c-jun原癌基因在鼠牙胚中的表达

目的 通过观察ｃ－ｊｕｎ原癌基因在鼠牙胚中的表达，探讨成牙本质细胞分化的转录调节。方法 利用免疫组化方法检测ｃ－ｊｕｎ原癌基因在鼠牙胚中的表达。结果 ｃ－ｊｕｎ原癌基因在小鼠牙胚的蕾状期、帽状期呈阴性表达，在钟状期牙胚的成牙本质细胞中呈阳性表达。结论 ｃ－ｊｕｎ可能参与了成牙本质细胞分化的转录调节，并且可能成为牙本质细胞的标志分子之一。     

Complex cellular responses to tooth wear in rodent molar

The arrangement and roles of the odontoblast and its process in sensing and responding to injuries such as tooth wear are incompletely understood. Evidence is presented that dentine exposure by tooth wear triggers structural and functional changes that aim to maintain tooth integrity.Mandibular first molars from freshly culled 8 week Wistar rats were prepared for light microscopy ground-sections (n = 6), or fixed in 4% paraformaldehyde, decalcified in 17% EDTA, sectioned and stained with antibodies to cyto-skeletal proteins (vimentin (vim), α-tubulin (tub) and α-actin), cellular homeostatic elements (sodium potassium ATPase (NaK-ATPase) and sodium hydrogen exchanger (NHE-1)), and sensory nerve fibres (CGRP) (n = 10) for fluorescence microscopy of worn and unworn regions of the mesial cusp.Immunoreactivity (IR) to vim, actin, NaK-ATPase and CGRP was confined to the pulpal third of odontoblast processes (OPs). IR to tub and nhe-1 was expressed by OPs in full dentine thickness. In areas associated with dentine exposure, the tubules contained no OPs. In regions with intact dentine, odontoblasts were arranged in a single cell layer and easily distinguished from the sub-odontoblast cells. In regions with open tubules, the odontoblasts were in stratified or pseudo-stratified in arrangement.Differences in structural antibody expression suggest a previously unreported heterogeneity of the odontoblast population and variations in different regions of the OP. This combined with differences in OPs extension and pulp cellular arrangement in worn and unworn regions suggests active and dynamic cellular responses to the opening of dentinal tubules by tooth wear.     

The biosynthesis of dentin phosphophoryns by rat incisor odontoblasts in organ culture

Summary Anin vitro system consisting of rat incisor fragments was used to study the process of dentinogenesis. In order to establish the usefulness of the organ culture, the biosynthesis and deposition of the major noncollagenous components of dentin, the phosphophoryns, were followed for specific lengths of time in culture. Three criteria were satisfied: (1) the synthesis of proteins which appeared to be chemically identical to the native proteins of dentin, (2) the accumulation of the phosphophoryns within the matrix or time, and (3) the association of the secreted proteins with the mineral phase of dentin The synthesis of phosphophoryns was determined by using both (³H)-serine and (³²P)-inorganic phosphate as precursors for synthesis of protein and post-translational modification of serine to phosphoserine.In vitro synthesized phosphophoryns were characterized by 1) their accumulation and EDTA extractability from within dentin, 2) calcium chloride precipitability, 3) elution on anion-exchange columns (DEAE cellulose and AGMP50), and 4) Mr's on SDS-PAGE and Sepharose CL-6B columns. This novel system of studying dentinogenesis provides a model with which to study the regulation of extracellular matrix protein synthesis and may be useful for revealing the effect of other agents which influence tooth development and mineralized tissue metabolism in general.     

Removal of the apical one-third of the root improves the fixation process of the dental pulp in teeth

The fixation process in histology is an important process that will eventually determine the quality of the histology slides. Fixation of the dental pulp involves the entry of the fixative agent into the dental pulp through the root canals that are found at the apical part of the root. The objective of this study was to evaluate the effectiveness of four methods of tooth preparation (teeth cut longitudinally or cervically, removal of apical third of root and whole uncut teeth) on the fixation process of the dental pulp for producing high quality histology slides. Among the four methods of tooth preparation, removal of the apical one-third of the root produced high quality histology slides as fixation of the dental pulp was improved and hence, preservation of the pulp’s architecture and contents were achieved. It is concluded that removal of the apical one-third of the root improves the fixation process of the dental pulp in teeth.     

Effects of low-power red laser on dentine-pulp interface after cavity preparation. An ultrastructural study

OBJECTIVE: Studies on the influence of low-power red laser on the repair of dental structures are very scarce. This study investigated the effects of the laser therapy on the ultrastructure of the dentine-pulp interface after conservative class I cavity preparation. DESIGN: Two female volunteers with 8 premolars indicated for extraction for orthodontic reasons were recruited. Class I cavities were prepared and the teeth were randomly divided into two groups. The first group received treatment with a GaA1As laser, lambda=660nm, power of 30mW and energy dose of 2J/cm(2), directly and perpendicularly into the cavity in a single visit. After the irradiation, the cavities were filled with composite resin. The second group received the same treatment, except by the laser therapy. RESULTS: Twenty-eight days post-preparation, the teeth were extracted and processed for transmission electron microscopy analysis. Two sound teeth, without cavity preparation, were also studied. The irradiated group presented odontoblast process in higher contact with the extracellular matrix and the collagen fibrils appeared more aggregated and organised than those of control group. These results were also observed in the healthy teeth. CONCLUSION: These findings suggest that laser irradiation accelerates the recovery of the dental structures involved in the cavity preparation at the predentine region.     

