SCF promotes dental pulp progenitor migration, neovascularization, and collagen remodeling - potential applications as a homing factor in dental pulp regeneration

Regenerative endodontic therapy: From laboratory bench to clinical practice

BACKGROUND

Maintaining the vitality and functionality of dental pulp is paramount for tooth integrity, longevity, and homeostasis. Aiming to treat irreversible pulpitis and necrosis, there has been a paradigm shift from conventional root canal treatment towards regenerative endodontic therapy.

AIM OF REVIEW

This extensive and multipart review presents crucial laboratory and practical issues related to pulp-dentin complex regeneration aimed towards advancing clinical translation of regenerative endodontic therapy and enhancing human life quality.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this multipart review paper, we first present a panorama of emerging potential tissue engineering strategies for pulp-dentin complex regeneration from cell transplantation and cell homing perspectives, emphasizing the critical regenerative components of stem cells, biomaterials, and conducive microenvironments. Then, this review provides details about current clinically practiced pulp regenerative/reparative approaches, including direct pulp capping and root revascularization, with a specific focus on the remaining hurdles and bright prospects in developing such therapies. Next, special attention was devoted to discussing the innovative biomimetic perspectives opened in establishing functional tissues by employing exosomes and cell aggregates, which will benefit the clinical translation of dental pulp engineering protocols. Finally, we summarize careful consideration that should be given to basic research and clinical applications of regenerative endodontics. In particular, this review article highlights significant challenges associated with residual infection and inflammation and identifies future insightful directions in creating antibacterial and immunomodulatory microenvironments so that clinicians and researchers can comprehensively understand crucial clinical aspects of regenerative endodontic procedures.

Stem Cells Derived from Human Exfoliated Deciduous Teeth Functional Assessment: Exploring the Changes of Free Fatty Acids Composition during Cultivation

The metabolic regulation of stemness is widely recognized as a crucial factor in determining the fate of stem cells. When transferred to a stimulating and nutrient-rich environment, mesenchymal stem cells (MSCs) undergo rapid proliferation, accompanied by a change in protein expression and a significant reconfiguration of central energy metabolism. This metabolic shift, from quiescence to metabolically active cells, can lead to an increase in the proportion of senescent cells and limit their regenerative potential. In this study, MSCs from human exfoliated deciduous teeth (SHEDs) were isolated and expanded in vitro for up to 10 passages. Immunophenotypic analysis, growth kinetics, in vitro plasticity, fatty acid content, and autophagic capacity were assessed throughout cultivation to evaluate the functional characteristics of SHEDs. Our findings revealed that SHEDs exhibit distinctive patterns of cell surface marker expression, possess high self-renewal capacity, and have a unique potential for neurogenic differentiation. Aged SHEDs exhibited lower proliferation rates, reduced potential for chondrogenic and osteogenic differentiation, an increasing capacity for adipogenic differentiation, and decreased autophagic potential. Prolonged cultivation of SHEDs resulted in changes in fatty acid composition, signaling a transition from anti-inflammatory to proinflammatory pathways. This underscores the intricate connection between metabolic regulation, stemness, and aging, crucial for optimizing therapeutic applications.

Epigenetic therapeutics in dental pulp treatment: Hopes, challenges and concerns for the development of next-generation biomaterials

This opinion-led review paper highlights the need for novel translational research in vital-pulp-treatment (VPT), but also discusses the challenges in translating evidence to clinics. Traditional dentistry is expensive, invasive and relies on an outmoded mechanical understanding of dental disease, rather than employing a biological perspective that harnesses cell activity and the regenerative-capacity. Recent research has focussed on developing minimally-invasive biologically-based 'fillings' that preserve the dental pulp; research that is shifting the paradigm from expensive high-technology dentistry, with high failure rates, to smart restorations targeted at biological processes. Current VPTs promote repair by recruiting odontoblast-like cells in a material-dependent process. Therefore, exciting opportunities exist for development of next-generation biomaterials targeted at regenerative processes in the dentin-pulp complex. This article analyses recent research using pharmacological-inhibitors to therapeutically-target histone-deacetylase (HDAC) enzymes in dental-pulp-cells (DPCs) that stimulate pro-regenerative effects with limited loss of viability. Consequently, HDAC-inhibitors have the potential to enhance biomaterial-driven tissue responses at low concentration by influencing the cellular processes with minimal side-effects, providing an opportunity to develop a topically-placed, inexpensive bio-inductive pulp-capping material. Despite positive results, clinical translation of these innovations requires enterprise to counteract regulatory obstacles, dental-industry priorities and to develop strong academic/industry partnerships. The aim of this opinion-led review paper is to discuss the potential role of therapeutically-targeting epigenetic modifications as part of a topical VPT strategy in the treatment of the damaged dental pulp, while considering the next steps, material considerations, challenges and future for the clinical development of epigenetic therapeutics or other 'smart' restorations in VPT.

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

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

Advances in Scaffolds Used for Pulp-Dentine Complex Tissue Engineering - A Narrative Review

Pulp necrosis in immature teeth disrupts root development and predisposes roots to fracture as a consequence of their thin walls and open apices. Regenerative endodontics is a developing treatment modality whereby necrotic pulps are replaced with newly formed healthy tissue inside the root canal. Many clinical studies have demonstrated the potential of this strategy to stimulate root maturation and apical root-end closure. However, clinical outcomes are patient-dependent and unpredictable. The development of predictable clinical protocols is achieved through the interplay of the three classical elements of tissue engineering, namely, stem cells, signaling molecules, and scaffolds. Scaffolds provide structural support for cells to adhere and proliferate and also regulate cell differentiation and metabolism. Hence, designing and fabricating an appropriate scaffold is a crucial step in tissue engineering. In this review, four main classes of scaffolds used to engineer pulp-dentine complexes, including bioceramic-based scaffolds, synthetic polymer-based scaffolds, natural polymer-based scaffolds, and composite scaffolds, are covered. Additionally, recent advances in the design, fabrication, and application of such scaffolds are analysed along with their advantages and limitations. Finally, the importance of vascular network establishment in the success of pulp-dentine complex regeneration and strategies used to create scaffolds to address this challenge are discussed.

Influencing factors of pulp-dentin complex regeneration and related biological strategies

Regenerative endodontic therapy (RET) utilizing tissue engineering approach can promote the regeneration of pulp-dentin complex to restore pulp vascularization, neuralization, immune function and tubular dentin, therefore the regenerated pulp-dentin complex will have normal function. Multiple factors may significantly affect the efficacy of RET, including stem cells, biosignaling molecules and biomaterial scaffolds. Stem cells derived from dental tissues (such as dental pulp stem cells) exhibit certain advantages in RET. Combined application of multiple signaling molecules and activation of signal transduction pathways such as Wnt/β-catenin and BMP/Smad play pivotal roles in enhancing the potential of stem cell migration, proliferation, odontoblastic differentiation, and nerve and blood vessel regeneration. Biomaterials suitable for RET include naturally-derived materials and artificially synthetic materials. Artificially synthetic materials should imitate natural tissues for biomimetic modification in order to realize the temporal and spatial regulation of pulp-dentin complex regeneration. The realization of pulp-dentin complex regeneration depends on two strategies: stem cell transplantation and stem cell homing. Stem cell homing strategy does not require the isolation and culture of stem cells in vitro, so is better for clinical application. However, in order to achieve the true regeneration of pulp-dentin complex, problems related to improving the success rate of stem cell homing and promoting their proliferation and differentiation need to be solved. This article reviews the influencing factors of pulp-dentin complex regeneration and related biological strategies, and discusses the future research direction of RET, to provide reference for clinical translation and application of RET.

