Expression of Oct-4, SOX-2, and MYC in dental papilla cells and dental follicle cells during in-vivo tooth development and in-vitro co-culture

Apical Papilla Regulates Dental Follicle Fate via the OGN-Hh Pathway

Root apical complex, including Hertwig's epithelial root sheath, apical papilla, and dental follicle (DF), is the germinal center of root development, wherein the DF constantly develops into periodontal tissue. However, whether DF development is regulated by the adjacent apical papilla remains largely unknown. In this study, we employed a transwell coculture system and found that stem cells from the apical papilla (SCAPs) inhibit the differentiation and maintain the stemness of dental follicle stem cells (DFSCs). Meanwhile, partial SCAP differentiation markers were upregulated after DFSC coculture. High-throughput RNA sequencing revealed that the Hedgehog (Hh) pathway was significantly downregulated in DFSCs cocultured with SCAPs. Upregulation or downregulation of the Hh pathway can respectively activate or inhibit the multidirectional differentiation of DFSCs. Osteoglycin (OGN) (previously known as mimecan) is highly expressed in the dental papilla, similarly to Hh pathway factors. By secreting OGN, SCAP regulated the stemness and multidirectional differentiation of DFSCs via the OGN-Hh pathway. Finally, Ogn^-/- mice were established using the CRISPR/Cas9 system. We found that the root length growth rate was accelerated during root development from PN0 to PN30 in Ogn^-/- mice. Moreover, the hard tissues (including dentin and cementum) of the root in Ogn^-/- mice were thicker than those in wild-type mice. These phenotypes were likely due to Hh pathway activation and the increased cell proliferation and differentiation in both the apical papilla and DF. The current work elucidates the molecular regulation of early periodontal tissue development, providing a theoretical basis for future research on tooth root biology and periodontal tissue regeneration.

Nuclear Factor I-C Regulates Stemness Genes and Proliferation of Stem Cells in Various Mineralized Tissue through Epithelial-Mesenchymal Interactions in Dental Epithelial Stem Cells

Tooth development includes numerous cell divisions and cell-cell interactions generating the stem cell niche. After an indefinite number of divisions, pluripotent cells differentiate into various types of cells. Nuclear factor I (NFI) transcription factors are known as crucial regulators in various organ development and stem cell biology. Among its members, nuclear factor I-C (NFI-C) has been reported to play an essential role in odontogenesis. Nfic knockout mice show malformation in all mineralized tissues, but it remains unclear which stage of development Nfic is involved in. We previously reported that Nfic induces the differentiation of ameloblast, odontoblast, and osteoblast. However, the question remains whether Nfic participates in the late stage of development, perpetuating the proliferation of stem cells. This study aimed to elucidate the underlying mechanism of NFI-C function in stem cells capable of forming hard tissues. Here, we demonstrate that Nfic regulates Sox2 and cell proliferation in diverse mineralized tissue stem cells such as dental epithelial stem cells (DESCs), dental pulp stem cells, and bone marrow stem cells, but not in fibroblasts. It was also involved in the expression of pluripotency genes Lin28 and NANOG. Especially in DESCs, Nfic regulates the proliferation of epithelial cells via epithelial-mesenchymal interactions, which are the Fgf8-Nfic-Sox2 pathway in epithelium and Nfic-Fgf10 in the mesenchyme. Moreover, Nfic slightly increased reprogramming efficiency in induced pluripotent stem cells of mineralized tissues, but not in soft tissues. In conclusion, these results suggest that Nfic is a crucial factor for maintaining the stem cell niche of mineralized tissues and provides a possibility for Nfic as an additional factor in improving reprogramming efficiency.

Genetic Analyses of Enamel Hypoplasia in Multiethnic Cohorts

Enamel hypoplasia causes reduction in the thickness of affected enamel and is one of the most common dental anomalies. This defect is caused by environmental and/or genetic factors that interfere with tooth formation, emphasizing the importance of investigating enamel hypoplasia on an epidemiological and genetic level. A genome-wide association of enamel hypoplasia was performed in multiple cohorts, overall comprising 7,159 individuals ranging in age from 7-82 years. Mixed-models were used to test for genetic association while simultaneously accounting for relatedness and genetic population structure. Meta-analysis was then performed. More than 5 million single-nucleotide polymorphisms were tested in individual cohorts. Analyses of the individual cohorts and meta-analysis identified association signals close to genome-wide significance (P < 510-8), and many suggestive association signals (510-8 < P < 510-6) near genes with plausible roles in tooth/enamel development. The strongest association signal (P = 1.5710-9) was observed near BMP2K in one of the individual cohorts. Additional suggestive signals were observed near genes with plausible roles in tooth development in the meta-analysis, such as SLC4A4 which can influence enamel hypoplasia. Additional human genetic studies are needed to replicate these results and functional studies in model systems are needed to validate our findings.

