Disparate effects of relaxin and TGFbeta1: relaxin increases, but TGFbeta1 inhibits, the relaxin receptor and the production of IGFBP-1 in human endometrial stromal/decidual cells

Pathologic maternal and neonatal outcomes associated with programmed embryo transfer: potential etiologies and strategies for prevention

PURPOSE

In the first of two companion papers, we comprehensively reviewed the recent evidence in the primary literature, which addressed the increased prevalence of hypertensive disorders of pregnancy, late-onset or term preeclampsia, fetal overgrowth, postterm birth, and placenta accreta in women conceiving by in vitro fertilization. The preponderance of evidence implicated frozen embryo transfer cycles and, specifically, those employing programmed endometrial preparations, in the higher risk for these adverse maternal and neonatal pregnancy outcomes. Based upon this critical appraisal of the primary literature, we formulate potential etiologies and suggest strategies for prevention in the second article.

METHODS

Comprehensive review of primary literature.

RESULTS

Presupposing significant overlap of these apparently diverse pathological pregnancy outcomes within subjects who conceive by programmed autologous FET cycles, shared etiologies may be at play. One plausible but clearly provocative explanation is that aberrant decidualization arising from suboptimal endometrial preparation causes greater than normal trophoblast invasion and myometrial spiral artery remodeling. Thus, overly robust placentation produces larger placentas and fetuses that, in turn, lead to overcrowding of villi within the confines of the uterine cavity which encroach upon intervillous spaces precipitating placental ischemia, oxidative and syncytiotrophoblast stress, and, ultimately, late-onset or term preeclampsia. The absence of circulating corpus luteal factors like relaxin in most programmed cycles might further compromise decidualization and exacerbate the maternal endothelial response to deleterious circulating placental products like soluble fms-like tyrosine kinase-1 that mediate disease manifestations. An alternative, but not mutually exclusive, determinant might be a thinner endometrium frequently associated with programmed endometrial preparations, which could conspire with dysregulated decidualization to elicit greater than normal trophoblast invasion and myometrial spiral artery remodeling. In extreme cases, placenta accreta could conceivably arise. Though lower uterine artery resistance and pulsatility indices observed during early pregnancy in programmed embryo transfer cycles are consistent with this initiating event, quantitative analyses of trophoblast invasion and myometrial spiral artery remodeling required to validate the hypothesis have not yet been conducted.

CONCLUSIONS

Endometrial preparation that is not optimal, absent circulating corpus luteal factors, or a combination thereof are attractive etiologies; however, the requisite investigations to prove them have yet to be undertaken. Presuming that in ongoing RCTs, some or all adverse pregnancy outcomes associated with programmed autologous FET are circumvented or mitigated by employing natural or stimulated cycles instead, then for women who can conceive using these regimens, they would be preferable. For the 15% or so of women who require programmed FET, additional research as suggested in this review is needed to elucidate the responsible mechanisms and develop preventative strategies.

Increased Expression of TGF-β1 Contributes to the Downregulation of Progesterone Receptor Expression in the Eutopic Endometrium of Infertile Women with Minimal/Mild Endometriosis

Endometriosis is a hormone-dependent disease associated with impaired immunoregulation. In our recent study, we have characterized the trascriptomic transformation of eutopic endometrium from patients with minimal/mild endometriosis and controls across the menstrual cycle. However, the regulatory mechanism of altered immune microenvironment in eutopic endometrial stromal cells (ESCs) remains unclear. Here, we want to explore the regulation of immune cell to progesterone resistance and endometrial receptivity in the eutopic ESCs by cytokine (TGF-β1), and to understand the effect of TGF-β1 on the decidualization of the eutopic ESCs. Primary culture of eutopic ESCs was performed to explore the effects of TGF-β1 on the expression of Smad and progesterone receptor (PR) and the in vitro decidualization. Additionally, co-immunoprecipitation (Co-IP) was used to explore the direct interaction between Smad and PR. We found an attenuate expression of PRB protein (p=0.026) after using TGF-β1 in eutopic ESCs, although the difference of PRA before and after treatment was not significant (p=0.678). Similarly, the results of qRT-PCR showed that the mRNA level of PR (p<0.001), PRB (p=0.003) and HOXA10 (p<0.001) decreased significantly after TGF-β1 treatment, but that increased (p<0.023, for all) after SB431542 treatment in the eutopic ESCs. Moreover, TGF-β1 has a negative effect on the in vitro decidualization of eutopic ESCs (p=0.003). And the group with treatment of both TGF-β1 and SB435142 in eutopic ESCs showed significant decidual-like changes with increased prolactin level (p=0.01). We did not observe any physical interaction between the PR and p-Smad3/Smad3 proteins by using Co-IP. By activating TGF-β/Smad signaling in eutopic ESCs, elevated TGF-β1 from CD45+ immune cells could attenuate expression of PR, and further decrease endometrial receptivity.

Serelaxin Alleviates Fibrosis in Thyroid-Associated Ophthalmopathy via the Notch Pathway

Fibrosis is the late stage of thyroid-associated ophthalmopathy (TAO), resulting in serious complications. Effective therapeutic drugs are still lacking. We aimed to explore the mechanism of TAO fibrosis and to find a targeted drug. High-throughput RNA sequencing was performed on orbital connective tissues from twelve patients with TAO and six healthy controls. Protein-protein interaction (PPI) network was constructed using the Search Tool for the Retrieval of Interacting Genes (STRING) database and we identified the hub gene by Cytoscape software. Additionally, the RNA sequencing results were validated by quantitative real-time polymerase chain reaction (qRT-PCR). Bioinformatic prediction identified the functions of differentially expressed genes (DEGs). Further orbital connective tissue and serum samples of the TAO and control groups were collected for subsequent experiments. Histologic staining, Western blotting (WB), qRT-PCR, enzyme-linked immunosorbent assays (ELISAs), gene overexpression through lentiviral infection or silencing gene by short interfering RNA (siRNA) were performed. We found that the relaxin signaling pathway is an important regulatory pathway in TAO fibrosis pathogenesis. Serelaxin exerts antifibrotic and anti-inflammatory effects in TAO. Furthermore, the downstream Notch pathway was activated by serelaxin and was essential to the antifibrotic effect of serelaxin in TAO. The antifibrotic effect of serelaxin is dependent on RXFP1.

Single-cell analysis of prostaglandin E2-induced human decidual cell in vitro differentiation: a minimal ancestral deciduogenic signal†

The decidua is a hallmark of reproduction in many placental mammals. Differentiation of decidual stromal cells is known to be induced by progesterone and the cyclic AMP/protein kinase A (cAMP/PKA) pathway. Several candidates have been identified as the physiological stimulus for adenylyl cyclase activation, but their relative importance remains unclear. To bypass this uncertainty, the standard approach for in vitro experiments uses membrane-permeable cAMP and progestin. We phylogenetically infer that prostaglandin E2 (PGE2) likely was the signal that ancestrally induced decidualization in conjunction with progesterone. This suggests that PGE2 and progestin should be able to activate the core gene regulatory network of decidual cells. To test this prediction, we performed a genome-wide study of gene expression in human endometrial fibroblasts decidualized with PGE2 and progestin. Comparison to a cAMP-based protocol revealed shared activation of core decidual genes and decreased induction of senescence-associated genes. Single-cell transcriptomics of PGE2-mediated decidualization revealed a distinct, early-activated state transitioning to a differentiated decidual state. PGE2-mediated decidualization was found to depend upon progestin-dependent induction of PGE2 receptor 2 (PTGER2) which in turn leads to PKA activation upon PGE2 stimulation. Progesterone-dependent induction of PTGER2 is absent in opossum, an outgroup taxon of placental mammals which is incapable of decidualization. Together, these findings suggest that the origin of decidualization involved the evolution of progesterone-dependent activation of the PGE2/PTGER2/PKA axis, facilitating entry into a PKA-dominant rather than AKT-dominant cellular state. We propose the use of PGE2 for in vitro decidualization as an alternative to 8-Br-cAMP.

Characterizing relaxin receptor expression and exploring relaxin's effect on tissue remodeling/fibrosis in the human bladder

Background

Relaxin is an endogenous protein that has been shown to have antifibrotic properties in various organ systems. There has been no characterization of relaxin’s role in the human bladder. Our objective was to characterize relaxin receptor expression in the human bladder and assess relaxin’s effect on tissue remodeling/fibrosis pathways in bladder smooth muscle cells.

