IMMUNOCYTOCHEMICAL IDENTIFICATION OF THE ESTROGEN-RECEPTOR IN THE NUCLEI OF CULTURED HUMAN PLACENTAL SYNCYTIOTROPHOBLASTS

We have shown that oestrogen has a central integrative role in regulat ing key components of the progesterone biosynthetic and corticosteroid metabolic pathways within syncytiotrophoblasts that govern placental function and maturation of the fetal pituitary-adrenocortical axis. St udies utilizing classic binding procedures and RNAse protection have d emonstrated that human placental villous tissue exhibits specific high affinity oestrogen binding and expresses the mRNA for the oestrogen r eceptor. However, it is not known whether the oestrogen receptor is ex pressed specifically in syncytiotrophoblasts. Therefore, the present s tudy determined whether the oestrogen receptor protein was detectable by immunocytochemistry in cultured human syncytiotrophoblast maintaine d in a low oestrogen/progestin environment. Cytotrophoblasts were isol ated from human term placentae by trypsin dispersion and Percoll gradi ent centrifugation and cultured for 5, 7 or 10 days. Incubation of syn cytiotrophoblast with 5-10 mu g/ml of the anti-oestrogen receptor rat monoclonal antibody D-75, which is specific for the primate oestrogen receptor, resulted in identification of the oestrogen receptor in the nuclei of these cells. In contrast, there was no reactivity of the tro phoblasts to either rat IgG or an irrelevant rat monoclonal antibody I gG2a against mouse common leukocyte antigen T200. Collectively, these findings indicate that oestrogen receptor is expressed in the nuclei o f human placental syncytiotrophoblasts and support the suggestion that the syncytiotrophoblast is an oestrogen-responsive tissue. (C) 1997 W . B. Saunders Company Ltd.