast growth factor-2, transforming growth factor-β1, and platelet-derived growth factor-BB at 2 weeks compared with baseline, followed by reductions at 4 and 6 weeks. The OFD+PRF group showed significantly higher growth factor levels compared with the OFD group at 2 and 4 weeks.

CONCLUSION

PRF membrane combined with OFD provides significantly higher GCF concentrations of angiogenic biomarkers for ≈2 to 4 weeks and better periodontal healing in terms of conventional flap sites.

Leveraging Stem Cell Homing for Therapeutic Regeneration

Resident stem cell pools in many tissues/organs are responsible not only for tissue maintenance during physiologic turnover but also for the process of wound repair following injury. With inspiration from stem cell trafficking within the body under physiologic and pathologic conditions, recent advances have been made toward inducing stem cell mobilization and directing patients' own cells to sites of interest for treating a broad spectrum of diseases. An evolving body of work corroborates that delivering guidance cues can mobilize stem cells from the bone marrow and drive these cells toward a specific region. In addition, the transplantation of cell-friendly biomaterials incorporating certain biomolecules has led to the regeneration of lost/damaged tissue without the need for delivering cellular materials manipulated ex vivo. Recently, cell homing has resulted in remarkable biological discoveries in the laboratory as well as great curative successes in preclinical scenarios. Here, we review the biological evidence underlying in vivo cell mobilization and homing with the aim of leveraging endogenous reparative cells for therapeutic applications. Considering both the promise and the obstacles of this approach, we discuss how matrix components of the in vivo milieu can be modified to promote the native regenerative process and inspire future tissue-engineering design.

Engineering a Cell Home for Stem Cell Homing and Accommodation

Distilling complexity to advance regenerative medicine from laboratory animals to humans, in situ regeneration will continue to evolve using biomaterial strategies to drive endogenous cells within the human body for therapeutic purposes; this approach avoids the need for delivering ex vivo-expanded cellular materials. Ensuring the recruitment of a significant number of reparative cells from an endogenous source to the site of interest is the first step toward achieving success. Subsequently, making the "cell home" cell-friendly by recapitulating the natural extracellular matrix (ECM) in terms of its chemistry, structure, dynamics, and function, and targeting specific aspects of the native stem cell niche (e.g., cell-ECM and cell-cell interactions) to program and steer the fates of those recruited stem cells play equally crucial roles in yielding a therapeutically regenerative solution. This review addresses the key aspects of material-guided cell homing and the engineering of novel biomaterials with desirable ECM composition, surface topography, biochemistry, and mechanical properties that can present both biochemical and physical cues required for in situ tissue regeneration. This growing body of knowledge will likely become a design basis for the development of regenerative biomaterials for, but not limited to, future in situ tissue engineering and regeneration.

Periodontal tissue engineering: current strategies and the role of platelet rich hemoderivatives

Periodontal tissue engineering procures to regenerate the periodontal tissue assuring the right combination of scaffolds, biochemical cues and cells. The platelet rich hemoderivatives might provide the adequate growth factors and structural proteins for the predictable regeneration of periodontium.

Production and characterization of hyaluronic acid microparticles for the controlled delivery of growth factors using a spray/dehydration method

Hyaluronic acid is the main polysaccharide present in the connective tissue. Besides its structural function as backbone of the extracellular matrix, hyaluronic acid plays staple roles in several biological processes including the modulation of inflammation and wound healing processes. The application of hyaluronic acid in regenerative medicine, either as cells and/or drug/growth factors delivery vehicles, relies on its ability to be cross-linked using a plethora of reactions, producing stable hydrogels. In this work, we propose a novel method for the production of hyaluronic acid microparticles that presents several advantages over others that have been used. Basically, droplets of hyaluronic acid solution produced with a nozzle are collected in an isopropanol dehydration bath, and stabilized after crosslinking with adipic acid dihydrazide, using a cabodiimide-based chemistry. The size and morphology of the hyaluronic acid microparticles produced by this method varied with the molecular weight and concentration of the hyaluronic acid solution, the nozzle chamber pressure, the distance between the nozzle and the crosslinking solution, and the number of crosslinking steps. The degree of crosslinking of the hyaluronic acid microparticles produced was tunable and allowed to control the rate of the degradation promoted by hyaluronidase. Moreover, the particles were loaded with platelet lysate, a hemoderivative rich in cytokines with interest for regenerative medicine applications. The hyaluronic acid microparticles showed potential to bind selectively to positively charged molecules, as the factors present in the platelet lysate. It is envisioned that these can be further released in a sustained manner by ion exchange or by the degradation of the hyaluronic acid microparticles matrix promoted by extracellular matrix remodeling.

