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Hua Xi Kou Qiang Yi Xue Za Zhi = Huaxi... Jun 2019The polarity of ameloblasts and odontoblasts is crucial for their differentiation and function. Polarity-related molecules play an important role in this process. This... (Review)
Review
The polarity of ameloblasts and odontoblasts is crucial for their differentiation and function. Polarity-related molecules play an important role in this process. This review summarizes the process of polarity formation of ameloblasts and odontoblasts and their related regulators.
Topics: Ameloblasts; Cell Differentiation; Odontoblasts
PubMed: 31218868
DOI: 10.7518/hxkq.2019.03.016 -
Frontiers in Physiology 2023The intracellular Ca2+ sensor stromal interaction molecule 1 (STIM1) is thought to play a critical role in enamel development, as its mutations cause Amelogenesis...
The intracellular Ca2+ sensor stromal interaction molecule 1 (STIM1) is thought to play a critical role in enamel development, as its mutations cause Amelogenesis Imperfecta (AI). We recently established an ameloblast-specific (AmelX-iCre) Stim1 conditional deletion mouse model to investigate the role of STIM1 in controlling ameloblast function and differentiation (Stim1 cKO). Our pilot data (Said et al., J. Dent. Res., 2019, 98, 1002-1010) support our hypothesis for a broad role of Stim1 in amelogenesis. This paper aims to provide an in-depth characterization of the enamel phenotype observed in our Stim1 cKO model. We crossed AmelX-iCre mice with Stim1-floxed animals to develop ameloblast-specific Stim1 cKO mice. Scanning electron microscopy, energy dispersive spectroscopy, and micro- CT were used to study the enamel phenotype. RNAseq and RT-qPCR were utilized to evaluate changes in the gene expression of several key ameloblast genes. Immunohistochemistry was used to detect the amelogenin, matrix metalloprotease 20 and kallikrein 4 proteins in ameloblasts. Stim1 cKO animals exhibited a hypomineralized AI phenotype, with reduced enamel volume, diminished mineral density, and lower calcium content. The mutant enamel phenotype was more severe in older Stim1 cKO mice compared to younger ones and changes in enamel volume and mineral content were more pronounced in incisors compared to molars. Exploratory RNAseq analysis of incisors' ameloblasts suggested that ablation of Stim1 altered the expression levels of several genes encoding enamel matrix proteins which were confirmed by subsequent RT-qPCR. On the other hand, RT-qPCR analysis of molars' ameloblasts showed non-significant differences in the expression levels of enamel matrix genes between control and -deficient cells. Moreover, gene expression analysis of incisors' and molars' ameloblasts showed that ablation caused changes in the expression levels of several genes associated with calcium transport and mitochondrial kinetics. Collectively, these findings suggest that the loss of in ameloblasts may impact enamel mineralization and ameloblast gene expression.
PubMed: 36935757
DOI: 10.3389/fphys.2023.1100714 -
BMC Biology Dec 2019Polarity is necessary for epithelial cells to perform distinct functions at their apical and basal surfaces. Oral epithelial cell-derived ameloblasts at secretory stage...
BACKGROUND
Polarity is necessary for epithelial cells to perform distinct functions at their apical and basal surfaces. Oral epithelial cell-derived ameloblasts at secretory stage (SABs) synthesize large amounts of enamel matrix proteins (EMPs), largely amelogenins. EMPs are unidirectionally secreted into the enamel space through their apical cytoplasmic protrusions, or Tomes' processes (TPs), to guide the enamel formation. Little is known about the transcriptional regulation underlying the establishment of cell polarity and unidirectional secretion of SABs.
