Comparison of stem-cell-mediated osteogenesis and dentinogenesis

Investigation of the Effects of Thymoquinone and Dental Pulp-Derived Mesenchymal Stem Cells on Tibial Bone Defect Models

The thymoquinone obtained from Nigella sativa increases osteoblastic activity and significantly reduces the number of osteoclasts, thereby accelerating bone healing. In addition, mesenchymal stem cells isolated from various tissues are considered a potential cell source for bone regenerative therapies. The aim of this study is to investigate the effectiveness of thymoquinone, a current and novel agent, in combination with mesenchymal stem cells derived from the dental pulp in promoting bone healing. In the study, 28 male Sprague Dawley rats were used. The rats were divided into 4 groups, each consisting of 7 rats: the control group (group 1) (n=7), thymoquinone group (group 2) (n=7), stem cell group (group 3) (n=7), stem cell+thymoquinone group (group 4) (n=7). A bone defect of 4 mm in diameter and 5 mm in length was created in the left tibial bones of all rats with a trephine bur. In group 1, no procedure was applied to the defect area. Group 2 was applied thymoquinone (10 mg/kg) with oral gavage. In group 3, stem cells were used locally to the defect area. In group 4, stem cells and thymoquinone (10 mg/kg) was applied to the defect area. All rats were killed on the 28th day of the experiment. Tibia tissues extracted during sacrifice were histomorphologically examined in a fixative solution. Significant differences were found in terms of new bone formation and osteoblastic activity values in the "thymoquinone" (P<0.05), "stem cell" (P<0.05), and "stem cell+thymoquinone" (P<0.05) groups compared to the "control" group. In addition, while there was no significant difference in the "thymoquinone" group compared to these stem cell+thymoquinone group in terms of osteoblastic activity (P>0.05), the difference in terms of new bone formation was found to be significantly lower. No significant differences among the other groups were observed in new bone formation and osteoblastic activity (P>0.05). According to the results of our study, stem cell+thymoquinone treatment for bone defects is not only more effective than thymoquinone or stem cell treatment alone but also induces greater development of bone trabeculae, contributes to the matrix and connective tissue formation, and increases the number of osteoblasts and osteocytes involved in bone formation.

Dual-signal readout sensing of ATP content in single dental pulp stem cells during differentiation via functionalized glass nanopipettes

Adenosine triphosphate (ATP) is regarded as the "energy currency" in living cells, so real-time quantification of content variation of intracellular ATP is highly desired for understanding some important physiological processes. Due to its single-molecule readout ability, nanopipette sensing has emerged as a powerful technique for molecular sensing. In this study, based on the effect of targeting-aptamer binding on ionic current, and fluorescence resonance energy transfer (FRET), we reported a dual-signal readout nanopipette sensing system for monitoring ATP content variation at the subcellular level. In the presence of ATP, the complementary DNA-modified gold nanoparticles (cDNAs-AuNPs) were released from the inner wall of the nanopipette, which leads to sensitive response variations in ionic current rectification and fluorescence intensity. The developed nanopipette sensor was capable of detecting ATP in single cells, and the fluctuation of ATP content in the differentiation of dental pulp stem cells (DPSCs) was further quantified with this method. The study provides a more reliable nanopipette sensing platform due to the introduction of fluorescence readout signals. Significantly, the study of energy fluctuation during cell differentiation from the perspective of energy metabolism is helpful for differentiation regulation and cell therapy.

Stem cells in clinical dentistry

BACKGROUND

Stem cells are present in most of the tissues in the craniofacial complex and play a major role in tissue homeostasis and repair. These cells are characterized by their capacity to differentiate into multiple cell types and to self-renew to maintain a stem cell pool throughout the life of the tissue.

TYPES OF STUDIES REVIEWED

The authors discuss original data from experiments and comparative analyses and review articles describing the identification and characterization of stem cells of the oral cavity.

RESULTS

Every oral tissue except enamel, dentin, and cementum contains stem cells for the entire life span. These stem cells self-renew to maintain a pool of cells that can be activated to replace terminally differentiated cells (for example, odontoblasts) or to enable wound healing (for example, dentin bridge in pulp exposures and healing of periodontal tissues after surgery). In addition, dental stem cells can differentiate into functional blood vessels and nerves. Initial clinical trials have shown that transplanting dental pulp stem cells into disinfected necrotic teeth has allowed for the recovery of tooth vitality and vertical and horizontal root growth in immature teeth with incomplete root formation.

PRACTICAL IMPLICATIONS

As a consequence of these groundbreaking discoveries, stem cell banks are now offering services for the cryopreservation of dental stem cells. The future use of stem cell-based therapies in the clinic will depend on the collaboration of clinicians and researchers in projects designed to understand whether these treatments are safe, efficacious, and clinically feasible.

Biomechanical Modulation of Dental Pulp Stem Cell (DPSC) Properties for Soft Tissue Engineering

Dental pulp regeneration strategies frequently result in hard tissue formation and pulp obliteration. The aim of this study was to investigate whether dental pulp stem cells (DPSCs) can be directed toward soft tissue differentiation by extracellular elasticity. STRO-1-positive human dental pulp cells were magnetically enriched and cultured on substrates with elasticities of 1.5, 15, and 28 kPa. The morphology of DPSCs was assessed visually. Proteins relevant in mechanobiology ACTB, ITGB1, FAK, p-FAK, TALIN, VINCULIN, PAXILLIN, ERK 1/2, and p-ERK 1/2 were detected by immunofluorescence imaging. Transcription of the pulp marker genes BMP2, BMP4, MMP2, MMP3, MMP13, FN1, and IGF2 as well as the cytokines ANGPT1, VEGF, CCL2, TGFB1, IL2, ANG, and CSF1 was determined using qPCR. A low stiffness, i.e., 1.5 kPa, resulted in a soft tissue-like phenotype and gene expression, whereas DPSCs on 28 kPa substrates exhibited a differentiation signature resembling hard tissues with a low cytokine expression. Conversely, the highest cytokine expression was observed in cells cultured on intermediate elasticity, i.e., 15 kPa, substrates possibly allowing the cells to act as “trophic mediators”. Our observations highlight the impact of biophysical cues for DPSC fate and enable the design of scaffold materials for clinical pulp regeneration that prevent hard tissue formation.

A Compilation of Study Models for Dental Pulp Regeneration

Efforts to heal damaged pulp tissue through tissue engineering have produced positive results in pilot trials. However, the differentiation between real regeneration and mere repair is not possible through clinical measures. Therefore, preclinical study models are still of great importance, both to gain insights into treatment outcomes on tissue and cell levels and to develop further concepts for dental pulp regeneration. This review aims at compiling information about different in vitro and in vivo ectopic, semiorthotopic, and orthotopic models. In this context, the differences between monolayer and three-dimensional cell cultures are discussed, a semiorthotopic transplantation model is introduced as an in vivo model for dental pulp regeneration, and finally, different animal models used for in vivo orthotopic investigations are presented.

