The role of tissue factor in regulating endometrial haemostasis: implications for progestin-only contraception

Abnormal uterine bleeding accounts for the unacceptably high discontinuation rate of progestin-only contraceptives. Previously, we found that in-vivo and in-vitro decidualization of human endometrial stromal cells was associated with elevated concentrations of tissue factor (TF), the primary initiator of haemostasis. Moreover, enhanced TF expression required progesterone receptor (PR) and epidermal growth factor receptor (EGFR) mediation. In the current study, endometrial biopsies were sampled from bleeding (BL) and non-bleeding (NBL) sites under camera-directed hysteroscopic guidance after Depo-provera injections. When compared with control biopsies, immunohistochemical examination revealed that 3 months of Depo-provera contraception reduced TF concentrations at the BL sites. However, there were ample EGFR and PR concentrations at BL and NBL sites. Moreover, there was a trend towards the appearance of pathologically enlarged blood vessels at the BL sites. The use of Western blotting revealed that after 3 months of Depo-provera, concentrations of both PRB and PRA isoforms were lower at BL versus NBL sites with decreased PRA concentrations attaining statistical significance. Separate sampling of endometrial BL and NBL sites as shown here for Depo-provera contraception could prove particularly useful in identifying local factors that determine the onset of bleeding during the more protracted time-course of Norplant contraception.