Adrenomedullin and pregnancy: perspectives from animal models to humans

Grimm S, Coarfa C, Theis F, Simon LM, Shivanna B. Leveraging Integrated RNA Sequencing to Decipher Adrenomedullin's Protective Mechanisms in Experimental Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic lung disease commonly affecting premature infants, with limited therapeutic options and increased long-term consequences. Adrenomedullin (Adm), a proangiogenic peptide hormone, has been found to protect rodents against experimental BPD. This study aims to elucidate the molecular and cellular mechanisms through which Adm influences BPD pathogenesis using a lipopolysaccharide (LPS)-induced model of experimental BPD in mice. Bulk RNA sequencing of Adm-sufficient (wild-type or Adm+/+) and Adm-haplodeficient (Adm+/-) mice lungs, integrated with single-cell RNA sequencing data, revealed distinct gene expression patterns and cell type alterations associated with Adm deficiency and LPS exposure. Notably, computational integration with cell atlas data revealed that Adm-haplodeficient mouse lungs exhibited gene expression signatures characteristic of increased inflammation, natural killer (NK) cell frequency, and decreased endothelial cell and type II pneumocyte frequency. Furthermore, in silico human BPD patient data analysis supported our cell type frequency finding, highlighting elevated NK cells in BPD infants. These results underscore the protective role of Adm in experimental BPD and emphasize that it is a potential therapeutic target for BPD infants with an inflammatory phenotype.

Endometrial TGFβ signaling fosters early pregnancy development by remodeling the fetomaternal interface

The endometrium is a unique and highly regenerative tissue with crucial roles during the reproductive lifespan of a woman. As the first site of contact between mother and embryo, the endometrium, and its critical processes of decidualization and immune cell recruitment, play a leading role in the establishment of pregnancy, embryonic development, and reproductive capacity. These integral processes are achieved by the concerted actions of steroid hormones and a myriad of growth factor signaling pathways. This review focuses on the roles of the transforming growth factor β (TGFβ) pathway in the endometrium during the earliest stages of pregnancy through the lens of immune cell regulation and function. We discuss how key ligands in the TGFβ family signal through downstream SMAD transcription factors and ultimately remodel the endometrium into a state suitable for embryo implantation and development. We also focus on the key roles of the TGFβ signaling pathway in recruiting uterine natural killer cells and their collective remodeling of the decidua and spiral arteries. By providing key details about immune cell populations and TGFβ signaling within the endometrium, it is our goal to shed light on the intricate remodeling that is required to achieve a successful pregnancy.

Adrenomedullin has a pivotal role in trophoblast differentiation: A promising nanotechnology-based therapeutic target for early-onset preeclampsia

Early-onset preeclampsia (EOPE) is a severe pregnancy complication associated with defective trophoblast differentiation and functions at implantation, but manifestation of its phenotypes is in late pregnancy. There is no reliable method for early prediction and treatment of EOPE. Adrenomedullin (ADM) is an abundant placental peptide in early pregnancy. Integrated single-cell sequencing and spatial transcriptomics confirm a high ADM expression in the human villous cytotrophoblast and syncytiotrophoblast. The levels of ADM in chorionic villi and serum were lower in first-trimester pregnant women who later developed EOPE than those with normotensive pregnancy. ADM stimulates differentiation of trophoblast stem cells and trophoblast organoids in vitro. In pregnant mice, placenta-specific ADM suppression led to EOPE-like phenotypes. The EOPE-like phenotypes in a mouse PE model were reduced by a placenta-specific nanoparticle-based forced expression of ADM. Our study reveals the roles of trophoblastic ADM in placental development, EOPE pathogenesis, and its potential clinical uses.

Animal models of the placenta accreta spectrum: current status and further perspectives

Placenta accreta spectrum disorder (PAS) is a kind of disease of placentation defined as abnormal trophoblast invasion of part or all of the placenta into the myometrium, even penetrating the uterus. Decidual deficiency, abnormal vascular remodeling in the maternal-fetal interface, and excessive invasion by extravillous trophoblast (EVT) cells contribute to its onset. However, the mechanisms and signaling pathways underlying such phenotypes are not fully understood, partly due to the lack of suitable experimental animal models. Appropriate animal models will facilitate the comprehensive and systematic elucidation of the pathogenesis of PAS. Due to the remarkably similar functional placental villous units and hemochorial placentation to humans, the current animal models of PAS are based on mice. There are various mouse models induced by uterine surgery to simulate different phenotypes of PAS, such as excessive invasion of EVT or immune disturbance at the maternal-fetal interface, which could define the pathological mechanism of PAS from the perspective of the "soil." Additionally, genetically modified mouse models could be used to study PAS, which is helpful to exploring the pathogenesis of PAS from the perspectives of both "soil" and "seed," respectively. This review details early placental development in mice, with a focus on the approaches of PAS modeling. Additionally, the strengths, limitations and the applicability of each strategy and further perspectives are summarized to provide the theoretical foundation for researchers to select appropriate animal models for various research purposes. This will help better determine the pathogenesis of PAS and even promote possible therapy.

