Exosomes Derived From Hypoxia-Conditioned Stem Cells of Human Deciduous Exfoliated Teeth Enhance Angiogenesis via the Transfer of let-7f-5p and miR-210-3p

3D-Printed Titanium Trabecular Scaffolds with Sustained Release of Hypoxia-Induced Exosomes for Dual-Mimetic Bone Regeneration

Current Ti-6Al-4V bone implants lack trabecular structure and pro‑angiogenic cues, both essential for regeneration. Herein, a dual biomimetic strategy is devised that integrates a 3D-printed biomimetic trabecular porous Ti-6Al-4V scaffold (BTPS) with exosome-loaded PEGDA/GelMA hydrogel microspheres (PGHExo) designed for sustained release. BTPS is designed using Voronoi algorithms and imaging data, and replicates the geometry and mechanical properties of natural bone. Hypoxia-induced human umbilical vein endothelial cell (HUVEC) derived exosomes (HExo) are encapsulated in PGHExo microspheres via microfluidic technology, enabling controlled release of HExo, and anchored onto BTPS using polydopamine (pDA) modification (BTPS&pDA@PGHExo). BTPS exhibited an elastic modulus of ≈3.2 GPa and a permeability of 11.52 × 10-8 mm2, mimicking natural bone. In vitro assays demonstrated that BTPS&pDA@PGHExo significantly enhanced osteogenesis and angiogenesis. mRNA-Seq analysis suggested that BTPS&pDA@PGHExo regulates osteogenic and angiogenic gene expression through the activation of pathways including MAPK, mTOR, HIF-1, and VEGF. In vivo, BTPS&pDA@PGHExo improved bone volume, density, and neovascularization in a rabbit model. This dual biomimetic strategy offers a promising clinical solution, addressing the limitations of conventional Ti-6Al-4V scaffolds and providing an innovative approach for personalized bone defect repair.

The Protective Effects of MSC-Derived Exosomes Against Chemotherapy-Induced Parotid Gland Cytotoxicity

Background: Fluorouracil (5-FU) is one of the most popular chemotherapeutic agents used in various cancer therapy protocols. Cell-free therapy utilizing exosomes is gaining increased popularity as a safer option due to concerns over potential tumor progression following stem cell therapy. Methods: Parotid glands of albino were treated with a single bone marrow mesenchymal stem cell (BMMSC)-derived exosomes injection (100 μg/kg/dose suspended in 0.2 mL phosphate-buffered saline [PBS]), a single 5-Fu injection (20 mg/kg), and BMMSC-derived exosomes plus 5-FU and compared to control group (daily saline injections). After 30 days, the parotid glands were examined using qualitative histological evaluation, immunohistochemical evaluation using rabbit polyclonal mouse antibody to Ki-67, caspase 3, and iNOS, as well as quantitative real-time polymerase chain reaction (RT-PCR) to evaluate gene expression of TGFβ1, TNF-α, and BCL-2. Results: Histological examination of the parotid gland revealed that BMMSC-derived exosomes restored the glands' architecture and repaired most of the distortion created by 5-FU. Immunohistochemical expression of tumor proliferation and cell death markers were restored to normal levels in the exosome-treated groups that were similar to the control group. Furthermore, BMMSC-derived exosomes reversed the effects of 5-FU on quantitative gene expression levels and showed a significant decrease in TNF-α (p < 0.001) and a significant increase in TGFβ (p < 0.0001) and BCL-2 (p < 0.05) when compared to 5-FU treatment. Conclusion: Within the limitations of the current study, BMMSC-derived exosomes have the potential to counteract the cytotoxic effects of 5-FU on the parotid glands of rats in vivo. Further studies are deemed necessary to simulate clinical scenarios.

Human Umbilical Cord Mesenchymal Stem Cells-Derived Exosomes Attenuates Experimental Periodontitis in Mice Partly by Delivering miRNAs

Introduction

Periodontitis is the most common non-communicable disease in humans. The main challenge in the treatment of periodontitis is to effectively control periodontal inflammation and promote tissue repair. Human umbilical cord mesenchymal stem cells-derived exosomes (hucMSCs-exo) have been reported to modulate inflammatory responses and promote tissue repairment mainly through miRNAs in several diseases. However, the effect of hucMSCs-exo on periodontitis remains unknown. In this study, we hypothesized that hucMSCs-exo could inhibit bone destruction in periodontitis mice.

