Tl. Toth et al., CRYOPRESERVATION OF HUMAN PROPHASE-I OOCYTES COLLECTED FROM UNSTIMULATED FOLLICLES, Fertility and sterility, 61(6), 1994, pp. 1077-1082
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 cry
opreserved 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. Sett
ing: Basic research center at a medical school. Patients: Patients und
ergoing 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. Resu
lts: With method I, a survival rate of 15.6% was obtained with 58.3% o
f 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 o
ocytes 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 re
sults demonstrate that human prophase I oocytes obtained from unstimul
ated antral follicles are capable of meiotic maturation after cryopres
ervation.