Dental pulp stem cells suppress the proliferation of lymphocytes via transforming growth factor-β1

Flow Cytometry Illuminates Dental Stem Cells: a Systematic Review of Immunomodulatory and Regenerative Breakthroughs

BACKGROUND

Dental stem cells hold significant potential in regenerative medicine due to their multipotency, accessibility, and immunomodulatory effects. Flow cytometry is a critical tool for analyzing these cells, particularly in identifying and characterizing immunomodulatory markers that enhance their clinical applications. This systematic review aims to answer the question: "How does flow cytometry facilitate the identification and characterization of immunomodulatory markers in dental stem cells to enhance their application in regenerative medicine?".

METHODS

An exhaustive literature search was conducted in PubMed, retrieving 430 studies, of which 284 met inclusion criteria. Studies were selected based on the use of flow cytometry to analyze immunomodulatory markers in dental stem cells, focusing on methodologies, key findings, and challenges.

RESULTS

Of the 284 articles, 229 employed flow cytometry, with 115 reporting relevant results. Flow cytometry revealed important insights into the immunological interactions of various dental stem cells, including dental pulp stem cells, stem cells from human exfoliated deciduous teeth, periodontal ligament stem cells, and stem cells from the apical papilla, by identifying and characterizing immunomodulatory markers such as PD-L1, IDO, and TGF-β1.

CONCLUSIONS

Flow cytometry is essential for advancing the understanding of dental stem cells' immunomodulatory properties. Standardization of methodologies is required to overcome technical challenges and enhance the clinical applications of dental stem cells in regenerative medicine and immunotherapy.

Molars to Medicine: A Focused Review on the Pre-Clinical Investigation and Treatment of Secondary Degeneration following Spinal Cord Injury Using Dental Stem Cells

Spinal cord injury (SCI) can result in the permanent loss of mobility, sensation, and autonomic function. Secondary degeneration after SCI both initiates and propagates a hostile microenvironment that is resistant to natural repair mechanisms. Consequently, exogenous stem cells have been investigated as a potential therapy for repairing and recovering damaged cells after SCI and other CNS disorders. This focused review highlights the contributions of mesenchymal (MSCs) and dental stem cells (DSCs) in attenuating various secondary injury sequelae through paracrine and cell-to-cell communication mechanisms following SCI and other types of neurotrauma. These mechanistic events include vascular dysfunction, oxidative stress, excitotoxicity, apoptosis and cell loss, neuroinflammation, and structural deficits. The review of studies that directly compare MSC and DSC capabilities also reveals the superior capabilities of DSC in reducing the effects of secondary injury and promoting a favorable microenvironment conducive to repair and regeneration. This review concludes with a discussion of the current limitations and proposes improvements in the future assessment of stem cell therapy through the reporting of the effects of DSC viability and DSC efficacy in attenuating secondary damage after SCI.

Dental Pulp Cell Transplantation Combined with Regenerative Endodontic Procedures Promotes Dentin Matrix Formation in Mature Mouse Molars

Regenerative endodontic procedures (REPs) are promising for dental pulp tissue regeneration; however, their application in permanent teeth remains challenging. We assessed the potential combination of an REP and local dental pulp cell (DPC) transplantation in the mature molars of C57BL/6 mice with (REP + DPC group) or without (REP group) transplantation of DPCs from green fluorescent protein (GFP) transgenic mice. After 4 weeks, the regenerated tissue was evaluated by micro-computed tomography and histological analyses to detect odontoblasts, vasculogenesis, and neurogenesis. DPCs were assessed for mesenchymal and pluripotency markers. Four weeks after the REP, the molars showed no signs of periapical lesions, and both the REP and REP + DPC groups exhibited a pulp-like tissue composed of a cellular matrix with vessels surrounded by an eosin-stained acellular matrix that resembled hard tissue. However, the REP + DPC group had a broader cellular matrix and uniquely contained odontoblast-like cells co-expressing GFP. Vasculogenesis and neurogenesis were detected in both groups, with the former being more prominent in the REP + DPC group. Overall, the REP was achieved in mature mouse molars and DPC transplantation improved the outcomes by inducing the formation of odontoblast-like cells and greater vasculogenesis.

IWP-2 modulates the immunomodulatory properties of human dental pulp stem cells in vitro

AIM

To investigate the effect of IWP-2, Wnt inhibitor, on human dental pulp stem cells (hDPSCs) responses.

METHODOLOGY

hDPSCs were isolated from human dental pulp tissues. Cells were treated with 25 μM IWP-2 for 24 h, and subsequently, the gene expression profile was examined using high-throughput RNA sequencing. The mRNA expression was analysed using qPCR. The effect of IWP-2 was investigated in both normal and LPS-induced hDPSCs (inflamed hDPSCs). CD4+ T cells and CD14+ monocyte-derived macrophages were cultured with conditioned media of IWP-2 treated hDPSCs to observe the immunosuppressive property.

