Comparative characterization of STRO-1(neg)/CD146(pos) and STRO-1(pos)/CD146(pos) apical papilla stem cells enriched with flow cytometry

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Cell Homing Strategies in Regenerative Endodontic Therapy

Cell homing, a process that leverages the body's natural ability to recruit cells and repair damaged tissues, presents a promising alternative to cell transplantation methods. Central to this approach is the recruitment of endogenous stem/progenitor cells-such as those from the apical papilla, bone marrow, and periapical tissues-facilitated by chemotactic biological cues. Moreover, biomaterial scaffolds embedded with signaling molecules create supportive environments, promoting cell migration, adhesion, and differentiation for the regeneration of the pulp-dentin complex. By analyzing in vivo animal studies using cell homing strategies, this review explores how biomolecules and scaffold materials enhance the recruitment of endogenous stem cells to the site of damaged dental pulp tissue, thereby promoting repair and regeneration. It also examines the key principles, recent advancements, and current limitations linked to cell homing-based regenerative endodontic therapy, highlighting the interplay of biomaterials, signaling molecules, and their broader clinical implications.

The Immunophenotype and the Odontogenic Commitment of Dental Pulp Stem Cells Co-Cultured with Macrophages Under Inflammatory Conditions Is Modulated by Complex Magnetic Fields

Dental inflammatory diseases remain a challenging clinical issue, whose causes and development are still not fully understood. During dental caries, bacteria penetrate the tooth pulp, causing pulpitis. To prevent pulp necrosis, it is crucial to promote tissue repair by recruiting immune cells, such as macrophages, able to secrete signal molecules for the pulp microenvironment and thus to recruit dental pulp stem cells (DPSCs) in the damaged site. To date, root canal therapy is the standard for dental caries, but alternative regenerative treatments are gaining attention. Complex Multifrequency Magnetoelectric Fields (CMFs) represent an interesting tool due to their potential anti-inflammatory activity. Against this background, the present work aims at investigating whether the CMF treatment might restore redox balance in a co-culture model of DPSCs and inflamed macrophages mimicking an inflammatory condition, like pulpitis. Results show that superoxide anion levels and markers related to the polarization of macrophages are modulated by the CMF treatment. In parallel, the use of CMFs discloses an impact on the odontogenic commitment of DPSCs, their immunophenotype being considerably modified. In conclusion, CMFs, by modulating the odontogenic commitment and the anti-inflammatory response of DPSCs, might represent a suitable therapeutic tool against pulpitis and, in general, towards dental inflammatory diseases.

CD49f and CD146: A Possible Crosstalk Modulates Adipogenic Differentiation Potential of Mesenchymal Stem Cells

BACKGROUND

The lack of appropriate mesenchymal stem cells (MSCs) selection methods has given the challenges for standardized harvesting, processing, and phenotyping procedures of MSCs. Genetic engineering coupled with high-throughput proteomic studies of MSC surface markers arises as a promising strategy to identify stem cell-specific markers. However, the technical limitations are the key factors making it less suitable to provide an appropriate starting material for the screening platform. A more accurate, easily accessible approach is required to solve the issues.

METHODS

This study established a high-throughput screening strategy with forward versus side scatter gating to identify the adipogenesis-associated markers of bone marrow-derived MSCs (BMSCs) and tonsil-derived MSCs (TMSCs). We classified the MSC-derived adipogenic differentiated cells into two clusters: lipid-rich cells as side scatter (SSC)-high population and lipid-poor cells as SSC-low population. By screening the expression of 242 cell surface proteins, we identified the surface markers which exclusively found in lipid-rich subpopulation as the specific markers for BMSCs and TMSCs.

RESULTS

High-throughput screening of the expression of 242 cell surface proteins indicated that CD49f and CD146 were specific for BMSCs and TMSCs. Subsequent immunostaining confirmed the consistent specific expression of CD49f and CD146 and in BMSCs and TMSCs. Enrichment of MSCs by CD49f and CD146 surface markers demonstrated that the simultaneous expression of CD49f and CD146 is required for adipogenesis and osteogenesis of mesenchymal stem cells. Furthermore, the fate decision of MSCs from different sources is regulated by distinct responses of cells to differentiation stimulations despite sharing a common CD49f+CD146+ immunophenotype.

CONCLUSIONS

We established an accurate, robust, transgene-free method for screening adipogenesis associated cell surface proteins. This provided a valuable tool to investigate MSC-specific markers. Additionally, we showed a possible crosstalk between CD49f and CD146 modulates the adipogenesis of MSCs.

Clinical usage of dental stem cells and their derived extracellular vesicles

Stem cell-based therapies remain at the forefront of tissue engineering and regenerative medicine because stem cells are a unique cell source with enormous potential to treat incurable diseases and even extend lifespans. The search for the best stem cell candidates continues to evolve and in recent years, dental stem cells have received significant attention due to their easy accessibility, high plasticity, and multipotential properties. Dental stem cells have been the subject of extensive research in both animal models and human clinical trials over the past two decades, and have demonstrated significant potential in ocular therapy, bone tissue engineering, and, of course, therapeutic applications in dentistry such as regenerative endodontics and periodontal tissue regeneration. These new sources of cells may be advantageous for cellular therapy and the advancement of regenerative medicine strategies, such as allogeneic transplantation or therapy with extracellular vesicles (EVs), which are functional nanoscale membrane vesicles produced by cells. This chapter discusses the accumulating research findings on cell-based regenerative therapy utilizing dental stem cells and their derived EVs, which could be a viable tool for the treatment of a variety of diseases and hence extremely valuable to mankind in the long run.

3D Organoids for Regenerative Endodontics

Apical periodontitis is the inflammation and destruction of periradicular tissues, mediated by microbial factors originating from the infected pulp space. This bacteria-mediated inflammatory disease is known to interfere with root development in immature permanent teeth. Current research on interventions in immature teeth has been dedicated to facilitating the continuation of root development as well as regenerating the dentin-pulp complex, but the fundamental knowledge on the cellular interactions and the role of periapical mediators in apical periodontitis in immature roots that govern the disease process and post-treatment healing is limited. The limitations in 2D monolayer cell culture have a substantial role in the existing limitations of understanding cell-to-cell interactions in the pulpal and periapical tissues. Three-dimensional (3D) tissue constructs with two or more different cell populations are a better physiological representation of in vivo environment. These systems allow the high-throughput testing of multi-cell interactions and can be applied to study the interactions between stem cells and immune cells, including the role of mediators/cytokines in simulated environments. Well-designed 3D models are critical for understanding cellular functions and interactions in disease and healing processes for future therapeutic optimization in regenerative endodontics. This narrative review covers the fundamentals of (1) the disease process of apical periodontitis; (2) the influence and challenges of regeneration in immature roots; (3) the introduction of and crosstalk between mesenchymal stem cells and macrophages; (4) 3D cell culture techniques and their applications for studying cellular interactions in the pulpal and periapical tissues; (5) current investigations on cellular interactions in regenerative endodontics; and, lastly, (6) the dental-pulp organoid developed for regenerative endodontics.