CGRP physiology, pharmacology, and therapeutic targets: migraine and beyond

Calcitonin gene-related peptide (CGRP) is a neuropeptide with diverse physiological functions. Its two isoforms (α and β) are widely expressed throughout the body in sensory neurons as well as in other cell types, such as motor neurons and neuroendocrine cells. CGRP acts via at least two G protein-coupled receptors that form unusual complexes with receptor activity-modifying proteins. These are the CGRP receptor and the AMY1 receptor; in rodents, additional receptors come into play. Although CGRP is known to produce many effects, the precise molecular identity of the receptor(s) that mediates CGRP effects is seldom clear. Despite the many enigmas still in CGRP biology, therapeutics that target the CGRP axis to treat or prevent migraine are a bench-to-bedside success story. This review provides a contextual background on the regulation and sites of CGRP expression and CGRP receptor pharmacology. The physiological actions of CGRP in the nervous system are discussed, along with updates on CGRP actions in the cardiovascular, pulmonary, gastrointestinal, immune, hematopoietic, and reproductive systems and metabolic effects of CGRP in muscle and adipose tissues. We cover how CGRP in these systems is associated with disease states, most notably migraine. In this context, we discuss how CGRP actions in both the peripheral and central nervous systems provide a basis for therapeutic targeting of CGRP in migraine. Finally, we highlight potentially fertile ground for the development of additional therapeutics and combinatorial strategies that could be designed to modulate CGRP signaling for migraine and other diseases.

Sustained Activation of CLR/RAMP Receptors by Gel-Forming Agonists

Background: Adrenomedullin (ADM), adrenomedullin 2 (ADM2), and CGRP family peptides are important regulators of vascular vasotone and integrity, neurotransmission, and fetoplacental development. These peptides signal through CLR/RAMP1, 2, and 3 receptors, and protect against endothelial dysfunction in disease models. As such, CLR/RAMP receptor agonists are considered important therapeutic candidates for various diseases. Methods and Results: Based on the screening of a series of palmitoylated chimeric ADM/ADM2 analogs, we demonstrated a combination of lipidation and accommodating motifs at the hinge region of select peptides is important for gaining an enhanced receptor-activation activity and improved stimulatory effects on the proliferation and survival of human lymphatic endothelial cells when compared to wild-type peptides. In addition, by serendipity, we found that select palmitoylated analogs self-assemble to form liquid gels, and subcutaneous administration of an analog gel led to the sustained presence of the peptide in the circulation for >2 days. Consistently, subcutaneous injection of the analog gel significantly reduced the blood pressure in SHR rats and increased vasodilation in the hindlimbs of adult rats for days. Conclusions: Together, these data suggest gel-forming adrenomedullin analogs may represent promising candidates for the treatment of various life-threatening endothelial dysfunction-associated diseases such as treatment-resistant hypertension and preeclampsia, which are in urgent need of an effective drug.

Spatial transcriptomic profiles of mouse uterine microenvironments at pregnancy day 7.5†

Uterine dysfunctions lead to fertility disorders and pregnancy complications. Normal uterine functions at pregnancy depend on crosstalk among multiple cell types in uterine microenvironments. Here, we performed the spatial transcriptomics and single-cell RNA-seq assays to determine local gene expression profiles at the embryo implantation site of the mouse uterus on pregnancy day 7.5 (D7.5). The spatial transcriptomic annotation identified 11 domains of distinct gene signatures, including a mesometrial myometrium, an anti-mesometrial myometrium, a mesometrial decidua enriched with natural killer cells, a vascular sinus zone for maternal vessel remodeling, a fetal-maternal interface, a primary decidual zone, a transition decidual zone, a secondary decidual zone, undifferentiated stroma, uterine glands, and the embryo. The scRNA-Seq identified 12 types of cells in the D7.5 uterus including three types of stromal fibroblasts with differentiated and undifferentiated markers, one cluster of epithelium including luminal and glandular epithelium, mesothelium, endothelia, pericytes, myelomonocytic cell, natural killer cells, and lymphocyte B. These single-cell RNA signatures were then utilized to deconvolute the cell-type compositions of each individual uterine microenvironment. Functional annotation assays on spatial transcriptomic data revealed uterine microenvironments with distinguished metabolic preferences, immune responses, and various cellular behaviors that are regulated by region-specific endocrine and paracrine signals. Global interactome among regions is also projected based on the spatial transcriptomic data. This study provides high-resolution transcriptome profiles with locality information at the embryo implantation site to facilitate further investigations on molecular mechanisms for normal pregnancy progression.

