MicroRNAs, immune cells and pregnancy

Abstract

MicroRNAs (miRNAs) are a recently discovered class of non-coding RNAs that are expressed in many cell types, where they regulate the expression of complementary RNAs, thus modulating the stability and translation of mRNAs. miRNAs are predicted to regulate the expression of ∼50% of all protein coding genes in mammals. Therefore, they participate in virtually all cellular processes investigated so far. Altered miRNAs expressions are associated with both physiological (pregnancy) and pathological processes (cancer). As the dynamic maternal-fetal interface plays a critical role in the maintenance of successful pregnancy, it is not surprising that the miRNAs that are unique to reproductive tissues are abundantly expressed. Research in this field has demonstrated the presence and dysregulation of a distinct set of pregnancy-associated miRNAs; however, most studies have centered on localizing various miRNAs in reproductive microdomains associated with normal or complicated pregnancies. Although several independent miRNA regulatory mechanisms associated with endometrial receptivity, immune cells, angiogenesis and placental development have been studied, miRNA-mediated regulation of pregnancy remains poorly understood. This review provides a summary of the current data on miRNA regulation as well as functional profiles of miRNAs that are found in the uterus, in immune cells associated with maternal tolerance to the fetus, and those involved in angiogenesis and placental development.

Figure 1

A summary of the miRNAs documented during pregnancy. Several studies have demonstrated the presence of miRNAs in the pregnant uterus, placental tissues and immune cells of various species. While much of the current literature focuses on human and mouse pregnancy, the conserved nature of miRNAs across species suggest that they are likely universally involved in pregnancy, placentation, immune tolerance and angiogenesis at the maternal-fetal interface. As negative regulators of gene expression miRNAs are poised to have profound effects during pregnancy, and their dysregulation has already been associated with reproductive pathologies. Here presented is a short list of the miRNAs documented in this review as they relate to location (uterus, placenta or immune cells) or function (angiogenesis) during pregnancy in a variety of species. miRNA, microRNA.