Study of osteopontin synthesis and the expression during dentinogenesis

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We found that rat clonal dental pulp cells, RDP4-1 and RPC-C2A eclls, produce and secrete osteopontin(OPN). The dental pulp OPN was highly phosphorylated and identified by thrombin susceptibility and immunoprecipitation with rat monoclonal OPN antibody. OPN expression and synthesis were increased by 1,25-dihydroxyvitamin D3(1,25D3). This increase pattern by 1,25D3 was reportedly observed in many osteoblastic cells such as calvaria and bone marrow. Phosphorylated OPN synthesis increased dose-dependently at 10^<-10>-10^<-7> M levels and showed maximum level at 48 h after addition of 12,5D3. Northern hybridization analysis revealed that 1,25D3 greatly increased the level of OPN mRNA in both clonal dental pulp cell lines. This study indicates that these cells can produce OPN and that 1,25D3 stimulate the OPN expression by a mechanism which involves de novo synthesis and transcriptional control.