Clinical trials using dental stem cells: 2022 update

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

Odontogenic MSC Heterogeneity: Challenges and Opportunities for Regenerative Medicine

Cellular heterogeneity refers to the genetic and phenotypic differences among cells, which reflect their various fate choices, including viability, proliferation, self-renewal probability, and differentiation into different lineages. In recent years, research on the heterogeneity of mesenchymal stem cells has made some progress. Odontogenic mesenchymal stem cells share the characteristics of mesenchymal stem cells, namely, good accessibility, low immunogenicity and high stemness. In addition, they also exhibit the characteristics of vasculogenesis and neurogenesis, making them attractive for tissue engineering and regenerative medicine. However, the usage of mesenchymal stem cell subgroups differs in different diseases. Furthermore, because of the heterogeneity of odontogenic mesenchymal stem cells, their application in tissue regeneration and disease management is restricted. Findings related to the heterogeneity of odontogenic mesenchymal stem cells urgently need to be summarized, thus, we reviewed studies on odontogenic mesenchymal stem cells and their specific subpopulations, in order to provide indications for further research on the stem cell regenerative therapy.

Dynamically Bioresponsive DNA Hydrogel Incorporated with Dual-Functional Stem Cells from Apical Papilla-Derived Exosomes Promotes Diabetic Bone Regeneration

The regeneration of bone defects in patients with diabetes mellitus (DM) is remarkably impaired by hyperglycemia and over-expressed proinflammatory cytokines, proteinases (such as matrix metalloproteinases, MMPs), etc. In view of the fact that exosomes represent a promising nanomaterial, herein, we reported the excellent capacity of stem cells from apical papilla-derived exosomes (SCAP-Exo) to facilitate angiogenesis and osteogenesis whether in normal or diabetic conditions in vitro. Then, a bioresponsive polyethylene glycol (PEG)/DNA hybrid hydrogel was developed to support a controllable release of SCAP-Exo for diabetic bone defects. This system could be triggered by the elevated pathological cue (MMP-9) in response to the dynamic diabetic microenvironment. It was further confirmed that the administration of the injectable SCAP-Exo-loaded PEG/DNA hybrid hydrogel into the mandibular bone defect of diabetic rats demonstrated a great therapeutic effect on promoting vascularized bone regeneration. In addition, the miRNA sequencing suggested that the mechanism of dual-functional SCAP-Exo might be related to highly expressed miRNA-126-5p and miRNA-150-5p. Consequently, our study provides valuable insights into the design of promising bioresponsive exosome-delivery systems to improve bone regeneration in diabetic patients.

Deciphering the Epigenetic Code of Stem Cells Derived From Dental Tissues

Stem cells derived from dental tissues (DSCs) exhibit multipotent regenerative potential in pioneering tissue engineering regimens. The multipotency of DSCs is critically regulated by an intricate range of factors, of which the epigenetic influence is considered vital. To gain a better understanding of how epigenetic alterations are involved in the DSC fate determination, the present review overviews the current knowledge relating to DSC epigenetic modifications, paying special attention to the landscape of epigenetic modifying agents as well as the related signaling pathways in DSC regulation. In addition, insights into the future opportunities of epigenetic targeted therapies mediated by DSCs are discussed to hold promise for the novel therapeutic interventions in future translational medicine.

A pilot study on biological characteristics of human CD24(+) stem cells from the apical papilla

BACKGROUND/PURPOSE

CD24 is a specific cell surface marker for undifferentiated dental stem cells from apical papilla (SCAPs) seen only during root development, before the tooth emerges through gum. But the comprehensive role of CD24 in the SCAPs is unclear. This study aims to clarify the exact roles of CD24 in SCAPs.

MATERIALS AND METHODS

SCAPs were divided into CD24 (+)-SCAPs (high percentage CD24) and CD24 (-)-SCAPs (low percentage CD24) via flow cytometry. The proliferation, migration and osteogenic/adipogenic differentiation of the two groups were detected, RT-PCR was performed to detect the expression of osteogenic/adipogenic related genes and thegene expression were analyzed.

RESULTS

The proliferative and migratory ability of CD24 (-)-SCAPs were significantly stronger than that of CD24 (+)-SCAPs. Although, the mineralization process and the osteogenic genes expression were not significantly difference in the two groups. Both CD24 (+)-SCAPs and CD24 (-)-SCAPs differentiated into adipocytes. The adipogenic differentiation in CD24 (+)-SCAPs was better than that in CD24 (-)-SCAPs, after 3 weeks of adipogenic induction. However, the expression of adipogenic related gene, PPAR γ2 mRNA in CD24 (+)-SCAPs was lower than that in CD24 (-)-SCAPs after 1 week of adipogenic induction. But the trend changed for the opposite after 3 weeks.

CONCLUSION

The study proposes that CD24 has a regulatory effect on the adipogenic differentiation of SCAPs, and this may be attained by targeting the PPAR γ2 mRNA. Concurrently, it was found that CD24 plays an inhibitory role in the proliferation and migration of SCAPs, which may minimize the manifestation of diseases caused by an abnormal cell growth.

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.

Dorsomorphin attenuates Jagged1-induced mineralization in human dental pulp cells

AIM

To investigate whether TGF-β/BMP signalling participates in Jagged1-induced osteogenic differentiation in human dental pulp cells (hDPs).

METHODOLOGY

Bioinformatic analysis of publicly available RNA sequencing data of Jagged1-treated hDPs was performed using NetworkAnalyst. The mRNA expression was validated using real-time polymerase chain reaction. hDPs were seeded on Jagged1 immobilized surfaces in the presence or absence of TGF-β or BMP inhibitor. Osteogenic differentiation was evaluated using alkaline phosphatase staining, osteogenic marker gene expression and mineralization assay. Statistical analyses were performed using a Kruskal-Wallis test, followed by a pairwise comparison for more than three group comparison. Mann-Whitney U-test was employed for two group comparison. The statistical significance was considered at p < .05.

RESULTS

Jagged1 treatment in growth medium significantly promoted TGFB1, TGFB2 and TGFB3 whilst significantly inhibited BMP2, BMP4 and BMP6 mRNA expression (p < .05). In osteogenic induction medium, Jagged1 significantly up-regulated TGFB1, TGFB2 and TGFB3 at days 1 and 3 (p < .05). Pre-treatment with TGF-β1, TGF-β2 or TGF-β3 prior to osteogenic induction resulted in the significant increase of osteogenic marker gene expression, collagen type 1 protein expression, alkaline phosphatase enzymatic activity and mineral deposition (p < .05). However, TGF-β signalling inhibition with SB431542 (4 μmol L^-1 ) or SB505124 (47 and 129 nmol L^-1 ) failed to attenuate the effect of Jagged1-induced osteogenic differentiation in hDPs. Dorsomorphin (4 and 8 μmol L^-1 ) treatment significantly abolished the effect of Jagged1 on mineralization by hDPs (p < .05).

CONCLUSION

Notch signalling activation by Jagged1 modulated TGF-β and BMP ligand expression. Dorsomorphin, but not TGF-β receptor inhibitor, attenuated Jagged1-induced osteogenic differentiation in hDPs.

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

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

In vivo study of the angiogenesis potential of bone marrow-derived mesenchymal stem cell aggregates in their niche like environment

BACKGROUND

Sufficient blood vessel formation in bioengineered tissues is essential in order to keep the viability of the organs. Impaired development of blood vasculatures results in failure of the implanted tissue. The cellular source which is seeded in the scaffold is one of the crucial factors involved in tissue engineering methods.

