MicroRNAs: are they the missing link between hypoxia and pre-eclampsia?

Pre-eclampsia is a multisystem disorder that occurs in the second half of pregnancy affecting 5% of pregnancies. It remains the leading cause of maternal and perinatal mortality and morbidity worldwide. Impaired placental implantation, hypoxia, endothelial dysfunction and systemic inflammation are thought to have a role in the pathogenesis of pre-eclampsia. MicroRNAs (miRNAs) are short non-coding RNAs. They are important regulators of gene expression and have been found to affect cell development, proliferation, differentiation and function. Specific patterns of miRNAs have been detected in the placenta and there is altered miRNA expression in the placenta of patients with pre-eclampsia to but their role in the pathogenesis remains unclear. Furthermore, deregulated miRNAs have also been reported in human villous trophoblasts during hypoxic stress. One of the more consistently elevated miRNAs by hypoxia and in the placenta of patients with pre-eclampsia is miR-210. Whether such miRNAs are bystander markers of hypoxia, or are directly involved in the pathogenesis of pre-eclampsia, needs to be clarified. There is potential for miRNAs to be used as predictors, markers or therapy in pre-eclampsia. This review provides current knowledge about miRNAs, particularly hypoxia-related miRNAs and the interaction of hypoxia, miRNAs and placenta in pre-eclampsia.