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 μg/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
μg/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.