RESULTS

RNA sequencing indicated that IWP-2 significantly downregulated several KEGG pathways, including cytokine-cytokine receptor interaction, IL-17 signalling pathway, and TNF signalling pathway. In both normal and inflamed conditions, IWP-2 markedly upregulated TGFB1 mRNA expression while the mRNA expression of pro-inflammatory cytokines, TNFA, IL1B, IFNG, and IL6, was inhibited. In the inhibition experiment, the pretreatment with p38, MAPK, or PI3K inhibitors abolished the effects of IWP-2 in LPS-induced inflammation. In terms of immune cells, IWP-2-treated-inflamed hDPSCs conditioned media attenuated T cell proliferation and regulated regulatory T cell differentiation. In addition, the migratory property of macrophage was decreased after being exposed to IWP-2-treated inflamed hDPSCs conditioned media.

CONCLUSION

IWP-2 suppressed inflammatory cytokine expression in both normal and inflamed hDPSCs. Moreover, hDPSCs exerted the immunosuppressive property after IWP-2 treatment. These results suggest the role of Wnt in inflammatory responses and immunomodulation in dental pulp tissues.

Dental pulp stem cells accelerate wound healing through CCL2-induced M2 macrophages polarization

The crosstalk between mesenchymal stem cells (MSCs) and the host immune function plays a key role in the efficiency of tissue regeneration and wound healing. However, the difference in immunological modulation and tissue regeneration function between MSCs from different sources remains unclear. Compared to PDLSCs, BMMSCs, and ADSCs, DPSCs exhibited greater tissue regeneration potential and triggered more M2 macrophages in vivo. DPSCs elicited the polarization of M2a macrophages by conditioned medium and transwell assay and exhibited higher expression levels of C-C motif chemokine ligand 2 (CCL2). Specific blocking of CCL2 could significantly inhibit the DPSCs-induced polarization of M2 macrophages. DPSCs promoted wound healing of the palatal mucosa and M2 macrophages polarization in vivo, which could be significantly impaired by CCL2-neutralized antibody. Our data indicate that DPSCs exert better tissue regeneration potential and immunoregulatory function by secreting CCL2, which can enhance MSCs-mediated tissue regeneration or wound healing.

Dental Pulp Stem Cells for Bone Tissue Engineering: A Literature Review

Bone tissue engineering (BTE) is a promising approach for repairing and regenerating damaged bone tissue, using stem cells and scaffold structures. Among various stem cell sources, dental pulp stem cells (DPSCs) have emerged as a potential candidate due to their multipotential capabilities, ability to undergo osteogenic differentiation, low immunogenicity, and ease of isolation. This article reviews the biological characteristics of DPSCs, their potential for BTE, and the underlying transcription factors and signaling pathways involved in osteogenic differentiation; it also highlights the application of DPSCs in inducing scaffold tissues for bone regeneration and summarizes animal and clinical studies conducted in this field. This review demonstrates the potential of DPSC-based BTE for effective bone repair and regeneration, with implications for clinical translation.

Immunomodulatory Mechanism and Potential Application of Dental Pulp-Derived Stem Cells in Immune-Mediated Diseases

Dental pulp stem cells (DPSCs) are mesenchymal stem cells (MSCs) derived from dental pulp tissue, which have high self-renewal ability and multi-lineage differentiation potential. With the discovery of the immunoregulatory ability of stem cells, DPSCs have attracted much attention because they have similar or even better immunomodulatory effects than MSCs from other sources. DPSCs and their exosomes can exert an immunomodulatory ability by acting on target immune cells to regulate cytokines. DPSCs can also migrate to the lesion site to differentiate into target cells to repair the injured tissue, and play an important role in tissue regeneration. The aim of this review is to summarize the molecular mechanism and target cells of the immunomodulatory effects of DPSCs, and the latest advances in preclinical research in the treatment of various immune-mediated diseases, providing new reflections for their clinical application. DPSCs may be a promising source of stem cells for the treatment of immune-mediated diseases.

Advances in novel therapeutic approaches for periodontal diseases

Periodontal diseases are pathological processes resulting from infections and inflammation affecting the periodontium or the tissue surrounding and supporting the teeth. Pathogenic bacteria living in complex biofilms initiate and perpetuate this disease in susceptible hosts. In some cases, broad-spectrum antibiotic therapy has been a treatment of choice to control bacterial infection. However, increasing antibiotic resistance among periodontal pathogens has become a significant challenge when treating periodontal diseases. Thanks to the improved understanding of the pathogenesis of periodontal disease, which involves the host immune response, and the importance of the human microbiome, the primary goal of periodontal therapy has shifted, in recent years, to the restoration of homeostasis in oral microbiota and its harmonious balance with the host periodontal tissues. This shift in therapeutic goals and the drug resistance challenge call for alternative approaches to antibiotic therapy that indiscriminately eliminate harmful or beneficial bacteria. In this review, we summarize the recent advancement of alternative methods and new compounds that offer promising potential for the treatment and prevention of periodontal disease. Agents that target biofilm formation, bacterial quorum-sensing systems and other virulence factors have been reviewed. New and exciting microbiome approaches, such as oral microbiota replacement therapy and probiotic therapy for periodontal disease, are also discussed.

