The Autophagy-Lysosomal Machinery Enhances Cytotrophoblast–Syncytiotrophoblast Fusion Process

Poor placentation is closely related with the etiology of preeclampsia and may impact fetal growth restriction. For placental developmental growth, we have demonstrated that dysregulation of autophagy, a key mechanism to maintain cellular homeostasis, in trophoblasts contributes to the pathophysiology of preeclampsia, a severe pregnancy complication, associated with poor placentation. It remains, however, unknown whether autophagy inhibition affects trophoblast syncytialization. This study evaluated the effect of autophagy in an in vitro syncytialization method using BeWo cells and primary human trophoblasts (PHT). In this study, we observed that autophagic activity decreased in PHT and BeWo cells during syncytialization. This decreased activity was accompanied by downregulation of the transcription factor, TFEB. Next, bafilomycin A1, an inhibitor of autophagy via suppressing V-ATPase in lysosomes, inhibited hCG production, CYP11A1 expression (a marker of differentiation), p21 expression (a senescence marker), and cell fusion in BeWo cells and PHT cells. Finally, LLOMe, an agent inducing lysosomal damage, also inhibited syncytialization and led to TFEB downregulation. Taken together, the autophagy-lysosomal machinery plays an important role in cytotrophoblast fusion, resulting in syncytiotrophoblasts. As autophagy inhibition contributed to the failure of differentiation in cytotrophoblasts, this may result in the poor placentation observed in preeclampsia.