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Structural Changes in Cattle Immature Oocytes Subjected to Slow Freezing and Vitrification
 
H. Wahid*, M. Thein1, E.A. El-Hafez2, M.O. Abas3, K. Mohd Azam4, O. Fauziah5, Y. Rosnina and H. Hajarian6
Faculty of Veterinary Medicine, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia; 1Department of Surgery and Reproduction, Faculty of Veterinary Science, Yezin, Nay Pyi Taw, Myanmar;  2Faculty of Veterinary Medicine, Assiut University, Egypt; 3Agro-Biotechnology Institute, Ministry of Science, Technology and Innovation, Aras 3-7, Blok C4, Parcel C, 62662 Putrajaya, Malaysia; 4Faculty of Veterinary Medicine, Universiti Malaysia Kelantan, Karung Berkunci 36, Pengkalan Chepa, 16100 Kota Bharu, Kelantan, Malaysia; 5Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia; 6Department of Animal Science, Faculty of Agriculture, Razi University, Iran.

Abstract   

This study was conducted to evaluate the effect of different cryopreservation methods (slow-freezing and vitrification) on structural changes of bovine immature oocytes. Bovine ovaries were collected from local abattoirs. Cumulus-oocyte-complexes (COCs) were retrieved using aspiration method from 2-6 mm follicles. In Experiment 1, selected oocytes were randomly divided into 4 treatment groups namely freezing solution-exposed, frozen-thawed, vitrification solution-exposed and vitrified-thawed and then oocytes abnormalities were examined under a stereomicroscope. In Experiment 2, oocytes were randomly allocated to the same grouping as experiment 1 plus control group. Following freezing or vitrification, all oocytes were fixed in glutaraldehyde and processed for transmission electron microscopy. In experiment 1, there was a higher incidence of abnormalities in the frozen-thawed and vitrified-warmed oocytes compared to those in freezing solution and vitrification solution-exposed groups (P<0.05). In experiment 2, there were marked alterations in the perivitelline space, microvilli and vesicles of frozen-thawed and vitrified-warmed oocytes characterized by loss of elasticity and integrity of cytoplasmic processes and microvilli following cooling and warming. In conclusion, ethylene glycol-based freezing and vitrification solutions are suitable choices for cryopreservation of immature oocytes and most organelles are able to retain their normal morphology following cryopreservation and thawing processes.

Key words: Bovine, Cryopreservation, Oocyte, Ultrastructure, Vitrification

 
   

ISSN 0253-8318 (Print)
ISSN 2074-7764 (Online)



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