In-vitro studies on ‘spare’ human preimplantation embryos in culture

Abstract

Methods previously used for the biopsy of preimplantation mouse embryos have been applied to individual 'spare' human embryos. Early cleavage-stage human embryos have been cultured and individual blastomeres removed following zonae thinning or drilling. Embryos have also been cultured to the blastocyst stage for the biopsy of three to five trophectoderm cells. Both the biopsied embryo and the biopsied cells have been allowed to develop and/or grow in vitro.

The unknown human trophectoderm: implication for biopsy at the blastocyst stage

“…In both human and animal models, the biological effects of TE biopsy are limited to the observation of simplistic parameters like blastocoel re-expansion, hatching from the zona pellucida, and embryo survival which are apparently reassuring [130][131][132][133][134][135][136][137][138]. However, these parameters may not be fully informative regarding the biological status of the embryo, as is the case of "assisted" hatching which does not necessarily reflect the capacity of the embryo to hatch spontaneously if left untouched and can artificially rescue embryos otherwise not developing [80,139].…”

Biopsy of Gametes and Preimplantation Embryos in Genetic Diagnosis

“…Trophectoderm biopsy at the blastocyst stage has been investigated in mice, primates, and humans (Table 4). [35][36][37][38][39][40][41][42][43] Viable mice and monkeys have been delivered after trophectoderm biopsy. [35][36][37][38][39] A herniation method has been described by several investigators.…”

“…22,43 Aspiration through an intact zona is difficult at the blastocyst stage, and acid Tyrode's is necessary to facilitate the stitching movements of the microneedle. 43 Aspiration and stitch and pull are advantaged by there being no need to wait for herniation of trophectoderm cells. The argument is that the additional culture time of 12 to 24 hours waiting for herniation leaves less time for analytic procedures.…”

“…11 In summary, it appears that biopsy techniques in both 4-to 8-cell stage embryos and in blastocysts are possible and probably sufficiently safe for investigation in humans. [1][2][3]22,33,[41][42][43][44][45] Sufficient cells can be acquired from 8-cell mouse embryos (1-2 cells) and from blastocysts (10-30 cells) to permit genetic diagnosis by molecular methods. For reasons to be discussed, biopsy methods delivering greater numbers of cells are preferable from the laboratory standpoint and should give the most reliable results.…”