The role of stem cell therapy in regeneration of dentine-pulp complex: a systematic review. Prog Biomater. 2018;7:249-268. [PMID: 30267369 PMCID: PMC6304177 DOI: 10.1007/s40204-018-0100-7]

Green synthesis of nanohydroxyapatite with Elaeagnus angustifolia L. extract as a metronidazole nanocarrier for in vitro pulpitis model treatment

The aim of this study is to introduce a dental capping agent for the treatment of pulp inflammation (pulpitis). Nanohydroxyapatite with Elaeagnus angustifolia L. extract (nHAEA) loaded with metronidazole (nHAEA@MTZ) was synthesized and evaluated using a lipopolysaccharide (LPS) in vitro model of pulpitis. nHAEA was synthesized through sol-gel method and analyzed using Scanning Electron Microscopy, Transmission Electron Microscopy, and Brunauer Emmett Teller. Inflammation in human dental pulp stem cells (HDPSCs) induced by LPS. A scratch test assessed cell migration, RT PCR measured cytokines levels, and Alizarin red staining quantified odontogenesis. The nHAEA nanorods were 17-23 nm wide and 93-146 nm length, with an average pore diameter of 27/312 nm, and a surface area of 210.89 m2/g. MTZ loading content with controlled release, suggesting suitability for therapeutic applications. nHAEA@MTZ did not affect the odontogenic abilities of HDPSCs more than nHAEA. However, it was observed that nHAEA@MTZ demonstrated a more pronounced anti-inflammatory effect. HDPSCs treated with nanoparticles exhibited improved migration compared to other groups. These findings demonstrated that nHAEA@MTZ could be an effective material for pulp capping and may be more effective than nHAEA in reducing inflammation and activating HDPSCs to enhance pulp repair after pulp damage.

Advancements and challenges in stem/progenitor cell transplantation for dentin-pulp regeneration: a systematic review of animal studies (part I)

Dentin-pulp regeneration through stem/progenitor cell transplantation represents a promising frontier in regenerative endodontics. This systematic review meticulously evaluates animal studies to investigate the efficacy of stem cell therapy in repairing/regenerating the dentine-pulp complex in mature/immature animal teeth. Employing a comprehensive electronic search of PubMed and Scopus databases up to October 2023, relevant English studies were identified/assessed. Evaluation parameters encompassed radiographic and histological assessments of dentin-pulp complex formation. Outcome measures included pulp-like and dentin-like tissues regeneration, apical healing, dentin thickening, apical closure, and dentinal bridge formation. The risk-of-bias assessment adhered to the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) guidelines. Out of 3250 identified articles, 23 animal experiments were included, categorized into regenerative procedures in mature teeth (n=11), regenerative procedures in immature teeth (n=4), and vital pulp therapy (n=8). Despite the promising potential, the bias in the included studies was high. Notably, Various scaffolds, and growth factors were employed, highlighting the heterogeneity across the studies. Dental pulp stem cells (DPSCs) and bone marrow stem cells, especially specific subfractions, demonstrated notable regenerative potential: hypoxic conditions and extracellular vesicles from preconditioned DPSCs enhanced regeneration, with considerations of cell fate. Donor age impacted regeneration, and challenges persisted in pulpotomy and direct pulp capping. Scaffold and growth factor choices influenced outcomes, underscoring the need for standardized strategies. Despite the promise, clinical viability faces hurdles, necessitating further investigation into adverse effects, optimized scaffolds, and regulatory considerations. This systematic review illuminates the potential of stem cell transplantation for dentin-pulp complex regeneration. The overall evidence quality, influenced by study heterogeneity and biases, underscores the need for cautious interpretation of findings. Future studies should refine methodologies and establish reliable histological parameters for meaningful advancements in dentin-pulp 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.

Crucial Factors Influencing the Involvement of Odontogenic Exosomes in Dental Pulp Regeneration

Recent progress in exosome based studies has revealed that they possess several advantages over cells, including "cell-free" properties, low immunogenicity and ethical controversy, high biological safety and effective action. These characteristics confer exosomes significant advantages that allow them to overcome the limitations associated with traditional "cell therapy" by circumventing the issues of immune rejection, scarcity of donor cells, heterogeneity, and ethical concerns. Identification of a complete and effective radical treatment for irreversible pulpal disease, a common clinical problem, continues to pose challenges. Although traditional root canal therapy remains the primary clinical treatment, it does not fully restore the physiological functions of pulp. Although stem cell transplantation appears to be a relatively viable treatment strategy for pulp disease, issues such as cell heterogeneity and poor regeneration effects remain problematic. Dental pulp regeneration strategies based on "cell-free" exosome therapies explored by numerous studies appear to have shown significant advantages. In particular, exosomes derived from odontogenic stem cells have demonstrated considerable potential in tooth tissue regeneration engineering, and continue to exhibit superior therapeutic effects compared to non-odontogenic stem cell-derived exosomes. However, only a few studies have comprehensively summarised their research results, particularly regarding the critical factors involved in the process. Therefore, in this study, our purpose was to review the effects exerted by odontogenic exosomes on pulp regeneration and to analyse and discus crucial factors related to this process, thereby providing scholars with a feasible and manageable new concept with respect to regeneration schemes.

Effect of rapamycin on human periodontal ligament stem cells that have been exposed to sodium hypochlorite

AIMS

The present study investigated the effect of rapamycin on the viability and osteogenic differentiation potential of human periodontal ligament stem cells (hPDLSCs) in the presence of sodium hypochlorite (NaOCl).

MAIN METHODS

After determining the minimum inhibitory concentration of NaOCl and optimum concentration of rapamycin, the viability of hPDLSCs was evaluated using the MTT assay subsequent to their exposure to NaOCl, rapamycin, or a combination of both. Osteogenic differentiation was evaluated by the cell mineralization assay performed by alizarin red S staining, alkaline phosphatase activity, and monitoring the expression of osteogenic genes markers Runt-related transcription factor 2, osteocalcin, and osteoprotegerin, using real-time quantitative polymerase chain reaction (RT-qPCR). The expression of autophagy-related genes PI3K, Akt, and mTOR, was also analyzed with RT-qPCR.

KEY FINDINGS

Stem cells treated with rapamycin showed the highest percentage of viable cells in the presence of NaOCl. The same trend was observed for all osteogenic differentiation assays. The hPDLSCs treated with rapamycin demonstrated the highest calcium nodule deposition, alkaline phosphatase activity, and the expression of osteogenic gene markers. These effects were not adversely affected by the presence of NaOCl. Rapamycin significantly inhibited mTOR gene expression, while there were no differences in the gene expression of PI3K and Akt.

SIGNIFICANCE

Rapamycin counteracts the cytotoxic effect of NaOCl by enhancing the viability and osteogenic differentiation potential of hPDLSCs. Rapamycin appears to accomplish these processes via autophagy activation, by inhibiting mTOR gene expression. The incorporation of rapamycin in regenerative endodontic therapy may encourage a higher success rate.