MATERIALS AND METHODS

Considering the notable competence of Bone Marrow derived Mesenchymal Stem Cell aggregates for tissue engineering purposes, in this study BM-aggregates and expanded BM-MSCs were applied without any inductive agent or co-cultured cells, in order to investigate their own angiogenesis potency in vivo. BM-aggregates and BM-MSC were seeded in Poly-L Lactic acid (PLLA) scaffold and implanted in the peritoneal cavity of mice.

RESULT

Immunohistochemistry results indicated that there was a significant difference (p < 0.050) in CD31+ cells between PLLA scaffolds contained cultured BM-MSC; PLLA scaffolds contained BM-aggregates and empty PLLA. According to morphological evidence, obvious connections with recipient vasculature and acceptable integration with surroundings were established in MSC and aggregate-seeded scaffolds.

CONCLUSION

Our findings revealed cultured BM-MSC and BM-aggregates, capacity in order to develop numerous connections between PLLA scaffold and recipient's vasculature which is crucial to the survival of tissues, and considerable tendency to develop constructs containing CD31+ endothelial cells which can contribute in vessel's tube formation.

Characteristics, Classification, and Application of Stem Cells Derived from Human Teeth

Since mesenchymal stem cells derived from human teeth are characterized as having the properties of excellent proliferation, multilineage differentiation, and immune regulation. Dental stem cells exhibit fibroblast-like microscopic appearance and express mesenchymal markers, embryonic markers, and vascular markers but do not express hematopoietic markers. Dental stem cells are a mixed population with different sensitive markers, characteristics, and therapeutic effects. Single or combined surface markers are not only helpful for understanding the subpopulation of mixed stem cell populations according to cell function but also for improving the stable treatment effect of dental stem cells. Focusing on the discovery and characterization of stem cells isolated from human teeth over the past 20 years, this review outlines the effect of marker sorting on cell proliferation and differentiation ability and the assessment of the clinical application potential. Classified dental stem cells from markers and functional molecules can solve the problem of heterogeneity and ensure the efficacy of cell therapy strategies including dentistry, neurologic diseases, bone repair, and tissue engineering.

Key Markers and Epigenetic Modifications of Dental-Derived Mesenchymal Stromal Cells

As a novel research hotspot in tissue regeneration, dental-derived mesenchymal stromal cells (MSCs) are famous for their accessibility, multipotent differentiation ability, and high proliferation. However, cellular heterogeneity is a major obstacle to the clinical application of dental-derived MSCs. Here, we reviewed the heterogeneity of dental-derived MSCs firstly and then discussed the key markers and epigenetic modifications related to the proliferation, differentiation, immunomodulation, and aging of dental-derived MSCs. These messages help to control the composition and function of dental-derived MSCs and thus accelerate the translation of cell therapy into clinical practice.

Unraveling the Role of the Apical Papilla During Dental Root Maturation

The apical papilla is a stem cell rich tissue located at the base of the developing dental root and is responsible for the progressive elongation and maturation of the root. The multipotent stem cells of the apical papilla (SCAP) are extensively studied in cell culture since they demonstrate a high capacity for osteogenic, adipogenic, and chondrogenic differentiation and are thus an attractive stem cell source for stem cell-based therapies. Currently, only few studies are dedicated to determining the role of the apical papilla in dental root development. In this review, we will focus on the architecture of the apical papilla and describe the specific SCAP signaling pathways involved in root maturation. Furthermore, we will explore the heterogeneity of the SCAP phenotype within the tissue and determine their micro-environmental interaction. Understanding the mechanism of postnatal dental root growth could further aid in developing novel strategies in dental root regeneration.

STRO-1 positive cell expansion during osteogenic differentiation: A comparative study of three mesenchymal stem cell types of dental origin

OBJECTIVE

Although the osteogenic differentiation potential of mesenchymal stem cells of dental origin is well established, the roles of different marker proteins in this process remain to be clarified. Our aim was to compare the cellular and molecular changes, focusing in particular on mesenchymal stem cell markers, during in vitro osteogenesis in three dental stem cell types: dental follicle stem cells (DFSCs), periodontal ligament stem cells (PDLSCs) and dental pulp stem cells (DPSCs).

DESIGN

Human DFSCs, PDLSCs and DPSCs were isolated, cultured and their osteogenic differentiation was induced for 3 weeks. Mineralization was assessed by von Kossa staining and calcium concentration measurements. The expression of mesenchymal and osteogenic markers was studied by immunocytochemistry and qPCR techniques. Alkaline phosphatase (ALP) activity and the frequency of STRO-1 positive cells were also quantified.

RESULTS

The three cultures all showed abundant mineralization, with high calcium content by day 21. The expression of vimentin and nestin was sustained after osteogenic induction. The osteogenic medium induced a considerable elevation of STRO-1 positive cells. By day 7, the ALP mRNA level had increased more than 100-fold in DFSCs, PDLSCs, and DPSCs. Quantitative PCR results indicated dissimilarities of osteoblastic marker levels in the three dental stem cell cultures.

CONCLUSIONS

DFSCs, PDLSCs and DPSCs have similar functional osteogenic differentiation capacities although their expressional profiles of key osteogenic markers show considerable variations. The STRO-1 positive cell fraction expands during osteogenic differentiation while vimentin and nestin expression remain high. For identification of stemness, functional studies rather than marker expressions are needed.

Toll-like Receptor Expression Profile of Human Stem/Progenitor Cells Form the Apical Papilla

INTRODUCTION

Stem/progenitor cells from the apical papilla (SCAPs) demonstrate remarkable regenerative and immunomodulatory properties. During their regenerative events, SCAPs, similar to other stem/progenitor cells, could interact with their local inflammatory microenvironment via their expressed toll-like receptors (TLRs). The present study aimed to describe for the first time the unique TLR expression profile of SCAPs.

METHODS

Cells were isolated from the apical papilla of extracted wisdom teeth (n = 8), STRO-1 immunomagnetically sorted, and cultured to obtain single colony-forming units. The expression of CD14, 34, 45, 73, 90, and 105 were characterized on the SCAPs, and their multilineage differentiation potential was examined to prove their multipotent aptitude. After their incubation in basic or inflammatory medium (25 ng/mL interleukin 1 beta, 10³ U/mL interferon gamma, 50 ng/mL tumor necrosis factor alpha, and 3 × 10³ U/mL interferon alpha), a TLR expression profile for SCAPs under uninflamed as well as inflamed conditions was respectively generated.

RESULTS

SCAPs demonstrated all predefined stem/progenitor cell characteristics. In basic medium, SCAPs expressed TLRs 1-10. The inflammatory microenvironment up-regulated the expression of TLR1, TLR2, TLR4, TLR5, TLR6, and TLR9 and down-regulated the expression of TLR3, TLR7, TLR8, and TLR10 in SCAPs under the inflamed condition.

CONCLUSIONS

The present study defines for the first time a distinctive TLR expression profile for SCAPs under uninflamed and inflamed conditions. This profile could greatly impact SCAP responsiveness to their inflammatory microenvironmental agents under regenerative conditions in vivo.