Methods

Relaxin family peptide receptor 1 (RXFP1) and RXFP2 expression was assessed using quantitative reverse transcriptase-PCR (qRT-PCR) and immunohistochemistry (IHC) on primary bladder tissue. Primary human smooth muscle bladder cells were cultured and stimulated with various concentrations of relaxin. Western blot, qRTPCR, ELISA, and zymogram assays were used to analyze fibrosis/tissue remodeling pathway proteins.

Results

There was universal mRNA transcript detection and protein expression of relaxin receptors in primary bladder specimens. Immunohistochemistry demonstrated RXFP1 and RXFP2 localizing to both urothelial and smooth muscle cell layers of the bladder. 24 h of in vitro relaxin stimulation did not affect mRNA expression of selected proteins in human bladder smooth muscle cells. However, 48 h of in vitro relaxin stimulation resulted in upregulation of active (p = 0.004) and latent (p = 0.027) MMP-2 in cell lysate, and upregulation of active MMP-2 in supernatant (p = 0.04). There was a dose dependent relationship with increasing expression of MMP-2 with increasing relaxin concentration. Relaxin stimulation resulted in decreased levels of active and total TGF-β1 in supernatant and extracellular matrix (p < 0.005 with 100 ng/mL relaxin stimulation).

Conclusions

In the human bladder, relaxin receptors are expressed at the dome and trigone and localize to the urothelium and smooth muscle cell layers. Stimulation of human bladder SMCs with relaxin in vitro affects expression of MMP-2 and TGF-β1.

The role of mesenchymal-epithelial transition in endometrial function

BACKGROUND

The human uterine endometrium undergoes significant remodeling and regeneration on a rapid and repeated basis, after parturition, menstruation, and in some cases, injury. The ability of the adult endometrium to undergo cyclic regeneration and differentiation/decidualization is essential for successful human reproduction. Multiple key physiologic functions of the endometrium require the cells of this tissue to transition between mesenchymal and epithelial phenotypes, processes known as mesenchymal-epithelial transition (MET) and epithelial-mesenchymal transition (EMT). Although MET/EMT processes have been widely characterized in embryonic development and in the context of malignancy, mounting evidence demonstrates the importance of MET/EMT in allowing the endometrium the phenotypic and functional flexibility necessary for successful decidualization, regeneration/re-epithelialization and embryo implantation.

OBJECTIVE AND RATIONALE

The objective of this review is to provide a comprehensive summary of the observations concerning MET and EMT and their regulation in physiologic uterine functions, specifically in the context of endometrial regeneration, decidualization and embryo implantation.

SEARCH METHODS

Using variations of the search terms 'mesenchymal-epithelial transition', 'mesenchymal-epithelial transformation', 'epithelial-mesenchymal transition', 'epithelial-mesenchymal transformation', 'uterus', 'endometrial regeneration', 'endometrial decidualization', 'embryo implantation', a search of the published literature between 1970 and 2018 was conducted using the PubMed database. In addition, we searched the reference lists of all publications included in this review for additional relevant original studies.

OUTCOMES

Multiple studies demonstrate that endometrial stromal cells contribute to the regeneration of both the stromal and epithelial cell compartments of the uterus, implicating a role for MET in mechanisms responsible for endometrial regeneration and re-epithelialization. During decidualization, endometrial stromal cells undergo morphologic and functional changes consistent with MET in order to accommodate embryo implantation. Under the influence of estradiol, progesterone and multiple other factors, endometrial stromal fibroblasts acquire epithelioid characteristics, such as expanded cytoplasm and rough endoplasmic reticulum required for greater secretory capacity, rounded nuclei, increased expression of junctional proteins which allow for increased cell-cell communication, and a reorganized actin cytoskeleton. During embryo implantation, in response to both maternal and embryonic-derived signals, the maternal luminal epithelium as well as the decidualized stromal cells acquire the mesenchymal characteristics of increased migration/motility, thus undergoing EMT in order to accommodate the invading trophoblast.

WIDER IMPLICATIONS

Overall, the findings support important roles for MET/EMT in multiple endometrial functions required for successful reproduction. The endometrium may be considered a unique wound healing model, given its ability to repeatedly undergo repair without scarring or loss of function. Future studies to elucidate how MET/EMT mechanisms may contribute to scar-free endometrial repair will have considerable potential to advance studies of wound healing mechanisms in other tissues.

Predictive and diagnostic biomarkers for gestational diabetes and its associated metabolic and cardiovascular diseases

Gestational diabetes mellitus (GDM) is defined as the presence of high blood glucose levels with the onset, or detected for the first time during pregnancy, as a result of increased insulin resistance. GDM may be induced by dysregulation of pancreatic β-cell function and/or by alteration of secreted gestational hormones and peptides related with glucose homeostasis. It may affect one out of five pregnancies, leading to perinatal morbidity and adverse neonatal outcomes, and high risk of chronic metabolic and cardiovascular injuries in both mother and offspring. Currently, GDM diagnosis is based on evaluation of glucose homeostasis at late stages of pregnancy, but increased age and body-weight, and familiar or previous occurrence of GDM, may conditionate this criteria. In addition, an earlier and more specific detection of GDM with associated metabolic and cardiovascular risk could improve GDM development and outcomes. In this sense, 1st-2nd trimester-released biomarkers found in maternal plasma including adipose tissue-derived factors such as adiponectin, visfatin, omentin-1, fatty acid-binding protein-4 and retinol binding-protein-4 have shown correlations with GDM development. Moreover, placenta-related factors such as sex hormone-binding globulin, afamin, fetuin-A, fibroblast growth factors-21/23, ficolin-3 and follistatin, or specific micro-RNAs may participate in GDM progression and be useful for its recognition. Finally, urine-excreted metabolites such as those related with serotonin system, non-polar amino-acids and ketone bodies, may complete a predictive or early-diagnostic panel of biomarkers for GDM.

MicroRNA-144-3p targets relaxin/insulin-like family peptide receptor 1 (RXFP1) expression in lung fibroblasts from patients with idiopathic pulmonary fibrosis

The hormone relaxin is considered a potential therapy for idiopathic pulmonary fibrosis (IPF). We have previously shown that a potential limitation to relaxin-based IPF therapy is decreased expression of a relaxin receptor, relaxin/insulin-like family peptide receptor 1 (RXFP1), in IPF fibroblasts. The mechanism that down-regulates RXFP1 in IPF remains unclear. To determine whether microRNAs (miRs) regulate RXFP1 gene expression, here we employed a bioinformatics approach to identify miRs predicted to target RXFP1 and identified a putative miR-144-3p target site in the RXFP1 mRNA. In situ hybridization of IPF lung biopsies revealed that miR-144-3p is expressed in fibroblastic foci. Furthermore, we found that miR-144-3p is up-regulated in IPF fibroblasts compared with lung fibroblasts from healthy donors. Transforming growth factor β increased miR-144-3p expression in both healthy and IPF lung fibroblasts in a SMAD family 2/3 (SMAD2/3)-dependent manner, and Jun proto-oncogene AP-1 transcription factor subunit (AP-1) was required for constitutive miR-144-3p expression. Overexpression of an miR-144-3p mimic significantly reduced RXFP1 mRNA and protein levels and increased expression of the myofibroblast marker α-smooth muscle actin (α-SMA) in healthy lung fibroblasts. IPF lung fibroblasts transfected with anti-miR-144-3p had increased RXFP1 expression and reduced α-SMA expression. Of note, a lentiviral luciferase reporter carrying the WT 3' UTR of RXFP1 was significantly repressed in IPF lung fibroblasts, whereas a reporter carrying a mutated miR-144-3p-binding site exhibited less sensitivity toward endogenous miR-144-3p expression, indicating that miR-144-3p down-regulates RXFP1 in IPF lung fibroblasts by targeting its 3' UTR. We conclude that miR-144-3p directly represses RXFP1 mRNA and protein expression.

