Dental follicle stem cells and tissue engineering

Stem Cells in the Periodontium-Anatomically Related Yet Physiologically Diverse

Periodontitis is a complex chronic disease discernible by the deterioration of periodontal tissue. The goal of periodontal therapy is to achieve complete tissue regeneration, and one of the most promising treatment options is to harness the regenerative potential of stem cells available within the periodontal complex. Periodontal ligament stem cells, gingival mesenchymal stem cells, oral periosteal stem cells, and dental follicle stem cells have structural similarities, but their immunological responses and features differ. The qualities of diverse periodontal stem cells, their immune-modulatory effects, and variances in their phenotypes and characteristics will be discussed in this review. Although there is evidence on each stem cell population in the periodontium, understanding the differences in markers expressed, the various research conducted so far on their regenerative potential, will help in understanding which stem cell population will be a better candidate for tissue engineering. The possibility of selecting the most amenable stem cell population for optimal periodontal regeneration and the development and current application of superior tissue engineering treatment options such as autologous transplantation, three-dimensional bioengineered scaffolds, dental stem cell-derived extracellular vesicles will be explored.

Therapeutic Potential of Oral-Derived Mesenchymal Stem Cells in Retinal Repair

The retina has restricted regeneration ability to recover injured cell layer because of reduced production of neurotrophic factors and increased inhibitory molecules against axon regrowth. A diseased retina could be regenerated by repopulating the damaged tissue with functional cell sources like mesenchymal stem cells (MSCs). The cells are able to release neurotrophic factors (NFs) to boost axonal regeneration and cell maintenance. In the current study, we comprehensively explore the potential of various types of stem cells (SCs) from oral cavity as promising therapeutic options in retinal regeneration. The oral MSCs derived from cranial neural crest cells (CNCCs) which explains their broad neural differentiation potential and secret rich NFs. They are comprised of dental pulp SCs (DPSCs), SCs from exfoliated deciduous teeth (SHED), SCs from apical papilla (SCAP), periodontal ligament-derived SCs (PDLSCs), gingival MSCs (GMSCs), and dental follicle SCs (DFSCs). The Oral MSCs are becoming a promising source of cells for cell-free or cell-based therapeutic approach to recover degenerated retinal. These cells have various mechanisms of action in retinal regeneration including cell replacement and the paracrine effect. It was demonstrated that they have more neuroprotective and neurotrophic effects on retinal cells than immediate replacement of injured cells in retina. This could be the reason that their therapeutic effects would be weakened over time. It can be concluded that neuronal and retinal regeneration through these cells is most likely due to their NFs that dramatically suppress oxidative stress, inflammation, and apoptosis. Although, oral MSCs are attractive therapeutic options for retinal injuries, more preclinical and clinical investigations are required.

Advancing Dentistry through Bioprinting: Personalization of Oral Tissues

Despite significant advancements in dental tissue restoration and the use of prostheses for addressing tooth loss, the prevailing clinical approaches remain somewhat inadequate for replicating native dental tissue characteristics. The emergence of three-dimensional (3D) bioprinting offers a promising innovation within the fields of regenerative medicine and tissue engineering. This technology offers notable precision and efficiency, thereby introducing a fresh avenue for tissue regeneration. Unlike the traditional framework encompassing scaffolds, cells, and signaling factors, 3D bioprinting constitutes a contemporary addition to the arsenal of tissue engineering tools. The ongoing shift from conventional dentistry to a more personalized paradigm, principally under the guidance of bioprinting, is poised to exert a significant influence in the foreseeable future. This systematic review undertakes the task of aggregating and analyzing insights related to the application of bioprinting in the context of regenerative dentistry. Adhering to PRISMA guidelines, an exhaustive literature survey spanning the years 2019 to 2023 was performed across prominent databases including PubMed, Scopus, Google Scholar, and ScienceDirect. The landscape of regenerative dentistry has ushered in novel prospects for dentoalveolar treatments and personalized interventions. This review expounds on contemporary accomplishments and avenues for the regeneration of pulp-dentin, bone, periodontal tissues, and gingival tissues. The progressive strides achieved in the realm of bioprinting hold the potential to not only enhance the quality of life but also to catalyze transformative shifts within the domains of medical and dental practices.

Evaluation of the follicular space volume of lower third molars with different impaction positions and angulations: A cone-beam computed tomography and histopathological study

Objective

To quantify the volume of the follicular spaces of impacted lower third molars (ILTMs) with different impaction positions and angulations using cone-beam computed tomography (CBCT) and to determine its association with the histopathological findings.

Study design

This study included 103 ILTMs of 33 men and 70 women aged 18-46 years (mean age, 29.18 years). The follicular space volumes were measured on CBCT by manual segmentation and correlated with the histopathological diagnosis of each ILTM having different impaction positions and angulations. Statistical Product and Service Solutions, version 24, was used for statistical analyses by applying the t-test and binary logistic regression and multiple linear regression tests (p < 0.05).

Results

Overall, 83 (80.6%) dental follicles presented a non-pathological diagnosis (mean follicular volume, 0.10 cm³), whereas 20 (19.4%) presented a pathological diagnosis (mean follicular volume, 0.32 cm³; p = 0.001). Similarly, the impaction depth in Position C cases was associated with a pathological diagnosis (p = 0.010).

Conclusion

The follicular volume of the ILTMs varied significantly in teeth with a histopathological diagnosis of a follicular cyst and was associated with the impaction depth, mainly in Position C cases, and its relationship with the mandibular ramus. A mean follicular volume of 0.32 cm³ was associated with a greater probability of a pathological diagnosis.

Changes in AMPK activity induces cellular senescence in human dental follicle cells

Dental Follicle Cells (DFCs) are somatic stem cells with a limited lifespan, but little is known about a possible mechanism of cellular senescence. Previous studies have shown that cellular senescence is associated with increased demand of glycolsis or the "glycolytic metabotype", which can be induced by activation of 5' adenosine monophosphate-activated protein kinase (AMPK), and decreased autophagy. This study examined the role of AMPK in inducing senescence in DFCs. During the induction of cellular senescence, AMPK activity was impaired, suggesting a negative impact on senescence induction. In line with this assumption, cellular senescence was induced upon inhibition of AMPK with a specific siRNA. In addition, after this inhibition, autophagy was also inhibited. Moreover, specific inhibition of autophagy promoted cellular senescence. However, inducers of AMPK such as metformin or AICAR surprisingly increased senescence in DFCs. Interestingly, autophagy was impaired after long-term induction of AMPK with AICAR and metformin. Moreover, activation of AMPK induces the consumption of glucose but decreases NAD/NADH ratio in DFCs that suggest not only "glycolytic metabotype" of DFCs but also Mitochondrial Dysfunction Associated Senescence (MiDAS). Both changes are highly associated with the induction of cellular senescence. Hence, both AMPK activation and inhibition promote the induction of cellular senecence of DFCs.

