Assessment of the impact of two different isolation methods on the osteo/odontogenic differentiation potential of human dental stem cells derived from deciduous teeth

The influence of fetal bovine serum concentration on stemness and neuronal differentiation markers in stem cells from human exfoliated deciduous teeth

Dental Stem Cells (DSCs) from discarded teeth are a non-invasive and ethically favorable source with the potential for neurogenesis due to their ectodermal origin. Stem cells from human exfoliated deciduous teeth (SHED) are particularly promising due to their high differentiation potential and relative immaturity compared to other Mesenchymal Stromal Cells (MSCs). Markers like CD56 and CD271 are critical in identifying MSC subpopulations for therapeutic applications because of their roles in neurodevelopment and maintaining stemness. This study investigates how fetal bovine serum (FBS) concentrations affect the expression of CD56 and CD271 in SHED, influencing their stemness and neuronal differentiation potential. SHEDs were isolated from various donors, cultured, and characterized for MSC traits using markers such as CD14, CD19, CD29, CD34, CD45, CD73, CD90, CD105, CD56, and CD271. Culturing SHED in different FBS conditions (standard 15 %, reduced 1 % and 5 %, and FBS-free) showed that lower FBS concentrations increase CD271 and CD56 expression while maintaining the standard MSC immunophenotype. Importantly, the enhanced expression of these markers can be induced even after SHEDs have been expanded in standard FBS concentrations. These findings suggest that FBS concentration can optimize SHED culture conditions, enhancing their suitability for regenerative medicine and tissue engineering applications.

Differentiation of Spiral Ganglion Neurons from Human Dental Pulp Stem Cells: A Further Step towards Autologous Auditory Nerve Recovery

The degeneration of spiral ganglion neurons (SGNs), which convey auditory signals from hair cells to the brain, can be a primary cause of sensorineural hearing loss (SNHL) or can occur secondary to hair cell loss. Emerging therapies for SNHL include the replacement of damaged SGNs using stem cell-derived otic neuronal progenitors (ONPs). However, the availability of renewable, accessible, and patient-matched sources of human stem cells is a prerequisite for successful replacement of the auditory nerve. In this study, we derived ONP and SGN-like cells by a reliable and reproducible stepwise guidance differentiation procedure of self-renewing human dental pulp stem cells (hDPSCs). This in vitro differentiation protocol relies on the modulation of BMP and TGFβ pathways using a free-floating 3D neurosphere method, followed by differentiation on a Geltrex-coated surface using two culture paradigms to modulate the major factors and pathways involved in early otic neurogenesis. Gene and protein expression analyses revealed efficient induction of a comprehensive panel of known ONP and SGN-like cell markers during the time course of hDPSCs differentiation. Atomic force microscopy revealed that hDPSC-derived SGN-like cells exhibit similar nanomechanical properties as their in vivo SGN counterparts. Furthermore, spiral ganglion neurons from newborn rats come in close contact with hDPSC-derived ONPs 5 days after co-culturing. Our data demonstrate the capability of hDPSCs to generate SGN-like neurons with specific lineage marker expression, bipolar morphology, and the nanomechanical characteristics of SGNs, suggesting that the neurons could be used for next-generation cochlear implants and/or inner ear cell-based strategies for SNHL.

Insulin promotes the bone formation capability of human dental pulp stem cells through attenuating the IIS/PI3K/AKT/mTOR pathway axis

BACKGROUND

Insulin has been known to regulate bone metabolism, yet its specific molecular mechanisms during the proliferation and osteogenic differentiation of dental pulp stem cells (DPSCs) remain poorly understood. This study aimed to explore the effects of insulin on the bone formation capability of human DPSCs and to elucidate the underlying mechanisms.

METHODS

Cell proliferation was assessed using a CCK-8 assay. Cell phenotype was analyzed by flow cytometry. Colony-forming unit-fibroblast ability and multilineage differentiation potential were evaluated using Toluidine blue, Oil red O, Alizarin red, and Alcian blue staining. Gene and protein expressions were quantified by real-time quantitative polymerase chain reaction and Western blotting, respectively. Bone metabolism and biochemical markers were analyzed using electrochemical luminescence and chemical colorimetry. Cell adhesion and growth on nano-hydroxyapatite/collagen (nHAC) were observed with a scanning electron microscope. Bone regeneration was assessed using micro-CT, fluorescent labeling, immunohistochemical and hematoxylin and eosin staining.

RESULTS

Insulin enhanced the proliferation of human DPSCs as well as promoted mineralized matrix formation in a concentration-dependent manner. 10- 6 M insulin significantly up-regulated osteogenic differentiation-related genes and proteins markedly increased the secretion of bone metabolism and biochemical markers, and obviously stimulated mineralized matrix formation. However, it also significantly inhibited the expression of genes and proteins of receptors and receptor substrates associated with insulin/insulin-like growth factor-1 signaling (IIS) pathway, obviously reduced the expression of the phosphorylated PI3K and the ratios of the phosphorylated PI3K/total PI3K, and notably increased the expression of the total PI3K, phosphorylated AKT, total AKT and mTOR. The inhibitor LY294002 attenuated the responsiveness of 10- 6 M insulin to IIS/PI3K/AKT/mTOR pathway axis, suppressing the promoting effect of insulin on cell proliferation, osteogenic differentiation and bone formation. Implantation of 10- 6 M insulin treated DPSCs into the backs of severe combined immunodeficient mice and the rabbit jawbone defects resulted in enhanced bone formation.

CONCLUSIONS

Insulin induces insulin resistance in human DPSCs and effectively promotes their proliferation, osteogenic differentiation and bone formation capability through gradually inducing the down-regulation of IIS/PI3K/AKT/mTOR pathway axis under insulin resistant states.

Comparative Evaluation of the Differentiation and Proliferation Potential of Dental Pulp Stem Cells on Hydroxyapatite/Beta-Tricalcium Bone Graft and Bovine Bone Graft: An In Vitro Study

BACKGROUND

Stem cells of mesenchymal origin have good proliferative capacity when compared to other stem cell types. Dental pulp stem cells (DPSCs) are a variety of mesenchymal cells obtained from the pulpal tissue of teeth and are abundantly available and easy to obtain. DPSCs facilitate and improve the formation of new bone using different bone graft scaffolds. This present study aims to evaluate and compare the osteogenic potential of DPSCs on alloplastic and xenogeneic bone grafts.

MATERIALS AND METHODS

Hydroxyapatite and beta-tricalcium bone graft and bovine bone graft were used in a triplicate manner in the laboratory. DPSCs were obtained from the pulpal tissue of extracted third molars in the laboratory. The cytotoxicity, osteogenic potential, and difference in the rate of proliferation of mesenchymal cells on the biomaterials were assessed.

RESULTS

Darker purple staining was seen in the case of hydroxyapatite/beta-tricalcium bone graft on MTT colorimetric assay stating that there was an increase in cell viability in hydroxyapatite/beta-tricalcium bone graft as compared to the bovine bone graft. Hydroxyapatite/beta-tricalcium bone graft showed more osteogenic potential as compared to the bovine bone graft as a higher degree of red staining was seen in Alizarin staining.

CONCLUSION

Higher cell viability and higher osteogenic proliferation and differentiation were seen on the hydroxyapatite/beta-tricalcium bone graft compared to the bovine bone scaffold.

Isolation and Culture of Primary Human Dental Pulp Cells-A Description of Technical and Methodological Steps to Maximise Predictability and Yield

The dental pulp has critical functions in tooth development as well as an ongoing role in promoting and maintaining the vitality of teeth. In particular, its regenerative ability allows dental tissues to be restored following damage caused by traumatic injury or caries. Regenerative endodontic procedures aim to utilise these processes to stimulate dental pulp repair in a minimally invasive manner and reduce the need for more invasive procedures such as root canal treatment. Dental pulp is a source of dental pulp cells (DPCs), which has a subpopulation of dental pulp stem cells (DPSCs), which are attractive for use in regenerative medicine due to their high proliferation rate, ability to differentiate into multiple cell types, and their preserved vitality following cryopreservation. The development of next-generation clinical therapeutics that maximise the potential of dental pulp relies on strong empirical evidence arising from in vitro experimentation. Here, we describe a modified method for the efficient isolation of primary human DPCs from sound third molar teeth for culture using an explant outgrowth method on basement membrane-coated flasks, as well as using high-resolution macro-photography to illustrate the methods. Critically, steps are taken to minimise potential physical and mechanical trauma to the cells and maximise yield. Human DPCs cultured using this method can be further expanded in cell culture flasks to facilitate their use in various in vitro experimental procedures.

