Functionalized scaffolds to control dental pulp stem cell fate

Effects of Hispidulin on the Osteo/Odontogenic and Endothelial Differentiation of Dental Pulp Stem Cells

Background: Human dental pulp stem cells (HDPSCs) with multi-lineage differentiation potential and migration ability are required for HDPSC-based bone and dental regeneration. Hispidulin is a naturally occurring flavonoid with diverse pharmacological activities, but its effects on biological properties of HDPSCs remain unknown. Therefore, we investigated the effects of hispidulin on the differentiation potential and migration ability of HDPSCs and elucidated their underlying mechanisms. Methods: The osteo/odontogenic capacity of HDPSCs was assessed using the alkaline phosphatase (ALP) and Alizarin Red S (ARS) staining. The migration ability of HDPSCs was evaluated using a scratch wound assay. Furthermore, the endothelial differentiation of HDPSCs was examined by using a capillary sprouting assay and by assessing CD31 expression. Results: Hispidulin significantly enhanced the osteo/odontogenic differentiation of HDPSCs with increased expression of osteo/odontogenic differentiation markers. Hispidulin increased the migration of HDPSCs, which was mediated by the upregulation of C-X-C chemokine receptor type 4 (CXCR4). The treatment of HDPSCs with hispidulin enhanced the differentiation of HDPSCs into endothelial cells, as evidenced by increased capillary sprouting and endothelial marker expression. In addition, we demonstrated that hispidulin activated the ERK1/2 signaling, and its inhibition by U0126 significantly suppressed the hispidulin-induced endothelial differentiation of HDPSCs. Conclusions: These findings demonstrate that hispidulin effectively promotes the osteo/odontogenic and endothelial differentiation, and migration of HDPSCs. These results suggest that hispidulin may have potential therapeutic applications in dental pulp regeneration and tissue engineering.

Guidance for evaluating biomaterials' properties and biological potential for dental pulp tissue engineering and regeneration research

BACKGROUND

Dental pulp regeneration is a complex and advancing field that requires biomaterials capable of supporting the pulp's diverse functions, including immune defense, sensory perception, vascularization, and reparative dentinogenesis. Regeneration involves orchestrating the formation of soft connective tissues, neurons, blood vessels, and mineralized structures, necessitating materials with tailored biological and mechanical properties. Numerous biomaterials have entered clinical practice, while others are being developed for tissue engineering applications. The composition and a broad range of material properties, such as surface characteristics, degradation rate, and mechanical strength, significantly influence cellular behavior and tissue outcomes. This underscores the importance of employing robust evaluation methods and ensuring precise and comprehensive reporting of findings to advance research and clinical translation.

AIMS

This article aims to present the biological foundations of dental pulp tissue engineering alongside potential testing methodologies and their advantages and limitations. It provides guidance for developing research protocols to evaluate the properties of biomaterials and their influences on cell and tissue behavior, supporting progress toward effective dental pulp regeneration strategies.

Improving Antimicrobial Properties of GelMA Biocomposite Hydrogels for Regenerative Endodontic Treatment

Regenerative endodontics is a developing field involving the restoration of tooth structure and re-vitality of necrotic pulp. One of the most critical clinical considerations for regenerative endodontic procedures is the disinfection of the root canal system, since infection interferes with regeneration, repair, and stem cell activity. In this study, we aimed to provide the synthesis of injectable biopolymeric tissue scaffolds that can be used in routine clinical and regenerative endodontic treatment procedures using Gelatin methacryloyl (GelMA), and to test the antimicrobial efficacy of Gelatin methacryloyl/Silver nanoparticles (GelMA/AgNP), Gelatin methacryloyl/Hyaluronic acid (GelMA/HYA), and Gelatin methacryloyl/hydroxyapatite (GelMA/HA) composite hydrogels against microorganisms that are often encountered in stubborn infections in endodontic microbiology. Injectable biocomposite hydrogels exhibiting effective antimicrobial activity and non-cytotoxic behavior were successfully synthesized. This is also promising for clinical applications of regenerative endodontic procedures with hydrogels, which are proposed based on the collected data. The GelMA hydrogel loaded with hyaluronic acid showed the highest efficacy against Enterococcus faecalis, one of the stubborn bacteria in the root canal. The GelMA hydrogel loaded with hydroxyapatite also showed a significant effect against Candida albicans, which is another bacteria responsible for stubborn infections in the root canal.

Dental-derived stem cells in tissue engineering: the role of biomaterials and host response

Dental-derived stem cells (DSCs) are attractive cell sources due to their easy access, superior growth capacity and low immunogenicity. They can respond to multiple extracellular matrix signals, which provide biophysical and biochemical cues to regulate the fate of residing cells. However, the direct transplantation of DSCs suffers from poor proliferation and differentiation toward functional cells and low survival rates due to local inflammation. Recently, elegant advances in the design of novel biomaterials have been made to give promise to the use of biomimetic biomaterials to regulate various cell behaviors, including proliferation, differentiation and migration. Biomaterials could be tailored with multiple functionalities, e.g., stimuli-responsiveness. There is an emerging need to summarize recent advances in engineered biomaterials-mediated delivery and therapy of DSCs and their potential applications. Herein, we outlined the design of biomaterials for supporting DSCs and the host response to the transplantation.

Hydrogels for Oral Tissue Engineering: Challenges and Opportunities

Oral health is crucial to daily life, yet many people worldwide suffer from oral diseases. With the development of oral tissue engineering, there is a growing demand for dental biomaterials. Addressing oral diseases often requires a two-fold approach: fighting bacterial infections and promoting tissue growth. Hydrogels are promising tissue engineering biomaterials that show great potential for oral tissue regeneration and drug delivery. In this review, we present a classification of hydrogels commonly used in dental research, including natural and synthetic hydrogels. Furthermore, recent applications of these hydrogels in endodontic restorations, periodontal tissues, mandibular and oral soft tissue restorations, and related clinical studies are also discussed, including various antimicrobial and tissue growth promotion strategies used in the dental applications of hydrogels. While hydrogels have been increasingly studied in oral tissue engineering, there are still some challenges that need to be addressed for satisfactory clinical outcomes. This paper summarizes the current issues in the abovementioned application areas and discusses possible future developments.

Lipoplex-Functionalized Thin-Film Surface Coating Based on Extracellular Matrix Components as Local Gene Delivery System to Control Osteogenic Stem Cell Differentiation

A gene-activated surface coating is presented as a strategy to design smart biomaterials for bone tissue engineering. The thin-film coating is based on polyelectrolyte multilayers composed of collagen I and chondroitin sulfate, two main biopolymers of the bone extracellular matrix, which are fabricated by layer-by-layer assembly. For further functionalization, DNA/lipid-nanoparticles (lipoplexes) are incorporated into the multilayers. The polyelectrolyte multilayer fabrication and lipoplex deposition are analyzed by surface sensitive analytical methods that demonstrate successful thin-film formation, fibrillar structuring of collagen, and homogenous embedding of lipoplexes. Culture of mesenchymal stem cells on the lipoplex functionalized multilayer results in excellent attachment and growth of them, and also, their ability to take up cargo like fluorescence-labelled DNA from lipoplexes. The functionalization of the multilayer with lipoplexes encapsulating DNA encoding for transient expression of bone morphogenetic protein 2 induces osteogenic differentiation of mesenchymal stem cells, which is shown by mRNA quantification for osteogenic genes and histochemical staining. In summary, the novel gene-functionalized and extracellular matrix mimicking multilayer composed of collagen I, chondroitin sulfate, and lipoplexes, represents a smart surface functionalization that holds great promise for tissue engineering constructs and implant coatings to promote regeneration of bone and other tissues.

