The rescue of dentin matrix protein 1 (DMP1)-deficient tooth defects by the transgenic expression of dentin sialophosphoprotein (DSPP) indicates that DSPP is a downstream effector molecule of DMP1 in dentinogenesis

Knocking out FAM20C in pre-osteoblasts leads to up-regulation of osteoclast differentiation to affect long bone development

Family with sequence similarity 20 member C (FAM20C) is a Golgi casein kinase that phosphorylates extracellularly-secreted regulatory proteins involved in bone development and mineralization, but its specific role in bone development is still largely unknown. In this study, to examine the specific mechanisms that FAM20C influences bone development, we cross-bred Osx-Cre with FAM20Cflox/flox mice to establish a Osx-Cre; FAM20Cflox/flox knockout (oKO) mouse model; FAM20C was KO in pre-osteoblasts. oKO development was examined at 1-10 weeks, in which compared to control FAM20Cflox/flox, they had lower body weights and bone tissue mineralization. Furthermore, oKO had lower bone volume fractions, thickness, and trabecular numbers, along with higher degrees of trabecular separation. These mice also had decreased femoral metaphyseal cartilage proliferation layer, along with thickened hypertrophic layer and increased apoptotic cell counts. Transcriptomic analysis found that differentially-expressed genes in oKO were concentrated in the osteoclast differentiation pathway, in line with increased osteoclast presence. Additionally, up-regulation of osteoclast-related, and down-regulation of osteogenesis-related genes, were identified, in which the most up-regulated genes were signal regulatory protein β-1 family (Sirpb1a-c) and mitogen-activated protein kinase 13. Overall, FAM20C KO in pre-osteoblasts leads to abnormal long bone development, likely due to subsequent up-regulation of osteoclast differentiation-associated genes.

Effect of 3D-printed polycaprolactone/osteolectin scaffolds on the odontogenic differentiation of human dental pulp cells

Cell-based tissue engineering often requires the use of scaffolds to provide a three-dimensional (3D) framework for cell proliferation and tissue formation. Polycaprolactone (PCL), a type of polymer, has good printability, favorable surface modifiability, adaptability, and biodegradability. However, its large-scale applicability is hindered by its hydrophobic nature, which affects biological properties. Composite materials can be created by adding bioactive materials to the polymer to improve the properties of PCL scaffolds. Osteolectin is an odontogenic factor that promotes the maintenance of the adult skeleton by promoting the differentiation of LepR+ cells into osteoblasts. Therefore, the aim of this study was to evaluate whether 3D-printed PCL/osteolectin scaffolds supply a suitable microenvironment for the odontogenic differentiation of human dental pulp cells (hDPCs). The hDPCs were cultured on 3D-printed PCL scaffolds with or without pores. Cell attachment and cell proliferation were evaluated using EZ-Cytox. The odontogenic differentiation of hDPCs was evaluated by alizarin red S staining and alkaline phosphatase assays. Western blot was used to evaluate the expression of the proteins DSPP and DMP-Results: The attachment of hDPCs to PCL scaffolds with pores was significantly higher than to PCL scaffolds without pores. The odontogenic differentiation of hDPCs was induced more in PCL/osteolectin scaffolds than in PCL scaffolds, but there was no statistically significant difference. 3D-printed PCL scaffolds with pores are suitable for the growth of hDPCs, and the PCL/osteolectin scaffolds can provide a more favorable microenvironment for the odontogenic differentiation of hDPCs.

Constitutive expression of spliced X-box binding protein 1 inhibits dentin formation in mice

Upon endoplasmic reticulum (ER) stress, inositol-requiring enzyme 1 (IRE1) is activated, which subsequently converts an unspliced X-box binding protein 1 (XBP1U) mRNA to a spliced mRNA that encodes a potent XBP1S transcription factor. XBP1S is essential for relieving ER stress and secretory cell differentiation. We previously established Twist2-Cre;Xbp1 CS/+ mice that constitutively expressed XBP1S in the Twist2-expressing cells as well as in the cells derived from the Twist2-expressing cells. In this study, we analyzed the dental phenotype of Twist2-Cre;Xbp1 CS/+ mice. We first generated a mutant Xbp1s minigene that corresponds to the recombinant Xbp1 Δ26 allele (the Xbp1 CS allele that has undergone Cre-mediated recombination) and confirmed that the Xbp1s minigene expressed XBP1S that does not require IRE1α activation in vitro. Consistently, immunohistochemistry showed that XBP1S was constitutively expressed in the odontoblasts and other dental pulp cells in Twist2-Cre;Xbp1 CS/+ mice. Plain X-ray radiography and µCT analysis revealed that constitutive expression of XBP1S altered the dental pulp chamber roof- and floor-dentin formation, resulting in a significant reduction in dentin/cementum formation in Twist2-Cre;Xbp1 CS/+ mice, compared to age-matched Xbp1 CS/+ control mice. However, there is no significant difference in the density of dentin/cementum between these two groups of mice. Histologically, persistent expression of XBP1S caused a morphological change in odontoblasts in Twist2-Cre;Xbp1 CS/+ mice. Nevertheless, in situ hybridization and immunohistochemistry analyses showed that continuous expression of XBP1S had no apparent effects on the expression of the Dspp and Dmp1 genes. In conclusion, these results support that sustained production of XBP1S adversely affected odontoblast function and dentin formation.

A leptin-loaded poly-ϵ-caprolactone 3D printing scaffold for odontoblastic differentiation in human dental pulp cells

This study investigated the effects on odontoblast differentiation of a 3D-printed poly-ϵ-caprolactone (PCL) scaffold that incorporated leptin. Material extrusion-type 3D printing with a 43 000-molecular weight PCL material was used to fabricate a PCL scaffold with a 6 mm diameter, 1 mm height, and 270-340 µm pore size. The experimental groups were PCL scaffolds (control group), PCL scaffolds with aminated surfaces (group A), and PCL scaffolds with leptin on the aminated surface (group L). The aminated surface was treated with 1,6-hexanediamine and verified by ninhydrin analysis. Leptin loading was performed using Traut's reagent and 4-(N-Maleimidomethyl)cyclohexane-1-carboxylic acid 3-sulfo-N-hydroxysuccinimide ester sodium salt (Sulfo-SMCC). Groups A and L showed significantly higher surface wettability, pulp cell adhesion, and proliferation than the control group. Group L exhibited increased alkaline phosphatase, calcification deposits, and mRNA and protein expression of dentin sialophosphoprotein and dentin matrix acidic phosphoprotein 1 compared with the control group. In this study, a 3D-printed PCL scaffold containing leptin was enhanced odontoblast differentiation and dental pulp cells adhesion and proliferation.

Current concepts of microRNA-mediated regulatory mechanisms in human pulp tissue-derived stem cells: a snapshot in the regenerative dentistry

One of the most studied class of non-coding RNAs is microRNAs (miRNAs) which regulate more than 60% of human genes. A network of miRNA gene interactions participates in stem cell self-renewal, proliferation, migration, apoptosis, immunomodulation, and differentiation. Human pulp tissue-derived stem cells (PSCs) are an attractive source of dental mesenchymal stem cells (MSCs) which comprise human dental pulp stem cells (hDPSCs) obtained from the dental pulp of permanent teeth and stem cells isolated from exfoliated deciduous teeth (SHEDs) that would be a therapeutic opportunity in stomatognathic system reconstruction and repair of other damaged tissues. The regenerative capacity of hDPSCs and SHEDs is mediated by osteogenic, odontogenic, myogenic, neurogenic, angiogenic differentiation, and immunomodulatory function. Multi-lineage differentiation of PSCs can be induced or inhibited by the interaction of miRNAs with their target genes. Manipulating the expression of functional miRNAs in PSCs by mimicking miRNAs or inhibiting miRNAs emerged as a therapeutic tool in the clinical translation. However, the effectiveness and safety of miRNA-based therapeutics, besides higher stability, biocompatibility, less off-target effects, and immunologic reactions, have received particular attention. This review aimed to comprehensively overview the molecular mechanisms underlying miRNA-modified PSCs as a futuristic therapeutic option in regenerative dentistry.

Tideglusib enhances odontogenic differentiation in human dental pulp stem cells in vitro

AIM

Tideglusib is a small molecule agonist of the canonical Wnt pathway. The present study investigated the influence of Tideglusib on human dental pulp stem cell (hDPSC) proliferation, apoptosis, migration and odonto/osteogenic differentiation.

