Expression of Nfic during root formation in first mandibular molar of rat

NFIC1 inhibits the migration and invasion of MDA-MB-231 cells through S100A2-mediated inactivation of MEK/ERK pathway

NFIC is a potent transcriptional factor involved in many physiological and pathological processes, including tumorigenesis. However, the role of NFIC1, the longest isoform of NFIC, in the progression of triple negative breast cancer (TNBC) remains elusive. Our study demonstrates that overexpression of NFIC1 inhibits the migration and invasion of TNBC MDA-MB-231 cells. NFIC1 regulates the expression of S100A2, and knockdown of S100A2 reverses the inhibitive effects of NFIC1 on the migration and invasion of MDA-MB-231 cells. Furthermore, knockdown of S100A2 activates the MEK/ERK signaling transduction pathway that is inhibited by NFIC1 overexperssion. Treatment with MEK/ERK pathway inhibitor, U0126, abolishes the effects of S100A2 knockdown. In addition, overexpression of NFIC1 in MDA-MB-231 cells increases the expression of epithelial markers and decreases the expression of mesenchymal markers, and these effects could also be reversed by knockdown of S100A2. Collectively, these results demonstrate that NFIC1 inhibits the Epithelial-mesenchymal transition (EMT) of MDA-MB-231 cells by regulating S100A2 expression, which suppress the activation of MEK/ERK pathway. Therefore, our study confirms the role of NFIC1 as a tumor repressor in TNBC, and reveals the molecular mechanism through which NFIC1 inhibits the migration and invasion of MDA-MB-231 cells.

The critical role of nuclear factor I-C in tooth development

OBJECTIVES

Nuclear factor I-C (NFIC) plays a critical role in regulating epithelial-mesenchymal crosstalk during tooth development. However, it remains largely unknown about how NFIC functions in dentin and enamel formation. In the present review, we aim to summarize the most recent discoveries in the field and gain a better understanding of the roles NFIC performs during tooth formation.

SUBJECTS AND METHODS

Nfic^-/- mice exhibit human dentin dysplasia type I (DDI)-like phenotypes signified by enlarged pulp chambers, the presence of short-root anomaly, and failure of odontoblast differentiation. Although loss of NFIC has little effect on molar crown morphology, researchers have detected aberrant microstructures of enamel in the incisors. Recently, accumulating evidence has further uncovered the novel function of NFIC in the process of enamel and dentin formation.

RESULTS

During epithelial-mesenchyme crosstalk, the expression of NFIC is under the control of SHH-PTCH-SMO-GLI1 pathway. NFIC is closely involved in odontoblast lineage cells proliferation and differentiation, and the maintenance of NFIC protein level in cytoplasm is negatively regulated by TGF-β signaling pathway. In addition, NFIC has mild effect on ameloblast differentiation, enamel mineralization and cementum formation.

CONCLUSIONS

NFIC plays an important role in tooth development and is required for the formation of dentin, enamel as well as cementum.

Immortalized Hertwig's epithelial root sheath cell line works as model for epithelial-mesenchymal interaction during tooth root formation

Hertwig's epithelial root sheath (HERS) is critical for epithelial-mesenchymal interaction (EMI) during tooth root formation. However, the exact roles of HERS in odontogenic differentiation by EMI have not been well characterized, because primary HERS cells are difficult to obtain. Immortalized cell lines constitute crucial scientific tools, while there are few HERS cell lines available. Our previous study has successfully established immortalized HERS cell lines. Here, we confirmed the phenotype of our HERS-H1 by verifying its characteristics and functions in odontogenic differentiation through EMI. The HERS-H1-conditioned medium (CM-H1) effectively enhanced odontogenic differentiation of dental papilla cells (DPCs) in vitro. Furthermore, Smad4 and p-Smad1/5/8 were significantly activated in DPCs treated with CM-H1, and this activation was attenuated by noggin. In vivo, our implanted recombinants of HERS-H1 and DPCs exhibited mineralized tissue formation and expression of Smad4, p-Smad1/5/8, and odontogenic differentiation markers. Our results indicated that HERS-H1 promoted DPCs odontoblastic differentiation via bone morphogenetic protein/Smad signaling. HERS-H1 exhibits relevant key molecular characteristics and constitutes a new biological model for basic research on HERS and the dental EMI during root development and regeneration.

Molecular mechanisms for short root anomaly

Short root anomaly (SRA) is a dental disorder that presents an abnormal root morphology with short and blunt dental roots. In this situation, many dental treatments face a difficult challenge, especially orthodontic and prosthodontic treatments. Therefore, an understanding of how SRA develops is urgently needed. Here we describe that the abnormal expression of nuclear factor I C-type (Nfic), osterix (Osx), hedgehog (Hh), bone morphogenetic proteins (BMPs), transforming growth factor-β (TGF-β), Smad, Wnt, β-catenin, and dickkopf-related protein 1 (DKK1) leads to SRA. These factors interact with each other and constitute complicated signaling network in tooth formation. Specifically, BMP signaling inhibits the activity of Wnt/β-catenin directly or by inducing Osx via Runx2-dependent and Runx2-independent pathways. And Osx is a main inhibitor of Wnt/β-catenin signaling. In return, Wnt/β-catenin signaling has an antagonistic action of BMP pathway and a stimulation of Runx2. We highlight the importance of Wnt/β-catenin signaling in the pathological mechanisms. Either suppression or overactivation of this signaling influences the normal odontogenesis. Finally, we list rescue experiments on animal models, which have been reported to restore the interrupted cell differentiation and impaired tooth formation. We hope to find potential treatments for SRA based on these evidences in the future.