RESULTS
The higher-order chromatin architecture of eukaryotic genome plays important roles in cell- and stage-specific transcriptional programming. A genome organizer, special AT-rich sequence-binding protein 1 (SATB1), was discovered to be significantly upregulated in ameloblasts compared to oral epithelial cells using a whole-transcript microarray analysis. The Satb1 mice possessed deformed ameloblasts and a thin layer of hypomineralized and non-prismatic enamel. Remarkably, Satb1 ameloblasts at the secretory stage lost many morphological characteristics found at the apical surface of wild-type (wt) SABs, including the loss of Tomes' processes, defective inter-ameloblastic adhesion, and filamentous actin architecture. As expected, the secretory function of Satb1 SABs was compromised as amelogenins were largely retained in cells. We found the expression of epidermal growth factor receptor pathway substrate 8 (Eps8), a known regulator for actin filament assembly and small intestinal epithelial cytoplasmic protrusion formation, to be SATB1 dependent. In contrast to wt SABs, EPS8 could not be detected at the apical surface of Satb1 SABs. Eps8 expression was greatly reduced in small intestinal epithelial cells in Satb1 mice as well, displaying defective intestinal microvilli.
CONCLUSIONS
Our data show that SATB1 is essential for establishing secretory ameloblast cell polarity and for EMP secretion. In line with the deformed apical architecture, amelogenin transport to the apical secretory front and secretion into enamel space were impeded in Satb1 SABs resulting in a massive cytoplasmic accumulation of amelogenins and a thin layer of hypomineralized enamel. Our studies strongly suggest that SATB1-dependent Eps8 expression plays a critical role in cytoplasmic protrusion formation in both SABs and in small intestines. This study demonstrates the role of SATB1 in the regulation of amelogenesis and the potential application of SATB1 in ameloblast/enamel regeneration.
Topics: Ameloblasts; Amelogenesis; Animals; Cell Differentiation; Cell Polarity; Dental Enamel; Humans; Matrix Attachment Region Binding Proteins; Mice
PubMed: 31830989
DOI: 10.1186/s12915-019-0722-9 -
Frontiers in Bioengineering and... 2022The transcriptional regulation of induced pluripotent stem cells (iPSCs) holds promise for their directed differentiation into ameloblasts, which are usually lost after...
The transcriptional regulation of induced pluripotent stem cells (iPSCs) holds promise for their directed differentiation into ameloblasts, which are usually lost after tooth eruption. Ameloblast differentiation is regulated by multiple signaling molecules, including bone morphogenetic proteins (BMPs). Epiprofin (Epfn), a transcription factor, is expressed in the dental epithelium, and epithelial Epfn overexpression results in ectopic ameloblast differentiation and enamel formation in mouse incisor, a striking phenotype resembling that of mice with deletion of follistatin (a BMP inhibitor). However, it remains unknown whether and how Epfn transcriptional activation promotes ameloblast induction from mouse iPSCs. Here, we generated doxycycline-inducible -expressing mouse iPSCs (Epfn-iPSCs). Ameloblasts, which are characterized by positive staining for keratin 14 and amelogenin and alizarin red S staining, were successfully derived from Epfn-iPSCs based on a stage-specific induction protocol, which involved the induction of the surface ectoderm, dental epithelial cells, and ameloblasts at stages 1, 2, and 3, respectively. activation by doxycycline at stages 2 and/or 3 decreased cell proliferation and promoted ameloblast differentiation, along with the upregulation of p-Smad1/5/8, a key regulator of the BMP-Smad signaling pathway. Gene analysis of the BMP-Smad signaling pathway-associated molecules revealed that activation decreased follistatin expression at stage 2, but increased expression at stage 3. Perturbations in the ameloblast differentiation process were observed when the BMP-Smad signaling pathway was inhibited by a BMP receptor inhibitor (LDN-193189). Simultaneous LDN-193189 treatment and activation largely reversed the perturbations in ameloblast induction, with partial recovery of p-Smad1/5/8 expression, suggesting that activation promotes ameloblast induction from mouse iPSCs partially by upregulating BMP-Smad activity. These results reveal the potential regulatory networks between Epfn and the BMP-Smad pathway and suggest that Epfn is a promising target for inducing the differentiation of ameloblasts, which can be used in enamel and tooth regeneration.