Botanicals and Oral Stem Cell Mediated Regeneration: A Paradigm Shift from Artificial to Biological Replacement

Stem cells are a well-known autologous pluripotent cell source, having excellent potential to develop into specialized cells, such as brain, skin, and bone marrow cells. The oral cavity is reported to be a rich source of multiple types of oral stem cells, including the dental pulp, mucosal soft tissues, periodontal ligament, and apical papilla. Oral stem cells were useful for both the regeneration of soft tissue components in the dental pulp and mineralized structure regeneration, such as bone or dentin, and can be a viable substitute for traditionally used bone marrow stem cells. In recent years, several studies have reported that plant extracts or compounds promoted the proliferation, differentiation, and survival of different oral stem cells. This review is carried out by following the PRISMA guidelines and focusing mainly on the effects of bioactive compounds on oral stem cell-mediated dental, bone, and neural regeneration. It is observed that in recent years studies were mainly focused on the utilization of oral stem cell-mediated regeneration of bone or dental mesenchymal cells, however, the utility of bioactive compounds on oral stem cell-mediated regeneration requires additional assessment beyond in vitro and in vivo studies, and requires more randomized clinical trials and case studies.

Plumping up a Cushion of Human Biowaste in Regenerative Medicine: Novel Insights into a State-of-the-Art Reserve Arsenal

Major breakthroughs and disruptive methods in disease treatment today owe their thanks to our inch by inch developing conception of the infinitive aspects of medicine since the very beginning, among which, the role of the regenerative medicine can on no account be denied, a branch of medicine dedicated to either repairing or replacing the injured or diseased cells, organs, and tissues. A novel means to accomplish such a quest is what is being called “medical biowaste”, a large assortment of biological samples produced during a surgery session or as a result of physiological conditions and biological activities. The current paper accentuating several of a number of promising sources of biowaste together with their plausible applications in routine clinical practices and the confronting challenges aims at inspiring research on the existing gap between clinical and basic science to further extend our knowledge and understanding concerning the potential applications of medical biowaste.

An Up-To-Date Overview of Dental Tissue Regeneration Using Dental Origin Mesenchymal Stem Cells: Challenges and Road Ahead

Stem cells (SCs) research has experienced exponential growth in recent years. SC-based treatments can enhance the lives of people suffering from cardiac ischemia, Alzheimer’s disease, and regenerative drug conditions, like bone or loss of teeth. Numerous kinds of progenitor/SCs have been hypothesized to depend on their potential to regain and/or heal wounded tissue and partly recover organ function. Growing data suggest that SCs (SCs) are concentrated in functions and that particular tissues have more SCs. Dental tissues, in particular, are considered a significant cause of mesenchymal stem cells (MSCs) cells appropriate for tissue regeneration uses. Tissue regeneration and SCs biology have particular attention in dentistry because they may give a novel method for creating clinical material and/or tissue redevelopment. Dental pulp, dental papilla, periodontal ligament, and dental follicle contain mesenchymal SCs. Such SCs, which must be identified and cultivated in specific tissue culture environments, may be used in tissue engineering applications such as tooth tissue, nerve regeneration, and bone redevelopment. A new cause of SCs, induced pluripotent SCs, was successfully made from human somatic cells, enabling the generation of the patient and disease-specific SCs. The dental SC’s (DSCs) multipotency, rapid proliferation rate, and accessibility make it an ideal basis of MSC for tissue redevelopment. This article discusses current advances in tooth SC investigation and its possible application in tissue redevelopment.

Blockade of PD-L1/PD-1 signaling promotes osteo-/odontogenic differentiation through Ras activation

The programmed cell death ligand 1 (PD-L1) and its receptor programmed cell death 1 (PD-1) deliver inhibitory signals to regulate immunological tolerance during immune-mediated diseases. However, the role of PD-1 signaling and its blockade effect on human dental pulp stem cells (hDPSCs) differentiation into the osteo-/odontogenic lineage remain unknown. We show here that PD-L1 expression, but not PD-1, is downregulated during osteo-/odontogenic differentiation of hDPSCs. Importantly, PD-L1/PD-1 signaling has been shown to negatively regulate the osteo-/odontogenic differentiation of hDPSCs. Mechanistically, depletion of either PD-L1 or PD-1 expression increased ERK and AKT phosphorylation levels through the upregulation of Ras enzyme activity, which plays a pivotal role during hDPSCs osteo-/odontogenic differentiation. Treatment with nivolumab (a human anti-PD-1 monoclonal antibody), which targets PD-1 to prevent PD-L1 binding, successfully enhanced osteo-/odontogenic differentiation of hDPSCs through enhanced Ras activity-mediated phosphorylation of ERK and AKT. Our findings underscore that downregulation of PD-L1 expression accompanies during osteo-/odontogenic differentiation, and hDPSCs-intrinsic PD-1 signaling inhibits osteo-/odontogenic differentiation. These findings provide a significant basis that PD-1 blockade could be effective immunotherapeutic strategies in hDPSCs-mediated dental pulp regeneration.

Dental Pulp Stem Cell Heterogeneity: Finding Superior Quality "Needles" in a Dental Pulpal "Haystack" for Regenerative Medicine-Based Applications

Human dental pulp stem/stromal cells (hDPSCs) derived from the permanent secondary dentition are recognised to possess certain advantageous traits, which support their potential use as a viable source of mesenchymal stem/stromal cells (MSCs) for regenerative medicine-based applications. However, the well-established heterogeneous nature of hDPSC subpopulations, coupled with their limited numbers within dental pulp tissues, has impeded our understanding of hDPSC biology and the translation of sufficient quantities of these cells from laboratory research, through successful therapy development and clinical applications. This article reviews our current understanding of hDPSC biology and the evidence underpinning the molecular basis of their heterogeneity, which may be exploited to distinguish individual subpopulations with specific or superior characteristics for regenerative medicine applications. Pertinent unanswered questions which still remain, regarding the developmental origins, hierarchical organisation, and stem cell niche locations of hDPSC subpopulations and their roles in hDPSC heterogeneity and functions, will further be explored. Ultimately, a greater understanding of how key features, such as specific cell surface, senescence and other relevant genes, and protein and metabolic markers, delineate between hDPSC subpopulations with contrasting stemness, proliferative, multipotency, immunomodulatory, anti-inflammatory, and other relevant properties is required. Such knowledge advancements will undoubtedly lead to the development of novel screening, isolation, and purification strategies, permitting the routine and effective identification, enrichment, and expansion of more desirable hDPSC subpopulations for regenerative medicine-based applications. Furthermore, such innovative measures could lead to improved cell expansion, manufacture, and banking procedures, thereby supporting the translational development of hDPSC-based therapies in the future.

Platelet lysate functionalized gelatin methacrylate microspheres for improving angiogenesis in endodontic regeneration

Rapid angiogenesis is one of the challenges in endodontic regeneration. Recently, tailored polymeric microsphere system that loaded pro-angiogenic growth factors (GFs) is promising in facilitating vascularization in dental pulp regeneration. In addition, the synergistic effect of multiple GFs is considered more beneficial, but combination usage of them is rather complex and costly. Herein, we aimed to incorporate human platelet lysate (PL), a natural-derived pool of multiple GFs, into gelatin methacrylate (GelMA) microsphere system (GP), which was further modified by Laponite (GPL), a nanoclay with efficient drug delivery ability. These hybrid microspheres were successfully fabricated by electrostatic microdroplet technique with suitable size range (180∼380 µm). After incorporation of the PL and Laponite with GelMA, the Young's modulus of the hybrid hydrogel increased up to about 3-fold and the swelling and degradation rate decreased simultaneously. The PL-derived GFs continued to release up to 28 days from both the GP and GPL microspheres, while the latter released relatively more slowly. What's more, the released GFs could effectively induce tubule formation of human umbilical endothelial cells (HUVECs) and also promote human dental pulp stem cells (hDPSCs) migration. Additionally, the PL component in the GelMA microspheres significantly improved the proliferation, spreading, and odontogenic differentiation of the encapsulated hDPSCs. As further verified by the subcutaneous implantation results, both of the GP and GPL groups enhanced microvascular formation and pulp-like tissue regeneration. This work demonstrated that PL-incorporating GelMA microsphere system was a promising functional vehicle for promoting vascularized endodontic regeneration. STATEMENT OF SIGNIFICANCE: Polymeric microsphere system loaded with pro-angiogenic growth factors (GFs) shows great promise for regeneration of vascularized dental pulp. Herein, we prepared a functional GelMA microsphere system incorporated with human platelet lysates (PL) and nanoclay Laponite by the electrostatic microdroplet method. The results demonstrated that the GelMA/PL/Laponite microspheres significantly improved the spreading, proliferation, and odontogenic differentiation of the encapsulated hDPSCs compared with pure GelMA microspheres. Moreover, they also enhanced microvascular formation and pulp-like tissue regeneration in vivo. This hybrid microsphere system has great potential to accelerate microvessel formation in regenerated dental pulp and other tissues.