NFIC promotes the vitality and osteogenic differentiation of rat dental follicle cells

Nuclear factor I-C (NFIC) plays critical roles in the regulation of tooth development by influencing the biological behaviors of stem cells in the dental germ. This study aimed to investigate the effect of NFIC on the vitality and osteogenic/cementogenic differentiation of rat dental follicle cells (DFCs). DFCs were isolated from dental follicles in the first molars of neonatal rats. DFCs expressed mesenchymal stromal cell markers CD29, CD44 and CD90 and had capabilities for self-renewal and multipotent differentiation. Overexpression of NFIC promoted the proliferation of DFCs without markedly influencing the apoptosis of DFCs. Moreover, NFIC increased alkaline phosphatase (ALP) activity in DFCs and upregulated the mRNA levels of osteogenic-related markers, namely, collagen type I (Col I), Runt-related transcription factor 2 (Runx2) and ALP, as well as β-catenin. In contrast, silencing NFIC by siRNA increased the apoptosis of DFCs and downregulated the expression of osteogenic-related markers. In conclusion, these results suggested that upregulation of NFIC may promote the proliferation and osteogenic/cementogenic differentiation of DFCs.

Changes of mitochondrial respiratory function during odontogenic differentiation of rat dental papilla cells

Dental papilla cells (DPCs) belong to precursor cells differentiating to odontoblasts and play an important role in dentin formation and reproduction. This study aimed to explore the changes and and involvement of mitochondrial respiratory function during odontogenic differentiation. Primary DPCs were obtained from first molar dental papilla of neonatal rats and cultured in odontogenic medium for 7, 14, 21 days. DPCs, which expressed mesenchymal surface markers CD29, CD44 and CD90, had the capacity for self-renewal and multipotent differentiation. Odontoblastic induction increased mineralized matrix formation in a time-dependent manner, which was accompanied by elevated alkaline phosphatase (ALP), dentin sialophosphoprotein and dentin matrix protein 1 expression at mRNA and protein levels. Notably, odontogenic medium led to an increase in adenosine-5'-triphosphate content and mitochondrial membrane potential, whereas a decrease in intercellular reactive oxygen species production and NAD⁺/NADH ratio. Furthermore, odontogenic differentiation was significantly suppressed by treatment with rotenone, an inhibitor of mitochondrial respiratory chain. These results demonstrate that enhanced mitochondrial function is crucial for odontogenic differentiation of DPCs.

The role of nuclear factor I-C in tooth and bone development

Nuclear factor I-C (NFI-C) plays a pivotal role in various cellular processes such as odontoblast and osteoblast differentiation. Nfic-deficient mice showed abnormal tooth and bone formation. The transplantation of Nfic-expressing mouse bone marrow stromal cells rescued the impaired bone formation in Nfic^-/- mice. Studies suggest that NFI-C regulate osteogenesis and dentinogenesis in concert with several factors including transforming growth factor-β1, Krüppel-like factor 4, and β-catenin. This review will focus on the function of NFI-C during tooth and bone formation and on the relevant pathways that involve NFI-C.

Hyaluronan and hyaluronan synthases expression and localization in embryonic mouse molars

Hyaluronan (HA) and hyaluronan synthases (HASs) have been shown to play critical roles in embryogenesis and organ development. However, there have not been any studies examining HA and HAS expression and localization during tooth development. The present study was designed to investigate the expression of HA and three isoforms of HASs (HAS1, 2, 3) in embryonic mouse molars. The first mandibular embryonic mouse molars were examined by immunohistochemistry at E11.5, E13.5, E14.5, E16.5, and E18.5. PCR and western blot analyses were performed on RNA and proteins samples from E13.5 to E18.5 tooth germs. At the initial stage (E11.5), HA and HASs were expressed in the dental epithelium but not the underlying dental mesenchyme. HA immunostaining gradually increased in the enamel organ from the bud stage (E13.5) to the late bell stage (E18.5), and HA and HASs were highly expressed in the stellate reticulum and stratum intermedium. HA immunostaining was also enhanced in the dental mesenchyme and its derived tissues, but it was not expressed in the ameloblast and odontoblast regions. The three HAS isoforms had distinct expression patterns, and they were expressed in the dental mesenchyme and odontoblast at various levels. Furthermore, HAS1 and HAS2 expression decreased, while HAS3 expression increased from E13.5 to E18.5. These results suggested that HA synthesized by different HASs is involved in embryonic mouse molar morphogenesis and cytodifferentiation.

