Cryopreservation of embryos defines the long-term preservation of the preimplantation embryos which suspends its metabolism and development by freezing and storing them in liquid nitrogen. Should the need arise, the cryopreserved embryos can be thawed and implanted into pseudopregnant females in order to produce pups which can be bred to establish a colony. Our Muring IVF and Cryopreservation Laboratory (MICL) routinely performs cryopreservation services, and have successfully cryoarchived and recovered thousands of mouse lines on various backgrounds.
Mouse embryos at 2-cell stage derived from IVF are cryopreserved using PROH (1,2-Propanediol) as cryoprotectant (Renard and Babinet, 1984) and a programmable freezer. Our cryopreservation lab attempts to preserve up to 300 embryos (20-25 embryos per straw) per strain using two IVF attempts. Some mutant strains cannot provide that number of embryos from two IVF procedures, and additional charges may be incurred if additional attempts are required.
For heterozygous line embryo cryopreservation, we prefer to receive 2-4 males from our customer, and we will purchase the wildtype female mice on an appropriate genetic background as egg donors for IVF.
For homozygous line embryo cryopreservation, we like to receive 2-4 males and at least 10-15 mutant females per line.
The optimal male age is 11-20 weeks old, and the optimal female age is 3-8 weeks old. The fee for embryo cryopreservation includes up to two IVF procedures, cryoarchiving up to 250-300 embryos, and the storage of the cryopreserved materials for one year.
An embryo test thaw to culture or to live pups may be requested to examine the recovery potential of the cryoarchived embryos. Test thaw of one embryo straw to culture allows us to assess the blastocyst formation rate in vitro, a good marker of embryo quality. A test thaw to live pups allows for the frozen-thawed embryos to be transferred into oviducts of pseudo-pregnant recipients in our conventional facility for production of live pups to determine the full developmental potential of the cryopreserved embryos.
Renard JP, Babinet C 1984 High survival of mouse embryos after rapid freezing and thawing inside plastic straws with 1–2 propanediol as cryoprotectant. Journal of Experimental Zoology 230: 443–448.