Peripheral Nerve Regeneration by Secretomes of Stem Cells from Human Exfoliated Deciduous Teeth

Human cytomegalovirus infection impairs neural differentiation via repressing sterol regulatory element binding protein 2-mediated cholesterol biosynthesis

Congenital human cytomegalovirus (HCMV) infection is a major cause of abnormalities and disorders in the central nervous system (CNS) and/or the peripheral nervous system (PNS). However, the complete pathogenesis of neural differentiation disorders caused by HCMV infection remains to be fully elucidated. Stem cells from human exfoliated deciduous teeth (SHEDs) are mesenchymal stem cells (MSCs) with a high proliferation and neurogenic differentiation capacity. Since SHEDs originate from the neural crest of the early embryonic ectoderm, SHEDs were hypothesized to serve as a promising cell line for investigating the pathogenesis of neural differentiation disorders in the PNS caused by congenital HCMV infection. In this work, SHEDs were demonstrated to be fully permissive to HCMV infection and the virus was able to complete its life cycle in SHEDs. Under neurogenic inductive conditions, HCMV infection of SHEDs caused an abnormal neural morphology. The expression of stem/neural cell markers was also disturbed by HCMV infection. The impairment of neural differentiation was mainly due to a reduction of intracellular cholesterol levels caused by HCMV infection. Sterol regulatory element binding protein-2 (SREBP2) is a critical transcription regulator that guides cholesterol synthesis. HCMV infection was shown to hinder the migration of SREBP2 into nucleus and resulted in perinuclear aggregations of SREBP2 during neural differentiation. Our findings provide new insights into the prevention and treatment of nervous system diseases caused by congenital HCMV infection.

Dental Pulp-Derived Mesenchymal Stem Cells Increase Axon Numbers in Mental Nerve Repair

Aim

The mental nerve, the extended part of the inferior alveolar nerve, is often injured during dentoalveolar, orthognathic, or tumor surgery. Numerous therapeutic interventions, including surgery and pharmacotherapy, have been used to enhance the recovery of nerve injuries. Dental pulp stem cells (DPSCs) represent an easily accessible source of adult stem cells that can be isolated from the pulp of extracted teeth. This study evaluated the effect of DPSCs on the regeneration of the mental nerve injury model of rabbits.

Methods

In this presented study, DPSCs were cultured and cell characterizations were performed by using flow cytometry and immunostainings. Bilateral mental nerve injury models of rabbits were created. In the control group (n = 10), saline was applied, and in the study group (n = 10), 2 × 106 DPSCs were applied to the repaired nerve areas. After 3 weeks, animals were killed and histological examination was obtained by using Masson's trichrome staining. An unpaired Student's t test was used when comparing the groups. Differences were considered to be statistically significant at P values of less than 0.05.

Results

The DPSCs demonstrated a homogeneous population of mesenchymal stromal cells which expressed cluster of differentiation CD44, CD73, CD90, and CD105 and lack of CD34, CD45, and HLA-DR. Our finding clearly demonstrated that a lower number of cross-sectioned axons were founded in the control group (60.18 ± 2.52) compared to the study group (72.96 ± 2.43) (p = 0.00).

Conclusions

DPSCs promote mental nerve axonal regeneration. These results suggest that DPSCs provide an important accessible source of adult stem cells for mental nerve regeneration.

Bone marrow stromal cell-conditioned medium regenerates injured sciatic nerve by increasing expression of MPZ and NGF and decreasing apoptosis

Objectives

Despite the many benefits of mesenchymal stem cell (MSC) transplantation for tissue regeneration, there are some limitations to using them, including the high costs, applying invasive procedures, the possibility of transplant rejection, and cell malignancy. This study aimed to investigate the effect of secretions of bone marrow stromal cells (BMSCs) with the cell-free strategy on damaged sciatic nerve with an emphasis on the role of apoptosis and the expression of myelin protein zero (MPZ) and nerve growth factor (NGF) proteins.

Materials and Methods

BMSCs were cultured and a 25-fold concentrated conditioned medium (CM) from the cells was provided. After creating a crush injury in the left sciatic nerve of male rats, BMSCs or CM were injected into the injured site of the nerve. Four weeks later, the expression of MPZ, NGF, Bax, and Bcl-2 proteins in the sciatic nerve and histological parameters of the sciatic nerve and gastrocnemius muscle were assessed.

Results

The results demonstrated that injection of CM decreased apoptosis and increased expression of MPZ and NGF proteins, improving remyelination and regeneration of the sciatic nerve almost as much as the transplantation of the BMSCs themselves compared to the control group.

Conclusion

The results suggest that BMSC secretions may improve remyelination and regeneration of damaged sciatic nerve by increasing the expression of MPZ and NGF and decreasing apoptosis.

Stem cells from human exfoliated deciduous teeth rejuvenate the liver in naturally aged mice by improving ribosomal and mitochondrial proteins

BACKGROUND AIMS

Aging is accompanied by a decline in cellular proteome homeostasis, mitochondrial, and metabolic function. Mesenchymal stromal cell (MSC) therapies have been reported to extend lifespan and delay some age-related pathologies, yet the anti-aging rate and mechanisms remain unclear. Here, we investigated the effects and mechanism by transplantation of stem cells from human exfoliated deciduous teeth (SHED) into the naturally aged mice model.

METHODS

SHED were cultured in vitro and injected into mice by caudal vein. The in vivo imaging uncovered that SHED labeled by DiR dye mainly migrated to the liver, spleen, and lung organs of wild-type mice. As the main metabolic organ and SHED homing place, the liver was selected for proteomics and aging clock algorithm (LiverClock) analysis, which was constructed to estimate the proteomic pattern related to liver age state.

RESULTS

After 6 months of continuous SHED injections, the liver proteomic pattern was reversed from senescent (∼30 months) to a youthful state (∼3 months), accompanied with upregulation of hepatocytes marker genes, anti-aging protein Klotho, a global improvement of liver functional pathways proteins, and a dramatic regulation of ribosomal and mitochondrial proteins, including upregulation of translation elongation and ribosome-sparing proteins Rpsa and Rplp0; elongation factors Eif4a1, Eef1b2, Eif5a; protein-folding chaperones Hsp90aa and Hspe1; ATP synthesis proteins Atp5b, Atp5o, Atp5j; and downregulation of most ribosomal proteins, suggesting that the proteome homeostasis destruction and mitochondria dysfunction in the aged mice liver might be relieved after SHED treatment.

CONCLUSIONS

SHED treatment could dramatically relieve the senescent state of the aged liver, affect ribosome component proteins and upregulate the ribosomal biogenesis proteins in the aged mice liver. These results may help understand the improvements and mechanisms of SHED treatment in anti-aging.

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.