Influence of HEMA on LPS- and LTA-stimulated IL-6 release from human dental pulp cells

ObjectiveDental pulp cells interact with immunogenic components such as LPS (lipopolysaccharide) or LTA (lipoteichoic acid) released from microorganisms in carious lesions. In the present investigation, the formation of the pro-inflammatory cytokines TNFα and IL-6 in LPS- or LTA-stimulated cells from the dental pulp interface and pulp fibroblasts was analyzed in the presence of the resin monomer 2-hydroxyethyl methacrylate (HEMA) under varying cellular redox conditions.MethodHuman pulp fibroblasts (HPC) or cells from the dental pulp interface expressing an odontoblast phenotype (hOD-1) were exposed to LTA, LPS or HEMA for 1 h or 24 h. Redox homeostasis was modified by the prooxidant BSO (L-buthionine sulfoximine) or the antioxidant NAC (N-acetyl cysteine). Formation of TNFα or IL-6 was analyzed by ELISA, and cell survival was determined by a crystal violet assay. Statistical analyses were performed using the Mann-Whitney-U-test.ResultsSecretion of TNFα was not detected in LPS- or LTA-stimulated HPC or hOD-1, and IL-6 was not found after a short exposure (1 h). After a 24 h exposure, LPS induced a 3-fold increase in IL-6 formation in HPC, while LTA stimulated IL-6 release about 20-fold. Likewise, LTA was more effective than LPS in hOD-1 stimulating IL-6 levels about 50-fold. HEMA inhibited the LPS- and LTA-induced IL-6 release, and this effect was enhanced by BSO but counteracted by NAC in both cell types. IL-6 release was independent of cell survival rates.ConclusionsThe protective immune response in odontoblasts and pulp fibroblasts is impaired by monomers such as HEMA through the disturbance of the redox homeostasis.     

纤维粘连蛋白及骨形成蛋白-2、4在牙胚发育中的表达研究

目的 观察纤维粘连蛋白(fibronectin,FN)和骨形成蛋白-2、4(BMP-2、4)在大鼠牙胚发育中的表达,探讨其在成牙本质细胞分化及成熟过程的时空表达关系,为明确牙齿发育的分子调控网络提供理论和实验基础.方法 获取SD大鼠蕾状期和钟状期第一磨牙牙胚,通过免疫组化LsAB法观察FN和BMP-2、4的表达差异及相互关系.结果 FN在蕾状期和钟状期都有表达,蕾状期主要分布在牙上皮、牙间质,周围非牙间质细胞为阴性,钟状期主要分布在成牙本质细胞分化活跃的区域和分化中的内釉上皮细胞.钟状期BMP-2、4的表达较强,主要分布在成牙本质细胞分化活跃的区域. 结论 BMP-2、4和FN在牙齿发育的蕾状期和钟状期均有表达,但表达的阳性分布区不同.     

EphrinB2 signaling enhances osteogenic/odontogenic differentiation of human dental pulp stem cells

ObjectiveTo investigate the role of the EphrinB2 signaling pathway in the osteogenesis/odontogenesis of human dental pulp stem cells (DPSCs).DesignThe endogenous expression levels of EphrinB2 and its cognate receptors EphB2 and EphB4 in DPSCs were analyzed by qRT-PCR and Western blotting after 7, 14 and 21 days of osteogenic/odontogenic induction culture. Additionally, the phosphorylation of EphrinB2, EphB4 and ERK1/2 proteins at early time-points following osteogenic induction, were also investigated by Western blots. Subsequently, we investigated whether supplementation of recombinant EphrinB2-Fc within the induction milieu can enhance the osteogenic/odontogenic differentiation of DPSCs.ResultsEndogenous gene and protein expression levels of EphrinB2, EphB2 and EphB4 were upregulated in induced versus non-induced DPSCs, over 21 days of osteogenic/odontogenic induction. Western blots showed increase in phosphorylated EphrinB2, EphB4 and ERK1/2 proteins at early time-points following osteogenic induction. Preliminary investigation of a concentration range (0, 0.5, 1 and 2 μg/ml) of recombinant EphrinB2-Fc within osteogenic induction media, showed that 0.5 μg/ml was optimal for enhancing the osteogenic/odontogenic differentiation of DPSCs over a culture duration of 14 days. Subsequently, more comprehensive qRT-PCR analysis with 0.5 μg/ml EphrinB2-Fc revealed significant upregulation of several key osteogenic marker genes in treated versus untreated DPSCs after 21 days of osteogenic/odontogenic induction. By 7 days of osteogenic induction, DPSCs treated with 0.5 μg/ml EphrinB2-Fc exhibited significantly more calcium mineralization (Alizarin red S staining) and alkaline phosphatase activity than the untreated control.ConclusionsEphrinB2 signaling plays a key role in the osteogenic/odontogenic differentiation of DPSCs.     

Expression of heat shock protein 27 in adult human third molar dental pulp

This study is the first to define the expression of hsp 27 in the pulp of the adult human third molar. Using a monoclonal antibody against human hsp 27, immuno-reactivity was demonstrated in the odomoblasts. odontoblast processes, pulp fi-broblasts, and smooth muscle and endothelial cells of vessel walls. Nerves were negative. Pulp fibroblasts were characterized by cytoplasraic staining and variable nuclear staining. Odontoblasts also displayed consistent cytoplasmic staining and variable nuclear staining. Western. Northern, and RT-PCR analysis confirmed the expression of hsp 27 mRNA and protein. Hsp 27 was also shown to be present in both the unphosphorylated and phosphorylated isoforms. In general, nuclear localization and phosphorylation of hsp 27 has been correlated with cells responding to stress or other stimuli. This study demonstrates that pulp from a single human third molar provides sufficient material to support a detailed molecular analysis of gene expression.