The Role of Placental Hormones in Mediating Maternal Adaptations to Support Pregnancy and Lactation

During pregnancy, the mother must adapt her body systems to support nutrient and oxygen supply for growth of the baby in utero and during the subsequent lactation. These include changes in the cardiovascular, pulmonary, immune and metabolic systems of the mother. Failure to appropriately adjust maternal physiology to the pregnant state may result in pregnancy complications, including gestational diabetes and abnormal birth weight, which can further lead to a range of medically significant complications for the mother and baby. The placenta, which forms the functional interface separating the maternal and fetal circulations, is important for mediating adaptations in maternal physiology. It secretes a plethora of hormones into the maternal circulation which modulate her physiology and transfers the oxygen and nutrients available to the fetus for growth. Among these placental hormones, the prolactin-growth hormone family, steroids and neuropeptides play critical roles in driving maternal physiological adaptations during pregnancy. This review examines the changes that occur in maternal physiology in response to pregnancy and the significance of placental hormone production in mediating such changes.

Expression of RXFP1 Is Decreased in Idiopathic Pulmonary Fibrosis. Implications for Relaxin-based Therapies

RATIONALE

Relaxin is a hormone that has been considered as a potential therapy for patients with fibrotic diseases.

OBJECTIVES

To gauge the potential efficacy of relaxin-based therapies in idiopathic pulmonary fibrosis (IPF), we studied gene expression for relaxin/insulin-like family peptide receptor 1 (RXFP1) in IPF lungs and controls.

METHODS

We analyzed gene expression data obtained from the Lung Tissue Research Consortium and correlated RXFP1 gene expression data with cross-sectional clinical and demographic data. We also employed ex vivo donor and IPF lung fibroblasts to test RXFP1 expression in vitro. We tested CGEN25009, a relaxin-like peptide, in lung fibroblasts and in bleomycin injury.

MEASUREMENTS AND MAIN RESULTS

We found that RXFP1 is significantly decreased in IPF. In patients with IPF, the magnitude of RXFP1 gene expression correlated directly with diffusing capacity of the lung for carbon monoxide (P < 0.0001). Significantly less RXFP1 was detected in vitro in IPF fibroblasts than in donor controls. Transforming growth factor-β decreased RXFP1 in both donor and IPF lung fibroblasts. CGEN25009 was effective at decreasing bleomycin-induced, acid-soluble collagen deposition in vivo. The relaxin-like actions of CGEN25009 were abrogated by RXFP1 silencing in vitro, and, in comparison with donor lung fibroblasts, IPF lung fibroblasts exhibited decreased sensitivity to the relaxin-like effects of CGEN25009.

CONCLUSIONS

IPF is characterized by the loss of RXFP1 expression. RXFP1 expression is directly associated with pulmonary function in patients with IPF. The relaxin-like effects of CGEN25009 in vitro are dependent on expression of RXFP1. Our data suggest that patients with IPF with the highest RXFP1 expression would be predicted to be most sensitive to relaxin-based therapies.

Human relaxins (RLNH1, RLNH2), their receptor (RXFP1) and fetoplacental growth

Relaxin, a systemic and placental hormone, has potential roles in fetoplacental growth. Human placenta expresses two RLN genes, RLNH1 and RLNH2 Maternal obesity is common and is associated with abnormal fetal growth. Our aims were to relate systemic and cord blood RLNH2, placental RLNs and their receptor (RXFP1) with fetoplacental growth in context of maternal body mass index, and associations with insulin-like growth factor 2 (IGF2) and vascular endothelial growth factor A (VEGFA) in the same placentas. Systemic, cord blood and placental samples were collected prior to term labor, divided by prepregnancy body mass index: underweight/normal (N = 25) and overweight/obese (N = 44). Blood RLNH2 was measured by ELISA; placental RLNH2, RLNH1, RXFP1, IGF2 and VEGFA were measured by quantitative immunohistochemistry and mRNAs were measured by quantitative reverse transcription PCR. Birthweight increased with systemic RLNH2 only in underweight/normal women (P = 0.036). Syncytiotrophoblast RLNH2 was increased in overweight/obese patients (P = 0.017) and was associated with placental weight in all subjects (P = 0.038). RLNH1 had no associations with birthweight or placental weight, but was associated with increased trophoblast and endothelial IGF2 and VEGFA, due to female fetal sex. Thus, while systemic RLNH2 may be involved in birthweight regulation in underweight/normal women, placental RLNH2 in all subjects may be involved in placental weight. A strong association of trophoblast IGF2 with birthweight and placental weight in overweight/obese women suggests its importance. However, an association of only RLNH1 with placental IGF2 and VEGFA was dependent upon female fetal sex. These results suggest that both systemic and placental RLNs may be associated with fetoplacental growth.

Progestagenic Effects of Tibolone are Target Gene—Specific In Human Endometrial Cells

OBJECTIVES

Tibolone (Tib) exhibits progestagenic activities in addition to its tissue-specific estrogenic activities. The purpose of the current study was to determine the progestagenic actions of Tib and its metabolites using target genes known to be regulated by progestins in human endometrial glandular and stromal cells.

METHODS

Human endometrial glandular and stromal cells were isolated from endometrial tissue fragments and separately incubated with Tib and its metabolites. Real-time polymerase chain reaction (PCR) was used to determine the mRNA content of 17betahydroxy steroid dehydrogenase (17betaHSD, type 2) and sulfotransferase (SULT1E1) in endometrial glandular cells, and prolactin (PRL) and insulin-like growth factor binding protein-1 (IGFBP1) in endometrial stromal cells.

RESULTS

In glandular cells, Tib and Delta4-tibolone (Delta4Tib) significantly increased the content of 17betaHSD and SULT1E1 mRNA. In stromal cells, Tib and Delta4Tib increased PRL mRNA ( approximately 30% of the capacity compared to progesterone) and had little effect on IGFBP1 mRNA. Anti-progestin, RU486, reversed the induction of SULT1E1 and PRL by progesterone or Tib. Also, the two 3 hydroxyl tobolone metabolites, especially 3betaOHTib, showed some progestagenic effects.

CONCLUSIONS

The data showed that Tib and Delta4Tib exhibited clear progestagenic effects in endometrial glandular cells by inducing 17betaHSD and SULT1E1, while in stromal cells the response was weaker in the induction of PRL and had little effect on IGFBP1. In addition, the 3betaOHTib metabolite expressed progestagenic activity. These disparate effects in two types of cells may be beneficial for maintaining endometrial cells in a quiescent state.

G-Protein-coupled receptors as potential drug candidates in preeclampsia: targeting the relaxin/insulin-like family peptide receptor 1 for treatment and prevention

BACKGROUND

Important roles for G-protein-coupled receptors (GPCRs) have been identified in the maternal physiological adaptations to pregnancy and in the pathogenesis of preeclampsia. On this basis, GPCRs are potential therapeutic targets for preeclampsia.

OBJECTIVES AND RATIONALE

In this review, vasopressin and apelin are initially considered in this context before the focus on the hormone relaxin and its cognate receptor, the relaxin/insulin-like family peptide receptor 1 (RXFP1). Based on both compelling scientific rationale and a promising safety profile, the relaxin ligand-receptor system is comprehensively evaluated as a potential therapeutic endpoint in preeclampsia.

SEARCH METHODS

The published literature relating to the topic was searched through January 2016 using PubMed.

OUTCOMES

Relaxin is a peptide hormone secreted by the corpus luteum; it circulates in the luteal phase and during pregnancy. Activation of RXFP1 is vasodilatory; thus, relaxin supplementation is expected to at least partly restore the fundamental vasodilatory changes of normal pregnancy, thereby alleviating maternal organ hypoperfusion, which is a major pathogenic manifestation of severe preeclampsia. Specifically, by exploiting its pleiotropic hemodynamic attributes in preeclampsia, relaxin administration is predicted to (i) reverse robust arterial myogenic constriction; (ii) blunt systemic and renal vasoconstriction in response to activation of the angiotensin II receptor, type 1; (iii) mollify the action of endogenous vasoconstrictors on uterine spiral arteries with failed remodeling and retained smooth muscle; (iv) increase arterial compliance; (v) enhance insulin-mediated glucose disposal by promoting skeletal muscle vasodilation and (vi) mobilize and activate bone marrow-derived angiogenic progenitor cells, thereby repairing injured endothelium and improving maternal vascularity in organs such as breast, uterus, pancreas, skin and fat. By exploiting its pleiotropic molecular attributes in preeclampsia, relaxin supplementation is expected to (i) enhance endothelial nitric oxide synthesis and bioactivity, as well as directly reduce vascular smooth muscle cytosolic calcium, thus promoting vasodilation; (ii) improve the local angiogenic balance by augmenting arterial vascular endothelial and placental growth factor (VEGF and PLGF) activities; (iii) ameliorate vascular inflammation; (iv) enhance placental peroxisome proliferator-activated receptor gamma, coactivator 1 alpha (PCG1α) expression, and hence, peroxisome proliferator-activated receptor gamma (PPAR-γ) activity and (v) confer cytotrophoblast and endothelial cytoprotection. Insofar as impaired endometrial maturation (decidualization) predisposes to the development of preeclampsia, relaxin administration in the late secretory phase and during early pregnancy would be anticipated to improve decidualization, and hence trophoblast invasion and spiral artery remodeling, thereby reducing the risk of preeclampsia. Relaxin has a favorable safety profile both in the non-pregnant condition and during pregnancy.