METHODOLOGY

hDPSCs were treated with 50, 100 nM or 200 nM Tideglusib. β-catenin accumulation was detected by immunofluorescence staining. Colony-forming unit ability was assessed by staining with Coomassie blue. Cell cycle progression and cell apoptosis were investigated using flow cytometry. Cell migration was examined using an in vitro wound-healing assay. Osteogenic differentiation was examined using alkaline phosphatase (ALP) staining, alizarin red S staining and osteogenic-related gene expression. The gene expression profile was examined using a high-throughput RNA sequencing technique. All experiments were repeated using cells derived from at least four different donors (n = 4). The Mann-Whitney U-test was used to identify significant differences between two independent group comparisons. For three or more group comparisons, statistical differences were assessed using the Kruskal-Wallis test followed by pairwise comparison. The significance level was set at 5% (p < .05).

RESULTS

Tideglusib activated the Wnt signalling pathway in hDPSCs as demonstrated by an increase in cytoplasmic β-catenin accumulation and nuclear translocation. Tideglusib did not affect hDPSC proliferation, cell cycle progression, cell apoptosis or cell migration. In contrast, 50 and 100 nM Tideglusib significantly enhanced mineralization and osteogenic marker gene expression (RUNX2, ALP, BMP2 and DSPP; p < .05).

CONCLUSIONS

Tideglusib enhanced the odonto/osteogenic differentiation of hDPSCs. Therefore, incorporating this bioactive molecule in a pulp-capping material could be a promising strategy to promote dentine repair.

Contributions of Resin Cast Etching to Visualising the Osteocyte Lacuno-Canalicular Network Architecture in Bone Biology and Tissue Engineering

Recent years have witnessed an evolution of imaging technologies towards sophisticated approaches for visualising cells within their natural environment(s) and for investigating their interactions with other cells, with adjacent anatomical structures, and with implanted biomaterials. Resin cast etching (RCE) is an uncomplicated technique involving sequential acid etching and alkali digestion of resin embedded bone to observe the osteocyte lacuno-canalicular network using scanning electron microscopy. This review summarises the applicability of RCE to bone and the bone-implant interface. Quantitative parameters such as osteocyte size, osteocyte density, and number of canaliculi per osteocyte, and qualitative metrics including osteocyte shape, disturbances in the arrangement of osteocytes and canaliculi, and physical communication between osteocytes and implant surfaces can be investigated. Ageing, osteoporosis, long-term immobilisation, spinal cord injury, osteoarthritis, irradiation, and chronic kidney disease have been shown to impact osteocyte lacuno-canalicular network morphology. In addition to titanium, calcium phosphates, and bioactive glass, observation of direct connectivity between osteocytes and cobalt chromium provides new insights into the osseointegration potential of materials conventionally viewed as non-osseointegrating. Other applications include in vivo and in vitro testing of polymer-based tissue engineering scaffolds and tissue-engineered ossicles, validation of ectopic osteochondral defect models, ex vivo organ culture of whole bones, and observing the effects of gene dysfunction/deletion on the osteocyte lacuno-canalicular network. Without additional contrast staining, any resin embedded specimen (including clinical biopsies) can be used for RCE. The multitude of applications described here attest to the versatility of RCE for routine use within correlative analytical workflows, particularly in biomaterials science.

Effects of platelet-rich plasma local injection on dentin sialo protein and dentin matrix acidic phosphoprotein 1 levels of secretion in gingival sulcular fluid during orthodontic movement in animal samples

Background

Prolonged orthodontic treatment causes complications such as root resorption, gingivitis, and caries. Platelet-rich plasma (PRP) can accelerate the dental movements of orthodontic treatments. The aim of the present study was to evaluate the effect of local PRP injection on the secretion of dentin sialoprotein (DSP) and dentin matrix acidic phosphoprotein (DMP1) biomarkers in gingival crevicular fluid during orthodontic movements in animal samples.

Materials and Methods

In this experimental study, one maxillary quadrant of six beagle dogs was randomly selected as the experimental group, and the other side was considered as the control group. Afterward, maxillary of the first premolars was extracted, and then, a titanium nickel coil spring (150 g) was then used between the second premolar and the canine. PRP that was previously activated with CaCl 2-thrombin was injected intraligaman to the experimental side at days 0, 21, and 42. Moreover, the mixture of the CaCl 2-thrombin with placebo was injected in to the control side. The study period was 63 days. Sampling was performed on days 0, 1, 2, 7, 21, 42, and 63. Then, in all the samples, the DSP and DMP1 level was measured using special kits by ELISA method. Data were analyzed by the analysis of variance and t-test.

Results

Upon the application of orthodontic forces, the mean DMP1 and DSP levels in the experimental group at different times were significantly increased compared to the control group (P < 0.001).

Conclusion

PRP injection enhanced DMP1 and DSP level with probable rise in the rate of root resorption.

Characterization of SIBLING Proteins in the Mineralized Tissues

The SIBLING proteins are a family of non-collagenous proteins (NCPs) previously thought to be expressed only in dentin but have been demonstrated in other mineralized and non-mineralized tissues. They are believed to play vital roles in both osteogenesis and dentinogenesis. Since they are tightly regulated lifelong processes and involve a peak of mineralization, three different age groups were investigated. Fifteen wild-type (WT) mice were euthanized at ages 1, 3, and 6 months. Hematoxylin and eosin staining (H&E) was performed to localize various microscopic structures in the mice mandibles and tibias. The immunostaining pattern was compared using antibodies for dentin sialoprotein (DSP), dentin matrix protein 1 (DMP1), bone sialoprotein (BSP), and osteopontin (OPN). Immunostaining of DSP in tibia showed its most noticeable staining in the 3-month age group. DSP was expressed in alveolar bone, cellular cementum, and PDL. A similar expression of DMP1 was seen in the tibia and dentin. BSP was most noticeably detected in the tibia and acellular cementum. OPN was mainly expressed in the bone. A lower level of OPN was observed at all age groups in the teeth. The immunostaining intensity was the least detected for all proteins in the 6-month tibia sample. The expression patterns of the four SIBLING proteins showed variations in their staining intensity and temporospatial patterning concordant with skeletal and dental maturity. These findings suggest some role in this tightly regulated mineralization process.

A WWP2-PTEN-KLF5 signaling axis regulates odontoblast differentiation and dentinogenesis in mice

WW domain–containing E3 Ubiquitin-protein ligase 2 (WWP2) has been found to positively regulate odontoblastic differentiation by monoubiquitinating the transcription factor Kruppel-like factor 5 (KLF5) in a cell culture system. However, the in vivo role of WWP2 in mouse teeth remains unknown. To explore this, here we generated Wwp2 knockout (Wwp2 KO) mice. We found that molars in Wwp2 KO mice exhibited thinner dentin, widened predentin, and reduced numbers of dentinal tubules. In addition, expression of the odontoblast differentiation markers Dspp and Dmp1 was decreased in the odontoblast layers of Wwp2 KO mice. These findings demonstrate that WWP2 may facilitate odontoblast differentiation and dentinogenesis. Furthermore, we show for the first time that phosphatase and tensin homolog (PTEN), a tumor suppressor, is expressed in dental papilla cells and odontoblasts of mouse molars and acts as a negative regulator of odontoblastic differentiation. Further investigation indicated that PTEN is targeted by WWP2 for degradation during odontoblastic differentiation. We demonstrate PTEN physically interacts with and inhibits the transcriptional activity of KLF5 on Dspp and Dmp1. Finally, we found WWP2 was able to suppress the interaction between PTEN and KLF5, which diminished the inhibition effect of PTEN on KLF5. Taken together, this study confirms the essential role of WWP2 and the WWP2–PTEN–KLF5 signaling axis in odontoblast differentiation and dentinogenesis in vivo.

The Roles of SIBLING Proteins in Dental, Periodontal and Craniofacial Development

The majority of dental, periodontal, and craniofacial tissues are derived from the neural crest cells and ectoderm. Neural crest stem cells are pluripotent, capable of differentiating into a variety of cells. These cells can include osteoblasts, odontoblasts, cementoblasts, chondroblasts, and fibroblasts which are responsible for forming some of the tissues of the oral and craniofacial complex. The hard tissue forming cells deposit a matrix composed of collagen and non-collagenous proteins (NCPs) that later undergoes mineralization. The NCPs play a role in the mineralization of collagen. One such category of NCPs is the small integrin-binding ligand, N-linked glycoprotein (SIBLING) family of proteins. This family is composed of dentin sialophosphosprotein (DSPP), osteopontin (OPN), dentin matrix protein 1 (DMP1), bone sialoprotein (BSP), and matrix extracellular phosphoglycoprotein (MEPE). The SIBLING family is known to have regulatory effects in the mineralization process of collagen fibers and the maturation of hydroxyapatite crystals. It is well established that SIBLING proteins have critical roles in tooth development. Recent literature has described the expression and role of SIBLING proteins in other areas of the oral and craniofacial complex as well. The objective of the present literature review is to summarize and discuss the different roles the SIBLING proteins play in the development of dental, periodontal, and craniofacial tissues.

