The functional significance of dentin sialoprotein-phosphophoryn and dentin sialoprotein. Int J Oral Sci. 2018;10:31. [PMID: 30393383 PMCID: PMC6215839 DOI: 10.1038/s41368-018-0035-9]

Progress in the pathogenic mechanism, histological characteristics of hereditary dentine disorders and clinical management strategies

Hereditary dentine disorders are autosomal dominant diseases that affect the development and structure of dentine, leading to various dental abnormalities and influencing the individual's oral health. It is generally classified as dentinogenesis imperfecta (DGI) and dentine dysplasia (DD). Specifically, DGI is characterized by the abnormal formation of dentine, resulting in teeth that are discolored, translucent, and prone to fracture or wear down easily. DD is characterized by abnormal dentine development, manifested as teeth with short roots and abnormal pulp chambers, leading to frequent tooth loss. Up to now, the pathogenesis of hereditary dentine disorders has been poorly clarified and the clinical intervention is limited. Treatment for hereditary dentine disorders focuses on managing the symptoms and preventing further dental problems. Genetic counseling and testing may also be recommended as these conditions can be passed on to future generations. In this review, we summarize the clinical features, pathogenic genes, histomorphological characteristics and therapy of hereditary dentine disorders. Due to the limited understanding of the disease at present, we hope this review could improve the recognition of the disease by clinicians, stimulate more scholars to further study the deeply detailed mechanisms of the disease and explore potential therapeutic strategies, thus achieving effective, systematic management of the disease and improving the life quality of patients.

Decorin in the spatial control of collagen mineralization

Understanding the molecular mechanism by which the periodontal ligament (PDL) is maintained uncalcified between two mineralized tissues (cementum and bone) may facilitate the functional repair and regeneration of the periodontium complex, disrupted in the context of periodontal diseases. However, research that explores the control of type I collagen (COL I) mineralization fails to clarify the detailed mechanism of regulating spatial collagen mineralization, especially in the periodontium complex. In the present study, decorin (DCN), which is characterized as abundant in the PDL region and rare in mineralized tissues, was hypothesized to be a key regulator in the spatial control of collagen mineralization. The circular dichroism results confirmed that DCN regulated the secondary structure of COL I, and the surface plasmon resonance results indicated that COL I possessed a higher affinity for DCN than for other mineralization promoters, such as DMP-1, OPN, BSP and DSPP. These features of DCN may contribute to blocking intrafibrillar mineralization in COL I fibrils during the polymer-induced liquid-precursor mineralization process when the fibrils are cross-linked with DCN. This effect was more remarkable when the fibrils were phosphorylated by sodium trimetaphosphate, as shown by the observation of a tube-like morphology via TEM and mineral sheath via SEM. This study enhances the understanding of the role of DCN in mineralization regulation among periodontal tissues. This provides insights for the development of biomaterials for the regeneration of interfaces between soft and hard tissues.

Bioceramic versus traditional biomaterials for endodontic sealers according to the ideal properties

Odontology, as a scientific discipline, continuously collaborates with biomaterials engineering to enhance treatment characteristics and patients' satisfaction. Endodontics, a specialized field of dentistry, focuses on the study, diagnosis, prevention, and treatment of dental disorders affecting the dental pulp, root, and surrounding tissues. A critical aspect of endodontic treatment involves the careful selection of an appropriate endodontic sealer for clinical use, as it significantly influences treatment outcomes. Traditional sealers, such as zinc oxide-eugenol, fatty acid, salicylate, epoxy resin, silicone, and methacrylate resin systems, have been extensively used for decades. However, advancements in endodontics have given rise to bioceramic-based sealers, offering improved properties and addressing new challenges in endodontic therapy. In this review, a classification of these materials and their ideal properties are presented to provide evidence-based guidance to clinicians. Physicochemical properties, including sealing ability, stability over time and space, as well as biological properties such as biocompatibility and antibacterial characteristics, along with cost-effectiveness, are essential factors influencing clinicians' decisions based on individual patient evaluations.

