Role of Sphingosine-1-Phosphate in Human Dental Pulp Cells to Form Hard Tissue

Preservation of the dental pulp depends on the stimulation of hard tissue formation within the pulp itself. The presence of sphingosine-1-phosphate (S1P) in vivo has attracted considerable attention. S1P reportedly promotes osteoblast differentiation, and is believed to be involved in hard tissue formation. In the present study, we assessed the ability of S1P to induce hard tissue formation in cultured human dental pulp cells (hDPCs). hDPCs were cultured from aseptically extracted pulp tissue obtained from the first premolar of 20s-year-old patients that required orthodontic treatment. The effect of S1P on hard tissue formation was observed by measuring alkaline phosphatase (ALP) activity and performing alizarin red staining. Additionally, BMP-2 mRNA, and BMP-2 and DSPP protein expression levels were examined to confirm hard tissue formation. We also investigated the expression of the S1P receptor mRNA in without stimulation by S1P and changes in intracellular calcium ion concentration ([Ca]i) dynamics in S1P-stimulated hDPCs. Stimulation of cultured hDPCs with S1P increased ALP activity and enhanced alizarin red staining. Additionally, S1P elevated BMP-2 mRNA expression, BMP-2 and DSPP protein levels. Moreover, mRNA expressions of S1P receptors 1-3 were also observed in cultured hDPCs. S1P enhanced hard tissue formation and the expressions of markers of hard tissue formation including BMP-2 and DSPP incltured hDPCs. Moreover, S1P induces an increase in [Ca]i levels by facilitating the release of Ca from the endoplasmic reticulum via S1P receptor 1-3.