Methods

In this study, we constructed and characterized the exo@H drug delivery platform. Lipopolysaccharide was used to construct an inflammatory microenvironment in vitro to detect MC3T3-E1 cells proliferation and bone regeneration capacity. Ligation induced to construct an experimental periodontitis mouse model. The distance of the cement-enamel junction (CEJ) to the alveolar bone crest (ABC) was measured for bone resorption evaluation. Hematoxylin-eosin (H&E) staining and Tartrate resistant acid phosphatase (TRAP) staining were used to observe periodontal tissue changes. MicroRNA (miRNA) sequencing was used to detect differential genes and for bioinformatics analysis. Real-time quantitative polymerase chain reaction (qRT-PCR). WB assay and dual luciferase assay were used to further validate the screened differentially expressed miRNAs and the targeted binding relationship with the corresponding target genes.

Results

We found that lyophilized hucMSCs-exo promoted the proliferation and osteogenic differentiation of MC3T3-E1 cells, and showed more significant proliferative and osteogenic differentiation abilities in combination with the hydrogel (P < 0.05). Using periodontitis mice, bone resorption evaluation revealed a significant reduction in alveolar bone resorption in the exo@H group compared to the hydrogel group (P < 0.01), and exo@H was able to reduce the inflammatory response of periodontal tissues and the number of osteoclasts on the surface of the alveolar bone compared to the hydrogel group. Moreover, 59 miRNAs were upregulated, such as let-7f-5p and miR-203-3p, which positively targeted IL-13 and Nit2, respectively.

Discussion

These results suggest that exo@H provides protection against periodontitis partly by delivering miRNAs to periodontal tissue. Our results confirm the feasibility of the exo@H delivery platform we constructed and the effectiveness of its use for periodontitis treatment, and this study provides a promising approach for the treatment of periodontitis via miRNA.

Angiogenic and neurogenic potential of dental-derived stem cells for functional pulp regeneration: A narrative review

BACKGROUND

Dental pulp tissue engineering is expected to become an ideal treatment for irreversible pulpitis and apical periodontitis. However, angiogenesis and neurogenesis for functional pulp regeneration have not yet met the standard for large-scale clinical application, and need further research.

OBJECTIVE

This review focused on the potential mechanisms of angiogenesis and neurogenesis in pulp regeneration, including stem cell types, upstream and downstream regulatory molecules and cascade signalling pathways, thereby providing a theoretical basis and inspiring new ideas to improve the effectiveness of dental pulp tissue engineering.

METHODS

An electronic literature search was carried out using the keywords of 'pulp regeneration', 'stem cell transplantation', 'dental pulp stem cells', 'angiogenesis' and 'neurogenesis'. The resulting literature was screened and reviewed.

RESULTS

Stem cells used in dental pulp tissue engineering can be classified as dental-derived and non-dental-derived stem cells, amongst which dental pulp stem cells (DPSC) have achieved promising results in animal experiments and clinical trials. Multiple molecules and signalling pathways are involved in the process of DPSC-mediated angiogenic and neurogenetic regeneration. In order to promote angiogenesis and neurogenesis in pulp regeneration, feasible measures include the addition of growth factors, the modulation of transcription factors and signalling pathways, the use of extracellular vesicles and the modification of bioscaffold materials.

CONCLUSION

Dental pulp tissue engineering has had breakthroughs in preclinical and clinical studies in vivo. Overcoming difficulties in pulpal angiogenesis and neurogenesis, and achieving functional pulp regeneration will lead to a significant impact in endodontics.

Age-Related Oral and Para-Oral Tissue Disorders: The Evolving Therapeutic and Diagnostic Potential of Exosomes

This review highlights the key molecular and cellular mechanisms contributing to aging, such as DNA damage, mitochondrial dysfunction, telomere shortening, protein dysfunction, and defective autophagy. These biological mechanisms are involved in various oral health conditions prevalent in the elderly, including periodontal disease, oral cancer, xerostomia, dental caries, and temporomandibular joint disorders. Exosomes generated by mesenchymal stem cells possess substantial therapeutic potential. These exosomes are nanosized extracellular vesicles derived from cells and are involved in essential intercellular communication and tissue homeostasis. The exosome-based therapies proved superior to traditional cell-based approaches, due to lower immunogenicity, ease of storage, and avoidance of complications associated with cell transplantation. Furthermore, the diagnostic potential of exosomes as non-invasive biomarkers for aging processes and age-related oral diseases offers insights into disease diagnosis, staging, and monitoring. Among the challenges and future perspectives of translating exosome research from preclinical studies to clinical applications is the need for standardized procedures to fully harness the therapeutic and diagnostic capabilities of exosomes.

