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Cryopreservation of human prophase I oocytes collected from unstimulated follicles
T L Toth1, S E Lanzendorf, B A Sandow
1Department of Obstetrics and Gynecology, The Jones Institute for Reproductive Medicine, Eastern Virgina Medical School, Norfolk 23507.
Objective:
To evaluate the cryopreservation of immature human oocytes obtained from unstimulated ovarian tissue.
Design:
Immature prophase I oocytes were obtained from unstimulated follicles and were either cryopreserved or cultured as controls. Cryopreservation was performed in a programmable freezing machine using one of two protocols. Method I (n = 133) used a one-step addition of cryoprotectant followed by a slow freeze and thaw protocol. With method II (n = 95), the cryoprotectant was added in a stepwise manner with cryopreservation performed in the presence of 0.2 M sucrose followed by rapid freezing and thawing.
Setting:
Basic research center at a medical school.
Patients:
Patients undergoing oophorectomy for nonovarian pathology.
Main Outcome Measures:
Rates of survival and maturation to metaphase II were compared between control oocytes and oocytes cryopreserved with methods I and II.
Results:
With method I, a survival rate of 15.6% was obtained with 58.3% of surviving oocytes reaching metaphase II after culture compared with 50.0% of nonfrozen control oocytes. Method II produced a survival rate of 43.3% with 27.3% maturing to metaphase II. Maturation of control oocytes for method II was 46.4%. Although the survival rate with method II was significantly higher than with method I, the rate of in vitro maturation to metaphase II showed no difference.
Conclusions:
These results demonstrate that human prophase I oocytes obtained from unstimulated antral follicles are capable of meiotic maturation after cryopreservation.