Pregnancy-Related MiRNAs Participate in the Regulation of the Immune System during the Gestational Period

Abstract

Pregnancy is a wonderful and complex example of immunomodulation. The regulation that occurs during pregnancy involves hormones, major histocompatibility molecules, cytokines and different types of cells. Recent evidence shows a significant role for miRNAs in the regulation of the immune system´s cells during the gestational period. Placental miRNAs, found in both normal and complicated pregnancies, are primarily localized in four clusters. These are the chromosome 19-miRNA cluster (C19MC), the miR-371-3 cluster (also on chromosome 19), the chromosome 14-miRNA cluster (M14MC), and the miR-17-92 cluster. Pregnancy-associated miRNAs may be involved in angiogenesis, trophoblast differentiation, and in the regulation of the immune system. However, their role has not been clearly elucidated. miRNAs hold promise as biomarkers in clinical settings, as altered miRNA expression may be present in pregnancy complications. Several miRNAs can regulate leukocytes because they target genes necessary for their development and/or function. Among them are miR-29a, miR-181, miR-125b, miR-17 and miR-92a. Although many miRNAs related to healthy pregnancies or to pregnancy complications have been identified, there remains a lack of information regarding their target genes and the behavior of different miRNAs from the same cluster, particularly with regards to their ability to modulate immune system cells.