Therapeutic Potential of Feline Adipose-Derived Stem Cell Exosomes in the Treatment of Feline Idiopathic Cystitis: A Characterization and Functional Analysis of miRNA Content

Feline Idiopathic Cystitis (FIC), is a chronic lower urinary tract condition in cats analogous to PBS/IC in women, which presents significant treatment challenges due to its idiopathic nature. Recent advancements in regenerative medicine highlight the potential of Adipose Tissue-Derived Stem Cells (ADSCs), particularly through their secretome, which includes mediators, bioactive molecules, and extracellular vesicles (EVs). Notably, exosomes, a subset of EVs, facilitate cell-to-cell communication and, when derived from ADSCs, exhibit anti-inflammatory properties and contribute to tissue regeneration. In this work, we aim to characterize the content of exosomes derived from feline ADSCs (fADSCs) to elucidate their mechanisms of action on recipient cells and assess their therapeutic potential for FIC. Exosomes were isolated from fADSCs and their microRNA (miRNA) content sequenced using Illumina technology. Our findings demonstrate that fADSC-derived exosomes harbor miRNAs that can induce regenerative processes, such as cell proliferation, immune modulation, angiogenesis, and anti-inflammatory responses. Key miRNAs identified include fca-miR-221, fca-let-7f-5p, fca-miR-337-5p, fca-miR-542-5p, fca-miR-24-3p, fca-miR-205, and fca-miR-23a, which promote proliferative, angiogenic, differentiation, and regenerative mechanisms. Additionally, miRNAs with anti-inflammatory effects, such as fca-miR-193a-5p and fca-miR-127-3p, and those positively regulating the immune system, including fca-let-7a-5p and fca-miR-chrC1_18846-5p, were identified. Of particular interest, fca-miR-219-5p (has-miR-6766-3p) has been reported to suppress liver fibrosis.These results underline the therapeutic potential of fADSC-derived exosomes in treating FIC and suggest innovative strategies for feline veterinary medicine.

Apoptosis-induced exosomes from human exfoliated deciduous teeth enhance angiogenesis in human umbilical vein endothelial cells

Exosomes derived from the stem cells of human exfoliated deciduous teeth (SHED) hold promise for tissue regeneration. Apoptotic cells release a variety of extracellular vesicles that affect intercellular communication. This study aimed to investigate the angiogenic effects of SHED-derived exosomes modified via apoptosis induction on human umbilical vein endothelial cells (HUVECs). Apoptosis was induced in SHED via serum starvation for 3 weeks and confirmed by the upregulation of the apoptotic genes, caspase 3 and 9, and via annexin V staining. The apoptotic SHED-derived exosomes were isolated, characterized, and subjected to proteomic analysis. In vitro experiments were performed to assess the effects of apoptotic SHED exosomes on the proliferation, migration, and tube formation of HUVECs. The apoptosis-induced SHED showed increased cell viability and decreased numbers of dead cells compared with those of conventional cultures while retaining their identity as mesenchymal stem cells positive for CD44, CD73, and CD90. The apoptotic SHED-derived exosomes exhibited characteristic features, such as standard size, cup-shaped morphology, and positive staining, for exosomal markers CD9, CD63, and CD81. Proteins associated with apoptosis, programmed cell death, and cellular senescence were downregulated in the apoptotic SHED exosomes, whereas those associated with extracellular matrix organization were upregulated, indicating positive angiogenesis. HUVECs treated with apoptotic SHED exosomes exhibited significantly enhanced proliferation and migration compared with those treated with normal SHED exosomes. The mesh-like structures in the apoptotic SHED exosomes exhibited significantly increased signs of angiogenesis. The findings of this study provide new insights into the potential use of apoptotic SHED-derived exosomes in regenerative medicine.

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.

Advances in application of hypoxia-preconditioned mesenchymal stem cell-derived exosomes

Mesenchymal stem cells (MSCs) primarily secrete physiologically functional exosomes via paracrine effects that act on various adjacent and distant cells, thus exerting their therapeutic effects. In recent years, hypoxic preconditioning, as a novel MSC culture mode, has emerged as a research hotspot. Many previous studies have shown the role and underlying regulatory mechanisms of hypoxic preconditioning in various diseases, which has provided sufficient reference materials for the MSC research field. Therefore, this review summarizes the progress in application of hypoxia-preconditioned MSC-derived exosomes that substantially increases and improves the biological activity of specific molecules, such as microRNA.

