CPNE7, a preameloblast-derived factor, regulates odontoblastic differentiation of mesenchymal stem cells

Regenerative endodontic therapy: From laboratory bench to clinical practice

BACKGROUND

Maintaining the vitality and functionality of dental pulp is paramount for tooth integrity, longevity, and homeostasis. Aiming to treat irreversible pulpitis and necrosis, there has been a paradigm shift from conventional root canal treatment towards regenerative endodontic therapy.

AIM OF REVIEW

This extensive and multipart review presents crucial laboratory and practical issues related to pulp-dentin complex regeneration aimed towards advancing clinical translation of regenerative endodontic therapy and enhancing human life quality.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this multipart review paper, we first present a panorama of emerging potential tissue engineering strategies for pulp-dentin complex regeneration from cell transplantation and cell homing perspectives, emphasizing the critical regenerative components of stem cells, biomaterials, and conducive microenvironments. Then, this review provides details about current clinically practiced pulp regenerative/reparative approaches, including direct pulp capping and root revascularization, with a specific focus on the remaining hurdles and bright prospects in developing such therapies. Next, special attention was devoted to discussing the innovative biomimetic perspectives opened in establishing functional tissues by employing exosomes and cell aggregates, which will benefit the clinical translation of dental pulp engineering protocols. Finally, we summarize careful consideration that should be given to basic research and clinical applications of regenerative endodontics. In particular, this review article highlights significant challenges associated with residual infection and inflammation and identifies future insightful directions in creating antibacterial and immunomodulatory microenvironments so that clinicians and researchers can comprehensively understand crucial clinical aspects of regenerative endodontic procedures.

The impact of selcopintide on periodontal regeneration in a class II furcation defect model: a radiographic and histomorphometric analysis

OBJECTIVES

This study investigated the effect of Selcopintide (SCPT) on periodontal regeneration using surgically created class II furcation defects in an animal model, employing both radiographical and histological evaluations.

MATERIALS AND METHODS

Class II furcation defects were surgically induced in six beagle dogs. Each defect was unilaterally and randomly assigned to one of five treatment groups: (1) no treatment (control), (2) guided tissue regeneration (GTR) with a collagenated bone substitute and a collagen membrane, (3) GTR with an enamel matrix derivative (GTR/EMD), (4) GTR with 2 mg/ml SCPT (GTR/SCPT2), or (5) GTR with 4 mg/ml SCPT (GTR/SCPT4). Six weeks after initial surgery, identical procedures were performed on the contralateral area. Healing outcomes were assessed at 6 and 12 weeks through radiographic and histomorphometric analyses. The primary outcome was the length of the root surface covered by new cementum assessed histologically and the secondary outcome included other histomorphometric and radiographic healing outcomes.

RESULTS

Radiographically, the GTR/SCPT groups showed significantly greater new bone volume than the control group at both 6- and 12-week timepoints (p < 0.05). Histologically, specimens treated with both formulations of SCPT displayed better-organized periodontal ligaments and improved cementum formation, similar to those treated with EMD. The group with the highest concentration of SCPT (GTR/SCPT4) exhibited the greatest amount of new cementum formation.

CONCLUSIONS

Within the limitations of this study, both formulations of SCPT demonstrated significant regenerative potential in periodontal tissues, with outcomes comparable to those of EMD treatment, suggesting SCPT's viability as an alternative bioactive agent for periodontal regeneration in class II furcation defects.

CLINICAL RELEVANCE

This study suggests that SCPT could serve as a viable alternative bioactive agent for periodontal regeneration in class II furcation defect in clinical settings.

Artemisinin regulates cell proliferation, apoptosis, and the inflammatory response of human dental pulp stem cells through the p53 signaling pathway under LPS-induced inflammation

OBJECTIVE

The purpose of this study was to investigate the effects and mechanism of artemisinin (ART) on the proliferation, apoptosis, and inflammatory response of human dental pulp stem cells (HDPSCs) under lipopolysaccharide (LPS)-induced inflammation.

METHODS

HDPSCs were isolated, cultured, and identified by flow cytometry and three-directional differentiation induction. A suitable concentration of LPS was selected to mimic the inflammatory condition in vitro. After culturing with ART and LPS for 48 h, cell proliferation was observed by CCK-8 assay; cell apoptosis was observed by flow cytometry, western blot, and Caspase-3 activity; and the inflammatory response was observed by qRT-PCR and ELISA. Transcriptome sequencing, immunofluorescence staining, qRT-PCR, western blot, and RITA were used to explore the underlying mechanism.

RESULTS

HDPSCs were successfully isolated and exhibited the potential for multilineage differentiation. 0.1 μg/mL of LPS was utilized to mimic the inflammatory condition. ART promoted HDPSCs proliferation but repressed apoptosis and the inflammatory response under LPS-induced inflammation. Further, ART exerted its effect through the p53 signaling pathway.

CONCLUSION

ART inhibited the p53 signaling pathway to promote HDPSCs proliferation, but hinder apoptosis and the inflammatory response under LPS-induced inflammation.

CLINICAL SIGNIFICANCE

This study demonstrates that ART facilitates the alleviation of inflammation and preserves the viability of HDPSCs. Therefore, ART may serve as a promising therapeutic drug for the repair and regeneration of dental pulp in the treatment of deep caries and reversible pulpitis.

Odontogenic exosomes simulating the developmental microenvironment promote complete regeneration of pulp-dentin complex in vivo

INTRODUCTION

Establishing an optimized regenerative microenvironment for pulp-dentin complex engineering has become increasingly critical. Recently, exosomes have emerged as favorable biomimetic nanotherapeutic tools to simulate the developmental microenvironment and facilitate tissue regeneration.

OBJECTIVES

This study aimed to elucidate the multifaceted roles of exosomes from human dental pulp stem cells (DPSCs) that initiated odontogenic differentiation while sustaining mesenchymal stem cell (MSC) characteristics in odontogenesis, angiogenesis, and neurogenesis during pulp-dentin complex regeneration.

METHODS

Differential centrifugation was performed to isolate exosomes from normal DPSCs (DPSC-Exos) and DPSCs that initially triggered odontogenic differentiation (DPSC-Od-Exos). The impact of these exosomes on the biological behavior of DPSCs and human umbilical vein endothelial cells (HUVECs) was examined in vitro through CCK-8 assay and Transwell migration assay, as well as assays dedicated to assessing odontogenic, angiogenic, and neurogenic capabilities. In vivo, Matrigel plugs and human tooth root fragments incorporating either DPSC-Exos or DPSC-Od-Exos were subcutaneously transplanted into mouse models. Subsequent histological, immunohistochemical, and immunofluorescent analyses were conducted to determine the regenerative outcomes.

RESULTS

DPSC-Exos and DPSC-Od-Exos revealed no remarkable difference in their characteristics. In vitro analyses indicated that DPSC-Od-Exos significantly facilitated the proliferation, migration, and multilineage differentiation of DPSCs compared with DPSC-Exos. Furthermore, DPSC-Od-Exos elicited a more pronounced effect on the tubular structure formation of HUVECs. Consistently, Matrigel plug assays confirmed that DPSC-Od-Exos exhibited superior performance in promoting endothelial differentiation of DPSCs and stimulating angiogenesis in HUVECs. Notably, DPSC-Od-Exos contributed to complete pulp-dentin complex regeneration in human tooth root fragments, characterized by enriched neurovascular structures and a continuous layer of odontoblast-like cells, which extended cytoplasmic projections into the newly formed dentinal tubules.

CONCLUSION

By simulating the developmental microenvironment, multifunctional DPSC-Od-Exos demonstrated promising potential for reconstructing dentin-like tissue, vascular networks, and neural architectures, thereby enhancing our understanding of the therapeutic implications of DPSC-Od-Exos in regenerative endodontic treatment.

