Early-onset preeclampsia (PE) is a pregnancy complication that can lead to severe adverse maternal and fetal outcomes. However, the mechanisms underlying the development of early-onset PE are not fully understood. Ribosomal protein L39 (RPL39) is a member of the S39E family of ribosomal proteins that plays an important role in stem cell self-renewal, cancer metastasis, and chemoresistance. In this study, we aimed to explore the potential function of RPL39 in placental trophoblast cells. We analyzed the expression of RPL39 in early-onset PE and normal placental tissues using real-time PCR, western blot analysis, and immunohistochemistry. The results showed that RPL39 was markedly downregulated in early-onset PE placental tissues. RPL39 knockdown inhibited trophoblast cell proliferation, migration, and invasion, as well as placental explant outgrowth. Flow cytometry analysis suggested that knockdown of RPL39 resulted in cell cycle arrest at the G0/G1 phase, but had no significant effect on cell apoptosis. We also found that RPL39 knockdown could alter cell morphology. We then measured the expression of the epithelial cell marker E-cadherin following knockdown of RPL39 in Bewo and HTR8/SVneo cells. RPL39 knockdown increased the expression of E-cadherin. Furthermore, E-cadherin expression was upregulated in placental explant outgrowth tissues transfected with RPL39 small interfering RNA. In conclusion, RPL39 plays an essential role in proliferation, invasion, and migration of trophoblast cells by targeting E-cadherin. Our findings provide novel insight into the mechanisms underlying the occurrence of early-onset PE.

Background: Pre-eclampsia (PE) is a major cause of maternal and neonatal mortality and morbidity. Abnormal invasion of trophoblast cells is a major pathogenesis observed in PE. In the present study, we aimed to explore the association between forkhead box A1 (FOXA1) and early-onset pre-eclampsia (EOPE) and to determine the effects of FOXA1 on trophoblast cell apoptosis, migration and invasion. Methods: Clinical data and placentas of patients with EOPE and normal pregnant women were collected in the First Affiliated Hospital of Hainan Medical College. The protein expression levels of FOXA1 in the clinical samples were evaluated by western blotting and immunohistochemistry. The effects of FOXA1 knockdown on HTR-8/SVneo cell apoptosis, migration and invasion were evaluated by flow cytometry, wound healing and transwell invasion assays, respectively. Results: The western blot and immunohistochemical analysis showed that FOXA1 protein expression in placenta of EOPE group was significantly lower than that of normal group. The expression of FOXA1 in the placentas of EOPE and normal pregnant women was negatively correlated with systolic pressure and diastolic pressure. The expression of FOXA1 in EOPE and normal pregnant women was positively correlated with gestation weeks at delivery and neonatal birthweight. In vitro functional studies showed that silencing FOXA1 increased apoptosis, and inhibited the migration and invasion of HTR-8/ SVneo cells. Conclusions: Down-regulation of FOXA1 in the placentas may indicate poor prognosis of EOPE. Silencing of FOXA1 induced apoptosis in trophoblast cells, and impaired the migratory and invasive capacity of trophoblast cells. FOXA1 may represent a potential therapeutic target for EOPE. Juan Zhu and Yunjian Wei equally contributed to this work.