Mesenchymal stem cells in the dental tissues: perspectives for tissue regeneration

Mesenchymal Stem Cell-based Scaffolds in Regenerative Medicine of Dental Diseases

Biomedical engineering breakthroughs and increased patient expectations and requests for more comprehensive care are propelling the field of regenerative dentistry forward at a fast pace. Stem cells (SCs), bioactive compounds, and scaffolds are the mainstays of tissue engineering, the backbone of regenerative dentistry. Repairing damaged teeth and gums is a significant scientific problem at present. Novel therapeutic approaches for tooth and periodontal healing have been inspired by tissue engineering based on mesenchymal stem cells (MSCs). Furthermore, as a component of the MSC secretome, extracellular vesicles (EVs) have been shown to contribute to periodontal tissue repair and regeneration. The scaffold, made of an artificial extracellular matrix (ECM), acts as a supporting structure for new cell development and tissue formation. To effectively promote cell development, a scaffold must be non-toxic, biodegradable, biologically compatible, low in immunogenicity, and safe. Due to its promising biological characteristics for cell regeneration, dental tissue engineering has recently received much attention for its use of natural or synthetic polymer scaffolds with excellent mechanical properties, such as small pore size and a high surface-to-volume ratio, as a matrix. Moreover, as a bioactive material for carrying MSC-EVs, the combined application of scaffolds and MSC-EVs has a better regenerative effect on dental diseases. In this paper, we discuss how MSCs and MSC-derived EV treatment may be used to regenerate damaged teeth, and we highlight the role of various scaffolds in this process.

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.

Hopes and opportunities of stem cells from human exfoliated deciduous teeth (SHED) in cartilage tissue regeneration

Cartilage lesions are common conditions, affecting elderly and non-athletic populations. Despite recent advances, cartilage regeneration remains a major challenge today. The absence of an inflammatory response following damage and the inability of stem cells to penetrate into the healing site due to the absence of blood and lymph vessels are assumed to hinder joint repair. Stem cell-based regeneration and tissue engineering have opened new horizons for treatment. With advances in biological sciences, especially stem cell research, the function of various growth factors in the regulation of cell proliferation and differentiation has been established. Mesenchymal stem cells (MSCs) isolated from different tissues have been shown to increase into therapeutically relevant cell numbers and differentiate into mature chondrocytes. As MSCs can differentiate and become engrafted inside the host, they are considered suitable candidates for cartilage regeneration. Stem cells from human exfoliated deciduous teeth (SHED) provide a novel and non-invasive source of MSCs. Due to their simple isolation, chondrogenic differentiation potential, and minimal immunogenicity, they can be an interesting option for cartilage regeneration. Recent studies have reported that SHED-derived secretome contains biomolecules and compounds that efficiently promote regeneration in damaged tissues, including cartilage. Overall, this review highlighted the advances and challenges of cartilage regeneration using stem cell-based therapies by focusing on SHED.

The current regenerative medicine approaches of craniofacial diseases: A narrative review

Craniofacial deformities (CFDs) develop following oncological resection, trauma, or congenital disorders. Trauma is one of the top five causes of death globally, with rates varying from country to country. They result in a non-healing composite tissue wound as they degenerate in soft or hard tissues. Approximately one-third of oral diseases are caused by gum disease. Due to the complexity of anatomical structures in the region and the variety of tissue-specific requirements, CFD treatments present many challenges. Many treatment methods for CFDs are available today, such as drugs, regenerative medicine (RM), surgery, and tissue engineering. Functional restoration of a tissue or an organ after trauma or other chronic diseases is the focus of this emerging field of science. The materials and methodologies used in craniofacial reconstruction have significantly improved in the last few years. A facial fracture requires bone preservation as much as possible, so tiny fragments are removed initially. It is possible to replace bone marrow stem cells with oral stem cells for CFDs due to their excellent potential for bone formation. This review article discusses regenerative approaches for different types of craniofacial diseases.

Enhanced effects of antagomiR-3074-3p-conjugated PEI-AuNPs on the odontogenic differentiation by targeting FKBP9

The odontogenic differentiation of dental pulp stem cells (DPSCs), which is vital for tooth regeneration, was regulated by various functional molecules. In recent years, a growing body of research has shown that miRNAs play a crucial role in the odontogenic differentiation of human dental pulp stem cells (hDPSCs). However, the mechanisms by which miRNAs regulated odontogenic differentiation of hDPSCs remained unclear, and the application of miRNAs in reparative dentin formation in vivo was also rare. In this study, we first discovered that miR-3074-3p had an inhibitory effect on odontogenic differentiation of hDPSCs and antagomiR-3074-3p-conjugated PEI-AuNPs effectively promoted odontogenic differentiation of hDPSCs in vitro. AntagomiR-3074-3p-conjugated PEI-AuNPs was further applied to the rat pulp-capping model and showed the increased formation of restorative dentin. In addition, the results of lentivirus transfection in vitro suggested that FKBP9 acted as the key target of miR-3074-3p in regulating the odontogenic differentiation of hDPSCs. These findings might provide a new strategy and candidate target for dentin restoration and tooth regeneration.

Dental follicle cells show potential for treating Parkinson's disease through dopaminergic-neuronogenic differentiation

Among all the adult stem cells, odontogenic stem cells inherit the characterization of neurogenic potential of their precursor ones-the cranial crest cells. Dental follicle cells (DFCs), one of the special kind of odontogenic stem cells, are raising interest in applying to regenerative medicine for they possess multi-differentiation potential, relatively free access and ethic-friendly characteristic. Parkinson's disease (PD), as one of the common neurodegenerative disorders, affects about 0.3% of the general population. Stem cell therapies are thought to be effective to treat it. Aiming at tackling ethical-concernings, confined sources and practically applicational limits, we made use of dopaminergic neurongenic differentiation potential of the DFCs and dedicated every effort to applying them as promising cell source for treating PD. Dental follicle cells were cultured from human dental follicle tissues collected from 12 to 18-year-old teenagers' completely impacted third molars. Our data demonstrated that hDFCs were expressing mesenchymal stem cell-associated surface markers, and possessed the ability of osteogenic, adipogenic and neurogenic differentiation in vitro. Additionally, hDFCs formed neuron-like cells in vitro and in vivo, as well as expressing dopaminergic-neuronogenic marker-TH. Moreover, hDFCs survived in the transplanted areas of the Parkinson's disease model of mouse over six weeks post-surgery, and the number of TH-positive DFCs in the DFCs-Grafted group surpassed its counterpart of the MPTP group with statistically significant difference. This study indicated that hDFCs might be a promising source of dopaminergic neurons for functional transplantation, and encouraged further detailed studies on the potential of hDFCs for treating PD.

PLGA Nanoparticles Uptake in Stem Cells from Human Exfoliated Deciduous Teeth and Oral Keratinocyte Stem Cells

Polymeric nanoparticles have been introduced as a delivery vehicle for active compounds in a broad range of medical applications due to their biocompatibility, stability, controlled release of active compounds, and reduced toxicity. The oral route is the most used approach for delivery of biologics to the body. The homeostasis and function of oral cavity tissues are dependent on the activity of stem cells. The present work focuses, for the first time, on the interaction between two types of polymeric nanoparticles, poly (lactic-co-glycolic acid) or PLGA and PLGA/chitosan, and two stem cell populations, oral keratinocyte stem cells (OKSCs) and stem cells from human exfoliated deciduous teeth (SHEDs). The main results show that statistical significance was observed in OKSCs uptake when compared with normal keratinocytes and transit amplifying cells after 24 h of incubation with 5 and 10 µg/mL PLGA/chitosan. The CD117⁺ SHED subpopulation incorporated more PLGA/chitosan nanoparticles than nonseparated SHED. The uptake for PLGA/chitosan particles was better than for PLGA particles with longer incubation times, yielding better results in both cell types. The present results demonstrate that nanoparticle uptake depends on stem cell type, incubation time, particle concentration, and surface properties.

