Extracellular vesicles delivering nuclear factor I/C for hard tissue engineering: Treatment of apical periodontitis and dentin regeneration

Critical roles of extracellular vesicles in periodontal disease and regeneration

Extracellular vesicles (EVs) are evolutionarily conserved communication mediators that play key roles in the development of periodontal disease as well as in regeneration processes. This concise review first outlines the pathogenic mechanisms through which EVs derived from bacteria lead to the progression of periodontitis, with a focus on the enrichment of virulence factors, the amplification of immune responses, and the induction of bone destruction as key aspects influenced by bacterial EVs. This review aims to elucidate the positive effects of EVs derived from mesenchymal stem cells (MSC-EVs) on periodontal tissue regeneration. In particular, the anti-inflammatory properties of MSC-EVs and their impact on the intricate interplay between MSCs and various immune cells, including macrophages, dendritic cells, and T cells, are described. Moreover, recent advancements regarding the repair-promoting functions of MSC-EVs are detailed, highlighting the mechanisms underlying their ability to promote osteogenesis, cementogenesis, angiogenesis, and the homing of stem cells, thus contributing significantly to periodontal tissue regeneration. Furthermore, this review provides insights into the therapeutic efficacy of MSC-EVs in treating periodontitis within a clinical context. By summarizing the current knowledge, this review aims to provide a comprehensive understanding of how MSC-EVs can be harnessed for the treatment of periodontal diseases. Finally, a discussion is presented on the challenges that lie ahead and the potential practical implications for translating EV-based therapies into clinical practices for the treatment of periodontitis.

Emerging roles of extracellular vesicles in oral and maxillofacial areas

The oral and maxillofacial region is a highly complex area composed of multiple tissue types and bears various critical functions of the human body. Diseases in this region pose significant diagnostic and management challenges; therefore, exploring new strategies for early diagnosis, targeted treatment, and tissue reconstruction is key to improving patient prognosis and quality of life. Extracellular vesicles are a group of heterogeneous lipid-bilayer membrane structures secreted by most cell types, including exosomes, microvesicles, and apoptotic bodies. Present in various body fluids and tissues, they act as messengers via the transfer of nucleic acids, proteins, and metabolites to recipient cells. To date, studies have revealed the different roles of extracellular vesicles in physiological or pathological processes, as well as applications in disease diagnosis, prognosis, and treatment. The importance and tissue specificity of the dental and maxillofacial tissues indicate that extracellular vesicles derived from this region are promising for further research. This paper reviews the published data on extracellular vesicles derived from cells, body fluids, and tissues in oral and maxillofacial regions, summarizes the latest advances in extracellular vesicles from extensive sources, and concludes with a focus on the current research progress and application prospects of engineered exosomes in oral science.

Synthetic Vesicle-Based Drug Delivery Systems for Oral Disease Therapy: Current Applications and Future Directions

Oral diseases such as dental caries, periodontitis, and oral cancer are prevalent and present significant challenges to global public health. Although these diseases are typically treated through procedures like dental preparation and resin filling, scaling and root planning, or surgical excision, these interventions are often not entirely effective, and postoperative drug therapy is usually required. Traditional drug treatments, however, are limited by factors such as poor drug penetration, significant side effects, and the development of drug resistance. As a result, there is a growing need for novel drug delivery systems that can enhance therapeutic efficacy, reduce side effects, and improve treatment outcomes. In recent years, drug-loaded vesicles, such as liposomes, polymersomes, and extracellular vesicles (EVs), have emerged as promising drug delivery platforms due to their high drug encapsulation efficiency, controlled release properties, and excellent biocompatibility. This review provides an in-depth examination of the characteristics, advantages, and limitations of liposomes, polymersomes, and extracellular vesicles in the context of oral disease treatment. It further explores the reasons for their advantages and limitations and discusses the specific applications, development prospects, and strategies for optimizing these vesicle-based systems for improved clinical outcomes.