The role of complement C5a receptor in DPSC odontoblastic differentiation and in vivo reparative dentin formation

Therapeutic dentin regeneration remains difficult to achieve, and a majority of the attention has been given to anabolic strategies to promote dentinogenesis directly, whereas, the available literature is insufficient to understand the role of inflammation and inflammatory complement system on dentinogenesis. The aim of this study is to determine the role of complement C5a receptor (C5aR) in regulating dental pulp stem cells (DPSCs) differentiation and in vivo dentin regeneration. Human DPSCs were subjected to odontogenic differentiation in osteogenic media treated with the C5aR agonist and C5aR antagonist. In vivo dentin formation was evaluated using the dentin injury/pulp-capping model of the C5a-deficient and wild-type mice. In vitro results demonstrate that C5aR inhibition caused a substantial reduction in odontogenic DPSCs differentiation markers such as DMP-1 and DSPP, while the C5aR activation increased these key odontogenic genes compared to control. A reparative dentin formation using the C5a-deficient mice shows that dentin regeneration is significantly reduced in the C5a-deficient mice. These data suggest a positive role of C5aR in the odontogenic DPSCs differentiation and tertiary/reparative dentin formation. This study addresses a novel regulatory pathway and a therapeutic approach for improving the efficiency of dentin regeneration in affected teeth.

Effect of two different concentrations of 1α,25-dihydroxyvitamin D3 on odontogenic differentiation of stem cells from human exfoliated deciduous teeth

Background:

Stem cells from human exfoliated deciduous teeth (SHEDs) can transform into odontoblasts in vitro and in vivo. The role of 1α, 25-dihydroxyvitamin D3 (1α,25 vitD3) has been reported in the mineralization of hard tissues and teeth, as well as osteoblastic differentiation. This study aimed to assess the effect of different concentrations of 1α,25 vitD3 on odontogenic differentiation of SHEDs.

Materials and Methods:

In this experimental study, second-passage SHEDs were exposed to odontogenic medium along with 0, 10, 50, 100, and 150 nmol concentrations of in 1α, 25 vitD3 to determine its optimal concentration for odontogenic differentiation. The methyl thiazolyl tetrazolium (MTT) assay was performed. Odontogenic differentiation was evaluated by QRT- polymerase chain reaction for dentin matrix protein (DMP1) and dentin sialophosphoprotein (DSPP) genes. Morphology of differentiated cells was studied by Scanning Electron Microscopy. Data were analyzed using the Kruskal–Wallis, Mann–Whitney, Friedman, and Chi-square test. P < 0.05 is considered statistically significant.

Results:

MTT test result showed the two groups of odontogenic medium + 10 nm 1α,25 vitD3 and odontogenic medium + 150 nm 1α,25 vitD3 provided the most suitable conditions for cell viability at 72 h. Expression of both genes significantly increased in the presence of 1α,25 vitD3 (P < 0.001). Expression of both genes was significantly higher at 14 days compared with 7 days (P < 0.01). At both time points, expression of both genes was significantly higher in the presence of 150 nm 1α,25 vitD3 compared with 10 nm (P < 0.01). The accumulation of cells with odontoblastic morphology, cell interactions, and calcifications were evident.

Conclusion:

1α,25 vitD3 upregulates DMP1 and DSPP and results in odontogenic differentiation of SHEDs in odontogenic medium. This upregulation increases with time and by an increase in concentration of 1α,25 vitD3.

Hsa-miRNA-143-3p regulates the odontogenic differentiation of human stem cells from the apical papilla by targeting NFIC

AIM

To evaluate the effects of hsa-miRNA-143-3p on the cytodifferentiation of human stem cells from the apical papilla (hSCAPs) and the post-transcriptional regulation of Nuclear factor I-C (NFIC).

METHODOLOGY

miRNA expression profiles in human immature permanent teeth and during hSCAP differentiation were examined. hSCAPs were treated with miR-143-3p overexpression or silencing viruses, and the proliferation and odontogenic and osteogenic differentiation of these stem cells, and the involvement of the NFIC pathway, were investigated. Luciferase reporter and NFIC mutant plasmids were used to confirm NFIC mRNA as a direct target of miR-143-3p. NFIC expression analysis in the miR-143-3p overexpressing hSCAPs was used to investigate whether miR-143-3p functioned by targeting NFIC. Student's t-test and chi-square tests were used for statistical analysis.

RESULTS

miR-143-3p expression was screened by microarray profiling and was found to be significantly reduced during hSCAP differentiation (p < .05). Overexpression of miR-143-3p inhibited the mineralization of hSCAPs significantly (p < .05) and downregulated the levels of odontogenic differentiation markers (NFIC [p < .05], DSP [p < .01] and KLF4 [p < .01]), whereas silencing of miR-143-3p had the opposite effect. The luciferase reporter gene detection and bioinformatic approaches identified NFIC mRNA as a potential target of miR-143-3p. NFIC overexpression reversed the inhibitory effect of miR-143-3p on the odontogenic differentiation of hSCAPs.

CONCLUSIONS

miR-143-3p maintained the stemness of hSCAPs and modulated their differentiation negatively by directly targeting NFIC. Thus, inhibition of this miRNA represents a potential strategy to promote the regeneration of damaged tooth roots.

Enamel Defects Associated With Dentin Sialophosphoprotein Mutation in Mice

Dentin sialophosphoprotein (DSPP) is an extracellular matrix protein that is highly expressed in odontoblasts, but only transiently expressed in presecretory ameloblasts during tooth development. We previously generated a knockin mouse model expressing a mouse equivalent (DSPP, p.P19L) of human mutant DSPP (p.P17L; referred to as “Dspp^P19L/+”), and reported that Dspp^P19L/+ and Dspp^P19L/P19L mice manifested a dentin phenotype resembling human dentinogenesis imperfecta (DGI). In this study, we analyzed pathogenic effects of mutant P19L-DSPP on enamel development in Dspp^P19L/+ and Dspp^P19L/P19L mice. Micro-Computed Tomography (μCT) analyses of 7-week-old mouse mandibular incisors showed that Dspp^P19L/P19L mice had significantly decreased enamel volume and/or enamel density at different stages of amelogenesis examined. Acid-etched scanning electron microscopy (SEM) analyses of mouse incisors demonstrated that, at the mid-late maturation stage of amelogenesis, the enamel of wild-type mice already had apparent decussating pattern of enamel rods, whereas only minute particulates were found in Dspp^P19L/+ mice, and no discernible structures in Dspp^P19L/P19L mouse enamel. However, by the time that incisor enamel was about to erupt into oral cavity, distinct decussating enamel rods were evident in Dspp^P19L/+ mice, but only poorly-defined enamel rods were revealed in Dspp^P19L/P19L mice. Moreover, μCT analyses of the mandibular first molars showed that Dspp^P19L/+ and Dspp^P19L/P19L mice had a significant reduction in enamel volume and enamel density at the ages of 2, 3, and 24weeks after birth. Backscattered and acid-etched SEM analyses revealed that while 3-week-old Dspp^P19L/+ mice had similar pattern of enamel rods in the mandibular first molars as age-matched wild-type mice, no distinct enamel rods were observed in Dspp^P19L/P19L mice. Yet neither Dspp^P19L/+ nor Dspp^P19L/P19L mice showed well-defined enamel rods in the mandibular first molars by the age of 24weeks, as judged by backscattered and acid-etched SEM. In situ hybridization showed that DSPP mRNA level was markedly reduced in the presecretory ameloblasts, but immunohistochemistry revealed that DSP/DSPP immunostaining signals were much stronger within the presecretory ameloblasts in Dspp mutant mice than in wild-type mice. These results suggest that mutant P19L-DSPP protein caused developmental enamel defects in mice, which may be associated with intracellular retention of mutant DSPP in the presecretory ameloblasts.

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.

The colocalizations of pulp neural stem cells markers with dentin matrix protein-1, dentin sialoprotein and dentin phosphoprotein in human denticle (pulp stone) lining cells

BACKGROUND

The primary dentin, secondary dentin, and reactive tertiary dentin are formed by terminal differentiated odontoblasts, whereas atubular reparative tertiary dentin is formed by odontoblast-like cells. Odontoblast-like cells differentiate from pulpal stem cells, which express the neural stem cell markers nestin, S100β, Sox10, and P0. The denticle (pulp stone) is an unique mineralized extracellular matrix that frequently occurs in association with the neurovascular structures in the dental pulp. However, to date, the cellular origin of denticles in human dental pulp is unclear. In addition, the non-collagenous extracellular dentin matrix proteins dentin matrix protein 1 (DMP1), dentin sialoprotein (DSP), and dentin phosphoprotein (DPP) have been well characterized in the dentin matrix, whereas their role in the formation and mineralization of the denticle matrix remains to be clarified.