Combination stem cell therapy using dental pulp stem cells and human umbilical vein endothelial cells for critical hindlimb ischemia

Narrowing of arteries supplying blood to the limbs provokes critical hindlimb ischemia (CLI). Although CLI results in irreversible sequelae, such as amputation, few therapeutic options induce the formation of new functional blood vessels. Based on the proangiogenic potentials of stem cells, in this study, it was examined whether a combination of dental pulp stem cells (DPSCs) and human umbilical vein endothelial cells (HUVECs) could result in enhanced therapeutic effects of stem cells for CLI compared with those of DPSCs or HUVECs alone. The DPSCs+ HUVECs combination therapy resulted in significantly higher blood flow and lower ischemia damage than DPSCs or HUVECs alone. The improved therapeutic effects in the DPSCs+ HUVECs group were accompanied by a significantly higher number of microvessels in the ischemic tissue than in the other groups. In vitro proliferation and tube formation assay showed that VEGF in the conditioned media of DPSCs induced proliferation and vessel-like tube formation of HUVECs. Altogether, our results demonstrated that the combination of DPSCs and HUVECs had significantly better therapeutic effects on CLI via VEGF-mediated crosstalk. This combinational strategy could be used to develop novel clinical protocols for CLI proangiogenic regenerative treatments.

Combination stem cell therapy using dental pulp stem cells and human umbilical vein endothelial cells for critical hindlimb ischemia

Narrowing of arteries supplying blood to the limbs provokes critical hindlimb ischemia (CLI). Although CLI results in irreversible sequelae, such as amputation, few therapeutic options induce the formation of new functional blood vessels. Based on the proangiogenic potentials of stem cells, in this study, it was examined whether a combination of dental pulp stem cells (DPSCs) and human umbilical vein endothelial cells (HUVECs) could result in enhanced therapeutic effects of stem cells for CLI compared with those of DPSCs or HUVECs alone. The DPSCs+ HUVECs combination therapy resulted in significantly higher blood flow and lower ischemia damage than DPSCs or HUVECs alone. The improved therapeutic effects in the DPSCs+ HUVECs group were accompanied by a significantly higher number of microvessels in the ischemic tissue than in the other groups. In vitro proliferation and tube formation assay showed that VEGF in the conditioned media of DPSCs induced proliferation and vessel-like tube formation of HUVECs. Altogether, our results demonstrated that the combination of DPSCs and HUVECs had significantly better therapeutic effects on CLI via VEGF-mediated crosstalk. This combinational strategy could be used to develop novel clinical protocols for CLI proangiogenic regenerative treatments. [BMB Reports 2022; 55(7): 336-341].

Different Sources of Mesenchymal Stem Cells for Tissue Regeneration: A Guide to Identifying the Most Favorable One in Orthopedics and Dentistry Applications

The success of regenerative medicine in various clinical applications depends on the appropriate selection of the source of mesenchymal stem cells (MSCs). Indeed, the source conditions, the quality and quantity of MSCs, have an influence on the growth factors, cytokines, extracellular vesicles, and secrete bioactive factors of the regenerative milieu, thus influencing the clinical result. Thus, optimal source selection should harmonize this complex setting and ensure a well-personalized and effective treatment. Mesenchymal stem cells (MSCs) can be obtained from several sources, including bone marrow and adipose tissue, already used in orthopedic regenerative applications. In this sense, for bone, dental, and oral injuries, MSCs could provide an innovative and effective therapy. The present review aims to compare the properties (proliferation, migration, clonogenicity, angiogenic capacity, differentiation potential, and secretome) of MSCs derived from bone marrow, adipose tissue, and dental tissue to enable clinicians to select the best source of MSCs for their clinical application in bone and oral tissue regeneration to delineate new translational perspectives. A review of the literature was conducted using the search engines Web of Science, Pubmed, Scopus, and Google Scholar. An analysis of different publications showed that all sources compared (bone marrow mesenchymal stem cells (BM-MSCs), adipose tissue mesenchymal stem cells (AT-MSCs), and dental tissue mesenchymal stem cells (DT-MSCs)) are good options to promote proper migration and angiogenesis, and they turn out to be useful for gingival, dental pulp, bone, and periodontal regeneration. In particular, DT-MSCs have better proliferation rates and AT and G-MSC sources showed higher clonogenicity. MSCs from bone marrow, widely used in orthopedic regenerative medicine, are preferable for their differentiation ability. Considering all the properties among sources, BM-MSCs, AT-MSCs, and DT-MSCs present as potential candidates for oral and dental regeneration.

Immunomodulating Profile of Dental Mesenchymal Stromal Cells: A Comprehensive Overview

Dental mesenchymal stromal cells (MSCs) are multipotent cells present in dental tissues, characterized by plastic adherence in culture and specific surface markers (CD105, CD73, CD90, STRO-1, CD106, and CD146), common to all other MSC subtypes. Dental pulp, periodontal ligament, apical papilla, human exfoliated deciduous teeth, alveolar bone, dental follicle, tooth germ, and gingiva are all different sources for isolation and expansion of MSCs. Dental MSCs have regenerative and immunomodulatory properties; they are scarcely immunogenic but actively modulate T cell reactivity. in vitro studies and animal models of autoimmune diseases have provided evidence for the suppressive effects of dental MSCs on peripheral blood mononuclear cell proliferation, clearance of apoptotic cells, and promotion of a shift in the Treg/Th17 cell ratio. Appropriately stimulated MSCs produce anti-inflammatory mediators, such as transforming growth factor-β (TGF-β), prostaglandin E2, and interleukin (IL)-10. A particular mechanism through which MSCs exert their immunomodulatory action is via the production of extracellular vesicles containing such anti-inflammatory mediators. Recent studies demonstrated MSC-mediated inhibitory effects both on monocytes and activated macrophages, promoting their polarization to an anti-inflammatory M2-phenotype. A growing number of trials focusing on MSCs to treat autoimmune and inflammatory conditions are ongoing, but very few use dental tissue as a cellular source. Recent results suggest that dental MSCs are a promising therapeutic tool for immune-mediated disorders. However, the exact mechanisms responsible for dental MSC-mediated immunosuppression remain to be clarified, and impairment of dental MSCs immunosuppressive function in inflammatory conditions and aging must be assessed before considering autologous MSCs or their secreted vesicles for therapeutic purposes.

Craniofacial Bone Tissue Engineering: Current Approaches and Potential Therapy

Craniofacial bone defects can result from various disorders, including congenital malformations, tumor resection, infection, severe trauma, and accidents. Successfully regenerating cranial defects is an integral step to restore craniofacial function. However, challenges managing and controlling new bone tissue formation remain. Current advances in tissue engineering and regenerative medicine use innovative techniques to address these challenges. The use of biomaterials, stromal cells, and growth factors have demonstrated promising outcomes in vitro and in vivo. Natural and synthetic bone grafts combined with Mesenchymal Stromal Cells (MSCs) and growth factors have shown encouraging results in regenerating critical-size cranial defects. One of prevalent growth factors is Bone Morphogenetic Protein-2 (BMP-2). BMP-2 is defined as a gold standard growth factor that enhances new bone formation in vitro and in vivo. Recently, emerging evidence suggested that Megakaryocytes (MKs), induced by Thrombopoietin (TPO), show an increase in osteoblast proliferation in vitro and bone mass in vivo. Furthermore, a co-culture study shows mature MKs enhance MSC survival rate while maintaining their phenotype. Therefore, MKs can provide an insight as a potential therapy offering a safe and effective approach to regenerating critical-size cranial defects.

Identification of stemness and differentially expressed genes in human cementum-derived cells

Purpose

Periodontal treatment aims at complete regeneration of the periodontium, and developing strategies for periodontal regeneration requires a deep understanding of the tissues composing the periodontium. In the present study, the stemness characteristics and gene expression profiles of cementum-derived cells (CDCs) were investigated and compared with previously established human stem cells. Candidate marker proteins for CDCs were also explored.