Potential Application of Orofacial MSCs in Tissue Engineering Nerve Guidance for Peripheral Nerve Injury Repair

Injury to the peripheral nerve causes potential loss of sensory and motor functions, and peripheral nerve repair (PNR) remains a challenging endeavor. The current clinical methods of nerve repair, such as direct suture, autografts, and acellular nerve grafts (ANGs), exhibit their respective disadvantages like nerve tension, donor site morbidity, size mismatch, and immunogenicity. Even though commercially available nerve guidance conduits (NGCs) have demonstrated some clinical successes, the overall clinical outcome is still suboptimal, especially for nerve injuries with a large gap (≥ 3 cm) due to the lack of biologics. In the last two decades, the combination of advanced tissue engineering technologies, stem cell biology, and biomaterial science has significantly advanced the generation of a new generation of NGCs incorporated with biological factors or supportive cells, including mesenchymal stem cells (MSCs), which hold great promise to enhance peripheral nerve repair/regeneration (PNR). Orofacial MSCs are emerging as a unique source of MSCs for PNR due to their neural crest-origin and easy accessibility. In this narrative review, we have provided an update on the pathophysiology of peripheral nerve injury and the properties and biological functions of orofacial MSCs. Then we have highlighted the application of orofacial MSCs in tissue engineering nerve guidance for PNR in various preclinical models and the potential challenges and future directions in this field.

From Teeth to Therapy: A Review of Therapeutic Potential within the Secretome of Stem Cells from Human Exfoliated Deciduous Teeth

Stem cells derived from human exfoliated deciduous teeth (SHED) have emerged as an alternative stem cell source for cell therapy and regenerative medicine because they are readily available, pose fewer ethical concerns, and have low immunogenicity and tumourigenicity. SHED offer a number of advantages over other dental stem cells, including a high proliferation rate with the potential to differentiate into multiple developmental lineages. The therapeutic effects of SHED are mediated by multiple mechanisms, including immunomodulation, angiogenesis, neurogenesis, osteogenesis, and adipogenesis. In recent years, there is ample evidence that the mechanism of action of SHED is mainly due to its paracrine action, releasing a wide range of soluble factors such as cytokines, chemokines, and trophic factors (also known as 'secretome') into the local tissue microenvironment to promote tissue survival and recovery. This review provides an overview of the secretome derived from SHED and highlights the bioactive molecules involved in tissue regeneration and their potential applications in regenerative medicine.

Development of a simultaneous and noninvasive measuring method using high-frame rate videography and motion analysis software for the assessment of facial palsy recovery in a rat model

BACKGROUND

For the development of new therapeutic and reconstructive methods for facial nerve palsy, it is critical to validate them in animal models. This study developed a novel evaluation method using a high-speed camera and motion analysis software for rat facial paralysis models. The validity of the new method was verified using normal rats and rats with facial paralysis.

METHODS

The whisker movement was recorded using a high-frame video camera. The video files were processed using motion analysis software, and the angular velocities were measured. The score was calculated as the percentage of movement on the side that had palsy compared with the movement on the normal side. Normal rats were used to examine which of the four indices of angular velocity is appropriate for this evaluation method. Using this method, two types of facial nerve palsy models were compared. Furthermore, the three agents that were predicted to promote axon regeneration from previous studies were evaluated.

RESULTS

The two averages of the protraction and retraction movement velocities of the whiskers were considered as the most appropriate indicators for this new method. Compared with the saline group, all agent groups showed significant differences in the improvement of facial palsy recovery.

CONCLUSIONS

This method is an evaluation method for the effects of therapeutic intervention for facial nerve paralysis in real time without sacrificing animals.

Engineered hydrogels for peripheral nerve repair

Peripheral nerve injury (PNI) is a complex disease that often appears in young adults. It is characterized by a high incidence, limited treatment options, and poor clinical outcomes. This disease not only causes dysfunction and psychological disorders in patients but also brings a heavy burden to the society. Currently, autologous nerve grafting is the gold standard in clinical treatment, but complications, such as the limited source of donor tissue and scar tissue formation, often further limit the therapeutic effect. Recently, a growing number of studies have used tissue-engineered materials to create a natural microenvironment similar to the nervous system and thus promote the regeneration of neural tissue and the recovery of impaired neural function with promising results. Hydrogels are often used as materials for the culture and differentiation of neurogenic cells due to their unique physical and chemical properties. Hydrogels can provide three-dimensional hydration networks that can be integrated into a variety of sizes and shapes to suit the morphology of neural tissues. In this review, we discuss the recent advances of engineered hydrogels for peripheral nerve repair and analyze the role of several different therapeutic strategies of hydrogels in PNI through the application characteristics of hydrogels in nerve tissue engineering (NTE). Furthermore, the prospects and challenges of the application of hydrogels in the treatment of PNI are also discussed.

Stem cell-derived exosomes from human exfoliated deciduous teeth promote angiogenesis in hyperglycemic-induced human umbilical vein endothelial cells

OBJECTIVE

To investigate the angiogenesis in human umbilical vein endothelial cells (HUVEC) under high glucose concentration, treated with exosomes derived from stem cells from human exfoliated deciduous teeth (SHED).

METHODOLOGY

SHED-derived exosomes were isolated by differential centrifugation and were characterized by nanoparticle tracking analysis, transmission electron microscopy, and flow cytometric assays. We conducted in vitro experiments to examine the angiogenesis in HUVEC under high glucose concentration. Cell Counting Kit-8, migration assay, tube formation assay, quantitative real-time PCR, and immunostaining were performed to study the role of SHED-derived exosomes in cell proliferation, migration, and angiogenic activities.

RESULTS

The characterization confirmed SHED-derived exosomes: size ranged from 60-150 nm with a mode of 134 nm, cup-shaped morphology, and stained positively for CD9, CD63, and CD81. SHED-exosome significantly enhanced the proliferation and migration of high glucose-treated HUVEC. A significant reduction was observed in tube formation and a weak CD31 staining compared to the untreated-hyperglycemic-induced group. Interestingly, exosome treatment improved tube formation qualitatively and demonstrated a significant increase in tube formation in the covered area, total branching points, total tube length, and total loop parameters. Moreover, SHED-exosome upregulates angiogenesis-related factors, including the GATA2 gene and CD31 protein.

CONCLUSIONS

Our data suggest that the use of SHED-derived exosomes potentially increases angiogenesis in HUVEC under hyperglycemic conditions, which includes increased cell proliferation, migration, tubular structures formation, GATA2 gene, and CD31 protein expression. SHED-exosome usage may provide a new treatment strategy for periodontal patients with diabetes mellitus.

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.

Clinical trials using dental stem cells: 2022 update

For nearly 20 years, dental stem cells (DSCs) have been successfully isolated from mature/immature teeth and surrounding tissue, including dental pulp of permanent teeth and exfoliated deciduous teeth, periodontal ligaments, dental follicles, and gingival and apical papilla. They have several properties (such as self-renewal, multidirectional differentiation, and immunomodulation) and exhibit enormous potential for clinical applications. To date, many clinical articles and clinical trials using DSCs have reported the treatment of pulpitis, periapical lesions, periodontitis, cleft lip and palate, acute ischemic stroke, and so on, and DSC-based therapies obtained satisfactory effects in most clinical trials. In these studies, no adverse events were reported, which suggested the safety of DSC-based therapy. In this review, we outline the characteristics of DSCs and summarize clinical trials and their safety as DSC-based therapies. Meanwhile, we also present the current limitations and perspectives of DSC-based therapy (such as harvesting DSCs from inflamed tissue, applying DSC-conditioned medium/DSC-derived extracellular vesicles, and expanding-free strategies) to provide a theoretical basis for their clinical applications.

