Fertilization and cleavage of mouse oocytes exposed to the conditions of human oocyte retrieval for in vitro fertilization*

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AbstractOva from two strains of mice (a hybrid-inbred strain, B6D2F1, and a random-bred strain, CD1) were shocked by exposure to environmental conditions possibly encountered by human oocytes retrieved for in vitro fertilization (IVF). Shocked and control mouse ova were fertilized in vitro in either simple or complex media and zygote development to morulae and blastocyst stages compared with that of zygotes fertilized in vivo. Development of the hybrid-inbred zygotes following fertilization in the simple media of shocked and control ova was essentially the same as for ova fertilized in vivo (84 ± 6.6, 89 ± 1.6, 87 ± 6.0% to the 2-cell stage and 89 ± 5.2, 94 ± 2.3, 99 ± 1.0% of two cells to blastocysts, respectively); development in the complex media also was the same following fertilization of shocked and control ova (80 ± 8.7, 90 ± 2.7% to two cells and 33 ± 3.5, 35 ± 4.5% of two cells to blastocysts, respectively) but lower than that of in vivo zygotes (92 ± 4.6 to two cells, 58± 4.7 two cells to blastocysts). In contrast, the fertilization and development in the simple media of shocked and control random-bred ova was lower and more variable (90 ± 5.8, 67 ± 11.1% to two cells and 17 ± 8.3, 42 ± 13.6% two cells to blastocysts, respectively) than the development of in vivo zygotes (96 ± 1.5% to two cells, 51 ± 5.5 two cells to blastocysts). Thus, in these studies, fertilization and development of ovulated mouse ova were more dependent on the strain of mouse and the culture media conditions than on transient environmental shocks encountered before fertilization.