Distinguished properties of cells isolated from the dentin-pulp interface

Engineering soft-hard tissue interfaces in dental and craniofacial system by spatially controlled bioactivities

The interface between soft and hard tissues is constituted by a gradient change of cell types and matrix compositions that are optimally designed for proper load transmission and injury protection. In the musculoskeletal system, the soft-hard tissue interfaces at tendon-bone, ligament-bone, and meniscus-bone have been extensively researched as regenerative targets. Similarly, extensive research efforts have been made to guide the regeneration of multi-tissue complexes in periodontium. However, the other soft-hard tissue interfaces in the dental and craniofacial system have been somewhat neglected. This review discusses the clinical significance of developing regenerative strategies for soft-hard tissue interfaces in the dental and craniofacial system. It also discusses the research progress in the field focused on bioengineering approaches using 3D scaffolds equipped with spatially controlled bioactivities. The remaining challenges, future perspectives, and considerations for the clinical translation of bioactive scaffolds are also discussed.

The Immunophenotype and the Odontogenic Commitment of Dental Pulp Stem Cells Co-Cultured with Macrophages Under Inflammatory Conditions Is Modulated by Complex Magnetic Fields

Dental inflammatory diseases remain a challenging clinical issue, whose causes and development are still not fully understood. During dental caries, bacteria penetrate the tooth pulp, causing pulpitis. To prevent pulp necrosis, it is crucial to promote tissue repair by recruiting immune cells, such as macrophages, able to secrete signal molecules for the pulp microenvironment and thus to recruit dental pulp stem cells (DPSCs) in the damaged site. To date, root canal therapy is the standard for dental caries, but alternative regenerative treatments are gaining attention. Complex Multifrequency Magnetoelectric Fields (CMFs) represent an interesting tool due to their potential anti-inflammatory activity. Against this background, the present work aims at investigating whether the CMF treatment might restore redox balance in a co-culture model of DPSCs and inflamed macrophages mimicking an inflammatory condition, like pulpitis. Results show that superoxide anion levels and markers related to the polarization of macrophages are modulated by the CMF treatment. In parallel, the use of CMFs discloses an impact on the odontogenic commitment of DPSCs, their immunophenotype being considerably modified. In conclusion, CMFs, by modulating the odontogenic commitment and the anti-inflammatory response of DPSCs, might represent a suitable therapeutic tool against pulpitis and, in general, towards dental inflammatory diseases.

In vitro biocompatibility of ammonia-free silver fluoride products on human dental pulp stem cells

OBJECTIVES

Silver fluoride (SF) is a preventive and therapeutic option for dental pathological processes involving structural alterations of the hard tissues, either during their formation or those caused by caries or other pathological reasons. This study aimed to compare the biological properties of two commercial SF products, one of them with ammonium (Riva Star; SDF) and the other ammonium-free (Riva Star Aqua; AgF), both with or without potassium iodide (KI), by the assessment of the cytotoxicity of the materials' eluates.

METHODS

Human dental pulp stem cells (hDPSCs) were obtained from healthy 18-23-year-old donors. Three dilutions were prepared for the tested materials (0.005%, 0.0005%, and 0.0001%). The following groups were assessed: (AgF, AgF+KI, SDF, SDF+KI, KI, negative control). A series of cytocompatibility assays were performed: MTT assay, IC50 assay, wound healing (migration) assay, cell cytoskeleton staining, analysis of cell apoptosis and necrosis, and reactive oxygen species production. The normality in the distribution of the data was previously confirmed via a Q-Q plot. Statistical significance was tested using one way ANOVA and Tukey's post hoc test.

RESULTS

The incorporation of KI improved the cytocompatibility of both SF products in terms of viability, migration, morphology, apoptosis, and reactive oxygen species production. This difference was higher in the AgF group. The lowest dilutions of SF+KI and AgF+KI showed a similar cytocompatibility to that of the control group (MTT assay (p > 0.05 after 24, 48, and 72 h of culture); migration assay (p > 0.05 after 24, 48, and 72 h of culture); reactive oxygen species production (p > 0.05 after 72 h of culture).

SIGNIFICANCE

Riva Star Aqua shows lower cytotoxicity than Riva Star on hDPSCs. It can be considered as a good alternative in the conservative treatment of dental caries and in the preservation and remineralisation of viable dentine tissue.

Endodontic Tissue Regeneration: A Review for Tissue Engineers and Dentists

The paradigm shift in the endodontic field from replacement toward regenerative therapies has witnessed the ever-growing research in tissue engineering and regenerative medicine targeting pulp-dentin complex in the past few years. Abundant literature on the subject that has been produced, however, is scattered over diverse areas of knowledge. Moreover, the terminology and concepts are not always consensual, reflecting the range of research fields addressing this subject, from endodontics to biology, genetics, and engineering, among others. This fact triggered some misinterpretations, mainly when the denominations of different approaches were used as synonyms. The evaluation of results is not precise, leading to biased conjectures. Therefore, this literature review aims to conceptualize the commonly used terminology, summarize the main research areas on pulp regeneration, identify future trends, and ultimately clarify whether we are really on the edge of a paradigm shift in contemporary endodontics toward pulp regeneration.