Chitosan Tubes Inoculated with Dental Pulp Stem Cells and Stem Cell Factor Enhance Facial Nerve-Vascularized Regeneration in Rabbits

Facial nerve injury is a common clinical condition that leads to disfigurement and emotional distress in the affected individuals, and the recovery presents clinical challenges. Tissue engineering is the standard method to repair nerve defects. However, nerve regeneration is still not satisfactory because of poor neovascularization after implantation, especially for the long-segment nerve defects. In the current study, we aimed to investigate the potential of chitosan tubes inoculated with stem cell factor (SCF) and dental pulp stem cells (DPSCs) in facial nerve-vascularized regeneration. In the in vitro experiment, DPSCs were isolated, cultured, and then identified. The optimal concentration of SCF was screened by CCK8. Cytoskeleton and living-cell staining, migration, CCK8 test, and neural differentiation assays were performed, revealing that SCF promoted the biological activity of DPSCs. Surprisingly, SCF increased the neural differentiation of DPSCs. The migration and angiogenesis experiments were carried out to show that SCF promoted the angiogenesis and migration of human umbilical vein endothelial cells (HUVECs). In the facial nerve, 7 mm defects of New Zealand white rabbits, hematoxylin-eosin (HE), immunohistochemistry, toluidine blue staining, and transmission electron microscopy observation were performed at 12 weeks postsurgery to show more nerve fibers and better myelin sheath in the SCF + DPSC group. In addition, the whisker movements, Masson's staining, and western blot assays were performed, demonstrating functional repair and that the expression level of CD31 protein in the group SCF + DPSCs was relatively close to that in the group Autograft. In summary, chitosan tubes inoculated with SCF and DPSCs increased neurovascularization and provided an effective method for repairing facial nerve defects, indicating great promise for clinical application.

Changes in Migratory Speed Rate of Human Dental Pulp Stromal Cells Cultured in Advanced Platelet-Rich Fibrin

OBJECTIVE

 Migratory speed rate evaluation of human dental pulp stromal cells (hDP-SCs) is one of the important steps in dental pulp regeneration. Therefore, the aim of the study is to analyze various concentrations of advanced platelet-rich fibrin (A-PRF) culture media toward hDP-SCs' migratory speed rate evaluations.

MATERIALS AND METHODS

 The hDP-SCs were divided into four groups: control: hDP-SCs in Dulbecco's modified Eagle medium + 10% fetal bovine serum group; hDP-SCs in 1% A-PRF group; hDP-SCs in 5% A-PRF group; and hDP-SCs in 10% A-PRF group, which were planted in 24-well (5 × 10⁴ cell/well). The migratory speed rate of all groups was measured by using cell migration assay (scratch wound assay) after 24 hours. Cell characteristics were evaluated under microscope (Inverted microscope, Zeiss, Observer Z1, UK) that can be read through image-J interpretation. This image J represented the measurement of migratory speed rate (nm/h) data. Statistical analysis was conducted using one-way analysis of variance and post hoc Tamhane's test (p < 0.05) (IBM SPSS Statistics Software, version 22.0).

RESULTS

 There was a statistically significant difference in the migratory speed rates of hDP-SCs among various concentration groups of A-PRF (1, 5, and 10%) compared with the control group.

CONCLUSION

The increase in the migratory speed rate of hDP-SCs was highest in 10% A-PRF group.

Biomaterials for recruiting and activating endogenous stem cells in situ tissue regeneration

Over the past two decades in situ tissue engineering has emerged as a new approach where biomaterials are used to harness the body's own stem/progenitor cells to regenerate diseased or injured tissue. Immunomodulatory biomaterials are designed to promote a regenerative environment, recruit resident stem cells to diseased or injured tissue sites, and direct them towards tissue regeneration. This review explores advances gathered from in vitro and in vivo studies on in situ tissue regenerative therapies. Here we also examine the different ways this approach has been incorporated into biomaterial sciences in order to create customized biomaterial products for therapeutic applications in a broad spectrum of tissues and diseases. STATEMENT OF SIGNIFICANCE: Biomaterials can be designed to recruit stem cells and coordinate their behavior and function towards the restoration or replacement of damaged or diseased tissues in a process known as in situ tissue regeneration. Advanced biomaterial constructs with precise structure, composition, mechanical, and physical properties can be transplanted to tissue site and exploit local stem cells and their micro-environment to promote tissue regeneration. In the absence of cells, we explore the critical immunomodulatory, chemical and physical properties to consider in material design and choice. The application of biomaterials for in situ tissue regeneration has the potential to address a broad range of injuries and diseases.

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.

Successful Application of a Galanin-Coated Scaffold for Periodontal Regeneration

The nervous system exerts finely tuned control over all aspects of the life of an organism, including pain, sensation, growth, and development. Recent developments in tissue regeneration research have increasingly turned to small molecule peptides to tailor and augment the biological response following tissue loss or injury. In the present study, we have introduced the small molecule peptide galanin (GAL) as a novel scaffold-coating agent for the healing and regeneration of craniofacial tissues. Using immunohistochemistry, we detected GAL and GAL receptors in healthy periodontal tissues and in the proximity of blood vessels, while exposure to our periodontal disease regimen resulted in a downregulation of GAL. In a 3-dimensional bioreactor culture, GAL coating of collagen scaffolds promoted cell proliferation and matrix synthesis. Following subcutaneous implantation, GAL-coated scaffolds were associated with mineralized bone-like tissue deposits, which reacted positively for alizarin red and von Kossa, and demonstrated increased expression and protein levels of RUNX2, OCN, OSX, and iBSP. In contrast, the GAL receptor antagonist galantide blocked the effect of GAL on Runx2 expression and inhibited mineralization in our subcutaneous implantation model. Moreover, GAL coating promoted periodontal regeneration and a rescue of the periodontal defect generated in our periodontitis model mice. Together, these data demonstrate the efficacy of the neuropeptide GAL as a coating material for tissue regeneration. They are also suggestive of a novel role for neurogenic signaling pathways in craniofacial and periodontal regeneration.

A narrative overview of utilizing biomaterials to recapitulate the salient regenerative features of dental-derived mesenchymal stem cells

Tissue engineering approaches have emerged recently to circumvent many limitations associated with current clinical practices. This elegant approach utilizes a natural/synthetic biomaterial with optimized physiomechanical properties to serve as a vehicle for delivery of exogenous stem cells and bioactive factors or induce local recruitment of endogenous cells for in situ tissue regeneration. Inspired by the natural microenvironment, biomaterials could act as a biomimetic three-dimensional (3D) structure to help the cells establish their natural interactions. Such a strategy should not only employ a biocompatible biomaterial to induce new tissue formation but also benefit from an easily accessible and abundant source of stem cells with potent tissue regenerative potential. The human teeth and oral cavity harbor various populations of mesenchymal stem cells (MSCs) with self-renewing and multilineage differentiation capabilities. In the current review article, we seek to highlight recent progress and future opportunities in dental MSC-mediated therapeutic strategies for tissue regeneration using two possible approaches, cell transplantation and cell homing. Altogether, this paper develops a general picture of current innovative strategies to employ dental-derived MSCs combined with biomaterials and bioactive factors for regenerating the lost or defective tissues and offers information regarding the available scientific data and possible applications.

