Vitrification of human single pronuclear oocytes following two approaches to polar body biopsy

Abstract

The purpose of the present study was to investigate whether the size of the opening in the zona pellucida (ZP) of
human single pronuclear (1PN) oocytes made by laser and partial zona dissection (PZD) techniques might
interfere with the survival and subsequent development to blastocyst stage upon vitrification and warming.
Moreover, the viability of these blastocysts was evaluated by comparing their total cell number (TCN) to the
TCN of blastocysts developed from control non-vitrified zona-intact 1PN oocytes. Prior to vitrification, a total of
97 and 88 1PN oocytes were subjected to polar body biopsy using laser-assisted and PZD techniques,
respectively. The size of ZP opening made by laser and PZD techniques did not interfere with survival (94.8%
and 95.4%) or development to the blastocyste stage (27.8% and 26.1%). However, the TCN of laser-derived
blastocysts was significantly lower than the TCN of blastocysts developed from non-vitrified control 1PN
oocytes (48.7 ± 3.4 vs. 70.8 ± 7.1, P < 0.028). The vitrification protocol used here is thus revealed to be an
effective method for cryopreservation of 1PN oocytes following polar body biopsy. However, the viability of
blastocysts developed from laser-treated 1PN oocytes seems to be influenced negatively by this method of
biopsy.