Interleukin-1beta induces the expression of insulin-like growth factor binding protein-1 during decidualization in the primate

The Known, the Unknown and the Future of the Pathophysiology of Endometriosis

Endometriosis is one of the most common causes of chronic pelvic pain and infertility, affecting 10% of women of reproductive age. A delay of up to 9 years is estimated between the onset of symptoms and the diagnosis of endometriosis. Endometriosis is currently defined as the presence of endometrial epithelial and stromal cells at ectopic sites; however, advances in research on endometriosis have some authors believing that endometriosis should be re-defined as "a fibrotic condition in which endometrial stroma and epithelium can be identified". There are several theories on the etiology of the disease, but the origin of endometriosis remains unclear. This review addresses the role of microRNAs (miRNAs), which are naturally occurring post-transcriptional regulatory molecules, in endometriotic lesion development, the inflammatory environment within the peritoneal cavity, including the role that cytokines play during the development of the disease, and how animal models have helped in our understanding of the pathology of this enigmatic disease.

Organoid co-culture model of the human endometrium in a fully synthetic extracellular matrix enables the study of epithelial-stromal crosstalk

BACKGROUND

The human endometrium undergoes recurring cycles of growth, differentiation, and breakdown in response to sex hormones. Dysregulation of epithelial-stromal communication during hormone-mediated signaling may be linked to myriad gynecological disorders for which treatments remain inadequate. Here, we describe a completely defined, synthetic extracellular matrix that enables co-culture of human endometrial epithelial and stromal cells in a manner that captures healthy and disease states across a simulated menstrual cycle.

METHODS

We parsed cycle-dependent endometrial integrin expression and matrix composition to define candidate cell-matrix interaction cues for inclusion in a polyethylene glycol (PEG)-based hydrogel crosslinked with matrix metalloproteinase-labile peptides. We semi-empirically screened a parameter space of biophysical and molecular features representative of the endometrium to define compositions suitable for hormone-driven expansion and differentiation of epithelial organoids, stromal cells, and co-cultures of the two cell types.

FINDINGS

Each cell type exhibited characteristic morphological and molecular responses to hormone changes when co-encapsulated in hydrogels tuned to a stiffness regime similar to the native tissue and functionalized with a collagen-derived adhesion peptide (GFOGER) and a fibronectin-derived peptide (PHSRN-K-RGD). Analysis of cell-cell crosstalk during interleukin 1B (IL1B)-induced inflammation revealed dysregulation of epithelial proliferation mediated by stromal cells.

CONCLUSIONS

Altogether, we demonstrate the development of a fully synthetic matrix to sustain the dynamic changes of the endometrial microenvironment and support its applications to understand menstrual health and endometriotic diseases.

FUNDING

This work was supported by The John and Karine Begg Foundation, the Manton Foundation, and NIH U01 (EB029132).

Towards a Better Understanding of Endometriosis-Related Infertility: A Review on How Endometriosis Affects Endometrial Receptivity

Endometriosis is the most common cause of infertility. Endometrial receptivity has been suggested to contribute to infertility and poor reproductive outcomes in affected women. Even though experimental and clinical data suggest that the endometrium differs in women with endometriosis, the pathogenesis of impaired endometrial receptivity remains incomplete. Therefore, this review summarizes the potential mechanisms that affect endometrial function and contribute to implantation failure. Contemporary data regarding hormone imbalance, inflammation, and immunoregulatory dysfunction will be reviewed here. In addition, genetic, epigenetic, glycosylation, metabolism and microRNA in endometriosis-related infertility/subfertility will be summarized. We provide a brief discussion and perspectives on their future clinical implications in the diagnosis and therapy to improve endometrial function in affected women.

Molecular mechanisms in IL-1β-mediated decorin production by decidual cells

Decorin, a small leucine-rich proteoglycan produced by decidual cells restrains trophoblast differentiation, migration and invasiveness of extra-villous trophoblast cells. Decidual overproduction of decorin is associated with preeclampsia, and elevated decorin levels in maternal plasma are a predictive biomarker of preeclampsia. Furthermore, decorin plays an autocrine role in maturation of human endometrial stromal cells into decidual cells. Thus, a balanced decorin production by the decidua is critical for healthy pregnancy. However, the molecular mechanisms regulating decorin production by the decidua are unclear. Interleukin-1 beta is an inflammation-associated multi-functional cytokine, and is reported to induce decidualization in primates. Hence, the present study was designed: (i) to test if exogenous Interleukin-1 beta stimulated decorin production by human endometrial stromal cells; and if so, (ii) to identify the cellular source of Interleukin-1 beta in first trimester decidual tissue; (iii) to identify the downstream molecular partners in Interleukin-1 beta mediated decorin production by human endometrial stromal cells. Results revealed that (i) amongst multiple pro-inflammatory cytokines tested, Interleukin-1 beta alone stimulated decorin production by these cells; (ii) both macrophages and decidual cells in first trimester decidua produced Interleukin-1 beta; (iii) Interleukin-1 beta mediated decorin production was dependent on Interleukin-1 receptor activation, followed by activation and nuclear translocation of nuclear factor kappa B and its binding to the decorin promoter. These results reveal that Interleukin-1 beta plays a novel role in inducing decorin production by human endometrial stromal cells by activating nuclear factor kappa B.

Inflammasomes in the Pathophysiology of Maternal Obesity: Potential Therapeutic Targets to Reduce Long-Term Adverse Health Outcomes in the Mother and Offspring

Over the past 20 years, the prevalence of obesity has risen dramatically worldwide, with an increase in occurrence among women in their reproductive age. Obesity during pregnancy is associated with significantly increased maternal and fetal morbidity and mortality. In addition to the short-term adverse health outcomes, both mother and the child are prone to develop cardiovascular, metabolic and neurological disorders. Although associations between obesity during pregnancy and adverse maternalfetal health outcomes are clear, the complex molecular mechanisms underlying maternal obesity remain largely unknown. This review describes multimeric self-assembling protein complexes, namely inflammasomes, as potential molecular targets in the pathophysiology of maternal obesity. Inflammasomes are implicated in both normal physiological and in pathophysiological processes that occur in response to an inflammatory milieu throughout gestation. This review highlights the current knowledge of inflammasome expression and its activity in pregnancies affected by maternal obesity. Key discussions in defining pharmacological inhibition of upstream as well as downstream targets of the inflammasome signaling cascade; and the inflammasome platform, as a potential therapeutic strategy in attenuating the pathophysiology underpinning inflammatory component in maternal obesity are presented herein.

Physiologic Events of Embryo Implantation and Decidualization in Human and Non-Human Primates

Reproduction is a fundamental process for the preservation of the human species. This process requires a sequence of orchestrated events that are necessary for a successful pregnancy. Two of the most critical steps in the establishment of human pregnancy are implantation and decidualization, which are required for maternal interactions with the developing embryo. This review primarily highlights the physiological aspects of these two events and the adverse pregnancy outcomes from defective implantation and decidualization. The focus of this review is to provide a general concept of the mechanisms involved during the window of implantation, description of components involved in the process and possible pathologies that could disrupt the embryo implantation and decidualization and specifically as it applies to women and non-human primates.