Towards a New Concept of Regenerative Endodontics Based on Mesenchymal Stem Cell-Derived Secretomes Products

The teeth, made up of hard and soft tissues, represent complex functioning structures of the oral cavity, which are frequently affected by processes that cause structural damage that can lead to their loss. Currently, replacement therapy such as endodontics or implants, restore structural defects but do not perform any biological function, such as restoring blood and nerve supplies. In the search for alternatives to regenerate the dental pulp, two alternative regenerative endodontic procedures (REP) have been proposed: (I) cell-free REP (based in revascularization and homing induction to remaining dental pulp stem cells (DPSC) and even stem cells from apical papilla (SCAP) and (II) cell-based REP (with exogenous cell transplantation). Regarding the last topic, we show several limitations with these procedures and therefore, we propose a novel regenerative approach in order to revitalize the pulp and thus restore homeostatic functions to the dentin-pulp complex. Due to their multifactorial biological effects, the use of mesenchymal stem cells (MSC)-derived secretome from non-dental sources could be considered as inducers of DPSC and SCAP to completely regenerate the dental pulp. In partial pulp damage, appropriate stimulate DPSC by MSC-derived secretome could contribute to formation and also to restore the vasculature and nerves of the dental pulp.

Mineral-induced bubbling effect and biomineralization as strategies to create highly porous and bioactive scaffolds for dentin tissue engineering

The objective of the study was to assess the biological and mechanical characteristics of chitosan-based scaffolds enriched by mineral phases and biomineralized in simulated body fluid (SBF) as a possible biomaterial for dentin regeneration. Thus, porous chitosan scaffolds were prepared by the mineral-induced bubbling-effect technique and subjected to biomineralization to create biomimetic scaffolds for dentin tissue engineering. Suspensions containing calcium hydroxide, nanohydroxyapatite, or β-tricalcium phosphate were added to the chitosan (CH) solution and subjected to gradual freezing and freeze-drying to obtain CHCa, CHnHA, and CHβTCP porous scaffolds, respectively, by the bubbling effect. Then, scaffolds were incubated in SBF for 5 days at 37°C, under constant stirring, to promote calcium-phosphate (CaP) biomineralization. Scanning electron microscopy revealed increased pore size and porosity degree on mineral-containing scaffolds, with CHCa and CHnHA presenting as round, well-distributed, and with an interconnected pore network. Nevertheless, incubation in SBF disrupted the porous architecture, except for CHCa_SBF , leading to the deposition of CaP coverage, confirmed by Fourier Transform Infrared Spectroscopy analyses. All mineral-containing and SBF-treated formulations presented controlled degradation profiles and released calcium throughout 28 days. When human dental pulp cells (HDPCs) were seeded onto scaffold structures, the porous and interconnected architecture of CHCa, CHnHA, and CHCa_SBF allowed cells to infiltrate and spread throughout the scaffold structure, whereas in other formulations cells were dispersed or agglomerated. It was possible to determine a positive effect on cell proliferation and odontogenic differentiation for mineral-containing formulations, intensely improved by biomineralization. A significant increase in mineralized matrix deposition (by 8.4 to 18.9 times) was observed for CHCa_SBF , CHnHA_SBF , and CHβTCP_SBF in comparison with plain CH. The bioactive effect on odontoblastic marker expression (ALP activity and mineralized matrix) was also observed for HDPCs continuously cultivated with conditioned medium obtained from scaffolds. Therefore, biomineralization of chitosan scaffolds containing different mineral phases was responsible for increasing the capacity for mineralized matrix deposition by pulpal cells, with potential for use in dentin tissue engineering.

Bioactive Materials for Direct and Indirect Restorations: Concepts and Applications

Currently, minimally invasive restorations could be made in dentistry applying adhesive materials and adhesion principles to the dental structures. Following this philosophy, endodontic interventions have been avoided largely, preserving hard tissues, and maintaining dental vitality. Advances in biologically favorable bioactive materials enabled clinicans to induce repair and regeneration of dental tissues. Such materials are primarily used for pulp protection and cementation of indirect restorations. This review highlights current bioactive materials available, principles of bioactivity and their mechanisms of action.

Reducing Intervention in the COVID-19 Era: Opportunities for Vital Pulp Treatment

Over the last 12 months, the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-COV-2) virus has emerged as a significant global health problem with extensive repercussions for the practise of dentistry. As the principle transmission-route is via droplet-spread, aerosol-generating dental procedures (AGPs) present an exquisite challenge, which either has to be avoided or performed using strict infection-control measures, which increase the deployment of resources and cost. This new working environment necessitates the adoption of simplified, yet effective procedures that reduce intervention and minimise clinical chair time to short, single visits. Vital pulp treatment (VPT) has emerged as an attractive, technically less-complicated group of biologically-based management strategies that are aimed at maintaining pulp vitality and avoiding root canal treatment (RCT). These procedures are carried out in a strict aseptic environment using a rubber dam and have a reported high success rate, suggesting that they could be considered as effective and simple alternative therapies to relieve pain and avoid multiple visit RCT and other endodontic procedures. The relevance of promoting a simple, predictable and effective alternative to traditional, more complex dentistry has never been more compelling. In this perspective article, the latest advances in VPT are highlighted, along with an analysis of their relative success and compelling reasons why we as dentists should be adopting these treatment approaches. Thereafter, case selection, prognostic factors, techniques, limitations and future prospects of these procedures are discussed.

Development and characterization of a new chitosan-based scaffold associated with gelatin, microparticulate dentin and genipin for endodontic regeneration

OBJECTIVE

An ideal scaffold for endodontic regeneration should allow the predictableness of the new tissue organization and limit the negative impact of residual bacteria. Therefore, composition and functionalization of the scaffold play an important role in tissue bioengineering. The objective of this study was to assess the morphological, physicochemical, biological and antimicrobial properties of a new solid chitosan-based scaffold associated with gelatin, microparticulate dentin and genipin.

METHODS

Scaffolds based on chitosan (Ch); chitosan associated with gelatin and genipin (ChGG); and chitosan associated with gelatin, microparticulate dentin and genipin (ChGDG) were prepared by using the freeze-drying method. The morphology of the scaffolds was analyzed by scanning electron microscopy (SEM). The physicochemical properties were assessed for biodegradation, swelling and total released proteins. The biological aspects of the scaffolds were assessed using human cells from the apical papilla (hCAPs). Cell morphology and adhesion to the scaffolds were evaluated by SEM, cytotoxicity and cell proliferation by MTT reduction-assay. Cell differentiation in scaffolds was assessed by using alizarin red assay. The antimicrobial effect of the scaffolds was evaluated by using the bacterial culture method, and bacterial adhesion to the scaffolds was observed by SEM.

RESULTS

All the scaffolds presented porous structures. The ChCDG had more protein release, adhesion, proliferation and differentiation of hCAPs, and bacteriostatic effect on Enterococcus faecalis than Ch and ChGG (p < 0.05).

SIGNIFICANCE

The chitosan associated with gelatin, microparticulate dentin and genipin has morphological, physicochemical, biological and antibacterial characteristics suitable for their potential use as scaffold in regenerative endodontics.

Deciphering Reparative Processes in the Inflamed Dental Pulp

Research over several decades has increased our understanding of the nature of reparative and regenerative processes in the dental pulp, at both the cellular and molecular level. However, advances in scientific knowledge have not translated into novel clinical treatment strategies for caries-induced pulpitis. This narrative review explores the evidence regarding the ability of inflamed pulp tissue to heal and how this knowledge may be used therapeutically. A literature search and evidence analysis covering basic, translational and clinical pulp biology research was performed. The review focuses on (1) the regenerative and defense capabilities of the pulp during caries-induced inflammation; (2) the potential of novel biomaterials to harness the reparative and regenerative functions of the inflamed pulp; and (3) future perspectives and opportunities for conservative management of the inflamed pulp. Current conservative management strategies for pulpitis are limited by a combination of unreliable diagnostic tools and an outdated understanding of pulpal pathophysiological responses. This approach leads to the often unnecessary removal of the entire pulp. Consequently, there is a need for better diagnostic approaches and a focus on minimally-invasive treatments utilizing biologically-based regenerative materials and technologies.