Methods

Periodontal ligament stem cells (PDLSCs), pulp stem cells (PULPSCs), and CDCs were isolated and cultured from extracted human mandibular third molars. Human bone marrow stem cells (BMSCs) were used as a positive control. To identify the stemness of CDCs, cell differentiation (osteogenic, adipogenic, and chondrogenic) and surface antigens were evaluated through flow cytometry. The expression of cementum protein 1 (CEMP1) and cementum attachment protein (CAP) was investigated to explore marker proteins for CDCs through reverse-transcription polymerase chain reaction. To compare the gene expression profiles of the 4 cell types, mRNA and miRNA microarray analysis of 10 samples of BMSCs (n=1), PDLSCs (n=3), PULPSCs (n=3), and CDCs (n=3) were performed.

Results

The expression of mesenchymal stem cell markers with a concomitant absence of hematopoietic markers was observed in PDLSCs, PULPSCs, CDCs and BMSCs. All 4 cell populations also showed differentiation into osteogenic, adipogenic, and chondrogenic lineages. CEMP1 was strongly expressed in CDCs, while it was weakly detected in the other 3 cell populations. Meanwhile, CAP was not found in any of the 4 cell populations. The mRNA and miRNA microarray analysis showed that 14 mRNA genes and 4 miRNA genes were differentially expressed in CDCs vs. PDLSCs and PULPSCs.

Conclusions

Within the limitations of the study, CDCs seem to have stemness and preferentially express CEMP1. Moreover, there were several up- or down-regulated genes in CDCs vs. PDLSCs, PULPSCs, and BMSCs and these genes could be candidate marker proteins of CDCs.

Osteogenic differentiation potential and quantification of fresh and cryopreserved dental follicular stem cells-an in vitro analysis

Purpose: To isolate and characterize mesenchymal stem cells of dental follicle from fresh and cryopreserved samples and to test any significant difference in their osteogenic differentiation potential by using digital imaging software. We also investigated whether the cryoprotectant used and its concentration is able to maintain cell count and viability. Methods: Mesenchymal stem cells (MSCs) were isolated from dental follicle of impacted third molars. The osteogenic differentiation potential of dental follicle stem cells was assessed using alizarin red and alkaline phosphatase staining followed by digital imaging quantification of the stains. Results: Dental follicle cells have shown typical characterisation by exhibiting the stem cell stromal markers and hematopoietic markers, but there was variance in the percentage of expression in fresh and cryopreserved samples. There was considerable osteogenic differentiation potential in the fresh sample compared to cryopreserved sample. The cell count and viability were preserved in both samples. Conclusions: The results in the study have shown wide variation of osteogenic differentiation potential in fresh and cryopreserved samples. Also, the cryoprotectant was found to be effective in its purpose at the specified concentration.

Recent Advances in Cone-beam CT in Oral Medicine

BACKGROUND

The cone-beam computed tomography (CBCT) technology has continuously evolved since its appearance in oral medicine in the early 2000s.

OBJECTIVES

To present recent advances in CBCT in oral medicine: i) selection of recent and consensual evidence-based sources, ii) structured summary of the information based on an iterative framework and iii) compliance with ethical, public health and patient-centered concerns.

MAIN FINDINGS

We will focus on technological advances, such as sensors and reconstruction algorithms used to improve the constant quality of the image and dosimetry. CBCT examination is now performed in almost all disciplines of oral medicine: currently, the main clinical disciplines that use CBCT acquisitions are endodontics and oral surgery, with clearly defined indications. Periodontology and ear, nose and throat medicine are more recent fields of application. For a given application and indication, the smallest possible field of view must be used. One of the major challenges in contemporary healthcare is ensuring that technological developments do not take precedence over admitted standards of care. The entire volume should be reviewed in full, with a systematic approach. All findings are noted in the patient's record and explained to the patient, including incidental findings. This presupposes the person reviewing the images is sufficiently trained to interpret such images, inform the patient and organize the clinical pathway, with referrals to other medical or oral medicine specialties as needed.

CONCLUSION

A close collaboration between dentists, medical physicists, radiologists, radiographers and engineers is critical for all aspects of CBCT technology.

In vitro biocompatibility and bioactivity of calcium silicate‑based bioceramics in endodontics (Review)

Calcium silicate-based bioceramics have been applied in endodontics as advantageous materials for years. In addition to excellent physical and chemical properties, the biocompatibility and bioactivity of calcium silicate-based bioceramics also serve an important role in endodontics according to previous research reports. Firstly, bioceramics affect cellular behavior of cells such as stem cells, osteoblasts, osteoclasts, fibroblasts and immune cells. On the other hand, cell reaction to bioceramics determines the effect of wound healing and tissue repair following bioceramics implantation. The aim of the present review was to provide an overview of calcium silicate-based bioceramics currently applied in endodontics, including mineral trioxide aggregate, Bioaggregate, Biodentine and iRoot, focusing on their in vitro biocompatibility and bioactivity. Understanding their underlying mechanism may help to ensure these materials are applied appropriately in endodontics.

Differentiation capacity of dental pulp stem cell into inner ear hair cell using an in vitro assay: a preliminary step toward treating sensorineural hearing loss

PURPOSE

Sensorineural hearing loss (SNHL) is commonly caused by the death or dysfunction of cochlear cell types as a result of their lack of regenerative capacity. However, regenerative medicine, such as stem cell therapy, has become a promising tool to cure many diseases, including hearing loss. In this study, we determined whether DPSCs could differentiate into cochlear hair cell in vitro.

METHODS

DPSCs derived from human third molar dental pulp were induced into NSCs using a medium containing basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF) for 7 days, and then into cochlear hair cell using a medium containing EGF and IGF-1 for the next 14 days. We used the neuroepithelial protein marker nestin and cochlear hair cell marker myosin VIIa as the markers for cells differentiation. Cells expressing the positive markers under the microscope were confirmed to have differentiated into cochlear hair cell.

RESULTS

DPSCs were successfully induced to differentiate into NSCs, with mean 24% nestin-positive cells. We found that DPSC-derived NSCs have a great capacity in differentiating into inner ear hair cell-like cells with an average of 81% cells presenting myosin VIIa. Thus, DPSCs have high potential to serve as a good resource for SNHL treatment.

CONCLUSION

We found the high potential of DPSCs to differentiate into NSC. The ability of DPSCs in differentiating into neural lineage cell made them a good candidate for regenerative therapy in neural diseases, such as SNHL.

Cryopreservation of mesenchymal stem cells derived from dental pulp: a systematic review

Objectives

The aim of the present systematic review was to investigate the cryopreservation process of dental pulp mesenchymal stromal cells and whether cryopreservation is effective in promoting cell viability and recovery.

Materials and Methods

This systematic review was developed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and the research question was determined using the population, exposure, comparison, and outcomes strategy. Electronic searches were conducted in the PubMed, Cochrane Library, Science Direct, LILACS, and SciELO databases and in the gray literature (dissertations and thesis databases and Google Scholar) for relevant articles published up to March 2019. Clinical trial studies performed with dental pulp of human permanent or primary teeth, containing concrete information regarding the cryopreservation stages, and with cryopreservation performed for a period of at least 1 week were included in this study.

Results

The search strategy resulted in the retrieval of 185 publications. After the application of the eligibility criteria, 21 articles were selected for a qualitative analysis.

Conclusions

The cryopreservation process must be carried out in 6 stages: tooth disinfection, pulp extraction, cell isolation, cell proliferation, cryopreservation, and thawing. In addition, it can be inferred that the use of dimethyl sulfoxide, programmable freezing, and storage in liquid nitrogen are associated with a high rate of cell viability after thawing and a high rate of cell proliferation in both primary and permanent teeth.