Challenge Tooth Regeneration in Adult Dogs with Dental Pulp Stem Cells on 3D-Printed Hydroxyapatite/Polylactic Acid Scaffolds

Tooth regeneration is an important issue. The purpose of this study was to explore the feasibility of using adult dental pulp stem cells on polylactic acid scaffolds for tooth regeneration. Three teeth were extracted from each side of the lower jaws of two adult dogs. In the experimental group, dental pulp stem cells were isolated and seeded in the 3D-printed hydroxyapatite/polylactic acid (HA/PLA) scaffolds for transplantation into left lower jaw of each dog. The right-side jaw of each dog was transplanted with cell-free scaffolds as the control group. Polychrome sequentially labeling was performed for observation of mineralization. Dental cone beam computed tomography (CBCT) irradiation was used for assessment. Nine months after surgery, dogs were euthanized, and the lower jaws of dogs were sectioned and fixed for histological observation with hematoxylin and eosin staining. The results showed that the degree of mineralization in the experimental group with cells seeded in the scaffolds was significantly higher than that of the control group transplanted with cell-free scaffolds. However, the HA/PLA scaffolds were not completely absorbed in both groups. It is concluded that dental pulp stem cells are important for the mineralization of tooth regeneration. A more rapid absorbable material was required for scaffold design for tooth regeneration.

Comparative Analysis of Dental Pulp and Periodontal Stem Cells: Differences in Morphology, Functionality, Osteogenic Differentiation and Proteome

Dental stem cells are heterogeneous in their properties. Despite their common origin from neural crest stem cells, they have different functional capacities and biological functions due to niche influence. In this study, we assessed the differences between dental pulp stem cells (DPSC) and periodontal ligament stem cells (PDLSC) in their pluripotency and neuroepithelial markers transcription, morphological and functional features, osteoblast/odontoblast differentiation and proteomic profile during osteogenic differentiation. The data were collected in paired observations: two cell cultures, DPSC and PDLSC, were obtained from each donor. Both populations had the mesenchymal stem cells surface marker set exposed on their membranes but differed in Nestin (a marker of neuroectodermal origin) expression, morphology, and proliferation rate. OCT4 mRNA was revealed in DPSC and PDLSC, while OCT4 protein was present in the nuclei of DPSC only. However, transcription of OCT4 mRNA was 1000-10,000-fold lower in dental stem cells than in blastocysts. DPSC proliferated at a slower rate and have a shape closer to polygonal but they responded better to osteogenic stimuli as compared to PDLSC. RUNX2 mRNA was detected by qPCR in both types of dental stem cells but RUNX2 protein was detected by LC-MS/MS shotgun proteomics only in PDLSC suggesting the posttranscriptional regulation. DSPP and DMP1, marker genes of odontoblastic type of osteogenic differentiation, were transcribed in DPSC but not in PDLSC samples. Our results prove that DPSC and PDLSC are different in their biology and therapeutic potential: DPSC are a good candidate for osteogenic or odontogenic bone-replacement cell-seeded medicines, while fast proliferating PDLSC are a prospective candidate for other cell products.

In Vivo Evaluation of Decellularized Human Tooth Scaffold for Dental Tissue Regeneration

Conventional root canal treatment may result in loss of tooth vitality, which can lead to unfavorable treatment outcomes. Notably, a ceased tooth development of immature permanent teeth with open apices, regeneration of periodontal ligaments (PDL), and pulp is highly expected healing process. For regeneration, the scaffold is one of the critical components that carry biological benefits. Therefore, this study evaluated a decellularized human tooth as a scaffold for the PDL and pulp tissue regeneration. A tooth scaffold was fabricated using an effective decellularization method as reported in previous studies. PDL stem cells (PDLSCs) and dental pulp stem cells (DPSCs) obtained from human permanent teeth were inoculated onto decellularized scaffolds, then cultured to transplant into immunosuppressed mouse. After 9 weeks, PDLSCs and DPSCs that were inoculated onto decellularized tooth scaffolds and cultured in an in vivo demonstrated successful differentiation. In PDLSCs, a regeneration of the cementum/PDL complex could be expected. In DPSCs, the expression of genes related to revascularization and the hard tissue regeneration showed the possibility of pulp regeneration. This study suggested that the potential possible application of decellularized human tooth could be a scaffold in regeneration PDL and pulp tissue along with PDLSCs and DPSCs, respectively, as a novel treatment method.

The self-renewal dental pulp stem cell microtissues challenged by a toxic dental monomer

Dental pulp stem cells (DPSCs) regenerate injured/diseased pulp tissue and deposit tertiary dentin. DPSCs stress response can be activated by exposing cells to the monomer triethyleneglycol dimethacrylate (TEGDMA) and inducing the DNA-damage inducible transcript 4 (DDIT4) protein expression. The goal of the present study was to determine the impact of TEGDMA on the ability of DPSCs to maintain their self-renewal capabilities, develop and preserve their 3D structures and deposit the mineral. Human primary and immortalized DPSCs were cultured in extracellular matrix/basement membrane (ECM/BM) to support stemness and to create multicellular interacting layers (microtissues). The microtissues were exposed to the toxic concentrations of TEGDMA (0.5 and 1.5 mmol/l). The DPSCs spatial architecture was assessed by confocal microscopy. Mineral deposition was detected by alizarin red staining and visualized by stereoscopy. Cellular self-renewal transcription factor SOX2 was determined by immunocytochemistry. The microtissue thicknesses/vertical growth, surface area of the mineralizing microtissues, the percentage of area covered by the deposited mineral, and the fluorescence intensity of the immunostained cells were quantified ImageJ. DDIT4 expression was determined by a single molecule RNA-FISH technique and the cell phenotype was determined morphologically. DDIT4 expression was correlated with the cytotoxic phenotype. TEGDMA affected the structures of developing and mature microtissues. It inhibited the deposition of the mineral in the matrix while not affecting the SOX2 expression. Our data demonstrate that DPSCs retained their self-renewal capacity although their other functions were impeded. Since the DPSCs pool remained preserved, properties effected by the irritant should be restored by a proper rescue therapy.

