PARENT SESSION
OVARIAN GERM CELLS AND FERTILITY
Laurel
7:30 AM-10:00 AM

(270) IDENTIFICATION OF A MOLECULAR MARKER(S) FOR OOCYTE QUALITY IN CYCLIC RATS.

Zhao, Jia¹, Verhaert, Peter², Smits, Anke¹, van der Locht, Sandra², Schoondermark, Mieke¹, Hanssen, Rob¹, ¹ Section of Female Infertility and Contraception, Department of Pharmacology, Research and Development, N.V.Organon, Oss, the Netherlands² Department of Target Discovery, Research and Development, N.V.Organon, Oss, the Netherlands

ABSTRACT- In the current in vitro fertilization (IVF) protocols, follicle stimulating hormone (FSH) is used to induce follicular growth which eventually results in ovulation of multiple oocytes. However, after IVF, only a limited percentage of these oocytes develop into a healthy fetus. Currently, no reliable criteria are available to evaluate oocyte quality. The present study is designed (1) to test the hypothesis that stimulation by high doses of exogenous FSH compromises the quality of ovulated oocytes and (2) to search for a molecular marker(s) which is predictive for the developmental competence of a given oocyte. Firstly, an animal model was set up to yield oocytes of 'good' or 'bad' quality. This was done in adult rats with normal estrous cycles. Blastocyst yield was used as the parameter for oocyte quality. In control groups, no gonadotropins were administrated to the animals which were allowed to mate with males after natural ovulation. Five days after copulation, blastocysts were collected from the uterus and their number recorded. In the test groups, rats were stimulated with recombinant FSH (rFSH) at different concentrations (2.5, 5, 10, 20 IU/kg) to induce follicle development. Ovulation was induced by hCG. Mating and blastocyst evaluation were carried out as described for the control group. It was found that the blastocyst yield was significantly lower in rats treated with 5, 10 and 20 IU/ml rFSH (5%), compared to the control groups (66%). This confirmed the hypothesis that a high dose of rFSH stimulation compromises oocyte quality. Furthermore, granulosa cells, which are long known to closely interact with their respective oocytes, were isolated from preovulatory follicles in control (GC-C) and rFSH-stimulated groups (GC-S). These samples were subjected to genomic and proteomic analyses for potential molecular markers for oocyte quality. Using real-time quantitative reverse transcriptase polymerase chain reaction (RT-PCR), the expression of several selected genes were compared in GC-C and in GC-S. Obvious up- and down-regulation of various genes were detected. In addition, high resolution 2-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and computerized gel image analysis were used to compare the protein profiles in GC-C and GC-S. Distinctive differences in protein profiles of GC-C and GC-S were observed. The identification of these proteins is in progress.

KEY WORDS: oocyte , hyperstimulation, proteomics, genomics