ABSTRACT
Objective:To investigate the molecular mechanism for regulation of trophoblast invasion by piR-3127964, which is differentially expressed in placental tissues of preeclamptic and healthy pregnant women.Methods:Placenta samples of healthy (control group, n=12) and preeclamptic pregnant (PE group, n=10) women who delivered by caesarean section and chorionic villi specimens of patients undergoing artificial abortion were collected in the Department of Obstetrics of the First Affiliated Hospital of Chongqing Medical University during November 2020 to August 2021. Total RNA was extracted from placenta samples and sequenced and the expression of piR-3127964 in different tissues was determined by real-time quantitative-polymerase chain reaction (qRT-PCR). The expressions of PIWI proteins including PIWIL-1, PIWIL-2 and PIWIL-3 in different tissues were detected by Western blot. The expressions of two candidate targets, guanine nucleotide-binding protein-like 3-like (GNL3L) mRNA and sialophorin (SPN) mRNA were evaluated by qRT-PCR after exogenous treating HTR-8/SVneo cells with mimics, inhibitor or negative control of piR-3127964, respectively. qRT-PCR was also used to detect the relative expression of GNL3L and SPN at mRNA level in placentas of all women. The interactions between GNL3L/SPN and piR-3127964 were analyzed by double luciferase reporter gene detection. The localization of piR-3127964 and SPN in chorionic villi was detected by fluorescence in situ hybridization and immunofluorescence. Transwell assay was performed to analyze the influence of piR-3127964 on the invasion of HTR-8/SVneo cells and the possible mechanism. Independent sample t-test, analysis of variance, and LSD post test were used for analysis Results:(1) Enrichment pathways of candidate targets predicted by differentially expressed piR-3127964 were associated with cell motility. There were statistically significant differences in piR-3127964 expression in villi, healthy and preeclamptic placentas (2.950±0.853 vs 1.036±0.303 vs 0.254±0.155, F=27.35, P<0.05), and piR-3127964 was predominantly expressed in extravillous cytotrophoblasts (EVTs). (2) The expression of PIWIL-3 protein in placentas of preeclamptic patients was significantly lower than that in healthy placentas and villi (0.810±0.400 vs 3.175±0.429 and 6.843±1.379, F=49.36, P<0.05). (3) Compared with the control group, exogenous piR-3127964 mimics (piR-mimics) and inhibitors (piR-inhibitor) significantly affected the expression of SPN mRNA (0.971±0.045 vs 0.732±0.010, F=6.50; 1.076±0.073 vs 1.293±0.092, F=7.58; both P<0.05), while the expression of GNL3L mRNA had no significant correlation with piR-3127964 level. (4) The luciferase activity of wild-type SPN (SPN-WT) plasmids was significantly affected by piR-mimics (1.010±0.049 vs 0.645±0.047, t=9.34, P<0.05) and piR-inhibitor (1.035±0.058 vs 1.397±0.015, t=－10.60, P<0.05). (5) SPN mRNA was significantly upregulated in placentas of preeclamptic patients than in healthy placentas (2.097±0.239 vs 1.305±0.290, t=－4.22, P<0.05), but no significant difference in the expression of GNL3L mRNA was observed. Immunofluorescence experiment showed that SPN was expressed in EVTs. (6) The invasive potential of HTR8/SVneo cells treated with piR-inhibitor was significantly inhibited, but this effect could be reversed by SPN knockdown (160.714±53.860 vs 371.667±103.061 and 344.333±120.267, F=9.76, both P<0.05). Conclusions:piR-3127964 expression is abnormally downregulated in placentas of preeclamptic patients, resulting in inhibition of trophoblasts invasion through upregulation of SPN expression, which may be related to the pathogenesis of preeclampsia.