Dentine matrix proteins: isolation and effects on human pulp cells

Specific cell subclusters of dental pulp stem cells respond to distinct pathogens through the ROS pathway

Introduction

Microbial pathogens invade various human organs, including the oral cavity. Candida albicans (C.a) and Streptococcus mutans (S.m) served respectively as representative oral pathogenic fungi and bacteria to stimulate dental pulp stem cells (DPSCs) and to screen the DPSC subcluster that specifically responded to fungal infection.

Methods

DPSCs were obtained from the impacted third molars of six healthy subjects. Then, cells were mixed and divided into three samples, two of which were stimulated with C.a and S.m, respectively; the third sample was exposed to cell medium only (Ctrl). Single-cell mRNA sequencing analysis of treated DPSCs was performed.

Results

DPSCs were composed of four major clusters of which one, DPSC.7, exhibited unique changes compared to those of other subclusters. The DPSC.7 cell percentage of the C.a sample was twice those of the Ctrl and S.m samples. DPSC.7 cells expressed genes associated with the response to reactive oxygen species (ROS) response. DPSC.7 subgroup cells established characteristic aggregation under the stimulation of different pathogens in UMAP. The MAPK/ERK1/2 and NF-κB pathways were up-regulated, DUSP1/5/6 expressions were suppressed, FOS synthesis was activated, the immune-related pathway was induced, and the levels of cytokines, including IL-6 and CCL2, were up-regulated in DPSC.7 cells when stimulated with C.a.

Conclusions

Our study analyzed the cellular and molecular properties of DPSCs infected by oral fungi and bacteria with single-cell RNA sequencing. A subcluster of DPSCs responded specifically to infections with different pathogens, activating the MAPK and NF-κB pathways to induce immune responses via the ROS pathway. This suggests novel treatment strategies for fungal infections.

Heparin-Functionalized Bioactive Glass to Harvest Endogenous Growth Factors for Pulp Regeneration

Pulp and periapical diseases can lead to the cessation of tooth development, resulting in compromised tooth structure and functions. Despite numerous efforts to induce pulp regeneration, effective strategies are still lacking. Growth factors (GFs) hold considerable promise in pulp regeneration due to their diverse cellular regulatory properties. However, the limited half-lives and susceptibility to degradation of exogenous GFs necessitate the administration of supra-physiological doses, leading to undesirable side effects. In this research, a heparin-functionalized bioactive glass (CaO-P2O5-SiO2-Heparin, abbreviated as PSC-Heparin) with strong bioactivity and a stable neutral pH is developed as a promising candidate to addressing challenges in pulp regeneration. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis reveal the successful synthesis of PSC-Heparin. Scanning electron microscopy and X-ray diffraction show the hydroxyapatite formation can be observed on the surface of PSC-Heparin after soaking in simulated body fluid for 12 h. PSC-Heparin is capable of harvesting various endogenous GFs and sustainably releasing them over an extended duration by the enzyme-linked immunosorbent assay. Cytological experiments show that developed PSC-Heparin can facilitate the adhesion, migration, proliferation, and odontogenic differentiation of stem cells from apical papillae. Notably, the histological analysis of subcutaneous implantation in nude mice demonstrates PSC-Heparin is capable of promoting the odontoblast-like layers and pulp-dentin complex formation without the addition of exogenous GFs, which is vital for clinical applications. This work highlights an effective strategy of harvesting endogenous GFs and avoiding the involvement of exogenous GFs to achieve pulp-dentin complex regeneration, which may open a new horizon for regenerative endodontic therapy.

Advances in Regenerative Dentistry Approaches: An Update

Regenerative dentistry is a rapidly evolving field in dentistry, which has been driven by advancements in biomedical engineering research and the rising treatment expectations and demands that exceed the scope of conventional approaches. Tissue engineering, the foundation of regenerative dentistry, mainly focuses on 3 key components: stem cells, bioactive molecules, and scaffolds. Dental tissue-derived stem cells are especially significant in this regard due to their remarkable properties. Regenerative techniques have provided novel approaches to many conventional treatment strategies in various disciplines of dentistry. For instance, regenerative endodontic procedures such as pulp revascularisation have provided an alternative approach to conventional root canal treatment. In addition, conventional surgical and nonsurgical periodontal treatment is being taken over by modified approaches of guided tissue regeneration with the aid of 3-dimensional bioprinting and computer-aided design, which has revolutionised oral and maxillofacial tissue engineering. This review presents a concise overview of the latest treatment strategies that have emerged into clinical practice, potential future technologies, and the role of dental tissue-derived stem cells in regenerative dentistry.