Expression of SOX2 and OCT4 in odontogenic cysts and tumors

Background

Aberrant expression of stem cell markers has been observed in several types of neoplasms. This trait attributes to the acquired stem-like property of tumor cells and can impact patient prognosis. The objective of this study was to comparatively analyze the expression and significance of SOX2 and OCT4 in various types of odontogenic cysts and tumors.

Methods

Fifty-five cases of odontogenic cysts and tumors, including 15 ameloblastomas (AM), 5 adenomatoid odontogenic tumors (AOT), 5 ameloblastic fibromas (AF), 5 calcifying odontogenic cysts (COC), 10 dentigerous cysts (DC) and 15 odontogenic keratocysts (OKC) were investigated for the expression of SOX2 and OCT4 immunohistochemically.

Results

Most OKCs (86.7 %) and all AFs expressed SOX2 in more than 50 % of epithelial cells. Its immunoreactivity was moderate-to-strong in all epithelial cell types in both lesions. In contrast, SOX2 expression was undetectable in AOTs and limited to the ameloblast-like cells in a minority of AM and COC cases. Most DCs showed positive staining in less than 25 % of cystic epithelium. Significantly greater SOX2 expression was noted in OKC compared with DC or AM, and in AF compared with COC or AOT. OCT4 rarely expressed in odontogenic lesions with the immunoreactivity being mild and present exclusively in OKCs.

Conclusions

SOX2 is differentially expressed in odontogenic cysts and tumors. This could be related to their diverse cells of origin or stages of histogenesis. The overexpression of SOX2 and OCT4 in OKC indicates the acquired stem-like property. Future studies should investigate whether the overexpression of OCT4 and SOX2 contributes to the aggressive behaviors of the tumors.

Direct reprogramming of epithelial cell rests of malassez into mesenchymal-like cells by epigenetic agents

The DNA demethylating agent, 5-Azacytidine (5Aza), and histone deacetylase inhibitor, valproic acid (Vpa), can improve the reprogramming efficiencies of pluripotent cells. This study aimed to examine the roles of 5Aza and Vpa in the dedifferentiation of epithelial cell rests of Malassez (ERM) into stem-like cells. Additionally, the ability of stem-like cells to differentiate into mesenchymal cells was evaluated. ERM was cultured in embryonic stem cell medium (ESCM) with 1 µM of 5Aza, or 2 mM of Vpa, or a combination of 5Aza and Vpa. The cells stimulated with both 5Aza and Vpa were named as progenitor-dedifferentiated into stem-like cells (Pro-DSLCs). The Pro-DSLCs cultured in ESCM alone for another week were named as DSLCs. The stem cell markers were significantly higher in the DSLCs than the controls (no additions). The mRNA and protein levels of the endothelial, mesenchymal stem, and osteogenic cell markers were significantly higher in the Pro-DSLCs and DSLCs than the controls. The combination of a demethylating agent and a deacetylated inhibitor induced the dedifferentiation of ERM into DSLCs. The Pro-DSLCs derived from ERM can be directly reprogrammed into mesenchymal-like cells without dedifferentiation into stem-like cells. Isolated ERM treated with epigenetic agents may be used for periodontal regeneration.

Pluripotency of Dental Pulp Cells and Periodontal Ligament Cells Was Enhanced through Cell-Cell Communication via STAT3/Oct-4/Sox2 Signaling