Exosomes derived from mesenchymal stromal cells: a promising treatment for pelvic floor dysfunction

Pelvic floor dysfunction (PFDs), which include pelvic organ prolapse (POP), stress urinary incontinence (SUI) and anal incontinence (AI), are common degenerative diseases in women that have dramatic effects on quality of life. The pathology of PFDs is based on impaired pelvic connective tissue supportive strength due to an imbalance in extracellular matrix (ECM) metabolism, the loss of a variety of cell types, such as fibroblasts, muscle cells, peripheral nerve cells, and oxidative stress and inflammation in the pelvic environment. Fortunately, exosomes, which are one of the major secretions of mesenchymal stromal cells (MSCs), are involved in intercellular communication and the modulation of molecular activities in recipient cells via their contents, which are bioactive proteins and genetic factors such as mRNAs and miRNAs. These components modify fibroblast activation and secretion, facilitate ECM modelling, and promote cell proliferation to enhance pelvic tissue regeneration. In this review, we focus on the molecular mechanisms and future directions of exosomes derived from MSCs that are of great value in the treatment of PFD.

Implantation with SHED sheet induced with homogenate protein of spinal cord promotes functional recovery from spinal cord injury in rats

Introduction: After spinal cord injury (SCI) occurs, the lesion is in a growth inhibitory microenvironment that severely hinders neural regeneration. In this microenvironment, inhibitory factors are predominant and factors that promote nerve regeneration are few. Improving neurotrophic factors in the microenvironment is the key to treating SCI.

Methods: Based on cell sheet technology, we designed a bioactive material with a spinal cord‐like structure –SHED sheet induced with homogenate protein of spinal cord (hp–SHED sheet). Hp–SHED sheet was implanted into the spinal cord lesion for treating SCI rats with SHED suspensions as a control to investigate the effects on nerve regeneration.

Results: Hp–SHED sheet revealed a highly porous three–dimensional inner structure, which facilitates nerve cell attachment and migration. Hp-SHED sheet in vivo restored sensory and motor functions in SCI rats by promoting nerve regeneration, axonal remyelination, and inhibiting glial scarring.

Discussion: Hp–SHED sheet maximally mimics the microenvironment of the natural spinal cord and facilitate cell survival and differentiation. Hp–SHED sheet could release more neurotrophins and the sustained action of neurotrophins improves the pathological microenvironment, which effectively promotes nerve regeneration, axonal extension, and inhibits glial scarring, thereby promoting the in situ centralis neuroplasticity. Hp–SHED sheet therapy is a promising strategy for effective treatment of SCI based on neurotrophins delivery.

Stem Cells and Tissue Engineering-Based Therapeutic Interventions: Promising Strategies to Improve Peripheral Nerve Regeneration

Unlike the central nervous system, the peripheral one has the ability to regenerate itself after injury; however, this natural regeneration process is not always successful. In fact, even with some treatments, the prognosis is poor, and patients consequently suffer with the functional loss caused by injured nerves, generating several impacts on their quality of life. In the present review we aimed to address two strategies that may considerably potentiate peripheral nerve regeneration: stem cells and tissue engineering. In vitro studies have shown that pluripotent cells associated with neural scaffolds elaborated by tissue engineering can increase functional recovery, revascularization, remyelination, neurotrophin expression and reduce muscle atrophy. Although these results are very promising, it is important to note that there are some barriers to be circumvented: the host's immune response, the oncogenic properties attributed to stem cells and the duration of the pro-regenerative effects. After all, more studies are still needed to overcome the limitations of these treatments; those that address techniques for manipulating the lesion microenvironment combining different therapies seem to be the most promising and proactive ones.

The potential roles of dental pulp stem cells in peripheral nerve regeneration

Peripheral nerve diseases are significantly correlated with severe fractures or trauma and surgeries, leading to poor life quality and impairment of physical and mental health. Human dental pulp stem cells (DPSCs) are neural crest stem cells with a strong multi-directional differentiation potential and proliferation capacity that provide a novel cell source for nerve regeneration. DPSCs are easily extracted from dental pulp tissue of human permanent or deciduous teeth. DPSCs can express neurotrophic and immunomodulatory factors and, subsequently, induce blood vessel formation and nerve regeneration. Therefore, DPSCs yield valuable therapeutic potential in the management of peripheral neuropathies. With the purpose of summarizing the advances in DPSCs and their potential applications in peripheral neuropathies, this article reviews the biological characteristics of DPSCs in association with the mechanisms of peripheral nerve regeneration.

Effects of Human Deciduous Dental Pulp-Derived Mesenchymal Stem Cell-Derived Conditioned Medium on the Metabolism of HUVECs, Osteoblasts, and BMSCs

In this study, we assessed the effects of human deciduous dental pulp-derived mesenchymal stem cell-derived conditioned medium (SHED-CM) on the properties of various cell types. The effects of vascular endothelial growth factor (VEGF) in SHED-CM on the luminal architecture, proliferative ability, and angiogenic potential of human umbilical vein endothelial cells (HUVECs) were determined. We also investigated the effects of SHED-CM on the proliferation of human-bone-marrow mesenchymal stem cells (hBMSCs) and mouse calvarial osteoblastic cells (MC3T3-E1) as well as the expression of ALP, OCN, and RUNX2. The protein levels of ALP were examined using Western blot analysis. VEGF blockade in SHED-CM suppressed the proliferative ability and angiogenic potential of HUVECs, indicating that VEGF in SHED-CM contributes to angiogenesis. The culturing of hBMSCs and MC3T3-E1 cells with SHED-CM accelerated cell growth and enhanced mRNA expression of bone differentiation markers. The addition of SHED-CM enhanced ALP protein expression in hBMSCs and MT3T3-E1 cells compared with that of the 0% FBS group. Furthermore, SHED-CM promoted the metabolism of HUVECs, MC3T3-E1 cells, and hBMSCs. These findings indicate the potential benefits of SHED-CM in bone tissue regeneration.

Assessment of angiogenic potential of mesenchymal stem cells derived conditioned medium from various oral sources

Background

Abnormal angiogenesis hamper blood vessel proliferation implicated in various biological processes. The current method available to clinically treat patients to enhance angiogenesis is administering the angiogenic growth factors. However, due to a lack of spatiotemporal control over the substantial release of these factors, numerous drawbacks are faced such as leaky vasculature. Hence, stem-cell-based therapeutic applications are running their race to evolve as potential targets for deranged angiogenesis. In clinical dentistry, adequate tissue vascularization is essential for successful endodontic therapies such as apexogenesis and apexification. Furthermore, wound healing of the extraction socket and tissue regeneration post-surgical phase of treatment including implant placement require angiogenesis as a foundation for the ultimate success of treatment. Mesenchymal stem cells (MSCs) secrete certain growth factors and cytokines in the culture medium during the proliferation. These factors and cytokines are responsible for various biological activities inside human body. Oral cavity-derived stem cells can secrete growth factors that enhance angiogenesis.

Aim

The aim of the study was to investigate the angiogenic potential of conditioned medium (CM) of MSCs derived from different oral sources.