An in vitro coculture approach to study the interplay between dental pulp cells and Streptococcus mutans

AIM

To develop a new coculture system that allows exposure of dental pulp cells (DPCs) to Streptococcus mutans and dentine matrix proteins (eDMP) to study cellular interactions in dentine caries.

METHODOLOGY

Dental pulp cells and S. mutans were cocultured with or without eDMP for 72 h. Cell proliferation and viability were assessed by cell counting and MTT assays, while bacterial growth and viability were determined by CFU and LIVE/DEAD staining. Glucose catabolism and lactate excretion were measured photometrically as metabolic indicators. To evaluate the inflammatory response, the release of cytokines and growth factors (IL-6, IL-8, TGF-β1, VEGF) was determined by ELISA. Non-parametric statistical analyses were performed to compare all groups and time points (Mann-Whitney U test or Kruskal-Wallis test; α = .05).

RESULTS

While eDMP and especially S. mutans reduced the number and viability of DPCs (p ≤ .0462), neither DPCs nor eDMP affected the growth and viability of S. mutans during coculture (p > .0546). The growth of S. mutans followed a common curve, but the death phase was not reached within 72 h. S. mutans consumed medium glucose in only 30 h, whereas in the absence of S. mutans, cells were able to catabolize glucose throughout 72 h, resulting in the corresponding amount of l-lactate. No change in medium pH was observed. S. mutans induced IL-6 production in DPCs (p ≤ .0011), whereas eDMP had no discernible effect (p > .7509). No significant changes in IL-8 were observed (p > .198). TGF-β1, available from eDMP supplementation, was reduced by DPCs over time. VEGF, on the other hand, was increased in all groups during coculture.

CONCLUSIONS

The results show that the coculture of DPCs and S. mutans is possible without functional impairment. The bacterially induced stimulation of proinflammatory and regenerative cytokines provides a basis for future investigations and the elucidation of molecular biological relationships in pulp defence against caries.

Approaches to vital pulp therapies

Tooth decay, which leads to pulpal inflammation due to the pulp's response to bacterial components and byproducts is the most common infectious disease. The main goals of clinical management are to eliminate sources of infection, to facilitate healing by regulating inflammation indental tissue, and to replace lost tissues. A variety of novel approaches from tissue engineering based on stem cells, bioactive molecules, and extracellular matrix-like scaffold structures to therapeutic applications, or a combination of all these are present in the literature. Shortcomings of existing conventional materials for pulp capping and the novel approches aiming to preserve pulp vitality highligted the need for developing new targeted dental materials. This review looks at the novel approches for vital pulp treatments after briefly addresing the conventional vital pulp treatment as well as the regenerative and self defense capabilities of the pulp. A narrative review focusing on the current and future approaches for pulp preservation was performed after surveying the relevant papers on vital pulp therapies including pulp capping, pulpotomy, and potential approaches for facilitating dentin-pulp complex regeneration in PubMed, Medline, and Scopus databases.

Effects of L-Chg10-Teixobactin on Viability, Proliferation, and Osteo/Odontogenic Differentiation of Stem Cells from Apical Papilla

INTRODUCTION

Intracanal medicament is one of the essential steps for ensuring success in regenerative endodontic procedures. _L-Chg₁₀-teixobactin is a novel antimicrobial agent that exhibited potent antibacterial and antibiofilm effects against Enterococcusfaecalis at low concentrations compared with ampicillin. At the same time, its cytotoxicity on dental stem cells has not been studied. This study aimed to investigate the effects of _L-Chg₁₀-teixobactin on the viability, proliferation, migration, and osteo/odontogenic differentiation of stem cells from apical papilla (SCAPs).

MATERIALS AND METHODS

SCAPs isolated from immature human third molars were treated with various concentrations of _L-Chg₁₀-teixobactin, calcium hydroxide, and dimethyl sulfoxide. The viability and proliferation of SCAPs were assessed using the LIVE/DEAD Viability/Cytotoxicity Kit and Cell Counting Kit-8. A scratch wound healing test was used to evaluate the lateral migration capacity of SCAPs. Alkaline phosphatase (ALP) activity, calcium mineralization ability tests -ie, ALP staining and alizarin red S staining, and quantitative real-time polymerase chain reaction were performed to assess the osteo /odontogenic differentiation of SCAPs.

RESULTS

The tested concentrations of _L-Chg₁₀-teixobactin (0.01, 0.02, and 0.03 mg/mL), 1 mg/mL calcium hydroxide, and 0.03% dimethyl sulfoxide had no significant cytotoxic effect on SCAPs at any time point (P > .05). Besides, there were no significant differences between the control and experimental groups in SCAPs' viability, proliferation, and migration. _L-Chg₁₀-teixobactin upregulated the gene expression of osteo/odontogenic markers in SCAPs, while no significant difference was found in the ALP activity and alizarin red S staining.