Dental Pulp Stem Cell Heterogeneity: Finding Superior Quality "Needles" in a Dental Pulpal "Haystack" for Regenerative Medicine-Based Applications

Human dental pulp stem/stromal cells (hDPSCs) derived from the permanent secondary dentition are recognised to possess certain advantageous traits, which support their potential use as a viable source of mesenchymal stem/stromal cells (MSCs) for regenerative medicine-based applications. However, the well-established heterogeneous nature of hDPSC subpopulations, coupled with their limited numbers within dental pulp tissues, has impeded our understanding of hDPSC biology and the translation of sufficient quantities of these cells from laboratory research, through successful therapy development and clinical applications. This article reviews our current understanding of hDPSC biology and the evidence underpinning the molecular basis of their heterogeneity, which may be exploited to distinguish individual subpopulations with specific or superior characteristics for regenerative medicine applications. Pertinent unanswered questions which still remain, regarding the developmental origins, hierarchical organisation, and stem cell niche locations of hDPSC subpopulations and their roles in hDPSC heterogeneity and functions, will further be explored. Ultimately, a greater understanding of how key features, such as specific cell surface, senescence and other relevant genes, and protein and metabolic markers, delineate between hDPSC subpopulations with contrasting stemness, proliferative, multipotency, immunomodulatory, anti-inflammatory, and other relevant properties is required. Such knowledge advancements will undoubtedly lead to the development of novel screening, isolation, and purification strategies, permitting the routine and effective identification, enrichment, and expansion of more desirable hDPSC subpopulations for regenerative medicine-based applications. Furthermore, such innovative measures could lead to improved cell expansion, manufacture, and banking procedures, thereby supporting the translational development of hDPSC-based therapies in the future.

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.

Dental Pulp Stem Cells Derived From Adult Human Third Molar Tooth: A Brief Review

The fields of regenerative medicine and stem cell-based tissue engineering have the potential of treating numerous tissue and organ defects. The use of adult stem cells is of particular interest when it comes to dynamic applications in translational medicine. Recently, dental pulp stem cells (DPSCs) have been traced in third molars of adult humans. DPSCs have been isolated and characterized by several groups. DPSCs have promising characteristics including self-renewal capacity, rapid proliferation, colony formation, multi-lineage differentiation, and pluripotent gene expression profile. Nevertheless, genotypic, and phenotypic heterogeneities have been reported for DPSCs subpopulations which may influence their therapeutic potentials. The underlying causes of DPSCs' heterogeneity remain poorly understood; however, their heterogeneity emerges as a consequence of an interplay between intrinsic and extrinsic cellular factors. The main objective of the manuscript is to review the current literature related to the human DPSCs derived from the third molar, with a focus on their physiological properties, isolation procedures, culture conditions, self-renewal, proliferation, lineage differentiation capacities and their prospective advances use in pre-clinical and clinical applications.

Immunomodulatory effects of phytosomal curcumin on related-micro RNAs, CD200 expression and inflammatory pathways in dental pulp stem cells

Human dental pulp stem cells (hDPSCs) have significant potential of immunomodulatory for therapeutic and regenerative biomedical applications compared to other mesenchymal stem cells (MSCs). Nowadays, alteration of gene expression is an important way to improve the performance of MSCs in the clinic. MicroRNAs (miRs) and CD200 are known to modulate the immune system in MSCs. Curcumin is famous for its anti-inflammatory impacts. Phytosomal curcumin (PC) is a nanoparticle synthesized from curcumin that removes the drawbacks of curcumin. The purpose of this research was to assess the effects of PC on the expression of the CD200 and four key miRNAs in immune system. PC (30 μM) treatment of hDPSCs could ameliorate their immunoregulatory property, presented by reduced expressions of miR-21, miR-155 and miR-126, as well as enhanced expressions of miR-23 and CD200. The PC was also able to reduce PI3K\AKT1\NF-κB expressions that were target genes for these miRs and involved in inflammatory pathways. Moreover, PC was more effective than curcumin in improving the immune modulation of hDPSCs. Evidence in this study suggested that PC mediates immunoregulatory activities in hDPSC via miRs and CD200 to regulate PI3K\AKT1\NF-κB signalling pathways, which may provide a theoretical basis for PC in the treatment of many diseases. SIGNIFICANCE OF THE STUDY: Autoimmune diseases or tooth caries are partly attributed to global health problems and their common drug treatments have several side effects. The goal of this study is dentin regeneration and autoimmune diseases treatment via stem cell-based approaches with phytosomal curcumin (PC), for the first time. Because dental pulp stem cells have unique advantages (including higher immunomodulatory capacity) over other mesenchymal stem cells, we considered them the best option for treating these diseases. Using PC, we try to increase the immunomodulatory properties of these cells.