Toll-Like Receptors and Dental Mesenchymal Stromal Cells

Dental mesenchymal stromal cells (MSCs) are a promising tool for clinical application in and beyond dentistry. These cells possess multilineage differentiation potential and immunomodulatory properties. Due to their localization in the oral cavity, these cells could sometimes be exposed to different bacteria and viruses. Dental MSCs express various Toll-like receptors (TLRs), and therefore, they can recognize different microorganisms. The engagement of TLRs in dental MSCs by various ligands might change their properties and function. The differentiation capacity of dental MSCs might be either inhibited or enhanced by TLRs ligands depending on their nature and concentrations. Activation of TLR signaling in dental MSCs induces the production of proinflammatory mediators. Additionally, TLR ligands alter the immunomodulatory ability of dental MSCs, but this aspect is still poorly explored. Understanding the role of TLR signaling in dental MSCs physiology is essential to assess their role in oral homeostasis, inflammatory diseases, and tissue regeneration.

Tracking of Oral and Craniofacial Stem Cells in Tissue Development, Regeneration, and Diseases

PURPOSE OF REVIEW

The craniofacial region hosts a variety of stem cells, all isolated from different sources of bone and cartilage. However, despite scientific advancements, their role in tissue development and regeneration is not entirely understood. The goal of this review is to discuss recent advances in stem cell tracking methods and how these can be advantageously used to understand oro-facial tissue development and regeneration.

RECENT FINDINGS

Stem cell tracking methods have gained importance in recent times, mainly with the introduction of several molecular imaging techniques, like optical imaging, computed tomography, magnetic resonance imaging, and ultrasound. Labelling of stem cells, assisted by these imaging techniques, has proven to be useful in establishing stem cell lineage for regenerative therapy of the oro-facial tissue complex. Novel labelling methods complementing imaging techniques have been pivotal in understanding craniofacial tissue development and regeneration. These stem cell tracking methods have the potential to facilitate the development of innovative cell-based therapies.

Photobiomodulation therapy upregulates the growth kinetics and multilineage differentiation potential of human dental pulp stem cells-an in vitro Study

This study aims to evaluate the impact of red LED irradiation on the viability, proliferation, colonogenic potential, markers expression along with osteogenic and chondrogenic differentiation of dental pulp stem cells. DPSCs were isolated from sound human permanent teeth using enzymatic digestion method and seeded with regular culture media. Cells at P4 were irradiated using red LED Light (627 nm, 2 J/cm²) and examined for growth kinetics, and multilineage differentiation using the appropriate differentiation media. The irradiated groups showed an increase in cellular growth rates, cell viability, clonogenic potential, and decrease in population doubling time compared to the control group. Cells of the irradiated groups showed enhanced differentiation towards osteogenic and chondrogenic lineages as revealed by histochemical staining using alizarin red and alcian blue stains. Photobiomodulation is an emerging promising element of tissue engineering triad besides stem cells, scaffolds, and growth factors.

Cell-derived extracellular matrix materials for tissue engineering

The involvement of cell-derived extracellular matrix (CDM) in assembling tissue engineering scaffolds has yielded significant results. CDM possesses excellent characteristics, such as ideal cellular microenvironment mimicry and good biocompatibility, which make it a popular research direction in the field of bionanomaterials. CDM has significant advantages as an expansion culture substrate for stem cells, including stabilization of phenotype, reversal of senescence, and guidance of specific differentiation. In addition, the applications of CDM-assembled tissue engineering scaffolds for disease simulation and tissue organ repair are comprehensively summarized; the focus is mainly on bone and cartilage repair, skin defect or wound healing, engineered blood vessels, peripheral nerves, and periodontal tissue repair. We consider CDM a highly promising bionic biomaterial for tissue engineering applications and propose a vision for its comprehensive development.

Chondrogenic Potential of Dental-Derived Mesenchymal Stromal Cells

The field of tissue engineering has revolutionized the world in organ and tissue regeneration. With the robust research among regenerative medicine experts and researchers, the plausibility of regenerating cartilage has come into the limelight. For cartilage tissue engineering, orthopedic surgeons and orthobiologists use the mesenchymal stromal cells (MSCs) of various origins along with the cytokines, growth factors, and scaffolds. The least utilized MSCs are of dental origin, which are the richest sources of stromal and progenitor cells. There is a paradigm shift towards the utilization of dental source MSCs in chondrogenesis and cartilage regeneration. Dental-derived MSCs possess similar phenotypes and genotypes like other sources of MSCs along with specific markers such as dentin matrix acidic phosphoprotein (DMP) -1, dentin sialophosphoprotein (DSPP), alkaline phosphatase (ALP), osteopontin (OPN), bone sialoprotein (BSP), and STRO-1. Concerning chondrogenicity, there is literature with marginal use of dental-derived MSCs. Various studies provide evidence for in-vitro and in-vivo chondrogenesis by dental-derived MSCs. With such evidence, clinical trials must be taken up to support or refute the evidence for regenerating cartilage tissues by dental-derived MSCs. This article highlights the significance of dental-derived MSCs for cartilage tissue regeneration.

Revisiting the human dental follicle: From tooth development to its association with unerupted or impacted teeth and pathological changes

Dental follicles are involved in odontogenesis, periodontogenesis, and tooth eruption. Dental follicles are unique structures, considering that their remnants can persist within the jawbones after odontogenesis throughout life if the tooth does not erupt. Pathological changes may occur in these tissues as individuals age. The changes range from benign to life threatening. Thus, the assessment of age-related changes in dental follicles associated with unerupted teeth is of paramount importance. In this review, we summarize the physiological roles and changes in dental follicles in odontogenesis, tooth eruption, and aging, in addition to the pathological changes associated with these structures. We encourage investigators to consider this peculiar tissue as a unique model and explore its potential to clarify its importance from the viewpoints of developmental biology, tissue physiology, and pathology.

Function of Dental Follicle Progenitor/Stem Cells and Their Potential in Regenerative Medicine: From Mechanisms to Applications

Dental follicle progenitor/stem cells (DFPCs) are a group of dental mesenchyme stem cells that lie in the dental follicle and play a critical role in tooth development and maintaining function. Originating from neural crest, DFPCs harbor a multipotential differentiation capacity. More importantly, they have superiorities, including the easy accessibility and abundant sources, active self-renewal ability and noncontroversial sources compared with other stem cells, making them an attractive candidate in the field of tissue engineering. Recent advances highlight the excellent properties of DFPCs in regeneration of orofacial tissues, including alveolar bone repair, periodontium regeneration and bio-root complex formation. Furthermore, they play a unique role in maintaining a favorable microenvironment for stem cells, immunomodulation and nervous related tissue regeneration. This review is intended to summarize the current knowledge of DFPCs, including their stem cell properties, physiological functions and clinical application potential. A deep understanding of DFPCs can thus inspire novel perspectives in regenerative medicine in the future.