CONCLUSIONS

_L-Chg₁₀-teixobactin demonstrated excellent biocompatibility on SCAPs at concentrations from 0.01 to 0.03 mg/mL and potentially enhance the osteo/odontogenic differentiation of SCAPs; suggesting its promising role as root canal medicament for regenerative endodontic procedures.

Protective Actions in Apical Periodontitis: The Regenerative Bioactivities Led by Mesenchymal Stem Cells

Resulting from bacterial infection, apical periodontitis (AP) is a common inflammatory disease of the periapical region of the tooth. The regeneration of the destroyed periapical alveolar bone and the surrounding periodontium tissues has long been a difficult task in clinical practice. These lesions are closely related to pathogen invasion and an overreactive immune response. It is worth noting that the protective healing process occurs simultaneously, in which mesenchymal stem cells (MSCs) have a crucial function in mediating the immune system and promoting regeneration. Here, we review the recent studies related to AP, with a focus on the regulatory network of MSCs. We also discuss the potential therapeutic approaches of MSCs in inflammatory diseases to provide a basis for promoting tissue regeneration and modulating inflammation in AP. A deeper understanding of the protective action of MSCs and the regulatory networks will help to delineate the underlying mechanisms of AP and pave the way for stem-cell-based regenerative medicine in the future.

A Compilation of Study Models for Dental Pulp Regeneration

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

Biomaterial scaffolds for clinical procedures in endodontic regeneration

Regenerative endodontic procedures have been rapidly evolving over the past two decades and are employed extensively in clinical endodontics. These procedures have been perceived as valuable adjuvants to conventional strategies in the treatment of necrotic immature permanent teeth that were deemed to have poor prognosis. As a component biological triad of tissue engineering (i.e., stem cells, growth factors and scaffolds), biomaterial scaffolds have demonstrated clinical potential as an armamentarium in regenerative endodontic procedures and achieved remarkable advancements. The aim of the present review is to provide a broad overview of biomaterials employed for scaffolding in regenerative endodontics. The favorable properties and limitations of biomaterials organized in naturally derived, host-derived and synthetic material categories were discussed. Preclinical and clinical studies published over the past five years on the performance of biomaterial scaffolds, as well as current challenges and future perspectives for the application of biomaterials for scaffolding and clinical evaluation of biomaterial scaffolds in regenerative endodontic procedures were addressed in depth.

•

Overview of biomaterials for scaffolding in regenerative endodontics are presented.

•

Findings of preclinical and clinical studies on the performance of biomaterial scaffolds are summarized.

•

Challenges and future prospects in biomaterial scaffolds are discussed.

Odontogenic Differentiation Induced by TGF-β1 Binding Peptide-Modified Bioglass

Emerging evidence suggests that growth factors are crucial in regenerative endodontic therapy. To achieve the desired effects, the systematic administration of supraphysiologic concentrations of exogenous growth factors is commonly performed, but this is usually associated with high costs, technique, and safety issues. Here, we describe a novel biomaterial that can manipulate endogenous growth factors without the need for adding exogenous growth factors. Transforming growth factor β1 binding peptide (TGFp) was grafted onto the surface of a neutral pH phytic acid-derived bioactive glass (PSC) to synthesize modified bioactive glass (PSC-TGFp). Fourier transform infrared spectroscopy and thermogravimetric analysis results demonstrated that the TGFp was successfully grafted to the surface of the PSC. Scanning electron microscopy and x-ray diffraction showed that PSC-TGFp possessed good in vitro bioactivity. After soaking in simulated body fluid for 24 h, hydroxyapatite formed on the surface of PSC-TGFp. Enzyme-linked immunosorbent assay showed that PSC-TGFp could capture endogenous transforming growth factor β1 from dentin matrix-extracted proteins (DMEP) and release it slowly over 21 d. Cytologic experiments revealed that PSC-TGFp after adsorbing DMEP could enhance the adhesion, migration, viability, and odontogenic differentiation of stem cells from apical papilla. The results highlight that PSC-TGFp may be a promising biomaterial to manipulate endogenous growth factors for regenerative endodontic therapy in the future.

Human Amnion Epithelial Cells: A Potential Cell Source for Pulp Regeneration?

