Sterylsulfatase activity of human term placental cells in monolayer culture: Increase in XX but not in XY cells

Abstract

Term placental trophoblast cells, released by trypsin digestion of human placental villi and purified on a Percoll gradient, were maintained in serumcontaining medium up to 150 hours. The mononucleated cytotrophoblast-like cells at the start of culture differentiate within 90 hours in culture to multinucleated, syncytiotrophoblast-like cells. To determine the changes in enzyme activities that occur during this process of differentiation in vitro, we have measured the time course of specific activity of sterylsulfatase in comparison to alkaline phosphatase activity. The alkaline phosphatase activity, very low in the freshly isolated attached cells compared to placental tissue (about 5%), increased in all preparations about 2–4-fold within 90 hours in culture in parallel with syncytia formation. In contrast, the sterylsulfatase activity, similarly low (about 17%) in the mononucleated cells, increased 2–3 fold in female, but not in male cell preparations during cultivation. We conclude that placental trophoblast cells in primary culture show a sexspecific regulation of sterylsulfatase activity, perhaps as an unique feature of the sterylsulfatase gene, which is localized on the X-chromosome. Furthermore, the system described in this paper may offer a new possibility to study the inactivation/activation mechanism of a X-chromosome linked gene.