CircFBXW4 regulates human trophoblast cell proliferation and invasion via targeting miR-324-3p/TJP1 axis in recurrent spontaneous abortion.

Introduction: Increasing evidence has shown that circular RNAs (circRNAs) play vital roles in embryonic development. However, the function of circRNAs in recurrent spontaneous abortion (RSA) is largely unknown. This study aimed to investigate the expression profile of human circRNAs and their functional mechanisms in regulating RSA.

Methods: The profiles of circRNAs in placental villus tissues from women with RSA and healthy pregnancy with induced abortion were investigated using RNA-sequencing and bioinformatics. Nine circRNAs were verified in the 50 placental villus samples. RNase R digestion, actinomycin D treatment, and fluorescence in situ hybridization were performed to characterize circFBXW4. Furthermore, direct binding of circFBXW4 to miR-324-3p was confirmed by dual-luciferase reporter assay. The roles of circFBXW4 were determined by loss- and gain-of-function assays including cell proliferation, invasion, and apoptosis using CCK8 kit, transwell migration assay, and TUNEL kit in vitro, respectively.

Results: A total of 417 aberrantly expressed circRNAs was detected. circFBXW4, a circRNA significantly up-regulated in the RSA group, was further evaluated. circFBXW4 showed higher stability than FBXW4 mRNA and was localized in the cytoplasm and nucleus in HTR-8/SVneo cells. MiR-324-3p was lowly expressed in the RSA group, and directly regulated circFBXW4 and TJP1 expression in a targeted manner. Overexpression and knockdown of circFBXW4 and miR-324-3p mimic/inhibitor could increase or decrease HTR-8/SVneo cell proliferation and invasion. circFBXW4 regulated TJP1 expression, cell proliferation, and invasion by sponging miR-324-3p.

Discussion: The circFBXW4/miR-324-3p/TJP1 axis is involved in the occurrence and progression of RSA and may be a promising therapeutic target in RSA.