Molecular Signaling Regulating Endometrium-Blastocyst Crosstalk

Implantation of the embryo into the uterine endometrium is one of the most finely-regulated processes that leads to the establishment of a successful pregnancy. A plethora of factors are released in a time-specific fashion to synchronize the differentiation program of both the embryo and the endometrium. Indeed, blastocyst implantation in the uterus occurs in a limited time frame called the "window of implantation" (WOI), during which the maternal endometrium undergoes dramatic changes, collectively called "decidualization". Decidualization is guided not just by maternal factors (e.g., estrogen, progesterone, thyroid hormone), but also by molecules secreted by the embryo, such as chorionic gonadotropin (CG) and interleukin-1β (IL-1 β), just to cite few. Once reached the uterine cavity, the embryo orients correctly toward the uterine epithelium, interacts with specialized structures, called pinopodes, and begins the process of adhesion and invasion. All these events are guided by factors secreted by both the endometrium and the embryo, such as leukemia inhibitory factor (LIF), integrins and their ligands, adhesion molecules, Notch family members, and metalloproteinases and their inhibitors. The aim of this review is to give an overview of the factors and mechanisms regulating implantation, with a focus on those involved in the complex crosstalk between the blastocyst and the endometrium.

The Notch Family Transcription Factor, RBPJκ, Modulates Glucose Transporter and Ovarian Steroid Hormone Receptor Expression During Decidualization

During decidualization, endometrial stromal cells differentiate into a secretory phenotype to modulate the uterine microenvironment and promote embryo implantation. This highly metabolic process relies on ovarian steroid receptors and glucose transporters. Canonical Notch signaling is mediated by the transcription factor Recombination Signal Binding Protein for Immunoglobulin Kappa J Region (RBPJ). Loss of RBPJ in the mouse uterus (Pgr^cre/+Rbpj^flox/flox; Rbpj c-KO) results in subfertility in part due to an abnormal uterine-embryonic axis during implantation and, as described herein, decidualization failure. Induced in vivo decidualization in Rbpj c-KO mice was impaired with the downregulation of decidual markers and decreased progesterone receptor (Pgr) signaling. Consistent with in vivo mouse data, RBPJ knockdown during in vitro Human uterine fibroblast (HuF) cell decidualization results in the reduced expression of decidual marker genes along with PGR. Expression of the glucose transporter, SLC2A1, was decreased in the RBPJ-silenced HuF cells, which corresponded to decreased Slc2a1 in the secondary decidual zone of Rbpj c-KO mouse uteri. Exogenous administration of pyruvate, which bypasses the need for glucose, rescues PRL expression in RBPJ-deficient HuF cells. In summary, Notch signaling through RBPJ controls both ovarian steroid receptor PGR and glucose transporter SLC2A1 expression during decidualization, and this dysregulation likely contributes to embryo implantation failure.

Endometrial response to conceptus-derived estrogen and interleukin-1β at the time of implantation in pigs

The establishment of pregnancy is a complex process that requires a well-coordinated interaction between the implanting conceptus and the maternal uterus. In pigs, the conceptus undergoes dramatic morphological and functional changes at the time of implantation and introduces various factors, including estrogens and cytokines, interleukin-1β2 (IL1B2), interferon-γ (IFNG), and IFN-δ (IFND), into the uterine lumen. In response to ovarian steroid hormones and conceptus-derived factors, the uterine endometrium becomes receptive to the implanting conceptus by changing its expression of cell adhesion molecules, secretory activity, and immune response. Conceptus-derived estrogens act as a signal for maternal recognition of pregnancy by changing the direction of prostaglandin (PG) F_2α from the uterine vasculature to the uterine lumen. Estrogens also induce the expression of many endometrial genes, including genes related to growth factors, the synthesis and transport of PGs, and immunity. IL1B2, a pro-inflammatory cytokine, is produced by the elongating conceptus. The direct effect of IL1B2 on endometrial function is not fully understood. IL1B activates the expression of endometrial genes, including the genes involved in IL1B signaling and PG synthesis and transport. In addition, estrogen or IL1B stimulates endometrial expression of IFN signaling molecules, suggesting that estrogen and IL1B act cooperatively in priming the endometrial function of conceptus-produced IFNG and IFND that, in turn, modulate endometrial immune response during early pregnancy. This review addresses information about maternal-conceptus interactions with respect to endometrial gene expression in response to conceptus-derived factors, focusing on the roles of estrogen and IL1B during early pregnancy in pigs.

IL-1β Inhibits Connexin 43 and Disrupts Decidualization of Human Endometrial Stromal Cells Through ERK1/2 and p38 MAP Kinase

Inflammation can interfere with endometrial receptivity. We examined how interleukin 1β (IL-1β) affects expression of the uterine gap junction protein connexin 43 (Cx43), which is known to be critical for embryonic implantation. We used an in vitro model of human endometrial stromal cells (ESCs), Western blotting, and a combination of validated, selective kinase inhibitors to evaluate five canonical IL-1β signaling pathways. Cx43 and two other markers of ESC differentiation (prolactin and VEGF) were inhibited predominantly via IL-1β-activated ERK1/2 and p38 MAP kinase cascades. The findings were corroborated using small interfering RNA to silence critical genes in either pathway. By contrast, upregulation of endogenous pro-IL-1α and pro-IL-1β following recombinant IL-1β treatment was mediated via the Jun N-terminal kinase pathway. The clinicopharmacological significance of our findings is that multiple signaling cascades may need to be neutralized to reverse deleterious effects of IL-1β on human endometrial function.

Bisphenol A impairs decidualization of human uterine stromal fibroblasts

This study examined the effect of bisphenol A (BPA) exposure on human uterine stromal fibroblast cells (HuF) undergoing decidualization. HuF cells were isolated and cultured for eight days in the presence of a decidualization-inducing cocktail, while concurrently exposed to physiological and supra-physiologic doses of BPA (1ng/mL, 10ng/mL, 0.5μg/mL, 10μg/mL and 20μg/mL). Decidualization markers, steroid hormone receptors and cell cycle gene expression were detected by qRT-PCR and cellular proliferation was assessed by KI-67 immunofluorescent staining and MTS assay. BPA impaired decidualization at 10μg/mL and 20μg/mL, but not at lower doses. Additionally, BPA at 20μg/mL decreased progesterone receptor and estrogen receptor-alpha compared to controls. The highest dose of BPA also reduced cellular proliferation and cyclin D2 expression compared to controls. These findings demonstrate that BPA disrupts in vitro decidualization of uterine stromal fibroblasts by altering steroid hormone receptor expression at higher concentrations but not at lower physiological doses.

Induction of Insulin-Like Growth Factor Binding Protein-1 Expression in Baboon Endometrial Stromal Cells by Cells of Trophoblast Origin

OBJECTIVE

To determine the influence of the conceptus on the induction of decidualization in endometrial stromal cells from the baboon.

METHODS

For in vivo studies, implantation sites from day 22 of pregnancy in the baboon were analyzed for insulin-like growth factor-II (IGF-II) and insulin-like growth factor binding protein-1 (IGFBP-1) mRNAs using in situ hybridization. For in vitro studies, Jeg-3 cells or primary cytotrophoblasts isolated from term placenta were cocultured with a monolayer of stromal cells from the baboon endometrium. Cytotrophoblasts were placed either directly on top of the stromal cell monolayer or in transwell cell culture inserts and cultured for 7 days. No exogenous hormones were added. Stromal cells were analyzed for IGFBP-1 mRNA and protein by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunocytochemistry.

RESULTS

Examination of early implantation sites in the baboon revealed a high expression of IGF-II mRNA in the invading cytotrophoblasts. Conversely, the stromal cells of the endometrium directly adjacent to the cytotrophoblasts expressed IGFBP-1 mRNA. Endometrial stromal cells cocultured with Jeg-3 cells or primary cytotrophoblasts for 7 days expressed IGFBP-1 mRNA and protein. This expression occurred in both the direct coculture system and coculture using the cell culture inserts. Cytotrophoblasts also induced the expression of prolactin in stromal fibroblasts following coculture.

CONCLUSIONS

The conceptus is capable of inducing decidualization of endometrial stromal cells. This is shown in both the in vivo and in vitro systems.

