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Frontiers in Cell and Developmental... 2023Tooth formation relies on two types of dental cell populations, namely, the dental epithelium and dental mesenchyme, and the interactions between these cell populations...
Tooth formation relies on two types of dental cell populations, namely, the dental epithelium and dental mesenchyme, and the interactions between these cell populations are important during tooth development. Although human-induced pluripotent stem cells (hiPSCs) can differentiate into dental epithelial and mesenchymal cells, organoid research on tooth development has not been established yet. This study focused on the hiPSC-derived human ameloblast organoid (hAO) using a three-dimensional (3D) culture system. hAOs had similar properties to ameloblasts, forming enamel in response to calcium and mineralization by interaction with the dental mesenchyme. hAOs simultaneously had osteogenic and odontogenic differentiation potential. Furthermore, hAOs demonstrated tooth regenerative potential upon interaction with the mouse dental mesenchyme. Our findings provide new insights into a suitable hiPSC-derived dental source and demonstrate that hAOs can be beneficial not only for tooth regeneration but also for the study of various dental diseases for which treatment has not been developed yet.
PubMed: 37457296
DOI: 10.3389/fcell.2023.1164811 -
Journal of Experimental Zoology. Part... Jul 2009Late tooth morphogenesis is characterized by a series of events that determine crown morphogenesis and the histodifferentiation of epithelial cells into enamel-secreting... (Review)
Review
Late tooth morphogenesis is characterized by a series of events that determine crown morphogenesis and the histodifferentiation of epithelial cells into enamel-secreting ameloblasts and of mesenchymal cells into dentin-secreting odontoblasts. Functional ameloblasts are tall, columnar, polarized cells that synthesize and secrete a number of enamel-specific proteins. After depositing the full thickness of enamel matrix, ameloblasts shrink in size and regulate enamel maturation. Amelogenesis imperfecta (AI) is a heterogeneous group of inherited defects in enamel formation. Clinically, AI presents as a spectrum of enamel malformations that are categorized as hypoplastic, hypocalcified, or hypomaturation types, based upon the thickness and hardness of the enamel. The different types of AI are inherited, either as X-linked, autosomal-dominant, or autosomal-recessive traits. Recently, several gene mutations have been identified to cause the subtypes of AI. How these genes, however, coordinate their function to control amelogenesis is not understood. In this review, we discuss the role of genes that play definitive role on the determination of ameloblast cell fate and life cycle based on studies in transgenic animals.
Topics: Animals; Cell Adhesion; Cell Differentiation; Dental Enamel; Humans; Life Cycle Stages; Mice; Mice, Transgenic; Molecular Biology; Morphogenesis; Odontoblasts; Tooth; Tooth Crown
PubMed: 19090561
DOI: 10.1002/jez.b.21261 -
International Journal of Molecular... Apr 2021TRPM7 plays an important role in cellular Ca, Zn and Mg homeostasis. TRPM7 channels are abundantly expressed in ameloblasts and, in the absence of TRPM7, dental enamel...
TRPM7 plays an important role in cellular Ca, Zn and Mg homeostasis. TRPM7 channels are abundantly expressed in ameloblasts and, in the absence of TRPM7, dental enamel is hypomineralized. The potential role of TRPM7 channels in Ca transport during amelogenesis was investigated in the HAT-7 rat ameloblast cell line. The cells showed strong TRPM7 mRNA and protein expression. Characteristic TRPM7 transmembrane currents were observed, which increased in the absence of intracellular Mg ([Mg]), were reduced by elevated [Mg], and were inhibited by the TRPM7 inhibitors NS8593 and FTY720. Mibefradil evoked similar currents, which were suppressed by elevated [Mg], reducing extracellular pH stimulated transmembrane currents, which were inhibited by FTY720. Naltriben and mibefradil both evoked Ca influx, which was further enhanced by the acidic intracellular conditions. The SOCE inhibitor BTP2 blocked Ca entry induced by naltriben but not by mibefradil. Thus, in HAT-7 cells, TRPM7 may serves both as a potential modulator of Orai-dependent Ca uptake and as an independent Ca entry pathway sensitive to pH. Therefore, TRPM7 may contribute directly to transepithelial Ca transport in amelogenesis.