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

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

Viability and Stimulation of Human Stem Cells from the Apical Papilla (hSCAPs) Induced by Silicate-Based Materials for Their Potential Use in Regenerative Endodontics: A Systematic Review

Blood clot formation in the apical third of the root canal system has been shown to promote further root development and reinforcement of dentinal walls by the deposition of mineralized tissue, resulting in an advancement from traditional apexification procedures to a regenerative endodontic treatment (RET) for non-vital immature permanent teeth. Silicate-based hydraulic biomaterials, categorized as bioactive endodontic cements, emerged as bright candidates for their use in RET as coronal barriers, sealing the previously induced blood clot scaffold. Human stem cells from the apical papilla (hSCAPs) surviving the infection may induce or at least be partially responsible for the regeneration or repair shown in RET. The aim of this study is to present a qualitative synthesis of available literature consisting of in vitro assays which analyzed the viability and stimulation of hSCAPs induced by silicate-based hydraulic biomaterials. A systematic electronic search was carried out in Medline, Scopus, Embase, Web of Science, Cochrane and SciELO databases, followed by a study selection, data extraction, and quality assessment following the PRISMA protocol. In vitro studies assessing the viability, proliferation, and/or differentiation of hSCAPs as well as their mineralization potential and/or osteogenic, odontogenic, cementogenic and/or angiogenic marker expression in contact with commercially available silicate-based materials were included in the present review. The search identified 73 preliminary references, of which 10 resulted to be eligible for qualitative synthesis. The modal materials studied were ProRoot MTA and Biodentine. Both bioceramic materials showed significant positive results when compared to a control for hSCAP cell viability, migration, and proliferation assays; a significant up-regulation of hSCAP odontogenic/osteogenic marker (ALP, DSPP, BSP, Runx2, OCN, OSX), angiogenic growth factor (VEGFA, FIGF) and pro-inflammatory cytokine (IL-1α, IL-1β, IL-6, TNF-α) expression; and a significant increase in hSCAP mineralized nodule formation assessed by Alizarin Red staining. Commercially available silicate-based materials considered in the present review can potentially induce mineralization and odontogenic/osteogenic differentiation of hSCAPs, thus prompting their use in regenerative endodontic procedures.

An update on human periapical cyst-mesenchymal stem cells and their potential applications in regenerative medicine

The broad clinical applications of Mesenchymal Stem Cells (MSCs) in the regenerative medicine field is attributed to their ability to self-renew and differentiate into multiple cellular lineages. Nowadays, MSCs can be derived from a variety of adult and fetal tissues including bone marrow, adipose tissue, umbilical cord and placenta. The difficulties associated with the isolation of MSCs from certain tissues such as bone marrow promoted the search for alternative tissues which are easily accessible. Oral derived MSCs include dental pulp stem cells (DPSCs), dental follicle progenitor cells (DFPC), and periodontal ligament stem cells (PDLSC). Being abundant and easily accessible, oral derived MSCs represent an interesting alternative MSC type to be employed in regenerative medicine. Human periapical cyst-mesenchymal stem cells (hPCy-MSCs) correspond to a newly discovered and characterized MSC subtype. Interestingly, hPCy-MSCs are collected from periapical cysts, which are a biological waste, without any influence on the other healthy tissues in oral cavity. hPCy-MSCs exhibit cell surface marker profile similar to that of other oral derived MSCs, show high proliferative potency, and possess the potential to differentiate into different cell types such as osteoblasts, adipocytes and neurons-like cells. hPCy-MSCs, therefore, represent a novel promising MSCs type to be applied in regenerative medicine domain. In this review, we will compare the different types of dental derived MSCs, we will highlight the isolation technique, the characteristics, and the therapeutic potential of hPCy-MSCs.

Evaluation of the Apical Complex and the Coronal Pulp as a Stem Cell Source for Dentin-pulp Regeneration

INTRODUCTION

This study compared the stemness and differentiation potential of stem cells derived from the apical complex (apical complex cells [ACCs]) and coronal pulp (dental pulp stem cells [DPSCs]) of human immature permanent teeth with the aim of determining a more suitable source of stem cells for regeneration of the dentin-pulp complex.

METHODS

ACC and DPSC cultures were established from 13 human immature permanent teeth using the outgrowth method. The proliferation capacity and colony-forming ability of ACCs and DPSCs were evaluated. ACCs and DPSCs were analyzed for mesenchymal stem cell markers using flow cytometry. The adipogenic and osteogenic differentiation potential of ACCs and DPSCs were evaluated using the quantitative real-time polymerase chain reaction and histochemical staining. ACCs and DPSCs were transplanted subcutaneously in immunocompromised mice using macroporous biphasic calcium phosphate as a carrier. The histomorphologic characteristics of the newly formed tissues were verified using hematoxylin-eosin staining and immunohistochemical staining. Quantitative alkaline phosphatase analysis and quantitative real-time polymerase chain reaction using BSP, DSPP, POSTN, and ColXII were performed.

RESULTS

ACCs and DPSCs showed similar cell proliferation potential and colony-forming ability. The percentage of mesenchymal stem cell markers was similar between ACCs and DPSCs. In the in vitro study, ACCs and DPSCs showed adipogenic and osteogenic differentiation potential. In the in vivo study, ACCs and DPSCs formed amorphous hard tissue using macroporous biphasic calcium phosphate particles. The quantity and histomorphologic characteristics of the amorphous hard tissue were similar in the ACC and DPSC groups. Formation of periodontal ligament-like tissue, positive to Col XII, was observed in ACC transplants, which was absent in DPSC transplants.

CONCLUSIONS

ACCs and DPSCs showed similar stemness, proliferation rate, and hard tissue-forming capacity. The notable difference was the periodontal ligament-like fiber-forming capacity of ACCs, which indicates the presence of various lineages of stem cells in the apical complex compared with the coronal pulp. Regarding regeneration of the dentin-pulp complex, the coronal pulp can be a suitable source of stem cells considering its homogenous lineages of cells and favorable osteo/odontogenic differentiation potential.

Downregulation of miR-224-5p Promotes Migration and Proliferation in Human Dental Pulp Stem Cells

Introduction

Pulp regeneration, as a treatment for pulp necrosis, has significant advantages over root canal therapy for the preservation of living pulp. To date, research on pulp regeneration has mainly focused on the transplantation of pulp stem cells into the root canal, but there is still a lack of research on the migration of pulp cells into the root canal via cell homing. Stem cells from the apical tooth papilla (SCAP) are recognized as multidirectional stem cells, but these cells are difficult to obtain. MicroRNAs are small noncoding RNAs that play crucial roles in regulating normal and pathologic functions. We hypothesized that some types of microRNAs might improve the migration and proliferation function of dental pulp stem cells (DPSCs), which are easily obtained in clinical practice, and as a result, DPSCs might replace SCAP and provide valuable information for regenerative endodontics.

Methods

Magnetic activated cell sorting of DPSCs and SCAP was performed. Next-generation sequencing was performed to examine DPSCs and SCAP miRNAs expression and to identify the most significant differentially expressed miRNA. CCK-8 and transwell assays were used to determine the impact of this miRNA on DPSCs proliferation and migration.