Evaluation of Silk Fibroin-RGD-Stem Cell Factor Scaffold Effect on Adhesion, Migration, and Proliferation of Stem Cells of Apical Papilla

This study explored the effects of a silk fibroin-RGD-stem cell factor (SF-RGD-SCF) scaffold on the migration, proliferation, and attachment of stem cells of apical papilla (SCAPs). SF, SF-RGD, SF-SCF, and SF-RGD-SCF scaffolds were prepared, and laser confocal microscopy was used to observe the adhesion and growth status of SCAPs on the scaffolds. Furthermore, the numbers of SCAPs on the scaffolds were counted by a digestion counting method to evaluate their proliferation. Cells on the SF-RGD-SCF scaffold proliferated more than those on the other scaffolds and showed a more obvious tendency to migrate to the scaffold's deep porous structure after 7 d seeding. Live/dead cell staining results showed that almost all the adhered cells were alive after 7 d. Furthermore, cell counting showed that the number of cells on the SF-RGD-SCF scaffold was highest after both 1 and 7 d (P < 0.05). Thus, the SF-RGD-SCF composite is biocompatible and promotes the migration, adhesion, and proliferation of SCAPs, making it of potential use as a scaffold for cell-homing pulp regeneration.

Therapeutic applications of dental pulp stem cells in regenerating dental, periodontal and oral-related structures

Dental pulp stem cells (DPSCs) have emerged as a promising tool with great potential for use in tissue regeneration and engineering. Some of the main advantages of these cells are their multifaceted differentiation capacity, along with their high proliferation rate, a relative simplicity of extraction and culture that enables obtaining patient-specific cell lines for their use in autologous cell therapy. PubMed, Scopus and Google Scholar databases were searched for relevant articles related to the use of DPSCs in regeneration of dentin-pulp complex (DPC), periodontal tissues, salivary gland and craniomaxillofacial bone defects. Few studies were found regarding the use of DPSCs for regeneration of DPC. Scaffold-based combined with DPSCs isolated from healthy pulps was the strategy used for DPC regeneration. Studies involved subcutaneous implantation of scaffolds loaded with DPSCs pretreated with odontogenic media, or performed on human tooth root model as a root slice. Most of the studies were related to periodontal tissue regeneration which mainly utilized DPSCs/secretome. For periodontal tissues, DPSCs or their secretome were isolated from healthy or inflamed pulps and they were used either for preclinical or clinical studies. Regarding salivary gland regeneration, the submandibular gland was the only model used for the preclinical studies and DPSCs or their secretome were isolated only from healthy pulps and they were used in preclinical studies. Likewise, DPSCs have been studied for craniomaxillofacial bone defects in the form of mandibular, calvarial and craniofacial bone defects where DPSCs were isolated only from healthy pulps for preclinical and clinical studies. From the previous results, we can conclude that DPSCs is promising candidate for dental and oral tissue regeneration.

Microenvironment Influences Odontogenic Mesenchymal Stem Cells Mediated Dental Pulp Regeneration

Dental pulp as a source of nutrition for the whole tooth is vulnerable to trauma and bacterial invasion, which causes irreversible pulpitis and pulp necrosis. Dental pulp regeneration is a valuable method of restoring the viability of the dental pulp and even the whole tooth. Odontogenic mesenchymal stem cells (MSCs) residing in the dental pulp environment have been widely used in dental pulp regeneration because of their immense potential to regenerate pulp-like tissue. Furthermore, the regenerative abilities of odontogenic MSCs are easily affected by the microenvironment in which they reside. The natural environment of the dental pulp has been proven to be capable of regulating odontogenic MSC homeostasis, proliferation, and differentiation. Therefore, various approaches have been applied to mimic the natural dental pulp environment to optimize the efficacy of pulp regeneration. In addition, odontogenic MSC aggregates/spheroids similar to the natural dental pulp environment have been shown to regenerate well-organized dental pulp both in preclinical and clinical trials. In this review, we summarize recent progress in odontogenic MSC-mediated pulp regeneration and focus on the effect of the microenvironment surrounding odontogenic MSCs in the achievement of dental pulp regeneration.

The molecular functions of Biodentine and mineral trioxide aggregate in lipopolysaccharide-induced inflamed dental pulp cells

AIM

To explore the proliferation, adhesion and differentiation response and the underlying mechanisms that occur in lipopolysaccharide (LPS)-induced inflamed dental pulp cells (DPCs) in contact with Biodentine and mineral trioxide aggregate (MTA).

METHODOLOGY

The DPCs were isolated from three healthy donors and named DPC-H1 to DPC-H3. The DPCs were pre-cultured with 2 or 5 μg mL^-1 LPS for 24 h to induce inflammation. The expression of inflammation marker miR-146a was detected by q-PCR. The normal and LPS-induced DPCs were further treated with 0.14 mg mL^-1 Biodentine or 0.13 mg mL^-1 MTA for 24 h. MTT assay and adhesion assay were used to analyse the changes of cell phenotypes. DSPP, AKT and ERK expressions were detected by Western blotting. The data were analysed by Mann-Whitney test or two-way anova. Differences were considered statistically significant when P < 0.05.

RESULTS

In LPS-induced DPCs, Biodentine and MTA treatment neither induced nor aggravated LPS-induced inflammation, but their presence did increase the expression of the odontogenic differentiation marker DSPP. Under 2 or 5 μg mL^-1 LPS-induced inflammation, Biodentine and MTA promoted the proliferation of DPC cells, and significantly in DPC-H2 (P < 0.0001 for both reagents). With the treatment of 2 μg mL^-1 LPS, the cell adhesion of DPCs on the fibronectin-coated culture plates was increased significantly by Biodentine (P = 0.0413) and MTA (P < 0.0001). Biodentine and MTA regulated cell adhesion on the fibronectin-coated culture plates (P < 0.0001 for both reagents) and proliferation (P < 0.0001 for both reagents) via the AKT pathway. However, the AKT pathway was not involved in the expression of DSPP induced by Biodentine and MTA.

CONCLUSION

Biodentine and MTA enhanced the proliferation, adhesion and differentiation of LPS-induced DPCs. The proliferation and adhesion process induced by Biodentine and MTA was via the AKT pathway. However, the cellular differentiation process might not use the same pathway, and this needs to be explored in future studies.

Scaffold-based developmental tissue engineering strategies for ectodermal organ regeneration

Tissue engineering (TE) is a multidisciplinary research field aiming at the regeneration, restoration, or replacement of damaged tissues and organs. Classical TE approaches combine scaffolds, cells and soluble factors to fabricate constructs mimicking the native tissue to be regenerated. However, to date, limited success in clinical translations has been achieved by classical TE approaches, because of the lack of satisfactory biomorphological and biofunctional features of the obtained constructs. Developmental TE has emerged as a novel TE paradigm to obtain tissues and organs with correct biomorphology and biofunctionality by mimicking the morphogenetic processes leading to the tissue/organ generation in the embryo. Ectodermal appendages, for instance, develop in vivo by sequential interactions between epithelium and mesenchyme, in a process known as secondary induction. A fine artificial replication of these complex interactions can potentially lead to the fabrication of the tissues/organs to be regenerated. Successful developmental TE applications have been reported, in vitro and in vivo, for ectodermal appendages such as teeth, hair follicles and glands. Developmental TE strategies require an accurate selection of cell sources, scaffolds and cell culture configurations to allow for the correct replication of the in vivo morphogenetic cues. Herein, we describe and discuss the emergence of this TE paradigm by reviewing the achievements obtained so far in developmental TE 3D scaffolds for teeth, hair follicles, and salivary and lacrimal glands, with particular focus on the selection of biomaterials and cell culture configurations.