Immunomodulatory functions of oral mesenchymal stem cells: Novel force for tissue regeneration and disease therapy

Mesenchymal stem cells (MSCs)-based therapeutic strategies have achieved remarkable efficacies. Oral tissue-derived MSCs, with powerful self-renewal and multilineage differentiation abilities, possess the features of abundant sources and easy accessibility and hold great potential in tissue regeneration and disease therapies. Oral MSCs mainly consist of periodontal ligament stem cells, gingival mesenchymal stem cells, dental pulp stem cells, stem cells from human exfoliated deciduous teeth, stem cells from the apical papilla, dental follicle stem cells, and alveolar bone-derived mesenchymal stem. Early immunoinflammatory response stage is the prerequisite phase of healing process. Besides the potent capacities of differentiation and regeneration, oral MSCs are capable of interacting with various immune cells and function as immunomodulatory regulators. Consequently, the immunomodulatory effects of oral MSCs during damage repair seem to be crucial for exploring novel immunomodulatory strategies to achieve disease recovery and tissue regeneration. Herein, we reviewed various oral MSCs with their immunomodulatory properties and the potential mechanism, as well as their effects on immunomodulation-mediated disease therapies and tissue regeneration.

Dental-Derived Mesenchymal Stem Cells: State of the Art

Mesenchymal stem cells (MSCs) could be identified in mammalian teeth. Currently, dental-derived MSCs (DMSCs) has become a collective term for all the MSCs isolated from dental pulp, periodontal ligament, dental follicle, apical papilla, and even gingiva. These DMSCs possess similar multipotent potential as bone marrow-derived MSCs, including differentiation into cells that have the characteristics of odontoblasts, cementoblasts, osteoblasts, chondrocytes, myocytes, epithelial cells, neural cells, hepatocytes, and adipocytes. Besides, DMSCs also have powerful immunomodulatory functions, which enable them to orchestrate the surrounding immune microenvironment. These properties enable DMSCs to have a promising approach in injury repair, tissue regeneration, and treatment of various diseases. This review outlines the most recent advances in DMSCs' functions and applications and enlightens how these advances are paving the path for DMSC-based therapies.

Calreticulin as a special marker to distinguish dental pulp stem cells from gingival mesenchymal stem cells

The construction of protein abundance profiles helps to interpret the clinical applications of stem cells. Dental pulp stem cells (DPSCs) and gingival mesenchymal stem cells (GMSCs) can be isolated from teeth and used as a highly convenient clinical potential material. Here, we aimed to explore commonalities and differences of DPSCs and GMSCs at the protein level. TMT-based quantitative proteomics and two-dimensional gel electrophoresis technology were used in combination to describe the protein profile of DPSCs and GMSCs extracted from the same donor. A total of 2821 proteins were identified by LC-MS/MS, of which 248 differentially abundant proteins (DAPs) were highly expressed in GMSCs while 782 proteins were highly expressed in DPSCs. The biological functions and molecular pathways of DAPs were annotated with GO enrichment and KEGG analysis. The relationship between molecular abundance and cell characteristics including source, proliferation, angiogenesis and inflammation were connected by WGCNA. Special markers, including Calreticulin (CALR), Annexin A5 (ANXA5) and Rho GDP dissociation inhibitor alpha (GDIR1), were proposed to distinguish DPSCs from GMSCs. Our results provide a molecular basis for in-depth understanding of the protein composition and special functions of dental stem cells, and promote the potential clinical application.

Immunomodulation and Regeneration Properties of Dental Pulp Stem Cells: A Potential Therapy to Treat Coronavirus Disease 2019

The coronavirus disease 2019 (COVID-19) pandemic, originating from Wuhan, China, is known to cause severe acute respiratory symptoms. The occurrence of a cytokine storm in the lungs is a critical step in the disease pathogenesis, as it causes pathological lesions, pulmonary edema, and acute respiratory distress syndrome, potentially resulting in death. Currently, there is no effective treatment that targets the cytokine storm and helps regenerate the damaged tissue. Mesenchymal stem cells (MSCs) are known to act as anti-inflammatory/immunomodulatory candidates and activate endogenous regeneration. As a result, MSC therapy is a potential treatment approach for COVID-19. Intravenous injection of clinical-grade MSCs into COVID-19 patients can induce an immunomodulatory response along with improved lung function. Dental pulp stem cells (DPSCs) are considered a potential source of MSCs for immunomodulation, tissue regeneration, and clinical application. Although some current clinical trials have treated COVID-19 patients with DPSCs, this therapy has not been approved. Here, we review the potential use of DPSCs and their significance in the development of a therapy for COVID-19.