Results

The most significant differentially expressed miRNA between DPSCs and SCAP was miR-224-5p. Downregulating miR-224-5p promoted DPSCs proliferation and migration; the opposite results were observed when miR-224-5p was upregulated.

Conclusion

MiR-224-5p promotes proliferation and migration in DPSCs, a finding that is of great significance for further exploring the role of dental pulp stem cells in regenerative endodontics.

Stem Cells from the Apical Papilla: A Promising Source for Stem Cell-Based Therapy

Stem cells are biological cells that can self-renew and can differentiate into multiple cell lineages. Stem cell-based therapy is emerging as a promising alternative therapeutic option for various disorders. Mesenchymal stem cells (MSCs) are multipotent adult stem cells that are isolated from various tissues and can be used as an alternative to embryonic stem cells. Stem cells from the apical papilla (SCAPs) are a novel population of MSCs residing in the apical papilla of immature permanent teeth. SCAPs present the characteristics of expression of MSCs markers, self-renewal, proliferation, migration, differentiation, and immunosuppression, which support the application of SCAPs in stem cell-based therapy, including the immunotherapy and the regeneration of dental tissues, bone, neural, and vascular tissues. In view of these properties and therapeutic potential, SCAPs can be considered as promising candidates for stem cell-based therapy. Thus the aim of our review was to summarize the current knowledge of SCAPs considering isolation, characterization, and multilineage differentiation. The prospects for their use in stem cell-based therapy were also discussed.

Guanine and nucleotide binding protein 3 promotes odonto/osteogenic differentiation of apical papilla stem cells via JNK and ERK signaling pathways

Odonto/osteogenic differentiation of stem cells from the apical papilla (SCAPs) is a key process in tooth root formation and development. However, the molecular mechanisms underlying this process remain largely unknown. In the present study, it was identified that guanine and nucleotide binding protein 3 (GNAI3) was at least in part responsible for the odonto/osteogenic differentiation of SCAPs. GNAI3 was markedly induced in mouse tooth root development in vivo and in human SCAPs mineralization in vitro. Notably, knockdown of GNAI3 by lentiviral vectors expressing short-hairpin RNAs against GNAI3 significantly inhibited the proliferation, cell cycle progression and migration of SCAPs, as well as odonto/osteogenic differentiation of SCAPs in vitro, suggesting that GNAI3 may play an essential role in tooth root development. The promotive role of GNAI3 in odonto/osteogenic differentiation was further confirmed by downregulation of odonto/osteogenic makers in GNAI3-deficient SCAPs. In addition, knockdown of GNAI3 effectively suppressed activity of c-Jun N-terminal kinase (JNK) and extracellular-signal regulated kinase (ERK) signaling pathways that was induced during SCAPs differentiation, suggesting that GNAI3 promotes SCAPs mineralization at least partially via JNK/ERK signaling. Taken together, the present results implicate GNAI3 as a critical regulator of odonto/osteogenic differentiation of SCAPs in tooth root development, and suggest a possible role of GNAI3 in regeneration processes in dentin or other tissues.

The role of Rho-GEF Trio in regulating tooth root development through the p38 MAPK pathway

Trio, the Rho guanine nucleotide exchange factor (Rho-GEF), plays diverse roles in cell migration, cell axon guidance and cytoskeleton reorganization. Conserved during evolution, Trio encodes two guanine nucleotide exchange factor domains (GEFs) and activates small GTPases. The Rho-family small GTPases RhoA and Rac1, which are target molecules of Trio, have been described to engage in craniofacial development and tooth formation. However, the exact role of Trio in tooth development remains elusive. In this study, we generated Wnt1-cre;Trio^fl/fl mice to address the potential function of Trio in tooth development. Wnt1-cre;Trio^fl/fl mice showed short root deformity as well as decreased expression of odontogenic makers such as RUNX2, OSX, OCN, and OPN. In vitro, Trio was silenced in human stem cells of dental papilla (SCAPs). Compared with the control group, the proliferation and migration ability in the experimental group was disrupted. After knocking down Trio in SCAPs, the cells showed phenotypes of poor odontogenic differentiation and weak mineralized nodules. To study the underlying mechanism, we investigated the p38 MAPK pathway and found that loss of Trio blocked the cascade transduction of p38 MAPK signaling. In conclusion, we identified Trio as a novel coordinator in regulating root development and clarified its relevant molecular events.

Concise Review: Stem/Progenitor Cell Proteoglycans Decorated with 7-D-4, 4-C-3, and 3-B-3(-) Chondroitin Sulfate Motifs Are Morphogenetic Markers of Tissue Development

This study reviewed the occurrence of chondroitin sulfate (CS) motifs 4-C-3, 7-D-4, and 3-B-3(-), which are expressed by progenitor cells in tissues undergoing morphogenesis. These motifs have a transient early expression pattern during tissue development and also appear in mature tissues during pathological remodeling and attempted repair processes by activated adult stem cells. The CS motifs are information and recognition modules, which may regulate cellular behavior and delineate stem cell niches in developmental tissues. One of the difficulties in determining the precise role of stem cells in tissue development and repair processes is their short engraftment period and the lack of specific markers, which differentiate the activated stem cell lineages from the resident cells. The CS sulfation motifs 7-D-4, 4-C-3, and 3-B-3 (-) decorate cell surface proteoglycans on activated stem/progenitor cells and appear to identify these cells in transitional areas of tissue development and in tissue repair and may be applicable to determining a more precise role for stem cells in tissue morphogenesis. Stem Cells 2018;36:1475-1486.

Stem Cells From the Apical Papilla (SCAP) as a Tool for Endogenous Tissue Regeneration

Stem cells extracted from developing tissues possibly exhibit not only unique but also superior traits against their developed counterparts. Indeed, stem cells from the apical papilla (SCAP); a unique group of dental stem cells related to developing roots have been shown to be a promising tool for regenerative endodontic procedures and regeneration in general. Studies have characterized the phenotypic traits as well as other regenerative potentials of these cells. Specific sub-populations have been highlighted as well as their neurogenic and angiogenic properties. Nevertheless, in light of the previously discussed features and potential applications of SCAP, there is still much to understand and a lot of information to unravel. The current review will discuss the role of specific markers for detection of different functional populations of SCAP; including CD146 and STRO-1, as well as their true multilineage differentiation potential. In particular, the role of the secretome in association with paracrine signaling in inflammatory microenvironments is also tackled. Additionally, the role of SCAP both in vitro and in vivo during regenerative approaches and in response to different growth factors and biologic scaffolds is highlighted. Finally, this review will shed light on current knowledge regarding the clinical translational potential of SCAP and elucidate possible areas for future research applications.

