Direct effect of gonadotropins on decidualization of human endometrial stromal cells

Decidualization of stromal cells isolated from proliferative human endometrium was achieved by adding to the culture medium human gonadotropins (FSH, FSH + LH, hCG). In addition to changes in the morphology of the stromal cells to the decidual phenotype, decidualization was evident from the expression of prolactin (PRL), demonstrated immunocytochemically, by Western blotting analysis, and by measuring its output into the medium through solid phase enzyme immunoassay. Gonadotropins also induced cAMP formation in the endometrial stromal cells under the same experimental conditions. This finding suggests that the mechanism by which gonadotropins promote decidualization of human endometrial stromal cells in vitro involves the introduction of cAMP, a compound that we have found to elicit the expression of PRL in this system. PRL is likely to be a key intermediate in the process of decidualization since it is by itself capable of inducing differentiation of the endometrial stromal cells to the decidual phenotype. Awareness of direct actions of gonadotropins on the endometrial cells and, in particular, of the decidualizing effects of FSH (Metrodin), FSH + LH (Pergonal) and hCG may contribute to the understanding of physiologic as well as pathophysiologic conditions relevant to endometrial functions and fertility.