Effect of Natural and Artificial Dentin Conditioners on the Release of Vascular Endothelial Growth Factor

INTRODUCTION

The purpose of this study was to observe the release of vascular endothelial growth factor (VEGF) after conditioning with etidronic acid (also known as 1-hydroxyethylidene-1 and 1-bisphosphonate [HEDP]) and phytic acid (inositol hexakisphosphate [IP6]) in comparison with EDTA on human dentin disks and cylinders.

METHODS

Human dentin disks were disinfected and prepared by the standardized method. Seventeen percent EDTA, 9% HEDP, 1% IP6, and distilled water (5 minutes) were used to immerse dentin disks. The dentin cylinders were prepared by following disinfection and the standardized preparation method to achieve a truncated cone-shaped canal with a 1-mm open apex. The dentin cylinder samples were irrigated with sodium hypochlorite (5 mL/5 minutes) and then rinsed with 17% EDTA, 9% HEDP, 1% IP6 and distilled water (5 mL/5 min). Enzyme-linked immunosorbent essay was performed to measure VEGF release. One-way analysis of variance was used to compare the mean release of VEGF between study groups and controls at a significance level of .05. A post hoc Tukey test was used for multiple comparisons between study groups.

RESULTS

Among conditioners, HEDP released more VEGF from both disks and cylinders. In cylinders, VEGF release by HEDP was significantly greater than the other conditioners, whereas in disks the release of VEGF was similar with all conditioners.

CONCLUSIONS

The release of VEGF by 9% HEDP and 1% IP6 was comparable with 17% EDTA from dentin disks; however, HEDP demonstrated more release from dentin cylinders than EDTA and IP6.

Structured nanofilms comprising Laponite® and bone extracellular matrix for osteogenic differentiation of skeletal progenitor cells

Functionalized scaffolds hold promise for stem cell therapy by controlling stem cell fate and differentiation potential. Here, we have examined the potential of a 2-dimensional (2D) scaffold to stimulate bone regeneration. Solubilized extracellular matrix (ECM) from human bone tissue contains native extracellular cues for human skeletal cells that facilitate osteogenic differentiation. However, human bone ECM displays limited mechanical strength and degradation stability under physiological conditions, necessitating modification of the physical properties of ECM before it can be considered for tissue engineering applications. To increase the mechanical stability of ECM, we explored the potential of synthetic Laponite® (LAP) clay as a counter material to prepare a 2D scaffold using Layer-by-Layer (LbL) self-assembly. The LAP and ECM multilayer nanofilms (ECM/LAP film) were successfully generated through electrostatic and protein-clay interactions. Furthermore, to enhance the mechanical properties of the ECM/LAP film, application of a NaCl solution wash step, instead of deionized water following LAP deposition resulted in the generation of stable, multi-stacked LAP layers which displayed enhanced mechanical properties able to sustain human skeletal progenitor cell growth. The ECM/LAP films were not cytotoxic and, critically, showed enhanced osteogenic differentiation potential as a consequence of the synergistic effects of ECM and LAP. In summary, we demonstrate the fabrication of a novel ECM/LAP nanofilm layer material with potential application in hard tissue engineering.

Dentin-Pulp Tissue Regeneration Approaches in Dentistry: An Overview and Current Trends

Conventional treatment approaches in irreversible pulpitis and apical periodontitis include the disinfection of the pulp space followed by filling with various materials, which is commonly known as the root canal treatment. Disadvantages including the loss of tooth vitality and defense mechanism against carious lesions, susceptibility to fractures, discoloration and microleakage led to the development of regenerative therapies for the dentin pulp-complex. The goal of dentin-pulp tissue regeneration is to reestablish the physiological pulp function such as pulp sensibility, pulp repair capability by mineralization and pulp immunity. Recent dentin-pulp tissue regeneration approaches can be divided into cell homing and cell transplantation. Cell based approaches include a suitable scaffold for the delivery of potent stem cells with or without bioactive molecules into the root canal system while cell homing is based on the recruitment of host endogenous stem cells from the resident tissue including periapical region or dental pulp. This review discusses the recent treatment modalities in dentin-pulp tissue regeneration through tissue engineering and current challenges and trends in this field of research.

RGD- and VEGF-Mimetic Peptide Epitope-Functionalized Self-Assembling Peptide Hydrogels Promote Dentin-Pulp Complex Regeneration

INTRODUCTION

Cell-based tissue engineering is a promising method for dentin-pulp complex (DPC) regeneration. The challenges associated with DPC regeneration include the generation of a suitable microenvironment that facilitates the complete odontogenic differentiation of dental pulp stem cells (DPSCs) and the rapid induction of angiogenesis. Thus, the survival and subsequent differentiation of DPSCs are limited. Extracellular matrix (ECM)-like biomimetic hydrogels composed of self-assembling peptides (SAPs) were developed to provide an appropriate microenvironment for DPSCs. For functional DPC regeneration, the most important considerations are to provide an environment that promotes the adequate attachment of DPSCs and rapid vascularization of the regenerating pulp. Morphogenic signals in the form of growth factors (GFs) have been incorporated into SAPs to promote productive DPSC behaviors. However, the use of GFs has several drawbacks. We envision using a scaffold with SAPs coupled with long-term factors to increase DPSC attachment and vascularization as a method to address this challenge.

METHODS

In this study, we developed synthetic material for an SAP-based scaffold with RGD- and vascular endothelial growth factor (VEGF)-mimetic peptide epitopes with the dual functions of dentin and pulp regeneration. DPSCs and human umbilical vein endothelial cells (HUVECs) were used to evaluate the biological effects of SAP-based scaffolds. Furthermore, the pulpotomized molar rat model was employed to test the reparative and regenerative effects of SAP-based scaffolds.

RESULTS

This scaffold simultaneously presented RGD- and VEGF-mimetic peptide epitopes and provided a 3D microenvironment for DPSCs. DPSCs grown on this composite scaffold exhibited significantly improved survival and angiogenic and odontogenic differentiation in the multifunctionalized group in vitro. Histological and functional evaluations of a partially pulpotomized rat model revealed that the multifunctionalized scaffold was superior to other options with respect to stimulating pulp recovery and dentin regeneration in vivo.

CONCLUSION

Based on our data obtained with the functionalized SAP scaffold, a 3D microenvironment that supports stem cell adhesion and angiogenesis was generated that has great potential for dental pulp tissue engineering and regeneration.

Tooth Formation: Are the Hardest Tissues of Human Body Hard to Regenerate?

With increasing life expectancy, demands for dental tissue and whole-tooth regeneration are becoming more significant. Despite great progress in medicine, including regenerative therapies, the complex structure of dental tissues introduces several challenges to the field of regenerative dentistry. Interdisciplinary efforts from cellular biologists, material scientists, and clinical odontologists are being made to establish strategies and find the solutions for dental tissue regeneration and/or whole-tooth regeneration. In recent years, many significant discoveries were done regarding signaling pathways and factors shaping calcified tissue genesis, including those of tooth. Novel biocompatible scaffolds and polymer-based drug release systems are under development and may soon result in clinically applicable biomaterials with the potential to modulate signaling cascades involved in dental tissue genesis and regeneration. Approaches for whole-tooth regeneration utilizing adult stem cells, induced pluripotent stem cells, or tooth germ cells transplantation are emerging as promising alternatives to overcome existing in vitro tissue generation hurdles. In this interdisciplinary review, most recent advances in cellular signaling guiding dental tissue genesis, novel functionalized scaffolds and drug release material, various odontogenic cell sources, and methods for tooth regeneration are discussed thus providing a multi-faceted, up-to-date, and illustrative overview on the tooth regeneration matter, alongside hints for future directions in the challenging field of regenerative dentistry.

