Review: Relaxin expressed at the feto-maternal interface

The placental expression of relaxin, a member of the insulinlike family, has been studied in the placenta in various species with different histological types of materno-fetal interdigitation and trophoblast invasiveness. Placental relaxin expression in these species showed some common features. Relaxin was present in placental areas of intense feto-maternal nutrition- and gas-exchange and high growth potential, implicating relaxin to be involved in placental metabolism and placental growth. Differentiation of trophoblast cells along various lineage pathways affected relaxin gene activity and an inverse expression pattern of relaxin and MHC class I molecules was observed in equine pseudostratified trophoblast cells. A fall in peripheral plasma concentrations of relaxin prior to abortion appears to indicate impaired materno-fetal interdigitation which results in insufficient placentation.