Methods

Oral tissues such as dental pulp of adult and deciduous teeth, gingiva, and buccal fat were used to isolate dental pulp MSCs (DPSCs), exfoliated deciduous teeth, gingival MSCs, and buccal fat derived MSCs. MSCs conditioned medium (CM) from passage four cells from all the sources were obtained at 48 h interval and growth factor analysis was performed using flow cytometry. To assess the functionality of the CM, Chick Yolk Sac Membrane (YSM) assay was performed.

Results

CM obtained from DPSCs showed higher levels of vascular endothelial growth factor, fibroblast growth factor, and hepatocyte growth factor as evidenced by flow cytometry. Furthermore, DPSC-CM exhibited significantly higher pro-angiogenic potential when assessed in in-ovo YSM assay.

Conclusion

DPSCs so far seems to be the best source as compare to the rest of oral sources in promoting angiogenesis. A novel source of CM derived from buccal fat stem cells was used to assess angiogenic potential. Thus, the present study shows that CM derived from oral cavity-derived-MSCs has a dynamic and influential role in angiogenesis.

Relevance for Patients

CM derived from various oral sources of MSCs could be used along with existing therapies in medical practice where patients have compromised blood supply like in diabetes and in patients with debilitating disorders. In clinical dentistry, adequate tissue vascularization is essential for successful wound healing, grafting procedures, and endodontic therapies. DPSCs-CM shows better angiogenic potential in comparison with other oral sources of MSCs-CM. Our findings could be a turning point in the management of all surgical and regenerative procedures requiring increased angiogenesis.

The therapeutic effect of stem cells from human exfoliated deciduous teeth on a rat model of tracheal fistula

Background

Tracheal fistulas (TF) can be dangerous and even fatal in patients. The current treatment is really challenging. Previous studies reported that mesenchymal stem cells (MSCs) could be used to treat respiratory tract fistulas. Stem cells from human exfoliated deciduous teeth (SHED) are considered to be MSC-like cells that may also have the potential to treat the tracheal fistulas. In this study, we investigated the therapeutic effects of SHED in rat tracheal fistula models.

Methods

A total of 80 SD rats were randomly divided into five groups: a sham-operated group, a local PBS group (L-PBS), an intravenous PBS group (I-PBS), a local SHED treatment group (L-SHED), and an intravenous SHED treatment group (I-SHED). The L-SHED and I-SHED groups were given a topical application around the fistula or an intravenous injection of 1*10⁷ SHED via the tail vein, respectively, while the L-PBS and I-PBS groups were given an equivalent volume of PBS through local or intravenous administration. A stereomicroscope was used to observe fistula healing on the 2nd, 3rd, and 5th days following transplantation. On the 7th day, the survival of SHED was observed by immunofluorescence. The pathology of the lungs and fistulas was observed by hematoxylin and eosin (H&E) and Masson staining. The expression levels of the Toll-like receptor 4 (TLR4), interleukin (IL)-1β, IL-33, and IL-4 were measured using immunohistochemistry. The expression levels of TLR4, high mobility group box 1 (HMGB1), and myeloid differentiation factor 88 (MYD88) were studied using western blotting. On day 14, airway responsiveness of rats was detected and analyzed.

Results

Fistula healing in the L-SHED and I-SHED groups was faster than that in their respective PBS groups after transplantation. The fistula diameters in the L-SHED and I-SHED groups were significantly smaller than those in the L-PBS and I-PBS groups on the 3rd day. Moreover, the phenomenon of fibroblast proliferation and new blood vessel growth around the fistula seemed more pronounced in the L-SHED and I-SHED groups. Although no discernible difference was found in airway responsiveness after SHED treatment, the degree of inflammation in the lungs was reduced by intravenous SHED treatment. However, there was no significant reduction in lung inflammation by local SHED treatment. The expression levels of IL-1β and IL-33 were decreased in the I-SHED group, while IL-4 was elevated compared with the I-PBS group. Interestingly, intravenous SHED treatment inhibited the activation of HMGB1/TLR4/MYD88 in the lung tissues of TF rats.

Conclusions

SHED transplantation accelerated the rate of fistula healing in rats. Intravenous SHED treatment reduced lung inflammation. Thus, SHED may have potential in the treatment of tracheal fistula, providing hope for future therapeutic development for TF.

The Therapeutic Potential of Secreted Factors from Dental Pulp Stem Cells for Various Diseases

An alternative source of mesenchymal stem cells has recently been discovered: dental pulp stem cells (DPSCs), including deciduous teeth, which can thus comprise potential tools for regenerative medicine. DPSCs derive from the neural crest and are normally implicated in dentin homeostasis. The clinical application of mesenchymal stem cells (MSCs) involving DPSCs contains various limitations, such as high cost, low safety, and cell handling issues, as well as invasive sample collection procedures. Although MSCs implantation offers favorable outcomes on specific diseases, implanted MSCs cannot survive for a long period. It is thus considered that their mediated mechanism of action involves paracrine effects. It has been recently reported that secreted molecules in DPSCs-conditioned media (DPSC-CM) contain various trophic factors and cytokines and that DPSC-CM are effective in models of various diseases. In the current study, we focus on the characteristics of DPSC-CM and their therapeutic potential against various disorders.

Dental stem cell-conditioned medium for tissue regeneration: Optimization of production and storage

BACKGROUND

Mesenchymal stem cells (MSC) effects on tissue regeneration are mainly mediated by their secreted substances (secretome), inducing their paracrine activity. This Conditioned medium (CM), including soluble factors (proteins, nucleic acids, lipids) and extracellular vesicles is emerging as a potential alternative to cell therapy. However, the manufacturing of CM suffers from variable procedures and protocols leading to varying results between studies. Besides, there is no well-defined optimized procedure targeting specific applications in regenerative medicine.

AIM

To focus on conditioned medium produced from dental MSC (DMSC-CM), we reviewed the current parameters and manufacturing protocols, in order to propose a standardization and optimization of these manufacturing procedures.

METHODS

We have selected all publications investigating the effects of dental MSC secretome in in vitro and in vivo models of tissue regeneration, in accordance with the PRISMA guidelines.

RESULTS

A total of 351 results were identified. And based on the inclusion criteria described above, 118 unique articles were included in the systematic review. DMSC-CM production was considered at three stages: before CM recovery (cell sources for CM), during CM production (culture conditions) and after production (CM treatment).

CONCLUSION

No clear consensus could be recovered as evidence-based methods, but we were able to describe the most commonly used protocols: donors under 30 years of age, dental pulp stem cells and exfoliated deciduous tooth stem cells with cell passage between 1 and 5, at a confluence of 70% to 80%. CM were often collected during 48 h, and stored at -80 °C. It is important to point out that the preconditioning environment had a significant impact on DMSC-CM content and efficiency.