Integrating osteoimmunology and nanoparticle-based drug delivery systems for enhanced fracture healing

Fracture healing is a complex interplay of molecular and cellular mechanisms lasting from days to weeks. The inflammatory phase is the first stage of fracture healing and is critical in setting the stage for successful healing. There has been growing interest in exploring the role of the immune system and novel therapeutic strategies, such as nanoparticle drug delivery systems in enhancing fracture healing. Advancements in nanotechnology have revolutionized drug delivery systems to the extent that they can modulate immune response during fracture healing by leveraging unique physiochemical properties. Therefore, understanding the intricate interactions between nanoparticle-based drug delivery systems and the immune response, specifically macrophages, is essential for therapeutic efficacy. This review provides a comprehensive overview of the relationship between the immune system and nanoparticles during fracture healing. Specifically, we highlight the influence of nanoparticle characteristics, such as size, surface properties, and composition, on macrophage activation, polarization, and subsequent immune responses. IMPACT STATEMENT: This review provides valuable insights into the interplay between fracture healing, the immune system, and nanoparticle-based drug delivery systems. Understanding nanoparticle-macrophage interactions can advance the development of innovative therapeutic approaches to enhance fracture healing, improve patient outcomes, and pave the way for advancements in regenerative medicine.

Effects of histone acetyltransferase (HAT) and histone deacetylase (HDAC) inhibitors on proliferative, differentiative, and regenerative functions of Toll-like receptor 2 (TLR-2)-stimulated human dental pulp cells (hDPCs)

OBJECTIVES

This in vitro study aimed to modify TLR-2-mediated effects on the paracrine, proliferative, and differentiation potentials of human dental pulp-derived cells using histone acetyltransferase (HAT) and histone deacetylase (HDAC) inhibitors.

MATERIALS AND METHODS

Cell viability was assessed using the XTT assay. Cells were either treated with 10 μg/ml Pam3CSK4 only, or pre-treated with valproic acid (VPA) (3 mM), trichostatin A (TSA) (3 μM), and MG-149 (3 μM) for a total of 4 h and 24 h. Control groups included unstimulated cells and cells incubated with inhibitors solvents only. Transcript levels for NANOG, OCT3-4, FGF-1 and 2, NGF, VEGF, COL-1A1, TLR-2, hβD-2 and 3, BMP-2, DSPP, and ALP were assessed through qPCR.

RESULTS

After 24 h, TSA pre-treatment significantly upregulated the defensins and maintained the elevated pro-inflammatory cytokines, but significantly reduced healing and differentiation genes. VPA significantly upregulated the pro-inflammatory cytokine levels, while MG-149 significantly downregulated them. Pluripotency genes were not significantly affected by any regimen.

CONCLUSIONS

At the attempted concentrations, TSA upregulated the defensins gene expression levels, and MG-149 exerted a remarkable anti-inflammatory effect; therefore, they could favorably impact the immunological profile of hDPCs.

CLINICAL RELEVANCE

Targeting hDPC nuclear function could be a promising option in the scope of the biological management of inflammatory pulp diseases.

Research progress of biomimetic materials in oral medicine

Biomimetic materials are able to mimic the structure and functional properties of native tissues especially natural oral tissues. They have attracted growing attention for their potential to achieve configurable and functional reconstruction in oral medicine. Though tremendous progress has been made regarding biomimetic materials, significant challenges still remain in terms of controversy on the mechanism of tooth tissue regeneration, lack of options for manufacturing such materials and insufficiency of in vivo experimental tests in related fields. In this review, the biomimetic materials used in oral medicine are summarized systematically, including tooth defect, tooth loss, periodontal diseases and maxillofacial bone defect. Various theoretical foundations of biomimetic materials research are reviewed, introducing the current and pertinent results. The benefits and limitations of these materials are summed up at the same time. Finally, challenges and potential of this field are discussed. This review provides the framework and support for further research in addition to giving a generally novel and fundamental basis for the utilization of biomimetic materials in the future.

p75NTR promotes tooth rhythmic mineralization via upregulation of BMAL1/CLOCK

The circadian clock plays a critical role in dentomaxillofacial development. Tooth biomineralization is characterized by the circadian clock; however, the mechanisms underlying the coordination of circadian rhythms with tooth development and biomineralization remain unclear. The p75 neurotrophin receptor (p75NTR) is a clock factor that regulates the oscillatory components of the circadian rhythm. This study aims to investigate the impact of p75NTR on the rhythmic mineralization of teeth and elucidate its underlying molecular mechanisms. We generated p75NTR knockout mice to examine the effects of p75NTR deficiency on tooth mineralization. Ectomesenchymal stem cells (EMSCs), derived from mouse tooth germs, were used for in vitro experiments. Results showed a reduction in tooth mineral density and daily mineralization rate in p75NTR knockout mice. Deletion of p75NTR decreased the expression of DMP1, DSPP, RUNX2, and ALP in tooth germ. Odontogenic differentiation and mineralization of EMSCs were activated by p75NTR. Histological results demonstrated predominant detection of p75NTR protein in odontoblasts and stratum intermedium cells during rapid formation phases of dental hard tissue. The mRNA expression of p75NTR exhibited circadian variations in tooth germs and EMSCs, consistent with the expression patterns of the core clock genes Bmal1 and Clock. The upregulation of BMAL1/CLOCK expression by p75NTR positively regulated the mineralization ability of EMSCs, whereas BMAL1 and CLOCK exerted a negative feedback regulation on p75NTR by inhibiting its promoter activity. Our findings suggest that p75NTR is necessary to maintain normal tooth biomineralization. Odontogenic differentiation and mineralization of EMSCs is regulated by the p75NTR-BMAL1/CLOCK signaling axis. These findings offer valuable insights into the associations between circadian rhythms, tooth development, and biomineralization.

