J. Conaghan et al., CULTURE OF HUMAN PREIMPLANTATION EMBRYOS TO THE BLASTOCYST STAGE - A COMPARISON OF 3 MEDIA, The International journal of developmental biology, 42(7), 1998, pp. 885-893
Following culture for 2 days in Earle's balanced salt solution (EBSS),
human embryos which remained after transfer were cultured in one of 3
media for 4 days, from the 2- to 4-cell stage to the blastocyst stage
. Sibling embryos were divided equally between treatments. Throughout
the 4 day culture period, embryos were assessed for morphology and dev
elopment, as well as uptake and production of energy substrates. Cell
numbers in the inner cell mass and trophectoderm were determined for e
mbryos which reached the blastocyst stage. No significant effect was o
bserved in the extent or rate of development to the 8-cell, morula or
blastocyst stage between treatments. Uptake of pyruvate was related to
concentration in the medium and no differences in glucose uptake were
observed between media. Endogenous energy metabolism, as measured by
lactate production, was significantly higher in Ham's F12 than in EBSS
from day 3.5 onwards. Blastocyst cell numbers were also increased; 79
.6+/-7.7 in Ham's F12 (n=17) and 57.8+/-5.2 in EBSS (n=19), p<0.05. Of
the embryos which reached the blastocyst stage by day 5, 36% (14/25)
had degenerated by day 6 in EBSS compared to only 19% (5/27) in Ham's
F12 (p=0.06). Slightly higher rates of embryo survival between day 5 a
nd 6 in Ham's F12 may account for the observed increase in blastocyst
cell number. The results do not suggest that improved embryo developme
nt can be obtained using human tubal fluid or Ham's F12, in preference
to EBSS during early cleavage stages, but the use of Ham's F12 may im
prove embryo survival at later stages of development.