High Levels of Activin A Detected in Preeclamptic Placenta Induce Trophoblast Cell Apoptosis by Promoting Nodal Signaling

CONTEXT: The pregnancy-specific disorder preeclampsia is a major cause of maternal mortality and morbidity. Activin A has been suggested as a potential biomarker of the disease, but whether it plays a role in the pathology of preeclampsia or is just a manifestation of the disease is not fully understood. OBJECTIVE: The objective of the study was to examine the roles of Activin A on placental trophoblast cells under pathological conditions of preeclampsia. DESIGN: Placental and plasma productions of Activin A in healthy pregnant women and preeclamptic patients were compared by using clinical samples obtained from Peking University First Hospital during November 2005 to November 2007. The role of Activin A at pathological doses was investigated in human trophoblast cells. RESULTS: Plasma and placental productions of Activin A were significantly higher in preeclamptic patients when compared with normal pregnant subjects in a Chinese Han population. Treatment of trophoblast cells with high doses of Activin A resulted in a significant increase in cell apoptosis. This effect was blocked not only by silencing Activin A's receptor activin receptor-like kinase 4 but also by knockdown of Nodal's receptor ALK7. Important to note was that Activin A could significantly increase Nodal expression in trophoblast cells, and knockdown of Nodal resulted in evident blockage on Activin A-induced trophoblast cell apoptosis. CONCLUSION: High levels of Activin A observed in preeclamptic placenta may play a role in the pathogenesis of preeclampsia by inducing excessive apoptosis in placenta indirectly through enhancing Nodal expression.