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PubMed1992

An ultrastructural and autoradiographic analysis of primary and replacement odontoblasts following cavity preparation and wound healing in the rat molar.

Numerous studies using various animal and human models have reported changes in the morphology and metabolic activity of primary odontoblasts in the mature tooth pulp after perturbations of the tooth including cavity preparation and restoration, pulpal exposures and pulp capping with various capping agents. The first part of this study investigated changes in primary and replacement odontoblast activity after cavity preparation or pulpal exposure. Two groups of rats were used in this investigation. One group of rats had Class V cavities prepared to the DEJ of the first maxillary molars. These rats were immediately injected with 3H-proline and killed 15, 30 or 60 minutes later. Rats killed at day 1, 3, 5, 7, 10 or 14 were injected one hour prior to sacrifice. The second group of rats each had a pulp exposure that was capped with a calcium hydroxide containing material and restored with a composite resin. Rats were sacrificed as previously described. Tissue was processed routinely for ultrastructural analysis and E.M. autoradiography. The second part of this study consisted of an injection of 125I-fibrinogen one hour prior to a class V cavity preparation 1/2 the distance through dentin thickness. Rats were sacrificed at 5, 10, 15 and 30 minutes postsurgery. Differences in the location and distribution of the reduced silver halide grains were recorded as well as differences in the amount and distribution of the various organelles measured between primary and replacement odontoblasts. The results of this study suggests that primary and replacement odontoblasts were morphologically and physiologically dissimilar at the time periods tested in this study. 125I-fibrinogen was demonstrated within the dentinal tubules and in the floor of the cavity preparation as early as 5 minutes after completion of the cavity preparation. The preliminary results of the 125I-fibrinogen suggest that operative trauma can effect very rapid changes to the dental pulp leading to leakage of plasma proteins from the circulation, between odontoblasts, out of the tubules to the cut dentin surface.

Animals↗
PubMed2006

[Preliminary study on adult odontoblast culture in situ].

PURPOSE: To establish an in situ culture model of adult odontoblasts. METHODS: Thirty intact and healthy third molars freshly prepared from 20-30 year old individuals were randomly divided into three groups. Each group had 10 molars. Group 1 was pulp tissue extraction group. Group 2 was serum-containing culture group. Group 3 was serum-free culture group. The root was dissected from the crown and the pulp was pulled out to make odontoblasts remaining in the crown. The odontoblasts were cultured in situ either in medium containing serum or serum-free medium for up to 7 days. The growth status of the cells was examined by light microscopy and cell morphology and distribution was analyzed by scanning electron microscopy. Cell viability was determined by trypan blue staining. RESULTS: After pulp removal at room temperature, odontoblasts remained in the wall of the pulp chamber, and kept viable and good morphology during the 7-day culture. CONCLUSION: We have successfully established an in situ culture model of adult primary odontoblasts in either serum-containing or serum-free medium.

Adult↗
PubMed1980

Odontoblast metabolism in rats deficient in vitamin D and calcium. IV. Lysosomal and energy metabolic enzymes.

Young rats, fed a low calcium and vitamin D deficient diet for 2 weeks, developed hypocalcemia, an increased activity of serum alkaline phosphatase and an increase in the serum concentration of immunoreactive parathyroid hormone. An increased activity of lactate dehydrogenase and cytochrome oxidase in odontoblasts was found. No shift in the general energy metabolic pathway was found as visualized in the lactate dehydrogenase iso-enzyme pattern. The dominating lactate dehydrogenase isoenzyme in odontoblasts from both the normal and the deficient rats was LDH 1 (H4, LD5), thus indicating primarily an aerobic energy-metabolism Also the activities of the lysosomal enzymes acid phosphatase, cathepsin D and hyaluronidase in the odontoblasts from the deficient animals were increased when compared to the normal animals. No significant change could be demonstrated for beta-glucuronidase and beta-N-acetylglucosaminidase. It was earlier found that this deficient diet caused an increase in odontoblast alkaline phosphatase activities and protein synthesis in vitro. In view of the present findings it might be concluded that the low calcium and vitamin D deficient diet causes a general increase in the odontoblast metabolism. It is not known whether this is due to the increase in parathyroid hormone or if it is a direct effect of the lowered serum calcium concentration.

