Inorganic Phosphate Effect of on Human Dental Pulp Cell Cultures

Abstract

This study was designed to investigate the effect of inorganic phosphate (Pi) at different concentrations on odontogenesis of the normal human dental pulp cells (hDPCs). Normal human dental pulp cells derived from extracted pristine teeth were cultured in growth medium with supplements of inorganic phosphate (Pi) in 0 ppm, 2 ppm, 4 ppm, 5 ppm and 8 ppm, for the time intervals of 16 hours, 7, 14, and 21 days. Cell proliferation rates were measured by the optical density of crystal violet dye stained cells. ALP activity was measured by fluorometric assay. Expression of Dentin Sialoprotein (DSP) was measured by ELISA. The data were presented as the mean of triplicates. Statistical analysis was conducted using JMP Pro 12 (ver. 12.1.0) in one-way ANOVA and Tukey HSD post-hoc tests. Cell attachment efficiency was reduced significantly by additional Pi of 2, 4 and 5 ppm (P<0.05). At 21 days, cultures with 2, 4 and 5 ppm supplemental Pi displayed significantly higher cell proliferation rates compared to the control group at day 14 (P<0.05) and at day 21 (P<0.05). At day 7, cultures with 2, 4, 5 and 8 ppm supplemental Pi yield significantly higher levels of ALP activity (P<0.05) compared to the control group. At day 7, cultures with 5 ppm Pi supplement showed significantly higher levels of DSP expression (P<0.05) compared to the control group and the rest of the other groups. Supplemental Pi in concentration of 5 ppm could significantly induce proliferation and odontogenesis of hDPCs. This is the first report to demonstrate Pi-induced odontogenesis, leading to potential development and clinical application of future Pi containing dental pulp capping or root canal filling materials.