Use of Oocytes without Zona Pellucida for Treatmentof Infertility

Overview

Objective:
The study of zona free oocytes fertilization using intracytoplasmic sperm injection(ICSI) with the aim to increase the pregnancy rate in the assisted reproduction.Design: Pilot study.Setting: Assisted Reproduction Centre, Gynecology Obstetrics Department of the 1st MedicalFaculty and General Faculty Hospital, Charles University, Prague.Methods: Zona free oocytes were fertilized using ICSI and cultured in standard conditions in vitrofor 5 days until the blastocyst stage. Blastocysts were cryopreserved using 8% glycerol.Results: The fertilization process of zona free oocyte was physiological, oocytes expulsed the polarbody and in standard time, i.e. 18 hour post insemination, two distinct, morphologically normalpronuclei were apparent in cytoplasm. During early cleavage, from the first to the third day of invitro culture, the dynamics of cell division was normal, the three-dimensional arrangement ofcells was more flattened than in normal, zona intact embryo. The fourth and fifth day of culture,the morphological appearance of embryo corresponded to normal development.Conclusion: The fertilization of zona free oocytes using ICSI can give morphologically normalzygote and after 5 days culture in vitro these zygotes can develop into blastocyst stage. Thismethod can increase the pregnancy rate in patients with repeatedly low number of oocytes orwith defects of zona pellucida.

Key words:
zona free oocyte, ICSI, blastocyst development, differentiation, early embryo