Lipoxin A4 Attenuates the Inflammatory Response in Stem Cells of the Apical Papilla via ALX/FPR2

Similar to the onset phase of inflammation, its resolution is a process that unfolds in a manner that is coordinated and regulated by a panel of mediators. Lipoxin A4 (LXA₄) has been implicated as an anti-inflammatory, pro-resolving mediator. We hypothesized that LXA₄ attenuates or prevents an inflammatory response via the immunosuppressive activity of Stem Cells of the Apical Papilla (SCAP). Here, we report for the first time in vitro that in a SCAP population, lipoxin receptor ALX/FPR2 was constitutively expressed and upregulated after stimulation with lipopolysaccharide and/or TNF-α. Moreover, LXA₄ significantly enhanced proliferation, migration, and wound healing capacity of SCAP through the activation of its receptor, ALX/FPR2. Cytokine, chemokine and growth factor secretion by SCAP was inhibited in a dose dependent manner by LXA₄. Finally, LXA₄ enhanced immunomodulatory properties of SCAP towards Peripheral Blood Mononuclear Cells. These findings provide the first evidence that the LXA₄-ALX/FPR2 axis in SCAP regulates inflammatory mediators and enhances immunomodulatory properties. Such features of SCAP may also support the role of these cells in the resolution phase of inflammation and suggest a novel molecular target for ALX/FPR2 receptor to enhance a stem cell-mediated pro-resolving pathway.

Impaired bone healing at tooth extraction sites in CD24-deficient mice: A pilot study

AIM

To use a micro-computed tomography (micro-CT) to quantify bone healing at maxillary first molar extraction sites, and test the hypothesis that bone healing is impaired in CD24-knockout mice as compared with wild-type C57BL/6J mice.

MATERIALS AND METHODS

Under ketamine-xylazine general anaesthesia, mice had either extraction of the right maxillary first molar tooth or sham operation. Mice were sacrificed 1 (n = 12/group), 2 (n = 6/group) or 4 (n = 6/group) weeks postoperatively. The right maxillae was disected. Micro-CT was used to quantify differences in bone microstructural features at extrction sites, between CD24-knockout mice and wild-type mice.

RESULTS

CD24-Knockout mice displayed impaired bone healing at extraction sites that was manifested as decreased trabecular bone density, and decreased number and thickness of trabeculae.

CONCLUSIONS

This pilot study suggests that CD24 plays an important role in extraction socket bone healing and may be used as a novel biomarker of bone quality and potential therapeutic target to improve bone healing and density following alveolar bone injury.

CD146+ skeletal stem cells from growth plate exhibit specific chondrogenic differentiation capacity in vitro

Skeletal stem cells (SSCs) are a population of progenitor cells which give rise to postnatal skeletal tissues including bone, cartilage and bone marrow stroma, however not to adipose, haematopoietic or muscle tissue. Growth plate chondrocytes exhibit the ability of continuous proliferation and differentiation, which contributes to the continuous physiological growth. The growth plate has been hypothesized to contain SSCs which exhibit a desirable differentiation capacity to generate bone and cartilage. Due to the heterogeneity of the growth plate chondrocytes, SSCs in the growth plate are not well studied. The present study used cluster of differentiation (CD)146 and CD105 as markers to isolate purified SSCs. CD105+ SSCs and CD146+ SSCs were isolated using a magnetic activated cell sorting method. To quantitatively investigate the proliferation and differentiation ability, the colony-forming efficiency (CFE) and multi‑lineage differentiation capacity of CD105+ SSCs and CD146+ SSCs were compared with unsorted cells and adipose-derived stem cells (ASCs). It was revealed that CD105+ and CD146+ subpopulations represented subsets of SSCs which generated chondrocytes and osteocytes, however not adipocytes. Compared with CD105+ subpopulations and ASCs, the CD146+ subpopulation exhibited a greater CFE and continuous high chondrogenic differentiation capacity in vitro. Therefore, the present study suggested that the CD146+ subpopulation represented a chondrolineage‑restricted subpopulation of SSCs and may therefore act as a valuable cell source for cartilage regeneration.

Stem Cells of Dental Origin: Current Research Trends and Key Milestones towards Clinical Application

Dental Mesenchymal Stem Cells (MSCs), including Dental Pulp Stem Cells (DPSCs), Stem Cells from Human Exfoliated Deciduous teeth (SHED), and Stem Cells From Apical Papilla (SCAP), have been extensively studied using highly sophisticated in vitro and in vivo systems, yielding substantially improved understanding of their intriguing biological properties. Their capacity to reconstitute various dental and nondental tissues and the inherent angiogenic, neurogenic, and immunomodulatory properties of their secretome have been a subject of meticulous and costly research by various groups over the past decade. Key milestone achievements have exemplified their clinical utility in Regenerative Dentistry, as surrogate therapeutic modules for conventional biomaterial-based approaches, offering regeneration of damaged oral tissues instead of simply “filling the gaps.” Thus, the essential next step to validate these immense advances is the implementation of well-designed clinical trials paving the way for exploiting these fascinating research achievements for patient well-being: the ultimate aim of this ground breaking technology. This review paper presents a concise overview of the major biological properties of the human dental MSCs, critical for the translational pathway “from bench to clinic.”

Osteo-/odontogenic differentiation of BMP2 and VEGF gene-co-transfected human stem cells from apical papilla

Stem cells from apical papilla (SCAP) possess clear osteo-/odontogenic differentiation capabilities, and are regarded as the major cellular source for root dentin development. Bone morphogenetic protein 2 (BMP2) and vascular endothelial growth factor (VEGF) serve pivotal roles in the modulation of tooth development and dentin formation. However, the synergistic effects of BMP2 and VEGF on osteo-/odontogenic differentiation of SCAP remain unclear. The current study aimed to investigate the proliferative and osteo-/odontogenic differentiating capabilities of BMP2 and VEGF gene-co-transfected SCAP (SCAP-BMP2-VEGF) in vitro. The basic characteristics of the isolated SCAP were identified by the induction of multipotent differentiation and by flow cytometry. Lentiviral vector-mediated gene transfection was conducted with SCAP in order to construct blank vector-transfected SCAP (SCAP-green fluorescent protein), BMP2 gene-transfected SCAP (SCAP-BMP2), VEGF gene-transfected SCAP (SCAP-VEGF) and SCAP-BMP2-VEGF. The Cell Counting Kit 8 assay was used to analyze the proliferative capacities of the four groups of cells. The expression of osteo-/odontogenic genes and proteins in the cells were evaluated by reverse transcription-quantitative polymerase chain reaction and western blotting. The mineralized nodules formed by the four group cells were visualized by alkaline phosphatase (ALP) staining. Among the four groups of cells, SCAP-VEGF was demonstrated to exhibit increased proliferation, and SCAP-BMP2-VEGF exhibited reduced proliferation during eight days observation. SCAP-BMP2-VEGF exhibited significantly increased expression levels of ALP, osteocalcin, dentin sialophosphoprotein, dentin matrix acidic phosphoprotein gene 1 and dentin sialoprotein than the other three groups at the majority of the time points. Furthermore, the SCAP-BMP2-VEGF group exhibited a significantly greater number of ALP-positive mineralized nodules than the other groups following 16 days culture in vitro. In conclusion, lentiviral vector-mediated BMP2 and VEGF gene co-transfection significantly activated the osteo-/odontogenic differentiation of human SCAP.

