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PubMed1989

[Intranuclear rodlet in the odontoblast].

Lower incisors of 6 rabbits (about 3.5 kg, Japanese white, male) were observed by the electron microscopy. The life cycle of rabbit incisor odontoblast is classified into 4 stages by the dentine structure; 1st is outer, 2nd is middle, 3rd is inner and the 4th layer, that is the secondary dentine filling in the center of pulp. Fibrous intranuclear rodlets were observed in the odontoblast of late 2nd and 3rd stages, which forms thick inner half dentine. The odontoblasts of 2nd stage were tall and matrix formation cells, containing well developed golgi apparatus, many RER and secretory granules. The 3rd stage odontoblasts were short and formed the vaso-dentine in the lingual side. Intranuclear rodlets, about 5 nm thick, consisted of 5-20 fibrous or tubular structures. The arrangement of rodlets had no relation to the cell axis. These intranuclear rodlets might be observed only in the last stage odontoblast in the rat incisor. The morphological observations show 1) the term of life cycle of rabbit odontoblast may be more longer than the rat, 2) the intranuclear rodlets may be caused by the stress on the odontoblastic function such as the heat-shock treated fibroblasts.

Animals↗
PubMed1987

Change of microtubular arrangement around centrioles in rat incisor odontoblasts during cell differentiation.

Three stages during cell differentiation of rat incisor odontoblasts were classified, and change of microtubular arrangement around centrioles in the odontoblasts was examined with three-dimensional analyses using serial ultrathin sections. In the undifferentiated odontoblasts, microtubules were observed to radiate from the pericentriolar area, whereas, in the differentiating odontoblasts, some microtubules became poorly related to the centrioles. In the differentiated odontoblasts, arrangement of most microtubules appeared to have a poor relationship to the centrioles. Throughout the differentiation of the odontoblasts, one of the centriolar pair was ciliated, and Golgi apparatus was invariably observed near the centrioles. The present study suggests that a pericentriolar area, or a centrosome, could function as a microtubule-organizing center (MTOC) in the undifferentiated odontoblasts, but their function might be attenuated during cell differentiation.

Animals↗
PubMed1985

Odontoblast turnover in the impeded and unimpeded rat incisor derived from computerized histomorphometry.

A computerized histomorphometric method was devised to estimate the kinetics of odontoblast turnover and dentinogenesis in rat incisors. The method was applied to two groups of rats: one group with lower incisors in impeded eruption and another group with the left lower incisor in the unimpeded state. The teeth were divided into six equal segments, from which consecutive ground sections were obtained. The distance of each ground section from the posterior border of the alveolar bone was calculated. Each section was magnified, traced, and the tracings fed into a computer by a sonic digitizer. The perimeters and areas of dentine and pulp in each ground section were calculated by the computer. The mean odontoblast density along the predentine was evaluated from histological sections taken both from the same tooth segments and from teeth sectioned midsagittally. These served for the estimation of the predentine area occupied by the average odontoblast. In the impeded group, this area was 11% larger than in the unimpeded one. Outer dimensions of teeth, namely the circumference of the dentine, the labiolingual width, and the mesiolateral width remained constant and equal for both groups. Daily rates of dentine apposition were computed and were found to vary according to the age of the odontoblasts. Odontoblasts of impeded teeth started to secrete matrix at a rate of 17 microns/day, which increased slightly to 19 microns/day and later declined to 7 microns/day on the 38th day. Dentine production of unimpeded odontoblasts, on the other hand, started at a rate of 16 microns/day and gradually increased to 34 microns/day on the 17th day.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Evidence for tight junctions between odontoblasts in the rat incisor.