A novel chitosan-peptide system for cartilage tissue engineering with adipose-derived stromal cells

The natural healing process of cartilage injuries often fails to fully restore the tissue's biological and mechanical functions. Cartilage grafts are costly and require surgical intervention, often associated with complications such as intraoperative infection and rejection by the recipient due to ischemia. Novel tissue engineering technologies aim to ideally fill the cartilage defect to prevent disease progression or regenerate damaged tissue. Despite many studies on designing biocompatible composites to stimulate chondrogenesis, only few focus on peptides and carriers that promote stem cell proliferation or differentiation to promote healing. Our research aimed to design a carbohydrate chitosan-based biomaterial to stimulate stem cells into the chondrogenesis pathway. Our strategy was to combine chitosan with a novel peptide (UG28) that sequence was based on the copin protein. The construct stimulated human adipose-derived stem cells (AD-SCs) cells to undergo chondrogenic differentiation. Chitosan 75/500 allows AD-SCs to grow and has no harmful effects on the cells. The combination of UG28 peptide with the chitosan composite offers promising properties for cell differentiation, indicating its potential for clinical applications in cartilage regeneration.

Amelogenin-Inspired Autoadaptive Peptide in a Caries Microenvironment Facilitates Long-Term Protection of the Dentin-Pulp Complex

Dental caries, one of the most prevalent infectious diseases, is the primary contributor to the early loss of natural teeth and is a significant public health issue. Known as the tooth's bioactive core, the dentin-pulp complex (DPCX) comprises tightly connected hard and soft tissues that not only serve as a biological barrier for the inner tooth tissue but also produce reparative dentin following mild disruptions. While efforts to preserve DPCX are numerous, most strategies focus on temporary antibacterial measures, inflammation reduction, or tissue regeneration, lacking a comprehensive, long-lasting solution. In this study, TVH-19, an autoadaptive peptide mimicking the pH- and ion-responsive capacity of amelogenin, was designed to exert multifaceted preservation of DPCX, providing a comprehensive strategy for preserving vital pulp. Leveraging its unique amphiphilicity-related cell penetration and ion/pH-responsive self-assembly properties, TVH-19 outperforms conventional pulp preservation materials by being capable of rapid cell penetration, minimizing diffused side effects, providing environment-responsive self-assembly/disassembly for balanced long-term antibacterial and cell protection, and facilitating the formation of lysosomal-escaping intracellular aggregates for the continuous activation of PDGFRα+ dental pulp stem cells.

Cpne7 deficiency induces cellular senescence and premature aging of dental pulp

Once tooth development is complete, odontoblasts and their progenitor cells in the dental pulp play a major role in protecting tooth vitality from external stresses. Hence, understanding the homeostasis of the mature pulp populations is just as crucial as understanding that of the young, developing ones for managing age-related dentinal damage. Here, it is shown that loss of Cpne7 accelerates cellular senescence in odontoblasts due to oxidative stress and DNA damage accumulation. Thus, in Cpne7-null dental pulp, odontoblast survival is impaired, and aberrant dentin is extensively formed. Intraperitoneal or topical application of CPNE7-derived functional peptide, however, alleviates the DNA damage accumulation and rescues the pathologic dentin phenotype. Notably, a healthy dentin-pulp complex lined with metabolically active odontoblasts is observed in 23-month-old Cpne7-overexpressing transgenic mice. Furthermore, physiologic dentin was regenerated in artificial dentinal defects of Cpne7-overexpressing transgenic mice. Taken together, Cpne7 is indispensable for the maintenance and homeostasis of odontoblasts, while promoting odontoblastic differentiation of the progenitor cells. This research thereby introduces its potential in oral disease-targeted applications, especially age-related dental diseases involving dentinal loss.

Endodontic Tissue Regeneration: A Review for Tissue Engineers and Dentists

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

Dental Pulp Stem Cells and Current in vivo Approaches to Study Dental Pulp Stem Cells in Pulp Injury and Regeneration

Dental pulp stem cells (DPSCs) have garnered significant interest in dental research for their unique characteristics and potential in tooth development and regeneration. While there were many studies to define their stem cell-like characteristics and osteogenic differentiation functions that are considered ideal candidates for regenerating damaged dental pulp tissue, how endogenous DPSCs respond to dental pulp injury and supply new dentin-forming cells has not been extensively investigated in vivo. Here, we review the recent progress in identity, function, and regulation of endogenous DPSCs and their clinical potential for pulp injury and regeneration. In addition, we discuss current advances in new mouse models, imaging techniques, and its practical uses and limitations in the analysis of DPSCs in pulp injury and regeneration in vivo.

Role of CPNE1 in Odontoblastic Differentiation of Rat Stem Cells from Apical Papilla

CPNE1 is a calcium-dependent, phospholipid-binding protein that is ubiquitously expressed in various tissues and organs. This study investigates the expression and localization of CPNE1 in tooth germ development and the role of CPNE1 in odontoblastic differentiation. In rat tooth germs, CPNE1 is expressed in the odontoblasts and ameloblasts since the late bell stage. The depletion of CPNE1 in the stem cells from apical papilla (SCAPs) clearly inhibits the expression of odontoblastic-related genes and the formation of mineralized nodules during differentiation, while CPNE1 overexpression promotes this process. In addition, CPNE1 overexpression increases AKT phosphorylation during the odontoblastic differentiation of SCAPs. Furthermore, treatment with AKT inhibitor (MK2206) reduces the expression of odontoblastic-related genes in CPNE1 over-expressed SCAPs, and Alizarin Red staining shows reduced mineralization. These results suggest that CPNE1 plays a role in the tooth germ development as well as the odontblastic differentiation of SCAPs in vitro that is related to the AKT signaling pathway.

Development of a new universal adhesive containing CPNE7-derived peptide and its potential role in reducing postoperative sensitivity

Post-operative sensitivity (POS) is the most common clinical dental complaint after tooth preparation and resin-based composite restoration. In our previous study, copine 7 (CPNE7) and CPNE7-derived peptide (CPNE7-DP) induced in vitro odontoblast differentiation and in vivo dentin formation. Here, we incorporated CPNE7-DP into All-Bond Universal (ABU) adhesive, developing ABU/CPNE7-DP. This study aimed to investigate the possibility of reducing POS using ABU/CPNE7-DP. We first determined the stability of CPNE7-DP under low pH. Furthermore, we evaluated its dentinal tubule penetration, in vitro odontogenic differentiation potential, in vivo tertiary dentin formation and its effects on bonding performance. CPNE7-DP was stable at pH 1.2, even lower than ABU's pH of 3.2. ABU/CPNE7-DP can penetrate dentinal tubules, stimulate odontoblast differentiation in vitro and generate tertiary dentin with tubular structure in vivo without interfering with bonding performance. Therefore, ABU/CPNE7-DP may serve as a novel bioactive adhesive for reducing POS.

Epithelium-derived SCUBE3 promotes polarized odontoblastic differentiation of dental mesenchymal stem cells and pulp regeneration

BACKGROUND

Signal peptide-CUB-EGF domain-containing protein 3 (SCUBE3), a secreted multifunctional glycoprotein whose transcript expression is restricted to the tooth germ epithelium during the development of embryonic mouse teeth, has been demonstrated to play a crucial role in the regulation of tooth development. Based on this, we hypothesized that epithelium-derived SCUBE3 contributes to bio-function in dental mesenchymal cells (Mes) via epithelium-mesenchyme interactions.

METHODS

Immunohistochemical staining and a co-culture system were used to reveal the temporospatial expression of the SCUBE3 protein during mouse tooth germ development. In addition, human dental pulp stem cells (hDPSCs) were used as a Mes model to study the proliferation, migration, odontoblastic differentiation capacity, and mechanism of rhSCUBE3. Novel pulp-dentin-like organoid models were constructed to further confirm the odontoblast induction function of SCUBE3. Finally, semi-orthotopic animal experiments were performed to explore the clinical application of rhSCUBE3. Data were analysed using one-way analysis of variance and t-tests.

RESULTS

The epithelium-derived SCUBE3 translocated to the mesenchyme via a paracrine pathway during mouse embryonic development, and the differentiating odontoblasts in postnatal tooth germ subsequently secreted the SCUBE3 protein via an autocrine mechanism. In hDPSCs, exogenous SCUBE3 promoted cell proliferation and migration via TGF-β signalling and accelerated odontoblastic differentiation via BMP2 signalling. In the semi-orthotopic animal experiments, we found that SCUBE3 pre-treatment-induced polarized odontoblast-like cells attached to the dental walls and had better angiogenesis performance.

