Sildenafil stimulates human trophoblast invasion through nitric oxide and guanosine 3',5'-cyclic monophosphate signaling.

<bold>Objective: </bold>To determine the effect of sildenafil, a phosphodiesterase type 5 inhibitor, on trophoblast invasiveness.<bold>Design: </bold>Laboratory investigation.<bold>Setting: </bold>Academic medical center.<bold>Patient(s): </bold>Placental tissues discarded after first-trimester terminations were obtained from patients with informed consent.<bold>Intervention(s): </bold>A cell line, HTR-8/SVneo, established from first-trimester cytotrophoblast, and villous explants, was treated with or without sildenafil, guanosine 3',5'-cyclic monophosphate (cGMP) analog, cGMP inhibitor, or L-NAME (N(G)-nitro-L-arginine methyl ester hydrochloride) and cultured on fibronectin or Matrigel. Integrins α6β4 and α1β1 were detected by immunocytochemistry.<bold>Main Outcome Measure(s): </bold>Trophoblast outgrowth from villous tips, cytotrophoblast cell invasion, and integrin immunostaining were assessed in cytotrophoblast and explant cultures.<bold>Result(s): </bold>Integrin expression in trophoblast cells ex vivo switched from α6 to α1, and invasiveness increased, when exposed to sildenafil or cGMP agonist. Either cGMP antagonist or L-NAME blocked integrin switching and invasion induced by sildenafil. Elevation of nitric oxide pharmacologically induced invasion, but not when cGMP antagonist was present.<bold>Conclusion(s): </bold>Sildenafil altered trophoblast phenotype through a process dependent on nitric oxide availability and cGMP accumulation. In addition to its vasoactivity, sildenafil directly stimulates trophoblast extravillous differentiation, which would be favorable for implantation and reduce risk for adverse pregnancy outcomes. [ABSTRACT FROM AUTHOR]