Biological Effects of "Inflammageing" on Human Oral Cells: Insights into a Potential Confounder of Age-Related Diseases

OBJECTIVES

The term "inflammageing" describes the process of inflammation-induced aging that leads living cells to a state of permanent cell cycle arrest due to chronic antigenic irritation. This in vitro study aimed to shed light on the mechanisms of "inflammageing" on human oral cells.

METHODS

Primary cultures of human gingival fibroblasts (hGFs) were exposed to variable pro-inflammatory stimuli, including lipopolysaccharide (LPS), Tumor Necrosis Factor-alpha (TNFa), and gingival crevicular fluid (GCF) collected from active periodontal pockets of systemically healthy patients. Inflammageing was studied through two experimental models, employing either late-passage ("aged") cells (p. 10) that were exposed to the pro-inflammatory stimuli or early-passage ("young") cells (p. 1) continuously exposed during a period of several passages (up to p. 10) to the above-mentioned stimuli. Cells were evaluated for the expression of beta-galactosidase activity (histochemical staining), senescence-associated genes (qPCR analysis), and biomarkers related to a Senescence-Associated Secretory Phenotype (SASP), through proteome profile analysis and bioinformatics.

RESULTS

A significant increase (p < 0.05) in beta-galactosidase-positive cells was observed after exposure to each pro-inflammatory stimulus. The senescence-associated gene expression included upregulation for CCND1 and downregulation for SUSD6, and STAG1, a profile typical for cellular senescence. Overall, pro-inflammatory priming of late-passage cells caused more pronounced effects in terms of senescence than long-term exposure of early-passage cells to these stimuli. Proteomic analysis showed induction of SASP, evidenced by upregulation of several pro-inflammatory proteins (IL-6, IL-10, IL-16, IP-10, MCP-1, MCP-2, M-CSF, MIP-1a, MIP-1b, TNFb, sTNF-RI, sTNF-RII, TIMP-2) implicated in cellular aging and immune responses. The least potent impact on the induction of SASP was provoked by LPS and the most pronounced by GCF.

CONCLUSION

This study demonstrates that long-term exposure of hGFs to various pro-inflammatory signals induced or accelerated cellular senescence with the most pronounced impact noted for the late-passage cells. The outcome of these analyses provides insights into oral chronic inflammation as a potential confounder of age-related diseases.

Characterization of the soft-tissue wall lining residual periodontal pockets and implications in periodontal wound healing

AIM

To characterize the soft-tissue wall of remaining periodontal pockets for wound healing-related parameters versus healthy gingival crevices in the same individuals.

MATERIALS AND METHODS

Gingival tissues collected from the diseased interface of pockets (GT biopsies) and from healthy gingival crevices (G biopsies) were subjected to RT2-profiler PCR Array for wound healing-related markers and network analysis of differentially expressed genes. Lymphangiogenesis-related gene expression was determined by qRT-PCR. The migration potential of mesenchymal stem cells isolated from GT biopsies (GT-MSCs) and G biopsies (G-MSCs) was evaluated by the scratch- and the transwell migration assays. The total collagen protein content was determined in GT-MSCs and G-MSCs homogenates.

RESULTS

Gene-ontology analysis on significantly upregulated genes expressed in GT biopsies revealed enrichment of several genes involved in processes related to matrix remodeling, collagen deposition, and integrin signaling. No significantly expressed genes were seen in G biopsies. Regarding lymphangiogenesis-related genes, GT biopsies demonstrated greater expression for PROX1 than G biopsies (p = 0.05). Lower migration potential (p < 0.001), yet greater production of collagen protein (p = 0.05), was found for GT-MSCs over G-MSCs.

CONCLUSION

Differential expression patterns of various molecular pathways in biopsies and cell cultures of diseased versus healthy gingival tissues indicate a potential of the former for tissue remodeling and repair.

CLINICAL RELEVANCE

In the course of periodontitis, granulation tissue is formed within a periodontal defect in an attempt to reconstruct the site. Following treatment procedures periodontal granulation tissue remains inflamed but appears to retain healing potential.

Kappa-Carrageenan/Chitosan/Gelatin Scaffolds Provide a Biomimetic Microenvironment for Dentin-Pulp Regeneration

This study aims to investigate the impact of kappa-carrageenan on dental pulp stem cells (DPSCs) behavior in terms of biocompatibility and odontogenic differentiation potential when it is utilized as a component for the production of 3D sponge-like scaffolds. For this purpose, we prepared three types of scaffolds by freeze-drying (i) kappa-carrageenan/chitosan/gelatin enriched with KCl (KCG-KCl) as a physical crosslinker for the sulfate groups of kappa-carrageenan, (ii) kappa-carrageenan/chitosan/gelatin (KCG) and (iii) chitosan/gelatin (CG) scaffolds as a control. The mechanical analysis illustrated a significantly higher elastic modulus of the cell-laden scaffolds compared to the cell-free ones after 14 and 28 days with values ranging from 25 to 40 kPa, showing an increase of 27-36%, with the KCG-KCl scaffolds indicating the highest and CG the lowest values. Cell viability data showed a significant increase from days 3 to 7 and up to day 14 for all scaffold compositions. Significantly increasing alkaline phosphatase (ALP) activity has been observed over time in all three scaffold compositions, while the KCG-KCl scaffolds indicated significantly higher calcium production after 21 and 28 days compared to the CG control. The gene expression analysis of the odontogenic markers DSPP, ALP and RunX2 revealed a two-fold higher upregulation of DSPP in KCG-KCl scaffolds at day 14 compared to the other two compositions. A significant increase of the RunX2 expression between days 7 and 14 was observed for all scaffolds, with a significantly higher increase of at least twelve-fold for the kappa-carrageenan containing scaffolds, which exhibited an earlier ALP gene expression compared to the CG. Our results demonstrate that the integration of kappa-carrageenan in scaffolds significantly enhanced the odontogenic potential of DPSCs and supports dentin-pulp regeneration.

A Cell Culture Method for the Isolation and Study of Primary Human Dental Pulp Cells

Primary human dental pulp cell (HDPC) cultures contain dental pulp stem cell (DPSC) populations. DPSCs are multipotent mesenchymal cells residing inside the dental pulp where they can contribute to the regenerative potential of this and other tissues throughout the body. These cells are promising tools for cell-based therapies, including regenerative endodontic procedures. HDPCs can be readily isolated and expanded from extracted teeth either by the dental tissue explant method or enzymatic digestion method. This chapter describes the explant method, whereby cells outgrow from dissected pulp tissue, to generate HDPC cultures. We also provide protocols for HDPC passaging, cryopreservation, and basic immunocytochemical characterization.

Ruxolitinib inhibits IFNγ-stimulated Sjögren's salivary gland MSC HLA-DR expression and chemokine-dependent T cell migration

OBJECTIVES

Sjögren's disease (SjD) is a systemic autoimmune disease characterized by focal lymphocytic infiltrate of salivary glands (SGs) and high SG IFNγ, both of which are associated with elevated lymphoma risk. IFNγ is also biologically relevant to mesenchymal stromal cells (MSCs), a SG resident cell with unique niche regenerative and immunoregulatory capacities. In contrast to the role of IFNγ in SjD, IFNγ promotes an anti-inflammatory MSC phenotype in other diseases. The objective of this study was to define the immunobiology of IFNγ-exposed SG-MSCs with and without the JAK1 & 2 inhibitor, ruxolitinib.

METHODS

SG-MSCs were isolated from SjD and controls human subjects. SG-MSCs were treated with 10 ng/ml IFNγ +/- 1000 nM ruxolitinib. Experimental methods included flow cytometry, RNA-sequencing, chemokine array, ELISA and transwell chemotaxis experiments.

RESULTS

We found that IFNγ promoted expression of SG-MSC immunomodulatory markers, including HLA-DR, and this expression was inhibited by ruxolitinib. We confirmed the differential expression of CXCL9, CXCL10, CXCL11, CCL2 and CCL7, initially identified with RNA sequencing. SG-MSCs promoted CD4+ T cell chemotaxis when pre-stimulated with IFNγ. Ruxolitinib blocks chemotaxis through inhibition of SG-MSC production of CXCL9, CXCL10 and CXCL11.

CONCLUSIONS

These findings establish that ruxolitinib inhibits IFNγ-induced expression of SG-MSC immunomodulatory markers and chemokines. Ruxolitinib also reverses IFNγ-induced CD4+ T cell chemotaxis, through inhibition of CXCL9, -10 and -11. Because IFNγ is higher in SjD than control SGs, we have identified SG-MSCs as a plausible pathogenic cell type in SjD. We provide proof of concept supporting further study of ruxolitinib to treat SjD.

