Stem cells from exfoliated deciduous teeth alleviate hyposalivation caused by Sjögren syndrome

SHED-exos promote saliva secretion by suppressing p-ERK1/2-mediated apoptosis in glandular cells

OBJECTIVES

Confirm that stem cells from human exfoliated deciduous teeth-derived exosomes (SHED-exos) can limit inflammation-triggered epithelial cell apoptosis and explore the molecular mechanism.

METHODS

SHED-exos were injected into the submandibular glands (SMGs) of non-obese diabetic (NOD) mice, an animal model of Sjögren's syndrome (SS). Cell death was evaluated by western blotting and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling staining.

RESULTS

SHED-exos treatment promoted the saliva flow rates of NOD mice, accompanied by decreased cleaved caspase-3 levels and apoptotic cell numbers in SMGs. SHED-exos inhibited autophagy, pyroptosis, NETosis, ferroptosis, necroptosis and oxeiptosis marker expression in SS-damaged glands. Mechanistically, Kyoto Encyclopedia of Genes and Genomes analysis of exosomal miRNAs suggested that the rat sarcoma virus (RAS)/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway might play an important role. In vivo, the expression of Kirsten RAS, Harvey RAS, MEK1/2 and p-ERK1/2 was upregulated in SMGs, and this change was blocked by SHED-exos treatment. In vitro, SHED-exos suppressed p-ERK1/2 activation and increased cleaved caspase-3 and apoptotic cell numbers, which were induced by IFN-γ.

CONCLUSION

SHED-exos suppress epithelial cell death, which is responsible for promoting salivary secretion. SHED-exos inhibited inflammation-triggered epithelial cell apoptosis by suppressing p-ERK1/2 activation, which is involved in these effects.

SHED-derived exosomes ameliorate hyposalivation caused by Sjögren's syndrome via Akt/GSK-3β/Slug-mediated ZO-1 expression

BACKGROUND

Sjögren's syndrome (SS) is an autoimmune disorder characterized by sicca syndrome and/or systemic manifestations. The treatment is still challenging. This study aimed to explore the therapeutic role and mechanism of exosomes obtained from the supernatant of stem cells derived from human exfoliated deciduous teeth (SHED-exos) in sialadenitis caused by SS.

METHODS

SHED-exos were administered to the submandibular glands (SMGs) of 14-week-old non-obese diabetic (NOD) mice, an animal model of the clinical phase of SS, by local injection or intraductal infusion. The saliva flow rate was measured after pilocarpine intraperitoneal injection in 21-week-old NOD mice. Protein expression was examined by western blot analysis. Exosomal microRNA (miRNAs) were identified by microarray analysis. Paracellular permeability was evaluated by transepithelial electrical resistance measurement.

RESULTS

SHED-exos were injected into the SMG of NOD mice and increased saliva secretion. The injected SHED-exos were taken up by glandular epithelial cells, and further increased paracellular permeability mediated by zonula occluden-1 (ZO-1). A total of 180 exosomal miRNAs were identified from SHED-exos, and Kyoto Encyclopedia of Genes and Genomes analysis suggested that the phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt) pathway might play an important role. SHED-exos treatment down-regulated phospho-Akt (p-Akt)/Akt, phospho-glycogen synthase kinase 3β (p-GSK-3β)/GSK-3β, and Slug expressions and up-regulated ZO-1 expression in SMGs and SMG-C6 cells. Both the increased ZO-1 expression and paracellular permeability induced by SHED-exos were abolished by insulin-like growth factor 1, a PI3K agonist. Slug bound to the ZO-1 promoter and suppressed its expression. For safer and more effective clinical application, SHED-exos were intraductally infused into the SMGs of NOD mice, and saliva secretion was increased and accompanied by decreased levels of p-Akt/Akt, p-GSK-3β/GSK-3β, and Slug and increased ZO-1 expression.

CONCLUSION

Local application of SHED-exos in SMGs can ameliorate Sjögren syndrome-induced hyposalivation by increasing the paracellular permeability of glandular epithelial cells through Akt/GSK-3β/Slug pathway-mediated ZO-1 expression.

Dental Pulp Stem Cells for Salivary Gland Regeneration-Where Are We Today?