The Potential of Mesenchymal Stromal Cells in Neuroblastoma Therapy for Delivery of Anti-Cancer Agents and Hematopoietic Recovery

Neuroblastoma is one of the most common pediatric cancers and a major cause of cancer-related death in infancy. Conventional therapies including high-dose chemotherapy, stem cell transplantation, and immunotherapy approach a limit in the treatment of high-risk neuroblastoma and prevention of relapse. In the last two decades, research unraveled a potential use of mesenchymal stromal cells in tumor therapy, as tumor-selective delivery vehicles for therapeutic compounds and oncolytic viruses and by means of supporting hematopoietic stem cell transplantation. Based on pre-clinical and clinical advances in neuroblastoma and other malignancies, we assess both the strong potential and the associated risks of using mesenchymal stromal cells in the therapy for neuroblastoma. Furthermore, we examine feasibility and safety aspects and discuss future directions for harnessing the advantageous properties of mesenchymal stromal cells for the advancement of therapy success.

Reconstruction of parietal bone defects with adiposederived mesenchymal stem cells. Experimental study

Purpose:

This study assessed the regeneration potential of mesenchymal stem cells (MSC) from adipose tissue associated with platelet-rich plasma (PRP) in bone regeneration.

Methods:

Thirty Wistar rats (Rattus norvegicus albinos) were divided into five groups (according to the grafting material and time to euthanasia): (1) autograft - 14 days (control), (2) autograft - 28 days (control), (3) MSC + PRP - 14 days, (4) MSC + PRP + papaverine - 14 days and (5) MSC + PRP + papaverine - 28 days. After euthanasia, the graft was removed and histological slides were prepared. They were assessed by a blinded pathologist using a previously published histological scale as parameter.

Results:

There was some degree of neoformed bone trabeculae (NBT) in 93.3% of the samples, as well as osteoblastic activity (OA). The autograft groups (14 and 28 days) had higher levels in the formation of bone trabeculae. Nonparametric data were analyzed using the Wilcoxon-Mann-Whitney test and proved not to be statistically significant at p < 0.05.

Conclusions:

Experimental parietal bone reconstruction, combining MSC, PRP and papaverine presented regeneration in all groups with no significant difference among them.

Advances of nanomaterial applications in oral and maxillofacial tissue regeneration and disease treatment

Using bioactive nanomaterials in clinical treatment has been widely aroused. Nanomaterials provide substantial improvements in the prevention and treatment of oral and maxillofacial diseases. This review aims to discuss new progresses in nanomaterials applied to oral and maxillofacial tissue regeneration and disease treatment, focusing on the use of nanomaterials in improving the quality of oral and maxillofacial healthcare, and discuss the perspectives of research in this arena. Details are provided on the tissue regeneration, wound healing, angiogenesis, remineralization, antitumor, and antibacterial regulation properties of nanomaterials including polymers, micelles, dendrimers, liposomes, nanocapsules, nanoparticles and nanostructured scaffolds, etc. Clinical applications of nanomaterials as nanocomposites, dental implants, mouthwashes, biomimetic dental materials, and factors that may interact with nanomaterials behaviors and bioactivities in oral cavity are addressed as well. In the last section, the clinical safety concerns of their usage as dental materials are updated, and the key knowledge gaps for future research with some recommendation are discussed. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement.

Effects of p-Cresol on Senescence, Survival, Inflammation, and Odontoblast Differentiation in Canine Dental Pulp Stem Cells

Aging, defined by a decrease in the physical and functional integrity of the tissues, leads to age-associated degenerative diseases. There is a relation between aged dental pulp and the senescence of dental pulp stem cells (DPSCs). Therefore, it is important to investigate the molecular processes underlying the senescence of DPSCs to elucidate the dental pulp aging mechanisms. p-Cresol (PC), a uremic toxin, is strongly related to cellular senescence. Here, age-related phenotypic changes including senescence, apoptosis, inflammation, and declining odontoblast differentiation in PC-treated canine DPSCs were investigated. Under the PC condition, cellular senescence was induced by decreased proliferation capacity and increased cell size, senescence-associated β-galactosidase (SA-β-gal) activity, and senescence markers p21, IL-1β, IL-8, and p53. Exposure to PC could stimulate inflammation by the increased expression of IL-6 and cause the distraction of the cell cycle by the increased level of Bax protein and decreased Bcl-2. The levels of odontoblast differentiation markers, dentin sialophosphoprotein (DSPP), dentin matrix protein 1, and osterix, were decreased. Consistent with those findings, the alizarin red staining, alkaline phosphatase, and DSPP protein level were decreased during the odontoblast differentiation process. Taken together, these findings indicate that PC could induce cellular senescence in DPSCs, which may demonstrate the changes in aging dental pulp.

TiO2 nanoparticles synergize with substrate mechanics to improve dental pulp stem cells proliferation and differentiation

Multiple studies exist on the influence of TiO₂ nanoparticle uptake on cell behavior. Yet little is known about the lingering influence of nanoparticles accumulation within the external environment which is particularly important to stem cell differentiation. Herein, dental pulp stem cells were cultured on hard and soft polybutadiene substrates, where 0.1 mg/mL rutile TiO₂ nanoparticles were introduced once, 24 h after plating. In the absence of TiO₂, the doubling time on soft substrate is significantly longer, while addition of TiO₂ decreases it to the same level as on the hard substrate. FACS analysis indicates particle uptake initially at 25% is reduced to 2.5% after 14 days. In the absence of TiO₂, no biomineralization on the soft and snowflake-like hydroxyapatite deposits on the hard substrate are shown at week 4. With the addition of TiO₂, SEM/EDAX reveals copious mineral deposition templated on large banded collagen fibers on both substrates. The mineral-to-matrix ratios analyzed by Raman spectroscopy are unremarkable in the absence of TiO₂. However, with addition of TiO₂, the ratios are consistent with native bone on the hard and dentin on the soft substrates. This is further confirmed by RT-PCR, which showed upregulation of markers consistent with osteogenesis and odontogenesis, respectively.

Behaviour of human dental pulp stem cell in high glucose condition: impact on proliferation and osteogenic differentiation

OBJECTIVE

The aim of this study is to investigate the changes of human dental pulp stem cell (hDPSC) viability, proliferation and osteogenic differentiation in high glucose condition.

DESIGN

After 21 days of culture in low (5.5 mM) and high (20 mM) glucose medium, hDPSC viability and proliferation were assessed with respectively the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Hoechst assays. To investigate the influence of glucose on osteogenic differentiation hDPSCs were cultured for 28 days in low or high glucose medium with osteoinductive cocktail. Mineralization was examined by alizarin red staining/quantification and the expression of osteogenic-related genes [Runt-related transcription factor 2 (RUNX2), Osteocalcin (OCN), Collagen 1A1 (COL1A1)] analyzed by RT-qPCR.

RESULTS

We observed no significant difference (p >  0.05) on hDPSC proliferation or cell viability between low or high glucose groups. We did not highlight a significant difference after alizarin red staining and quantification between hDPSCs cultured with high or low glucose concentration in the culture medium. In the same manner, high glucose concentration did not appear to modify osteogenic gene expression: there was no significant difference in osteogenic-related gene expression between high or low glucose groups.

CONCLUSION

Proliferation, viability, and osteogenic differentiation of hDPSCs were not changed by high glucose environment.

Insight into the Role of Dental Pulp Stem Cells in Regenerative Therapy

Mesenchymal stem cells (MSCs) have the capacity for self-renewal and multilineage differentiation potential, and are considered a promising cell population for cell-based therapy and tissue regeneration. MSCs are isolated from various organs including dental pulp, which originates from cranial neural crest-derived ectomesenchyme. Recently, dental pulp stem cells (DPSCs) and stem cells from human exfoliated deciduous teeth (SHEDs) have been isolated from dental pulp tissue of adult permanent teeth and deciduous teeth, respectively. Because of their MSC-like characteristics such as high growth capacity, multipotency, expression of MSC-related markers, and immunomodulatory effects, they are suggested to be an important cell source for tissue regeneration. Here, we review the features of these cells, their potential to regenerate damaged tissues, and the recently acquired understanding of their potential for clinical application in regenerative medicine.