A critical review of in vitro research methodologies used to study mineralization in human dental pulp cell cultures

Background

The pulp contains a resident population of stem cells which can be stimulated to differentiate in order to repair the tooth by generating a mineralized extracellular matrix. Over recent decades there has been considerable interest in utilizing in vitro cell culture models to study dentinogenesis, with the aim of developing regenerative endodontic procedures, particularly where some vital pulp tissue remains.

Objectives

The purpose of this review is to provide a structured oversight of in vitro research methodologies which have been used to study human pulp mineralization processes.

Method

The literature was screened in the PubMed database up to March 2021 to identify manuscripts reporting the use of human dental pulp cells to study mineralization. The dataset identified 343 publications initially which were further screened and consequently 166 studies were identified and it was methodologically mined for information on: i) study purpose, ii) source and characterization of cells, iii) mineralizing supplements and concentrations, and iv) assays and markers used to characterize mineralization and differentiation, and the data was used to write this narrative review.

Results

Most published studies aimed at characterizing new biological stimulants for mineralization as well as determining the effect of scaffolds and dental (bio)materials. In general, pulp cells were isolated by enzymatic digestion, although the pulp explant technique was also common. For enzymatic digestion, a range of enzymes and concentrations were utilized, although collagenase type I and dispase were the most frequent. Isolated cells were not routinely characterized using either fluorescence‐activated cell sorting (FACS) and magnetic‐activated cell sorting (MACS) approaches and there was little consistency in terming cultures as dental pulp cells or dental pulp stem cells. A combination of media supplements, at a range of concentrations, of dexamethasone, ascorbic acid and beta‐glycerophosphate, were frequently applied as the basis for the experimental conditions. Alizarin Red S (ARS) staining was the method of choice for assessment of mineralization at 21‐days. Alkaline phosphatase assay was relatively frequently applied, solely or in combination with ARS staining. Further assessment of differentiation status was performed using transcript or protein markers, with dentine sialophosphoprotein (DSPP), osteocalcin and dentine matrix protein‐1 (DMP ‐1), the most frequent.

Discussion

While this review highlights variability among experimental approaches, it does however identify a consensus experimental approach.

Conclusion

Standardization of experimental conditions and sustained research will significantly benefit endodontic patient outcomes in the future.

Evaluation of stemness properties of cells derived from granulation tissue of peri-implantitis lesions

OBJECTIVES

Peri-implantitis (PI) is an inflammatory disease associated with peri-implant bone loss and impaired healing potential. There is limited evidence about the presence of mesenchymal stromal cells (MSCs) and their regenerative properties within the granulation tissue (GT) of infrabony peri-implantitis defects. The aim of the present study was to characterize the cells derived from the GT of infrabony PI lesions (peri-implantitis derived mesenchymal stromal cells-PIMSCs).

MATERIAL AND METHODS

PIMSC cultures were established from GT harvested from PI lesions with a pocket probing depth ≥6 mm, bleeding on probing/suppuration, and radiographic evidence of an infrabony component from four systemically healthy individuals. Cultures were analyzed for embryonic (SSEA4, NANOG, SOX2, OCT4A), mesenchymal (CD90, CD73, CD105, CD146, STRO1) and hematopoietic (CD34, CD45) stem cell markers using flow cytometry. PIMSC cultures were induced for neurogenic, angiogenic and osteogenic differentiation by respective media. Cultures were analyzed for morphological changes and mineralization potential (Alizarin Red S method). Gene expression of neurogenic (NEFL, NCAM1, TUBB3, ENO2), angiogenic (VEGFR1, VEGFR2, PECAM1) and osteogenic (ALPL, BGLAP, BMP2, RUNX2) markers was determined by quantitative RT-PCR.

RESULTS

PIMSC cultures demonstrated high expression of embryonic and mesenchymal stem cell markers with inter-individual variability. After exposure to neurogenic, angiogenic and osteogenic conditions, PIMSCs showed pronounced tri-lineage differentiation potential, as evidenced by their morphology and expression of respective markers. High mineralization potential was observed.

CONCLUSIONS

This study provides evidence that MSC-like populations reside within the GT of PI lesions and exhibit a multilineage differentiation potential. Further studies are needed to specify the biological role of these cells in the healing processes of inflamed PI tissues and to provide indications for their potential use in regenerative therapies.

Comparison of stem cells from human exfoliated deciduous posterior teeth with varying levels of root resorption

Background

Stem cells from human exfoliated deciduous teeth (SHED) are regarded as an attractive cell source for tissue regeneration. However, the effect of different levels of root resorption on the characteristics of SHED remains less understood. Thus, the tooth source that is most suitable for the isolation of SHEDs needs to be determined. To compare cellular and biological characteristics of stem cells from human exfoliated deciduous posterior teeth with varying levels of root resorption.

Methods

The pulp was obtained from the deciduous posterior teeth depending on the level of root resorption, and isolated SHEDs were grouped as follows: Teeth with 0 to 1/3^rd root resorption as SHEDs (G1) and 1/3^rd to 2/3^rd root resorption as SHEDs (G2). Teeth were also collected from >2/3^rd root resorption status, but failed to establish primary culture of SHED as the availability of pulp tissue was too less. Later, isolated SHEDs were compared on their morphology, viability, growth kinetics, colony-forming ability, expression of cell surface markers and in vitro differentiation into osteocytes and adipocytes.

Results

No major differences were observed in terms of cellular morphology, viability, proliferation rate, colony-forming ability, cell surface markers expression, and mesenchymal lineage differentiation of SHEDs isolated from posterior teeth with 0 to 1/3^rd and 1/3^rd to 2/3^rd root resorption. However, SHED from teeth with 0 to 1/3^rd root resorption (G1) displayed relatively higher proliferation capacity and expression of selected markers.

Conclusions

Collectively, SHEDs (G1) and SHEDs (G2) showed comparable cellular and biological characteristics that enable their possible applications in regenerative therapies.

Sinking Our Teeth in Getting Dental Stem Cells to Clinics for Bone Regeneration

Dental stem cells have been isolated from the medical waste of various dental tissues. They have been characterized by numerous markers, which are evaluated herein and differentiated into multiple cell types. They can also be used to generate cell lines and iPSCs for long-term in vitro research. Methods for utilizing these stem cells including cellular systems such as organoids or cell sheets, cell-free systems such as exosomes, and scaffold-based approaches with and without drug release concepts are reported in this review and presented with new pictures for clarification. These in vitro applications can be deployed in disease modeling and subsequent pharmaceutical research and also pave the way for tissue regeneration. The main focus herein is on the potential of dental stem cells for hard tissue regeneration, especially bone, by evaluating their potential for osteogenesis and angiogenesis, and the regulation of these two processes by growth factors and environmental stimulators. Current in vitro and in vivo publications show numerous benefits of using dental stem cells for research purposes and hard tissue regeneration. However, only a few clinical trials currently exist. The goal of this review is to pinpoint this imbalance and encourage scientists to pick up this research and proceed one step further to translation.

Minor salivary gland mesenchymal stromal cells derived from patients with Sjӧgren's syndrome deploy intact immune plasticity

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) provide minor salivary glands (MSGs) with support and niche cells for epithelial glandular tissue. Little is known about resident MSG-derived MSCs (MSG-MSCs) in primary Sjӧgren's syndrome (PSS). The authors' objective is to define the immunobiology of endogenous PSS MSG-MSCs.

METHODS

Using culture-adapted MSG-MSCs isolated from consenting PSS subjects (n = 13), the authors performed in vitro interrogation of PSS MSG-MSC immunobiology and global gene expression compared with controls. To this end, the authors performed phenotypic and immune functional analysis of indoleamine 2,3-dioxygenase (IDO), programmed death ligand 1 (PD-L1) and intercellular adhesion marker 1 (ICAM-1) before and after interferon γ (IFNγ) licensing as well as the effect of MSG-MSCs on T-cell proliferation. Considering the female predominance of PSS, the authors also addressed the influence of 17-β-estradiol on estrogen receptor α-positive-related MSC function.

RESULTS

The authors found that MSG-MSCs deployed normal immune regulatory functionality after IFNγ stimulation, as demonstrated by increased protein-level expression of IDO, PD-L1 and ICAM-1. The authors also found that MSG-MSCs suppressed T-cell proliferation in a dose-dependent manner independent of 17-β-estradiol exposure. Gene ontology and pathway analysis highlighted extracellular matrix deposition as a possible difference between PSS and control MSG-MSCs. MSG-MSCs demonstrated increased α-smooth muscle actin expression in PSS, indicating a partial myofibroblast-like adaptation.