An update of knowledge on the regulatory role of Treg cells in apical periodontitis

Apical periodontitis (AP) is a prevalent infectious and inflammatory disorder that involves inflammation of periapical tissues and the disintegration of alveolar bone. AP may eventually lead to tooth loss if not timely treated. This disease is caused by pathogenic bacteria in the necrotic pulps and root canals, thereby triggering responses from the innate and adaptive immune system of the periapical tissues. Regulatory T (Treg) cells play a major role in maintaining immune homoeostasis and immunological self-tolerance; however, these only account for roughly 5%-10% of human peripheral CD4⁺ T cells. Several studies have examined the possible role and underlying mechanism of Treg cells in different inflammatory and autoimmune disorders to facilitate the development of novel treatments for these diseases. Recent studies have indicated that Treg cells may gather at the sites of infection, thus limiting the generation of immune responses and bone resorption in the periapical area. This review will summarize studies regarding the presence and regulatory role of Treg cells in AP.

Oral Mesenchymal Stem/Progenitor Cells: The Immunomodulatory Masters

Oral mesenchymal stem/progenitor cells (MSCs) are renowned in the field of tissue engineering/regeneration for their multilineage differentiation potential and easy acquisition. These cells encompass the periodontal ligament stem/progenitor cells (PDLSCs), the dental pulp stem/progenitor cells (DPSCs), the stem/progenitor cells from human exfoliated deciduous teeth (SHED), the gingival mesenchymal stem/progenitor cells (GMSCs), the stem/progenitor cells from the apical papilla (SCAP), the dental follicle stem/progenitor cells (DFSCs), the bone marrow mesenchymal stem/progenitor cells (BM-MSCs) from the alveolar bone proper, and the human periapical cyst-mesenchymal stem cells (hPCy-MSCs). Apart from their remarkable regenerative potential, oral MSCs possess the capacity to interact with an inflammatory microenvironment. Although inflammation might affect the properties of oral MSCs, they could inversely exert a multitude of immunological actions to the local inflammatory microenvironment. The present review discusses the current understanding about the immunomodulatory role of oral MSCs both in periodontitis and systemic diseases, their "double-edged sword" uniqueness in inflammatory regulation, their affection of the immune system, and the underlying mechanisms, involving oral MSC-derived extracellular vesicles.

Inflammatory Cytokines and Biodegradable Scaffolds in Dental Mesenchymal Stem Cells Priming

Mesenchymal stem cells (MSCs) are multipotent stem cells with wide-ranging clinical applications due to their ability to regenerate tissue from mesenchymal origin and their capability of suppressing immune responses, thus reducing the likelihood of graft versus host disease after transplantation. MSCs can be isolated from a variety of sources including bone marrow, adipose tissue, umbilical cord blood, and immature teeth. Dental stem cells (DSCs) possess progenitor and immunomodulatory abilities as the other MSC types and because they can be easily isolated, are considered as attractive therapeutic agents in regenerative dentistry. Recently, it has been shown that DSCs seeded onto newly developed synthetic biomaterial scaffolds have retained their potential for proliferation and at the same time have enhanced capabilities for differentiation and immunosuppression. The scaffolds are becoming more efficient at MSC priming as researchers learn how short peptide sequences alter the adhesive and proliferative capabilities of the scaffolds by stimulating or inhibiting classical osteogenic pathways. New findings on how to modulate the inflammatory microenvironment, which can prime DSCs for differentiation, combined with the use of next generation scaffolds may significantly improve their therapeutic potential. In this review, we summarize current findings regarding DSCs as a potential regenerative therapy, including stem cell priming with inflammatory cytokines, types of scaffolds currently being explored and the modulation of scaffolds to regulate immune response and promote growth.

Mesenchymal Stem/Stromal Cells Derived from Dental Tissues: A Comparative In Vitro Evaluation of Their Immunoregulatory Properties Against T cells

Bone marrow mesenchymal stem/stromal cells (BM-MSCs) have immunoregulatory properties and have been used as immune regulators for the treatment of graft-versus-host disease (GVHD). Human dental tissue mesenchymal stem cells (DT-MSCs) constitute an attractive alternative to BM-MSCs for potential clinical applications because of their accessibility and easy preparation. The aim of this in vitro study was to compare MSCs from dental pulp (DP-MSCs), gingival tissue (G-MSCs), and periodontal ligament (PDL-MSCs) in terms of their immunosuppressive properties against lymphoid cell populations enriched for CD3⁺ T cells to determine which MSCs would be the most appropriate for in vivo immunoregulatory applications. BM-MSCs were included as the gold standard. Our results demonstrated, in vitro, that MSCs from DP, G, and PDL showed immunoregulatory properties similar to those from BM, in terms of the cellular proliferation inhibition of both CD4⁺- and CD8⁺-activated T-cells. This reduced proliferation in cell co-cultures correlated with the production of interferon-γ and tumor necrosis factor alpha (TNF-α) and the upregulation of programmed death ligand 1 (PD-L1) in MSCs and cytotoxic T-cell-associated Ag-4 (CTLA-4) in T-cells and increased interleukin-10 and prostaglandin E₂ production. Interestingly, we observed differences in the production of cytokines and surface and secreted molecules that may participate in T-cell immunosuppression in co-cultures in the presence of DT-MSCs compared with BM-MSCs. Importantly, MSCs from four sources favored the generation of T-cell subsets displaying the regulatory phenotypes CD4⁺CD25⁺Foxp3⁺ and CD4⁺CD25⁺CTLA-4⁺. Our results in vitro indicate that, in addition to BM-MSCs, MSCs from all of the dental sources analyzed in this study might be candidates for future therapeutic applications.