CONCLUSION

SCUBE3 protein expression is transferred from the epithelium to mesenchyme during embryonic development. The function of epithelium-derived SCUBE3 in Mes, including proliferation, migration, and polarized odontoblastic differentiation, and their mechanisms are elaborated for the first time. These findings shed light on exogenous SCUBE3 application in clinic dental pulp regeneration.

Construction of a novel choline metabolism-related signature to predict prognosis, immune landscape, and chemotherapy response in colon adenocarcinoma

BACKGROUND

Colon adenocarcinoma (COAD) is a common digestive system malignancy with high mortality and poor prognosis. Accumulating evidence indicates that choline metabolism is closely related to tumorigenesis and development. However, the efficacy of choline metabolism-related signature in predicting patient prognosis, immune microenvironment and chemotherapy response has not been fully clarified.

METHODS

Choline metabolism-related differentially expressed genes (DEGs) between normal and COAD tissues were screened using datasets from The Cancer Genome Atlas (TCGA), Kyoto Encyclopedia of Genes and Genomes (KEGG), AmiGO2 and Reactome Pathway databases. Two choline metabolism-related genes (CHKB and PEMT) were identified by univariate and multivariate Cox regression analyses. TCGA-COAD was the training cohort, and GSE17536 was the validation cohort. Patients in the high- and low-risk groups were distinguished according to the optimal cutoff value of the risk score. A nomogram was used to assess the prognostic accuracy of the choline metabolism-related signature. Calibration curves, decision curve analysis (DCA), and clinical impact curve (CIC) were used to improve the clinical applicability of the prognostic signature. Gene Ontology (GO) and KEGG pathway enrichment analyses of DEGs in the high- and low-risk groups were performed. KEGG cluster analysis was conducted by the KOBAS-i database. The distribution and expression of CHKB and PEMT in various types of immune cells were analyzed based on single-cell RNA sequencing (scRNA-seq). The CIBERSORT and ESTIMATE algorithms evaluated tumor immune cell infiltration in the high- and low-risk groups. Evaluation of the half maximal inhibitory concentration (IC50) of common chemotherapeutic drugs based on the choline metabolism-related signature was performed. Small molecule compounds were predicted using the Connectivity Map (CMap) database. Molecular docking is used to simulate the binding conformation of small molecule compounds and key targets. By immunohistochemistry (IHC), Western blot, quantitative reverse transcription-polymerase chain reaction (qRT-PCR) experiments, the expression levels of CHKB and PEMT in human, mouse, and cell lines were detected.

RESULTS

We constructed and validated a choline metabolism-related signature containing two genes (CHKB and PEMT). The overall survival (OS) of patients in the high-risk group was significantly worse than that of patients in the low-risk group. The nomogram could effectively and accurately predict the OS of COAD patients at 1, 3, and 5 years. The DCA curve and CIC demonstrate the clinical utility of the nomogram. scRNA-seq showed that CHKB was mainly distributed in endothelial cells, while PEMT was mainly distributed in CD4+ T cells and CD8+ T cells. In addition, multiple types of immune cells expressing CHKB and PEMT differed significantly. There were significant differences in the immune microenvironment, immune checkpoint expression and chemotherapy response between the two risk groups. In addition, we screened five potential small molecule drugs that targeted treatment for COAD. Finally, the results of IHC, Western blot, and qRT-PCR consistently showed that the expression of CHKB in human, mouse, and cell lines was elevated in normal samples, while PMET showed the opposite trend.

CONCLUSION

In conclusion, we constructed a choline metabolism-related signature in COAD and revealed its potential application value in predicting the prognosis, immune microenvironment, and chemotherapy response of patients, which may lay an important theoretical basis for future personalized precision therapy.

Odontogenesis by Endocytosis of Peptide Embedding Bioactive Glass Composite

Limited therapeutic options are available for treating deep caries. Those materials with potential of a dual effect to remineralize hard tissue and regenerate defective dentin tissues could be used as a new strategy for deep caries treatment. However, the application of the single component remains a challenge mainly because they lack calcium and phosphorus, are easily degraded, and are difficult to retain in the intricate body fluid environment. Considering the abundant source of calcium and phosphorus as well as the delivery performance of mesoporous bioactive glass (MBG), an amelogenin-derived peptide (QP5), which has a significant role in hard tissue remineralization, was loaded to fabricate a novel composite. After the synthesis of highly ordered MBG using a sol-gel method, the QP5 peptide was loaded increasingly by its extensive porous structure and enhanced electrostatic absorption. When used in an acidic environment, the MBG/QP5 composite presented pH-responsiveness, releasing therapeutic ions and functional peptides in a sequential cascade, and eventually adjusted the pH to a neutral state. The composite was internalized by dental pulp cells through a clathrin-mediated pathway and influenced by cell membrane lipid raft regulation. It could be also transported through the macro-pinocytotic pathway. Compared to the single treatment of peptide QP5 in 48 h, the composite facilitated a higher level of retention of the intracellular peptides. The composite further promoted migration and odontogenesis of dental pulp cells, including the improved activity of alkaline phosphatase, increased formation of mineralized nodules, and upregulated expression of mineralization-related genes compared to using MBG or QP5 alone. The composite further induced the dentin-like layer in a rat pulp capping model. The results suggested that this intelligent material with pH-responsiveness provides a promising alternative treatment method for biomimetic restoration of deep caries.

Tubular dentin formation by TGF-β/BMP signaling in dental epithelial cells

OBJECTIVES

This study aimed to identify formation of tubular dentin induced by Transforming growth factor-β (TGF-β) and bone morphogenic protein (BMP) signaling pathway in dental epithelial cells.

METHODS

We collected conditioned medium (CM) of rTGF-β1/rBMP-2 treated HAT-7 and treated to MDPC-23 cells. The expression levels of odontoblast differentiation markers, KLF4, DMP1, and DSP were evaluated by real-time PCR and western blot analysis. To evaluate whether CM of rTGF-β1/rBMP-2 induces tubular dentin formation, we made a beagle dog tooth defect model.

RESULTS

Here, we show that Cpne7 is regulated by Smad4-dependent TGF-β1/BMP2 signaling pathway in dental epithelial cells. CM of rTGF-β1/rBMP-2 treated HAT-7, or rCPNE7 raises the expression levels of KLF4, DMP1, and DSP in MDPC-23 cells. When rTGF-β1 or rBMP-2 is directly treated to MDPC-23 cells, however, expression levels of Cpne7-regulated genes remain unchanged. In a beagle dog defect model, application of rTGF-β1/BMP2 treated CM resulted in tubular tertiary dentin mixed with osteodentin at cavity-prepared sites, while rTGF-β1 group exhibited homogenous osteodentin.

CONCLUSIONS

Taken together, Smad4-dependent TGF-β1/BMP2 signaling regulates Cpne7 in dental epithelial cells, and CPNE7 protein secreted from pre-ameloblasts mediates odontoblast differentiation via epithelial-mesenchymal interaction.

Exploration of the role of the subodontoblastic layer in odontoblast-like cell differentiation after tooth drilling using Nestin-enhanced green fluorescent protein transgenic mice

OBJECTIVES

Original odontoblasts and regenerated odontoblast-like cells (OBLCs) may differently regulate Nestin expression. This study aimed to investigate the role of the subodontoblastic layer (SOBL) using green fluorescent protein (GFP) reactivity in the process of OBLC differentiation after tooth drilling in Nestin-enhanced GFP transgenic mice.

METHODS

A groove-shaped cavity was prepared on the mesial surface of the maxillary first molars of 5- or 6-week-old mice under deep anesthesia. Immunohistochemical staining for Nestin and GFP and Nestin in situ hybridization were conducted on the sections obtained at 1-14 days postoperative.

RESULTS

Odontoblasts showed intense endogenous Nestin protein and mRNA expression, whereas the coronal SOBL cells showed a Nestin-GFP-positive reaction in the control groups. The injured odontoblasts had significantly decreased Nestin immunoreactivity as well as decreased expression of Nestin mRNA 1-2 days after the injury; subsequently, newly differentiated OBLCs were arranged along the pulp-dentin border, with significantly increased Nestin expression as well as increased expression of Nestin mRNA on days 3-5 to form reparative dentin. Nestin-GFP-positive cells at the pulp-dentin border significantly increased in number on days 1 and 2. GFP(+)/Nestin(+) and GFP(-)/Nestin(+) cells were intermingled in the newly differentiated OBLCs.