Odontoblasts are known to be involved in the process of dentinogenesis but it is not clear whether substances may also be deposited in predentine and dentine by passing between these cells. Although tight junctions have been described, it is not clear if they are macular or "leaky" as opposed to continuous or "tight". In this study use has been made of the permeability of fenestrated capillaries amongst the odontoblasts to deposit the penetrative tracer lanthanum in the interodontoblastic space. This was done by perfusion of anaesthetized rats with physiological solutions containing lanthanum nitrate at 37 degrees C. Immersion fixation of transverse segments of mandibular incisors and examination with an electron microscope showed that lanthanum could permeate 40-50 microns between the odontoblasts to reach the peripheral pulp. Towards the predentine, often less than 10 microns from the capillaries, its progress was abruptly and completely halted by the junctions at the apical ends of the odontoblast cell bodies. Lanthanum was not found in the predentine. The mature secretory odontoblasts in the rat incisor have therefore been shown to be joined by continuous tight junctions. In the process of dentinogenesis this means that all substances deposited in predentine and dentine must arrive by passing through the odontoblasts.

Animals↗
PubMed2000

Odontoblast differentiation of human dental pulp cells in explant cultures.

In order to elucidate the mechanisms involved in human dentin formation, we developed a cell culture system to promote differentiation of dental pulp cells into odontoblasts. Explants from human teeth were cultured in Eagle's basal medium supplemented with 10% or 15% fetal calf serum, with or without beta-glycerophosphate (beta GP). Addition of beta GP to the culture medium induced odontoblast features in the cultured pulp cells. Cells polarized and some of them exhibited a typical cellular extension. In some cases, cells aligned with their processes oriented in the same direction and developed junctional complexes similar to the terminal web linking odontoblasts in vivo. Fine structural analyses showed the presence of typical intracellular organelles of the odontoblast body, whereas the process contained only cytoskeleton elements and secretory vesicles. Polarized cells deposited onto the plastic dishes an abundant and organized type I collagen-rich matrix with areas of mineralization appearing thereafter. X-ray microanalysis showed the presence of calcium and phosphorus and the electron diffraction pattern confirmed the apatitic crystal structure of the mineral. High expression of alpha 1 (1) collagen mRNAs was detected in all polarized cells whereas dentin sialoprotein gene was mainly expressed in mineralizing areas. This cell culture system allowed for the differentiation of pulp cells into odontoblasts, at both the morphological and functional level. Moreover, these cells presented a spatial organization similar to the odontoblastic layer.

Adolescent↗
PubMed2000

Na+/Ca2+ exchanger isoforms of rat odontoblasts and osteoblasts.

In odontoblasts as well as osteoblasts, a number of mechanisms for the inflow and extrusion of Ca2+ have been demonstrated. The entrance of Ca2+ ions into odontoblasts occurs mainly through voltage-gated calcium channels. Extrusion of Ca2+ is found to be an ATP-dependent process and, in addition, Na+/Ca2+-antiports exist, which are provoked by extracellular Na+. The aim of this study was to identify the Na+/Ca2+-antiport isoforms expressed in dentinogenically active rat incisor odontoblasts and to make a comparison with different osteoblastic cells. Using RT-PCR and RNAse protection assay, we demonstrated the expression of three different isoforms, NaCa 3, 7, and 10, of the NCX1-encoded antiport in odontoblasts and osteoblastic cells. When incubated in the presence of Na+, dissected rat incisor odontoblasts as well as the osteoblastic cells extruded Ca2+ ions, as detected by chlorotetracycline and Fura-2 fluorometry, thus supporting a physiological role for the detected isoform expression. Odontoblasts and rat calvarial osteoblasts, as well as osteoblast-like cell lines UMR-106.01 and Saos-2, were shown to exhibit identical phenotypes of Na+/Ca2+-antiport isoform expression, different from the expression patterns of other tissues. The significance of this specific expression pattern is unknown, but there is a possibility that it is in some way related to the unique demands on these cell types to produce mineralized connective tissue.

Amino Acid Sequence↗
PubMed2004

Odontoblasts induced from mesenchymal cells of murine dental papillae in three-dimensional cell culture.

