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PubMed2005

An immunohistochemical study of the expression of heat-shock protein-25 and cell proliferation in the dental pulp and enamel organ during odontogenesis in rat molars.

OBJECTIVES: The aim of this study is to clarify the functional significance of heat-shock protein (HSP)-25 during tooth development. DESIGN: We compared the expression of HSP-25 in the dental epithelial and mesenchymal cells with their proliferative activity during odontogenesis in rat molars on postnatal days 1-100 by immunohistochemistry using anti-HSP-25 and anti-5-bromo-2'-deoxyuridine (BrdU) for cell proliferation assay. RESULTS: On day 1, BrdU-immunoreactive cells were densely located in the inner enamel epithelium in the cervical loop and intercusped areas and the dental pulp adjacent to them, whereas HSP-25-immunoractivity (IR) was restricted to the cusped area where odontoblasts and ameloblasts had already differentiated. Subsequently, BrdU-IR shifted in the apical direction to be localized around Hertwig's epithelial root sheath during days 5-30, never overlapping with concomitantly apically-shifted HSP-25-IR. On days 60-100, BrdU-immunoreactive cells were hardly recognizable in the dental pulp, where HSP-25-IR was exclusively localized in the odontoblast layer. Furthermore, the odontoblast- and ameloblast-lineage cells exhibited two steps in the expression of HSP-25 throughout the postnatal stages: first, dental epithelial and pulpal mesenchymal cells showed a weak IR for HSP-25 after the cessation of their proliferative activity, and subsequently odontoblasts and ameloblasts consistently expressed an intense HSP-25-IR. CONCLUSION: Odontoblast- and ameloblast-lineage cells acquire HSP-25-IR after they complete their cell division, suggesting that this protein acts as a switch between cell proliferation and differentiation during tooth development. The consistent expression of HSP-25-IR in the formative cells may be involved in the maintenance of their functional integrity.

Amelogenesis↗
PubMed2004

Regulation of tenascin expression in cultured rat dental pulp cells.

Tenascin (TN) is a glycoprotein of extracellular matrix abundantly present in embryonic mesenchymal tissues. Transforming growth factor-beta1 (TGF-beta1), basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), hepatocyte growth factor (HGF), and retinoic acid (RA) are important regulators of dentinogenesis. Dental pulp cells have the capacity to differentiate into odontoblast-like cells. In this study, we investigated the effects of growth factors on TN expression and adhesive function using rat clonal dental pulp cells, RPC-C2A. Analyses of reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting revealed that RPC-C2A cells expressed TN molecules and that TGF-beta1, HGF, and RA increased expression of TN at the mRNA and protein level, while bFGF and EGF showed a weak effect. An adhesion assay revealed that treatment with TGF-beta1, HGF, and RA induced a marked reduction of cell attachment to fibronectin (FN)-coated surfaces, whereas there was no change with bFGF and EGF. Functional blocking of growth factor-stimulated TN protein by pretreating cells with anti-TN antibodies restored cell attachment to control levels. These findings suggest that TGF-beta1, HGF, and RA may regulate pulpal cell adhesion to FN-coated surfaces and that this effect is mediated by TN.

Animals↗
PubMed1991

Enamel surface roughness and dental pulp response to coaxial carbon dioxide-neodymium: YAG laser irradiation.

The purpose of this study was to evaluate the effect of a coaxial carbon dioxide/neodymium:yttrium aluminium garnet laser beam on enamel surface roughness and the dental pulps of mongrel dogs. In four dogs, four maxillary left posterior teeth were irradiated at 16 cm source-tooth distances. Two teeth were irradiated with 16 W CO2/16 W Nd:YAG and the remaining two with 16 W CO2/40 W Nd:YAG. Two maxillary right teeth were untreated controls. In addition, mandibular premolars were irradiated at the same distance and power levels, extracted, and analysed for surface roughness. Significant differences in surface roughness were found between control samples and either power level, but not between enamel surfaces at the two power levels. Maxillary teeth were removed at 10 days postoperatively, sectioned and stained (H & E). The reaction of pulpal cells to irradiation was scored. Data analysis revealed statistically significant differences between the control and lower power Nd:YAG groups and between the control and higher power Nd:YAG groups. The difference in pulpal response between both laser groups approached significance.

Aluminum Silicates↗
PubMed1975

Effect of soluble plaque factors on inflammatory reactions in the dental pulp.