3D culture inhibits replicative senescence of SCAPs via UQCRC2-mediated mitochondrial oxidative phosphorylation

Stem cells derived from the apical papilla (SCAPs) play a crucial role in tooth root development and dental pulp regeneration. They are important seed cells for bone/tooth tissue engineering. However, replicative senescence remains an unavoidable issue as in vitro amplification increases. This study investigated the effect of a three-dimensional (3D) culture environment constructed with methylcellulose on SCAPs senescence. It was observed that 3D culture conditions can delay cellular senescence, potentially due to changes in mitochondrial function and oxidative phosphorylation. Transcriptome high-throughput sequencing technology revealed that the different mitochondrial states may be related to UQCRC2. Knocking down UQCRC2 expression in the 3D culture group resulted in increased production of mitochondrial reactive oxygen species, decreased mitochondrial membrane potential, and a decline in the oxygen consumption rate for oxidative phosphorylation, accelerating cell senescence. The results of this study indicated that 3D culture can mitigate SCAPs aging by maintaining UQCRC2-mediated mitochondrial homeostasis. These findings provide a new solution for the senescence of SCAPs during in vitro amplification and can promote the applications of SCAPs-based clinical translation.

Histological Evaluation of Sodium Iodide-Based Root Canal Filling Materials in Canine Teeth

A novel water-soluble root canal filling material based on sodium iodide (NaI) has been developed to overcome the limitations of existing iodine-based formulations. However, the biological stability of this approach in animal studies remains unverified. This study evaluated the biocompatibility of NaI compared to commercial root canal filling materials (Calcipex II and Vitapex®) in pulpectomized canine teeth to assess its clinical applicability. Following a four-week observation period, none of the experimental groups exhibited tooth mobility or fistula formation. Radiographic and micro-CT analyses revealed no radiolucency in periapical lesions. Histopathologic evaluation demonstrated the absence of inflammatory responses in periapical regions across all material groups, with histological inflammation scoring 0. High-magnification histological examination of periapical areas showed well-preserved periodontal ligament tissue in all groups. Despite certain limitations of NaI-based fillings in the pulp cavity, including loss of radiopacity and tooth discoloration, NaI demonstrates potential as a safe and effective alternative for pulp filling material, particularly due to its minimal risk of root resorption and inflammatory response.

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.

Tissue engineering approaches for dental pulp regeneration: The development of novel bioactive materials using pharmacological epigenetic inhibitors

The drive for minimally invasive endodontic treatment strategies has shifted focus from technically complex and destructive root canal treatments towards more conservative vital pulp treatment. However, novel approaches to maintaining dental pulp vitality after disease or trauma will require the development of innovative, biologically-driven regenerative medicine strategies. For example, cell-homing and cell-based therapies have recently been developed in vitro and trialled in preclinical models to study dental pulp regeneration. These approaches utilise natural and synthetic scaffolds that can deliver a range of bioactive pharmacological epigenetic modulators (HDACis, DNMTis, and ncRNAs), which are cost-effective and easily applied to stimulate pulp tissue regrowth. Unfortunately, many biological factors hinder the clinical development of regenerative therapies, including a lack of blood supply and poor infection control in the necrotic root canal system. Additional challenges include a need for clinically relevant models and manufacturing challenges such as scalability, cost concerns, and regulatory issues. This review will describe the current state of bioactive-biomaterial/scaffold-based engineering strategies to stimulate dentine-pulp regeneration, explicitly focusing on epigenetic modulators and therapeutic pharmacological inhibition. It will highlight the components of dental pulp regenerative approaches, describe their current limitations, and offer suggestions for the effective translation of novel epigenetic-laden bioactive materials for innovative therapeutics.

Functional extracellular vesicles from SHEDs combined with gelatin methacryloyl promote the odontogenic differentiation of DPSCs for pulp regeneration

BACKGROUND

Pulp regeneration is a novel approach for the treatment of immature permanent teeth with pulp necrosis. This technique includes the combination of stem cells, scaffolds, and growth factors. Recently, stem cell-derived extracellular vesicles (EVs) have emerged as a new methodology for pulp regeneration. Emerging evidence has proven that preconditioning is an effective scheme to modify EVs for better therapeutic potency. Meanwhile, proper scaffolding is of great significance to protect EVs from rapid clearance and destruction. This investigation aims to fabricate an injectable hydrogel loaded with EVs from pre-differentiated stem cells from human exfoliated deciduous teeth (SHEDs) and examine their effects on pulp regeneration.