Facioscapulohumeral muscular dystrophy (FSHD) region gene 1 (FRG1) expression and possible function in mouse tooth germ development

Abnormal expression of Facioscapulohumeral muscular dystrophy (FSHD) region gene 1 (FRG1) is involved in the pathogenesis of FSHD. FRG1 is also important for the normal muscular and vascular development. Our previous study showed that FRG1 is one of the highly expressed genes in the mandible on embryonic day 10.5 (E10.5) than on E12.0. In this study, we investigated the temporospatial expression pattern of FRG1 mRNA and protein during the development of the mouse lower first molar, and also evaluated the subcellular localization of the FRG1 protein in mouse dental epithelial (mDE6) cells. The FRG1 expression was identified in the dental epithelial and mesenchymal cells at the initiation and bud stages. It was detected in the inner enamel epithelium at the cap and early bell stages. At the late bell and root formation stages, these signals were detected in ameloblasts and odontoblasts during the formation of enamel and dentin matrices, respectively. The FRG1 protein was localized in the cytoplasm in the mouse tooth germ in vivo, while FRG1 was detected predominantly in the nucleus and faintly in the cytoplasm in mDE6 cells in vitro. In mDE6 cells treated with bone morphogenetic protein 4 (BMP4), the protein expression of FRG1 increased in cytoplasm, suggesting that FRG1 may translocate to the cytoplasm. These findings suggest that FRG1 is involved in the morphogenesis of the tooth germ, as well as in the formation of enamel and dentin matrices and that FRG1 may play a role in the odontogenesis in the mouse following BMP4 stimulation.

Spatiotemporal expression of caveolin-1 and EMMPRIN during mouse tooth development

Caveolin-1 is a scaffolding protein involved in the formation of cholesterol-rich caveolae lipid rafts within the plasma membrane and is capable of collecting signaling molecules into the caveolae and regulating their activity, including extracellular matrix metalloproteinase inducer (EMMPRIN). However, detailed expression patterns of caveolin-1 and EMMPRIN in the developing dental germ are largely unknown. The present study investigated the expression patterns of caveolin-1 and EMMPRIN in the developing mouse tooth germ by immunohistochemistry and real-time polymerase chain reaction. At the bud stage, caveolin-1 expression was initiated in the epithelium bud and mesenchymal cells, while EMMPRIN was weakly expressed at this stage. At the cap stage, caveolin-1 protein was located in the lingual part of the tooth germ; however, EMMPRIN protein was located in the labial part. From the bell stage to 2 days postnatal, caveolin-1 expression was detected in the ameloblasts and cervical loop area; with EMMPRIN expression in the ameloblasts and odontoblasts. Real-time polymerase chain reaction results showed that both caveolin-1 and EMMPRIN mRNA levels increased gradually with progression of developmental stages, and peaked at day two postnatal. The current finding suggests that both caveolin-1 and EMMPRIN take part in mouse tooth development, especially in the differentiation and organization of odontogenic tissues.

NFI-C2 temporal-spatial expression and cellular localization pattern during tooth formation

Currently, little is known regarding critical signaling pathways during later stages of tooth development, especially those associated with root formation. Nfi-c null mice, lacking molar roots, have implicated the transcription factor NFI-C as having an essential role in root development. Previously, we identified three NFI-C isoforms expressed in dental tissues with NFI-C2 being the major transcript. However, the expression pattern of the NFI-C2 protein is not characterized. In this study we performed in situ hybridization and immunohistochemistry using isoform specific probes. We show the production of a NFI-C2 peptide antibody, its characterization, the temporal-spatial expression pattern of the NFI-C2 protein during odontogenesis and sub-cellular localization in dental cells. Moderate NFI-C2 staining, as early as bud stage, was detected mostly in the condensing dental ectomesenchyme. This staining intensified within the dental pulp at later stages culminating in high expression in the dentin producing odontoblasts. The dental epithelium showed slight staining until cytodifferentiation of enamel organ into ameloblasts and stratum intermedium. During root formation NFI-C2 expression was high in the Hertwig's epithelial root sheath and later was found in the fully developed root and its supporting tissues. NFI-C2 cellular staining was cytosolic, associated with the Golgi, and nuclear. These data suggest a broader role for NFI-C during tooth formation than limited to root and periodontal ligament development.

Functional role of EMMPRIN in the formation and mineralisation of dental matrix in mouse molars

Our previous research has shown that the extracellular matrix metalloproteinase inducer (EMMPRIN) is expressed during and may function in the early development of tooth germs. In the present study, we observed the specific expression of EMMPRIN in ameloblasts and odontoblasts during the middle and late stages of tooth germ development using immunohistochemistry. Furthermore, to extend our understanding of the function of EMMPRIN in odontogenesis, we used an anti-EMMPRIN function-blocking antibody to remove EMMPRIN activity in tooth germ culture in vitro. Both the formation and mineralisation of dental hard tissues were suppressed in the tooth germ culture after the abrogation of EMMPRIN. Meanwhile, significant reductions in VEGF, MMP-9, ALPL, ameloblastin, amelogenin and enamelin expression were observed in antibody-treated tooth germ explants compared to control and normal serum-treated explants. The current results illustrate that EMMPRIN may play a critical role in the processing and maturation of the dental matrix.