Sildenafil Effect on Nitric Oxide Secretion by Normal Human Endometrial Epithelial Cells Cultured In vitro

BACKGROUND: Sildenafil is a selective inhibitor of cyclic-guanosine monphosphat-specific phosphodiesterase type 5. It increases intracellular nitric oxide (NO) production in some cells. There are reports on its positive effect on uterine circulation, endometrial thickness, and infertility improvement. Endometrial epithelial cells (EEC) play an important role in embryo attachment and implantation. The present work investigates the effect of sildenafil on human EEC and their NO secretion in vitro. MATERIALS AND METHODS: In this experimental in vitro study, endometrial biopsies (n=10) were washed in a phosphate buffered solution (PBS) and digested with collagenase I (2 mg/ml in DMEM/ F12 medium) at 37°C for 90 minutes. Epithelial glands were collected by sequential filtration through nylon meshes (70 and 40 μm pores), respectively. Epithelial glands were then treated with trypsin to obtain individual cells. The cells were counted and divided into four groups: control and 1, 10, and 20 μM sildenafil concentrations. Cells were cultured for 15 days at 37ºC and 5% CO2; the media were changed every 3 days, and their supernatants were collected for the NO assay. NO was measured by standard Greiss methods. Data were analyzed by one way ANOVA. RESULTS: There was no significant difference between groups in cell count and NO secretion, but the level of NO increased slightly in the experimental groups. The 10 μM dose showed the highest cell count. EEC morphology changed into long spindle cells in the case groups. CONCLUSION: Sildenafil (1, 10, and 20 μM) showed a mild proliferative effect on human EEC numbers, but no significant change was seen in NO production.