RESULTS

We successfully employed the odontogenic induction medium (OM) of SHEDs to generate functional EV (OM-EV). The OM-EV at a concentration of 20 µg/mL was demonstrated to promote the proliferation and migration of dental pulp stem cells (DPSCs). The results revealed that OM-EV has a better potential to promote odontogenic differentiation of DPSCs than common EVs (CM-EV) in vitro through Alizarin red phalloidin, alkaline phosphatase staining, and assessment of the expression of odontogenic-related markers. High-throughput sequencing suggests that the superior effects of OM-EV may be attributed to activation of the AMPK/mTOR pathway. Simultaneously, we prepared a photocrosslinkable gelatin methacryloyl (GelMA) to construct an OM-EV-encapsulated hydrogel. The hydrogel exhibited sustained release of OM-EV and good biocompatibility for DPSCs. The released OM-EV from the hydrogel could be internalized by DPSCs, thereby enhancing their survival and migration. In tooth root slices that were subcutaneously transplanted in nude mice, the OM-EV-encapsulated hydrogel was found to facilitate dentinogenesis. After 8 weeks, there was more formation of mineralized tissue, as well as higher levels of dentin sialophosphoprotein (DSPP) and dentin matrix protein-1 (DMP-1).

CONCLUSIONS

The effects of EV can be substantially enhanced by preconditioning of SHEDs. The functional EVs from SHEDs combined with GelMA are capable of effectively promoting dentinogenesis through upregulating the odontogenic differentiation of DPSCs, which provides a promising therapeutic approach for pulp regeneration.

Preparation of genetically or chemically engineered exosomes and their therapeutic effects in bone regeneration and anti-inflammation

The treatment of bone or cartilage damage and inflammation-related diseases has been a long-standing research hotspot. Traditional treatments such as surgery and cell therapy have only displayed limited efficacy because they can't avoid potential deterioration and ensure cell activity. Recently, exosomes have become a favorable tool for various tissue reconstruction due to their abundant content of proteins, lipids, DNA, RNA and other substances, which can promote bone regeneration through osteogenesis, angiogenesis and inflammation modulation. Besides, exosomes are also promising delivery systems because of stability in the bloodstream, immune stealth capacity, intrinsic cell-targeting property and outstanding intracellular communication. Despite having great potential in therapeutic delivery, exosomes still show some limitations in clinical studies, such as inefficient targeting ability, low yield and unsatisfactory therapeutic effects. In order to overcome the shortcomings, increasing studies have prepared genetically or chemically engineered exosomes to improve their properties. This review focuses on different methods of preparing genetically or chemically engineered exosomes and the therapeutic effects of engineering exosomes in bone regeneration and anti-inflammation, thereby providing some references for future applications of engineering exosomes.

Kidney tissue regeneration using bioactive scaffolds incorporated with differentiating extracellular vesicles and intermediate mesoderm cells

BACKGROUND

To overcome the limitations of current alternative therapies for chronic kidney disease (CKD), tissue engineering-mediated regeneration strategies have demonstrated the possibilities for complete kidney tissue regeneration. Given the challenges associated with the reproducibility of renal basal cells, the incorporation of intermediate mesoderm (IM) cells and bioactive materials to control bioactivities of cells with supported scaffolds should be considered as a viable approach to enable the regeneration of the complex kidney structure via renal differentiation.

METHODS

We developed PMEZ scaffolds by combining crucial bioactive components, such as ricinoleic acid-grafted Mg(OH)2 (M), extracellular matrix (E), and alpha lipoic acid-conjugated ZnO (Z) integrated into biodegradable porous PLGA (P) platform. Additionally, we utilized differentiating extracellular vesicles (dEV) isolated during intermediate mesoderm differentiation into kidney progenitor cells, and IM cells were serially incorporated to facilitate kidney tissue regeneration through their differentiation into kidney progenitor cells in the 3/4 nephrectomy mouse model.

RESULTS

The use of differentiating extracellular vesicles facilitated IM differentiation into kidney progenitor cells without additional differentiation factors. This led to improvements in various regeneration-related bioactivities including tubule and podocyte regeneration, anti-fibrosis, angiogenesis, and anti-inflammation. Finally, implanting PMEZ/dEV/IM scaffolds in mouse injury model resulted in the restoration of kidney function.

