Developmental changes in the incidence of chromosome anomalies of bovine embryos fertilized in vitro

Abstract

In total, 196 two- to 32-cell bovine embryo and 104 blastocysts were obtained by the in vitro fertilization of follicular oocytes matured in vitro, and 15 blastocysts fertilized in vivo were used. Chromosomal anomalies in these embryos and the inner cell mass (ICM) separated immunologically were investigated. Chromosomal anomalies were observed in 12.1% (5/41) of 2-cell embryos, 20.0-36.4% of 4- to 16-cell embryos, 7.1% (1/14) of 17- to 32-cell embryos, 44.2% (15/34) of blastocysts, and 18.6% (13/70) of ICM cells derived from in vitro fertilization. These anomalies were mainly 3N and 4N at 2-cell stage, 1N and 1N/2N at 4- to 32-cell stages, and 2N/4N in blastocysts and in their ICM cells. Chromosomal anomalies of blastocysts from in vivo fertilization and their ICM were observed in 20.0% (1/5) of blastocysts and 33.3% (3/9) of ICM cells and these compositions were mainly 2N/4N. These results indicate that the abnormalities at early and blastocyst stages of embryos derived from in vitro fertilization were caused by abnormal fertilization in vitro and abnormal cleavage, respectively. Furthermore, a definite location of the chromosomal anomalies was observed in the trophectoderm of blastocysts derived from in vitro fertilization.

Transition of Cell Numbers in Bovine Preimplantation Embryos: In Vivo Collected and In Vitro Produced Embryos

“…It is also known that the inner cell mass/trophectoderm (ICM/TE) ratio after blastocyst formation is about 25% [15,29] and that this ratio is maintained until they had become 10 d embryos that have at least 1000 cells [34]. Taken together, these results suggest that there is no difference in the segmental speed between the ICM and TE.…”

“…We also know that the developmental speed of bovine preimplantation embryos changes during periods of early cleavage stages, such as pronuclear formation in the first CD and genomic shift from the maternal to embryonic genome in the 3-4th CD [10,11,27,28], and during periods of morphological change, such as compact formation and hatching from zona pellucidae [10,27,29]. Characteristic changes in cell division, such as chromosomal abnormalities [29][30][31] and a difference in the developmental process because of the sex of embryos [32,33], were also found after blastocyst formation. Using VIVO embryos collected from superovulated donors, we previously observed developmentally retarded embryos and embryos with degenerated blastomeres, as described in other similar reports [20][21][22].…”

Effect of Administration with Low-dose FSH to Recipient Cows on Embryonic Survival after Bilateral Nonsurgical Embryo Transfer.

“…In general, early embryonic loss could result from chromosomal abnormalities. However, the proportions of these abnormalities appeared to be much less than the early embryonic loss rate [36,37], even in the case of in vitro-produced embryos [38]. It is further concluded that chromosomal abnormalities do not explain the high rate of early embryonic loss.…”

In-Vitro Development of Aggregates of Bovine Inner Cell Mass Cells or Bovine Mammary Cells and Putative Tetraploid Embryos Produced by Electrofusion.

“…F 1 (Japanese Black Cattle breed × Holstein breed) oocytes which were matured in vitro in TCM199 supplemented with 5% fetal bovine serum (FBS) were used for in-vitro fertilization with frozenthawed sperm of Japanese Black Cattle as described previously [9]. Then the embryos were cultured in a drop of CR1aa supplemented with 5% FBS under mineral oil (Squibb, USA) at 38.5 C, 3% CO 2 in air.…”