Photobiomodulation therapy improves human dental pulp stem cell viability and migration in vitro associated to upregulation of histone acetylation

This in vitro study evaluated the role of photobiomodulation therapy (PBMT) on viability and migration of human dental pulp stem cells (hDPSCs) and its association to epigenetic mechanisms such as histone acetylation. The hDPSCs were characterized and assigned into control and PBMT groups. For the PBMT, five laser irradiations at 6-h intervals were performed using a continuous-wave InGaAlP diode laser. Viability (MTT), migration (scratch), and histone acetylation H3 (H3K9ac immunofluorescence) were evaluated immediately after the last irradiation. PBMT significantly increased the viability (P = 0.004). Also, PBMT group showed significantly increased migration of cells in the wound compared to the control in 6 h (P = 0.002), 12 h (P = 0.014) and 18 h (P = 0.083) being faster than the control, which only finished the process at 24 h. PBMT induced epigenetic modifications in hDPSC due to increased histone acetylation (P = 0.001). PBMT increased viability and migration of hDPSCs, which are related with the upregulation of histone acetylation and could be considered a promising adjuvant therapy for regenerative endodontic treatment.

Pulp-Dentin Tissue Healing Response: A Discussion of Current Biomedical Approaches

Dental pulp tissue exposed to mechanical trauma or cariogenic process results in root canal and/or periapical infections, and conventionally treated with root canal procedures. The more recent regenerative endodontic procedure intends to achieve effective root canal disinfection and adequate pulp–dentin tissue regeneration; however, numerous limitations are reported. Because tooth is composed of vital soft pulp enclosed by the mineralized hard tissue in a highly organized structure, complete pulp–dentin tissue regeneration has been challenging to achieve. In consideration of the limitations and unique dental anatomy, it is important to understand the healing and repair processes through inflammatory-proliferative-remodeling phase transformations of pulp–dentin tissue. Upon cause by infectious and mechanical stimuli, the innate defense mechanism is initiated by resident pulp cells including immune cells through chemical signaling. After the expansion of infection and damage to resident pulp–dentin cells, consequent chemical signaling induces pluripotent mesenchymal stem cells (MSCs) to migrate to the injury site to perform the tissue regeneration process. Additionally, innovative biomaterials are necessary to facilitate the immune response and pulp–dentin tissue regeneration roles of MSCs. This review highlights current approaches of pulp–dentin tissue healing process and suggests potential biomedical perspective of the pulp–dentin tissue regeneration.

Concentrated Growth Factor Promotes Dental Pulp Cells Proliferation and Mineralization and Facilitates Recovery of Dental Pulp Tissue

Background

Dental pulp cells (DPCs) play vital roles in the recovery of dental pulp tissue. Concentrated growth factor (CGF) can promote proliferation and mineralization of various cells. However, the functions of CGF on DPCs and dental pulp tissue are unclear. The object of our study was to identify the roles of CGF in DPCs proliferation and mineralization in vitro and to assess the effects of CGF on direct pulp capping in vivo.

Material/Methods

We performed CCK-8 and Transwell assay to detect proliferation and migration activity of DPCs. Alizarin Red staining was performed to examine mineralized nodules. Alkaline phosphatase activity test was used to measure the mineralization capacity of DPCs. We assessed the odontogenic differentiation gene expression level by Western blot and qPCR. The effect of CGF on direct pulp capping in vivo were evaluated by radiography and histopathology.

Results

CGF increased the number of proliferative and migratory DPCs. CGF enhanced DPCs mineralized nodules and improved the gene expression levels of DSPP, DMP-1, BSP, and ALP. CGF upregulated the protein levels of ALP, BMP2, SMAD5, Runx2, and p-Smad, and the effect could be partially reversed by Noggin. CGF promoted pulp recovery and kept its vitality in directly pulp capping.

Conclusions

CGF promotes DPCs proliferation and mineralization. It regulates the mineralization of DPCs via the BMP2/SMAD5/Runx2 signaling pathway. CGF can be used as the effective graft for direct pulp capping.

Influence of photobiomodulation therapy on root development of rat molars with open apex and pulp necrosis

This study aimed to evaluate the role of photobiomodulation (PBM) in apexification and apexogenesis of necrotic rat molars with an open apex. Rat molars were exposed to the oral environment for 3 weeks. Canals were rinsed with 2.5% NaOCl and 17% EDTA, filled with antibiotic paste and sealed. After 7 days, canals were rinsed and divided into six groups (n=6): mineral trioxide aggregate (MTA); blood clot (BC); human dental pulp stem cells (hDPSC); MTA+PBM; BC+PBM; and hDPSC+PBM. In hDPSC groups, a 1% agarose gel scaffold was used. Two groups were not exposed: healthy tooth+PBM (n = 6), healthy tooth (n = 3); and one was exposed throughout the experiment: necrotic tooth (n = 3). In PBM groups, irradiation was performed with aluminum gallium indium phosphide (InGaAlP) diode laser for 30 days within 24-h intervals. After that, the specimens were processed for histological and immunohistochemical analyses. Necrotic tooth showed greater neutrophil infiltrate (p < 0.05). Necrotic tooth, healthy tooth, and healthy tooth+PBM groups showed absence of a thin layer of fibrous condensation in the periapical area. All the other groups stimulated the formation of a thicker layer of fibers (p < 0.05). All groups formed more mineralized tissue than necrotic tooth (p < 0.05). PBM associated with MTA, BC, or hDPSC formed more mineralized tissue (p < 0.05). MTA+PBM induced apexification (p < 0.05). Rabbit polyclonal anti-bone sialoprotein (BSP) antibody confirmed the histological findings of mineralized tissue formation, and hDPSC groups exhibited higher percentage of BSP-positive cells. It can be concluded that PBM improved apexification and favored apexogenesis in necrotic rat molars with an open apex.

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

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

Novel Calcium Phosphate Cement with Metformin-Loaded Chitosan for Odontogenic Differentiation of Human Dental Pulp Cells

Metformin is an old and widely accepted first-line drug for treating type 2 diabetes. Our previous studies demonstrate that metformin can stimulate the osteo/odontogenic differentiation of human-induced pluripotent stem cell-derived mesenchymal stem cells and human dental pulp cells (DPCs). Due to the rapid dilution of metformin from the defect area, the aim of this study was to develop a drug delivery system with controlled release of metformin to promote cell viability and odontogenic differentiation of DPCs favoring dentin regeneration. Calcium phosphate cement (CPC) containing chitosan and metformin as a scaffold was synthesized. DPCs were seeded onto the scaffold, and the viability and proliferation were evaluated at several time points. For osteogenic differentiation analysis, alkaline phosphatase (ALP) activity was tested, cells were stained with Alizarin Red, and the expression of odontogenic markers was evaluated by real-time polymerase chain reaction. DPCs remained viable and attached well to the CPC-chitosan composite scaffold. Moreover, the addition of metformin to the CPC-chitosan composite did not adversely affect cell proliferation, compared to that of CPC control. Our data further revealed that the novel CPC-chitosan-metformin composite enhanced the odontogenic differentiation of DPCs, as evidenced by higher ALP activity, elevated expression of odontoblastic markers, and strong mineral deposition. These results suggest that the new CPC-chitosan-metformin composite is a highly promising scaffold with the potential for tissue engineering applications including dentin regeneration.

