Maternal exposure to silicon dioxide nanoparticles reduces hippocampal neurogenesis and synaptogenesis and induces neurodegeneration in rat offspring hippocampus

Silicon dioxide nanoparticles (SiO2-NPs) are among the most widely used nanoparticles because of their chemical-physical properties. Since most brain maturation occurs in the neonatal period in humans and many mammals, it is important to understand how NPs may affect this process. This study tested the hypothesis that SiO2-NPs from treated dams could affect the hippocampus of neonatal rats during lactation. Twenty-four pregnant rats, after delivery, were divided into three groups of control, SiO2-NPs (25 mg/kg) and SiO2-NPs (100 mg/kg). The rats were treated from 2nd to 21st days post-delivery by gavage and the effects of these NPs were evaluated in the offspring's hippocampi to reveal the effects of maternal exposure to SiO2-NPs during lactation on the offspring's hippocampi. The offspring in the SiO2-NPs groups had higher malondialdehyde concentration and lower antioxidant activity in the hippocampi than the non-treated control group. The mean number of doublecortin positive (DCX+) cells and synaptophysin expression in the hippocampi of the SiO2-NPs groups were significantly lower than the control group, whereas the mean number of dark neurons was significantly higher. Also, animals in the SiO2-NPs groups had a weak cognitive performance in adulthood. In conclusion, maternal exposure to SiO2-NPs via breastfeeding could affect offspring's hippocampal neurogenesis and synaptogenesis, leading to impaired cognitive performance.