An Overview of Protocols for the Neural Induction of Dental and Oral Stem Cells In Vitro

To date, various adult stem cells have been identified within the oral cavity, including dental pulp stem cells, dental follicle stem cells, stem cells from apical papilla, stem cells from human exfoliated deciduous teeth, periodontal ligament stem cells, and mesenchymal stem cells from the gingiva. All of these possess neurogenic potential due to their common developmental origin from the embryonic neural crest. Besides the relative ease of isolation of these adult stem cells from readily available biological waste routinely produced during dental treatment, these cells also possess the advantage of immune compatibility in autologous transplantation. In recent years, much interest has been focused on the derivation of neural lineages from these adult stem cells for therapeutic applications in the brain, spinal cord, and peripheral nerve regeneration. In addition, there are also promising nontherapeutic applications of stem cell-derived neurons in pharmacological and toxicological screening of neuroactive drugs, and for in vitro modeling of neurodevelopmental and neurodegenerative diseases. Hence, this review will critically examine the diverse array of in vitro neural induction protocols that have been devised for dental and oral-derived stem cells. These protocols are defined not only by the culture milieu comprising the basal medium plus growth factors, small molecules, and other culture supplements but also by the substrata/surface coatings utilized, the presence of multiple culture stages, the total culture duration, the initial seeding density, and whether the spheroid/neurosphere formation is being utilized to recapitulate the three-dimensional neural differentiation microenvironment that is naturally present physiologically in vivo.

Single CD271 marker isolates mesenchymal stem cells from human dental pulp

Mesenchymal stem cells (MSCs) are a promising tool in regenerative medicine due to their capacity to differentiate into multiple lineages. In addition to MSCs isolated from bone marrow (BMSCs), adult MSCs are isolated from craniofacial tissues including dental pulp tissues (DPs) using various stem cell surface markers. However, there has been a lack of consensus on a set of surface makers that are reproducibly effective at isolating putative multipotent dental mesenchymal stem cells (DMSCs). In this study, we used different combinations of surface markers (CD51/CD140α, CD271, and STRO-1/CD146) to isolate homogeneous populations of DMSCs from heterogeneous dental pulp cells (DPCs) obtained from DP and compared their capacity to undergo multilineage differentiation. Fluorescence-activated cell sorting revealed that 27.3% of DPCs were CD51⁺/CD140α⁺, 10.6% were CD271⁺, and 0.3% were STRO-1⁺/CD146⁺. Under odontogenic conditions, all three subsets of isolated DMSCs exhibited differentiation capacity into odontogenic lineages. Among these isolated subsets of DMSCs, CD271⁺ DMSCs demonstrated the greatest odontogenic potential. While all three combinations of surface markers in this study successfully isolated DMSCs from DPCs, the single CD271 marker presents the most effective stem cell surface marker for identification of DMSCs with high odontogenic potential. Isolated CD271⁺ DMSCs could potentially be utilized for future clinical applications in dentistry and regenerative medicine.

Characterization of the osteogenic potential of mesenchymal stem cells from human periodontal ligament based on cell surface markers

Mesenchymal stem cell (MSC)-mediated therapy has been shown to be clinically effective in regenerating tissue defects. For improved regenerative therapy, it is critical to isolate homogenous populations of MSCs with high capacity to differentiate into appropriate tissues. The utilization of stem cell surface antigens provides a means to identify MSCs from various tissues. However, few surface markers that consistently isolate highly regenerative MSCs have been validated, making it challenging for routine clinical applications and making it all the more imperative to identify reliable surface markers. In this study, we used three surface marker combinations: CD51/CD140α, CD271, and STRO-1/CD146 for the isolation of homogenous populations of dental mesenchymal stem cells (DMSCs) from heterogeneous periodontal ligament cells (PDLCs). Fluorescence-activated cell sorting analysis revealed that 24% of PDLCs were CD51⁺/CD140α⁺, 0.8% were CD271⁺, and 2.4% were STRO-1⁺/CD146⁺. Sorted cell populations were further assessed for their multipotent properties by inducing osteogenic and chondrogenic differentiation. All three subsets of isolated DMSCs exhibited differentiation capacity into osteogenic and chondrogenic lineages but with varying degrees. CD271⁺ DMSCs demonstrated the greatest osteogenic potential with strong induction of osteogenic markers such as DLX5, RUNX2, and BGLAP. Our study provides evidence that surface marker combinations used in this study are sufficient markers for the isolation of DMSCs from PDLCs. These results provide important insight into using specific surface markers for identifying homogenous populations of DMSCs for their improved utilization in regenerative medicine.

Mesenchymal Stem Cells Obtained from Synovial Fluid Mesenchymal Stem Cell-Derived Induced Pluripotent Stem Cells on a Matrigel Coating Exhibited Enhanced Proliferation and Differentiation Potential

Induced pluripotent stem cell-derived mesenchymal stem cells (iPSC-MSCs) serve as a promising source for cell-based therapies in regenerative medicine. However, optimal methods for transforming iPSCs into MSCs and the characteristics of iPSC-MSCs obtained from different methods remain poorly understood. In this study, we developed a one-step method for obtaining iPSC-MSCs (CD146+STRO-1+ MSCs) from human synovial fluid MSC-derived induced iPSCs (SFMSC-iPSCs). CD146-STRO-1-SFMSCs were reprogrammed into iPSCs by transduction with lentivirus-mediated Sox2, Oct-3/4, klf4, and c-Myc. SFMSC-iPSCs were maintained with mTeSR1 medium in Matrigel-coated culture plates. Single dissociated cells were obtained by digesting the SFMSC-iPSCs with trypsin. The dissociated cells were then plated into Matrigel-coated culture plate with alpha minimum essential medium supplemented with 10% fetal bovine serum, 1× Glutamax, and the ROCK inhibitor Y-27632. Cells were then passaged in standard cell culture plates with alpha minimum essential medium supplemented with 10% fetal bovine serum and 1× Glutamax. After passaging in vitro, the cells showed a homogenous spindle-shape similar to their ancestor cells (SFMSCs), but with more robust proliferative activity. Flow cytometric analysis revealed typical MSC surface markers, including expression of CD73, CD90, CD105, and CD44 and lack of CD45, CD34, CD11b, CD19, and HLA-DR. However, these cells were positive for CD146 and stro-1, which the ancestor cells were not. Moreover, the cells could also be induced to differentiate in osteogenic, chondrogenic, and adipogenic lineages in vitro. The differentiation potential was improved compared with the ancestor cells in vitro. The cells were not found to exhibit oncogenicity in vivo. Therefore, the method presented herein facilitated the generation of STRO-1+CD146+ MSCs from SFMSC-iPSCs exhibiting enhanced proliferation and differentiation potential.

NOTCH3 is expressed in human apical papilla and in subpopulations of stem cells isolated from the tissue

NOTCH plays a role in regulating stem cell function and fate decision. It is involved in tooth development and injury repair. Information regarding NOTCH expression in human dental root apical papilla (AP) and its residing stem cells (SCAP) is limited. Here we investigated the expression of NOTCH3, its ligand JAG1, and mesenchymal stem cell markers CD146 and STRO-1 in the AP or in the primary cultures of SCAP isolated from AP. Our in situ immunostaining showed that in the AP NOTCH3 and CD146 were co-expressed and associated with blood vessels having NOTCH3 located more peripherally. In cultured SCAP, NOTCH3 and JAG1 were co-expressed. Flow cytometry analysis showed that 7%, 16% and 98% of the isolated SCAP were positive for NOTCH3, STRO-1 and CD146, respectively with a rare 1.5% subpopulation of SCAP co-expressing all three markers. The expression level of NOTCH3 reduced when SCAP underwent osteogenic differentiation. Our findings are the first step towards defining the regulatory role of NOTCH3 in SCAP fate decision.

