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

Objective: To compare the ultrastructural appearance of oocytes after vitrification and warming with two different devices. Design: 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. Setting: Pordenone Hospital IVF Unit and Medical Morphological Research Department, University of Udine. Patient(s): 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. Intervention(s): Oocytes with normal invertoscopic appearance underwent vitrification and warming with closed (CryoTip) or open (Cryotop) devices and were processed for transmission electron microscopy. Main Outcome Measure(s): Cryodamage extent and cell alterations in oocytes after open or closed vitrification and warming procedures and their rehydration rate. Result(s): A higher rate of complete oocyte rehydration and less-severe ultrastructural alterations were observed after vitrification and warming with the open Cryotop device. Conclusion(s): These preliminary data suggest that oocyte ultrastructure is better preserved with an open rather than closed vitrification and warming protocol