Artemisinin protects DPSC from hypoxia and TNF-α mediated osteogenesis impairments through CA9 and Wnt signaling pathway

Dental pulp stem cells (DPSCs) possess the ability of multi-lineage differentiation, and are excellent sources of tissue engineering and regenerative medicine. Oxygen concentration and inflammation are two critical environmental factors that affect the osteogenic differentiation of DPSCs. We aimed to study the role of the antimalarial drug artemisinin on the osteogenic differentiation of human DPSCs under the hypoxia and inflammation conditions. We demonstrated that hypoxia (5% O₂) and inflammation (20 ng/mL TNF-α), alone or in combination, significantly diminished in vitro cell survival and increased apoptotic rates. Notably, hypoxia and TNF-α exerted accumulative effect in suppressing the osteogenic differentiation of DPSCs, as evidenced by reduced expression levels of osteogenesis-associated genes including ALP, RUNX2 and OCN in osteogenic condition, as well as reduced mineral nodules formation as indicated by alizarin red staining. Artemisinin at the dose of 40 μM markedly reversed the suppression in cell survival caused by hypoxia or inflammation, and reduced apoptotic rates and the expressions of pro-apoptotic proteins. Additionally, artemisinin restored osteogenic differentiation of DPSCs under the hypoxia or/and inflammation conditions. Moreover, the beneficial effect of artemisinin was dependent on upregulated expression of CA9 and CA9-mediated antioxidant responses, as CA9 knockdown abolished the protective role of artemisinin on DPSC osteogenesis. Furthermore, while hypoxia or/and inflammation significantly inactivated the Wnt/β-catenin signaling in DPSCs, additional exposure to artemisinin re-activated this pathway to promote osteogenic differentiation of DPSCs. Our results provide novel insight on the link between artemisinin and DPSC osteogenesis, and suggest promising artemisinin-based strategies for better dentin/pulp tissue engineering.

Nestin and dental pulp stones - a case report-driven hypothesis

The dental pulp stem cells (DPSCs) are mesenchymal stem/stromal cells (MSCs) with multilineage potential of differentiation. Different studies investigated dental pulp stones (PS), the calcified masses in the dental pulp, in regard to their prevalence, topography and structure. The etiology of PS is still unclear and, to our knowledge, the DPSCs were not attributed yet specific roles in PS formation. We report here an immunohistochemical study of a PS-embedding dental pulp from an impacted third mandibular molar of an adult patient, in which we used antibodies against CD34, Ki67, glial fibrillary acidic protein (GFAP), α-smooth muscle actin (α-SMA) and nestin. While endothelial cells expressed CD34 and pericytes or vascular smooth muscle cells expressed α-SMA, DPSCs and the osteoblasts coating the PS were exclusively labeled with nestin antibody. Stromal networks of nestin-expressing DPSCs were regarded as in situ providers of osteogenic progenitors involved in PS formation. Further experimental studies, with larger lots of tissue samples, as well as extended panels of markers, are needed in order to elucidate the DPSC hypothesis in the PS etiology.

Cannabidiol and Vitamin D3 Impact on Osteogenic Differentiation of Human Dental Mesenchymal Stem Cells

Background and objective: The aim of the present study was to establish a new differentiation protocol using cannabidiol (CBD) and vitamin D3 (Vit. D3) for a better and faster osteogenic differentiation of dental tissue derived mesenchymal stem cells (MSCs). Materials and methods: MSCs were harvested from dental follicle (DFSCs), dental pulp (DPSCs), and apical papilla (APSCs) of an impacted third molar of a 17-year old patient. The stem cells were isolated and characterized using flow cytometry; reverse transcription polymerase chain reaction (RT-PCR); and osteogenic, chondrogenic, and adipogenic differentiation. The effects of CBD and Vit. D3 on osteogenic differentiation of dental-derived stem cell were evaluated in terms of viability/metabolic activity by alamar test, expression of collagen1A, osteopontin (OP), osteocalcin (OC), and osteonectin genes and by quantification of calcium deposits by alizarin red assay. Results: Stem cell characterization revealed more typical stemness characteristics for DFSCs and DPSCs and atypical morphology and markers expression for APSCs, a phenotype that was confirmed by differences in multipotential ability. The RT-PCR quantification of bone matrix proteins expression revealed a different behavior for each cell type, APSCs having the best response for CBD. DPSCs showed the best osteogenic potential when treated with Vit. D3. Cultivation of DFSC in standard stem cell conditions induced the highest expression of osteogenic genes, suggesting the spontaneous differentiation capacity of these cells. Regarding mineralization, alizarin red assay indicated that DFSCs and APSCs were the most responsive to low doses of CBD and Vit. D3. DPSCs had the lowest mineralization levels, with a slightly better response to Vit. D3. Conclusions: This study provides evidence that DFSCs, DPSCs, and APSCs respond differently to osteoinduction stimuli and that CBD and Vit. D3 can enhance osteogenic differentiation of these types of cells under certain conditions and doses.

Isolation and Characterization of Human Synovial Fluid-Derived Mesenchymal Stromal Cells from Popliteal Cyst

Mesenchymal stem cells (MSCs) are multipotent progenitor cells in adult tissues. The aim of this study is to isolate and identify synovial fluid-derived mesenchymal stromal cells (SF-MSCs) from the popliteal cyst fluid of pediatric patients. SF-MSCs were collected from the popliteal cyst fluid of pediatric patients during cystectomy surgery. After cyst fluid extraction and adherent culturing, in vitro morphology, growth curve, and cell cycle were observed. The expression of stem cell surface markers was analyzed by flow cytometry, and expression of cell marker protein was detected by immunofluorescence. SF-MSCs were cultured in osteogenic, adipogenic, and chondrogenic differentiation medium. The differentiation potential of SF-MSCs was analyzed by alkaline phosphatase (Alizarin Red), Oil Red O, and Alcian blue. Antibody detection of human angiogenesis-related proteins was performed compared with bone marrow mesenchymal stem cells (BM-MSCs). The results show that SF-MSCs from the popliteal cyst fluid of pediatric patients showed a shuttle appearance and logarithmic growth. Flow cytometry analysis revealed that SF-MSCs were negative for hematopoietic lineage markers (CD34, CD45) and positive for MSC markers (CD44, CD73, CD90, and CD105). Interstitial cell marker (vimentin) and myofibroblast-like cell marker alpha-smooth muscle actin (α-SMA) were positive. These cells could differentiate into osteogenic, adipogenic, and chondrogenic lineages, respectively. Several types of human angiogenesis-related proteins were detected in the cell secretory fluid. These results show that we successfully obtained SF-MSCs from the popliteal cyst fluid of pediatric patients, which have the potential to be a valuable source of MSCs.

Influence of resveratrol application with pulp-capping materials on the genetic expression levels of stem cells

AIM

To evaluate in a laboratory setting the response of human mesenchymal stem cells (MSCs) to pulp-capping materials with and without resveratrol (RSV).

METHODOLOGY

Five materials, Calcimol LC, Life, TheraCal LC, ProRoot MTA and Biodentine, were prepared according to the manufacturers' instructions. Human MSCs were then exposed to these materials, with and without RSV, for 24 h (n = 8). Cell viability was evaluated using the MTT assay, and total cell death was quantified by annexin V-FITC staining with flow cytometry. The expression levels of the IL-8, IL-10, HBD-2 and BCL-2 genes were investigated using real-time polymerase chain reaction (RT-PCR). Data obtained from MTT test were analysed using one-way anova, and Tukey's multiple-comparison test. The paired Student t test was employed to compare the effects of materials on gene expression (significance level of 5%).

RESULTS

The group cell viabilities were Calcimol LC 53%, Life 43%, TheraCal LC 78%, ProRoot MTA 75% and Biodentine 78%. Calcimol LC and Life exhibited significant differences compared with the control groups (P < 0.05). The percentages of necrotic/late apoptotic cells associated with Calcimol LC and TheraCal LC were greater than in the other materials. However, when RSV was added to wells containing materials, cell viability increased to Calcimol LC 63%, Life 52%, TheraCal LC 82%, ProRoot MTA 91% and Biodentine 96%, and the percentages of early apoptotic and late apoptotic/necrotic cells decreased. Calcimol LC + RSV and Life + RSV differed significantly from the control group (P < 0.05). The expression of IL-8 gene was high for all materials, ProRoot MTA caused significant overexpression, and the addition of RSV reduced the expression of IL-8 in the Calcimol LC, TheraCal LC and ProRoot MTA groups and led to increased expression of IL-10 in the Calcimol LC, Life and Biodentine groups. HBD-2 and BCL-2 exhibited increased expression in ProRoot MTA with RSV (P < 0.05).

