Sperm Injection at the Para-Polar Body Site in Piezo-Intracytoplasmic Sperm Injection Improves Subsequent Early Development of Bovine Embryos.

Abstract

Purpose: In piezo-ICSI, the first polar body (PB) of a metaphase II (MII) oocyte is generally oriented in the 6 or 12 o'clock position relative to sperm injection at 3 o'clock. However, the ooplasmic cell membrane may be damaged during drilling of the zona pellucida by piezo pulses. Here, we tested a new piezo-ICSI method in which the PB is set at the 2 or 4 o'clock position, so that zona drilling is performed through the widest position in the perivitelline space (para-PB piezo).

Methods: The effect of piezo pulse position was evaluated by propidium iodide staining and cytoplasmic Ca²⁺ levels. The effect of injection site on integrity and movement of the meiotic spindle was evaluated by microscopy and an Oosight imaging system. Bovine oocyte survival rate, developmental competence, and chromosomal integrity at the blastocyst stage were compared between para-PB piezo and conventional piezo groups.

Results: Piezo pulses may induce slight changes in the ooplasmic cell; our piezo-ICSI method can improve oocyte survival by minimizing damage to the ooplasmic cell membrane during zona drilling and consequently increasing the number of embryos available for transfer.

Conclusions: Para-PB site piezo-ICSI is an improvement on current ICSI technology for animal and human reproduction.