Effects of retinoic acid on pre-implantation embryo development in mice

Background: In a previous study we had investigated the effect of in utero retinoic acid (RA) exposure on early post-implantation development at the blastocyst stage before implantation and immediately after implantation to understand the possible roles of RA in embryogenesis. The results showed that excess RA affected early post-implantation embryogenesis adversely. We designed the present study to investigate the effect of in utero RA exposure on pre-implantation embryos. Methods: In the prospective animal study, pregnant female mice received early pre-implantation peanut oil with 50 mg/kg t-RA or 100 mg/kg t-RA by oral gavage on the morning of day 1 and 2 or late pre-implantation exposure on the night of day 2 and morning of day 3 of gestation. Mice were sacrificed late in day 3. The number and morphology embryos were recorded. Results: All mice given oral RA were sacrificed on the same day. The mean number of embryos per mouse and the percentage of different embryo stages in the t-RA treated mice administered at early pre-implantation embryo or late pre-implantation embryo stage were not significantly different from the controls. The mean number of embryos per 50 mg/kg mouse and the percentage of expanded blastocysts or early blastocysts/morulas did not differ from controls. In addition, the percentage of expanded blastocysts or early blastocysts/morulas was also not significantly different from the control group in 100 mg/kg late pre-implantation mice. Conclusion: Mouse embryo development may not experience dose related adverse effects from non-physiological RA exposure during pre-implantation.