OBJECTIVETo observe the effects of nicotine on the proliferation of odontoblasts and explore the possible mechanism.

METHODSOdontoblasts MDPC-23 were cultured, inoculated and divided into two groups randomly. With no stimuli added for the control group, the experimental group was stimulated by 100 microg/mL nicotine. After 8 hours, 10 micromol/L BrdU was added to label cells at S stage in cell cycle. 24 hours later, odontoblasts were fixed and immunofluorescence staining was performed with specific mouse BrdU antibody. After counterstaining with propidium iodide, BrdU positive cells were arbitrarily scored microscopically by an independent estimation conducted three times, and the corresponding total cell number in the same vision were counted in both groups. BrdU positive cell rates were calculated and compared statistically. At the same time, odontoblasts MDPC-23 were cultured and stimulated by 100 microg/mL nicotine, the dynamic Ca2+ concentration inside the cytoplasm were detected immediately by a confocal laser scanning microscope.

RESULTSThe ratio of S stage cells in the experimental group was 36.3% significantly lower than that (48.2%) in the control group. After the addition of 100 microg/mL nicotine, the Ca2+ concentration inside the cytoplasm rose rapidly, sustained at a high level for a short time and then relapsed gradually.

CONCLUSIONNicotine had inhibitory effects on the proliferation of odontoblasts MDPC-23, which might be related to the increased Ca2+ concentration in the cytoplasm.

The polarity of ameloblasts and odontoblasts is crucial for their differentiation and function. Polarity-related molecules play an important role in this process. This review summarizes the process of polarity formation of ameloblasts and odontoblasts and their related regulators.
Ameloblasts ; Cell Differentiation ; Odontoblasts

OBJECTIVEThe Sonic hedgehog signalling peptide has been demonstrated to play important roles in the growth and patterning of the tooth development. This study aims on whether the antagonist beta-transduction repeat containing protein of Sonic hedgehog signal transduction expressed in tooth germs ameloblast and odontoblast or not.

METHODSThe mouse embryo heads of different developmental stages of E10.5, E13.5, E14.5, E16.5, E18.5 and P0, P3, P6 after birth were acquired fixed with 4% paraformaldehyde for 48 hours, embeded with Paraffin and examined using LsAB (labelled streptavidin-biotin) method to observe the beta-TrCP expression pattern in tooth germs, ameloblast and odontoblast.

RESULTSIt was demonstrated that beta-TrCP expressed in oral epithelium, tooth bud, mesenchymal cell cytoplasm of ameloblast and odontoblast of different stage of tooth development.

CONCLUSIONbeta-TrCP expressed from early stage to later stage of murine tooth development. And these findings provide the evidence of antagonist regulatory pathways for shh in teeth development.

Ameloblasts are responsible for the formation and maintenance of enamel which is an epithelially derived protective covering for teeth. Ameloblast differentiation is controlled by sequential epithelial-mesenchymal interactions. However, little is known about the differentiation and maturation mechanisms. OD314 was firstly identified from odontoblasts by subtraction between odontoblast/pulp cells and osteoblast/dental papilla cells, even though OD314 protein was also expressed in ameloblast during tooth formation. In this study, to better understand the biological function of OD314 during amelogenesis, we examined expression of the OD314 mRNA and protein in various stages of ameloblast differentiation using in-situ hybridization and immunohistochemistry. The results were as follows : 1. The ameloblast showed 4 main morphological and functional stages referred to as the presecretory, secretory, smooth-ended, and ruffle-ended. 2. OD314 mRNA was expressed in secretory ameloblast and increased according to the maturation of the cells. 3. OD314 protein was not expressed in presecretory ameloblast but expressed in secretory ameloblast and maturative ameloblast. OD314 protein was distributed in entire cytoplasm of secretory ameloblast. However, OD314 was localized at the proxiamal and distal portion of the cytoplasm of smooth-ended and ruffle-ended ameloblast. These results suggest that OD314 may play important roles in the ameloblast differentiation and maturation.
Ameloblasts* ; Amelogenesis ; Cytoplasm ; Dental Enamel ; Immunohistochemistry ; Odontoblasts ; RNA, Messenger ; Tooth

