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PubMed1981

[3H]glucosamine and [3H]proline radioautography of embryonic mouse dental basement membrane.

[3H]proline and [3H]glucosamine radioautography was performed to analyze the labeling pattern of mouse embryonic dental basement membrane before and during odontoblast terminal differentiation. Sixteen- and eighteen-day-old first lower molars and trypsin-isolated enamel organs, as well as EDTA-isolated dental papillae, were used. Continuous labeling for 12 to 24 hr was required with [3H]proline to obtain a clear labeling of epithelial-mesenchymal junction in intact tooth germs or accumulation of surface label in trypsin-isolated enamel organs. With [3H]glucosamine, after 6-hr labeling, the epithelial-mesenchymal junction was heavily labeled and the trypsin-isolated enamel organs accumulated substantial amounts of surface label, corresponding to the redeposited basement membrane. At Day 16 stage, these labels always had a uniform distribution and decreased during chase without any redistribution. At Day 18 stage, when the terminal differentiation of odontoblasts occurred the label accumulated in a unique pattern: much more label was at the epithelial surface corresponding to the top of the cusps than in the apical parts. During chase and only in intact tooth germs epithelial surfaces which had labeled poorly during pulse became labeled, but those labeling heavily during pulse lost label. This pattern existed only in the presence of mesenchyme. EDTA treatment of [3H]glucosamine-labeled teeth enabled us to obtain isolated dental papillae with surface label. Distribution of this label was exactly the same as that for the epithelial-mesenchymal junction of intact teeth. During chase, these dental papillae completely lost the surface label. The mesenchyme seen to control the synthesis and/or the degradation of epithelially derived [3H]glucosamine-labeled material.

Animals↗
PubMed1995

Basic mechanisms of cytodifferentiation and dentinogenesis during dental pulp repair.

Based on recent literature, the specific potential of mature pulp cells to differentiate into polarized cells able to elaborate reparative dentin is described. These odontoblast-like cells are distinguished, by morphological criteria, from the other matrix-formative cells involved in non-specific defensive mechanisms of dental pulp. The suitable tissue conditions and the normal cascade of reparative events, allowing initiation of dentinogenesis in sites of amputated pulp, are presented. This is followed by a review of current observations on specific dentinogenic events, induced in various culture systems or in intrapulpal sites of mature teeth by artificial bio-molecules or bio-matrices. Data from these experiments are focused on the role of extracellular matrix molecules and growth factors in acquisition of the odontoblast-like cell phenotype and initiation of reparative dentinogenesis.

Animals↗
PubMed1994

Localization of ornithine decarboxylase in mouse teeth. An in vitro and in vivo study.

Ornithine decarboxylase (ODC), a key enzyme in polyamine biosynthesis, and thus in tissue growth and development, has been localized in mouse dental tissues, in vivo as well as in vitro by light and electron microscopic autoradiography with radiolabeled alpha-difluoromethylornithine ([3H]DFMO). Mandibular first molar germs from day-18 fetuses were incubated in vitro in the presence of [3H]DFMO and processed for autoradiography. For ODC localization in vivo, 3-day old puppies received [3H]DFMO by injection. As controls, puppies were injected either with unlabeled DFMO, or with cycloheximide before administration of isotope. Kidneys and mandibles were excised and processed for autoradiography. In vitro, labeling was found in all cell types of the tooth germ, but with a more intense labeling in ameloblasts and odontoblasts. In both these, radioactivity decreased from the tip of the cusps to the cervical loop. In vivo the binding of [3H]DFMO in cells of the ameloblast and odontoblast lineages, respectively, showed a gradual increase form the posterior end of the incisor to its anterior end. The distribution of radioactivity in the kidney was in accordance with findings by others. Both the kidney and tooth cell labeling decreased strongly after cycloheximide treatment. The results show that ODC is expressed in tooth-forming cells, and that ODC is not only present in differentiating cells but occurs at higher amounts in mature, secreting cells. The findings suggest that polyamines have a central role in tooth development.

Aging↗
PubMed1994

Cloning and sequence determination of rat dentin sialoprotein, a novel dentin protein.

