Analysis of gene expression during mouse preimplantation development in vitro, with or without a background of exogenous ovarian stimulation (superovulation)

Among the different procedures of the assisted reproductive technologies (ARTs), the purpose of ovarian stimulation with gonadotropins is to maximize the number of oocytes retrieved, and facilitate scheduling and planning of patient treatment. However, the doses of the gonadotropins required to increase the number of growing ovarian follicles, and, thereby, the number of oocytes, have been found to affect the quality of embryos in the mouse model of human reproduction (PMID 16569317, PMID 22802074, PMID 11387298, PMID 11157810). In order to clarify this issue, we compared the gene expression of mouse embryos with vs without a background of ovarian stimulation with PMSG and hCG. Pronuclear oocytes were cultured in KSOM(aa) and developmental stages were collected based on morphology. Analysis of transcriptome signal intensities showed similar profiles and produced the expected clustering (one cluster from oocyte to 2-cell stage, another cluster from 4-cell stage to blastocyst) regardless of whether the embryos were produced in stimulated or non-stimulated ovarian cycles; however, the expression levels of some genes were different depending on the ovarian stimulation. Oocytes or embryos were collected in a total of 4 runs with superovulation (n=3096), and 9 runs without superovulation (n=989), during the time from November 2015 to March 2016. The lysates were pooled by developmental stage, keeping the hormonal backgrounds separate. Knowing how many embryos had been accumulated for each stage, we took a subvolume of the total lysate corresponding to 20 oocytes or embryos (of each stage). These subvolumes were subjected to Affymetrix microarray analysis, performed by Anika Witten c/o Institut fuer Humangenetik, Universitaetsklinikum Muenster.