Extracellular Vesicles Suppress Basal and Lipopolysaccharide-Induced NFκB Activity in Human Periodontal Ligament Stem Cells

A nucleoside-based supramolecular hydrogel integrating localized self-delivery and immunomodulation for periodontitis treatment

Periodontitis is a highly prevalent oral disease characterized by bacterial-induced hyperactivation of the host immune system, leading to a sustained inflammatory response and osteoclastic activity, which ultimately results in periodontal destruction. In this work, an immunomodulatory supramolecular hydrogel for the topical treatment of periodontitis was synthesized using a simple one-pot method. This phenylboronate ester-based 8AGPB hydrogel exhibited excellent stability, self-healing properties, injectability, and biocompatibility. During degradation, the 8AGPB hydrogel releases immunomodulatory agent 8-aminoguanosine (8AG), which regulates MAPK and NF-κB signaling pathways by modulation of second messengers in macrophages. In combination with 1,4-phenylenediboronic acid (PBA), which possesses antioxidant properties, 8AG effectively inhibits ROS production and oxidative damage in LPS-stimulated macrophages, lowering the M1/M2 macrophage polarization ratio and reducing the secretion of pro-inflammatory factors. In an experimental periodontitis model using C57BL/6 mice, periodontal injection of the 8AGPB hydrogel reduced inflammatory infiltration and osteoclastic activity through immunomodulation and inhibition of osteoclast differentiation, thereby ameliorating periodontal destruction during periodontitis progression. Overall, the 8AGPB supramolecular hydrogel, serving as an injectable self-delivery platform for 8AG, may represent a promising novel strategy for periodontitis treatment and offer insights for the development of future topical anti-inflammatory systems.

Extracellular vesicles as therapeutic tools in regenerative dentistry

Dental and maxillofacial diseases are always accompanied by complicated hard and soft tissue defects, involving bone, teeth, blood vessels and nerves, which are difficult to repair and severely affect the life quality of patients. Recently, extracellular vesicles (EVs) secreted by all types of cells and extracted from body fluids have gained more attention as potential solutions for tissue regeneration due to their special physiological characteristics and intrinsic signaling molecules. Compared to stem cells, EVs present lower immunogenicity and tumorigenicity, cause fewer ethical problems, and have higher stability. Thus, EV therapy may have a broad clinical application in regenerative dentistry. Herein, we reviewed the currently available literature regarding the functional roles of EVs in oral and maxillofacial tissue regeneration, including in maxilla and mandible bone, periodontal tissues, temporomandibular joint cartilage, dental hard tissues, peripheral nerves and soft tissues. We also summarized the underlying mechanisms of actions of EVs and their delivery strategies for dental tissue regeneration. This review would provide helpful guidelines and valuable insights into the emerging potential of EVs in future research and clinical applications in regenerative dentistry.

Metformin enhances the therapeutic effects of extracellular vesicles derived from human periodontal ligament stem cells on periodontitis

Metformin has shown outstanding anti-inflammatory and osteogenic abilities. Mesenchymal stem cell-derived extracellular vesicles (EVs) reveal promising therapeutic potency by carrying various biomolecules. This study explored the effects of metformin on the therapeutic potential of EVs derived from human periodontal ligament stem cells (PDLSCs) for periodontitis. PDLSCs were cultured in osteogenic medium with or without metformin, and the supernatant was then collected separately to extract EVs and metformin-treated EVs (M-EVs). After identifying the characteristics, we evaluated the anti-inflammatory and osteogenic effects of EVs and M-EVs in vivo and in vitro. Osteogenic differentiation of PDLSCs was markedly enhanced after metformin treatment, and the effect was dramatically inhibited by GW4896, an inhibitor of EVs' secretion. Metformin significantly increased EVs' yields and improved their effects on cell proliferation, migration, and osteogenic differentiation. Moreover, metformin significantly enhanced the osteogenic ability of EVs on inflammatory PDLSCs. Animal experiments revealed that alveolar bone resorption was dramatically reduced in the EVs and M-EVs groups when compared to the periodontitis group, while the M-EVs group showed the lowest levels of alveolar bone loss. Metformin promoted the osteogenic differentiation of PDLSCs partly through EVs pathway and significantly enhanced the secretion of PDLSCs-EVs with superior pro-osteogenic and anti-inflammatory potential, thus improving EVs' therapeutic potential on periodontitis.