The aim of this study was to analyze the suitability of pluripotent stem cells derived from the amnion (hAECs) as a potential cell source for revitalization in vitro. hAECs were isolated from human placentas, and dental pulp stem cells (hDPSCs) and dentin matrix proteins (eDMPs) were obtained from human teeth. Both hAECs and hDPSCs were cultured with 10% FBS, eDMPs and an osteogenic differentiation medium (StemPro). Viability was assessed by MTT and cell adherence to dentin was evaluated by scanning electron microscopy. Furthermore, the expression of mineralization-, odontogenic differentiation- and epithelial–mesenchymal transition-associated genes was analyzed by quantitative real-time PCR, and mineralization was evaluated through Alizarin Red staining. The viability of hAECs was significantly lower compared with hDPSCs in all groups and at all time points. Both hAECs and hDPSCs adhered to dentin and were homogeneously distributed. The regulation of odontoblast differentiation- and mineralization-associated genes showed the lack of transition of hAECs into an odontoblastic phenotype; however, genes associated with epithelial–mesenchymal transition were significantly upregulated in hAECs. hAECs showed small amounts of calcium deposition after osteogenic differentiation with StemPro. Pluripotent hAECs adhere on dentin and possess the capacity to mineralize. However, they presented an unfavorable proliferation behavior and failed to undergo odontoblastic transition.

Molecular Biological Comparison of Dental Pulp- and Apical Papilla-Derived Stem Cells

Both the dental pulp and the apical papilla represent a promising source of mesenchymal stem cells for regenerative endodontic protocols. The aim of this study was to outline molecular biological conformities and differences between dental pulp stem cells (DPSC) and stem cells from the apical papilla (SCAP). Thus, cells were isolated from the pulp and the apical papilla of an extracted molar and analyzed for mesenchymal stem cell markers as well as multi-lineage differentiation. During induced osteogenic differentiation, viability, proliferation, and wound healing assays were performed, and secreted signaling molecules were quantified by enzyme-linked immunosorbent assays (ELISA). Transcriptome-wide gene expression was profiled by microarrays and validated by quantitative reverse transcription PCR (qRT-PCR). Gene regulation was evaluated in the context of culture parameters and functionality. Both cell types expressed mesenchymal stem cell markers and were able to enter various lineages. DPSC and SCAP showed no significant differences in cell viability, proliferation, or migration; however, variations were observed in the profile of secreted molecules. Transcriptome analysis revealed the most significant gene regulation during the differentiation period, and 13 biomarkers were identified whose regulation was essential for both cell types. DPSC and SCAP share many features and their differentiation follows similar patterns. From a molecular biological perspective, both seem to be equally suitable for dental pulp tissue engineering.

Isolation of Endogenous TGF-β1 from Root Canals for Pulp Tissue Engineering: A Translational Study

Simple Summary

Tissue engineering of the dental pulp has been a goal of dental research for years. In this translational study, a chairside protocol is designed using endogenous dentin matrix proteins as signaling molecules for pulp regeneration. These bioactive molecules can be isolated from root canals by ultrasonic-activated irrigation, further processed chairside, and mixed with a hydrogel. The scaffold material is to be injected into the root canal and effect cell homing, i.e., allowing stem cells from the periapical space to migrate into the root canal. The aim of this innovative approach is the formation of an innervated and vascularized connective tissue that resembles the pulp in form and function.

Abstract

Cell homing for dental pulp tissue engineering has been advocated as a feasible approach to regenerate dental pulp in a clinical setting. In order to develop a translational protocol for clinical application, we wanted to determine the effects of disinfectants on the availability of growth factors from the root canal, the amount that can be obtained in this context, and whether they can be processed for use in tissue engineering procedures. The extraction of growth factors should also be confirmed in a clinical setting. Root canals were prepared in 36 extracted mature teeth, and the amount of TGF-β1 in solution was quantified after different irrigation protocols (sodium hypochlorite, chlorhexidine) and after intracanal medication (calcium hydroxide). Centrifugal filters with a cut-off of 10,000 Da and 3000 Da were used for efficient concentration, and volumes and amounts of retained TGF-β1 were measured at different time points. During conventional endodontic treatment, ethylenediaminotetraacetic acid (EDTA) solution was collected after ultrasonic activation from the root canals of mature teeth of 38 patients, and growth factor content was quantified via enzyme-linked immunosorbent assay (ELISA). Irrigation with sodium hypochlorite reduced TGF-β1 release into EDTA. This effect was partially reversed by canal enlargement after the use of sodium hypochlorite and by subsequent use of calcium hydroxide. A few minutes of centrifugation with a cut-off of 10,000 Da reduced the initial volume of the irrigant by 90% and led to a continuous increase in concentration to the same extent. Furthermore, TGF-β1 was obtained from root canals of mature teeth during endodontic treatment in quantities that have been shown to elicit desirable cellular responses in a subsequent clinical application. A mixture with a suitable scaffold material and injection into the root canal has the potential to promote dental pulp regeneration.