CONCLUSIONS

These findings establish similar immune regulatory function of MSG-MSCs in both PSS and control patients, precluding intrinsic MSC immune regulatory defects in PSS. PSS MSG-MSCs show a partial imprinted myofibroblast-like phenotype that may arise in the setting of chronic inflammation, providing a plausible etiology for PSS-related glandular fibrosis.

Geometrical Structure of Honeycomb TCP to Control Dental Pulp-Derived Cell Differentiation

Recently, dental pulp has been attracting attention as a promising source of multipotent mesenchymal stem cells (MSCs) for various clinical applications of regeneration fields. To date, we have succeeded in establishing rat dental pulp-derived cells showing the characteristics of odontoblasts under in vitro conditions. We named them Tooth matrix-forming, GFP rat-derived Cells (TGC). However, though TGC form massive dentin-like hard tissues under in vivo conditions, this does not lead to the induction of polar odontoblasts. Focusing on the importance of the geometrical structure of an artificial biomaterial to induce cell differentiation and hard tissue formation, we previously have succeeded in developing a new biomaterial, honeycomb tricalcium phosphate (TCP) scaffold with through-holes of various diameters. In this study, to induce polar odontoblasts, TGC were induced to form odontoblasts using honeycomb TCP that had various hole diameters (75, 300, and 500 μm) as a scaffold. The results showed that honeycomb TCP with 300-μm hole diameters (300TCP) differentiated TGC into polar odontoblasts that were DSP positive. Therefore, our study indicates that 300TCP is an appropriate artificial biomaterial for dentin regeneration.

Immunocytochemical characterization of primary teeth pulp stem cells from three stages of resorption in serum-free medium

BACKGROUND/AIMS

Dental pulp stem cells from primary teeth cultured in serum-free conditions may have clinical use for the repair and regeneration of teeth as well as other complex tissues and organs. The aim of this study was to test the change in the stem cell markers expression/ stem cell population in human primary pulp cells at the different stages of root resorption.

METHODS

Caries-free human primary canines at defined stages of physiological root resorption were included (n = 9). In vitro cultures were established in xeno-free, serum-free Essential 8™ medium with human truncated vitronectin for cell attachment. An embryonic stem cell line (GENEA002) was used as a positive control. The expression of embryonic stem cell markers (Oct4, Nanog and Sox2), neural crest stem cell markers (nestin and Dlx2) and mesenchymal stem cell surface markers (CD90, CD73 and CD105) were investigated by immunocytochemistry. Mesenchymal stem cell markers CD105, CD73 and CD90 and haematopoietic markers: CD45, CD34, CD11b, CD19 and HLA-DR were quantified with flow cytometry.

RESULTS

The early neural progenitor markers nestin and Dlx2 were detected in most serum-free cultured dental pulp stem cells, regardless of the tooth resorption stage from which they were harvested. Only isolated cells were found that expressed the embryonic stem cell transcription factors Oct4A, Nanog and Sox2, and in the late stages of resorption, no Oct4A was detected. The majority expressed the mesenchymal stem cell markers CD90, CD73 and CD105. Flow cytometry found positive signals for CD90 > 97.3%, CD73 > 99.6% and CD105 > 82.5%, with no detectable differences between resorption stages.

CONCLUSIONS

This study identified populations of dental pulp cells in vitro with markers characteristically associated with embryonic stem cells, neural crest-derived cells and mesenchymal stem cells. Flow cytometry found CD105 expressed at lower levels than CD90 and CD73. The consistency of stem cell marker expression in cells cultured from teeth at different resorption stages suggests that pre-exfoliated primary teeth that are free of caries may provide a convenient source of multipotent stem cells for use in regenerative medicine.

Dental Pulp Stem Cells in Neuroregeneration

Neurological diseases and injuries affect the routine life of patients. Current medical and surgical treatment has not improved the quality of life to desired limits. Neural regeneration through stem cells may be ideal choice in current scenario. Dental pulp stem cells (DPSCs), which are isolated from dental pulp, have shown excellent neuroregenerative properties in various animal studies. This review outlines the clinical perspective of DPSCs in neuroregeneration.

A compound of concentrated growth factor and periodontal ligament stem cell-derived conditioned medium

The aim of this study was to determine the in vitro effect of a compound of concentrated growth factor (CGF) and periodontal ligament stem cell-derived conditioned medium (PDLSCs-CM) as a potential product for future applications in periodontal tissue regeneration. Isolated PDLSCs were characterized using flow cytometry and differentiation into osteoblasts and adipocytes cells. PDLSCs-CM and CGF were prepared and lyophilized. To determine the optimal concentration of the CGF-CM compound, the proliferation of PDLSCs after exposure to a wide range of different concentrations of CGF, CM, or their combination (CGF + CM) was investigated by methyl thiazol tetrazolium assay. Successful isolation of PDLSCs was confirmed by high expression of mesenchymal surface markers and differentiation into osteoblasts and adipocytes. PDLSCs showed higher proliferation in the 6.25 mg/mL concentration of CM and 94 μg/mL concentration of CGF. High concentrations of CGF and CM markedly inhibited the proliferation of PDLCs (p < 0.05). The exposure of PDLSCs to the compound of 10% CM + 90% CGF significantly increased the cell proliferation (p < 0.05). The results showed that CGF, CM, or their combination exert a proliferative effect on cells at a certain concentration. Further investigation on the synergistic effect of this compound may approve its application for periodontal regeneration.

Effects of radiopaque double antibiotic pastes on the proliferation, alkaline phosphatase activity and mineral deposition of dental pulp stem cells

OBJECTIVE

The aim of this study was to investigate the effects of two radiopaque agents, barium sulfate (BaSO₄) or zirconium oxide (ZrO₂) in double antibiotic paste (DAP), on the proliferation and mineral deposition of human dental pulp stem cells (DPSC).

MATERIALS AND METHODS

Radiopaque antimicrobial medicaments composed of methylcellulose (MC) thickening polymer with BaSO₄ or ZrO₂ and either 1 or 5 mg/mL DAP (equal portions of metronidazole and ciprofloxacin) were used to investigate DPSC proliferation after 3 days, and alkaline phosphatase (ALP) activity and mineral deposition after 7 and 14 days. Radiopaque agents without DAP and Ca(OH)₂ were used as controls.

RESULTS

MC-BaSO₄ DAP and MC-ZrO₂ DAP at 1 or 5 mg/mL had no adverse effect on DPSC proliferation, compared to the media and MC controls. MC-ZrO₂ (DAP-free) greatly increased ALP activity after 7 days. DPSC mineral deposition was modestly reduced at 7 days by MC-BaSO₄ DAP and MC-ZrO₂ DAP, but not by DAP-free radiopaque agents, and was most reduced by 5 mg/mL DAP in the 14-day cultures.

CONCLUSIONS

MC-BaSO₄ or MC-ZrO₂ medicaments containing up to 5 mg/mL of DAP supported the proliferation and early osteogenic differentiation of DPSC. Low DAP concentrations and short culture times led to more favorable effects on ALP activity and mineral deposition by DPSC. The findings suggest that radiopaque agents added for the purpose of detecting whether medicaments occupy the full extent of the root canal may have clinical applications. Radiopaque antibiotic medicaments containing low DAP concentrations may be an alternative to Ca(OH)₂ for regenerative endodontic procedures.

Osteogenic and odontogenic differentiation potential of dental pulp stem cells isolated from inflamed dental pulp tissues (I-DPSCs) by two different methods

Objective: The objective of the present study is to isolate stem cells from inflamed dental pulp tissues (I-DPSCs) and study the characteristic such as surface markers, osteo/odontogenic differentiation potential between the outgrowth (OG) and enzymatic digestion (COL) methods.Materials and methods: I-DPSCs harvested by both methods were analysed for Mesenchymal Stem Cell marker expression by flow cytometry. The metabolic activity of the isolated cells was assessed by MTT assay. The Alkaline Phosphatase (ALP) and Alizarin red staining was done to analyse the osteogenic potential of isolated cells. The osteo/odontogenic differentiation was done by checking the expression of Dentine Matrix Protein 1 (DMP1), Dentine Sialophosphoprotein (DSPP), ALP and Bone Gamma-Carboxyglutamate Protein (BGLAP) by Real time PCR.Results: The isolated cells were positive for MSC markers such as CD-90, CD-105 and CD-73 and negative for CD-14, CD-45 and STRO-1. MTT assay indicated that the I-DPSCs from OG method showed higher metabolic activity than cells from COL. However, the osteo/odontogenic differentiation was in favour of cells isolated by COL method.Conclusion: Although the cell metabolic rate was more in OG, the osteo/odontogenic differentiation was higher in COL, suggesting that the isolation method and culture conditions do affect the differentiation capacity of isolated cells.