PubMed: 35800329
DOI: 10.3389/fbioe.2022.890882 -
Ecotoxicology and Environmental Safety Jul 2023Perfluorooctanoic acid (PFOA) is an artificial fluorinated organic compound that has generated increased public attention due to its potential health hazards. Unsafe...
Perfluorooctanoic acid (PFOA) is an artificial fluorinated organic compound that has generated increased public attention due to its potential health hazards. Unsafe levels of PFOA exposure can affect reproduction, growth and development. During tooth enamel development (amelogenesis), environmental factors including fluoride can cause enamel hypoplasia. However, the effects of PFOA on ameloblasts and tooth enamel formation remain largely unknown. In the present study we demonstrate several PFOA-mediated cell death pathways (necrosis/necroptosis, and apoptosis) and assess the roles of ROS-MAPK/ERK signaling in PFOA-mediated cell death in mouse ameloblast-lineage cells (ALC). ALC cells were treated with PFOA. Cell proliferation and viability were analyzed by MTT assays and colony formation assays, respectively. PFOA suppressed cell proliferation and viability in a dose dependent manner. PFOA induced both necrosis (PI-positive cells) and apoptosis (cleaved-caspase-3, γH2AX and TUNEL-positive cells). PFOA significantly increased ROS production and up-regulated phosphor-(p)-ERK. Addition of ROS inhibitor N-acetyl cysteine (NAC) suppressed p-ERK and decreased necrosis, and increased cell viability compared to PFOA alone, whereas NAC did not change apoptosis. This suggests that PFOA-mediated necrosis was induced by ROS-MAPK/ERK signaling, but apoptosis was not associated with ROS. Addition of MAPK/ERK inhibitor PD98059 suppressed necrosis and increased cell viability compared to PFOA alone. Intriguingly, PD98059 augmented PFOA-mediated apoptosis. This suggests that p-ERK promoted necrosis but suppressed apoptosis. Addition of the necroptosis inhibitor Necrostatin-1 restored cell viability compared to PFOA alone, while pan-caspase inhibitor Z-VAD did not mitigate PFOA-mediated cell death. These results suggest that 1) PFOA-mediated cell death was mainly caused by necrosis/necroptosis by ROS-MAPK/ERK signaling rather than apoptosis, 2) MAPK/ERK signaling plays the dual roles (promoting necrosis and suppressing apoptosis) under PFOA treatment. This is the initial report to indicate that PFOA could be considered as a possible causative factor for cryptogenic enamel malformation. Further studies are required to elucidate the mechanisms of PFOA-mediated adverse effects on amelogenesis.
Topics: Mice; Animals; Reactive Oxygen Species; Ameloblasts; Cell Death; Necrosis
PubMed: 37271104
DOI: 10.1016/j.ecoenv.2023.115089 -
Journal of the Mechanics and Physics of... Feb 2016We argue in favor of representing living cells as automata and review demonstrations that autonomous cells can form patterns by responding to local variations in the...