Adult Mesenchymal Stem Cells from Oral Cavity and Surrounding Areas: Types and Biomedical Applications

Adult mesenchymal stem cells are those obtained from the conformation of dental structures (DMSC), such as deciduous and permanent teeth and other surrounding tissues. Background: The self-renewal and differentiation capacities of these adult stem cells allow for great clinical potential. Because DMSC are cells of ectomesenchymal origin, they reveal a high capacity for complete regeneration of dental pulp, periodontal tissue, and other biomedical applications; their differentiation into other types of cells promotes repair in muscle tissue, cardiac, pancreatic, nervous, bone, cartilage, skin, and corneal tissues, among others, with a high predictability of success. Therefore, stem and progenitor cells, with their exosomes of dental origin and surrounding areas in the oral cavity due to their plasticity, are considered a fundamental pillar in medicine and regenerative dentistry. Tissue engineering (MSCs, scaffolds, and bioactive molecules) sustains and induces its multipotent and immunomodulatory effects. It is of vital importance to guarantee the safety and efficacy of the procedures designed for patients, and for this purpose, more clinical trials are needed to increase the efficacy of several pathologies. Conclusion: From a bioethical and transcendental anthropological point of view, the human person as a unique being facilitates better clinical and personalized therapy, given the higher prevalence of dental and chronic systemic diseases.

Fabrication and characterization of a novel injectable human amniotic membrane hydrogel for dentin-pulp complex regeneration

OBJECTIVE

Injectable biomaterials that can completely fill the root canals and provide an appropriate environment will have potential application for pulp regeneration in endodontics. This study aimed to fabricate and characterize a novel injectable human amniotic membrane (HAM) hydrogel scaffold crosslinked with genipin, enabling the proliferation of Dental Pulp Stem Cells (DPSCs) and optimizing pulp regeneration.

METHODS

HAM extracellular matrix (ECM) hydrogels (15, 22.5, and 30 mg/ml) crosslinked with different genipin concentrations (0, 0.1, 0.5, 1, 5, and 10 mM) were evaluated for mechanical properties, tooth discoloration, cell viability, and proliferation of DPSCs. The hydrogels were subcutaneously injected in rats to assess their immunogenicity. The hydrogels were applied in a root canal model and subcutaneously implanted in rats to determine their regenerative potential for eight weeks, and histological and immunostaining analyses were performed.

RESULTS

Hydrogels crosslinked with low genipin concentration demonstrated low tooth discoloration, but 0.1 mM genipin crosslinked hydrogels were excluded due to their unfavourable mechanical properties. The degradation ratio was lower in hydrogels crosslinked with 0.5 mM genipin. The 30 mg/ml-0.5 mM crosslinked hydrogel exhibited a microporous structure, and the modulus of elasticity was 1200 PA. In vitro, cell culture showed maximum viability and proliferation in 30 mg/ml-0.5 mM crosslinked hydrogel. All groups elicited minimum immunological responses, and highly vascularized pulp-like tissue was formed in human tooth roots in both groups with/without DPSCs.

SIGNIFICANCE

Genipin crosslinking improved the biodegradability of injectable HAM hydrogels and conferred higher biocompatibility. Hydrogels encapsulated with DPSCs can support stem cell viability and proliferation. In addition, highly vascularized pulp-like tissue formation by this biomaterial displayed potential for pulp regeneration.

Using Odontoblasts Derived from Dog Endometrial Stem Cells Encapsulated in Fibrin Gel Associated with BMP-2 in a Rat Pulp-Capping Model

This study aimed to treat dental injuries by utilizing one of the most advanced tissue engineering techniques. In this study, an in vitro model was employed to investigate the proliferation and odontogenic differentiation of canine endometrial stem cells (C-EnSCs). Furthermore, the dentin regeneration potential of odontoblast like-cells (OD) derived from C-EnSCs was assessed in rats. The C-EnSCs were isolated by the enzymatic method and identified by flow cytometry. The C-EnSCs were encapsulated in fibrin gel associated with signaling factors to create the proper conditions for cell growth and differentiation. Then, the OD cells were associated with bone morphologic protein-2 (BMP-2) to promote dentin formation in vivo. The animal model used to evaluate the regenerative effect of cells and biomaterials included the preparation of the left maxillary first molar of rats for direct pulp capping operation. Animals were divided into four groups: group 1, a control group without any treatment, group 2, which received fibrin, group 3, which received fibrin with ODs (fibrin/ODs), and group 4, which received fibrin with ODs and BMP-2 (fibrin/ODs/BMP-2). The morphological observations showed the differentiation of C-EnSCs into adipose, bone, neural cells, and ODs. Furthermore, the histomorphometric data of the treated teeth showed how fibrin gel and BMP2 at a concentration of 100 ng/mL provided an optimal microenvironment for regenerating dentin tissue in rats, which was increased significantly with the presence of OD cells within eight weeks. Our study showed that using OD cells derived from C-EnSCs encapsulated in fibrin gel associated with BMP2 can potentially be an appropriate candidate for direct pulp-capping and dentin regeneration.

Encapsulation of human endometrial stem cells in chitosan hydrogel containing titanium oxide nanoparticles for dental pulp repair and tissue regeneration in male Wistar rats

This study aimed to determine the impact of human endometrial stem cells (EnSCs) and titanium oxide nanoparticles (TiO₂ NPs) on dental pulp repair and regeneration in an animal model through dentine development and tissue regeneration. The EnSCs were put on a three-dimensional (3D) chitosan scaffold containing TiO₂ NPs after obtaining and purifying the collagenase enzyme. Pulps were exposed on the maxillary left first molar of all rats followed by direct pulp capping with the experimental scaffolds, as follows. Groups were: 1, control group without any treatment; 2, chitosan group (CS); 3, chitosan group with stem cells (CS/SCs); 4, chitosan group with stem cells and TiO₂ NPs (CS/EnSCs/TiO₂). Glass ionomer was used as a sealant in all groups. The teeth were extracted and histologically evaluated after 8 weeks. The quality and amount of dentine in the CS/EnSCs/TiO₂ group were higher than in the other groups. The combination of EnSCs with TiO₂ NPs and 3D chitosan scaffolds had a synergistic effect on each other, evidencing increased speed and quality of dentine formation. Using EnSCs with TiO₂ NPs on a 3D chitosan scaffold can be a suitable combination for direct pulp capping and dentine regeneration in a rat molar tooth model.

Application of Biocompatible Scaffolds in Stem-Cell-Based Dental Tissue Engineering

Tissue engineering as an important field in regenerative medicine is a promising therapeutic approach to replace or regenerate injured tissues. It consists of three vital steps including the selection of suitable cells, formation of 3d scaffolds, and adding growth factors. Mesenchymal stem cells (MSCs) and embryonic stem cells (ESCs) are mentioned as two main sources for this approach that have been used for the treatment of various types of disorders. However, the main focus of literature in the field of dental tissue engineering is on utilizing MSCs. On the other hand, biocompatible scaffolds play a notable role in this regenerative process which is mentioned to be harmless with acceptable osteoinductivity. Their ability in inhibiting inflammatory responses also makes them powerful tools. Indeed, stem cell functions should be supported by biomaterials acting as scaffolds incorporated with biological signals. Naturally derived polymeric scaffolds and synthetically engineered polymeric/ceramic scaffolds are two main types of scaffolds regarding their materials that are defined further in this review. Various strategies of tissue bioengineering can affect the regeneration of dentin-pulp complex, periodontium regeneration, and whole teeth bioengineering. In this regard, in vivo/ex vivo experimental models have been developed recently in order to perform preclinical studies of dental tissue engineering which make it more transferable to be used for clinic uses. This review summarizes dental tissue engineering through its different components. Also, strategies of tissue bioengineering and experimental models are introduced in order to provide a perspective of the potential roles of dental tissue engineering to be used for clinical aims.