Osteogenically differentiated mesenchymal stem cells induced by hydrolyzed fish collagen maintain their immunomodulatory effects

AIMS

The reciprocity between stem cells and biomaterials is an essential topic in bone tissue engineering. Bone marrow mesenchymal stromal cells (BMSCs) have attracted considerable attention in regenerative medicine owing to their ability to self-renew and differentiate into osteoblasts, and more importantly, their immunomodulatory effects on the immune response. Ideal biomaterials should be osteo-inductive, environmentally sustainable, and economical. Our previous study showed that hydrolyzed fish collagen (HFC) can meet each of the above requirements. However, it is still unclear whether BMSCs maintain their immunomodulatory properties after osteogenic differentiation induced by HFC.

MAIN METHODS

Non-commercial sources of BMSCs were isolated from Sprague-Dawley (SD) rats. Osteogenically differentiated BMSCs induced by HFC and undifferentiated BMSCs were co-cultured with PBMC or NR 8383 macrophages, respectively. Cell proliferation of PBMC was examined using a BrdU uptake assay. In addition, the IL-6, TGF-β1, IL-10, PGE2, and nitric oxide levels were determined. The expressions of TSG-6 (TNF-stimulated gene 6) and IDO (indoleamine 2, 3-dioxygenase) genes were analyzed using qRT-PCR.

KEY FINDINGS

The results revealed that HFC-induced BMSCs suppressed the proliferation of PBMC. The expression levels of anti-inflammatory mediators including IL-6, TGF-β1, and PGE2 significantly increased after 48 h of co-culture. Moreover, the nitric oxide production increased during osteogenesis induced by HFC, whereas the level of TSG-6 and IDO remained unchanged after osteogenic differentiation. HFC-BMSCs inhibited the inflammatory mediator production (IL-1β, TNF-α) in LPS-stimulated macrophages.

SIGNIFICANCE

Taken together, these findings suggest that the immunomodulation ability is still retained in osteogenically differentiated BMSCs induced by HFC.

Angiogenic properties of dental pulp stem cells conditioned medium on endothelial cells in vitro and in rodent orthotopic dental pulp regeneration

Objectives

To evaluate the effect of SHED-CM on the proliferation, differentiation, migration ability, cell death, gene expression and production of VEGF of HUVEC in vitro and in a rodent orthotopic dental pulp regeneration.

Methods

Three culture media [M199, DMEM/Ham's F12 and DMEM/Ham's F12 conditioned by SHEDs] were used as experimental groups. SHED-CM was prepared maintaining confluent cells in culture without serum for 3 days. The proliferation and cell death marker of HUVECs were assessed using flow cytometry. The capacity of formation of vascular-like structures was analyzed in cells grown over Matrigel^® in hypoxic condition. HUVECs migration was followed using the scratch test. VEGF-A expression in HUVECs was assessed using real time RT-qPCR; and VEGF synthesis with ELISA test. SHED-CM was also applied in rodent ortotopic model of dental pulp regeneration in rats. The formed tissue was submitted to histological and immunohistochemical analyses.

Results

SHED-CM promoted significantly lower expression of 7AAD in HUVECs; whereas the expression of the Ki67 was similar in all groups. The vascular-like structures were observed in all groups. Migration of SHED-CM group was faster than DMEM/Ham's F12. SHED-CM induced similar expression of VEGF-A than M199, and higher than DMEM/Ham's F12. SHED-CM induced significantly higher VEGF synthesis than other media. SHED-CM induced formation of a vascularized connective tissue inside the root canal.

Conclusion

The study showed that SHEDs release angiogenic and cytoprotective factors, which are of great importance for tissue engineering.

Clinical significance

SHED-CM could be an option to the use of stem cells in tissue engineering.

The Presence and involvement of interleukin-17 in apical periodontitis

Apical periodontitis (AP) is a chronic inflammatory disease characterized by periapical tissue inflammation and destruction of the associated alveolar bone. It is caused by microbial infections within the root canal and the resultant host immune responses in the periapical tissues. The proinflammatory cytokine interleukin (IL)-17 has been shown to play an important role in many inflammatory diseases. There is increasing evidence of the presence of IL-17 in AP, which might be associated with disease pathogenesis. Moreover, several animal studies indicate the potential role of IL-17 in periapical inflammation and the resultant bone resorption in AP. This article reviews recent studies regarding the collective in vitro, in vivo and clinical evidence of the presence and involvement of IL-17 in AP. A search related to IL-17 in apical periodontitis was conducted on PubMed, EMBASE and Web of Science databases using keywords and controlled vocabulary. Two independent reviewers first screened titles and abstracts and then the full texts that were included. A total of 25 papers were identified, of the 25 included articles, 7 involved laboratory studies on cell cultures, 11 involved animal experimentations, and 7 were observational studies using human clinical samples. In conclusion, evidence for the presence of IL-17 in AP from human and animal models is clear. However, there is relatively little information currently available that would highlight the specific role of IL-17 in AP.