Highly Structured 3D Electrospun Conical Scaffold: A Tool for Dental Pulp Regeneration

New procedures envisioned for dental pulp regeneration after pulpectomy include cell homing strategy. It involves host endogenous stem cell recruitment and activation. To meet this cell-free approach, we need to design a relevant scaffold to support cell migration from tissues surrounding the dental root canal. A composite membrane made of electrospun poly(lactic acid) nanofibers and electrosprayed polycaprolactone with tannic acid (TA) microparticles which mimics the architecture of the extracellular matrix was first fabricated. After rolling the membrane in the form of a 3D conical scaffold and subsequently coating it with gelatin, it can be directly inserted into the root canal. The porous morphology of the construct was characterized by SEM at different length scales. It was shown that TA was released from the 3D conical scaffold after 2 days in PBS at 37 °C. Biocompatibility studies were first assessed by seeding human dental pulp stem cells (DPSCs) on planar membranes coated or not coated with gelatin to compare the surfaces. After 24 h, the results highlighted that the gelatin-coating increased the membrane biocompatibility and cell viability. Similar DPSC morphology and proliferation on both membrane surfaces were observed. The culture of DPSCs on conical scaffolds showed cell colonization in the whole cone volume, proving that the architecture of the conical scaffold was suitable for cell migration.

Alkaline activation of endogenous latent TGFβ1 by an injectable hydrogel directs cell homing for in situ complex tissue regeneration

Utilization of the body's regenerative potential for tissue repair is known as in situ tissue regeneration. However, the use of exogenous growth factors requires delicate control of the dose and delivery strategies and may be accompanied by safety, efficacy and cost concerns. In this study, we developed, for the first time, a biomaterial-based strategy to activate endogenous transforming growth factor beta 1 (TGFβ1) under alkaline conditions for effective in situ tissue regeneration. We demonstrated that alkaline-activated TGFβ1 from blood serum, bone marrow fluids and soaking solutions of meniscus and tooth dentin was capable of increasing cell recruitment and early differentiation, implying its broad practicability. Furthermore, we engineered an injectable hydrogel (MS-Gel) consisting of gelatin microspheres for loading strong alkaline substances and a modified gelatin matrix for hydrogel click crosslinking. In vitro models showed that alkaline MS-Gel controllably and sustainably activated endogenous TGFβ1 from tooth dentin for robust bone marrow stem cell migration. More importantly, infusion of in vivo porcine prepared root canals with alkaline MS-Gel promoted significant pulp-dentin regeneration with neurovascular stroma and mineralized tissue by endogenous proliferative cells. Therefore, this work offers a new bench-to-beside translation strategy using biomaterial-activated endogenous biomolecules to achieve in situ tissue regeneration without the need for cell or protein delivery.

•

Nonphysiological pH activates latent TGFβ1 in various tissue sources.

•

Alkaline activation of endogenous TGFβ1 directs cell homing.

•

Biomaterial-activated endogenous TGFβ1 induces regeneration of complex tissues.

Influence of human teeth matrix on the cellular and biological properties of dental pulp stem cells - An in vitro study

Background

A major challenge in bone tissue regeneration is the use of right combination of stem cells with osteoinductive biomaterials. Hence, the present in vitro study was aimed at evaluating the effect of mineralized teeth matrix (MTM) and demineralized teeth matrix (DTM) on the selected cellular and biological characteristics of human dental pulp stem cells (DPSCs).

Methods

Established DPSCs were cultured in conditioned media (CM) of MTM and DTM and analyzed on their morphology, proliferation rate, population doubling time (PDT), viability, migration ability, ploidy and expression of cell surface markers, Further, the effect of MTM and DTM on the biocompatibility and osteogenic differentiation ability of DPSCs was evaluated.

Results

The DPSCs exhibited a fibroblast-like morphology with >80% viability. Cells were highly proliferative with an average PDT of 61 ​± ​12 ​h. A greater proliferation of DPSCs in the scratched area was observed when cultured in CM of teeth matrix compared to the cells in basal media. Moreover, no chromosomal abnormalities were induced during the culture of DPSCs. Flow cytometry analysis showed that DPSCs in basal media and CM of MTM and DTM were positive for CD29, CD44, CD73, CD90 (>70%), and negative for CD34 and CD45 (<0.1%). Alizarin red staining showed the higher deposition of mineralized nodules in DPSCs cultured with DTM compared to MTM.