Tissue Engineering with Stem Cell from Human Exfoliated Deciduous Teeth (SHED) and Collagen Matrix, Regulated by Growth Factor in Regenerating the Dental Pulp

Maintaining dental pulp vitality and preventing tooth loss are two challenges in endodontic treatment. A tooth lacking a viable pulp loses its defense mechanism and regenerative ability, making it more vulnerable to severe damage and eventually necessitating extraction. The tissue engineering approach has drawn attention as an alternative therapy as it can regenerate dentin-pulp complex structures and functions. Stem cells or progenitor cells, extracellular matrix, and signaling molecules are triad components of this approach. Stem cells from human exfoliated deciduous teeth (SHED) are a promising, noninvasive source of stem cells for tissue regeneration. Not only can SHEDs regenerate dentin-pulp tissues (comprised of fibroblasts, odontoblasts, endothelial cells, and nerve cells), but SHEDs also possess immunomodulatory and immunosuppressive properties. The collagen matrix is a material of choice to provide structural and microenvironmental support for SHED-to-dentin pulp tissue differentiation. Growth factors regulate cell proliferation, migration, and differentiation into specific phenotypes via signal-transduction pathways. This review provides current concepts and applications of the tissue engineering approach, especially SHEDs, in endodontic treatment.

Cells and material-based strategies for regenerative endodontics

<p class = "Abstract" style = "margin: 0 cm; line-height: 32px; font-size: 12 pt; font-family: "Times New Roman", serif; color: rgb(0, 0, 0); "><span lang = "EN-US">The carious process leads to inflammation of pulp tissue. Current care options include root canal treatment or apexification. These procedures, however, result in the loss of tooth vitality, sensitivity, and healing. Pulp capping and dental pulp regeneration are continually evolving techniques to regenerate pulp tissue, avoiding necrosis and loss of vitality. Many studies have successfully employed stem/progenitor cell populations, revascularization approaches, scaffolds or material-based strategies for pulp regeneration. Here we outline advantages and disadvantages of different methods and techniques which are currently being used in the field of regenerative endodontics. We also summarize recent findings on efficacious peptide-based materials which target the dental niche.<o:p></o:p></span></p>

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Pulp infection necessitates removal of necrotic, inflamed and infected tissue.

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Materials used clinically are inert (such as gutta percha, mineral trioxide aggregate).

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Recent developments in materials (angiogenic hydrogels, stem cell composites) have tuneable bioactivity.

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Dental pulp regeneration may now be possible through the use of bioactive systems, that guide regeneration.

Phenytoin Is Promoting the Differentiation of Dental Pulp Stem Cells into the Direction of Odontogenesis/Osteogenesis by Activating BMP4/Smad Pathway

Background

The purpose of this study was the evaluation of the potential and mechanism of phenytoin to promote differentiation of human dental pulp stem cells (hDPSC) into odontoblasts/osteoblasts.

Methods

Fourth-generation human hDPSC originating from healthy pulp of third molars was cultured in control as well as phenytoin-containing media (PHT) for 14 days. qPCR was applied to detect the expression of DSPP, DMP1, and ALP genes. Western blot analysis was used to confirm the findings. One-way analysis of variance (ANOVA) was used for statistical analysis (p < 0.05). Information about phenytoin was assessed from PubChem database, while targets of phenytoin were assessed from six databases. Drug targets were extracted based on the differentially expressed genes (‖logFC‖ ≥ 1, p < 0.05) in the experimental group (50 mg/L PHT, 14 days). GO BP and KEGG pathway enrichment analysis on the obtained drug targets was performed and the target protein functional network diagram was constructed.

Results

A concentration below 200 mg/L PHT had no obvious toxicity to hDPSC. The expression of DSPP, DMP1, and ALP genes in the 50 mg/L PHT concentration group increased significantly. The WB experiment showed that the protein content of BMP4, Smad1/5/9, and p-Smad1/5 was significantly increased in 50 mg/L PHT in comparison with the NC group (the group without treatment of PHT) at 14 days.

Conclusion

Phenytoin has the ability of promoting the differentiation of hDPSC into odontoblasts and osteoblasts. BMP4/Smad pathway, inducing odontogenic/osteogenic differentiation of hDPSC, appears a main process in this context.

Endothelial Cells Promote Osteogenesis by Establishing a Functional and Metabolic Coupling With Human Mesenchymal Stem Cells

Bone formation involves a complex crosstalk between endothelial cells (EC) and osteodifferentiating stem cells. This functional interplay is greatly mediated by the paracrine and autocrine action of soluble factors released at the vasculature-bone interface. This study elucidates the molecular and functional responses triggered by this intimate interaction. In this study, we showed that human dermal microvascular endothelial cells (HMEC) induced the expression of pro-angiogenic factors in stem cells from human exfoliated deciduous teeth (SHED) and sustain their osteo-differentiation at the same time. In contrast, osteodifferentiating SHED increased EC recruitment and promoted the formation of complex vascular networks. Moreover, HMEC enhanced anaerobic glycolysis in proliferating SHED without compromising their ability to undergo the oxidative metabolic shift required for adequate osteo-differentiation. Taken together, these findings provide novel insights into the molecular mechanism underlying the synergistic cooperation between EC and stem cells during bone tissue renewal.

Regenerative Endodontics Success Factors and their Overall Effectiveness: An Umbrella Review

Introduction

Regenerative endodontics is a developing field of dentistry and aims to recover the physiological and anatomical functions of the tooth for cases of severe dental caries, pulpal pathologies and dental trauma.

Materials and Methods

This umbrella review seeks to discover the scientific evidence on the effectiveness and the factors result in successful regenerative endodontic therapies in teeth with necrotic pulps and with incomplete root development. The study was conducted following the PRISMA Guidelines. There were no restrictions regarding search period. A comprehensive literature search was carried out in EMBASE, LILACS, PubMed, Cochrane, Scopus, and Google Scholar. A quality evaluation was conducted by using AMSTAR-2. A descriptive analysis of the included systematic reviews and meta-analysis were conducted.

Results

Thirteen descriptive systematic reviews and 7 meta-analyses were included. Three articles evidenced low methodological quality according to AMSTAR-2 tool. Overall success rates for the endodontic regeneration procedures ranged from 50% to 98% and the survival rates were between 94% and 100%. Pulp regeneration had a high success rate, evidenced by factors such as the resolution of symptoms, healing, increased root length, dentin thickening and recovery of sensitivity. Follow-up varied from 1 to 48 months for the original studies included in the systematic reviews and meta-analyses.