Growth Factors and Cell Homing in Dental Tissue Regeneration

Purpose of Review

To summarize current views on the role and therapeutic potential of growth factors (GFs) within endodontic cell homing.

Recent Findings

Cell homing/revitalization techniques aim to regenerate dentin and pulp using endogenous cells. Clinically, revitalization has successfully created new vital tissue in necrotic permanent teeth with an open apex; however, there is no evidence of new odontoblasts, pulp tissue, or predictable extension in root length. Although the response is reparative rather than regenerative, exciting opportunities to improve these biologically-based strategies remain by (1) efficiently sequestering dentin-matrix-components (DMCs) using irrigants and dental materials (2) designing next-generation GF-releasing scaffold materials and (3) utilizing other sources of GF such as cells and plasma-rich plasma and plasma-rich fibrin.

Summary

GFs can promote reparative-dentinogenesis and pulp-like tissue formation. The future development and clinical approval of GF-functionalized-scaffolds is a priority; however, current focus should be to harness DMCs and target the interaction of stem cells and GFs.

Novel Biological and Technological Platforms for Dental Clinical Use

Human teeth have a limited capacity to regenerate and thus biological reconstruction of damaged or lost dental tissues remains a significant challange in modern dentistry. Recent efforts focus on alternative therapeutic approaches for partial or whole tooth regeneration that complement traditional dental treatments using sophisticated materials and dental implants. These multidisciplinary approaches are based on the combination of stem cells with advanced tissue engineer products and computing technology, and they hold great promise for future applications in dentistry. The administration to patients of dynamic biological agents composed by stem cells and scaffolds will certainly increase the regenerative capacity of dental pathological tissues. The design of innovative materials for tissue restoration, diagnostics, imaging, and targeted pharmaceutical treatment will significantly improve the quality of dental care and will have a major societal impact. This review depicts the current challenges in dentistry and describes the possibilities for novel and succesful therapeutic applications in the near future.

Hyaluronic acid hydrogels incorporating platelet lysate enhance human pulp cell proliferation and differentiation

The restoration of dentine-pulp complex remains a challenge for dentists; nonetheless, it has been poorly addressed. An ideal system should modulate the host response, as well as enable the recruitment, proliferation and differentiation of relevant progenitor cells. Herein was proposed a photocrosslinkable hydrogel system based on hyaluronic acid (HA) and platelet lysate (PL). PL is a cocktail of growth factors (GFs) and cytokines involved in wound healing orchestration, obtained by the cryogenic processing of platelet concentrates, and was expected to provide the HA hydrogels specific biochemical cues to enhance pulp cells' recruitment, proliferation and differentiation. Stable HA hydrogels incorporating PL (HAPL) were prepared after photocrosslinking of methacrylated HA (Met-HA) previously dissolved in PL, triggered by the Ultra Violet activated photoinitiator Irgacure 2959. Both the HAPL and plain HA hydrogels were shown to be able to recruit cells from a cell monolayer of human dental pulp stem cells (hDPSCs) isolated from permanent teeth. The hDPCs were also seeded directly over the hydrogels (5 × 10⁴ cells/hydrogel) and cultured in osteogenic conditions. Cell metabolism and DNA quantification were higher, in all time-points, for PL supplemented hydrogels (p < 0,05). Alkaline phosphatase (ALPL) activity and calcium quantification peaks were observed for the HAPL group at 21 days (p < 0,05). The gene expression for ALPL and COLIA1 was up-regulated at 21 days to HAPL, compared with HA group (p < 0,05). Within the same time point, the gene expression for RUNX2 did not differ between the groups. Overall, data demonstrated that the HA hydrogels incorporating PL increased the cellular metabolism and stimulate the mineralized matrix deposition by hDPSCs, providing clear evidence of the potential of the proposed system for the repair of damaged pulp/dentin tissue and endodontics regeneration.

Bioactive treatments in bone grafts for implant-based rehabilitation: Systematic review and meta-analysis

BACKGROUND

The use of bioactive proteins, such as rhBMP-2, may improve bone regeneration in oral and maxillofacial surgery.

PURPOSE

Analyze the effect of using bioactive proteins for bone regeneration in implant-based rehabilitation.

MATERIALS AND METHODS

Seven databases were screened. Only clinical trials that evaluated the use of heterologous sources of bioactive proteins for bone formation prior to implant-based rehabilitation were included. Statistical analyses were carried out using a random-effects model by comparing the standardized mean difference between groups for bone formation, and risk ratio for implant survival (P ≤ .05).

RESULTS

Seventeen studies were included in the qualitative analysis, and 16 in the meta-analysis. For sinus floor augmentation, bone grafts showed higher amounts of residual bone graft particles than bioactive treatments (P ≤ .05). While for alveolar ridge augmentation bioactive treatments showed a higher level of bone formation than control groups (P ≤ .05). At 3 years of follow-up, no statistically significant differences were observed for implant survival (P > .05).

CONCLUSIONS

Bioactive proteins may improve bone formation in alveolar ridge augmentation, and reduce residual bone grafts in sinus floor augmentation. Further studies are needed to evaluate the long-term effect of using bioactive treatments for implant-based rehabilitation.

Biological response to self-etch adhesive after partial caries removal in rats

OBJECTIVES

The purposes of this study were to evaluate a model of slow caries progression and to investigate the performance of a self-etch adhesive system for partial caries removal.

MATERIALS AND METHODS

Rat molars were infected with Streptococcus sobrinus 6715 culture. Different time points were analyzed: days 78, 85, and 95 (± 2). After this, the samples were processed for morphological analysis. Additionally, the first molars were restored with zinc oxide and eugenol (IRM™; Dentsply; Brazil) or adhesive system (Clearfil SE Bond™; Kuraray Medical; Japan) 78 days after caries induction. After, 3 or 15 days post-treatment, the animals were euthanized, and their mandibles were processed for morphological analysis, classified by means of scores, and submitted to statistical analysis. Subsequently, immunohistochemical analysis was performed for osteonectin (OSN) and transforming growth factor-ß1 (TGF-ß1) expression.

RESULTS

According to the caries induction model used, on day 95 greater inflammatory infiltration (p < 0.001), and more extensive degradation of secondary/primary dentin were demonstrated than on day 78 (p < 0.05). Furthermore, the restorative materials presented similar performance (p > 0.05) and proved to be fundamental to control the carious lesion. The TGF-ß1 and OSN were shown to be active during the caries process.

CONCLUSIONS

The slow caries lesion model was feasible for morphological analysis of the dentin-pulp complex. The self-etch adhesive system triggered no acute inflammatory infiltration or pulp necrosis, instead it seemed to stimulate early pulp repair.

CLINICAL RELEVANCE

Clearfil SE Bond™ applied directly on caries-affected dentin did not predispose to pulp inflammation; instead, it appeared to provide early biological benefits.

Effects of Epigallocatechin Gallate, an Antibacterial Cross-linking Agent, on Proliferation and Differentiation of Human Dental Pulp Cells Cultured in Collagen Scaffolds

INTRODUCTION

This study aimed to evaluate the efficacy of epigallocatechin gallate (EGCG), an antibacterial cross-linking agent, on the proliferation and differentiation of human dental pulp cells (hDPCs) cultured in hydrogel collagen scaffolds.

METHODS

The odontogenic differentiation induced by EGCG was evaluated by alkaline phosphatase (ALP) activity and odontogenic-related gene expression using real-time polymerase chain reaction. The antibacterial effect of EGCG was investigated by a disc diffusion assay in comparison with glutaraldehyde. Proliferation was analyzed by cell number counting under both optical and confocal laser scanning microscopes. To assess the mechanical properties of collagen treated with EGCG, the setting time, surface roughness, and compressive strength were measured.