CONCLUSIONS

The addition of RSV exerted a protective effect on MSCs and regulated the inflammatory process by altering the expression levels of pro- and anti-inflammatory genes.

Emerging functions and clinical applications of exosomes in human oral diseases

Exosomes are cell-derived membranous vesicles of endosomal origin secreted by all type of cells and present in various body fluids. Exosomes are enriched in peptides, lipids, and nucleic acids, emerging as vital modulators in intercellular communication. Exosomes are increasingly being evaluated as biomarkers for diagnosis and prognosis of diseases, because the constituents of exosomes could be reprogrammed depending on the states of diseases. These features also make exosomes a research hotspot in oral diseases in recent years. In this review, we outlined the characteristics of exosomes, focused on the differential expressions and altered biological functions of exosomes in oral diseases, including oral squamous cell carcinoma, oral leukoplakia, periodontitis, primary Sjögren’s syndrome, oral lichen planus, as well as hand foot and mouth disease. Besides, accumulated evidence documents that it is implementable to consider the natural nanostructured exosomes as a new strategy for disease treatment. Herein, we highlighted the therapeutic potential of exosomes in oral tissue regeneration, oncotherapy, wound healing, and their superiority as therapeutic drug delivery vehicles.

Mesenchymal Stem Cells Derived from Human Inflamed Dental Pulp Exhibit Impaired Immunomodulatory Capacity In Vitro

INTRODUCTION

Dental pulp stem cells (DPSC) are very attractive in regenerative medicine. In this study, we focused on the characterization of the functional properties of mesenchymal stem cells derived from DPSCs. Currently, it is unknown whether inflammatory conditions present in an inflamed dental pulp tissue could alter the immunomodulatory properties of DPSCs. This study aimed to evaluate the immunomodulatory capacity in vitro of DPSCs derived from healthy and inflamed dental pulp.

METHODS

DPSCs from 10 healthy and inflamed dental pulps (irreversible pulpitis) were characterized according to the minimal criteria of the International Society for Cell Therapy, proliferation, differential potential, and colony-forming units. Furthermore, the immunomodulatory capacity of DPSCs was tested on the proliferation of T lymphocytes by flow cytometry and the in vitro enzyme activity of indoleamine 2, 3-dioxygenase.

RESULTS

There were no significant differences in the DPSC characteristics and properties such as immunophenotype, tridifferentiation, colony-forming units, and proliferation of the DPSCs derived from normal and inflamed pulp tissue. Furthermore, there were significant differences in the immunomodulatory capacity of DPSCs obtained from human healthy dental pulp and with the diagnosis of irreversible pulpitis.

CONCLUSIONS

Our results showed that DPSCs isolated from inflamed dental pulp showed typical characteristics of MSCs and diminished immunosuppressive capacity in vitro in comparison with MSCs derived from healthy dental pulp. Further investigation in vivo is needed to clarify the mechanism of this diminished immunosuppressive capacity.

Irradiation with blue light-emitting diode enhances osteogenic differentiation of stem cells from the apical papilla

This study aimed to evaluate the effects of low-energy blue LED irradiation on the osteogenic differentiation of stem cells from the apical papilla (SCAPs). SCAPs were derived from human tooth root tips and were irradiated with 0 (control group), 1 J/cm², 2 J/cm², 3 J/cm², or 4 J/cm² blue light in osteogenic induction medium. Cell proliferation was analyzed using the 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay. Osteogenic differentiation activity was evaluated by monitoring alkaline phosphatase (ALP), alizarin red staining, and real-time polymerase chain reaction (RT-PCR). The results of the MTT assay indicated that SCAPs in the LED groups exhibited a lower proliferation rate than those in the control group, and there were statistically differences between the 2 J/cm², 3 J/cm², and 4 J/cm² groups and the control group (P < 0.05). The results of the ALP and alizarin red analyses showed that blue LED promoted osteogenic differentiation of the SCAPs. And 4 J/cm² blue light upregulates the expression levels of the osteogenic/dentinogenic genes ALP, dentin sialophosphoprotein (DSPP), dentin matrix protein-1 (DMP-1), and osteocalcin (OCN) in SCAPs. Our results confirmed that low-energy blue LED at 1 J/cm², 2 J/cm², 3 J/cm², and 4 J/cm² could inhibit the proliferation of SCAPs and promotes osteogenic differentiation of SCAPs. Further in vitro studies are required to explore the mechanisms of the effects by low-energy blue LED.

A Bibliometric Analysis of Articles Published in Brazilian Dental Journal over 30 years

This study assessed bibliometric characteristics of all articles published in Brazilian Dental Journal (BDJ) in its 30 years of existence (1990-2019) and factors associated with citation rates. A document search was carried out in Scopus in December, 2019 and information about the articles were exported, including citations. Type of study and main subject in each article were categorized. Number of citations was categorized in tertiles. Logistic regression models were used to assess the association between variables related to articles' characteristics and number of citations. In 30 years, 1705 articles were published and 18507 citations received, with average 57 articles and 334 pages published yearly and 10.9 cites/doc. The most frequent types of study were laboratorial (63%), clinical (18.5%), and case reports (11%); the main subjects were dental materials (21.6%), endodontics (19.3%), and oral pathology/stomatology (13.1%). Most articles had origin in Brazil (90%), followed by USA (4.6%) and UK (1.5%). Aside from BDJ, Journal of Endodontics (3.5%) and International Endodontic Journal (2.2%) were journals that most often cited BDJ. Main origins of citations were Brazil (36.7%), USA (10.6%), and India (9%). Older articles had higher odds to be highly cited (12% increase/year), longer articles had lower odds (9% decrease/page). Narrative reviews and epidemiological studies were associated with more citations and systematic reviews with less citations. In conclusion, BDJ covered many subjects and study types in 30 years, showing increased growth in international audience. The journal may be regarded as one of the leading Brazilian journals in dentistry published in English.

The Contribution of the Brazilian Dental Journal to the Brazilian Scientific Research over 30 Years

The Brazilian Dental Journal (BDJ) was officially launched in 1990, stimulated by the courage and boldness of researchers dedicated to teaching and research in dentistry. The journal was conceived in a worldwide coverage and universal language to allow publication of the results of Brazilian studies, which otherwise would not be accessible to the scientific dental community. In the year we celebrate the thirtieth anniversary of BDJ, this article presents a brief overview of Brazilian dental research and a bibliometric analysis of the articles published in this journal as a contribution to our readers and fellow researchers. The purpose was to identify the mot frequent categories of study, the most published areas of dentistry and BDJ's top 50 most-cited articles in the Scopus and Google Scholar databases. A search was performed on all BDJ online issues published from 1990 to 2019. In this period, BDJ published 1,710 articles. Based on their distribution by category of study, 557 articles were in the basic research/dental materials area, 527 in the basic research/biology area and 280 in the clinical research area. Eight articles were cited more than 100 times in the Scopus database and 266 times in the Google Scholar database. Endodontics was the most published area. This overview of BDJ production over those 30 years allows establishing a profile of the characteristics, impact and trends of the published studies, as well as the journal's contribution to the top 50 most-cited articles in the Scopus and Google Scholar databases.

Characterization and therapeutic applications of mesenchymal stem cells for regenerative medicine

BACKGROUND

Mesenchymal stem cells (MSCs) are multipotent, genomic stable, self-renewable, and culturally expandable adult stem cells. MSCs facilitate tissue development, maintenance and repair, and produce secretory factors that support engraftment and trophic functions, marking them an attractive option in cell therapy, regenerative medicine and tissue engineering.

METHOD

In this review, we summarize the recent researches regarding the isolation and characterization of MSCs, therapeutic applications and advanced engineering techniques. We also discuss the advantages and limitations that remain to be overcome for MSCs based therapy.

RESULTS

It has been demonstrated that MSCs are able to modulate endogenous tissue and immune cells. Preclinical studies and early phase clinical trials have shown their great potential for tissue engineering of bone, cartilage, marrow stroma, muscle, fat, and other connective tissues.

CONCLUSIONS

MSC-based therapy show considerable promise to rebuild damaged or diseased tissues, which could be a promising therapeutic method for regeneration medicine.

