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 blastocyst 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 versus 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 negatively affected by this method of biopsy.

Successful implantation and live birth of a healthy boy after triple biopsy and double vitrification of oocyte-embryo-blastocyst

“…Biopsy of the oocyte prior to fertilization is ethically accepted since it does not require manipulation of the pre-embryo. Our study confirms that aspiration of the first polar body seems to have no detrimental effects on fertilization or quality of the embryonic development until to the blastocyst stage because it is not involved in all these processes (Macas et al 2011 ). Different studies, on the contrary, showed that day 3 embryos that undergone blastomere biopsy had more fragmentation and showed a slower cell division if compared with unbiopsied controls, but no definitive conclusion on the safety of PB biopsy with respect to the embryo implantation potential is available at present because all the published studies are underpowered (Montag et al 2013 ; Levin et al 2012 ).…”

Ultra-Rapid Warming Yields High Survival of Mouse Oocytes Cooled to −196°C in Dilutions of a Standard Vitrification Solution

“…Two years later, An et al [30] reported that the percentage of ICR 2-cell embryos derived by IVF after PZD that develop to blastocysts is the same or higher than that of 2-cell embryos with intact zonae. A more recent example is the 2011 report by Macas et al [31] that the percentage of human oocytes that develop to blastocysts after IVF is the same for oocytes with intact zonae, those with partially dissected zonae, and those with zonae in which various-sized holes has been created by laser. Thus, the use of PZD is not a problem.…”

Impact of polar body biopsy on embryo morphokinetics—back to the roots in preimplantation genetic testing?

“…An interesting side effect of our study was the evaluation of laser beam influences on embryo development. Debates on the safety of the laser systems used in biopsy approaches are still ongoing with contradicting results [ 37 , 38 ]. However, we provided evidence that the opening of the zona pellucida with laser beam had no influence on the morphokinetic parameters of early embryonal development.…”