Fractalkine’s dual role in inflammation and hard tissue formation in cultured human dental pulp cells

This study aimed to explore the potential roles of fractalkine/CX3CR1, primarily expressed in vascular endothelial cells and has recently been identified in dental pulp cells at sites of pulp tissue inflammation, not only in inflammation but also in pulp hard tissue formation. To this end, cultured human dental pulp cells were grown in 10% FBS-supplemented α-MEM. Fractalkine was introduced to the culture, and COX-2 and dentin sialophosphoprotein (DSPP) expression levels were evaluated via western blotting. Real-time PCR was used to examine BMP-2 and Osterix mRNA expression. Calcified nodule formation was evaluated with Alizarin red staining. Results revealed that fractalkine increased COX-2 protein expression, calcified nodule formation, and BMP-2 and Osterix mRNA expression in a concentration- and time-dependent manner. DSPP protein expression also increased upon fractalkine addition. This effect of fractalkine on expression of DSPP protein was inhibited in the presence of the CX3CR1 inhibiter ADZ8797. In conclusion, our findings suggest a dual role for fractalkine in promoting pulp inflammation via COX-2 production and contributing to pulp hard tissue formation by stimulating the expression of hard tissue formation markers.