RESULTS

EGCG itself did not up-regulate the odontogenic-related markers (P > .05) although ALP activity was slightly increased. The proliferation and differentiation of hDPCs cultured in collagen increased significantly in the presence of EGCG (P < .05). The antibacterial activity of EGCG was similar to that of glutaraldehyde. The setting time of collagen was significantly shortened when it was treated with EGCG (P < .05). The surface roughness and compressive strength of the cross-linked collagen were higher than those of collagen without EGCG (P < .05).

CONCLUSIONS

Our results showed that EGCG, the antibacterial cross-linking agent, promoted the proliferation and differentiation of hDPCs cultured in collagen scaffolds. Furthermore, the enhanced mechanical properties of collagen scaffolds induced by EGCG may play important roles in cell behavior. Consequently, the application of EGCG to collagen scaffolds might be beneficial for regenerative endodontic therapy.

VEGF/BMP-2 loaded three-dimensional model for enhanced angiogenic and odontogenic potential of dental pulp stem cells

AIM

To investigate the proliferation and differentiation potential of human dental pulp stem cells (DPSCs) in a three-dimensional culture model (TDM) by incorporation of VEGF and BMP-2.

METHODOLOGY

TDM was established using fibrin gel (fg) as a soft tissue matrix and demineralized dentine disc (dd) as a hard tissue matrix. DPSCs and vascular endothelial growth factor (VEGF) were encapsulated in fibrin gel (fg-VEGF) and then inserted into bone morphogenetic protein (BMP-2)-coated demineralized dentine discs (dd-BMP-2). DPSCs were incubated for 28 days in various fg/dd combinations in the absence or presence of VEGF and BMP-2. Proliferation and morphology of DPSCs in fibrin gel were analysed using MTT and Live&Dead assays. Release profiles of VEGF and BMP-2 from fibrin gel and dentine discs were quantified using ELISA, and the expressions of angiogenic and odontogenic differentiation markers were determined with RT-qPCR analysis. Data were analysed statistically using Wilcoxon signed rank tests, Kruskal-Wallis tests with Mann-Whitney U tests and Bonferroni adjustment. The level of significance was set at P < 0.05.

RESULTS

DPSCs were able to proliferate and showed interconnected cellular elongations in fibrin gel depending on fibrinogen concentration whilst monolayer control group showed typical fibroblast-like cell morphology. Encapsulating of VEGF in fibrin gel and BMP-2 in gelatin that was used to coat dentine discs allowed the controlled releases of growth factors, which induced angiogenic and odontogenic gene expressions by DPSCs. Higher expressions of PECAM as an angiogenic factor, and BSP, DMP-1, OCN and CBFA as odontogenic factors, were observed in TDM as compared to the other fg/dd combinations and the monolayer control group (P < 0.05).

CONCLUSIONS

TDM consisting of fibrin gel and dentine matrix allowed cell-cell interactions. TDM was highly effective in delivering both VEGF and BMP-2 that enhanced the angiogenic and odontogenic potential of DPSCs.

Investigation of Human Dental Pulp Cells on a Potential Injectable Poly(lactic-co-glycolic acid) Microsphere Scaffold

INTRODUCTION

Poly(lactic-co-glycolic acid) (PLGA) has been extensively explored in the tissue engineering field with good biocompatibility and biodegradability. PLGA microspheres' injectable potency makes it highly desirable in dentin-pulp complex regeneration. Therefore, we investigated the cell adhesion, proliferation, odontogenic differentiation, and matrix mineralization of human dental pulp cells (HDPCs) on a PLGA microsphere scaffold. We hypothesized that this scaffold might be suitable for dentin-pulp complex regeneration.

METHODS

PLGA microsphere scaffolds were fabricated using the double-emulsion solvent extraction technique with or without type I collagen surface modification. HDPCs were isolated from freshly extracted premolar or third molar teeth with patients' informed consent and ethical approval. Fourth-passage HDPCs (1 × 105 cells/ml) were seeded onto surface-modified or -unmodified PLGA microspheres and cultured in vitro. Cell adhesion, proliferation, and alkaline phosphatase activity were evaluated at different time points. Odontogenic-related gene expression (DMP1, DSPP, COL1, OPN, and OCN) were analyzed using quantitative real-time polymerase chain reaction. After 8 weeks of culture, samples were observed under scanning electron microscopy.

RESULTS

Surface modification using type I collagen significantly enhanced HDPC attachment to the PLGA microspheres and promoted cell spreading. Alkaline phosphatase activity and odontogenic-related gene expression of HDPCs cultured with PLGA microsphere scaffolds were enhanced significantly compared with HDPCs cultured without PLGA microsphere scaffolds. After 8 weeks of culture, HDPCs combined with PLGA microspheres formed 3-dimensional structures. Partial degradation of the scaffolds and matrix mineralization were also observed.

CONCLUSIONS

HDPCs can adhere to the PLGA microspheres, proliferate and differentiate into odontoblastlike cells, and form a 3-dimensional complex with matrix mineralization. This study may provide insight into the clinical dentin-pulp complex restoration with HDPCs and PLGA microsphere constructs.

Odontogenic differentiation potential of human dental pulp cells cultured on a calcium-aluminate enriched chitosan-collagen scaffold

OBJECTIVE

The study aims to evaluate the odontogenic potential of human dental pulp cells (HDPCs) in contact with an experimental porous chitosan-collagen scaffold (CHC) enriched or not with a mineral phase of calcium-aluminate (CHC-CA).

MATERIAL AND METHODS

To assess the chemotactic effect of the materials, we placed HDPCs seeded on transwell membranes in intimate contact with the CHC or CHC-CA surface, and the cell migration was monitored for 48 h. Additionally, cells were seeded onto the material surface, and the viability and proliferation were evaluated at several time points. To assess the odontoblastic differentiation, we evaluated ALP activity, DSPP/DMP-1 gene expression, and mineralized matrix deposition. HDPCs cultured onto a polystyrene surface (monolayer) were used as negative control group.

RESULTS

The experimental CHC-CA scaffold induced intense migration of HDPCs through transwell membranes, with cells attaching to and spreading on the material surface after 24-h incubation. Also, the HDPCs seeded onto the CHC-CA scaffold were capable of migrating inside it, remaining viable and featuring a proliferative rate more rapid than that of CHC and control groups at 7 and 14 days of cell culture. At long-term culture, cells in the CHC-CA scaffold featured the highest deposition of mineralized matrix and expression of odontoblastic markers (ALP activity and DSPP/DMP-1 gene expression).

CONCLUSIONS

According to the results, the CHC-CA scaffold is a bioactive and cytocompatible material capable of increasing the odontogenic potential of human pulp cells. Based on analysis of the positive data obtained in this study, one can suggest that the CHC-CA scaffold is an interesting future candidate for the treatment of exposed pulps.

CLINICAL RELEVANCE

The experimental scaffold composed by a chitosan-collagen matrix mineralized with calcium aluminate seems to be an interesting candidate for in vivo application as a cell-free approach to dentin tissue engineering, which may open a new perspective for the treatment of exposed pulp tissue.