Role of gingival mesenchymal stem cell exosomes in macrophage polarization under inflammatory conditions

OBJECTIVE

Exosomes have been shown to play a strong role in intercellular communication. While GMSCs have been extensively studied, less research exists on exosomes derived from GMSCs, especially on how exosomes affect macrophages. This study aimed to investigate the impact of GMSC-derived exosomes on macrophage polarization and phenotype under inflammatory conditions.

METHODS

Exosomes were isolated from GMSCs-conditioned media by ultracentrifugation (UC) and characterized by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA) and western blot (WB). In vitro, GMSC-derived exosomes were co-incubated with macrophages for 24 h in the absence or presence of M1 polarizing conditions in the six-well plate. The protein and mRNA expression levels of M1 and M2 macrophage markers were detected and the supernatants were collected for an enzyme-linked immunosorbent assay (ELISA).

RESULTS

Exosomes were successfully isolated from GMSCs. Macrophages co-cultured with exosomes showed significantly decreased levels of the M1 markers Tumor Necrosis Factor-α (TNF-α), Interleukin-12 (IL-12), CD86 and Interleukin-1β (IL-1β). By contrast, M2 marker Interleukin-10 (IL-10) levels moderately increased. Meanwhile, similar results were acquired in the cell culture supernatants.

CONCLUSION

GMSC-derived exosomes may promote M1 macrophage transformation into M2 macrophages, reducing the pro-inflammatory factors produced by M1 macrophages.

miR-224-5p protects dental pulp stem cells from apoptosis by targeting Rac1

Dental pulp stem cells (DPSCs) are reported to be enriched in stem/progenitor cells, however to the best of our knowledge they have yet to be well documented and characterized. In the present study, in order to characterize DPSCs and the effect of microRNAs (miRs/miRNAs) on DPSC properties, a miRNA array was performed between dental periodontal ligament cells (DPLCs) and DPSCs. The results revealed that miR-224-5p (miR-224) was highly expressed in the DPSCs compared with that in the DPLCs. The transfection of DPSCs with an miR-224 inhibitor impaired cell viability. In addition, miR-224 inhibition significantly promoted cell apoptosis in DPSCscompared with the NC group. In silico analysis and a dual-luciferase reporter assay demonstrated that miR-224 targets the 3′-untranslated region of the Rac family small GTPase 1 (Rac1) gene. miR-224 downregulation resulted in the increased expression of Rac1 in DPSCs compared with DPLCs. Furthermore, miR-224 inhibition caused augmented mitogen-activated protein kinase 8, caspase-3, caspase-9 and Fas ligand expression in DPSC, which may be recovered by Rac1 silencing with transfection with short hairpin RNA-Rac1. Furthermore, Annexin V-fluorescein isothiocyanate/propidium iodide flow cytometry indicated that the silencing of Rac1 restored the pro-apoptotic DPSC cell number with miR-224 transfection. Therefore, the results of the present study suggested miR-224 in DPSC serves an important function in protecting cells against apoptosis by downregulating Rac1 expression, and also identified miR-224 as a novel miRNA in regulating the features of DPSC.

Human Dental Pulp Stem Cells in Rat Mandibular Bone Defects

This study aimed to evaluate the use of human dental pulp stem cells (hDPSCs) in non-critical-sized mandibular bone defects in rats. hDPSCs from permanent teeth were isolated and engrafted in mandibular bone defects in rats for 7, 14, and 28 days; bone defects without cells formed the control group. Samples were evaluated by scanning electron microscopy (SEM), light microscopy (hematoxylin and eosin staining), and the regeneration area was measured by the Image J program. Before surgery procedures, the human dental pulp cells were characterized as dental pulp stem cells: fusiform morphology, plastic-adherent; expression of CD105, CD73, and CD90; lack of expression of CD45 and CD34, and differentiated into osteoblasts, adipocytes, and chondroblasts. The results indicated that within 7 days the control group presented a pronounced bone formation when compared with the treated group (p < 0.05). After 14 days, the treated group showed an increase in bone formation, but with no statistical difference among the groups (p > 0.05). In the final evaluated period there was no difference between the control group and the treated group (p > 0.05). There was a significant difference between 7 and 14 days (p < 0.05) and between 7 and 28 days (p < 0.05) in the treated group. In conclusion, there is no evidence that the use of hDPSCs in the conditions of this study could improve bone formation in non-critical-sized mandibular bone defects.

Rabbit palatum-derived mesenchymal progenitor cells tri-lineage differentiation on 2D substrates and 3D printed constructs

Hard palate, developed by embryo neural crest stem cells, is a tissue with strong regenerative abilities. It is considered an abundant source of progenitor cells, forming various mesenchymal tissues. Rabbits are more suitable models than murine animals for regenerative preclinical study of the head and neck, owing to their larger size. However, there are no reports of the existence or characteristics of neural crest stem cells in the hard palate of rabbits. In this study, we demonstrate for the first time the presence of nestin-, Sox2-, and p75-positive neural crest stem cells obtained from the hard palate of rabbits and the properties of these cells. Flow cytometry analysis revealed that CD29, CD44, and CD81 were positive; and CD11b, CD34, and CD90 were negative on the ex vivo expanded palatal progenitor cells. Finally, we differentiated them into cells of mesenchymal lineages (bone, cartilage, and fat) in vitro, and in three-dimensional fabricated polycaprolactone and polycaprolactone-tricalcium phosphate scaffolds. Taken together, our data showed the existence of rabbit palatum-derived mesenchymal progenitor cells, and successful fabrication of progenitor cell-loaded biodegradable scaffold using three-dimensional printing. This study will open avenues for new tissue engineering strategies for cell therapy using three-dimensional printing with scaffolds for reconstruction of head and neck defects.

Improving stemness and functional features of mesenchymal stem cells from Wharton's jelly of a human umbilical cord by mimicking the native, low oxygen stem cell niche

INTRODUCTION

Mesenchymal stem cells from Wharton's Jelly of a human umbilical cord (WJ-MSCs) are a potential tool in regenerative medicine based on their availability, proliferative potential and differentiation capacity. Since their physiological niche contains low oxygen levels, we investigated whether cultivation of WJ-MSCs at 3% O₂ affects their main features.

METHODS

WJ-MSCs were cultured under 21% and 3% O₂. Proliferation rate was followed by short and long term proliferation assays, clonogenic capacity by CFU-F assay and cell cycle and death by flow cytometry. Differentiation capacity was investigated by histochemical staining after induced differentiation. Pluripotency and differentiation markers' expression was determined by RT-PCR. Migration capacity was followed by scratch assay and mobilization from collagen, and the activity of proteolytic enzymes by zymography. Specific inhibitors of MAPK and Wnt/β-catenin pathways were used to investigate underlying molecular mechanisms.

RESULTS

Compared to standard 21% O_2, cultivation of WJ-MSCs at 3% O₂ did not influence their immunophenotype, while it modulated their differentiation process and enhanced their clonogenic and expansion capacity. 3% O₂ induced transient change in cell cycle and prevented cell death. The expression of NANOG, OCT4A, OCT4B and SOX2 was increased at 3% O₂. Both cultivation and preculturing of WJ-MSCs at 3% O₂ increased their in vitro migratory capacity and enhanced the activity of proteolytic enzymes. ERK1/2 mediated WJ-MSCs' mobilization from collagen regardless of oxygen levels, while Wnt/β-catenin pathway was activated during migration and mobilization at standard conditions.

CONCLUSION

Culturing of WJ-MSCs under 3% O₂ should be considered a credible condition when investigating their properties and potential use.

Osteogenic capacity and cytotherapeutic potential of periodontal ligament cells for periodontal regeneration in vitro and in vivo

Background

The periodontal ligament cells (PDLCs) contain heterogeneous cell populations and possess stem-cell-like properties. PDLCs have attracted considerable attention as an option for periodontal regeneration. However, the osteogenic differentiation of PDLCs remains obscure owing to variable osteo-inductive methods and whether PDLCs could be directly used for periodontal regeneration without stem cell enrichment is uncertain. The aim of the present study was to clarify the osteogenic differentiation capacity of PDLCs and test PDLCs as an alternative to stem cells for periodontal regeneration.

