Role of apoptosis in prevention of valproic acid‐induced neural tube defects by maternal immune stimulation in CD‐1 mouse embryos

Abstract

Dysregulation of apoptosis during development is a possible mechanism for teratogen‐induced birth defects. Neural tube defects (NTDs) are the second most common birth defects. Non‐specific maternal immune stimulation prevents birth defects. This study investigated the role of altered apoptosis in formation of valproic acid (VA)‐induced NTDs. Interferon‐ γ (IFN γ) was used to stimulate maternal immunity to evaluate the role of altered apoptosis in this protective mechanism. Apoptotic percentages were quantified by flow cytometry and apoptotic regions were identified by Terminal Transferase dUTP Nick End Labeling (TUNEL) assay in gestation day 9 mouse embryonic heads exposed to VA with or without maternal immune stimulation. Increased apoptosis, suggesting involvement in VA teratogenicity, was observed along the neural tube in both normal and abnormal embryos from VA‐exposed dams. Increased apoptosis in normal VA‐exposed embryos suggests that VA may alter other cellular processes such as cell proliferation and differentiation in addition to apoptosis. Apoptotic percentages in embryos with NTDs from IFNγ+VA dams were similar to controls, which indicated resistance to teratogen‐induced apoptosis. In IFNγ+VA‐exposed embryos with NTDs, immune stimulation failed to prevent apoptosis. This suggests immune stimulation protects embryos from teratogenicity of VA by preventing VA‐induced apoptosis.