Effect of slow freeze versus vitrification on the oocyte: an animal model

This study adds to the increasing body of evidence that cryopreservation protocols vary in their impact upon the oocyte.

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Weihong Hu, M.D., Ph.D., Dennis Marchesi, Ph.D., Jie Qiao, M.D., Ph.D., Huai L. Feng, Ph.D., H.C.L.D., E.L.D.

Vol 98, Issue 3, Pages 752-760.e3



To determine whether there is a deleterious effect on dynamic events in the nucleus and cytoplasm of oocytes by using different cryopreservation protocols in an animal model.


Prospective study


University hospitals


Immunostaining and confocal laser scanning microscope techniques were used.

Main outcome measure(s):

The spindle and chromosomal configurations, as well as dynamic changes of the cortical granules (CGs) and mitochondria in different cryo groups.


After thawing/warming of bovine oocytes, CGs became more dispersed in the cytoplasm, particularly in the DMSO group. A significant reduction in normal spindle and chromosomal configurations was observed in all three cryo-groups, particularly in the PROH group, when compared with the Fresh group. Global DNA methylation levels were significantly reduced in the Slow and DMSO groups, as compared to the Fresh grouphowever, methylation levels were significantly increased in the PROH group. The proportion of severely apoptotic oocytes was dramatically increased in all three cryo-groups, compared with Fresh group.


Overall, results demonstrate that using DMSO as the cryoprotectant is better in preserving the cellular and nuclear integrity of the oocyte. The PROH method makes the oocyte more vulnerable to increased DNA methylation, which may be associated with imprinting gene alteration. This study adds to the increasing body of evidence that cryopreservation protocols vary in their impact upon the oocyte.

Read the full text at: http://www.fertstert.org/article/S0015-0282(11)01393-8/fulltext

Fertility and Sterility

Editorial Office, American Society for Reproductive Medicine

Fertility and Sterility® is an international journal for obstetricians, gynecologists, reproductive endocrinologists, urologists, basic scientists and others who treat and investigate problems of infertility and human reproductive disorders. The journal publishes juried original scientific articles in clinical and laboratory research relevant to reproductive endocrinology, urology, andrology, physiology, immunology, genetics, contraception, and menopause. Fertility and Sterility® encourages and supports meaningful basic and clinical research, and facilitates and promotes excellence in professional education, in the field of reproductive medicine.

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