CONCLUSIONS

The commitment of Nestin-GFP-positive cells into Nestin-positive OBLCs suggests that the restriction of endogenous Nestin protein and mRNA expression in the static SOBL cells was removed by exogenous stimuli, resulting in their migration along the pulp-dentin border and their differentiation into OBLCs.

Upregulation of CPNE7 in mesenchymal stromal cells promotes oral squamous cell carcinoma metastasis through the NF-κB pathway

A remarkable shift in Mesenchymal stromal cells (MSCs) plays an important role in cancer metastasis, but the molecular mechanism is still unclear. CPNE7, a calcium-dependent phospholipid-binding protein, mediates signal transduction and metastasis in many tumours. Here, we demonstrated that MSCs derived from OSCC (OSCC-MSCs) promoted the metastasis of OSCC cells by transwell assay and animal models through epithelial to mesenchymal transition (EMT) (p < 0.05). RNA-sequencing, ELISA, neutralizing antibody and CXCR2 inhibitor assay confirmed that CXCL8 secreted by OSCC-MSCs was associated with the upregulated expression of CPNE7 by immunohistochemical and western blotting (p < 0.05). This is mechanistically linked to the activation of CPNE7 to NF-κB pathway-induced metastasis, including phosphorylated p65 and IκBa. CPNE7 silencing inhibited metastatic abilities and the expression of CXCL8, phosphorylated p65, IκBa, and p65 nuclear translocation by western blotting and immunofluorescence, while CPNE7 overexpression markedly promoted these events (p < 0.05). We also identified that Nucleolin could be bind CPNE7 and IκBa by co-immunoprecipitation. Together, our results suggest that upregulation of CPNE7 in MSCs interacted with surface receptor -Nucleolin and then combined with IκBa to promoted phosphorylated IκBa and p65 nuclear translocation to active NF-κB pathway, and then regulates CXCL8 secretion to promote the metastasis of OSCC cells. Therefore, CPNE7 in MSCs could be promising therapeutic targets in OSCC.

Mesenchymal stem cells: A comprehensive methods for odontoblastic induction

BACKGROUND

In the area of oral and maxillofacial surgery, regenerative endodontics aims to present alternative options to conventional treatment strategies. With continuous advances in regenerative medicine, the source of cells used for pulp tissue regeneration is not only limited to mesenchymal stem cells as the non-mesenchymal stem cells have shown capabilities too. In this review, we are systematically assessing the recent findings on odontoblastic differentiation induction with scaffold and non-scaffold approaches.

METHODS

A comprehensive search was conducted in Pubmed, and Scopus, and relevant studies published between 2015 and 2020 were selected following the PRISMA guideline. The main inclusion criteria were that articles must be revolving on method for osteoblast differentiation in vitro study. Therefore, in vivo and human or animal clinical studies were excluded. The search outcomes identified all articles containing the word "odontoblast", "differentiation", and "mesenchymal stem cell".

RESULTS

The literature search identified 99 related studies, but only 11 articles met the inclusion criteria. These include 5 odontoblastic differentiation induction with scaffold, 6 inductions without scaffolds. The data collected were characterised into two main categories: type of cells undergo odontoblastic differentiation, and odontoblastic differentiation techniques using scaffolds or non-scaffold.

CONCLUSION

Based on the data analysis, the scaffold-based odontoblastic induction method seems to be a better option compared to the non-scaffold method. In addition of that, the combination of growth factors in scaffold-based methods could possibly enhance the differentiation. Thus, further detailed studies are still required to understand the mechanism and the way to enhance odontoblastic differentiation.

Dental-Derived Mesenchymal Stem Cells: State of the Art

Mesenchymal stem cells (MSCs) could be identified in mammalian teeth. Currently, dental-derived MSCs (DMSCs) has become a collective term for all the MSCs isolated from dental pulp, periodontal ligament, dental follicle, apical papilla, and even gingiva. These DMSCs possess similar multipotent potential as bone marrow-derived MSCs, including differentiation into cells that have the characteristics of odontoblasts, cementoblasts, osteoblasts, chondrocytes, myocytes, epithelial cells, neural cells, hepatocytes, and adipocytes. Besides, DMSCs also have powerful immunomodulatory functions, which enable them to orchestrate the surrounding immune microenvironment. These properties enable DMSCs to have a promising approach in injury repair, tissue regeneration, and treatment of various diseases. This review outlines the most recent advances in DMSCs' functions and applications and enlightens how these advances are paving the path for DMSC-based therapies.

CPNE7-Induced Autophagy Restores the Physiological Function of Mature Odontoblasts

Dentin, which composes most of the tooth structure, is formed by odontoblasts, long-lived post-mitotic cells maintained throughout the entire life of the tooth. In mature odontoblasts, however, cellular activity is significantly weakened. Therefore, it is important to augment the cellular activity of mature odontoblasts to regenerate physiological dentin; however, no molecule regulating the cellular activity of mature odontoblasts has yet been identified. Here, we suggest that copine-7 (CPNE7) can reactivate the lost functions of mature odontoblasts by inducing autophagy. CPNE7 was observed to elevate the expression of microtubule-associated protein light chain 3-II (LC3-II), an autophagy marker, and autophagosome formation in the pre-odontoblast and mature odontoblast stages of human dental pulp cells. CPNE7-induced autophagy upregulated DSP and DMP-1, odontoblast differentiation and mineralization markers, and augmented dentin formation in mature odontoblasts. Furthermore, CPNE7 also upregulated NESTIN and TAU, which are expressed in the physiological odontoblast process, and stimulated the elongation of the odontoblast process by inducing autophagy. Moreover, lipofuscin, which progressively accumulates in long-lived post-mitotic cells and hinders their proper functions, was observed to be removed in recombinant CPNE7-treated mature odontoblasts. Thus, CPNE7-induced autophagy reactivated the function of mature odontoblasts and promoted the formation of physiological dentin in vivo. On the other hand, the well-known autophagy inducer, rapamycin, promoted odontoblast differentiation in pre-odontoblasts but did not properly reactivate the function of mature odontoblasts. These findings provide evidence that CPNE7 functionally reactivates mature odontoblasts and introduce its potential for dentinal loss-targeted clinical applications.

Comparison and Contrast of Bone and Dentin in Genetic Disorder, Morphology and Regeneration: A Review

The bone and dentin have distinct healing processes. The healing process of bones is regenerative, as newly formed tissues are morphologically and functionally similar to the original bone structures. In contrast, the healing process of dentin is reparative due to its failure to replicate some of its key morphological features. In this review, we compare and contrast the healing processes of bone and dentin. We describe how distinct morphological and physiological structures of the 2 tissues translate into different signaling molecules, growth factors, and matrix protein secretion.

Diagnostic and prognostic values of AKR1C3 and AKR1D1 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common histological type of primary liver cancer and the majority of patients are diagnosed at an advanced stage and have a poor prognosis. AKR1C3 (Aldo-keto reductase family 1 member C3) and AKR1D1 (Aldo-keto reductase family 1 member D1) catalyze the conversion of aldehydes and ketones to alcohols and play crucial roles in multiple cancers. However, the functions of AKR1C3 and AKR1D1 in HCC remain unclear. In our study, data from the public databases were selected as training and validation sets, then 76 HCC patients in our center were chosen as a test set. Bioinformatics methods suggested AKR1C3 was overexpressed in HCC and AKR1D1 was down-regulated. The receiver operating characteristic curve (ROC) analysis was performed and the area under curve (AUC) values of AKR1C3 and AKR1D1 were above 0.7 (0.948, 0.836, respectively). Also, the high expression of AKR1C3 and low expression of AKR1D1 predicted poor prognosis and short median survival time. Then, the knockdown of AKR1C3 and overexpression of AKR1D1 in HCC cells were achieved with lentivirus. And both decreased cell proliferation, restrained cell viability, and inhibited tumorigenesis. Moreover, the gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were conducted and the results showed that AKR1C3 and AKR1D1 might participate in the MAPK/ERK and androgen receptor (AR) signaling pathway. Furthermore, the AR and phosphorylated ERK1/2 were significantly reduced after the suppression of AKR1C3 or overexpression of AKR1D1. Collectively, AKR1C3 and AKR1D1 might serve as candidate diagnostic and prognostic biomarkers for HCC and provide potential targets for HCC treatment.