Temporal and spatial expression of adrenomedullin and its receptors in the porcine uterus and peri-implantation conceptuses

Adrenomedullin (ADM) is an evolutionarily conserved multi-functional peptide hormone that regulates implantation, embryo spacing and placentation in humans and rodents. However, the potential roles of ADM in implantation and placentation in pigs, as a litter-bearing species, are not known. This study determined abundances of ADM in uterine luminal fluid, and the patterns of expression of ADM and its receptor components (CALCRL, RAMP2, RAMP3, and ACKR3) in uteri from cyclic and pregnant gilts, as well as conceptuses (embryonic/fetus and its extra-embryonic membranes) during the peri-implantation period of pregnancy. Total recoverable ADM was greater in the uterine fluid of pregnant compared with cyclic gilts between Days 10 and 16 post-estrus, and was from uterine luminal epithelial (LE) and conceptus trophectoderm (Tr) cells. Uterine expression of CALCRL, RAMP2, and ACKR3 were affected by day (P < 0.05), pregnant status (P < 0.01) and/or day x status (P < 0.05). Within porcine conceptuses, expression of CALCRL, RAMP2 and ACKR3 increased between Days 10 and 16 of pregnancy. Using an established porcine trophectoderm (pTr1) cell line, it was determined that 10-7 M ADM stimulated proliferation of pTr1 cells (P < 0.05) at 48 h, and increased phosphorylated mechanistic target of rapamycin (p-MTOR) and 4E binding protein 1 (p-4EBP1) by 6.1- and 4.9-fold (P < 0.0001), respectively. These novel results indicate a significant role for ADM in uterine receptivity for implantation and conceptus growth and development in pigs. They also provide a framework for future studies of ADM signaling to affect proliferation and migration of Tr cells, spacing of blastocysts, implantation and placentation in pigs.

SUV39H2 controls trophoblast stem cell fate

BACKGROUND

The placenta is formed by the coordinated expansion and differentiation of trophoblast stem (TS) cells along a multi-lineage pathway. Dynamic regulation of histone 3 lysine 9 (H3K9) methylation is pivotal to cell differentiation for many cell lineages, but little is known about its involvement in trophoblast cell development.

METHODS

Expression of H3K9 methyltransferases was surveyed in rat TS cells maintained in the stem state and following differentiation. The role of suppressor of variegation 3-9 homolog 2 (SUV39H2) in the regulation of trophoblast cell lineage development was investigated using a loss-of-function approach in rat TS cells and ex vivo cultured rat blastocysts.

RESULTS

Among the twelve-known H3K9 methyltransferases, only SUV39H2 exhibited robust differential expression in stem versus differentiated TS cells. SUV39H2 transcript and protein expression were high in the stem state and declined as TS cells differentiated. Disruption of SUV39H2 expression in TS cells led to an arrest in TS cell proliferation and activation of trophoblast cell differentiation. SUV39H2 regulated H3K9 methylation status at loci exhibiting differentiation-dependent gene expression. Analyses of SUV39H2 on ex vivo rat blastocyst development supported its role in regulating TS cell expansion and differentiation. We further identified SUV39H2 as a downstream target of caudal type homeobox 2, a master regulator of trophoblast lineage development.

CONCLUSIONS

Our findings indicate that SUV39H2 contributes to the maintenance of TS cells and restrains trophoblast cell differentiation.

GENERAL SIGNIFICANCE

SUV39H2 serves as a contributor to the epigenetic regulation of hemochorial placental development.

Short tandem repeat near hypoxia response element (HRE) instead of HRE genetic variants in promoter calcitonin receptor-like receptor (CRLR) gene as risk factor in severe preeclampsia: a preliminary study

Objective

Calcitonin receptor-like receptor (CRLR) regulates vasoconstriction and dilatation; the expression increases during hypoxia via activation of hypoxia response element (HRE) in CRLR gene promoter region. Variant in HRE, as well short tandem repeat (STR) variants near HRE in CRLR alters the gene expression. This study focused on a case–control study to investigate the expression of genetic typing CLRL promoter variant in pregnant women with severe preeclampsia and normal pregnancies, we also tried to describe interesting findings of the genetic expression in anemic patients in the severe preeclampsia group. Our aimed to observe the correlation of CRLR gene promoter variant and anemia in severe preeclampsia.

Results

There was no nucleotide variant in HRE; CACA box prior to HRE varied in length (15–24); CACA box with length > 20 was used as cut off point. Hb was lower in CACA box length ≥ 21 (10.33 ± 1.57) vs. < 21 (11.01 ± 1.67; p = 0.391). CACA box polymorphism and anemia were correlated in severe preeclampsia (p = 0.005) OR 0.038 (CI 0.003–0.544); not in normal (p = 0.069).