Identification of DSPP novel variants and phenotype analysis in dentinogenesis dysplasia Shields type II patients

OBJECTIVES

To investigate the genetic causes and teeth characteristics of dentin dysplasia Shields type II(DD-II) in three Chinese families.

MATERIALS AND METHODS

Data from three Chinese families affected with DD-II were collected. Whole-exome sequencing (WES) and whole-genome sequencing (WGS) were conducted to screen for variations, and Sanger sequencing was used to verify mutation sites. The physical and chemical characteristics of the affected teeth including tooth structure, hardness, mineral content, and ultrastructure were investigated.

RESULTS

A novel frameshift deletion mutation c.1871_1874del(p.Ser624fs) in DSPP was found in families A and B, while no pathogenic mutation was found in family C. The affected teeth's pulp cavities were obliterated, and the root canals were smaller than normal teeth and irregularly distributed comprising a network. The patients' teeth also had reduced dentin hardness and highly irregular dentinal tubules. The Mg content of the teeth was significantly lower than that of the controls, but the Na content was obviously higher than that of the controls.

CONCLUSIONS

A novel frameshift deletion mutation, c.1871_1874del (p.Ser624fs), in the DPP region of the DSPP gene causes DD-II. The DD-II teeth demonstrated compromised mechanical properties and changed ultrastructure, suggesting an impaired function of DPP. Our findings expand the mutational spectrum of the DSPP gene and strengthen the understanding of clinical phenotypes related to the frameshift deletion in the DPP region of the DSPP gene.

CLINICAL RELEVANCE

A DSPP mutation can alter the characteristics of the affected teeth, including tooth structure, hardness, mineral content, and ultrastructure.

Biomineralization-inspired mineralized hydrogel promotes the repair and regeneration of dentin/bone hard tissue

Maxillofacial hard tissue defects caused by trauma or infection often affect craniofacial function. Taking the natural hard tissue structure as a template, constructing an engineered tissue repair module is an important scheme to realize the functional regeneration and repair of maxillofacial hard tissue. Here, inspired by the biomineralization process, we constructed a composite mineral matrix hydrogel PAA-CMC-TDM containing amorphous calcium phosphates (ACPs), polyacrylic acid (PAA), carboxymethyl chitosan (CMC) and dentin matrix (TDM). The dynamic network composed of Ca²⁺·COO^- coordination and ACPs made the hydrogel loaded with TDM, and exhibited self-repairing ability and injectability. The mechanical properties of PAA-CMC-TDM can be regulated, but the functional activity of TDM remains unaffected. Cytological studies and animal models of hard tissue defects show that the hydrogel can promote the odontogenesis or osteogenic differentiation of mesenchymal stem cells, adapt to irregular hard tissue defects, and promote in situ regeneration of defective tooth and bone tissues. In summary, this paper shows that the injectable TDM hydrogel based on biomimetic mineralization theory can induce hard tissue formation and promote dentin/bone regeneration.

Dentin Sialoprotein/Phosphophoryn (DSP/PP) as Bio-Inductive Materials for Direct Pulp Capping