Electrical Stimulation Decreases Dental Pulp Stem Cell Osteo-/Odontogenic Differentiation

Dental pulp stem cells (DPSCs) have great potential for use in tissue engineering (TE)-based dental treatments. Electrical stimulation (EStim) has been shown to influence cellular functions that could play an important role in the success of TE treatments. Despite many recent studies focused on DPSCs, few have investigated the effect EStim has on these cells. The aim of this research was to investigate the effects of direct current (DC) EStim on osteo-/odontogenic differentiation of DPSCs. To do so cells were isolated from male Sprague Dawley rats (7-8 weeks old), and phenotype characterization and multilineage differentiation analysis were conducted to verify their "stemness." Different voltages of DC EStim were administrated 1 h/day for 7 days, and the effect of EStim on DPSC osteo-/odontogenic differentiation was assessed by measuring calcium and collagen deposition, alkaline phosphatase (ALP) activity, and expression of osteo- and odontogenic marker genes at days 7 and 14 of culture. We found that while 10 and 50 mV/mm of EStim had no effect on cell number or metabolic activity, 100 mV/mm caused a significant reduction in cell number, and 150 mV/mm resulted in cell death. Despite increased gene expression of osteo-/odontogenic gene markers, Osteocalcin, RunX2, BSP, and DMP1, at day 7 in EStim treated cells, 50 mV/mm of EStim decreased collagen deposition and ALP activity at both time points, and calcium deposition was found to be lower at day 14. In conclusion, under the conditions tested, EStim appears to impair DPSC osteo-/odontogenic differentiation. Additional studies are needed to further characterize and understand the mechanisms involved in DPSC response to EStim, with an eye toward its potential use in TE-based dental treatments.

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

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

Concanavalin A Enhanced Proliferation and Osteogenic Differentiation of Dental Pulp Stem Cells

Objective  Dental pulp stem cells (DPSCs) can be used as a component in the formation of regenerative dentine during direct pulp capping therapy. Concanavalin A (ConA) is a type of lectin with a molecular weight of 26 kDa derived from the Canavalia ensiformis plant. Lectins possess strong proliferation and differentiation abilities in various animal cells including lymphocytes, osteoblasts, and chondrocytes. The aim of study was to determine the effect of ConA on the proliferation and osteogenic differentiation of DPSCs in vitro .

Materials and Methods  In this in vitro study, DPSCs were isolated from third molars before ConA induction was performed at concentrations of 5 and 10 μg/mL. The proliferation assay was determined by 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. Osteogenic differentiation was determined by means of mineralization.

Statistical Analysis  Data were analyzed using analysis of variance and a Student’s t -test. The p -value was set at 0.05.

Results  The addition of 5 and 10 µg/mL of ConA to DPSCs can significantly increase the proliferation and osteogenic differentiation of DPSCs ( p ≤0.05).

Conclusion  ConA can increase the proliferation and osteogenic differentiation of DPSCs.

Comparative Secretome Analysis of Mesenchymal Stem Cells From Dental Apical Papilla and Bone Marrow During Early Odonto/Osteogenic Differentiation: Potential Role of Transforming Growth Factor-β2

To understand the functions of secretory proteins in odontogenesis and to further the understanding of the different molecular events during odontogenesis and osteogenesis, we induced the odonto/osteogenic differentiation of stem cells from dental apical papilla (SCAPs) and bone marrow-derived stem cells (BMSCs) in vitro and compared the expression of secretory proteins during early odonto/osteogenic differentiation using high-performance liquid chromatography with tandem mass spectrometry. The results revealed significant changes by at least 50% in 139 SCAP proteins and 203 BMSC proteins during differentiation. Of these, 92 were significantly upregulated and 47 were significantly downregulated during the differentiation of SCAPs. Most of these proteins showed the same trend during the differentiation of BMSCs. Among the proteins that showed significantly changes during the differentiation of SCAPs and BMSCs, we found that transforming growth factor-β2 (TGFβ2) is a key protein in the network with powerful mediation ability. TGFβ2 was secreted more by SCAPs than BMSCs, was significantly upregulated during the differentiation of SCAPs and was significantly downregulated during the differentiation of BMSCs. Furthermore, the effects of recombinant human TGFβ2 and TGFβ1 on the odonto/osteogenic differentiation of SCAPs and BMSCs were investigated. Real-time reverse transcription polymerase chain reaction (RT-PCR) and western blotting data revealed that TGFβ2 enhanced the odontogenic-related markers [dentin sialophosphoprotein (DSPP), dentin matrix protein 1 (DMP1)] and inhibited the osteogenic-related marker bone sialoprotein (BSP) in SCAPs, whereas TGFβ1 enhanced the BSP expression and inhibited the DSPP and DMP1 expression at early odonto/osteogenic differentiation of SCAPs. However, in BMSCs, TGFβ2 enhanced the expression of alkaline phosphatase (ALP), runt-related transcription factor 2 (RUNX2), DSPP, and DMP1, whereas TGFβ1 enhanced the expression of ALP and RUNX2, with no significant intergroup difference of DSPP at the early odonto/osteogenic differentiation of BMSCs. TGFβ2 is a potentially important molecule with a distinct function in the regulation of odontogenesis and osteogenesis.

Molecular Profiling of Dental Pulp Stem Cells during Cell Differentiation by Surface Enhanced Raman Spectroscopy

Dental pulp stem cells (DPSCs) are considered one of the key cells in tooth regeneration engineering. Understanding molecular biological information on DPSCs during differentiation is of great significance for the construction of tissue-engineered teeth. In this study, we investigated the differentiation process of DPSCs stimulated by drugs and gained molecular insights in the process. By using label-free and noninvasive surface enhanced Raman spectroscopy (SERS) to monitor molecular change profiling in the cell nucleus of single DPSCs during the differentiation process, we found that two pivotal differentiation biomarkers, alkaline phosphatase (ALP) and dentin sialophosphoprotein (DSPP), were overexpressed during the process. Continuous and intermittent monitoring of SERS spectra from the nuclear region indicated that the expression of proteins and related amino acids of tryptophan were markedly increased until peak period of differentiation (on day 14). Meanwhile corresponding transformation of DNA/RNA backbone vibrational modes was also observed during the differentiation process, indicating the occurrence of replication or transcription of DNA. The method provides a useful tool for the molecular biology studies of DPSCs differentiation, and the finding will broaden our understanding of DPSCs differentiation.