Investigation of angiogenesis in bioactive 3-dimensional poly(d,l-lactide-co-glycolide)/nano-hydroxyapatite scaffolds by in vivo multiphoton microscopy in murine calvarial critical bone defect

Reconstruction of critical size bone defects remains a major clinical challenge because of poor bone regeneration, which is usually due to poor angiogenesis during repair. Satisfactory vascularization is a prerequisite for the survival of grafts and the integration of new tissue with existing tissue. In this work, we investigated angiogenesis in 3D scaffolds by in vivo multiphoton microscopy during bone formation in a murine calvarial critical bone defect model and evaluated bone regeneration 8weeks post-implantation. The continuous release of bioactive lentiviral vectors (LV-pdgfb) from the scaffolds could be detected for 5days in vitro. In vivo, the released LV-pdgfb transfected adjacent cells and expressed PDGF-BB, facilitating angiogenesis and enhancing bone regeneration. The expression of both pdgfb and the angiogenesis-related genes vWF and VEGFR2 was significantly increased in the pdgfb gene-carrying scaffold (PHp) group. In addition, microCT scanning and histomorphology results proved that there was more new bone ingrowth in the PHp group than in the PLGA/nHA (PH) and control groups. MicroCT parameters, including BMD, BV/TV, Tb.Sp, and Tb.N indicated that there was significantly more new bone formation in the PHp group than in the other groups. With regard to neovascularization, 8weeks post-implantation, blood vessel areas (BVAs) were 9428±944μm(2), 4090±680.3μm(2), and none in the PHp, PH, and control groups, respectively. At each time point, BVAs in the PHp scaffolds were significantly higher than in the PH scaffolds. To our knowledge, this is the first use of multiphoton microscopy in bone tissue-engineering to investigate angiogenesis in scaffolds in vivo. This method represents a valuable tool for investigating neovascularization in bone scaffolds to determine if a certain scaffold is beneficial to neovascularization. We also proved that delivery of the pdgfb gene alone can improve both angiogenesis and bone regeneration Acronyms.

STATEMENT OF SIGNIFICANCE

Reconstruction of critical size bone defects remains a major clinical challenge because of poor bone regeneration, which is usually due to poor angiogenesis during repair. Satisfactory vascularization is a prerequisite for the survival of grafts and the integration of new tissue with existing tissue. In this work, we investigated angiogenesis in 3D scaffolds by in vivo multiphoton microscopy during bone formation in a murine calvarial critical bone defect model and evaluated bone regeneration 8weeks post-implantation. To verify that pdgfb-expressing vectors carried by the scaffolds can promote angiogenesis in 3D-printed scaffolds in vivo, we monitored angiogenesis within the implants by multiphoton microscopy. To our knowledge, this is the first study to dynamically investigate angiogenesis in bone tissue engineering scaffolds in vivo.

Fabrication of gelatin methacrylate/nanohydroxyapatite microgel arrays for periodontal tissue regeneration

INTRODUCTION

Periodontitis is a chronic infectious disease and is the major cause of tooth loss and other oral health issues around the world. Periodontal tissue regeneration has therefore always been the ultimate goal of dentists and researchers. Existing fabrication methods mainly focused on a top-down tissue engineering strategy in which several drawbacks remain, including low throughput and limited diffusion properties resulting from a large sample size. Gelatin methacrylate (GelMA) is a kind of photocrosslinkable and biocompatible hydrogel, with the capacities of enabling cell encapsulation and regeneration of functional tissues. Here, we developed a novel method to fabricate GelMA/nanohydroxylapatite (nHA) microgel arrays using a photocrosslinkable strategy. The viability, proliferation, and osteogenic differentiation and in vivo osteogenesis of human periodontal ligament stem cells (hPDLSCs) encapsulated in microgels were evaluated. The results suggested that such microgels provide great potential for periodontal tissue repair and regeneration.

METHODS

Microgel arrays were fabricated by blending different weight ratios of GelMA and nHA. hPDLSCs were encapsulated in GelMA/nHA microgels of various ratios for a systematic evaluation of cell viability, proliferation, and osteogenic differentiation. In vivo osteogenesis in nude mice was also studied.

RESULTS

The GelMA/nHA microgels exhibited appropriate microarchitecture, mechanical strength, and surface roughness, thus enabling cell adhesion and proliferation. Additionally, the GelMA/nHA microgels (10%/2% w/v) enhanced the osteogenic differentiation of hPDLSCs by elevating the expression levels of osteogenic biomarker genes, such as ALP, BSP, OCN, and RUNX2. In vivo ectopic transplantation results showed that GelMA/nHA microgels (10%/2% w/v) increased mineralized tissue formation with abundant vascularization, compared with the 1%, 3%, and the pure GelMA group.