Methods

We tested the performance of human PDLCs in osteo-inductive culture and transplantation in vivo while taking human bone marrow derived mesenchymal stem cells (hMSCs) as positive control. Proliferation of PDLCs and hMSCs in osteo-inductive condition were examined by MTT assay and colony formation assay. The osteogenic differentiations of PDLCs and hMSCs were assessed by Alkaline phosphatase (ALP) activity measurement, von Kossa staining, Alizarin red S staining and quantitative RT-PCR of osteogenic marker gene including RUNX2, ALP, OCN, Col I, BSP, OPN. We transplanted osteo-inductive PDLCs and hMSCs with hydroxyapatite/tricalcium phosphate (HA/TCP) scaffolds to immunodeficient mice to explore their biological behaviors in vivo by histological staining and immunohistochemical evaluation.

Results

After 14 days of osteo-induction, PDLCs exhibited significantly higher proliferation rate but lower colony-forming ability comparing with hMSCs. PDLCs demonstrated lower ALP activity and generated fewer mineralized nodules than hMSCs. PDLCs showed overall up-regulated expression of RUNX2, ALP, OCN, Col I, BSP, OPN after osteo-induction. Col I level of PDLCs in osteo-inductive group was significantly higher while RUNX2, ALP, OCN were lower than that of hMSCs. Massive fiber bundles were produced linking or circling the scaffold while the bone-like structures were limited in the PDLCs-loaded HA/TCP samples. The fiber bundles displayed strong positive Col I, but weak OCN and OPN staining. The in vivo results were consistent with the in vitro data, which confirmed strong collagen forming ability and considerable osteogenic potential of PDLCs.

Conclusion

It is encouraging to find that PDLCs exhibit higher proliferation, stronger collagen fiber formation capacity, but lower osteogenic differentiation ability in comparison with hMSCs. This characteristic is essential for the successful periodontal reconstruction which is based on the synchronization of fiber formation and bone deposition. Moreover, PDLCs have advantages such as good accessibility, abundant source, vigorous proliferation and evident osteogenic differentiation capacity when triggered properly. They can independently form PDL-like structure in vivo without specific stem cell enrichment procedure. The application of PDLCs may offer a novel cytotherapeutic option for future clinical periodontal reconstruction.

The Potential of Different Origin Stem Cells in Modulating Oral Bone Regeneration Processes

Tissue engineering has gained much momentum since the implementation of stem cell isolation and manipulation for regenerative purposes. Despite significant technical improvements, researchers still have to decide which strategy (which type of stem cell) is the most suitable for their specific purpose. Therefore, this short review discusses the advantages and disadvantages of the three main categories of stem cells: embryonic stem cells, mesenchymal stem cells and induced pluripotent stem cells in the context of bone regeneration for dentistry-associated conditions. Importantly, when deciding upon the right strategy, the selection needs to be made in concordance with the morbidity and the life-threatening level of the condition in discussion. Therefore, even when a specific type of stem cell holds several advantages over others, their availability, invasiveness of the collection method and ethical standards become deciding parameters.

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

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

An In Vitro Comparative Study of Multisource Derived Human Mesenchymal Stem Cells for Bone Tissue Engineering

Mesenchymal stem cells (MSCs) have been considered promising tools for tissue engineering and regenerative medicine. However, the optimal cell source for bone regeneration remains controversial. To better identify seed cells for bone tissue engineering, we compared MSCs from seven different tissues, including four from dental origins, dental pulp stem cells (DPSCs), periodontal ligament stem cells (PDLSCs), gingival MSCs (GMSCs), and dental follicle stem cells (DFSCs); two from somatic origins, bone marrow-derived MSCs (BM-MSCs) and adipose-derived stem cells (ADSCs); and one from birth-associated perinatal tissue umbilical cord (UCMSCs). We cultured the cells under a standardized culture condition and studied their biological characteristics. According to our results, these cells exhibited similar immunophenotype and had potential for multilineage differentiation. MSCs from dental and perinatal tissues proliferated more rapidly than those from somatic origins. Simultaneously, DPSCs and PDLSCs owned stronger antiapoptotic ability under the microenvironment of oxidative stress combined with serum deprivation. In respect to osteogenic differentiation, the two somatic MSCs, BM-MSCs and ADSCs, demonstrated the strongest ability for osteogenesis compared to PDLSCs and DFSCs, which were just a little bit weaker than the formers. However, GMSCs and UCMSCs were the most pertinacious ones to differentiate to osteoblasts. We also revealed that the canonical intracellular protein kinase-based cascade signaling pathways, including PI3K/AKT, MAPK/ERK, and p38 MAPK, possessed different levels of activation in different MSCs after osteoblast induction. Our conclusions suggest that PDLSCs might be a good potential alternative to BM-MSCs for bone tissue engineering.

Intracardiac Injection of Dental Pulp Stem Cells After Neonatal Hypoxia-Ischemia Prevents Cognitive Deficits in Rats

Neonatal hypoxia-ischemia (HI) is associated to cognitive and motor impairments and until the moment there is no proven treatment. The underlying neuroprotective mechanisms of stem cells are partially understood and include decrease in excitotoxicity, apoptosis and inflammation suppression. This study was conducted in order to test the effects of intracardiac transplantation of human dental pulp stem cells (hDPSCs) for treating HI damage. Seven-day-old Wistar rats were divided into four groups: sham-saline, sham-hDPSCs, HI-saline, and HI-hDPSCs. Motor and cognitive tasks were performed from postnatal day 30. HI-induced cognitive deficits in the novel-object recognition test and in spatial reference memory impairment which were prevented by hDPSCs. No motor impairments were observed in HI animals. Immunofluorescence analysis showed human-positive nuclei in hDPSC-treated animals closely associated with anti-GFAP staining in the lesion scar tissue, suggesting that these cells were able to migrate to the injury site and could be providing support to CNS cells. Our study evidence novel evidence that hDPSC can contribute to the recovery following hypoxia-ischemia and highlight the need of further investigation in order to better understand the exact mechanisms underlying its neuroprotective effects.

Osteogenic potential of cell spheroids composed of varying ratios of gingiva-derived and bone marrow stem cells using concave microwells

The aim of the current study was to evaluate cell viability and osteogenic differentiation potential in cell spheroids composed of varying ratios of gingiva-derived and bone marrow stem cells cultured in concave microwells. Cell spheroids were established from bone marrow and gingiva-derived stem cells in ratios of 6:0 (Group 1), 2:1 (Group 2), 3:3 (Group 3), 1:2 (Group 4), and 0:6 (Group 5). On days 3 and 5, the viability of the cell spheroids was qualitatively analyzed using a calcein acetoxymethyl ester working solution and an ethidium homodimer-1 live/dead assay. On days 1, 3, 5 and 7, a quantitative cell viability analysis was performed using a Cell Counting Kit-8. Alkaline phosphatase activity assays were performed using a commercially available kit on day 7 to assess osteogenic differentiation. In addition, reverse transcription-quantitative polymerase chain reaction and western blot analysis were performed to evaluate runt-related transcription factor 2 (Runx2) and osteocalcin expression. The ratio of gingiva-derived to bone marrow stem cells did not affect the stem cell spheroid morphology. No significant changes in cell viability were noted among the different groups following incubation for 7 days. A consistent alkaline phosphatase activity was measured in co-cultured gingiva-derived and bone marrow stem cell spheroids of varying compositions. Runx2 and osteocalcin expression was increased when co-cultured compared with pure gingiva-derived or bone marrow stem cells. In conclusion, stem cell spheroids established by co-culturing maintained morphology, viability and a high osteogenic differentiation potential during the experimental period of 7 days. These spheroids containing human gingiva-derived and bone marrow stem cells may enhance the osteogenic differentiation potential. The use of multicell spheroids may be a simple and effective strategy for improving stem cell therapy.

