The effect of biopsy during precompacted morula stage on post vitrification development of blastocyst derived bovine embryos

چکیده مقاله

Abstract
Improvements on embryo micromanipulation techniques led to the use of
embryo biopsy in commercial embryo transfer programs for genetic analysis
of preimplantation bovine embryos. The aim of this study was to evaluate the
quality of bovine blastocyst derived from embryos biopsied at different precompacted
morulae stages by assessment of cryosurvivability of the resulting
blastocysts. The in vitro produced bovine embryos were subjected to biopsy at
days 2, 3, and 4 post-insemination with different cell numbers (4 to 16-cells).
Embryo cell biopsy was carried out in a 100 μl drop of H-SOF following
pronase drilling by aspiration of one blastomere. The biopsied embryos were
then cultured in SOFaaBSA co-cultured with oviduct cells-monolayer until
blastocyst formation. The blastocysts were cryopreserved at room temperature
after exposure of equilibration (glycerol 1.4 M for 5 min and then glycerol
1.4 M and ethylene glycol 3.6 M for 5 min) and vitrification solutions (3.4 M
glycerol and 4.6 M ethylene glycol). The blastocysts were loaded into the
center of 0.25 ml straws separated by air bubbles from 2 columns of sucrose
0.5 M and plunged immediately into liquid nitrogen. There was no significant
difference in cryosurvivability of vitrified-warmed blastocysts derived form
biopsied embryos at different pre-compacted morula stages. The quality of
biopsy derived blastocysts was identical to that of non-biopsy derived ones in
terms of post vitrifcation survival and hatching rates. In conclusion there was
no preference between different times of embryo biopsy at precompacted
morula stages in term of cryosurvivability of biopsy derived bovine blastocysts.