Stem Cell-based Dental Pulp Regeneration: Insights From Signaling Pathways

Deep caries, trauma, and severe periodontitis result in pulpitis, pulp necrosis, and eventually pulp loss. However, no clinical therapy can regenerate lost pulp. A novel pulp regeneration strategy for clinical application is urgently needed. Signaling transduction plays an essential role in regulating the regenerative potentials of dental stem cells. Cytokines or growth factors, such as stromal cell-derived factor (SDF), fibroblast growth factor (FGF), bone morphogenetic protein (BMP), vascular endothelial growth factor (VEGF), WNT, can promote the migration, proliferation, odontogenic differentiation, pro-angiogenesis, and pro-neurogenesis potentials of dental stem cells respectively. Using the methods of signaling modulation including growth factors delivery, genetic modification, and physical stimulation has been applied in multiple preclinical studies of pulp regeneration based on cell transplantation or cell homing. Transplanting dental stem cells and growth factors encapsulated into scaffold regenerated vascularized pulp-like tissue in the root canal. Also, injecting a flowable scaffold only with chemokines recruited endogenous stem/progenitor cells for pulp regeneration. Notably, dental pulp regeneration has gradually developed into the clinical phase. These findings enlightened us on a novel strategy for structural and functional pulp regeneration through elaborate modulation of signaling transduction spatially and temporally via clinically applicable growth factors delivery. But challenges, such as the adverse effects of unphysiological signaling activation, the controlled drug release system, and the safety of gene modulation, are necessary to be tested in future works for promoting the clinical translation of pulp regeneration.

SETD1 and NF-κB Regulate Periodontal Inflammation through H3K4 Trimethylation

The inflammatory response to periodontal pathogens is dynamically controlled by the chromatin state on inflammatory gene promoters. In the present study, we have focused on the effect of the methyltransferase SETD1B on histone H3 lysine K4 (H3K4) histone trimethylation on inflammatory gene promoters. Experiments were based on 3 model systems: 1) an in vitro periodontal ligament (PDL) cell culture model for the study of SETD1 function as it relates to histone methylation and inflammatory gene expression using Porphyromonas gingivalis lipopolysaccharide (LPS) as a pathogen, 2) a subcutaneous implantation model to determine the relationship between SETD1 and nuclear factor κB (NF-κB) through its activation inhibitor BOT-64, and 3) a mouse periodontitis model to test whether the NF-κB activation inhibitor BOT-64 reverses the inflammatory tissue destruction associated with periodontal disease. In our PDL progenitor cell culture model, P. gingivalis LPS increased H3K4me3 histone methylation on IL-1β, IL-6, and MMP2 gene promoters, while SETD1B inhibition decreased H3K4me3 enrichment and inflammatory gene expression in LPS-treated PDL cells. LPS also increased SETD1 nuclear localization in a p65-dependent fashion and the nuclear translocation of p65 as mediated through SETD1, suggestive of a synergistic effect between SETD1 and p65 in the modulation of inflammation. Confirming the role of SETD1 in p65-mediated periodontal inflammation, BOT-64 reduced the number of SETD1-positive cells in inflamed periodontal tissues, restored periodontal tissue integrity, and enhanced osteogenesis in a periodontal inflammation model in vivo. Together, these results have established the histone lysine methyltransferase SETD1 as a key factor in the opening of the chromatin on inflammatory gene promoters through histone H3K4 trimethylation. Our studies also confirmed the role of BOT-64 as a potent molecular therapeutic for the restoration of periodontal health through the inhibition of NF-κB activity and the amelioration of SETD1-induced chromatin relaxation.

Dental stem cells: The role of biomaterials and scaffolds in developing novel therapeutic strategies

Dental stem cells (DSCs) are self-renewable cells that can be obtained easily from dental tissues, and are a desirable source of autologous stem cells. The use of DSCs for stem cell transplantation therapeutic approaches is attractive due to their simple isolation, high plasticity, immunomodulatory properties, and multipotential abilities. Using appropriate scaffolds loaded with favorable biomolecules, such as growth factors, and cytokines, can improve the proliferation, differentiation, migration, and functional capacity of DSCs and can optimize the cellular morphology to build tissue constructs for specific purposes. An enormous variety of scaffolds have been used for tissue engineering with DSCs. Of these, the scaffolds that particularly mimic tissue-specific micromilieu and loaded with biomolecules favorably regulate angiogenesis, cell-matrix interactions, degradation of extracellular matrix, organized matrix formation, and the mineralization abilities of DSCs in both in vitro and in vivo conditions. DSCs represent a promising cell source for tissue engineering, especially for tooth, bone, and neural tissue restoration. The purpose of the present review is to summarize the current developments in the major scaffolding approaches as crucial guidelines for tissue engineering using DSCs and compare their effects in tissue and organ regeneration.

SCF/C-Kit Signaling Induces Self-Renewal of Dental Pulp Stem Cells

INTRODUCTION

The maintenance of a stem cell pool is imperative to enable healing processes in the dental pulp tissue throughout life. As such, knowing mechanisms underlying stem cell self-renewal is critical to understand pulp pathophysiology and pulp regeneration. The purpose of this study was to evaluate the impact of stem cell factor (SCF) signaling through its receptor tyrosine kinase (c-Kit) on the self-renewal of human dental pulp stem cells (hDPSCs).

METHODS

The hDPSCs were stably transduced with lentiviral vectors expressing shRNA-c-Kit or vector control. The impact of the SCF/c-Kit axis on hDPSC self-renewal was evaluated by using a pulpsphere assay in low attachment conditions and by evaluating the expression of polycomb complex protein Bmi-1 (master regulator of self-renewal) by Western blot and flow cytometry.

RESULTS

The c-Kit-silenced hDPSCs formed fewer pulpspheres when compared with hDPSCs transduced with control vector (P < .05). Evaluation of pulpsphere morphology revealed the presence of 3 distinct sphere types, ie, holospheres, merospheres, and paraspheres. Although c-Kit silencing decreased the number of holospheres compared with control cells (P < .05), it had no effect on the number of merospheres and paraspheres. Recombinant human stem cell factor (rhSCF) increased the number of holospheres (P < .05) and induced dose-dependent Bmi-1 expression in hDPSCs. As expected, the inductive capacity of rhSCF on Bmi-1 expression and fraction of Bmi-1-positive cells was inhibited when we silenced c-Kit in hDPSCs.

CONCLUSIONS

These results unveiled the role of SCF/c-Kit signaling on the self-renewal of hDPSCs and suggested that this pathway enables long-term maintenance of stem cell pools in human dental pulps.

A Customized Self-Assembling Peptide Hydrogel-Wrapped Stem Cell Factor Targeting Pulp Regeneration Rich in Vascular-Like Structures

Pulp regeneration is to replace the inflamed/necrotic pulp tissue with regenerated pulp-like tissue to rejuvenate the teeth. Self-assembling peptide hydrogels RADA16-I (Ac-(RADA16-I)₄-CONH₂) can provide a three-dimensional environment for cells. The stem cell factor (SCF) plays a crucial role in homing stem cells. Combining these advantages, our study investigated the effects of SCF-RADA16-I on adhesion, proliferation, and migration of human dental pulp stem cells (DPSCs) and the angiogenesis of human umbilical vein endothelial cells (HUVECs). The β-sheet and grid structure were observed by circular dichroism (CD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Cytoskeleton staining, living cell staining, cell viability, cell migration, angiogenesis, and western blot assays were performed, and the results indicated that all the SCF groups were superior to the corresponding non-SCF groups in cell adhesion, proliferation, migration, and angiogenesis. RADA16-I provided a three-dimensional environment for DPSCs. Besides, the SCF promoted HUVECs to form more vascular-like structures and release more vascular endothelial growth factor A. In summary, the SCF-loaded RADA16-I scaffold improved adhesion, proliferation, and migration of DPSCs and the formation of more vascular-like structures of HUVECs. SCF-RADA16-I holds promise for guided pulp regeneration, and it can potentially be applied widely in tissue engineering and translational medicine in the future.