In an organ culture system under a three-dimensional microenvironment that provides the conditions needed for odontoblast differentiation, a row of odontoblasts can be induced (Kikuchi et al. 1996, 2001). Therefore, in a newly designed three-dimensional cell culture system that fulfils the conditions necessary for odontoblast differentiation (Kikuchi et al. 2002), we examined whether dental papilla cells in rat mandibular incisors could differentiate into tubular dentine-forming cells. In our previously established organ culture system, CM-Dil-labeled cells that were microinjected into isolated dental papillae were replaced by a row of odontoblasts. In a three-dimensional cell culture system, which consists of two kinds of type I collagen in the upper layer over multi-layered cells seeded onto collagen containing Matrigel in the lower layer and which acts as a structural meshwork, dental papilla cells were incubated as multi-layered cells in an artificial extracellular matrix (ECM). The cells aggregated to form a cell mass and invaginated as a cell mass into the ECM. The cells also extended fine fibrillar processes into the ECM. With regard to invagination, the proteolytic activities of matrix metalloproteinase-2 (MMP-2)/membrane type 1-matrix metalloproteinase (MT 1-MMP) were observed on the outer multi-layers of cells within a cell mass adjacent to the ECM. The cell mass progressively shrank to about one-half to one-third of its original diameter and was organized as a tissue surrounded by a newly secreted ECM, like dental pulp-dentine. The cells adjacent to the secreted ECM were constructed as a row of polarized columnar cells. They extended slender processes into the new ECM, which is characteristic of tubular matrix. Dentine sialophosphoprotein (DSPP) and dentine matrix protein 1 (DMP 1) genes, which are specific for odontoblast differentiation, were expressed in an aggregated cell mass where tubular matrix-forming cells were induced. Furthermore, the tubular matrix became mineralized under prolonged culture. These results imply that the putative progenitor cells/stem cells residing in dental papillae can differentiate into odontoblasts under appropriate conditions in vitro.

Animals↗
PubMed2007

Sequential expression of endothelial nitric oxide synthase, inducible nitric oxide synthase, and nitrotyrosine in odontoblasts and pulp cells during dentin repair after tooth preparation in rat molars.

Nitric oxide (NO) stimulates osteoblast differentiation, but whether NO contributes to odontoblast differentiation during dentin repair is unknown. By using reverse transcription/polymerase chain reaction and immunostaining, we investigated the gene expression and/or immunolocalization of endothelial NO synthase (eNOS), inducible NOS (iNOS), and nitrotyrosine (a biomarker for NO-derived peroxinitrite), and alkaline phosphatase (ALP) and osteocalcin (early and terminal differentiation markers of odontoblasts, respectively) in dental pulp tissue after rat tooth preparation. At the early stage (1-3 days) post-preparation, markedly increased expression of iNOS and nitrotyrosine was found in odontoblasts and pulp cells beneath the cavity, whereas eNOS expression was significantly decreased. ALP mRNA expression was significantly increased after 1 day but decreased after 3 days, whereas ALP activity was weak in the dentin-pulp interface under the cavity after 1 day but strong after 3 days. Osteocalcin mRNA expression was significantly increased at this stage. At 7 days post-preparation, tertiary dentin was formed under the cavity. All the molecules studied were expressed at control levels in odontoblasts/pulp cells beneath the cavity. These findings show that abundant NO is released from odontoblasts and pulp cells at an early stage after tooth preparation and indicate that, after tooth preparation, the up-regulation of iNOS and nitrotyrosine in odontoblasts is synchronized with increased cellular expression of ALP and osteocalcin. Therefore, the NO synthesized by iNOS after tooth preparation probably participates in regulating odontoblast differentiation during tertiary dentinogenesis.

Alkaline Phosphatase↗
PubMed1982

Ultrastructure of odontoblasts in kitten tooth germs as revealed by freeze-fracture.