Conclusions

Endodontic practice offers the clinician a good treatment option in case of necrotic pulp with immature roots such as the endodontic regeneration, that is supported by high and moderate quality scientific literature.

Human amniotic membrane extracellular matrix scaffold for dental pulp regeneration in vitro and in vivo

AIM

In order to obtain a 3-dimentional scaffold with predictable clinical results for pulp regeneration, this study aims to fabricate and characterize a porous decellularized human amniotic membrane (HAM) extracellular matrix (ECM) scaffold, and evaluate its potential to promote pulp regeneration in vitro and in vivo.

METHODOLOGY

The HAM was decellularized, and its histology and DNA content were analysed to confirm decellularization. The scaffolds were synthesized with 15, 22.5 and 30 mg/ml concentrations. The porosity, pore size, phosphate-buffered saline (PBS) absorption and degradation rate of the scaffolds were assessed. In vitro experiments were performed on human dental pulp stem cells (hDPSCs) to assess their viability, proliferation, adhesion and migration on the scaffolds. The optimal group was selected for in vivo immunogenicity assessment and was also used as the cell-free or cell-loaded scaffold in root segment models to evaluate pulp regeneration. All nonparametric data were analysed with the Kruskal-Wallis test followed by Dunn's post hoc test, whilst quantitative data were analysed with one-way anova.

RESULTS

Decellularization of HAM was confirmed (p < .05). The porosity of all scaffolds was more than 95%, and the pore size decreased with an increase in ECM concentration (p < .01). PBS absorption was not significantly different amongst the groups, whilst 30 mg/ml ECM scaffold had the highest degradation rate (p < .01). The hDPSCs adhered to the scaffold, whilst their proliferation rate increased over time in all groups (p < .001). Cell migration was higher in 30 mg/ml ECM scaffold (p < .05). In vivo investigation with 30 mg/ml ECM scaffold revealed mild to moderate inflammatory response. In root segments, both cell-free and cell-loaded 30 mg/ml scaffolds were replaced with newly formed, pulp-like tissue with no significant difference between groups. Immunohistochemical assessments revealed high revascularization and collagen content with no significant difference amongst the groups.

CONCLUSION

The 30 mg/ml HAM ECM scaffold had optimal physical properties and better supported hDPSC migration. The HAM ECM scaffold did not interfere with formation of pulp-like tissue and revascularization within the root canal when employed as both cell-free and cell-loaded scaffold. These results highlight the potential of HAM ECM membrane for further investigations in regenerative endodontics.

Advances of adipose-derived mesenchymal stem cells-based biomaterial scaffolds for oral and maxillofacial tissue engineering

The management of oral and maxillofacial tissue defects caused by tumors, trauma, and congenital or acquired deformities has been a major challenge for surgeons over the last few decades. Autologous tissue transplantation, the gold standard of tissue reconstruction, is a valid method for repairing the oral and maxillofacial functions and aesthetics. However, several limitations hinder its clinical applications including complications of donor sites, limited tissue volume, and uncertain long-term outcomes. Adipose-derived mesenchymal stem cells (ADMSCs) widely exist in adipose tissue and can be easily obtained through liposuction. Like the bone marrow-derived mesenchymal stem cells (BMSCs), ADMSCs also have the multi-pluripotent potencies to differentiate into osteoblasts, chondrocytes, neurons, and myocytes. Therefore, the multilineage capacity of ADMSCs makes them valuable for cell-based medical therapies. In recent years, researchers have developed many candidates of ADMSCs-based biomaterial scaffolds to cater for the needs of oral and maxillofacial tissue engineering due to their superior performance. This review presents the advances and applications of ADMSCs-based biomaterial scaffolds, and explores their tissue engineering prospects in oral and maxillofacial reconstructions.

Review of the Applications of Biomedical Compositions Containing Hydroxyapatite and Collagen Modified by Bioactive Components

Regenerative medicine is becoming a rapidly evolving technique in today’s biomedical progress scenario. Scientists around the world suggest the use of naturally synthesized biomaterials to repair and heal damaged cells. Hydroxyapatite (HAp) has the potential to replace drugs in biomedical engineering and regenerative drugs. HAp is easily biodegradable, biocompatible, and correlated with macromolecules, which facilitates their incorporation into inorganic materials. This review article provides extensive knowledge on HAp and collagen-containing compositions modified with drugs, bioactive components, metals, and selected nanoparticles. Such compositions consisting of HAp and collagen modified with various additives are used in a variety of biomedical applications such as bone tissue engineering, vascular transplantation, cartilage, and other implantable biomedical devices.

Cytokine Secretion, Viability, and Real-Time Proliferation of Apical-Papilla Stem Cells Upon Exposure to Oral Bacteria

The use of stem cells from the apical papilla (SCAPs) has been proposed as a means of promoting root maturation in permanent immature teeth, and plays a significant role in regenerative dental procedures. However, the role of SCAPs may be compromised by microenvironmental factors, such as hypoxic conditions and the presence of bacteria from infected dental root canals. We aim to investigate oral bacterial modulation of SCAP in terms of binding capacity using flow cytometry and imaging, real-time cell proliferation monitoring, and cytokine secretion (IL-6, IL-8, and TGF-β isoforms) under anaerobic conditions. SCAPs were exposed to key species in dental root canal infection, namely Actinomyces gerensceriae, Slackia exigua, Fusobacterium nucleatum, and Enterococcus faecalis, as well as two probiotic strains, Lactobacillus gasseri strain B6 and Lactobacillus reuteri (DSM 17938). We found that A. gerensceriae, S. exigua, F. nucleatum, and E. faecalis, but not the Lactobacillus probiotic strains bind to SCAPs on anaerobic conditions. Enterococcus faecalis and F. nucleatum exhibited the strongest binding capacity, resulting in significantly reduced SCAP proliferation. Notably, F. nucleatum, but not E. faecalis, induce production of the proinflammatory chemokine IL-8 and IL-10 from SCAPs. Production of TGF-β1 and TGF-β2 by SCAPs was dependent on species, cell line, and time, but secretion of TGF-β3 did not vary significantly over time. In conclusion, SCAP response is compromised when exposed to bacterial stimuli from infected dental root canals in anaerobic conditions. Thus, stem cell-mediated endodontic regenerative studies need to include microenvironmental conditions, such as the presence of microorganisms to promote further advantage in the field.

Regenerative Endodontic Procedures: An Umbrella Review

The Regenerative Endodontic Procedure (REP) is a biologically based method in which a damaged pulp-dentin complex is replaced by a new vital tissue. This umbrella review aimed to critically assess the available systematic reviews (SRs) on REP. An electronic database search was conducted (PubMed-Medline, CENTRAL, Scielo, Web of Science, and LILACS) until December 2020. Studies were included if they were an SR on REP. The Risk of Bias (RoB) of SRs was analyzed using the Measurement Tool to Assess SRs criteria 2 (AMSTAR2). The primary outcome was the methodological quality in each specific section of REP protocols and outcomes. From 403 entries, 29 SRs were included. Regarding the methodological quality, ten studies were of critically low, three of low, fourteen of moderate, and two were rated as high quality. The quality of evidence produced by the available SRs was not favorable. Future high standard SRs and well-designed clinical trials are warranted to better elucidate the clinical protocols and outcomes of REP.