Epigenetic age and pregnancy outcomes: GrimAge acceleration is associated with shorter gestational length and lower birthweight

BACKGROUND

Advanced biological aging, as measured by epigenetic aging indices, is associated with early mortality and morbidity. Associations between maternal epigenetic aging indices in pregnancy and pregnancy outcomes, namely gestational length and birthweight, have not been assessed. The purpose of this study was to examine whether epigenetic age during pregnancy was associated with gestational length and birthweight.

RESULTS

The sample consisted of 77 women from the Los Angeles, CA, area enrolled in the Healthy Babies Before Birth study. Whole blood samples for DNA methylation assay were obtained during the second trimester (15.6 ± 2.15 weeks gestation). Epigenetic age indices GrimAge acceleration (GrimAgeAccel), DNAm PAI-1, DNAm ADM, and DNAm cystatin C were calculated. Gestational length and birthweight were obtained from medical chart review. Covariates were maternal sociodemographic variables, gestational age at blood sample collection, and pre-pregnancy body mass index. In separate covariate-adjusted linear regression models, higher early second trimester GrimAgeAccel, b(SE) = - .171 (.056), p = .004; DNAm PAI-1, b(SE) = - 1.95 × 10-4 (8.5 × 10-5), p = .004; DNAm ADM, b(SE) = - .033 (.011), p = .003; and DNAm cystatin C, b(SE) = 2.10 × 10-5 (8.0 × 10-5), p = .012, were each associated with shorter gestational length. Higher GrimAgeAccel, b(SE) = - 75.2 (19.7), p < .001; DNAm PAI-1, b(SE) = - .079(.031), p = .013; DNAm ADM, b(SE) = - 13.8 (3.87), p = .001; and DNAm cystatin C, b(SE) = - .010 (.003), p = .001, were also associated with lower birthweight, independent of gestational length.

DISCUSSION

Higher maternal prenatal GrimAgeAccel, DNAm PAI-1, DNAm ADM, and DNAm cystatin C were associated with shorter gestational length and lower birthweight. These findings suggest that biological age, as measured by these epigenetic indices, could indicate risk for adverse pregnancy outcomes.

RAMPs as allosteric modulators of the calcitonin and calcitonin-like class B G protein-coupled receptors

Receptor activity-modifying proteins (RAMPs) are a family of three single span transmembrane proteins in humans that interact with many GPCRs and can modulate their function. RAMPs were discovered as key components of the calcitonin gene-related peptide and adrenomedullin receptors. They are required for transport of this class B GPCR, calcitonin receptor-like receptor (CLR), to the cell surface and determine its peptide ligand binding preferences. Soon thereafter RAMPs were shown to modulate the binding of calcitonin and amylin peptides to the related calcitonin receptor (CTR) and in the years since an ever-growing number of RAMP-interacting receptors have been identified including most if not all of the 15 class B GPCRs and several GPCRs from other families. Studies of CLR, CTR, and a handful of other GPCRs revealed that RAMPs are able to modulate various aspects of receptor function including trafficking, ligand binding, and signaling. Here, we review RAMP interactions and functions with an emphasis on class B receptors for which our understanding is most advanced. A key focus is to discuss recent evidence that RAMPs serve as endogenous allosteric modulators of CLR and CTR. We discuss structural studies of RAMP-CLR complexes and CTR and biochemical and pharmacological studies that collectively have significantly expanded our understanding of the mechanistic basis for RAMP modulation of these class B GPCRs. Last, we consider the implications of these findings for drug development targeting RAMP-CLR/CTR complexes.

Emerging roles of atypical chemokine receptor 3 (ACKR3) in normal development and physiology

The discovery that atypical chemokine receptors (ACKRs) can initiate alternative signaling pathways rather than classical G-protein coupled receptor (GPCR) signaling has changed the paradigm of chemokine receptors and their roles in modulating chemotactic responses. The ACKR family has grown over the years, with discovery of new functions and roles in a variety of pathophysiological conditions. However, the extent to which these receptors regulate normal physiology is still continuously expanding. In particular, atypical chemokine receptor 3 (ACKR3) has proven to be an important receptor in mediating normal biological functions, including cardiac development and migration of cortical neurons. In this review, we illustrate the versatile and intriguing role of ACKR3 in physiology.

Lymphatic Function and Dysfunction in the Context of Sex Differences

Endothelial cells are the building blocks of the blood vascular system and exhibit well-characterized sexually dimorphic phenotypes with regard to chromosomal and hormonal sex, imparting innate genetic and physiological differences between male and female vascular systems and cardiovascular disease. However, even though females are predominantly affected by disorders of lymphatic vascular function, we lack a comprehensive understanding of the effects of sex and sex hormones on lymphatic growth, function, and dysfunction. Here, we attempt to comprehensively evaluate the current understanding of sex as a biological variable influencing lymphatic biology. We first focus on elucidating innate and fundamental differences between the sexes in lymphatic function and development. Next, we delve into lymphatic disease and explore the potential underpinnings toward bias prevalence in the female population. Lastly, we incorporate more broadly the role of the lymphatic system in sex-biased diseases such as cancer, cardiovascular disease, reproductive disorders, and autoimmune diseases to explore whether and how sex differences may influence lymphatic function in the context of these pathologies.

