Methods for Fertility Preservation: Impact of Vitrification on in Vitro Matured Oocytes

Overview

During the last decades, there was an improvement of the cancer treatments of the woman and the teenagers. Therefore higher survival rate is described. However, cancer treatments can alter the reproduction functions and reduce considerably the window of the fertility to the adulthood. Therefore, it is recommended to proceed to a fertility preservation by oocytes vitrification when it is possible. The vitrification is a freezing technique allowing high survival rate and similar results by assisted reproductive technologies compared with the use of fresh oocytes. An innovative method of automated vitrification was recently developed. The usual protocol consist to vitrify mature oocytes. However, this strategy cannot be used for hormone -sensitive cancer or when ovarian stimulation is not possible. In these situations, immature oocytes can be collected. It is also necessary to realize an in vitro maturation step for a use by assisted reproductive technology. According to the recent data of the literature, it remains unclear whether the vitrification of ovocytes must be performed before or after in vitro maturation (IVM). Therefore the aim of this study is to study the impact on structure and functions of ovocytes when vitrification is performed before or after IVM. The vitrification will be performed by a semi-automatic method which is an innovative method.

To perform this study, investigator will compare three groups. Group 1: immature ovocytes vitrified before IVM; Group 2: immature oocytes vitrified after IVM; Group3: fresh immature oocytes treated by IVM (without vitrification, control group). The immature oocytes provide from ICSI patients. In routine these oocytes (germinal vesicle) are normally destroyed because they cannot be used for injection. The women will give an informed and written consent. Inclusion criteria are women less 37 years without dysovulation. The vitrification will be performed with the semi-automatic method (Gavi, Merck). The kinetic and maturation rate will be analysed by time lapse (Primovision, Vitrolife) In the mature oocytes, the actin and tubulin cytoskeleton, the spindle organization and the cortical granules will be studied by immunofluorescence and 3D confocal microscopy. The expression of maternal factors transcription will be analyzed by RT-PCR. The ploidy will be analysed by multiFISH and/or CGH array.