Dental mesenchymal stem cells and neuro-regeneration: a focus on spinal cord injury

Regenerative medicine is a branch of translational research that aims to reestablish irreparably damaged tissues and organs by stimulating the body's own repair mechanisms via the implantation of stem cells differentiated into specialized cell types. A rich source of adult stem cells is located inside the tooth and is represented by human dental pulp stem cells, or hDPSCs. These cells are characterized by a high proliferative rate, have self-renewal and multi-lineage differentiation properties and are often used for tissue engineering and regenerative medicine. The present review will provide an overview of hDPSCs and related features with a special focus on their potential applications in regenerative medicine of the nervous system, such as, for example, after spinal cord injury. Recent advances in the identification and characterization of dental stem cells and in dental tissue engineering strategies suggest that bioengineering approaches may successfully be used to regenerate districts of the central nervous system, previously considered irreparable.

Evaluation of the biological behaviour of various dental implant abutment materials on attachment and viability of human gingival fibroblasts

OBJECTIVE

This study aimed to investigate the biological effects of yttria-stabilized zirconia (Y-TZP) compared to other dental implant abutment materials, i.e. lithium disilicate (LS2) and titanium alloy (Ti), as well as the effects of aging of Y-TZP on viability/proliferation and attachment properties of Human Gingival Fibroblasts (HGFs).

METHODS

Cylindrical specimens of each material were prepared as per manufacturer's instructions. Y-TZP specimens were divided into three groups: 1. no aging (Zr0), 2. aging for 5 h, 134 °C, 2 bars, 100% humidity (Zr5), 3. aging for 10 h under the same conditions (Zr10). Surface roughness was evaluated by optical profilometry; cell metabolic activity/viability by MTT assay, morphological changes by Scanning Electron Microscopy (SEM) and ratio of live/dead cells by confocal microscopy.

RESULTS

Results showed statistically significant reduction of HGF metabolic activity/viability in contact with Y-TZP after aging. Nevertheless, non-aged zirconia showed no significant differences compared with LS2, Ti and control cultures. In contrast, significant stimulation of cell metabolic activity/viability was observed in HGFs exposed to LS2 eluates. Differential morphological patterns were observed for HGF in contact with different materials/treatments, with obviously increased number of dead cells and sparser distribution of HGFs cultured on Zr10 specimens. These effects were not correlated with surface topography, since Y-TZP aging did not alter surface micro-roughness.

SIGNIFICANCE

These findings indicate that Y-TZP shows comparable biological properties to Ti and LS2 as implant abutment material. Nevertheless, Y-TZP aging might influence gingival cell attachment and proliferation properties, providing an alert to a potentially negative effect on the long-term maintenance of gingival architecture.

Long term explant culture for harvesting homogeneous population of human dental pulp stem cells

Dental pulp stem cells have emerged as a preferred source of mesenchymal stem cells, because of its easy availability and high stem cell content. Dental pulp is a specific fibrous tissue that contains heterogeneous populations of odontoblasts, fibroblasts, pericytes, progenitors, stem cells, leukocytes and neuronal cells. In this study, we propose sustained explant culture as a simple, economical and efficient process to isolate dental pulp stem cells from human Dental pulp Tissue. Historically explant cultures were used to get fibroblast cells from embryonic chick heart using plasma clot cultures. The subculture was performed by lifting mother explant (original explant) and grafting it in a new plasma clot. We modified this age old technique to suit the modern times. Here we demonstrate for the first time that the mother explant (E0) of human dental pulp tissue could be sub-cultured consecutively seven times (E7) without displacement. This technique is highly reproducible and permits growth and proliferation of dental pulp stem cells yielding an enriched homogeneous mesenchymal stem cells population in the first passage itself as revealed by surface marker expression. These dental pulp stem cells exhibit differentiation into adipogenic, chondrogenic and osteogenic lineage revealing their mesenchymal stem cell nature. We propose that dental pulp stem cells isolated by sustained explant culture are phenotypically and functionally comparable to those obtained by enzymatic method. It is a simple, inexpensive and gentle method, which may be preferred over the conventional techniques for obtaining stem cells from other tissue sources as well especially in cases of limited starting material.

N-acetyl-L-cysteine protects dental tissue stem cells against oxidative stress in vitro

OBJECTIVES

The aim of our study was to investigate whether N-acetyl-L-cysteine (NAC) could protect stem cells from exfoliated deciduous teeth (SHED) against oxidative damage, during in vitro cultivation, to preserve regenerative potential of these cells. Accordingly, we examined the potential of cell culture supplementation with NAC in prevention of lipid peroxidation, unfavorable changes of total lipids fatty acid composition, and the effects on the activity of antioxidant enzymes.

MATERIAL AND METHODS

We analyzed the extent of oxidative damage in SHED after 48 h treatment with different NAC concentrations. Cellular lipid peroxidation was determined upon reaction with thiobarbituric acid. All enzyme activities were measured spectrophotometrically, based on published methods. Fatty acid methyl esters were analyzed by gas-liquid chromatography.

RESULTS

Concentration of 0.1 mM NAC showed the most profound effects on SHED, significantly decreasing levels of lipid peroxidation in comparison to control. This dose also diminished the activities of antioxidant enzymes. Furthermore, NAC treatment significantly changed fatty acid composition of cells, reducing levels of oleic acid and monounsaturated fatty acids and increasing linoleic acid, n-6, and total polyunsaturated fatty acid (PUFA) proportions.

CONCLUSION

Low dose of NAC significantly decreased lipid peroxidation and altered fatty acid composition towards increasing PUFA. The reduced oxidative damage of cellular lipids could be strongly related to improved SHED survival in vitro.

CLINICAL RELEVANCE

Low doses of antioxidants, applied during stem cells culturing and maintenance, could improve cellular characteristics in vitro. This is prerequisite for successful use of stem cells in various clinical applications.

Biological interactions of a calcium silicate based cement (Biodentine™) with Stem Cells from Human Exfoliated Deciduous teeth

OBJECTIVE

To investigate the biological interactions of a calcium silicate based cement (Biodentine™) with Stem Cells from Human Exfoliated Deciduous teeth (SHED), focusing on viability/proliferation, odontogenic differentiation, biomineralization and elemental release/exchange.

METHODS

Biodentine™ specimens were used directly or for eluate preparation at serial dilutions (1:1-1:64). SHED cultures were established from deciduous teeth of healthy children. Viability/proliferation and morphological characteristics were evaluated by live/dead fluorescent staining, MTT assay and Scanning Electron Microscopy. Odontogenic differentiation by qRT-PCR, biomineralization by Alizarin red S staining, while ion elution by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES).

RESULTS

SHED effectively attached within the crystalline surface of Biodentine™ specimens acquiring a spindle-shaped phenotype. Statistically significant stimulation of cell proliferation was induced at day 3 by eluates in dilutions from 1:16 to 1:64. Differential, concentration- and time-dependent expression patterns of odontogenic genes were observed under non-inductive and inductive (osteogenic) conditions, with significant up-regulation of DSPP and Runx2 at higher dilutions and a peak in expression of BMP-2, BGLAP and MSX-2 at 1:8 dilution on day 7. Progressive increase in mineralized tissue formation was observed with increasing dilutions of Biodentine™ eluates. ICP-OES indicated that Biodentine™ absorbed Ca, Mg and P ions from culture medium, while releasing Si and Sr ions from its backbone.

SIGNIFICANCE

Biodentine™ interacts through elemental release/uptake with the cellular microenvironment, triggering odontogenic differentiation and biomineralization in a concentration-dependent manner. These results reveal a promising strategy for application of the calcium silicate based cement (Biodentine™) for vital pulp therapies of deciduous teeth in Paediatric Dentistry.

Evaluation of immunophenotyping, proliferation and osteogenic differentiation potential of SSEA-4 positive stem cells derived from pulp of deciduous teeth

OBJECTIVES

Despite the increased interest in stem cells isolated from remnant pulp of deciduous teeth, no specific marker has been yet established for them. The present study aimed to investigate whether SSEA-4 (stage-specific embryonic antigen) would be a suitable marker to isolate stem cells from Human Exfoliated Deciduous teeth (SHEDs) in order to increase its differentiation potential toward osseous tissue.