Dentin sialoprotein (DSP) is a 53-kDa protein isolated from rat dentin. It contains 29.6% carbohydrate (including 9% sialic acid) and has an overall composition similar to that of the bone sialoproteins osteopontin and bone sialoprotein (i.e. rich in Asp, Ser, Glu, and Gly). Using a monospecific anti-DSP polyclonal antibody to screen a rat incisor odontoblast cDNA library, a cDNA clone was isolated and sequenced. This approximately 750-base pair clone contained a DNA sequence corresponding to the NH2-terminal 9 amino acids of DSP. A second cDNA clone was isolated by using the first cDNA as a probe to rescreen the library. This second clone had the full-length DSP coding region. From the sequence, we deduced that the DSP cDNA coded for 366 amino acids, predominantly Asp, Ser, Glu, and Gly. The amino acid composition calculated for this sequence was very similar to that for purified DSP reported earlier; likewise the deduced molecular weight (53,045) was essentially identical to that determined by sedimentation equilibrium. Six potential N-linked glycosylation sites were present in the predicted DSP sequence. No Arg-Gly-Asp sequence was found, and the sequence for DSP was dissimilar to those of osteopontin and bone sialoprotein. Multiple transcripts near 4.6 and 1.5 kilobases were detected by Northern blot analysis in the incisor of 21-day-old rat and the tooth germ of the newborn rat. Consistent with previous immunohistochemical findings, no transcripts were detected in brain, salivary gland, heart, muscle, spleen, kidney, intestine, lung, liver, pancreas, tibia, calvaria, or osteoblast-like osteosarcoma (ROS 17/2.8) cells, indicating that DSP is specifically expressed by odontoblasts and related cells.

Amino Acid Sequence↗
PubMed1994

Isolation of dental papilla from young rat lower incisor by three step digestion.

In order to establish an in vitro model system, a three step digestion procedure, trypsin + collagenase pretreatment, followed by trypsin or collagenase treatment, and then trypsin posttreatment, was employed for the dissociation of rat lower incisors into dental papilla and enamel organ. Both the pre- and post-treatments promoted destruction of the basement membrane located between the dental papilla and enamel organ, resulting in effective dissociation of the tissues. The isolated dental papilla, including differentiating odontoblasts, was well preserved after this treatment. The results indicated that the three step digestive treatment may be very useful in isolating the dental papilla from the rat-incisor enamel organ accompanied by the basement membrane. The material provides a model system for studying odontoblast differentiation, development, and maturation in vitro.

Animals↗
PubMed1995

Expression of the intermediate filament nestin during rodent tooth development.

The developing tooth represents a suitable model for understanding the molecular mechanisms involved in induction, morphogenesis and differentiation of organs. It is conceivable that the developmental changes could be reflected in the distribution of different cytoskeletal components and in this report we analyze the expression of the intermediate filament nestin during rodent tooth development at the protein and mRNA levels (by immuno light and electron microscopy, and by in situ hybridization). Nestin is expressed at all stages of tooth development, but the expression levels increase after birth in both ectodermal and ectomesenchymal derivatives. The shift in nestin distribution, from the proliferating dental lamina to the dental mesenchyme, indicates that nestin may be involved in inductive phenomena. At early stages of mineralization, nestin is seen within the apical parts of the presecretory ameloblasts. Nestin is also expressed in odontoblasts, both during odontogenesis and after tooth eruption. The increase in nestin expression from early to late developmental stages and sustained expression in a differentiated cell type contrasts with previously observed patterns of nestin expression during nerve and muscle development. This suggests that nestin could be used as a specific marker for the odontoblast.

Animals↗
PubMed1976

An ultrastructural survey of cat dentinal tubules.

The extent of the odontoblast process, the distribution of intratubular nerve-like structures, and tubule dimensions, have been measured in cat dentine. The odontoblast process varies in extent throughout the tooth. At most levels it is limited to inner dentine, extending further out only in the cervical region. This variation supports the view that the limited extent of the process occurs in vivo and is not an artefact of fixation. No nerve-like processes were found within dentinal tubules in this study, indicating the rarity of such structures. The tubules in the dentine of the cat are more variable in number but narrower than those of man and occupy a relatively smaller proportion of the volume of the tissue. Some factor other than tubule numbers and size must be responsible for the greater access which chemical stimuli seem to have to nerve terminals beneath cat, as opposed to human, dentine.

