The Investigation Of Regulatory Factors Affecting First Cleavage Of One-cell Embryos During Culture In Vitro

During the procedure of in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI), some zygotes are unable to achieve successful cleavage. In fact, in some patients the majority of their zygotes are unable to complete their first cell cleavage. The causes and underlying mechanisms are largely unknown. Therefore, it is of the utmost interest and importance to determine the major regulatory factors affecting the first cell cleavage of the zygotes. It is hoped that our study may provide a new avenue of research to overcome this problem.Objective:To investigate the expression of PLK1 during the procedure of first cleavage of mouse one-cell embryos.Methods:The expression of PLK1 during the first zygotic division (16h,24h,28h, 32h and 36h post-HCG injection) was detected by using Western blot. The correlation between PLK1 expression and the process of the first zygotic division were analyzed.Results:PLK1 expression increased gradually during the first zygotic division. From 32h to 36h post-HCG injection, there was a high level of PLK1 expression in the zygotes, which was significantly higher than that of the other groups (16h,24h, and 28h, P<0.01)Conclusion:The expression of PLK1 peaked in the first M phase of zygotic division. PLK1 may play an important role in the first cleavage of one-cell embryos. Objective:To investigate the influence of removing zona pellucida on the first cleavage of mouse zygotes.Methods:Mice were superovulated by pregnant mare serum gonadotropin (PMSG). After fertilized in vivo, one-cell embryos were collected, and were divided into two groups: with zona pellucida and without zona pellucida. These one-cell embryos were cultured in vitro, and the first cleavage rates of two groups were evaluated.Results:The cleavage rate of the group without ZP is 64.12%±1.61%; the cleavage rate of the group with ZP is 63.06%±1.48%. There is not significant difference between the two groups (P>0.05).Conclusion:The zygote without ZP can cleave into two-cell embryo successfully in vitro. There is not influence of removing ZP on the early development of one-cell embryo in vitro.Objective:To investigate the influence of PLK1 deficiency on the first cleavage of mouse one-cell embryos.Methods:RNA interference (siRNA) was used to down-regulate the PLK1 expression in the one-cell mouse embryo. And the effect of siRNA was proved by Western blot. After this treatment, the first cleavage rates were evaluated, including four groups:PLK1 siRNA, siRNA control, mock transfection, and only ZP removal.Results:The relative amount of PLK1 of the mouse zygotes was reduced significantly after siRNA transfection (P=0.000). The first cleavage rate of the Plkl siRNA group was significantly less than that of other groups (siRNA control, mock transfection, and only ZP removal, P=0.000).Conclusion:PLK1 siRNA can reduce the expression of PLK1 in zygotes efficiently. The zygotes without PLK1 are not able to divide successfully. PLK1 plays a crucial role during the first cleavage of one-cell embryos.Objective:To investigate the nuclear/chromosome and microtubule/spindle abnormalities in arrested human zygotes in vitro.Methods:To investigate this, fluorescence and confocal laser scanning microscopy were used, following immunolabelling with antibodies specific for a-tubulin, combined with DNA fluorochrome.Results:62.50% of the arrested human zygotes have abnormalities in the organization of microtubule, and 37.50% of the arrested human zygotes are in the interphase of the cell cycle.Conclusions:We propose that interphase/metaphase transition arrest, microtubule organization and spindle abnormalities cause human one-cell embryo development arrest.