Dental Pulp Stem Cells: Advances to Applications

Dental pulp stem cells (DPSCs) have a high capacity for differentiation and the ability to regenerate a dentin/pulp-like complex. Numerous studies have provided evidence of DPSCs’ differentiation capacity, such as in neurogenesis, adipogenesis, osteogenesis, chondrogenesis, angiogenesis, and dentinogenesis. The molecular mechanisms and functions of DPSCs’ differentiation process are affected by growth factors and scaffolds. For example, growth factors such as basic fibroblast growth factor (bFGF), transforming growth factor-β (TGF-β), nerve growth factor (NGF), platelet-derived growth factor (PDGF), and bone morphogenic proteins (BMPs) influence DPSC fate, including in differentiation, cell proliferation, and wound healing. In addition, several types of scaffolds, such as collagen, hydrogel, decellularized bioscaffold, and nanofibrous spongy microspheres, have been used to characterize DPSC cellular attachment, migration, proliferation, differentiation, and functions. An appropriate combination of growth factors and scaffolds can enhance the differentiation capacity of DPSCs, in terms of optimizing not only dental-related expression but also dental pulp morphology. For a cell-based clinical approach, focus has been placed on the tissue engineering triad [cells/bioactive molecules (growth factors)/scaffolds] to characterize DPSCs. It is clear that a deep understanding of the mechanisms of stem cells, including their aging, self-renewal, microenvironmental homeostasis, and differentiation correlated with cell activity, the energy for which is provided from mitochondria, should provide new approaches for DPSC research and therapeutics. Mitochondrial functions and dynamics are related to the direction of stem cell differentiation, including glycolysis, oxidative phosphorylation, mitochondrial metabolism, mitochondrial transcription factor A (TFAM), mitochondrial elongation, and mitochondrial fusion and fission proteins. This review summarizes the effects of major growth factors and scaffolds for regenerating dentin/pulp-like complexes, as well as elucidating mitochondrial properties of DPSCs for the development of advanced applications research.

WITHDRAWN: Overexpression of GLI2 induces odontogenic differentiation in human dental pulp stem cells through activation of the Wnt/β-catenin signaling pathway

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

3D cellular visualization of intact mouse tooth using optical clearing without decalcification

Dental pulp is composed of nerves, blood vessels, and various types of cells and surrounded by a thick and hard enamel-dentin matrix. Due to its importance in the maintenance of tooth vitality, there have been intensive efforts to analyze the complex cellular-level organization of the dental pulp in teeth. Although conventional histologic analysis has provided microscopic images of the dental pulp, 3-dimensional (3D) cellular-level visualization of the whole dental pulp in an intact tooth has remained a technically challenging task. This is mainly due to the inevitable disruption and loss of microscopic structural features during the process of mechanical sectioning required for the preparation of the tooth sample for histological observation. To accomplish 3D microscopic observation of thick intact tissue, various optical clearing techniques have been developed mostly for soft tissue, and their application for hard tissues such as bone and teeth has only recently started to be investigated. In this work, we established a simple and rapid optical clearing technique for intact mouse teeth without the time-consuming process of decalcification. We achieved 3D cellular-level visualization of the microvasculature and various immune cell distributions in the whole dental pulp of mouse teeth under normal and pathologic conditions. This technique could be used to enable diverse research methods on tooth development and regeneration by providing 3D visualization of various pulpal cells in intact mouse teeth.

The Therapeutic Potential of Mesenchymal Stem Cell-Derived Exosomes in Treatment of Neurodegenerative Diseases. Mol Neurobiol. 2019;56:8157-8167. [PMID: 31197655 DOI: 10.1007/s12035-019-01663-0]

Neurologic complications are commonly regarded as irreversible impairments that stem from limited potential of regeneration of the central nervous system (CNS). On the other side, the regenerative potential of stem cells has been evaluated in basic research, as well as in preclinical studies. Mesenchymal stem cells (MSCs) have been regarded as candidate cell sources for therapeutic purposes of various neurological disorders, because of their self-renewal ability, plasticity in differentiation, neurotrophic characteristics, and immunomodulatory properties. Exosomes are extracellular vesicles which can deliver biological information over long distances and thereby influencing normal and abnormal processes in cells and tissues. The therapeutic capacity of exosomes relies on the type of cell, as well as on the physiological condition of a given cell. Therefore, based on tissue type and physiological condition of CNS, exosomes may function as contributors or suppressors of pathological conditions in this tissue. When it comes to the therapeutic viewpoint, the most promising cellular source of exosomes is considered to be MSCs. The aim of this review article is to discuss the current knowledge around the potential of stem cells and MSC-derived exosomes in the treatment of neurodegenerative diseases.

Regulating substrate mechanics to achieve odontogenic differentiation for dental pulp stem cells on TiO2 filled and unfilled polyisoprene

We have shown that materials other than hydrogels commonly used in tissue engineering can be effective in enabling differentiation of dental pulp stem cells (DPSC). Here we demonstrate that a hydrophobic elastomer, polyisoprene (PI), a component of Gutta-percha, normally used to obturate the tooth canal, can also be used to initiate differentiation of the pulp. We showed that PI substrates without additional coating promote cell adhesion and differentiation, while their moduli can be easily adjusted either by varying the coating thickness or incorporation of inorganic particles. DPSC plated on those PI substrates were shown, using SPM and hysitron indentation, to adjust their moduli to conform to differentially small changes in the substrate modulus. In addition, optical tweezers were used to separately measure the membrane and cytoplasm moduli of DPSC, with and without Rho kinase inhibitor. The results indicated that the changes in modulus were attributed predominantly to changes within the cytoplasm, rather than the cell membrane. CLSM was used to identify cell morphology. Differentiation, as determined by qRT-PCR, of the upregulation of OCN, and COL1α1 as well as biomineralization, characterized by SEM/EDAX, was observed on hard PI substrates in the absence of induction factors, i.e. dexamethasone, with moduli 3-4 MPa, regardless of preparation. SEM showed that even though biomineralization was deposited on both spun cast thin PI and filled thick PI substrates, the minerals were aggregated into large clusters on thin PI, and uniformly distributed on filled thick PI, where it was templated within banded collagen fibers. STATEMENT OF SIGNIFICANCE: This manuscript demonstrates the potential of polyisoprene (PI), an elastomeric polymer, for use in tissue engineering. We show how dental pulp stem cells adjust their moduli continuously to match infinitesimally small changes in substrate mechanics, till a critical threshold is reached when they will differentiate. The lineage of differentiation then becomes a sensitive function of both mechanics and morphology for a given chemical composition. Since PI is a major component of Gutta-percha, the FDA approved material commonly used for obturating the root canal, this work suggests that it can easily be adapted for in vivo use in dental regeneration.

The influence of roughness on stem cell differentiation using 3D printed polylactic acid scaffolds

With the increase in popularity of 3D printing, an important question arises as to the equivalence between devices manufactured by standard methods vs. those presenting with identical bulk specifications, but manufactured via fused deposition modeling (FDM) printing. Using thermal imaging in conjunction with electron and atomic force microscopy, we demonstrate that large thermal gradients, whose distribution is difficult to predict, are associated with FDM printing and result in incomplete fusion and sharkskin of the printing filament. Even though these features are micro or submicron scale, and hence may not interfere with the intended function of the device, they can have a profound influence if the device comes in contact with living tissue. Dental pulp stem cells were cultured on substrates of identical dimensions, which were either printed or molded from the same PLA stock material. The cultures exhibited significant differences in plating efficiency, migration trajectory, and morphology at early times stemming from attempts by the cells to minimize cytoplasm deformation as they attempt to adhere on the printed surfaces. Even though biomineralization without dexamethasone induction was observed in all cultures at later times, different gene expression patterns were observed on the two surfaces. (Osteogenic markers were upregulated on molded substrates, while odontogenic markers were upregulated on the FDM printed surfaces.) Our results clearly indicate that the method of manufacturing is an important consideration in comparing devices, which come in contact with living tissues.

