Viability of primary term cytotrophoblast cell culture in normoxia and hypoxia.

Cytotrophoblast (CT) cells isolated and purified from term placenta are able to differentiate into syncytiotrophoblast cells. Previous reports suggested that hypoxia is an inhibitor of this differentiation and also increases apoptosis. As visual observations of our CT cell cultures indicated a better development in hypoxia than in normoxia (defined as 2.5 and 21% O(2), respectively), we decided to assess the effect of low oxygen tension on in vitro CT cell differentiation by measuring cell viability, apoptosis and CT cell fusion and differentiation. We observed a 45% decrease in cell viability 24 h after plating both in normoxia and in hypoxia but no difference between the two oxygen conditions. Cell viability remained stable during the 4-day culture. Apoptosis also did not increase in hypoxia. Apoptotic index and caspase activation were even lower in hypoxia than in normoxia at Day 1 and Day 4 of the culture. Finally, we observed a 5-fold and 6-fold increase in Syncytin-1 mRNA expression in normoxia and in hypoxia, respectively, indicating that hypoxia did not inhibit CT cell fusion. CT cells differentiated as well in hypoxia as an increase in inhibin α subunit mRNA was evidenced during the 4-day culture. This increase was even higher in hypoxia than in normoxia. In conclusion, hypoxia defined as 2.5% O(2) based on first trimester placental pO(2) did not decrease term primary CT cell viability and did not increase apoptosis. Moreover, it did not inhibit either CT cell fusion or differentiation.