Animals↗
PubMed1997

Expression of GDNF and its receptors in developing tooth is developmentally regulated and suggests multiple roles in innervation and organogenesis.

Glial cell line-derived neurotrophic factor (GDNF) is a recently identified survival factor for several populations of neurons in the central and peripheral nervous system that also regulates kidney development. To study the roles of GDNF in the regulation of tooth innervation and formation, we analyzed by in situ hybridization the expression patterns of GDNF and its receptors Ret, GDNF family receptor alpha-1 (GFRalpha-1), and GFRalpha-2 from the initiation of first molar formation to the completion of crown morphogenesis. At the time of trigeminal axon ingrowth, GDNF mRNAs were expressed in the mesenchyme around the tooth germ (i.e., target field of the dental innervation), suggesting that it is involved in the regulation of the embryonic tooth innervation. This hypothesis was supported by the ability of GDNF to induce neurite outgrowth from embryonic day 12 (E12) to E15 trigeminal ganglia. This timing correlated with the appearance of Ret in the subset of cells in the trigeminal ganglion at E12, whereas GFRalpha-1 and GFRalpha-2 receptors were constantly expressed in trigeminal ganglion during E11-E15. After birth, GDNF expression showed apparent correlation with the ingrowth and presence of trigeminal nerve fibers in the tooth, suggesting that GDNF is involved in the regulation of innervation of the dental papilla and dentin postnatally. Ret, GFRalpha-1, and GFRalpha-2 mRNAs were expressed in the dental epithelial and mesenchymal cells at stages when epithelial-mesenchymal signalling regulates critical steps of tooth morphogenesis. Ret and GFRalpha-2 were colocalized in the dental mesenchyme during bud and cap stages. Expression of GFRalpha-1 associated with the formation of the epithelial enamel knot, which is a putative embryonic signalling center regulating tooth shape. During postnatal development, GDNF and its receptors were expressed in dental papilla mesenchyme. In addition, GDNF and GFRalpha-1 transcripts were seen in the preodontoblasts and odontoblasts, suggesting that they may be involved in differentiation and maintenance of functional properties of the odontoblasts. Taken together, these results suggest that GDNF acts as a target-derived neurotrophic factor during tooth innervation. In addition, GDNF and its receptors may have nonneuronal organogenetic functions during tooth morphogenesis.

Animals↗
PubMed1996

Gene expression of TGF-beta 1 and elaboration of extracellular matrix using in situ hybridization and EM radioautography during dentinogenesis.

BACKGROUND AND METHODS: The expressions of TGF-beta 1 and Type I collagen mRNA were studied by in situ hybridization and immunohistochemistry then the secretory pathway of dentin phosphoprotein was investigated electron microscopic radioautography in rat incisors. RESULTS AND CONCLUSIONS: Expression of TGF-beta 1 mRNA was observed in dental papilla cells before dentin formation. The signals were most intense in pre- and postodontoblasts and during dentinogenesis, but became weaker in the secretory region during the dentin formation. Type I collagen mRNA was expressed in essentially the same as that of TGF-beta 1. These results suggest that TGF-beta 1 plays an important role in the differentiation of, and collagen synthesis by odontoblasts. Radioautography showed radioactivity in the rough endoplasmic reticulum 5 min after injection of 3H-serine. Silver grains were observed over the cylindrical portions of the cis-face of the Golgi apparatus at 10 min and over the cylindrical portions of the transface at 20 min. The secretory granules showed the strongest reaction between 20 min and 1 h after injection. At 45 min, a significant labeled band appeared at the mineralization front. The pathway of 3H-proline was essentially the same as that of 3H-serine, but 3H-proline moved more slowly. Secretory granules were heavily labeled from 30 min; no labeling was found at the mineralization front at 45 min. The labeling pattern with 3H-serine appears to be closely related to the localization of phosphoproteins. Dentin phosphoproteins are related to secretory granules and are secreted by odontoblasts as the mineralization front, being involved in the process of dentin mineralization.

Animals↗
PubMed1999

Development of dermal denticles in skates (Chondrichthyes, Batoidea): patterning and cellular differentiation.