Dental pulp stem cells overexpressing stromal-derived factor-1α and vascular endothelial growth factor in dental pulp regeneration

OBJECTIVES

The current study aimed to investigate the effects of vascular endothelial growth factor (VEGF) and stromal cell-derived factor-1α (SDF-1α) overexpressing dental pulp stem cells (DPSCs) in vascularized dental pulp regeneration in vivo.

MATERIALS AND METHODS

Human DPSCs were transfected with VEGF or SDF-1α using premade lentiviral particles. Overexpression was verified by quantitative polymerase chain reaction (q-PCR), enzyme-linked immunosorbent assay (ELISA), and western blot analysis. Effects of SDF-1α and VEGF overexpressing DPSCs on their proliferation (CCK-8 and MTT assays) and endothelial vascular-tube formation (Matrigel assay) were investigated in vitro. Human tooth roots sectioned into 6-mm segments were injected with gene-modified DPSCs encapsulated in PuraMatrix hydrogel and implanted in the dorsum of severe-combined-immunodeficient (SCID) mice. Implants were retrieved after 4 weeks and examined for regenerated pulp-like tissue and vascularization using histology and immunohistochemistry. p < 0.05 was considered statistically significant.

RESULTS

Gene-modified DPSCs expressed significantly high levels (p < 0.05) of SDF-1α and VEGF mRNA and proteins, respectively. Transfected DPSCs showed a significantly higher cell proliferation compared to that of wild-type DPSCs. Furthermore, they enhanced endothelial cell migration and vascular-tube formation on Matrigel in vitro. When injected into tooth root canals and implanted in vivo, DPSCs/SDF-1α + DPSCs/VEGF-mixed group resulted in significantly increased length of regenerated pulp-like tissue within the root canals compared to that of wild-type DPSCs/VEGF and DPSCs/SDF-1α groups. Vessel area density was significantly higher in DPSCs/SDF-1α and mixed DPSCs/SDF-1α + DPSCs/VEGF groups than in DPSCs-VEGF alone or wild-type DPSCs groups.

CONCLUSION

A combination of VEGF-overexpressing and SDF-1α-overexpressing DPSCs could enhance the area of vascularized dental pulp regeneration in vivo.

CLINICAL RELEVANCE

Enhancing vascularization in pulp regeneration is crucial to overcome the clinical limitation of the limited blood supply to the root canals via a small apical foramen enclosed by hard dentin.

Current and future options for dental pulp therapy

Dental pulp is a connective tissue and has functions that include initiative, formative, protective, nutritive, and reparative activities. However, it has relatively low compliance, because it is enclosed in hard tissue. Its low compliance against damage, such as dental caries, results in the frequent removal of dental pulp during endodontic therapy. Loss of dental pulp frequently leads to fragility of the tooth, and eventually, a deterioration in the patient’s quality of life. With the development of biomaterials such as bioceramics and advances in pulp biology such as the identification of dental pulp stem cells, novel ideas for the preservation of dental pulp, the regenerative therapy of dental pulp, and new biomaterials for direct pulp capping have now been proposed. Therapies for dental pulp are classified into three categories; direct pulp capping, vital pulp amputation, and treatment for non-vital teeth. In this review, we discuss current and future treatment options in these therapies.

Mesenchymal Stem Cells and Their Role in Dental Medicine

Mesenchymal stem cells (MSCs) have been discovered in almost every organ and tissue. MSCs are a heterogeneous population of cells with the capacity to self-renew and show multilineage differentiation. MSCs possess immunomodulatory properties by regulating multiple types of immune cells. They are emerging as a promising therapeutic agent, and have been widely used for cell-based tissue regeneration and immune therapies. A further understanding of the biological characteristics of MSCs is a prerequisite to develop more efficient MSC-based therapies. This article reviews the current understanding of different MSC populations in orofacial tissue compared with those derived from bone marrow.

Use of 0.4-Tesla static magnetic field to promote reparative dentine formation of dental pulp stem cells through activation of p38 MAPK signalling pathway

AIM

To investigate whether static magnetic fields (SMFs) have a positive effect on the migration and dentinogenesis of dental pulp stem cells (DPSCs) to promote reparative dentine formation.

METHODOLOGY

In vitro scratch assays and a traumatic pulp exposure model were performed to evaluate the effect of 0.4-Tesla (T) SMF on DPSC migration. The cytoskeletons of the DPSCs were identified by fluorescence immunostaining and compared with those of a sham-exposed group. Dentinogenic evaluation was performed by analysing the expressions of DMP-1 and DSPP marker genes using a quantitative real-time polymerase chain reaction (qRT-PCR) process. Furthermore, the formation of calcified deposits was examined by staining the dentinogenic DPSCs with Alizarin Red S dye. Finally, the role played by the p38 MAPK signalling pathway in the migration and dentinogenesis of DPSCs under 0.4-T SMF was investigated by incorporating p38 inhibitor (SB203580) into the in vitro DPSC experiments. The Student's t-test and the Kruskal-Wallis test followed by Dunn's post hoc test with a significance level of P < 0.05 were used for statistical analysis.

RESULTS

The scratch assay results revealed that the application of 0.4-T SMF enhanced DPSCs migration towards the scratch wound (P < 0.05). The cytoskeletons of the SMF-treated DPSCs were found to be aligned perpendicular to the scratch wound. After 20 days of culture, the SMF-treated group had a greater number of out-grown cells than the sham-exposed group (nonmagnetized control). For the SMF-treated group, the DMP-1 (P < 0.05) and DSPP genes (P < 0.05), analysed by qRT-PCR, exhibited a higher expression. The distribution of calcified nodules was also found to be denser in the SMF-treated group when stained with Alizarin Red S dye (P < 0.05). Given the incorporation of p38 inhibitor SB203580 into the DPSCs, cell migration and dentinogenesis were suppressed. No difference was found between the SMF-treated and sham-exposed cells (P > 0.05).

CONCLUSION

0.4-T SMF enhanced DPSC migration and dentinogenesis through the activation of the p38 MAPK-related pathway.

Endothelial cells and endothelin‑1 promote the odontogenic differentiation of dental pulp stem cells

It has been established that dental pulp stem cells (DPSCs) serve an important role in the restoration and regeneration of dental tissues. DPSCs are present in blood vessels and also exist in the vessel microenvironment in vivo and have a close association with endothelial cells (ECs). The present study aimed to evaluate the influence of ECs and their secretory product endothelin-1 (ET-1) on the differentiation of DPSCs. In the present study, cells were divided into four groups: i) a DPSC-only control group; ii) a DPSC with ET-1 administration group; iii) a DPSC and human umbilical vein endothelial cell (HUVEC) direct co-culture group; and iv) a DPSC and HUVEC indirect co-culture group using a Transwell system. Reverse transcription-quantitative polymerase chain reaction was used to detect the expression of the odontoblastic differentiation-associated genes, including dentin sialoprotein (DSP) and dentin matrix acidic phosphoprotein 1 (DMP-1) at days 4, 7, 14 and 21. Alizarin Red S staining, immunofluorescence and western blot analyses were also conducted to assess the differentiation of the DPSCs in each group. The highest expression levels of odontoblastic differentiation-associated genes were observed on day 7 and in the two co-culture groups were increased compared with the DPSC-only and DPSC + ET-1 culture groups at all four time points. However, expression levels in the DPSC + ET-1 group were not downregulated as notably as in the co-culture groups on days 14 and 21. The Transwell group exhibited the greatest ability for odontoblastic differentiation compared with the other groups according to staining with Alizarin Red S, immunofluorescence and western blot analysis results. According to the results of the present study, the culture solution with HUVECs affected the differentiation of DPSCs. In addition, ET-1 may promote the odontoblastic differentiation of DPSCs.

