[Healing of dental pulp injury].
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Animals↗
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[The healing potential of dental pulp].
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Dental Caries↗
[Substance P in the primary sensory neurons innervating the dental pulp in the guinea pig].
Primary sensory trigeminal neurons supplying the dental pulp of incisors in guinea pigs were labelled by retrograde axonal transport. Using an autometallographic intensification procedure, 48 h after injection of wheat germ agglutinin/colloidal gold in the pulp, gold particles were detected in the cytoplasm of the neurons as black granulations. A morphometric study showed a bimodal repartition of the labelled neurons of the ganglion. By submitting ganglion slices to an anti-substance P immunserum revealed by immunocytochemistry, it could be observed that, among the neurons supplying the dental pulp of incisors, the majority of the largest were substance P immunopositive while the smallest were substance P immunonegative. These observations suggest that there could be at least two different populations of nerve fibres supplying the guinea pig incisor dental pulp. Substance P negative neurons could express different neurotransmitters.
Animals↗
Appearance and distribution of dendritic cells and macrophages in dental pulp during early postnatal morphogenesis of mouse mandibular first molars.
Dendritic cells and macrophages were examined in dental pulp during the postnatal development of mouse mandibular first molars, by immuno- and enzyme histochemistry. F4/80 antibody against dendritic cells and macrophages demonstrated labeled cells predominantly in and around the odontoblastic layer during tooth development from postnatal day 0 (PN0) to PN5. Labeling with Mac-1, Mac-2, and MOMA-2 antibodies against macrophages showed varied distribution patterns. Mac-1-positive cells were not detected in the dental pulp. Mac-2-positive cells appeared in the dental pulp at PN0, but not in or around the odontoblastic layer, and disappeared by PN3. A few MOMA-2-positive cells were detected in the dental pulp during the period examined. The F4/80-positive cells in and around the odontoblastic layer did not exhibit acid phosphatase or non-specific esterase activities. In addition, the F4/80-positive cells showed continued expression of Fcgamma receptor, but not class II major histocompatibility complex (MHC). Other antibodies against dendritic cells (NLDC-145, MIDC-8, and 33D1) did not label the F4/80-positive cells. We concluded that the F4/80-positive and class II MHC-negative cells in and around the odontoblastic layer may be immature dendritic cells in the early stages before eruption, weaning, and crucial exposure to antigenic stimuli. They may not only act primarily as immunosurveillance cells, but also play a role in a regulatory function and differentiation of odontoblasts.
Acid Phosphatase↗
Relative cerebral glucose metabolism evoked by dental-pulp stimulation in the rat.
Electrical stimulation of dental pulp is widely acknowledged to produce a sensation that is predominantly or exclusively noxious in character. The authors report the pattern of local cerebral glucose utilization evoked by dental-pulp stimulation in the barbiturate-anesthetized rat, using the [14C]2-deoxyglucose method of Sokoloff. Autoradiographs were prepared from cryostat-cut brain sections of animals given an intravenous pulse of [14C]2-deoxyglucose and sacrificed after 45 minutes of continuous bipolar stimulation of the incisor tooth pulp. Areas of high optical density on the autoradiographs identified brain regions where glucose consumption, and hence functional activity, was maximal. Stimulus-related increases in glucose utilization were seen ipsilaterally in an uninterrupted column from the lower levels of trigeminal nucleus caudalis to the rostral extent of the main sensory nucleus. Mandibular incisor pulp stimulation yielded increased deoxyglucose uptake in relatively restricted dorsal portions of the nuclei, while maxillary pulp stimulation produced a more extensive area of uptake ventrally. Elevated deoxyglucose uptake was also seen in the contralateral ventrobasal thalamus and sensory cortex with maxillary, but not mandibular, pulp stimulation. No changes in metabolic activity were detected in extralemniscal or limbic structures. These initial results suggest that the [14C]2-deoxyglucose method may be a useful means of mapping central structures involved in nociception.
Animals↗
MEPE is downregulated as dental pulp stem cells differentiate.