CONCLUSION

The GelMA/nHA microgels (10%/2% w/v) facilitated hPDLSCs viability, proliferation, and osteogenic differentiation in vitro and further promoted new bone formation in vivo, suggesting that the GelMA/nHA microgels (10%/2% w/v) provide great potential for periodontal tissue regeneration.

Synergistic Approach Using Platelet-Rich Fibrin and 1% Alendronate for Intrabony Defect Treatment in Chronic Periodontitis: A Randomized Clinical Trial

BACKGROUND

Platelet-rich fibrin (PRF) is a reservoir of concentrated platelets that provides a pool of biologic growth-promoting factors and cytokines, which help in mediating regeneration of lost bone and soft tissue maturation. Alendronate (ALN), a member of the amino-bisphosphonate group, is known to enhance periodontal tissue regeneration by inhibiting osteoclast-mediated bone resorption and promoting osteoblast-mediated osteogenesis. The current intervention aims to assess combined effectiveness of PRF and 1% ALN with access therapy in intrabony defect (IBD) treatment in patients with chronic periodontitis (CP).

METHODS

Single IBDs in 90 patients were categorized into three groups: 1) group 1 had access therapy alone; 2) group 2 had access therapy with PRF; and 3) group 3 had access therapy with PRF + 1% ALN. Site-specific plaque index, modified sulcus bleeding index, probing depth (PD), clinical attachment level (CAL), and gingival marginal level, included as parameters for clinical assessment, were evaluated before surgery at baseline and 9 months postoperatively. Percentage IBD depth reduction, assessed using radiographs, was evaluated at baseline and postoperatively.

RESULTS

Compared with groups 1 and 2, group 3 exhibited significantly greater reduction in PD and gain in CAL postoperatively. Significantly greater IBD depth reduction was shown in group 3 (54.05% ± 2.88%) compared with group 2 (46% ± 1.89%) and group 1 (7.33% ± 4.86%) postoperatively.

CONCLUSION

Combined approach therapy of PRF + 1% ALN for IBD treatment in patients with CP showed better clinical parameter outcomes with greater IBD depth reduction compared with PRF and access therapy alone.

Recent advancements in regenerative dentistry: A review

Although human mouth benefits from remarkable mechanical properties, it is very susceptible to traumatic damages, exposure to microbial attacks, and congenital maladies. Since the human dentition plays a crucial role in mastication, phonation and esthetics, finding promising and more efficient strategies to reestablish its functionality in the event of disruption has been important. Dating back to antiquity, conventional dentistry has been offering evacuation, restoration, and replacement of the diseased dental tissue. However, due to the limited ability and short lifespan of traditional restorative solutions, scientists have taken advantage of current advancements in medicine to create better solutions for the oral health field and have coined it "regenerative dentistry." This new field takes advantage of the recent innovations in stem cell research, cellular and molecular biology, tissue engineering, and materials science etc. In this review, the recently known resources and approaches used for regeneration of dental and oral tissues were evaluated using the databases of Scopus and Web of Science. Scientists have used a wide range of biomaterials and scaffolds (artificial and natural), genes (with viral and non-viral vectors), stem cells (isolated from deciduous teeth, dental pulp, periodontal ligament, adipose tissue, salivary glands, and dental follicle) and growth factors (used for stimulating cell differentiation) in order to apply tissue engineering approaches to dentistry. Although they have been successful in preclinical and clinical partial regeneration of dental tissues, whole-tooth engineering still seems to be far-fetched, unless certain shortcomings are addressed.

Emerging regenerative approaches for periodontal reconstruction: a systematic review from the AAP Regeneration Workshop

More than 30 years have passed since the first successful application of regenerative therapy for treatment of periodontal diseases. Despite being feasible, periodontal regeneration still faces numerous challenges, and complete restoration of structure and function of the diseased periodontium is often considered an unpredictable task. This review highlights developing basic science and technologies for potential application to achieve reconstruction of the periodontium. A comprehensive search of the electronic bibliographic database PubMed was conducted to identify different emerging therapeutic approaches reported to influence either biologic pathways and/or tissues involved in periodontal regeneration. Each citation was assessed based on its abstract, and the full text of potentially eligible reports was retrieved. Based on the review of the full papers, their suitability for inclusion in this report was determined. In principle, only reports from scientifically well-designed studies that presented preclinical in vivo (animal studies) or clinical (human studies) evidence for successful periodontal regeneration were included. Hence, in vitro studies, namely those conducted in laboratories without any live animals, were excluded. In case of especially recent and relevant reviews with a narrow focus on specific regenerative approaches, they were identified as such, and thereby the option of referring to them to summarize the status of a specific approach, in addition to or instead of listing each separately, was preserved. Admittedly, the presence of subjectivity in the selection of studies to include in this overview cannot be excluded. However, it is believed that the contemporary approaches described in this review collectively represent the current efforts that have reported preclinical or clinical methods to successfully enhance regeneration of the periodontium. Today's challenges facing periodontal regenerative therapy continue to stimulate important research and clinical development, which, in turn, shapes the current concept of periodontal tissue engineering. Emerging technologies--such as stem cell therapy, bone anabolic agents, genetic approaches, and nanomaterials--also offer unique opportunities to enhance the predictability of current regenerative surgical approaches and inspire development of novel treatment strategies.

