ASEPTIC VITRIFICATION OF HUMAN GERMINAL VESICLE OOCYTES USING DIMETHYL SULFOXIDE AS A CRYOPROTECTANT

OBJECTIVE: To evaluate the viability of vitrified human germinal vesicle (GV)-oocytes to mature to metaphase II (MII) stage after "rapid" cooling directly in liquid nitrogen in comparison with "slow" cooling in a closed 0.5-mL straw (aseptic system), with or without dimethyl sulfoxide (DMSO) in vitrification solution. The possibility of avoiding parthenogenesis of the oocytes after vitrification using DMSO was investigated.
DESIGN:
In vitro maturation after vitrification.
SETTING:
Assisted reproduction centers.
PATIENT(S):
Patients undergoing standard superovulation treatment and having GV-oocytes after follicular puncture.
INTERVENTION(S):
The GV-oocytes were vitrified with long/short exposure to DMSO using slow or rapid cooling, then warmed and matured in vitro.
MAIN OUTCOME MEASURE(S):
Maturation after warming.
RESULT(S):
Oocyte development up to MII stage after vitrification with DMSO was 71% in the group with "rapid" cooling, and in groups with "slow" cooling, 68% and 72% for long and short exposure to DMSO, respectively. The maturation rate of GV-oocytes after slow cooling without DMSO was 51%. In the vitrification with long-term contact of oocytes with DMSO group, a high rate of parthenogenesis was observed. When vitrification with short-term contact of oocytes with DMSO at room temperature was used, no parthenogenesis was observed.
CONCLUSION(S):
Cryopreservation of human GV-oocytes in open-pulled straws OPS) using an aseptic slow cooling method gives high maturation rates but only in combination with DMSO. To avoid spontaneous parthenogenesis, the exposure to DMSO must occur for a reduced time and at room temperature.