Alternation in culture environment due to cell-cell communications can rejuvenate the biological activity of aged/differentiated cells and stimulate the expression of pluripotency markers. Dental pulp cells (DPCs) and periodontal ligament cells (PDLCs) are promising candidates in dental tissue regeneration. However, the molecular network that underlies cell-cell communications between dental-derived cells and the microenvironment remains to be identified. To elucidate the signaling network that regulates the pluripotency of DPCs and PDLCs, proliferation, apoptosis, cell cycle, and the expression of Oct-4/Sox2/c-Myc in DPCs and PDLCs with indirect/direct coculture were examined. PCR arrays were constructed to identify genes that were differentially expressed, and the results were confirmed by a rat model with injury. Further research on the mechanism of the related signaling pathways was investigated by overexpression/silence of STAT3, ChIP, the dual-luciferase reporter assay, and EMSA. We found that the proliferation and apoptosis of DPCs and PDLCs were inhibited, and their cell cycles were arrested at the G0/G1 phase after coculture. Oct-4, Sox2, and STAT3 expression significantly increased and PAX5 expression decreased in the coculture systems. Oct-4/Sox2/STAT3/PAX5 was actively expressed in the rat defect model. Moreover, STAT3 was directly bound to the Oct-4 and Sox2 gene promoter regions and activated the expression of those genes. Our data showed that the pluripotency of DPCs and PDLCs was enhanced through cell-cell communication. STAT3 plays essential roles in regulating the pluripotency of DPCs and PDLCs by targeting Oct-4 and Sox2 both in vitro and in vivo.

Dental follicle stem cells rescue the regenerative capacity of inflamed rat dental pulp through a paracrine pathway

Background

Pulpitis is a common dental disease characterized by sustained inflammation and impaired pulp self-repair. Mesenchymal stem cell-based minimally invasive vital pulp therapy (MSC-miVPT) is a potential treatment method, but its application is limited by the difficulty in acquiring MSCs. We recently revealed the immunomodulatory effects of rat dental follicle stem cells (rDFSCs) on acute lung injury. The present study focused on the paracrine effects of rDFSCs on the inflammation and regeneration of rat injured dental pulp to detect whether DFSCs are a potential candidate for MSC-miVPT.

Methods

Conditioned medium from rDFSCs (rDFSC-CM) was applied to lipopolysaccharide (LPS)-induced inflammatory rat dental pulp cells (rDPCs). The inflammation and regeneration of rDPCs were detected by RT-qPCR, Western blotting, immunofluorescence staining, Cell Counting Kit-8 (CCK-8) assay, flow cytometry, wound-healing assay, and Masson’s staining. The effects of rDFSC-CM on inflamed rat dental pulp were further evaluated by hematoxylin-eosin and immunohistochemical staining.

Results

rDFSC-CM downregulated the ERK1/2 and NF-κB signaling pathways, which resulted in suppression of the expression of IL-1β, IL-6, and TNF-α and promotion of the expression of IL-4 and TGF-β, and these findings lead to the attenuation of rDPC inflammation. rDFSC-CM enhanced the in vitro proliferation, migration, and odontogenic differentiation of inflammatory rDPCs and their in vivo ectopic dentinogenesis. Furthermore, rDFSC-CM inhibited inflammatory cell infiltration in rat pulpitis and triggered Runx2 expression in some of the odontoblast-like cells surrounding the injured site, and these effects were conducive to the repair of inflamed dental pulp.

Conclusions

rDFSC-CM exhibits therapeutic potential by rescuing the regeneration of the inflamed rat dental pulp through an immunomodulatory mechanism, indicating the application prospects of DFSCs in biological regenerative endodontics.

Dental Follicle Cells: Roles in Development and Beyond

Dental follicle cells (DFCs) are a group of mesenchymal progenitor cells surrounding the tooth germ, responsible for cementum, periodontal ligament, and alveolar bone formation in tooth development. Cascades of signaling pathways and transcriptional factors in DFCs are involved in directing tooth eruption and tooth root morphogenesis. Substantial researches have been made to decipher multiple aspects of DFCs, including multilineage differentiation, senescence, and immunomodulatory ability. DFCs were proved to be multipotent progenitors with decent amplification, immunosuppressed and acquisition ability. They are able to differentiate into osteoblasts/cementoblasts, adipocytes, neuron-like cells, and so forth. The excellent properties of DFCs facilitated clinical application, as exemplified by bone tissue engineering, tooth root regeneration, and periodontium regeneration. Except for the oral and maxillofacial regeneration, DFCs were also expected to be applied in other tissues such as spinal cord defects (SCD), cardiomyocyte destruction. This article reviewed roles of DFCs in tooth development, their properties, and clinical application potentials, thus providing a novel guidance for tissue engineering.

Non-syndromic cleft lip with or without palate-susceptible SNPs is associated with hyperdontia

BACKGROUND

Non-syndromic supernumerary teeth (NSST) or hyperdontia may share common genetic determinants with non-syndromic cleft lip with or without palate (NSCL/P). The aim of this study was to test the associations between five genome-wide-associated NSCL/P-susceptible single nucleotide polymorphisms (SNPs) (rs2235371, rs7078160, rs8049367, rs4791774, and rs13041247) and the occurrence of NSST.