Dental Stem Cell-Derived Exosomes: A Review of Their Isolation, Classification, Functions, and Mechanisms

The scientific field concerned with the study of regeneration has developed rapidly in recent years. Stem cell therapy is a highly promising therapeutic modality for repairing tissue defects; however, several limitations exist, such as cytotoxicity, potential immune rejection, and ethical issues. Exosomes secreted by stem cells are cell-specific secreted vesicles that play a regulatory role in many biological functions in the human body; they not only have a series of functional roles of stem cells and exert the expected therapeutic effects, but they can also overcome the mass limitations of stem cells and are thus considered in the research as an alternative treatment strategy for stem cells. Since dental stem cell-derived exosomes (DSC-Exos) are easy to acquire and present modulating effects in several fields, including neurovascular regeneration and craniofacial soft and hard tissue regeneration processes, they are served as an emerging cell-free therapeutic strategy in various systematic diseases. There is a growing body of research on various types of DSC-Exos; however, they lack systematic elaboration and tabular summarization. Therefore, this review presents the isolation, characterization, and phenotypes of DSC-Exos and focuses on their current status of functions and mechanisms, as well as the multiple challenges prior to clinical applications.

Extracellular vesicles promote autophagy in human microglia through lipid raft-dependent mechanisms

Autophagy dysfunction has been closely related with pathogenesis of many neurodegenerative diseases and therefore represents a potential therapeutic target. Extracellular vesicles (EVs) may act as potent anti-inflammatory agents and also modulators of autophagy in target cells. However, the molecular mechanisms by which EVs modulate autophagy flux in human microglia remain largely unexplored. In the present study, we investigated the effects of EVs derived from human oral mucosa stem cells on the autophagy in human microglia. We demonstrate that EVs promoted autophagy and autophagic flux in human microglia and that this process was dependent on the integrity of lipid rafts. Lipopolysaccharide (LPS) also activated autophagy, but combined treatment with EVs and LPS suppressed autophagy response, indicating interference between these signaling pathways. Blockage of Toll-like receptor 4 (TLR4) with anti-TLR4 antibody suppressed EV-induced autophagy. Furthermore, inhibition of the EV-associated heat shock protein (HSP70) chaperone which is one of the endogenous ligands of the TLR4 also suppressed EV-induced lipid raft formation and autophagy. Pre-treatment of microglia with a selective inhibitor of αvβ3/αvβ5 integrins cilengitide inhibited EV-induced autophagy. Finally, blockage of purinergic P2X4 receptor (P2X4R) with selective inhibitor 5-BDBD also suppressed EV-induced autophagy. In conclusion, we demonstrate that EVs activate autophagy in human microglia through interaction with HSP70/TLR4, αVβ3/αVβ5, and P2X4R signaling pathways and that these effects depend on the integrity of lipid rafts. Our findings could be used to develop new therapeutic strategies targeting disease-associated microglia.

Emerging role of mesenchymal stem cell-derived extracellular vesicles in periodontal regeneration

Periodontitis is a prevalent oral ailment that harms both hard and soft tissues of the periodontium, leading to loosening and eventual removal of the teeth. Current clinical treatments have limitations in achieving complete periodontal tissue regeneration. Mesenchymal stem cells (MSCs) have garnered attention due to their unique characteristics and potential as a promising new therapy for periodontitis. Research suggests that the role of MSCs in regenerative medicine primarily occurs through the paracrine pathway, involving the emission of particles encased by lipids called extracellular vesicles (EVs) abundant in bioactive compounds. These EVs play a vital function in controlling the activities of periodontal tissues and immune system cells, and by influencing the immediate surrounding, thus fostering the healing of periodontal damage and renewal of tissues. EVs obtained from MSCs (MSC-EVs), in the form of a cell-free treatment, offer advantages in terms of stability, reduced immune rejection, and ethical considerations, elevating their potential as a hopeful choice for broad clinical applications. This concise overview highlights the mechanisms of MSC-EVs and the possibilities they hold in clinical application for periodontal regeneration.