Implantation and Establishment of Pregnancy in Human and Nonhuman Primates

Implantation and the establishment of pregnancy are critical for the propagation of the species, but yet remain the limiting steps in human and primate reproduction. Successful implantation requires a competent blastocyst and a receptive endometrium during a specific window of time during the menstrual cycle to initiate the bilateral communication required for the establishment of a successful pregnancy. This chapter provides an overview of these processes and discusses the molecular mechanisms associated with implantation of the blastocyst and decidualization of the uterus in primates.

Cyclic decidualization of the human endometrium in reproductive health and failure

Decidualization denotes the transformation of endometrial stromal fibroblasts into specialized secretory decidual cells that provide a nutritive and immunoprivileged matrix essential for embryo implantation and placental development. In contrast to most mammals, decidualization of the human endometrium does not require embryo implantation. Instead, this process is driven by the postovulatory rise in progesterone levels and increasing local cAMP production. In response to falling progesterone levels, spontaneous decidualization causes menstrual shedding and cyclic regeneration of the endometrium. A growing body of evidence indicates that the shift from embryonic to maternal control of the decidual process represents a pivotal evolutionary adaptation to the challenge posed by invasive and chromosomally diverse human embryos. This concept is predicated on the ability of decidualizing stromal cells to respond to individual embryos in a manner that either promotes implantation and further development or facilitates early rejection. Furthermore, menstruation and cyclic regeneration involves stem cell recruitment and renders the endometrium intrinsically capable of adapting its decidual response to maximize reproductive success. Here we review the endocrine, paracrine, and autocrine cues that tightly govern this differentiation process. In response to activation of various signaling pathways and genome-wide chromatin remodeling, evolutionarily conserved transcriptional factors gain access to the decidua-specific regulatory circuitry. Once initiated, the decidual process is poised to transit through distinct phenotypic phases that underpin endometrial receptivity, embryo selection, and, ultimately, resolution of pregnancy. We discuss how disorders that subvert the programming, initiation, or progression of decidualization compromise reproductive health and predispose for pregnancy failure.

Lysophosphatidic acid enhanced the angiogenic capability of human chondrocytes by regulating Gi/NF-kB-dependent angiogenic factor expression

Lysophosphatidic acid (LPA) has been found to mediate myeloid differentiation, stimulate osteogenesis, alter cell proliferation and migration, and inhibit apoptosis in chondrocytes. The effect of LPA on the angiogenic capability of chondrocytes is not clear. This study aimed to investigate its effect on the angiogenic capability of human chondrocytes and the underlying mechanism of these effects. Human chondrocyte cell line, CHON-001, commercialized human chondrocytes (HC) derived from normal human articular cartilage, and human vascular endothelial cells (HUVECs) were used as cell models in this study. The angiogenic capability of chondrocytes was determined by capillary tube formation, monolayer permeability, cell migration, and cell proliferation. An angiogenesis protein array kit was used to evaluate the secretion of angiogenic factors in conditioned medium. Angiogenin, insulin-like growth factor-binding protein 1 (IGFBP-1), interleukin (IL)-8, monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinase (MMP)-9, and vascular endothelial growth factor (VEGF) mRNA and protein expressions were evaluated by Q-RT-PCR and EIA, respectively. LPA receptor (LPAR) expression was determined by RT-PCR. Signaling pathways were clarified using inhibitors, Western blot analysis, and reporter assays. The LPA treatment promoted the angiogenic capability of CHON-001 cells and HC, resulting in enhanced HUVEC capillary tube formation, monolayer permeability, migration, and cell growth. Angiogenin, IGFBP-1, IL-8, MCP-1, MMP-9, and VEGF mRNA and protein expressions were significantly enhanced in LPA-treated chondrocytes. LPA2, 3, 4 and 6 were expressed in CHON-001 and HC cells. Pretreatment with the Gi/o type G protein inhibitor, pertussis toxin (PTX), and the NF-kB inhibitor, PDTC, significantly inhibited LPA-induced angiogenin, IGFBP-1, IL-8, MCP-1, MMP-9, and VEGF expressions in chondrocytes. The PTX pretreatment also inhibited LPA-mediated NF-kB activation, suggesting the presence of active Gi/NF-kB signaling in CHON-001 and HC cells. The effect of LPA on the angiogenesis-inducing capacity of chondrocytes may be due to the increased angiogenesis factor expression via the Gi/NF-kB signaling pathway.

ISGylation: a conserved pathway in mammalian pregnancy

Successful pregnancy includes remodeling and differentiation of the endometrium in response to sex steroid hormones, development of maternal immunotolerance to the implanting embryo, and modification of the local uterine environment by the embryo to suit its own needs. The major signal released by the ruminant conceptus during establishment of pregnancy is interferon-tau (IFNT) that stimulates the expression of many genes in the endometrium and ovary. One of these genes is called interferon stimulated gene 15 (ISG15), which encodes a ubiquitin homolog with a C-terminal Gly that becomes covalently attached to Lys residues on targeted proteins through an ATP-dependent multi-step enzymatic reaction called ISGylation. The conceptus-derived induction of endometrial ISGs also occurs in mouse and human deciduas and placenta, in response to pregnancy presumably through action of cytokines such as interleukins and type I IFN. Described herein is evidence to support the concept that ISGylation is a maternal response to the developing conceptus, implantation and placentation that is conserved across mammalian pregnancy. Although the precise role for ISG15 remains elusive during pregnancy, it is clear that up-regulation in response to pregnancy may impart a pre-emptive defense to infection or other environmental insults, and protection of the conceptus against inflammatory insults across species.

Conceptus-derived prostaglandins regulate gene expression in the endometrium prior to pregnancy recognition in ruminants

In cattle, the blastocyst hatches from the zona pellucida on days 8-9 and then forms a conceptus that grows and elongates into an ovoid and then filamentous shape between days 9 and 16. The growing conceptus synthesizes and secretes prostaglandins (PGs) and interferon τ (IFNT). Our hypothesis was that the ovoid conceptus exerts a local effect on the endometrium prior to maternal recognition of pregnancy on day 16 in cattle. In study one, synchronized cyclic heifers received no blastocysts or 20 in vitro-produced blastocysts on day 7 and their uteri were collected on day 13. IFNT was not detected by RIA in the uterine flushing samples of pregnant heifers containing multiple ovoid conceptuses; however, total PG levels were higher in the uterine lumen of pregnant heifers than in that of cyclic heifers. Microarray analysis revealed that the expression of 44 genes was increased in the endometria of day 13 pregnant heifers when compared with that in the endometria of cyclic heifers, and many of these genes were classical Type I IFN-stimulated genes (ISGs). In studies two and three, the effects of infusing PGs at the levels produced by the elongating day 14 conceptus into the uterine lumen of cyclic ewes on ISG expression in the endometrium were determined. Results indicated that the infusion of PGs increased the abundance of several ISGs in the endometrium. These studies support the hypothesis that the day 13 conceptus secretes PGs that act locally in a paracrine manner to alter gene expression in the endometrium prior to pregnancy recognition in cattle.

