| Dentin non-collagenous proteins (NCPs) play very important roles in odontoblast induction, differentiation and dentin mineralization. Dentin matrix protein 1 is one important member of the mineralization tissue-specific poteins in dentin matrix. The present, studies in this field mainly focus on its biological structure, physical and chemical characteristics. Up to date, however, little is known about its functions. And few reports about its role during dentinogenesis and dental pulp repair after injury are available. Questions like how the odontoblasts synthesize and secrete DMP1, which genes are involved in this process and whether it is involved in dental pulp repair after injury remain unanswered. Therefore, this study aimed at getting a better understanding on these questions. The main contents and results of the study are presented as follows: 1. Expression of DMP 1 at different developmental stages in human toothgermImmunohistochemical staining was performed on prepared specimens ofdifferent stages of developing human tooth germ. The results showed that the expression of DMP1 was mainly detected in the secreting parts of odontoblast plasm and pre-odontoblasts. DMP1 was expressed weakly in dental papilla andtransiently in secreting ameloblasts when enamel matrix was initially secreted. The expression of DMP1 was detected at different stages of developing human tooth germ. These results suggested that DMP1 could regulate the differentiation of odontoblast and ameloblast cells, and might modulate dentinogenesis.2. Immunohistochemical localization of DMP 1 in carious human permanent teethImmunohistochemical staining was performed on prepared specimens of healthy and carious teeth, and the results were analyzed by Image Analysis System. We found that DMP1 was mainly detected in cytoplasm, the processes of odontoblasts and odontoblast-like cells. DMP1 was weakly expressed in odontoblasts and pre-dentin of superficial caries group. Significantly higher levels of DMP1 were found in odontoblasts or odontoblast-like cell cytoplasm and processes of intermediate and deep caries group, and it was strongly detected in reparative dentin in specimens of the deep caries group. These results indicated that DMP1 was involved in the differentiation and secretion of odontoblast-like cells, as well as in the formation of reparative and reactive dentin.3. Effect of parathyroid hormone (PTH) on the expression of DMP1 in human dental papilla cells in vitroImmunohistochemical staining was performed on human dental papilla cells (HDPC) derived from primary culture on stimulation from different doses of PTH, and difference of the amount of DMP1 expression was determined by the Medical Image Analysis System. The expression of DMP1 was mainly found in HDPC plasm on stimulation from PTH, and the effect of PTH on the expression of DMP1 was related to the concentration of PTH. These results suggested that PTH might be involved in the expression of DMP1 in HDPC in vitro and it might act as one of the mediators in the differentiation of odontoblasts.4. Effect of antisense oligonucleotide against DMP 1 on ALP activity and mineralization ability of odontoblast cell line MDPC-23The ALP activity of MDPC-23 cells was measured at different times after antisense oligonucleotide (AS-ODN), a blocking agent, in different concentrations, was added to the target cells. The mineralized nodules were compared with those in the control group after lOd's effect on the cells with 10mol/L AS-ODN, and the expression of DMP1 in these cells was detected by Western blot at different times. Compared with the control groups, the ALP activity of MDPC-23 cells decreased by AS-ODN in different concentrations, especially in 10mol/L dose. The expression of DMP1 in MDPC-23 cells was only slightly detectable at 12h and became negative after 24h. von Kossa staining demonstrated that the both the number and size of mineralized nodules were smaller than those in the contol group. These results seemed to indicate that antisense oli...
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