WIDER IMPLICATIONS

There is a strong scientific rationale for RXFP1 activation in severe preeclampsia by administration of relaxin, relaxin analogs or small molecule mimetics, in order to mollify the disease pathogenesis for safe prolongation of pregnancy, thus allowing time for more complete fetal maturation, which is a primary therapeutic endpoint in treating the disease. In light of recent data implicating deficient or defective decidualization as a potential etiological factor in preeclampsia and the capacity of relaxin to promote endometrial maturation, the prophylactic application of relaxin to reduce the risk of preeclampsia is a plausible therapeutic approach to consider. Finally, given its pleiotropic and beneficial attributes particularly in the cardiovascular system, relaxin, although traditionally considered as a 'pregnancy' hormone, is likely to prove salutary for several disease indications in the non-pregnant population.

Endometrial LGR7 expression and implantation failure

Implantation failure is considered as a major cause of infertility in women with recurrent pregnancy loss (RPL) and in otherwise healthy women with unexplained infertility. Preliminary data in primates suggested that relaxin (RLX) is involved in endometrial preparation for implantation. In a prospective observational study, the endometrial RLX receptor (LGR7) expression was assessed in three groups of patients with regular ovulatory cycle and normal uterine cavity: 23 with RPL (Group A), 23 with unexplained infertility undergone at least three cycles of failed in vitro fertilization (IVF) reporting good oocyte and embryo quality (Group B), 23 with proven fertility (Group C). Assessment of LGR7 expression was performed with both polymerase chain reaction (PCR) analysis and immunohistochemistry on endometrial samples obtained with hysteroscopic biopsy performed in the secretory phase of the menstrual cycle. Endometrial LGR7 was less expressed in group A and B versus C, both by PCR analysis (p = 0.024) and immunohistochemistry. The decreased expression of the endometrial RLX receptor in women with implantation failures, both in vitro fertilization failure and recurrent pregnancy loss, suggests that RLX may play a crucial role in the structural and functional changes of the endometrium during the window of implantation.

Relaxin deficiency results in increased expression of angiogenesis- and remodelling-related genes in the uterus of early pregnant mice but does not affect endometrial angiogenesis prior to implantation

BACKGROUND

Extensive uterine adaptations, including angiogenesis, occur prior to implantation in early pregnancy and are potentially regulated by the peptide hormone relaxin. This was investigated in two studies. First, we took a microarray approach using human endometrial stromal (HES) cells treated with relaxin in vitro to screen for target genes. Then we aimed to investigate whether or not relaxin deficiency in mice affected uterine expression of representative genes associated with angiogenesis and uterine remodeling, and also blood vessel proliferation in the pre-implantation mouse endometrium.

METHODS

Normal HES cells were isolated and treated with recombinant human relaxin (10 ng/ml) for 24 h before microarray analysis. Reverse transcriptase PCR was used to analyze gene expression of relaxin and its receptor (Rxfp1) in ovaries and uteri; quantitative PCR was used to analyze steroid receptor, angiogenesis and extracellular matrix remodeling genes in the uteri of wild type (Rln+/+) and Rln-/- mice on days 1-4 of pregnancy. Immunohistochemistry localized endometrial endothelial cell proliferation and mass spectrometry measured steroid hormones in the plasma.

RESULTS

Microarray analysis identified 63 well-characterized genes that were differentially regulated in HES cells after relaxin treatment. Expression of some of these genes was increased in the uterus of Rln+/+ mice by day 4 of pregnancy. There was significantly higher vascular endothelial growth factor A (VegfA), estrogen receptor 1 (Esr1), progesterone receptor (Pgr), Rxfp1, egl-9 family hypoxia-inducible factor 1 (Egln1), hypoxia inducible factor 1 alpha (Hif1α), matrix metalloproteinase 14 (Mmp14) and ankryn repeat domain 37 (Ankrd37) in Rln-/- compared to Rln+/+ mice on day 1. Progesterone receptor expression and plasma progesterone levels were higher in Rln-/- mice compared to Rln+/+ mice. However, endometrial angiogenesis was not advanced as pre-implantation endothelial cell proliferation did not differ between genotypes.

CONCLUSIONS

Relaxin treatment modulates expression of a variety of angiogenesis-related genes in HES cells. However, despite accelerated uterine gene expression of steroid receptor, progesterone and angiogenesis and extracellular matrix remodeling genes in Rln-/- mice, there was no impact on angiogenesis. We conclude that although relaxin deficiency results in phenotypic changes in the pre-implantation uterus, endogenous relaxin does not play a major role in pre-implantation angiogenesis in the mouse uterus.

Relaxin family peptides and their receptors

There are seven relaxin family peptides that are all structurally related to insulin. Relaxin has many roles in female and male reproduction, as a neuropeptide in the central nervous system, as a vasodilator and cardiac stimulant in the cardiovascular system, and as an antifibrotic agent. Insulin-like peptide-3 (INSL3) has clearly defined specialist roles in male and female reproduction, relaxin-3 is primarily a neuropeptide involved in stress and metabolic control, and INSL5 is widely distributed particularly in the gastrointestinal tract. Although they are structurally related to insulin, the relaxin family peptides produce their physiological effects by activating a group of four G protein-coupled receptors (GPCRs), relaxin family peptide receptors 1-4 (RXFP1-4). Relaxin and INSL3 are the cognate ligands for RXFP1 and RXFP2, respectively, that are leucine-rich repeat containing GPCRs. RXFP1 activates a wide spectrum of signaling pathways to generate second messengers that include cAMP and nitric oxide, whereas RXFP2 activates a subset of these pathways. Relaxin-3 and INSL5 are the cognate ligands for RXFP3 and RXFP4 that are closely related to small peptide receptors that when activated inhibit cAMP production and activate MAP kinases. Although there are still many unanswered questions regarding the mode of action of relaxin family peptides, it is clear that they have important physiological roles that could be exploited for therapeutic benefit.

Preimplantation human blastocyst-endometrial interactions: the role of inflammatory mediators

Immune factors such as cytokines, chemokines, and growth factors are known to play important roles in the preimplantation interactions and communication between the blastocyst and receptive endometrium. This crucial dialog occurs during the stages when the blastocyst is in the uterine cavity immediately preceding implantation and the establishment of pregnancy. Human preimplantation processes are difficult to study due to restrictions on tissue availability. This review focuses on the expression and role of immune factors in human blastocyst-endometrial dialog during the very early stages of implantation. It highlights the importance of immune regulators and the need to develop new models to study human implantation.

The metastatic potential of canine mammary tumours can be assessed by mRNA expression analysis of connective tissue modulators

Metastases are the crucial factor for the prognosis of canine mammary tumours (CMTs). In women, the peptide hormone relaxin is linked with metastatic breast cancer. Therefore, the impact of relaxin and its receptors on matrix metalloproteinase (MMP) expression, metastatic disease and survival was analysed using qRT-PCR and immunohistochemistry of CMT samples from 59 bitches. The expression of relaxin and its receptor RXFP1 (relaxin family peptide receptor 1) was discovered on gene and protein levels. Intratumoural relaxin mRNA expression and relaxin plasma levels had no prognostic value. High mRNA levels RXFP1 were an independent marker of metastatic potential, with a more than 15-fold risk increase, and a predictor for shorter survival. Also, MMP-2 expression was associated with early death because of CMT. The mRNA expressions of relaxin, RXFP1 and MMP-2 were positively correlated indicating a common pathogenetic linkage. Thus, RXFP1 is proposed as a new early marker of metastatic potential in CMT and a possible therapeutic target.