Conclusion

MTM and DTM-derived CM enhanced the proliferation and selected phenotypic markers expression with no chromosomal abnormalities in DPSCs. In addition, both matrices were biocompatible with DPSCs and increased the osteogenic differentiation through higher nodule formation.

Exploiting dentine matrix proteins in cell-free approaches for periradicular tissue engineering

The recent discovery of mesenchymal stem cells within periapical lesions (PL-MSC) has presented novel opportunities for managing periradicular diseases in adult teeth by way of enhancing tissue regeneration. This discovery coincides with the current paradigm shift toward biologically driven treatment strategies in endodontics, which have typically been reserved for non-vital immature permanent teeth. One such approach that shows promise is utilizing local endogenous non-collagenous dentine extracellular matrix components (dECM) to recruit and upregulate the intrinsic regenerative capacity of PL-MSCs in situ. At picogram levels, these morphogens have demonstrated tremendous ability to enhance the cellular activities in in vitro and in vivo animal studies that would otherwise be necessary for periradicular regeneration. Briefly, these include proliferation, viability, migration, differentiation, and mineralization. Therefore, topical application of dECMs during ortho- or retrograde root canal treatment could potentially enhance and sustain the regenerative mechanisms within diseased periapical tissues that are responsible for attaining favorable clinical and radiographic outcomes. This would provide many advantages when compared with conventional antimicrobial-only therapies for apical periodontitis (AP), which do not directly stimulate healing and have had stagnant success rates over the past five decades despite significant advances in operative techniques. The aim of this narrative review was to present the novel concept of exploiting endogenous dECMs as clinical tools for treating AP in mature permanent teeth. A large scope of literature was summarized to discuss the issues associated with conventional treatment modalities; current knowledge surrounding PL-MSCs; composition of the dECM; inductive potentials of dECM morphogens in other odontogenic stem cell niches; how treatment protocols can be adapted to take advantage of dECMs and PL-MSCs; and finally, the challenges currently impeding successful clinical translation alongside directions for future research.

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.

Inflammatory Response Mechanisms of the Dentine-Pulp Complex and the Periapical Tissues

The macroscopic and microscopic anatomy of the oral cavity is complex and unique in the human body. Soft-tissue structures are in close interaction with mineralized bone, but also dentine, cementum and enamel of our teeth. These are exposed to intense mechanical and chemical stress as well as to dense microbiologic colonization. Teeth are susceptible to damage, most commonly to caries, where microorganisms from the oral cavity degrade the mineralized tissues of enamel and dentine and invade the soft connective tissue at the core, the dental pulp. However, the pulp is well-equipped to sense and fend off bacteria and their products and mounts various and intricate defense mechanisms. The front rank is formed by a layer of odontoblasts, which line the pulp chamber towards the dentine. These highly specialized cells not only form mineralized tissue but exert important functions as barrier cells. They recognize pathogens early in the process, secrete antibacterial compounds and neutralize bacterial toxins, initiate the immune response and alert other key players of the host defense. As bacteria get closer to the pulp, additional cell types of the pulp, including fibroblasts, stem and immune cells, but also vascular and neuronal networks, contribute with a variety of distinct defense mechanisms, and inflammatory response mechanisms are critical for tissue homeostasis. Still, without therapeutic intervention, a deep carious lesion may lead to tissue necrosis, which allows bacteria to populate the root canal system and invade the periradicular bone via the apical foramen at the root tip. The periodontal tissues and alveolar bone react to the insult with an inflammatory response, most commonly by the formation of an apical granuloma. Healing can occur after pathogen removal, which is achieved by disinfection and obturation of the pulp space by root canal treatment. This review highlights the various mechanisms of pathogen recognition and defense of dental pulp cells and periradicular tissues, explains the different cell types involved in the immune response and discusses the mechanisms of healing and repair, pointing out the close links between inflammation and regeneration as well as between inflammation and potential malignant transformation.

Effect of Intracanal Medicaments and Irrigants on the Release of Transforming Growth Factor Beta 1 and Vascular Endothelial Growth Factor from Cervical Root Dentin

INTRODUCTION

This study aimed to evaluate (1) the effect of irrigating solutions and intracanal medicaments on the release of transforming growth factor beta 1 (TGF-β1) and vascular endothelial growth factor (VEGF) from cervical root dentin and (2) the effect of associating triple antibiotic paste (TAP) and calcium hydroxide paste (CH) with 2% chlorhexidine (CHX) on TGF-β1 release.

