Peng_2016_Placenta_46_92

INTRODUCTION: The invasion of extravillous cytotrophoblasts (EVTs) into the maternal uterine decidua and vasculature is critical for human placenta development and pregnancy maintenance. The imprinted gene MEST/PEG1 has been implicated in trophoblast development; however, the role of MEST in EVT invasion and the accompanying early pregnancy complications are not fully understood. METHODS: Western blot, immunofluorescence and immunohistochemistry were used to detect MEST protein expression and localization by using antibodies recognize 2 reported isoforms. Specific small interference RNA (siRNA) targeting both of the MEST isoforms was applied to silence MEST expression in extravillous explants and HTR8/SVneo cells. Cell invasion and migration were assessed using the Matrigel invasion, Transwell migration assay and the xCELLigence system. Promoter DNA methylation was examined using bisulfite-sequencing polymerase chain reaction (BSP). RESULTS: MEST protein was highly expressed in EVTs in the first trimester placenta and in the invasive EVT cell lines HTR-8/Svneo and HPT-8. Weak MEST expression was found in cytotrophoblasts (CTBs) and the choriocarcinoma-derived CTB cell line JEG-3. The specific siRNA knockdown of MEST expression significantly reduced HTR-8/Svneo cell invasion and migration as well as extravillous explant outgrowth, which were associated with the downregulation of Twist, N-cadherin and Vimentin. Decreased MEST protein expression with isoform 2 promoter hypermethylation was observed in the placentas of missed abortions, suggesting a possible pathological mechanism of missed abortion. CONCLUSIONS: Suppressed expression of MEST was associated with its isoform 2 promoter hypermethylation ex vivo placenta tissues and in vitro cultured EVT cell lines. The present results provide a possible pathological mechanism of missed abortion.