Sheep trophoblast in monolayer cell culture

Methods are described for the preparation and maintenance of ovine trophoblast in monolayer cell culture, and for the preparation of cultured cells for ultrastructural examination. Monolayers grown from dispersed and explanted primary cultures were maintained in consecutive subcultures for periods of 12 to 16 weeks. Towards the end of the first week of incubation ovine placental lactogen could be detected in the culture medium: it rose to relatively high concentrations as the cultures developed. In the second week of incubation small binucleate cells were seen in cultures prepared for electron microscopy. By the 14th day larger binucleate cells were visible at the outer edges of the developing monolayer, and by the third to fourth week 35 to 40 per cent of the cells in culture were in binucleate form. Mature binucleate cells seeded in primary dispersed cultures did not survive beyond the 14th day. The results suggest that (a) the binucleate cells which first appear in monolayers of cultured trophoblast during the second week of incubation are formed by nuclear division of uninucleate cells and not from mature binucleate cells seeded in primary dispersed cultures; and (b) there may be a correlation between the numbers of binucleate cells present in the monolayer and the rate of production of ovine placental lactogen. Monolayer cultures of sheep trophoblast may well provide a useful and relatively inexpensive experimental system for the study of binucleate cells and the mechanisms of placental hormone production.