Vrije Universiteit Brussel

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Cryopreservation of oocytes and embryos

Principal Investigator: Etienne Van Den Abbeel PhD student: Neelke De Munk

In the cryopreservation programme, not all oocytes and embryos survive the cryopreservation with all cells intact. If they survive, they will only be transferred if 50% of the initial cells survive the thawing procedure. Moreover, these oocytes and embryos have a reduced implantation potential as compared to fully intact embryos.

For embryos and blastocysts, we will determine the effect of cell loss after a freezing-thawing cycle and try to understand why they have a reduced implantation potential.

For oocytes, we will determine the effect of vitrification on the different maturation stages of oocytes.

In a first phase, vitrified MII oocytes will be thawed. We will look at the oocyte characteristics, time-lapse analysis up to the 2-cell stage, blastocyst formation and to their metabolomic data in order to detect differences between frozen-thawed and fresh oocytes.

In a second phase, germinal vesicle oocytes will be vitrified and thawed. Due to their different configuration they might have a different response to cryopreservation. We will determine the influence of the cryoprotective agents on the physiology of the germinal vesicle and on their capacity to mature in vitro to metaphase II oocytes and their further development to blastocysts. And finally, we'll try to detect the different effect of vitrification between metaphase II and germinal vesicle oocytes with respect to their developmental capacities.

In this way, we should be able to develop a robust, safe and effective vitrification procedure for human oocytes, embryos and blastocysts.

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