Vitrification of bovine IVF blastocysts in an ethylene glycol/sucrose solution and heat-stable plant-extracted proteins.
The use of heat-stable plant proteins in an ethylene glycol-based solution for the vitrification of in vitro-derived embryos was examined. Day 7, 8 and 9 bovine in vitro matured, fertilized and cultured (IVMFC), full and expanded blastocysts were vitrified in solutions composed of 40% ethylene glycol (EG) plus 0.3 M sucrose supplemented with 20% Ficoll and 0.3% BSA (VF-1), 25 mg/ml heat-stable plant proteins (HSPP; VF-2), or with no supplement (VF-3). In Experiment 1, embryos were expelled from the straw after thawing, and EG was diluted from embryos with 0.5 M sucrose. There were no differences in post-thaw embryo survival rates or in hatching/hatched rates after 24 h of culture between the VF-1, VF-2 and VF-3 solutions (40.1, 54.1 and 50.8% and 10.7, 16.4 and 17.5%, respectively). Transfer of 12 frozen/thawed embryos to 6 recipients (2 recipients per treatment) resulted in 2 pregnancies from the VF-2 group and 1 pregnancy from the VF-3 group. In Experiment 2, EG was diluted from embryos after thawing within the straw with 0.5 M sucrose. There were no differences in post-thaw survival or hatching/hatched rates after 24 h of culture (19.0, 13.6 and 23.8% and 9.5, 9.0 and 14.4% for VF-1, VF-2 and VF-3, respectively). Transfer of 6 frozen/thawed embryos to 3 recipients (1 recipient per treatment) resulted in no pregnancies. The post-thaw histology of Day 7, 8 and 9 IVMFC blastocysts showed typical ultrastructure with well preserved cell-to-cell contacts. There were no major differences in the fine structure of blastocysts regardless of treatment. The use of HSPP at a concentration of 25 mg/ml in the vitrification medium did not affect the post-thaw embryo survival over that of no protein supplementation. The presence of macro molecules in a 40% EG/sucrose vitrification solution also did not improve post-thaw viability of IVMFC-derived blastocysts.
Palasz
A T
AT
Department of Obstetrics and Gynaecology, Faculty of Veterinary Medicine, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden.
Gustafsson
H
H
Rodriguez-Martinez
H
H
Gusta
L
L
Larsson
B
B
Mapletoft
R J
RJ