The Effect Of pH On Cellular Attachment, Proliferation, And Differentiation Of Human Dental Pulp Cells

Abstract

Background: The materials used by dentists vary in their pH levels and come into direct and indirect contact with human dental pulp tissue. Ample studies exploring the effect of different materials on dental pulp tissue suggested that the material’s pH plays a significant role in the outcome. However, the biological effect of pH on dental pulp tissue is still unknown. Moreover, there were no studies evaluating the effect of pH levels on Dental pulp tissue in a direct method. Objective: This study was designed to investigate the effect of different pH levels on the phenotypic behavior of normal human dental pulp cells (hDPCs). Methods: Normal hDPCs were derived from human sound 3rd molars, and cultured in triplicate in growth media with various pH levels: 4.5, 6.5, 8.5, and 9 as the study groups and pH 7.3 as the control. The time intervals were 4, 7, and 10 days. Cell proliferation was measured by crystal violet dye staining. Alkaline phosphatase (ALP) activity was measured by fluorometric assay (ab83371). Expression of Dentin Sialoprotein (DSP) was measured by ELISA (XpressBio). The data were normalized per cell basis. Statistical analysis was done using ANOVA and Tukey multiple comparison post hoc test. Results: Cell attachment was downregulated by increasing or decreasing pH levels (P<0.05). pH 8.5 proliferated faster on day 4 compared with other groups except for the control pH 7.3 (P<0.05). ALP enzymatic activity was upregulated in growth medium pH groups 4.5, 6.5, and 9 when compared to control pH (7.3) on days 7 and 10 (P<0.05). The highest DSP expression was observed in cells grown in media pH 8.5 and pH 9 when compared to control pH 7.3(P<0.05). Conclusion: Acidic and alkaline pH levels can affect hDPCs ALP activity and DSP expression. Acidic and alkaline pH levels can downregulate cellular attachment and proliferation rate, except at pH 8.5 where hDPCs proliferation is substantially upregulated at day 7 compared to other sample groups.