Studies Related To Oocyte Zona Pellucida And Factors Affecting The Developmental Potential Of Oocyte In Human IVF Cycles

In in-vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) cycles of human assisted reproduction, the precise evaluating quality of oocyte with the potential to develop to implantation-competent embryos is crucial for the success of clinical treatment. In recent years, zona pellucida (ZP) has been found to be a valuable predictive marker for evaluation of oocyte and embryo quality. Currently, polarized light microscopy has been introduced to facilitate the non-invasive visualization of the oocyte ZP. Through this technique, the zona birefringence (ZB) and light retardance of oocytes as new prognostic factors of the oocyte quality were proposed. However, the previously reported results mainly focused on the ICSI cycles. The aim of the present study was to explore the relationship between ZB and oocyte quality and the factors affecting the developmental potential of oocyte in human IVF cycles.1. To examine if the age of the female patients, oocyte maturation stage, pronuclei, embryonic quality, and cycle outcome are related to the zona birefringence (ZB) intensity of oocytes in IVF cycles, a retrospective study on214IVF cycles with a polarization imaging system was conducted. The score of ZB intensity was closely correlated with the age of female patients and the maturation stage of oocytes, but not with the embryonic quality and gestation rate. These results indicate that the score of ZB intensity is related to the quality of oocyte and can be used as a reference for early selection of reproductive oocyte and embryo in IVF cycles.2. Effects of sperm-oocyte coincubation time on the fertility, cleavage, embryo quality, ZB and zona thickness (ZT) were investigated. It was found that properly shortening the sperm-oocyte coincubation time could increase the fertiliy rate, cleavage, implantation and pregnancy rate, moreover, ZB values were increased with the increase of sperm-oocyte incubation time. However, the time of sperm-oocyte coincubation did not effect ZT on day1. 3. Effects of clinical diseases such as tubal factor infertile、polycystic ovarian syndrome (PCOS)、endometriosis and unexplained infertility on the ZP of oocyte, embryo development and clinical outcome in IVF cycles were analyzed. It was found that different diseases had different effects on the retrieved oocyte number, the rate of fertility, implant and pregnancy, ZB and ZT. Endometriosis had the most obvious effects, particularly with significantly lower ZB and significantly higher ZT than those effects caused by other diseases. Therefore, ZB and ZT of oocyte could indicate the effects of different diseases on developmental potential of oocytes to some extent.4. The efficiency of different superovulation protocols, including standard GnRH agonist long protocol, short protocol, GnRH antagonist protocol and minimal stimulation protocol on developmental potential of oocytes, clinical effects, pregnancy, and ZB of oocytes were compared. No statistic difference was found in maturation, fertilization, mulfertilization, cleavage, embryo quality, implantation, pregnancy and cycle concel with the different superovulation protocols when the patient age and etiology were comparative. However, the different superovulation protocols had distinct influence on the ZB and ZT of oocytes. Particularly, ZB could reflect the effects of different superovulation protocols on oocyte quality to some extent.5. Effects of human menopausal gonadotropin (hMG) in superovulation treatment on follicle stimulating hormone (FSH) dosage, the number of oocytes retrieved, fertilization rate, cleavage rate, embryo quality, pregnancy rate, embryo implantation and the ZB and ZT of oocyte were investigated. The maturation rate, fertilization rate, cleavage rate, embryo quality, pregnancy and embryo implantation rate were higher in rFSH+hMG group than those in rFSH group, whereas, the number of oocytes retrieved was lower in the former. The ZB was lower in rFSH+hMG group than that in the rFSH group, which indicates that luteinizing hormone (LH) can not only promote the recover of oocyte meiosis but also facilitate the maturation of ZP. LH played the two-way role for ZT of oocytes, which implies that exceptionally high or low level of LH is detrimental for the development of oocyte ZP.