Relationship between timing of development, morula morphology, and cell allocation to inner cell mass and trophectoderm in in vitro‐produced bovine embryos

Abstract

Noninvasive measurements of bovine embryo quality, such as timing of cleavage, morula morphology, blastocyst formation, and hatching ability, were linked with the number of inner cell mass (ICM) cells and trophectoderm (TE) cells of the resulting embryos. First, it was confirmed that fast-cleaving embryos proved to have significantly higher chances to reach advanced developmental stages vs. intermediate and slow cleavers (P = 0.01). They also showed significantly less fragmentation at the morula stage, implying the presence of more excellent morulae among fast-cleaving embryos (P < 0.05). Second, the quality of hatched blastocysts, resulting from morulae of different morphological grades, was examined by differential staining. The total cell and ICM cell numbers were significantly lower for hatched blastocysts developed from poor morulae compared to hatched blastocysts developed from excellent, good, or fair morulae. However, hatched blastocysts with < 10 ICM cells were seen in embryos belonging to all four morphological scores. Finally, it was found that timing of first cleavage was not significantly correlated with timing of blastocyst formation or with cell number of blastocysts. Timing of blastocyst formation, however, was significantly correlated with cell number: day 8 blastocysts had significantly lower total cell and ICM cell numbers than day 6 and day 7 blastocysts (P < 0.001). These results suggest that the quality of in vitro-produced bovine embryos is very variable and cannot be linked with a single criterion such as embryo morphology and/or hatching ability. Timing of blastocyst formation was the most valuable criterion with regard to embryonic differentiation.

Cell Cycle Duration at the Time of Maternal Zygotic Transition for In Vitro Produced Bovine Embryos: Effect of Oxygen Tension and Transcription Inhibition1

“…But here, only blastocysts were analyzed and there was no correlation between fourth cell-cycle duration and the timing of first cleavage. However, embryos with a short fourth cell cycle had a better blastocyst rate as the fast-cleaving embryos reported with coculture [47]. But blastocysts emerging from embryos with a short fourth cell cycle did not have a higher number of cells.…”

In Vitro Embryo Production Efficiency in Cattle and Its Association with Oocyte Adenosine Triphosphate Content, Quantity of Mitochondrial DNA, and Mitochondrial DNA Haplogroup

“…Further statistical analysis showed that animals in H-235 had a higher blastocyst rate at Days 6 and 7 (P Ͻ 0.05, no difference detected at Day 8) than animals in H-146, indicating a difference in kinetics of blastocyst formation. This suggests the existence of differences in embryo quality between the two haplogroups, as early blastocyst formation is a sign of embryo quality [35]. However, we cannot confirm this observation because blastocyst quality was not evaluated.…”

Activation with Ionomycin followed by Dehydroleucodine and Cytochalasin B for the Production of Parthenogenetic and Cloned Bovine Embryos

“…to the blastocyst stage than 5 mM DhL. Total blastocyst cell numbers did not differ significantly between DhL and control groups, indicating equivalent embryo quality according to this parameter (Van Soom et al, 1997). Independently of the embryo production system employed, blastocysts cell numbers were low.…”