[Spindle and chromosome configuration of human in vitro matured oocytes after slow freezing-fast thawing]

To evaluate the development of immature oocytes after freezing-thawing by conventional cryopreservation method for mature oocytes.

Immature oocytes were collected from stimulated ovaries of intracytoplasmic sperm injection (ICSI) cycles. Immature oocytes were in vitro matured directly or after slow freezing-fast thawing and immunostained for tubulin and chromatin and at last visualized by confocal microscopy.

No statistical difference was found in maturity rate between freezing groups and the controls. There was a statistically significant increase in abnormalities of chromosome (23.7% vs. 50%) and spindle (28.9% vs. 53.9%) in the GV freezing group compared with the GV control (P < 0.05). MI groups gave the same results. But we did not find any statistical difference between GV frozen group and MI frozen group.

Cryopreservation decreases the ability of immature oocytes to form normal meiosis spindle and induce abnormal division of chromosomes. This suggests that the routine slow freezing-fast thawing procedure for mature oocyte couldn't preserve the ability well to form normal meiosis spindle during in vitro maturation.