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PubMed1989

[Study of trace elements in bovine permanent teeth germ].

It is well documented that uptake of various trace elements take place during tooth development. The purpose of this experiment was to analyze the uptake amount of these various trace elements, in particular Cd, Zn, Pb and Cu throughout the tooth germ formation all the way up to the eruption stage. Bovine permanent tooth germs were used in this experiment. Instead of the conventional morphologic stages, further subdivision into eight groups were employed. The resultant findings were as follows: 1) Uptake of Cd and Zn were verified during the root development to early tooth eruption stage in enamel. Meanwhile, for dentin, the uptake was corroborated from the root development to the late tooth eruption stage. 2) Uptake of Cu was verified during the late tooth eruption stage in enamel. However, no uptake occurred in dentin in any of the various stages. 3) Uptake of Pb occurred during the late tooth eruption stage in enamel. Meanwhile, in dentin, constant equivalent amount of uptake was seen throughout all of the stages. 4) Quantitative analysis of the Cd, Zn and Pb uptake in both enamel and dentin clearly indicated that enamel showed much higher values. The uptake of Cu was found to be significantly high in the groups of the coronal one-third and the eruption four-fifth groups for enamel. Meanwhile, the crown completion group to the half erupted group showed significantly high values for dentin. Based on the above findings, one can deduce clear correlation between enamel organ development and the uptake of the said various trace elements.

Animals↗
PubMed1991

Distribution of extracellular matrix proteins in odontogenic tumours and developing teeth.

The distribution of two cellular fibronectins (cFn), tenascin, laminin, as well as type VII collagen was studied in 14 benign odontogenic tumours of epithelial (ameloblastoma) and epithelial-ectomesenchymal (ameloblastic fibroma) origins, as well as in developing human teeth by immunocytochemical means using monoclonal antibodies (Mabs). An extradomain sequence-A-containing form of cFn (EDA-cFn) was seen in the extracellular matrix (ECM) of all tumours studied and in the mesenchyme of the developing tooth germs, indicating that cFn in these tissues are predominantly produced locally. A form of cFn containing an oncofetal domain (Onc-cFn), hitherto found only in carcinomas, was detected focally in the stroma of most ameloblastomas but was absent from ameloblastic fibromas and tooth germs. Tenascin was strongly expressed in the basement membrane (BM) zone of all odontogenic tumours and in that of the early tooth germs. Focal absence of laminin and type VII collagen from the BM of some ameloblastomas and the presence of Onc-cFn in the ECM of most ameloblastomas may correlate with their aggressive behaviour. The results also suggest that EDA-cFn and tenascin are involved in epithelial-mesenchymal interactions during tooth development and in odontogenic tumours.

Adolescent↗
PubMed2003

Comparison of expression patterns between CREB family transcription factor OASIS and proteoglycan core protein genes during murine tooth development.

The transcription factor OASIS gene, which encodes for a CREB/ATF family member, is specifically expressed in the salivary gland, the cartilage and the tooth germs of the mouse embryo. In the present study, the expression patterns were compared between OASIS mRNA and major vertebrate proteoglycans, which might be the downstream genes of OASIS in the tooth germs of mouse first mandibular molars, through in situ hybridization histochemistry. OASIS mRNA expression was observed in the inner enamel epithelium during the cap and bell stages (E14.5-E18.5) in the preodontoblasts during differentiation stage (E18.5-P0) and in the differentiating odontoblasts during the early secretory stage (P2.5-P4.5). Proteoglycans (versican, decorin, biglycan, glypican, syndecan-1, and syndecan-3) were expressed in the tooth germs in various patterns. Decorin, biglycan, syndecan-1 and syndecan-3 showed gene expressions overlapping with OASIS. Especially the expression pattern of decorin and syndecan-3 coincided temporally and spatially exactly with that of OASIS. These results suggest that the OASIS gene might be related to proteoglycan expression and may play an important role in the differentiation of the odontoblast and cells in inner enamel epithelium.