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.

Apoptotic Extracellular Vesicles from Supernumerary Tooth-Derived Pulp Stem Cells Transfer COL1A1 to Promote Angiogenesis via PI3K/Akt/VEGF Pathway

Purpose

Angiogenesis is a tightly controlled process that initiates the formation of new vessels and its dysfunction can lead to life-threatening diseases. Apoptotic extracellular vesicles (ApoEVs) have emerged as a proangiogenic agent with high safety and isolation efficiency profile, and ApoEVs from supernumerary tooth-derived pulp stem cells (SNTSC-ApoEVs) have their unique advantages with an easily accessible parental cell source and non-invasive cell harvesting. However, the detailed characteristics of SNTSC-ApoEVs are largely unknown. This study aimed to investigate the proangiogenic capacity and function molecule of SNTSC-ApoEVs.

Methods

SNTSC-ApoEVs were isolated and characterized. In vitro effects of SNTSC-ApoEVs on the proliferation, migration, and tube formation of human umbilical vein endothelial cells (HUVECs) were evaluated by CCK-8, wound healing, transwell, and tube formation assays. The mRNA and protein levels of proangiogenic genes were quantified by qRT-PCR, Western blot, and immunofluorescence analysis. A Matrigel plug model was established in 6-week-old male nu/nu mice for one week, and the in vivo impact of SNTSC-ApoEVs on micro-vessel formation was assessed by histological analysis. Proteomic analysis and RNA sequencing were performed to explore the active ingredients and underlying mechanisms.

Results

SNTSC-ApoEVs enhanced the proliferation, migration, and angiogenesis of HUVECs in vitro. In the Matrigel plug model in vivo, SNTSC-ApoEVs promoted CD31-positive luminal structure formation. Apart from expressing general ApoEV markers, SNTSC-ApoEVs were enriched with multiple proteins related to extracellular matrix-cell interactions. Mechanistically, SNTSC-ApoEVs transferred COL1A1 to HUVECs and promoted endothelial functions by activating the PI3K/Akt/VEGF cascade.

Conclusion

SNTSC-ApoEVs can promote angiogenesis by transferring the functional molecule COL1A1 and activating the PI3K/Akt/VEGF pathway, making SNTSC-ApoEVs a promising strategy for the treatment of angiogenesis-related diseases.

Role of Hypoxia in Mesenchymal Stem Cells from Dental Pulp: Influence, Mechanism and Application

Mesenchymal stem cells (MSCs) from dental pulp (DP-MSCs), which include dental pulp stem cells (DPSCs) isolated from permanent teeth and stem cells from human exfoliated deciduous teeth (SHED), have emerged as highly promising cell sources for tissue regeneration, due to their high proliferative rate, multi-lineage differentiation capability and non-invasive accessibility. DP-MSCs also exert extensive paracrine effects through the release of extracellular vesicles (EVs) and multiple trophic factors. To be noted, the microenvironment, commonly referred to as the stem cell niche, plays a crucial role in shaping the functionality and therapeutic effects of DP-MSCs, within which hypoxia has garnered considerable attention. Extensive research has demonstrated that hypoxic conditions profoundly impact DP-MSCs. Specifically, hypoxia promotes DP-MSC proliferation, survival, stemness, migration, and pro-angiogenic potential while modulating their multi-lineage differentiation capacity. Furthermore, hypoxia stimulates the paracrine activities of DP-MSCs, leading to an increased production of EVs and soluble factors. Considering these findings, hypoxia preconditioning has emerged as a promising approach to enhance the therapeutic potential of DP-MSCs. In this comprehensive review, we provide a systematic overview of the influence of hypoxia on DP-MSCs, shedding light on the underlying mechanisms involved. Moreover, we also discuss the potential applications of hypoxia-preconditioned DP-MSCs or their secretome in tissue regeneration. Additionally, we delve into the methodologies employed to simulate hypoxic environments. This review aims to promote a comprehensive and systematic understanding of the hypoxia-induced effects on DP-MSCs and facilitate the refinement of regenerative therapeutic strategies based on DP-MSCs.

miR-21 Expressed by Dermal Fibroblasts Enhances Skin Wound Healing Through the Regulation of Inflammatory Cytokine Expression