Engineering the Future of Dental Health: Exploring Molecular Advancements in Dental Pulp Regeneration

Protected by the surrounding mineralized barriers of enamel, dentin, and cementum, dental pulp is a functionally versatile tissue that fulfills multiple roles [...].

Immunohistochemical analysis of S100-proteins in normal and irreversibly inflamed human dental pulps

AIM

S100 proteins convey important roles in innate immune responses to infection and regenerative processes. Their role in inflammatory or regenerative processes of the human dental pulp, however, is poorly elucidated. Aim of the present study was to detect, localize and compare the occurrence of eight S100 proteins in normal, symptomatic, and asymptomatic irreversibly inflamed dental pulp specimens.

METHODOLOGY

Human dental pulp specimens from forty-five individuals were clinically assigned to three groups of pulpal diagnosis, "normal pulp" (NP; n=17), "asymptomatic irreversible pulpitis" (AIP; n=13), and "symptomatic irreversible pulpitis" (SIP; n=15). The specimens were prepared and immunohistochemically stained for proteins S100A1, -A2, -A3, -A4, -A6, -A7, -A8, and -A9. Staining was classified using semi quantitative analysis and a four-degree staining score ("no", "decent", "medium" and "intense" staining) at four different anatomical or functional regions [odontoblast layer (OL), pulpal stroma (PS), border area of calcifications (BAC), and vessel walls (VW)]. Distribution of staining degrees between the three diagnostic groups was calculated using fisher´s exact text (p≤0.5) at the four regions.

RESULTS

Significant differences in staining were observed mainly in the OL, PS, and at BAC. The most significant differences were detected in PS and when comparing NP with one of the two irreversibly inflamed pulpal tissues (AIP or SIP). The inflamed tissues were then invariably stained more intensely than their normal counterparts at this location (S100A1, -A2, -A3, -A4, -A8, and -A9). In the OL, NP tissue was significantly stronger stained for S100A1, -A6, -A8, and -A9 compared with SIP, and for S100A9 when compared with AIP. Differences between AIP and SIP in direct comparison were rare and found only for one protein (S100A2) at the BAC. Also at the VW, only one statistical difference in staining was observed (SIP was stronger stained than NP for protein S100A3).

CONCLUSIONS

Occurrence of proteins S100A1, -A2, -A3, -A4, -A6, -A8, and -A9 is significantly altered in irreversibly inflamed compared with normal dental pulp tissue at different anatomical localizations. Some members of S100 proteins obviously participate in focal calcification processes and pulp stone formation of the dental pulp.

The Inhibition of the Inducible Nitric Oxide Synthase Enhances the DPSC Mineralization under LPS-Induced Inflammation

Nitric oxide (NO) is a key messenger in physiological and pathological processes in mammals. An excessive NO production is associated with pathological conditions underlying the inflammation response as a trigger. Among others, dental pulp inflammation results from the invasion of dentin by pathogenic bacteria. Vital functions of pulp mesenchymal stem cells (DPSCs, dental pulp stem cells), such as mineralization, might be affected by the inducible NOS (iNOS) upregulation. In this context, the iNOS selective inhibition can be considered an innovative therapeutic strategy to counteract inflammation and to promote the regeneration of the dentin-pulp complex. The present work aims at evaluating two acetamidines structurally related to the selective iNOS inhibitor 1400W, namely CM544 and FAB1020, in a model of LPS-stimulated primary DPSCs. Our data reveal that CM544 and even more FAB1020 are promising anti-inflammatory compounds, decreasing IL-6 secretion by enhancing CD73 expression-levels, a protein involved in innate immunity processes and thus confirming an immunomodulatory role of DPSCs. In parallel, cell mineralization potential is retained in the presence of compounds as well as VEGF secretion, and thus their angiogenetic potential. Data presented lay the ground for further investigation on the anti-inflammatory potential of acetamidines selectively targeting iNOS in a clinical context.

Effects of inflammation in dental pulp cell differentiation and reparative response

The responsiveness of the dentin-pulp complex is possible due to the stimulation of dental pulp cells, which begin to synthesize and secrete dentin matrix. The inflammatory process generated by harmful stimuli should be understood as a natural event of the immune response, resulting in the recruitment of hematopoietic cells, which cross the endothelial barrier and reach the site affected by the injury in order to eliminate the damage and provide an appropriate environment for the restoration of homeostasis. The repair process occurs in the presence of adequate blood supply, absence of infection, and with the participation of pro-inflammatory cytokines, growth factors, extracellular matrix components, and other biologically active molecules. Prostaglandins and leukotrienes are bioactive molecules derived from the metabolism of arachidonic acid, as a result of a variable range of cellular stimuli. The aim of this review is to describe the process of formation and biomineralization of the dentin-pulp complex and how pro-inflammatory events can modify this response, with emphasis on the lipid mediators prostaglandins and leukotrienes derived from arachidonic acid metabolism.

