Effect Of Combinations Of Different Sperm Concentration And Different Oocytes On Fertilization And Early Embryo Development

In vitro fertilization (IVF) is an assisted reproductive technology (ART) that widely used in clinical research. Quality of oocytes and concentration of sperm play crucial roles in the process of fertilization. In some cases, because of disease, or self-ovulation problem, or operation failure during oocytes collection, denuded oocyte (DO) without cumulus layer or oocytes without zona pellucida (OZ-) were frequently obtained. Although the insemination condition was fully studied with cumulus-oocyte complex (COC), the fertilization procedure as well as the sperm concentration for DO and OZ-have not been fully investigated.In this study, we got three kinds of mouse oocytes which were gradually diminishing in structure:COC obtained by superovulation, DO obtained by removing cumulus layer with hyaluronidase, and OZ-obtained by removing zona pellucida with tyrode solution (acid M2 medium). The optimal sperm concentration for fertilization was determined through the following experiments:same type of oocytes mixed with different concentration of sperm to determine the optimal sperm concentration; same concentration of sperm mixed with different types of oocytes to determine the most suitable type of oocytes.Our results showed that the best sperm concentration for IVF is 106/ml in COCs, 107/ml in DOs or OZ-. When the sperm concentration is 103/ml or 104/ml, DOs got the highest fertilization and embryo developmental rate. When the sperm concentration is 105/ml or 106/ml, COCs got the highest fertilization and embryo developmental rate. When the sperm concentration is 107/ml, OZ-got the highest fertilization and the embryo development rate. Optimal concentration of sperm determined by above experiments were used for COC, DO and OZ-insemination. Blastocysts obtained from these oocytes were checked. Our results showed that the cell number and diameter is similar between group of COC and DO, which was much better than the group of OZ-In sum, combination of COCs with 106/ml of sperm concentration obtained the highest fertilization and embryo developmental rate. In the situation of less COCs, DO can be used for fertilization under the concentration of 107/ml sperm. OZ-were not recommended for fertilization due to the extremely low embryo development rate.