LAPTM5 is transactivated by RUNX2 and involved in RANKL trafficking in osteoblastic cells.

The present study aimed to investigate the role of lysosomal­associated transmembrane protein 5 (LAPTM5) in osteoclast differentiation induced by osteoblasts. The results demonstrated that the expression levels of LAPTM5 were downregulated following runt­related transcription factor 2 (RUNX2) silencing and upregulated following RUNX2 overexpression in ST2 cells. Chromatin immunoprecipitation analysis identified the binding of RUNX2 to the LAPTM5 promoter at the ­1176 to ­1171 position. Dual­luciferase reporter assays confirmed that RUNX2 directly activated the LAPTM5 gene. The concentration of receptor activator of nuclear factor­κB ligand (RANKL) protein in the cytoplasm and in the media was significantly increased following LAPTM5 knockdown. LAPTM5 silencing in ST2 cells enhanced osteoclastic differentiation of co­cultured RAW264.7 cells. The present study indicated that expression of LAPTM5 was regulated by the interaction of RUNX2 with its promoter region and that LAPTM5 was involved in the trafficking of RANKL. These findings suggested a possible coupling mechanism between osteogenesis and osteoclastogenesis in which RUNX2 may be involved in osteoclast differentiation through the regulation of the lysosome­associated genes that modulate RANKL expression.

[Research on anatomy of posterior tooth in the Beagle dog and mini-screw implant implantation].

OBJECTIVE: The morphological characteristics of posterior tooth in the Beagle dog were investigated in order to provide reference to mini-screw implant (MSI) implantation in the root furcation site. METHODS: Seventy posterior teeth of five Beagle dogs were collected and measured as follows: First, the greatest mesio-distal diameter AB of the crown was measured, which was perpendicular to the tooth long axis. Second, mesial cusp of maxillary posterior tooth or central cusp of mandibular was marked as the piont C, and CD which was equal and perpendicular to AB was drawn. The piont D was planned to be the reference point for MSI implantation. Finally, Dm, Dd and Df were measured, which were the distance from the point D to the mesial and distal root surface and root furcation. RESULTS: The difference between the left and right sides teeth with the same name had no statistical significant (P > 0.05). The measurement results of all indices assumed a Gaussian distribution. The mean Dd was basically equal to Dm. All the average Df were more than 4 mm. CONCLUSION: The point D could be used as a reference point for MSI implantation in the root furcation site of posterior tooth in the Beagle dog. The data of this study can provide certain reference for MSI implantation in the study of the biomechanics of anchorage stability, and provide certain reference for MSI implantation in the study of root repair after injury.