Aggrecans↗
PubMed1991

The homeobox gene Hox 7.1 has specific regional and temporal expression patterns during early murine craniofacial embryogenesis, especially tooth development in vivo and in vitro.

Hox 7.1 is a murine homeobox-containing gene expressed in a range of neural-crest-derived tissues and areas of putative epithelial-mesenchymal interactions during embryogenesis. We have examined the expression of Hox 7.1 during craniofacial development in the mouse embryo between days 8 and 16 of development. Whereas facial expression at day 10 of gestation is broadly localised in the neural-crest-derived mesenchyme of the medial nasal, lateral nasal, maxillary and mandibular processes, by day 12 expression is restricted to the mesenchyme immediately surrounding the developing tooth germs in the maxillary and mandibular processes. Hox 7.1 expression in the mesenchyme of the dental papilla and follicle is maximal at the cap stage of development and progressively declines in the bell stage prior to differentiation of odontoblasts and ameloblasts. Hox 7.1 expression in tooth germs is independent of overall embryonic stage of development but is dependent on stage of development of the individual tooth. Similar patterns of transient Hox 7.1 expression can also be detected in tooth germs in vitro in organ cultures of day 11 first branchial arch explants cultured for up to 7 days. Hox 7.1 is also expressed early in development (days 10/11) in the epithelium of the developing anterior pituitary (Rathke's pouch), the connective tissue capsule and meninges of the developing brain, and specific regions of neuroepithelium in the developing brain.

Animals↗
PubMed2005

Tooth development in vitro in two teleost fish, the cichlid Hemichromis bimaculatus and the cyprinid Danio rerio.

A technique for organotypic in vitro culture with serum-free medium was tested for its appropriateness to mimic normal odontogenesis in the cichlid fish Hemichromis bimaculatus and the zebrafish Danio rerio. Serial semithin sections were observed by light microscopy to collect data on tooth patterning and transmission electron microscopy was used to compare cellular and extracellular features of tooth germs developing in vitro with the situation in vivo. Head explants of H. bimaculatus from 120 h post-fertilization (hPF) to 8.5 days post-fertilization (dPF) and of zebrafish from 45 hPF to 79 hPF and adults kept in culture for 3, 4 or 7 days revealed that tooth germs developed in vitro from explants in which the buccal or pharyngeal epithelium was apparently undifferentiated and, when present at the time of explantation, they continued their development up to a stage of attachment. In addition, the medium allowed the morphogenesis and cytodifferentiation of the tooth germs similar to that observed in vivo and the establishment of a dental pattern (place and order of tooth appearance and of attachment) that mimicked that in vivo. Organotypic culture in serum-free conditions thus provides us with the means of studying epithelial-mesenchymal interactions during tooth development in teleost fish and of analysing the genetic control of either mandibular or pharyngeal tooth development and replacement in these polyphyodont species. Importantly, it allows heads from embryonically lethal (zebrafish) mutants or from early lethal knockdown experiments to develop beyond the point at which the embryos normally die. Such organotypic culture in serum-free conditions could therefore become a powerful tool in developmental studies and open new perspectives for craniofacial research.

Animals↗
PubMed1979

Uptake of radioactive calcium by hard tissue cells.

45Ca was injected into prenatal mice to study the calcium uptake by tooth germ cells. Both dental papillae, containing the odontoblasts, and the enamel organs were found to actively metabolized the labeled calcium. The maximum specific radioactivity occurred at 15 minutes after injection. The subcellular organelles (e.g. mitochondria) of the papillae were more active in metabolizing the labeled calcium whereas a large portion of the radioactivity of the enamel organ was found in a fraction containing the precalcified material. In fetal tooth germs, the rate of incorporation of labeled calcium into the precalcified material was slower than in the postnatal tooth germs since a large portion of the radioactivity remained in the soluble fraction.