Acetylglucosaminidase↗
PubMed1984

Endocytotic activity of kitten odontoblasts in early dentinogenesis. 1. Thin section and freeze-fracture study.

The morphological features of odontoblast processes in young kitten odontoblasts were studied by thin section and freeze-fracture electron microscopy. Freeze-fracture replication revealed depressions with particles on the plasma membranes of the proximal parts of odontoblast processes. Comparison with thin sections suggested that these depressions represented sites of endocytosis. Frequent depressions with particles (corresponding to coated pits in thin sections) indicate the high absorptive activity of young odontoblasts. The results indicate that odontoblasts, especially in the proximal parts of their processes, play a significant functional role in the modification of the predentine matrix during early dentinogenesis.

Animals↗
PubMed1994

Comparative analysis of TGF beta s, BMPs, IGF1, msxs, fibronectin, osteonectin and bone sialoprotein gene expression during normal and in vitro-induced odontoblast differentiation.

Immobilized TGF beta 1 and BMP2 are able to promote the differentiation of odontoblast-like cells in isolated mouse dental papillae cultured in vitro. These cells polarize and accumulate predentin-like matrix at their apical pole. Immobilized IGF1 mainly promoted polarization with disturbed matrix accumulation. In situ hybridization demonstrated that TGF beta 1 combined with heparin mirrored the physiological processes of odontoblast differentiation. Normal odontoblast and in vitro induced odontoblast-like cells expressed transcripts encoding for TGF beta 1 and 3, BMP2 and 4, bone sialoprotein and osteonectin whereas either ubiquitous expression or no expression could be detected for TGF beta 2, IGF1 or fibronectin mRNAs. Odontoblast-like cells obtained in the presence of IGF-1 combined with heparin did not express TGF beta 1 transcripts and expressed weakly TGF beta 3 transcripts. Our results suggest that in vivo an epithelial-derived member of the TGF beta family trapped by basement membrane-associated components interacts with competent preodontoblasts and promotes the polarization by triggering the transcription of growth factor gene(s) like TGF beta itself and/or selector gene(s) like msx2.

Animals↗
PubMed1993

[Response of odontoblastic and pulpal cells to carious lesions].

The odontoblast responds to caries by the formation of sclerotic as well as reparative dentin. Sclerotic dentin is deposited during the early stages of the dentinal injury. It is characterized by the amplification of the collagen synthesis and the increase in alkaline phosphatase activity in the odontoblastic cell layer. Reparative dentin will be deposited under the sclerotic zone after the destruction of odontoblasts. At this stage, specific components from damaged dentinal tissues and/or odontoblastic necrotic debris will trigger pulpal cells to elaborate a cartilage-like matrix layer (fibrodentin). The latter may induce pulpal odontoblast-like cells to give rise to the tubular reparative dentin. Thus, pulpal cell response seems to be similar to bone-cell response to injury. Molecular signals responsible for this tissular healing remain largely unknown, but dentin is a potential source of matrical or soluble organic molecules that may be released after demineralization. Some of these factors have been identified in the sound tissue (glycoproteins, proteoglycans, growth factors, ...), but their role in the stimulation of the elaboration of the cicatricial tissue remains to be elucidated.

Cell Differentiation↗
PubMed1997

Measurements of cytosolic free Ca2+ concentrations in odontoblasts.

To investigate the responsiveness of odontoblasts to electrical and mechanical stimuli, the concentrations of cytosolic free Ca2+ ([Ca2+]i) were measured using fura-2 microfluorometry in slice preparations of rat dental pulp. [Ca2+]i under resting conditions (basal [Ca2+]i) were 258.0 +/- 37.7 nM (mean +/- S.E., n = 113). The basal [Ca2+]i of the odontoblasts with remarkably active responses to stimuli were 221.0 +/- 81.1 nM (mean +/- S.E., range: 16-685 nM). Depolarization by high extracellular K+ concentration ([K+]o) caused a rapid increase in [Ca2+]i. The depolarization-induced increase in [Ca2+]i was enhanced by caffeine. The intense depolarization elicited [Ca2+]i oscillation in odontoblasts, which was enhanced by caffeine and suppressed by dantrolene. Hypotonic stimulation also induced an increase in [Ca2+]i of odontoblasts. The results indicate that the odontoblast possesses voltage-dependent Ca2+ channels, caffeine-sensitive Ca2+ stores and mechanosensitive cation channels.

