Maternal exposure to 17-alpha-ethinylestradiol alters embryonic development of GnRH-1 neurons in mouse

To evaluate the potentially disrupting effects of environmental estrogens on neuroendocrine networks controlling reproduction, we studied the impact of the pharmaceutical product 17-α-ethinylestradiol (EE2) on gonadotropin-releasing hormone (GnRH-1) neuron development in mouse embryo. Pregnant mice were treated per os with EE2 at 0.01, 0.1 or 1 μg/kg/day, between embryonic days 10.5 (E10.5) and E13.5, a period during which GnRH-1 neurons are generated and start their intra-nasal migration. Embryos at E13.5 were examined and processed for GnRH-1 immunohistochemistry. Immunopositive neurons were counted all along their migratory path. A short oral administration of environmentally relevant doses of EE2 to pregnant mice had a significant impact on whole embryo development, leading to a limited but significant growth retardation. The total number of GnRH-1 neurons was statistically significantly increased in a dose-dependent manner. The repartition of GnRH-1 neurons along their migratory path was not affected by EE2 treatment. These results suggest an impact of environmental EE2 concentrations on embryonic GnRH-1 development through a modulation of neurogenesis and/or apoptosis.

► Environmental levels of 17-alpha-ethinylestradiol increase developing GnRH-1 neurons.
► Maternal exposure to 17-alpha-ethinylestradiol alters embryo neuroendocrine networks.
► Maternal exposure to low levels 17-alpha-ethinylestradiol and embryo GnRH-1 neurons.