The management of skin wound healing is still a challenge. MicroRNA-21 (miR-21) has been reported to play important roles in wound repair; however, the underlying mechanism needs to be further clarified. The present study aimed to study the direct role of miR-21 in skin wound healing in miR-21 KO mice and to investigate the role of miR-21 in controlling the migration and proliferation of primary human skin cells and its underlying mechanism(s). miR-21 KO and wild-type (WT) mice were used for in vivo wound healing assays, while mouse and human primary skin cells were used for in vitro assays. miR-21 inhibitors or mimics or negative control small RNAs were transfected to either inhibit or enhance miR-21 expression in the human primary dermal fibroblasts or epidermal cells. RNA sequencing analysis was performed to identify the potential molecular pathways involved. We found that the loss of miR-21 resulted in slower wound healing in miR-21 KO mouse skin and especially delayed the healing of dermal tissue. In vitro assays demonstrated that the reduced expression of miR-21 caused by its inhibitor inhibited the migration of human primary dermal fibroblasts, which could be enhanced by increased miR-21 expression caused by miR-21 mimics. RNA-sequence analysis revealed that the inhibition of miR-21 expression downregulated the inflammatory response pathways associated with the decreased expression of inflammatory cytokines, and the addition of IL-1β into the culture medium enhanced the migration and proliferation of dermal fibroblasts in vitro. In conclusion, miR-21 in dermal fibroblasts can promote the migration and growth of epidermal and dermal cells to enhance skin wound healing through controlling the expression of inflammatory cytokines.

Exosomes as Promising Therapeutic Tools for Regenerative Endodontic Therapy

Pulpitis is a common and frequent disease in dental clinics. Although vital pulp therapy and root canal treatment can stop the progression of inflammation, they do not allow for genuine structural regeneration and functional reconstruction of the pulp-dentin complex. In recent years, with the development of tissue engineering and regenerative medicine, research on stem cell-based regenerative endodontic therapy (RET) has achieved satisfactory preliminary results, significantly enhancing its clinical translational prospects. As one of the crucial paracrine effectors, the roles and functions of exosomes in pulp-dentin complex regeneration have gained considerable attention. Due to their advantages of cost-effectiveness, extensive sources, favorable biocompatibility, and high safety, exosomes are considered promising therapeutic tools to promote dental pulp regeneration. Accordingly, in this article, we first focus on the biological properties of exosomes, including their biogenesis, uptake, isolation, and characterization. Then, from the perspectives of cell proliferation, migration, odontogenesis, angiogenesis, and neurogenesis, we aim to reveal the roles and mechanisms of exosomes involved in regenerative endodontics. Lastly, immense efforts are made to illustrate the clinical strategies and influencing factors of exosomes applied in dental pulp regeneration, such as types of parental cells, culture conditions of parent cells, exosome concentrations, and scaffold materials, in an attempt to lay a solid foundation for exploring and facilitating the therapeutic strategy of exosome-based regenerative endodontic procedures.

Exosomes from preconditioned mesenchymal stem cells: Tissue repair and regeneration

As a prominent research area in tissue repair and regeneration, mesenchymal stem cells (MSCs) have garnered substantial attention for their potential in the treatment of various diseases. It is now widely recognized that the therapeutic effects of MSCs primarily occur through paracrine mechanisms. Among these mechanisms, exosomes play a crucial role by exerting a series of regulatory effects on surrounding cells and tissues. While exosomes have shown promise in treating various diseases, they do have some limitations, such as limited secretion, poor targeting, and single functionality. However, MSC preconditioning can enhance the production of exosomes, lead to more stable functionality and improve therapeutic effects. Moreover, exosomes could also serve as carriers for specific drugs or genes, enabling more precise treatments of diseases. This review summarizes the most recent literatures on how preconditioning of MSCs influences the regenerative potential of their exosomes in tissue repair and provides new insights into the therapeutic application of exosomes derived from MSCs.

Multifunctional Exosomes Derived from M2 Macrophages with Enhanced Odontogenesis, Neurogenesis and Angiogenesis for Regenerative Endodontic Therapy: An In Vitro and In Vivo Investigation

INTRODUCTION

Exosomes derived from M2 macrophages (M2-Exos) exhibit tremendous potential for inducing tissue repair and regeneration. Herein, this study was designed to elucidate the biological roles of M2-Exos in regenerative endodontic therapy (RET) compared with exosomes from M1 macrophages (M1-Exos).