Recent Advances in Tissue Engineering Strategies for the Treatment of Joint Damage

PURPOSE OF REVIEW

While the clinical potential of tissue engineering for treating joint damage has yet to be realized, research and commercialization efforts in the field are geared towards overcoming major obstacles to clinical translation, as well as towards achieving engineered grafts that recapitulate the unique structures, function, and physiology of the joint. In this review, we describe recent advances in technologies aimed at obtaining biomaterials, stem cells, and bioreactors that will enable the development of effective tissue-engineered treatments for repairing joint damage.

RECENT FINDINGS

3D printing of scaffolds is aimed at improving the mechanical structure and microenvironment necessary for bone regeneration within a damaged joint. Advances in our understanding of stem cell biology and cell manufacturing processes are informing translational strategies for the therapeutic use of allogeneic and autologous cells. Finally, bioreactors used in combination with cells and biomaterials are promising strategies for generating large tissue grafts for repairing damaged tissues in pre-clinical models. Together, these advances along with ongoing research directions are making tissue engineering increasingly viable for the treatment of joint damage.

Dental Stem Cells Harvested from Third Molars Combined with Bioactive Glass Can Induce Signs of Bone Formation In Vitro

Objectives

The aim of this study was to assess the interaction of a bioactive glass scaffold with cells derived from dental pulp, dental follicle and periodontal ligament.

Material and Methods

Impacted third molars were surgically removed from three young donors. Cells from the dental pulp, follicle and periodontal ligament tissues were isolated and expanded. Different cell populations were characterised using specific CD markers. Expanded pulp, follicle and periodontal cells were then seeded onto bioactive glass scaffolds and cultured in osteogenic medium or basic medium. Cell attachment, viability, proliferation and alkaline phosphatase activity were assessed.

Results

This study revealed good biocompatibility of the specific bioactive glass configuration tested and the osteogenic induction of cells derived from dental pulp, dental follicle and periodontal ligament. Osteogenic medium seemed to increase the differentiation pattern and dental pulp stem cells showed the most positive results compared to periodontal ligament and dental follicle stem cells.

Conclusions

Dental pulp stem cells combined with a bioactive glass scaffold and exposed to osteogenic medium in vitro represent a promising combination for future study of hard tissue regeneration in the cranio-maxillofacial skeleton.

Progress in the use of dental pulp stem cells in regenerative medicine

The field of tissue engineering is emerging as a multidisciplinary area with promising potential for regenerating new tissues and organs. This approach requires the involvement of three essential components: stem cells, scaffolds and growth factors. To date, dental pulp stem cells have received special attention because they represent a readily accessible source of stem cells. Their high plasticity and multipotential capacity to differentiate into a large array of tissues can be explained by its neural crest origin, which supports applications beyond the scope of oral tissues. Many isolation, culture and cryopreservation protocols have been proposed that are known to affect cell phenotype, proliferation rate and differentiation capacity. The clinical applications of therapies based on dental pulp stem cells demand the development of new biomaterials suitable for regenerative purposes that can act as scaffolds to handle, carry and implant stem cells into patients. Currently, the development of xeno-free culture media is emerging as a means of standardization to improve safe and reproducibility. The present review aims to describe the current knowledge of dental pulp stem cells, considering in depth the key aspects related to the characterization, establishment, maintenance and cryopreservation of primary cultures and their involvement in the multilineage differentiation potential. The main clinical applications for these stem cells and their combination with several biomaterials is also covered.

Mesenchymal Stem Cells: Cell Fate Decision to Osteoblast or Adipocyte and Application in Osteoporosis Treatment. Int J Mol Sci. 2018;19. [PMID: 29370110 PMCID: PMC5855582 DOI: 10.3390/ijms19020360]

Osteoporosis is a progressive skeletal disease characterized by decreased bone mass and degraded bone microstructure, which leads to increased bone fragility and risks of bone fracture. Osteoporosis is generally age related and has become a major disease of the world. Uncovering the molecular mechanisms underlying osteoporosis and developing effective prevention and therapy methods has great significance for human health. Mesenchymal stem cells (MSCs) are multipotent cells capable of differentiating into osteoblasts, adipocytes, or chondrocytes, and have become the favorite source of cell-based therapy. Evidence shows that during osteoporosis, a shift of the cell differentiation of MSCs to adipocytes rather than osteoblasts partly contributes to osteoporosis. Thus, uncovering the molecular mechanisms of the osteoblast or adipocyte differentiation of MSCs will provide more understanding of MSCs and perhaps new methods of osteoporosis treatment. The MSCs have been applied to both preclinical and clinical studies in osteoporosis treatment. Here, we review the recent advances in understanding the molecular mechanisms regulating osteoblast differentiation and adipocyte differentiation of MSCs and highlight the therapeutic application studies of MSCs in osteoporosis treatment. This will provide researchers with new insights into the development and treatment of osteoporosis.

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

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

Hydrogel elasticity and microarchitecture regulate dental-derived mesenchymal stem cell-host immune system cross-talk

The host immune system (T-lymphocytes and their pro-inflammatory cytokines) has been shown to compromise bone regeneration ability of mesenchymal stem cells (MSCs). We have recently shown that hydrogel, used as an encapsulating biomaterial affects the cross-talk among host immune cells and MSCs. However, the role of hydrogel elasticity and porosity in regulation of cross-talk between dental-derived MSCs and immune cells is unclear. In this study, we demonstrate that the modulus of elasticity and porosity of the scaffold influence T-lymphocyte-dental MSC interplay by regulating the penetration of inflammatory T cells and their cytokines. Moreover, we demonstrated that alginate hydrogels with different elasticity and microporous structure can regulate the viability and determine the fate of the encapsulated MSCs through modulation of NF-kB pathway. Our in vivo data show that alginate hydrogels with smaller pores and higher elasticity could prevent pro-inflammatory cytokine-induced MSC apoptosis by down-regulating the Caspase-3- and 8- associated proapoptotic cascades, leading to higher amounts of ectopic bone regeneration. Additionally, dental-derived MSCs encapsulated in hydrogel with higher elasticity exhibited lower expression levels of NF-kB p65 and Cox-2 in vivo. Taken together, our findings demonstrate that the mechanical characteristics and microarchitecture of the microenvironment encapsulating MSCs, in addition to presence of T-lymphocytes and their pro-inflammatory cytokines, affect the fate of encapsulated dental-derived MSCs.

STATEMENT OF SIGNIFICANCE

In this study, we demonstrate that alginate hydrogel regulates the viability and the fate of the encapsulated dental-derived MSCs through modulation of NF-kB pathway. Alginate hydrogels with smaller pores and higher elasticity prevent pro-inflammatory cytokine-induced MSC apoptosis by down-regulating the Caspase-3- and 8- associated proapoptotic cascade, leading to higher amounts of ectopic bone regeneration. MSCs encapsulated in hydrogel with higher elasticity exhibited lower expression levels of NF-kB p65 and Cox-2 in vivo. These findings confirm that the fate of encapsulated MSCs are affected by the stiffness and microarchitecture of the encapsulating hydrogel biomaterial, as well as presence of T-lymphocytes/pro-inflammatory cytokines providing evidence concerning material science, stem cell biology, the molecular mechanism of dental-derived MSC-associated therapies, and the potential clinical therapeutic impact of MSCs.