Role of Maternal Dietary Antioxidant Supplementation in Murine Placental and Fetal Limb Development

Methylnitrosourea (MNU) is a multisystem teratogen that damages proliferating cells through macromolecule alkylation and generation of reactive oxygen species (ROS). Murine dams exposed to MNU midgestation produce offspring with distal limb malformations, an outcome reduced by maternal immune stimulation. Immunostimulatory effects of antioxidant therapy may in part explain this improved birth outcome. The present study hypothesizes that placental, rather than fetal, damage from excessive ROS may contribute to MNU-induced embryopathy. Fetal limbs and placentas were examined in immunotolerant CD-1 and immunosensitive C57BL/6N mice exposed to MNU, dietary antioxidant butylated hydroxytoluene (BHT), or both. MNU increased fetal resorptions and incidence of syndactyly, oligodactyly, polydactyly, and interdigital webbing, and decreased fetal size in both mouse strains. BHT reduced syndactyly and oligodactyly in both strains, and reduced polydactyly in C57BL/6N mice. Increased webbing in MNU and MNU + BHT groups likely represented maturational delay. Placentas from CD-1 and C57BL/6N MNU-exposed dams demonstrated decreased trophoblasts and increased necrosis of endothelium. Similar to distal limb defects, placental damage was reduced in mice receiving MNU + BHT. These results suggest that placental damage and fetal defects caused by MNU are in part ROS-mediated, and reduced distal limb defects following MNU + BHT may be related to improved placental integrity and function.