Extracellular vesicles from oral mucosa stem cells promote lipid raft formation in human microglia through TLR4, P2X4R, and αVβ3/αVβ5 signaling pathways

Targeting of disease-associated microglia represents a promising therapeutic approach that can be used for the prevention or slowing down neurodegeneration. In this regard, the use of extracellular vesicles (EVs) represents a promising therapeutic approach. However, the molecular mechanisms by which EVs regulate microglial responses remain poorly understood. In the present study, we used EVs derived from human oral mucosa stem cells (OMSCs) to investigate the effects on the lipid raft formation and the phagocytic response of human microglial cells. Lipid raft labeling with fluorescent cholera toxin subunit B conjugates revealed that both EVs and lipopolysaccharide (LPS) by more than two times increased lipid raft formation in human microglia. By contrast, combined treatment with LPS and EVs significantly decreased lipid raft formation indicating possible interference of EVs with the process of LPS-induced lipid raft formation. Specific inhibition of Toll-like receptor 4 (TLR4) with anti-TLR4 antibody as well as inhibition of purinergic P2X4 receptor (P2X4R) with selective antagonist 5-BDBD inhibited EVs- and LPS-induced lipid raft formation. Selective blockage of αvβ3/αvβ5 integrins with cilengitide suppressed EV- and LPS-induced lipid raft formation in microglia. Furthermore, inhibition of TLR4 and P2X4R prevented EV-induced phagocytic activity of human microglial cells. We demonstrate that EVs induce lipid raft formation in human microglia through interaction with TLR4, P2X4R, and αVβ3/αVβ5 signaling pathways. Our results provide new insights about the molecular mechanisms regulating EV/microglia interactions and could be used for the development of new therapeutic strategies against neurological disorders.

Advances in oral mesenchymal stem cell-derived extracellular vesicles in health and disease

Extracellular vesicles (EVs) are nano-size vesicles secreted naturally by all cells into the extracellular space and have been recognized as important cell-cell mediators in multicellular organisms. EVs contain nucleic acids, proteins, lipids, and other cellular components, regulating many basic biological processes and playing an important role in regenerative medicine and diseases. EVs can be traced to their cells of origin and exhibit a similar function. Moreover, EVs demonstrate low immunogenicity, good biocompatibility, and fewer side effects, compared to their parent cells. Mesenchymal stem cells (MSCs) are one of the most important resource cells for EVs, with a great capacity for self-renewal and multipotent differentiation, and play an essential role in stem cell therapy. The mechanism of MSC therapy was thought to be attributed to the differentiation of MSCs after targeted migration, as previously noted. However, emerging evidence shows the previously unknown role of MSC-derived paracrine factors in stem cell therapy. Especially EVs derived from oral tissue MSCs (OMSC-EVs), show more advantages than those of all other MSCs in tissue repair and regeneration, due to their lower invasiveness and easier accessibility for sample collection. Here, we systematically review the biogenesis and biological characteristics of OMSC-EVs, as well as the role of OMSC-EVs in intercellular communication. Furthermore, we discuss the potential therapeutic roles of OMSC-EVs in oral and systemic diseases. We highlight the current challenges and future directions of OMSC-EVs to focus more attention on clinical translation. We aim to provide valuable insights for the explorative clinical application of OMSC-EVs.

Prospective applications of extracellular vesicle-based therapies in regenerative medicine: implications for the use of dental stem cell-derived extracellular vesicles

In the 21st century, research on extracellular vesicles (EVs) has made remarkable advancements. Recently, researchers have uncovered the exceptional biological features of EVs, highlighting their prospective use as therapeutic targets, biomarkers, innovative drug delivery systems, and standalone therapeutic agents. Currently, mesenchymal stem cells stand out as the most potent source of EVs for clinical applications in tissue engineering and regenerative medicine. Owing to their accessibility and capability of undergoing numerous differentiation inductions, dental stem cell-derived EVs (DSC-EVs) offer distinct advantages in the field of tissue regeneration. Nonetheless, it is essential to note that unmodified EVs are currently unsuitable for use in the majority of clinical therapeutic scenarios. Considering the high feasibility of engineering EVs, it is imperative to modify these EVs to facilitate the swift translation of theoretical knowledge into clinical practice. The review succinctly presents the known biotherapeutic effects of odontogenic EVs and the underlying mechanisms. Subsequently, the current state of functional cargo loading for engineered EVs is critically discussed. For enhancing EV targeting and in vivo circulation time, the review highlights cutting-edge engineering solutions that may help overcome key obstacles in the clinical application of EV therapeutics. By presenting innovative concepts and strategies, this review aims to pave the way for the adaptation of DSC-EVs in regenerative medicine within clinical settings.