Animals↗
PubMed2004

Immunohistochemical localization of periostin in tooth and its surrounding tissues in mouse mandibles during development.

Previous reports have shown expression of immunoreactivity for periostin, originally identified as osteoblast-specific factor-2, in the periosteum and periodontal ligament. However, the developmental changes in its expression and the detailed immunolocalization have remained veiled. The present study was undertaken to examine the spatiotemporal expression of this protein in teeth and their associated tissues of mice during development at light and electron microscopic levels. In tooth germs at cap stage, periostin immunoreactivity was recognizable in the interface between inner enamel epithelium and preodontoblasts as well as in the mesenchymal tissues around cervical loop. Dental follicles around tooth germs at bell stage localized periostin immunopositivity in addition to the immunopositive areas observed in cap-staged tooth germs, although the functional significance of periostin has remained unclear in tooth development. Furthermore, periostin immunoreactivity was also found in the alveolar bone surface. In the incisors of both 7- and 21-day-old mice, immunoreaction for periostin was discernible in the lingual periodontal ligament and labial fibrous tissue adjacent to the papillary layer. After postnatal day 7, immunoreaction for periostin came to be restricted to the fibrous bundles in the periodontal ligament in accordance with the organization of the periodontal fibers, indicating its localization matched the morphogenesis of the periodontal ligament. Immunoelectron microscopic observation of the mature periodontal ligament verified the localization of periostin between the cytoplasmic processes of periodontal fibroblasts and cementoblasts and the adjacent collagen fibrils. Our findings suggest that periostin is involved at the sites of the cell-to-matrix interaction, serving as adhesive equipment for bearing mechanical forces, including occlusal force and tooth eruption.

Animals↗
PubMed2000

Early development of the tush and the tusk of the African elephant (Loxodonta africana).

This early development was studied from a serial histological sections of eight elephant embryos with masses varying between 1 and 240 g. The tush and the tusk develop from one tooth germ in a deciduous to permanent tooth relation. In order to study the mineralization of the dental organ of the tush and cap and bell stage of the tusk, embryos older than 3-months' gestation (weighing more than 250 g) would be required.

Animals↗
PubMed1993

In vivo and in vitro study of the effects of chlorpromazine on tooth mineralization in rats and mice.

The effects of chlorpromazine (CPZ) on tooth mineralization were examined using incisor dentine in adult rats and cultured tooth germs of mandibular first molars dissected from mouse embryos. CPZ (10, 50 and 250 mg/kg, s.c.) substantially inhibited dentine mineralization as evaluated by contact microradiographs. Plasma calcium and phosphorus concentrations were not decreased by CPZ (10 and 50 mg/kg). Physicochemical effects were not involved in the action of CPZ on the mineralization. In vitro experiments showed that CPZ (1 and 10 microM) inhibited mineralization and alkaline phosphatase (ALP) activity in the tooth germs. As CPZ has the properties of a calmodulin antagonist, the calmodulin antagonists W-7 and W-5 were also examined. Both inhibited mineralization and ALP activity in tooth germs; W-5 had less effect than W-7. These in vivo and in vitro findings suggest that CPZ inhibited cell-mediated mineralization in dentine without affecting the calcium-regulating system and physicochemical mineral deposition. In addition, calmodulin could be involved in cell-mediated mineralization.

Alkaline Phosphatase↗
PubMed2004

Tissue distribution and nucleotide sequence of bovine mRNA for salivary proline-rich protein P-B.

