Thrombin impairs human endometrial endothelial angiogenesis; implications for progestin-only contraceptive-induced abnormal uterine bleeding.

Abstract Objective Progestin-only contraceptives induce abnormal uterine bleeding, accompanied by prothrombin leakage from dilated endometrial microvessels and increased thrombin generation by human endometrial stromal cell (HESC)-expressed tissue factor. Initial studies of the thrombin-treated HESC secretome identified elevated levels of cleaved chondroitin sulfate proteoglycan 4 (CSPG4), impairing pericyte–endothelial interactions. Thus, we investigated direct and CSPG4-mediated effects of thrombin in eliciting abnormal uterine bleeding by disrupting endometrial angiogenesis. Study design Liquid chromatography/tandem mass spectrometry, enzyme-linked immunosorbent assay (ELISA) and quantitative real-time-polymerase chain reaction (PCR) evaluated conditioned medium supernatant and cell lysates from control versus thrombin-treated HESCs. Pre- and post-Depo medroxyprogesterone acetate (DMPA)-administered endometria were immunostained for CSPG4. Proliferation, apoptosis and tube formation were assessed in human endometrial endothelial cells (HEECs) incubated with recombinant human (rh)-CSPG4 or thrombin or both. Results Thrombin induced CSPG4 protein expression in cultured HESCs as detected by mass spectrometry and ELISA (p 02, n =3). Compared to pre-DMPA endometria ( n =5), stromal cells in post-DMPA endometria ( n =5) displayed stronger CSPG4 immunostaining. In HEEC cultures ( n =3), total tube-formed mesh area was significantly higher in rh-CSPG4 versus control (p 05). However, thrombin disrupted HEEC tube formation by a concentration- and time-dependent reduction of angiogenic parameters (p 05), whereas CSPG4 co-treatment did not reverse these thrombin-mediated effects. Conclusion These results suggest that disruption of HEEC tube formation by thrombin induces aberrant angiogenesis and abnormal uterine bleeding in DMPA users. Implications Mass spectrometry analysis identified several HESC-secreted proteins regulated by thrombin. Therapeutic agents blocking angiogenic effects of thrombin in HESCs can prevent or minimize progestin-only contraceptive-induced abnormal uterine bleeding.