Production and Utility of Extracellular Vesicles with 3D Culture Methods

In recent years, extracellular vesicles (EVs) have emerged as promising biomarkers, cell-free therapeutic agents, and drug delivery carriers. Despite their great clinical potential, poor yield and unscalable production of EVs remain significant challenges. When using 3D culture methods, such as scaffolds and bioreactors, large numbers of cells can be expanded and the cell environment can be manipulated to control the cell phenotype. This has been employed to successfully increase the production of EVs as well as to enhance their therapeutic effects. The physiological relevance of 3D cultures, such as spheroids, has also provided a strategy for understanding the role of EVs in the pathogenesis of several diseases and to evaluate their role as tools to deliver drugs. Additionally, 3D culture methods can encapsulate EVs to achieve more sustained therapeutic effects as well as prevent premature clearance of EVs to enable more localised delivery and concentrated exosome dosage. This review highlights the opportunities and drawbacks of different 3D culture methods and their use in EV research.

Mechanisms and clinical application potential of mesenchymal stem cells-derived extracellular vesicles in periodontal regeneration

Periodontitis is a high prevalence oral disease which damages both the hard and soft tissue of the periodontium, resulting in tooth mobility and even loss. Existing clinical treatment methods cannot fully achieve periodontal tissue regeneration; thus, due to the unique characteristics of mesenchymal stem cells (MSCs), they have become the focus of attention and may be the most promising new therapy for periodontitis. Accumulating evidence supports the view that the role of MSCs in regenerative medicine is mainly achieved by the paracrine pathway rather than direct proliferation and differentiation at the injured site. Various cells release lipid-enclosed particles known as extracellular vesicles (EVs), which are rich in bioactive substances. In periodontitis, EVs play a pivotal role in regulating the biological functions of both periodontal tissue cells and immune cells, as well as the local microenvironment, thereby promoting periodontal injury repair and tissue regeneration. As a cell-free therapy, MSCs-derived extracellular vesicles (MSC-EVs) have some preponderance on stability, immune rejection, ethical supervision, and other problems; therefore, they may have a broad clinical application prospect. Herein, we gave a brief introduction to MSC-EVs and focused on their mechanisms and clinical application in periodontal regeneration.

Regulation of the Host Immune Microenvironment in Periodontitis and Periodontal Bone Remodeling

The periodontal immune microenvironment is a delicate regulatory system that involves a variety of host immune cells including neutrophils, macrophages, T cells, dendritic cells and mesenchymal stem cells. The dysfunction or overactivation of any kind of local cells, and eventually the imbalance of the entire molecular regulatory network, leads to periodontal inflammation and tissue destruction. In this review, the basic characteristics of various host cells in the periodontal immune microenvironment and the regulatory network mechanism of host cells involved in the pathogenesis of periodontitis and periodontal bone remodeling are summarized, with emphasis on the immune regulatory network that regulates the periodontal microenvironment and maintains a dynamic balance. Future strategies for the clinical treatment of periodontitis and periodontal tissue regeneration need to develop new targeted synergistic drugs and/or novel technologies to clarify the regulatory mechanism of the local microenvironment. This review aims to provide clues and a theoretical basis for future research in this field.

The role of extracellular vesicles in periodontitis: pathogenesis, diagnosis, and therapy

Periodontitis is a prevalent disease and one of the leading causes of tooth loss. Biofilms are initiating factor of periodontitis, which can destroy periodontal tissue by producing virulence factors. The overactivated host immune response is the primary cause of periodontitis. The clinical examination of periodontal tissues and the patient's medical history are the mainstays of periodontitis diagnosis. However, there is a lack of molecular biomarkers that can be used to identify and predict periodontitis activity precisely. Non-surgical and surgical treatments are currently available for periodontitis, although both have drawbacks. In clinical practice, achieving the ideal therapeutic effect remains a challenge. Studies have revealed that bacteria produce extracellular vesicles (EVs) to export virulence proteins to host cells. Meanwhile, periodontal tissue cells and immune cells produce EVs that have pro- or anti-inflammatory effects. Accordingly, EVs play a critical role in the pathogenesis of periodontitis. Recent studies have also presented that the content and composition of EVs in saliva and gingival crevicular fluid (GCF) can serve as possible periodontitis diagnostic indicators. In addition, studies have indicated that stem cell EVs may encourage periodontal regeneration. In this article, we mainly review the role of EVs in the pathogenesis of periodontitis and discuss their diagnostic and therapeutic potential.

Galangin inhibits lipopolysaccharide-induced inflammation and stimulates osteogenic differentiation of bone marrow mesenchymal stem cells via regulation of AKT/mTOR signaling

BACKGROUND

Bone marrow mesenchymal stem cells (BMSCs), with the abilities of multidirectional differentiation and self-renewal, have been widely used in bone repair and regeneration of inflammation-stimulated oral diseases. Galangin is a flavonoid isolated from Alpinia officinarum, exerts anti-obesity, antitumor, and anti-inflammation pharmacological effects. The roles of galangin in lipopolysaccharide-induced inflammation and osteogenic differentiation of BMSCs were investigated.

