Historical data in the 1950s suggests that 7%, 11%, 33%, and 87% of couples were infertile by ages 30, 35, 40 and 45, respectively. Up to 22.3% of infertile couples have unexplained infertility. Oxidative stress is associated with male and female infertility. However, there is insufficient evidence relating to the influence of oxidative stress on the maintenance of a viable pregnancy, including pregnancy complications and fetal development. Recently, we have established Tet-mev-1 conditional transgenic mice, which can express the doxycycline-induced mutant SDHC(V69E) transgene and experience mitochondrial respiratory chain dysfunction leading to intracellular oxidative stress. In this report, we demonstrate that this kind of abnormal mitochondrial respiratory chain-induced chronic oxidative stress affects fertility, pregnancy and delivery rates as well as causes recurrent abortions, occasionally resulting in maternal death. Despite this, spermatogenesis and early embryogenesis are completely normal, indicating the mutation's effects to be rather subtle. Female Tet-mev-1 mice exhibit thrombocytosis and splenomegaly in both non-pregnant and pregnant mice as well as placental angiodysplasia with reduced Flt-1 protein leading to hypoxic conditions, which could contribute to placental inflammation and fetal abnormal angiogenesis. Collectively these data strongly suggest that chronic oxidative stress caused by mitochondrial mutations provokes spontaneous abortions and recurrent miscarriage resulting in age-related female infertility.
Keywords: Abortion; Infertility; Mitochondria; NGF, non-growing follicles; Oxidative stress; PLGF, placenta growth factor; ROS, reactive oxygen species; SDH, succinate dehydrogenase; SDHC; SDHC, succinate dehydrogenase C subunit; TUNEL, terminal deoxynucleotidyl transferase dUTP nick end labeling; VEGF, vascular endothelial growth factors; VEGFR-1, VEGF receptor-1.