Conventional direct pulp capping, such as calcium hydroxide (Ca(OH)₂) or silicate products, usually induces an inflammatory reaction to provoke pulp regeneration. Phosphophoryn (PP) and dentin sialoprotein (DSP), the two most abundant non-collagenous proteins in the dentin matrix, are responsible for dentin mineralization, pulp cell migration, and differentiation. Here we examined the PP and combined DSP/PP as bio-inductive pulp capping materials by in vitro and in vivo tests. Firstly, the effects of the PP dose on pulp cell migration and matrix protein expression were examined by an agarose bead test. Secondly, the role of recombinant DSP (recDSP) and recDSP/PP on stimulating DSP-PP transcript expression was examined by RT-PCR. DSPP mRNA was also knocked down by RNA interference (RNAi) to examine their functions on dentin matrix mineralization. Finally, we used ferret animal models to test PP and recDSP/PP acting as capping agents on in vivo pulp responses and reparative dentin formation. The result showed that intermediate-dose PP was the most effective to enhance cell migration and differentiation. RecDSP/PP strongly enhanced the DSP-PP transcript expression, while inhibition of DSPP mRNA expression by siRNAs partially or completely affected dental pulp cell mineralization. The in vivo results showed that intermediate-dose PP and recDSP/PP proteins induced less pulp inflammation and promoted reparative dentin formation. Contrarily, conventional calcium hydroxide induced severe pulp inflammation. With these findings, DSP and PP could serve as capping agents for pulp capping therapy.

Label-free quantitative proteomics reveals molecular correlates of altered biomechanical properties in molar incisor hypomineralization (MIH): an in vitro study

PURPOSE

Molar-incisor hypomineralization (MIH) is a qualitative developmental defect of enamel that affects first permanent molars with or without affecting permanent incisors. We aimed to carry out a quantitative proteomics-based study to compare and evaluate proteins in sound and MIH-affected enamel.

MATERIALS AND METHODS

Ten blocks each of the MIH-affected enamel and sound enamel were processed and prepared for LC-MS/MS analysis. Label-free quantitation was carried out to evaluate the differentially expressed proteins in the two groups of samples.

RESULTS

A significant increase in the number of proteins in MIH-affected enamel (50.3 ± 29.6) was observed compared to the sound enamel (21.4 ± 3.2). While proteins like collagens, α1-anti-trypsin, kallikrein-4 (KLK4), matrix metalloprotease-20 (MMP-20), alpha-2-macroglobulin, and alpha-2-HS-glycoprotein were upregulated in sound enamel, there was over-expression of albumin, calcium-binding proteins, anti-thrombin III, and dentin sialophosphoprotein (DSPP), along with proteins implicated in stress response and inflammatory processes in MIH.

CONCLUSION

We propose that altered biomechanical properties of the enamel in MIH samples arise due to (i) down-regulation of proteins contributing to collagen biosynthesis and fibril formation; (ii) an overall imbalance in required levels of proteases (KLK4 and MMP-20) and anti-proteases (anti-thrombin-III which inhibits KLK-4), essential for optimal mineralization; (iii) very low levels of alpha-2-macroglobulin with important consequences in enamel mineralization and amelogenesis; and (iv) increased albumin in MIH, preventing proper growth of hydroxyapatite crystals. Increased inflammatory component was also seen in MIH; however, whether inflammation is a cause or consequence of the poor mineralization process needs to be assessed.

Phenotype and molecular characterizations of a family with dentinogenesis imperfecta shields type II with a novel DSPP mutation

Background

Dentinogenesis imperfecta (DGI), Shields type-II is an autosomal dominant genetic disease which severely affects the function of the patients’ teeth. The dentin sialophosphoprotein (DSPP) gene is considered to be the pathogenic gene of DGI-II. In this study, a DGI-II family with a novel DSPP mutation were collected, functional characteristics of DGI cells and clinical features were analyzed to better understand the genotype-phenotype relationship of this disease.

Methods

Clinical data were collected, whole exome sequencing (WES) was conducted, and Sanger sequencing was used to verify the mutation sites. Physical characteristics of the patient’s teeth were examined using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The localization of green fluorescent protein (GFP)-fused wild-type (WT) dentin sialoprotein (DSP) and its variant were evaluated via an immunocytochemistry (ICC) assay. The behaviors of human dental pulp stem cells (hDPSCs) were investigated by flow cytometry, osteogenic differentiation, and quantitative real-time polymerase chain reaction (qRT-PCR).

Results

A novel heterozygous mutation c.53T > G (p. Val18Gly) in DSPP was found in this family. The SEM results showed that the participants’ teeth had reduced and irregular dentinal tubes. The EDS results showed that the Ca/P ratio of the patients’ teeth was significantly higher than that of the control group. The ICC assay showed that the mutant DSP was entrapped in the endoplasmic reticulum (ER), while the WT DSP located mainly in the Golgi apparatus. In comparison with normal cells, the patient’s cells exhibited significantly decreased mineralization ability and lower expression levels of DSPP and RUNX2.

Conclusions

The c.53T > G (p. Val18Gly) DSPP variant was shown to present with rare hypoplastic enamel defects. Functional analysis revealed that this novel variant disturbs dentinal characteristics and pulp cell behavior.