METHODS

BMSCs were isolated from rat bone marrow and identified by flow cytometry. The isolated BMSCs were treated with 1 μg/mL lipopolysaccharides or cotreated with lipopolysaccharides and different concentrations of galangin. Cell viability and apoptosis were detected by MTT (tetrazolium component) and flow cytometry. ELISA was used to detect inflammation. Alizarin red staining was used to investigate osteogenic differentiation.

RESULTS

The rat BMSCs showed negative rate of CD34, and positive rate of CD29 and CD44. Lipopolysaccharides treatment reduced cell viability of BMSCs, and promoted the cell apoptosis. Incubation with galangin enhanced cell viability of lipopolysaccharide-stimulated BMSCs, and suppressed the cell apoptosis. Galangin decreased levels of TNF-α, IL-1β, and IL-6 in lipopolysaccharide-stimulated BMSCs through down-regulation of NF-κB phosphorylation (p-NF-κB). Galangin up-regulated expression of osteo-specific proteins, collagen type I alpha 1 (COL1A1), osteopontin (OPN), and runt-related transcription factor 2 (RUNX2), to promote the osteogenic differentiation of lipopolysaccharide-stimulated BMSCs. Protein expression of p-AKT and p-mTOR in lipopolysaccharide-stimulated BMSCs were increased by galangin treatment.

CONCLUSION

Galangin exerted an anti-inflammatory effect against lipopolysaccharide- stimulated BMSCs and promoted osteogenic differentiation through the activation of AKT/ mTOR signaling.

New frontiers of oral sciences: Focus on the source and biomedical application of extracellular vesicles

Extracellular vesicles (EVs) are a class of nanoparticles that are derived from almost any type of cell in the organism tested thus far and are present in all body fluids. With the capacity to transfer "functional cargo and biological information" to regulate local and distant intercellular communication, EVs have developed into an attractive focus of research for various physiological and pathological conditions. The oral cavity is a special organ of the human body. It includes multiple types of tissue, and it is also the beginning of the digestive tract. Moreover, the oral cavity harbors thousands of bacteria. The importance and particularity of oral function indicate that EVs derived from oral cavity are quite complex but promising for further research. This review will discuss the extensive source of EVs in the oral cavity, including both cell sources and cell-independent sources. Besides, accumulating evidence supports extensive biomedical applications of extracellular vesicles in oral tissue regeneration and development, diagnosis and treatment of head and neck tumors, diagnosis and therapy of systemic disease, drug delivery, and horizontal gene transfer (HGT). The immune cell source, odontoblasts and ameloblasts sources, diet source and the application of EVs in tooth development and HGT were reviewed for the first time. In conclusion, we concentrate on the extensive source and potential applications offered by these nanovesicles in oral science.

Osteogenic differentiation of periodontal membrane stem cells in inflammatory environments

Periodontitis is a common disease that is difficult to treat, and if not controlled in time, it causes severe conditions, such as alveolar bone resorption and tooth loosening and loss. Periodontal ligament stem cells constitute a promising cell source for regenerative treatment of periodontitis due to their high osteogenic differentiation capacity. PDLSC osteogenesis plays a central role in periodontal regeneration through successive cytokine-mediated signaling pathways and various biochemical and physicochemical factors. However, this process is inhibited in the inflammatory periodontitis environment due to high concentrations of lipopolysaccharide. Here, we review the mechanisms that influence the osteogenic differentiation of periodontal stem cells in this inflammatory microenvironment.

Exosomes as Neurological Nanosized Machines

In the past few decades, nanomedicine research has advanced dramatically. In spite of this, traditional nanomedicine faces major obstacles, such as blood-brain barriers, low concentrations at target sites, and rapid removal from the body. Exosomes as natural extracellular vesicles contain special bioactive molecules for cell-to-cell communications and nervous tissue function, which could overcome the challenges of nanoparticles. Most recently, microRNAs, long noncoding RNA, and circulating RNA of exosomes have been appealing because of their critical effect on the molecular pathway of target cells. In this review, we have summarized the important role of exosomes of noncoding RNAs in the occurrence of brain diseases.