Animals↗
PubMed2000

Dissection of the odontoblast differentiation process in vitro by a combination of FGF1, FGF2, and TGFbeta1.

Dental papillae (DP) isolated from first lower molars of 17-day-old mouse embryos were cultured in the presence of combinations of the following growth factors: FGF1, FGF2, and TGFbeta1. After 6 days in culture, only the DP treated with FGF1+TGFbeta1 contained differentiated odontoblast-like cells at the periphery of the explants, and these cells secreted extracellular matrix similar to predentin. Surprisingly, treatments with FGF2+TGFbeta1 induced cell polarization at the surface of the explants but no matrix secretion was observed. Electron microscopy and histochemical analysis of odontoblast markers showed that differentiated cells induced by FGF1+TGFbeta1 exhibited cytological features of functional odontoblasts with matrix vesicle secretion and mineral formation, positive alkaline-phosphatase activity, and type-I collagen production. DP cultured in the presence of FGF2+TGFbeta1 showed cell polarization and long and thin cell processes containing matrix vesicles; however, type-I collagen secretion was not detected and alkaline-phosphatase activity was completely inhibited. Our results indicate that, in our culture system, exogenous combinations of FGF1, FGF2, and TGFbeta1 interact with preodontoblasts and induce cell polarization or differentiation, which can be studied separately in vitro. Thus, FGF1 and TGFbeta1 do have a synergic effect to promote morphological and functional features of differentiated odontoblasts whereas FGF2 seems to modulate TGFbeta1 action, causing morphological polarization of preodontoblasts but limiting the functional activity of these cells in terms of type-I collagen secretion and alkaline-phosphatase activity.

Alkaline Phosphatase↗
PubMed1993

Fate of odontoblasts and blood capillaries in the incisal region of the rat incisor pulp.

Transmission electron microscopy of thin sections of the rat incisor pulp revealed that in the middle region of the incisor there were fenestrated capillaries in the "predentinal plexus" and that this region contained the tallest odontoblasts. The odontoblasts gradually became shortened in the incisal part of this region; the fenestrated capillaries in the predentinal plexus changed to continuous type capillaries. Almost all the odontoblasts had degenerated near the incisal end of the tooth. The predentinal plexus disappeared in this region, but the "subodontoblastic capillary plexus" persisted. In a specific region just beneath the worn incisal end, numerous macrophages and polymorphonuclear neutrophils appeared and scavenged the degenerating cells, possibly including the odontoblasts.

Animals↗
PubMed2004

Tight junctions in differentiating ameloblasts and odontoblasts differentially express ZO-1, occludin, and claudin-1 in early odontogenesis of rat molars.

Little is known about the expression of associated proteins during the assembly of tight junctions (TJs). We studied the distribution of ZO-1, occludin, and claudin-1 between differentiating ameloblasts and odontoblasts in molar tooth germs from 1- to 3-day-old rats by confocal laser scanning microscopy. Immunoreactivity for ZO-1 was strong at proximal and distal junctional complexes of differentiating ameloblasts, while it was weak and punctuate at the distal region of differentiating odontoblasts. Occludin was immunoreactive at distal and proximal complexes of early differentiating ameloblasts and at distal regions of differentiating odontoblasts. However, in more advanced stages, occludin was only evident at the proximal complex of ameloblasts. Claudin-1 was strongly detected at the proximal complex but it was weak at distal complex of late differentiating ameloblasts. Thus, our results showed that ZO-1, occludin, and claudin-1 are differentially expressed as TJs assemble for regulating polarity and/or paracellular permeability in differentiating ameloblasts and odontoblasts.

Ameloblasts↗
PubMed2002

Influence of resinous monomers on the differentiation in vitro of human pulp cells into odontoblasts.

