Objectives: The purpose of this study was therefore to assess the effects of the combination of G, V and BPA on tooth enamel.
Methods: Rats were exposed daily in utero and after birth to low doses of EDs mimicking human exposure during the critical fetal and suckling periods when amelogenesis takes place. Enamel was carefully observed and defects were scored according to their importance. Ameloblasts were microdissected and enamel gene expression was analyzed by RT-QPCR. In parallel, rat HAT-7 ameloblastic cells were treated by the three EDs separately or in combination. KLK4 and enamelin, two enamel key genes impacted by EDs in vivo, were investigated for their transcription modulations.
Results: The proportion of rats presenting opaque areas of enamel hypomineralization was 75% when rats were treated with BPA alone, whereas only 37,5% of rats were affected when treated with a combination of EDs. The levels of mRNAs encoding the main enamel proteins varied with BPA treatment alone and did not differ significantly between controls and combined treatment groups. In vitro, BPA induced enamelin and reduced klk4 expression and transcriptional activity, whereas G had no such effects and V reduced enamelin expression.
Conclusion: These findings suggest that combinations of EDs may affect enamel less severely than one ED alone, and indicate that enamel hypomineralization may differ according to the characteristics of the ED exposure.