Sandra Y. Yamamoto

Sequential appearance of relaxin, prolactin and IGFBP-1 during growth and differentiation of the human endometrium.

Relaxin (RLX) is a product of the human corpus luteum, pregnancy decidua and placenta, prolactin (PRL) and insulin-like growth factor binding protein-1 (IGFBP-1) are products of the cyclic endometrium and of the pregnancy decidua. All three proteins are thought to function interdependently in endometrium/decidua as local factors within the uterus without reaching the systemic circulation. In this study, the avidin-biotin immunoperoxidase method for immunolocalization with monoclonal or polyclonal antibodies has been applied to serial sections of endometria obtained from patients at different stages of the menstrual cycle and in early and late gestation. This allowed the cellular localization of the three proteins to be followed simultaneously through the reproductive stages from cyclic endometrium to term gestational decidua. The production, as opposed to sequestration of RLX from an ovarian source was demonstrated by the application in parallel of an antibody to the processed hormone and its connecting peptide. RLX was shown localized to the glandular and luminal epithelia in the proliferative and secretory phases. The decidualized stromal cells also immunostained for RLX in the late secretory phase and in early and late pregnancy. PRL was localized first to the glandular epithelium and then stroma, appearing after RLX, IGFBP-1 appeared later in the secretory phase and predominantly in the decidualized stromal cells confirming previous studies. In contrast, all three proteins were immunostained in early pregnancy and increased to term gestation.(ABSTRACT TRUNCATED AT 250 WORDS)

A relaxin-mediated pathway to preterm premature rupture of the fetal membranes that is independent of infection.

OBJECTIVE This study was designed to show whether the overexpression of relaxin in the decidua of patients with preterm premature rupture of the membranes is independent of or a consequence of chorioamnionitis. STUDY DESIGN Two experiments were conducted. In the first experiment fetal membranes and decidua were collected from patients with preterm premature rupture of the membranes (n = 17) or preterm labor (n = 17) and were divided according to their degree of histologic infection. Messenger ribonucleic acid was isolated from the tissues and quantitative, sequential Northern analyses were carried out for the expression of human relaxin, interleukin-1beta, interleukin-6, and interleukin-8. The second experiment was aimed at increasing the numbers of messenger ribonucleic acid preparations in the two extreme categories, uninfected and severely infected tissues, with preterm premature rupture of the membranes and preterm labor. Some samples of messenger ribonucleic acid from the first experiment were rerun with the Northern analyses in the second experiment. These repeat samples showed no statistical differences in the results run at different times. Therefore the data from the respective groups of patients in both experiments were pooled for statistical analysis. RESULTS In both the first experiment and in the pooled data of the two experiments the expression of the relaxin genes was significantly greater (P < .005) in the tissues from patients with preterm premature rupture of the membranes compared with those with preterm labor, in the absence of infection. No effect of the level of infection on the expression of relaxin was noted. In contrast, interleukin-6 gene expression was significantly increased (P < .05) in severely infected tissues, which was independent of whether the delivery was from preterm premature rupture of the membranes or preterm labor. The expression of the interleukin-1beta and interleukin-8 genes were only marginally increased even in severe infection. Marked patient variability in expression of the interleukin genes, especially in severe infection, was noted. CONCLUSION A relaxin-mediated pathway that leads to preterm premature rupture of the membranes may exist independent of infection.

Relaxin and the Human Fetal Membranes

The human fetal membranes are complex tissues that perform many important functions during gestation. The extracellular matrix provides their strength to withstand the forces directed from the fetus and myometrium. Relaxin is a collagenolytic hormone that causes increased production of the matrix metalloproteinases. Its expression from the decidua is increased in patients with preterm premature rupture of the membranes, and its leucine-rich G receptor 7 is upregulated at preterm. The authors previously showed that relaxin is not involved in the infection-mediated cytokine response, but in the absence of infection, it causes increased secretion of both interleukin -6 and interleukin-8 from the membranes. In this article, the authors propose that relaxin is one of a number of sterile stimuli capable of causing increased proinflammatory cytokines, similar to but less robust than the effects of infection. These probably represent distinct inflammatory pathways involving different intracellular signaling events, which can result in either preterm premature rupture of the membranes or preterm labor. The current challenge is to fully understand these pathways and to clarify their similarities and differences.