Pulp stem cells derived from human permanent and deciduous teeth: Biological characteristics and therapeutic applications

Human pulp stem cells (PSCs) include dental pulp stem cells (DPSCs) isolated from dental pulp tissues of human extracted permanent teeth and stem cells from human exfoliated deciduous teeth (SHED). Depending on their multipotency and sensitivity to local paracrine activity, DPSCs and SHED exert therapeutic applications at multiple levels beyond the scope of the stomatognathic system. This review is specifically concentrated on PSC-updated biological characteristics and their promising therapeutic applications in (pre)clinical practice. Biologically, distinguished from conventional mesenchymal stem cell markers in vitro, NG2, Gli1, and Celsr1 have been evidenced as PSC markers in vivo. Both perivascular cells and glial cells account for PSC origin. Therapeutically, endodontic regeneration is where PSCs hold the most promises, attributable of PSCs' robust angiogenic, neurogenic, and odontogenic capabilities. More recently, the interplay between cell homing and liberated growth factors from dentin matrix has endowed a novel approach for pulp-dentin complex regeneration. In addition, PSC transplantation for extraoral tissue repair and regeneration has achieved immense progress, following their multipotential differentiation and paracrine mechanism. Accordingly, PSC banking is undergoing extensively with the intent of advancing tissue engineering, disease remodeling, and (pre)clinical treatments.

Dental stem cells in tooth repair: A systematic review

Background: Dental stem cells (DSCs) are self-renewable teeth cells, which help maintain or develop oral tissues. These cells can differentiate into odontoblasts, adipocytes, cementoblast-like cells, osteoblasts, or chondroblasts and form dentin/pulp. This systematic review aimed to summarize the current evidence regarding the role of these cells in dental pulp regeneration. Methods: We searched the following databases: PubMed, Cochrane Library, MEDLINE, SCOPUS, ScienceDirect, and Web of Science using relevant keywords. Case reports and non-English studies were excluded. We included all studies using dental stem cells in tooth repair whether in vivo or in vitro studies. Results: Dental pulp stem cell (DPSCs) is the most common type of cell. Most stem cells are incorporated and implanted into the root canals in different scaffold forms. Some experiments combine growth factors such as TDM, BMP, and G-CSF with stem cells to improve the results. The transplant of DPSCs and stem cells from apical papilla (SCAPs) was found to be associated with pulp-like recovery, efficient revascularization, enhanced chondrogenesis, and direct vascular supply of regenerated tissue. Conclusion: The current evidence suggests that DPSCs, stem cells from human exfoliated deciduous teeth, and SCAPs are capable of providing sufficient pulp regeneration and vascularization. For the development of the dental repair field, it is important to screen for more effective stem cells, dentine releasing therapies, good biomimicry scaffolds, and good histological markers.

Histone Methylation Mechanisms Modulate the Inflammatory Response of Periodontal Ligament Progenitors

Inflammatory conditions affect periodontal ligament (PDL) homeostasis and diminish its regenerative capacity. The complexity of biological activities during an inflammatory response depends on genetic and epigenetic mechanisms. To characterize the epigenetic changes in response to periodontal pathogens we have focused on histone lysine methylation as a relatively stable chromatin modification involved in the epigenetic activation and repression of transcription and a prime candidate mechanism responsible for the exacerbated and prolonged response of periodontal cells and tissues to dental plaque biofilm. To determine the effect of inflammatory conditions on histone methylation profiles, related gene expression and cellular functions of human periodontal ligament (hPDL) progenitor cells, a hPDL cell culture system was subjected to bacterial cell wall toxin exposure [lipopolysaccharide (LPS)]. Chromatin immunoprecipitation-on-chip analysis revealed that healthy PDL cells featured high enrichment levels for the active H3K4me3 mark at COL1A1, COL3, and RUNX2 gene promoters, whereas there were high occupancy levels for the repressive H3K27me3 marks at DEFA4, CCL5, and IL-1β gene promoters. In response to LPS, H3K27me3 enrichment increased on extracellular matrix and osteogenesis lineage gene promoters, whereas H3K4me3 enrichment increased on the promoters of inflammatory response genes, suggestive of an involvement of epigenetic mechanisms in periodontal lineage differentiation and in the coordination of the periodontal inflammatory response. On a gene expression level, LPS treatment downregulated COL1A1, COL3A1, and RUNX2 expression and upregulated CCL5, DEFA4, and IL-1β gene expression. LPS also greatly affected PDL progenitor function, including a reduction in proliferation and differentiation potential and an increase in cell migration capacity. Confirming the role of epigenetic mechanisms in periodontal inflammatory conditions, our studies highlight the significant role of histone methylation mechanisms and modification enzymes in the inflammatory response to LPS bacterial cell wall toxins and periodontal stem cell function.

Acellular biomaterial strategies for endodontic regeneration

Dental decay is treated by removing infected dental tissues such as dentine and restoring the tooth with a material. However, the vast majority of these materials have been designed to be mechanically robust and bioinert, whereas the potential regenerative properties of a biomaterial have not been considered. In endodontics for example, materials are used to seal the pulp cavity to avoid bacterial colonisation of the tooth and prevent further infection. While these treatments are effective in the short term, many of these materials have not been designed to interface with the pulp tissue in a biocompatible manner and are often cytotoxic. This can lead to less favourable long-term outcomes such as devitalisation of the tooth via root-canal therapy or extraction of the tooth. Clinical outcomes could be improved if regenerative approaches were followed whereby the biology of the tooth is engineered for repair and regeneration often with the support of a biomaterial. Within these, acellular or cell homing approaches are particularly interesting, as some regulatory hurdles associated with cellular therapies could be circumvented which may aid their clinical translation. In this review, we highlight progress in regenerative dentistry and focus on exciting developments using acellular biomaterials for regenerating dental tissues.

[Effects of electrospun collagen nanofibrous matrix on the biological behavior of human dental pulp cells]

OBJECTIVE

To compare cell adhesion, proliferation and odontoblastic differentiation of human dental pulp cells (hDPCs) on electrospun collagen nanofibrous matrix (Col_NFM) with that on collagen flat film (Col-FF), to investigate the biological effect of collagen nanofibrous matrix on hDPCs.

METHODS

The surface morphology of the two different collagen scaffold was analyzed by scanning electron microscopy (SEM), and the contact angle and the swelling ratio were also measured. Then hDPCs were implanted on the two different collagen scaffolds, the cell morphology was observed using SEM and laser scanning microscope (LSM), and cell proliferation was evaluated by the CCK-8 assay. After hDPCs cultured on the two different collagen scaffold with odontoblastic medium for 14 days, the expression of odontoblastic differentiation related genes was detected by real-time PCR, and alizarin red staining was used to test the formation of mineralized nodules.

RESULTS

From the SEM figures, the fibers' diameter of Col_NFM was (884±159) nm, and there were abundant three dimensional connected pore structures between the fibers of Col_NFM, while the surface of Col_FF was completely flat without pore structure. The contact angle at 0 s of Col_NFM was 85.03°±4.45°, and that of Col_FF was 98.98°±5.81°. The swelling ratio of Col_NFM was approximately 3 folds compared with dry weight sample, while that of Col_FF was just 1 fold. Thus Col_NFM indicated better hydrophilicity and swelling property. SEM and LSM showed that hDPCs on Col_NFM presented an irregular and highly branched phenotype, and could penetrate into the nanofibrous scaffold. In contrast, the cells were spread only on the surface of Col_FF with a spindle-shaped morphology. CCK-8 assays showed that hDPCs on Col_NFM showed higher proliferation rate than on Col_FF. After hDPCs were cultured on the two different collagen scaffolds with odontoblastic medium for 14 days, more expressions of odontoblastic differentiation related genes, such as dentin sialophosphoprotein (DSPP) and dentin matrix proten-1 (DMP1) were determined in Col_NFM group (P<0.05), and more mineralization depositions were also observed in Col_NFM group according to the results of alizarin red staining.

CONCLUSION

Col_NFM with nanoscale microstructure achieves better hydrophilic and swelling properties than Col_FF, and hDPCs cultured with Col_NFM present higher activity on cell adhesion, proliferation and odontoblastic differentiation.