METHODS

To characterize the formation of denticle, healthy human third molars (n = 59) were completely sectioned and evaluated by HE staining in different layers at 720 µm intervals. From these samples, molars with (n = 5) and without denticles (n = 8) were selected. Using consecutive cryo-sections from a layer containing denticles of different sizes, we examined DMP1, DSP, and DPP in denticle lining cells and tested their co-localizations with the glial stem cell markers nestin, S100β, Sox10, and P0 by quantitative and double staining methods.

RESULTS

DMP1, DSP and DPP were found in odontoblasts, whereas denticle lining cells were positive only for DMP1 and DSP but not for DPP. Nestin was detected in both odontoblasts and denticle lining cells. S100β, Sox10, and P0 were co-localized with DMP1 and DSP in different subpopulations of denticle lining cells.

CONCLUSIONS

The co-localization of S100β, Sox10, and P0 with DMP1 and DSP in denticle lining cells suggest that denticle lining cells are originated from glial and/or endoneurial mesenchymal stem cells which are involved in biomineralization of denticle matrix by secretion of DMP1 and DSP. Since denticles are atubular compared to primary, secondary, reactionary tertiary dentin and denticle formed by odontoblasts, our results suggest that DPP could be one of the proteins involved in the complex regulation of dentinal tubule formation.

Long-range linkage disequilibrium in French beef cattle breeds

BACKGROUND

Linkage disequilibrium (LD) is a key parameter to study the history of populations and to identify and fine map quantitative trait loci (QTL) and it has been studied for many years in animal populations. The advent of new genotyping technologies has allowed whole-genome LD studies in most cattle populations. However, to date, long-range LD (LRLD) between distant variants on the genome has not been investigated in detail in cattle. Here, we present the first comprehensive study of LRLD in French beef cattle by analysing data on 672 Charolais (CHA), 462 Limousine (LIM) and 326 Blonde d'Aquitaine (BLA) individuals that were genotyped on the Illumina BovineHD Beadchip. Furthermore, whole-genome LD and haplotype block structure were analysed in these three breeds.

RESULTS

We computed linkage disequilibrium (r²) values for 5.9, 5.6 and 6.0 billion pairs of SNPs on the 29 autosomes of CHA, LIM and BLA, respectively. Mean r² values drop to less than 0.1 for distances between SNPs greater than 120 kb. However, for the first time, we detected the existence of LRLD in the three main French beef breeds. In total, 598, 266, and 795 LRLD events (r² ≥ 0.6) were detected in CHA, LIM and BLA, respectively. Each breed had predominantly population-specific LRLD interactions, although shared LRLD events occurred in a number of regions (55 LRLD events were shared between two breeds and nine between the three breeds). Examples of possible functional gene interactions and QTL co-location were observed with some of these LRLD events, which suggests epistatic selection.

CONCLUSIONS

We identified long-range linkage disequilibrium for the first time in French beef cattle populations. Epistatic selection may be the main source of the observed LRLD events, but other forces may also be involved. LRLD information should be accounted for in genome-wide association studies.

Agarose-based spheroid culture enhanced stemness and promoted odontogenic differentiation potential of human dental follicle cells in vitro

Human dental follicle cells (HDFCs) are an ideal cell source of stem cells for dental tissue repair and regeneration and they have great potential for regenerative medicine applications. However, the conventional monolayer culture usually reduces cell proliferation and differentiation potential due to the continuous passage during in vitro expansion. In this study, primary HDFC spheroids were generated on 1% agarose, and the HDFCs spontaneously formed cell spheroids in the agarose-coated dishes. Compared with monolayer culture, the spheroid-derived HDFCs exhibited increased proliferative ability for later passage HDFCs as analysed by Cell Counting Kit-8 (CCK-8). The transcription-quantitative polymerase chain reaction (qRT-PCR), western blot and immunofluorescence assay showed that the expression of stemness marker genes Sox2, Oct4 and Nanog was increased significantly in the HDFC spheroids. Furthermore, we found that the odontogenic differentiation capability of HDFCs was significantly improved by spheroid culture in the agarose-coated dishes. On the other hand, the osteogenic differentiation capability was weakened compared with monolayer culture. Our results suggest that spheroid formation of HDFCs in agarose-coated dishes partially restores the proliferative ability of HDFCs at later passages, enhances their stemness and improves odontogenic differentiation capability in vitro. Therefore, spheroid formation of HDFCs has great therapeutic potential for stem cell clinical therapy.

The effects and potential applications of concentrated growth factor in dentin-pulp complex regeneration

The dentin-pulp complex is essential for the long-term integrity and viability of teeth but it is susceptible to damage caused by external factors. Because traditional approaches for preserving the dentin-pulp complex have various limitations, there is a need for novel methods for dentin-pulp complex reconstruction. The development of stem cell-based tissue engineering has given rise to the possibility of combining dental stem cells with a tissue-reparative microenvironment to promote dentin-pulp complex regeneration. Concentrated growth factor, a platelet concentrate, is a promising scaffold for the treatment of dentin-pulp complex disorders. Given its characteristics of autogenesis, convenience, usability, and biodegradability, concentrated growth factor has gained popularity in medical and dental fields for repairing bone defects and promoting soft-tissue healing. Numerous in vitro studies have demonstrated that concentrated growth factor can promote the proliferation and migration of dental stem cells. Here, we review the current state of knowledge on the effects of concentrated growth factor on stem cells and its potential applications in dentin-pulp complex regeneration.

BMP4-regulated human dental pulp stromal cells promote pulp-like tissue regeneration in a decellularized dental pulp matrix scaffold

Pulp regeneration with stem cells is a promising alternative for treating periapical and pulp diseases of young permanent teeth. The aim of this study was to characterize decellularized dental pulp extracellular matrix (dECM) and investigate whether bone morphogenetic protein 4 (BMP4) regulates dental pulp stromal cells (DPSC)-mediated pulp regeneration combined with dECM. Dental pulp isolated from healthy third molars was decellularized with 10% sodium dodecyl sulfate (SDS) and Triton X-100. H&E staining, DAPI staining and electron microscopy were used to observe the dECM structure. The Cell Counting Kit-8 assay was used to analyse cell proliferation. Recombinant adenovirus was used to overexpress BMP4 in DPSCs. The cells were cultured in dECM and dECM + three-dimensional (3D) Vitrogel systems, and bone/dentin/angiogenesis marker expression was evaluated by real-time polymerase chain reaction (RT-PCR) and ALP staining. DPSCs mixed with dECM and BMP4 were transplanted into nude mice, and pulp-like tissue formation was evaluated. The expression of osteogenic and angioblastic genes was increased, and pulp-like tissue formed in vivo. Thus, dECM promotes DPSC proliferation, BMP4 and dECM together accelerate pulp-like tissue formation by DPSCs in vitro.

In vitro biocompatibility and bioactivity of calcium silicate‑based bioceramics in endodontics (Review)

Calcium silicate-based bioceramics have been applied in endodontics as advantageous materials for years. In addition to excellent physical and chemical properties, the biocompatibility and bioactivity of calcium silicate-based bioceramics also serve an important role in endodontics according to previous research reports. Firstly, bioceramics affect cellular behavior of cells such as stem cells, osteoblasts, osteoclasts, fibroblasts and immune cells. On the other hand, cell reaction to bioceramics determines the effect of wound healing and tissue repair following bioceramics implantation. The aim of the present review was to provide an overview of calcium silicate-based bioceramics currently applied in endodontics, including mineral trioxide aggregate, Bioaggregate, Biodentine and iRoot, focusing on their in vitro biocompatibility and bioactivity. Understanding their underlying mechanism may help to ensure these materials are applied appropriately in endodontics.

Constitutive expression of spliced XBP1 causes perinatal lethality in mice

Upon endoplasmic reticulum (ER) stress, inositol-requiring enzyme 1 (IRE1) is activated and catalyzes nonconventional splicing of an unspliced X-box binding protein 1 (XBP1U) mRNA to yield a spliced XBP1 (XBP1S) mRNA that encodes a potent XBP1S transcription factor. XBP1S is a key mediator of the IRE1 branch that is essential for alleviating ER stress. We generated a novel mouse strain (referred to as "Xbp1^CS/+ " mice) that constitutively expressed XBP1S after Cre recombinase-mediated recombination. Further breeding of these mice with Twist2 Cre recombinase (Twist2-Cre) knock-in mice generated Twist2-Cre;Xbp1^CS/+ mice. Most Twist2-Cre;Xbp1^CS/+ mice died shortly after birth. Reverse-transcription polymerase chain reaction (RT-PCR) showed that constitutive expression of XBP1S occurred in various mouse tissues examined, but not in the brain. Immunohistochemistry confirmed that although the immunostaining signals for total XBP1 (XBP1U and XBP1S) were found in the calvarial bones in both Twist2-Cre;Xbp1^CS/+ and control mice, the signals for XBP1S were only detected in the Twist2-Cre;Xbp1^CS/+ mice, but not in the control mice. These results suggest that a precise control of XBP1S production is essential for normal mouse development.