UNLABELLED: Previous studies on dental pulp cell culture have described heterogenous mixtures of cells that differentiate into odontoblasts and form mineralized dentin. OBJECTIVE: The aim of this study was to characterize the matrix extracellular phosphoglycoprotein (MEPE) expression by dental pulp stem cells (DPSC), related to cell differentiation. DESIGN: DPSC differentiation to form mineralized nodules was characterized by Alizarin red staining and micro-Raman spectroscopy. Osteogenesis SuperArray analysis was used to broadly screen for osteogenesis-related genes altered by DPSC differentiation. Relative levels of expression of MEPE and DSP were determined by semiquantitative RT-PCR and Western blot. RESULTS: Mineral analysis showed that as DPSC differentiated, they formed a carbonated hydroxyapatite mineral. Differentiation was initially marked by upregulation by Runx2, TGFbeta-related genes, EGFR and genes involved in collagen metabolism. ALP activity first increased, as DPSCs reached confluence but later decreased when cells further differentiated three weeks after confluence. MEPE was the only marker that was downregulated as DPSCs differentiated. CONCLUSION: DPSC differentiation can be characterized by downregulation of MEPE as other markers of DPSC differentiation, such as DSP, are upregulated. Expression of MEPE related to DSP and can be used to monitor DPSC as they are used for studies of odontoblast differentiation, tissue engineering or vital pulp therapy. The downregulation of MEPE as DPSC differentiate, suggests that MEPE is an inhibitor of mineralization.
Biomarkers↗
[Acute effect of calcium hydroxide-containing material in the rat's dental pulp microcirculation].
Experimental stimulation and clinical procedures applied on the crown of the tooth cause vascular reaction in the dental pulp. Laser-Doppler flowmetry is a good method for determining the blood flow of the dental pulp. The aim of these experiments was to study the acute effect of a calcium hydroxide-containing pulp-capping material (Dycal, DeTrey) on blood flow of the dental pulp after the application into a deep test-cavity. Two groups of male Sprague-Dawley rats (308 g +/- 50 S.E.) were used: control- and test-group, n = 10. A standardised deep class five cavity was prepared in the left lower incisor of each rat. Laser-Doppler flowmeter was used to measure the vascular reaction of the pulp. The levels of blood flow were recorded prior to (0 min.) and after the application (1, 5, 15, 30, 60 min.) of Dycal. Results were evaluated with one-way ANOVA. Significantly higher pulpal blood flow was found only in the first minute after the application of Dycal. In any other time no significant difference was found between the results before and after (5, 15, 30, 60 min.) the application in test- and control-group.
Analysis of Variance↗
Clonal dental pulp cells (RDP4-1, RPC-C2A) synthesize and secrete osteopontin (SPP1, 2ar).
Dental pulp cells play an important role in maintaining dental mineralized tissue throughout life. Supplementary mineralization such as reparative dentin and pulp stone frequently occurs after primary dentin formation. Dental pulp cells are thought to be closely associated with such mineralization. We found that clonal rat dental pulp cells, RDP4-1 and RPC-C2A, produce and secrete osteopontin, but do not synthesize phosphophoryn which is a major noncollagenous protein found in dentin. The dental pulp osteopontin was highly phosphorylated and identified by thrombin susceptibility and immunoprecipitation with osteopontin/2ar antibody. Osteopontin synthesis markedly increased by 12-O-tetradecanoylphorbol-13-acetate (TPA) as observed in many osteoblastic cells. This study indicates that these cells can produce osteopontin as a major phosphoprotein and suggests that the synthesis of osteopontin could be used as a characteristic marker of dental pulp cells.
Animals↗
[The roles of Notch2-Delta signaling in the differentiation of long-term cultured human dental pulp cells].