Endometrial expression of relaxin and relaxin receptor in endometriosis

Our studies demonstrate significantly lower expression of relaxin and its receptor in ectopic endometriotic tissues than their expression in eutopic endometrium and in endometrium from normal controls. These data suggest that in normal and eutopic endometrium, relaxin may exert a protective effect against endometriosis.

Cytokines and Growth Factors in Implantation

Implantation failure is the most important rate limiting factor in the success of assisted reproductive techniques like In vitro fertilization–embryo transfer (IVF-ET). Cytokines are multifunctional signaling molecules having an implicit role in the human implantation process. This review focuses on the redundant roles of cytokines during the various stages of implantation. It also indicates that levels of cytokines in biological fluids like serum and follicular fluid obtained during oocyte retrieval might act as determinants of implantation potential of the blastocyst. Thus a holistic, metabolomic approach of analyzing biological fluids may provide a simpler approach to study the hitherto enigmatic process rather than the proteomic and genomic approach.

TGFβ1 attenuates expression of prolactin and IGFBP-1 in decidualized endometrial stromal cells by both SMAD-dependent and SMAD-independent pathways

BACKGROUND

Decidualization (differentiation) of the endometrial stromal cells during the secretory phase of the menstrual cycle is essential for successful implantation. Transforming Growth Factor β1 (TGFβ1) canonically propagates its actions via SMAD signalling. A role for TGFβ1 in decidualization remains to be established and published data concerning effects of TGFβ1 on markers of endometrial decidualization are inconsistent.

METHODOLOGY/PRINCIPAL FINDINGS

Non-pregnant endometrial stromal cells (ESC) and first trimester decidual stromal cells (DSC) were cultured in the presence or absence of a decidualizing stimulus. Incubation of ESCs with TGFβ1 (10 ng/ml) down-regulated the expression of transcripts encoding the decidual marker proteins prolactin (PRL), insulin-like growth factor binding protein-1 (IGFBP-1) and tissue factor (TF). TGFβ1 also inhibited secretion of PRL and IGFBP-1 proteins by ESCs and surprisingly this response preceded down-regulation of their mRNAs. In contrast, DSCs were more refractory to the actions of TGFβ1, characterized by blunted and delayed down-regulation of PRL, IGFBP-1, and TF transcripts, which was not associated with a significant reduction in secretion of PRL or IGFBP-1 proteins. Addition of an antibody directed against TGFβ1 increased expression of IGFBP-1 mRNA in decidualised cells. Knockdown of SMAD 4 using siRNAs abrogated the effect of TGFβ1 on expression of PRL in ESCs but did not fully restore expression of IGFBP-1 mRNA and protein.

CONCLUSIONS/SIGNIFICANCE

TGFβ1 inhibits the expression and secretion of decidual marker proteins. The impact of TGFβ1 on PRL is SMAD-dependent but the impact on IGFBP1 is via an alternative mechanism. In early pregnancy, resistance of DSC to the impact of TGFβ1 may be important to ensure tissue homeostasis.

Down syndrome screening: imagining the screening test of the future

Prenatal screening for Down syndrome (DS) is performed by risk calculation based on biochemical and biometric parameters. This way, approximately 75-85% of all DS cases can be detected. A way to improve detection rates is to search for new screening markers. Since the majority of biomarkers used in current DS screening are predominantly produced by the placenta, and the presence of an extra chromosome (as in DS) complicates placental development and function, it is plausible to assume that new potential screening markers may also originate from the placenta. Any alterations in these markers can be attributed to abnormal placental development and function. This article focuses on normal early placental development and function compared with that in DS pregnancies. Using this knowledge, we reason towards candidate biomarkers that may be useful in screening for DS.

Membrane receptors: structure and function of the relaxin family peptide receptors

The receptors for members of the relaxin peptide family have only recently been discovered and are G-protein-coupled receptors (GPCRs). Relaxin and insulin-like peptide 3 (INSL3) interact with the leucine-rich-repeat-containing GPCRs (LGRs) LGR7 and LGR8, respectively. These receptors show closest similarity to the glycoprotein hormone receptors and contain large ectodomains with 10 leucine-rich repeats (LRRs) but are unique members of the LGR family (class C) as they have an LDL class A (LDLa) module at their N-terminus. In contrast, relaxin-3 and INSL5 interact with another class of type I GPCRs which lack a large ectodomain, the peptide receptors GPCR135 and GPCR142, respectively. These receptors are now classified as relaxin family peptide (RXFP) receptors, RXFP1 (LGR7), RXFP2 (LGR8), RXFP3 (GPCR135) and RXFP4 (GPCR142). This review outlines the identification of the peptides and receptors, their expression profiles and physiological roles and the functional interactions of the peptides with their unique receptors.

Relaxin stimulates osteoclast differentiation and activation

Relaxin is a pleiotropic hormone with actions in reproductive and non-reproductive tissues, and has a role in tumor biology. It can promote growth, differentiation and invasiveness of different tumors, especially those that give bone metastases, and relaxin serum concentrations are increased in patients with bone metastasis. In osteolytic metastasis the destruction of bone is mediated by osteoclasts that are multinucleated cells derived from hematopoietic progenitors. We found that human hematopoietic precursors and mature osteoclasts express the relaxin receptor RXFP1. Then, we investigated the effects of relaxin on the differentiation, activation and gene expression of osteoclasts during in vitro osteoclastogenesis from human hematopoietic progenitor cells. Relaxin alone was able to induce the multistep differentiation process of human osteoclastogenesis with timing similar to that obtained with the classical stimulators of osteoclastogenesis RANKL, M-CSF and PTH. The expression profile of several osteoclast genes was studied with quantitative RT-PCR during the entire process of osteoclastogenesis. This analysis showed that relaxin induced genes that are implicated in the differentiation, survival and activation of osteoclasts. Relaxin-induced osteoclasts were fully differentiated, positive for tartrate resistant acid phosphatase and vitronectin receptor, expressing a typical F-actin ring and able to resorb the bone. Furthermore, relaxin induced the expression of its specific receptor RXFP1 in osteoclasts. This study demonstrates for the first time that relaxin is a potent stimulator of osteoclastogenesis from hematopoietic precursors and regulates the activity of mature osteoclasts, opening new perspectives on the role of this hormone in bone physiology, diseases and metastasis.

Expression of LGR7 in the primate corpus luteum implicates the corpus luteum as a relaxin target organ

In women, the corpus luteum is the source of circulating relaxin. No previous studies have addressed whether the corpus luteum is also a relaxin target organ. We determined relaxin receptor LGR7 mRNA expression in human term pregnancy corpora lutea and nonhuman primate corpora lutea obtained during the menstrual cycle. Real-time reverse transcription-PCR demonstrated the expression of LGR7 mRNA in both human and rhesus monkey corpora lutea. Rhesus monkey corpora lutea were obtained from naturally cycling animals following documented luteinizing hormone (LH) surges at early, mid-, mid-late, and late luteal phases. Luteal expression of LGR7 mRNA did not show temporal variation. Since the primate corpus luteum is LH dependent, we assessed LGR7 mRNA expression in corpora lutea from rhesus monkeys treated with a gonadotropin-releasing hormone (GnRH) antagonist, which significantly suppressed pituitary LH levels. GnRH antagonist treatment, which also inhibits both progesterone and relaxin production, resulted in a fivefold increase in luteal LGR7 mRNA expression. These data suggest that luteal LGR7 mRNA expression may be regulated by relaxin and/or LH and that the primate corpus luteum is a target organ for relaxin.

Characterization of relaxin receptor (RXFP1) desensitization and internalization in primary human decidual cells and RXFP1-transfected HEK293 cells

We report here the desensitization and internalization of the relaxin receptor (RXFP1) after agonist activation in both primary human decidual cells and HEK293 cells stably transfected with RXFP1. The importance of beta-arrestin 2 in these processes has also been demonstrated. Thus, in HEK-RXFP1 cells the desensitization of RXFP1 was significantly increased when beta-arrestin 2 was overexpressed. After relaxin activation, beta-arrestin 2 was translocated to the cell membrane and RXFP1 underwent rapid internalization. We have previously shown that RXFP1 forms dimers/oligomers during its biosynthesis and trafficking to the plasma membrane, we now show that internalization of RXFP1 occurs through this dimerization/oligomerization. In nonagonist stimulated cells, it is known that the majority of the RXFP1 is located intracellularly and was confirmed in the cells used here. Constitutive internalization of RXFP1 could account for this and indeed, slow but robust constitutive internalization, which was increased after agonist stimulation was demonstrated. A carboxyl-terminal deleted RXFP1 variant had a similar level of constitutive agonist-independent internalization as the wild-type RXFP1 but lost sensitivity to agonist stimulation. This demonstrated the importance of the carboxyl terminus in agonist-stimulated receptor internalization. These data suggest that the autocrine/paracrine actions of relaxin in the decidua are under additional controls at the level of expression of its receptor on the surface of its target cells.

