Ovarian steroid hormones differentially regulate thrombospondin-1 expression in cultured endometrial stromal cells: implications for endometriosis

Thrombospondin-1 messenger RNA and protein levels in cultured human endometrial stromal cells (ESCs) treated with 17-β estradiol (10 nM) were reduced by 47.6% (±6.5% SD; P < 0.05) and 49.0% (±8.6%; P < 0.05) compared with untreated cells, whereas thrombospondin-1mRNA and protein levels in ESCs treated with progesterone (10 μM) were 2.1-fold (±0.4 SD; P < 0.05) and 2.3-fold (±0.6; P < 0.05) higher than those in untreated cells. These findings not only provide evidence for the estrogen dependence of endometriosis, but also partly explain the mechanisms by which progestins exert their therapeutic activities in endometriosis.