Conceptus-derived prostaglandins regulate endometrial function in sheep

In sheep, the trophectoderm of the elongating conceptus secretes interferon tau (IFNT) and prostaglandins (PGE2, PGF2alpha, PGI2). The PGs are derived from PG synthase 2 (PTGS2), and inhibition of PTGS2 in utero prevents conceptus elongation. IFNT increases expression of many genes in the endometrial epithelia that regulate conceptus elongation. This study tested the hypothesis that PGs secreted by the conceptus regulate endometrial functions that govern conceptus elongation. Cyclic ewes received intrauterine infusions of control vehicle or early pregnancy levels of IFNT, PGE2, PGF2alpha, or PGI2 from Days 10-14 postestrus. Expression levels of endometrial GRP, IGFBP1, and LGALS15, whose products stimulate trophectoderm cell migration and attachment, were increased by PGE2, PGI2, and IFNT. All PGs and IFNT increased expression of the HEXB protease gene, but only IFNT increased the CST6 protease inhibitor gene. Differential effects of PGs were observed for expression of the CTSL protease gene and its inhibitor, CST3. IFNT, PGF2alpha, and PGI2 increased ANGPTL3 expression, but only IFNT and PGE2 increased HIF1A expression, both of which regulate angiogenesis. For glucose transporters, IFNT and all PGs increased SLC2A1 expression, but only PGs increased SLC2A5 expression, whereas endometrial SLC2A12 and SLC5A1 expression levels were increased by IFNT, PGE2, and PGF2alpha. Infusions of all PGs and IFNT increased the amino acid transporter SLC1A5, but only IFNT increased SLC7A2 expression. In the uterine lumen, only IFNT increased glucose levels, and only PGE2 and PGF2alpha increased total amino acids. These results indicate that PGs and IFNT from the conceptus coordinately regulate endometrial functions important for growth and development of the conceptus during the peri-implantation period of pregnancy.

EMMPRIN is secreted by human uterine epithelial cells in microvesicles and stimulates metalloproteinase production by human uterine fibroblast cells

Endometrial remodeling is a physiological process involved in the gynecological disease, endometriosis. Tissue remodeling is directed by uterine fibroblast production of matrix metalloproteinases (MMPs). Several MMPs are regulated directly by the protein extracellular matrix metalloproteinase inducer (EMMPRIN) and also by proinflammatory cytokines such as interleukin (IL)1-α/β. We hypothesized that human uterine epithelial cells (HESs) secrete intact EMMPRIN to stimulate MMPs. Microvesicles from HES cell-conditioned medium (CM) expressed intact EMMPRIN protein. Treatment of HES cells with estradiol or phorbyl 12-myristate-13-acetate increased the release of EMMPRIN-containing microvesicles. The HES CM stimulated MMP-1, -2, and -3 messenger RNA levels in human uterine fibroblasts (HUFs) and EMMPRIN immunodepletion from HES-cell concentrated CM reduced MMP stimulation (P < .05). Treatment of HUF cells with low concentrations of IL-1β/α stimulated MMP production (P < .05). These results indicate that HES cells regulate MMP production by HUF cells by secretion of EMMPRIN, in response to ovarian hormones, proinflammatory cytokines as well as activation of protein kinase C.

Notch1 is regulated by chorionic gonadotropin and progesterone in endometrial stromal cells and modulates decidualization in primates

No other tissue in the body undergoes such a vast and extensive growth and remodeling in a relatively short period of time as the primate endometrium. Endometrial integrity is coordinated by ovarian hormones, namely, estrogens, progesterone, and the embryonic hormone chorionic gonadotropin (CG). These regulated events modulate the menstrual cycle and decidualization. The Notch family of transmembrane receptors regulate cellular proliferation, differentiation, and apoptosis, cellular processes required to maintain endometrial integrity. In two primate models, the human and the simulated pregnant baboon model, we demonstrated that Notch1 is increased during the window of uterine receptivity, concomitant with CG. Furthermore, CG combined with estrogens and progesterone up-regulate the level of Notch1, whereas progesterone increases the intracellular transcriptionally competent Notch1, which binds in a complex with progesterone receptor. Inhibition of Notch1 prevented decidualization, and alternatively, when decidualization is biochemically recapitulated in vitro, Notch1 is down-regulated. A focused microarray demonstrated that the Notch inhibitor, Numb, dramatically increased when Notch1 decreased during decidualization. We propose that in the endometrium, Notch has a dual role during the window of uterine receptivity. Initially, Notch1 mediates a survival signal in the uterine endometrium in response to CG from the implanting blastocyst and progesterone, so that menstrual sloughing is averted. Subsequently, Notch1 down-regulation may be critical for the transition of stromal fibroblast to decidual cells, which is essential for the establishment of a successful pregnancy.

Interaction of the conceptus and endometrium to establish pregnancy in mammals: role of interleukin 1β

Implantation and the establishment of pregnancy in mammals involves an intricate interplay of hormones, cytokines, growth factors, proteins, lipids, ions and the extracellular matrix between the uterine epithelium, stroma, immune cells and the conceptus trophectoderm. The divergent nature of implantation in the mouse, human and pig provides not only an interesting contrast in the establishment of pregnancy and early embryonic development but also intriguing similarities with regard to early endometrial-conceptus signaling. An interesting pro-inflammatory cytokine expressed in a number of mammalian species during the period of implantation is interleukin-1β (IL1B). The presence of IL1B might be involved with immunotolerance at the maternal-placental interface and has been proposed as one of the mediators in placental viviparity. The production of IL1B and other proinflammatory cytokines might play a role in establishing pregnancy through modulation of the nuclear factor kappa-B (NFKB) system in a number of species. A model for the regulation of cellular progesterone receptor expression and NFKB activation for endometrial receptivity and conceptus attachment is continuing to evolve and is discussed in the present review.

Deletion of the Isg15 gene results in up-regulation of decidual cell survival genes and down-regulation of adhesion genes: implication for regulation by IL-1beta

The ubiquitin homolog interferon stimulated gene 15 (ISG15) is up-regulated in the endometrium in response to pregnancy in primates, ruminants, pigs, and mice. ISG15 covalently attaches to intracellular proteins (isgylation) and regulates numerous intracellular responses. We hypothesized that ISG15 depletion (Isg15(-/-)) alters decidual tissue gene expression and that IL-1beta induces ISG15 expression and isgylation in cultured murine decidual explants and human uterine fibroblasts (HuFs). After studying the reproductive phenotype, contrary to earlier reports, up to 50% of the fetuses die between 7.5 and 12.5 d post coitum (dpc) in Isg15(-/-) mothers when mated to Isg15(-/-) fathers. Using microarray analysis, over 500 genes are differentially regulated in 7.5 dpc deciduas from Isg15(-/-) compared with Isg15(+/+) mice. The gene for interferon-inducible protein 202b, which functions in cell-survival mechanisms, was up-regulated (mRNA and protein) in deciduas from Isg15(-/-) mice. Culture of Isg15(+/+) mouse decidual explants (7.5 dpc) with IL-1beta decreased Isg15 mRNA but increased free and conjugated ISG15. In predecidual HuF cells, IL-1beta treatment increased ISG15 mRNA and isgylation. Additionally, IL-1beta up-regulated expression of enzymes (HERC5, UBCH8) that coordinate the covalent conjugation of ISG15 to target proteins, as well as the gene that encodes the deisglyation enzyme UBP43 in HuF cells. In conclusion, deletion of Isg15 gene results in 50% fetal loss after 7.5 dpc, which can be explained through differential decidual gene expression that is functionally tied to cell survival and adhesion pathways. This fetal death also might relate to impaired IL-1beta signaling, because ISG15 and isgylation are induced by IL-1beta in human and murine endometrial stromal cells.