Fifteen kittens were perfused with 2.5 per cent glutaraldehyde or modified Karnovsky fixative. Distribution and structural features of the three kinds of intercellular junctions; gap junctions, macular tight junctions and desmosome-like junctions were clarified by correlated observations using thin sections and freeze-fracture replicas. Distal junctional complexes of the odontoblasts were composed of both gap and macular tight junctions and sealed extracellular spaces incompletely, because of the poor sealing capacities of macular tight junctions. Therefore, there was no predentine-pulp barrier in the odontoblast layer. Except for the junctional complex, no tight junction was observed in the odontoblasts. Gap junctions and desmosome-like junctions were found between adjacent odontoblasts and between odontoblasts and neighbouring pulp cells. Gap junctions were similar to those of many other tissues but the desmosome-like junctions were different from mature desmosomes in the epithelial cells and showed immature features. Each intercellular junction of odontoblasts is considered to form a site of intercellular communication and cell-to-cell attachment.

Animals↗
PubMed1989

Ultrastructure of a new generation of odontoblasts in grafted coronal tissues of mouse molar tooth germs.

Third molar tooth germs were removed from 14-day-old mice and freed from the enamel organ and follicle. After section of the apical tissues, including Hertwig's sheath, they were transplanted in 1-day-old newborn mice of the same lineage. Electron microscopy of grafts removed 7, 14 and 21 days later showed that, following the disappearance of the initial layer of odontoblasts and a period of adaptation, 14 days after transplantation newly differentiated odontoblasts deposited tubular dentine. The dentine matrix production was increased over that of controls, demonstrating that synthesis was accelerated, possibly because of lack of nerves in the grafts. Numerous characteristic structures that might be involved in the transit of proteoglycans from the Golgi apparatus were seen, as far as the extremity of the odontoblast processes. The particular experimental conditions allowed the observation in the neck region of the odontoblast of a concentration of coated vesicles which might be involved in cellular lengthening. Thus, in the presence of a fine and regular vascular network, a new generation of odontoblasts may differentiate, even in the absence of epithelial and nervous elements, and so predentine may contain inductive factors that allow the odontoblastic differentiation of pulp cells in contact with it.

Animals↗
PubMed1990

Autoradiographic analysis of odontoblast replacement following pulp exposure in primate teeth.

Cell migration and replication associated with odontoblast replacement occurring soon after pulp exposure in primate teeth were studied. Class 5 cavity preparations resulting in pulp exposures were restored with a calcium hydroxide-containing capping agent and amalgam. Eighty-four and 96 h after this the animals were injected with 0.5 microCi/g body wt tritiated thymidine (sp. act. 6.7 Ci/mM). Teeth were extracted 6, 8, 10 and 12 days after treatment. The number of labelled cells as well as the number of grains per labelled cell were counted for odontoblast-like, fibroblast-like and perivascular cells in three 60 x 260 microns zones. These zones represented the odontoblast and cell-free (zone 1), cell-rich (zone 2) and deep pulp (zone 3) areas of normal pulp tissue. Ten sections centred around the mid-point of the exposure were counted for each tooth. Matrix formation and labelled odontoblast-like cells were observed at the interface between the capping agent and the pulp as early as day 8. Other significant findings were: (1) an increase in labelled odontoblast-like cells in zone 1 over time, suggesting a continual influx of differentiating cells; (2) an increase in labelled cells in zone 1 over time with a concurrent decrease in zone 3, suggesting that the influx of cells in zone 1 was from the deeper pulp; and (3) differences in grain counts between zones, treatment times and cell types, indicating that at least two DNA replications had occurred between initial treatment and final odontoblast-like cell differentiation.

Animals↗
PubMed1994

Odontoblast stimulation in ferrets by dentine matrix components.

