Human Pronuclear Transfer with Discarded Triploid Zygotes

[Objective] To establish a micromanipulation-electrofusion procedure for human pronuclear transfer with discarded triploid zygotes. [Materials] A total of 117 oocytes showing 3 pronuclears and 2 polar bodies 16-19 h after in vitro fertilization(IVF), were considered as triploid zygotes and used after informed patient consents. Different fusion media protocols (containing 0.05 mmol/L and 0.1 mmol/L calcium chloride) and electrofusion conditions(1 800 V/cm and 2 000 V/cm voltage) were used to assess their influences on the reconstructed zygote development potential. [Result] The manipulation successful rate was 70.1%. The karyoplast fusion success rate was 59.8%. Forty-three reconstructed zygotes cleaved, among which 23 embryos reached 6-cell stage (53.5% of 2-cell embryos) and 14 developed to 8-cell stage with 3 blastocysts. When the voltage was decreased from 2 000 V/cm to 1 800 V/cm, the fusion rate, cleavage rate, and blastocyst rate between these two groups were not statistically different (P 0.05), but the 6-cell embryo rate significantly increased (22.2% vs. 60.9%, P=0.049). The fusion rate was significantly increased by increasing the calcium concentration from 0.05 mmol/L to 0.1 mmol/L (39.3% vs. 69.0%, P = 0.014). However, no statistical difference was observed in cleavage rate, the 6-cell rate and the blastocyst rate between the two groups(P 0.05). [Conclusion] Using discarded triploid zygote to reconstruct diploid zygote with micromanipulation-electrofusion method is a practicable and economical method to get cytoplasmic-nuclear heteroplasmic embryo model.