METHODS

First, 119 specimens from roots (cervical thirds) were obtained and were distributed into 5 groups: 2% CHX, 2.5% sodium hypochlorite, TAP, CH, and 10% EDTA by each growth factor (TGF-β1 [n = 8] and VEGF [n = 8]). Then, specimens were distributed as follows (n = 13): TAP + 2% CHX, CH + 2% CHX, and 10% EDTA and treated with irrigating solutions and intracanal medicaments. After the treatments, the specimens were immersed in 10% EDTA (20 minutes), and the solution was analyzed using the enzyme-linked immunosorbent assay. The data were submitted to normality, homogeneity of variance, and Mann-Whitney tests (P < .05).

RESULTS

Significant differences were found between the irrigating solutions (P < .05) and intracanal medicaments for TGF-β1 (P < .05). No VEGF release was detected for any group. Our results showed no significant differences among the TAP + 2% CHX and EDTA groups for TGF-β1 but a significant difference between CH + 2% CHX and the other groups (P < .05).

CONCLUSIONS

The use of 2% CHX as the irrigating solution, CH as the intracanal medicament, and 10% EDTA as the final irrigation provides higher TGF-β1 release from the cervical root dentin, whereas VEGF was not detected. Moreover, TAP and 2% CHX with 10% EDTA as the final irrigation resulted in greater TGF-β1 release from cervical root dentin than CH + 2% CHX.

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

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

Treated dentin matrix particles combined with dental follicle cell sheet stimulate periodontal regeneration

OBJECTIVE

Periodontal tissue engineering is an attractive approach for restoring periodontal-supporting structures and functions. However, complete periodontal regeneration has not been accomplished. Previous studies demonstrated the feasibility of using cell sheets and treated dentin matrix (TDM) to regenerate bio-roots.

METHODS

In this study, we regenerated periodontal tissue using cell sheets combined with TDM particles (TDMPs). Human dental follicle cells (hDFCs) were isolated and characterized. Human dental follicle cells sheets (hDFCSs) and human TDMPs (hTDMP) were fabricated and characterized. The osteogenic effect of hTDMP was evaluated on human bone marrow stromal cells (hBMSCs) in vitro and a rat calvarial bone defect in vivo. Real-time PCR, western blotting, radiograph analysis, and histological analysis were performed to evaluate the periodontal induction capacity of hTDMP. One-wall periodontal intrabony defects were prepared to evaluate the periodontal regeneration capacity of TDMP/DFCSs on beagle dogs.

RESULTS

The results showed that hDFCs were mesenchymal stem cells. hTDMP promoted the proliferation and osteogenic differentiation of hBMSCs. New bone formation was observed in the rat calvarial bone defect zone in both the hTDMP and hydroxyapatite/β-tricalcium phosphate groups. Periodontal-like tissues showed better regeneration in the canine TDMP+DFCS group than in the other groups.

SIGNIFICANCE

These results demonstrate the potential of using TDMP/DFCSs in periodontal regeneration.

Neurotrophic Proteins in Dentin and Their Effect on Trigeminal Sensory Neurons

INTRODUCTION

A plethora of bioactive molecules present during tooth formation become sequestered in the mineralized dentin matrix and can be released into the pulp tissue after demineralization from carious lesions. However, neurotrophic factors are differentially expressed and secreted during various stages of odontogenesis. Thus, the aims of this study were (1) to investigate their presence and relative abundance in crown and root dentin and (2) to evaluate the bioactivity of dentin-derived proteins on neuronal cells.

METHODS

Dentin matrix proteins (DMPs) were isolated from matched roots and crowns of extracted healthy human third molars. The total protein amount as well as the concentration of growth factors and neurotrophic proteins were quantified. The impact on neuritogenesis was determined with mouse trigeminal neurons in vitro and by a hydrogel implant model in vivo. Transient receptor potential cation channel subfamily V member 1 (TRPV1) sensitization of DMP-conditioned neurons was evaluated by single-cell calcium imaging.

RESULTS

The relative concentration of neurotrophic molecules revealed that nerve growth factor is the most abundant neurotrophin with 3-fold increased expression in radicular dentin. Similarly, brain-derived neurotrophic factor and neurotrophin 3 are more abundant in radicular than coronal dentin. Conversely, glial cell line-derived neurotrophic factor is more abundant in coronal dentin, whereas neurotrophin 4 is equally distributed. Dentin matrix proteins promoted neurite outgrowth in vitro and axonal targeting in vivo, with a greater effect observed by radicular dentin extracts. Furthermore, DMPs sensitized TRPV1 responses in mouse trigeminal neurons with greater activity seen with extracts from root dentin.