MATERIALS AND METHODS

A total of 163 cases and 326 controls were recruited and their genomic DNA was extracted from blood samples. Five NSCL/P-susceptible SNPs (rs2235371, rs7078160, rs8049367, rs4791774, and rs13041247) were genotyped by TaqMan method. Odds ratio (OR) and 95% confidence interval (CI) were used to estimate the associations between the SNPs and the risk of NSST by PLINK software.

RESULTS

Rs4791774 (A > G) and rs13041247 (T > C) were associated with risk of NSST (rs4791774: P_add  = 0.011, OR, 95% CI = 0.62, 0.43-0.90; rs13041247: P_homo  = 0.031, OR, 95% CI = 1.79, 1.05-3.05) and one supernumerary tooth (rs4791774: P_dom  = 0.009, OR, 95% CI = 0.56, 0.36-0.87; rs13041247: P_homo  = 0.034, OR, 95% CI = 1.82, 1.05-3.15). Rs4791774 (A > G) was also showed association with risk of upper arch supernumerary teeth only (P_add  = 0.010, OR, 95% CI = 0.60, 0.41-0.89).

CONCLUSION

Non-syndromic cleft lip with or without palate-susceptible loci rs4791774 (A > G) and rs13041247 (T > C) were associated with the risk of supernumerary teeth.

Non-syndromic cleft lip with or without palate susceptible loci is associated with tooth agenesis

OBJECTIVE

Non-syndromic tooth agenesis (NSTA) may share common genetic factors with non-syndromic cleft lip with or without cleft palate (NSCL/P). Single-nucleotide polymorphisms (SNPs) were associated with individual's susceptibility to these anomalies. We selected five NSCL/P-associated SNPs from our previous genome-wide association study (GWAS) to test for the associations with NSTA.

MATERIALS AND METHODS

A total of 677 NSTA cases and 1,144 healthy controls were recruited in this case-control study. Five genome-wide NSCL/P-associated SNPs (rs2235371, rs7078160, rs8049367, rs4791774, and rs13041247) were genotyped by TaqMan platform and evaluated for the associations with NSTA using plink software.

RESULTS

No significant associations between these SNPs and risk of NSTA were observed in the overall analysis and subgroup analysis with the number of missing teeth. However, in the subgroup analysis by tooth position, rs8049367 was nominally associated with mandibular premolar agenesis (Dominant model: OR_dom  = 0.66, 95% CI_dom  = 0.47-0.93, p_dom  = 0.016; Heterozygote model: OR_het  = 0.60, 95% CI_het  = 0.41-0.88, P_het  = 0.008). Rs4791774 showed a nominal association with congenitally missing maxillary canine (Dominant model: OR_dom  = 0.53, 95% CI_dom  = 0.28-0.98, p_dom  = 0.041; Heterozygote model: OR_het  = 0.50, 95% CI_het  = 0.26-0.97, P_het  = 0.041) and premolar (Additive model: OR = 0.59, 95% CI = 0.36-0.96, p = 0.035).

CONCLUSION

This study showed that NSCL/P susceptible loci rs8049367 and rs4791774 were probably associated with the risk of NSTA.

Microenvironmental Stiffness Regulates Dental Papilla Cell Differentiation: Implications for the Importance of Fibronectin-Paxillin-β-Catenin Axis

The mechanical stiffness of substrates is recognized to be an important physical cue in the microenvironment of local cellular residents in mammalian species due to their great capacity in regulating cell behavior. Dental papilla cells (DPCs) play an important role in the field of dental tissue engineering for their stem cell-like properties. Therefore, it is essential to provide the suitable microenvironment by combining with the physical cues of biomaterials for DPCs to carry out the function of effective tissue regeneration. However, how the substrate stiffness influences the odontogenic differentiation of DPCs is still unclear. Thus, we fabricated poly(dimethylsiloxane) substrates with varied stiffness for cell behavior. Both cell morphology and focal adhesion were shown to have significant changes in response to varied stiffness. Paxillin, an important protein adapter of focal adhesion kinase protein, was shown to interact with both ectoplasmic fibronectin and cytoplasmic β-catenin by coimmunoprecipitation. The resultant changes of β-catenin by varied stiffness were confirmed by immunofluorescent stain and western blotting. Further, the higher quantity nuclear translocation of β-catenin and the less phospho-β-catenin on the stiff substrate were detected. This nuclear translocation in the stiff substrate finally led to an increased mineralization of DPCs relative to the soft substrate detected by Von Kossa and Alizarin Red stain. Taken together, this work not only points out that the substrate stiffness can regulate the odontogenic differentiation potential of DPCs via fibronectin/paxillin/β-catenin pathway but also provides significant consequence for biomechanical control of cell behavior in cell-based tooth tissue regeneration.