Efficacy of Mesenchymal Stem Cells from Human Exfoliated DeciduousTeeth and their Derivatives in Inflammatory Diseases Therapy

Mesenchymal stem cells derived from postnatal orofacial tissues can be readily isolated and possess diverse origins, for example, from surgically removed teeth or gingiva. These cells exhibit stem cell properties, strong potential for self-renewal, and show multi-lineage differentiation, and they have therefore been widely employed in stem cell therapy, tissue regeneration, and inflammatory diseases. Among them, stem cells from human exfoliated deciduous teeth [SHED] and their derivatives have manifested wide application in the treatment of diseases because of their outstanding advantages- including convenient access, easy storage, and less immune rejection. Numerous studies have shown that most diseases are closely associated with inflammation and that inflammatory diseases are extremely destructive, can lead to necrosis of organ parenchymal cells, and can deposit excessive extracellular ma- trix in the tissues. Inflammatory diseases are thus the principal causes of disability and death from many diseases worldwide. SHED and their derivatives not only exhibit the basic characteristics of stem cells but also exhibit some special properties of their own, particularly with regard to their great potential in inhib- iting inflammation and tissue regeneration. SHED therapy may provide a new direction for the treatment of inflammation and corresponding tissue defects. In this review, we critically analyze and summarize the latest findings on the behaviors and functions of SHED, serum‑free conditioned medium from SHED [SHED-CM], and extracellular vesicles, especially exosomes, from SHED [SHED-Exos], and discuss their roles and underlying mechanisms in the control of inflammatory diseases, thus further highlighting additional functions for SHED and their derivatives in future therapies.

Investigating the Effects of Conditioned Media from Stem Cells of Human Exfoliated Deciduous Teeth on Dental Pulp Stem Cells

Pulp regeneration has recently attracted interest in modern dentistry. However, the success ratio of pulp regeneration is low due to the compromising potential of stem cells, such as their survival, migration, and odontoblastic differentiation. Stem cells from human exfoliated deciduous teeth (SHED) have been considered a promising tool for regenerative therapy due to their ability to secrete multiple factors that are essential for tissue regeneration, which is achieved by minimally invasive procedures with fewer ethical or legal concerns than those of other procedures. The aim of this study is to investigate the potency of SHED-derived conditioned media (SHED CM) on dental pulp stem cells (DPSCs), a major type of mesenchymal stem cells for dental pulp regeneration. Our results show the promotive efficiency of SHED CM on the proliferation, survival rate, and migration of DPSCs in a dose-dependent manner. Upregulation of odontoblast/osteogenic-related marker genes, such as ALP, DSPP, DMP1, OCN, and RUNX2, and enhanced mineral deposition of impaired DPSCs are also observed in the presence of SHED CM. The analysis of SHED CM found that a variety of cytokines and growth factors have positive effects on cell proliferation, migration, anti-apoptosis, and odontoblast/osteogenic differentiation. These findings suggest that SHED CM could provide some benefits to DPSCs in pulp regeneration.

Multipotency and Immunomodulatory Benefits of Stem Cells From Human Exfoliated Deciduous Teeth

Stem cells derived from human exfoliated deciduous teeth (SHEDs) are considered a promising cell population for cell-based or cell-free therapy and tissue engineering because of their proliferative, multipotency and immunomodulator. Based on recent studies, we find that SHEDs show the superior ability of nerve regeneration in addition to the potential of osteogenesis, odontogenesis owing to their derivation from the neural crest. Besides, much evidence suggests that SHEDs have a paracrine effect and can function as immunomodulatory regents attributing to their capability of secreting cytokines and extracellular vesicles. Here, we review the characteristic of SHEDs, their multipotency to regenerate damaged tissues, specifically concentrating on bones or nerves, following the paracrine activity or immunomodulatory benefits of their potential for clinical application in regenerative medicine.

Dental Mesenchymal Stem Cell Secretome: An Intriguing Approach for Neuroprotection and Neuroregeneration

Mesenchymal stem cells (MSCs) are known for their beneficial effects and regenerative potential. In particular, dental-derived MSCs have the advantage of easier accessibility and a non-invasive isolation method. Moreover, thanks to their neural crest origin, dental MSCs seem to have a more prominent neuroregenerative potential. Indeed, in basal conditions they also express neuronal markers. However, it is now well known that the beneficial actions of MSCs depend, at least in part, on their secretome, referring to all the bioactive molecules released in the conditioned medium (CM) or in extracellular vesicles (EVs). In this review we focus on the applications of the secretome derived from dental MSCs for neuroregeneration and neuroprotection. The secretomes of different dental MSCs have been tested for their effects for neuroregenerative purposes, and the secretomes of dental pulp stem cells and stem cells from human exfoliated deciduous teeth are the most studied. Both the CM and EVs obtained from dental MSCs showed that they are able to promote neurite outgrowth and neuroprotective effects. Interestingly, dental-derived MSC secretome showed stronger neuroregenerative and neuroprotective effects compared to that obtained from other MSC sources. For these reasons, the secretome obtained from dental MSCs may represent a promising approach for neuroprotective treatments.

Tissue Engineering in Stomatology: A Review of Potential Approaches for Oral Disease Treatments

Tissue engineering is an emerging discipline that combines engineering and life sciences. It can construct functional biological structures in vivo or in vitro to replace native tissues or organs and minimize serious shortages of donor organs during tissue and organ reconstruction or transplantation. Organ transplantation has achieved success by using the tissue-engineered heart, liver, kidney, and other artificial organs, and the emergence of tissue-engineered bone also provides a new approach for the healing of human bone defects. In recent years, tissue engineering technology has gradually become an important technical method for dentistry research, and its application in stomatology-related research has also obtained impressive achievements. The purpose of this review is to summarize the research advances of tissue engineering and its application in stomatology. These aspects include tooth, periodontal, dental implant, cleft palate, oral and maxillofacial skin or mucosa, and oral and maxillofacial bone tissue engineering. In addition, this article also summarizes the commonly used cells, scaffolds, and growth factors in stomatology and discusses the limitations of tissue engineering in stomatology from the perspective of cells, scaffolds, and clinical applications.

Application of dental stem cells in three-dimensional tissue regeneration

Dental stem cells can differentiate into different types of cells. Dental pulp stem cells, stem cells from human exfoliated deciduous teeth, periodontal ligament stem cells, stem cells from apical papilla, and dental follicle progenitor cells are five different types of dental stem cells that have been identified during different stages of tooth development. The availability of dental stem cells from discarded or removed teeth makes them promising candidates for tissue engineering. In recent years, three-dimensional (3D) tissue scaffolds have been used to reconstruct and restore different anatomical defects. With rapid advances in 3D tissue engineering, dental stem cells have been used in the regeneration of 3D engineered tissue. This review presents an overview of different types of dental stem cells used in 3D tissue regeneration, which are currently the most common type of stem cells used to treat human tissue conditions.

Conditioned medium derived from 3D tooth germs: A novel cocktail for stem cell priming and early in vivo pulp regeneration

OBJECTIVES

Conditioned medium (CM) from 2D cell culture can mitigate the weakened regenerative capacity of the implanted stem cells. However, the capacity of 3D CM to prime dental pulp stem cells (DPSCs) for pulp regeneration and its protein profile are still elusive. We aim to investigate the protein profile of CM derived from 3D tooth germs, and to unveil its potential for DPSCs-based pulp regeneration.

MATERIALS AND METHODS

We prepared CM of 3D ex vivo cultured tooth germ organs (3D TGO-CM) and CM of 2D cultured tooth germ cells (2D TGC-CM) and applied them to prime DPSCs. Influences on cell behaviours and protein profiles of CMs were compared. In vivo pulp regeneration of CMs-primed DPSCs was explored using a tooth root fragment model on nude mice.