Human transcriptional coactivator with PDZ-binding motif (TAZ) is downregulated during decidualization

Transcriptional coactivator with PDZ-binding motif (TAZ) is known to bind to a variety of transcription factors to control cell differentiation and organ development. However, its role in uterine physiology has not yet been described. To study its regulation during the unique process of differentiation of fibroblasts into decidual cells (decidualization), we utilized the human uterine fibroblast (HuF) in vitro cell model. Immunocytochemistry data demonstrated that the majority of the TAZ protein is localized in the nucleus. Treatment of HuF cells with the embryonic stimulus cytokine interleukin 1 beta in the presence of steroid hormones (estradiol-17 beta and medroxyprogesterone acetate) for 13 days did not cause any apparent TAZ mRNA changes but resulted in a significant TAZ protein decline (approximately 62%) in total cell lysates. Analysis of cytosolic and nuclear extracts revealed that the decline of total TAZ was caused primarily by a drop of TAZ protein levels in the nucleus. TAZ was localized on the peroxisome proliferator-activated receptor response element site (located at position -1200 bp relative to the transcription start site) of the genomic region of decidualization marker insulin-like growth factor-binding protein 1 (IGFBP1) in HuF cells as detected by chromatin immunoprecipitation. TAZ is also present in human endometrium tissue as confirmed by immunohistochemistry. During the secretory phase of the menstrual cycle, specific TAZ staining particularly diminishes in the stroma, suggesting its participation during the decidualization process, as well as implantation. During early baboon pregnancy, TAZ protein expression remains minimal in the endometrium close to the implantation site. In summary, the presented evidence shows for the first time to date TAZ protein in the human uterine tract, its downregulation during in vitro decidualization, and its localization on the IGFBP1 promoter region, all of which indicate its presence in the uterine differentiation program during pregnancy.

Endometrial responses to embryonic signals in the primate

The delicate interaction between an embryo and the uterus to initiate implantation and maintain pregnancy is one of the most elegant and fascinating interactions in human biology. Understanding the molecular events of embryo-maternal interaction is of interest to reproductive biologists, clinicians and couples affected by infertility. We have established the baboon as the non-human primate model for studying embryo implantation. Infusion of chorionic gonadotropin (CG), the major embryonic signal of primates, into the uterine cavity of normal cycling baboons during the window of receptivity induces a myriad of morphological, biochemical and molecular changes in the estrogen and progesterone primed endometrium. The luminal epithelium responds by forming plaques, the overall secretory function of the glandular epithelium increases and the stromal response is characterized by induction of alpha-smooth muscle actin (alphaSMA). Cross talk between ovarian and embryonic hormones is evidenced by the fact that these responses are inhibited upon treatment with a progesterone receptor antagonist. CG signals principally through the seven transmembrane LH/CG G-protein coupled receptor, and activates a mitogen activated protein kinase pathway in the endometrial epithelium that is unique and independent of all the classical signaling pathways. In the stromal compartment, CG both rescues stromal fibroblasts from their apoptotic demise and also differentiates them into the decidualized phenotype. We propose that stromal cell survival and differentiation is mediated by a critical modulator of cell fate, Notch-1. Thus, CG is an important embryonic signal which modulates communication between the embryo and the endometrium and induces changes that are critical to successful implantation.

Species Comparison of the Role of p38 MAP Kinase in the Female Reproductive System

The p38 mitogen-activated protein kinases (MAPKs) are members of discrete signal transduction pathways that have significant regulatory roles in a variety of biological processes, depending on the cell, tissue and organ type. p38 MAPKs are involved in inflammation, cell growth and differentiation and cell cycle. In the female reproductive system, p38 MAPKs are known to regulate various aspects of the reproductive process such as mammalian estrous and menstrual cycles as well as early pregnancy and parturition. p38 MAPKs have also been implicated in alterations and pathologies observed in the female reproductive system. Therefore, pharmacologic modulation of p38 MAPKs, and inter-connected signaling pathways (e.g., estrogen receptor signaling, c-fos, c-jun), may influence reproductive physiology and function. This article provides a critical, comparative review of available data on the roles of p38 MAPKs in the mammalian female reproductive system and in reproductive pathophysiology in humans and preclinical species. We first introduce fundamental differences and similarities of the mammalian female reproductive system that should be considered by toxicologists and toxicologic pathologists when assessing the effects of new pharmacologic agents on the female reproductive system. We then explore in detail the known roles for p38 MAPKs and related molecules in female reproduction. This foundation is then extended to pathological conditions in which p38 MAPKs are thought to play an integral role.

Decidualization attenuates the contractility of eutopic and ectopic endometrial stromal cells: implications for hormone therapy of endometriosis

CONTEXT

Decidualization of the endometrium involves the morphological and biochemical reprogramming of the estrogen-primed proliferative endometrial stromal compartment under the continuing influence of progesterone.

OBJECTIVES

The aim of this study was to evaluate the involvement of the extracellular matrix contractility of eutopic and ectopic endometrial stromal cells during the tissue remodeling processes associated with decidualization.

DESIGN

The effect of decidualization on the contractile profile of the endometriotic cyst stromal cells and eutopic endometrial stromal cells with or without endometriosis in the three-dimensional collagen gel culture was investigated using laser scanning microscopy, collagen gel contraction assays, and Western blot analysis.

RESULTS

Decidualized ectopic and eutopic endometrial stromal cells in the three-dimensional collagen gel culture mimicked the morphology of decidual tissue in vivo. In vitro decidualization inhibited the contractility of these eutopic and ectopic endometrial stromal cells. Down-regulation of integrin alpha1beta1 and alpha2beta1 expression, suppression of Ras homology A (Rho A), Rho-associated coiled-coil-forming protein kinase (ROCK)-I and ROCK-II expression, inhibition of the differentiation into the myofibroblastic phenotype, and induction of differentiation into epithelioid decidual phenotype were observed in these cells during decidualization.

CONCLUSIONS

It is suggested that the attenuation of eutopic endometrial stromal cell-mediated contractility by decidualization is a novel and integral mechanism of the physiological endometrial tissue remodeling process during menstrual cycles. Although ectopic endometrial stromal cells have enhanced contractile profile, decidualization can attenuate the contractility of these cells. These findings may be one of the action mechanisms by which oral contraceptives and progestins ameliorate endometriosis.

Manipulating actin dynamics affects human in vitro decidualization

The differentiation of uterine stromal fibroblasts into decidual cells is critical for establishing pregnancy. This process, called decidualization, requires the reorganization of the actin cytoskeleton, which mainly depends on actin dynamics and the phosphorylation status of the myosin light chain. We manipulated actin dynamics with jasplakinolide (100 nM) and latrunculin B (1 microM), both of which significantly inhibited the synthesis of decidualization markers induced by 6 days of treatment with embryo-mimicking stimulus interleukin 1beta (IL1B) and steroid hormones (SHs; 17beta-estradiol and medroxyprogesterone acetate) in the human uterine fibroblast (HuF) in vitro model. However, only jasplakinolide had long-lasting effects on the G-actin:F-actin ratio and prevented decidualization induced by the artificial stimulus cAMP (and SHs). Actin-binding protein cofilin mainly colocalized with G-actin in the nucleus as well as the cytoplasm. Only some spots of colocalization between cofilin and F-actin were detected in the cytoplasm. Brief extraction of cytosolic proteins from living cells revealed that in cells treated with IL1B or cAMP (and SHs) for 6 days, cofilin was mainly detected in the nucleus. The translocation of cofilin from cytosol to nucleus was also detected in HuFs treated for 12 days with SHs, IL1B and SHs, and cAMP and SHs. The same significant translocation was confirmed in primary baboon stromal uterine fibroblasts. We conclude that changes in actin dynamics, particularly the stabilization of F-actin, have a significant negative impact on decidualization, and the translocation of cofilin to the nucleus is a key feature of this process in the primate.

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.

Insulin-like growth factor-1 and lean body mass in HIV-infected children

OBJECTIVES

To describe insulin-like growth factor-1 (IGF-1) and insulin-like growth factor-1-binding protein-1 (IGFBP-1) and IGFBP-3 in HIV+ children before and after initiating or changing antiretroviral therapy and to evaluate association of growth and body composition to growth factors at baseline and over time.

