SHP is Involved in BMP2-induced Odontoblast Differentiation

Abstract

Small Heterodimer Partner (SHP) interacts with diversetranscription factors such as Runx2 and regulates manycellular events including differentiation, proliferation,and energy metabolism. SHP is reported to be a positiveregulator of BMP2-induced bone formation. This studyaimed to clarify the role of SHP in odontoblast differentiationand matrix mineralization. Rat tooth germs wereisolated, and gene expression was determined byRT-PCR and real-time PCR. Localization of SHP proteinexpression was identified by immunofluorescent analysis.Primary human dental pulp cells (HDPCs) werecultured with BMP2 and/or Ad-siSHP. Matrix mineralizationwas evaluated by Alizarin red staining. Transienttransfection experiment was performed with the SHP orDlx5 expressional plasmids and the DSPP gene. In toothgerms from post-natal days 3 to 9, BMP-2 and SHPexpression increased with DSPP and DMP1 mRNAexpression. In an immunostaining study, SHP wasexpressed in odontoblasts and surrounding osteoblasts.When HDPCs were cultured with BMP2 in mineralization-inducing medium, SHP expression also increasedwith an increase in DSPP expression. Down-regulationof SHP by Ad-siSHP inhibited matrix mineralization. Intransient transfection experiments, overexpression ofSHP was shown to enhance DSPP promoter activitythrough interactions between SHP and Dlx5. Theseresults suggest that SHP may mediate BMP2 signaling topromote mineralization of the dentin matrix.