The role of growth factors and cytokines during implantation: endocrine and paracrine interactions

Implantation, a critical step for establishing pregnancy, requires molecular and cellular events resulting in uterine growth and differentiation, blastocyst adhesion, invasion, and placental formation. Successful implantation requires a receptive endometrium, a normal and functional embryo at the blastocyst stage, and a synchronized dialogue between maternal and embryonic tissues. In addition to the well-characterized role of sex steroids, the complexity of embryo implantation and placentation is exemplified by the number of cytokines and growth factors with demonstrated roles in these processes. Disturbances in the normal expression and action of these cytokines result in an absolute or partial failure of implantation and abnormal placental formation in mice and human. Members of the gp130 cytokine family, interleukin-11 (IL-11) and leukemia inhibitory factor, the transforming growth factor beta superfamily, the colony-stimulating factors, and the IL-1 and IL-15 systems are crucial molecules for a successful implantation. Chemokines are also important, both in recruiting specific cohorts of leukocytes to the implantation site and in trophoblast trafficking and differentiation. This review provides discussion of the embryonic and uterine factors that are involved in the process of implantation in autocrine, paracrine, and/or juxtacrine manners at the hormonal, cellular, and molecular levels.

The human insulin superfamily of polypeptide hormones

The identification in the 1950s of insulin, an essential carbohydrate regulatory hormone, as consisting of not one but two peptide chains linked by three disulfide bonds in a distinctive pattern was a milestone in peptide chemistry. When it was later found that relaxin also possessed a similar overall structure, the term 'insulin superfamily' was coined. Use of methods of conventional protein chemistry followed by recombinant DNA and more recently bioinformatics has led to the recognition that insulin is the precursor to a large protein superfamily that extends beyond the human. Insulin-like peptides are found not only in vertebrates such as mammals, birds, reptiles, amphibians but also in the invertebrates such as chordates, molluscs and insects. All superfamily members share the distinctive insulin structural motif. In the human, there exists ten members of the superfamily, each of which are expressed on the ribosome as a single-chain pre-prohormone that undergoes proteolytic processing to produce eight double-chain mature proteins and two single-chain forms. The six cysteine residues that form the three insulin disulfide cross-links - one intramolecular within the A-chain and two intermolecular between that A- and B-chains - are absolutely conserved across all members of the superfamily. They are responsible for imparting a similar overall tertiary structure. The human insulin superfamily members have each evolved to assume remarkably distinctive biological functions ranging from glucose homeostasis to neuroendocrine actions. That such diversity is contained within a modestly sized superfamily is testament to efficiency of the insulin structural motif as an evolutionary template.

Relaxin physiology in the female reproductive tract during pregnancy

The characteristic functions of relaxin are associated with female reproductive tract physiology. These include the regulation of biochemical processes involved in remodeling the extracellular matrix of the cervix and vagina during pregnancy and rupture of the fetal membranes at term. Such modifications enable the young to move unimpeded through the birth canal and prevent dystocia. However, relaxin's physiological actions are not limited to late gestation. New functions for this peptide hormone in implantation and placentation are also emerging. Relaxin promotes uterine and placental growth and influences vascular development and proliferation in the endometrium. This chapter provides an overview of the current literature on relaxin physiology in the uterus, cervix and vagina of pregnant females and the impact on fetal health. It also outlines the potential mechanisms of relaxin action, particularly in the cervical extracellular matrix and uterine endometrium.

Steroidogenic enzyme and key decidualization marker dysregulation in endometrial stromal cells from women with versus without endometriosis

Identification of mechanisms underlying endometriosis pathogenesis will facilitate understanding and treatment of infertility and pain associated with this disorder. Herein, we investigated the expression of steroidogenic pathway enzymes and key decidualization biomarkers in endometrial tissue and in eutopic endometrial stromal fibroblasts (hESFs) from women with vs. those without endometriosis, and subsequently treated in vitro with 8-bromo-cAMP (8-Br-cAMP) or progesterone (P4). Real-time quantitative PCR, immunohistochemistry, ELISA, and radiometric aromatase activity assay were used. The results demonstrate significantly increased (14.5-fold; P=0.037) expression of aromatase in eutopic endometrium of women with disease. In 8-Br-cAMP-treated hESF from eutopic endometrium of women with endometriosis, the balance in estradiol (E2) and P4 biosynthetic and metabolizing enzymes is disturbed (decreased HSD3B1 and HSD17B2, and increased HSD17B1 and aromatase), with the equilibrium being shifted towards an E2-enriched milieu. However, hESF from the same group of women treated with P4 did not demonstrate such responsiveness. Lower expression of IGFBP1 and prolactin mRNA and protein was observed in hESF from women with vs. those without endometriosis in response to 8-Br-cAMP, but not P4, suggesting a blunted response of these decidual biomarkers to activation of the PKA pathway in eutopic endometrium in women with disease. The dichotomy of 8-Br-cAMP regulation of select steroidogenic enzymes leading to an enriched E2 milieu within the endometrium and a blunted response of decidual biomarkers to this decidualizing agent of hESF from women with endometriosis suggests resistance to full decidualization of the stromal fibroblasts and mechanisms underlying implantation failure and the pathophysiology of this disorder.

Relaxin reduces xenograft tumour growth of human MDA-MB-231 breast cancer cells

Introduction

Relaxin levels are increased in cases of human breast cancer and has been shown to promote cancer cell migration in carcinoma cells of the breast, prostate gland and thyroid gland. In oestrogen receptor alpha-negative MDA-MB-231 human breast cancer cells, relaxin was shown to down-regulate the metastasis-promoting protein S100A4 (metastasin), a highly significant prognostic factor for poor survival in breast cancer patients. The cellular mechanisms of relaxin exposure in breast cancer cells are not fully understood. The aim of this study was to investigate short-term and long-term effects of relaxin on cancer cell motility and S100A4 expression and to determine the long-term effects of relaxin on in vivo tumour growth in an oestrogen-independent context.

Method

We have established stable transfectants of highly invasive oestrogen-receptor alpha-negative MDA-MB-231 human breast cancer cells with constitutive expression of bioactive H2-relaxin (MDA/RLN2). RLN2 secretion was determined by ELISA. Relaxin receptor RXFP1 (Relaxin-family-peptide) was detected by reverse transcription (RT) PCR and its activation was assessed by induction of cyclic adenosine monophosphate (cAMP). Stable MDA/RLN2 clones and RLN2 treated MDA-MB-231 cells were subjected to motility and in vitro-invasion assays. Proliferation was assessed in bromodeoxyuridine (BrdU) and MTT assays. S100A4 expression was determined by RT-PCR and Western blot. Specific small interfering RNA was employed to down-regulate relaxin receptor and S100A4. MDA/EGFP vector control and two MDA/RLN2 clones were injected subcutaneously in nude mice to determine tumour growth and cancer cell invasiveness in vivo. Xenograft tumour tissues were assessed by histology and immunohistochemistry and frozen tissues were used for the detection of S100A4 and RLN2.

Results

Short-term exposure to relaxin for 24 hours increased cell motility in a relaxin receptor-dependent manner. This increase in cell motility was mediated by S100A4. Long-term exposure to relaxin secreted from stable transfectants reduced cell motility and in vitro invasiveness. Relaxin decreased cell proliferation and down-regulated cellular S100A4 levels in MDA-MB-231 and T47D breast cancer cells. Stable MDA/RLN2 transfectants produced smaller xenograft tumours containing reduced S100A4 protein levels in vivo.

Conclusion

Our results indicate that long-term exposure to relaxin confers growth inhibitory and anti-invasive properties in oestrogen-independent tumours in vivo, which may in part be mediated through a down-regulation of S100A4.