Oct-4 and CD44 in epithelial stem cells like of benign odontogenic lesions

Benign epithelial odontogenic lesions are great clinical importance entities that develop in the jaws from the tissues that form teeth. It has been shown that benign and malignant tumors are present in a large number of tumor stem cells, which has great implications in the development of these lesions. Oct-4 and CD44 have been demonstrated as important markers for tumoral stem cells. The aim of this study was investigate the presence of stem cell markers Oct-4 and CD44 in benign epithelial odontogenic lesions. Twenty odontogenic keratocysts (OKC), 20 ameloblastomas (AMB) of the solid/multicystic type and 20 adenomatoid odontogenic tumors (AOT) were retrospectively analyzed for immunohistochemical detection of Oct-4 and CD44 in their epithelial component. All cases were positive for the two markers, with the majority exhibiting a high expression. Analysis of the expression of Oct-4 revealed no statistically significant differences (p = 0.406) between the lesions studied. Regarding CD44, there was a significant difference between the cases of AMB and AOT in relation with OKC, with the latter presenting a greater labelling (p = 0.034). No statistically significant correlation between Oct-4 and CD44 was observed in the lesions. In our findings, the presence of stem cell-like phenotype at various sites of the epithelial component of the odontogenic lesions was identified, suggesting its possible participation in histogenesis and differentiation without, however, exerting influence on the aggressiveness of the lesions.

Colorectal Cancer-Associated Genes Are Associated with Tooth Agenesis and May Have a Role in Tooth Development

Previously reported co-occurrence of colorectal cancer (CRC) and tooth agenesis (TA) and the overlap in disease-associated gene variants suggest involvement of similar molecular pathways. Here, we took an unbiased approach and tested genome-wide significant CRC-associated variants for association with isolated TA. Thirty single nucleotide variants (SNVs) in CRC-predisposing genes/loci were genotyped in a discovery dataset composed of 440 individuals with and without isolated TA. Genome-wide significant associations were found between TA and ATF1 rs11169552 (P = 4.36 × 10-10) and DUSP10 rs6687758 (P = 1.25 × 10-9), and positive association found with CASC8 rs10505477 (P = 8.2 × 10-5). Additional CRC marker haplotypes were also significantly associated with TA. Genotyping an independent dataset consisting of 52 cases with TA and 427 controls confirmed the association with CASC8. Atf1 and Dusp10 expression was detected in the mouse developing teeth from early bud stages to the formation of the complete tooth, suggesting a potential role for these genes and their encoded proteins in tooth development. While their individual contributions in tooth development remain to be elucidated, these genes may be considered candidates to be tested in additional populations.

SCAPs Regulate Differentiation of DFSCs During Tooth Root Development in Swine

The tooth root transmits and balances occlusal forces through the periodontium to the alveolar bone. The periodontium, including the gingiva, the periodontal ligament, the cementum and the partial alveolar bone, derives from the dental follicle (DF), except for the gingiva. In the early developmental stages, the DF surrounds the tooth germ as a sphere and functions to promote tooth eruption. However, the morphological dynamics and factors regulating the differentiation of the DF during root elongation remain largely unknown. Miniature pigs are regarded as a useful experimental animal for modeling in craniofacial research because they are similar to humans with respect to dentition and mandible anatomy. In the present study, we used the third deciduous incisor of miniature pig as the model to investigate the factors influencing DF differentiation during root development. We found that the DF was shaped like a crescent and was located between the root apical and the alveolar bone. The expression levels of WNT5a, β-Catenin, and COL-I gradually increased from the center of the DF (beneath the apical foramen) to the lateral coronal corner, where the DF differentiates into the periodontium. To determine the potential regulatory role of the apical papilla on DF cell differentiation, we co-cultured dental follicle stem cells (DFSCs) with stem cells of the apical papilla (SCAPs). The osteogenesis and fibrogenesis abilities of DFSCs were inhibited when being co-cultured with SCAPs, suggesting that the fate of the DF can be regulated by signals from the apical papilla. The apical papilla may sustain the undifferentiated status of DFSCs before root development finishes. These data yield insight into the interaction between the root apex and surrounding DF tissues in root and periodontium development and shed light on the future study of root regeneration in large mammals.