Xerostomia is the phenomenon of dry mouth and is mostly caused by hypofunction of the salivary glands. This hypofunction can be caused by tumors, head and neck irradiation, hormonal changes, inflammation or autoimmune disease such as Sjögren's syndrome. It is associated with a tremendous decrease in health-related quality of life due to impairment of articulation, ingestion and oral immune defenses. Current treatment concepts mainly consist of saliva substitutes and parasympathomimetic drugs, but the outcome of these therapies is deficient. Regenerative medicine is a promising approach for the treatment of compromised tissue. For this purpose, stem cells can be utilized due to their ability to differentiate into various cell types. Dental pulp stem cells are adult stem cells that can be easily harvested from extracted teeth. They can form tissues of all three germ layers and are therefore becoming more and more popular for tissue engineering. Another potential benefit of these cells is their immunomodulatory effect. They suppress proinflammatory pathways of lymphocytes and could therefore probably be used for the treatment of chronic inflammation and autoimmune disease. These attributes make dental pulp stem cells an interesting tool for the regeneration of salivary glands and the treatment of xerostomia. Nevertheless, clinical studies are still missing. This review will highlight the current strategies for using dental pulp stem cells in the regeneration of salivary gland tissue.

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.

Therapeutic benefits of factors derived from stem cells from human exfoliated deciduous teeth for radiation-induced mouse xerostomia

Radiation therapy for head and neck cancers is frequently associated with adverse effects on the surrounding normal tissue. Irreversible damage to radiation-sensitive acinar cells in the salivary gland (SG) causes severe radiation-induced xerostomia (RIX). Currently, there are no effective drugs for treating RIX. We investigated the efficacy of treatment with conditioned medium derived from stem cells from human exfoliated deciduous teeth (SHED-CM) in a mouse RIX model. Intravenous administration of SHED-CM, but not fibroblast-CM (Fibro-CM), prevented radiation-induced cutaneous ulcer formation (p < 0.0001) and maintained SG function (p < 0.0001). SHED-CM treatment enhanced the expression of multiple antioxidant genes in mouse RIX and human acinar cells and strongly suppressed radiation-induced oxidative stress. The therapeutic effects of SHED-CM were abolished by the superoxide dismutase inhibitor diethyldithiocarbamate (p < 0.0001). Notably, quantitative liquid chromatography-tandem mass spectrometry shotgun proteomics of SHED-CM and Fibro-CM identified eight proteins activating the endogenous antioxidant system, which were more abundant in SHED-CM than in Fibro-CM (p < 0.0001). Neutralizing antibodies against those activators reduced antioxidant activity of SHED-CM (anti-PDGF-D; p = 0.0001, anti-HGF; p = 0.003). Our results suggest that SHED-CM may provide substantial therapeutic benefits for RIX primarily through the activation of multiple antioxidant enzyme genes in the target tissue.

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

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

Therapeutic potential of dental pulp stem cells and their derivatives: Insights from basic research toward clinical applications

For more than 20 years, researchers have isolated and identified postnatal dental pulp stem cells (DPSCs) from different teeth, including natal teeth, exfoliated deciduous teeth, healthy teeth, and diseased teeth. Their mesenchymal stem cell (MSC)-like immunophenotypic characteristics, high proliferation rate, potential for multidirectional differentiation and biological features were demonstrated to be superior to those of bone marrow MSCs. In addition, several main application forms of DPSCs and their derivatives have been investigated, including stem cell injections, modified stem cells, stem cell sheets and stem cell spheroids. In vitro and in vivo administration of DPSCs and their derivatives exhibited beneficial effects in various disease models of different tissues and organs. Therefore, DPSCs and their derivatives are regarded as excellent candidates for stem cell-based tissue regeneration. In this review, we aim to provide an overview of the potential application of DPSCs and their derivatives in the field of regenerative medicine. We describe the similarities and differences of DPSCs isolated from donors of different ages and health conditions. The methodologies for therapeutic administration of DPSCs and their derivatives are introduced, including single injections and the transplantation of the cells with a support, as cell sheets, or as cell spheroids. We also summarize the underlying mechanisms of the regenerative potential of DPSCs.