Mechanisms underlying dental-derived stem cell-mediated neurorestoration in neurodegenerative disorders

BACKGROUND

Neurodegenerative disorders have a complex pathology and are characterized by a progressive loss of neuronal architecture in the brain or spinal cord. Neuroprotective agents have demonstrated promising results at the preclinical stage, but this has not been confirmed at the clinical stage. Thus far, no neuroprotective drug that can prevent neuronal degeneration in patients with neurodegenerative disorders is available.

MAIN BODY

Recent studies have focused on neurorestorative measures, such as cell-based therapy, rather than neuroprotective treatment. The utility of cell-based approaches for the treatment of neurodegenerative disorders has been explored extensively, and the results have been somewhat promising with regard to reversing the outcome. Because of their neural crest origin, ease of harvest, accessibility, ethical suitability, and potential to differentiate into the neurogenic lineage, dental-derived stem cells (DSCs) have become an attractive source for cell-based neurorestoration therapies. In the present review, we summarize the possible use of DSC-based neurorestoration therapy as an alternative treatment for neurodegenerative disorders, with a particular emphasis on the mechanism underlying recovery in neurodegenerative disorders.

CONCLUSION

Transplantation research in neurodegenerative diseases should aim to understand the mechanism providing benefits both at the molecular and functional level. Due to their ease of accessibility, plasticity, and ethical suitability, DSCs hold promise to overcome the existing challenges in the field of neurodegeneration through multiple mechanisms, such as cell replacement, bystander effect, vasculogenesis, synaptogenesis, immunomodulation, and by inhibiting apoptosis.

The role of TGF-beta signaling in dendritic cell tolerance

Transforming growth factor beta (TGF-β) is a pleiotropic cytokine present in vertebrate and invertebrate organisms that functions in numerous physiological and pathological processes. TGF-β impacts all the cells of the immune system, and of the three known TGF-β isoforms, TGF-β1 is the predominant isoform expressed in immune cells. TGF-β1 is known to play a pivotal role in the function of all immune cells especially in the regulation of T cell development and in the induction of immunological tolerance in dendritic cells (DCs). Based on the importance of DCs in regulation of the innate and adaptive arms of the immune system, in this review we explore the regulatory functions of TGF-β required for establishment and maintenance of DC-mediated immune tolerance.

Dental Mesenchymal Stem Cell-Based Translational Regenerative Dentistry: From Artificial to Biological Replacement

Dentistry is a continuously changing field that has witnessed much advancement in the past century. Prosthodontics is that branch of dentistry that deals with replacing missing teeth using either fixed or removable appliances in an attempt to simulate natural tooth function. Although such "replacement therapies" appear to be easy and economic they fall short of ever coming close to their natural counterparts. Complications that arise often lead to failures and frequent repairs of such devices which seldom allow true physiological function of dental and oral-maxillofacial tissues. Such factors can critically affect the quality of life of an individual. The market for dental implants is continuously growing with huge economic revenues. Unfortunately, such treatments are again associated with frequent problems such as peri-implantitis resulting in an eventual loss or replacement of implants. This is particularly influential for patients having co-morbid diseases such as diabetes or osteoporosis and in association with smoking and other conditions that undoubtedly affect the final treatment outcome. The advent of tissue engineering and regenerative medicine therapies along with the enormous strides taken in their associated interdisciplinary fields such as stem cell therapy, biomaterial development, and others may open arenas to enhancing tissue regeneration via designing and construction of patient-specific biological and/or biomimetic substitutes. This review will overview current strategies in regenerative dentistry while overviewing key roles of dental mesenchymal stem cells particularly those of the dental pulp, until paving the way to precision/translational regenerative medicine therapies for future clinical use.

Allogeneic transplantation of mobilized dental pulp stem cells with the mismatched dog leukocyte antigen type is safe and efficacious for total pulp regeneration

Background

We recently demonstrated that autologous transplantation of mobilized dental pulp stem cells (MDPSCs) was a safe and efficacious potential therapy for total pulp regeneration in a clinical study. The autologous MDPSCs, however, have some limitations to overcome, such as limited availability of discarded teeth from older patients. In the present study, we investigated whether MDPSCs can be used for allogeneic applications to expand their therapeutic use.