Patterning, cellular differentiation, and developmental sequences of dermal denticles (denticles) are described for the skate Leucoraja erinacea. Development of denticles proceeds caudo-rostrally in the tail and trunk. Once three rows of denticles form in the tail and trunk, denticles begin to appear in the region of the pelvic girdle, medio-caudal to the eyes and on the pectoral fins. Although timing of cellular differentiation of denticles differs among different locations of the body, cellular development of a denticle is identical in all locations. Thickening of the epidermis as a denticle lamina marks initiation of development. A single lamina for each denticle forms, and a small group of mesenchymal cells aggregates underneath it. The lamina then invaginates caudo-rostrally to form the inner- and outer-denticle epithelia (IDE and ODE, respectively). Before nuclei of IDE cells are polarized, enameloid matrix appears between the basement membrane of the IDE and the apical surface of the pre-odontoblasts. Pre-dentin is then laid down along with collagenous materials. Von Kossa stain visualizes initial mineralization of dentin, but not enameloid. During the growth of a denticle, dense fibrous connective tissue of the dermis forms the deep dermal tissue over the dorsal musculature. Attachment fibers and tendons anchor denticles and dorsal musculature, respectively, on deep dermal tissue. Basal tissue of the denticles develops as the denticle crown grows. If the basal tissue is bone of attachment, then the cells along the basal tissue would be osteoblasts. However, these cells could not be distinguished from odontoblasts using immunolocalization of type I pro-collagen (Col I), alkaline phosphatase (APase), and neural cell adhesion molecule (N-CAM). Well-developed dentin, (not pre-dentin), the enameloid matrix (probably when it begins to mineralize), and deep dermal tissue are Verhoeff stain-positive, suggesting that these tissues contain elastin and/or elastin-like molecules. Our study demonstrates that the cellular development of denticles resembles tooth development in elasmobranchs, but that dermal denticles differ from teeth in forming from a single denticle lamina. Whether the basal tissue of denticles is bone of attachment remains undetermined. Confirmation and function of Verhoeff-positive proteins in enameloid, dentin, and deep dermal tissue remain to be determined. We discuss these issues along with an analysis of recent findings of enamel and enameloid matrices.

Animals↗
PubMed1999

Microscopic and histochemical study of odontoclasts in physiologic resorption of teeth of the polyphyodont lizard, Liolaemus gravenhorsti.

Using tartrate-resistant acid phosphatase (TRAP), we examined the cytodifferentiation of odontoclast cells in resorbing areas of dental tissues during the replacement of teeth in a polyphyodont lizard, Liolaemus gravenhorsti. We also report, by means of Lectin-HRP histochemistry, the distribution pattern of some specific sugar residues of TRAPase-positive cells. For detection of TRAPase activity, the azo dye-coupling technique was used. Lectin binding sites were demonstrated by means of specific HRP-lectins. The process of tooth resorption was divided into four stages: 1) preresorption-the wall of the dental pulp is covered with an odontoblast layer, and no TRAP-positive cells are in the dental pulp; 2) early resorption-TRAP-positive multinucleate odontoclasts are present on the dental wall, but the rest of the pulp surface is still covered with an odontoblast layer; 3) later resorption-the entire surface of the pulp chamber is lined with multinucleate odontoclasts; and 4) final resorption-the tooth has been totally resorbed. Odontoclasts are usually detached from the resorbed surface, and show signs of degeneration. Of the six lectins used, PNA, ECA, and UEA-1 bind to multinucleated but not mononuclear cells. All the remaining lectins, BS-1, RCA(120), and LTA showed no binding to any cells of the teeth. The significance of saccharidic moieties such as acetyl-galactosamine, acetyl-glucosamine, and fucose sugar residues is difficult to ascertain. Perhaps these oligosaccharides might be borne on molecules associated with odontoclastic resorption or associated with multinucleation of odontoclasts after attachment to the dentine surface.

Acetylgalactosamine↗
PubMed2000

Associations of FGF-3 and FGF-10 with signaling networks regulating tooth morphogenesis.