Could the application of bioactive molecules improve vital pulp therapy success? A systematic review

This study aimed to systematically review the literature of animal studies to evaluate whether bioactive dentin proteins could improve vital pulp therapy success. The review is reported in accordance with the PRISMA Statement. Two reviewers independently conducted a literature search of seven databases: PubMed (Medline), Lilacs, IBECS, BBO, Web of Science, Scopus, and SciELO. Animal experiments in which bioactive dentin proteins were applied directly or indirectly to the pulp tissue were included. Data regarding the characteristics of the proteins evaluated, the delivery systems used and the main findings from each study were tabulated to assess the outcomes of interest (tertiary dentin formation, inflammatory response, intratubular mineralization). After screening, 32 papers were subjected to qualitative analysis. In 75% of the studies, direct pulp capping was performed. Additionally, the most studied proteins were BMP-7, TGF-β1, and extracted soluble dentin matrix proteins. In conclusion, there is evidence in the literature suggesting that bioactive dentin molecules could enhance tertiary dentin formation with fewer initial inflammatory responses in direct and indirect pulp therapy in animal models. There are potential areas to be explored for novel therapeutic approaches for dental tissue repair and regeneration with bioactive materials. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 941-956, 2017.

Fifty years of Brazilian Dental Materials Group: scientific contributions of dental materials field evaluated by systematic review

Objective

A systematic review was conducted to analyze Brazilian scientific and technological production related to the dental materials field over the past 50 years.

Material and Methods

This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (Prisma) statement. Searches were performed until December 2014 in six databases: MedLine (PubMed), Scopus, LILACS, IBECS, BBO, and the Cochrane Library. Additionally, the Brazilian patent database (INPI - Instituto Nacional de Propriedade Industrial) was screened in order to get an overview of Brazilian technological development in the dental materials field. Two reviewers independently analyzed the documents. Only studies and patents related to dental materials were included in this review. Data regarding the material category, dental specialty, number of documents and patents, filiation countries, and the number of citations were tabulated and analyzed in Microsoft Office Excel (Microsoft Corporation, Redmond, Washington, United States).

Results

A total of 115,806 studies and 53 patents were related to dental materials and were included in this review. Brazil had 8% affiliation in studies related to dental materials, and the majority of the papers published were related to dental implants (1,137 papers), synthetic resins (681 papers), dental cements (440 papers), dental alloys (392 papers) and dental adhesives (361 papers). The Brazilian technological development with patented dental materials was smaller than the scientific production. The most patented type of material was dental alloys (11 patents), followed by dental implants (8 patents) and composite resins (7 patents).

Conclusions

Dental materials science has had a substantial number of records, demonstrating an important presence in scientific and technological development of dentistry. In addition, it is important to approximate the relationship between academia and industry to expand the technological development in countries such as Brazil.

PDGFRβ+/c-kit+ pulp cells are odontoblastic progenitors capable of producing dentin-like structure in vitro and in vivo

Background

Successful pulp regeneration depends on identification of pulp stem cells capable of differentiation under odontoblastic lineage and producing pulp-dentinal like structure. Recent studies demonstrate that platelet-derived growth factor (PDGF) plays an important role in damage repair and tissue regeneration. The aim of this study was to identify a subpopulation of dental pulp cells responsive to PDGF and with dentin regeneration potential.

Methods

Pulp tissues were isolated from 12 freshly extracted human impacted third molars. Pulp cells were sorted by their expression of PDGFRβ and stem cell marker genes via flow cytometry. For the selected cells, proliferation was analyzed by a colorimetric cell proliferation assay, differentiation was assessed by real time PCR detection the expression of odontoblast marker genes, and mineralization was evaluated by Alizarin Red S staining. GFP marked PDGFRβ⁺/c-kit⁺ pulp cells were transplanted into emptied root canals of nude rat lower left incisors. Pulp-dentinal regeneration was examined by immunohistochemistry.

Results

PDGFRβ⁺/c-kit⁺ pulp cells proliferated significantly faster than whole pulp cells. In mineralization media, PDGFRβ⁺/c-kit⁺ pulp cells were able to develop under odontoblastic linage as demonstrated by a progressively increased expression of DMP1, DSPP, and osteocalcin. BMP2 seemed to enhance whereas PDGF-BB seemed to inhibit odontoblastic differentiation and mineralization of PDGFRβ⁺/c-kit⁺ pulp cells. In vivo root canal transplantation study revealed globular dentin and pulp-like tissue formation by PDGFRβ⁺/c-kit⁺ cells.

Conclusions

PDGFRβ⁺/c-kit⁺ pulp cells appear to have pulp stem cell potential capable of producing dentinal like structure in vitro and in vivo.

Electronic supplementary material

The online version of this article (doi:10.1186/s12903-016-0307-8) contains supplementary material, which is available to authorized users.

Effect of low-level laser irradiation on proliferation of human dental mesenchymal stem cells; a systemic review

CONTEXT

Identification of factors that enhance the proliferation of human dental mesenchymal stem cells (DMSCs) is vital to facilitate tissue regeneration. The role of low-level laser irradiation (LLLI) on proliferation of human DMSCs has not been well established.

OBJECTIVE

To assess the effect of LLLI on proliferation of human DMSCs when applied in-vitro.

DATA SOURCES

Electronic search of literature was conducted (2000-2016) on PubMed, Web of Science, and Scopus databases. Search terms included low-level light therapy, low-level laser irradiation, low-level light irradiation, LLLT, humans, adolescent, adult, cells, cultured, periodontal ligament, dental pulp, stem cells, dental pulp stem cells, mesenchymal stem cells, periodontal ligament stem cell, deciduous teeth, cell proliferation, adult stem cells, radiation, and proliferation.

RESULTS

The literature search identified 165 studies with 6 being eligible for inclusion; all used diode lasers; 5 studies used InGaAIP diode lasers; 4 used 660nm, and the other two applied 810nm or 980nm wavelength LLLI. The distance between the DMSCs and the laser spot ranged between 0.5mm to 2mm. The time intervals of cell proliferation analysis ranged from 0h to 7days after LLLI. After 660nm LLLI, an increase in the DMSC's proliferation was reported [DMSCs extracted from dental pulp of deciduous teeth (two irradiations, 3J/cm(2), 20mW was more effective than 40mW), adult teeth (two irradiations, 0.5 and 1.0J/cm(2), 30mW), and from adult periodontal ligament (two irradiations, 1.0J/cm(2) was more effective than 0.5J/cm(2), 30mW)]. Similarly, an increase in the proliferation of DMSCs extracted from dental pulp of adult teeth was reported after 810nm LLLI (7 irradiations in 7days, 0.1 and 0.2J/cm(2), 60mW) or 980nm LLLI (single irradiation, 3J/cm(2), 100mW). However, 660nm LLLI in one study did not increase the proliferation of DMSCs (single irradiation, energy densities of 0.05, 0.30, 7, and 42J/cm(2), 28mW).

CONCLUSION

There is limited evidence that in-vitro LLLI (660/810/980nm, with energy densities of 0.1-3J/cm(2)) increases the proliferation of DMSCs. Considering the limited evidence and their method heterogeneity it is difficult to reach a firm conclusion. Further research is necessary to identify the optimal characteristics of the LLLI setting (wave length, energy density, power output, frequency/duration of irradiations, distance between the cells and the laser spot/probe) to increase proliferation of DMSCs, and assess its impact on replicative senescence, as well as determine feasibility of the use in the clinical setting.

Immunohistological Evaluation of Revascularized Immature Permanent Necrotic Teeth Treated by Platelet-Rich Plasma: An Animal Investigation

Objective

Pulp regeneration within the root canal of necrotic teeth is considered an ideal treatment to allow for continued root development and recover teeth vitality. This study aims to evaluate the inductive effect of platelet-rich plasma (PRP) on expression of angiogenesis factors and pulpal revascularization of immature necrotic teeth.