OBJECTIVE: To study the roles of the Notch2-Delta signaling in the differentiation of dental pulp cells into odontoblasts in vitro. METHODS: A long-term culture system was used as a model for the study of proliferation and differentiation of pulp cells into preodontoblasts. The expression patterns of Notch2 and its ligand Delta in different phases of long-term cultured dental pulp cells were studied by immunohistochemistry and western blotting. Furthermore, the effects of rhBMP-2 on the expression of Notch signaling members were studied. RESULTS: Notch2 and its ligand Delta expressed in all phases of dental pulp cells and the sites and levels of their expression changed with different phases. rhBMP-2 could significantly up-regulated the expression of Delta in the phase of later cell nodule formation. CONCLUSION: This study demonstrated that Notch signaling pathway played roles in the differentiation of long-term cultured human dental pulp cells which formed nudules that were slightly mineralized and had ultrastructural features reminiscient of preodontoblasts, and it may be the mechanism that control pulpal cell's responsiveness to signaling molecules in the healing of wound pulp.
Bone Morphogenetic Protein 2↗
Vasoactive intestinal polypeptide (VIP) and VPAC1 receptor in adult human dental pulp in relation to caries.
OBJECTIVE: To quantitatively measure VIP levels and to qualitatively study the distribution of VIP fibres and demonstrate the presence of the VPAC1 receptor in human dental pulp from carious and non-carious adult human teeth. DESIGN: Dental pulp samples were collected from non-carious, moderately carious and grossly carious adult human teeth. VIP levels were determined using radioimmunoassay. The distribution of VIP fibres was studied using immunohistochemistry. The VPAC1 receptor protein expression was determined by Western blotting. RESULTS: VIP levels were found to be significantly elevated in the dental pulp of moderately carious compared with non-carious (p=0.0032) or grossly carious teeth (p=0.0029). The distribution of VIP fibres was similar in non-carious and carious teeth, except that nerve bundles appeared thicker in the pulp samples from carious compared with non-carious teeth. Western blotting indicated that the VPAC1 receptor proteins were detected in similar levels in pooled dental pulp samples from both carious and non-carious teeth. CONCLUSION: It is concluded that quantitative changes in the levels of VIP in human dental pulp during the caries process and the expression of VPAC1 receptor proteins in membrane extracts from carious and non-carious teeth suggests a role for VIP in modulating pulpal health and disease.
Adult↗
Extraction of latent-type collagenase from cultured bovine dental pulps with NaCl or urea or by collagen degradation.
All of the collagenase activity extracted from cultured bovine dental pulp tissue with NaCl or urea solutions was due to enzyme in a latent form and identified as a typical animal collagenase. Isotonic sucrose solution solubilized no detectable collagenase activity from cultured dental pulps. Also, no collagenase activity was extracted from either fresh bovine dental pulps or those cultured in Tyrode's solution containing 50 micrograms/ml cycloheximide. A two-day difference was observed between the appearance of collagenase activity in the cultured pulps and in the culture medium. The activity profiles in the culture media showed essentially no difference with or without the addition of cyclohexamide on and after the 10th day of culture, indicating that the biosynthesis of collagenase in the cultured pulp might have terminated around that time. About 80% of the total pulp collagenase activity was extracted by a bacterial collagenase procedure. Nearly half (43.5%) of the collagenase activity extracted from the cultured pulps with NaCl or urea solution was precipitated with collagen molecules in the presence NaCl, and most of the precipitated activity retained in the precipitate even after washing it with NaCl-buffer solution. These facts suggest a close association of collagenase with the collagen in cultured dental pulp tissue.
Animals↗
Platelet-derived growth factor exerts disparate effects on odontoblast differentiation depending on the dimers in rat dental pulp cells.
