Cryopreservation of mouse embryos by vitrification: a meta-analysis.
A meta-analysis of cryopreservation studies vitrifying mouse embryos was undertaken to determine the treatment effect of vitrification. Treatment by vitrification decreased embryo viability compared with controls: the odds ratio was 9.02 (CI: 3.73-21.78; P < 0.001), a 24.90% (CI: 14.88-34.91; P < 0.001) reduction in risk was associated with embryos in the control group, and for every 4.00 (CI: 3.91-4.09) embryos treated by vitrification, one does not survive. A multiple regression analysis evaluated covariates of embryo survival. For each hour increase post-hCG treatment when embryos were cryopreserved, there was a decrease of 0.36% (SEM +/- 0.01) in survival (P < 0.001). The number of embryos surviving vitrification decreased 0.25% (SEM +/- 0.02) per day increase in age of the female mouse (P < 0.001), whereas there was no significant difference for control group embryos. For each 1 h increase post-hCG treatment after cryopreservation when blastocysts were assessed for viability, there was a decrease of 0.13% (SEM +/- 0.01) in survival. The later interval post-hCG treatment when blastocysts were assessed, the less viable they were compared with earlier blastocysts, independent of the vitrification protocol. This effect was not observed for control embryos. A high percentage of variability in the treatment effect for vitrification was likely due to underlying heterogeneity among studies. A portion of the risk associated with vitrification could be attributed to the general effects of cryopreservation. Future research should identify effects in a cryopreservation protocol specific to vitrification that affect viability of mouse embryos.
Manno
Francis Anthony Michael
FA
Department of Biology, Virginia Wesleyan College, Norfolk, VA 23502-5599, USA. vitamus@gmail.com
D000818:Animals; D015925:Cryopreservation / Q000379:methods / Q000662:veterinary*; D004622:Embryo, Mammalian; D005260:Female; D051379:Mice / Q000196:embryology*; D018570:Risk Assessment