Influence of HEMA on LPS- and LTA-stimulated IL-6 release from human dental pulp cells

OBJECTIVE

Dental pulp cells interact with immunogenic components such as LPS (lipopolysaccharide) or LTA (lipoteichoic acid) released from microorganisms in carious lesions. In the present investigation, the formation of the pro-inflammatory cytokines TNFα and IL-6 in LPS- or LTA-stimulated cells from the dental pulp interface and pulp fibroblasts was analyzed in the presence of the resin monomer 2-hydroxyethyl methacrylate (HEMA) under varying cellular redox conditions.

METHOD

Human pulp fibroblasts (HPC) or cells from the dental pulp interface expressing an odontoblast phenotype (hOD-1) were exposed to LTA, LPS or HEMA for 1 h or 24 h. Redox homeostasis was modified by the prooxidant BSO (L-buthionine sulfoximine) or the antioxidant NAC (N-acetyl cysteine). Formation of TNFα or IL-6 was analyzed by ELISA, and cell survival was determined by a crystal violet assay. Statistical analyses were performed using the Mann-Whitney-U-test.

RESULTS

Secretion of TNFα was not detected in LPS- or LTA-stimulated HPC or hOD-1, and IL-6 was not found after a short exposure (1 h). After a 24 h exposure, LPS induced a 3-fold increase in IL-6 formation in HPC, while LTA stimulated IL-6 release about 20-fold. Likewise, LTA was more effective than LPS in hOD-1 stimulating IL-6 levels about 50-fold. HEMA inhibited the LPS- and LTA-induced IL-6 release, and this effect was enhanced by BSO but counteracted by NAC in both cell types. IL-6 release was independent of cell survival rates.

CONCLUSIONS

The protective immune response in odontoblasts and pulp fibroblasts is impaired by monomers such as HEMA through the disturbance of the redox homeostasis.

Expression profiling of S100-proteins in healthy and irreversibly inflamed human dental pulps

AIM

Several S100 proteins have been shown to play an important role in the innate immune response to infection and in regenerative processes. However, they have scarcely been investigated during inflammation of the dental pulp. Therefore, in this study we performed gene expression profiling of S100 proteins in healthy and inflamed human dental pulps.

METHODOLOGY

Tissue samples of human dental pulps were used including fifteen clinically diagnosed as symptomatic irreversible pulpitis (SIP), seven as asymptomatic irreversible pulpitis (AIP), and nineteen as healthy pulp (HP). S100 gene expression levels were quantitatively evaluated for S100 A1, A2, A3, A4, A6, A7, A8, A9, A10, A11, A13, A14, and A16 by qPCR technique. In order to monitor the status of inflammation and degradation of pulp tissues, IL-8, COX-2, and HMGB-1 gene expression was also analysed, with GAPDH serving as reference gene. Differential expression rates for each target gene between SIP, AIP, and HP were evaluated by analysis of variance (ANOVA) followed by Bonferroni post-hoc-test.

RESULTS

Significantly reduced gene expression levels could be detected in SIP compared to HP for S100A1, A2, A3, A4, A6, A10, A13, and for HMGB-1, while gene expression of S100A8, A14, and IL-8 were significantly increased. In AIP, significantly increased expression levels compared to HP were only detected for S100A14, A16, and for IL-8, with other genes of interest not being altered.

CONCLUSIONS

The present study revealed significant differences in gene expression profiles of S100 proteins comparing samples from healthy and inflamed dental pulps. More pronounced differences were observed for symptomatic than for asymptomatic pulpitis.

Relevance of Cellular Redox Homeostasis for Vital Functions of Human Dental Pulp Cells

Odontogenic MSCs are vulnerable to LPS-triggered bacterial infections, and they respond by secreting inflammatory mediators, such as IL-6, and with mineralization. Since both processes might be prone to a disturbance of the redox homeostasis, the oxidative stress influence on vital functions of human dental pulp cells (HPCs) was investigated. With these aims, a model of LPS-stimulated primary HPCs was established, and anti- and pro-oxidant substances were administered up to 21 days to measure inflammation and mineralization parameters. LPS-stimulated HPCs retained mineralization potential, which was decreased with the antioxidants NAC and fisetin and the pro-oxidant BSO. The expression of surface markers related to odontogenic commitment was influenced accordingly but counteracted by the enhanced expression of BMP2 and ALP at the transcriptional level. LPS triggers an early IL-6 production in non-odontogenic conditions, while it can be measured only after 15 days in the presence of the differentiation medium. The present study shows that HPCs functions causally depend on a tightly regulated cellular redox balance. Our data demonstrate a redox control of pulp MSC odontogenic commitment along with a potential association between an IL-6 late secretion and mineralization. These findings lay the groundwork for investigations on the molecular role of IL-6 in dental hard tissue metabolism.