The tissue distribution of P-B was investigated to obtain information on the physiological significance of this proline-rich protein. To design primers and probes for a tissue distribution analysis, a polymerase chain reaction (PCR)-based cloning of bovine P-B cDNA was performed using tooth germ and the nucleotide sequence was determined. The cloned bovine P-B cDNA was composed of 356 bp and included the region corresponding to the mature P-B protein and part of the 3' non-coding sequence. This part of the sequence is identical to the corresponding region of human P-B cDNA from the submaxillary gland. DNA corresponding to the P-B mRNA was amplified by PCR using cDNAs from various bovine tissues including tooth germ, submaxillary gland, parotid gland, lachrymal gland, heart, liver, stomach, pancreas, spleen, kidney, adrenal, and ovary. A quantitative analysis indicated the heart, submaxillary gland, tooth germ and kidney to be major sites of P-B expression. The ubiquitous distribution of P-B mRNA among bovine tissues together with findings of the presence of genes hybridizable with a DNA probe for P-B among species such as human, bovine, rat, mouse, and yeast as reported previously suggested a fundamental physiological role for this protein.

Amino Acid Sequence↗
PubMed1978

Ultrastructural and cytochemical studies on the matrix vesicle calcification in the teeth of the killifish, Oryzias latipes.

Tooth germs of killifish were examined by both ultrastructural and cytochemical methods. The ultrastructure of the dentin in the early calcification stage of its development resembled that of mammals. Numerous extracellular membrane-bounded vesicles, matrix vesicles, were seen in the predentinal space, especially abundantly in the basal portion of the tooth germ. They were more numerous and more uniform in appearance than in any other higher vertebrates. Where calcification was going to start, slightly identifiable needles of apatite crystals were found in the vesicular structures. Crystals increase in number filling up the vesicles and then ther surroundings, finally to form many calcified spherules. Where calcification was more extensive, the matrix vesicles were no longer visible having been buried calcified among spherules. Contrary, to popular belief, there was no relationship seen between collagen fibrils and the initial deposits of minerals, that is, collagen fibrils did not seem to work as the initial site of calcification. Instead, matrix vesicles and plasma membranes of odontoblasts likely were involved in calcification as they both showed alkaline phosphatase activity. The ultrastructural and cytochemical findings from this study thus indicated that calcification of the killifish tooth germs was initiated not in the enamel, but in their dentin by the matrix vesicles which were liberated into the dentin matrix from odontoblasts mainly by way of fragmentation of cell processes.

Animals↗
PubMed1978

In vitro inhibition of mouse dental development by tetracycline.

Embryonic molars and incisors were dissected from mandibles of 15-day post-fertilization C57BL/10 mouse embryos and were cultured in vitro for six days on agar-solidified Eagle's basal medium. Experimental explants were cultured on medium which was the same as the control except that 50, 75 or 100 microgram/ml tetracycline was added. Treated explants of both incisors and molars were suppressed in development and reduced in size. Enamel organs and dental papillae of all tooth germs subjected to higher tetracycline concentrations were abnormal in structure and differentiation of ameloblasts and odontoblasts was inhibited. Explants treated with higher dosage levels of the drug were more severely affected than those exposed to lower concentrations. Recovery from the suppression induced by tetracycline was observed in explants transferred to control medium for four days of growth following treatment. Differentiated ameloblasts and odontoblasts observed in the recovering tooth germs indicated that the inhibition in development was temporary. The results of this study showed that tetracycline can alter dental development in vitro prior to mineralization. The observed inhibition may be related to a disruption of collagen biosynthesis which is thought to play a role in the controlling epithelial-mesenchymal interaction involved in tooth germ morphogenesis.

Animals↗
PubMed1996

Light microscopic detection of sugar residues in rabbit embryo teeth with lectin-horseradish peroxidase conjugates.