METHODS

Ninety-seven prepubertal HIV+ children aged 1 month to younger than 13 years were observed over 48 weeks after beginning or changing antiretroviral therapy. Serum IGF-1, IGFBP-1, and IGFBP-3 were measured and compared with age- and sex-specific norms. Anthropometric measures were compared as follows: subjects vs matched children from (a) the National Health and Nutrition Examination Survey to generate z scores and (b) HIV-exposed, uninfected children from Women and Infants Transmission Study; and subjects with normal vs abnormal IGF-1 and IGFBP concentrations at baseline. Anthropometric changes were compared for children whose IGF-1 level normalized vs remaining subjects. Multivariate analysis adjusting for sex, race, and baseline age evaluated associations between anthropometry and IGF-1 and IGFBP concentrations.

RESULTS

In multivariate analysis, lower baseline IGF-1 and IGFBP-3 were associated with lower mean weight, height, mid-arm muscle circumference, and mid-thigh circumference z scores. Twenty-four percent of children had a low IGF-1 level at baseline, 50% of whom normalized IGF-1 on study. Children whose IGF-1 normalized had greater increases in mean mid-arm muscle circumference z score (1.00 vs -0.03, P = 0.029), but a trend toward lesser mean height increase (P = 0.082) than remaining subjects. Likewise, in comparison to controls from Women and Infants Transmission Study, mean mid-arm muscle circumference also increased more in children whose IGF-1 normalized (P = 0.024) but mean height changed less (P = 0.003). Fifty-five percent of children had elevated IGFBP-1 at baseline, 69% of whom normalized.

CONCLUSIONS

IGF-1 increases and IGFBP-1 decreases in HIV-infected children upon initiation or change in antiretroviral therapy. Improved muscle mass, but not linear growth, is associated with normalized IGF-1 concentration. These findings suggest that IGF-1 may merit evaluation as a potential therapeutic strategy to improve lean body mass in HIV-infected children.

Multipotent properties of myofibroblast cells derived from human placenta

Human uterine fibroblasts (HuF) isolated from the maternal part (decidua parietalis) of a term placenta provide a useful model of in vitro cell differentiation into decidual cells (decidualization, a critical process for successful pregnancy). After isolation, the cells adhere to plastic and have either a small round or spindle-shaped morphology that later changes into a flattened pattern in culture. HuF robustly proliferate in culture until passage 20 and form colonies when plated at low densities. The cells express the mesenchymal cell markers fibronectin, integrin-beta1, ICAM-1 (CD54), and collagen I. Flow cytometry of HuF has detected the presence of CD34, a marker of the hematopoietic stem cell lineage, and an absence of CD10, CD11b/Mac, CD14, CD45, and HLA type II. Furthermore, they also express the pluripotency markers SSEA-1, SSEA-4, Oct-4, Stro-1, and TRA-1-81 as detected by confocal microscopy. Treatment for 14-21 days with differentiation-inducing media leads to the differentiation of HuF into osteoblasts, adipocytes, and chondrocytes. The presence of alpha-smooth muscle actin, calponin, and myosin light-chain kinase in cultured HuF implies their similarity to myofibroblasts. Treatment of the HuF with dimethyl sufoxide causes reversion to the spindle-shaped morphology and a loss of myofibroblast characteristics, suggesting a switch into a less differentiated phenotype. The unique abilities of HuF to exhibit multipotency, even with myofibroblast characteristics, and their ready availability and low maintenance requirements make them an interesting cell model for further exploration as a possible tool for regenerative medicine.

Transforming growth factor (TGF)-beta1-induced human endometrial stromal cell decidualization through extracellular signal-regulated kinase and Smad activation in vitro: peroxisome proliferator-activated receptor gamma acts as a negative regulator of TGF-beta1

OBJECTIVE

To investigate the effect of transforming growth factor (TGF)-beta1 on the extracellular signal-regulated kinase (ERK) and Smad pathway and the role of peroxisome proliferator-activated receptor (PPAR)-gamma in cultured human endometrial stromal cells.

DESIGN

Experimental study.

SETTING

Infertility center of a tertiary university hospital. MATERIAL(S): Human endometrial tissues obtained by hysterectomy from patients with conditions other than endometrial diseases.

INTERVENTION(S)

Endometrial stromal cells were cultured under normal laboratory conditions. TGF-beta1, rosiglitazone (PPARgamma agonist), and PD98059 (ERK inhibitor) were added to endometrial stromal cell culture according to experimental purposes.

MAIN OUTCOME MEASURE(S)

Cell count, PRL expression, Smad and ERK phosphorylation, cyclooxygenase (COX)-2 expression, and prostaglandin E(2) (PGE(2)) release.

RESULT(S)

TGF-beta1 inhibited cellular proliferation and induced the expressions of COX-2, PGE(2), and PRL of cultured human endometrial stromal cells. These effects may be mediated by Smad and ERK phosphorylation. Treatment with rosiglitazone, a PPARgamma agonist, reversed the TGF-beta1 effect by antagonizing the activation of ERK and Smad that was induced by TGF-beta1.

CONCLUSION(S)

PPARgamma plays a negative role by directly acting on Smad and ERK phosphorylation in human endometrial cell decidualization that is induced by TGF-beta1 in vitro.

Effect of interferon-gamma treatment on the expression of interleukin-1beta at the maternal-fetal interface of pregnant rats

In the present study, the possible mechanisms by which interferon (IFN)-gamma affects pregnancy were investigated using the cytokine network model. The IFN-gamma-induced expression of interleukin (IL)-1beta was examined using western blotting, immunohistochemistry and immunofluorescence. The results showed that IFN-gamma treatment significantly decreased the expression of uterine IL-1beta protein during the preimplantation, post-implantation and mid-gestation periods. The expression of IL-1beta protein was increased after IFN-gamma treatment compared with the control group in late pregnancy. In the placenta, IL-1beta protein levels were significantly increased after IFN-gamma treatment in early and mid-pregnancy. In late pregnancy, IFN-gamma treatment significantly decreased placental IL-1beta protein levels. IL-1beta was mainly expressed in the myometrium, uterine arteries, decidua basalis, trophospongium of the junctional layer and trophoblastic epithelium of the labyrinthine layers. IL-1beta was mainly located in the cytoplasm of in vitro cultured endometrial stromal cells (ESCs). IFN-gamma treatment did not affect the distribution of IL-1beta, only the expression of IL-1beta. The effects of IFN-gamma on the proliferation of ESCs were determined using an MTS (a novel tetrazolium compound) assay. IFN-gamma treatment inhibited the proliferation of ESCs and decreased the weight of the fetus and placenta. These results indicate that exogenous IFN-gamma affects the expression of IL-1beta and inhibits ESC proliferation.

Increased phosphorylation of myosin light chain prevents in vitro decidualization

Differentiation of stromal cells into decidual cells, which is critical to successful pregnancy, represents a complex transformation requiring changes in cytoskeletal architecture. We demonstrate that in vitro differentiation of human uterine fibroblasts into decidual cells includes down-regulation of alpha-smooth muscle actin and beta-tubulin, phosphorylation of focal adhesion kinase, and redistribution of vinculin. This is accompanied by varied adhesion to fibronectin and a modified ability to migrate. Cytoskeletal organization is determined primarily by actin-myosin II interactions governed by the phosphorylation of myosin light chain (MLC20). Decidualization induced by cAMP [with estradiol-17beta (E) and medroxyprogesterone acetate (P)] results in a 40% decrease in MLC20 phosphorylation and a 55% decline in the long (214 kDa) form of myosin light-chain kinase (MLCK). Destabilization of the cytoskeleton by inhibitors of MLCK (ML-7) or myosin II ATPase (blebbistatin) accelerates decidualization induced by cAMP (with E and P) but inhibits decidualization induced by IL-1beta (with E and P). Adenoviral infection of human uterine fibroblast cells with a constitutively active form of MLCK followed by decidualization stimuli leads to a 30% increase in MLC20 phosphorylation and prevents decidualization. These data provide evidence that the regulation of cytoskeletal dynamics by MLC20 phosphorylation is critical for decidualization.