Odontoblasts are highly differentiated postmitotic cells, which under pathological conditions such as carious lesions and dental injuries may degenerate and be replaced by other pulp cells. A recent work showed that this physiological event can be reproduced in an in vitro assay system. The purpose of the present study was to evaluate the effects of resinous monomers on odontoblast differentiation in vitro. Pulp cores from extracted human third molars were cultured with beta-glycerophosphate (2 mM) and used to evaluate the effects of TEGDMA, HEMA, UDMA, and Bis-GMA on the differentiation of pulp fibroblasts into odontoblasts. The effect of the monomers was studied by evaluating the expression of several odontoblast specific genes. In the absence of monomers, mineral nodule formation was observed. Pulp cells contributing to the nodule formation synthesized type I collagen, osteonectin, and dentin sialoprotein (DSP). In addition, Fourier transform infrared microspectroscopy showed that the mineral and organic composition of the nodules were characteristic of dentin. When the monomers were added at nontoxic concentrations, the effects of HEMA and Bis-GMA were more evident than that of TEGDMA and UDMA on collagen 1, osteonectin, and DSP expression. However, all monomers significantly decreased DSP expression and completely inhibited the mineral nodule formation.

Acrylates↗
PubMed1989

Gap junctions between odontoblasts revealed by transjunctional flux of fluorescent tracers.

Cell communication between odontoblasts was investigated with the use of fluorescent-dye tracers; Lucifer Yellow CH (molecular weight = 457.3), and dextran-Lucifer Yellow CH (average molecular weight = 10,000). Dyes were injected into cell bodies of individual odontoblasts via an intracellular microelectrode or into a group of cells through their processes, and passage to adjacent cells was examined with a fluorescence microscope. Lucifer Yellow CH appeared to diffuse very easily among odontoblasts, while dextran-Lucifer Yellow remained within the injected cell or cells. This efficient migration of Lucifer Yellow CH can be considered a functional manifestation of gap junctions between odontoblasts.

Animals↗
PubMed1979

Basal bodies in the odontoblasts of the limpet, Patella coerulea L. (Gastropoda).

The odontoblasts in the long radular gland of Patella coerulea L. are arranged in a terminal position; therefore newly formed teeth already have an upright position. The long and slender odontoblasts have only one to three lengthy and ramifying apical microvilli. Between these pinnate microvilli a fine filamentous material appears which probably corresponds to chitin microfibrils. Therefore, the pattern of chitin microfibrils seems to depend on the arrangement of odontoblasts' microvilli. For the first time, basal bodies were found in the apical part of odontoblasts which led to the assumption that the radular gland originally might have been a mucous gland, the secretion of which was transported by cilia.

Animals↗
PubMed1987

Neuroregulation of protein synthesis in odontoblasts of the first molar of the rat after wounding.

Odontoblasts respond to occlusal trauma by increased elaboration of a matrix which is subsequently calcified to form reparative dentin. The purpose of the present study was to analyze quantitatively and compare the ability of odontoblasts to synthesize collagen after wounding in rats with an intact innervation (baseline) and in rats with sensory (inferior alveolar nerve, IAN) and/or sympathetic (superior cervical ganglion, SCG) surgical denervation. Surgery was performed 7 days prior to wounding. All rats had 1 mm of enamel and dentin removed from the occlusal surface of the first mandibular molar (resected side) with the contralateral tooth serving as a control. Rats were killed 1 h after injection with 3H-proline on days 0, 5, 10 or 15 after wounding, and mandibles were removed and processed for autoradiography. Grain counts were performed over odontoblasts throughout the pulp horns for each time period and for control and experimental molars in intact (baseline) and denervated groups. When compared to the control baseline, the experimental baseline data showed increased 3H-proline uptake throughout the study with a peak at 5 days. When compared to the baseline data, IAN and SCG results demonstrated a delay or attenuation of the protein synthetic response. The results indicate that the sensory and sympathetic neural components may regulate odontoblastic response to wounding.

Animals↗
PubMed2001

Junctional proteins and Ca2+ transport in the rat odontoblast-like cell line MRPC-1.

A transcellular bulk flow of Ca2+ ions through the odontoblast layer is of central importance during dentinogenesis. For this, specialized mechanisms may exist, which by a concerted action, gate Ca2+ into the proximal end of the cells and extrude the ions towards the mineralization front. To elucidate these mechanisms, an in vitro model would be useful. Mature odontoblasts are, however, post-mitotic cells and cannot be propagated in cell culture. The aim of the present study was, therefore, to characterize the odontoblast-like rat cell line MRPC-1(1) with regard to transcellular Ca2+ transport, barrier function, and intercellular junctions when cultured on membranes in Transwell chambers. The MRPC-1 cells grew as epithelial-like cells in a continuous bilayer separated by a thin collagenous matrix and with intercellular junctional complexes. They exhibited properties of a low-resistance epithelium, maintained a Ca(2+)-dependent diffusion barrier, and exhibited a functional diversity between the two cell layers. MRPC-1 cells expressed ZO-1, occludin, E-, and N-cadherins in addition to alpha-, beta-, gamma- and p120cat catenins, thereby demonstrating some traits in common with, but also differences from, epithelial cells and major differences from fibroblasts. The transcellular Ca2+ flux was inhibitable by nifedipine unidirectionally, giving evidence for an active intracellular Ca2+ transport through voltage-gated channels of the L-type. Similarities with native odontoblasts indicate that MRPC-1 cells may be useful for in vitro studies of transcellular Ca2+ transport mechanisms of importance for the calcification process.