Demineralized Dentin Matrix Particle-Based Bio-Ink for Patient-Specific Shaped 3D Dental Tissue Regeneration

Demineralized dentin matrix (DDM)-based materials have been actively developed and are well-known for their excellent performance in dental tissue regeneration. However, DDM-based bio-ink suitable for fabrication of engineered dental tissues that are patient-specific in terms of shape and size, has not yet been developed. In this study, we developed a DDM particle-based bio-ink (DDMp bio-ink) with enhanced three-dimensional (3D) printability. The bio-ink was prepared by mixing DDM particles and a fibrinogen–gelatin mixture homogeneously. The effects of DDMp concentration on the 3D printability of the bio-ink and dental cell compatibility were investigated. As the DDMp concentration increased, the viscosity and shear thinning behavior of the bio-ink improved gradually, which led to the improvement of the ink’s 3D printability. The higher the DDMp content, the better were the printing resolution and stacking ability of the 3D printing. The printable minimum line width of 10% w/v DDMp bio-ink was approximately 252 μm, whereas the fibrinogen–gelatin mixture was approximately 363 μm. The ink’s cytocompatibility test with dental pulp stem cells (DPSCs) exhibited greater than 95% cell viability. In addition, as the DDMp concentration increased, odontogenic differentiation of DPSCs was significantly enhanced. Finally, we demonstrated that cellular constructs with 3D patient-specific shapes and clinically relevant sizes could be fabricated through co-printing of polycaprolactone and DPSC-laden DDMp bio-ink.

Evaluation of odonto/osteogenic differentiation potential from different regions derived dental tissue stem cells and effect of 17β-estradiol on efficiency

Background

The dentin is a tissue, which is formed by odontoblasts at the pulp interface of the teeth that supports the enamel. Odontoblasts, the cranial neural crest cells are derived from ectodermal mesenchymal stem cells (MSCs) and are long and polarized cells. They are present at the outer surface of dentin and play a prominent role about dentin formation. Recently, attention has been focused on induction of odontoblast using various type of MSCs and effects of the 17ß-estradiol supplementation. In this study, we establish an efficient odonto/osteoblast differentiation protocol using 17ß-estradiol supplementation while comparing the odonto/osteoblast ability of various dental MSCs.

Methods

Same donor derived four types of dental MSCs namely dental pulp stem cells (DPSCs), stem cells from apical papilla (SCAP), dental follicle stem cells (DFSCs), and periodontal ligament stem cells (PDLSCs) were evaluated for their stemness characteristics and potency towards odonto/osteoblast (Induced odonto/osteoblast) differentiation. Then 17ß-estradiol supplementation of 0 and 10 µM was applied to the odonto/osteoblast differentiation media for 14 days respectively. Furthermore, mRNA and protein levels of odonto/osteoblast markers were evaluated.

Results

All of the experimental groups displayed stemness characteristics by showing adipocyte and chondrocyte differentiation abilities, expression for cell surface markers and cell proliferation capacity without any significant differences. Moreover, all dental derived MSCs were shown to have odonto/osteoblast differentiation ability when cultured under specific conditions and also showed positive expression for odontoblast markers at both mRNA and protein level. Among all, DPSCs revealed the higher differentiation potential than other dental MSCs. Furthermore, odonto/osteoblast differentiation potential was enhanced by supplementing the differentiation media with 17ß-estradiol (E2).

Conclusions

Thus, DPSCs possess higher odonto/osteogenic potential than the SCAPs, DFSCs, PDLSCs and their differentiation capacity can by further enhanced under E2 supplementation.

The interaction of sodium trimetaphosphate with collagen I induces conformational change and mineralization that prevents collagenase proteolytic attack

OBJECTIVES

This study evaluated the cell viability and expression of different major genes involved in mineralization in odontoblast-like cells exposed to sodium trimetaphosphate (STMP). It was also investigated the influence of STMP on the rate of calcium phosphate crystal growth, its anti-proteolytic action against the enzymatic degradation of type I collagen, the binding mechanism of STMP to collagen fibrils, and the potential mechanism to induce collagen stabilization.

METHODS

Immortalized rat odontoblast MDPC-23 cells were cultured. Cell viability was assessed by trypan blue staining, and the changes in gene expression balance induced by STMP were assessed by quantitative reverse transcription (qRT) PCR assays. Crystalline particle formation was monitored by light-scattering detectors to estimate pH variation and the radial size of the crystalline particles as a function of reaction time (pH 7.4, 25°C) in the presence of STMP in supersaturated calcium phosphate solution (Ca/P=1.67). Images were obtained under atomic force microscopy (AFM) to measure the particle size in the presence of STMP. A three-point bending test was used to obtain the elastic modulus of fully demineralized dentin beams after immersion in STMP solution. The binding mechanism of STMP to collagen fibrils and potential stabilization mechanism was assessed with circular dichroism spectrometry (CD). The data were analyzed statistically (α=0.05).

RESULTS

STMP had no significant influence on the cell viability and gene expression of the MDPC-23 cells. STMP greatly increased the rate of crystal growth, significantly increasing the average radial crystal size. AFM corroborated the significant increase of STPM-treated crystal size. Mineralized collagen I fibrils exhibited less collagenase degradation with lower STMP concentration. CD analysis demonstrated changes in the conformational stability after STMP binding to type I collagen.

SIGNIFICANCE

The increased resistance of collagen against the proteolytic activity of collagenases appears to be related to the conformational change induced by STMP binding in collagen I and the STMP capacity for promoting biomimetic mineralization in type I collagen fibrils.

Noggin inhibition of mouse dentinogenesis

OBJECTIVES

The Bone Morphogenetic Proteins (BMPs) direct tooth development and still express in the adult tooth. We hypothesized that inhibition of BMP function would therefore disrupt dentinogenesis by differentiated odontoblasts.

METHODS

We generated mice overexpressing the BMP-inhibitory protein Noggin in differentiated odontoblasts and osteocytes under control of a Dmp1 promoter-driven cre transgene. We compared the dentin phenotype in these mice with that in WT littermates and in mice with a Smad4 odontoblast/osteocyte knockout mediated by the same cre and therefore lacking all BMP and Tgfβ signaling in the same tissues.

RESULTS

Three-month-old first molars from both Noggin-expressing and Smad4-deleted mice showed decreased dentin volume with enlarged pulp cavities, and both displayed less organized and mineralized dentinal tubules compared to WT. The Smad4-ablated phenotype was more severe. While dentin sialophosphoprotein (DSPP) and bone sialoprotein (BSP) were decreased in the dentin of both lines, dentin matrix protein 1 (DMP1) was sharply increased in Noggin-expressing teeth.

CONCLUSIONS

The phenotypes we observed in Noggin-overexpressing and Smad4-conditional knockout teeth resemble the phenotype of Dentinogenesis Imperfecta (DGI) type III. Our results show that BMPs regulate post-natal dentinogenesis and that BMP-inhibitory proteins like Noggin play a role in that regulation. The increased severity of the Smad4 phenotype indicates that Tgfβ ligands, in addition to BMPs, play a crucial role in post-developmental dentinogenesis.

FAM20A is essential for amelogenesis, but is dispensable for dentinogenesis

Mutations in the gene encoding family with sequence similarity 20, member A (FAM20A) caused amelogenesis imperfecta (AI), in humans. However, the roles of FAM20A in amelogenesis and dentinogenesis are poorly understood. In this study, we generated a Fam20a knockout (Sox2-Cre;Fam20a^fl/fl) mouse model by crossing Fam20a^fl/fl mice with Sox2-Cre transgenic mice, in which Fam20a was ablated in both dental epithelium and dental mesenchyme. We found that these mice developed an enamel phenotype that resembles human AI associated with FAM20A mutations, but did not have apparent dentin defects. The secretory stage ameloblasts in the mandibular incisors from the Sox2-Cre;Fam20a^fl/fl mice were shorter and detached from the enamel matrix, and subsequently lost their polarity, became disorganized and formed numerous spherical extracellular matrices in place of normal enamel. At the molecular level, the Sox2-Cre;Fam20a^fl/fl mice displayed dramatically reduced expression levels of the genes encoding the enamel matrix proteins, but unaltered levels of the genes encoding the dentin matrix proteins. Moreover, Fam20a ablation resulted in a great decrease in FAM20C protein level, but it did not alter the intracellular localization of FAM20C protein in ameloblasts and odontoblasts. These results indicate that FAM20A is essential for amelogenesis, but is dispensable for dentinogenesis.