Concentration of dentin sialoprotein at the initial stage of orthodontic treatment using self-ligating and conventional preadjusted brackets: A pilot study

OBJECTIVES:

This study evaluated differences in concentration of dentin sialoprotein (DSP) in gingival crevicular fluid (GCF) relating to orthodontically induced inflammatory root resorption (OIIRR) at the initial stage of orthodontic treatment using self-ligating and conventional preadjusted brackets.

MATERIALS AND METHODS:

Eighteen patients were assigned to three groups of equal size. Two experimental groups received non-extraction orthodontic treatment using passive self-ligating or conventional preadjusted bracket. The control group included patients without orthodontic treatment. GCF was collected from five proximal sites of maxillary anterior teeth at subsequent intervals: immediately prior to orthodontic treatment (T0), and at three and 12 weeks after initiation of treatment (T1 and T2). DSP concentration was evaluated by enzyme-linked immunoabsorbent assay and the differences in DSP levels were analyzed between and within groups.

RESULTS:

There were no significant differences in DSP levels within both experimental groups and the control group during T0-T1-T2 (P ≥ 0.05). A significant difference of DSP concentration was found between the conventional preadjusted bracket and the control group at T2 (P = 0.038). However, it was thought to be clinically insignificant.

CONCLUSION:

The study showed no significant difference in DSP concentration at the initial stage of orthodontic treatment with either self-ligating or conventional preadjusted bracket.

Effects of DSPP Gene Mutations on Periodontal Tissues

Dentin sialophosphoprotein ( DSPP ) gene mutations cause autosomal dominantly inherited diseases. DSPP gene mutations lead to abnormal expression of DSPP, resulting in a series of histological, morphological, and clinical abnormalities. A large number of previous studies demonstrated that DSPP is a dentinal-specific protein, and DSPP gene mutations lead to dentin dysplasia and dentinogenesis imperfecta. Recent studies have found that DSPP is also expressed in bone, periodontal tissues, and salivary glands. DSPP is involved in the formation of the periodontium as well as tooth structures. DSPP deficient mice present furcation involvement, cementum, and alveolar bone defect. We speculate that similar periodontal damage may occur in patients with DSPP mutations. This article reviewed the effects of DSPP gene mutations on periodontal status. However, almost all of the research is about animal study, there is no evidence that DSPP mutations cause periodontium defects in patients yet. We need to conduct systematic clinical studies on DSPP mutation families in the future to elucidate the effect of DSPP gene on human periodontium.

Preparation of Absorption-Resistant Hard Tissue Using Dental Pulp-Derived Cells and Honeycomb Tricalcium Phosphate

In recent years, there has been increasing interest in the treatment of bone defects using undifferentiated mesenchymal stem cells (MSCs) in vivo. Recently, dental pulp has been proposed as a promising source of pluripotent mesenchymal stem cells (MSCs), which can be used in various clinical applications. Dentin is the hard tissue that makes up teeth, and has the same composition and strength as bone. However, unlike bone, dentin is usually not remodeled under physiological conditions. Here, we generated odontoblast-like cells from mouse dental pulp stem cells and combined them with honeycomb tricalcium phosphate (TCP) with a 300 μm hole to create bone-like tissue under the skin of mice. The bone-like hard tissue produced in this study was different from bone tissue, i.e., was not resorbed by osteoclasts and was less easily absorbed than the bone tissue. It has been suggested that hard tissue-forming cells induced from dental pulp do not have the ability to induce osteoclast differentiation. Therefore, the newly created bone-like hard tissue has high potential for absorption-resistant hard tissue repair and regeneration procedures.

A Bioinformatics Systems Biology Analysis of the Current Oral Proteomic Biomarkers and Implications for Diagnosis and Treatment of External Root Resorption

External root resorption (ERR) is a silent destructive phenomenon detrimental to dental health. ERR may have multiple etiologies such as infection, inflammation, traumatic injuries, pressure, mechanical stimulations, neoplastic conditions, systemic disorders, or idiopathic causes. Often, if undiagnosed and untreated, ERR can lead to the loss of the tooth or multiple teeth. Traditionally, clinicians have relied on radiographs and cone beam computed tomography (CBCT) images for the diagnosis of ERR; however, these techniques are not often precise or definitive and may require exposure of patients to more ionizing radiation than necessary. To overcome these shortcomings, there is an immense need to develop non-invasive approaches such as biomarker screening methods for rapid and precise diagnosis for ERR. In this review, we performed a literature survey for potential salivary or gingival crevicular fluid (GCF) proteomic biomarkers associated with ERR and analyzed the potential pathways leading to ERR. To the best of our knowledge, this is the first proteomics biomarker survey that connects ERR to body biofluids which represents a novel approach to diagnose and even monitor treatment progress for ERR.