The possible effects of isolated dentine matrix components on odontoblast secretory activity were investigated in vivo by implantation of lyophilized fractions of these components into cavities prepared in ferret canine teeth. After implantations as short as 14 days there was significant deposition of reactionary dentine by the odontoblasts beneath the cavity and this response increased in a non-linear manner with time of implantation. In contrast, control cavities lacking the dentine matrix components showed no evidence of reactionary dentine deposition. Examination of teeth at early periods of implantation (2 and 5 days) indicated that odontoblast death had not occurred as a result of the operative procedures and that the response was one of stimulation of existing odontoblasts rather than that of induction of a new generation of odontoblast-like cells. The mechanisms of odontoblast stimulation by the dentine matrix components remain to be elucidated, but could be mediated by growth factors within the dentine matrix preparations.

Animals↗
PubMed2005

Rapid penetration of lucifer yellow into vital teeth and dye coupling between odontoblasts and neighbouring pulp cells in the cat.

The location and long process of odontoblasts appear well suited to detection of external stimuli. The odontoblasts may transmit the information not individually but as a syncytium via gap junction, which functions as a mechanism for intercellular linking cells and as the route for dye coupling. The aims of the present study were to examine dye penetration through enamel and dentin, and to confirm dye coupling between odontoblasts (OBs) or between odontoblasts and other pulpal cells beneath the odontoblastic layer (PCs). Either lucifer yellow (LY) or borate buffer (control) was applied to etched enamel surface of feline canines for 30 min at atmospheric pressure. In the decalcified sections, lucifer yellow positive cells were found not only in but also beneath the odontoblastic layer (experiment 1). In the isolated pulp cells, all OBs (27/27) and some PCs (6/9) that were immunocytochemically differentiated using two monoclonal antibodies were labelled with LY (experiment 2). These results indicate the remarkably quick movement of LYE through enamel and dentin into the superficial pulp. In experiment 3, fresh OBs and PCs were isolated from feline canines to which LY had not been applied. LY was iontophoretically injected into an OB-like cell that had an oval cell body and a long monopolar process. Some PCs and OBs identified immunocytochemically were labelled with LY, with the exception of a few LY-negative cells. These findings indicate that dye coupling exists not only between OBs but also between OBs and PCs. Thus, the coupling provides evidence for a functional link via which information is transmitted between OBs and PCs.

Animals↗
PubMed2006

Ultrastructural patterns of human dentinal tubules, odontoblasts processes and nerve fibres.

The structure of the dentin, consists of the following elements: the odontoblastic processes, dentinal tubules and their periodontoblastic spaces. The odontoblasts are aligned in a single layer in the periphery of the dental pulp and secrete the organic components of dentin. The vitality of dentin is mediated too by the nerve fibres. The ultrastructure of the trigeminal sensory nerves in dentin, especially in relation to odontoblasts remains to be clarified. We studied the third molars and young premolars. The specimens were fixed in glutaraldehyde immediately after extraction. Our investigations give evidence to prove that the distribution of the dentinary tubules is homogeneous, containing a principal odontoblastic prolongation in the regions of the inner dentine, and only in special cases more than one. The area of the dentinary tubules and the odontoblastic prolongations' area were studied. The nervous fibres appeared accompanying 30-70% of the odontoblastic prolongations and their synapsis-like relation with the odontotoblastic processes was demonstrated. The existence of very few periodontoblastic spaces, and intradentinal sensory axons, as well as the intercellular connections will allow us to discover more about the mechanisms of the dentinary permeability, and its significance in maintenance and repair of the human pulpodentinal complex.

Adolescent↗
PubMedDate not supplied

Effect of mechanical removal of the pulp upon the retention of odontoblasts around the pulp chamber of human third molars.

The pulp chambers of 11 freshly extracted human third molars were exposed by cutting off the roots apical to the cervical margin and the pulps were either removed with forceps and discarded or left in situ. The teeth were fixed, demineralized, divided longitudinally, embedded in resin and 2-micron sections stained with toluidine blue were examined by light microscopy. In pulp-removed specimens the percentage retention of the odontoblast layer with the predentine varied near the longitudinal division but when sectioned deeper all six specimens displayed 100% retention. The intactness of the retained odontoblast layer was mostly good as judged by the mutual close apposition of the distal ends of the cell bodies and their relation to the predentine. The retention of the odontoblast layer with the predentine may be due to the distribution of fibronectin, which others have shown is present between odontoblasts, and between odontoblasts and predentine, but lacking beneath the odontoblast layer.

