Ultrastructure of bovine embryos developed from in vitro-matured and -fertilized oocytes: comparative morphological evaluation of embryos cultured either in serum-free medium or in serum-supplemented medium.
The ultrastructure of bovine embryos developed from in vitro-matured and -fertilized oocytes, cocultured with bovine cumulus/granulosa cells either in a serum-free medium (IVMD101) or in a serum-containing medium (TCM199+CS) was compared. Embryos up to the eight-cell stage had many cellular organelles and cytoplasmic components that were randomly distributed in the cytoplasm. Mitochondria were spherical or ovoid and had only a few peripheral cristae. There were no obvious differences in the ultrastructure between embryos developed in IVMD101 and TCM199+CS up to the eight-cell stage. However, conspicuous differences in the ultrastructural features between the embryos cultured in IVMD101 and TCM199+CS were observed at the morula and blastocyst stages. At the morula stage, embryos cultured in IVMD101 had cells containing elongated mitochondria, well-developed Golgi apparatus, lipid droplets, and large vesicles resembling lysosomes. The lysosome-like vesicles were partially filled with electron-dense materials and were frequently fused with lipid droplets. The blastomeres of morulae cultured in TCM199+CS contained numerous large lipid droplets and fewer lysosome-like vesicles than those cultured in IVMD101. In blastocysts cultured in IVMD101, lysosome-like vesicles were frequently observed in the trophoblast cells and lipid droplets were present in the cytoplasm of trophoblast and inner cell mass (ICM)-cells, but they were not abundant. On the other hand, the blastocysts developed in TCM199+CS contained fewer lysosome-like vesicles and large numbers of lipid droplets. This accumulation of lipid droplets was higher in the trophoblast cells than in the ICM-cells. This study showed major differences in the ultrastructural features between the morulae and blastocysts from serum-free and serum-supplemented cultures, suggesting that the ultrastructural differences may reflect physiological characteristics of embryos.
Abe
H
H
Research Institute for the Functional Peptides, Yamagata, Japan. abeh@po.iijnet.or.jp
Yamashita
S
S
Itoh
T
T
Satoh
T
T
Hoshi
H
H
D000818:Animals; D001755:Blastocyst / Q000648:ultrastructure; D002417:Cattle; D003470:Culture Media; D016895:Culture Media, Serum-Free; D005314:Embryonic and Fetal Development; D005260:Female; D005307:Fertilization in Vitro; D008297:Male; D009028:Morula / Q000648:ultrastructure; D009865:Oocytes / Q000648:ultrastructure*; D015053:Zygote / Q000648:ultrastructure*
D003470:Culture Media; D016895:Culture Media, Serum-Free