Primary observation of the role of posttranslational modification of dentin sialophosphoprotein (DSPP) on postnatal development of mandibular condyle in mice

OBJECTIVES

We aimed to observe the posttranslational role of dentin sialophosphoprotein (DSPP) on postnatal development of mandibular condyle in mice.

METHODS

To explore the function of full-length DSPP, four groups of mice were employed: (1) wild type (WT) mice; (2)Dspp knockout (Dspp KO) mice; (3) mice expressing the normal DSPP transgene in the Dspp KO background (Dspp KO/normal Tg); (4) mice expressing the uncleavable full-length DSPP in the Dspp KO background (Dspp KO/D452A Tg). Firstly, Plain X-ray Radiography and Micro-computed Tomography were used to observe the condylar morphology changes of Dspp KO/D452A Tg mice in comparison with the other three groups. Then, Hematoxylin & eosin and toluidine blue staining were applied to uncover the histological changes of mandibular condylar cartilage (MCC) of Dspp KO/D452A Tg mice. To explore the function of the NH2-terminal fragments (i.e. DSP/DSP-PG), three groups of mice were employed: (1) WT mice; (2) Dspp KO mice; (3) mice expressing the NH2-terminal fragments of DSPP in the Dspp-null background (Dspp KO/DSP Tg). The former strategies were utilized to examine the differences of condylar morphology and histological structures changes within three groups of mice.

RESULTS

Transgenic full-length DSPP partially maintained mandibular condylar morphology and MCC thickness of Dspp KO mice. Transgenic DSP failed to do so, but led to smaller mandibular condyle and disordered cartilage structure.

CONCLUSIONS

Our observations provide insight into the role of posttranslational modification of DSPP in the postnatal development of healthy MCC and maintenance of condylar morphology.

Dentin Phosphophoryn-Derived Peptide Promotes Odontoblast Differentiation In Vitro and Dentin Regeneration In Vivo

The purpose of the present study was to investigate the effect of a peptide (i.e., SESDNNSSSRGDASYNSDES) derived from dentin phosphophoryn (DPP) with arginine-glycine-aspartic acid (RGD) motifs on odontoblast differentiation in vitro and to compare it with calcium hydroxide—a material used conventionally for vital pulp therapy—in terms of reparative dentin formation and pulp inflammation in vivo. Alkaline phosphatase activity assay and alizarin red S staining were performed to evaluate odontoblast-differentiation in cell culturing experiments. To observe the reparative dentin formation and pulp inflammation animal experiment was performed and examined by histological methods. The difference between the experimental group and the control group was analyzed statistically using a one-way ANOVA test. The results revealed that the DPP-derived RGD-containing peptide triggered odontoblast differentiation and mineralization in vitro. In rats undergoing direct pulp capping, the DPP-derived RGD-containing peptide was found to induce intensively formed reparative dentin with high compactness at week 4. On histological and morphometrical examinations, a smaller degree of pulpitis was observed in the specimens treated with the peptide than in those treated with calcium hydroxide. This study suggests that the DPP-derived RGD-containing peptide is a biocompatible, biodegradable and bioactive material for dentin regeneration.

Role of connexin 43 in odontoblastic differentiation and structural maintenance in pulp damage repair

Dental pulp can initiate its damage repair after an injury of the pulp–dentin complex by rearrangement of odontoblasts and formation of newly differentiated odontoblast-like cells. Connexin 43 (Cx43) is one of the gap junction proteins that participates in multiple tissue repair processes. However, the role of Cx43 in the repair of the dental pulp remains unclear. This study aimed to determine the function of Cx43 in the odontoblast arrangement patterns and odontoblastic differentiation. Human teeth for in vitro experiments were acquired, and a pulp injury model in Sprague-Dawley rats was used for in vivo analysis. The odontoblast arrangement pattern and the expression of Cx43 and dentin sialophosphoprotein (DSPP) were assessed. To investigate the function of Cx43 in odontoblastic differentiation, we overexpressed or inhibited Cx43. The results indicated that polarized odontoblasts were arranged along the pulp–dentin interface and had high levels of Cx43 expression in the healthy teeth; however, the odontoblast arrangement pattern was slightly changed concomitant to an increase in the Cx43 expression in the carious teeth. Regularly arranged odontoblast-like cells had high levels of the Cx43 expression during the formation of mature dentin, but the odontoblast-like cells were not regularly arranged beneath immature osteodentin in the pulp injury models. Subsequent in vitro experiments demonstrated that Cx43 is upregulated during odontoblastic differentiation of the dental pulp cells, and inhibition or overexpression of Cx43 influence the odontoblastic differentiation. Thus, Cx43 may be involved in the maintenance of odontoblast arrangement patterns, and influence the pulp repair outcomes by the regulation of odontoblastic differentiation.

