Vitrification vs. Slow Freeze:

There are two basic techniques for cryropreserving embryos. The first involves a “slow freeze” process while a second technique uses a more rapid technique called vitrification. There is published data suggesting that vitrification may be better with regards to embryo survival and implantation. This study was designed to compare the two procedures.

Comparing Cryopreservation Methods Using Mouse Embryos
Jeremy McGuire, Andrew Bhatnagar, Ph.D. (4/2007)

Innovations in cryopreservation methods have led to successful cryopreservation of human oocytes and embryos. The present study was designed to compare efficacy of two cryopreservation techniques, the conventional “slow freeze” method and a new ultra rapid method of “vitrification”. Previously frozen 2-cell outbred strain of mouse embryos (BDF X CF1) were thawed and cultured in vitro in KSOM media for 24 hours to the 6-8 cell stage and then cryopreserved using 1,2-propanediol (PROH) as a cryoprotectant for the slow freeze method and ethylene glycol /dimethyl sulfoxide (EG/DMSO) for vitrification. Preliminary results suggest that vitrified embryos exhibited a higher post-thaw survival rate (100%) and improved blastocyst formation rate (88%) compared with the slow freeze method (71% % 59% respectively). Further experiments are in progress to statically confirm these results and to evaluate effectiveness of vitrification over current slow freeze methods for cryopreservation of human gametes and embryos in clinical IVF laboratories.

Dr. Sweet’s Comments:
This was our first study using vitrification. The data was intreaging although not conclusive. Published data regarding human embryos seems to also be leaning towards vitrification as a technique that improves the survival rates of cryopreserved-thawed embryos. The next study we have proposed involves human oocytes, a much more difficult cell to freeze, wherein we intend to compare two different storage containers with respect to embryologist satisfaction, survival and implantation rates. Stay tuned!
updated 6/9/09
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