Placental Vascular Calcification and Cardiovascular Health: It Is Time to Determine How Much of Maternal and Offspring Health Is Written in Stone

Vascular calcification is the deposition of calcium phosphate minerals in vascular tissue. Vascular calcification occurs by both active and passive processes. Extent and tissue-specific patterns of vascular calcification are predictors of cardiovascular morbidity and mortality. The placenta is a highly vascularized organ with specialized vasculature that mediates communication between two circulatory systems. At delivery the placenta often contains calcified tissue and calcification can be considered a marker of viral infection, but the mechanisms, histoanatomical specificity, and pathophysiological significance of placental calcification are poorly understood. In this review, we outline the current understanding of vascular calcification mechanisms, biomedical consequences, and therapeutic interventions in the context of histoanatomical types. We summarize available placental calcification data and clinical grading systems for placental calcification. We report on studies that have examined the association between placental calcification and acute adverse maternal and fetal outcomes. We then review the intersection between placental dysfunction and long-term cardiovascular health, including subsequent occurrence of maternal vascular calcification. Possible maternal phenotypes and trigger mechanisms that may predispose for calcification and cardiovascular disease are discussed. We go on to highlight the potential diagnostic value of placental calcification. Finally, we suggest avenues of research to evaluate placental calcification as a research model for investigating the relationship between placental dysfunction and cardiovascular health, as well as a biomarker for placental dysfunction, adverse clinical outcomes, and increased risk of subsequent maternal and offspring cardiovascular events.

Adrenomedullin improves fertility and promotes pinopodes and cell junctions in the peri-implantation endometrium

Implantation is a complex event demanding contributions from both embryo and endometrium. Despite advances in assisted reproduction, endometrial receptivity defects persist as a barrier to successful implantation in women with infertility. We previously demonstrated that maternal haploinsufficiency for the endocrine peptide adrenomedullin (AM) in mice confers a subfertility phenotype characterized by defective uterine receptivity and sparse epithelial pinopode coverage. The strong link between AM and implantation suggested the compelling hypothesis that administration of AM prior to implantation may improve fertility, protect against pregnancy complications, and ultimately lead to better maternal and fetal outcomes. Here, we demonstrate that intrauterine delivery of AM prior to blastocyst transfer improves the embryo implantation rate and spacing within the uterus. We then use genetic decrease-of-function and pharmacologic gain-of-function mouse models to identify potential mechanisms by which AM confers enhanced implantation success. In epithelium, we find that AM accelerates the kinetics of pinopode formation and water transport and that, in stroma, AM promotes connexin 43 expression, gap junction communication, and barrier integrity of the primary decidual zone. Ultimately, our findings advance our understanding of the contributions of AM to uterine receptivity and suggest potential broad use for AM as therapy to encourage healthy embryo implantation, for example, in combination with in vitro fertilization.

Elevated levels of adrenomedullin in eutopic endometrium and plasma from women with endometriosis

OBJECTIVE

To test adrenomedullin (Adm, ADM) as a downstream target of signal transducer and activator of transcription 3 (STAT3) in endometrial cells and to test midregional proadrenomedullin (MR-proADM) as a biomarker of endometriosis.

DESIGN

Cross-sectional analysis of Adm expression in eutopic endometrium and of MR-proADM in plasma from women with and without endometriosis; and prospective study of MR-proADM levels in women with endometriosis undergoing surgical resection of ectopic lesions.

SETTING

Academic medical centers.

PATIENT(S)

Fifteen patients with endometriosis and 11 healthy control subjects who donated eutopic endometrial biopsies; and 28 patients with endometriosis and 19 healthy control subjects who donated plasma for MR-proADM analysis.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Adm mRNA levels according to quantitative real-time polymerase chain reaction after activation of STAT3 by interleukin-6 (IL-6) in Ishikawa cells; immunohistochemistry for ADM in eutopic endometrial biopsies from women with endometriosis compared with healthy donors; and MR-proADM levels measured by commercial immunoassay in plasma from healthy women and women with endometriosis who subsequently underwent surgical resection of ectopic lesions.

RESULT(S)

Activation of STAT3 by IL-6 up-regulated Adm mRNA expression in Ishikawa cells. ADM protein levels were elevated in the eutopic endometrium of women with endometriosis. MR-proADM concentrations were higher in women with endometriosis but were not correlated with disease stage, corrected by surgery, or predictive of fertility outcome.

CONCLUSION(S)

MR-proADM may be able to serve as a biomarker of endometriosis, but it is unknown whether elevated MR-proADM levels are secondary to the estrogenic and inflammatory properties of endometriosis or an inciting pathogenic factor.