CONCLUSIONS

Neurotrophic factors are differentially distributed between coronal and radicular dentin with different effects of dentin-derived proteins on axonal growth and targeting as well as the sensitization of TRPV1. Thus, extracellular proteins from the dentin matrix are likely involved in neurogenic responses to caries and could be exploited in clinical regenerative endodontics to promote reinnervation and enhance tissue regeneration.

Shotgun Proteomics of Human Dentin with Different Prefractionation Methods

Human dentin is not only a composite material of a collagenous matrix and mineral to provide strength and elasticity to teeth, but also a precious reservoir full of bioactive proteins. They are released after demineralization caused by bacterial acids in carious lesions, by decalcifying irrigants or dental materials and they modulate tissue responses in the underlying dental pulp. This work describes a first-time analysis of the proteome of human dentin using a shotgun proteomic approach that combines three different protein fractionation methods. Dentin matrix proteins were extracted by EDTA and separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), OFFGEL isoelectric focusing (IEF) or strong cation exchange chromatography (SCX). Liquid chromatography tandem mass spectrometry (LC-MS/MS) identified 813 human proteins with high confidence, however, isoelectric focusing turned out to be the most beneficial prefractionation method. All Proteins were categorized based on the PANTHER system and representation analysis revealed 31 classes and subclasses to be overrepresented. The acquired knowledge provides a comprehensive insight into the number of proteins in human dentin as well as their physiological and pathological functions. Thus, the data presented paves the way to the analysis of specific functions of dentin matrix proteins in vivo and their potential in tissue engineering approaches to regenerate dental pulp.

Effect of Dentin Matrix Components on the Mineralization of Human Mesenchymal Stromal Cells

IMPACT STATEMENT

This research has been conducted with the aim to contribute to the development of treatment modalities for the reconstruction of lost/damaged mineralized tissues. Currently, determining the most appropriate stromal cell population and signaling cues stands at the core of developing effective treatments. We provide new insights into the effect of innate inductive cues found in human dentin matrix components, on the osteogenic differentiation of various human stromal cell types. The effects of dentin extracellular matrix components on umbilical cord mesenchymal stromal cells have not been investigated before. The findings of this study could underpin translational research based on the development of techniques for mineralized tissue engineering and will be of great interest for the readership of Tissue Engineering Part A.

Liposomal Delivery of Demineralized Dentin Matrix for Dental Tissue Regeneration

Current dental restorations have short longevity, and consequently, there is a need for novel tissue engineering strategies that aim to regenerate the dentin-pulp complex. Dentin matrix contains a myriad of bioactive growth factors and extracellular matrix proteins associated with the recruitment, proliferation, and differentiation of dental pulp progenitor cells. In this study, we show that demineralized dentin matrix (DDM), from noncarious dentine, can be encapsulated into liposomes for delivery to dental tissue to promote regeneration. Liposomes were formulated to encapsulate 0-100 μg/mL DDM, lysed with Triton X, and used in vascular endothelial growth factor (VEGF) and transforming growth factor-β1 (TGF-β1) enzyme-linked immunosorbent assays to quantify release. The encapsulation efficiencies were calculated to be 25.9% and 28.8% (VEGF/TGF-β1) for 50 μg/mL DDM liposomes and 39% and 146.7% (VEGF/TGF-β1) for 100 μg/mL DDM liposomes. All liposome formulations had no cytotoxic effects on a dental pulp stem cell (DPSC) clone, as shown by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltertrazolium bromide), Caspase 3/7 assays, and cell counts. The ability of the liposomes to stimulate DPSC chemotactic recruitment was tested by Boyden chamber chemotaxis assays. Unloaded liposomes alone stimulated significant progenitor cell recruitment, while DDM-loaded liposomes further promoted chemotactic recruitment in a dose-dependent manner. DDM liposomes promoted the upregulation of "osteodentin" markers osteocalcin and RUNX2 (Runt-related transcription factor 2) in DPSCs after 9 days of treatment, determined by real-time quantitative PCR. Furthermore, Alizarin Red S staining showed that unloaded liposomes alone induced biomineralization of DPSCs, and DDM liposomes further increased the amount of mineralization observed. DDM liposomes were more effective than free DDM (10 μg/mL) at activating recruitment and osteogenic differentiation of DPSC, which are key events in the endogenous repair of the dentin-pulp complex. The study has highlighted the therapeutic potential of bioactive DDM liposomes in activating dental tissue repair in vitro, suggesting that liposomal delivery from biomaterials could be a valuable tool for reparative dentistry and hard-tissue engineering applications.