PREIMPLANTATION DEVELOPMENT OF MOUSE AND HUMAN EMBRYOS BIOPSIED AT CLEAVAGE STAGES USING A MODIFIED DISPLACEMENT TECHNIQUE

A modified embryo biopsy method was tested on four- and eight-cell sta ge mouse embryos and used on human embryos to obtain blastomeres for p reimplantation genetic diagnosis. The biopsy method tested combines zo na drilling and fluid displacement to force one or two cells through a n opening in the zona pellucida of the cleavage-stage embryo. Rates of cell division and the percentage of mouse embryos forming blastocysts following biopsy at the eight-cell stage were not significantly diffe rent from those observed in unoperated control embryos. The percentage blastocyst formation was not significantly different in embryos biops ied at the four-cell stage and in control embryos, although cell divis ion was significantly retarded following biopsy. 96% of the mouse blas tomeres isolated at the eight-cell stage were recovered intact and 96% of those plated in culture underwent cell division. Survival and divi sion of cells isolated at the four-cell stage were 92 and 84% respecti vely Most of the cultured blastomeres cleaved several times and formed small trophoblast vesicles. Chromosomes were observed in 59% of blast omeres incubated in the presence of colcemid. In the initial use of th is biopsy technique for human preimplantation genetic diagnosis, blast ocyst formation was observed in 9 of 13 human embryos biopsied at the 7- to 10-cell stage. These findings support the use of this biopsy met hod as an alternative to aspiration techniques.