Contraction and Expansion of the Mouse Blastocyst In Vitro

Blastocyst hatching is a complex process that occurs about five days after fertilization. During the hatching process, the blastocyst will expand, inflate, and contract as it attempts to break from the zona pellucida. In this experiment, time-lapse microscopy will be used to analyze the expansions, contractions, inflations, and hatching of mouse blastocysts that have been exposed to varied conditions. The independent variable will be embryos that have been freshly ovulated with no changes to the zona, compared to embryos that have had the zona subjected to laser-assisted hatching or laser-zona thinning. The student and her mentor expect to see that the contractions are in some way related to the dynamic process of successful blastocyst hatching. The goal is to determine how the contraction cycles affect these processes, and to use this information to help make earlier predictions on the capability of a blastocyst to hatch normally. The results show that there seems to be no pattern, whether based on amplitude and/or time of contraction, that would indicate whether a blastocyst can successfully hatch. However, an interesting occurrence was that the number of contrations the mouse blastocysts experienced was higher than the total seen in past studies. The conclusion made was that the large number of contractions seen could illustrate a greater amount of suffering with a longer in vitro period, since the embryos used had been flushed from the uterus at an earlier stage than past experiments.