Bovine blastocyst-derived trophectoderm and endoderm cell cultures: Interferon tau and transferrin expression as respective in vitro markers

Continuous cultures of bovine trophectoderm (CT-1 and CT-5) and bovine endo derm (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- to 11-day in vitro- produced blastocysts. CE-1 and CE-2 were derived from the culture of immuno dissected inner cell masses of 7- to 8-day in vitro-produced blastocysts. T he cultures were routinely passaged by physical dissociation. Although morp hologically distinct, the trophectoderm and endoderm both grew as cell shee ts of polarized epithelium (dome formations) composed of approximately cubo idal cells. Both cell types, particularly the endoderm, grew on top of the feeder cells for the most part. Trophectoderm cultures grew faster, relativ e to endoderm, in large, rapidly extending colonies of initially flat cells with little or no visible lipid. The endoderm, in contrast, grew more slow ly as tightly knit colonies with numerous lipid vacuoles in the cells at th e colony centers. Ultrastructure analysis revealed that both cell types wer e connected by desmosomes and tight junctional areas, although these were m ore extensive in the trophectoderm. Endoderm was particularly rich in rough endoplasmic reticulum and Golgi apparatus indicative of cells engaged in h igh protein production and secretion. Interferon tau expression was specifi c to trophectoderm cultures, as demonstrated by reverse transcription-polym erase chain reaction, Western blot, and antiviral activity; and this proper ty may act as a marker for this cell type. Serum protein production specifi c to endoderm cultures was demonstrated by Western blot; this attribute may be a useful marker for this cell type. This simple coculture method for th e in vitro propagation of bovine trophectoderm and endoderm provides a syst em for assessing their biology in vitro.