Slc20a2 deficiency results in fetal growth restriction and placental calcification associated with thickened basement membranes and novel CD13 and lamininα1 expressing cells

The essential nutrient phosphorus must be taken up by the mammalian embryo during gestation. The mechanism(s) and key proteins responsible for maternal to fetal phosphate transport have not been identified. Established parameters for placental phosphate transport match those of the type III phosphate transporters, Slc20a1 and Slc20a2. Both members are expressed in human placenta, and their altered expression is linked to preeclampsia. In this study, we tested the hypothesis that Slc20a2 is required for placental function. Indeed, complete deficiency of Slc20a2 in either the maternal or embryonic placental compartment results in fetal growth restriction. We found that Slc20a2 null mice can reproduce, but are subviable; ∼50% are lost prior to weaning age. We also observed that 23% of Slc20a2 deficient females develop pregnancy complications at full term, with tremors and placental abnormalities including abnormal vascular structure, increased basement membrane deposition, abundant calcification, and accumulation of novel CD13 and lamininα1 positive cells. Together these data support that Slc20a2 deficiency impacts both maternal and neonatal health, and Slc20a2 is required for normal placental function. In humans, decreased levels of placental Slc20a1 and Slc20a2 have been correlated with early onset preeclampsia, a disorder that can manifest from placental dysfunction. In addition, preterm placental calcification has been associated with poor pregnancy outcomes. We surveyed placental calcification in human preeclamptic placenta samples, and detected basement membrane-associated placental calcification as well as a comparable lamininα1 positive cell type, indicating that similar mechanisms may underlie both human and mouse placental calcification.

Adrenomedullin in lymphangiogenesis: from development to disease

Over the past decade, we have begun to appreciate that the lymphatic vascular system does more than simply return plasma back into the circulatory system and, in fact, contributes to a wide variety of normal and disease states. For this reason, much research has been devoted to understanding how lymphatic vessels form and function, with a particular interest in which molecules contribute to lymphatic vessel growth and maintenance. In the following review, we focus on a potent lymphangiogenic factor, adrenomedullin, and its known roles in lymphangiogenesis, lymphatic function, and human lymphatic disease. As one of the first, pharmacologically tractable G protein-coupled receptor pathways characterized in lymphatic endothelial cells, the continued study of adrenomedullin effects on the lymphatic system may open new avenues for the modulation of lymphatic growth and function in a variety of lymphatic-related diseases that currently have few treatments.

Adrenomedullin and tumour microenvironment

Adrenomedullin (AM) is a regulatory peptide whose involvement in tumour progression is becoming more relevant with recent studies. AM is produced and secreted by the tumour cells but also by numerous stromal cells including macrophages, mast cells, endothelial cells, and vascular smooth muscle cells. Most cancer patients present high levels of circulating AM and in some cases these higher levels correlate with a worst prognosis. In some cases it has been shown that the high AM levels return to normal following surgical removal of the tumour, thus indicating the tumour as the source of this excessive production of AM. Expression of this peptide is a good investment for the tumour cell since AM acts as an autocrine/paracrine growth factor, prevents apoptosis-mediated cell death, increases tumour cell motility and metastasis, induces angiogenesis, and blocks immunosurveillance by inhibiting the immune system. In addition, AM expression gets rapidly activated by hypoxia through a HIF-1α mediated mechanism, thus characterizing AM as a major survival factor for tumour cells. Accordingly, a number of studies have shown that inhibition of this peptide or its receptors results in a significant reduction in tumour progression. In conclusion, AM is a great target for drug development and new drugs interfering with this system are being developed.

Decoy receptor CXCR7 modulates adrenomedullin-mediated cardiac and lymphatic vascular development

Atypical 7-transmembrane receptors, often called decoy receptors, act promiscuously as molecular sinks to regulate ligand bioavailability and consequently temper the signaling of canonical G protein-coupled receptor (GPCR) pathways. Loss of mammalian CXCR7, the most recently described decoy receptor, results in postnatal lethality due to aberrant cardiac development and myocyte hyperplasia. Here, we provide the molecular underpinning for this proliferative phenotype by demonstrating that the dosage and signaling of adrenomedullin (Adm, gene; AM, protein)-a mitogenic peptide hormone required for normal cardiovascular development-is tightly controlled by CXCR7. To this end, Cxcr7(-/-) mice exhibit gain-of-function cardiac and lymphatic vascular phenotypes that can be reversed upon genetic depletion of adrenomedullin ligand. In addition to identifying a biological ligand accountable for the phenotypes of Cxcr7(-/-) mice, these results reveal a previously underappreciated role for decoy receptors as molecular rheostats in controlling the timing and extent of GPCR-mediated cardiac and vascular development.