CONCLUSIONS

Our study has demonstrated that utilizing biodegradable PLGA-based scaffolds, which include multipotent cells capable of differentiating into various kidney progenitor cells along with supporting components, can facilitate kidney tissue regeneration in the mouse model that simulates CKD through 3/4 nephrectomy.

Exosomes derived from odontogenic stem cells: Its role in the dentin-pulp complex

Odontogenic stem cells originate from cranial neural crest cells and offer unique advantages in the regeneration of dentin-pulp complex. There is increasing evidence that stem cells exert their biological functions mainly through exosome-based paracrine effects. Exosomes contain DNA, RNA, proteins, metabolites, etc., which can play a role in intercellular communication and have similar therapeutic potential to stem cells. In addition, compared with stem cells, exosomes also have the advantages of good biocompatibility, high drug carrying capacity, easy to obtain, and few side effects. Odontogenic stem cell-derived exosomes mainly affect the regeneration of the dentin-pulp complex by regulating processes such as dentintogenesis, angiogenesis, neuroprotection and immunomodulation. This review aimed to describe "cell-free therapies" based on odontogenic stem cell-derived exosomes, which aim to regenerate the dentin-pulp complex.

Research progress of odontogenic extracellular vesicles in regeneration of dental pulp

It is well understood that maintaining viable pulp is critical for tooth retention. This review focused on cell-free therapy based on extracellular vesicles (EVs), a novel minimally invasive treatment strategy for endodontic restoration. This study was conducted by searching mainstream electronic databases such as Web of Science and PubMed for relevant studies on the therapeutic role of odontogenic EVs in pulp healing published in the last five years. We selected 89 relevant articles and discovered that dental stem cells (DSCs) derived EVs (DSC-EVs) have become a research hotspot in oral regenerative medicine, with significant advantages over cell transplantation in terms of low immunogenicity, ease of isolation, preservation, and management. Here, we introduce in detail the therapeutic effects of DSC-EVs for pulp restoration from three perspectives: excellent odontogenic properties, clinical applications, and possible molecular mechanisms. This article contributes a new viewpoint to the field of regenerative endodontics.

The odontoblastic differentiation of dental mesenchymal stem cells: molecular regulation mechanism and related genetic syndromes

Dental mesenchymal stem cells (DMSCs) are multipotent progenitor cells that can differentiate into multiple lineages including odontoblasts, osteoblasts, chondrocytes, neural cells, myocytes, cardiomyocytes, adipocytes, endothelial cells, melanocytes, and hepatocytes. Odontoblastic differentiation of DMSCs is pivotal in dentinogenesis, a delicate and dynamic process regulated at the molecular level by signaling pathways, transcription factors, and posttranscriptional and epigenetic regulation. Mutations or dysregulation of related genes may contribute to genetic diseases with dentin defects caused by impaired odontoblastic differentiation, including tricho-dento-osseous (TDO) syndrome, X-linked hypophosphatemic rickets (XLH), Raine syndrome (RS), hypophosphatasia (HPP), Schimke immuno-osseous dysplasia (SIOD), and Elsahy-Waters syndrome (EWS). Herein, recent progress in the molecular regulation of the odontoblastic differentiation of DMSCs is summarized. In addition, genetic syndromes associated with disorders of odontoblastic differentiation of DMSCs are discussed. An improved understanding of the molecular regulation and related genetic syndromes may help clinicians better understand the etiology and pathogenesis of dentin lesions in systematic diseases and identify novel treatment targets.