The role of stem cell therapy in regeneration of dentine-pulp complex: a systematic review

Infection of the dental pulp will result in inflammation and eventually tissue necrosis which is treated conventionally by pulpectomy and root canal treatment. Advances in regenerative medicine and tissue engineering along with the introduction of new sources of stem cells have led to the possibility of pulp tissue regeneration. This systematic review analyzes animal studies published since 2010 to determine the ability of stem cell therapy to regenerate the dentine-pulp complex (DPC) and the success of clinical protocols. In vitro and human clinical studies are excluded and only the experimental studies on animal models were included. Dental pulp stem cells constitute the most commonly used cell type. The majority of stem cells are incorporated into various types of scaffold and implanted into root canals. Some of the studies combine growth factors with stem cells in an attempt to improve the outcome. Studies of ectopic transplantation using small animal models are simple and non-systematic evaluation techniques. Stem cell concentrations have not been so far reported; therefore, the translational value of such animal studies remains questionable. Though all types of stem cells appear capable of regenerating a dentine-pulp complex, still several factors have been considered in selecting the cell type. Co-administrative factors are essential for inducing the systemic migration of stem cells, and their vascularization and differentiation into odontoblast-like cells. Scaffolds provide a biodegradable structure able to control the release of growth factors. To identify problems and reduce costs, novel strategies should be initially tested in subcutaneous or renal capsule implantation followed by root canal models to confirm results.

Dual ECM Biomimetic Scaffolds for Dental Pulp Regenerative Applications

Dental pulp is a highly vascularized and innervated tissue that provides sensitivity and vitality to the tooth. Chronic caries results in an infected pulp tissue prone to necrosis. Existing clinical treatments replace the living pulp tissue with a non-responsive resin filling resulting in loss of tooth vitality. Tissue engineering approaches to dental pulp tissue regeneration have been investigated to preserve tooth vitality and function. However, a critical criterion is the choice of growth factors that may promote mesenchymal stem cell differentiation and more importantly, vascularization. But, the problems associated with growth factor dosage, delivery, safety, immunological and ectopic complications affect their translatory potential severely. The purpose of this study is to develop, characterize and evaluate a biomimetic native extracellular matrix (ECM) derived dual ECM scaffold that consists of a pulp-specific ECM to promote MSC attachment, proliferation and differentiation and an endothelial ECM to promote migration of host endothelial cells and eventual vascularization in vivo. Our results show that the dual ECM scaffolds possess similar properties as a pulp-ECM scaffold to promote MSC attachment and odontogenic differentiation in vitro. Additionally, when implanted subcutaneously in a tooth root slice model in vivo, the dual ECM scaffolds promoted robust odontogenic differentiation of both dental pulp and bone marrow derived MSCs and also extensive vascularization when compared to respective controls. These scaffolds are mass producible for clinical use and hence have the potential to replace root canal therapy as a treatment for chronic dental caries.

Stem Cells from Human Extracted Deciduous Teeth Expanded in Foetal Bovine and Human Sera Express Different Paracrine Factors After Exposure to Freshly Prepared Human Serum

BACKGROUND

The response of stem cells to paracrine factors within the host's body plays an important role in the regeneration process after transplantation. The aim of this study was to determine the viability and paracrine factor profile of stem cells from human extracted deciduous teeth (SHED) pre-cultivated in media supplemented with either foetal bovine serum (FBS) or pooled human serum (pHS) in the presence of individual human sera (iHS).

METHODS

SHED (n = 3) from passage 4 were expanded in FBS (FBS-SHED) or pHS (pHS-SHED) supplemented media until passage 7. During expansion, the proliferation of SHED was determined. Cells at passage 7 were further expanded in human serum from four individual donors (iHS) for 120 h followed by assessment of cell viability and profiling of the secreted paracrine factors.

RESULTS

Proliferation of SHED was significantly higher (p < 0.05) in pHS supplemented media compared to FBS supplemented media. pHS-SHED also maintained their higher proliferation rate compared to FBS-SHED in the presence of iHS. In iHS supplemented media, FBS-SHED expressed significantly higher levels of SDF-1A (p < 0.05) after 24 h compared to pHS-SHED. Similar results were found for HGF (p < 0.01), LIF (p < 0.05), PDGF-BB (p < 0.05), SDF-1A (p < 0.01), and IL-10 (p < 0.05) when cell culture supernatants from FBS-SHED were profiled 120 h post-incubation.

CONCLUSION

SHED expanded in pHS instead of FBS have higher proliferative capacity and show an altered secretion profile. Further studies are needed to determine whether these differences could result in better engraftment and regeneration following transplantation.

Administration of signalling molecules dictates stem cell homing for in situ regeneration

Ex vivo-expanded stem cells have long been a cornerstone of biotherapeutics and have attracted increasing attention for treating intractable diseases and improving tissue regeneration. However, using exogenous cellular materials to develop restorative treatments for large numbers of patients has become a major concern for both economic and safety reasons. Advances in cell biological research over the past two decades have expanded the potential for using endogenous stem cells during wound healing processes, and in particular, recent insight into stem cell movement and homing has prompted regenerative research and therapy based on recruiting endogenous cells. Inspired by the natural healing process, artificial administration of specific chemokines as signals systemically or at the injury site, typically using biomaterials as vehicles, is a state-of-the-art strategy that potentiates stem cell homing and recreates an anti-inflammatory and immunomodulatory microenvironment to enhance in situ tissue regeneration. However, pharmacologically coaxing endogenous stem cells to act as therapeutics in the field of biomedicine remains in the early stages; its efficacy is limited by the lack of innovative methodologies for chemokine presentation and release. This review describes how to direct the homing of endogenous stem cells via the administration of specific signals, with a particular emphasis on targeted signalling molecules that regulate this homing process, to enhance in situ tissue regeneration. We also provide an outlook on and critical considerations for future investigations to enhance stem cell recruitment and harness the reparative potential of these recruited cells as a clinically relevant cell therapy.

Chick Embryo Model for Homing and Host Interactions of Tissue Engineering-Purposed Human Dental Stem Cells

Human dental stem cells (hDSC) have a potential for regenerative therapies and could differentiate in vitro into many tissues, such as dentin, nerve, and vascular endothelium. Gallus gallus domesticus developing fertilized egg or chick embryo is an experimental model absent of xenografts rejection, largely employed in replacement of mammal species in scientific research and preclinical studies to evaluate angiogenesis and vasculogenesis, tissue differentiation, and embryonic development. This multiscale research deals with the homing and cell signaling effects of a standardized hDSC toward the receptor tissues of G. gallus domesticus in ovo. The hDSC were obtained from the explantation from third molars, characterized by cell cytometry, and employed without any further purification procedure. Four experimental groups were studied, according to the kind of cell tracing strategy, named: Control, mCherry-labeled hDSC, QTracker-labeled hDSC, and QTracker-exposed controls. The eggs were kept in an incubator temperature of 37.6°C and humidity 86%, and the embryos were euthanized after 10 days of incubation. In vivo fluorescence and histological analysis were conducted. The fluorescence of the embryos inoculated with mCherry hDSC or the QTracker hDSC was associated with the bones and the beak tooth, and labeled cell islands could be localized in part of the samples. The inoculation of the QTracker probe resulted in proliferating bone tissue labeling. The hDSC inoculated groups presented cartilage plate hypertrophy and atypical morphology, meanwhile Control eggs were negative. The results demonstrated that hDSC can migrate to the cartilaginous tissues of the chick embryos, survive in this environment, implant, and interfere with the growth of developing bone.

