Ultrastructural evaluation of human metaphase II oocytes after vitrification: closed versus open devices

Abstract

To compare the ultrastructural appearance of oocytes after vitrification and warming with two different devices. Oocytes were examined by ultrastructural analysis after vitrification and warming with use of closed (CryoTip; Irvine Scientific, Santa Ana, CA) or open (Cryotop; Kitazato BioPharma Co., Ltd., Shizuoka, Japan) devices. Pordenone Hospital IVF Unit and Medical Morphological Research Department, University of Udine. Surplus oocytes from 10 patients (aged 31-39 years) undergoing assisted reproductive technologies at the Pathophysiology Unit of Human Reproduction and Sperm Bank between 2006 and 2008. Oocytes with normal invertoscopic appearance underwent vitrification and warming with closed (CryoTip) or open (Cryotop) devices and were processed for transmission electron microscopy. Cryodamage extent and cell alterations in oocytes after open or closed vitrification and warming procedures and their rehydration rate. A higher rate of complete oocyte rehydration and less-severe ultrastructural alterations were observed after vitrification and warming with the open Cryotop device. These preliminary data suggest that oocyte ultrastructure is better preserved with an open rather than closed vitrification and warming protocol.