Expression of the metastasis suppressor KAI1 in decidual cells at the human maternal-fetal interface: Regulation and functional implications

At the human maternal-fetal interface, the decidua forms a dense matrix that is believed to limit trophoblast invasion. We investigated whether the metastasis suppressor KAI1 (CD82) is expressed at the maternal-fetal interface. Immunohistochemistry showed strong expression of KAI1 in decidual cells, whereas trophoblast cells were negative for KAI1. In luteal phase endometrium, KAI1 was present in decidualizing endometrial stromal cells. We investigated whether KAI1 expression in endometrial stromal cells is regulated by the decidualizing stimuli cAMP and progesterone or by the cytokine interleukin (IL)-1beta. Western blot analysis revealed induction of KAI1 protein by cAMP analog, but not by progesterone, in a delayed fashion. In contrast, IL-1beta rapidly stimulated KAI1 expression at the transcript level and at the protein level. Cultured decidual cells from term placenta expressed a basal level of KAI1 protein that was elevated on cAMP stimulation. Silencing of KAI1 by RNA interference attenuated expression of decorin, a decidual product implicated in limiting trophoblast invasion. This study shows for the first time the expression of KAI1 in decidual cells at the human maternal-fetal interface, where the metastasis suppressor might participate in intercellular communication with trophoblast cells and the control of trophoblast invasion.

Decidualization Regulates the Expression of the Endometrial Chorionic Gonadotropin Receptor in the Primate1

Chorionic gonadotropin (CG) plays an important role in establishing a receptive endometrium by directly modulating the function of both endometrial stromal and epithelial cells in the baboon. The focus of this study was to characterize changes in CG receptor (LHCGR, also known as CG-R) expression during the menstrual cycle and early pregnancy, particularly during decidualization. LHCGR was localized by using a peptide-specific antibody generated against the extracellular domain. Immunostaining was absent in any of the cell types during the proliferative phase of the cycle. In contrast, during the secretory phase, both luminal and glandular epithelial cells stained positively. Stromal staining was confined to the cells around spiral arteries (SAs) and in the basalis layer. This stromal staining pattern persisted at the implantation site between Days 18 and 25 of pregnancy and after CG infusion. However, as pregnancy progressed (Days 40 to 60), staining for LHCGR was dramatically decreased in the stromal cells. These data were confirmed by nonisotopic in situ hybridization. To confirm whether the loss of LHCGR was associated with a decidual response, stromal fibroblasts were decidualized in vitro, and cell lysates obtained after 3, 6, and 12 days of culture were analyzed by Western blotting. LHCGR protein decreased with the onset of decidualization in vitro, confirming the in vivo results. Addition of CG to decidualized cells resulted in the reinduction of LHCGR in the absence of dbcAMP. We propose that CG acting via its R on stromal cells modulates SA in preparation for pregnancy and trophoblast invasion. As pregnancy progresses, further modification of SA by migrating endovascular trophoblasts and subsequent decidualization results in the downregulation of LHCGR. This inhibition of LHCGR expression also coincides with the decrease of measurable CG in peripheral circulation.

Human chorionic gonadotropin and decidualization in vitro inhibits cytochalasin-D-induced apoptosis in cultured endometrial stromal fibroblasts

Endometrial apoptosis increases from the proliferative phase through the secretory phase and peaks at menses. However, with the onset of pregnancy, the corpus luteum is rescued and stromal cells, instead of undergoing apoptosis, reorganize the cytoskeleton and then begin to differentiate. We hypothesized that in the presence of hormones (estradiol-17beta and medroxyprogesterone acetate), chorionic gonadotropin (hCG) as an early embryonic signal, and induction of decidualization by dibutyryl-cAMP (dbcAMP), endometrial stromal cells are rescued by the regulation of proteins that inhibit apoptosis. The percentage of cells stained with annexin V, an early apoptotic marker, increased dramatically after cytoskeletal disruption with cytochalasin D compared with non-cytochalasin-D-treated controls (P < 0.05). However, treatment of cells with hCG or dbcAMP in the presence of hormones significantly (P < 0.05) decreased the percentage of annexin-V-stained cells compared with cells treated with cytochalasin D alone. This inhibition was further confirmed by immunodetection of cleaved caspase-3 and terminal deoxynucleotidyl transferase dUTP nick end labeling staining. The inhibition of apoptosis by hCG and dbcAMP was via the intrinsic pathway because the cytochalasin-D-treated cells stained intensely for Bax, whereas the cells treated with hormones, hCG, or dbcAMP stained predominantly for Bcl-2. Treatment of cytochalasin-D-treated cells with hormones and dbcAMP resulted in an increase in the secretion of IGF-binding protein-1 (IGFBP-1) and prolactin. Treatment of cytochalasin-D-treated cells with recombinant IGFBP-1 and prolactin also inhibited apoptosis. These data suggest that under in vitro conditions, both hCG and the induction of decidualization play a direct role in preventing uterine stromal cells from undergoing apoptosis. Furthermore, this inhibition of apoptosis may be mediated in part by IGFBP-1 and prolactin and the alteration in the expression of Bcl-2 and Bax.

Decidual differentiation of stromal cells promotes Proprotein Convertase 5/6 expression and lefty processing

Lefty/Ebaf polypeptides, novel members of the TGF-beta superfamily, are involved in endometrial differentiation and embryo implantation. Recently, we showed that, during undisturbed estrous cycle, lefty is present in mouse uterine horn primarily in a precursor form. Here, we show that decidual differentiation of endometrial stroma leads to increased lefty (approximately 3.1- to 3.6-fold in vivo and 5- to 8-fold in vitro) and processing of its precursor primarily to its long form. This event occurs on d 5 of pregnancy, and is paralleled by proprotein convertase (PC)5/6 up-regulation (approximately 6-fold increase for PC5A and 3-fold increase for PC5B) in decidualized uterine horn, independent of embryo implantation. Among the known convertases, only PC5/6A processes lefty to its long form. Taken together, the findings show that decidualized differentiation of stroma, which is a prerequisite for embryo implantation, leads to processing of lefty by PC5/6A.

Interleukin-11 inhibits expression of insulin-like growth factor binding protein-5 mRNA in decidualizing human endometrial stromal cells

Differentiation of endometrial stromal cells into decidual cells is essential for successful embryo implantation. Interleukin (IL)-11 signalling is critical for normal decidualization in the mouse. The expression of IL-11 and its receptors during the menstrual cycle, and the effect of exogenous IL-11 on the decidualization of human endometrial stromal cells in vitro, suggests a role for this cytokine in human decidualization. As the downstream target genes of IL-11 are also likely to be critical mediators of this process, this study aimed to identify genes regulated by IL-11 in decidualizing human endometrial stromal cells in vitro. Stromal cells isolated from endometrial biopsies were decidualized with 17beta estradiol (E) and medroxyprogesterone acetate (EP) in the presence or absence of exogenous IL-11, and total RNA used for cDNA microarray analysis and real-time RT-PCR. Microarray analysis revealed 16 up-regulated and 11 down-regulated cDNAs in EP + IL-11-treated compared with EP-treated cells. The most down-regulated gene was insulin-like growth factor binding protein-5 (IGFBP-5) (3.6-fold). Using real-time RT-PCR, IL-11 was confirmed to decrease IGFBP-5 transcript abundance 102-fold (P = 0.016; n = 6). No difference in IGFBP-5 immunostaining intensity was detected in stromal cells decidualized in the presence or absence of IL-11, and there was no effect of exogenous IGFBP-5 on the progression of steroid-induced in vitro decidualization. Interactions between IL-11 and its target genes, including IGFBP-5, may contribute to the regulation of decidualization and/or mediate communication between the decidua and invading trophoblast at implantation.