We investigated the binding of five HRP-conjugated lectins to rabbit tooth germs at the cap and late bell stages of development. The results revealed some changes in the glycosylation patterns of the glycoconjugates. Sugar residues, such as alpha-D-mannose, methyl-D-glucose, N-acetylglucosamine, beta-D-galactosamine, D-galactose, and sialic acid, were detectable in some components of the tooth germs. The most conspicuous developmental change was increased binding of Con A and WGA. These lectins showed, at the cap stage, moderate binding to the (pre)-ameloblasts and (pre)-odontoblasts. With further development to the late bell stage, but prior to the achievement of well-defined morphological-functional characteristics, the odontoblasts and ameloblasts displayed considerable amounts of alpha-D-mannose, alpha-D-glucose as well as beta-D-acetylglucosamine and sialic acid. Appropriate control studies confirmed the specificity of the binding of the lectins. Two lectins (DBA and PNA) with known specificity for N-acetylgalactosamine groups were bound by the basement membranes in tooth germs at the cap stage. A third lectin (RCA) with the same specificity did not produce any detectable staining in the same material. Further studies must be planned to determine the specific functions and significance of lectin-HRP-binding glycoconjugates in odontogenesis.

Animals↗
PubMed1988

Effect of colchicine on the transport of precursor enamel protein in secretory ameloblasts studied by 3H-proline radioautography in vitro.

The incorporation of 3H-proline into the secretory ameloblasts of rat molar tooth germs cultured with or without colchicine was studied by light and electron microscope radioautography to determine the function of microtubules in the transport of precursor enamel protein from the rough-surfaced endoplasmic reticulum (rER) to the Golgi cisternae. The grain counts over the transitional vesicles, which accumulated in various cellular regions with colchicine treatment, continued to increase with chase time, unlike in controls. At 30 and 90 min chase, these counts were significantly higher than in controls. Moreover, the total grain count over the organelles (rER, pale granules, and transitional vesicles), which are positioned before the Golgi cisternae in the synthetic pathway, maintained a significantly higher level at 90 min chase in colchicine-treated tooth germs than in controls. The transport of synthesized protein to the Golgi cisternae via transitional vesicles was suppressed in colchicine-treated tooth germs. Some grains appeared with time over pale granular materials that appeared in the intercellular spaces of secretory ameloblasts with colchicine treatment. However, at each chase period, the grain count over pale granular materials was not so high as the count over the enamel in control. The present results indicate that colchicine affects the transport of newly synthesized protein from the rER to the Golgi cisterna via transitional vesicles, probably by interfering with the oriented transport related to microtubular function. It is suggested that the microtubular system may be concerned with the movement of the transitional vesicles.

Ameloblasts↗
PubMed1982

A morphometric and biochemical study of the pre-eruptive development of hamster molars in vivo.

Surface area measurements of cross-sections of M1 and M2 at 1-11 days were related to biochemical parameters for cell proliferation ([3H]-thymidine incorporation) and mineralization (45Ca uptake) and with increase in dry weight. The pre-eruptive development of molar tooth germs was divided into 4 phases which partly reflect the life cycle stages of the ameloblast. In phase 1 (proliferation phase, duration in M2 about 5 days) mitotic activity and increase in total area were great; ameloblasts were undifferentiated or in a pre-secretory state. In phase 2 (differentiation phase, duration 2-3 days) the number of secretory ameloblasts increased and 45Ca uptake started and increased rapidly. At the end of phase 2, crown morphogenesis was completed and cell proliferation ([3H]-thymidine incorporation) became less. In phase 3 (secretion phase, duration 0.5-1 days) all ameloblasts throughout the tooth germ had differentiated into secretory ameloblasts and enamel matrix surface area increased about twice as fast as that of dentine. At the end of phase 3, the surface area of the enamel matrix almost attained its final value. In phase 4 (maturation phase, duration in M1 till first eruption about 2-3 days), post-secretory ameloblasts increased in number and, in contrast to the surface area of the enamel matrix, that of the dentine continued to increase. The fast, linearly increasing total uptake of 45Ca during phase 4 which was attributed to the mineralization of both newly formed dentine and existing maturing enamel was the main cause of the rapid increase in dry weight of the whole tooth germ.

Amelogenesis↗
PubMed2002

Impaired dental cytodifferentiation in glial cell-line derived growth factor (GDNF) deficient mice.