DESIGN

The SHEDs were isolated and the expression patterns of mesenchymal, hematopoietic and embryonic stem cell markers were assessed. The cells were then divided into two groups of SSEA-4(+) and unsorted SHEDs and the cell proliferation rate and population-doubling-time (PDT) were calculated. Subsequently, the differentiation potentials were examined through alizarin-red staining and Quantitative real time-PCR (qRT-PCR).

RESULTS

Isolated cells were spindle-shaped with a high expression of mesenchymal stem cell markers and weak expression of hematopoietic markers. The mean expression of Oct-4 was 68.77%±1.28. Despite similar proliferation rates between SSEA-4(+) and unsorted SHEDs, because of differences in the shape of the growth curves, PDT was lower in unsorted SHEDs (P = 0.2 × 10^-4). Alizarin-red staining showed similar calcium deposition in both groups. Upon differentiation, the expression of osteocalcin was higher in unsorted SHEDs (P = 0.043), while, the expression of alkaline phosphatase was lower (P<0.001). The parathyroid hormone receptor (PTHR) expression was not significantly different (P = 0.0625).

CONCLUSIONS

The results of the present study revealed that SHEDs have high differentiation potentials even in the unsorted cells. Although the SSEA-4-positive SHEDs showed slightly better osteogenic potential, the differences were not abundant to link SSEA-4 expression with superior differentiation potency.

Erythropoietin (rhEPOa) promotes endothelial transdifferentiation of stem cells of the apical papilla (SCAP)

OBJECTIVE

Mesenchymal stem cells (MSCs) have attracted worldwide attention for their capacity to repair damaged tissue, immunosuppression, ability to differentiate into several cell types and their secretome. Earlier studies have demonstrated their angiogenic potential in vitro and in vivo. However, little is known regarding pro-angiogenic inducers of stable endothelial transdifferentiation of MSCs. Here, we employed human MSCs from the Apical Papilla (SCAP) and investigated whether recombinant human erythropoietin-alpha (rhEPOa) could act as such inducer.

DESIGN

Cultured SCAP cells were exposed to rhEPOa and assessed for cell growth kinetics, viability and morphology, as well as their capacity to form capillary tubule structures in selected microenvironments. RT-PCR was used to monitor endothelial markers and activation of EPO/EPOR pathway signaling components; while gelatin zymographies to assess activation of MMP-2.

RESULTS

rhEPOa treatment initially (48 h) accelerated cell proliferation and allowed SCAP to sprout micro-tubular structures. Morphological and biochemical differentiation was accompanied by activation of MMP-2 and upregulation of PECAM-1, VEGFR2, vWF and VE-cadherin/CDH5. SCAP expressed the cognate EPO-R, while rhEPOa-treated SCAP exhibited higher expression of molecules involved in EPO/EPOR pathway (EPOR and JAK2).

CONCLUSION

rhEPOa is capable of promoting endothelial transdifferentiation of SCAP which may be of clinical value in treating of ischemic disorders.

Comparison of two digestion strategies on characteristics and differentiation potential of human dental pulp stem cells

OBJECTIVE

This study aimed to compare the behavior of dental pulp stem cells (DPSCs) after isolation using solutions containing either collagenase/dispase or collagenase alone.

DESIGN

DPSCs were isolated by two digestion methods (collagenase/dispase or collagenase alone) from human third molars. Immunophenotypic features were confirmed by flow cytometry for cell markers STRO-1, cluster of differentiation (CD) 146, CD45, and collagen type-I. The proliferation potential of cells was evaluated by 5-bromo-2'-deoxyuridine (brdU) incorporation assay, and finally they were assessed for multi-lineage differentiation potential. Data were analyzed using one-way analysis of variance and independent t-tests.

RESULTS

DPSCs isolated by either method showed similar levels of STRO-1, CD45, and collagen type-I and similar incorporation of brdU (P > 0.05). However, DPSCs obtained by collagenase I/dispase treatment had significantly higher numbers of CD146⁺ cells and osteogenic and chondrogenic capacities compared to those obtained by treatment with collagenase I alone (P < 0.05). On the other hand, more STRO-1+/CD164-DPSCs were found in the collagenase alone group with higher adipogenic potential.

CONCLUSIONS

Different enzyme solutions gave rise to different populations of DPSCs. Dispase enhanced isolation of CD146⁺ DPSCs probably by disrupting the basement membranes of blood vessels and releasing DPCSs embedded in the perivascular niche. Furthermore, the differentiation potential of DPSCs was influenced by the change in enzyme solution.

Comparative characterization of SHED and DPSCs during extended cultivation in vitro

Dental pulp stem cells (DPSCs) and stem cells from human exfoliated deciduous teeth (SHED) are types of human dental tissue-derived mesenchymal stem cells (MSCs). These cells possess a capacity for self-renewal, multilineage differentiation potential and immunomodulatory functions. Previous studies have reported that DPSCs and SHED may be beneficial in regenerative treatments and immunotherapy. The substantial expansion of cells in vitro is a prerequisite to obtaining adequate cell numbers required for cell-based therapy. However, the regeneration and clinical potential of MSCs diminishes with long-term cell culture amplification. To assess the alterations in SHED and DPSCs characteristics that underlie cellular senescence and result from extended in vitro amplification, the biological properties of SHED and DPSCs at passages 4 (P4) and 20 (P20) were compared. The cells underwent senescence following serial expansion to P20, as determined by altered cell morphology, decreased proliferation and migration capacity, attenuated differentiation potential, elevated senescence-associated β-galactosidase (SA-β-gal)-positive rates and increased apoptosis. The phenotypic changes were also accompanied by a marked increase in the expression of p53, p21 and p16^Ink4a. The present study also identified that senescent DPSCs exhibited an increased number of positive cells in SA-β-gal staining and demonstrated varying expressions of p53, p21 and p16^Ink4a in comparison with SHED, indicating the involvement of diverse pathways in cellular senescence during long-term sequential in vitro culture and passage. Furthermore, at early and late passages, SHED exhibited a higher proliferation rate and osteogenic differentiation capability when compared with DPSCs. In addition, both cell types maintained their characteristic immunophenotype during long-term cultivation, while the expression levels of CD73 were higher in SHED at P20. The present study concluded that notable alterations were exhibited in SHED and DPSCs during the process of extensive expansion in vitro and the results may provide guidance for the selection of safe and effective expanded SHED and DPSCs for regenerative medicine and therapy.

Dental Stem Cells in Bone Tissue Engineering: Current Overview and Challenges

The treatment of bone that is impaired due to disease, trauma or tumor resection creates a challenge for both clinicians and researchers. Critical size bone defects are conventionally treated with autografts which are associated with risks such as donor site morbidity and limitations like donor shortage. Bone tissue engineering has become a promising area for the management of critical size bone defects by the employment of biocompatible materials and the discovery of novel stem cell sources. Mesenchymal stem cells (MSCs) can be isolated with ease from various dental tissues including dental pulp stem cells, stem cells from apical papilla, dental follicle stem cells, stem cells from human exfoliated deciduous teeth, periodontal ligament stem cells, gingival stem cells and tooth germ derived stem cells. Outcomes of dental MSC mediated bone tissue engineering is explored in various in vivo and in vitro preclinical studies. However, there are still obscurities regarding the mechanisms underlying in MSC mediated bone regeneration and challenges in applications of dental stem cells. In this review, we summarized dental stem cell sources and their characterizations, along with currently used biomaterials for cell delivery and future perspectives for dental MSCs in the field of bone tissue engineering. Further efforts are necessary before moving to clinical trials for future applications.

Isolation and prolonged expansion of oral mesenchymal stem cells under clinical-grade, GMP-compliant conditions differentially affects "stemness" properties

Background

Development of clinical-grade cell preparations is central to meeting the regulatory requirements for cellular therapies under good manufacturing practice-compliant (cGMP) conditions. Since addition of animal serum in culture media may compromise safe and efficient expansion of mesenchymal stem cells (MSCs) for clinical use, this study aimed to investigate the potential of two serum/xeno-free, cGMP culture systems to maintain long-term “stemness” of oral MSCs (dental pulp stem cells (DPSCs) and alveolar bone marrow MSCs (aBMMSCs)), compared to conventional serum-based expansion.

Methods

DPSC and aBMMSC cultures (n = 6/cell type) were established from pulp and alveolar osseous biopsies respectively. Three culture systems were used: StemPro_MSC/SFM_XenoFree (Life Technologies); StemMacs_MSC/XF (Miltenyi Biotek); and α-MEM (Life Technologies) with 15% fetal bovine serum. Growth (population doublings (PDs)), immunophenotypic (flow cytometric analysis of MSC markers) and senescence (β-galactosidase (SA-β-gal) activity; telomere length) characteristics were determined during prolonged expansion. Gene expression patterns of osteogenic (ALP, BMP-2), adipogenic (LPL, PPAR-γ) and chondrogenic (ACAN, SOX-9) markers and maintenance of multilineage differentiation potential were determined by real-time PCR.