Immunohistochemical expression of non-collagenous extracellular matrix molecules involved in tertiary dentinogenesis following direct pulp capping: a systematic review

BACKGROUND

Extracellular matrix molecules (ECMM) expression during tertiary dentinogenesis provides useful information for regenerative applications and efficacy of pulp capping materials.

AIM

To identify and review the expression and roles of non-collagenous ECMM after successful direct pulp capping (DPC), following mechanical pulp exposures, via immunohistochemistry (IHC). The study addressed the question of where will successful DPC impact the IHC expression of these molecules.

DATA SOURCES

In vivo animal and human original clinical studies reporting on ECMM in relation to different follow-up periods were screened and evaluated via descriptive analysis. The electronic literature search was carried out in three databases (MEDLINE/PubMed, Web of Science, Scopus), followed by manual screening of relevant journals and cross-referencing, up to December 2018.

STUDY ELIGIBILITY CRITERIA, PARTICIPANTS, AND INTERVENTIONS

Randomized and non-randomized controlled trials, conducted in humans and animals, were selected. Histological evidence for tertiary dentine formation was a prerequisite for IHC evaluation.

STUDY APPRAISAL AND SYNTHESIS METHODS

The methodological quality of the included articles was independently assessed using the Systematic Review Centre for Laboratory animal Experimentation (SYRCLE) and the Cochrane risk of bias tool (RoB 1), respectively.

RESULTS

From a total of 1534 identified studies, 18 were included. Thirteen papers evaluated animal subjects and five studies were carried out on humans. In animals and humans, fibronectin and tenascin expressions were detected in pulp and odontoblast-like cells (OLC); dentine sialoprotein was expressed in both soft and newly-formed mineralized tissue. In animals, bone sialoprotein was early expressed, in association with OLC and predentin; the immunoreactivity for dentine sialophosphoprotein and dentine matrix protein-1 was associated with the OLC and dentine bridge; osteopontin was expressed in OLC, predentine and reparative dentine. A considerable heterogeneity was found in the methodologies of the included studies, as well as interspecies variability of results in terms of time.

CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

Within the limited scientific evidence, all non-collagenous ECMM expressions during tertiary dentinogenesis are active and related to soft and hard tissues. There is a shortage of human studies, and future research directions should focus more on them. PROSPERO Protocol: CRD42019121304.

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

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

Retinoic Acid Signal Negatively Regulates Osteo/Odontogenic Differentiation of Dental Pulp Stem Cells

Retinoic acid (RA) signal is involved in tooth development and osteogenic differentiation of mesenchymal stem cells (MSCs). Dental pulp stem cells (DPSCs) are one of the useful MSCs in tissue regeneration. However, the function of RA in osteo/odontogenic differentiation of DPSCs remains unclear. Here, we investigated the expression pattern of RA in miniature pig tooth germ and intervened in the RA signal during osteo/odontogenic differentiation of human DPSCs. Deciduous canine (DC) germs of miniature pigs were observed morphologically, and the expression patterns of RA were studied by in situ hybridization (ISH). Human DPSCs were isolated and cultured in osteogenic induction medium with or without RA or BMS 493, an inverse agonist of the pan-retinoic acid receptors (pan-RARs). Alkaline phosphatase (ALP) activity assays, alizarin red staining, quantitative calcium analysis, CCK8 assay, osteogenesis-related gene expression, and in vivo transplantation were conducted to determine the osteo/odontogenic differentiation potential and proliferation potential of DPSCs. We found that the expression of RARβ and CRABP2 decreased during crown calcification of DCs of miniature pigs. Activation of RA signal in vitro inhibited ALP activities and mineralization of human DPSCs and decreased the mRNA expression of ALP, osteocalcin, osteopontin, and a transcription factor, osterix. With BMS 493 treatment, the results were opposite. Interference in RA signal decreased the proliferation of DPSCs. In vivo transplantation experiments suggested that osteo/odontogenic differentiation potential of DPSCs was enhanced by inversing RA signal. Our results demonstrated that downregulation of RA signal promoted osteo/odontogenic differentiation of DPSCs and indicated a potential target pathway to improve tissue regeneration.