In vivo infusion of interleukin-1beta and chorionic gonadotropin induces endometrial changes that mimic early pregnancy events in the baboon

Both human chorionic gonadotropin (hCG) and IL-1beta induce changes in the endometrium that are associated with the establishment of pregnancy. We investigated the synergistic effect of these two embryonic signals on endometrial function using a baboon model of simulated pregnancy. Recombinant hCG (30 IU/d) was infused between d 6 and 10 post ovulation (PO) to mimic blastocyst transit. On the expected day of implantation (d 10 PO), IL-1beta (12 ng/d) or IL-1 receptor antagonist (IL-1Ra; 12 ng/d) was infused for an additional 5 d. Endometria were harvested on d 15 PO. Both hCG and hCG plus IL-1beta induced marked differences in the distribution of alpha-smooth muscle actin, proliferation marker Ki67, decidualization marker IGF-binding protein-1, and cyclooxygenase-1. The most marked effect of IL-1beta was the induction of IGF-binding protein-1 protein in stromal cells close to the apical surface, whereas cyclooxygenase-1 was down-regulated in the glandular epithelium. Protein arrays of uterine flushings showed significant suppression of death receptors, Fas and TNF receptor 1, in the hCG- with or without IL-1beta-treated groups, suggesting an inhibition of apoptosis. Additionally, cytotoxic T lymphocyte antigen-4, matrix metalloproteinase-3, and IL-4 were suppressed in treated animals compared with controls. However, no differences were observed in cytokine profile between hCG-treated and hCG- plus IL-1beta-treated baboons. This study confirms that in preparation for pregnancy, the primate endometrium undergoes both morphological and functional changes, which are modulated by hCG and IL-1beta, that lead to the inhibition of apoptosis and the development of an immunotolerant environment. These changes suggest that infusion of IL-1beta at the time of implantation into the nonpregnant baboon treated with hCG synergizes with hCG and mimics the early endometrial events associated with the presence of an embryo.

Role of FOXO1A in the regulation of insulin-like growth factor-binding protein-1 in human endometrial cells: interaction with progesterone receptor

Insulin-like growth factor-binding protein-1 (IGFBP1) is a major secretory product of the decidualized endometrium. In the present study, we investigated the role of two transcription factors, progesterone receptor (PGR) and a member of the forkhead box class O family of transcription factors (FOXO1A), in the regulation of the IGFBP1 gene in endometrial cells. Human endometrial fibroblasts (HuF) expressed FOXO1A, progesterone receptor A (PGRA), and progesterone receptor B (PGRB) proteins, whereas the endometrial adenocarcinoma cell line, HEC-1B cells, expressed only FOXO1A and no detectable PGR proteins. When FOXO1A expression was silenced using small interference RNA, IGFBP1 expression decreased in both HuF and HEC-1B cells. Using the chromatin immunoprecipitation technique, we demonstrated that liganded PGR was recruited to the IGFBP1 promoter region (-358 to -49). In addition, immunoprecipitation of HuF nuclear proteins with a PGR antibody followed by immunoblotting with anti-FOXO1A revealed that these two proteins interact in these cells. Reporter studies demonstrated that whereas liganded PGRA or PGRB increased a progesterone response element-linked reporter construct, pPRE/ GRE.E1b.Luc, coexpression of FOXO1A inhibited the PGRB response in HuF and synergistically increased PGRA and PGRB response in HEC-1B cells. Furthermore, in HEC-1B cells, FOXO1A increased IGFBP1 promoter activity, and coexpression of PGRA or PGRB further increased the promoter activity in a cooperative manner. In HuF, the response to FOXO1A and PGR was not additive; in fact, it was lower than the sum of the individual responses. Thus, FOXO1A and PGR associate with one another, and each influences the transactivating potential of the other. The cell type-dependent responses strongly implicate the involvement of other cofactors.

Inhibiting Uterine PC6 Blocks Embryo Implantation: An Obligatory Role for a Proprotein Convertase in Fertility1

Successful embryo implantation involves complex interactions between the embryo and the uterus and is critical in establishing pregnancy. Proprotein convertase (PC) 6 (PC6) is one of the PC endoproteases regulating protein function through posttranslational activation of precursor proteins, including growth and differentiation factors. Here we show that PC6 protein is induced in the uterine stromal cells specifically at the site of embryo attachment during early pregnancy in mice. In vivo blocking of uterine production of PC6 protein using morpholino antisense oligonucleotides in mice resulted in total inhibition of implantation, revealing a vital role for PC6 in modulating the uterus for embryo implantation. Studies in primates (rhesus monkey and human) showed a dramatic upregulation of endometrial PC6 during the phase of uterine receptivity and at implantation, particularly during a critical uterine cell differentiation process termed decidualization. Thus, the current studies have demonstrated that PC6 is an essential molecule in modulating uterine function to support the establishment of embryo implantation. Interestingly, PC6 is one of the PCs identified to be important in processing the coat protein of HIV; inhibition of PCs has been suggested to be an effective approach to reduce HIV transmission. We therefore propose the novel concept that PC6 could be a potential nonhormonal target in the female reproductive tract for dual protection for women, both in preventing pregnancy and reducing HIV infection.

Induction of p38 mitogen-activated protein kinase-mediated apoptosis is involved in outgrowth of trophoblast cells on endometrial epithelial cells in a model of human trophoblast-endometrial interactions

During embryo implantation in species with hemochorial placentation, such as the mouse and human, trophoblast cells of the attached blastocyst penetrate the luminal epithelium of the endometrium before invasion into the endometrial stroma. Signs of apoptosis were demonstrated in luminal endometrial epithelial cells (EEC) adjacent to the trophoblast cells; however, the signaling mechanisms leading to apoptosis in EEC remain unclear. Because mitogen-activated protein kinases (MAPK) were shown to mediate apoptosis in several model systems and found to be activated in the uterus during decidualization, the possible involvement of MAPK during trophoblast-EEC interactions was studied. By coculturing BeWo human trophoblast spheroids with RL95-2 human EEC monolayers to mimic the blastocyst-endometrial interaction, we found that most spheroids rapidly attached to EEC monolayers and then progressively expanded, with marked dislodgment of EEC adjacent to the spreading trophoblast cells. Immunoblotting analysis showed that both p38 MAPK and extracellular signal-regulated kinase (ERK) were activated in EEC after coculture. However, only SB203580 (a p38 MAPK inhibitor), but not PD98059 (an ERK inhibitor), inhibited trophoblast outgrowth on EEC monolayers through the suppression of p38 MAPK activation in EEC. Furthermore, trophoblast expansion caused prominent EEC apoptosis at the spheroid-EEC interface, as detected by annexin V labeling and valyl-alanyl-aspartyl-[O-methyl]-fluoromethylketone (which binds activated caspases) staining, and SB203580 significantly decreased the percentage of apoptotic cells. Our results, based on a model of human trophoblast-EEC interactions, establish that trophoblast cells cause activation of p38 MAPK in EEC and, consequently, induce apoptosis and displacement of EEC, a process that may facilitate implantation.