Results

Similar isolation efficiency and stable growth dynamics up to passage 10 were observed for DPSCs under all expansion conditions. aBMMSCs showed lower cumulative PDs compared to DPSCs, and when StemMacs was used substantial delays in cell proliferation were noted after passages 6–7. Serum/xeno-free expansion produced cultures with homogeneous spindle-shaped phenotypes, while serum-based expansion preserved differential heterogeneous characteristics of each MSC population. Prolonged expansion of both MSC types but in particular the serum/xeno-free-expanded aBMMSCs was associated with downregulation of CD146, CD105, Stro-1, SSEA-1 and SSEA-4, but not CD90, CD73 and CD49f, in parallel with an increase of SA-gal-positive cells, cell size and granularity and a decrease in telomere length. Expansion under both serum-free systems resulted in “osteogenic pre-disposition”, evidenced by upregulation of osteogenic markers and elimination of chondrogenic and adipogenic markers, while serum-based expansion produced only minor changes. DPSCs retained a diminishing (CCM, StemPro) or increasing (StemMacs) mineralization potential with passaging, while aBMMSCs lost this potential after passages 6–7 under all expansion conditions.

Conclusions

These findings indicate there is still a vacant role for development of qualified protocols for clinical-grade expansion of oral MSCs; a key milestone achievement for translation of research from the bench to clinics.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0705-0) contains supplementary material, which is available to authorized users.

Comparison of in vitro properties of periodontal ligament stem cells derived from permanent and deciduous teeth

Background. Stem cells have contributed to the development of tissue-engineered-based regenerative periodontal therapies. In order to find the best stem cell sources for such therapies, the biologic properties of stem cells isolated from periodontal ligaments (PDL) of deciduous (DePDLSC) and permanent (PePDLSC) teeth were comparatively evaluated. Methods. PDL stem cells were isolated from six sound fully erupted premolars and six deciduous canines of healthy subjects. In vitro biologic characteristics such as colony formation, viability, stem cell marker identification and osteogenic differentiation (using alkaline phosphatase analysis and Alizarin red staining) were comparatively assessed using one-way ANOVA and post hoc Tukey tests using SPSS 13.0. Results. Stem cell populations isolated from both groups were CD105+ and CD90+ and CD45‒. No statistically significant differences were found in stem cell markers, colony formation and viability. Both groups were capable of osteogenic differentiation. However, alkaline phosphatase activity test showed a statistically significant difference, with PePDLSC exhibiting higher alkaline phosphatase activity (P=0.000). No statistically significant difference was seen in quantitative alizarine red staining (P=0.559). Conclusion. Mesenchymal stem cells of PDL could successfully be isolated from permanent and deciduous teeth. A minor difference was observed in the osteogenic properties of the two cell types, which might affect their future clinical applications.

Human dental pulp stem cells transplantation combined with treadmill training in rats after traumatic spinal cord injury

Spinal cord injury (SCI) is a disabling condition resulting in deficits of sensory and motor functions, and has no effective treatment. Considering that protocols with stem cell transplantation and treadmill training have shown promising results, the present study evaluated the effectiveness of stem cells from human exfoliated deciduous teeth (SHEDs) transplantation combined with treadmill training in rats with experimental spinal cord injury. Fifty-four Wistar rats were spinalized using NYU impactor. The rats were randomly distributed into 5 groups: Sham (laminectomy with no SCI, n=10); SCI (laminectomy followed by SCI, n=12); SHEDs (SCI treated with SHEDs, n=11); TT (SCI treated with treadmill training, n=11); SHEDs+TT (SCI treated with SHEDs and treadmill training; n=10). Treatment with SHEDs alone or in combination with treadmill training promoted functional recovery, reaching scores of 15 and 14, respectively, in the BBB scale, being different from the SCI group, which reached 11. SHEDs treatment was able to reduce the cystic cavity area and glial scar, increase neurofilament. Treadmill training alone had no functional effectiveness or tissue effects. In a second experiment, the SHEDs transplantation reduced the TNF-α levels in the cord tissue measured 6 h after the injury. Contrary to our hypothesis, treadmill training either alone or in combination, caused no functional improvement. However, SHEDs showed to be neuroprotective, by the reduction of TNF-α levels, the cystic cavity and the glial scar associated with the improvement of motor function after SCI. These results provide evidence that grafted SHEDs might be an effective therapy to spinal cord lesions, with possible anti-inflammatory action.

Heterogeneous Human Periodontal Ligament-Committed Progenitor and Stem Cell Populations Exhibit a Unique Cementogenic Property Under In Vitro and In Vivo Conditions

An undesirable complication that arises during dental treatments is external apical-root resorption, which causes root-cementum and root-dentin loss. To induce de novo cementogenesis, stem cell therapy is required. Cementum-forming cells (cementoblasts) are known to be differentiated from periodontal-lineage mesenchymal stem cells (MSCs), which are derived from the dental follicle (DF) in developing tissues and the periodontal ligament (PDL) in adult tissues, but the periodontal-lineage MSC type that is optimal for inducing de novo cementogenesis remains unidentified, as does the method to isolate these cells from harvested tissues. Thus, we investigated the cementogenic potential of DF- and PDL-derived MSCs that were isolated by using two widely used cell-isolation methods: enzymatic digestion and outgrowth (OG) methods. DF- and PDL-derived cells isolated by using both methods proliferated actively, and all four isolated cell types showed MSC gene/protein expression phenotype and ability to differentiate into adipogenic and chondrogenic lineages. Furthermore, cementogenic-potential analysis revealed that all cell types produced alizarin red S-positive mineralized materials in in vitro cultures. However, PDL-OG cells presented unique cementogenic features, such as nodular formation of mineralized deposits displaying a cellular intrinsic fiber cementum-like structure, as well as a higher expression of cementoblast-specific genes than in the other cell types. Moreover, in in vivo transplantation experiments, PDL-OG cells formed cellular cementum-like hard tissue containing embedded osteocalcin-positive cells, whereas the other cells formed acellular cementum-like materials. Given that the root-cementum defect is likely regenerated through cellular cementum deposition, PDL-OG cell-based therapies might potentially facilitate the de novo cellular cementogenesis required for regenerating the root defect.

Dental Tissue Engineering Research and Translational Approaches towards Clinical Application

Stem cell-based dental tissue regeneration is a new and exciting field that has the potential to transform the way that we practice dentistry. It is, however, imperative its clinical application is supported by solid basic and translational research. In this way, the full extent of the potential risks involved in the use of these technologies will be understood, and the means to prevent them will be discovered. Therefore, the aim of this chapter is to analyze the state-of-the-science with regard to dental pulp stem cell research in dental tissue engineering, the new developments in biomimetic scaffold materials customized for dental tissue applications, and to give a prospectus with respect to translational approaches of these research findings towards clinical application.

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.”

In vitro characterization of human dental pulp stem cells isolated by three different methods

OBJECTIVES

In this study, we characterized human dental pulp cells (HDPCs) obtained by different culture methods to establish the most suitable methodology for dental tissue engineering and regenerative endodontic applications.

MATERIALS AND METHODS

HDPCs were isolated by the outgrowth method (HDPCs-OG), the enzymatic digestion method (collagenase/dispase/trypsin, HDPCs-ED), or the combination of both methods (HDPCs-Combined). The expression of mesenchymal stem cell markers (CD105, CD90, and CD73) was investigated. In vitro differentiation capacities of HDPCs into adipogenic, osteogenic, and chondrogenic lineages were compared. Differentiation markers were analyzed by quantitative reverse-transcription polymerase chain reaction (RT-PCR) and western blotting.

RESULTS

Our data indicated that whole HDPCs-ED, HPDCs-OG, and HDPCs-Combined could be differentiated into adipogenic, chrondrogenic, and osteogenic cell types. However, we found that the methods for isolating and culturing HDPCs influence the differentiation capacities of cells. HDPCs-OG and HDPCs-ED were preferably differentiated into adipogenic and osteogenic cells, respectively. Differentiation markers shown by RT-PCR and western blotting analysis were mostly upregulated in the treated groups compared with the control groups.

CONCLUSIONS

Our findings confirmed that cell populations formed by two different culture methods and the combined culture method exhibited different properties. The results of this study could provide an insight into regenerative endodontic treatment using HDPCs.