Characteristics of Large Animal Models for Current Cell-Based Oral Tissue Regeneration

The recent advances in the field of cell-based therapeutics open promising perspectives for oral tissue regeneration. The development of large animal models, which overcome the limits of the rodent models and allow to emulate clinical situations, is crucial for the validation of regenerative strategies to move toward clinical application. Currently, porcine, canine, and ovine models are mainly developed for oral regeneration and their specific characteristics have an impact on the outcomes of the studies. Thus, this systematic review investigates the application of porcine, canine, and ovine models in present cell-based oral regeneration, according to the species characteristics and the targeted tissue to regenerate. A customized search of PubMed, EMBASE, Scopus, and Web of Science databases from January 2015 to March 2020 was conducted. Relevant articles about cell-based oral tissues engineering in porcine, canine, and ovine models were evaluated. Among the evaluated articles, 58 relevant studies about cell-based oral regeneration in porcine, canine, and ovine models matched the eligibility criteria and were selected for full analysis. Porcine models, the most similar species with humans, were mostly used for bone and periodontium regeneration; tooth regeneration was reported only in pig, except for one study in dog. Canine models were the most transversal models, successfully involved for all oral tissue regeneration and notably in implantology. However, differences with humans and ethical concerns affect the use of these models. Ovine models, alternative to porcine and canine ones, were mainly used for bone and, scarcely, periodontium regeneration. The anatomy and physiology of these animals restrain their involvement. If consistency was found in defect specificities and cell trends among different species animal models of bone, dentin-pulp complex, or tooth regeneration, variability appeared in periodontium. Regeneration assessment methods were more elaborate in porcines and canines than in ovines. Risk of bias was low for selection, attrition and reporting, but unclear for performance and detection. Overall, if none of the large animal models can be considered an ideal one, they are of deemed importance for oral cell-based tissue engineering and researchers should consider their relevance to establish favorable conditions for a given preclinical cell-based therapeutics.

Use of the pericoronal tissue of impacted third molar in subgingival connective tissue autograft: A case report

Introduction and importance

The pericoronal tissue, or dental follicle, is a connective tissue found around impacted teeth crown. The dental follicle is involved in odontogenesis, dental eruption and periodontogenesis.

Case presentation

A young woman presented a vestibular U-shaped periodontal recession localized in tooth 26. After consent the patient underwent a local intervention combining the extraction of her included 28 and a mucogingival management of her periodontal recession localized in 26, using the pericoronary sac of the tooth of 28 has been used as a subepithelial connective autograft.

The results 6 weeks after surgery showed a significant gain in thickness and a gain in height of attached gingiva of 26.

Clinical discussion

The success of the use of pericoronary sac in subepithelial connective autograft may allow to spare the use of a healthy harvesting site. Furthermore, the dental follicle is often available in young patients with prophylactic extraction of impacted 3rd molars. However, one pericoronary sac may provide enough connective tissue, only for the surgical treatment of a unique recession site.

Conclusion

The use of the pericoronal sac has shown promising results in the treatment of periodontal recessions. Wider applications could be investigated using the pericoronal sac in the future.

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The pericoronal tissue may be used in subepithelial autografting technics.

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The pericoronal tissue has the great histophysiological potential of pluripotent cells.

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Pericoronal tissues are easily collected in young patients.

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The use of pericoronal tissue may replace other conjonctive sampling methods.

Effects of rhBMP-2 on Bone Formation Capacity of Rat Dental Stem/Progenitor Cells from Dental Follicle and Alveolar Bone Marrow

Dental stem/progenitor cells are a promising cell sources for alveolar bone (AB) regeneration because of their same embryonic origin and superior osteogenic potential. However, their molecular processes during osteogenic differentiation remain unclear. The objective of this study was to identify the responsiveness of dental follicle cells (DFCs) and AB marrow-derived mesenchymal stem cells (ABM-MSCs) to recombinant human bone morphogenetic protein-2 (rhBMP-2). These cells expressed vimentin and MSC markers and did not express cytokeratin and hematopoietic stem cell markers and showed multilineage differentiation potential under specific culture conditions. DFCs exhibited higher proliferation and colony-forming unit-fibroblast efficiency than ABM-MSCs; rhBMP-2 induced DFCs to differentiate toward a cementoblast/osteoblast phenotype and ABM-MSCs to differentiate only toward a osteoblast phenotype; and rhBMP-2-induced DFCs exhibited higher osteogenic differentiation potential than ABM-MSCs. These cells adhered, grew, and produced extracellular matrix on nanohydroxyapatite/collagen/poly(l-lactide) (nHAC/PLA). During a 14-day culture on nHAC/PLA, the extracellular alkaline phosphatase (ALP) activity of DFCs decreased gradually and that of ABM-MSCs increased gradually; rhBMP-2 enhanced their extracellular ALP activity, intracellular osteocalcin (OCN), and osteopontin (OPN) protein expression; and DFCs exhibited higher extracellular ALP activity and intracellular OCN protein expression than ABM-MSCs. When implanted subcutaneously in severe combined immunodeficient mice for 3 months, DFCs+nHAC/PLA+rhBMP-2 obtained higher percentage of bone formation area, OCN, and cementum attachment protein expression and lower OPN expression than ABM-MSCs+nHAC/PLA+rhBMP-2. These results showed that DFCs possessed superior proliferation and osteogenic differentiation potential in vitro, and formed higher quantity and quality bones in vivo. It suggested that DFCs might exhibit a more sensitive responsiveness to rhBMP-2, so that DFCs enter a relatively mature stage of osteogenic differentiation earlier than ABM-MSCs after rhBMP-2 induction. The findings imply that these dental stem/progenitor cells are alternative sources for AB engineering in regenerative medicine, and developing dental tissue may provide better source for stem/progenitor cells.

Role and application of stem cells in dental regeneration: A comprehensive overview

Recently, a growing attention has been observed toward potential advantages of stem cell (SC)-based therapies in regenerative treatments. Mesenchymal stem/stromal cells (MSCs) are now considered excellent candidates for tissue replacement therapies and tissue engineering. Autologous MSCs importantly contribute to the state-of-the-art clinical strategies for SC-based alveolar bone regeneration. The donor cells and immune cells play a prominent role in determining the clinical success of MSCs therapy. In line with the promising future that stem cell therapy has shown for tissue engineering applications, dental stem cells have also attracted the attention of the relevant researchers in recent years. The current literature review aims to survey the variety and extension of SC-application in tissue-regenerative dentistry. In this regard, the relevant English written literature was searched using keywords: "tissue engineering", "stem cells", "dental stem cells", and "dentistry strategies". According to the available database, SCs application has become increasingly widespread because of its accessibility, plasticity, and high proliferative ability. Among the growing recognized niches and tissues containing higher SCs, dental tissues are evidenced to be rich sources of MSCs. According to the literature, dental SCs are mostly present in the dental pulp, periodontal ligament, and dental follicle tissues. In this regard, the present review has described the recent findings on the potential of dental stem cells to be used in tissue regeneration.

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

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

Bleomycin: A novel osteogenesis inhibitor of dental follicle cells via a TGF-β1/SMAD7/RUNX2 pathway

BACKGROUND AND PURPOSE

Tooth eruption is a complicated process regulated by the dental follicles (DF). Our recent study discovered that tooth eruption was inhibited upon injection of bleomycin into DF. However, the mechanisms were unknown.

EXPERIMENTAL APPROACH

Human dental follicle cells (hDFCs) were treated by bleomycin or exogenous TGF-β1 or transfected by plasmids loading SMAD7 or shRNA targeting SMAD7, followed by osteogenesis induction assay and signalling analysis. Human fresh DF tissues and Wistar rats were used to further confirm bleomycin function.

KEY RESULTS

Bleomycin decreased expression of RUNX2 and osteogenic genes in hDFCs, reducing osteogenic capacity. TGF-β1 expression was up-regulated in bleomycin-treated hDFCs. The effects of exogenous TGF-β1 were similar to those of bleomycin in hDFCs. Additionally, compared to SMAD2/3, SMAD7 expression increased more in bleomycin- or TGF-β1-treated hDFCs. Overexpression of SMAD7 likewise significantly decreased RUNX2 expression and osteogenic capacity of hDFCs. Knockdown of SMAD7 markedly attenuated the inhibitory effects of bleomycin and TGF-β1 on osteogenic capacity and RUNX2 expression of hDFCs. Most importantly, changes in TGF-β1, SMAD7, and RUNX2 expressions were similar in the DF of rats and humans treated with bleomycin.