Advancing biomaterials of human origin for tissue engineering

Biomaterials have played an increasingly prominent role in the success of biomedical devices and in the development of tissue engineering, which seeks to unlock the regenerative potential innate to human tissues/organs in a state of deterioration and to restore or reestablish normal bodily function. Advances in our understanding of regenerative biomaterials and their roles in new tissue formation can potentially open a new frontier in the fast-growing field of regenerative medicine. Taking inspiration from the role and multi-component construction of native extracellular matrices (ECMs) for cell accommodation, the synthetic biomaterials produced today routinely incorporate biologically active components to define an artificial in vivo milieu with complex and dynamic interactions that foster and regulate stem cells, similar to the events occurring in a natural cellular microenvironment. The range and degree of biomaterial sophistication have also dramatically increased as more knowledge has accumulated through materials science, matrix biology and tissue engineering. However, achieving clinical translation and commercial success requires regenerative biomaterials to be not only efficacious and safe but also cost-effective and convenient for use and production. Utilizing biomaterials of human origin as building blocks for therapeutic purposes has provided a facilitated approach that closely mimics the critical aspects of natural tissue with regard to its physical and chemical properties for the orchestration of wound healing and tissue regeneration. In addition to directly using tissue transfers and transplants for repair, new applications of human-derived biomaterials are now focusing on the use of naturally occurring biomacromolecules, decellularized ECM scaffolds and autologous preparations rich in growth factors/non-expanded stem cells to either target acceleration/magnification of the body's own repair capacity or use nature's paradigms to create new tissues for restoration. In particular, there is increasing interest in separating ECMs into simplified functional domains and/or biopolymeric assemblies so that these components/constituents can be discretely exploited and manipulated for the production of bioscaffolds and new biomimetic biomaterials. Here, following an overview of tissue auto-/allo-transplantation, we discuss the recent trends and advances as well as the challenges and future directions in the evolution and application of human-derived biomaterials for reconstructive surgery and tissue engineering. In particular, we focus on an exploration of the structural, mechanical, biochemical and biological information present in native human tissue for bioengineering applications and to provide inspiration for the design of future biomaterials.

Importance of dual delivery systems for bone tissue engineering

Bone formation is a complex process that requires concerted function of multiple growth factors. For this, it is essential to design a delivery system with the ability to load multiple growth factors in order to mimic the natural microenvironment for bone tissue formation. However, the short half-lives of growth factors, their relatively large size, slow tissue penetration, and high toxicity suggest that conventional routes of administration are unlikely to be effective. Therefore, it seems that using multiple bioactive factors in different delivery systems can develop new strategies for improving bone tissue regeneration. Combination of these factors along with biomaterials that permit tunable release profiles would help to achieve truly spatiotemporal regulation during delivery. This review summarizes the various dual-control release systems that are used for bone tissue engineering.

Directing immunomodulation using biomaterials for endogenous regeneration

Stem cell therapy and tissue engineering hold considerable potential for innovative and transformative strategies to repair damaged tissue form and function. Although many approaches are adopting ex vivo expanded cells for transplantation, an alternative is to manipulate the biomaterial-host interactions that recruit the patients' own stem cells endogenously for regeneration. There are several considerations in targeting the biomaterial-host interactions therapeutically, not the least of which is the biomimetic design of extracellular matrix (ECM)-mimicking materials and the administration of navigation cues and small molecules that target specific aspects of the native healing cascades to stimulate homing of endogenous stem cells and, thereafter, their expansion and differentiation. A sequence of coordinated interactions between the local niche cells and implanted biomaterials offers signals and sign posts that may instruct the cells traveling toward the injured tissues. Furthermore, stem cell function is critically influenced by extrinsic signals provided by the niche as well as by the implanted biomaterials. Novel strategies harnessing growth factors and immunological cues to design materials not only can modulate the behavior of stem cells but also can alter innate and adaptive immunity in a controlled manner. We envisage that successful and safe endogenous regeneration will involve at least three aspects, i.e., homing of sufficient stem cells, controlling cell fate determination, and blunting host immune responses to outside biomaterial devices. Improving our understanding of the biological and physicochemical signals of biomimetic biomaterials that govern immunomodulation for in situ tissue regeneration, particularly context-dependent macrophage (Mφ) polarization, will lead to a concurrent improvement in clinical outcomes.