Submitted to: Biology of Reproduction
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/21/1999
Publication Date: N/A
Citation: Interpretive Summary: Two important component cell types of the early cow embryo, before and after implantation in the cow's uterus, are the trophectoderm and endoderm. Trophectoderm and endoderm do not contribute to the developing fetus, but, instead, are of central importance in forming the placenta which supports the growth of the fetus. The growth of trophectoderm and endoderm outside of the cow, that is, in the laboratory as in vitro or "in glass" cultures, has not been possible. The ability to grow trophectoderm and endoderm outside of the cow is important so that the biology of these two cell types can be studied under controlled and simplified conditions. Cell lines of bovine trophectoderm and endoderm were established in culture from early bovine embryos. The cell lines provide in vitro models which closely mimic the natural, in cow, form and function of these two cell types. The results are important for studies aimed at understanding how to improve pregnancy rates and fetal survival rates in cattle.
Technical Abstract: Continuous cultures of bovine trophectoderm (CT-1 and CT-5) and bovine endoderm (CE-1 and CE-2) were initiated and maintained on STO feeder cells. CT-1 and CT-5 were derived from the culture of intact 10-11 day in vitro produced blastocysts. CE-1 and CE-2 were derived from the culture of immunodissected inner cell masses of 7-8 day in vitro produced blastocysts. .The cultures were routinely passaged by physical dissociation. Although morphologically distinct, the trophectoderm and endoderm both grew as cell sheets of polarized epithelium (dome-formations) composed of approximately cuboidal cells. Both cell types, particularly the endoderm, grew on top of the feeder cells for the most part. Trophectoderm culture grew faster, relative to endoderm, in large, rapidly extending colonies of initially flat cells with little or no visible lipid. The endoderm, in contrast, grew more slowly as tightly knit colonies with numerous lipid vacuoles in the cells at the colony centers. Ultrastructure analysis revealed both cells types were connected by desmosomes and tight junctional areas although these were more extensive in the trophectoderm. Endoderm was particularly rich in rough endoplasmic reticulum and Golgi apparatus indicative of cells engaged in high protein production and secretion. Interferon-tau expression specific to trophectoderm cultures was demonstrated by Northern blot, RT-PCR, Western blot and anti-viral activity, and this property may act as a marker for this cell type. Serum protein production specific to endoderm cultures was demonstrated by Western blot and this attribute may be a useful marker for this cell type.