Low expression of MFN2 is associated with early unexplained miscarriage by regulating autophagy of trophoblast cells

Miscarriage is a common complication during pregnancy. Mitofusin-2 (MFN2) deficiency in trophoblastic cells is reported to be an important cause for early miscarriage. MFN2 can regulate mitochondrial autophagy, although the mechanisms remain unknown. This study aims to investigate the roles of MFN2 and autophagy in early unexplained miscarriage. Immunohistochemistry and western blotting were used to detect the MFN2 expression in villous tissues from women who had early unexplained miscarriage. Western blotting was used to detect the expression of autophagy-related proteins (ATG5, BECLIN1, and LC3), MMP-2, MMP-9, and integrin β1. Immunofluorescence was used to detect the expression of autophagosome after transfection with GFP-LC3. We used JC-1 to measure the mitochondrial membrane potential and transmission electron microscopy (TEM) to observe the ultrastructure of mitochondria. The levels of β-hCG and progesterone in the trophoblast were determined by the chemiluminescence method. Immunofluorescence analysis demonstrated that MFN2 in the villous tissues of women with early unexplained miscarriage was significantly lower than that of women in the normal pregnancy group. Increased levels of LC3, ATG5, and BECLIN1 were observed by western blotting. After transfection with MFN2-siRNA, the level of MFN2 decreased, whereas LC3, ATG5, and BECLIN1 levels increased significantly in the trophoblasts. More autophagosomes and significant impairment of mitochondrial function were observed by TEM. The levels of β-hCG, progesterone, MMP-2, MMP-9, and integrin β1 were significantly reduced in the MFN2-siRNA group. Low expression of MFN2 leads to mitochondrial dysfunction, increased level of autophagy, and trophoblast cell dysfunction, which could be accounted for early unexplained miscarriage. •Mitofusin-2 (MFN2) level was reduced in the placental villi in early unexplained miscarriage.•More autophagy appeared in the placental villi of early unexplained miscarriage.•Low expression of MFN2 induced high levels of autophagy in trophoblast cells.•Low expression of MFN2 led to mitochondrial damage in trophoblast cells.•Low expression of MFN2 caused biological dysfunction of trophoblast cells.