Platelet-derived growth factor (PDGF) has recently been demonstrated to control the expression of alkaline phosphatase and proteoglycan synthesis of odontoblastic cells in dental pulp tissues. Although PDGF appears to be closely related to dentinogenesis, much about the mode of action of PDGF on odontoblast differentiation remains unclear. In this study, we examined the effects of three PDGF dimers (PDGF AA, AB, and BB) on odontoblastic differentiation of dental pulp cells in long-term mineralized cultures. Dental pulp cells isolated from rat lower incisors were continuously treated with each of PDGF AA, AB, and BB in separate cultures for 20 days. The three PDGF dimers suppressed alkaline phosphatase activity, osteocalcin and calcium content, and the formation of dentin-like nodules. The expression of mRNA for dentin sialoprotein (DSP) in the cells was inhibited by PDGF AA treatment, whereas PDGF AB and BB treatment stimulated the expression of DSP, even though the dentin-like nodule formation was inhibited. Although the effects of PDGF on odontoblastic differentiation varied among the dimers, the cells expressed both PDGF alpha and beta receptors, whose quantities were similar. These results suggest that PDGF exerts diverse effects on odontoblastic differentiation depending on its dimeric form. These in vitro findings explain, at least in part, the in vivo action of PDGF in dentinogenesis during the repair process of damaged dental pulp.
Alkaline Phosphatase↗
Transferrin subtyping in dental pulps.
Serum transferrin (TF) subtypes were also found in dental pulps by isoelectric focusing and immunoblotting. The types observed in dental pulps completely agreed with those in serum samples from the same individuals. The allele frequencies in 105 samples were TF*C1 = 0.757 and TF*C2 = 0.243. Reliable subtyping was possible for 4 weeks following extraction of the teeth. The TF system can provide a useful genetic marker for the medicolegal individualization of teeth.
Alleles↗
Quantitative analysis of catecholamines in human dental pulp.
Catecholamines are important elements of neuroendocrine regulation, and their concentrations in dental pulp are of interest. Two groups of teeth were used in this study: (i) healthy teeth and (ii) periodontally diseased teeth. After the processing of dental pulp obtained from the extracted teeth, the samples were analyzed in a computer-controlled Merck-Hitachi HPLC system at 280 nm wavelength. The external and internal standard methods of the HPLC Manager Program were used for validation. In healthy teeth the norepinephrine level of dental pulp was 4.86 +/- 0.96 micrograms/g, whereas the epinephrine level was 8.1 +/- 1.18 micrograms/g. In periodontally diseased teeth norepinephrine and epinephrine levels were significantly higher (p < 0.01) at 13.98 +/- 21.13 micrograms/g and 1.42 +/- 0.32 micrograms/g, respectively. Dopamine could not be demonstrated in 87% of the pulps. Summing up we succeeded in demonstrating norepinephrine and epinephrine in human pulp, but in most cases we could not demonstrate dopamine. Further investigations are needed on pulp tissue infected because of caries.
Adrenergic alpha-Agonists↗
Dental pulp cells provide neurotrophic support for dopaminergic neurons and differentiate into neurons in vitro; implications for tissue engineering and repair in the nervous system.
Glial cell line-derived neurotrophic factor (GDNF) mRNA is highly expressed by dental pulp cells (DPCs) prior to the initiation of dental pulp innervation. We show that radioactively labelled exogenous GDNF is retrogradely transported from neonatal teeth and vibrissae to the trigeminal neurons, indicating that GDNF acts as a classical neurotrophic factor in the trigeminal system. We also show that DPCs from both rats and humans produce nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and GDNF mRNAs in vitro, promote the survival and phenotypic characteristics of embryonic dopaminergic (DA) neurons and protect DA neurons against the neurotoxin 6-hydroxy-dopamine (6-OHDA) in vitro. By using inhibitory antibodies to NGF, BDNF and GDNF, we show that the promotion of DA neuron survival relates to the production and release of neurotrophic proteins by DPCs in vitro. We suggest that in vivo production of neurotrophic factors by DPCs play roles in tooth innervation. However, continued production of neurotrophic factors by the DPCs might have wider implications. We propose that the dental pulp is a viable source of easily attainable cells with possible potential for development of autologous cell transplantation therapies. We also show that a population of neural crest-derived dental pulp cells acquire clear neuronal morphology and protein expression profile in vitro, indicating the presence of a cell population in the dental pulp with neuronal differentiation capacity that might provide additional benefits when grafted into the CNS.
Adolescent↗
Immunohistochemical localization of collagenase inhibitor in bovine dental pulp, pulp cells in monolayer culture, and in some oral connective tissues.