Cell Adhesion↗
PubMed1998

The effects of estrogen deficiency on glycosylation of odontoblasts in rats.

To investigate the effects of estrogen deficiency on odontoblast metabolism, we induced osteoporosis in rats by ovariectomy and examined the glycosylation of the matrix component in odontoblasts. Peanut agglutinin (PNA) lectin histochemistry, which detects D-galactose and N-acetylgalactosamine sugars, was conducted in incisor odontoblasts of ovariectomized (OVX) and sham-operated (sham) rats. At 5 wk after the operation, bone mineral density and serum level of estrogen in OVX rats were lower than those in sham rats. PNA binding sites were found in the odontoblasts in incisors, and the binding sites in OVX rats were much stronger than those in sham rats. Furthermore, PNA binding sites were localized at the predentin matrix in OVX rats, but the reaction in sham rats was not detected. Because D-galactose and N-acetylgalactosamine sugars bound to PNA are important constituents of proteoglycans in dentin matrix and the PNA binding sites reflect the proteoglycan production of odontoblasts, these results indicated that galactosyl glycosylation of proteoglycans in odontoblasts is influenced by estrogen deficiency in rat incisors.

Acetylgalactosamine↗
PubMed2003

Odontoblast morphology and dental repair.

OBJECTIVES: To investigate the changes in morphology and activity of pulp odontoblasts in response to cavity restoration variables and patient factors. METHODS: Class V non exposed cavities were prepared in the intact 1st or 2nd premolar teeth of 27 patients, aged between 9 and 17 years-old. Following tooth extraction, the area of reactionary dentine and the area of the odontoblasts were measured using computerised histomorphometry. RESULTS: The cytoplasm to nucleus ratio of the odontoblasts was found to increase beneath cut dentinal tubules, following the secretion of reactionary dentine. However, none of the patient or preparation variables were found to be correlated with changes in the odontoblast cytoplasm to nucleus ratio. CONCLUSIONS: Morphological changes in human odontoblasts is directly related to their capacity to repair dentine injuries and provide pulp protection. Changes in odontoblast morphology reflect secretory activity.

Adolescent↗
PubMed1999

Expression of IL-8 by cells of the odontoblast layer in vitro.

Due to their peripheral location in the dental pulp and their cellular extension into dentin, odontoblasts are the first pulpal cells to encounter dental pathogens. The association of odontoblasts with immunoglobulins and dendritic cells during microbial invasion of dentin implies that these cells may possess a role in the innate and adaptive pulpal immune responses, however this has not been examined. A pivotal step in the innate immune response is the detection of foreign antigen and the recruitment of immune effector cells to the area. IL-8 is a potent chemotactic cytokine that plays an important role in the inflammatory response. The purpose of this study was to determine if odontoblasts are capable of expressing the pro-inflammatory chemokine IL-8. Human odontoblasts from intact, noncarious third molars were maintained in culture and exposed to Escherichia coli lipopolysaccharide (LPS) (serotype 055:B5) on day 4 for 8-10 h in a humidified 5% CO2 incubator. Control and experimental samples were assayed by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot for the production of IL-8 mRNA and protein. Analysis of the PCR products revealed that cells of the odontoblast layer maintained in this culture model constitutively expressed low levels of IL-8, which were increased in response to E. coli LPS exposure. Western blotting confirmed that the mRNA was translated into protein. These results imply that odontoblasts are capable of producing of pro-inflammatory mediators, thereby actively participating in the recruitment of neutrophils in response to bacterial by-products.

Blotting, Western↗