17beta-estradiol promotes the odonto/osteogenic differentiation of stem cells from apical papilla via mitogen-activated protein kinase pathway

Introduction

Estrogen plays an important role in the osteogenic differentiation of mesenchymal stem cells, while stem cells from apical papilla (SCAP) can contribute to the formation of dentin/bone-like tissues. To date, the effects of estrogen on the differentiation of SCAP remain unclear.

Methods

SCAP was isolated and treated with 10^-7 M 17beta-estradiol (E2). The odonto/osteogenic potency and the involvement of mitogen-activated protein kinase (MAPK) signaling pathway were subsequently investigated by using methyl-thiazolyl-tetrazolium (MTT) assay, and other methods.

Results

MTT and flow cytometry results demonstrated that E2 treatment had no effect on the proliferation of SCAP in vitro, while alkaline phosphatase (ALP) assay and alizarin red staining showed that E2 can significantly promote ALP activity and mineralization ability in SCAP. Real-time reverse transcription polymerase chain reaction (RT-PCR) and western blot assay revealed that the odonto/osteogenic markers (ALP, DMP1/DMP1, DSPP/DSP, RUNX2/RUNX2, OSX/OSX and OCN/OCN) were significantly upregulated in E2-treated SCAP. In addition, the expression of phosphor-p38 and phosphor-JNK in these stem cells was enhanced by E2 treatment, as was the expression of the nuclear downstream transcription factors including phosphor-Sp1, phosphor-Elk-1, phosphor-c-Jun and phosphor-c-Fos, indicating the activation of MAPK signaling pathway during the odonto/osteogenic differentiation of E2-treated SCAP. Conversely, the differentiation of E2-treated SCAP was inhibited in the presence of MAPK specific inhibitors.

Conclusions

The ondonto/osteogenic differentiation of SCAP is enhanced by 10^-7 M 17beta-estradiol via the activation of MAPK signaling pathway.

Proliferation and odontogenic differentiation of BMP2 gene‑transfected stem cells from human tooth apical papilla: an in vitro study

Stem cells from the apical papilla (SCAP) have odontogenic potential, which plays a pivotal role in the root dentin development of permanent teeth. Human bone morphogenetic protein 2 (BMP2) is a well-known gene that participates in regulating the odontogenic differentiation of dental tissue-derived stem cells. However, little is known regarding the effects of the BMP2 gene on the proliferation and odontogenic differentiation of SCAP. This study aimed to evaluate the odontogenic differentiation potential of lentiviral-mediated BMP2 gene-transfected human SCAP (SCAP/BMP2) in vitro. SCAP were isolated by enzymatic dissociation of human teeth apical papillae. The multipotential of SCAP was verified by their osteogenic and adipogenic differentiation characteristics. The phenotype of SCAP was evaluated by flow cytometry (FCM). The proliferation status of the blank vector-transfected SCAP (SCAP/Vector) and SCAP/BMP2 was analyzed by a cell counting kit-8 (CCK-8). Odontogenic genes, including alkaline phosphatase (ALP), osteocalcin (OCN), dentin sialophosphoprotein (DSPP) and dentin matrix protein 1 (DMP1) of the two groups of cells were evaluated by quantitative polymerase chain reaction (qPCR). ALP staining and alizarin red (AR) staining of the cells was performed on the 16th day after transfection. In vitro results of CCK-8, qPCR, ALP and AR staining demonstrated that: i) SCAP/BMP2 had a comparable proliferation rate to SCAP/Vector; ii) SCAP/BMP2 presented significantly better potential to differentiate into odontoblasts compared to SCAP/Vector by upregulating ALP, OCN, DSPP and DMP1 genes; iii) more ALP granules and mineralized deposits were formed by SCAP/BMP2 as compared to SCAP/Vector. The results suggested that lentiviral-mediated BMP2 gene transfection enhances the odontogenic differentiation capacity of human SCAP in vitro.

White mineral trioxide aggregate induces migration and proliferation of stem cells from the apical papilla

INTRODUCTION

Regenerative endodontic protocols recommend white mineral trioxide aggregate (WMTA) as a capping material because of its osteoinductive properties. Stem cells from the apical papilla (SCAP) are presumed to be involved in this regenerative process, but the effects of WMTA on SCAP are largely unknown. Our hypothesis was that WMTA induces proliferation and migration of SCAP.

METHODS

Here we used an unsorted population of SCAP (passages 3-5) characterized by high CD24, CD146, and Stro-1 expression. The effect of WMTA on SCAP migration was assessed by using transwells, and its effect on proliferation was determined by the WST-1 assay. Fetal bovine serum (FBS) and calcium chloride-enriched medium were used as positive controls.

RESULTS

The SCAP analyzed here showed a low percentage of STRO-1+ and CD24+ cells. Both set and unset WMTA significantly increased the short-term migration of SCAP after 6 hours (P < .05), whereas calcium chloride-enriched medium did after 24 hours of exposure. Set WMTA significantly increased proliferation on days 1-5, whereas calcium-enriched medium showed a significant increase on day 7, with a significant reduction on proliferation afterwards. SCAP migration and proliferation were significantly and steadily induced by the presence of 2% and 10% FBS.

CONCLUSIONS

Collectively, these data demonstrate that WMTA induced an early short-term migration and proliferation of a mixed population of stem cells from apical papilla as compared with a later and longer-term induction by calcium chloride or FBS.

Cartilage tissue engineering: molecular control of chondrocyte differentiation for proper cartilage matrix reconstruction

BACKGROUND

Articular cartilage defects are a veritable therapeutic problem because therapeutic options are very scarce. Due to the poor self-regeneration capacity of cartilage, minor cartilage defects often lead to osteoarthritis. Several surgical strategies have been developed to repair damaged cartilage. Autologous chondrocyte implantation (ACI) gives encouraging results, but this cell-based therapy involves a step of chondrocyte expansion in a monolayer, which results in the loss in the differentiated phenotype. Thus, despite improvement in the quality of life for patients, reconstructed cartilage is in fact fibrocartilage. Successful ACI, according to the particular physiology of chondrocytes in vitro, requires active and phenotypically stabilized chondrocytes.

SCOPE OF REVIEW

This review describes the unique physiology of cartilage, with the factors involved in its formation, stabilization and degradation. Then, we focus on some of the most recent advances in cell therapy and tissue engineering that open up interesting perspectives for maintaining or obtaining the chondrogenic character of cells in order to treat cartilage lesions.

MAJOR CONCLUSIONS

Current research involves the use of chondrocytes or progenitor stem cells, associated with "smart" biomaterials and growth factors. Other influential factors, such as cell sources, oxygen pressure and mechanical strain are considered, as are recent developments in gene therapy to control the chondrocyte differentiation/dedifferentiation process.

GENERAL SIGNIFICANCE

This review provides new information on the mechanisms regulating the state of differentiation of chondrocytes and the chondrogenesis of mesenchymal stem cells that will lead to the development of new restorative cell therapy approaches in humans. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.