Oxidative Stress Gene Expression During Human Healthy Dental Pulp Development

Objectives: The aim of this study was to evaluate the gene expression of i-NOS in connection with oxidative stress and the network of antioxidant enzymes (SOD, CAT, GR and GPX) in order to highlight the possible role of Nitric Oxide (NO) in control mechanisms of oxidative stress occurred during tooth development.
Methods: Samples were obtained from human third molars pulp at three different stages: bud stage (average age 13), during apex maturation (average age 18) and from older subjects (average age 57). The measurement of gene expression was performed by Microarray analysis. Obtained data were statistically analyzed using the S.A.M system (Significance Analysis of Microarray) and I.P.A. (Ingenuity Pathways analysis). Finally, RT-PCR analysis was performed in order to validate microarray results.

Results: Expression of i-NOS gene decreased with progressive tissue maturation. I.P.A software identified networks and functional groups of interesting genes belonging to antioxidant enzymes. Among these, SOD, GR and GPX showed a high expression in samples from younger subjects, and only modest activity in adult dental pulp. On the contrary, CAT revealed lower values of activity in the dental pulp at first developmental stages compared to dental pulp from older subjects.

Conclusions: Mechanisms involving oxidative stress are present during the various developmental stages of healthy dental pulp. Moreover, the presence of high values of i-NOS in the samples from younger subjects compared to adult dental pulp could confirm how this enzyme acts as regulator of the apoptosis process during tooth development. The high expression of iNOS during proliferation or differentiation in embryonic tissues may indicate that the production of nitric oxide is induced to maintain a proper cell homeostasis by promoting a physiological tissue growth.