We argue in favor of representing living cells as automata and review demonstrations that autonomous cells can form patterns by responding to local variations in the strain fields that arise from their individual or collective motions. An autonomous cell's response to strain stimuli is assumed to be effected by internally-generated, internally-powered forces, which generally move the cell in directions other than those implied by external energy gradients. Evidence of cells acting as strain-cued automata have been inferred from patterns observed in nature and from experiments conducted in vitro. Simulations that mimic particular cases of pattern forming share the idealization that cells are assumed to pass information among themselves solely via mechanical boundary conditions, i.e., the tractions and displacements present at their membranes. This assumption opens three mechanisms for pattern formation in large cell populations: wavelike behavior, kinematic feedback in cell motility that can lead to sliding and rotational patterns, and directed migration during invasions. Wavelike behavior among ameloblast cells during amelogenesis (the formation of dental enamel) has been inferred from enamel microstructure, while strain waves in populations of epithelial cells have been observed in vitro. One hypothesized kinematic feedback mechanism, "enhanced shear motility", accounts successfully for the spontaneous formation of layered patterns during amelogenesis in the mouse incisor. Directed migration is exemplified by a theory of invader cells that sense and respond to the strains they themselves create in the host population as they invade it: analysis shows that the strain fields contain positional information that could aid the formation of cell network structures, stabilizing the slender geometry of branches and helping govern the frequency of branch bifurcation and branch coalescence (the formation of closed networks). In simulations of pattern formation in homogeneous populations and network formation by invaders, morphological outcomes are governed by the ratio of the rates of two competing time dependent processes, one a migration velocity and the other a relaxation velocity related to the propagation of strain information. Relaxation velocities are approximately constant for different species and organs, whereas cell migration rates vary by three orders of magnitude. We conjecture that developmental processes use rapid cell migration to achieve certain outcomes, and slow migration to achieve others. We infer from analysis of host relaxation during network formation that a transition exists in the mechanical response of a host cell from animate to inanimate behavior when its strain changes at a rate that exceeds 10-10s. The transition has previously been observed in experiments conducted in vitro.
PubMed: 31178602
DOI: 10.1016/j.jmps.2015.11.002 -
Frontiers in Endocrinology 2021Most cells use calcium (Ca) as a second messenger to convey signals that affect a multitude of biological processes. The ability of Ca to bind to proteins to alter their... (Review)
Review
Most cells use calcium (Ca) as a second messenger to convey signals that affect a multitude of biological processes. The ability of Ca to bind to proteins to alter their charge and conformation is essential to achieve its signaling role. Cytosolic Ca (Ca) concentration is maintained low at ~100 nM so that the impact of elevations in Ca is readily sensed and transduced by cells. However, such elevations in Ca must be transient to prevent detrimental effects. Cells have developed a variety of systems to rapidly clear the excess of Ca including Ca pumps, exchangers and sequestering Ca within intracellular organelles. This Ca signaling toolkit is evolutionarily adapted so that each cell, tissue, and organ can fulfill its biological function optimally. One of the most specialized cells in mammals are the enamel forming cells, the ameloblasts, which also handle large quantities of Ca. The end goal of ameloblasts is to synthesize, secrete and mineralize a unique proteinaceous matrix without the benefit of remodeling or repair mechanisms. Ca uptake into ameloblasts is mainly regulated by the store operated Ca entry (SOCE) before it is transported across the polarized ameloblasts to reach the insulated enamel space. Here we review the ameloblasts Ca signaling toolkit and address how the common electronegative non-metal fluoride can alter its function, potentially addressing the biology of dental fluorosis.
Topics: Ameloblasts; Animals; Calcification, Physiologic; Calcium; Dental Sac; Epithelial Cells; Fluorides; Humans
PubMed: 34456880
DOI: 10.3389/fendo.2021.730913 -
The International Journal of... Feb 1995The basic features on the vitamin D endocrine system, synthesis of the main metabolite 1,25-dihydroxyvitamin D3 (1,25) and its genomic action mediated via the vitamin D... (Review)
Review
The basic features on the vitamin D endocrine system, synthesis of the main metabolite 1,25-dihydroxyvitamin D3 (1,25) and its genomic action mediated via the vitamin D receptor (VDR), are reviewed. Calbindin-D9k, calbindin-D28k and osteocalcin are presented as the most-extensively investigated vitamin D-dependent calcium-binding proteins. The action of 1,25 on the basic process of proliferation and differentiation is introduced. Then, the basis of the systemic theory of vitamin D action on teeth (clinical and experimental data and the dissimilar distribution of VDR and of potential vitamin D-dependent proteins in dental cells) are exposed. Finally, the data obtained with calbindin-D9k, calbindin-D28k, osteocalcin and VDR, which supports the theory that ameloblasts and odontoblasts are target-cells for 1,25 is presented. As a perspective, a cross-survey of the 1,25 and tooth-related literature is proposed which may indicate potential target-genes for 1,25 in teeth as done previously for calbindins-D.
