Zinc influences the in vitro development of peri‐implantation mouse embryos

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Abstract
BACKGROUND For humans, it is estimated that over 70% of concepti are lost during early development. In culture, mouse peri‐implantation embryos can mimic development from the blastocyst to the egg cylinder stage of development, a period during which implantation occurs in vivo. We describe a novel application of this model to investigate nutritional factors that may influence this stage of development. We investigated the influence of zinc (Zn) deficiency on embryonic development at the time of embryo implantation. METHODS Mouse blastocysts were cultured for 144 hr in low Zn, Zn‐replete or control medium. RESULTS Embryos developed normally when they were cultured in the control and Zn‐replete media. Embryos cultured in the low Zn medium were significantly impaired in forming egg cylinder morphology. This was associated with a reduction in extraembryonic endoderm as determined by immunohistochemistry for markers of visceral and parietal endoderm and correlated with an increase in TUNEL positive cells in the low Zn group. There was no change in the frequency of cells positive for phosphorylated Histone H3, a marker for S‐phase, indicating that an increase in apoptosis was primarily responsible for the smaller size and reduction in extraembryonic endoderm. The increased cell death was not associated with an increase in reactive oxygen species (ROS) detected by dichlorodihydrofluorescein staining. CONCLUSIONS These data support an important role for Zn in promoting differentiation and cell survival in the early embryo and suggest that sub‐optimal nutrition is an important factor that contributes to defects in primary germ layers and early embryonic loss. Birth Defects Research (Part A) 67: 414–420, 2003.
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