RESUMEN
<p><b>OBJECTIVE</b>To examine the expression of LIM mineralization protein-1 (LMP-1) in the apical papilla and dental pulp tissues of human immature permanent teeth and to investigate the role of LMP-1 in the development and maturation of pulp-dentin complex.</p><p><b>METHODS</b>Forty-eight healthy premolars in need of extraction for orthodontic treatment were obtained with 24 immature permanent teeth and 24 mature permanent teeth. After extraction, the apical papilla was detached from the dental pulp in the immature permanent tooth and the dental pulp of mature permanent tooth was rapidly removed. The samples were divided into 3 groups: group 1, apical papilla of immature permanent teeth (root formed 2/3 of its full length); group 2, dental pulp tissues of immature permanent teeth; group 3, dental pulp tissues of mature permanent teeth. There were 24 samples for each group.Half of them were used for reverse transcriptien-PCR (RT-PCR) detection, and the other half were used for Western blotting detection. Band intensities were quantified using Meta Morph software 6.2.6 and subsequently normalized by dividing the band gray value of the target gene by the intensity of its corresponding β-actin. Two-sample t test was used to analyze the difference of expression intensity between group 1 and group 2 as well as group 2 and group 3 with SPSS 13.0 software package.Statistical significance was established as P < 0.05.</p><p><b>RESULTS</b>As indicated by RT-PCR, LMP-1 expressed in the apical papilla, dental pulp of immature permanent teeth and the dental pulp of mature permanent teeth were 0.25 ± 0.09, 0.46 ± 0.24 and 0.31 ± 0.10 respectively. The expression intensity of LMP-1 mRNA in the dental pulp tissues of human immature permanent teeth were significantly higher than that in the apical papilla tissues(t = 2.92) and that in the dental pulp tissues of human mature permanent teeth (t = 2.31) (P < 0.05). As indicated by Western blotting, LMP-1 expressed in the three groups were 0.33 ± 0.08, 0.82 ± 0.10 and 0.52 ± 0.19 respectively. The expression intensity of LMP-1 protein in the dental pulp tissues of human immature permanent teeth were significantly higher than that in the apical papilla tissues(t = 3.33) and that in the dental pulp tissues of human mature permanent teeth (t = 3.11) (P < 0.05).</p><p><b>CONCLUSIONS</b>LMP-1 were positively expressed in all the samples including apical papilla of immature permanent teeth, dental pulp of immature and mature permanent teeth at the level of both mRNA and protein, but with different intensity. LMP-1 could play an important role in the development and maturation of pulp-dentin complex.</p>