RESULTS

TGO-CM enhanced DPSCs proliferation, migration, in vitro mineralization, odontogenic differentiation, and angiogenesis performances. The TGO-CM group generated superior pulp structures, more odontogenic cells attachment, and enhanced vasculature at 4 weeks post-surgery, compared with the TGC-CM group. Secretome analysis revealed that TGO-CM contained more odontogenic and angiogenic growth factors and fewer pro-inflammatory cytokines. Mechanisms leading to the differential CM profiles may be attributed to the cytokine-cytokine receptor interaction and PI3K-Akt signalling pathway.

CONCLUSIONS

The unique secretome profile of 3D TGO-CM made it a successful priming cocktail to enhance DPSCs-based early pulp regeneration.

Peripheral Nerve Regeneration Using Different Germ Layer-Derived Adult Stem Cells in the Past Decade

Peripheral nerve injuries (PNIs) are some of the most common types of traumatic lesions affecting the nervous system. Although the peripheral nervous system has a higher regenerative ability than the central nervous system, delayed treatment is associated with disturbances in both distal sensory and functional abilities. Over the past decades, adult stem cell-based therapies for peripheral nerve injuries have drawn attention from researchers. This is because various stem cells can promote regeneration after peripheral nerve injuries by differentiating into neural-line cells, secreting various neurotrophic factors, and regulating the activity of in situ Schwann cells (SCs). This article reviewed research from the past 10 years on the role of stem cells in the repair of PNIs. We concluded that adult stem cell-based therapies promote the regeneration of PNI in various ways.

Maxillofacial-Derived Mesenchymal Stem Cells: Characteristics and Progress in Tissue Regeneration

Maxillofacial-derived mesenchymal stem cells (MFSCs) are a particular collective type of mesenchymal stem cells (MSCs) that originate from the hard and soft tissue of the maxillofacial region. Recently, many types of MFSCs have been isolated and characterized. MFSCs have the common characteristics of being extremely accessible and amazingly multipotent and thus have become a promising stem cell resource in tissue regeneration. However, different MFSCs can give rise to different cell lineages, have different advantages in clinical use, and regulate the immune and inflammation microenvironment through paracrine mechanisms in different ways. Hence, in this review, we will concentrate on the updated new findings of all types of MFSCs in tissue regeneration and also introduce the recently discovered types of MFSCs. Important issues about proliferation and differentiation in vitro and in vivo, up-to-date clinical application, and paracrine effect of MFSCs in tissue regeneration will also be discussed. Our review may provide a better guide for the clinical use of MFSCs and further direction of research in MFSC regeneration medicine.

Functional Dental Pulp Regeneration: Basic Research and Clinical Translation

Pulpal and periapical diseases account for a large proportion of dental visits, the current treatments for which are root canal therapy (RCT) and pulp revascularisation. Despite the clinical signs of full recovery and histological reconstruction, true regeneration of pulp tissues is still far from being achieved. The goal of regenerative endodontics is to promote normal pulp function recovery in inflamed or necrotic teeth that would result in true regeneration of the pulpodentinal complex. Recently, rapid progress has been made related to tissue engineering-mediated pulp regeneration, which combines stem cells, biomaterials, and growth factors. Since the successful isolation and characterisation of dental pulp stem cells (DPSCs) and other applicable dental mesenchymal stem cells, basic research and preclinical exploration of stem cell-mediated functional pulp regeneration via cell transplantation and cell homing have received considerably more attention. Some of this effort has translated into clinical therapeutic applications, bringing a ground-breaking revolution and a new perspective to the endodontic field. In this article, we retrospectively examined the current treatment status and clinical goals of pulpal and periapical diseases and scrutinized biological studies of functional pulp regeneration with a focus on DPSCs, biomaterials, and growth factors. Then, we reviewed preclinical experiments based on various animal models and research strategies. Finally, we summarised the current challenges encountered in preclinical or clinical regenerative applications and suggested promising solutions to address these challenges to guide tissue engineering-mediated clinical translation in the future.

Compounded topographical and physicochemical cueing by micro-engineered chitosan substrates on rat dorsal root ganglion neurons and human mesenchymal stem cells

Given the intertwined physicochemical effects exerted in vivo by both natural and synthetic (e.g., biomaterial) interfaces on adhering cells, the evaluation of structure-function relationships governing cellular response to micro-engineered surfaces for applications in neuronal tissue engineering requires the use of in vitro testing platforms which consist of a clinically translatable material with tunable physiochemical properties. In this work, we micro-engineered chitosan substrates with arrays of parallel channels with variable width (20 and 60 μm). A citric acid (CA)-based crosslinking approach was used to provide an additional level of synergistic cueing on adhering cells by regulating the chitosan substrate's stiffness. Morphological and physicochemical characterization was conducted to unveil the structure-function relationships which govern the activity of rat dorsal root ganglion neurons (DRGs) and human mesenchymal stem cells (hMSCs), ultimately singling out the key role of microtopography, roughness and substrate's stiffness. While substrate's stiffness predominantly affected hMSC spreading, the modulation of the channels' design affected the neuronal architecture's complexity and guided the morphological transition of hMSCs. Finally, the combined analysis of tubulin expression and cell morphology allowed us to cast new light on the predominant role of the microtopography over substrate's stiffness in the process of hMSCs neurogenic differentiation.

Tooth Repair and Regeneration: Potential of Dental Stem Cells

Tooth defects are an extremely common health condition that affects millions of individuals. Currently used dental repair treatments include fillings for caries, endodontic treatment for pulp necrosis, and dental implants to replace missing teeth, all of which rely on the use of synthetic materials. By contrast, the fields of tissue engineering and regenerative medicine and dentistry (TERMD) use biologically based therapeutic strategies for vital tissue regeneration, and thus have the potential to regenerate living tissues. Methods to create bioengineered replacement teeth benefit from a detailed understanding of the molecular signaling networks regulating natural tooth development. We discuss how key signaling pathways regulating natural tooth development are being exploited for applications in TERMD approaches for vital tooth regeneration.

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.

Potential therapeutic uses of intraoral mesenchymal stem cells in other tissues of the body: A review

BACKGROUND

Over the last few years, there has been a great advance in regenerative medicine, with various studies that have observed the ability to repair or regenerate dysfunctional tissues with the patient's own cells, such as with mesenchymal cells. In this area, mesenchymal stem cells (MSCs) from the oral cavity have attracted attention because of their easy access and multiple cellular differentiations. Multiple studies have shown the various clinical applications at the intraoral level, especially at the level of bone regeneration, but the potential applications of oral MSC at a systemic level have been scarcely described. Objective: The objective of this review was to describe the potential therapeutic uses of intraoral MSCs in other tissues of the organism.

MATERIAL AND METHODS

A review of the literature between 2000 and 2019. Only included those studies done on animals or humans.

RESULTS

Twenty five articles were selected, all performed on animals. The donor site most used were the temporary teeth exfoliated from humans, representing 56% of the total articles, followed by the dental pulp with 28% of the total articles included. Transplantation of intraoral mesenchymal cells in animals with neural tissue illness was the most studied therapy.