CONCLUSION AND IMPLICATIONS

SMAD7 was a negative regulator of osteogenic differentiation in DFCs through suppressing RUNX2 expression. Bleomycin or TGF-β1 inhibited osteogenic differentiation of DFCs via a TGF-β1/SMAD7/RUNX2 pathway. Our findings might be beneficial for enhancing the osteogenic activity of DFCs or inhibiting the eruption of undesirable teeth.

Advanced Biomaterials and Techniques for Oral Tissue Engineering and Regeneration-A Review

The reconstruction or repair of oral and maxillofacial functionalities and aesthetics is a priority for patients affected by tooth loss, congenital defects, trauma deformities, or various dental diseases. Therefore, in dental medicine, tissue reconstruction represents a major interest in oral and maxillofacial surgery, periodontics, orthodontics, endodontics, and even daily clinical practice. The current clinical approaches involve a vast array of techniques ranging from the traditional use of tissue grafts to the most innovative regenerative procedures, such as tissue engineering. In recent decades, a wide range of both artificial and natural biomaterials and scaffolds, genes, stem cells isolated from the mouth area (dental follicle, deciduous teeth, periodontal ligament, dental pulp, salivary glands, and adipose tissue), and various growth factors have been tested in tissue engineering approaches in dentistry, with many being proven successful. However, to fully eliminate the problems of traditional bone and tissue reconstruction in dentistry, continuous research is needed. Based on a recent literature review, this paper creates a picture of current innovative strategies applying dental stem cells for tissue regeneration in different dental fields and maxillofacial surgery, and offers detailed information regarding the available scientific data and practical applications.

Dental Pulp Stem Cell-Derived Extracellular Vesicles Mitigate Haematopoietic Damage after Radiation

Radiation therapy can cause haematopoietic damage, and mesenchymal stem cells (MSCs) derived extracellular vesicles (EVs) have been shown to reverse this damage. Our previous research showed that dental pulp stem cells (DPSCs) have a strong proliferation capacity and can produce abundant amounts of EVs to meet the requirements for use in vitro and in vivo. DPSCs derived EVs (DPSCs-EVs) are evaluated for their effect on reducing haematopoietic damage. Haematopoietic stem cell (HSC) numbers and function were assessed by flow cytometry, peripheral blood cell counts, histology and bone marrow transplantation. Epidermal growth factor (EGF) was used as a reference for evaluating the efficiency of EVs. miRNA microarray was employed to find out the changes of miRNA expression after cells being irradiated in vivo and the role they may play in mitigation the radiation caused injury. We observed the effect of DPSCs-EVs on promoting proliferation and inhibiting apoptosis of human umbilical vein endothelial cells (HUVECs) and FDC-P1 cells in vitro. We found that DPSCs-EVs and EGF could comparably inhibit the decrease in WBC, CFU count and KSL cells in vivo. We also verified that EVs could accelerate the recovery of long-term HSCs. In summary, DPSCs-EVs showed an apoptosis resistant effect on HUVECs and FDC-P1 cells after radiation injury in vitro. EVs from DPSCs were comparable to EGF in their ability to regulate haematopoietic regeneration after radiation injury in vivo. Radiation could alter the expression of some miRNAs in bone marrow cells, and EVs could correct these changes to some extent.

VPS4B mutation impairs the osteogenic differentiation of dental follicle cells derived from a patient with dentin dysplasia type I

A splicing mutation in VPS4B can cause dentin dysplasia type I (DD-I), a hereditary autosomal-dominant disorder characterized by rootless teeth, the etiology of which is genetically heterogeneous. In our study, dental follicle cells (DFCs) were isolated and cultured from a patient with DD-I and compared with those from an age-matched, healthy control. In a previous study, this DD-I patient was confirmed to have a loss-of-function splicing mutation in VPS4B (IVS7 + 46C > G). The results from this study showed that the isolated DFCs were vimentin-positive and CK14-negative, indicating that the isolated cells were derived from the mesenchyme. DFCs harboring the VPS4B mutation had a significantly higher proliferation rate from day 3 to day 8 than control DFCs, indicating that VPS4B is involved in cell proliferation. The cells were then replenished with osteogenic medium to investigate how the VPS4B mutation affected osteogenic differentiation. Induction of osteogenesis, detected by alizarin red and alkaline phosphatase staining in vitro, was decreased in the DFCs from the DD-I patient compared to the control DFCs. Furthermore, we also found that the VPS4B mutation in the DD-I patient downregulated the expression of osteoblast-related genes, such as ALP, BSP, OCN, RUNX2, and their encoded proteins. These outcomes confirmed that the DD-I-associated VPS4B mutation could decrease the capacity of DFCs to differentiate during the mineralization process and may also impair physiological root formation and bone remodeling. This might provide valuable insights and implications for exploring the pathological mechanisms underlying DD-I root development.

A three-dimensional analysis of primary failure of eruption in humans and mice

OBJECTIVES

Primary failure of eruption (PFE) is a genetic disorder exhibiting the cessation of tooth eruption. Loss-of-function mutations in parathyroid hormone (PTH)/parathyroid hormone-related peptide (PTHrP) receptor (PTH/PTHrP receptor, PPR) were reported as the underlying cause of this disorder in humans. We showed in a PFE mouse model that PTHrP-PPR signaling is responsible for normal dental follicle cell differentiation and tooth eruption. However, the mechanism underlying the eruption defect in PFE remains undefined. In this descriptive study, we aim to chronologically observe tooth eruption and root formation of mouse PFE molars through 3D microCT analyses.

SETTING AND SAMPLE POPULATION

Two individuals with PFE were recruited at Showa University. A mouse PFE model was generated by deleting PPR specifically in PTHrP-expressing dental follicle and divided into three groups, PPR^fl/fl ;R26R^tdTomato/+ (Control), PTHrP-creER;PPR^fl/+ ;R26R^tdTomato/+ (cHet), and PTHrP-creER;PRR^fl/fl ;R26R^tdTomato/+ (cKO).

MATERIALS AND METHODS

Images from human PFE subjects were acquired by CBCT. All groups of mouse samples were studied at postnatal days 14, 25, 91, and 182 after a tamoxifen pulse at P3, and superimposition of 3D microCT images among three groups was rendered.

RESULTS

Mouse and human PFE molars exhibited a similar presentation in the 3D CT analyses. The quantitative analysis in mice demonstrated a statistically significant decrease in the eruption height of cKO first and second molars compared to other groups after postnatal day 25. Additionally, cKO molars demonstrated significantly shortened roots with dilacerations associated with the reduced interradicular bone height.

CONCLUSIONS

Mouse PFE molars erupt at a much slower rate compared to normal molars, associated with shortened and dilacerated roots and defective interradicular bones.

Osteogenic differentiation of follicular stem cells on nano-Saghez scaffold containing BMP2

Background

Bone tissue is one of the tissues that are capable of self-regeneration. However, bone self-regeneration is defeated in the case of broad lesion of bone structure. Isolated stem cells from wisdom tooth follicles can potentially differentiate into ectodermal and mesodermal cells. Saghez is a natural substance that has been extracted from Pistacia terebinthus with unique features, such as high temperature and mechanical stability, adhesive structure, biocompatibility, and anti-neoplastic properties.