The effects of chitosan upon the experimentally induced differentiation of MDPC-23 cells, derived from mouse dental papilla cells, were investigated by RT-PCR, observations of cell morphology and Alizaline red-S staining. Chitosan was found to significantly increase and accelerate the expression of ALP mRNA but decrease the ColI transcript levels, as compared with the control, in a time-dependent manner during the differentiation of MDPC-23 cells. Chitosan also significantly downregulated ON mRNA expression and accelerated mineralization in differentiating MDPC-23 cells. These results suggest that chitosan facilitates odontoblast differentiation and mineralization and may have potential clinical applications as a dentin regeneration material.
Animals ; Chitosan ; Dental Papilla ; Dentin ; Mice ; Odontoblasts ; Regeneration ; RNA, Messenger

OBJECTIVEStudies have showed that L type calcium channel plays an important role in dentin calcification and affects tooth development and tooth reparation after injury. The objective of this article is to study the effects of nimodipine, blocking agent of L type calcium channel, on human dentinogenesis using human tooth slice organ culture in vitro.

METHODSYoung healthy human premolars were collected, and cut into 2 mm-thick transverse slices by low speed diamond saw. Agarose beads dipped in nimodipine solution and PBS weresy minetrically placed on tooth slices, and the slices were then embedded in a semisolid agarose-based medium and cultured with organ culture method for 1 week. Fluorescent band of tetracycline, Von-Kossa staining, immunohistochemical staining of the slices and transmission electron microscopy (TEM) of odontoblasts were observed to evaluate dentinogenesis changes of the slices.

RESULTSTooth slices were successfully cultured in vitro for 1 week and the odontoblasts could maintain their original morphology. After treatment with nimodipine, the fluorescent band of tetracycline was narrow and weak, and globular calcification in predentine was decreased compared with the control. TEM showed that secretory vesicles in odontoblast were somewhat increased, hut iminunohistochemical staining for collagen I showed no difference between the two groups.

CONCLUSIONNimodipine can influence the calcification of dentine, but has no obvious influence on the synthesis and secretion of dentine matrix. The results show that L type calcium channel is important in dentin calcification.

The ultimate goal of a regenerative pulp treatment strategy is to reconstitute normal tissue continuum at the pulp-dentin border, regulating tissue-specific processes of reparative dentinogenesis. However, little is known about the molecular mechanism of reparative dentinogenesis. The purpose of this study was to investigate the pulpal response after direct pulp capping and pulpotomy with mineral trioxide aggregate (MTA) by histological and immunohistochemical studies. There was continuous reparative dentin bridge formation at 2 weeks after treatment with MTA in both the pulp capping and the pulpotomy groups. The cells in the pulp capping group showed typical odontoblast characteristics, while the cells of reparative dentin in pulpotomy group were round in shape, lost their polarity, organized as a sheet of cells, and trapped in osteodentin-like mineralized tissue. In pulp capping group, upper layer of the reparative dentin showed cell lacunae indicating osteoblastic characteristics, whereas lower layer of the reparative dentin contained predentin and dentinal tubule-like structures as normal dentin. However, there was osteodentin formation in pulpotomy group. DSP protein was expressed at 4 weeks in odontoblasts of pulp capping group, while BSP was expressed at 4 weeks after pulpotomy. These results suggest that two different types of reparative dentin formation, dentin-like and bone-like dentin, may depend on the type and extent of the injury and the effect of the associated defense reaction on the structural and functional integrity at the dentin-pulp border.
Dental Pulp Capping* ; Dentin* ; Dentinogenesis ; Odontoblasts ; Osteoblasts ; Pulpotomy* ; Pemetrexed