CONCLUSIONS

Although obtaining MSC of intraoral origin has proven to be a good alternative in regenerative medicine, achieving therapeutic uses in bone tissue, nervous tissue, liver tissue, skin tissue, ocular tissue, reperfusion of tissues and in autoimmune diseases, there is a lack of clinical studies that allow its safe use in humans. Key words:Mesenchymal stem cells, stem cell transplantation, regenerative medicine, dental component.

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.

Identification of secreted factors in dental pulp cell-conditioned medium optimized for neuronal growth

With their potent regenerative and protective capacities, stem cell-derived conditioned media emerged as an effective alternative to cell therapy, and have a prospect to be manufactured as pharmaceutical products for tissue regeneration applications. Our study investigates the neuroregenerative potential of human dental pulp cells (DPCs) conditioned medium (CM) and defines an optimization strategy of DPC-CM for enhanced neuronal outgrowth. Primary sensory neurons from mouse dorsal root ganglia were cultured with or without DPC-CM, and the lengths of βIII-tubulin positive neurites were measured. The impacts of several manufacturing features as the duration of cell conditioning, CM storage, and preconditioning of DPCs with some factors on CM functional activity were assessed on neurite length. We observed that DPC-CM significantly enhanced neurites outgrowth of sensory neurons in a concentration-dependent manner. The frozen storage of DPC-CM had no impact on experimental outcomes and 48 h of DPC conditioning is optimal for an effective activity of CM. To further understand the regenerative feature of DPC-CM, we studied DPC secretome by human growth factor antibody array analysis and revealed the presence of several factors involved in either neurogenesis, neuroprotection, angiogenesis, and osteogenesis. The conditioning of DPCs with the B-27 supplement enhanced significantly the neuroregenerative effect of their secretome by changing its composition in growth factors. Here, we show that DPC-CM significantly stimulate neurite outgrowth in primary sensory neurons. Moreover, we identified secreted protein candidates that can potentially promote this promising regenerative feature of DPC-CM.

Secreted Factors from Stem Cells of Human Exfoliated Deciduous Teeth Directly Activate Endothelial Cells to Promote All Processes of Angiogenesis

Diabetes is a major risk factor for atherosclerosis and ischemic vascular diseases. Recently, regenerative medicine is expected to be a novel therapy for ischemic diseases. Our previous studies have reported that transplantation of stem cells promoted therapeutic angiogenesis for diabetic neuropathy and ischemic vascular disease in a paracrine manner, but the precise mechanism is unclear. Therefore, we examined whether secreted factors from stem cells had direct beneficial effects on endothelial cells to promote angiogenesis. The soluble factors were collected as conditioned medium (CM) 48 h after culturing stem cells from human exfoliated deciduous teeth (SHED) in serum-free DMEM. SHED-CM significantly increased cell viability of human umbilical vein endothelial cells (HUVECs) in MTT assays and accelerated HUVECs migration in wound healing and Boyden chamber assays. In a Matrigel plug assay of mice, the migrated number of primary endothelial cells was markedly increased in the plug containing SHED-CM or SHED suspension. SHED-CM induced complex tubular structures of HUVECs in a tube formation assay. Furthermore, SHED-CM significantly increased neovascularization from the primary rat aorta, indicating that SHED-CM stimulated primary endothelial cells to promote comprehensive angiogenesis processes. The angiogenic effects of SHED-CM were the same or greater than the effective concentration of VEGF. In conclusion, SHED-CM directly stimulates vascular endothelial cells to promote angiogenesis and is promising for future clinical application.

Dental Tissue-Derived Human Mesenchymal Stem Cells and Their Potential in Therapeutic Application

Human mesenchymal stem cells (hMSCs) are multipotent cells, which exhibit plastic adherence, express specific cell surface marker spectrum, and have multi-lineage differentiation potential. These cells can be obtained from multiple tissues. Dental tissue-derived hMSCs (dental MSCs) possess the ability to give rise to mesodermal lineage (osteocytes, adipocytes, and chondrocytes), ectodermal lineage (neurocytes), and endodermal lineages (hepatocytes). Dental MSCs were first isolated from dental pulp of the extracted third molar and till now they have been purified from various dental tissues, including pulp tissue of permanent teeth and exfoliated deciduous teeth, apical papilla, periodontal ligament, gingiva, dental follicle, tooth germ, and alveolar bone. Dental MSCs are not only easily accessible but are also expandable in vitro with relative genomic stability for a long period of time. Moreover, dental MSCs have exhibited immunomodulatory properties by secreting cytokines. Easy accessibility, multi-lineage differentiation potential, and immunomodulatory effects make dental MSCs distinct from the other hMSCs and an effective tool in stem cell-based therapy. Several preclinical studies and clinical trials have been performed using dental MSCs in the treatment of multiple ailments, ranging from dental diseases to nondental diseases. The present review has summarized dental MSC sources, multi-lineage differentiation capacities, immunomodulatory features, its potential in the treatment of diseases, and its application in both preclinical studies and clinical trials. The regenerative therapeutic strategies in dental medicine have also been discussed.

Modification of tubular chitosan-based peripheral nerve implants: applications for simple or more complex approaches

Surgical treatment of peripheral nerve injuries is still a major challenge in human clinic. Up to now, none of the well-developed microsurgical treatment options is able to guarantee a complete restoration of nerve function. This restriction is also effective for novel clinically approved artificial nerve guides. In this review, we compare surgical repair techniques primarily for digital nerve injuries reported with relatively high prevalence to be valuable attempts in clinical digital nerve repair and point out their advantages and shortcomings. We furthermore discuss the use of artificial nerve grafts with a focus on chitosan-based nerve guides, for which our own studies contributed to their approval for clinical use. In the second part of this review, very recent future perspectives for the enhancement of tubular (commonly hollow) nerve guides are discussed in terms of their clinical translatability and ability to form three-dimensional constructs that biomimick the natural nerve structure. This includes materials that have already shown their beneficial potential in in vivo studies like fibrous intraluminal guidance structures, hydrogels, growth factors, and approaches of cell transplantation. Additionally, we highlight upcoming future perspectives comprising co-application of stem cell secretome. From our overview, we conclude that already simple attempts are highly effective to increase the regeneration supporting properties of nerve guides in experimental studies. But for bringing nerve repair with bioartificial nerve grafts to the next level, e.g. repair of defects > 3 cm in human patients, more complex intraluminal guidance structures such as innovatively manufactured hydrogels and likely supplementation of stem cells or their secretome for therapeutic purposes may represent promising future perspectives.

Neuro-regenerative potential of dental stem cells: a concise review

This review will summarize the research information regarding the regenerative potential of dental stem cells for the treatment of neurodegenerative disorders. As compared to existing treatment modalities, the stem cell therapy seems promising, and accumulating evidences about the differentiation of stem cells into various lineages are proving it. The incidence of neurodegenerative diseases such as Alzheimer's, Parkinson's, stroke, and peripheral neuropathy is increasing due to the rise in life expectancies of people which have put a huge burden on economies. Finding a promising treatment could benefit not only the patients but also the communities. Dental stem cells hold a great potential to differentiate into neuronal cells. Many studies have reported the differentiation potential of the dental stem cells with the presence of neuronal lineage markers. In this review, we conferred how the use of dental stem cells can benefit the above-mentioned bedridden diseases.