Methods

In this study, Saghez-encapsulated BMP2 was applied as a scaffold for wisdom tooth follicle stem cell differentiation into the osteocyte. A total of three wisdom tooth follicles were obtained for stem cell isolation. For verification of differentiation of the isolated stem cells into osteocyte and adipocyte, Oil Red and Alizarin staining were applied, respectively. Moreover, mesenchymal stem cells were distinguished by profiling their cell surface markers, includingCD73, CD90, CD44, and CD105, by flow cytometry. Saghez scaffold loaded with BMP2 factor was prepared using sol-gel method. Four experimental groups were considered in this study: cells seeded on BMP2 encapsulated in Saghez scaffold, Saghez scaffold, osteogenic medium, and DMEM medium.

Results

Mechanical properties of Saghez scaffold, including tensile Young’s modulus, ultimate tensile stress, compression Young’s modulus, and complex shear modulus, were 19 MPa, 32 MPa, 0.42 MPa, and 0.9 MPa, respectively. The porosity of the scaffold was 70–140 μm, and the percentage of porosity was 75–98%. The results of flow cytometry studies indicated that CD44, CD73, CD90, and CD105 were positively expressed on the membrane of the tooth follicles’ stem cell. The results indicated that the rate of differentiation of the follicle stem cells into osteocyte was the highest in the Saghez-BMP2 scaffold containing differentiation medium groups. These findings were verified by morphological studies, osteoblast and osteocalcin gene and protein expression investigations, and alkaline phosphatase activity measurement. The highest osteopontin and osteocalcin genes expression levels (1.7 and 1.9) were seen in positive control, followed by DMEM + differentiation factor (1.5 and 1.6), scaffold + BMP2 (1.2 and 1.4), DMEM + stem cell (1 and 1) and scaffold (0.4 and 0.5), and negative control respectively.

Conclusion

This study provides a novel system for differentiation of the stem cell into osteocytes. The results of this study suggest that loaded BMP2 in Saghez scaffold possibly acts as an osteocyte differentiator factor.

Dental Follicle Cells: Roles in Development and Beyond

Dental follicle cells (DFCs) are a group of mesenchymal progenitor cells surrounding the tooth germ, responsible for cementum, periodontal ligament, and alveolar bone formation in tooth development. Cascades of signaling pathways and transcriptional factors in DFCs are involved in directing tooth eruption and tooth root morphogenesis. Substantial researches have been made to decipher multiple aspects of DFCs, including multilineage differentiation, senescence, and immunomodulatory ability. DFCs were proved to be multipotent progenitors with decent amplification, immunosuppressed and acquisition ability. They are able to differentiate into osteoblasts/cementoblasts, adipocytes, neuron-like cells, and so forth. The excellent properties of DFCs facilitated clinical application, as exemplified by bone tissue engineering, tooth root regeneration, and periodontium regeneration. Except for the oral and maxillofacial regeneration, DFCs were also expected to be applied in other tissues such as spinal cord defects (SCD), cardiomyocyte destruction. This article reviewed roles of DFCs in tooth development, their properties, and clinical application potentials, thus providing a novel guidance for tissue engineering.

In vitro periodontal ligament cell expansion by co-culture method and formation of multi-layered periodontal ligament-derived cell sheets

Objective

Per-implantitis is one of the implant treatment complications. Dentists have failed to restore damaged periodontium by using conventional therapies. Tissue engineering (stem cells, scaffold and growth factors) aims to reconstruct natural tissues. The paper aimed to isolate both periodontal ligament stem cells (PDLSCs) and bone marrow mesenchymal stem cells (BMMSCs) and use them in a co-culture method to create three-layered cell sheets for reconstructing natural periodontal ligament (PDL) tissue.

Materials and methods

BMMSCs were isolated from rabbit tibia and femur, and PDLSC culture was established from the lower right incisor. The cells were co-cultured to induce BMMSC differentiation into PDL cells. Cell morphology, stem cells and PDL-specific markers (CD90, CD34, and periostin) were also detected using immunofluorescent assay. Co-cultured cell monolayers were detached using temperature-responsive tissue culture dishes and collagen graft to create the three-layer construct. The 3D-engineered tissue was examined histologically and by field emission scanning electron microscopy (FESEM).

Results

BMMSCs co-cultured with PDLSCs successfully induced more PDL cells. The newly induced PDL cells exhibited periostin and CD90 expression. Fluorescence green intensity was measured for the co-cultured cells that were stained with periostin, the mean fluorescence green intensity (periostin expression) was significantly higher for the newly induced PDL cells after 1, 2, and 3 weeks when compared with control (BM-MSCs), at 21 days non-significant difference was measured when compared with control (PDLSCs).

The results showed the successful formation of 3D multilayer PDL tissue. Histological cross-section showed cell sheets and the stable adhesion between them. FESEM examination was conducted for the cross-section, showing three-layered cell sheets with stable adhesion between cells.

Conclusions

The results of this paper report that the three layered-cell sheets were successfully constructed by the novel use of collagen graft as a scaffold to be used in treatment of periodontitis and to envelop the dental implants to create biohybrid implant.

Low-intensity pulsed ultrasound promotes tissue regeneration in rat dental follicle cells in a porous ceramic scaffold

The aim of this study was to investigate the effects of low-intensity pulsed ultrasound (LIPUS) on the osteogenic differentiation of dental follicle cells (DFCs) in vitro and on the regenerative effects of DFC-OsteoBoneTM complexes in vivo. DFCs were isolated and characterized. In the in vitro study, DFCs were cultured in an osteogenic medium in the presence or absence of LIPUS. The expression levels of ALP, Runx2, OSX, and COL-I mRNA were analyzed using real-time polymerase chain reaction (RT-PCR) on day 7. Alizarin red staining was performed on day 21. The state of the growth of the DFCs that were seeded on the scaffold at 3, 5, 7, and 9 days was detected by using a scanning electron microscope. In our in vivo study, 9 healthy nude mice randomly underwent subcutaneous transplantation surgery in one of three groups: group A, empty scaffold; group B, DFCs + scaffold; and group C, DFCs + scaffold + LIPUS. After 8 weeks of implantation, a histological analysis was performed by HE and Mason staining. Our results indicate that LIPUS promotes the osteogenic differentiation of DFCs by increasing the expression of the ALP, Runx2, OSX, and COL-I genes and the formation of mineralized nodules. The cells can adhere and grow on the scaffolds and grow best at 9 days. The HE and Mason staining results showed that more cells, fibrous tissue and blood vessels could be observed in the DFCs + scaffold + LIPUS group than in the other groups. LIPUS could promote the osteogenic differentiation of DFCs in vitro and promote tissue regeneration in a DFCs-scaffold complex in vivo. Further studies should be conducted to explore the underlying mechanisms of LIPUS.

Recent Advances of Useful Cell Sources in the Periodontal Regeneration

Background:

Periodontitis is an inflammatory disease that can result in destruction of the tooth attachment apparatus. Therefore, periodontal tissue regeneration is currently an important focus of research in the field. Approaches using stem cells and reprogrammed cells, such as induced pluripotent stem cells (iPSCs) or trans-differentiated cells, represent the cutting edge in periodontal regeneration, and have led to many trials for their clinical application.

