Hormonal regulation of human endometrial stromal cells in culture: an in vitro model for decidualization

Stromal cells derived from proliferative or secretory human endometria, cultured in the absence of steroid hormones, grew as monolayers that showed only occasional areas of immunoreactive fibronectin and did not produce detectable levels of prolactin (PRL) or laminin. Treatment with physiological doses of estradiol and progesterone induced PRL production and stimulated cell proliferation, resulting in multilayering with an increase of the saturation density. Electron microscopy showed the development of gap junctions, whereas immunofluorescence revealed a dense pericellular matrix containing fibronectin and laminin. These findings show that human endometrial stromal cells in culture respond to physiological doses of ovarian hormones with ultrastructural, proliferative, and biochemical changes that are characteristic of decidualization in vivo. This culture system thus provides an in vitro model for human decidualization.