Glial cell line-derived neurotrophic factor promotes the survival of multiple neuron types in the central and peripheral nervous system. Moreover, it plays a key role in the development of the enteric nervous system and in the kidney organogenesis. Glial cell line-derived neurotrophic factor and their receptors are expressed in the developing tooth as well as in the trigeminal ganglion. However, the precise role of this growth factor in tooth morphogenesis and cell differentiation, or in the development of trigeminal ganglion cells, is still elusive. Using structural and ultrastructural techniques we analyzed in detail the first molar tooth germ of glial cell line-derived neurotrophic factor deficient mice as well as the neuronal density in trigeminal ganglion. The length and width of first molar tooth germ in knockout deficient animals showed no differences in the knockout animals in comparison with age-matched heterozygous or wild-type littermates. Nevertheless, in mice lacking glial cell line-derived neurotrophic factor, both ameloblasts and odontoblasts failed to fully develop and differentiate, and the enamel matrix and predentin layers were absent. On the other hand, the number of trigeminal sensory neurons and the structure of the nerves supplying first molar tooth germ were largely normal. Present results suggest a new non-neuronal role for glial cell line-derived neurotrophic factor in tooth development. Glial cell line-derived neurotrophic factor seems not to be involved in tooth initiation and morphogenesis, whereas it seems essential for cytodifferentiation. Conversely, neither development of trigeminal neuron nor nerve fibers supplying teeth are directly dependent on glial cell line-derived neutrophic factor.

Animals↗
PubMed1990

Immunohistochemical study of the relationship between extracellular matrix and root bifurcation in the mouse molar.

In order to investigate epithelial-mesenchymal interaction during root bifurcation, the distribution of type III and I collagen, fibronectin and laminin in the epithelial-mesenchymal junction between the dental epithelia (epithelial diaphragm and interradicular process) and the cells of the dental papilla (or pre-odontoblasts) was examined, using maxillary first molar tooth germs of CF1 mice from day 1-16 after birth. Three-dimensional reconstructions of the immunofluorescent patterns were made from serial sections of tooth germs from day 3-9, stained with the antibodies against the collagens. The findings were as follows. (1) Type III collagen was first seen in the epithelial-mesenchymal junction at the tip of the interradicular process, where it sprouted from the epithelial diaphragm, and spread along the interradicular process toward its base, accompanied its extension, and then disappeared on completion of root bifurcation. No staining was seen in the epithelial-mesenchymal junction at the epithelial diaphragm during and after root bifurcation. (2) Type I collagen appeared in the epithelial-mesenchymal junction at the base of the interradicular process, where it sprouted from the epithelial diaphragm and spread toward the tip of the interradicular process, following its extension, and increased on completion of the root bifurcation. No staining was seen in the epithelial-mesenchymal junction at the epithelial diaphragm during or after root bifurcation. (3) Fibronectin and laminin remained constant in the epithelial-mesenchymal junction, both at the interradicular process and the epithelial diaphragm, during and after root bifurcation. These findings suggest that type III collagen may play a significant role in the early stage of root bifurcation in the molar.

Animals↗
PubMed2005

Matrix metalloproteinase inhibition impairs the processing, formation and mineralization of dental tissues during mouse molar development.

Organotypic cultures of embryonic mouse tooth germs were used to investigate the developmental expression and roles of MMPs in the formation and mineralization of dentin and enamel matrices. The spatially and temporally regulated expression of MMP-2, MMP-9 and MMP-20 in developing mouse tooth germs in vivo was maintained in culture. The inhibition of metalloproteinases activity by marimastat altered the morphogenesis and mineralization of the tooth germs associated with an inhibition of the activation of both MMP-20 and MMP-2. MMP inhibition deregulated the molecular processing of two major dental matrix proteins, amelogenin and dentin sialoprotein (DSP). This coincided with their accumulation and the loss of their normal distribution within the extracellular matrix, resulting in a defective mineralization of dentin and enamel matrices. These findings demonstrate the critical role of MMPs in the processing and maturation of the dental matrix.

Amelogenesis↗