Objectives and Results:

In this review, we consider all available stem cell sources, methods to obtain the cells, their capability to differentiate into the desired cells, and the extent of their utilization in periodontal regeneration. In addition, we introduce the new concepts of using iPSCs and transdifferentiated cells for periodontal regeneration. Finally, we discuss the promise of tissue engineering for improving cell therapy outcomes for periodontal regeneration.

Conclusions:

Despite their limitations, iPSCs and trans-differentiated cells may be promising cell sources for periodontal tissue regeneration. Further collaborative investigation is required for the effective and safe application of these cells in combination with tissue engineering elements, like scaffolds and biosignals.

Bone Tissue Engineering Using Human Cells: A Comprehensive Review on Recent Trends, Current Prospects, and Recommendations

The use of proper cells for bone tissue engineering remains a major challenge worldwide. Cells play a pivotal role in the repair and regeneration of the bone tissue in vitro and in vivo. Currently, a large number of differentiated (somatic) and undifferentiated (stem) cells have been used for bone reconstruction alone or in combination with different biomaterials and constructs (e.g., scaffolds). Although the results of the cell transplantation without any supporting or adjuvant material have been very effective with regard to bone healing. Recent advances in bone scaffolding are now becoming new players affecting the osteogenic potential of cells. In the present study, we have critically reviewed all the currently used cell sources for bone reconstruction and discussed the new horizons that are opening up in the context of cell-based bone tissue engineering strategies.

Matrigel Scaffolding Enhances BMP9-induced Bone Formation in Dental Follicle Stem/Precursor Cells

Bone tissue engineering requires a combination of cells, efficient biochemical and physicochemical factors, and biocompatible scaffolds. In this study, we evaluated the potential use of injectable Matrigel as a scaffold for the delivery of rat dental follicle stem/precursor cells (rDFSCs) transduced by bone morphogenetic protein (BMP) 9 to enhance osteogenic differentiation in vitro and promote ectopic bone formation in vivo. Recombinant adenovirus was used to overexpress BMP9 in rDFSCs. Alkaline phosphatase activity was measured using a histochemical staining assay and a chemiluminescence assay kit. Quantitative real-time polymerase chain reaction was used to determine mRNA expression levels of bone-related genes including distal-less homeobox 5 (DLX5), osteopontin (OPN), osterix (Osx), and runt-related transcription factor 2 (Runx2). Matrix mineralization was examined by Alizarin Red S staining. rDFSCs proliferation was analyzed using the Cell Counting Kit-8 assay. Subcutaneous implantation of rDFSCs-containing Matrigel scaffolds was used, and micro-computed tomography analysis, histological evaluation, and trichrome staining of implants extracted at 6 weeks were performed. We found that BMP9 enhanced alkaline phosphatase activity and mineralization in rDFSCs. The expression of bone-related genes (DLX5, OPN, Osx, and Runx2) was also increased as a result of BMP9 stimulation. Micro-computed tomography analysis and histological evaluation revealed that the bone masses retrieved from BMP9-overexpressing rDFSCs were significantly more pronounced in those with than in those without Matrigel. Our results suggest that BMP9 effectively promote osteogenic differentiation of rDFSCs, and Matrigel facilitate BMP9-induced osteogenesis of rDFSCs in vivo.

WNT5A supports viability of senescent human dental follicle cells

The osteogenic differentiation of dental follicle cells (DFCs) is inhibited by the onset of cellular senescence, but the cause for this is largely unknown. Recently it was shown that WNT5a, which is an inductor of the non-canonical WNT pathway, stimulates both cellular senescence and osteogenic differentiation of different cell types. In this study, we investigated the role of WNT5a for viability and osteogenic differentiation in human DFCs after the induction of cellular senescence. DFCs were cultivated until the induction of cellular senescence. The induction of cellular senescence was confirmed by β-galactosidase staining, estimation of population doubling time, and slightly telomere length shortening. After induction of cellular senescence, the expression of WNT5A and the potential to induce the osteogenic differentiation decreased. Inhibition of WNT5A by specific siRNAs had significant effect on the viability of DFCs. Cell proliferation was reduced, whereas both cellular senescence and cell death were increased in DFCs. However, an inhibition of WNT5A did only slightly effect the osteogenic differentiation of DFCs. Our results suggest that WNT5A supports viability during both cell proliferation and osteogenic differentiation of DFCs.

Are Hertwig's epithelial root sheath cells necessary for periodontal formation by dental follicle cells?

OBJECTIVE

The role of Hertwig's epithelial root sheath (HERS) cells in periodontal formation has been controversial. This study aimed to further clarify whether HERS cells participate in formation of the periodontium, and the necessity of HERS cells in differentiation of dental follicle cells (DFCs) for periodontal regeneration.

DESIGN

HERS cells and DFCs were isolated and identified from post-natal 7-day Sprauge-Dawley rats. In vitro, direct co-culture of HERS cells and DFCs as well as the individual culture of HERS and DFCs were performed and followed by alizarin red staining and the quantitative real-time polymerase chain reaction analysis. For in vivo evaluation, the inactivated dentin matrix (iTDM) was fabricated. HERS cells and DFCs were seeded in combination or alone on iTDM and then transplanted into the rat omentum. Scanning electron microscope and further histological analysis were carried out.

RESULTS

In vitro, mineral-like nodules were found in the culture of HERS cells alone or HERS + DFCs either by alizarin red staining or scanning electronic microscope. The mineralization and fiber-forming relevant mRNA expressions, such as bone sialoprotein, osteopontin, collagen I and collagen III in HERS + DFCs were significantly higher than that of the HERS or DFCs alone group. After transplantation in vivo, cementum and periodontal ligament-like tissues were formed in groups of HERS + DFCs and HERS alone, while no evident hard tissues and attached fibers were found in DFCs alone.

CONCLUSIONS

Hertwig's epithelial root sheath cells directly participate in the formation of the periodontium, and they are essential for the differentiation of dental follicle cells to form periodontal structures. The combination use of Hertwig's epithelial root sheath cells and dental follicle cells is a promising approach for periodontal regeneration.

Effect of collagenase concentration on the isolation of small adipocytes from human buccal fat pad

Dedifferentiated fat (DFAT) cells were isolated from mature adipocytes using the ceiling culture method. Recently, we successfully isolated DFAT cells from adipocytes with a relatively small size (<40 μm). DFAT cells have a higher osteogenic potential than that of medium adipocytes. Therefore, the objective of this study was to determine the optimal concentration of collagenase solution for isolating small adipocytes from human buccal fat pads (BFPs). Four concentrations of collagenase solution (0.01%, 0.02%, 0.1%, and 0.5%) were used, and their effectiveness was assessed by the number of small adipocytes and DFAT cells isolated. The total number of floating adipocytes that dissociated with 0.02% collagenase was 2.5 times of that dissociated with 0.1% collagenase. The number of floating adipocytes with a diameter of ≤29 μm that dissociated with 0.02% collagenase was thrice of those dissociated with 0.1% and 0.5% collagenase. The number of DFAT cells that dissociated with 0.02% collagenase was 1.5 times of that dissociated with 0.1% collagenase. In addition, DFAT cells that dissociated with 0.02% collagenase had a higher osteogenic differentiation potential than those that dissociated with 0.1% collagenase. These results suggest that 0.02% is the optimal collagenase concentration for isolating small adipocytes from BFPs.