Syringic acid delivered via mPEG-PLGA-PLL nanoparticles enhances peripheral nerve regeneration effect

Aim: To deliver syringic acid (SA) with a nanocarrier and enhance its function. Materials & methods: mPEG-PLGA-PLL (PEAL) nanoparticles were used to deliver SA. The characterization, storage stability, drug release, blood-compatibility and biocompatibility of SA-PEAL were detected by in vitro and in vivo assays. Cellular phenotypic experiments and rat sciatic nerve injury models were used to evaluate the function of SA-PEALs. Results: SA-PEAL had good storage stability, blood-compatibility and biocompatibility and could slowly release SA. SA-PEAL significantly enhanced the proliferation and migration ability of Schwann cells and function recovery of injured sciatic nerves. Conclusion: Our study provides an effective nano-delivery system for enhancing the neural repair function of SA and promoting further applications of SA.

Neural crest derived stem cells from dental pulp and tooth-associated stem cells for peripheral nerve regeneration

The peripheral nerve injuries, representing some of the most common types of traumatic lesions affecting the nervous system, are highly invalidating for the patients besides being a huge social burden. Although peripheral nervous system owns a higher regenerative capacity than does central nervous system, mostly depending on Schwann cells intervention in injury repair, several factors determine the extent of functional outcome after healing. Based on the injury type, different therapeutic approaches have been investigated so far. Nerve grafting and Schwann cell transplantation have represented the gold standard treatment for peripheral nerve injuries, however these approaches own limitations, such as scarce donor nerve availability and donor site morbidity. Cell based therapies might provide a suitable tool for peripheral nerve regeneration, in fact, the ability of different stem cell types to differentiate towards Schwann cells in combination with the use of different scaffolds have been widely investigated in animal models of peripheral nerve injuries in the last decade. Dental pulp is a promising cell source for regenerative medicine, because of the ease of isolation procedures, stem cell proliferation and multipotency abilities, which are due to the embryological origin from neural crest. In this article we review the literature concerning the application of tooth derived stem cell populations combined with different conduits to peripheral nerve injuries animal models, highlighting their regenerative contribution exerted through either glial differentiation and neuroprotective/neurotrophic effects on the host tissue.

Multi-lineage differentiation and clinical application of stem cells from exfoliated deciduous teeth

Stem cells from human exfoliated deciduous teeth (SHED) have now been considered one of the most promising sources of stem cells for tissue engineering and stem cell therapies due to their stemness and potential to differentiate into other cell lines. The high proliferation rate, the differentiation capacity, the easy access and less ethical concerns make SHED a brilliant solution for many diseases. The purpose of this review is to describe current knowledge of SHED's capability of differentiation, applications and immune status and to draw attention to further research on the mechanism and the dependability of stem cell therapy with SHED.

Dental Stem Cell-Derived Secretome/Conditioned Medium: The Future for Regenerative Therapeutic Applications

Regenerative medicine literature has proposed mesenchymal stem/progenitor cell- (MSC-) mediated therapeutic approaches for their great potential in managing various diseases and tissue defects. Dental MSCs represent promising alternatives to nondental MSCs, owing to their ease of harvesting with minimally invasive procedures. Their mechanism of action has been attributed to their cell-to-cell contacts as well as to the paracrine effect of their secreted factors, namely, secretome. In this context, dental MSC-derived secretome/conditioned medium could represent a unique cell-free regenerative and therapeutic approach, with fascinating advantages over parent cells. This article reviews the application of different populations of dental MSC secretome/conditioned medium in in vitro and in vivo animal models, highlights their significant implementation in treating different tissue' diseases, and clarifies the significant bioactive molecules involved in their regenerative potential. The analysis of these recent studies clearly indicate that dental MSCs' secretome/conditioned medium could be effective in treating neural injuries, for dental tissue regeneration, in repairing bone defects, and in managing cardiovascular diseases, diabetes mellitus, hepatic regeneration, and skin injuries, through regulating anti-inflammatory, antiapoptotic, angiogenic, osteogenic, and neurogenic mediators.

Secreted factors from cultured dental pulp stem cells promoted neurite outgrowth of dorsal root ganglion neurons and ameliorated neural functions in streptozotocin-induced diabetic mice

AIMS/INTRODUCTION

Transplantation of stem cells promotes axonal regeneration and angiogenesis in a paracrine manner. In the present study, we examined whether the secreted factors in conditioned medium of stem cells from human exfoliated deciduous teeth (SHED-CM) had beneficial effects on diabetic polyneuropathy in mice.

MATERIALS AND METHODS

Conditioned medium of stem cells from human exfoliated deciduous teeth was collected 48 h after culturing in serum-free Dulbecco's modified Eagle's medium (DMEM), and separated into four fractions according to molecular weight. Dorsal root ganglion neurons from C57BL/6J mice were cultured with SHED-CM or DMEM to evaluate the effect on neurite outgrowth. Streptozotocin-induced diabetic mice were injected with 100 μL of SHED-CM or DMEM into the unilateral hindlimb muscles twice a week over a period of 4 weeks. Peripheral nerve functions were evaluated by the plantar test, and motor and sensory nerve conduction velocities. Intraepidermal nerve fiber densities, capillary number-to-muscle fiber ratio, capillary blood flow and morphometry of sural nerves were also evaluated.

RESULTS

Conditioned medium of stem cells from human exfoliated deciduous teeth significantly promoted neurite outgrowth of dorsal root ganglion neurons compared with DMEM. Among four fractions of SHED-CM, the only fraction of <6 kDa promoted the neurite outgrowth of dorsal root ganglion neurons. In addition, SHED-CM significantly prevented decline in sensory nerve conduction velocities compared with DMEM in diabetic mice. Although SHED-CM did not improve intraepidermal nerve fiber densities or morphometry of sural nerves, SHED-CM ameliorated the capillary number-to-muscle fiber ratio and capillary blood flow.

CONCLUSIONS

These results suggested that SHED-CM might have a therapeutic effect on diabetic polyneuropathy through promoting neurite outgrowth, and the increase in capillaries might contribute to the improvement of neural function.

Treatment with Stem Cells from Human Exfoliated Deciduous Teeth and Their Derived Conditioned Medium Improves Retinal Visual Function and Delays the Degeneration of Photoreceptors

Retinitis pigmentosa (RP) is a hereditary disease characterized by degeneration and the loss of photoreceptors. Stem cell-based therapy has emerged as a promising strategy for treating RP. Stem cells from exfoliated deciduous teeth (SHEDs), a type of mesenchymal stem cell from human exfoliated deciduous teeth, have the potential to differentiate into photoreceptor-like cells under specific induction in vitro. It has been confirmed that through paracrine secreta, SHEDs exert neurotrophic, angiogenic, immunoregulatory, and antiapoptotic functions in injured tissues. This study was designed to determine whether retinal-differentiated SHEDs and the conditioned medium derived from SHEDs (SHEDs-CM) have therapeutic effects in a mouse model of RP. The results showed that both SHEDs and SHEDs-CM improved electroretinogram responses, ameliorated photoreceptor degeneration, and maintained the structure of the outer segments of photoreceptors. The therapeutic effects were related to antiapoptotic activity of SHEDs and SHEDs-CM. Thus, SHEDs may be a promising stem cell source for treating retinal degeneration.