Amount of sFlt-1 in the culture supernatant of HUVECs incubated for 4 days with medium containing 30% granulosa cell (GC)-conditioned medium. Addition of GC-conditioned medium leads to a significant inhibition of sFlt-1 production of HUVECs (*). Treatment of granulosa cells with FCS or hCG during conditioning of medium has no influence on this inhibition. Incubation with follicular fluid (FF) of the same patients leads to a significant reduced production of sFlt-1 compared to controls as well as to treatment with GC-conditioned medium (**). p < 0.05.