Aspirin enhances endometrial decidualization markers in vitro among women with and without endometriosis

Decidualization of human endometrial stromal cells (ESCs) precedes the successful implantation of a human embryo. Improper decidualization has been reported in numerous conditions associated with infertility, including endometriosis. Multiple pathways, including aberrant cyclooxygenase (COX) expression, are associated with improper decidualization in endometriosis. Still, prior studies have not investigated the impact of aspirin (ASA) on ESC decidualization. After pre-treatment with vehicle or ASA (1-2.5 mM), ESCs were treated with 8-bromoadenosine 3',5'-cyclic monophosphate sodium salt (cAMP) or cAMP + medroxyprogesterone acetate (MPA) to stimulate decidualization markers. Insulin-like growth factor-binding protein-1 (IGFBP1) and prolactin (PRL), biomarkers of decidualization, were measured in culture supernatants by ELISA (n = 12). Proliferation assays were performed (n = 10), and cytotoxicity was assessed using neutral red staining (n = 10). Results were converted to fold-change with vehicle-control = 1. The potential mechanism of action was investigated using western blotting for AKT phosphorylation. ASA (1 and 2.5 mM) pre-treatment increased decidualization markers (IGFBP1 and PRL) compared to vehicle treatment by both cAMP- and cAMP + MPA-treated ESCs without inducing significant cytotoxicity. Data suggest that ASA (2.5 mM) inhibits AKT phosphorylation to promote decidualization. While ASA (1 mM) did not significantly affect ESC proliferation, ASA (2.5 mM) significantly reduced proliferation compared to vehicle treatment. For all outcome measures, there were no statistically significant differences in the effects of ASA on ESCs obtained from women with vs without endometriosis.

The human uterus prepares for pregnancy through natural changes to the lining of the uterus. In this process, the cells that line the inside of the uterus change to support implantation of a fertilized egg and growth of an embryo. Infertility and endometriosis, a condition where uterine-like cells grow outside of the uterus (e.g. ovaries, intestines, and other organs in the female pelvis), have been associated with a failure of these natural changes to the lining of the uterus. Prior studies have mostly relied on invasive procedures, such as uterine biopsies, to study these cells. Instead of painful uterine biopsies, we used period blood (or menstrual effluent, which contains shed uterine lining) to isolate and study the cells that line the inside of the uterus. We discovered that aspirin improves the ability of these cells to undergo the natural changes that prepare for pregnancy, without causing harm to the cells. These laboratory-based findings pave the way for future research to study the effects of aspirin on the cells that line the uterus among women with infertility and endometriosis who are taking aspirin.