Diagnosis And Regulatory Mechanisms Of MicroRNA-210 In Pregnancy-induced Hypertension

Pre-eclampsia is a multisystem disorder of unknown cause that is unique to human pregnancy. It is a major obstetric problem leading to maternal morbidity (acute and long-term) and mortality (15-20%in developed countries), perinatal deaths, preterm birth, and intrauterine growth restriction worldwide, especially in developing countries. Many biochemical markers have been proposed to predict which women are likely to develop pre-eclampsia. However, data for the reliability of these markers are not specific or predictive enough for routine use in clinical practice.MicroRNAs (miRNAs), members of a class of small, noncoding RNA molecules, have a critical role in posttranscriptional regulation of protein-coding genes. Originally identified in Caenorhabditis elegans, miRNAs have been shown to operate in a wide range of species, including humans. Primary miRNA, transcribed from DNA, is processed to a looped, imperfectly base paired approximately 70-mer oligonucleotide termed the miRNA precursor. Either arm of the miRNA precursor can be processed enzymatically to the mature, approximately 22-mer miRNA. The mechanism of translational inhibition by miRNA is dependent on complementarity between a 6-7 nucleotide "seed" region in the miRNA and targets in the 3'untranslated region of messenger RNA. Computational estimates predict that up to 30%of human genes are potential targets of miRNA. Studies of miRNA expression across several organs have revealed that miRNA expression is tissue-specific and that sequences may possess functions unique to organs or cell types.Although the cause of pre-eclampsia is unknown, it is agreed generally that pre-eclampsia results from the presence of a placenta because the only treatment for pre-eclampsia is the delivery of the placenta, after which the symptoms regress rapidly. Rcecent studies on miRNAs offer that many miRNAs are expressed abundantly in the human placenta. It has suggested that has-miR-210 expressed differentially in the human placenta with pre-eclampsia, compared with control subjects. Evidence shows that pre-eclampsia is associated with alterations in placental miRNA expression. But little is known about the role played by their expression patterns in placentas with distinct pathologies. Although it is clear that miRNA regulate gene expression at the post-transcriptional level via specific complementary sites at the 3'-UTR of target mRNAs, causing translational repression or degradation. The discoveries of fetal-derived mRNA transcripts have been shown in conditions with pre-eclampsia. In this report, it would also be interesting to investigate whether miR-210 produced by the placenta is also released into maternal plasma.Concordant with our hypothesis that miR-210 exist in maternal plasma, we recruited the second-and third-trimester participants'maternal peripheral blood. The participants were divided into normal pregnancies, hypertension (blood pressure up-regulated at least 4-6 h apart after the after the 20th week of gestation and no proteinuria) and mild pre-eclampsia(systolic blood pressure≥140 mm Hg or diastolic blood pressure≥90 mm Hg and proteinuria≥300 mg in a 24-hour urine collection or 1 dipstick measurement of>+) and severe pre-eclampsia(systolic blood pressure≥160 mm Hg or diastolic blood pressure≥100 mm Hg and proteinuria≥2.0 g in a 24-hour urine collection or 1 dipstick measurement of≥2+). By systematically searching with real-time PCR, we have identified miR-210 was increased and had a noticeably high level during the maternal peripheral blood obtained from patients with severe pre-eclampsia.The placental environment in the first trimester is typically low in oxygen; this relative hypoxia is probably physiologically important because increased intervillous flow is associated with adverse pregnancy outcome. To assess whether hypoxia regulates miR-210 expression in placenta, JAR were exposed to 1%oxygen for different time periods. As found in real-time PCR, miR-210 levels were increased more than 13-fold higher than normoxia and up-regulation was maintained for the next 72h. During the early weeks of gestation, cytotrophoblast cells stream out of the tips of the anchoring villi and develop into the cytotrophoblast shell. Trophoblast cells continue to migrate into the decidua and eventually colonise the placental bed's myometrium. Endovascular trophoblast cells replace the endothelium of spiral arteries and then invade the media, resulting in destruction of the medial elastic, muscular, and neural tissue in causing severe placental ischaemia. Thus, miR-210 was identified by in vitro analysis as being involved in regulating cell apoptosis and migration. Over-expression of miR-210 can significantly induced cell apoptosis, cell migration and cell invasion. By systematically searching and different experimental systems, HOXA9 and EFNA3 were then experimentally validated as the functional target of miR-210. Meanwhile, the expressions of the two target gene were detected down regulation both in samples from pre-eclampsia patients and JAR exposed to hypoxia. In the previous study, we characterized miR-210 regulation and its functional relevance in JAR response to hypoxia, in agreement with what other groups have reported recently. However, in these previously published reports, the structure of miR-210 promoter has not been analyzed. As found in different experimental systems, we identified that miR-210 is directly regulated by the transcription factor NF-κB1 (p50). Nduction of p50 is associated with the expression of miR-210 under hypoxia. Thus, our data indicate that, the hypoxia environment of placenta in first pregnancies activated NF-κB/miR-210 pathway, further to activated miR-210/HOXA9 and miR-210/EFNA3 pathway in the network and have impact on the cell differentiation and vascular remodeling. With the co-action on external factors, the fetal circulation causing severe ischaemia, is probably one of several predisposing factors for the pre-eclampsia syndrome. Collectively, our data demonstrate that miR-210 as candidate biomarker for monitoring pre-eclampsia in maternal plasma. Furthermore, these findings may shed new insight into elucidating the molecular mechanism of the development progression of pre-eclampsia.