Exosomes derived from stem cells from apical papilla promote angiogenesis via miR-126 under hypoxia

The Effects of Hypoxia-Preconditioned Dental Stem Cell-Derived Secretome on Tissue Regeneration

Mesenchymal stroma cells derived from oral tissues are known as dental stem cells (DSCs). Owing to their unique therapeutic niche and clinical accessibility, DSCs serve as a promising treatment option for bone defects and oral tissue regeneration. DSCs exist in a hypoxic microenvironment in vivo, which is far lower than the current 20% oxygen concentration used in in vitro culture. It has been widely reported that the application of an oxygen concentration less than 5% in the culture of DSCs is beneficial for preserving stemness and promoting proliferation, migration, and paracrine activity. The paracrine function of DSCs involves the secretome, which includes conditioned media (CM) and soluble bioactive molecules, as well as extracellular vesicles extracted from CM. Hypoxia can play a role in immunomodulation and angiogenesis by altering the protein or nucleic acid components in the secretory group, which enhances the therapeutic potential of DSCs. This review summarizes the biological characteristics of DSCs, the influence of hypoxia on DSCs, the impact of hypoxia on the secretory group of DSCs, and the latest progress on the use of DSCs secretory group in tissue regeneration based on hypoxia pretreatment. We highlighted the multifunctional biological effect of hypoxia culture on tissue regeneration and provided a summary of the current mechanism of hypoxia in the pretreatment of DSCs.

Odontogenic exosomes simulating the developmental microenvironment promote complete regeneration of pulp-dentin complex in vivo

INTRODUCTION

Establishing an optimized regenerative microenvironment for pulp-dentin complex engineering has become increasingly critical. Recently, exosomes have emerged as favorable biomimetic nanotherapeutic tools to simulate the developmental microenvironment and facilitate tissue regeneration.

OBJECTIVES

This study aimed to elucidate the multifaceted roles of exosomes from human dental pulp stem cells (DPSCs) that initiated odontogenic differentiation while sustaining mesenchymal stem cell (MSC) characteristics in odontogenesis, angiogenesis, and neurogenesis during pulp-dentin complex regeneration.

METHODS

Differential centrifugation was performed to isolate exosomes from normal DPSCs (DPSC-Exos) and DPSCs that initially triggered odontogenic differentiation (DPSC-Od-Exos). The impact of these exosomes on the biological behavior of DPSCs and human umbilical vein endothelial cells (HUVECs) was examined in vitro through CCK-8 assay and Transwell migration assay, as well as assays dedicated to assessing odontogenic, angiogenic, and neurogenic capabilities. In vivo, Matrigel plugs and human tooth root fragments incorporating either DPSC-Exos or DPSC-Od-Exos were subcutaneously transplanted into mouse models. Subsequent histological, immunohistochemical, and immunofluorescent analyses were conducted to determine the regenerative outcomes.

RESULTS

DPSC-Exos and DPSC-Od-Exos revealed no remarkable difference in their characteristics. In vitro analyses indicated that DPSC-Od-Exos significantly facilitated the proliferation, migration, and multilineage differentiation of DPSCs compared with DPSC-Exos. Furthermore, DPSC-Od-Exos elicited a more pronounced effect on the tubular structure formation of HUVECs. Consistently, Matrigel plug assays confirmed that DPSC-Od-Exos exhibited superior performance in promoting endothelial differentiation of DPSCs and stimulating angiogenesis in HUVECs. Notably, DPSC-Od-Exos contributed to complete pulp-dentin complex regeneration in human tooth root fragments, characterized by enriched neurovascular structures and a continuous layer of odontoblast-like cells, which extended cytoplasmic projections into the newly formed dentinal tubules.

CONCLUSION

By simulating the developmental microenvironment, multifunctional DPSC-Od-Exos demonstrated promising potential for reconstructing dentin-like tissue, vascular networks, and neural architectures, thereby enhancing our understanding of the therapeutic implications of DPSC-Od-Exos in regenerative endodontic treatment.

Osteo-immunomodulatory effects of macrophage-derived extracellular vesicles treated with biphasic calcium phosphate ceramics on bone regeneration

Literature on osteoimmunology has demonstrated that macrophages have a great influence on biomaterial-induced bone formation. However, there are almost no reports clarifying the osteo-immunomodulatory capacity of macrophage-derived extracellular vesicles (EVs). This study comprehensively investigated the effects of EVs derived from macrophages treated with biphasic calcium phosphate (BCP) ceramics (BEVs) on vital events associated with BCP-induced bone formation such as immune response, angiogenesis, and osteogenesis. It was found that compared with EVs derived from macrophages alone (control, CEVs), BEVs preferentially promoted macrophage polarization towards a wound-healing M2 phenotype, enhanced migration, angiogenic differentiation, and tube formation of human umbilical vein endothelial cells, and induced osteogenic differentiation of mesenchymal stem cells. Analysis of 15 differentially expressed microRNAs (DEMs) related to immune, angiogenesis, and osteogenesis suggested that BEVs exhibited good immunomodulatory, pro-angiogenic, and pro-osteogenic abilities, which might be attributed to their specific miRNA cargos. These findings not only deepen our understanding of biomaterial-mediated osteoinduction, but also suggest that EVs derived from biomaterial-treated macrophages hold great promise as therapeutic agents with desired immunomodulatory capacity for bone 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.

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.

Clinical usage of dental stem cells and their derived extracellular vesicles

Stem cell-based therapies remain at the forefront of tissue engineering and regenerative medicine because stem cells are a unique cell source with enormous potential to treat incurable diseases and even extend lifespans. The search for the best stem cell candidates continues to evolve and in recent years, dental stem cells have received significant attention due to their easy accessibility, high plasticity, and multipotential properties. Dental stem cells have been the subject of extensive research in both animal models and human clinical trials over the past two decades, and have demonstrated significant potential in ocular therapy, bone tissue engineering, and, of course, therapeutic applications in dentistry such as regenerative endodontics and periodontal tissue regeneration. These new sources of cells may be advantageous for cellular therapy and the advancement of regenerative medicine strategies, such as allogeneic transplantation or therapy with extracellular vesicles (EVs), which are functional nanoscale membrane vesicles produced by cells. This chapter discusses the accumulating research findings on cell-based regenerative therapy utilizing dental stem cells and their derived EVs, which could be a viable tool for the treatment of a variety of diseases and hence extremely valuable to mankind in the long run.

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.