Epidermal Growth Factor and Sex Steroids Dynamically Regulate a Marker of Endometrial Receptivity in Ishikawa Cells1

The factors regulating human endometrial receptivity remain poorly understood. The alpha v beta 3 integrin cell adhesion molecule appears to be regulated in the human endometrium, appearing on postovulatory days 5-6, corresponding to the time of initial embryo attachment. This integrin has been extensively studied as a potential marker of endometrial receptivity and is aberrantly expressed in the endometrial epithelium of some infertile women. Ishikawa cells are a well differentiated endometrial adenocarcinoma cell line that maintain functional estrogen and progesterone receptors and are a useful model to study steroid-mediated events in human endometrial epithelium. This cell line expresses most of the normal endometrial epithelial integrins, including the alpha v beta 3 vitronectin receptor. The regulation of this integrin was studied with fluorescence immunocytochemistry, flow cytometry, and Northern blot analysis. Estrogen with or without progesterone treatment down-regulates alpha v beta 3 in this cell line. Several growth factors, including epidermal growth factor and the closely related transforming growth factor-alpha significantly increase the expression of this integrin. We conclude that endometrial differentiation is influenced by both steroid hormones and growth factors. The alpha v beta 3 integrin appears to be an excellent marker to study the molecular events leading to the establishment of uterine receptivity and successful implantation.