The morphogenesis and cell differentiation in developing teeth is governed by interactions between the oral epithelium and neural crest-derived ectomesenchyme. The fibroblast growth factors FGF-4, -8, and -9 have been implicated as epithelial signals regulating mesenchymal gene expression and cell proliferation during tooth initiation and later during epithelial folding morphogenesis and the establishment of tooth shape. To further evaluate the roles of FGFs in tooth development, we analyzed the roles of FGF-3, FGF-7, and FGF-10 in developing mouse teeth. In situ hybridization analysis showed developmentally regulated expression during tooth formation for Fgf-3 and Fgf-10 that was mainly restricted to the dental papilla mesenchymal cells. Fgf-7 transcripts were restricted to the developing bone surrounding the developing tooth germ. Fgf-10 expression was observed in the presumptive dental epithelium and mesenchyme during tooth initiation, whereas Fgf-3 expression appeared in the dental mesenchyme at the late bud stage. During the cap and bell stage, both Fgf-3 and Fgf-10 were intensely expressed in the dental papilla mesenchymal cells both in incisors and molars. It is of interest that Fgf-3 expression was also observed in the primary enamel knot, a putative signaling center of the tooth, whereas no transcripts were seen in the secondary enamel knots that appear in the tips of future cusps of the bell stage tooth germs. Down-regulation of Fgf-3 and Fgf-10 expression in postmitotic odontoblasts correlated with the terminal differentiation of the odontoblasts and the neighboring ameloblasts. In the incisors, mesenchymal cells of the cervical loop area showed partially overlapping expression patterns for all studied Fgfs. In vitro analyses showed that expression of Fgf-3 and Fgf-10 in the dental mesenchyme was dependent on dental epithelium and that epithelially expressed FGFs, FGF-4 and -8 induced Fgf-3 but not Fgf-10 expression in the isolated dental mesenchyme. Beads soaked in Shh, BMP-2, and TGF-beta 1 protein did not induce either Fgf-3 or Fgf-10 expression. Cells expressing Wnt-6 did not induce Fgf-10 expression. Furthermore, FGF-10 protein stimulated cell proliferation in the dental epithelium but not in the mesenchyme. These results suggest that FGF-3 and FGF-10 have redundant functions as mesenchymal signals regulating epithelial morphogenesis of the tooth and that their expressions appear to be differentially regulated. In addition, FGF-3 may participate in signaling functions of the primary enamel knot. The dynamic expression patterns of different Fgfs in dental epithelium and mesenchyme and their interactions suggest existence of regulatory signaling cascades between epithelial and mesenchymal FGFs during tooth development.

3T3 Cells↗
PubMed1989

Epithelial cytodifferentiation and extracellular matrix formation in enamel-free areas of the occlusal cusp during development of mouse molars: light and electron microscopic studies.

Mandibular first molars in mice ranging in age from 18 days prenatal to 5 days postnatal were used for light and electron microscopic examinations of the enamel-free area (EFA) during development of the occlusal cusp (mesiobuccal cusp). Notable morphological changes in the inner enamel epithelium and the cells of the stratum intermedium were observed. At prenatal age of 18 days, the inner enamel epithelium of the EFA (EFA epithelium) was composed of a layer of columnar cells and covered by the cells of the stratum intermedium. Two days after birth, the EFA epithelium was made up largely of preameloblasts, with mitochondria located in the proximal side of the cells toward the stratum intermedium. The cells of the stratum intermedium were irregularly shaped, with wide intercellular spaces between them. At a postnatal age of 3 days, most of the EFA epithelial cells resembled maturation-stage ameloblasts, being short and columnar in shape and having nuclei located in their proximal side. Distal cell membranes were folded, and mitochondria were scattered throughout the cytoplasm. In 4-day-old mice, the EFA epithelium was found to be formed of short columnar or cuboidal cells with distinct intercellular spaces. The cells of the stratum intermedium could no longer be detected, and cells of the EFA epithelium could not be distinguished from those of the stellate reticulum. Odontoblasts of the EFA were arranged and polarized parallel to the basal lamina, and odontoblastic processes extended toward the cusp tip. The orientation of thin and thick collagen fibers within predentin and dentin was also parallel to the basal lamina. Even after dentin mineralization, disrupted basal lamina and long, aperiodic, fine fibrils were found between the epithelium and the dentin. Following the disappearance of the basal lamina and fine fibrils, stippled material and crystals appeared on the dentin surface. The mineralized matrix, which x-ray microanalytical energy peaks identified as containing calcium and phosphorus, was continuous with enamel in the distal slope of the cusp at the cusp tip. Thus, the inner enamel epithelium of the EFA differentiated into secretory cells capable of enamel-like matrix formation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2002

Immunohistochemical localization of heat shock protein 25 (HSP 25) during root formation of the rat molar.