Isolation, characterization and multi-lineage differentiation of stem cells from human exfoliated deciduous teeth

The aim of the present study was to isolate stem cells from human exfoliated deciduous teeth (SHEDs) and identify their phenotypes and multi‑lineage differentiation potential. Three SHED cell strains were successfully isolated from three exfoliated deciduous teeth from different human subjects using the outgrowth method. Flow cytometric analysis indicated that SHEDs displayed high expression of the mesenchymal cell markers CD73 and CD90 but low expression of the hematopoietic stem cell marker CD34. PCR analysis illustrated that SHEDs expressed the mesenchymal stem cell markers CD44, CD73 and CD90, the osteoblast markers Alpl, Runx2, CBFA1 and collagen Ⅰ, the cartilage cell markers Col10a1 and Acan, the adipose cell markers PPARγ2 and LPL, and the neuronal stem cell marker Nestin. In vitro induction experiments demonstrated the potential of the SHEDs for osteogenic, adipogenic and neurogenic differentiation. These SHED cells may be useful for further stem cell research and future therapeutic applications.

Sol-Gel Derived Mg-Based Ceramic Scaffolds Doped with Zinc or Copper Ions: Preliminary Results on Their Synthesis, Characterization, and Biocompatibility

Glass-ceramic scaffolds containing Mg have shown recently the potential to enhance the proliferation, differentiation, and biomineralization of stem cells in vitro, property that makes them promising candidates for dental tissue regeneration. An additional property of a scaffold aimed at dental tissue regeneration is to protect the regeneration process against oral bacteria penetration. In this respect, novel bioactive scaffolds containing Mg(2+) and Cu(2+) or Zn(2+), ions known for their antimicrobial properties, were synthesized by the foam replica technique and tested regarding their bioactive response in SBF, mechanical properties, degradation, and porosity. Finally their ability to support the attachment and long-term proliferation of Dental Pulp Stem Cells (DPSCs) was also evaluated. The results showed that conversely to their bioactive response in SBF solution, Zn-doped scaffolds proved to respond adequately regarding their mechanical strength and to be efficient regarding their biological response, in comparison to Cu-doped scaffolds, which makes them promising candidates for targeted dental stem cell odontogenic differentiation and calcified dental tissue engineering.

Mesenchymal Stem Cells Derived from Dental Pulp: A Review

The mesenchymal stem cells of dental pulp (DPSCs) were isolated and characterized for the first time more than a decade ago as highly clonogenic cells that were able to generate densely calcified colonies. Now, DPSCs are considered to have potential as stem cell source for orthopedic and oral maxillofacial reconstruction, and it has been suggested that they may have applications beyond the scope of the stomatognathic system. To date, most studies have shown that, regardless of their origin in third molars, incisors, or exfoliated deciduous teeth, DPSCs can generate mineralized tissue, an extracellular matrix and structures type dentin, periodontal ligament, and dental pulp, as well as other structures. Different groups worldwide have designed and evaluated new efficient protocols for the isolation, expansion, and maintenance of clinically safe human DPSCs in sufficient numbers for various therapeutics protocols and have discussed the most appropriate route of administration, the possible contraindications to their clinical use, and the parameters to be considered for monitoring their clinical efficacy and proper biological source. At present, DPSC-based therapy is promising but because most of the available evidence was obtained using nonhuman xenotransplants, it is not a mature technology.

Characteristics of stem cells from human exfoliated deciduous teeth (SHED) from intact cryopreserved deciduous teeth

The aim of this study is to compare the characteristics of stem cells derived from human exfoliated deciduous teeth (SHED) from cryopreserved intact deciduous teeth with those of fresh SHED. In total, 20 exfoliated deciduous teeth were randomly divided into a fresh group (f-SHED; n = 11) and cryopreserved group (c-SHED; n = 9; stored for 1-8 months). Following thawing and separation of the pulp, the SHED cells were cultured, and the characteristics as mesenchymal stem cells were investigated using proliferation assays, cell-cycle analysis, colony-forming unit-fibroblast (CFU-F) assays, and flow cytometry analyses. Furthermore, differentiation into adipogenic and osteogenic lineages was investigated in vitro as well as in vivo via transplantation in mice. We found no significant differences between the two groups in the proliferation analyses, in the expression of mesenchymal stem cell markers, or in the adipogenic and osteogenic differentiation in vitro (p < 0.05). Furthermore, the in vivo transplantation results showed no significant differences in the quantity of bone tissue that formed or in histochemistry performance (p < 0.05). In conclusion, cryopreservation of intact exfoliated deciduous teeth appears to be a useful method for preserving SHED.

Comparative Assessment of Oral Mesenchymal Stem Cells Isolated from Healthy and Diseased Tissues

The aim of the present study was to isolate human mesenchymal stem cells (MSCs) from palatal connective and periodontal granulation tissues and to comparatively evaluate their properties. MSCs were isolated using the explant culture method. Adherence to plastic, specific antigen makeup, multipotent differentiation potential, functionality, and ultrastructural characteristics were investigated. The frequency of colony-forming unit fibroblasts for palatal-derived mesenchymal stem cells (pMSCs) was significantly higher than that of granulation tissue-derived mesenchymal stem cells (gtMSCs). A significantly higher population doubling time and lower migration potential were recorded for gtMSCs than for pMSCs. Both cell lines were positive for CD105, CD73, CD90, CD44, and CD49f, and negative for CD34, CD45, and HLA-DR, but the level of expression was different. MSCs from both sources were relatively uniform in their ultrastructure. Generally, both cell lines possessed a large, irregular-shaped euchromatic nucleus, and cytoplasm rich in mitochondria, lysosomes, and endoplasmic reticulum. The periphery of the plasma membrane displayed many small filopodia. MSCs from both cell lines were successfully differentiated into osteogenic, adiopogenic, and chondrogenic lineages. Both healthy and diseased tissues may be considered as valuable sources of MSCs for regenerative medicine owing to the high acceptance and fewer complications during harvesting.

Osteogenic Potential of Dental Mesenchymal Stem Cells in Preclinical Studies: A Systematic Review Using Modified ARRIVE and CONSORT Guidelines

Background and Objective. Dental stem cell-based tissue engineered constructs are emerging as a promising alternative to autologous bone transfer for treating bone defects. The purpose of this review is to systematically assess the preclinical in vivo and in vitro studies which have evaluated the efficacy of dental stem cells on bone regeneration. Methods. A literature search was conducted in Ovid Medline, Embase, PubMed, and Web of Science up to October 2014. Implantation of dental stem cells in animal models for evaluating bone regeneration and/or in vitro studies demonstrating osteogenic potential of dental stem cells were included. The preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines were used to ensure the quality of the search. Modified ARRIVE (Animal research: reporting in invivo experiments) and CONSORT (Consolidated reporting of trials) were used to critically analyze the selected studies. Results. From 1914 citations, 207 full-text articles were screened and 137 studies were included in this review. Because of the heterogeneity observed in the studies selected, meta-analysis was not possible. Conclusion. Both in vivo and in vitro studies indicate the potential use of dental stem cells in bone regeneration. However well-designed randomized animal trials are needed before moving into clinical trials.

Long-Term Fluoride Release from Dental Resins Affects STRO-1+ Cell Behavior

Fluoride-releasing restorative dental materials can be beneficial to remineralize dentin and help prevent secondary caries. However, the effects of fluoride release from dental materials on the activity of dental pulp stem cells are not known. Here we investigate whether different fluoride release kinetics from dental resins supplemented with modified hydrotalcite (RK-F10) or fluoride-glass filler (RK-FG10) could influence the behavior of a human dental pulp stem cell subpopulation (STRO-1(+) cells) known for its ability to differentiate toward an odontoblast-like phenotype. The 2 resins, characterized by similar physicochemical properties and fluoride content, exhibited different long-term fluoride release kinetics. Our data demonstrate that long-term exposure of STRO-1(+) cells to a continuous release of a low amount of fluoride by RK-F10 increases their migratory response to transforming growth factor β1 (TGF-β1) and stromal cell-derived factor 1 (SDF-1), both important promoters of pulp stem cell recruitment. Moreover, the expression patterns of dentin sialoprotein (dspp), dentin matrix protein 1 (dmp1), osteocalcin (ocn), and matrix extracellular phosphoglycoprotein (mepe) indicate a complete odontoblast-like cell differentiation only when STRO-1(+) cells were cultured on RK-F10. On the contrary, RK-FG10, characterized by an initial fluoride release burst and reduced lifetime of the delivery, did not elicit any significant effect on both STRO-1(+) cell migration and differentiation. Taken together, our results highlight the importance of taking into account fluoride release kinetics in addition to fluoride concentration when designing new fluoride-restorative materials.