Relaxin stimulates interleukin-6 and interleukin-8 secretion from the extraplacental chorionic cytotrophoblast.

In the absence of infection, decidual relaxin (RLN) expression is increased in patients with preterm premature rupture of the membranes (PPROM) resulting in preterm birth, but it is not known whether inflammation stimulates RLN expression or vice versa. This study examined the effect of lipopolysaccharide (LPS) on the expression of RLN mRNA and secreted protein and whether RLN treatment influences secretion of proinflammatory cytokines from the fetal membranes. Explants of human fetal membranes in vitro and rhesus monkey fetal membranes in vivo were treated with LPS, which increased expression of IL-6 but had no effect on RLN. RLN treatment stimulated IL-6 and IL-8 secretion from choriodecidual explants in a subset of patients, as well as from isolated chorionic cytotrophoblast cells but not decidual cells. In vivo results obtained in rhesus monkeys after intra-amniotic infusion of RLN demonstrated increased IL-6 and IL-8 concentrations in amniotic fluid. Our results indicate that increased decidual RLN expression is independent of LPS but may induce a local sterile inflammatory process which potentially contributes to extracellular matrix degradation and weakening of the fetal membranes.

Human Decidual Relaxin and Preterm Birth

Abstract: Relaxin in human pregnancy is both a systemic hormone from the corpus luteum and an autocrine/paracrine hormone at the maternal‐fetal interface formed by the decidua/placenta and fetal membranes. We have focused our studies on the autocrine/paracrine roles of relaxin, especially in the preterm premature rupture of the fetal membranes, which causes 30‐40% of preterm births. By using different techniques and different tissue collections, our laboratory has shown that expression of the relaxin genes and proteins in the decidua and placenta is increased in patients with preterm premature rupture of the fetal membranes. Relaxin binding and the expression of LGR7 are primarily in the chorion and decidua and are downregulated after spontaneous labor and delivery both at term and preterm. However, expression of LGR7 in the fetal membranes is significantly greater in all clinical situations at preterm than term, suggesting an important role for relaxin in these tissues at that time. The roles of the relaxin system in three potential causes of preterm birth are discussed: in the growth and proliferation of the membranes important for fetal membrane accommodation to fetal and placental growth, in acute infection, and in the inflammatory response leading to the initiation of labor.

Human chorionic gonadotropin β-subunit-like immunoreactive material in the plasma of women wearing an intrauterine progesterone contraceptive system

A systematic study of the presence of human chorionic gonadotropin beta-subunit--like (hCG beta-like) material in the plasma of one woman sampled daily throughout one menstrual cycle and in nine women studied on a selected bleeding schedule has been carried out. Peaks of immunoreactive hCG beta-like activity were found in the follicular and luteal phases of these menstrual cycles which could not be explained by a cross-reaction of luteinizing hormone (LH) in the plasma. The same nine women were studied again 1 month after the insertion of the intrauterine progesterone contraceptive system (IPCS) and again 6 to 8 months later. Although the presence of hCG beta-like immunoactivity correlated with LH values in the cycles studied, there was a significant decrease in its presence 1 month after IPCS use and a highly significant decrease after 6 to 8 months of use.

Relaxin Receptors and a Study of the Physiological Roles of Relaxin

This paper will be divided into two sections, the first dealing with our work on relaxin receptors and the second with the current evidence for relaxin being a physiologically important hormone in the non-pregnant animal.

Identification of Relaxin-Responsive Cells in the Human Choriodecidua at Term

The decidua of the human maternal–fetal interface is a local source of intrauterine relaxin, and the choriodecidua expresses its receptor (LGR7). Since these tissues consist of a variety of cells, we sought to identify the primary cell(s) responsible for LGR7 expression and relaxin responsiveness.