METHODS

The internalization of M1-Exos and M2-Exos by dental pulp stem cells (DPSCs) and human umbilical vein endothelial cells (HUVECs) was detected by uptake assay. The effects of M1-Exos and M2-Exos on DPSC and HUVEC behaviors, including migration, proliferation, odonto/osteogenesis, neurogenesis, and angiogenesis were determined in vitro. Then, Matrigel plugs incorporating M2-Exos were transplanted subcutaneously into nude mice. Immunostaining for vascular endothelial growth factor (VEGF) and CD31 was performed to validate capillary-like networks.

RESULTS

M1-Exos and M2-Exos were effectively absorbed by DPSCs and HUVECs. Compared with M1-Exos, M2-Exos considerably facilitated the proliferation and migration of DPSCs and HUVECs. Furthermore, M2-Exos robustly promoted ALP activity, mineral nodule deposition, and the odonto/osteogenic marker expression of DPSCs, indicating the powerful odonto/osteogenic potential of M2-Exos. In sharp contrast with M1-Exos, which inhibited the neurogenic capacity of DPSCs, M2-Exos contributed to a significantly augmented expression of neurogenic genes and the stronger immunostaining of Nestin. Consistent with remarkably enhanced angiogenic markers and tubular structure formation in DPSCs and HUVECs in vitro, the employment of M2-Exos gave rise to more abundant vascular networks, dramatically higher VEGF expression, and widely spread CD31+ tubular lumens in vivo, supporting the enormous pro-angiogenic capability of M2-Exos.

CONCLUSIONS

The multifaceted roles of M2-Exos in ameliorating DPSC and HUVEC functions potentially contribute to complete functional pulp-dentin complex regeneration.

Understanding exosomes: Part 3-therapeutic + diagnostic potential in dentistry

Exosomes are the smallest subset of extracellular signaling vesicles secreted by most cells with the ability to communicate with other tissues and cell types over long distances. Their use in regenerative medicine has gained tremendous momentum recently due to their ability to be utilized as therapeutic options for a wide array of various diseases. Over 5000 publications are currently being published on this topic yearly, many of which in the dental space. This extensive review article is the first scoping review aimed at summarizing all therapeutic uses of exosomes in regenerative dentistry. A total of 944 articles were identified as using exosomes in the dental field for either their regenerative/therapeutic potential or for diagnostic purposes derived from the oral cavity. In total, 113 research articles were selected for their regenerative potential (102 in vitro, 60 in vivo, 50 studies included both). Therapeutic exosomes were most commonly derived from dental pulps, periodontal ligament cells, gingival fibroblasts, stem cells from exfoliated deciduous teeth, and the apical papilla which have all been shown to facilitate the regenerative potential of a number of tissues including bone, cementum, the periodontal ligament, nerves, aid in orthodontic tooth movement, and relieve temporomandibular joint disorders, among others. Results demonstrate that the use of exosomes led to positive outcomes in 100% of studies. In the bone field, exosomes were found to perform equally as well or better than rhBMP2 while significantly reducing inflammation. Periodontitis animal models were treated with simple gingival injections of exosomes and benefits were even observed when the exosomes were administered intravenously. Exosomes are much more stable than growth factors and were shown to be far more resistant against degradation by periodontal pathogens found routinely in a periodontitis environment. Comparative studies in the field of periodontal regeneration found better outcomes for exosomes even when compared to their native parent stem cells. In total 47 diagnostic studies revealed a role for salivary/crevicular fluid exosomes for the diagnosis of birth defects, cardiovascular disease, diabetes, gingival recession detection, gingivitis, irritable bowel syndrome, neurodegenerative disease, oral lichen planus, oral squamous cell carcinoma, oropharyngeal cancer detection, orthodontic root resorption, pancreatic cancer, periodontitis, peri-implantitis, Sjögren syndrome, and various systemic diseases. Hence, we characterize the exosomes as possessing "remarkable" potential, serving as a valuable tool for clinicians with significant advantages.