Dental pulp regeneration via cell homing

The typical treatment for irreversibly inflamed/necrotic pulp tissue is root canal treatment. As an alternative approach, regenerative endodontics aims to regenerate dental pulp-like tissues using two possible strategies: cell transplantation and cell homing. The former requires exogenously transplanted stem cells, complex procedures and high costs; the latter employs the host's endogenous cells to achieve tissue repair/regeneration, which is more clinically translatable. This systematic review examines cell homing for dental pulp regeneration, selecting articles on in vitro experiments, in vivo ectopic transplantation models and in situ pulp revascularization. MEDLINE/PubMed and Scopus databases were electronically searched for articles without limits in publication date. Two reviewers independently screened and included papers according to the predefined selection criteria. The electronic searches identified 46 studies. After title, abstract and full-text examination, 10 articles met the inclusion criteria. In vitro data highlighted that multiple cytokines have the capacity to induce migration, proliferation and differentiation of dental pulp stem/progenitor cells. The majority of the in vivo studies obtained regenerated connective pulp-like tissues with neovascularization. In some cases, the samples showed new innervation and new dentine deposition. The in situ pulp revascularization regenerated intracanal pulp-like tissues with neovascularization, innervation and dentine formation. Cell homing strategies for pulp regeneration need further understanding and improvement if they are to become a reliable and effective approach in endodontics. Nevertheless, cell homing currently represents the most clinically viable pathway for dental pulp regeneration.

Current Understanding of the Pathways Involved in Adult Stem and Progenitor Cell Migration for Tissue Homeostasis and Repair

With the advancements in the field of adult stem and progenitor cells grows the recognition that the motility of primitive cells is a pivotal aspect of their functionality. There is accumulating evidence that the recruitment of tissue-resident and circulating cells is critical for organ homeostasis and effective injury responses, whereas the pathobiology of degenerative diseases, neoplasm and aging, might be rooted in the altered ability of immature cells to migrate. Furthermore, understanding the biological machinery determining the translocation patterns of tissue progenitors is of great relevance for the emerging methodologies for cell-based therapies and regenerative medicine. The present article provides an overview of studies addressing the physiological significance and diverse modes of stem and progenitor cell trafficking in adult mammalian organs, discusses the major microenvironmental cues regulating cell migration, and describes the implementation of live imaging approaches for the exploration of stem cell movement in tissues and the factors dictating the motility of endogenous and transplanted cells with regenerative potential.

Secretome profiles of immortalized dental follicle cells using iTRAQ-based proteomic analysis

Secretomes produced by mesenchymal stromal cells (MSCs) were considered to be therapeutic potential. However, harvesting enough primary MSCs from tissue was time-consuming and costly, which impeded the application of MSCs secretomes. This study was to immortalize MSCs and compare the secretomes profile of immortalized and original MSCs. Human dental follicle cells (DFCs) were isolated and immortalized using pMPH86. The secretome profile of immortalized DFCs (iDFCs) was investigated and compared using iTRAQ labeling combined with mass spectrometry (MS) quantitative proteomics. The MS data was analyzed using ProteinPilotTM software, and then bioinformatic analysis of identified proteins was done. A total of 2092 secreted proteins were detected in conditioned media of iDFCs. Compared with primary DFCs, 253 differently expressed proteins were found in iDFCs secretome (142 up-regulated and 111 down-regulated). Intensive bioinformatic analysis revealed that the majority of secreted proteins were involved in cellular process, metabolic process, biological regulation, cellular component organization or biogenesis, immune system process, developmental process, response to stimulus and signaling. Proteomic profile of cell secretome wasn't largely affected after immortalization converted by this piggyBac immortalization system. The secretome of iDFCs may be a good candidate of primary DFCs for regenerative medicine.

Pooled Human Serum Increases Regenerative Potential of In Vitro Expanded Stem Cells from Human Extracted Deciduous Teeth

In regenerative therapy, in vitro expansion of stem cells is critical to obtain a significantly higher number of cells for successful engraftment after transplantation. However, stem cells lose its regenerative potential and enter senescence during in vitro expansion. In this study, the influence of foetal bovine serum (FBS) and pooled human serum (pHS) on the proliferation, morphology and migration of stem cells from human extracted deciduous teeth (SHED) was compared. SHED (n = 3) was expanded in KnockOut DMEM supplemented with either pHS (pHS-SM) or FBS (FBS-SM). pHS was prepared using peripheral blood serum of six healthy male adults, aged between 21 and 35 years old. The number of live SHED was significantly higher, from passage 5 to 7, when cultured in pHS-SM compared to those cultured in FBS-SM (p < 0.05). Number of cells having flattened morphology, characteristics of partially differentiated and senescent cells, was significantly lower (p < 0.05) in pHS-SM (3%) compared to those in FBS-SM (7%). Furthermore, migration of SHED in pHS-SM was found to be more directional. The presence of selected ten paracrine factors known for their proliferation and migration potential was detected in all six individual human sera, used to produce pHS, none of which were detected in FBS. Ingenuity Pathway Analysis showed the possible involvement of the 'ephrin receptor signalling pathway' to regulate the proliferation and migration of SHED in pHS-SM. In conclusion, pHS-SM showed significantly higher proliferation rate and could maintain significantly lower number of senescent cells and support directional migration of cells.

Effects of Stem Cell Factor on Cell Homing During Functional Pulp Regeneration in Human Immature Teeth

Conventional root canal treatment in immature permanent teeth can lead to early tooth loss in children because root formation is discontinued. We investigated whether the stem cell factor (SCF) could facilitate cell homing in the pulpless immature root canal and promote regeneration of a functional pulp. In vitro, human mesenchymal stem cells (hMSCs) were exposed to SCF at various concentrations for assessing cell migration, proliferation, and differentiation toward odonto/osteoblasts by 3D-chemotaxis slides, WST-1 assay, and alkaline phosphatase activity, respectively. Fibrin gels were used to deliver 15 μg/mL SCF for in vivo experiments. The release kinetic of SCF was assessed in vitro. Two corresponding human immature premolars, with or without SCF, were placed at rat calvariae for 6 and 12 weeks. All tooth specimens were either analyzed histologically and the percentage of tissue ingrowth determined or the cells were extracted from the pulp space, and the mRNA level of DMP1, DSPP, Col1, NGF, and VEGF were assessed by quantitative polymerase chain reaction. In the presence of SCF, we saw an increase in hMSCs directional migration, proliferation, and odonto/osteogenic differentiation. SCF also increased the extent of tissue ingrowth at 6 weeks but not at 12 weeks. However, at this time point, the formed tissue appeared more mature in samples with SCF. In terms of gene transcription, DMP1, Col1, and VEGF were the significantly upregulated genes, while DSPP and NGF were not affected. Our results suggest that SCF can accelerate cell homing and the maturation of the pulp-dentin complex in human immature teeth.

Pulp Regeneration: Current Approaches and Future Challenges

Regenerative endodontics aims to replace inflamed/necrotic pulp tissues with regenerated pulp-like tissues to revitalize teeth and improve life quality. Pulp revascularization case reports, which showed successful clinical and radiographic outcomes, indicated the possible clinical application of pulp regeneration via cell homing strategy. From a clinical point of view, functional pulp-like tissues should be regenerated with the characterization of vascularization, re-innervation, and dentin deposition with a regulated rate similar to that of normal pulp. Efficient root canal disinfection and proper size of the apical foramen are the two requisite preconditions for pulp regeneration. Progress has been made on pulp regeneration via cell homing strategies. This review focused on the requisite preconditions and cell homing strategies for pulp regeneration. In addition to the traditionally used mechanical preparation and irrigation, antibiotics, irrigation assisted with EndoVac apical negative-pressure system, and ultrasonic and laser irradiation are now being used in root canal disinfection. In addition, pulp-like tissues could be formed with the apical foramen less than 1 mm, although more studies are needed to determine the appropriate size. Moreover, signaling molecules including stromal cell derived factor (SDF-1α), basic Fibroblast Growth Factor (bFGF), Platelet Derived Growth Factor (PDGF), stem cell factor (SCF), and Granulocyte Colony-Stimulating Factor (G-CSF) were used to achieve pulp-like tissue formation via a cell homing strategy. Studies on the cell sources of pulp regeneration might give some indications on the signaling molecular selection. The active recruitment of endogenous cells into root canals to regenerate pulp-like tissues is a novel concept that may offer an unprecedented opportunity for the near-term clinical translation of current biology-based therapies for dental pulp regeneration.