The present study investigated the immunohistochemical localization of heat shock protein 25 (HSP 25) of rat molar teeth during root formation. Most, probably all, cells of the epithelial rest of Malassez (ERM cells) had immunoreaction for laminin, a marker protein for basement membrane. During root formation, HSP 25 immunoreactivity was observed in odontoblasts, cells at the subodontoblastic layer, and those in close proximity to the acellular cementum. HSP 25-immunopositive cells at the subodontoblastic layer were present only at the apical region. Most HSP 25-immunoreactive cells in close proximity to the cementum lacked laminin immunoreactivity. However, at postnatal day 28 a small number of cells showed immunoreaction for both HSP 25 and laminin at the cervical and bifurcational regions. Under the electron microscope, most HSP 25-immunoreactive cells along the surface of the cementum were round and contained rich organelles such as mitochondria and rough endoplasmic reticulum. They lay between fiber bundles of the periodontal ligament. The localization and morphological features of these HSP 25-immunoreactive cells resemble those of cementoblasts. On the other hand, HSP 25-immunoreactive cells at the cervical region were oval and contained few cell organelles. They were closely apposed to each other, and separated from the surrounding tissues with basal lamina. These features were similar to those of mature ERM cells. In contrast, cells with microvillus-like processes and relatively rich mitochondria, which were similar to immature ERM cells, had no immunoreaction for HSP 25. These results suggest that HSP 25 may be involved in shape alterations of ERM cells, cementoblasts, and odontoblasts during differentiation.

Animals↗
PubMed1981

Autoradiographic demonstration of ipsilateral and contralateral sensory nerve endings in cat dentin, pulp, and periodontium.

In order to determine the location of sensory nerve ending in cat teeth, 3H-proline and 3H-leucine were injected into the left trigeminal ganglion of eight cats aged 6.5-10 months; 24 hours was allowed for axonal transport of radioactive protein to dental nerve endings, and the endings were then detected by autoradiography. The pulps of most ipsilateral (left) teeth contained some labeled axons. These axons ended in the odontoblastic layer and predentin of roots and crown; at the tip of the pulp horn of each cusp, nerve endings also extended as far as 150 micrometer into dentinal tubules. Labeled nerve endings were extremely rare in contralateral (right) teeth; only one tooth of 83 studied (eight cats) contained heavily labeled axons, and one other had faintly labeled axons. Both labeled contralateral teeth were central maxillary incisors. Their labeled axons were unbranched in the root and arborized in the crown to end among odontoblasts and many adjacent dentinal tubules. Labeled periodontal nerve endings were most numerous in the apical one-third of the ligament, with some endings extending as far as the gingiva. The nerve endings in the periodontal ligament were often clustered and appeared to end freely between the collagen bundles; their radioactivity varied in the same way as that of pulp nerves in the adjacent root.

Animals↗
PubMed1987

Sensory innervation of pulp and dentin in adult dog teeth as demonstrated by autoradiography.

In order to study the location of sensory nerve fibers in dog teeth, we injected 3H-amino acids into the left trigeminal ganglion of 2 anesthetized adult dogs; we then waited 24 hours for axonal transport of labeled protein and prepared the fixed decalcified teeth for autoradiography. Heavily labeled sensory neurons were found in the maxillary and mandibular divisions of each injected ganglion and its peripheral nerves and central root. Numerous labeled axons were found entering dental roots; they arborized mostly in the crown to end in peripheral pulp or inner dentin. Some labeled fibers extended 150-175 microns into dentinal tubules, but most intradentinally labeled fibers were less than 100 microns long. The dentinal innervation was most concentrated in the crown, with autoradiographic label over more than 50% of the tubules at the tip of each pulp horn. Differences in innervation density for coronal, cervical, intercuspal, septal, radicular, and reparative dentin were analyzed. In some regions, labeled endings branched along the pulp-predentin border but did not enter the dentinal tubules. Electron microscopic autoradiograms were prepared to confirm specific labeling of nerve fibers and nerve endings, and to describe their ultrastructure and association with odontoblasts. The results show that labeled sensory fibers in dog teeth have an ultrastructure similar to that described previously for rat molars and for monkey and cat teeth. No specific junctions were found between labeled sensory fibers and odontoblasts, in agreement with previous studies of other teeth.