Silencing integrin α6 enhances the pluripotency-differentiation transition in human dental pulp stem cells

OBJECTIVES

Although integrins have been shown to be associated with proliferation and differentiation in some stem cells, the regulatory effect of integrin α6 (ITGα6) on the human dental pulp stem cells (hDPSCs) has not been reported. Here, we detected the roles of ITGα6 in hDPSCs.

MATERIALS AND METHODS

Attached to Cytodex 3 microcarriers, hDPSCs grown under stimulated microgravity (SMG) or conventional culture conditions were measured the proliferation and different gene expression. Further, ITGα6 was silenced in hDPSCs, and its effect on proliferation, differentiation, and cytoskeletal organization was analyzed.

RESULTS

SMG conditions increased the number of Ki67-positive hDPSCs and progression into S phase of cell cycle. WB analysis showed the expression of ITGα6 was upregulated in hDPSCs under SMG conditions. Knockdown of ITGα6 decreased the expression of stemness markers, CD105 and STRO-1 in hDPSCs, but promoted the osteogenic and odontogenic differentiation by increased ALP expression and Alizarin Red nodules. Moreover, RNA-seq demonstrated that RHO/ROCK signaling pathway upregulated silencing ITGα6-hDPSCs. Treatment with Y-27632 inhibited the effect of ITGα6 depletion on hDPSCs stemness, rearranged the cytoskeleton, promoted the pluripotency, proliferation ability, and inhibited the differentiation.

CONCLUSION

ITGα6 promotes hDPSCs stemness via inhibiting RHO/ROCK and restoring cytoskeleton.

Characterization of Odontogenic Differentiation from Human Dental Pulp Stem Cells Using TMT-Based Proteomic Analysis

Background

The repair of dental pulp injury relies on the odontogenic differentiation of dental pulp stem cells (DPSCs). To better understand the odontogenic differentiation of DPSCs and identify proteins involved in this process, tandem mass tags (TMTs) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) were applied to compare the proteomic profiles of induced and control DPSCs.

Methods

The proteins expressed during osteogenic differentiation of human DPSCs were profiled using the TMT method combined with LC-MS/MS analysis. The identified proteins were subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. Then, a protein-protein interaction (PPI) network was constructed. Two selected proteins were confirmed by western blotting (WB) analysis.

Results

A total of 223 proteins that were differentially expressed were identified. Among them, 152 proteins were significantly upregulated and 71 were downregulated in the odontogenic differentiation group compared with the control group. On the basis of biological processes in GO, the identified proteins were mainly involved in cellular processes, metabolic processes, and biological regulation, which are connected with the signaling pathways highlighted by KEGG pathway analysis. PPI networks showed that most of the differentially expressed proteins were implicated in physical or functional interaction. The protein expression levels of FBN1 and TGF-β2 validated by WB were consistent with the proteomic analysis.

Conclusions

This is the first proteomic analysis of human DPSC odontogenesis using a TMT method. We identified many new differentially expressed proteins that are potential targets for pulp-dentin complex regeneration and repair.

Hydrogels and Dentin-Pulp Complex Regeneration: From the Benchtop to Clinical Translation

Dentin-pulp complex is a term which refers to the dental pulp (DP) surrounded by dentin along its peripheries. Dentin and dental pulp are highly specialized tissues, which can be affected by various insults, primarily by dental caries. Regeneration of the dentin-pulp complex is of paramount importance to regain tooth vitality. The regenerative endodontic procedure (REP) is a relatively current approach, which aims to regenerate the dentin-pulp complex through stimulating the differentiation of resident or transplanted stem/progenitor cells. Hydrogel-based scaffolds are a unique category of three dimensional polymeric networks with high water content. They are hydrophilic, biocompatible, with tunable degradation patterns and mechanical properties, in addition to the ability to be loaded with various bioactive molecules. Furthermore, hydrogels have a considerable degree of flexibility and elasticity, mimicking the cell extracellular matrix (ECM), particularly that of the DP. The current review presents how for dentin-pulp complex regeneration, the application of injectable hydrogels combined with stem/progenitor cells could represent a promising approach. According to the source of the polymeric chain forming the hydrogel, they can be classified into natural, synthetic or hybrid hydrogels, combining natural and synthetic ones. Natural polymers are bioactive, highly biocompatible, and biodegradable by naturally occurring enzymes or via hydrolysis. On the other hand, synthetic polymers offer tunable mechanical properties, thermostability and durability as compared to natural hydrogels. Hybrid hydrogels combine the benefits of synthetic and natural polymers. Hydrogels can be biofunctionalized with cell-binding sequences as arginine-glycine-aspartic acid (RGD), can be used for local delivery of bioactive molecules and cellularized with stem cells for dentin-pulp regeneration. Formulating a hydrogel scaffold material fulfilling the required criteria in regenerative endodontics is still an area of active research, which shows promising potential for replacing conventional endodontic treatments in the near future.

The role of insulin-like growth factors in modulating the activity of dental mesenchymal stem cells

Regenerative treatment protocols are an exciting prospect in the management of oral pathology, as they allow for tissues to be restored to their original form and function, as compared to the reparative healing mechanisms which currently govern the outcomes of the majority of dental treatment. Stem cell therapy presents with a great deal of untapped potential in this pursuit of tissue regeneration, and, in particular, mesenchymal stem cells (MSCs) derived from dental tissues are of specific relevance with regards to their applications in engineering craniofacial tissues. A number of mediatory factors are involved in modulating the actions of dental MSCs, and, of these, insulin like growth factors (IGFs) are known to have potent effects in governing the behavior of these cells. The IGF family comprises a number of primary ligands, receptors, and binding proteins which are known to modulate the key properties of dental MSCs, such as their proliferation rates, differentiation potential, and mineralisation. The aims of this review are three-fold: (i) to present an overview of dental MSCs and the role of growth factors in modulating their characteristics, (ii) to discuss in greater detail the specific role of IGFs and the benefits they may convey for tissue engineering, and (iii) to provide a summary of potential for in vivo clinical translation of the current in vitro body of evidence.

Dental regenerative therapy targeting sphingosine-1-phosphate (S1P) signaling pathway in endodontics

The establishment of regenerative therapy in endodontics targeting the dentin-pulp complex, cementum, periodontal ligament tissue, and alveolar bone will provide valuable information to preserve teeth. It is well known that the application of stem cells such as induced pluripotent stem cells, embryonic stem cells, and somatic stem cells is effective in regenerative medicine. There are many somatic stem cells in teeth and periodontal tissues including dental pulp stem cells (DPSCs), stem cells from the apical papilla, and periodontal ligament stem cells. Particularly, several studies have reported the regeneration of clinical pulp tissue and alveolar bone by DPSCs transplantation. However, further scientific issues for practical implementation remain to be addressed. Sphingosine-1-phosphate (S1P) acts as a bioactive signaling molecule that has multiple biological functions including cellular differentiation, and has been shown to be responsible for bone resorption and formation. Here we discuss a strategy for bone regeneration and a possibility for regenerative endodontics targeting S1P signaling pathway as one of approaches for induction of regeneration by improving the regenerative capacity of endogenous cells.