Exosomes Derived from Stem Cells from the Apical Papilla Promote Dentine-Pulp Complex Regeneration by Inducing Specific Dentinogenesis

Regenerative endodontic procedures (REPs) are a new option for the treatment of dental pulp or periapical diseases in permanent teeth with open apices. Histologically, the new tissues formed in the root canal after REPs are mainly cementum- or bone-like mineralised tissues, but not the real dentine-pulp complex. Therefore, how to promote dentine-pulp complex regeneration and improve the clinical effects of REPs has become a prominent research topic. Stem cells from apical papilla (SCAP) are derived from the dental papilla that can differentiate into primary odontoblasts and dental pulp cells that produce root dentine and dental pulp. Exosomes are the key regulator for the paracrine activity of stem cells and can influence the function of recipient cells. In this study, SCAP-derived exosomes (SCAP-Exo) were introduced into the root fragment containing bone marrow mesenchymal stem cells (BMMSCs) and transplanted subcutaneously into immunodeficient mice. We observed that dental pulp-like tissues were present and the newly formed dentine was deposited onto the existing dentine in the root canal. Afterwards, the effects of SCAP-Exo on the dentinogenesis of BMMSCs were elucidated in vitro. We found that the gene and protein expression of dentine sialophosphoprotein and mineralised nodule formation in BMMSCs treated with SCAP-Exo were significantly increased. In summary, SCAP-Exo were endocytosed by BMMSCs and obviously improved their specific dentinogenesis. The use of exosomes derived from dental stem cells could comprise a potential therapeutic approach for dentine-pulp complex regeneration in REPs.

Exploring the molecular disorder and dysfunction mechanism of human dental pulp cells under hypoxia by comprehensive multivariate analysis

Dental pulp cells (DPCs) are multipotent cells, which can differentiate into various tissues and have the potential to treat many diseases. However, little is known about the molecular disorder mechanism. To explore the mechanism of molecular disorders and dysfunction of DPCs under hypoxia, we investigated the molecular effects of two hypoxic time lengths on DPCs. Differential analysis, protein interaction network (PPI), enrichment analysis and coupling analysis were further synthesized to identify human dental pulp cell dysfunction modules under hypoxic conditions. Based on the module aggregation of 579 genes, 13 dental pulp cell dysfunction modules were obtained. Importantly, we found that up to 12 modules were significantly involved in positive regulation of neurogenesis, positive regulation of nervous system development. Based on the predictive analysis of regulators, we identified a series of ncRNAs (including CRNDE, MALAT1, microRNA-140-5p, microRNA-300 and microRNA-30a-5p) and transcription factors (including E2F1). Based on the comprehensive functional module analysis, we identified the dysfunction module of human dental pulp cells (HDPCs) under hypoxia. The results suggest that nerve regulation plays an important role in regulating the dysfunction module of DPCs. These prominent pivotal regulators in the module were used as an important part of the molecular disorders of DPCs, may be an important part of the subnetwork of the manipulation module and affect the molecular dysregulation mechanism of DPCs. This study provides new directions and potential targets for further research.

Natural protein bioinspired materials for regeneration of hard tissues

This review describes the protein bioinspired materials for the repair of hard tissues such as enamel, dentin and bone.

Differentiation of Rat Mesenchymal Stem Cells toward Osteogenic Lineage on Extracellular Matrix Protein Gradients

This report addresses the issue of optimizing extracellular matrix protein density required to support osteogenic lineage differentiation of mesenchymal stem cells (MSCs) by culturing MSCs on surface-bound density gradients of immobilized collagen type I (COL1) and osteopontin (OPN). A chemical surface gradient is prepared by tailoring the surface chemical composition from high hydroxyl groups to aldehyde groups using a diffusion-controlled plasma polymerization technique. Osteogenesis on the gradient surface is determined by immunofluorescence staining against Runx2 as an early marker and by staining of calcium phosphate deposits as a late stage differentiation marker. The Runx2 intensity and calcified area increase with increasing COL1 density up to a critical value corresponding to 124.2 ng cm^-2 , above which cell attachment and differentiation do not rise further, while this critical value for OPN is 19.0 ng cm^-2 . This gradient approach may facilitate the screening of an optimal biomolecule surface density on tissue-engineered scaffolds, implants, or tissue culture ware to obtain the desired cell response, and may generate opportunities for more cost-effective regenerative medicine.