Topics: Ameloblasts; Anilides; Animals; Calcium; Cell Line; Humans; Hydrogen-Ion Concentration; Incisor; Ion Channel Gating; Ion Transport; Mibefradil; Mice; Models, Biological; Naltrexone; Rats; TRPM Cation Channels; Thiadiazoles
PubMed: 33924361
DOI: 10.3390/ijms22083992 -
Stem Cells and Development Aug 2021The growth of long and polarized ameloblast-like cells has long been heralded as a major prerequisite for enamel tissue engineering. In this study, we have designed...
The growth of long and polarized ameloblast-like cells has long been heralded as a major prerequisite for enamel tissue engineering. In this study, we have designed three-dimensional bioreactor/scaffold microenvironments to propagate and assess the ability of cervical loop derivatives to become long and polarized ameloblast-like cells. Our studies demonstrated that cervical loop/periodontal progenitor coculture in a growth-factor-enriched medium resulted in the formation of ameloblast-like cells expressing high levels of amelogenin and ameloblastin. Coculture of cervical loop cells with dental pulp cells on tailored collagen scaffolds enriched with leucine-rich amelogenin peptide (LRAP) and early enamel matrix resulted in singular, elongated, and polarized ameloblast-like cells that expressed and secreted ameloblastin and amelogenin enamel proteins. Bioreactor microenvironments enriched with enamel matrix and LRAP also proved advantageous for the propagation of HAT-7 cells, resulting in a ∼20-fold higher expression of amelogenin and ameloblastin enamel proteins compared with controls growing on plain scaffolds. Together, studies presented here highlight the benefits of microgravity culture systems combined with ameloblast-specific microenvironments and tailored scaffolds for the growth of ameloblast-like cells.
Topics: Ameloblasts; Amelogenin; Bioreactors; Cell Differentiation; Coculture Techniques; Dental Pulp
PubMed: 34060920
DOI: 10.1089/scd.2021.0115 -
Frontiers in Physiology 2020Enamel is the most calcified tissue in vertebrates. Enamel formation and mineralization is a two-step process that is mediated by ameloblast cells during their secretory...
Enamel is the most calcified tissue in vertebrates. Enamel formation and mineralization is a two-step process that is mediated by ameloblast cells during their secretory and maturation stages. In these two stages, ameloblasts are characterized by different morphology and function, which is fundamental for proper mineral growth in the extracellular space. Ultrastructural studies have shown that the mitochondria in these cells localize to different subcellular regions in both stages. However, limited knowledge is available on the role/s of mitochondria in enamel formation. To address this issue, we analyzed mitochondrial biogenesis and respiration, as well as the redox status of rat primary enamel cells isolated from the secretory and maturation stages. We show that maturation stage cells have an increased expression of PGC1α, a marker of mitochondrial biogenesis, and of components of the electron transport chain. Oxygen consumption rate (OCR), a proxy for mitochondrial function, showed a significant increase in oxidative phosphorylation during the maturation stage, promoting ATP production. The GSH/GSSG ratio was lower in the maturation stage, indicative of increased oxidation. Because higher oxidative phosphorylation can lead to higher ROS production, we tested if ROS affected the expression of and genes that are essential for enamel formation. The ameloblast cell line LS8 treated with HO to promote ROS elicited significant expression changes in and . Our data highlight important metabolic and physiological differences across the two enamel stages, with higher ATP levels in the maturation stage indicative of a higher energy demand. Besides these metabolic shifts, it is likely that the enhanced ETC function results in ROS-mediated transcriptional changes.