Expression and function of dopamine in odontoblasts

Dopamine (DA) is produced from tyrosine by tyrosine hydroxylase (TH). A recent study has reported that DA promotes the mineralization of murine preosteoblasts. However, the role of DA in odontoblasts has not been examined. Therefore, in this investigation, we researched the expression of TH and DA in odontoblasts and the effects of DA on the differentiation of preodontoblasts (KN-3 cells). Immunostaining showed that TH and DA were intensely expressed in odontoblasts and preodontoblasts of rat incisors and molars. KN-3 cells expressed D1-like and D2-like receptors for DA. Furthermore, DA promoted odontoblastic differentiation of KN-3 cells, whereas an antagonist of D1-like receptors and a PKA signaling blocker, inhibited such differentiation. However, antagonists of D2-like receptors promoted differentiation. These results suggested that DA in preodontoblasts and odontoblasts might promote odontoblastic differentiation through D1-like receptors, but not D2-like receptors, and PKA signaling in an autocrine or paracrine manner and plays roles in dentinogenesis.

Mutant Dentin Sialophosphoprotein Causes Dentinogenesis Imperfecta

Dentin sialophosphoprotein (DSPP) is an extracellular matrix protein highly expressed by odontoblasts in teeth. DSPP mutations in humans may cause dentinogenesis imperfecta (DGI), an autosomal dominant dentin disorder. We recently generated a mouse model (named "Dspp^P19L/+ mice") that expressed a mutant DSPP in which the proline residue at position 19 was replaced by a leucine residue. We found that the Dspp^P19L/+ and Dspp^P19L/P19L mice at a younger age displayed a tooth phenotype resembling human DGI type III characterized by enlarged dental pulp chambers, while the teeth of older Dspp^P19L/+ and Dspp^P19L/P19L mice had smaller dental pulp chambers mimicking DGI type II. The teeth of Dspp^P19L/+ and Dspp^P19L/P19L mice had a narrower pulp chamber roof predentin layer, thinner pulp chamber roof dentin, and thicker pulp chamber floor dentin. In addition, these mice also had increased enamel attrition, accompanied by excessive deposition of peritubular dentin. Immunohistochemistry, in situ hybridization, and real-time polymerase chain reaction analyses showed that the odontoblasts in both Dspp^P19L/+ and Dspp^P19L/P19L mice had reduced DSPP expression, compared to the wild-type mice. We also observed that the levels of DSPP expression were much higher in the roof-forming odontoblasts than in the floor-forming odontoblasts in the wild-type mice and mutant mice. Moreover, immunohistochemistry showed that while the immunostaining signals of dentin sialoprotein (N-terminal fragment of DSPP) were decreased in the dentin matrix, they were remarkably increased in the odontoblasts of the Dspp^P19L/+ and Dspp^P19L/P19L mice. Consistently, our in vitro studies showed that the secretion of the mutant DSPP was impaired and accumulated within endoplasmic reticulum. These findings suggest that the dental phenotypes of the mutant mice were associated with the intracellular retention of the mutant DSPP in the odontoblasts of the DSPP-mutant mice.

The miR-3940-5p inhibits cell proliferation of gingival mesenchymal stem cells

OBJECTIVES

Drug-induced gingival overgrowth (DIGO) is a well-recognized side effect of nifedipine (NIF). However, the molecular mechanisms of DIGO are still unknown. Here, we explored the possible role of miR-3940-5p in DIGO using NIF-treated gingival mesenchymal stem cells (GMSCs).

MATERIAL AND METHODS

CFSE and cell cycle assays were used to examine cell proliferation. The alkaline phosphatase (ALP) activity assay, Alizarin Red staining, quantitative calcium analysis, and osteogenesis-related gene expression were used to examine osteo/dentinogenic differentiation.

RESULTS

The CFSE assay showed that NIF enhanced cell proliferation, and the over-expression of miR-3940-5p inhibited the proliferation of GMSCs with or without NIF stimulation. Cell cycle assays revealed that the cell cycle was arrested at the G0/G1 phase. Furthermore, it was found that the over-expression of miR-3940-5p upregulated p15^INK4b , p18^INK4c , p19^INK4d , and Cyclin A and downregulated Cyclin E in GMSCs with or without NIF treatment. In addition, the over-expression of miR-3940-5p enhanced ALP activity and mineralization in vitro and increased the expression of the osteo/dentinogenic differentiation markers DSPP and DMP1 and the key transcription factor DLX5 in GMSCs.

CONCLUSIONS

miR-3940-5p inhibited cell proliferation, enhanced the osteo/dentinogenic differentiation of GMSCs, and might play a role in DIGO as a potent agent in the treatment of nifedipine-induced gingival overgrowth.

iMatrix-511 Stimulates the Proliferation and Differentiation of MDPC-23 Cells into Odontoblastlike Phenotype

INTRODUCTION

iMatrix-511 is a novel integrin-binding fragment derived from laminin-511. Previous studies showed its superiority as a culture substrate for xeno-free culture and maintenance of pluripotency in stem cells. However, its effects in the dental field remain largely unknown. The aim of the present study was to unravel the in vitro effects of iMatrix-511 in comparison with vitronectin (VN).

METHODS

Biochemical assays were performed in vitro in MDPC-23 cells. The optimal coating density for 2 proteins was determined using the cell counting kit-8. To evaluate cell proliferation to both proteins, MDPC-23 cells were directly seeded onto the iMatrix-511 or VN-modified polystyrene and analyzed by the cell counting kit-8. The phenotype of cells seeded on iMatrix-511 and VN was characterized. Phenotypic characterization included real-time reverse-transcription polymerase chain reaction and alizarin red staining.

RESULTS

The optimal coating density for iMatrix-511 and VN was determined to be 1 μg/cm² and 0.25 μg/cm², respectively. Cells cultured on iMatrix-511 showed higher cell proliferative activity than the noncoated control and VN on days 1, 2, and 4. Cell morphology observation revealed MDPC-23 cells attach preferentially to iMatrix-511 and start to spread as early as 1 hour after inoculation. MDPC-23 cells exhibited more potent odontogenic differentiation on iMatrix-511 than the control and VN as shown by the marked enhancement of dentin matrix protein 1 and dentin sialophosphoprotein messenger RNA expression. Although both proteins showed more mineralized nodule formation than the control, iMatrix-511 remained to be the one that elicited stronger calcific deposition.

CONCLUSIONS

iMatrix-511 supported the proliferation and acquisition of odontogenic cell phenotype in vitro, rendering this novel material a potential candidate for dentin regeneration.

Conditional Knockout of Raptor/mTORC1 Results in Dentin Malformation

mTORC1 signaling plays an important role in extracellular and intracellular signals, including growth factors, nutrients, energy metabolism, and stress. However, the functional role of mTORC1 in dentinogenesis is unknown. To study the role of Raptor/mTORC1 in dentinogenesis, an Raptor^fl/fl; Osx-Cre (Rap-Osx) mouse, in which Raptor was conditionally deleted in odontoblasts and dental mesenchymal cells, was generated, and postnatal tooth development was compared between Rap-Osx mice and control littermates. Rap-Osx mice presented a phenotype known as dentinogenesis imperfecta and had smaller tooth volume, a thinner dentin layer and a larger pulp chamber. The proliferation and differentiation of odontoblasts/preodontoblasts were attenuated in mutant mice, which was likely responsible for the defects in dentinogenesis. Raptor/mTORC1-pS6K1 signaling was inactivated during tooth development in Rap-Osx mice, whereas it was activated in control mice. These results indicate that Raptor/mTORC1 plays a critical role in dentinogenesis via promoting odontoblasts/preodontoblasts proliferation and differentiation. Raptor/mTORC1 might regulate tooth development through the pS6K1 signaling pathway.

Oxidative stress induced by self-adhesive resin cements affects gene expression, cellular proliferation and mineralization potential of the MDPC-23 odontoblast-like cells

OBJECTIVE

Clinical issues have been raised about problems related to cytotoxic effects caused when applying self-adhesive cement. It was hypothesized that byproducts eluted from self-adhesive cements modulate oxidative stress response, the gene expression of signaling pathways of inflammatory process/transcriptional activators, and the expression and activity of interstitial collagenases, and modify the phenotypic characteristics of cellular proliferation and mineral deposition in odontoblastic-like cells.