The present investigation was undertaken to determine whether soluble factors from human dental plaque are capable of inducing or mediating pathological alterations in the dental pulp. The experiment was performed in three monkeys and involved 40 teeth in all: 20 test and 20 control teeth. Class V cavities were prepared on the buccal surface close to the marginal gingiva. In the test cavities an extract of human dental plaque was applied once very 5 min during an 8-h period. The cavities of the contralateral teeth were treated in an identical manner but with Ringer's solution. The animals were sacrificed 10 or 32 h after the initiation of the test. Two hours prior to sacrifice the animals were injected with colloidal carbon and then perfused with 10% neutral buffered formalin. Histologic examination demonstrates that the pulp tissue response to topical application of a plaque extract was characterized by (1) increased degree of carbon retention - indicative of vascular exudation and (2) enhanced rate of emigration of neutrophils and monocytes.

Animals↗
PubMed1980

Dipeptidyl peptidase II of bovine dental pulp. Initial demonstration and characterization as a fibroblastic, lysosomal peptidase of the serine class active on collagen-related peptides.

Dipeptidyl peptidase II (dipeptidylpeptide hydrolase, EC 3.4.14.2), previously known as dipeptidyl aminopeptidase II, was shown to be present in relatively high concentrations in bovine dental pulp. Based on the DNA content of tissue homogenates, the fibroblasts of this connective tissue appeared to contain more dipeptidyl peptidase II than the cells of lysosome-rich tissues such as bovine spleen and rat liver. The newly-recognized properties of dipeptidyl peptidase II, from both pulp and pituitary sources, included a marked propensity for hydrolyzing prolyl bonds at acidic pH. Lys-Pro-2-NNap and Lys-Pro-2(4-methoxy)naphthylamide (designed for cytochemical application) were hydrolyzed at rates equal to that of Lys-Ala-2-NNap. The impure pulp enzyme and the authentic pituitary enzyme showed comparable relative rates of hydrolysis on a variety of fluorogenic substrates with the general structure X-Pro-2-NNap (X = Lys, Arg, Phe, Ala or Gly), and on a variety of collagen-related tripeptides represented by X-Pro-Ala (X = Gly, Ala or Lys). The highest rates wee obtained on Lys-Ala-Ala and Lys-Ala-Pro. The pH optima for the hydrolysis of the 2-naphthylamide derivatives varied from 5.0 to 5.7, and for tripeptides from 4.2 to 5.3. In all cases the N-terminal dipeptide was released intact. Although previously unrecognized as a serine protease, dipeptidyl peptidase II (of pulp and pituitary origin) was strongly inhibited by (1 mM) diisopropyl phosphorofluoridate, p-nitrophenyl-p'-guanidinobenzoate, and phenylmethylsulfonyl fluoride. The enzyme, from both sources, was fully inhibited by 0.1 mM Lys-Ala chloromethyl ketone, a newly-designed, active-site-directed inhibitor. The numerous properties shared by the putative dipeptidyl peptidase II of bovine dental pulp and an authentic preparation of the bovine pituitary enzyme provided strong support for their having a common identity.

Animals↗
PubMed1999

Tissue-non-specific alkaline phosphatase mRNA expression and alkaline phosphatase activity following application of retinoic acid in cultured human dental pulp cells.

Retinoic acid is a potent inducer of tissue-non-specific alkaline phosphatase (TNSALP) expression in various osteoblastic and fibroblastic cells, and may be involved in morphogenesis, cellular growth and differentiation. This study investigates the effects of retinoic acid on alkaline phosphatase activity and TNSALP gene expression in human dental pulp cells. Cultured cells were treated with various concentrations of retinoic acid (0, 10(-7), 10(- 6), 10 (-5) M) in 0.5% bovine serum albumin without serum. Alkaline phosphatase activity was determined by the rate of p-nitrophenyl phosphate hydrolysis and was also assayed in the presence of various inhibitors and under thermal inactivation. A set of specific oligonucleotide primers was selected, based on the nucleotide sequences of two human TNSALP mRNA (bone and liver) types, and reverse transcription-polymerase chain reaction (RT-PCR) performed. Inhibitory and thermal inactivation experiments revealed that the elevated alkaline phosphatase activity had properties of the TNSALP type. RT-PCR showed that retinoic acid enhanced the expression of bone-type TNSALP mRNA in pulp cells. However, the liver-type TNSALP mRNA was not detected. These findings suggest that the high alkaline phosphatase activity of retinoic acid-treated dental pulp cells is associated with increased transcription of the bone-type mRNA of the TNSALP gene and not with liver-type.