Delivery of Apical Mesenchymal Stem Cells into Root Canals of Mature Teeth

Regenerative endodontic procedures are stem cell-based treatments for immature teeth with pulp necrosis. The translation of regenerative endodontic procedures into treating mature teeth depends, among other factors, on the availability and delivery of mesenchymal stem cells (MSCs) into the root canal system. The aim of this clinical study was to evaluate whether evoked bleeding from the periapical tissues elicits the influx of MSCs into the root canal system in mature teeth with apical lesions. Participants included in this study (N = 20) were referred for endodontic treatment of mature teeth with apical lesions. Following chemomechanical debridement, intracanal bleeding from the periapical tissues was achieved, and intracanal blood samples were collected. A positive blood aspirate was also collected in the cartridges during local anesthesia. Total RNA was isolated and used as a template in quantitative reverse transcription polymerase chain reactions using MSC-specific arrays. Data were analyzed with the Wilcoxon signed-rank test, and correlation between gene expression and sex or age was tested with Spearman's rank correlation coefficient test. In addition, MSCs were isolated from an intracanal bleeding sample and subjected to flow cytometry and quantitative osteogenesis assay. Last, the presence and distribution of MSCs within periradicular lesions were evaluated with immunohistochemistry (n = 4). The MSC markers CD73, CD90, CD105, and CD146 were significantly upregulated, with median fold change values of 2.9, 31.7, 4.6, and 6.8, respectively. Conversely, the negative marker for MSCs, CD45, was significantly downregulated (median, -2.7). There was no correlation with age, sex, tooth type, or treatment for any of the evaluated genes. Isolated intracanal cells coexpressed MSC markers and demonstrated robust mineralizing differentiation potential. Finally, immunohistochemical analysis revealed that MSCs were found compartmentalized mainly within vasculature structures located in periapical lesions. Collectively, findings indicate that the evoked-bleeding technique delivers MSCs into the root canal system in mature teeth with apical lesions.

Role of angiogenesis in endodontics: contributions of stem cells and proangiogenic and antiangiogenic factors to dental pulp regeneration

INTRODUCTION

Dental pulp regeneration is a part of regenerative endodontics, which includes isolation, propagation, and re-transplantation of stem cells inside the prepared root canal space. The formation of new blood vessels through angiogenesis is mandatory to increase the survival rate of re-transplanted tissues. Angiogenesis is defined as the formation of new blood vessels from preexisting capillaries, which has great importance in pulp regeneration and homeostasis. Here the contribution of human dental pulp stem cells and proangiogenic and antiangiogenic factors to angiogenesis process and regeneration of dental pulp is reviewed.

METHODS

A search was performed on the role of angiogenesis in dental pulp regeneration from January 2005 through April 2014. The recent aspects of the relationship between angiogenesis, human dental pulp stem cells, and proangiogenic and antiangiogenic factors in regeneration of dental pulp were assessed.

RESULTS

Many studies have indicated an intimate relationship between angiogenesis and dental pulp regeneration. The contribution of stem cells and mechanical and chemical factors to dental pulp regeneration has been previously discussed.

CONCLUSIONS

Angiogenesis is an indispensable process during dental pulp regeneration. The survival of inflamed vital pulp and engineered transplanted pulp tissue are closely linked to the process of angiogenesis at sites of application. However, the detailed regulatory mechanisms involved in initiation and progression of angiogenesis in pulp tissue require investigation.

Promotion of Dental Pulp Cell Migration and Pulp Repair by a Bioceramic Putty Involving FGFR-mediated Signaling Pathways

Mineral trioxide aggregate is the currently recommended material of choice for clinical pulp repair despite several disadvantages, including handling inconvenience. Little is known about the signaling mechanisms involved in bioceramic-mediated dental pulp repair-particularly, dental pulp cell (DPC) migration. This study evaluated the effects of iRoot BP Plus, a novel ready-to-use nanoparticulate bioceramic putty, on DPC migration in vitro and pulp repair in vivo, focusing on possible involvement of fibroblast growth factor receptor (FGFR)-related signaling, including mitogen-activated protein kinase and Akt pathways. Treatment with iRoot BP Plus extracts enhanced horizontal and vertical migration of DPCs, which was comparable with the effects induced by mineral trioxide aggregate extracts. The DPCs exposed to iRoot BP Plus extracts demonstrated no evident apoptosis. Importantly, treatment with iRoot BP Plus extracts resulted in rapid activation of FGFR, p38 mitogen-activated protein kinase, extracellular signal-regulated kinase (ERK) 1/2, c-Jun-N-terminal kinase (JNK), and Akt signaling in DPCs. Confocal immunofluorescence staining revealed that iRoot BP Plus stimulated focal adhesion formation and stress fiber assembly in DPCs, in addition to upregulating the expression of focal adhesion molecules, including p-focal adhesion kinase, p-paxillin, and vinculin. Moreover, activation of FGFR, ERK, JNK, and Akt were found to mediate the upregulated expression of focal adhesion molecules, stress fiber assembly, and enhanced DPC migration induced by iRoot BP Plus. Consistent with the in vitro results, we observed induction of homogeneous dentin bridge formation and expression of p-focal adhesion kinase, p-FGFR, p-ERK 1/2, p-JNK, and p-Akt near injury sites by iRoot BP Plus in an in vivo pulp repair model. These data demonstrate that iRoot BP Plus can promote DPC migration and pulp repair involving the FGFR-mediated ERK 1/2, JNK, and Akt pathways. These findings provide valuable insights into the signaling mechanisms underlying nanoparticulate bioceramic-mediated pulp repair.

Dental pulp stem cells: state of the art and suggestions for a true translation of research into therapy

OBJECTIVES

Stem cells have the ability to rescue and/or repair injured tissue. In humans, it is possible to isolate different types of stem cells from the body. Among these, dental pulp stem cells (DPSCs) are relatively easily obtainable and exhibit high plasticity and multipotential capabilities. In particular they represent a gold standard for neural-crest-derived bone reconstruction in humans and can be used for the repair of body defects in low-risk autologous therapeutic strategies.

SOURCES

An electronic search was conducted on PubMed databases and supplemented with a manual study of relevant references.

RESULTS

All research described in this review highlight that DPSCs are mesenchymal stem cells that could be used in clinical applications. Unfortunately, very few clinical trials have been reported. Major obstacles imposed on researchers are hindering the translation of potentially effective therapies to the clinic. Both researchers and regulatory institutions need to develop a new approach to this problem, drawing up a new policy for good manufacturing practice (GMP) procedures. We strongly suggest that only general rules be standardized rather than everything. Importantly, this would not have an effect on the safety of patients, but may very well affect the results, which cannot be identical for all patients, due to physiological diversity in the biology of each patient. Alternatively, it would be important to study the role of specific molecules that recruit endogenous stem cells for tissue regeneration. In this way, the clinical use of stem cells could be successfully developed.

CONCLUSIONS

DPSCs are mesenchymal stem cells that differentiate into different tissues, maintain their characteristics after cryopreservation, differentiate into bone-like tissues when loaded on scaffolds in animal models, and regenerate bone in human grafts. In summary, all data reported up to now should encourage the development of clinical procedures using DPSCs.