Leptin promotes dentin sialophosphoprotein expression in human dental pulp

Introduction: Leptin, an inflammation-related adipokine, and its receptor (LEPR) are expressed in human dental pulp. Dentin sialophosphoprotein (DSPP) is involved in dentinogenesis and the dental pulp reparative response. The cell type expressing LEPR in dental human pulp and the resultant effect of the binding of leptin to LEPR remain unknown. This study describes the immmunohistochemical localization of LEPR and the effect of leptin on DSPP expression in human dental pulp.

Methods: Twenty-five dental pulp specimens were obtained from freshly extracted caries-free and restoration-free human third molars. LEPR localization was examined by immunohistochemistry using the antihuman LEPR monoclonal antibody. The effect of leptin on DSPP expression was determined by immunoblot analysis and quantitative real-time polymerase chain reaction.

Results: Immunoreactivity for LEPR concentrated in the odontoblast layer but was not evident in the central zone of the dental pulp. Leptin dose dependently stimulated DSPP expression. Western blot analysis revealed the presence of a protein with an apparent molecular weight of ∼00 kDa, the estimated molecular weight of DSPP. The expression of DSPP messenger RNA was confirmed by quantitative real-time polymerase chain reaction, and the size of the amplified fragments (298 bp) was confirmed by agarose gel electrophoresis.

Conclusions: The present study shows that human dental pulp is immunoreactive for LEPR, with the immunoreactivity concentrated in the odontoblast layer, and that leptin stimulates, in a dose-dependent manner, DSPP protein and messenger RNA (mRNA) expression in human dental pulp. These findings further support the functional role of leptin in the dentin mineralization process and/or in dental pulp reparative and immune responses.