Adrenomedullin and endocrine control of immune cells during pregnancy

The immunology of pregnancy is complex and incompletely understood. Aberrant immune activity in the decidua and in the placenta is believed to play a role in diseases of pregnancy, such as infertility, miscarriage, fetal growth restriction and preeclampsia. Here, we briefly review the endocrine control of uterine natural killer cell populations and their functions by the peptide hormone adrenomedullin. Studies in genetic animal models have revealed the critical importance of adrenomedullin dosage at the maternal-fetal interface, with cells from both the maternal and fetal compartments contributing to essential aspects underlying appropriate uterine receptivity, implantation and vascular remodeling of spiral arteries. These basic insights into the crosstalk between the endocrine and immune systems within the maternal-fetal interface may ultimately translate to a better understanding of the functions and consequences of dysregulated adrenomedullin levels in clinically complicated pregnancies.

Midregional pro-adrenomedullin plasma concentrations are blunted in severe preeclampsia

Levels of the peptide hormone adrenomedullin (AM) are elevated during normal pregnancy, but whether this differs during complications of pregnancy remains unresolved. AM can be quantified by measuring its pre-prohormone byproduct, midregional pro-adrenomedullin (MR-proADM). MR-proADM has shown prognostic value as a biomarker of heart failure, sepsis, and community-acquired pneumonia. Given the relevance of AM to pregnancy, we tested the hypothesis that MR-proADM provides a biomarker for preeclampsia. We find that MR-proADM plasma concentrations are blunted in severe preeclampsia and that MR-proADM is similarly effective as established biomarkers endoglin and placental growth factor at discriminating patients with severe preeclampsia from controls.

Plasma adrenomedullin concentrations in critically ill neonatal foals

Background

Bacterial sepsis remains a leading cause of morbidity and mortality in neonatal foals, but accurate diagnostic and prognostic markers are lacking. Adrenomedullin (AM) is a polypeptide with diverse biologic effects on the cardiovascular system that increases in septic humans and laboratory animals.

Hypotheses

Plasma AM concentration (p[AM]) is increased in septic neonatal foals compared to sick nonseptic and healthy control foals, and p[AM] is predictive of survival in septic neonatal foals.

Animals

Ninety critically ill (42 septic, 48 sick nonseptic) and 61 healthy foals <1 week of age.

Methods

A prospective observational clinical study was performed. Venous blood was collected from critically ill foals at admission and from healthy foals at 24 hours of age. Critically ill foals were categorized as septic or sick nonseptic based on blood culture results and sepsis score. Plasma [AM] was measured by using a commercially available ELISA for horses. Data were analyzed by using the Mann‐Whitney U‐test and P < .05 was considered significant.

Results

Plasma [AM] was not significantly different between septic and sick nonseptic foals (P = .71), but critically ill foals had significantly increased p[AM] compared to healthy controls (P < .0001). In critically ill foals, p[AM] was not predictive of survival (P = .051). A p[AM] cutoff concentration of 0.041 ng/mL provided a test sensitivity of 91% and specificity of 54% to predict illness.

Conclusions and Clinical Relevance

Plasma [AM] shows promise as a marker of health in neonatal foals, but p[AM] increases nonspecifically during perinatal illnesses and is not necessarily associated with sepsis.

Adrenomedullin signaling pathway polymorphisms and adverse pregnancy outcomes

OBJECTIVE

Reduced maternal plasma levels of the peptide vasodilator adrenomedullin have been associated with adverse pregnancy outcomes. We measured the extent to which genetic polymorphisms in the adrenomedullin signaling pathway are associated with birth weight, glycemic regulation, and preeclampsia risk.

STUDY DESIGN

We genotyped 1,353 women in the Pregnancy, Infection, and Nutrition Postpartum Study for 37 ancestry-informative markers and for single-nucleotide polymorphisms in adrenomedullin (ADM), complement factor H variant (CFH), and calcitonin receptor-like receptor (CALCRL). We used linear and logistic regression to model the association between genotype and birth weight, glucose loading test (GLT) results, preeclampsia, and gestational diabetes (GDM). All models were adjusted for pregravid body mass index, maternal age, and probability of Yoruban ancestry. p values of < 0.05 were considered statistically significant.

RESULTS

Among Caucasian women, ADM rs57153895, a proxy for rs11042725, was associated with reduced birth weight z-score. Among African-American women, ADM rs57153895 was associated with increased birth weight z-score. Two CALCRL variants were associated with GDM risk. CFH rs1061170 was associated with higher GLT results and increased preeclampsia risk.

CONCLUSION

Consistent with studies of plasma adrenomedullin and adverse pregnancy outcomes, we found associations between variants in the adrenomedullin signaling pathway and birth weight, glycemic regulation, and preeclampsia.