TVH-19, a synthetic peptide, induces mineralization of dental pulp cells in vitro and formation of tertiary dentin in vivo

Functional peptides derived from the active domains of odontogenesis-related proteins have been reported to promote dental hard tissue regeneration. The purpose of this study was to evaluate the effects of an artificially synthesized peptide, TVH-19, on odontoblast differentiation and tertiary dentin formation in indirect pulp capping (IPC) using in vitro and in vivo experiments. TVH-19 did not exhibit any effect on the proliferation of human dental pulp cells (hDPCs) but significantly promoted cell migration, compared with the control (p < 0.05). TVH-19-treated hDPCs showed significantly higher alkaline phosphatase (ALP) activity and stronger alizarin red staining (ARS) reactivity than the control group (p < 0.05). TVH-19 also upregulated the mRNA and protein expression levels of odontogenic genes. After generating IPC in rats, the samples of teeth were studied using micro-computed tomography (Micro-CT), hematoxylin & eosin (HE) staining, and immunohistochemical staining to investigate the functions of TVH-19. The in vivo results showed that TVH-19 induced the formation of tertiary dentin, and reduced inflammation and apoptosis, as evident from the downregulated expression of interleukin 6 (IL-6) and cleaved-Caspase-3 (CL-CASP3). Overall, the results of our study suggest that TVH-19 induces differentiation of hDPCs, promotes tertiary dentin formation, relieves inflammation, and reduces apoptosis, indicating the potential applications of TVH-19 in IPC.

Tubular Dentin Regeneration Using a CPNE7-Derived Functional Peptide

We aim to examine the effects of a newly developed peptide derived from CPNE7 (Cpne7-DP) in tertiary dentin formation and peritubular space occlusion, and comprehensively evaluate its potential as a bioactive therapeutic agent. Human dental pulp cells (HDPCs) and a mouse pre-odontoblast cell line, MDPC-23, were chosen for in vitro studies to characterize lineage-specific cell responses after Cpne7-DP treatment. Whether Cpne7-DP reproduces the dentin regenerative potential of CPNE7 was tested using a beagle dog model by generating dentinal defects of various degrees in vivo. Peritubular space occlusion was further examined by scanning electron microscopy and microleakage test, while overall mineralization capacity of Cpne7-DP was tested ex vivo. CPNE7 promotes tubular dentin formation under both shallow and deep dentinal defects, and the functional peptide Cpne7-DP induces odontoblast-like differentiation in vitro, mineralization ex vivo, and tubular dentin formation in in vivo beagle dog dentin exposure and pulp exposure models. Moreover, Cpne7-DP leads to peritubular space occlusion and maintains stability under different conditions. We show that CPNE7 and its derivative functional peptide Cpne7-DP promotes dentin regeneration in dentinal defects of various degrees and that the regenerated hard tissue demonstrates the characteristics of true dentin. Limitations of the current dental materials including post-operative hypersensitivity make biological repair of dentin a field of growing interest. Here, we suggest that the dual functions of Cpne7-DP in tubular dentin formation and peritubular space occlusion are promising for the treatment of dentinal loss and sensitivity.

Pulp/Dentin Regeneration: It Should Be Complicated

Stem cell-mediated regenerative endodontics has reached the human clinical trial phase; however, many issues still exist that prevent such technology to be a widely used clinical practice. These issues are not straightforward and are complicated. They should be because pulp regeneration is dealing with a small dead-end space. In addition, when regeneration is needed, the space is often heavily infected. The true standard of pulp regeneration should be everything except generation of some fibrous connective tissue and amorphous mineral deposit. As of now, we are still far short of reaching the standard of complete vascularized and innervated pulp regeneration with newly formed tubular dentin in all types of teeth. Thus, we need to go back to the bench and use established animal models or create new animal models to tackle those issues. This article will address several key issues including the possibility of pulp regeneration in small canals of molar teeth by enhancing the neovascularization, and whether the organized tubular dentin can be generated on the canal walls. Data from our semi-orthotopic tooth fragment mouse model have shown that complete pulp regeneration using dental pulp stem cells (DPSCs) in small canal has been inconsistent because of limited blood supply. This inconsistency is similar in our orthotopic miniature swine model, although in some cases vascularized pulp-like tissue can be formed throughout the canal space after DPSC transplantation. Furthermore, no tubular dentin was observed in the orthotopic pulp regeneration, despite the fact that DPSCs have the capacity to generate some tubular dentin-like structure in the hydroxyapatite/tricalcium phosphate-mediated ectopic pulp/dentin formation model in mice. Potential strategies to be tested to address these regeneration issues are discussed herein.

Different Responsiveness of Alveolar Bone and Long Bone to Epithelial-Mesenchymal Interaction-Related Factor

Alveolar bone is both morphologically and functionally different from other bones of the axial or peripheral skeleton. Because of its sensitive nature to external stimuli including mechanical stress, bone loss stimuli, and medication-related osteonecrosis of the jaw, alveolar bone rendering is seen as an important factor in various dental surgical processes. Although multiple studies have validated the response of long bone to various factors, how alveolar bone responds to functional stimuli still needs further clarification. To examine the characteristics of bone in vitro, we isolated cells from alveolar, femur, and tibia bone tissue. Although primary cultured mouse alveolar bone-derived cells (mABDCs) and mouse long bone-derived cells (mLBDCs) exhibited similar osteoblastic characteristics, morphology, and proliferation rates, both showed distinct expression of neural crest (NC) and epithelial-mesenchymal interaction (EMI)-related genes. Furthermore, they showed significantly different mineralization rates. RNA sequencing data demonstrated distinct transcriptome profiles of alveolar bone and long bone. Osteogenic, NC-, and EMI-related genes showed distinct expression between mABDCs and mLBDCs. When the gene expression patterns during osteogenic differentiation were analyzed, excluding several osteogenic genes, NC- and EMI-related genes showed different expression patterns. Among EMI-related proteins, BMP4 elevated the expression levels of osteogenic genes, Msx2, Dlx5, and Bmp2 the most, more noticeably in mABDCs than in mLBDCs during osteogenic differentiation. In in vivo models, the BMP4-treated mABDC group showed massive bone formation and maturation as opposed to its counterpart. Bone sialoprotein expression was also validated in calcified tissues. Overall, our data suggest that alveolar bone and long bone have different responsiveness to EMI by distinct gene regulation. In particular, BMP4 has critical bone formation effects on alveolar bone, but not on long bone. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

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

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

GATA Binding Protein 4 Regulates Tooth Root Dentin Development via FBP1

Tooth development is a complex process that is regulated precisely by several signalling pathways and transcription factors. GATA-binding protein 4 (GATA4) is a DNA binding transcription factor, and our previous study showed that GATA4 is a novel regulator of root development. However, it remains unclear whether GATA4 is necessary for odontoblast differentiation and dentin formation. Here, we evaluated the phenotypic changes of Wnt1-Cre;GATA4^fl/fl mice. The mutant mice showed defective dentin and short root deformity. The odontoblasts lost polarity instead of exhibiting a shorter height and flattened morphology. Moreover, the expression of several molecules, such as DSPP, COL-1, DCN, and PCNA, were downregulated during mutant tooth development. In vivo, we injected lentivirus to overexpress GATA4 in mice root. The dentin formation and the expression of odonto/osteogenic markers (DSPP, COL-1, DCN) were enhanced in the GATA4 overexpression group. During the in vitro study, the ability of proliferation, migration and odonto/osteogenic differentiation was declined by GATA4 knockdown approach in human dental pulp stem cells (DPSCs). The expression of odonto/osteogenic markers (DSPP, BMP4, RUNX2, OSX, OPN, OCN) was reduced in the shGATA4 group, while overexpressing GATA4 in DPSCs promoted mineralization. Furthermore, an immunoprecipitation-mass spectrometry procedure was used to confirm the interaction between GATA4 and Fructose-1, 6-bisphosphatase 1 (FBP1). We used gain and lose-of-function to delineated the role of GATA4 in regulating FBP1 expression. Knocking down GATA4 in DPSCs resulted in decreased glucose consumption and lactate production. We used small hairpin RNA targeting FBP1 to reduce the expression of FBP1 in DPSCs, which significantly increased glucose consumption and lactate production. Together, the results suggested that GATA4 is important for root formation and odontoblast polarity, as it promotes the growth and differentiation of dental mesenchymal cells around the root and affects the glucose metabolism of DPSCs via the negative regulation of FBP1.