Exosome-based engineering strategies for the diagnosis and treatment of oral and maxillofacial diseases

Oral and maxillofacial diseases are one of the most prevalent diseases in the world, which not only seriously affect the health of patients' oral and maxillofacial tissues, but also bring serious economic and psychological burdens to patients. Therefore, oral and maxillofacial diseases require effective treatment. Traditional treatments have limited effects. In recent years, nature exosomes have attracted increasing attention due to their ability to diagnose and treat diseases. However, the application of nature exosomes is limited due to low yield, high impurities, lack of targeting, and high cost. Engineered exosomes can be endowed with better comprehensive therapeutic properties by modifying exosomes of parent cells or directly modifying exosomes, and biomaterial loading exosomes. Compared with natural exosomes, these engineered exosomes can achieve more effective diagnosis and treatment of oral and maxillary system diseases, and provide reference and guidance for clinical application. This paper reviews the engineering modification methods of exosomes and the application of engineered exosomes in oral and maxillofacial diseases and looks forward to future research directions.

Crucial Factors Influencing the Involvement of Odontogenic Exosomes in Dental Pulp Regeneration

Recent progress in exosome based studies has revealed that they possess several advantages over cells, including "cell-free" properties, low immunogenicity and ethical controversy, high biological safety and effective action. These characteristics confer exosomes significant advantages that allow them to overcome the limitations associated with traditional "cell therapy" by circumventing the issues of immune rejection, scarcity of donor cells, heterogeneity, and ethical concerns. Identification of a complete and effective radical treatment for irreversible pulpal disease, a common clinical problem, continues to pose challenges. Although traditional root canal therapy remains the primary clinical treatment, it does not fully restore the physiological functions of pulp. Although stem cell transplantation appears to be a relatively viable treatment strategy for pulp disease, issues such as cell heterogeneity and poor regeneration effects remain problematic. Dental pulp regeneration strategies based on "cell-free" exosome therapies explored by numerous studies appear to have shown significant advantages. In particular, exosomes derived from odontogenic stem cells have demonstrated considerable potential in tooth tissue regeneration engineering, and continue to exhibit superior therapeutic effects compared to non-odontogenic stem cell-derived exosomes. However, only a few studies have comprehensively summarised their research results, particularly regarding the critical factors involved in the process. Therefore, in this study, our purpose was to review the effects exerted by odontogenic exosomes on pulp regeneration and to analyse and discus crucial factors related to this process, thereby providing scholars with a feasible and manageable new concept with respect to regeneration schemes.

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.

Prevascularization techniques for dental pulp regeneration: potential cell sources, intercellular communication and construction strategies

One of the difficulties of pulp regeneration is the rapid vascularization of transplanted engineered tissue, which is crucial for the initial survival of the graft and subsequent pulp regeneration. At present, prevascularization techniques, as emerging techniques in the field of pulp regeneration, has been proposed to solve this challenge and have broad application prospects. In these techniques, endothelial cells and pericytes are cocultured to induce intercellular communication, and the cell coculture is then introduced into the customized artificial vascular bed or induced to self-assembly to simulate the interaction between cells and extracellular matrix, which would result in construction of a prevascularization system, preformation of a functional capillary network, and rapid reconstruction of a sufficient blood supply in engineered tissue after transplantation. However, prevascularization techniques for pulp regeneration remain in their infancy, and there remain unresolved problems regarding cell sources, intercellular communication and the construction of prevascularization systems. This review focuses on the recent advances in the application of prevascularization techniques for pulp regeneration, considers dental stem cells as a potential cell source of endothelial cells and pericytes, discusses strategies for their directional differentiation, sketches the mechanism of intercellular communication and the potential application of communication mediators, and summarizes construction strategies for prevascularized systems. We also provide novel ideas for the extensive application and follow-up development of prevascularization techniques for dental pulp regeneration.

Bioactive Spinal Cord Scaffold Releasing Neurotrophic Exosomes to Promote In Situ Centralis Neuroplasticity

Spinal cord injury (SCI), one of the most serious injuries of the central nervous system, causes physical functional dysfunction and even paralysis in millions of patients. As a matter of necessity, redressing the neuroleptic pathologic microenvironment to a neurotrophic microenvironment is essential in order to alleviate this dilemma and facilitate the recovery of the spinal cord. Herein, based on cell-sheet technology, two functional cell types─uninduced and neural-induced stem cells from human exfoliated deciduous teeth─were formed into a composite membrane that subsequently self-assembled to form a bioactive scaffold with a spinal-cord-like structure, called a spinal cord assembly (SCA). In a stable extracellular matrix microenvironment, SCA continuously released SCA-derived exosomes containing various neurotrophic factors, which effectively promoted neuronal regeneration, axonal extension, and angiogenesis and inhibited glial scar generation in a rat model of SCI. Neurotrophic exosomes significantly improved the pathological microenvironment and promoted in situ centralis neuroplasticity, ultimately eliciting a strong repair effect in this model. SCA therapy is a promising strategy for the effective treatment of SCI based on neurotrophic exosome delivery.