The development of an antiserum, monospecific to the collagenase inhibitor, from bovine dental pulps permitted localization of immunoreactive inhibitor protein, by means of both immunofluorescence and immunoperoxidase-staining techniques in sections of bovine dental pulps. The immunoreactive inhibitor protein in bovine dental pulps is present both in cells and extracellular matrices. When cultured in Eagle minimal essential medium, coronal pulps from bovine-unerupted teeth were shown, by assay of the medium, to produce only about 1/10 of the amount of inhibitor produced by the root pulps. When compared by immunohistochemical observation, however, essentially no differences in fluorescent activity was found between coronal and root pulps. Specific cytoplasmic staining was seen both in explanted root-pulp tissues and in immature fibroblast-like pulp cells from monolayer cell cultures of bovine root pulps, which indicate that the pulp cells are responsible for inhibitor production. Sections of dental follicle and gingiva from the same animal, showed a distribution of immunoreactive inhibitor protein similar to that in dental pulps.
Animals↗
The behaviour and proliferation of human dental pulp cell strains in vitro, and their response to the application of platelet-derived growth factor-BB and insulin-like growth factor-1.
Human dental pulp fibroblast strains were established from explants of dental pulps using identical culture techniques. To determine proliferative activity, a 3H-thymidine uptake and a crystal violet dye-binding assay were performed at passage numbers seven and eight. Assays were performed in the presence of either 0% fetal calf serum (FCS), 0.2% FCS or 10% FCS. Considerable variation in the overall proliferative activity of the different pulp cell strains (when averaged over all other variables) was noted. All dental pulp cell strains demonstrated significantly different proliferative activity from each other. In addition, the level of proliferative response and 3H-thymidine incorporation decreased as the passage number of the cells increased. This was in accordance with the findings of Tardieu-Moreau et al. (1992). It is proposed that the differences in proliferative activity are most likely attributable to inherent variability within the established pulp cell strains. Platelet derived growth factor-BB (PDGF-BB) and insulin-like growth factor-1 (IGF-1) were added to the human pulp cells both separately and in combination. All of the pulp cells exhibited increased proliferative activity in the presence of the growth factors with the combination of PDGF-BB/IGF-1 having the greatest mitogenic effect. There was also significant variability in the level of response of all pulp cell strains to the different growth factors. This study identified significant variability in the responsiveness to the growth factors between the pulp cell strains when the results of the 3H-thymidine and dye binding assays were compared. These findings reinforce the thesis that different assay procedures may also influence the findings of biological investigations involving the human dental pulp. The results of this study confirm that when comparing the findings of different in vitro studies involving human pulp cells, variations in experimental data can be strongly influenced by the pulp cell strain used and the culture technique employed. Indeed, studies of human pulp cell proliferation using pulp cells which are not of the same transfer number may not be relevant.
Adult↗
Pulpal exposure alters neuropeptide levels in inflamed dental pulp and trigeminal ganglia: evaluation of axonal transport.
Dental pulp is richly innervated with neurons containing calcitonin gene-related peptide (CGRP) or substance P (SP). Prior studies have demonstrated that inflammation alters these pulpal neuropeptides. In this study, we used a radioimmunoassay to evaluate the specificity of this response and the contribution of axonal transport. Rat mandibular molars were exposed and immunoreactive CGRP (iCGRP) and immunoreactive SP were measured. At 7 to 14 days after exposure, both pulpal iCGRP (73%) and immunoreactive SP (135%) displayed peak increases above control levels. This response was somatotopically restricted, with no changes observed in contralateral (intact) molars, or in ipsilateral mandibular molars after exposure of maxillary molars. Transection of the inferior alveolar nerve on day 13 significantly reduced pulpal levels of iCGRP on day 14. Collectively, these studies indicate that pulpal inflammation evokes a selective alteration in neuropeptide levels, due at least in part to alterations in transport or synthesis of neuropeptides in the trigeminal ganglion.
Analysis of Variance↗