Osteogenic Differentiation Modulates the Cytokine, Chemokine, and Growth Factor Profile of ASCs and SHED

Great efforts have been made to improve bone regeneration techniques owing to a growing variety of sources of stem cells suitable for autologous transplants. Specifically, adipose-derived stem cells (ASCs) and stems cells from human exfoliated deciduous teeth (SHED) hold great potential for bone tissue engineering and cell therapy. After a preliminary characterization of the main biomolecules ASCs and SHED released in their conditioned media, cells were kept both in normal and osteo-inducing conditions. Conventional assays were performed to prove their osteogenic potential such as quantitative real-time polymerase chain reaction (qRT-PCR) (for RUNX-2, collagen type I, osteopontin and osteonectin), alkaline phosphatase activity, osteocalcin production, and von Kossa staining. Conditioned media were tested again after the osteogenic induction and compared to maintaining condition both at base line and after 14 days of culture. The osteogenic condition inhibited the release of all the biomolecules, with the exception, concerning SHED, of growth-regulated alpha protein precursor (GROα), and, to a lesser extent, interleukin (IL)-8. In conclusion, our data support that undifferentiated ASCs and SHED may be preferable to committed ones for general cell therapy approaches, due to their higher paracrine activity. Osteoinduction significantly affects the cytokine, chemokine, and growth factor profile in a differential way, as SHED kept a more pronounced pro-angiogenic signature than ASCs.

Cementum regeneration using stem cells in the dog model: A systematic review

OBJECTIVE

Restoring lost tissues of the periodontium, such as cementum, is essential in reducing the risk of tooth loss due to periodontitis and/or severe root resorption. Stem cell therapy is a regenerative strategy in cementum regeneration. This systematic review aimed to analyze the effect of various stem cells and their transplantation method on cementum regeneration in the dog model.

METHODS

Electronic databases were searched, in addition to performing hand searches and a gray literature search. Titles and abstracts were searched according to the inclusion criteria and full texts were selected to be included in this systematic review. Data was extracted from each article and risk of bias was assessed for individual studies.

RESULTS

Most studies reported that the treatment using a variety of stem cells resulted in significantly greater cementum regeneration.

CONCLUSIONS

Because of variations in additional factors included in each study and varied risk of bias among those studies, the effect of each type of stem cell on cementum regeneration in dogs is difficult to clarify. Additional information needs to be obtained from each study in order to further analyze the individual effect of stem cells on cementum regeneration in dogs.

Use of Autologous Stem Cells for the Regeneration of Periodontal Defects in Animal Studies: a Systematic Review and Meta-Analysis

OBJECTIVES

To overview preclinical animal trials and quantify the effect size that stem cell therapy has on the regeneration of periodontal tissue complex.

MATERIAL AND METHODS

A systematic MEDLINE (PubMed) online library search was conducted for preclinical animal studies in vivo , using autologous periodontal ligament, dental pulp, cementum, alveolar periosteal, gingival margin or adipose stem cell types for periodontal tissue complex regeneration purposes. Studies had to be published between 2007.09.01 and 2017.09.01 in the English language.

RESULTS

Online library search yielded 2099 results. After the title, abstract and full-text screening ten studies fit inclusion criteria and were pooled into meta-analysis. Overall the stem cell regenerative therapy had a statistically significant positive influence on the periodontal tissue regeneration when compared to the control groups. The biggest influence was made to the regeneration of cementum (standardised mean difference [SMD] 2.25 [95% confidence interval (CI) = 1.31 to 3.2]) while the smallest influence was made to the alveolar bone (SMD 1.47 [95% CI = 0.7 to 2.25]) the effect size for periodontal ligament regeneration was (SMD 1.8 [95% CI = 1 to 2.59]). Subgroup analysis showed statistically significant (P < 0.05) differences between different cell types in the alveolar bone and cementum regeneration groups and in alveolar bone group in relation to scaffold materials.

CONCLUSIONS

Stem cell therapy has a positive impact on periodontal tissue complex regeneration. Such therapy has the biggest influence on cementum regeneration meanwhile alveolar bone regeneration is influenced by the least amount. However more and less diverse preclinical studies are needed to have a greater statistical power in future meta-analyses.

Functional and molecular characterization of transmembrane intracellular pH regulators in human dental pulp stem cells

OBJECTIVE

Homeostasis of intracellular pH (pH_i) plays vital roles in many cell functions, such as proliferation, apoptosis, differentiation and metastasis. Thus far, Na⁺-H⁺ exchanger (NHE), Na⁺-HCO₃^- co-transporter (NBC), Cl^-/HCO₃^- exchanger (AE) and Cl^-/OH^- exchanger (CHE) have been identified to co-regulate pH_i homeostasis. However, functional and biological pH_i-regulators in human dental pulp stem cells (hDPSCs) have yet to be identified.

DESIGN

Microspectrofluorimetry technique with pH-sensitive fluorescent dye, BCECF, was used to detect pH_i changes. NH₄Cl and Na⁺-acetate pre-pulse were used to induce intracellular acidosis and alkalosis, respectively. Isoforms of pH_i-regulators were detected by Western blot technique.

RESULTS

The resting pH_i was no significant difference between that in HEPES-buffered (nominal HCO₃^--free) solution or CO₂/HCO₃-buffered system (7.42 and 7.46, respectively). The pH_i recovery following the induced-intracellular acidosis was blocked completely by removing [Na⁺]_o, while only slowed (-63%) by adding HOE694 (a NHE1 specific inhibitor) in HEPES-buffered solution. The pH_i recovery was inhibited entirely by removing [Na⁺]_o, while adding HOE 694 pulse DIDS (an anion-transporter inhibitor) only slowed (-55%) the acid extrusion. Both in HEPES-buffered and CO₂/HCO₃-buffered system solution, the pH_i recovery after induced-intracellular alkalosis was entirely blocked by removing [Cl^-]_o. Western blot analysis showed the isoforms of pH_i regulators, including NHE1/2, NBCe1/n1, AE1/2/3/4 and CHE in the hDPSCs.

CONCLUSIONS

We demonstrate for the first time that resting pH_i is significantly higher than 7.2 and meditates functionally by two Na⁺-dependent acid extruders (NHE and NBC), two Cl^--dependent acid loaders (CHE and AE) and one Na⁺-independent acid extruder(s) in hDPSCs. These findings provide novel insight for basic and clinical treatment of dentistry.

miR-143 suppresses the osteogenic differentiation of dental pulp stem cells by inactivation of NF-κB signaling pathway via targeting TNF-α

BACKGROUND

Dental pulp stem cells (DPSCs) are multipotent and play an important role in repairing damaged and/or defective dentinogenesis/osteogenesis. Recent studies have documented the implication of miR-143 in osteogenic differentiation of DPSCs. Nevertheless, the detailed mechanisms of miR-143 involved in the osteogenic differentiation of DPSCs remain to be further elaborated.

METHODS

Isolated DPSCs were incubated with osteogenic differentiation medium to induce osteogenic differentiation. qRT-PCR and western blot were performed to determine the expressions of miR-143 and tumor necrosis factor α (TNF-α). Luciferase reporter assay was used to confirm whether TNF-α was a target of miR-143. Osteogenic differentiation of DPSCs was evaluated by alkaline phosphatase (ALP) activity assay, ALP staining, and western blot analyses of osteogenic-markers including bone morphogenetic protein 2 (BMP2), ALP, runt-related transcription factor 2 (RUNX2) and collagen type I (COLI).

RESULTS

miR-143 was downregulated and TNF-α was upregulated during osteogenic differentiation of DPSCs. miR-143 posttranscriptionally regulated TNF-α expression in DPSCs by binding to its 3'UTR. miR-143 overexpression suppressed osteogenic differentiation of DPSCs, as demonstrated by the decrease of ALP activity, ALP positive cell ratio, as well as BMP2, ALP, RUNX2, and COLI expressions. Moreover, miR-143 reversed TNF-α-induced osteogenic differentiation of DPSCs. Finally, the osteogenic differentiation of DPSCs induced by miR-143 inhibitor was attenuated following inactivation of nuclear factor kappa B (NF-κB) signaling pathway.

CONCLUSION

miR-143 suppressed the osteogenic differentiation of DPSCs by blockade of NF-κB signaling pathway via targeting TNF-α.