Decellularized Matrix Derived from Neural Differentiation of Embryonic Stem Cells Enhances the Neurogenic Potential of Dental Follicle Stem Cells

INTRODUCTION

Dental follicle stem cells (DFSCs) possess neurogenic potential because they originate from the embryonic neural crest. This study investigated whether neural differentiation of DFSCs can be enhanced by culture on decellularized matrix substrata (NSC-DECM) derived from neurogenesis of human embryonic stem cells (hESCs).

METHODS

The hESCs were differentiated into neural stem cells (NSCs), and NSC-DECM was extracted from confluent monolayers of NSCs through treatment with deionized water. DFSCs seeded on NSC-DECM, Geltrex, and tissue culture polystyrene (TCPS) were subjected to neural induction during a period of 21 days. Expression of early/intermediate (Musashi1, PAX6, NSE, and βIII-tubulin) and mature/late (NGN2, NeuN, NFM, and MASH1) neural markers by DFSCs was analyzed at the 7-, 14-, and 21-day time points with quantitative real-time polymerase chain reaction. Immunocytochemistry for detection of βIII-tubulin, PAX6, and NGN2 expression by DFSCs on day 7 of neural induction was also carried out.

RESULTS

Quantitative RT-PCR showed that expression of PAX6, Musashi1, βIII-tubulin, NSE, NGN2, and NFM by DFSCs was enhanced on NSC-DECM versus either the Geltrex or TCPS groups. Immunocytochemistry showed that DFSCs in the NSC-DECM group displayed more intense staining for βIII-tubulin, PAX6, and NGN2 expression, together with more neurite outgrowths and elongated morphology, as compared with either Geltrex or TCPS.

CONCLUSIONS

DECM derived from neurogenesis of hESCs can enhance the neurogenic potential of DFSCs.

Advanced 3D Models Cultured to Investigate Mesenchymal Stromal Cells of the Human Dental Follicle

The human dental follicle (hDF) contains the developing tooth and is involved in regulating tooth maturation and eruption. To investigate the mesenchymal stromal cells of the dental follicle, 2 three-dimensional (3D) culture models were used, based on a dynamic bioreactor: the Rotary Cell Culture System (RCCS™) and the 3D culture of precursor cells isolated from follicular tissue (human dental follicle cells [hDFCs]). The hDFCs were obtained from impacted third molars of 20 patients. Two 3D culture models were tested. In the first model, intact hDF explants were cultured in 3D conditions, preserving the original tissue architecture; they were studied using histomorphological and molecular analyses. The second model involved the 3D culture of hDFCs, which were characterized to evaluate their multipotency in terms of differentiation capability. Of the biomarkers known to characterize hDFCs, hDF precursors were selected for our study. The immunophenotype and in situ immunocytochemistry were evaluated for markers CD44, CD90, CD146, CD105, CD31, CD34, and CD45 Ag. The results show that the conditions provided by the RCCS preserve the original organizational architecture of the cells. The 3D conditions of the model enhanced differentiation in response to adipogenic, osteogenic, and chondrogenic inductive growth media. The immunophenotype and the immunocytochemistry showed generally high expression of CD90, CD44, and CD105, while CD146 expression was more restricted to ∼30% of cells. No expression was observed for CD31, CD34, and CD45 Ags. Two 3D tissue- and cell-based ex vivo models of the hDF supported the long-term maintenance of hDF-specific cell phenotypes and their ability to recapitulate typical cellular differentiation states. As such, these ex vivo models could be used to study the physiopathology of human odontogenesis. In addition, in a therapeutic context, they could be used to examine the role of specific chemical signals (e.g., new therapeutic agents) in the processes of dental tissue repair and regeneration.

SCAPs Regulate Differentiation of DFSCs During Tooth Root Development in Swine

The tooth root transmits and balances occlusal forces through the periodontium to the alveolar bone. The periodontium, including the gingiva, the periodontal ligament, the cementum and the partial alveolar bone, derives from the dental follicle (DF), except for the gingiva. In the early developmental stages, the DF surrounds the tooth germ as a sphere and functions to promote tooth eruption. However, the morphological dynamics and factors regulating the differentiation of the DF during root elongation remain largely unknown. Miniature pigs are regarded as a useful experimental animal for modeling in craniofacial research because they are similar to humans with respect to dentition and mandible anatomy. In the present study, we used the third deciduous incisor of miniature pig as the model to investigate the factors influencing DF differentiation during root development. We found that the DF was shaped like a crescent and was located between the root apical and the alveolar bone. The expression levels of WNT5a, β-Catenin, and COL-I gradually increased from the center of the DF (beneath the apical foramen) to the lateral coronal corner, where the DF differentiates into the periodontium. To determine the potential regulatory role of the apical papilla on DF cell differentiation, we co-cultured dental follicle stem cells (DFSCs) with stem cells of the apical papilla (SCAPs). The osteogenesis and fibrogenesis abilities of DFSCs were inhibited when being co-cultured with SCAPs, suggesting that the fate of the DF can be regulated by signals from the apical papilla. The apical papilla may sustain the undifferentiated status of DFSCs before root development finishes. These data yield insight into the interaction between the root apex and surrounding DF tissues in root and periodontium development and shed light on the future study of root regeneration in large mammals.

Stem Cells from Dental Pulp: What Epigenetics Can Do with Your Tooth

Adult stem cells have attracted scientific attention because they are able to self-renew and differentiate into several specialized cell types. In this context, human dental tissue-derived mesenchymal stem cells (hDT-MSCs) have emerged as a possible solution for repairing or regenerating damaged tissues. These cells can be isolated from primary teeth that are naturally replaced, third molars, or other dental tissues and exhibit self-renewal, a high proliferative rate and a great multilineage potential. However, the cellular and molecular mechanisms that determine lineage specification are still largely unknown. It is known that a change in cell fate requires the deletion of existing transcriptional programs, followed by the establishment of a new developmental program to give rise to a new cell lineage. Increasing evidence indicates that chromatin structure conformation can influence cell fate. In this way, reversible chemical modifications at the DNA or histone level, and combinations thereof can activate or inactivate cell-type-specific gene sequences, giving rise to an alternative cell fates. On the other hand, miRNAs are starting to emerge as a possible player in establishing particular somatic lineages. In this review, we discuss two new and promising research fields in medicine and biology, epigenetics and stem cells, by summarizing the properties of hDT-MSCs and highlighting the recent findings on epigenetic contributions to the regulation of cellular differentiation.

Dental stem cells in tooth regeneration and repair in the future

INTRODUCTION

Human dental stem cells can be obtained from postnatal teeth, extracted wisdom teeth or exfoliated deciduous teeth. Due to their differentiation potential, these mesenchymal stem cells are promising for tooth repair. Therefore, the development of dental tissue regeneration represents a suitable but challenging, target for dental stem cell therapies. Areas covered: Expert opinion:

AREAS COVERED

In this review, the authors provide an overview of human dental stem cells and their properties for regeneration medicine. Numerous preclinical studies have shown that dental stem cells improve bone augmentation and healing of periodontal diseases. Clinical trials are ongoing to validate the clinical feasibility of these approaches. Dental stem cells are also important for basic research.

