〔Abstract〕 ObjectiveTo explore the role of N6-methyladenosine (m6A) modification of RNA and Methyltransferase like Protein 14 methyltransferase (METTL14) in the pathogenesis of early-onset preeclampsia (ePE). MethodsPlacental tissues of 15 pregnant women with early-onset preeclampsia and 15 normal pregnant women were collected. The level of m6A was determined by colorimetry, and the expression of METTL14 was determined by RT-qPCR, Western blot and immunohistochemistry (IHC) experiments. By transfecting siRNA and plasmid, METTL14 levels of trophoblast cells were knocked down and overexpressed, and cell phenotype experiments were carried out in vitro. The effects of METTL14 on the proliferation, migration and invasion of trophoblast cells were investigated by CCK-8, scratch assay, Transwell assay and invasion assay. Results The level of m6A in placental tissue of ePE was lower than that of normal pregnancy. METTL14 was mainly expressed in the nuclei of trophoblast cells. Compared with normal pregnancy, the expression of METTL14 in placental tissue of ePE decreased, and the level of METTL14 mRNA was positively correlated with the level of m6A in placental tissue. The results of the CCK-8 experiment showed that compared with the control group, knockdown of METTL14 expression in trophoblast cells significantly reduced the cell proliferation rate, while the proliferation ability of trophoblast cells with overexpressed METTL14 was enhanced. The results of the scratch test showed that compared with the control group, the relative healing rate of scratches was significantly reduced after METTL14 knockdown, while it increased after the overexpression of METTL14. The results of the Transwell assay and invasion assay showed that compared with the control group, after knockdown of METTL14, the number of trophoblast cells passing through the chamber was significantly reduced, while the number of trophoblast cells with overexpressed METTL14 passing through the chamber increased. ConclusionThe total RNA m6A modification level in placental tissue of ePE is lower than that in the normal pregnancy group. The down-regulation of methyltransferase METTL14 is involved in the regulation of the total RNA m6A modification level. The overexpression of METTL14 can enhance the proliferation, migration and invasion abilities of trophoblast cells. It provides a new perspective for exploring the pathogenesis of early-onset preeclampsia.