The glucocorticoid receptor is specifically expressed in the stromal compartment of the human endometrium

The human endometrium is a classical target tissue for steroid hormones. Wh ile the expression pattern and functional roles of both the estrogen recept or (ER) and the progesterone, receptor (PR) are well defined, expression of the glucocorticoid. receptor (GR) in this tissue has not been described so far. In the present study, we used immunohistochemistry to analyze the exp ression of GR in the normal human endometrium throughout the menstrual cycl e. The expression of GR was compared to that of ER and PR, which were analy zed in parallel. We show that GR is expressed in the human endometrium with a pattern that markedly differs from the expression patterns of ER and PR. ER and PR are expressed in the nuclei of endometrial glands, whereas GR is completely absent from these structures. However, GR is strongly expressed in the stromal compartment of the endometrium. throughout the cycle. Both stromal fibroblasts and lymphocytes are GR-positive. In addition, GR expres sion is also observed in the endothelium of small endometrial blood vessels , which are ER- and PR-negative, Western blot analysis performed on endomet rial tumor call lines of glandular (HEC-1B) and mesodermal (SKUT-1B) origin , respectively, showed GR expression only in the latter. In summary, we dem onstrate that GR is expressed in fibroblasts, lymphocytes and endothelial c ells of the human endometrial stroma, while it is absent from the glandular compartment. The specific expression pattern of GR within the human endome trium. points to a possible functional role of glucocorticoids in the proce ss of decidualization which occurs primarily in the stromal compartment.