PubMed: 32547417
DOI: 10.3389/fphys.2020.00538 -
International Journal of Molecular... Nov 2020Dental enamel is hardest tissue in the body and is produced by dental epithelial cells residing in the tooth. Their cell fates are tightly controlled by transcriptional... (Review)
Review
Dental enamel is hardest tissue in the body and is produced by dental epithelial cells residing in the tooth. Their cell fates are tightly controlled by transcriptional programs that are facilitated by fate determining transcription factors and chromatin regulators. Understanding the transcriptional program controlling dental cell fate is critical for our efforts to build and repair teeth. In this review, we describe the current understanding of these regulators essential for regeneration of dental epithelial stem cells and progeny, which are identified through transgenic mouse models. We first describe the development and morphogenesis of mouse dental epithelium in which different subpopulations of epithelia such as ameloblasts contribute to enamel formation. Then, we describe the function of critical factors in stem cells or progeny to drive enamel lineages. We also show that gene mutations of these factors are associated with dental anomalies in craniofacial diseases in humans. We also describe the function of the master regulators to govern dental lineages, in which the genetic removal of each factor switches dental cell fate to that generating hair. The distinct and related mechanisms responsible for the lineage plasticity are discussed. This knowledge will lead us to develop a potential tool for bioengineering new teeth.
Topics: Ameloblasts; Animals; Cell Differentiation; Epithelial Cells; Epithelium; Gene Expression Regulation; Humans; Mice; Mice, Transgenic; Odontogenesis; Tooth; Transcription, Genetic
PubMed: 33255698
DOI: 10.3390/ijms21238952 -
The Journal of Physiology May 2017Dental enamel is one of the most remarkable examples of matrix-mediated biomineralization. Enamel crystals form de novo in a rich extracellular environment in a... (Review)
Review
Dental enamel is one of the most remarkable examples of matrix-mediated biomineralization. Enamel crystals form de novo in a rich extracellular environment in a stage-dependent manner producing complex microstructural patterns that are visually stunning. This process is orchestrated by specialized epithelial cells known as ameloblasts which themselves undergo striking morphological changes, switching function from a secretory role to a cell primarily engaged in ionic transport. Ameloblasts are supported by a host of cell types which combined represent the enamel organ. Fully mineralized enamel is the hardest tissue found in vertebrates owing its properties partly to the unique mixture of ionic species represented and their highly organized assembly in the crystal lattice. Among the main elements found in enamel, Ca is the most abundant ion, yet how ameloblasts modulate Ca dynamics remains poorly known. This review describes previously proposed models for passive and active Ca transport, the intracellular Ca buffering systems expressed in ameloblasts and provides an up-dated view of current models concerning Ca influx and extrusion mechanisms, where most of the recent advances have been made. We also advance a new model for Ca transport by the enamel organ.
Topics: Ameloblasts; Animals; Biological Transport; Calcium; Calcium Signaling; Dental Enamel; Humans
PubMed: 27510811
DOI: 10.1113/JP272775 -
Journal of Structural Biology Dec 2021During enamel formation, the organic enamel protein matrix interacts with calcium phosphate minerals to form elongated, parallel, and bundled enamel apatite crystals of... (Review)
Review
During enamel formation, the organic enamel protein matrix interacts with calcium phosphate minerals to form elongated, parallel, and bundled enamel apatite crystals of extraordinary hardness and biomechanical resilience. The enamel protein matrix consists of unique enamel proteins such as amelogenin, ameloblastin, and enamelin, which are secreted by highly specialized cells called ameloblasts. The ameloblasts also facilitate calcium and phosphate ion transport toward the enamel layer. Within ameloblasts, enamel proteins are transported as a polygonal matrix with 5 nm subunits in secretory vesicles. Upon expulsion from the ameloblasts, the enamel protein matrix is re-organized into 20 nm subunit compartments. Enamel matrix subunit compartment assembly and expansion coincide with C-terminal cleavage by the MMP20 enamel protease and N-terminal amelogenin self-assembly. Upon enamel crystal precipitation, the enamel protein phase is reconfigured to surround the elongating enamel crystals and facilitate their elongation in C-axis direction. At this stage of development, and upon further amelogenin cleavage, central and polyproline-rich fragments of the amelogenin molecule associate with the growing mineral crystals through a process termed "shedding", while hexagonal apatite crystals fuse in longitudinal direction. Enamel protein sheath-coated enamel "dahlite" crystals continue to elongate until a dense bundle of parallel apatite crystals is formed, while the enamel matrix is continuously degraded by proteolytic enzymes. Together, these insights portrait enamel mineral nucleation and growth as a complex and dynamic set of interactions between enamel proteins and mineral ions that facilitate regularly seeded apatite growth and parallel enamel crystal elongation.
