Human decidual and placental relaxins

The human placenta and decidua are intrauterine production sites for a range of polypeptide hormones. Relaxin is one of these hormones, its production having been demonstrated by immunocytochemistry and Northern analysis. There are two relaxin genes in the human genome, termed H1 and H2; only the latter is expressed in cyclic and pregnant corpus luteum. However, it has recently been shown that both genes are expressed in the decidua and placenta. It is not known whether both are translated. These hormone(s) may act in a paracrine fashion and be partly responsible for the control of enzymes and inhibitors involved in collagen remodelling in the fetal membranes in the last weeks of pregnancy. An autocrine role of decidual relaxin and a possible decidual-cell/macrophage/extracellular-matrix interaction is described; this may act as a unit in the elaboration of a range of hormones.