Methods

Analysis of dog leukocyte antigen (DLA) was performed using polymerase chain reaction from blood. Canine allogeneic MDPSCs with the matched and mismatched DLA were transplanted with granulocyte-colony stimulating factor in collagen into pulpectomized teeth respectively (n = 7, each). Results were evaluated by hematoxylin and eosin staining, Masson trichrome staining, PGP9.5 immunostaining, and BS-1 lectin immunostaining performed 12 weeks after transplantation. The MDPSCs of the same DLA used in the first transplantation were further transplanted into another pulpectomized tooth and evaluated 12 weeks after transplantation.

Results

There was no evidence of toxicity or adverse events of the allogeneic transplantation of the MDPSCs with the mismatched DLA. No adverse event of dual transplantation of the MDPSCs with the matched and mismatched DLA was observed. Regenerated pulp tissues including neovascularization and neuronal extension were quantitatively and qualitatively similar at 12 weeks in both matched and mismatched DLA transplants. Regenerated pulp tissue was similarly observed in the dual transplantation as in the single transplantation of MDPSCs both with the matched and mismatched DLA.

Conclusions

Dual allogeneic transplantation of MDPSCs with the mismatched DLA is a safe and efficacious method for total pulp regeneration.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0855-8) contains supplementary material, which is available to authorized users.

The Crosstalk between HDPSCs and HUCMSCs on Proliferation and Osteogenic Genes Expression in Coculture System

Objectives: The present study established a non-contact coculture system in vitro, aiming to investigate the crosstalk between human dental pulp stem cells (hDPSCs) and human umbilical cord mesenchymal stem cells (hUCMSCs) on proliferation activity and osteogenic genes expression through paracrine. Materials and methods: The stemness of hDPSCs and hUCMSCs were identified by flow cytometric analysis and multipotential differentiation assays. With the help of transwell inserts, the non-contact coculture system in vitro was established between hDPSCs and hUCMSCs. EdU labeling analysis and Western Blot were used to detect the proliferation activity. The mRNA and protein levels of osteogenic genes were evaluated by RT-PCR and Western Blot. The expression of elements in Akt/mTOR signaling pathway were detected by Western Blot. Results: Both hDPSCs and hUCMSCs were positive to MSCs specific surface markers and had multi-differentiation potential. The proportion of EdU-positive cells increased and the expression of CDK6 and CYCLIN A were up-regulated in cocultured hDPSCs. Both prior coculture and persistent coculture improved mRNA and protein levels of osteogenic genes in hDPSCs. While in cocultured hUCMSCs, no statistical differences were observed on proliferation and osteogenesis. The phosphorylation of Akt and mTOR was up-regulated in cocultured hDPSCs. Conclusions: The crosstalk between hDPSCs and hUCMSCs in coculture system increased the proliferation activity and enhanced osteogenic genes expression in hDPSCs. Akt/mTOR signaling pathway might take part in the enhancing effects in both cell proliferation and gene expression.

Human Dental Pulp Stem Cells Suppress Alloantigen-induced Immunity by Stimulating T Cells to Release Transforming Growth Factor Beta

INTRODUCTION

Human dental pulp stem cells (hDPSCs) are ideal candidates for regenerating damaged dental tissue. To examine the possibility that hDPSCs may be used to regenerate pulp, we tested their in vitro effects on acute allogeneic immune responses.

METHODS

A peripheral blood mononuclear cell (PBMC) proliferation assay and immunoglobulin (Ig) production assay were performed to evaluate the immunosuppressive properties of hDPSCs.

RESULTS

The mixed lymphocyte reaction was suppressed by incubation with hDPSCs. Transforming growth factor beta (TGF-β) was the major soluble factor responsible for inhibiting the allogeneic proliferation of PBMCs. The production of IgM and IgG by allogeneic activation of responder B lymphocytes was also completely abrogated by TGF-β released from hDPSCs via interferon gamma in response to activation of the responder T lymphocytes.

CONCLUSIONS

hDPSCs inhibit acute allogeneic immune responses by their release of TGF-β as a result of allogeneic stimulation of T lymphocytes. This study provides an insight into the potential clinical use of hDPSCs for allogeneic transplantation.

The Neurovascular Properties of Dental Stem Cells and Their Importance in Dental Tissue Engineering

Within the field of tissue engineering, natural tissues are reconstructed by combining growth factors, stem cells, and different biomaterials to serve as a scaffold for novel tissue growth. As adequate vascularization and innervation are essential components for the viability of regenerated tissues, there is a high need for easily accessible stem cells that are capable of supporting these functions. Within the human tooth and its surrounding tissues, different stem cell populations can be distinguished, such as dental pulp stem cells, stem cells from human deciduous teeth, stem cells from the apical papilla, dental follicle stem cells, and periodontal ligament stem cells. Given their straightforward and relatively easy isolation from extracted third molars, dental stem cells (DSCs) have become an attractive source of mesenchymal-like stem cells. Over the past decade, there have been numerous studies supporting the angiogenic, neuroprotective, and neurotrophic effects of the DSC secretome. Together with their ability to differentiate into endothelial cells and neural cell types, this makes DSCs suitable candidates for dental tissue engineering and nerve injury repair.