Expression Of LIM Mineralization Protein 1 In The Apical Papilla And Dental Pulp Tissues Of Human Immature Permanent Teeth And Mature Permanent Teeth

ObjectiveDental papilla mesenchymal cells differentiate into primary odontoblasts and form primary dentin during tooth development. After tooth eruption, in pathologic conditions that originate from external stimuli such as caries, attrition, and restorative procedures, tertiary dentin including reactionary and reparative dentin is produced by surviving odontoblasts or newly differentiated odontoblast-like cells in the pulp. It shows that pulp tissue has a strong self-defense capability and potential for self-repair. A number of studies have indicated that some biomolecules such as transcription factors, signaling molecules, growth factors and extracellular matrix molecules are able to regulate cell proliferation, differentiation and matrix synthesis in dental pulp tissue. But precise mechanism of dentinogenesis and differentiation of odontoblasts and odontoblast-like cells is still not clear.LIM mineralization protein-1(LMP-1), an intracellular signaling molecule, is a member of the heterogeneous LIM-domain family of proteins. It is widespread existed in a variety of tissues. LMP-1 regulates osteoblasts differentiation and maturation, as well as bone formation. According to recent literature report, LMP-1 was primarily immunohistologically localized in the predentin, the odontoblasts, unmineralized reparative dentin, odontoblast-like cells, the endothelial cells of the blood vessels and pulp fibroblasts in human healthy mature pulp-dentin complex. However, the comparison of LMP-1 expression among immature permanent tooth pulp, apical papilla tissues and mature permanent tooth pulp has not been reported yet. The further study and discussion on this question will help us disclose the mechanisms in the formation of pulp-dentin complex and provide some theoretic basis for the vital pulp conservation treatment.The present study aimed to compare the expression of LMP-1 mRNA and protein in the apical papilla and dental pulp tissues of human immature permanent teeth and mature permanent teeth using the RT-PCR and Western-blot technique and to explore the role of LMP-1 during the development and maturation of pulp-dentin complex, thus provide some theoretic basis for new methods in vital pulp treatment.Materials and MethodsForty-eight healthy caries-free permanent teeth in need of extraction were obtained. The age of the subjects ranged from 11 to 30 years old. All subjects had no systematic disease and didn't take any immune-inhibited drugs or antibiotics within three months. After tooth extraction, the apical papilla was detached with a pair of tweezers, and then the dental pulp was rapidly removed.Based on the teeth root development status, the samples were classified into three groups:apical papilla, dental pulps tissues of human immature and dental pulp tissues of mature permanent teeth. There were 24 samples for each group. Half of them were used for RT-PCR detection, and half of them were used for Western-blot detection.RT-PCR and Western-blot technique were used to examine the expression of LMP-1 at the level of protein and mRNA. ANOVA was used to analyze the relative intensity with SPSS 11.0 software. P-values less than 0.05 were considered statistically significant.ResultsThe expression of LMP-1 at the level of protein and mRNA were detected with different intensity in every group. The expression of LMP-1 in the dental pulp tissues of human immature permanent teeth were significantly higher than that of mature permanent teeth and the apical papilla as well (P<0.05), but no significant difference was found between the apical closed group and the apical papilla group (P>0.05).Conclusions1. Our experiment was the first to detect and compare the expression of LMP-1 at the level of protein and mRNA in the apical papilla and in the dental pulp tissues of human immature permanent teeth and permanent teeth using RT-PCR and Western-blot technique. 2. The expression of LMP-1 mRNA and protein in the dental pulp of immature permanent teeth were significantly higher than that in the apical papilla and the pulp of mature permanent teeth as well.