Osteopontin Facilitated Dental Pulp Cell Adhesion and Differentiation: A Laboratory Investigation

Aim: To investigate the effects of osteopontin (OPN) on cultured human dental pulp cells (hDPCs) in relation to adhesion, proliferation, differentiation, and mineralization. Methodology: Subcultured hDPCs isolated from healthy human wisdom teeth were inoculated on noncoated (NC, control) and OPN-coated nontissue culture-treated polystyrene plates (Non-TCPS). Cell adhesion and proliferation were analyzed by crystal violet staining and the CCK-8 assay, respectively. Expressions of cell adhesion-related protein markers such as FAK and Akt were visualized by the Western blot. Expressions of tooth-related mRNA markers were evaluated by qRT-PCR. The localization of the OPN protein in reparative dentine formation was visualized using immunofluorescence staining. Data were analyzed using the Tukey's multiple comparison test. Results: Cell adhesion was significantly higher in OPN 1 mu g/mL-coated group of the OPN, which is also comparable to that of the positive control (COL-1 group). Cell proliferation data showed a similar tendency. pFAK was activated as early as 3 h after cell inoculation in the 1 mu g/mL-coated group of the OPN and COL-1 group. Moreover, the OPN stimulated hDPC mineralization in a time- and dose-dependent manner. Regarding the qPCR results, it was shown that OPN stimulated DMP-1 and DSPP expression on days 10 and 14. The RNA sequencing data implicated that the OPN promoted the gene expression of HLA-DRA, CD74, ENSG00000283390, MRPL53, NOP2, and KRTAP1-3. Finally, pulp exposure wound healing in SD rats showed that OPN expression was primarily localized in the forming reparative dentine instead of formed reparative dentine. Conclusion: Coated OPN promoted hDPC adhesion, proliferation, differentiation, and mineralization.