RNA Demethylase FTO Mediated RNA m6A Modification Is Involved in Maintaining Maternal-Fetal Interface in Spontaneous Abortion

Abstract

The N6-methyladenosine (m⁶A) RNA modification regulates the expression of genes associated with various biological and pathological processes, including spontaneous abortion (SA). The aim of this study was to determine the role of the m⁶A demethylase fat mass and obesity (FTO)- associated protein in SA. The <i>FTO</i>,<i>IGF2BP1</i> and <i>IGF2BP2</i> mRNA levels were significantly lower in the chorionic villi obtained from spontaneously aborted pregnancies compared to that of normal pregnancies, while the expression levels of <i>METTL3</i> and <i>WTAP</i> were significantly elevated. However, <i>ALKBH5</i>, <i>YTHDF2</i>, and <i>IGF2BP3</i> were elevated with no statistical significance between groups. In addition, MDA was elevated and SOD levels were decreased in the villi tissues of the SA group compared to the normal group, which was indicative of placental oxidative stress in the former. Furthermore, the expression of FTO and HLA-G were significantly decreased in the trophoblasts of the SA patients compared to that of normal pregnant women, while that of m⁶A was markedly higher in the former. In addition, the <i>HLA-G</i> and <i>VEGFR</i> mRNA levels were downregulated in the SA versus the control group, and that of <i>MMP2</i>, <i>MMP7</i>, <i>MMP9</i> and <i>VEGFA</i> were upregulated. Finally, The RIP assay showed significantly decreased levels of FTO-bound <i>HLA-G</i>, <i>VEGFR</i> and <i>MMP9</i> RNA in SA patients (<i>P</i> < 0.05), which corresponded to an increase in transcripts enriched with the m⁶A antibody (<i>P</i> < 0.05). However, compared with normal pregnant women, the levels of <i>HLA-G</i>, <i>VEGFA</i>, <i>VEGFR</i>, and <i>MMP2</i> mRNA bound by YTHDF2 were significantly decreased in SA patients. Compared to the normal pregnant women, both FTO- and m⁶A-bound <i>MMP7</i> were significantly increased in SA patients (<i>P</i> < 0.05), but YTHDF2 almost unbound to <i>MMP7</i> mRNA. In summary, the downregulation of FTO in the chorionic villi disrupts immune tolerance and angiogenesis at the maternal-fetal interface, resulting in aberrant methylation and oxidative stress that eventually leads to SA.