Animals↗
PubMed2005

Characteristic distribution of immunoreaction for estrogen receptor alpha in rat ameloblasts.

Estrogen has a diverse function, including cell proliferation and differentiation via estrogen receptors (ER), which have been reported to be the case in various tissues in addition to female reproductive organs. A recent immunocytochemical study has reported the expression of ERalpha, a subtype of ER, in rat odontoblasts, suggesting an involvement of estrogen in the differentiation of tooth-forming cells. However, there is no information on the ERalpha immunoexpression in ameloblasts. The present study was therefore undertaken to examine the localization of ERalpha immunoreaction in rat ameloblasts during amelogenesis. A computer-assisted quantitative analysis under a confocal laser scanning microscope was employed to demonstrate the stage-specific localization pattern of ERalpha immunoreaction. Immunohistochemistry of the rat enamel organ revealed ERalpha expression as nuclear localization in ameloblasts, stratum intermedium, stellate reticulum, and papillary layer, in addition to mature and immature odontoblasts. The ratio of immunopositive nuclei to total nuclei (immunopositive ratio) in ameloblasts was high at the apical loop region and gradually declined at the presecretory stage to zero at the secretory stage with statistically significant difference. The ERalpha immunolabeling pattern exhibited a periodic change at the maturation stage proper with constant higher labeling in ruffle-ended ameloblasts than in smooth-ended ameloblasts. The positive ratio was then followed by a statistically significant increase in immunolabeling thereafter. This stage-specific immunolabeling pattern during amelogenesis suggests a possible role of ERalpha in ameloblast proliferation and differentiation.

Ameloblasts↗
PubMed1992

Analysis of low affinity nerve growth factor receptor during pulpal healing and regeneration of myelinated and unmyelinated axons in replanted teeth.

Nerve regeneration was examined in rat molars that were briefly extracted and then replanted in the socket for 1-90 days. Immunocytochemistry was used to evaluate neural and nonneural immunoreactivity (IR) for low affinity nerve growth factor receptor (p75-NGFR) and for laminin and calcitonin gene-related peptide (CGRP). Three different types of pulpal response to replantation were found. Type I: Some replanted teeth had mild injury and still contained coronal odontoblasts and associated fibroblasts that retained p75-NGFR-IR; they continued regular dentin formation and had excellent reinnervation. Type II: Teeth with intermediate injury lost most or all of the coronal pulp tissue, but they regenerated odontoblast-like cells that formed irregular dentin, they had numerous dispersed p75-NGFR-IR fibroblasts in crown pulp during early regeneration, and they had excellent reinnervation. Type III: Severely injured teeth lost their original pulp; they filled with dense connective tissue and bone and had poor reinnervation. After Type I or II injury the Schwann cells around degenerating myelinated and unmyelinated axons had increased expression of p75-NGFR by 1-3 days. By 7-10 days those Schwann cells had formed hollow tubes (bands of Bungner) along the degenerating axon tracks. They maintained their increased p75-NGFR-IR during and after regeneration of unmyelinated axons, whereas Schwann cells involved in remyelination lost p75-NGFR-IR at that stage. The number of CGRP-IR axons in the regenerating pulp increased from 7 to 90 days. Laminin-IR increased in all replanted teeth at 3-10 days and only returned to normal patterns in teeth with Type I or Type II response at 20-90 days. The special p75-NGFR-IR of pulpal fibroblasts of adult rat molars did not usually persist in regenerated, reinnervated pulp. The extensive depletion of fibroblast p75-NGFR-IR and the continuing enhanced p75-NGFR-IR in unmyelinated nerve fibers at 90 days show that altered growth factor conditions characterize regenerated pulp of replanted teeth.

Animals↗