Bimodal expression of Wnt5a in the tooth germ: A comparative study using in situ hybridization and immunohistochemistry

BACKGROUND

During tooth development, Wnt5a, a member of the noncanonical Wnt ligand, is expressed prominently in the dental mesenchyme. However, the spatiotemporal profiles of Wnt5a protein production and distribution in tooth germs are largely unknown, which impairs elucidation of the Wnt5a-mediated regulatory mechanism of tooth development.

METHODS

We performed analyzes of the spatiotemporal expression of Wnt5a in embryonic tooth germs (E11.5-E18.5) by using in situ hybridization and immunohistochemistry in parallel. The developmental stages of the embryonic tooth germs were determined by HE staining. In order to compare the spatiotemporal distribution patterns of Wnt5a mRNA-expressing cells and those of Wnt5a protein-expressing cells, serial frontal sections of paraffinized mouse embryo heads were used for the analyzes. When needed, the immunohistochemistry images were subjected to digital detection analysis of Wnt5a immunostaining signal using the WinROOF 2018 Ver. 4.19.0 image processing software program.

RESULTS

Throughout the developmental process, cells expressing Wnt5a mRNA were found in various tissues including the dental follicle, dental papilla, inner and outer enamel epithelium, stratum intermediate, and stellate reticulum. However, odontoblasts differentiating and polarizing at E18.5 were the only cells representing an accumulation of Wnt5a protein in the apical region of the odontoblast process. The Wnt5a protein was undetectable in undifferentiated mesenchymal cells as well as any other cells positive for Wnt5a mRNA.

CONCLUSION

Differentiating odontoblasts execute Wnt5a expression, the mode of which is distinct from that executed by the other cells constituting tooth germ. Change of the mode of Wnt5a expression begins to take place in the mesenchymal cells by E18.5, starting the elongation of the cytoplasmic process.

Understanding collagen interactions and their targeted regulation by novel drugs

Introduction: Among protein and fibers in the extracellular matrix (ECM), collagen is the most copious and widely employed in cosmetic, food, pharmaceutical, and biomedical industries due to its extensive biocompatible and versatile properties. In the last years, the knowledge about functions of collagens increased and expanded dramatically. Once considered only crucial for the ECM scaffolding and mechanotransduction, additional functional roles have now been ascribed to the collagen superfamily which are defined by other recently discovered domains, supramolecular assembly and receptors.Areas covered: Given the importance of each step in the collagen biosynthesis, folding and signaling, medicinal chemists have explored small molecules, peptides, and monoclonal antibodies to modulate enzymes, receptors and interactions with the physiological ligands of collagen. These compounds were also explored toward diseases and pathological conditions. The authors discuss this providing their expert perspectives on the subject area.Expert opinion: Understanding collagen protein properties and its interactome is beneficial for therapeutic drug design. Nevertheless, compounds targeting collagen-based interactome suffered from the presence of different isoforms for each target and the lack of specific 3D crystal structures able to guide properly drug design.

Antlerogenic stem cells extract accelerate chronic wound healing: a preliminary study

BACKGROUND

Chronic wounds constitute a significant medical and social problem. Chronic wound treatment may be supported by various techniques, such as negative pressure therapy, phototherapy or stem cells therapy, yet most of those supporting therapies need more evidence to be used for standard wound care. Current study covers the use of sonicated Antlerogenic Stem Cells (ASC) extract on chronic wounds.

METHODS

Study was performed on 20 dermatological patients with venous leg ulcers, divided into two groups - treated with and without ASC extract respectively. The area and circumference of the wounds during the follow-up visits were measured on the wound imprint. Dynamics of wound healing was determined and compared between control and study group; statistics includes changes in absolute values (wound area, circumference), as well as relative (percentage of wound decrease, circumference/area ratio) and their change in time. For the purpose of Ki-67 immunohistochemical staining, sections were sampled from the wound edge at distinct check-points during therapy. Results of both groups were compared with Student test or Mann-Whitney test, depending on results distribution.

RESULTS

Besides Ki-67 expression, all tested wound healing parameters (including relative and absolute wound decrease and changes in circumference/area ratio) were statistically significant more favorable in experimental group.

CONCLUSION

ASC extract significantly supported standard chronic wound treatment. Due to small population of study the results should be considered preliminary, yet promising for further research.

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.