Stem cells from exfoliated deciduous teeth transplantation ameliorates Sjögren's syndrome by secreting soluble PD-L1

Mesenchymal stem cell transplantation (MSCT) regulates immune cells, and is a promising therapeutic approach for treating autoimmune diseases. Stem cells from human exfoliated deciduous teeth (SHED) are a unique postnatal stem cell population from the cranial neural crest with high self-renewal, multipotent differentiation, and superior immunomodulatory properties. However, the mechanisms by which SHED can treat autoimmune diseases remain unclear. Sjögren's syndrome (SS) is an autoimmune disease histologically characterized by high lymphocytic infiltration in the salivary and lacrimal glands that results in dryness symptoms. This study explores the potential of systemic transplantation of SHED to ameliorate SS-induced dryness symptoms in mice. Overall, SHED could rescue the balance of regulatory T cell (Treg)/T helper cell 17 (Th17) in the recipient SS mice. Mechanistically, SHED promoted Treg conversion and inhibited Th17 function via paracrine effects, which were related to the secretion of soluble programmed cell death ligand 1 (sPD-L1). Moreover, it directly induced Th17 apoptosis via cell-cell contact, leading to the up-regulation of Treg and down-regulation of Th17 cells. In summary, SHED-mediated rescue of Treg/Th17 balance via the sPD-L1/PD-1 pathway ameliorates the gland inflammation and dryness symptoms in SS mice. These findings suggest that SHED are a promising stem cell source for the treatment of autoimmune diseases in the clinical setting.

Treatment of Sjögren's Syndrome with Mesenchymal Stem Cells: A Systematic Review

Mesenchymal stem cells (MSCs) are ubiquitous in the human body. Mesenchymal stem cells were initially isolated from bone marrow and later from other organs such as fatty tissues, umbilical cords, and gingiva. Their secretory capacities give them interesting immunomodulatory properties in cell therapy. Some studies have explored the use of MSCs to treat Sjögren's syndrome (SS), a chronic inflammatory autoimmune disease that mainly affects exocrine glands, including salivary and lacrimal glands, although current treatments are only palliative. This systematic review summarizes the current data about the application of MSCs in SS. Reports show improvements in salivary secretions and a decrease in lymphocytic infiltration in salivary glands in patients and mice with SS after intravenous or infra-peritoneal injections of MSCs. MSC injections led to a decrease in inflammatory cytokines and an increase in anti-inflammatory cytokines. However, the intrinsic mechanism of action of these MSCs currently remains unknown.

Tetrahedral Framework Nucleic Acids Reestablish Immune Tolerance and Restore Saliva Secretion in a Sjögren's Syndrome Mouse Model

As one of the most frequent autoimmune diseases, Sjogren's syndrome (SS) is characterized by overactive lymphocytic infiltration in the exocrine glands, with ensuing dry mouth and dry eyes. Unfortunately, so far, there are no appropriate therapies without causing overall immunosuppression. Tetrahedral framework nucleic acids (tFNAs) were regarded as promising nanoscale materials whose immunomodulatory capabilities have already been verified. Herein, we reveal, for the first time, that tFNAs were utilized to treat SS in female nonobese diabetic (NOD) mice, the animal model used for SS. We proved a 250 nM tFNA treatment was successful in suppressing inflammation and stimulating saliva secretion in NOD mice. Specialised proteins for the secretory function and structure of acinar cells in submandibular glands (SMGs) were restored. It has been the permanent goal for SS treatment to establish immune tolerance and stop disease development. Surprisingly, tFNA treatment guided T cells toward regulatory T cells (Tregs), while suppressing T helper (Th) cell responses. Th cells include Th1, Th17, and follicular helper T (Tfh) cells. Tregs are highly significant in immune tolerance. Inducing Tregs is a promising approach to reestablish immune tolerance. Comparable results were also observed in B cell responses. Reductions in the percentage of germinal center (GC) B cells and plasma cells were detected, and a marked increase in the percentage of regulatory B cells (Bregs) was also noticed. The mechanisms of inducing Tregs may associated with cytokine changes. Changes of T cell subsets, especially changes of Tfh, may influence the differentiation of B cells accordingly. Collectively, our results demonstrated the immunomodulatory capacities of tFNAs once again, which may provide a novel, safe, and effective option for the treatment of SS and other autoimmune diseases.

Labial gland-derived mesenchymal stem cells and their exosomes ameliorate murine Sjögren's syndrome by modulating the balance of Treg and Th17 cells

Background

Sjögren's syndrome (SS) is a chronic, systemic autoimmune disorder characterized by sicca syndrome and/or systemic manifestations. The disease severely affects the health and life of patients, and the treatment of SS has always been a clinical challenge and essentially palliative. Mesenchymal stem cells (MSCs) have been reported to exert immunomodulatory effects and as a potential novel therapeutic strategy for SS. Labial gland-derived MSCs (LGMSCs) are a population of resident stem cells in the labial gland, first isolated by our group. Exosomes released by MSCs contain a large variety of bioactive molecules and considered to function as an extension of MSCs.

