Hippocampal Morphological Alterations and Oxidative Stress in Autism Spectrum Disorder Model Induced by Prenatal Exposure to Valproic Acid in Male and Female Mice

Abstract

Valproic acid (VPA), a first-line antiepileptic and mood-stabilizing drug, has been linked to congenital malformations, cognitive disabilities, and an elevated risk of autism spectrum disorder (ASD) when used during pregnancy. ASD is a lifelong developmental disorder characterized by impaired social interaction, repetitive behaviors, and cognitive deficits, with a higher prevalence in males. Growing evidence highlights that hippocampal circuits, particularly CA1 and dentate gyrus (DG) subregions, are crucial for cognitive and social functions often impaired in ASD. Notably, VPA exposure at embryonic day 12.5 (E12.5) coincides with critical neurodevelopmental processes in the hippocampus, making it highly susceptible to oxidative damage and structural disruptions. Using a mouse model of ASD induced by a single prenatal VPA injection (400 mg/kg) at E12.5, this study assessed morphological and oxidative changes in the hippocampus. Male and female offspring were evaluated for core behavioral and cognitive alterations of ASD. After the behavioral tests, their brains were processed for Golgi-Cox staining and antioxidant enzyme dosage. The results showed that prenatal exposure to VPA indeed induces ASD-like behaviors, including reduced sociability, increased repetitive behaviors, and impaired working memory. Sholl analysis showed increased dendritic branching in granule and CA1 pyramidal neurons of VPA male mice, while VPA female mice exhibited hypoarborization in dentate gyrus granule cells. Both male and female VPA mice displayed higher dendritic spine density. Concurrently, oxidative stress was increased in the hippocampi of the VPA mice, as evidenced by alterations in oxidative stress biomarkers. Our work underscores gender differences in the effects of prenatal VPA exposure and points to a possible role for hippocampal neuron morphology and oxidative stress in the pathophysiology of ASD.