In brief: Insufficiency of extravillous trophoblast (EVT) cell invasion is implicated in pregnancy complications. This study reveals the roles of the miR-486-5p/Smad2 pathway in lipopolysaccharide (LPS)-induced EVT dysfunctions and in the pathogenesis of early pregnancy loss (EPL).
Abstract: Placenta-associated pathologies, including EPL and preeclampsia, are characterized by insufficient EVT invasion. Previously, downregulated miR-486-5p expression was shown to inhibit the invasion of EVTs, and decreased peripheral miR-486-5p expression was associated with EPL. However, the exact roles of miR-486-5p in the pathogenesis of EPL, as well as the molecular pathway underlying the role of miR-486-5p in EVT invasion, remain poorly understood. In this study, decreased miR-486-5p expression in the uterine embryo implantation site on gestational day 8.5 and increased uterine expression of Smad2, a target of miR-486-5p, were observed in an LPS-induced EPL model. The invasion and viability of the immortalized human EVT line, HTR-8/SVneo, were inhibited by LPS, accompanied by reduced miR-486-5p expression. LPS promoted Smad2 expression, which was attenuated by the miR-486-5p mimics. The downregulation of Smad2 effectively restored the impaired invasion and viability of HTR-8/SVneo cells caused by LPS or the miR-486-5p inhibitor. Furthermore, LPS promoted TNFα production in HTR-8/SVneo cells, whereas both siSMAD2 and miR-486-5p mimics reversed this effect. An analysis of human decidua single-cell RNA sequencing and transcriptome datasets derived from Gene Expression Omnibus revealed that, compared with that in control early pregnant women, SMAD2 expression was significantly increased in recurrent miscarriage patients. Collectively, these data suggest that decreased miR-486-5p expression might lead to EPL, at least partially by inhibiting invasion and/or promoting TNFα production in EVTs by targeting SMAD2.
Keywords: SMAD2; early pregnancy loss; extravillous trophoblasts; miR-486-5p.