METHODS

Cements (MaxCem Elite [MAX] and RelyX U200 [U200)]) were mixed, dispensed into moulds, and photoactivated according to the manufacturers' instructions. Immortalized rat odontoblast-like cells (MDPC-23) were cultured and exposed to polymerized specimens of cements for 4 h. Reactive oxidative specimen production and quantification of gene expression were evaluated. Cell proliferation assay and alizarin red staining were also performed to evaluate the disturbance induced by the cements on cellular proliferation and mineralization.

RESULTS

Despite their cytotoxic effects, both self-adhesive cements influenced the metabolism in the odontoblast cells on different scales. MAX induced significantly higher oxidative stress in odontoblast cells than U200. Gene expression varied as a function of exposure to self-adhesive cements; MAX induced the expression of pro-inflammatory cytokines such as TNF-α, whereas U200 downregulated, virtually depleted TNF-α expression, also inducing overexpression of the transcriptional factor Runx2. Overexpression of heme oxygenase-1 (HO-1) and thioredoxin reductase 1 (TRXR1) occurred after exposure to both cements, antioxidant genes that are downstream of Keap1-Nrf2-ARE system. MAX significantly induced the overexpression of collagenase MMP-1, and U200 induced the expression of gelatinase MMP-2. MAX significantly inhibited cell proliferation whereas U200 significantly activated cell proliferation. Alizarin red staining revealed significantly decreased mineral deposition especially when exposed to MAX.

SIGNIFICANCE

These results support the hypothesis that byproducts of different self-adhesive cements play important roles in the highly orchestrated process which ultimately affect the cellular proliferation and the mineral deposition in odontoblastic-like cells, possibly delaying the reparative dentin formation after cementation of indirect restorations, especially on recently exposed dentin preparations.

WIF1 enhanced dentinogenic differentiation in stem cells from apical papilla

Background

Odontogenic mesenchymal stem cells (MSCs) isolated from tooth tissues are a reliable resource that can be utilized for dental tissue regeneration. Exploration of the mechanisms underlying the regulation of their differentiation may be helpful for investigating potential clinical applications. The stem cell niche plays an important role in maintaining cell functioning. Previous studies found that Wnt inhibitory factor 1 (WIF1) is more highly expressed in apical papilla tissues than in stem cells from apical papilla (SCAPs) using microarray analysis. However, the function of WIF1 in SCAPs remains unclear. In the present study, we investigated the function of WIF1 during dentinogenic differentiation in SCAPs.

Methods

A retrovirus containing HA-WIF1 was used to overexpress WIF1 in SCAPs. Using Western blot analysis, we verified the expression of HA-WIF1. Alkaline phosphatase (ALP) activity assays, Alizarin Red staining and quantitative calcium analysis were performed to investigate the in vitro potential for dentinogenic differentiation in SCAPs. The expression of dentinogenesis-associated genes DSPP, DMP1, Runx2 and OSX were assayed using real-time RT-PCR. Transplantation experiments were used to measure dentinogenesis potential in vivo.

Results

The real time RT-PCR results showed that WIF1 was more highly expressed in apical papilla tissues than in SCAPs, and its expression was increased during the process of dentinogenic differentiation. Overexpression of WIF1 enhanced ALP activity and mineralization in vitro, as well as the expression of DSPP, DMP1 and OSX in SCAPs. Moreover, in vivo transplantation experiments revealed that dentinogenesis in SCAPs was enhanced by WIF1 overexpression.

Conclusion

These results suggest that WIF1 may enhance dentinogenic differentiation potential in dental MSCs via its regulation of OSX and identified potential target genes that could be useful for improving dental tissue regeneration.

Vps4b heterozygous mice do not develop tooth defects that replicate human dentin dysplasia I

BACKGROUND

Vacuolar protein sorting-associated protein 4B (VPS4B) is a member of the ATP enzyme AAA protein family, and is mainly involved in protein degradation and cell membrane fusion. Recently, a dominant mutation in this gene was identified in human dentin dysplasia type I (DD-I). Herein, we report the generation of Vps4b knockout (Vps4b KO) mice; however, the homozygous Vps4b KO mutation was embryonic lethal at the early stages of embryo development, and we therefore report the results of heterozygous mutant mice.

RESULTS

Mice heterozygous for Vps4b did not develop tooth defects replicating human DD-I. Immunohistochemistry showed that gene KO was successful, as there was decreased expression of Vps4b in heterozygous mice; hematoxylin and eosin (H&E) staining also showed that the width of the pre-dentin zone was increased in heterozygous mice, although the arrangement of the odontoblasts was not significantly different from wild-type (WT) mice. However, H&E staining showed no obvious abnormalities in the bones of heterozygous mice. Moreover, stereomicroscopic and X-ray radiography results indicated no abnormal manifestations in teeth or bones. Furthermore, statistical analysis of the volume and density of dentin and enamel, as well as skeletal analysis, including the volume and separation of trabecular bone analyzed by micro-CT, all showed no differences between Vps4b heterozygotes and WT mice. In addition, there also were no significant differences in bone or cartilage mineralization as evaluated by Alcian blue-Alizarin red staining.

CONCLUSIONS

The heterozygous Vps4b KO mice do not develop tooth defects that replicate human DD-I and this is likely to be due to differences in tooth development between the two species. Consequently, further studies are needed to determine whether mice are an appropriate animal model for human tooth diseases.

Downregulated microRNA-488 enhances odontoblast differentiation of human dental pulp stem cells via activation of the p38 MAPK signaling pathway

Human dental pulp stem cells (hDPSCs) are primarily derived from the pulp tissues of permanent third molar teeth. They were widely used in human bone tissue engineering. It was previously indicated that microRNA (miR) expressions are closely associated with hDPSCs development. However, the specific effect of miR-488 on hDPSCs still remains unclear. In this study, we aimed to investigate effects of miR-488 on the differentiation of hDPSCs into odontoblast cells through the p38 mitogen-activated protein kinases (MAPK) signaling pathway by binding to MAPK1. The hDPSCs were isolated and cultured in vitro. Dual-luciferase reporter gene assay was performed to test the relationship between MAPK1 (p38) and miR-488. Reverse transcription quantitative polymerase chain reaction and western blot analysis were used to detect the mRNA and protein expressions of p38 MAPK signaling pathway-related genes (MAPK1, Ras, and Mitogen-activated protein kinase kinase 3/6 [MKK3/6]), along with expressions of dentin Sialophosphoprotein (DSPP), alkaline phosphatase (ALP), and osteonectin (OCN). ALP staining and alizarin red staining were conducted to detect ALP activity and degree of mineralization. Initially, we found that MAPK1 was the target gene of miR-488. Besides, downregulation of miR-488 was observed to stimulate the p38 MAPK signaling pathway and to increase the messenger RNA and protein expressions of DSPP, ALP, and OCN. Furthermore, ALP activity and formation of a mineralized nodule in hDPSCs were enhanced upon downregulation of miR-488. The aforementioned findings provided evidence supporting that downregulation of miR-488 promotes odontoblastic differentiation of hDPSCs through the p38 MAPK signaling pathway by targeting MAPK1, paving the basis for further study about hDPSCs.

Oestrogen receptor α regulates the odonto/osteogenic differentiation of stem cells from apical papilla via ERK and JNK MAPK pathways

OBJECTIVES

Oestrogen receptor (ER) is a common nucleus receptor that is essential for the regulation of cell growth, proliferation and differentiation. This study was to examine whether ERα can affect the proliferation and odonto/osteogenic differentiation of stem cells from apical papilla (SCAPs).

MATERIALS AND METHODS

Stem cells from apical papillas were isolated, purified and then transfected with ERα lentiviruses. The proliferation capacity was investigated by cell counting kit-8 (CCK-8) assay and flow cytometry. The odonto/osteogenic differentiation ability was analysed by alkaline phosphatase (ALP) activity, alizarin red staining, western blot assay (WB) and real-time RT-PCR. MAPK pathway and its downstream transcriptional factors were explored by WB assay.

RESULTS

As indicated by CCK-8 assay and flow cytometry, ERα had no significant effect on the proliferation of SCAPs. When ERα was overexpressed, the ALP activity and the formation of calcified nodules were significantly enhanced in SCAPs. Moreover, the odonto/osteogenic markers (DMP1/DMP1, DSPP/DSP, RUNX2/RUNX2, OCN/OCN) in SCAPs were significantly up-regulated at both mRNA and protein levels. On the contrary, the odonto/osteogenic differentiation ability of SCAPs was remarkably inhibited after suppression of ERα. Mechanistically, the protein levels of phosphorylated ERK and JNK significantly increased after ERα overexpression. Moreover, some downstream transcriptional factors of MAPK pathway were simultaneously activated by ERα overexpression.

