Placental improvement and reduced distal limb defects by maternal interferon-γ injection in methylnitrosourea-exposed mice

BACKGROUND: Methylnitrosourea (MNU), an alkylating agent derived from creatinine metabolism, is cytotoxic, genotoxic, and mutagenic. Midgestational exposure to MNU leads to distal limb defects in mice. Previous studies have shown that nonspecific maternal immune stimulation protects against MNU-induced teratogenesis. A role for immune-mediated placental improvement in this effect remains uncertain. METHODS: The immune system of timed-pregnant C57BL/6N and CD-1 mice was stimulated by GD 7 intraperitoneal (IP) injection with the cytokine interferon-γ (IFN-γ). A teratogenic dose of MNU was then administered by IP injection on the morning of GD 9 to disrupt distal limb formation. Fetal limb length, body length, digital deformities, and placental integrity were evaluated on GD 14. RESULTS: The incidence of syndactyly, polydactyly, and interdigital webbing in MNU-exposed mice was decreased by maternal IFN-γ treatment. In C57BL/6N mice, these defects were reduced by 47, 100, and 63%, respectively, as compared to previous reports on CD-1 mice, by 39, 71, and 20%, respectively. Administration of IFN-γ significantly diminished MNU-induced endothelial and trophoblast placental damage in both strains of mice. CONCLUSIONS: These findings support a possible link between maternal immunity, placental integrity, and fetal distal limb development. Further, these results suggest that IFN-γ might act through placental improvement to indirectly protect against MNU-induced fetal limb malformations.