Methods

LGMSCs were isolated from patients who were needed surgery to remove the lip mucocele and LGMSCs derived exosomes (LGMSC-Exos) were isolated by ultracentrifugation. The non-obese diabetic (NOD) mice were treated with LGMSCs or LGMSC-Exos by tail vein injection. The saliva flow rate of mice was determined and salivary glands were dissected and stained with hematoxylin and eosin. In vitro, peripheral blood mononuclear cells (PBMCs) from SS patients were cocultured with LGMSCs or LGMSC-Exos. Percentage of T helper 17 (Th17) cells and regulatory T (Treg) cells were determined by flow cytometry. The serum levels of cytokines in NOD mice and in the supernatant of the co-culture system by ELISA.

Results

Treatment with LGMSCs or LGMSC-Exos reduced inflammatory infiltration in the salivary glands, and restored salivary gland secretory function in NOD mice. Importantly, LGMSCs or LGMSC-Exos were demonstrated to inhibit the differentiation of Th17 cells but promote the induction of Treg cells in NOD mice and PBMCs from SS patients in vitro, accompanied by reduced interleukin 17 (IL-17), interferon gamma, and IL-6 levels and enhanced transforming growth factor beta and IL-10 secretion by T cells.

Conclusions

LGMSCs are potential candidates for MSCs-based therapy and LGMSC-Exos might be utilized for establishing a new cell-free therapy against SS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02541-0.

Secreted factors from dental pulp stem cells improve Sjögren's syndrome via regulatory T cell-mediated immunosuppression

Background

Sjögren’s syndrome (SS) is a chronic autoimmune disease primarily characterized by inflammation in the salivary and lacrimal glands. Activated T cells contribute to disease pathogenesis by producing proinflammatory cytokines, which leads to a positive feedback loop establishment. The study aimed to evaluate the effects of secreted factors derived from dental pulp stem cells (DPSCs) or bone marrow mesenchymal stem cells (BMMSCs) on hyposalivation in SS and to investigate the mechanism involved.

Methods

Eighty percent confluent stem cells were replenished with serum-free Dulbecco’s modified Eagle’s medium and incubated for 48 h; following which, conditioned media from DPSCs (DPSC-CM) and BMMSCs (BMMSC-CM) were collected. Cytokine array analysis was performed to assess the types of cytokines present in the media. Flow cytometric analysis was performed to evaluate the number of activated T cells cultured in DPSC-CM or BMMSC-CM. Subsequently, DPSC-CM or BMMSC-CM was administered to an SS mouse model. The mice were categorized into the following groups (n = 6 each): non-treatment, Dulbecco’s modified Eagle’s medium (−), BMMSC-CM, and DPSC-CM. Histological analysis of the salivary glands was performed. The gene and protein expression levels of cytokines associated with T helper subsets in the submandibular glands (SMGs) were evaluated.

Results

DPSC-CM contained more secreted factors with tissue-regenerating mechanisms, such as cell proliferation, anti-inflammatory effects, and immunomodulatory effects. DPSC-CM was more effective in suppressing the activated T cells than other groups in the flow cytometric analysis. The stimulated salivary flow rate increased in SS mice with DPSC-CM compared with that in the other groups. In addition, the number of inflammation sites in SMGs of the mice administered with DPSC-CM was lower than that in the other groups. The expression levels of interleukin (Il)-10 and transforming growth factor-β1 were upregulated in the DPSC-CM group, whereas those of Il-4 and Il-17a were downregulated. The DPSC-CM-administered group presented with a significantly increased percentage of regulatory T (Treg) cells and a significantly decreased percentage of type 17 Th (Th17) cells compared with the other groups.

Conclusions

These results indicated that DPSC-CM ameliorated SS by promoting Treg cell differentiation and inhibiting Th17 cell differentiation in the mouse spleen.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02236-6.

Dental pulp-derived stem cell-conditioned media attenuates secondary Sjögren's syndrome via suppression of inflammatory cytokines in the submandibular glands

Introduction

Sjögren's syndrome (SS) is a chronic inflammatory autoimmune disease, which affects the exocrine glands. Its primary symptoms are decreased moisture in the mouth and eyes. Therapies are limited to treatment with steroids, which has unpleasant side effects, so new treatments would be beneficial. One possibility might be stem cells, such as bone marrow mesenchymal stem cells (BMMSCs) or dental pulp-derived stem cells (DPSCs); these have been reported to exert immunomodulatory effects on activated lymphoid cells. This study aimed to evaluate the effects of conditioned media from DPSCs (DPSC-CM) or BMMSCs (BMMSC-CM) on salivary functions in SS.