Molecular Mechanisms of Dentine-Pulp Complex Response Induced by Microbiome of Deep Caries

Deep caries progress is associated with tertiary dentin formation and additional reversible or irreversible dental pulp inflammation. It seems that some particular signs of pain in irreversible pulpitis are associated to a particular caries microflora. Streptococcus species, Parvimonas micra and Dialister invisus are prevailing in cases of throbbing pain while Streptococcus mutans is incriminated in sensitivity to vertical percussion of tooth. Continuous pain is thought to be the clinical outcome of Lactobacillus implication. A better understanding of molecular signals and mechanisms induced by microbiome of deep caries that orchestrate the modulation of dental pulp complex response toward tertiary dentinogenesis or pulp inflammation it is supposed to improve diagnosis and conservative therapies of vital pulp.

Dental stem cells in tooth repair: A systematic review

Background: Dental stem cells (DSCs) are self-renewable teeth cells, which help maintain or develop oral tissues. These cells can differentiate into odontoblasts, adipocytes, cementoblast-like cells, osteoblasts, or chondroblasts and form dentin/pulp. This systematic review aimed to summarize the current evidence regarding the role of these cells in dental pulp regeneration. Methods: We searched the following databases: PubMed, Cochrane Library, MEDLINE, SCOPUS, ScienceDirect, and Web of Science using relevant keywords. Case reports and non-English studies were excluded. We included all studies using dental stem cells in tooth repair whether in vivo or in vitro studies. Results: Dental pulp stem cell (DPSCs) is the most common type of cell. Most stem cells are incorporated and implanted into the root canals in different scaffold forms. Some experiments combine growth factors such as TDM, BMP, and G-CSF with stem cells to improve the results. The transplant of DPSCs and stem cells from apical papilla (SCAPs) was found to be associated with pulp-like recovery, efficient revascularization, enhanced chondrogenesis, and direct vascular supply of regenerated tissue. Conclusion: The current evidence suggests that DPSCs, stem cells from human exfoliated deciduous teeth, and SCAPs are capable of providing sufficient pulp regeneration and vascularization. For the development of the dental repair field, it is important to screen for more effective stem cells, dentine releasing therapies, good biomimicry scaffolds, and good histological markers.

Dentin Matrix Protein 1 Compensates for Lack of Osteopontin in Regulating Odontoblastlike Cell Differentiation after Tooth Injury in Mice

INTRODUCTION

Although dentin matrix protein 1 (DMP1) and osteopontin (OPN) act as substrates and signaling molecules for odontoblastlike cell differentiation after tooth injury, the mutual interaction between these proteins in the mechanism of odontoblastlike cell differentiation remains to be clarified. This study aimed to elucidate the role of DMP1 and OPN in regulating odontoblastlike cell differentiation after tooth injury.

METHODS

A groove-shaped cavity was prepared on the mesial surface of the upper first molars in wild-type and Opn knockout (KO) mice. The demineralized paraffin sections were processed for immunohistochemistry for nestin and DMP1 and in situ hybridization for Dmp1. For the in vitro assay, the experiments of organ culture for evaluating dentin-pulp complex regeneration using small interfering RNA treatment were performed.

RESULTS

Once preexisting odontoblasts died, nestin-positive newly differentiated odontoblastlike cells were arranged along the pulp-dentin border and began to express DMP1/Dmp1. In Opn KO mice, the expression of DMP1/Dmp1 was up-regulated compared with that of wild-type mice. The in vitro assay showed that the gene suppression of Dmp1 by small interfering RNA showed a tendency to decrease the differentiation rate of odontoblastlike cells from 70.1% to 52.2% in wild-type teeth. In addition, the suppression of Dmp1 in Opn KO teeth tended to lead to the inhibition of odontoblastlike cell differentiation.

CONCLUSIONS

These results suggest that the expression of Dmp1 is up-regulated in Opn KO mice both in vivo and in vitro, and DMP1 compensates for the lack of OPN in regulating odontoblastlike cell differentiation after tooth injury.

The effect of CPNE7 on periodontal regeneration

Introduction: Preameloblast-conditioned medium (PA-CM), as a mixture of dental epithelium-derived factors, has been reported to regenerate dentin and periodontal tissues in vitro and in vivo. The aim of this study was to investigate the biological effect of Cpne7 on the proliferation, migration, and cementoblast differentiation of periodontal cells in vitro, and on the regeneration of periodontal tissue using periodontal defect model with canine in vivo. Materials and methods: The effect of Cpne7 on cell proliferation, migration, and cementoblast differentiation of periodontal cells were evaluated in vitro. A periodontal defect canine model was designed and the defects were divided into five groups: Group 1: No treatment (negative control), Group 2: Collagen carrier only, Group 3: PA-CM with collagen carrier (positive control), Group 4: PA-CM + CPNE7 Antibody (Ab) with collagen carrier, and Group 5: recombinant CPNE7 (rCPNE7) protein with collagen carrier. Results: Cpne7 was expressed in HERS cells and periodontal ligament (PDL) fibers. By real-time PCR, Cpne7 increased expression of Cap compared to the control. In the periodontal defect canine model, rCPNE7 or PA-CM regenerated periodontal complex, and the arrangement of the newly formed PDL-like fibers were perpendicular to the newly formed cementum and alveolar bone like Sharpey's fibers in natural teeth, while PA-CM + CPNE7 Ab showed irregular arrangement of the newly formed PDL-like fibers compared to the rCPNE7 or PA-CM group. Conclusion: These findings suggest that Cpne7 may have a functional role in periodontal regeneration by supporting periodontal cell attachment to cementum and facilitating physiological arrangement of PDL fibers.

CPNE7 Induces Biological Dentin Sealing in a Dentin Hypersensitivity Model

Dentin hypersensitivity commonly occurs due to opened dentinal tubules for many reasons. In our previous study, copine 7 (CPNE7) could induce dentin formation for an indirect pulp-capping model in vivo. This study aims to investigate the formation of tertiary dentin when CPNE7 is applied to intentionally exposed dentin with nothing over it in vivo, whether it affects microleakage of the teeth, and the penetration ability of CPNE7 molecules through dentinal tubules in vitro. Cervical dentin areas of 6 maxillary incisors of 5 beagles were exposed to a class V–like lesion, and 1 side of 3 maxillary incisors was adapted with recombinant CPNE7 protein for 5 min as the experimental group. The other side was the control group, and there was no treatment of ethylenediaminetetraacetic acid (EDTA) and CPNE7 after preparation. The defects were exposed without any restorations, and all beagles were sacrificed after 4 wk. The fluid penetration of exposed dentin areas was investigated by a microleakage-testing device and confocal laser scanning microscope. Tertiary dentin formation was confirmed with histological scanning electronic microscopic analysis. Tertiary dentin formation reduces dentinal fluid flow due to occluded tubules or discontinuity with primary or secondary dentin. The in vivo hypersensitivity model with the anterior teeth of beagle dogs showed newly formed tertiary dentin at the dentin-pulp boundary in recombinant CPNE7–treated teeth when compared with the untreated control group in histologic analysis. Scanning electronic microscopic analysis revealed occluded sites with mineral deposition of intratubular dentin. In the permeability test, the mean microleakage value of the CPNE7-treated group was significantly lower than that of the control group ( P < 0.05). The tubular penetration of rhodamine B–combined CPNE7 was confirmed under confocal laser scanning microscope. CPNE7 induces formation of tertiary dentin through shallowly exposed dentinal tubules, which decreases dentin permeability.

A Regenerative Endodontic Approach in Mature Ferret Teeth Using Rodent Preameloblast-conditioned Medium

BACKGROUND

This study evaluated the effectiveness of a regenerative endodontic approach to regenerate the pulp tissue in mature teeth of ferret. The presence of odontoblast-like cells in the newly-formed tissue of teeth treated with or without preameloblast-conditioned medium was evaluated based on morphological criteria.