Nuclear factor I-C (NFI-C) plays a pivotal role in various cellular processes such as odontoblast and osteoblast differentiation. Nfic-deficient mice showed abnormal tooth and bone formation. The transplantation of Nfic-expressing mouse bone marrow stromal cells rescued the impaired bone formation in Nfic(-/-) mice. Studies suggest that NFI-C regulate osteogenesis and dentinogenesis in concert with several factors including transforming growth factor-β1, Krüppel-like factor 4, and β-catenin. This review will focus on the function of NFI-C during tooth and bone formation and on the relevant pathways that involve NFI-C.
Animals ; Bone Development* ; Dentinogenesis ; Mesenchymal Stromal Cells ; Mice ; NFI Transcription Factors* ; Odontoblasts ; Osteoblasts ; Osteogenesis ; Osteoporosis ; Tooth*

Theoretically, if the odontoblastic layer on the pulpal surface of the dentin is removed, it is impossible to find nucleus after the teeth has undergone endodontic therapy. So dentin does not contain genomic DNA. But it is in existence the possibility that blood permeates into the dentin by endodontic therapy and trauma. Therefore DNA in blood can be detected from the dentin layer. The purpose of this investigation is to evaluate the possibility of individual identification after detection of DNA in the dentin of endodontic created teeth. The authors isolated the human DNA from 40 endodontic treated teeth, performed AmpFLPs by PCR and electrophoresed for detection of STR loci F13A01, LPL gene and X-Y homologous amelogenin gene. The following results were obtained: 1) DNA extraction was possible in 19 endodontic treated teeth out of 40. 2) Sex determination was possible in 12 endodontic treated teeth out of 40 by detection of X-Y homologous amelogenin gene 3) F13A01 locus was detected in 6 endodontic treated teeth out of 40, observed 4 alleles(3.2, 4, 5, 6) and 5 genotypes(3.2-3.2, 3.2-4, 3.2-5, 4-5, 6-6). 4) LPL locus was detected in 7 endodontic treated teeth out of 40, observed 3 alleles(10, 11, 12) and 3 genotypes(10-10, 10-12, 11-12). From the above results DNA extraction, sex determination, amplification of STR locus F13A01, and LPL gene were possible in the endodontic treated teeth and it was suggested that endodontic treated teeth were useful and applicatable as molecular biological samples for individual identification.
Amelogenin* ; Dentin* ; DNA ; Humans ; Odontoblasts ; Polymerase Chain Reaction ; Tooth ; Tooth, Nonvital*

Dentin is the major part of tooth and formed by odontoblasts. Under the influence of the inner enamel epithelium, odontoblasts differentiate from ectomesenchymal cells of the dental papilla and secrete pre-dentin which then undergo mineralization into dentin. Transforming growth factor-beta (TGF-β)/bone morphogenetic protein (BMP) signaling is essential for dentinogenesis; however, the precise molecular mechanisms remain unclear. To understand the role of TGF-β/BMP signaling in odontoblast differentiation and dentin formation, we generated mice with conditional ablation of Smad4, a key intracellular mediator of TGF-β/BMP signaling, using Osr2 or OC-Cre mice. Here we found the molars of Osr2(Cre)Smad4 mutant mice exhibited impaired odontoblast differentiation, and normal dentin was replaced by ectopic bone-like structure. In Osr2(Cre)Smad4 mutant mice, cell polarity of odontoblast was lost, and the thickness of crown dentin was decreased in later stage compared to wild type. Moreover, the root dentin was also impaired and showed ectopic bone-like structure similar to Osr2(Cre)Smad4 mutant mice. Taken together, our results suggest that Smad4-dependent TGF-β/BMP signaling plays a critical role in odontoblast differentiation and dentin formation during tooth development.
Animals ; Cell Polarity ; Crowns ; Dental Enamel ; Dental Papilla ; Dentin* ; Dentinogenesis ; Epithelium ; Mice ; Miners ; Molar ; Odontoblasts* ; Tooth