Materials and Methods

In this experimental animal study, we randomly divided 28 immature premolars from two mixed breed dogs into four groups, two experimental, negative and a positive control. Premolars in negative control group were left intact to develop normally. In the positive control and experimental groups, we removed the pulps and induced pulp necrosis, after which the chambers were sealed. Then, we applied the revascularization protocol in the experimental teeth located in the right quadrant. Two months later, the same protocol was applied to the left quadrant. The root canals were disinfected by irrigation with sodium hypochlorite (NaOCl) solution and application a triple antibiotic past. Following the induction of a blood clot (BC) inside the canal space, the coronal portion of the canals was assigned to either of two experimental groups: group 1 [BC+PRP+ mineral trioxide aggregate (MTA)], group 2 (BC+MTA). Access cavities were sealed with a Glass Ionomer. The jaws that held the teeth were processed for histologic analysis of newly formed tissue and immunohistochemical evaluation according to vascular endothelial growth factor (VEGF) and factor VIII expressions in the canals.

Results

Histological analysis demonstrated no significant difference in the formation of new vital tissue inside the root canals between groups1 (42.8%) and 2 (43.5%, P>0.05). Based on immunohistochemical evaluation, micro-vessel density (MVD) of the granulation tissues in both groups were similar and were higher compared with the normal pulp. We observed strongly positive expressions of VEGF and factor VIII in the stromal and endothelial cells, with severe intensity after one month. Both factors showed downregulation at three months postoperative.

Conclusion

PRP could not increase the formation of new vital tissue. The immunohistochemical results showed that VEGF and factor VIII played a pivotal role in the formation of new vessels inside the root canals of immature, non-vital teeth.

Differentiation of Dental Pulp Stem Cells on Gutta-Percha Scaffolds

Advances in treatment of tooth injury have shown that tooth regeneration from the pulp was a viable alternative of root canal therapy. In this study, we demonstrated that Gutta-percha, nanocomposites primarily used for obturation of the canal, are not cytotoxic and can induce differentiation of dental pulp stem cells (DPSC) in the absence of soluble mediators. Flat scaffolds were obtained by spin coating Si wafers with three Gutta-percha compounds: GuttaCore™, ProTaper™, and Lexicon™. The images of annealed surfaces showed that the nanoparticles were encapsulated, forming surfaces with root mean square (RMS) roughness of 136⁻211 nm. Then, by culturing DPSC on these substrates we found that after some initial difficulty in adhesion, confluent tissues were formed after 21 days. Imaging of the polyisoprene (PI) surfaces showed that biomineral deposition only occurred when dexamethasone was present in the media. Spectra obtained from the minerals was consistent with that of hydroxyapatite (HA). In contrast, HA deposition was observed on all Gutta-percha scaffolds regardless of the presence or absence of dexamethasone, implying that surface roughness may be an enabling factor in the differentiation process. These results indicate that Gutta-percha nanocomposites may be good candidates for pulp regeneration therapy.

Priming Dental Pulp Stem Cells With Fibroblast Growth Factor-2 Increases Angiogenesis of Implanted Tissue-Engineered Constructs Through Hepatocyte Growth Factor and Vascular Endothelial Growth Factor Secretion

Tissue engineering strategies based on implanting cellularized biomaterials are promising therapeutic approaches for the reconstruction of large tissue defects. A major hurdle for the reliable establishment of such therapeutic approaches is the lack of rapid blood perfusion of the tissue construct to provide oxygen and nutrients. Numerous sources of mesenchymal stem cells (MSCs) displaying angiogenic potential have been characterized in the past years, including the adult dental pulp. Establishment of efficient strategies for improving angiogenesis in tissue constructs is nevertheless still an important challenge. Hypoxia was proposed as a priming treatment owing to its capacity to enhance the angiogenic potential of stem cells through vascular endothelial growth factor (VEGF) release. The present study aimed to characterize additional key factors regulating the angiogenic capacity of such MSCs, namely, dental pulp stem cells derived from deciduous teeth (SHED). We identified fibroblast growth factor-2 (FGF-2) as a potent inducer of the release of VEGF and hepatocyte growth factor (HGF) by SHED. We found that FGF-2 limited hypoxia-induced downregulation of HGF release. Using three-dimensional culture models of angiogenesis, we demonstrated that VEGF and HGF were both responsible for the high angiogenic potential of SHED through direct targeting of endothelial cells. In addition, FGF-2 treatment increased the fraction of Stro-1+/CD146+ progenitor cells. We then applied in vitro FGF-2 priming to SHED before encapsulation in hydrogels and in vivo subcutaneous implantation. Our results showed that FGF-2 priming is more efficient than hypoxia at increasing SHED-induced vascularization compared with nonprimed controls. Altogether, these data demonstrate that FGF-2 priming enhances the angiogenic potential of SHED through the secretion of both HGF and VEGF.

Behaviour of human dental pulp cells cultured in a collagen hydrogel scaffold cross-linked with cinnamaldehyde

AIM

To investigate the effects of the cross-linking agent cinnamaldehyde (CA) on differentiation of human dental pulp cells (hDPCs) cultured in a collagen hydrogel, which may be useful as a scaffold for regenerative endodontic therapy.

METHODOLOGY

The odontogenic potential of hDPCs exposed to CA was examined using alkaline phosphatase (ALP) activity, Alizarin red S staining and real-time polymerase chain reaction for odontogenic gene expression. The morphological features of hDPCs cultured in CA-treated collagen were evaluated by scanning electron microscopy. Determination of cell numbers for evaluating proliferation was assessed by optical and fluorescence microscopy. To assess the mechanical properties of collagen treated with CA, setting time, compressive strength and surface roughness were measured. Statistical analysis was performed using Student's t-test compared with control (P = 0.05).

RESULTS

CA per se did not increase ALP activity, calcium nodule formation and expression of odontogenic-related markers (P > 0.05). On the contrary, the proliferation and odontogenic differentiation of hDPCs cultured in a collagen scaffold was promoted in the presence of CA (P < 0.05). The setting time was significantly shortened, and the compressive strength and surface roughness were increased by treatment with CA (P < 0.05).

CONCLUSIONS

Cross-linking of collagen scaffolds by CA had beneficial effects with respect to attachment, proliferation and differentiation of hDPCs. Consequently, the application of cross-linking agents such as CA may represent a new strategy for dentine-pulp complex regeneration.

Genipin, a cross-linking agent, promotes odontogenic differentiation of human dental pulp cells

INTRODUCTION

The aim of this study was to investigate the effects of genipin, a natural collagen cross-linking agent, on odontogenic differentiation of human dental pulp cells (hDPCs) because the mechanical properties of collagen allow it to serve as a scaffold for engineering of pulp-dentin complex. Furthermore, the role of extracellular signal-regulated kinase (ERK) was investigated as a mediator of the differentiation.

METHODS

The odontogenic differentiation was analyzed by alkaline phosphatase activity, real time-polymerase chain reaction, Western blotting, and alizarin red S staining. The morphologic features of hDPCs cultured in genipin-treated collagen were evaluated by scanning electron microscopy. For the assessment of mechanical properties of collagen treated with genipin, the surface roughness and compressive strength were measured.

RESULTS

Alkaline phosphatase activity, the expression of odontogenic markers, and mineralized nodule formation increased in the genipin-treated group. Genipin also activated ERK, and treatment with ERK inhibitor blocked the expression of the markers. The cells cultured in genipin-treated collagen spread across the substrate and attached in close proximity to one another. The proliferation and differentiation of hDPCs cultured in genipin-treated collagen were facilitated. The mechanical properties of collagen, such as surface roughness and compressive strength, were increased by treatment with genipin.

CONCLUSIONS

Our results show that genipin promotes odontogenic differentiation of hDPCs via the ERK signaling pathway. Furthermore, the enhanced mechanical properties of the collagen scaffold induced by genipin may play important roles in cell fate. Consequently, the application of genipin might be a new strategy for dentin-pulp complex regeneration.