Epidermal growth factor and its receptor in human implantation trophoblast: immunohistochemical evidence for autocrine/paracrine function.

Epidermal growth factor (EGF) and its receptor (EGF-R) were immunohistochemically localized in trophoblast during human implantation from intrauterine and ectopic pregnancies. EGF immunostaining was absent to light in the cytotrophoblast (CT), light to moderate in intermediate trophoblast (IT), and intense in the syncytiotrophoblast (ST). In ST, EGF immunostaining was found mostly in the cytoplasm; however, staining of the plasma membrane was also noted. Immunostaining for the EGF-R was absent to light in the CT and moderate to intense in the IT. Immunostaining for the EGF-R was intense in the ST, with moderate staining in the cytoplasm and intense staining in the plasma membrane. Staining was most intense on the microvilli of the ST. Additionally, EGF-R immunostaining could be demonstrated on nuclear membranes. The increase in the intensity of the immunostaining for both EGF and EGF-R noted in CT, IT, and ST suggests a differentiated expression of this receptor-ligand system in human trophoblast and provides evidence for an autocrine/paracrine role for EGF in trophoblast function. The presence of this receptor-ligand system during early human implantation strongly supports a role for EGF and the EGF-R in embryo-uterine signalling and the implantation process.