SCIENTIFIC FIELD OF DENTAL SCIENCE

Endodontology.

Optimizing Methods for Bovine Dental Pulp Decellularization

INTRODUCTION

This study aimed to characterize the decellularization effects of different treatment protocols on the bovine dental pulp extracellular matrix (ECM) for tissue regeneration.

METHODS

Seven different decellularization protocols consisting of trypsin/EDTA (for 1 hour, 24 hours, or 48 hours), sodium dodecyl sulfate (SDS, for 24 hours or 48 hours), Triton X-100 (for 1 hour), and deoxyribonuclease treatments were tested on bovine dental pulp tissue. The posttreatment samples were evaluated for remaining DNA and cellular contents, structural durability, immunofluorescence analysis, and in vivo immune responses.

RESULTS

A complete decellularization process in all of the experimental groups was observed. The protocol that included 1 hour of Triton X-100 treatment and 12 hours of trypsin/EDTA treatment with no SDS treatment (P7 [12E-0S-1T]) showed the highest retention of glycosaminoglycan and the absence of nuclei in 4,6-diamidino-2-phenylindole. All groups showed significantly lower DNA content compared with native pulp tissue (P < .05), whereas compared with other protocols, protocols 1 (1 hour of EDTA/trypsin, 24 hours of SDS, and 1 hour of Triton X-100) and 4 (1 hour of EDTA/Trypsin, 48 hours of SDS, and no Triton X-100) resulted in the highest DNA contents (P < .05). Based on these results, P7 was further evaluated by immunofluorescence and in vivo immunogenicity. P7 specimens preserved collagen type I, whereas mononuclear cell infiltration along with neovascularization was observed in vivo.

CONCLUSIONS

All tested treatments displayed the potential ability to decellularize pulp tissue and are viable options for a xenogeneic dental pulp ECM scaffold. The P7 (12E-0S-1T) protocol resulted in decellularized ECM with minimal organic matrix/ultrastructural detriments and an acceptable host immune response.

Dental stem cells: The role of biomaterials and scaffolds in developing novel therapeutic strategies

Dental stem cells (DSCs) are self-renewable cells that can be obtained easily from dental tissues, and are a desirable source of autologous stem cells. The use of DSCs for stem cell transplantation therapeutic approaches is attractive due to their simple isolation, high plasticity, immunomodulatory properties, and multipotential abilities. Using appropriate scaffolds loaded with favorable biomolecules, such as growth factors, and cytokines, can improve the proliferation, differentiation, migration, and functional capacity of DSCs and can optimize the cellular morphology to build tissue constructs for specific purposes. An enormous variety of scaffolds have been used for tissue engineering with DSCs. Of these, the scaffolds that particularly mimic tissue-specific micromilieu and loaded with biomolecules favorably regulate angiogenesis, cell-matrix interactions, degradation of extracellular matrix, organized matrix formation, and the mineralization abilities of DSCs in both in vitro and in vivo conditions. DSCs represent a promising cell source for tissue engineering, especially for tooth, bone, and neural tissue restoration. The purpose of the present review is to summarize the current developments in the major scaffolding approaches as crucial guidelines for tissue engineering using DSCs and compare their effects in tissue and organ regeneration.

Prospects of Advanced Therapy Medicinal Products-Based Therapies in Regenerative Dentistry: Current Status, Comparison with Global Trends in Medicine, and Future Perspectives

INTRODUCTION

Regenerative medicine offers innovative approaches to restore damaged tissues on the basis of tissue engineering (TE). Although research on advanced therapy medicinal products (ATMPs) has been very active in recent years, the number of licensed products remains surprisingly low and restricted to the treatment of severe, incurable diseases.

METHODS

This paper provides a critical review of current literature on the regulatory, clinical, and commercial status of ATMP-based therapies in the EU and worldwide and the hurdles to overcome for their broader application in Regenerative Dentistry.

RESULTS

Competent authorities have focused on developing regulatory pathways to address unmet patient needs. Oncology represents the dominating field, followed by cardiovascular, musculoskeletal, neurodegenerative, immunologic, and inherited diseases. Yet, the status remains in early development, and scientific, regulatory, and cost-effectiveness issues impose considerable hurdles toward marketing authorization, technology adoption, and patient accessibility. In this context, although regenerative dentistry has achieved breakthrough innovations in TE of several dental/oral tissues in preclinical models, it has hardly harnessed research progress to integrate innovative regenerative treatments into clinical practice.

CONCLUSION

Global demographic changes, which demonstrate a steady increase of the aging population, highlight the societal need for the application of ATMP-based therapies in the treatment of noncommunicable diseases (NCDs). Although oral diseases, as an integral part of NCDs, are not life-threatening and largely preventable, they sustain high prevalence, with severe burden on economy and quality of life. In this perspective, the urgent request to ultimately translate draining research in dental TE conducted during the last decades into innovative treatments brought safely and cost-effectively into society at large still holds the stage. This review provides an overview of the regulatory, clinical, and commercial status of ATMP-based therapies in the European Union and worldwide and the hurdles to overcome for their broader application in regenerative dentistry.

Dental Tissue-Derived Human Mesenchymal Stem Cells and Their Potential in Therapeutic Application

Human mesenchymal stem cells (hMSCs) are multipotent cells, which exhibit plastic adherence, express specific cell surface marker spectrum, and have multi-lineage differentiation potential. These cells can be obtained from multiple tissues. Dental tissue-derived hMSCs (dental MSCs) possess the ability to give rise to mesodermal lineage (osteocytes, adipocytes, and chondrocytes), ectodermal lineage (neurocytes), and endodermal lineages (hepatocytes). Dental MSCs were first isolated from dental pulp of the extracted third molar and till now they have been purified from various dental tissues, including pulp tissue of permanent teeth and exfoliated deciduous teeth, apical papilla, periodontal ligament, gingiva, dental follicle, tooth germ, and alveolar bone. Dental MSCs are not only easily accessible but are also expandable in vitro with relative genomic stability for a long period of time. Moreover, dental MSCs have exhibited immunomodulatory properties by secreting cytokines. Easy accessibility, multi-lineage differentiation potential, and immunomodulatory effects make dental MSCs distinct from the other hMSCs and an effective tool in stem cell-based therapy. Several preclinical studies and clinical trials have been performed using dental MSCs in the treatment of multiple ailments, ranging from dental diseases to nondental diseases. The present review has summarized dental MSC sources, multi-lineage differentiation capacities, immunomodulatory features, its potential in the treatment of diseases, and its application in both preclinical studies and clinical trials. The regenerative therapeutic strategies in dental medicine have also been discussed.

