Chromosome and spindle configurations of human oocytes matured in vitro after cryopreservation at the germinal vesicle stage

Objective: To investigate effects of cryoprotectant and cryopreservation on the chromosome and microtubule configuration of human immature oocytes.Design: Intact cumulus-enclosed immature oocytes were collected from unstimulated ovaries and divided into three groups: group 1, no treatment (control); group 2, only 1,2-propanediol treatment, and group 3, cryopreserved oocytes. Oocytes in groups 1 and 2, and oocytes that survived after cryopreservation in group 3 were cultured for 48 hours.Setting: Infertility Medical Center at the CHA General Hospital, Seoul, Korea.Patient(s): Oocytes were obtained from patients undergoing gynecologic surgery.Main Outcome Measure(s): Maturation rate and abnormality in chromosomes by fluorescence in situ hybridization and in the spindle by immunostaining for tubulin.Result(s): There was no effect of propanediol-only treatment on the chromosomal (41.4%) and spindle abnormalities (35.3%) in group 2 compared with control oocytes (31.8% and 22.2%, respectively), whereas a statistically significant increase in abnormalities in chromosomes (77.8%) and spindles (70%) was found in group 3.Conclusion(s): Human oocytes matured in vitro after cryopreservation at the germinal vesicle stage showed increased incidence of chromosomal and spindle abnormalities. These abnormalities may impair the capacity for further development of the embryos derived from frozen-thawed oocytes.