MATERIALS AND METHODS

Twenty-four canines from six ferrets were treated. The pulp was removed, and the apical foramen was enlarged. After inducing the formation of a blood clot, a collagen sponge with or without preameloblast-conditioned medium was placed underneath the cementoenamel junction. The samples were analyzed at the eighth week of follow-up.

RESULTS

Vascularized connective tissue was observed in 50% of teeth, without differences between groups. The tissue occupied the apical third of the root canals. Odontoblast-like cells were not observed in any group.

CONCLUSION

Revitalization of mature teeth is possible, at least in the apical third of the root canal. Further experimental research is needed to produce more reliable outcomes.

Animal Models for Stem Cell-Based Pulp Regeneration: Foundation for Human Clinical Applications

IMPACT STATEMENT

Animal models are essential for tissue regeneration studies. This review summarizes and discusses the small and large animal models, including mouse, ferret, dog, and miniswine that have been utilized to experiment and to demonstrate stem cell-mediated dental pulp tissue regeneration. We describe the models based on the location where the tissue regeneration is tested-either ectopic, semiorthotopic, or orthotopic. Developing and utilizing optimal animal models for both mechanistic and translational studies of pulp regeneration are of critical importance to advance this field.

Cell polarization: From epithelial cells to odontoblasts

Cell polarity identifies the asymmetry of a cell. Various types of cells, including odontoblasts and epithelial cells, polarize to fulfil their destined functions. Odontoblast polarization is a prerequisite and fundamental step for tooth development and tubular dentin formation. Current knowledge of odontoblast polarization, however, is very limited, which greatly impedes the development of novel approaches for regenerative endodontics. Compared to odontoblasts, epithelial cell polarization has been extensively studied over the last several decades. The knowledge obtained from epithelia polarization has been found applicable to other cell types, which is particularly useful considering the remarkable similarities of the morphological and compositional features between polarized odontoblasts and epithelia. In this review, we first discuss the characteristics, the key regulatory factors, and the process of epithelial polarity. Next, we compare the known facts of odontoblast polarization with epithelial cells. Lastly, we clarify knowledge gaps in odontoblast polarization and propose the directions for future research to fill the gaps, leading to the advancement of regenerative endodontics.

Effect of preameloblast-conditioned medium and CPNE7 on root surfaces in dogs: a histologic and histomorphometric evaluation

Preameloblast-conditioned medium (PACM) has been reported as a potent dentin regenerative material, but its effects as a mixture on periodontal regeneration and the role of CPNE7 in PACM are not known. The purpose of this study is to evaluate the histologic and histomorphometric effects of preameloblast-conditioned medium (PACM) and CPNE7 on periodontal tissue healing in dogs. Seventy-two mandibular premolar roots from ten dogs were extracted and randomly divided into six groups (n = 12 each): (1) positive control group; (2) negative control group; (3) cementum-removed and PACM-treated group; (4) cementum-preserved and PACM-treated group; (5) CPNE7-inactivated PACM-treated group; and (6) recombinant CPNE7-treated group. The extracted roots were replanted into extraction sockets for 4 and 8 weeks and analyzed histologically. Most of the root surfaces in the negative control group showed ankylosis; and those in the experimental groups showed newly formed PDL-like and cementum-like tissues. Histomorphometric analysis of horizontal sections showed that the mean length of the PDL on the roots of the positive controls was similar to those in cementum-removed or -preserved and PACM-treated group at 8 weeks (p = 1.08). Sagittal sections showed that the mean length of the new cementum on the roots in cementum-removed and PACM-treated group was significantly greater than that in CPNE7-inactivated PACM-treated group (p = 0.037). The mean length of the newly formed PDL on the roots in CPNE7- inactivated PACM-treated and rCPNE7-treated groups was significantly greater than that in the negative controls at 8 weeks (p = 0.037, p = 0.036). The use of PACM and CPNE7 in tooth replantation resulted in increased PDL and cementum formation, suggesting the beneficial role of PACM and CPNE7 in periodontal tissue healing.

A Miniature Swine Model for Stem Cell-Based De Novo Regeneration of Dental Pulp and Dentin-Like Tissue

The goal of this study was to establish mini-swine as a large animal model for stem cell-based pulp regeneration studies. Swine dental pulp stem cells (sDPSCs) were isolated from mini-swine and characterized in vitro. For in vivo studies, we first employed both ectopic and semi-orthotopic study models using severe combined immunodeficiency mice. One is hydroxyapatite-tricalcium phosphate (HA/TCP) model for pulp-dentin complex formation, and the other is tooth fragment model for complete pulp regeneration with new dentin depositing along the canal walls. We found that sDPSCs are similar to their human counterparts exhibiting mesenchymal stem cell characteristics with ability to form colony forming unit-fibroblastic and odontogenic differentiation potential. sDPSCs formed pulp-dentin complex in the HA/TCP model and showed pulp regeneration capacity in the tooth fragment model. We then tested orthotopic pulp regeneration on mini-swine including the use of multi-rooted teeth. Using autologous sDPSCs carried by hydrogel and transplanted into the mini-swine root canal space, we observed regeneration of vascularized pulp-like tissue with a layer of newly deposited dentin-like (rD) tissue or osteodentin along the canal walls. In some cases, dentin bridge-like structure was observed. Immunohistochemical analysis detected the expression of nestin, dentin sialophosphoprotein, dentin matrix protein 1, and bone sialoprotein in odontoblast-like cells lining against the produced rD. We also tested the use of allogeneic sDPSCs for the same procedures. Similar findings were observed in allogeneic transplantation. This study is the first to show an establishment of mini-swine as a suitable large animal model utilizing multi-rooted teeth for further cell-based pulp regeneration studies.

Dentin sialophosphoprotein expression in enamel is regulated by Copine-7, a preameloblast-derived factor

OBJECTIVE

Dentin sialophosphoprotein (Dspp) is expressed in odontoblasts and transiently expressed in early ameloblasts. However, the origin of Dspp in ameloblasts remains unclear. Our previous studies demonstrated that copine-7 (CPNE7), a molecule that is secreted by the dental epithelium, is expressed in early ameloblasts and is then translocated to differentiating odontoblasts; its expression levels correlate with odontoblast differentiation under the control of Dspp expression. The objective of this study is to figure out the relationship between CPNE7 and Dspp during amelogenesis.

DESIGN

The gene expression patterns of CPNE7 and dentin sialoprotein (DSP) were examined by immunohistochemistry, western blot analysis, and real-time polymerase chain reaction. The effects of CPNE7 on Dspp regulation were investigated using luciferase and chromatin immunoprecipitation assays in ameloblastic HAT-7 cells.

RESULTS

The gene expression pattern of Cpne7 was similar to that of Dspp during ameloblast differentiation. Moreover, Gene expression omnibus profiles indicated that there is a close correlation between Cpne7 and Dspp expression in various normal human tissues. We also confirmed the effects of CPNE7 on the induction of Dspp in ameloblastic HAT-7 cells. Cpne7 overexpression promoted Dspp expression, whereas Dspp expression was down-regulated by Cpne7 inactivation.

CONCLUSIONS

These results suggest that the expression of Dspp in early amelogenesis is linked to CPNE7, a preameloblast-derived factor.

Copine-7 binds to the cell surface receptor, nucleolin, and regulates ciliogenesis and Dspp expression during odontoblast differentiation

Tooth development is a progressive process regulated by interactions between epithelial and mesenchymal tissues. Our previous studies showed that copine-7 (Cpne7), a dental epithelium-derived protein, is a signalling molecule that is secreted by preameloblasts and regulates the differentiation of preodontoblasts into odontoblasts. However, the mechanisms involved in the translocation of Cpne7 from preameloblasts to preodontoblasts and the functions of Cpne7 during odontogenesis are poorly understood. Here, we showed that the internalization of Cpne7 was mediated primarily by caveolae. This process was initiated by Cpne7 binding to the cell surface protein, nucleolin. Treatment with recombinant Cpne7 protein (rCpne7) in human dental pulp cells (hDPCs) caused an increase in the number of ciliated cells. The expression level of cilium components, Ift88 and Kif3a, and Dspp were increased by rCpne7. Treatment with Ift88 siRNA in hDPCs and MDPC-23 cells significantly down-regulated the expression of Dspp, an odontoblastic differentiation marker gene. Furthermore, the treatment with nucleolin siRNA in MDPC-23 cells decreased the expression of Dmp1, Dspp, and cilium components. Our findings suggested that the binding of Cpne7 with its receptor, nucleolin, has an important function involving Cpne7 internalization into preodontoblasts and regulation of Dspp expression through ciliogenesis during odontoblast differentiation.