Exosomes Derived From Human Gingival Mesenchymal Stem Cells Attenuate the Inflammatory Response in Periodontal Ligament Stem Cells

This study aimed to explore the effects of exosomes derived from human gingival mesenchymal stem cells (GMSC-Exo) on the inflammatory response of periodontal ligament stem cells (PDLSCs) in an inflammatory microenvironment in order to restore the regenerative potential of PDLSCs, which promotes periodontal tissue regeneration in patients with periodontitis. Periodontitis is a chronic infectious disease characterized by periodontal tissue inflammation and alveolar bone destruction. PDLSCs are regarded as promising seed cells for restoring periodontal tissue defects because of their ability to regenerate cementum/PDL-like tissue and alveolar bone. However, PDLSCs in the inflammatory environment show significantly attenuated regenerative potential. GMSC-Exo have been reported to have anti-inflammatory and immunosuppressive properties. In this study, we investigated the effects of GMSC-Exo on the inflammatory response of PDLSCs induced by lipopolysaccharides (LPS). LPS was used to simulate the inflammatory microenvironment of periodontitis in vitro. GMSC-Exo were extracted from the culture supernatant of GMSCs by ultracentrifugation. We found that GMSC-Exo attenuated the inflammatory response of PDLSCs induced by LPS. Furthermore, compared to treatment with LPS, treatment with GMSC-Exo attenuated the expression of NF-κB signaling and Wnt5a in LPS-induced PDLSCs. In conclusion, we confirmed that GMSC-Exo could suppress the inflammatory response of PDLSCs by regulating the expression of NF-κB signaling and Wnt5a, which paves the way for the establishment of a therapeutic approach for periodontitis.

Effects of nuclear factor-κB signaling pathway on periodontal ligament stem cells under lipopolysaccharide-induced inflammation

Lipopolysaccharide (LPS) induces inflammatory stress and apoptosis. This study focused on the effect of nuclear factor kappa B (NF-κB) signaling pathway on proliferation and osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) after LPS induction and its mechanism. We first isolated hPDLSCs from human tooth root samples in vitro. Then, flow cytometry detected positive expression of cell surface antigens CD146 and STRO-1 and negative expression of CD45, suggesting the hPDLSCs were successfully isolated. LPS significantly induced increased apoptosis and diminished proliferation of hPDLSCs. The NF-κB pathway agonist phorbol 12-myristate 13-acetate (PMA) or p65 overexpression inhibited the proliferation of LPS-treated hPDLSCs and promoted apoptosis. PMA also promoted LPS-induced up-regulation of the expression of inflammatory factors TNF-α and IL-6 and down-regulation of the expression of anti-inflammatory factor IL-10. Additionally, LPS was confirmed to lead to a reduction of alkaline phosphatase (ALP) activity, calcium nodules, and expression of osteogenic markers Runt-related transcription factor 2 (Runx2) and osteopontin. This reduction could be promoted by PMA. Western blotting further indicated that PMA could promote LPS-induced decrease of expression of p65 (cytoplasm), and total cellular proteins IKKα and IKKβ in hPDLSCs, while protein expression of p-IκBα (cytoplasm) and p65 (nucleus), and p-IκBα/IκBα ratio was elevated. By contrast, inhibition of the NF-κB pathway (PDTC) or small-interfering RNA targeting NF-κB/p65 (p65 siRNA) showed the opposite results. In conclusion, activation of NF-κB signaling in LPS-induced inflammatory environment can inhibit the proliferation and osteogenic differentiation of hPDLSCs. This study provides a theory foundation for the clinical treatment of periodontitis.

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.

Periodontal and Dental Pulp Cell-Derived Small Extracellular Vesicles: A Review of the Current Status

Extracellular vesicles (EVs) are membrane-bound lipid particles that are secreted by all cell types and function as cell-to-cell communicators through their cargos of protein, nucleic acid, lipids, and metabolites, which are derived from their parent cells. There is limited information on the isolation and the emerging therapeutic role of periodontal and dental pulp cell-derived small EVs (sEVs, <200 nm, or exosome). In this review, we discuss the biogenesis of three EV subtypes (sEVs, microvesicles and apoptotic bodies) and the emerging role of sEVs from periodontal ligament (stem) cells, gingival fibroblasts (or gingival mesenchymal stem cells) and dental pulp cells, and their therapeutic potential in vitro and in vivo. A review of the relevant methodology found that precipitation-based kits and ultracentrifugation are the two most common methods to isolate periodontal (dental pulp) cell sEVs. Periodontal (and pulp) cell sEVs range in size, from 40 nm to 2 μm, due to a lack of standardized isolation protocols. Nevertheless, our review found that these EVs possess anti-inflammatory, osteo/odontogenic, angiogenic and immunomodulatory functions in vitro and in vivo, via reported EV cargos of EV–miRNAs, EV–circRNAs, EV–mRNAs and EV–lncRNAs. This review highlights the considerable therapeutic potential of periodontal and dental pulp cell-derived sEVs in various regenerative applications.