Methods

Cytokine array analysis was performed to assess the types of cytokines present in the media. DPSC-CM or BMMSC-CM was administered in an SS mouse model. Histological analysis of the salivary glands was performed, and gene expression levels of inflammatory and anti-inflammatory cytokines in the submandibular glands (SMGs) were evaluated.

Results

DPSC-CM contained more anti-inflammatory factors than BMMSC-CM. The mice that were given DPSC-CM had a lower number of inflammation sites in the SMGs than those in the other experimental groups, and their salivary flow rate increased. The expression levels of interleukin (IL)-10 and transforming growth factor-β1 increased in the DPSC-CM group, while those of Il-4, Il-6, and Il-17a decreased. The mice that received DPSC-CM showed a significantly increased percentage of regulatory T cells and a significantly decreased percentage of type T helper 17 cells compared to other groups.

Conclusions

These results indicate that DPSC-CM could be an effective therapy for SS-induced hyposalivation, since it decreases the number of inflammatory cytokines and regulates the local inflammatory microenvironment in the SMGs.

Angiogenesis in Regenerative Dentistry: Are We Far Enough for Therapy?

Angiogenesis is a broad spread term of high interest in regenerative medicine and tissue engineering including the dental field. In the last two decades, researchers worldwide struggled to find the best ways to accelerate healing, stimulate soft, and hard tissue remodeling. Stem cells, growth factors, pathways, signals, receptors, genetics are just a few words that describe this area in medicine. Dental implants, bone and soft tissue regeneration using autologous grafts, or xenografts, allografts, their integration and acceptance rely on their material properties. However, the host response, through its vascularization, plays a significant role. The present paper aims to analyze and organize the latest information about the available dental stem cells, the types of growth factors with pro-angiogenic effect and the possible therapeutic effect of enhanced angiogenesis in regenerative dentistry.

Exosomes derived from human exfoliated deciduous teeth ameliorate adult bone loss in mice through promoting osteogenesis

Cell-free based therapy is an effective strategy in regenerative medicine as it avoids controversial issues, such as immunomodulation and stability. Recently, exosomes have been explored as a favorable substitution for stem cell therapy as they exhibit multiple advantages, such as the ability to be endocytosed and innate biocompatibility. This study aimed to investigate the effects of stem cells from human exfoliated deciduous teeth (SHED)-derived exosomes (SHED-Exo) on bone marrow stromal cells (BMSCs) osteogenesis and bone recovery. SHED-Exo were isolated, characterized, and applied to the bone loss area caused by periodontitis in a mouse model. We found that the injection of SHED-Exo restored bone loss to the same extent as original stem cells. Without affecting BMSCs proliferation, SHED-Exo mildly inhibited apoptosis. Moreover, SHED-Exo specifically promoted BMSCs osteogenesis and inhibited adipogenesis compared with SHED-derived conditioned medium. The expression of osteogenic marker genes, alkaline phosphatase activity, and Alizarin Red S staining of BMSCs was significantly increased by co-culturing with SHED-Exo. Moreover, Western blot analysis showed that Runx2, a key transcriptional factor in osteogenic differentiation, and p-Smad5 were upregulated upon SHED-Exo stimulation. Expression of the adipogenic marker PPARγ and the amount of lipid droplets decreased when exosomes were present. Low doses of exosomes inhibited the expression of the inflammatory cytokines IL-6 and TNF-α. In conclusion, SHED-Exo directly promoted BMSCs osteogenesis, differentiation, and bone formation. Therefore, exosomes have the potential to be utilized in the treatment of periodontitis and other bone diseases.

Insight into the Role of Dental Pulp Stem Cells in Regenerative Therapy

Mesenchymal stem cells (MSCs) have the capacity for self-renewal and multilineage differentiation potential, and are considered a promising cell population for cell-based therapy and tissue regeneration. MSCs are isolated from various organs including dental pulp, which originates from cranial neural crest-derived ectomesenchyme. Recently, dental pulp stem cells (DPSCs) and stem cells from human exfoliated deciduous teeth (SHEDs) have been isolated from dental pulp tissue of adult permanent teeth and deciduous teeth, respectively. Because of their MSC-like characteristics such as high growth capacity, multipotency, expression of MSC-related markers, and immunomodulatory effects, they are suggested to be an important cell source for tissue regeneration. Here, we review the features of these cells, their potential to regenerate damaged tissues, and the recently acquired understanding of their potential for clinical application in regenerative medicine.