Asian Journal of Applied Sciences (ISSN: 2321 – 0893) Volume 02 – Issue 04, August 2014 Asian Online Journals (www.ajouronline.com ) 505 Studies on Cryopreservation of Human Oocytes using Verification Technique El Ghareeb A. a,* , Hamdi H. a , Mansour R. b , Abdel-Fatah M. b a Zoology Department, Faculty of science, Cairo University, Cairo, Egypt. b Egyptian IVF-ET centre, Cairo, Egypt * Corresponding author email: drelghareeb {at} yahoo.com _________________________________________________________________________________________________ ABSTRACT--- This study aims to extend the applications of oocytes cryopreservation into the clinical practice of ART. Using the vitrification method applied on 676 human oocytes divided into four groups based on their maturation stage, presence of corona cells and the time to start cryopreservation. Group (A) includes 177 MII oocytes, fully denuded and vitrified 3-5 hours after pick up, (B) includes 194 GV/MI oocytes fully denuded and vitrified 3-5 hours after pick up, (C) contains 103 oocytes vitrified 24 hours from retrieval at the MII stage and fully denuded and (D) contains 202 oocytes vitrified with the corona cells at the MII stage 3-5 hours after pick up. Survivability is determined one hour after thawing then the survived oocytes undergo ICSI procedure. Group (A), after thawing 161 oocytes (91%) survived, 111 (69%) got fertilized, and only 38 (34%) developed into blastocysts. Group (B), 167 oocytes (86%) survived then 60 (36%) matured to MII, and 40 (67 %) got fertilized, then 11 embryos (28%) developed into blastocyst. Group C, 67 oocytes survived (65%), 44 got fertilized (66%) and 8 embryos (18%) reached blastocyst stage. Group D, 188 oocytes survived (93%), 126 got fertilized (67%) and 39 embryos developed into blastocyst (31%). The vitrification method of oocytes is very successful in preserving viability and fertilization .The presence or removal of the corona cells before vitrification didn't affect the results. Delaying vitrification 24 hours significantly lowered them. Vitrifying GV oocytes resulted in a reasonable survival rate; however the fertilization rate was very low. Keywords--- Oocytes cryopreservation, vitrification, IVF, ICSI. _____________________________________________________________________________________________ 1. INTRODUCTION Cryogenic preservation of the reproductive tissues (gametes and embryos) has become of greater importance nowadays in the programs of the in vitro fertilization (IVF) all over the world and it might play a significant role over the next few years 1 . The aimed oocytes cryopreservation or freezing may have the potential to be an important adjunct to assisted reproductive technologies (ART) in humans and animals as well 2 . The results from the recent studies suggest that the survival of human oocytes after cryopreservation can be affected by many factors including the oocytes stage of maturation, their quality and other biophysical factors resulting from the freezing technique used 3 .The incorporation of oocyte cryopreservation into the clinical practice of assisted reproduction programs was the aim of many practitioners in order to extend its applications to other cases 4 . Many reasons that bring the human oocytes cryopreservation into the interest, those reasons are widely known and can be summarized including: diseases, treatments, legal, ethical, social, and practical problems may also require oocyte cryopreservation 5 . For many cases cryopreservation offers the opportunity for preserving women oocytes who are at risk of losing ovarian function as many women experience certain conditions that may result in diminishing or even losing fertility due to age as in premature menopause and other circumstances as in oncology treatment, pelvic disease, surgery, or clinical treatment involving radiotherapy or chemotherapy 6 . Also, women who are in their late reproductive or menopausal years, who have hereditary diseases, abnormal oocytes, or who have had a history of difficulty with oocyte retrieval for in vitro fertilization (IVF) treatment may also benefit from oocyte banking 7 . Despite approximately 20 years of effort, the results in oocytes cryopreservation remain highly variable, and human oocyte cryopreservation is still considered as an experimental procedure. However, both methods have resulted in a successful cryopreservation of human oocytes and embryos, but the slow freezing technique has given much doubted efficiency and consistency. The relatively poor performance of slow-cooling has been highlighted in recently published reports. Therefore, during the past few years, opinion articles as well studies initiated to underline that vitrification might be a better alternative for cryopreserving human zygotes and embryos rather than the slow-rate method. Vitrification methods have been applied to cryopreserve human oocytes to determine if improvements can be made, some of these