Tertiary Dentin Formation after Indirect Pulp Capping Using Protein CPNE7

If there is a partial loss of dentin, the exposed dentinal surface should be protected by an indirect pulp capping (IPC) procedure to preserve pulp vitality and prevent symptoms of dentin hypersensitivity. In our previous study, copine7 (CPNE7) induced odontoblast differentiation in vitro and promoted dentin formation in vivo. The aim of this study was to investigate the possibility of IPC therapy using the CPNE7 protein at the exposed dentinal surface and the resulting effects on tertiary dentin formation in a beagle model. CPNE7 promoted mineralization of odontoblasts and had high calcium ion-binding capacity. The in vivo IPC model with canine teeth showed that regeneration of physiologic reactionary dentin with dentinal tubule structures was clearly observed beneath the remaining dentin in the CPNE7 group, whereas irregular features of reparative dentin were generated in the mineral trioxide aggregate (MTA) group. The CPNE7+MTA group also showed typical reactionary dentin without reparative dentin, showing synergistic effects of CPNE7 with MTA. A scanning electron microscopy analysis showed that dentinal tubules beneath the original dentin were occluded by the deposition of peritubular dentin in the CPNE7 and CPNE7+MTA groups, whereas those in the control group were opened. Therefore, CPNE7 may be able to serve as a novel IPC material and improve symptoms of dentin hypersensitivity.

Osteopontin Is Essential for Type I Collagen Secretion in Reparative Dentin

Osteopontin (OPN) is a highly phosphorylated glycoprotein that is a prominent component of the mineralized extracellular matrix of bone. The secretion of OPN by immunocompetent cells plays a role in the differentiation of odontoblast-like cells during pulpal healing following tooth transplantation. This study aimed to clarify the role of OPN during reparative dentinogenesis. A groove-shaped cavity was prepared on the mesial surface of the upper first molars of wild-type (WT) and Opn knockout (KO) mice, and the samples were collected at intervals of 1 to 14 d. The demineralized sections were processed for immunohistochemistry for Ki67, nestin, OPN, dentin sialoprotein (DSP), integrin αvβ3, and type I collagen; in situ hybridization for Opn, col1a1, and dentin sialophosphoprotein (Dspp); and apoptosis assay. For the loss and gain of function experiments, an in vitro culture assay for evaluating dentin-pulp complex regeneration was performed. On day 1 in WT mice, odontoblasts beneath the affected dentin lost nestin immunoreactivity. On day 3, the expression of Opn was recognized at the mesial dental pulp, and OPN was deposited along the predentin-dentin border. Nestin-positive newly differentiated odontoblast-like cells expressed both Dspp and col1a1 and showed positive immunoreactivity for integrin αvβ3, DSP, and type I collagen. Until day 14, reparative dentin formation continued next to the preexisting dentin at the mesial coronal pulp. In contrast, there was no reparative dentin in the Opn KO mice where nestin- and DSP-positive newly differentiated odontoblast-like cells lacked immunoreaction for type I collagen. The in vitro organ culture demonstrated that the administration of recombinant OPN rescued the type I collagen secretion by odontoblast-like cells in the Opn KO mice. The results suggested that the deposition of OPN at the calcification front is essential for the type I collagen secretion by newly differentiated odontoblast-like cells to form reparative dentin during pulpal healing following cavity preparation.

Preameloblast-Derived Factors Mediate Osteoblast Differentiation of Human Bone Marrow Mesenchymal Stem Cells by Runx2-Osterix-BSP Signaling

Epithelial-mesenchymal interaction occurs during development of various tissues, including teeth and bone. Recently, a preameloblast-conditioned medium (PA-CM) from mouse apical bud cells (ABCs), a type of dental epithelial cell, was found to induce odontogenic differentiation of dental pulp stem cells and promote dentin formation. The aims of the present study were to investigate the effects of PA-CM on human bone marrow mesenchymal stem cells (hBMSCs) in vitro, and to investigate the bone regenerative capacity in vivo through epithelial-mesenchymal interactions of developmental osteogenesis. Coculturing with ABCs and PA-CM treatment upregulated osteoblast differentiation markers of hBMSCs compared to cells cultured alone. PA-CM accelerated mineralized nodule formation and also increased bone sialoprotein promoter activity in hBMSCs. PA-CM facilitated the migration of hBMSCs, but did not significantly influence proliferation. PA-CM promoted bone formation of hBMSCs in vivo. Radiographic and histologic findings showed that PA-CM induced the bony regeneration at calvarial defects in rat. Taken together, these data show that PA-CM enhances the migration and osteogenic differentiation of hBMSCs in vitro and induces bone formation in vivo.

Increased expression of copine VI in patients with refractory epilepsy and a rat model

Copine VI (CPNE6) is a member of copines family, a calcium-dependent phospholipids-binding protein group found in many diverse eukaryotic organisms. Although earlier studies have shown that CPNE6 is almost exclusively expressed in brain, the exact biological functions remain unclear. The purpose of this study is to explore the relationship between epilepsy and CPNE6 expression. In present study, we investigated the expression pattern and distribution of CPNE6 in patients with refractory epilepsy and in a chronic pilocarpine-induced epileptic rat model by quantitative real-time PCR, Western blot and immunofluorescence. The results showed that the expression of CPNE6 increased remarkably in epileptic patients and in experimental epileptic rats. Double immunofluorescence labeling studies have revealed that CPNE6 protein is mainly expressed in neurons, demonstrated by co-localization with the dendritic marker, MAP2. Our results are the first to indicate that the abnormal expression of the CPNE6 in epileptic brain tissue may play an important role in epilepsy, especially refractory epilepsy.

Periodontal healing with a preameloblast-conditioned medium in dogs

BACKGROUND AND OBJECTIVE

The predictability of conventional periodontal treatments for damaged periodontal tissue is limited, particularly on the regeneration of new cementum. As signaling molecules, a range of growth factors has been used to promote periodontal regeneration on periodontal ligament (PDL) and cementum defects. A preameloblast-conditioned medium (PA-CM) was prepared from cultured murine apical bud cells, which can differentiate into ameloblasts. We examined the effect of PA-CM on PDL cells and cementoblasts in vitro and evaluated histologically the effects of PA-CM on the regeneration of experimentally induced periodontal defects in vivo.

MATERIAL AND METHODS

In vitro, the effects of PA-CM on the migration of human PDL cells were examined using a scratch wound healing assay and a transwell assay. The differentiation and mineralization potential of PA-CM-treated human PDL cells and murine cementoblastic OCCM-30 cells was examined by real-time polymerase chain reaction and Alizarin red-S staining. In vivo, six mongrel dogs (12-16 kg; 6-8 mo old) were used. Twenty-four roots were replanted with either, (i) only periodontal defects (n = 12; control group), or (ii) periodontal defects and PA-CM treatment (n = 12; experimental group). In the experimental group, the PDL and cementum between notches was removed using a Gracey curette and soaked in 0.08 mL water containing 80 μg of a PA-CM for 2 min. The dogs were killed at 4 and 8 wk post-surgery.

RESULTS

The in vitro results showed that PA-CM stimulated the migration of PDL cells and promoted the differentiation and mineralization of PDL cells and cementoblasts. Real-time polymerase chain reaction analysis revealed stronger expression of Runx2, Osx, OC, Bsp and Cap mRNAs in the PA-CM-treated PDL cells and cementoblasts than those in the control cells. In vivo, newly formed PDL-like tissue and cementum-like tissue were observed partially between the root surfaces and newly formed bone in the experimental group. The regenerated PDL-like tissue in the experimental group was significantly higher than that in the control group at 8 wk (p < 0.05). The replacement resorption on the experimental group was significantly lower than that in the control group at 8 wk (p < 0.05). In addition, the amount of newly formed cementum-like tissue in the experimental group was significantly higher than that in the control group at 4 and 8 wk (p < 0.05).

CONCLUSION

These results suggest that PA-CM has the potential to regenerate periodontal tissues in PDL and cementum defects.