MicroRNA miR-126 attenuates brain injury in septic rats via NF-κB signaling pathway

The purpose of this study was to investigate the impact and mechanism of microRNA miR-126 on brain injury induced by blood-brain barrier (BBB) damage in septic rats. We used cecal ligation and perforation (CLP) to create a rat model of sepsis. The experimental rats were randomly divided into Control group, CLP group, CLP + miR-NC group, CLP + miR-126 group and CLP + miR-126 + NF-κB pathway agonist (PMA) group. MiR-126 expressed in the brain tissue of CLP rats was down-regulated by qRT-PCR. Upregulation of miR-126 in CLP rats could improve brain injury and BBB marker protein level, reduce brain water content, Evans blue extravasation, inflammation, and excessive oxidative stress. This could also result in an inhibition of NF-κB signaling pathway activity. In conclusion, miR-126 overexpression can prevent brain injury caused by BBB damage via the inhibition of NF-κB signaling pathway activity.

Multidifferentiation potential of dental-derived stem cells

Tooth-related diseases and tooth loss are widespread and are a major public health issue. The loss of teeth can affect chewing, speech, appearance and even psychology. Therefore, the science of tooth regeneration has emerged, and attention has focused on tooth regeneration based on the principles of tooth development and stem cells combined with tissue engineering technology. As undifferentiated stem cells in normal tooth tissues, dental mesenchymal stem cells (DMSCs), which are a desirable source of autologous stem cells, play a significant role in tooth regeneration. Researchers hope to reconstruct the complete tooth tissues with normal functions and vascularization by utilizing the odontogenic differentiation potential of DMSCs. Moreover, DMSCs also have the ability to differentiate towards cells of other tissue types due to their multipotency. This review focuses on the multipotential capacity of DMSCs to differentiate into various tissues, such as bone, cartilage, tendon, vessels, neural tissues, muscle-like tissues, hepatic-like tissues, eye tissues and glands and the influence of various regulatory factors, such as non-coding RNAs, signaling pathways, inflammation, aging and exosomes, on the odontogenic/osteogenic differentiation of DMSCs in tooth regeneration. The application of DMSCs in regenerative medicine and tissue engineering will be improved if the differentiation characteristics of DMSCs can be fully utilized, and the factors that regulate their differentiation can be well controlled.

Potential Therapeutic Effects of Exosomes in Regenerative Endodontics

OBJECTIVE

This review aims to describe the basic characteristics of exosomes, and summarize their possible source and potential biological effects in pulp regeneration, providing new insights into the therapeutic role of exosomes for regenerative endodontics in the future.

DESIGN

A comprehensive review of scientific literature related to exosomes potentially used for pulp regeneration was conducted.

RESULTS

Dental mesenchymal stem cells (MSCs) play an important role in dental pulp regeneration. MSC-derived exosomes, as important biotransmitters in intercellular communication, have been shown to replicate the therapeutic effects of their parental cells. These exosomes have better stability, lower immunogenicity, higher safety and clinical efficiency, making it possible to apply them in pulp regeneration. Existing research suggests that exosomes could trigger the regeneration of dentin/pulp-like tissue in vivo, which may attribute to their role in promoting pulp angiogenesis, regulating dental cell proliferation, migration and differentiation, and providing neuroprotection.

CONCLUSIONS

The applications of exosomes in the treatment of pulp regeneration have great potential, and exosomes may become ideal therapeutic biomaterial in regenerative endodontics.