Topics: Ameloblasts; Amelogenesis; Amelogenin; Animals; Apatites; Calcium; Calcium Phosphates; Crystallization; Dental Enamel; Dental Enamel Proteins; Humans; Microscopy, Electron; Minerals
PubMed: 34748943
DOI: 10.1016/j.jsb.2021.107809 -
Matrix Biology : Journal of the... 2016Several diseases such as proximal and distal renal tubular acidosis and osteoporosis are related to intracellular pH dysregulation resulting from mutations in genes... (Review)
Review
Several diseases such as proximal and distal renal tubular acidosis and osteoporosis are related to intracellular pH dysregulation resulting from mutations in genes coding for ion channels, including proteins comprising the proton-pumping V-type ATPase. V-type ATPase is a multi-subunit protein complex expressed in enamel forming cells. V-type ATPase plays a key role in enamel development, specifically lysosomal acidification, yet our understanding of the relationship between the endocytotic activities and dental health and disease is limited. The objective of this study is to better understand the ameloblast-associated pH regulatory networks essential for amelogenesis. Quantitative RT-PCR was performed on tissues from secretory-stage and maturation-stage enamel organs to determine which of the V-type ATPase subunits are most highly upregulated during maturation-stage amelogenesis: a time when ameloblast endocytotic activity is highest. Western blot analyses, using specific antibodies to four of the V-type ATPase subunits (Atp6v0d2, Atp6v1b2, Atp6v1c1 and Atp6v1e1), were then applied to validate much of the qPCR data. Immunohistochemistry using these same four antibodies was also performed to identify the spatiotemporal expression profiles of individual V-type ATPase subunits. Our data show that cytoplasmic V-type ATPase is significantly upregulated in enamel organ cells during maturation-stage when compared to secretory-stage. These data likely relate to the higher endocytotic activities, and the greater need for lysosomal acidification, during maturation-stage amelogenesis. It is also apparent from our immunolocalization data, using antibodies against two of the V-type ATPase subunits (Atp6v1c1 and Atp6v1e1), that significant expression is seen at the apical membrane of maturation-stage ameloblasts. Others have also identified this V-type ATPase expression profile at the apical membrane of maturation ameloblasts. Collectively, these data better define the expression and role of the V-type ATPase proton pump in the enamel organ during amelogenesis.
Topics: Ameloblasts; Animals; Cytoplasm; Dental Enamel; Enamel Organ; Endosomes; Gene Expression Regulation, Developmental; Lysosomes; Male; Rats; Vacuolar Proton-Translocating ATPases
PubMed: 26586472
DOI: 10.1016/j.matbio.2015.11.004 -
Organoids from mouse molar and incisor as new tools to study tooth-specific biology and development.Stem Cell Reports May 2023Organoid models provide powerful tools to study tissue biology and development in a dish. Presently, organoids have not yet been developed from mouse tooth. Here, we...
Organoid models provide powerful tools to study tissue biology and development in a dish. Presently, organoids have not yet been developed from mouse tooth. Here, we established tooth organoids (TOs) from early-postnatal mouse molar and incisor, which are long-term expandable, express dental epithelium stem cell (DESC) markers, and recapitulate key properties of the dental epithelium in a tooth-type-specific manner. TOs display in vitro differentiation capacity toward ameloblast-resembling cells, even more pronounced in assembloids in which dental mesenchymal (pulp) stem cells are combined with the organoid DESCs. Single-cell transcriptomics supports this developmental potential and reveals co-differentiation into junctional epithelium- and odontoblast-/cementoblast-like cells in the assembloids. Finally, TOs survive and show ameloblast-resembling differentiation also in vivo. The developed organoid models provide new tools to study mouse tooth-type-specific biology and development and gain deeper molecular and functional insights that may eventually help to achieve future human biological tooth repair and replacement.
Topics: Animals; Mice; Humans; Incisor; Ameloblasts; Molar; Cell Differentiation; Organoids; Biology
PubMed: 37084723
DOI: 10.1016/j.stemcr.2023.03.011