Introduction: Dentin sialoprotein (DSP) and phosphophoryn (PP) are two major dentin specific proteins. These proteins are believed to play a role in dentin mineralization and are known to be derived from a single DSP-PP transcript that belongs to the family of acidic proteins termed SIBLING proteins. Rat DSP, a 53 kDa glycoprotein containing 29.6% carbohydrates, comprises 5-8% of dentin noncollagenous proteins (NCPs). DSP protein is predominantly expressed by odontoblasts and linked to dentin mineralization. Phosphophoryn, the most abundant NCP (>50%) in dentin, is secreted by odontoblasts through odontoblast processes and appears at the mineralization front. Transient DSP-PP expression in preameloblasts and substantial expression in odontoblasts implicated DSP or PP proteins, secreted by preameloblasts, may affect mesenchymal cell differentiation and maturation. Methods: We first asked whether DSP/PP proteins could affect rat dental pulp cell (MRPC-1) differentiation and maturation. We then tested whether highly phosphorylated protein (HP) or recombinant DSP/PP could serve as biomimetic materials during reparative dentin formation in a ferret tooth cavity model. Results: Recombinant DSP/PP protein mixtures up-regulated DSP-PP mRNA expression in rat dental pulp MRPC-1 cells. Recombinant DSP/PP proteins induced DSP-PP mRNA expression in a dose-dependent manner. Native HP was found to promote reparative dentin formation in ferret.Recombinant DSP/PP also promoted reparative dentin formation in ferret. Conclusions: DSP/PP proteins may participate in regulating odontoblast differentiation and maturation. Since native HP and recombinant DSP/PP promoted reparative dentin formation, they may also have the potential to serve as a capping agent in clinical applications. This work is supported by NIH DE11442-8 to HHR.

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