Relaxin (RLX) and estrogen affect estrogen receptor α, vascular endothelial growth factor, and RLX receptor expression in the neonatal porcine uterus and cervix

The porcine female reproductive tract undergoes estrogen receptor (ER) α-dependent development after birth (postnatal day=PND 0), the course of which can determine adult uterine function. Uterotrophic effects of relaxin (RLX) in the porcine neonate are age specific and may involve ER activation. Here, objectives were to determine effects of RLX and estrogen administered from birth on uterine and cervical growth and expression of ERα, vascular endothelial growth factor (VEGF), and the RLX receptor (RXFP1). On PND 0, gilts were treated with the antiestrogen ICI 182 780 (ICI) or vehicle alone and, 2 h later, were given estradiol-17β (E) or porcine RLX for 2 days. Neither RLX nor E affected uterine wet weight or protein content on PND 2. However, RLX, but not E, increased cervical wet weight and protein content when compared with controls. Pretreatment with ICI did not inhibit RLX-stimulated cervical growth. Uterine and cervical ERα increased in response to RLX, but not E. Both RLX and E increased VEGF in the uterus and cervix on PND 2. Pretreatment with ICI increased VEGF in both tissues and increased RLX-induced cervical VEGF. In the uterus E, but not RLX, increased RXFP1 mRNA. In the cervix, E increased RXFP1 gene expression whereas RLX decreased it. Results indicate that the neonatal uterus and cervix are sensitive to E and RLX and that growth responses to RLX in these tissues differ by PND 2. Effects of RLX on uterine and cervical ERα and VEGF expression may be important for neonatal reproductive tract development.

Expression of Delta-like protein 4 in the human endometrium

Activation of Delta-Notch signaling pathway promotes the development of the vascular system in embryo, normal adult tissues, and cancerous lesions. Delta and Notch genes are known to be expressed in endothelial cells, and little is known of their expression beyond the vascular system. The purpose of this study was to investigate whether Delta gene would be expressed in cells of the uterine endometrium. In this study, we found that the human endometrial cells expressed one of the Delta ligands, Delta-like 4 protein (Dll4). Dll4 was expressed in human endometrium in a spatiotemporal fashion. Immunohistochemistry studies showed the cytoplasm as well as membrane staining with apical localization both in the luminal and glandular epithelium and moderate diffuse staining in the cytoplasm of the stromal cells. Western blot analysis showed that the size of the endometrial Dll4 was identical to that in the human umbilical endothelial cells. The expression of Dll4 mRNA in human endometrial cells was quantitatively determined by real-time PCR. Dll4 mRNA expressed in the glandular epithelium showed large variations, and it was significantly elevated in the mid and late proliferative and early secretory endometrium. Endometrial stromal cells contained less Dll4 mRNA and had no clear correlation with the menstrual cycle. The effect of hormones was studied in the primary culture of isolated glandular epithelial and stromal cells. In glandular cells, estradiol had little effect, and medroxyprogesterone acetate significantly reduced the mRNAs compared with that of control. Relaxin induced the Dll4 mRNA. In stromal cells, both estradiol and medroxyprogesterone acetate reduced the Dll4 mRNA. To our knowledge, this is the first report of the expression of Dll4 in the endometrium. We propose that endometrial Dll4 may enhance the development of the endometrial microvascular system and facilitate the implantation of blastocyst in a fertile cycle.

Relaxin family peptide receptors--former orphans reunite with their parent ligands to activate multiple signalling pathways

The relaxin family peptides, although structurally closely related to insulin, act on a group of four G protein-coupled receptors now known as Relaxin Family Peptide (RXFP) Receptors. The leucine-rich repeat containing RXFP1 and RXFP2 and the small peptide-like RXFP3 and RXFP4 are the physiological targets for relaxin, insulin-like (INSL) peptide 3, relaxin-3 and INSL5, respectively. RXFP1 and RXFP2 have at least two binding sites--a high-affinity site in the leucine-rich repeat region of the ectodomain and a lower-affinity site in an exoloop of the transmembrane region. Although they respond to peptides that are structurally similar, RXFP3 and RXFP4 demonstrate distinct binding properties with relaxin-3 being the only peptide that can recognize these receptors in addition to RXFP1. Activation of RXFP1 or RXFP2 causes increased cAMP and the initial response for both receptors is the resultant of Gs-mediated activation and G(oB)-mediated inhibition of adenylate cyclase. With RXFP1, an additional delayed increase in cAMP involves betagamma subunits released from G(i3). In contrast, RXFP3 and RXFP4 inhibit adenylate cyclase and RXFP3 causes ERK1/2 phosphorylation. Drugs acting at RXFP1 have potential for the treatment of diseases involving tissue fibrosis such as cardiac and renal failure, asthma and scleroderma and may also be useful to facilitate embryo implantation. Activators of RXFP2 may be useful to treat cryptorchidism and infertility and inhibitors have potential as contraceptives. Studies of the distribution and function of RXFP3 suggest that it is a potential target for anti-anxiety and anti-obesity drugs.

Effects of uteroplacental restriction on the relaxin-family receptors, Lgr7 and Lgr8, in the uterus of late pregnant rats

The peptide hormone relaxin stimulates uterine growth and endometrial angiogenesis and inhibits myometrial contractions in a variety of species. The receptor for relaxin is a leucine-rich repeat containing G-protein-coupled receptor Lgr7 (RXFP1) that is highly expressed in the myometrium of late pregnant mice, with a significant decrease in receptor density observed at term. The present study first compared the expression of Lgr7 with another relaxin-family receptor Lgr8 (RXFP2) in the uterus and placenta of late pregnant rats. The uterus was separated into endometrial and myometrial components, and the myometrium into fetal and non-fetal sites, for further analysis. We then assessed the response of these receptors to uteroplacental restriction (UPR). Expression of the Lgr7 gene was significantly higher in the uterus compared with the placenta. Within the uterus, on Day 20 of gestation, there was equivalent expression of Lgr7 in fetal and non-fetal sites of the myometrium, as well as in the endometrium v. myometrium. The second receptor investigated, Lgr8, was also expressed in the endometrium and myometrium, but at significantly lower levels than Lgr7. Bilateral ligation of the maternal uterine blood vessels on Day 18 of gestation resulted in uteroplacental restriction, a decrease in fetal weight and litter size, and a significant upregulation in uterine, but not placental, Lgr7 and Lgr8 gene expression in UPR animals compared with controls. These data suggest that both relaxin family receptors are upregulated in response to a reduction in uteroplacental blood flow in rats.

Effects of tibolone on nuclear receptors in human endometrial cells

OBJECTIVE

Tibolone regulates estrogenic activity in a tissue-selective manner. The purpose of this study was to evaluate the effects of tibolone on the mRNA content of nuclear receptors, estrogen receptor-alpha and beta (ERalpha and ERbeta), progesterone receptor (PR), and androgen receptor (AR) in human endometrial stromal and glandular cells.

STUDY DESIGN

Human endometrial stromal and glandular cells were isolated from endometrial tissue fragments and separately incubated with tibolone and its metabolites. Nuclear receptor mRNA was determined using real-time polymerase chain reaction (PCR).

RESULTS

In endometrial stromal cells, tibolone, Delta4-tibolone, and 3betaOH-tibolone, but not 3alphaOH-tibolone, significantly reduced ERalpha mRNA by approximately 60% and ERalpha protein by approximately 80%. No reduction of ERalpha was observed in endometrial glandular cells. Tibolone induced PR mRNAs to various extents and reached up to 6-fold in glandular cells, but only a moderate increase (approximately 1.5-fold) in stromal cells. Tibolone increased ERbeta and had little effect on AR mRNA in endometrial cells.

CONCLUSION

The results showed the majority of the nuclear receptors were not significantly altered. However, tibolone significantly reduced ERalpha in stromal cells and increased PR in glandular cells. These biological effects may play essential roles in averting stimulation of the endometrium in tibolone users.