EXPERT OPINION

Dental stem cells offer numerous advantages for tooth repair and regeneration. Data obtained from different studies are encouraging. In the next few years, investigations on dental stem cells in basic research, pre-clinical research and clinical studies will pave the way to optimizing patient-tailored treatments for repair and regeneration of dental tissues.

Comparison of the osteogenic differentiation of orofacial bone marrow stromal cells prior to and following marsupialization in patients with odontogenic cyst

Decompression has been considered a valuable tool for odontogenic cystic lesions to minimize cyst size with low morbidity and recurrence. However, whether decompression has a role in regulating stem cell properties of orofacial bone marrow stromal cells (BMSCs) around the cysts has not been fully investigated. The present study compared the stem cell marker profile and osteogenic differentiation potential of orofacial BMSCs prior to and following marsupialization (pre-BMSCs vs. post-BMSCs) in the same individuals. The results demonstrated that post-BMSCs proliferated significantly faster, displayed higher colony-forming unit-fibroblast capacity and demonstrated higher expression of octamer binding protein 4, Nanog and SRY-related HMG box 2 when compared with the pre-BMSCs. Notably, the osteogenic potential was greater in the post-BMSCs compared with in pre-BMSCs, by demonstrating that the protein and mRNA expression levels of osteopontin, runt-related transcription factor 2, osteocalcin, alkaline phosphatase and osterix were upregulated in pre-BMSCs. Furthermore, the phosphorylated levels of extracellular signal-regulated kinase and c-Jun N-terminal kinase were enhanced in post-BMSCs. In conclusion, the study indicated that decompression influences the stem cell properties of orofacial BMSCs, and further studies are needed to verify the findings.

Adult Stem Cells of Orofacial Origin: Current Knowledge and Limitation and Future Trend in Regenerative Medicine

Stem cell research is one of the most rapidly expanding field of medicine which provides significant opportunities for therapeutic and regenerative applications. Different types of stem cells have been isolated investigating their accessibility, control of the differentiation pathway and additional immunomodulatory properties. Bulk of the literature focus has been on the study and potential applications of adult stem cells (ASC) because of their low immunogenicity and reduced ethical considerations. This review paper summarizes the basic available literature on different types of ASC with special focus on stem cells from dental and orofacial origin. ASC have been isolated from different sources, however, isolation of ASC from orofacial tissues has provided a novel promising alternative. These cells offer a great potential in the future of therapeutic and regenerative medicine because of their remarkable availability at low cost while allowing minimally invasive isolation procedures. Furthermore, their immunomodulatory and anti-inflammatory potential is of particular interest. However, there are conflicting reports in the literature regarding their particular biology and full clinical potentials. Sound knowledge and higher control over proliferation and differentiation mechanisms are prerequisites for clinical applications of these cells. Therefore, further standardized basic and translational studies are required to increase the reproducibility and reduce the controversies of studies, which in turn facilitate comparison of related literature and enhance further development in the field.

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.

The cell cycle regulator protein P16 and the cellular senescence of dental follicle cells

Cellular senescence is a restricting factor for regenerative therapies with somatic stem cells. We showed previously that the onset of cellular senescence inhibits the osteogenic differentiation in stem cells of the dental follicle (DFCs), although the mechanism remains elusive. Two different pathways are involved in the induction of the cellular senescence, which are driven either by the cell cycle protein P21 or by the cell cycle protein P16. In this study, we investigated the expression of cell cycle proteins in DFCs after the induction of cellular senescence. The induction of cellular senescence was proved by an increased expression of β-galactosidase and an increased population doubling time after a prolonged cell culture. Cellular senescence regulated the expression of cell cycle proteins. The expression of cell cycle protein P16 was up-regulated, which correlates with the induction of cellular senescence markers in DFCs. However, the expression of cyclin-dependent kinases (CDK)2 and 4 and the expression of the cell cycle protein P21 were successively decreased in DFCs. In conclusion, our data suggest that a P16-dependent pathway drives the induction of cellular senescence in DFCs.

The Sirt6 gene: Does it play a role in tooth development?

Dental Mesenchymal Cells (DMCs) are known to play a role in tooth development as well as in the repair and regeneration of dental tissue. A large number of signaling molecules regulate the proliferation and differentiation of DMC, though the underlying mechanisms are still not fully understood. Sirtuin-6 (SIRT6), a key regulator of aging, can exert an impact on embryonic stem cell (ESC) differentiation. The experimental deletion of Sirt6 in mouse bone marrow cells has been found to have an inhibiting impact on the bone mineral density and the osteogenic differentiation of these cells. The possible role of Sirt6 in tooth development, however, has at present remained largely unexplored. In the present study, we found that SIRT6 had no effect on tooth development before birth. However, Sirt6 gene deletion in knockout mice did have two post-natal impacts: a delay in tooth eruption and sluggishness in the development of dental roots. We propose an explanation of the possible molecular basis of the changes observed in Sirt6-/- mice. SIRT6 is expressed in mouse odontoblasts. Sirt6 deletion enhanced the proliferation of DMCs, as well as their capacity for adipogenic differentiation. On the other hand, it inhibited their capacity for in vitro osteogenic/chondrogenic differentiation. Further studies suggested that other factors may mediate the role of Sirt6 in odontogenesis. These include the nuclear factor kappa B (NF-κB), p38 mitogen-activated protein kinase (p38-MAPK), extracellular regulated MAP kinase (ERK) pathways and the mitochondrial energy. We demonstrated that Sirt6 plays a role in tooth root formation and confirmed that SIRT6 is necessary for DMC differentiation as well as for the development of the tooth root and for eventual tooth eruption. These results establish a new link between SIRT6 and tooth development.

Expression of odontogenic ameloblast-associated protein in the dental follicle and its role in osteogenic differentiation of dental follicle stem cells

OBJECTIVE

Odontogenic Ameloblast-Associated Protein (ODAM) is encoded by a secretory calcium-binding phosphoprotein cluster gene, which generally plays an important role for mineralization. Dental follicle (DF) is essential in regulating bone formation for tooth eruption. This study aims to reveal ODAM expression in the DFs of developing and erupting molars, and to determine the possible role of ODAM.

DESIGN

DFs were collected from human third molars and rat mandibular molars for gene expression assessment and for establishment of cell cultures. RT-PCR and western blot were conducted to determine ODAM expression. Over- or silencing expression of ODAM in the dental follicle stem cells (DFSCs) was done by transfecting the cells with ODAM plasmid or siRNA to evaluate ODAM effects on osteogenesis.

RESULTS

Rat DFs weakly expressed ODAM at early-postnatal days, but a chronological increment of ODAM expression from days 1 to 11 was observed. Differences in expression of ODAM were seen in the human DFs of different individuals. In vitro, ODAM was expressed in DFSCs, but almost no expression in DF-derived fibroblast-like cells. Forcing the DFSCs to overexpress ODAM accelerated osteogenesis, whereas continuously silencing the ODAM in the DFSCs reduced osteogenesis only at 2 weeks of osteogenic induction.

CONCLUSIONS

ODAM is differentially expressed in the DFs of different age molars. Its expression is coincident with the increased bone formation of tooth crypt during tooth eruption in rat DFs. Increase of ODAM expression may accelerate osteogenic differentiation of DFSCs. Thus, ODAM expression in the DF may regulate bone formation for timely tooth eruption.