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Human oocyte cryopreservation: new perspectives regarding oocyte survival
R Fabbri1, E Porcu, T Marsella
1IVF Center, Human Reproductive Medicine Unit, Institute of Obstetrics and Gynecology, University of Bologna, 40138 Bologna, Italy. rfabbri@orsola-malpighi.med.unibo.it
Human Reproduction (Oxford, England)
|March 3, 2001
Summary
Optimizing human oocyte cryopreservation involves adjusting sucrose concentration and exposure time to cryoprotectants. Tripling sucrose concentration significantly improved oocyte survival rates after thawing and subsequent intracytoplasmic sperm injection.
Area of Science:
- Reproductive biology
- Cryobiology
- In vitro fertilization
Background:
- Human oocyte cryopreservation is crucial for assisted reproductive technologies.
- Success rates are influenced by morphological and biophysical factors affecting post-thaw survival.
- Previous attempts yielded variable results, necessitating further investigation into optimal cryopreservation parameters.
Purpose of the Study:
- To investigate the impact of cumulus oophorus presence, sucrose concentration, and cryoprotectant exposure time on human oocyte survival after cryopreservation.
- To evaluate the subsequent fertilization and embryo development rates following intracytoplasmic sperm injection (ICSI) of thawed oocytes.
Main Methods:
- Human oocytes were cryopreserved using a slow-freezing, rapid-thawing protocol with 1,2-propanediol and varying sucrose concentrations.
- Oocytes were cryopreserved with partially removed, enzymatically removed, or intact cumuli.
- Exposure times to cryoprotectants were varied before freezing.
- Thawed oocytes underwent ICSI, and fertilization and embryo development were monitored.
Main Results:
- Cumulus oophorus removal method did not significantly affect post-thaw survival rates (56% vs. 53%).
- Increasing sucrose concentration from 0.2 mol/l to 0.3 mol/l significantly enhanced oocyte survival (60% vs. 82%, P < 0.001).
- Extended exposure time to cryoprotectants (10.5–15 min) significantly improved survival rates (P < 0.005).
- Post-thaw ICSI resulted in a 57% fertilization rate, 91% embryo cleavage rate, and satisfactory embryo morphology (14% grade I, 34% grade II).
Conclusions:
- Sucrose concentration and cryoprotectant exposure time are critical factors for improving human oocyte cryosurvival.
- Optimized cryopreservation protocols can yield viable oocytes for successful ICSI and subsequent embryo development.
- Further research can refine these parameters to enhance fertility treatment outcomes.