Melatonin-mediated malic enzyme 2 orchestrates mitochondrial fusion and respiratory functions to promote odontoblastic differentiation during tooth development

Tooth development is a complex process that is tightly controlled by circadian rhythm. Melatonin (MT) is a major hormonal regulator of the circadian rhythm, and influences dentin formation and odontoblastic differentiation during tooth development; however, the underlying mechanism remains elusive. This study investigated how MT regulates odontoblastic differentiation, with a special focus on its regulation of mitochondrial dynamics. In rat dental papilla cells (DPCs), we found that MT promotes odontoblastic differentiation concurrently with enhanced mitochondrial fusion, while disruption of mitochondrial fusion by depleting optic atrophy 1 (OPA1) impairs MT-mediated differentiation and mitochondrial respiratory functions. Through RNA sequencing, we discovered that MT significantly upregulated malic enzyme 2 (ME2), a mitochondrial NAD(P)⁺ -dependent enzyme, and identified ME2 as a critical MT downstream effector that orchestrates odontoblastic differentiation, mitochondrial fusion, and respiration functions. By detecting the spatiotemporal expression of ME2 in developing tooth germs, and using tooth germ reconstituted organoids, we also provided in vivo and ex vivo evidence that ME2 promotes dentin formation, indicating a possible involvement of ME2 in MT-modulated tooth development. Collectively, our findings offer novel understandings regarding the molecular mechanism by which MT affects cell differentiation and organogenesis, meanwhile, the critical role of ME2 in MT-regulated mitochondrial functions is also highlighted.

Extracellular Vesicles for Dental Pulp and Periodontal Regeneration

Extracellular vesicles (EVs) are lipid bound particles derived from their original cells, which play critical roles in intercellular communication through their cargoes, including protein, lipids, and nucleic acids. According to their biogenesis and release pathway, EVs can be divided into three categories: apoptotic vesicles (ApoVs), microvesicles (MVs), and small EVs (sEVs). Recently, the role of EVs in oral disease has received close attention. In this review, the main characteristics of EVs are described, including their classification, biogenesis, biomarkers, and components. Moreover, the therapeutic mechanism of EVs in tissue regeneration is discussed. We further summarize the current status of EVs in pulp/periodontal tissue regeneration and discuss the potential mechanisms. The therapeutic potential of EVs in pulp and periodontal regeneration might involve the promotion of tissue regeneration and immunomodulatory capabilities. Furthermore, we highlight the current challenges in the translational use of EVs. This review would provide valuable insights into the potential therapeutic strategies of EVs in dental pulp and periodontal regeneration.

The Potential Application of Human Gingival Fibroblast-Conditioned Media in Pulp Regeneration: An In Vitro Study

Regenerative endodontic treatment based on tissue engineering has recently gained interest in contemporary restorative dentistry. However, low survival rates and poor potential differentiation of stem cells could undermine the success rate of pulp regenerative therapy. Human gingival fibroblast-conditioned medium (hGF-CM) has been considered a potential therapy for tissue regeneration due to its stability in maintaining multiple factors essential for tissue regeneration compared to live cell transplantation. This study aimed to investigate the potency of hGF-CM on stem cells from human dental pulp (DPSC) in pulp regeneration. A series of experiments confirmed that hGF-CM contributes to a significant increase in proliferation, migration capability, and cell viability of DPSC after H2O2 exposure. Moreover, it has been proved to facilitate the odontogenic differentiation of DPSC via qRT-PCR, ALP (alkaline phosphatase), and ARS (Alizarin Red S) staining. It has been discovered that such highly upregulated odontogenesis is related to certain types of ECM proteins (collagen and laminin) from hGF-CM via proteomics. In addition, it is found that the ERK pathway is a key mechanism via inhibition assay based on RNA-seq result. These findings demonstrate that hGF-CM could be beneficial biomolecules for pulp regeneration.

Safety and biodistribution of exosomes derived from human induced pluripotent stem cells

As a new cell-free therapy, exosomes have provided new ideas for the treatment of various diseases. Human induced pluripotent stem cells (hiPSCs) cannot be used in clinical trials because of tumorigenicity, but the exosomes derived from hiPSCs may combine the advantages of iPSC pluripotency and the nanoscale size of exosomes while avoiding tumorigenicity. Currently, the safety and biodistribution of hiPSC-exosomes in vivo are unclear. Here, we investigated the effects of hiPSC-exosomes on hemolysis, DNA damage, and cytotoxicity through cell experiments. We also explored the safety of vein injection of hiPSC-exosomes in rabbits and rats. Differences in organ distribution after nasal administration were compared in normal and Parkinson’s disease model mice. This study may provide support for clinical therapy and research of intravenous and nasal administration of hiPSC-exosomes.