N‑acetyl cysteine inhibits the lipopolysaccharide‑induced inflammatory response in bone marrow mesenchymal stem cells by suppressing the TXNIP/NLRP3/IL‑1β signaling pathway

N-acetyl cysteine (NAC) has been used to inhibit lipopolysaccharide (LPS)-induced inflammation. However, the molecular mechanism underlying its anti-inflammatory effects remains to be elucidated. The present study aimed to determine the effect of NAC on the LPS-induced inflammatory response in bone marrow mesenchymal stem cells (BMSCs) and elucidate the underlying molecular mechanism. First, BMSCs were stimulated by LPS following pretreatment with NAC (0, 0.1, 0.5, 1 or 2 mM). A Cell Counting Kit 8 assay was used to determine the number of viable cells and 1 mM NAC was selected as the experimental concentration. Then, the secretion of inflammatory factors, including interleukin (IL)-1β, IL-6 and tumor necrosis factor-α was evaluated by enzyme-linked immunosorbent assay. Finally, the expression levels of mRNA and proteins, including apoptosis-associated speck-like protein containing a CARD (ASC), nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), caspase-1, thioredoxin-interacting protein (TXNIP), and thioredoxin (TRX), were evaluated by reverse transcription-quantitative PCR and western blot analysis, respectively. The results demonstrated that the secretion of inflammatory factors, which was increased by the administration of LPS, was reduced by pretreatment with NAC. Furthermore, NAC reduced the expression of ASC, NLRP3, caspase-1 and TXNIP, but enhanced that of TRX. To conclude, NAC had anti-inflammatory effects on LPS-stimulated BMSCs, which was closely associated with the TXNIP/NLRP3/IL-1β signaling pathway. Thus, NAC may be a promising treatment to attenuate the inflammatory response in LPS-induced BMSCs.

Mesenchymal Stem Cell-Derived Extracellular Vesicles for the Promotion of Tendon Repair - an Update of Literature

Tendon injuries are prevalent in physical activities and sports. Tendon heals slowly after injuries. The results of conservative treatments and surgery are not satisfactory with high re-injury rate and scar tissue formation. The application of mesenchymal stem cells (MSCs) to the injured tendons was reported to promote tendon repair. Recent studies have suggested that MSCs supported tendon repair via the secretion of paracrine factors. Extracellular vesicles (EVs) are a heterogeneous group of cell-derived membranous structures that are produced and secreted by most eukaryotic cells. They carry a plethora of proteins, lipids, microRNA and mRNA which reprogram the recipient cells and are involved in multiple physiological and pathological processes. EVs were shown to promote tissue repair and mediate the healing effects of MSCs. In this review, I aim to review the recent literature on the promotion of tendon repair using EVs-derived from MSCs (MSC-EVs). The mechanisms underlying these actions are also reviewed and future research directions are discussed. Better understanding of the roles of MSC-EVs in tendon repair would offer a new treatment strategy to circumvent this devastating soft tissue disorder. Graphical Abstract.

Maternally-Expressed Gene 3 (MEG3)/miR-143-3p Regulates Injury to Periodontal Ligament Cells by Mediating the AKT/Inhibitory κB Kinase (IKK) Pathway

Background

Dysregulated long noncoding RNAs (lncRNAs) are implicated in periodontitis development. Nevertheless, the role and mechanism of lncRNA maternally-expressed gene 3 (MEG3) in periodontitis progression remain unclear. This study aimed to explore how and whether MEG3 affect viability, apoptosis, and inflammatory response in lipopolysaccharide (LPS)-treated periodontal ligament cells (PDLCs).

Material/Methods

Periodontal ligament tissues were collected from periodontitis patients or normal individuals. PDLCs were obtained from normal periodontal ligament and treated with lipopolysaccharide (LPS). LPS-induced PDLCs injury was assessed via viability, apoptosis and inflammatory response using Cell Counting Kit-8, flow cytometry, quantitative reverse transcription polymerase chain reaction, enzyme-linked immunosorbent assay, and Western blot. The levels of MEG3 and microRNA (miR)-143-3p were examined via quantitative reverse transcription polymerase chain reaction. The protein kinase B(AKT)/inhibitory κB kinase (IKK) pathway was analyzed via Western blot. The target correlation of MEG3 and miR-143-3p was determined through dual-luciferase reporter analysis.

Results

MEG3 level was decreased and miR-143-3p level was upregulated in periodontitis and LPS-treated PDLCs. MEG3 overexpression or miR-143-3p knockdown alleviated LPS-induced viability inhibition, apoptosis promotion, and inflammatory response. MEG3 was a sponge for miR-143-3p. miR-143-3p overexpression weakened the effect of MEG3 on LPS-induced injury. MEG3 overexpression inhibited the activation of AKT/IKK pathway by sponging miR-143-3p in LPS-treated PDLCs.

Conclusions

MEG3 overexpression inhibited LPS-induced injury in PDLCs by inactivating the AKT/IKK pathway via sponging miR-143-3p, providing a potential target for treatment of periodontitis.