SHED promote angiogenesis in stem cell-mediated dental pulp regeneration

Dental pulp, plays an indispensable role in maintaining homeostasis of the tooth. Pulp necrosis always causes tooth nutrition deficiency and abnormal root development, which leads to tooth discoloration, fracture or even loss. Our previous study showed implantation of autologous SHED could regenerate functional dental pulp. However, the detailed mechanism of the implanted SHED participating in dental pulp regeneration remains unknown. In this study, we implanted SHED in a porcine dental pulp regeneration model to evaluate the regenerative effect and identify whether SHED promoted angiogenesis in regenerated dental pulp. Firstly we verified that xenogenous SHED had the ability to regenerated pulp tissue of host in vivo. Then we found the vasculature in regenerated pulp originated from implanted SHED. In addition, stem cells were isolated from regenerated dental pulp, which exhibited good multi-differentiation properties and promoted angiogenesis in pulp regeneration process and these results demonstrated that SHED promoted angiogenesis in stem cell-mediated dental pulp regeneration.

Regenerative Capacity of Dental Pulp Stem Cells: A Systematic Review

OBJECTIVES

The dental pulp contains undifferentiated mesenchymal cells, blood vessels and so on, which are responsible for routine functions of a tooth. The determination of stemness and regenerative properties using biomarkers and further application in routine practice may unravel its potential.

MATERIALS AND METHODS

Inclusion criteria-original research articles published in English, from 2000 to 2019, were collected both manually and by electronic search from databases of Cochrane, Medline, Embase, and PubMed. Exclusion criteria-articles other than English and review manuscripts were omitted. The shortlisted articles were reviewed for specific biomarkers, to assess the regenerative potential, stemness, and lineage of dental pulp stem cells.

RESULTS

Of 512 articles, 64 were selected and reviewed to determine the mesenchymal, neurogenic, vasculogenic, hematopoietic, and stem cell potential. On the basis of the search analysis, a panel of markers was proposed.

CONCLUSION

The application of proposed markers, on a pulpectomized tissue derived from human teeth, may be helpful to determine the regenerative potential and the usefulness in regenerative medicine and tissue engineering.

Allogeneic Cellular Therapy in a Mature Tooth with Apical Periodontitis and Accidental Root Perforation: A Case Report

INTRODUCTION

Cell therapy in regenerative endodontics introduces an alternative option to classic treatment strategies for complex endodontic cases. The aim of this case report was to describe cell-based therapy using allogeneic umbilical cord mesenchymal stem cells (UC-MSCs) encapsulated in a bioscaffold for a complex case of a mature permanent tooth with apical periodontitis and accidental root perforation.

METHODS

A healthy 19-year-old man undergoing orthodontic treatment was referred for endodontic treatment in tooth #7; he was diagnosed with apical periodontitis during a previously initiated treatment associated with accidental perforation of the radicular cervical third. The root perforation was sealed with glass ionomer and composite resin, and the root canal was instrumented, disinfected, and dressed with calcium hydroxide. After 3 weeks, allogeneic UC-MSCs were encapsulated in platelet-poor plasma and then implanted into the root canal, and Biodentine (Septodont, Saint-Maur-des-Fosses, France) was placed below the cementoenamel junction. Finally, the tooth was restored with composite resin.

RESULTS

Follow-up examinations were performed 6 months and 1 year later. The examinations included periapical radiography, cone-beam computed tomographic imaging, and sensitivity and vitality tests. Radiographic and cone-beam computed tomographic images indicated remission of the apical lesion. Clinical evaluations revealed normal responses to percussion and palpation tests; the tooth was responsive to the electric pulp test, and the vitality test indicated low blood perfusion units.

CONCLUSIONS

This case report reveals the potential use of allogeneic cellular therapy using encapsulated UC-MSCS in a platelet-poor plasma scaffold for a complex case of a permanent tooth with apical periodontitis and root perforation.

Efficacy of bioactive nanoparticles on tissue-endotoxin induced suppression of stem cell viability, migration and differentiation

AIM

To characterize a lipopolysaccharide (LPS)-treated dentine tissue model (LPS dentine) to analyse the efficacy of polycationic chitosan nanoparticles (CSnp) and/or dexamethasone conjugate chitosan nanoparticles (Dex-CSnp) on the viability/differentiation potential of stem cells from apical papilla (SCAP) when exposed to LPS dentine. A further aim was to understand the effect of macrophage-dependent inflammation on SCAP migration in the presence of LPS dentine.

METHODOLOGY

A total of 88 dentine slabs were used. TOF-SIMS analysis was performed amongst the LPS-treated and untreated dentine groups (n = 2/group). The study was conducted using four dentine groups: no treatment (control); LPS treatment only; LPS treatment followed by CSnp conditioning; and LPS treatment followed by Dex-CSnp conditioning groups. SCAP adherence, viability, differentiation and biomineralization potential on dentine from different groups were studied using fluorescent and scanning electron microscopy. Inflammation by macrophages in response to LPS dentine was quantified, and effect on SCAP migration was analysed. Statistical analysis was performed using Student's t-test with a significance level of P < 0.05.

RESULT

TOF-SIMS analysis confirmed LPS contamination. LPS dentine affected SCAP viability but not adherence to dentine (P < 0.001). Conditioning of LPS dentine with either nanoparticles improved SCAP viability (P < 0.01) and rescued other LPS related adverse effects on SCAPs, such as F-actin disruption, decrease in differentiation/biomineralization potential. IL-6 produced by macrophages in response to LPS-treated dentine impeded SCAP migration (P < 0.001), diminished on CSnp and Dex-CSnp conditioning groups (P < 0.01).

CONCLUSION

This study developed an LPS-dentine model and highlighted the ability of CSnp and Dex-CSnp to promote stem cell viability, migration, differentiation potential and reduce inflammation, providing an environment conducive for tissue regeneration/repair.

Evaluation of Chitosan Hydrogel for Sustained Delivery of VEGF for Odontogenic Differentiation of Dental Pulp Stem Cells

The pulpotomy with pulp capping is aimed at retaining vital pulp with reparative dentin formation. Vascular endothelial growth factor (VEGF) plays a crucial role in dentin regeneration; however, its constant administrations in the human body is still problematic. Chitosan was widely studied as an effective carrier to deliver bioactive molecules in regenerative medicine. In this study, we conducted a chitosan/β-glycerophosphate (CS/β-GP) hydrogel as a VEGF-sustained release system and explored its effects on dental pulp stem cells (DPSCs). CS/β-GP hydrogel was manufactured using a sol-gel method. SEM assay showed the spongy and porous microstructure of the lyophilized hydrogels. DPSCs cultured in the CS/β-GP hydrogel kept adhesion and vitality. CCK-8 assay tested the promoted proliferation activity of DPSCs on the hydrogel. Besides, the added VEGF protein could continually release from VEGF/CS/β-GP hydrogel. The VEGF/CS/β-GP hydrogel could promote the odontogenic differentiation of DPSCs better than VEGF treatment without hydrogel. Our results suggested that CS/β-GP hydrogel could continually release VEGF and contribute to odontogenic differentiation of DPSCs, thus may become a potential carrier of bioactive molecules in pulp capping therapy.