Topics: Ameloblasts; Animals; Calbindin 1; Calbindins; Calcitriol; Humans; Odontoblasts; Osteocalcin; Receptors, Calcitriol; S100 Calcium Binding Protein G; Tooth
PubMed: 7626415
DOI: No ID Found -
Calcified Tissue International Feb 2010During amelogenesis, extracellular matrix proteins interact with growing hydroxyapatite crystals to create one of the most architecturally complex biological tissues.... (Review)
Review
During amelogenesis, extracellular matrix proteins interact with growing hydroxyapatite crystals to create one of the most architecturally complex biological tissues. The process of enamel formation is a unique biomineralizing system characterized first by an increase in crystallite length during the secretory phase of amelogenesis, followed by a vast increase in crystallite width and thickness in the later maturation phase when organic complexes are enzymatically removed. Crystal growth is modulated by changes in the pH of the enamel microenvironment that is critical for proper enamel biomineralization. Whereas the genetic bases for most abnormal enamel phenotypes (amelogenesis imperfecta) are generally associated with mutations to enamel matrix specific genes, mutations to genes involved in pH regulation may result in severely affected enamel structure, highlighting the importance of pH regulation for normal enamel development. This review summarizes the intra- and extracellular mechanisms employed by the enamel-forming cells, ameloblasts, to maintain pH homeostasis and, also, discusses the enamel phenotypes associated with disruptions to genes involved in pH regulation.
Topics: Acid-Base Equilibrium; Ameloblasts; Amelogenesis; Calcification, Physiologic; Crystallization; Dental Enamel; Extracellular Matrix; Gene Expression Regulation, Developmental; Hydrogen-Ion Concentration; Tooth
PubMed: 20016979
DOI: 10.1007/s00223-009-9326-7 -
Journal of Dental Research Aug 2019Enamel formation and quality are dependent on environmental conditions, including exposure to fluoride, which is a widespread natural element. Fluoride is routinely used...
Enamel formation and quality are dependent on environmental conditions, including exposure to fluoride, which is a widespread natural element. Fluoride is routinely used to prevent caries. However, when absorbed in excess, fluoride may also lead to altered enamel structural properties associated with enamel gene expression modulations. As iron plays a determinant role in enamel quality, the aim of our study was to evaluate the iron metabolism in dental epithelial cells and forming enamel of mice exposed to fluoride, as well as its putative relation with enamel mechanical properties. Iron storage was investigated in dental epithelial cells with Perl's blue staining and secondary ion mass spectrometry imaging. Iron was mainly stored by maturation-stage ameloblasts involved in terminal enamel mineralization. Iron storage was drastically reduced by fluoride. Among the proteins involved in iron metabolism, ferritin heavy chain (Fth), in charge of iron storage, appeared as the preferential target of fluoride according to quantitative real-time polymerase chain reaction, Western blotting, and immunohistochemistry analyses. Fluorotic enamel presented a decreased quantity of iron oxides attested by electron spin resonance technique, altered mechanical properties measured by nanoindentation, and ultrastructural defects analyzed by scanning electron microscopy and energy dispersive x-ray spectroscopy. The in vivo functional role of Fth was illustrated with mice, which incorporated less iron into their dental epithelium and exhibited poor enamel quality. These data demonstrate that exposure to excessive fluoride decreases ameloblast iron storage, which contributes to the defective structural and mechanical properties in rodent fluorotic enamel. They raise the question of fluoride's effects on iron storage in other cells and organs that may contribute to its effects on population health.
Topics: Ameloblasts; Amelogenesis; Animals; Epithelial Cells; Fluorides; Fluorosis, Dental; Iron; Male; Mice; Mice, Inbred BALB C
PubMed: 31329045
DOI: 10.1177/0022034519855650