Animals↗
PubMed2005

Dexamethasone stimulates differentiation of odontoblast-like cells in human dental pulp cultures.

Regenerative dental pulp strategies require the identification of precursors able to differentiate into odontoblast-like cells that secrete reparative dentin after injury. Pericytes have the ability to give rise to osteoblasts, chondrocytes, and adipocytes, a feature that has led to the suggestion that odontoblast-like cells could derive from these perivascular cells. In order to gain new insights into this hypothesis, we investigated the effects of dexamethasone (Dex), a synthetic glucocorticoid employed to induce osteogenic differentiation in vitro, in a previously reported model of human dental pulp cultures containing pericytes as identified by their expression of smooth muscle actin (SMA) and their specific ultrastructural morphology. Our data indicated that Dex (10(-8) M) significantly inhibited cell proliferation and markedly reduced the proportion of SMA-positive cells. Conversely, Dex strongly stimulated alkaline phosphatase (ALP) activity and induced the expression of the transcript encoding the major odontoblastic marker, dentin sialophosphoprotein. Nevertheless, parathyroid hormone/parathyroid hormone-related peptide receptor, core-binding factor a1/osf 2, osteonectin, and lipoprotein lipase mRNA levels were not modified by Dex treatment. Dex also increased the proportion of cells expressing STRO-1, a marker of multipotential mesenchymal progenitor cells. These observations indicate that glucocorticoids regulate the commitment of progenitors derived from dental pulp cells to form odontoblast-like cells, while reducing the proportion of SMA-positive cells. These results provide new perspectives in deciphering the cellular and molecular mechanisms leading to reparative dentinogenesis.

Actins↗
PubMed1985

Radioautographic analysis of [3H]-fucose utilization by mouse odontoblasts with emphasis on intracytoplasmic and plasma membrane glycoproteins.

[3H]-fucose utilization by odontoblasts was studied by light and electron microscopic radioautography. At 10 min after injection, fucose label was concentrated in the Golgi area. By 20-30 min, there was a progressive decline in Golgi labelling with label present at the plasma membrane, terminal web, odontoblast process and predentine matrix. At 4 h, the predentine and the predentine-dentine junction were heavily labelled. At the ultrastructural level, Golgi labelling at 10 min was mostly localized to cisternal elements and at 20 and 30 min secretory granules and dense bodies were also labelled. Most of the silver grains observed in the terminal web were associated with microfilaments near the plasma membrane. In the predentine, the matrix itself accounted for 23.0 per cent of the label at 4 h and the plasma membrane of the odontoblast process accounted for 19 per cent. The results indicate that odontoblasts, in addition to secreting glycoproteins into the dentinal matrix, also continuously manufacture glycoproteins for incorporation into the cell surface, the lysosomal system and the terminal web.

Animals↗
PubMed1987

Ultrastructure of the relationship between odontoblast processes and nerve fibres in dentinal tubules of rat molar teeth.

Serial ultra-thin sections across tubules were analysed three-dimensionally. There was no difficulty in distinguishing nerve fibres and odontoblast processes. In many tubules, a bundle of naked nerve fibres accompanied the odontoblast process for up to 50 microns located in concavities of the surface of the process (type I relationship). No specialized membrane structures between the plasma membrane of nerves and odontoblast process, such as gap junction or membrane thickening similar to that of synapse, were encountered. In a few tubules, the lamellar cytoplasmic processes of the odontoblast extensively enveloped the terminal part of the nerve fibres (type II relationship). This pattern was found in an animal older than the others in which there were lucent tubules and perhaps arose from peripheral sensory stimuli.

Animals↗