Cigarette smoke-induced placental adrenomedullin expression and trophoblast cell invasion

Smoking in pregnancy reduces preeclampsia risk, but the mechanism of this effect is unknown. Prior studies have demonstrated that women with preeclampsia have lower placental adrenomedullin (AM) expression, and cigarette smoke extract (CSE) treatment of placental trophoblast cells in culture increases AM cellular production. We hypothesized that CSE alters trophoblast invasion through an AM-mediated mechanism, and that placental AM expression is greater among smokers. HTR-8/SVneo trophoblast cells were incubated for 24 hours in Matrigel-invasion chambers with 6 treatment groups: nonstimulated (NS), AM, AM inhibitor (AM22-52), 1% CSE, AM + AM22-52, and 1% CSE + AM22-52. Cells that penetrated the lower surface of the chambers were quantified, invasion indices were calculated, and compared using a 1-way analysis of variance with Bonferroni corrections for multiple comparisons. Trophoblast cells treated with both AM and 1% CSE demonstrated increased cellular invasion compared to NS controls (1.5-fold [P < .01] and 1.45-fold [P < .01], respectively). Cotreatment with the AM inhibitor significantly attenuated the increased invasion seen with both AM and CSE alone. Next, the placental tissue was obtained from 11 smokers and 11 nonsmokers at term and processed for immunohistochemistry (IHC) and real-time quantitative polymerase chain reaction (PCR) for AM. Placentas from smokers demonstrated more intense AM staining and increased AM gene (ADM) expression compared to placentas from nonsmokers (P = .004 for IHC, P = .022 for PCR). The CSE increases trophoblast cell invasion through an AM-mediated process, and placental AM expression is increased among term smokers compared to nonsmokers. These findings provide evidence that the AM pathway may play a role in the protection from preeclampsia seen in smokers.

Fetal-derived adrenomedullin mediates the innate immune milieu of the placenta

The remodeling of maternal uterine spiral arteries (SAs) is an essential process for ensuring low-resistance, high-capacitance blood flow to the growing fetus. Failure of SAs to remodel is causally associated with preeclampsia, a common and life-threatening complication of pregnancy that is harmful to both mother and fetus. Here, using both loss-of-function and gain-of-function genetic mouse models, we show that expression of the pregnancy-related peptide adrenomedullin (AM) by fetal trophoblast cells is necessary and sufficient to promote appropriate recruitment and activation of maternal uterine NK (uNK) cells to the placenta and ultimately facilitate remodeling of maternal SAs. Placentas that lacked either AM or its receptor exhibited reduced fetal vessel branching in the labyrinth, failed SA remodeling and reendothelialization, and markedly reduced numbers of maternal uNK cells. In contrast, overexpression of AM caused a reversal of these phenotypes with a concomitant increase in uNK cell content in vivo. Moreover, AM dose-dependently stimulated the secretion of numerous chemokines, cytokines, and MMPs from uNK cells, which in turn induced VSMC apoptosis. These data identify an essential function for fetal-derived factors in the maternal vascular adaptation to pregnancy and underscore the importance of exploring AM as a biomarker and therapeutic agent for preeclampsia.

Adrenomedullin is up-regulated in patients with pancreatic cancer and causes insulin resistance in β cells and mice

BACKGROUND & AIMS

New-onset diabetes in patients with pancreatic cancer is likely to be a paraneoplastic phenomenon caused by tumor-secreted products. We aimed to identify the diabetogenic secretory product(s) of pancreatic cancer.

METHODS

Using microarray analysis, we identified adrenomedullin as a potential mediator of diabetes in patients with pancreatic cancer. Adrenomedullin was up-regulated in pancreatic cancer cell lines, in which supernatants reduced insulin signaling in beta cell lines. We performed quantitative reverse-transcriptase polymerase chain reaction and immunohistochemistry on human pancreatic cancer and healthy pancreatic tissues (controls) to determine expression of adrenomedullin messenger RNA and protein, respectively. We studied the effects of adrenomedullin on insulin secretion by beta cell lines and whole islets from mice and on glucose tolerance in pancreatic xenografts in mice. We measured plasma levels of adrenomedullin in patients with pancreatic cancer, patients with type 2 diabetes mellitus, and individuals with normal fasting glucose levels (controls).

RESULTS

Levels of adrenomedullin messenger RNA and protein were increased in human pancreatic cancer samples compared with controls. Adrenomedullin and conditioned media from pancreatic cell lines inhibited glucose-stimulated insulin secretion from beta cell lines and islets isolated from mice; the effects of conditioned media from pancreatic cancer cells were reduced by small hairpin RNA-mediated knockdown of adrenomedullin. Conversely, overexpression of adrenomedullin in mice with pancreatic cancer led to glucose intolerance. Mean plasma levels of adrenomedullin (femtomoles per liter) were higher in patients with pancreatic cancer compared with patients with diabetes or controls. Levels of adrenomedullin were higher in patients with pancreatic cancer who developed diabetes compared those who did not.

CONCLUSIONS

Adrenomedullin is up-regulated in patients with pancreatic cancer and causes insulin resistance in β cells and mice.