Todorow S J, Siebzehnrübl E R, Koch R, Wildt L, Lang N
Unit of Reproductive Medicine, University Hospital of Obstetrics and Gynaecology, Friedrich-Alexander University Erlangen, FRG.
Hum Reprod. 1989 Oct;4(7):805-11. doi: 10.1093/oxfordjournals.humrep.a136990.
The achievement of successful pregnancies and births after in-vitro fertilization and embryo transfer of frozen-thawed human oocytes has stimulated further work on improving the established methodology. The present investigation was conducted on 1837 mouse oocytes, 1785 mouse pronuclear stage embryos, 1400 hamster oocytes and 1024 hamster pronuclear-stage embryos. In an effort to study the advantages and disadvantages of a newly introduced, 1,2-propanediol (1,2-PROH)-based system over the conventionally used dimethylsulphoxide (DMSO)-based methodology, a direct, prospective comparison between the two cryoprotectants was undertaken in a randomized trial. The combination of 1,2-PROH and DMSO potentiates their cryoprotective effect on mouse and hamster eggs. 1,2-PROH seems to improve cryopreservation in the animal system, though not significantly. Four different protocols were used to evaluate the effects of two changing experimental parameters. These were, firstly, the intermediary temperature attained before placing the cells into liquid nitrogen and, secondly, the modification of the method of adding and removing the cryoprotectant. The morphological survival rate, fertilization rate and developmental rate were significantly better in the low intermediary temperature compared with the high intermediary temperature system of cryopreservation. In addition, the rate of zona pellucida breakdown diminishes considerably in the former compared with the latter system. The 'rapid' sucrose method of cryoprotectant equilibrium and removal showed, in most groups, results which were lower than, or equal to, the traditionally used 'multiple-step', 'slow' method.