International Union of Pharmacology LVII: recommendations for the nomenclature of receptors for relaxin family peptides

Although the hormone relaxin was discovered 80 years ago, only in the past 5 years have the receptors for relaxin and three other receptors that respond to related peptides been identified with all four receptors being G-protein-coupled receptors. In this review it is suggested that the receptors for relaxin (LGR7) and those for the related peptides insulin-like peptide 3 (LGR8), relaxin-3 (GPCR135), and insulin-like peptide 5 (LGPCR142) be named the relaxin family peptide receptors 1 through 4 (RXFP1-4). RXFP1 and RXFP2 are leucine-rich repeat-containing G-protein-coupled receptors with complex binding characteristics involving both the large ectodomain and the transmembrane loops. RXFP1 activates adenylate cyclase, protein kinase A, protein kinase C, phosphatidylinositol 3-kinase, and extracellular signaling regulated kinase (Erk1/2) and also interacts with nitric oxide signaling. RXFP2 activates adenylate cyclase in recombinant systems, but physiological responses are sensitive to pertussis toxin. RXFP3 and RXFP4 resemble more conventional peptide liganded receptors and both inhibit adenylate cyclase, and in addition RXFP3 activates Erk1/2 signaling. Physiological studies and examination of the phenotypes of transgenic mice have established that relaxin has roles as a reproductive hormone involved in uterine relaxation (some species), reproductive tissue growth, and collagen remodeling but also in the cardiovascular and renal systems and in the brain. The connective tissue remodeling properties of relaxin acting at RXFP1 receptors have potential for the development of agents effective for the treatment of cardiac and renal fibrosis, asthma, and scleroderma and for orthodontic remodelling. Agents acting at RXFP2 receptors may be useful for the treatment of cryptorchidism and infertility, whereas antagonists may be used as contraceptives. The brain distribution of RXFP3 receptors suggests that actions at these receptors have the potential for the development of antianxiety and antiobesity drugs.

Receptors for Relaxin Family Peptides

Recent studies have identified four receptors that are the physiological targets for relaxin family peptides. All are class I (rhodopsin like) G-protein-coupled receptors with LGR7 (RXFP1) and LGR8 (RXFP2) being type C leucine-rich repeat-containing receptors, whereas GPCR135 (RXFP3) and GPCR142 (RXFP4) resemble receptors that respond to small peptides such as somatostatin and angiotensin II. The cognate ligands for the receptors have been identified: relaxin for RXFP1; INSL3 for RXFP2; relaxin 3 for RXFP3 and INSL5 for RXFP4. RXFP1 and RXFP2 receptors produce increases in intracellular cAMP levels upon stimulation, although the response is complex and contains a component sensitive to PI-3-kinase inhibitors. There is also evidence that RXFP1 can activate Erk1/2 and nitric oxide synthase, and relaxin has been reported to enter cells and activate glucocorticoid receptors. In contrast, RXFP3 and RXFP4 couple to Gi by a pertussis toxin-sensitive mechanism to cause inhibition of cAMP production. Now that the receptors for relaxin family peptides and their cognate ligands have been identified, we suggest a nomenclature for both the peptides and the receptors that we hope will be helpful to researchers in this rapidly advancing field.

Survival of dialysis patients after cardiac arrest and the impact of implantable cardioverter defibrillators

BACKGROUND

Sudden cardiac death is the single largest cause of mortality in dialysis patients. There are no published data on the use or survival impact of implantable cardioverter defibrillators (ICDs) in dialysis patients. The objective of this retrospective cohort study was to determine ICD use in dialysis patients and impact on survival.

METHODS

Dialysis patients hospitalized from 1996 to 2001 for ventricular fibrillation/cardiac arrest, having ICD implantation within 30 days of admission, discharged alive, and surviving at least 30 days from admission were identified from the 100% end-stage renal disease (ESRD) sample of the Medicare database. Long-term survival was estimated by life-table method. Impact of independent predictors on survival was examined in a comorbidity-adjusted Cox model and a propensity model.

RESULTS

There were 460 patients (7.6%) with ICD and 5582 patients (92.4%) without ICD. Estimated 1-, 2-, 3-, 4-, and 5-year survivals after day 30 of admission in the ICD group were 71%, 53%, 36%, 25%, and 22%, respectively; in the no-ICD group, 49%, 33%, 23%, 16%, and 12% (P < 0.0001). ICD implantation was independently associated with a 42% reduction in death risk [relative risk 0.58 (95% CI 0.50, 0.66)]. In the propensity model, the relative risks of death for the lower, middle, and upper third propensity groups were 0.45 (0.26, 0.81), 0.61 (0.45, 0.84), and 0.65 (0.55, 0.76), respectively. The C statistic for the propensity model equaled 0.81.

CONCLUSION

In dialysis patients, ICD therapy is apparently underused. ICD implantation in cardiac arrest survivors on dialysis is associated with greater survival.

The human relaxin receptor (LGR7): expression in the fetal membranes and placenta

The relaxin receptor has been recently described as a leucine-rich repeat G-protein coupled receptor and designated as LGR7. A closely related receptor, LGR8, is co-expressed by some cells. This study explored the expression of the genes for these receptors in the human fetal membranes and placenta by RT-PCR and the LGR7 protein by immunolocalization. The results showed that LGR7 was well expressed in the fetal membranes, with significantly more in the decidua (p<0.05) than in the amnion. On the other hand, relatively low levels were expressed in the placenta. The major splice variant of LGR7 was undetectable in either the placenta or fetal membranes. Expression of LGR8 was also below the level of detectability in either tissue. Immunostaining for LGR7 was conducted with antisera to both its endodomain and ectodomain, in order to seek evidence for a solubilized ectodomain. However, similar staining patterns were obtained with both antisera, with predominant staining in the cells of the amniotic epithelium, chorionic cytotrophoblast and decidua. Full-thickness fetal membranes from preterm deliveries, before and after labor or after preterm premature rupture of the membrane (PPROM) and labor were collected. In addition, membranes at term, both before and after spontaneous labor were used for analysis of LGR7 gene expression. There was significantly greater LGR7 expressed (p=0.01) in the preterm period compared to term, indicating a potentially important role for relaxin at this time. There was a marginal decline in LGR7 gene expression after labor and delivery both at preterm and term, which did not reach significance. Immunostaining patterns showed less inter-patient variability than did gene expression, with more intense staining for LGR7 after labor and delivery.

Cytokines, chemokines and growth factors in endometrium related to implantation

The complexity of the events of embryo implantation and placentation is exemplified by the number and range of cytokines with demonstrated roles in these processes. Disturbance of the normal expression or action of these cytokines results in complete or partial failure of implantation and abnormal placental formation in mice or humans. Of known importance are members of the gp130 family such as interleukin-11 (IL-11) and leukaemia inhibitory factor (LIF), the transforming growth factor beta (TGFbeta) superfamily including the activins, the colony-stimulating factors (CSF), the IL-1 system and IL-15 system. New data are also emerging for roles for a number of chemokines (chemoattractive cytokines) both in recruiting specific cohorts of leukocytes to implantation sites and in trophoblast differentiation and trafficking. This review focuses on those cytokines and chemokines whose expression pattern in the human endometrium is consistent with a potential role in implantation and placentation and for which some relevant actions are known. It examines what is known of their regulation and action along with alterations in clinically relevant situations.

Ligand activated relaxin receptor increases the transcription of IGFBP-1 and prolactin in human decidual and endometrial stromal cells

The aim of this study was to investigate relaxin (RLX) receptor-mediated gene activation in human endometrium. We determined the promoter activities of insulin-like growth factor binding protein-1 (IGFBP-1) and prolactin (PRL) and identified sequence(s) that mediate RLX activated transcription in human decidual cells and endometrial stromal cells. In human decidual cells, the promoter activity of IGFBP-1 was increased significantly in cells incubated with RLX. In endometrial stromal cells, the RLX mediated activation was enhanced only when stromal cells were co-transfected with RLX-receptor (LGR7) expression vector and RLX alone had little effect (Mazella et al., 2004). Deletion and mutation analysis showed that the cAMP regulatory element (CRE, -263 to -259 bp) in the IGFBP-1 promoter was essential for the activation. In addition, RLX increased the phosphorylation of CRE binding protein (CREB to p-CREB) and p-CREB resided in the nucleus, indicating that RLX activates the protein kinase (PKA) system in decidual cells. Gel shift assay showed that nuclear extracts prepared from RLX treated decidual cells increased the binding to the CRE site of the IGFBP-1 promoter. RLX increased the PRL promoter activity mediated through the region containing multiple CCAAT/enhancer-binding proteins (C/EBP) binding sites that have been shown to mediate the PRL gene activation by cAMP analogue (Pohnke et al., 1999). RLX enhanced IGFBP-1 promoter activity was inhibited by cAMP dependent PKA inhibitor, H-89. PRL promoter activity was inhibited by both H-89 and U0126 indicating multiple signalling pathways are activated by RLX in endometrial cells for different target gene activation.