The Emerging Biological Functions of Exosomes from Dental Tissue-Derived Mesenchymal Stem Cells

Exosomes are one kind of small-cell extracellular membranous vesicles that can regulate intercellular communication and give rise to mediating the biological behaviors of cells, involving in tissue formation, repair, the modulation of inflammation, and nerve regeneration. The abundant kinds of cells can secret exosomes, among them, mesenchymal stem cells (MSCs) are very perfect cells for mass production of exosomes. Dental tissue-derived mesenchymal stem cells (DT-MSCs), including dental pulp stem cells, stem cells from exfoliated deciduous teeth, stem cells from apical papilla, stem cells from human periodontal ligament (PDLSCs), gingiva-derived mesenchymal stem cells, dental follicle stem cells, tooth germ stem cells, and alveolar bone-derived mesenchymal stem cells, are now known as a potent tool in the area of cell regeneration and therapy, more importantly, DT-MSCs can also release numerous types of exosomes, participating in the biological functions of cells. Hence, we briefly depict the characteristics of exosomes, give a detailed description of the biological functions and clinical application in some respects of exosomes from DT-MSCs through systematically reviewing the latest evidence, and provide a rationale for their use as tools for potential application in tissue engineering.

Exosomes derived from hypoxia-preconditioned mesenchymal stem cells (hypoMSCs-Exo): advantages in disease treatment

Mesenchymal stem cells (MSCs)-based therapy has been reported to be a potential approach to treat various diseases and the paracrine role might be the underlying mechanism. Exosomes were considered an important part of this paracrine role. It was reported that maintenance of MSCs in hypoxia conditions for a short time has shown to be beneficial for the therapeutic effect of MSCs and MSCs-derived exosomes. In this review, we summarized the recent developments on exosomes derived from hypoxia-preconditioned mesenchymal stem cells (hypoMSCs-Exo), including the characteristics of hypoMSCs-Exo in morphology and contents, diseases in which hypoMSCs-Exo showed more effective, and the cellular and molecular mechanisms that hypoMSCs-Exo showed more effective in disease treatment. Besides, we also discussed the limitations of current studies and the issues that needed to be improved in the application of hypoMSCs-Exo. This review aimed to promote a comprehensive and systematic understanding of this type of exosome with great therapeutic potential.

Creating a Microenvironment to Give Wings to Dental Pulp Regeneration-Bioactive Scaffolds

Dental pulp and periapical diseases make patients suffer from acute pain and economic loss. Although root canal therapies, as demonstrated through evidence-based medicine, can relieve symptoms and are commonly employed by dentists, it is still difficult to fully restore a dental pulp's nutrition, sensory, and immune-regulation functions. In recent years, researchers have made significant progress in tissue engineering to regenerate dental pulp in a desired microenvironment. With breakthroughs in regenerative medicine and material science, bioactive scaffolds play a pivotal role in creating a suitable microenvironment for cell survival, proliferation, and differentiation, following dental restoration and regeneration. This article focuses on current challenges and novel perspectives about bioactive scaffolds in creating a microenvironment to promote dental pulp regeneration. We hope our readers will gain a deeper understanding and new inspiration of dental pulp regeneration through our summary.

Advances of Mesenchymal Stem Cells Released Extracellular Vesicles in Periodontal Bone Remodeling

Extracellular vesicles (EVs) are nanoparticles that include exosomes, microvesicles, and apoptotic bodies; they interact with target cell surface receptors and transport contents, including mRNA, proteins, and enzymes into the cytoplasm of target cells to function. The biological fingerprints of EVs practically mirror those of the parental cells they originated from. In the bone remodeling microenvironment, EVs could act on osteoblasts to regulate the bone formation, promote osteoclast differentiation, and regulate bone resorption. Therefore, there have been many attempts wherein EVs were used to achieve targeted therapy in bone-related diseases. Periodontitis, a common bacterial infectious disease, could cause severe alveolar bone resorption, resulting in tooth loss, whereas research on periodontal bone regeneration is also an urgent question. Therefore, EVs-related studies are important for periodontal bone remodeling. In this review, we summarize the current knowledge of mesenchymal stem cell-EVs involved in periodontal bone remodeling and explore the functional gene expression through a comparative analysis of transcriptomic content.