Synaptic vesicle protein 2b is expressed temporospatially in (pre)odontoblasts in developing molars.

The formation of dentin and enamel is initiated by the differentiation of odontogenic precursor cells into odontoblasts and ameloblasts, respectively. This study was performed to identify new molecules involved in the differentiation of odontogenic cells. The genes expressed differentially between the root stage (after the differentiation of odontogenic cells and dental hard-tissue formation) and the cap stage (before the differentiation of odontogenic cells and dental hard-tissue formation) were searched using differential display PCR. For the first time, synaptic vesicle protein (SV) 2b, an important transmembrane transporter of Ca(2+) -stimulated vesicle exocytosis, was identified as a differentially expressed molecule. Real-time PCR and western blotting revealed an increase in the transcriptional and translational levels of SV2b during or after the differentiation of odontogenic cells. Immunofluorescence revealed this molecule to be localized in not only fully differentiated odontoblasts but also in pre-odontoblasts before dentin matrix secretion. The expression pattern of the SV2a isoform was similar to that of the SV2b isoform, whereas the SV2c isoform showed a contrasting pattern of expression. After treatment with alendronate, an inhibitor of protein isoprenylation for the transport of secretory vesicles, the expression of SV2a and SV2b decreased, whereas that of SV2c increased. These results suggest that the SV2 isoforms are functional molecules of (pre)odontoblasts which may be involved in vesicle transport.

Relaxin is up-regulated in the rat ovary by orthodontic tooth movement.

Relaxin (Rln) is an ovarian hormone that stimulates osteoclastic and osteoblastic activities and connective tissue turnover. To investigate the expression of Rln during orthodontic tooth movement, rats were implanted with orthodontic appliances that connected a spring from the upper incisors to the first molar with a 70 cN force. Rats in each group were killed 6, 48, and 144 h after activating the appliance, and the levels of Rln1 and Rln3 expression in the ovary were determined by real-time RT-PCR, northern blots, western blots, and immunofluorescence analyses. The amount of tooth movement induced by the orthodontic force increased in a time-dependent manner. The levels of Rln1 mRNA increased by 12-, 41-, and 263-fold at 6, 48, and 144 h, respectively, after orthodontic tooth movement. The time-dependent increase in the concentration of Rln 1 protein in the ovary was also confirmed by western blotting. Rln 1 was localized in the granulosa cells of the ovarian follicles, and the immunoreactivity against Rln 1 was increased by the movement. In contrast, the concentration of Rln 3 was below the level of detection. The results of this study suggest that local changes in periodontal tissues induced by orthodontic tooth movement may affect Rln1 expression in the ovary. However, further studies are needed to decipher the mechanisms involved and the possible contribution of the increased level of expression of Rln 1 to the tooth movement.

Differential expression of cyclophilin A and EMMPRIN in developing molars of rats.

A complex and intricate cascade of gene expression is essential for late stage tooth development. This study was performed to detect molecules involved in dental hard tissue formation and tooth eruption by comparing gene expression in cap stage molar germs (before eruptive movement and dental hard tissue formation) with that in root formation stage molar germs (after eruptive movement and dental hard tissue formation). DD-PCR revealed that cyclophilin A (Cyp-A), a potent chemoattractant for monocytes as well as a ligand for extracellular matrix metalloproteinase inducer (EMMPRIN) was expressed differentially in the two stages molar germs. The levels of Cyp-A and EMMPRIN mRNA were significantly higher at the root formation stage than at the cap and crown stages of the molar germs. Immunofluorescence showed that Cyp-A and EMMPRIN were expressed strongly in the follicular cells overlaying the occlusal region of the molar germs at the root formation stage. In contrast, their immunoreactivity was weak in the follicular tissues and was not region-specific in molar germs at the cap stage. In addition, the MCP-1 and CSF-1 mRNA levels increased in parallel to that of Cyp-A mRNA and the increased number of osteoclasts at the occlusal region. Immunoreactivity against Cyp-A and EMMPRIN was also observed in the fully differentiated ameloblasts and odontoblasts. This study suggests that Cyp-A and EMMPRIN play roles in the maturation of dental hard tissue and the formation of an eruption pathway.

Improvement of the properties of mineral trioxide aggregate by mixing with hydration accelerators.

INTRODUCTION: Mineral trioxide aggregate (MTA) is used widely in endodontic therapy. This study examined the setting time, compressive strength, and pH of MTA mixed with several hydration accelerators (calcium chloride, low-dose citric acid, calcium lactate gluconate solution). METHODS: Group 1 (control) was obtained by mixing MTA with distilled water. In group 2, MTA containing 10% calcium chloride was mixed with distilled water. In group 3, MTA was mixed with 0.1% citric acid. In group 4, MTA was mixed with a calcium lactate gluconate solution. The setting time, compressive strength, and pH were examined. RESULTS: The setting time of MTA mixed with hydration accelerators was significantly shorter than that of MTA mixed with water (P < .01). In particular, replacing distilled water with a calcium lactate gluconate solution provided a significant decrease in setting time. The compressive strengths of MTA mixed with hydration accelerators were significantly lower than that of MTA mixed with water (P < .01), but those values increased with time. The pH of MTA mixed with hydration accelerators was significantly lower than that of MTA mixed with water (P < .01) but stable at a high level (pH 11-12). CONCLUSIONS: Hydration accelerators improved the setting time of MTA. Nevertheless, more study will be needed to improve MTA without impairing its preexisting advantages.