CONCLUSIONS

Together, the data accumulated here indicated that ERα can enhance the odonto/osteogenic differentiation of SCAPs via ERK and JNK MAPK pathways.

miR-675 promotes odontogenic differentiation of human dental pulp cells by epigenetic regulation of DLX3

In a previous study, we showed that microRNA-675 (miR-675) was significantly down-regulated in patients with tricho-dento-osseous (TDO) syndrome. One of the main features of TDO syndrome is dentin hypoplasia. Thus, we hypothesize that miR-675 plays a role in dentin development. In this study, we determined the role of miR-675 in the odontogenic differentiation of human dental pulp cells (hDPCs). Stable overexpression and knockdown of miR-675 in hDPCs were performed using recombinant lentiviruses containing U6 promoter-driven miR-675 and short hairpin-miR675 expression cassettes, respectively. Alkaline phosphatase (ALP) assay, Alizarin red staining assay, quantitative polymerase chain reaction (qPCR), Western blot analysis, and immunofluorescent staining revealed the promotive effects of miR-675 on the odontogenic differentiation of hDPCs. Further, we found that miR-675 facilitates the odontogenic differentiation process of hDPCs by epigenetic regulation of distal-less homeobox (DLX3). Thus, for the first time, we determined that miR-675 regulates the odontogenic differentiation of hDPCs by inhibiting the DNA methyltransferase 3 beta (DNMT3B)-mediated methylation of DLX3. Our findings uncover an unanticipated regulatory role for miR-675 in the odontogenic differentiation of hDPCs by epigenetic changes in DLX3 and provide novel insight into dentin hypoplasia feature in TDO patients.

Transgenic expression of dentin phosphoprotein (DPP) partially rescued the dentin defects of DSPP-null mice

Mutations in the dentin sialophosphoprotein (DSPP) gene cause dentinogenesis imperfecta. After synthesis, DSPP is proteolytically processed into NH2- and COOH-terminal fragments. The NH2-terminal fragment of DSPP is highly glycosylated but not phosphorylated, whereas the COOH-terminal fragment (named "dentin phosphoprotein" or "DPP") is highly phosphorylated but not glycosylated. These two fragments are believed to perform distinct roles in dentin formation. To analyze the functions of DPP in dentinogenesis, we created "Dspp-/-;DPP Tg mice", which expressed transgenic DPP driven by a Type I collagen promoter but lacked the endogenous Dspp gene. We characterized the dentin of the Dspp-/-;DPP Tg mice using X-ray radiography, histology, scanning electron microscopy, double fluorochrome labeling, immunohistochemistry and in situ hybridization. Micro-computed tomography analyses revealed that at postnatal 6 months, the transgenic expression of DPP increased the dentin thickness of the Dspp-null mice by 97.1% and restored the dentin material density by 29.5%. Histological analyses showed that the Dspp-null mice manifested an abnormal widening of the predentin while the predentin in Dspp-/-;DPP Tg mice was narrower than in the Dspp-null mice. Scanning electron microscopy analyses showed that the dentinal tubules in the Dspp-/-;DPP Tg mice were better organized than in the Dspp-null mice. The double fluorochrome labeling analyses demonstrated that the dentin mineral deposition rate in the Dspp-/-;DPP Tg mice was significantly improved compared to that in the Dspp-null mice. These findings indicate that the transgenic expression of DPP partially rescued the dentin defects of the DSPP-null mice, suggesting that DPP may promote dentin formation and that the coordinated actions between DPP and the NH2-terminal fragment of DSPP may be necessary for dentinogenesis.

KDM1A regulated the osteo/dentinogenic differentiation process of the stem cells of the apical papilla via binding with PLOD2

OBJECTIVES

Dental tissue-derived mesenchymal stem cells (MSCs)-mediated pulp-dentin regeneration is considered a potential approach for the regeneration of damaged teeth. Enhancing MSC-mediated pulp-dentin regeneration is based on an understanding of the molecular mechanisms underlying directed cell differentiation process. Histone demethylation enzyme, lysine demethylase 1A (KDM1A) can regulate the differentiation of some MSCs, but its role in dental tissue-derived MSCs is unclear.

MATERIAL AND METHODS

We obtained SCAPs from immature teeth. Alkaline phosphatase (ALP) activity assay, Alizarin red staining, quantitative calcium analysis, osteogenesis-related genes expression and in vivo transplantation experiment were used to explore the osteo/dentinogenic differentiation. Co-immunoprecipitation (Co-IP) assay was used to investigate the binding protein.

RESULTS

Knock-down of KDM1A reduced ALP activity and mineralization, promoted the expressions of osteo/dentinogenic differentiation markers DSPP, DMP1, BSP and key transcript factors, RUNX2, OSX, DLX2 in SCAPs, and also enhanced the osteo/dentinogenesis in vivo. In addition, KDM1A could associate with PLOD2 to form protein complex. And knock-down of PLOD2 inhibited ALP activity and mineralization, and promoted the expressions of DSPP, DMP1, BSP, RUNX2, OSX and DLX2 in SCAPs.

CONCLUSIONS

KDM1A might have different role in different stages of osteo/dentinogenic differentiation process by binding partner with PLOD2, and finally resulted in the inhibited function for the osteo/dentinogenesis in SCAPs. Our studies provided a further understanding of the regulatory mechanisms of dynamic osteo/dentinogenic differentiation process in dental tissue MSCs.

Hsa-let-7c controls the committed differentiation of IGF-1-treated mesenchymal stem cells derived from dental pulps by targeting IGF-1R via the MAPK pathways

The putative tumor suppressor microRNA let-7c is extensively associated with the biological properties of cancer cells. However, the potential involvement of let-7c in the differentiation of mesenchymal stem cells has not been fully explored. In this study, we investigated the influence of hsa-let-7c (let-7c) on the proliferation and differentiation of human dental pulp-derived mesenchymal stem cells (DPMSCs) treated with insulin-like growth factor 1 (IGF-1) via flow cytometry, CCK-8 assays, alizarin red staining, real-time RT-PCR, and western blotting. In general, the proliferative capabilities and cell viability of DPMSCs were not significantly affected by the overexpression or deletion of let-7c. However, overexpression of let-7c significantly inhibited the expression of IGF-1 receptor (IGF-1R) and downregulated the osteo/odontogenic differentiation of DPMSCs, as indicated by decreased levels of several osteo/odontogenic markers (osteocalcin, osterix, runt-related transcription factor 2, dentin sialophosphoprotein, dentin sialoprotein, alkaline phosphatase, type 1 collagen, and dentin matrix protein 1) in IGF-1-treated DPMSCs. Inversely, deletion of let-7c resulted in increased IGF-1R levels and enhanced osteo/odontogenic differentiation. Furthermore, the ERK, JNK, and P38 MAPK pathways were significantly inhibited following the overexpression of let-7c in DPMSCs. Deletion of let-7c promoted the activation of the JNK and P38 MAPK pathways. Our cumulative findings indicate that Let-7c can inhibit the osteo/odontogenic differentiation of IGF-1-treated DPMSCs by targeting IGF-1R via the JNK/P38 MAPK signaling pathways.

De Novo Genome and Transcriptome Assembly of the Canadian Beaver (Castor canadensis)

The Canadian beaver (Castor canadensis) is the largest indigenous rodent in North America. We report a draft annotated assembly of the beaver genome, the first for a large rodent and the first mammalian genome assembled directly from uncorrected and moderate coverage (< 30 ×) long reads generated by single-molecule sequencing. The genome size is 2.7 Gb estimated by k-mer analysis. We assembled the beaver genome using the new Canu assembler optimized for noisy reads. The resulting assembly was refined using Pilon supported by short reads (80 ×) and checked for accuracy by congruency against an independent short read assembly. We scaffolded the assembly using the exon–gene models derived from 9805 full-length open reading frames (FL-ORFs) constructed from the beaver leukocyte and muscle transcriptomes. The final assembly comprised 22,515 contigs with an N50 of 278,680 bp and an N50-scaffold of 317,558 bp. Maximum contig and scaffold lengths were 3.3 and 4.2 Mb, respectively, with a combined scaffold length representing 92% of the estimated genome size. The completeness and accuracy of the scaffold assembly was demonstrated by the precise exon placement for 91.1% of the 9805 assembled FL-ORFs and 83.1% of the BUSCO (Benchmarking Universal Single-Copy Orthologs) gene set used to assess the quality of genome assemblies. Well-represented were genes involved in dentition and enamel deposition, defining characteristics of rodents with which the beaver is well-endowed. The study provides insights for genome assembly and an important genomics resource for Castoridae and rodent evolutionary biology.