Dental stem cells in tooth repair: A systematic review

Background: Dental stem cells (DSCs) are self-renewable teeth cells, which help maintain or develop oral tissues. These cells can differentiate into odontoblasts, adipocytes, cementoblast-like cells, osteoblasts, or chondroblasts and form dentin/pulp. This systematic review aimed to summarize the current evidence regarding the role of these cells in dental pulp regeneration. Methods: We searched the following databases: PubMed, Cochrane Library, MEDLINE, SCOPUS, ScienceDirect, and Web of Science using relevant keywords. Case reports and non-English studies were excluded. We included all studies using dental stem cells in tooth repair whether in vivo or in vitro studies. Results: Dental pulp stem cell (DPSCs) is the most common type of cell. Most stem cells are incorporated and implanted into the root canals in different scaffold forms. Some experiments combine growth factors such as TDM, BMP, and G-CSF with stem cells to improve the results. The transplant of DPSCs and stem cells from apical papilla (SCAPs) was found to be associated with pulp-like recovery, efficient revascularization, enhanced chondrogenesis, and direct vascular supply of regenerated tissue. Conclusion: The current evidence suggests that DPSCs, stem cells from human exfoliated deciduous teeth, and SCAPs are capable of providing sufficient pulp regeneration and vascularization. For the development of the dental repair field, it is important to screen for more effective stem cells, dentine releasing therapies, good biomimicry scaffolds, and good histological markers.

Post-mitotic odontoblasts in health, disease, and regeneration

OBJECTIVE

Description of the odontoblast lifecycle, an overview of the known complex molecular interactions that occur when the health of the dental pulp is challenged and the current and future management strategies on vital and non-vital teeth.

METHODS

A literature search of the electronic databases included MEDLINE (1966-April 2019), CINAHL (1982-April 2019), EMBASE and EMBASE Classic (1947-April 2019), and hand searches of references retrieved were undertaken using the following MESH terms 'odontoblast*', 'inflammation', 'dental pulp*', 'wound healing' and 'regenerative medicine'.

RESULTS

Odontoblasts have a sensory and mechano-transduction role so as to detect external stimuli that challenge the dental pulp. On detection, odontoblasts stimulate the innate immunity by activating defence mechanisms key in the healing and repair mechanisms of the tooth. A better understanding of the role of odontoblasts within the dental pulp complex will allow an opportunity for biological management to remove the cause of the insult to the dental pulp, modulate the inflammatory process, and promote the healing and repair capabilities of the tooth. Current strategies include use of conventional dental pulp medicaments while newer methods include bioactive molecules, epigenetic modifications and tissue engineering.

CONCLUSION

Regenerative medicine methods are in their infancy and experimental stages at best. This review highlights the future direction of dental caries management and consequently research.

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.

Dentin tubule orientation determines odontoblastic differentiation in vitro: A morphological study

Odontoblasts are post-mitotic cells responsible for maintenance of the dentin, and are therefore important for dental health. In some cases, irreversible pulpitis leads to necrosis and consequently death of odontoblasts. Regenerative endodontics (RE) uses the concept of tissue engineering to restore the root canals to a healthy state, allowing for continued development of the root and surrounding tissue. Human dental pulp stem cells (hDPSCs) have been successfully used in RE to restore odontoblast function. Surface microgeometry is one of the most important factors involved in the induction of differentiation of hDPSCs into odontoblast-like cells. Although different authors have demonstrated the importance of a dentin-like surface with accessible dentin tubules to induce differentiation of hDPSCs, the ultrastructural characteristics of the cells and the secreted extracellular matrix have not been studied in depth. Here, we used an acellular dentin scaffold containing dentin tubules in different spatial geometries, which regulated their accessibility to cells. hDPSCs were cultured on the scaffolds for up to 6 weeks. Systematic characterization of differentiated cells was performed using both optical (hematoxylin and eosin, Masson trichrome, and immunohistochemical determination of dentin sialoprotein [DSSP]) and transmission electron microscopy. The results presented here indicated that cells grown on the dentin surface containing accessible dentin tubules developed a characteristic odontoblastic phenotype, with cellular processes similar to native odontoblasts. The cell organization and characteristics of secreted extracellular matrix were also similar to those of native dentin tissue. Cells grown on non-accessible dentin tubule surfaces secreted a more abundant and dense extracellular matrix, and developed a different phenotype consisting of secretory flat cells organized in layers. Cells grown far from the scaffold, i.e., directly on the culture well surface, developed a secretory phenotype probably influenced by biochemical factors released by the dentin scaffold or differentiated cells. The results presented here support the use of hDPSCs to regenerate dentin and show the utility of scaffold microgeometry for determining the differentiation and secretory phenotype of cultured cells.

Fabrication of Scaffolds for Bone-Tissue Regeneration

The present article describes the state of the art in the rapidly developing field of bone tissue engineering, where many disciplines, such as material science, mechanical engineering, clinical medicine and genetics, are interconnected. The main objective is to restore and improve the function of bone tissue by scaffolds, providing a suitable environment for tissue regeneration and repair. Strategies and materials used in oral regenerative therapies correspond to techniques generally used in bone tissue engineering. Researchers are focusing on developing and improving new materials to imitate the native biological neighborhood as authentically as possible. The most promising is a combination of cells and matrices (scaffolds) that can be fabricated from different kinds of materials. This review summarizes currently available materials and manufacturing technologies of scaffolds for bone-tissue regeneration.

Mechanical micronization of lipoaspirates for the treatment of hypertrophic scars

Background

Hypertrophic scars cause cosmetic and functional problems for patients, and their treatment remains challenging. Mechanical micronization of adipose tissue can remove adipocytes and concentrate functional cells. Stromal vascular fraction (SVF)-gel is obtained by a series of simple mechanical processes, including shifting between syringes and centrifugation. This study aimed to assess the therapeutic effect of SVF-gel on hypertrophic scars.

Methods

A model of hypertrophic scars was established in rabbit ears. SVF-gel and SVF cells were obtained from rabbit inguinal fat pads and injected into scars. Phosphate-buffered saline (PBS) was used as a control. Scars were structurally characterized by histologic and immunohistochemical analyses. Expression of inflammatory and fibrogenic genes was evaluated.

Results

Hypertrophic scars became less visible and softer following injection of SVF-gel or SVF cells. Dermal thickness was significantly lower in the groups treated with SVF-gel and SVF cells than in the PBS-treated group. Treatment with SVF-gel restored subcutaneous fat tissue in scars, while treatment with SVF cells and PBS did not. Injection of SVF-gel and SVF cells reduced macrophage infiltration in the dermal layer and decreased mRNA expression of interleukin-6 and monocyte chemoattractant protein-1. In addition, the level of myofibroblasts and collagen deposition were reduced in the groups treated with SVF-gel and SVF cells.

Conclusions

SVF-gel has therapeutic effects on hypertrophic scars. Injection of SVF-gel into hypertrophic scars restores subcutaneous fat tissue and reduces the levels of macrophages and myofibroblasts; thus, it decreased the dermal thickness of the scar.