Effects of Ooplasmic Transfer on Rabbit Oocyte Fertilization and Early Embryonic Development

摘要

In order to evaluate the effects of ooplasm on oocyte fertilization and early embryonic development and to study the mitochondrial DNA (mtDNA) heterogeneity of early embryos, microinjection was first performed to transfer a small amount (5 to 7%) of donor ooplasm into recipient oocytes, then the eggs were fertilized with rabbit sperm through intracytoplasmic sperm injection (ICSI). In group 1 (homogeneous ooplasmic transfer), both the donor and recipient rabbit oocytes were at metaphase Ⅱ (MⅡ). In group 2 (heterogeneous ooplasmic transfer), the donor was mouse MⅡ oocyte and the recipient was rabbit MⅡ oocyte. In the control group, only ICSI was done on rabbit oocyte without ooplasmic transfer. No significant difference (P > 0.05) was observed in blastocyst development rates between group 1 (13.0%, 3/23) and the control group (16.7%, 4/24), but significant difference (P < 0.05) was examined in blastocyst development rate between group 2 (0, 0/27) and the control group. Blastomeres cleaved unequally and embryonic fragments increased after ooplasmic transfer and ICSI. In early embryos, in group 2, donor mouse mtDNA was detected in 2-cell embryos (3/3), 4-cell embryos (3/4), 8-cell embryos (4/4), and morulae (2/2). The mtDNA fingerprinting analysis showed that mouse mtDNA detected in heterogeneous embryos of different developmental stages had exactly the same sequence as that of the donor mouse mtDNA, thus indicating that homogenous ooplasmic transfer had no significant influence on rabbit oocyte fertilization and early embryonic development, and that heterogeneous ooplasmic transfer did cause notable reduction in blastocyst development rate. Heterogeneous mtDNA sequence in early embryos did not mutate. Compared with the control group, the embryonic quality declined after ooplasmic transfer operation in the present experiment.