Alkaline Phosphatase↗
PubMed1994

[Influence exerted by environmental and physicochemical factors on the results of sex identification of human dental pulp by polymerase chain reaction].

Sex identification of human tooth is an important aspect of individual identification in forensic science practice. This study was designed to determine the effects of environmental and physicochemical factors (EPF) on the deoxyribonucleic acid (DNA) from dental pulp and PCR result. Extracted teeth were subjected to the following treatment varying pH (2, 7, 10) solution; 10% formalin, 75% ethanol; different temperature (-20 degrees C, 4 degrees C, 25 degrees C, 37 degrees C, boiling, burning); humidity (20%, 66%, water submergence); burying the teeth outdoors; and aging (teeth stored at room temperature for 1.5, 3.5 and 8 years). DNA was extracted from the tooth followed by agarose gel electrophoresis for the purpose of DNA assay and quantity determination. Amplification was carried out using a pairs of primer Y1.1 and Y1.2. The results of the study showed that, 154 bp fragment was obtained in all male teeth, whereas no 154 bp fragment was found in a female fresh tooth. 154 bp fragment bands were not observed in case of teeth subjected to burial outdoors for 10 weeks, submergence in water for 10 weeks, soak in pH 2 solution for 10 weeks, and combustion for 10 minutes; only faint bands were observed in case of teeth subjected to 66% humidity and pH 10 solution for 10 weeks and combustion for 5 minutes; obvious bands were observed in the rest cases. In addition, the quality of DNA from dental pulp affected PCR amplification result. The integrity of DNA isolated was categorized as being high-molecular-weight (HMW), HMW with partial degraded DNA, completely degraded DNA, completely degraded and not detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1999

Thrombin activates the growth, cell-cycle kinetics, and clustering of human dental pulp cells.

Thrombin is activated during vascular injury and inflammation of the dental pulp. In the present study, we found that thrombin can stimulate the proliferation of pulp cells in a dose-dependent manner as analyzed by modified MTT assay. The cell number increased by 1.6, 1.77, and 2.14-fold over that of control after exposure to 5, 10, and 20 units/ml of thrombin for 5 days. Flow cytometry studies also found that thrombin (10 units/ml) can induce the cell cycle progression of pulp cells after 24 h of incubation, as revealed by increasing the proportion of cells in the S phase and the G2/M phase from 29 to 72%. Moreover, exposure to thrombin (> 5 units/ml) for 3 days led to marked clustering of pulp cells. We concluded that thrombin can regulate the growth, cell cycle progression, and functional reorganization of the pulp tissue during pulp healing and inflammatory processes.

Cell Aggregation↗
PubMed2000

Isolation of proteoglycan (versican) aggregate from rat dental pulp.

Versican is a large interstitial proteoglycan that is believed to be able to bind hyaluronan to form large aggregate structures, but no study has isolated native versican aggregates from any tissue. In this study, ternary aggregate structures consisting of versican, hyaluronan, and link protein were isolated from rat dental pulp by associative extractions followed by caesium sulphate rate zonal sedimentation centrifugation. Fractions from the centrifugation were analysed by dot blot and Western blot using monoclonal antibodies and hyaluronan-binding protein. About 60% of the hexuronic acid was extracted by associative extractions. Positive reactions for versican, hyaluronan and link protein were clearly detected in the bottom fractions from the centrifugation, but were barely detectable in the top fractions. These results suggest that the majority of the versican, hyaluronan, and link protein forms ternary aggregate structures in the rat dental pulp.

Animals↗
PubMed1987

Supernatant from an activated human CD4+ T-cell clone modulates the proliferation and collagen synthesis of human dental pulp fibroblasts.

Several studies indicate a relationship between immunocompetent cells and fibroblast functions such as proliferation and collagen synthesis, which may be of importance in understanding the process of fibrosis. We demonstrate here the activity of supernatant from an activated human CD4+ proliferative T-cell clone (2F1) in stimulating the proliferation of human dental pulp fibroblasts, while inhibiting their soluble type I collagen secretion in either growing or confluent cultures. Taken together, our results indicate that T-cell derived lymphokines may be of importance in regulating normal dental pulp fibroblast functions.

Cell Division↗