E. Dimitriadis

Review: LIF and IL11 in trophoblast-endometrial interactions during the establishment of pregnancy.

Blastocyst implantation into the endometrium is critical for the establishment of pregnancy and is tightly regulated by factors within the blastocyst-endometrial micro-environment. Implantation is a continuum involving blastocyst adhesion to the endometrial epithelium followed by trophoblast penetration of the epithelium. The trophoblast proliferates and invades through the endometrium, with a subpopulation acting to remodel the spiral arteries. Trophoblast-endometrial interactions in humans involve carefully orchestrated temporal and spatial alterations in factors that are critical for pregnancy success. Emerging evidence suggests important roles for locally produced cytokines including interleukin 11 and leukemia inhibitory factor in the various stages of implantation. This review focuses on the role of these cytokines in trophoblast-endometrial interactions during the establishment of human pregnancy.

Leukemia inhibitory factor and interleukin-11: cytokines with key roles in implantation

Members of the interleukin-6 family of cytokines include leukaemia inhibitory factor (LIF), interleukin-6, interleukin-11, cardiotrophin, ciliary neurotropic growth factor, oncostatin M and the recently discovered cardiotropin-like cytokine (NNT-1). These ligands signal via heterodimeric receptors composed of ligand-specific alpha chains and the common signal-transducing subunit gp130. Gene targeting in mice provided the first indication of a role for interleukin 6 family cytokines in implantation with the generation of mice with a null mutation of the gene encoding LIF. LIF null female mice were infertile because of failure of blastocyst implantation. More recently, interleukin-11 signalling has been shown to be required for the uterine decidualization response. This review describes the insights into the role of interleukin-6 family cytokines in female fertility that have come from gene targeting experiments in mice.

IL-11 and IL-11Rα immunolocalisation at primate implantation sites supports a role for IL-11 in placentation and fetal development

Embryo implantation, endometrial stromal cell decidualization and formation of a functional placenta are critical processes in the establishment and maintenance of pregnancy. Interleukin (IL)-11 signalling is essential for adequate decidualization in the mouse uterus and IL-11 promotes decidualization in the human. IL-11 action is mediated via binding to the specific IL-11 receptor α (IL-11Rα). The present study examined immunoreactive IL-11 and IL-11Rα in cycling rhesus monkey endometrium, at implantation sites in cynomolgus and rhesus monkeys and in human first trimester decidua and defined distinct spatial and temporal patterns. In cycling rhesus monkey endometrium, IL-11 and IL-11Rα increased in both basalis and functionalis regions during the secretory compared with the proliferative phase, with changing cellular locations in luminal and glandular epithelium and stroma. The patterns were similar overall to those previously described in human endometrium. Differences were seen in immunostaining during implantation in cynomologus and rhesus monkey. In the cynomolgus, very little staining for IL-11 or IL-11Rα was seen in syncytio- and cyto-trophoblast cells in the villi between days 12 and 150 of pregnancy although there was moderate staining in cytotrophoblast in the shell between days 12 and 17 and in subpopulations of cytotrophoblast cells invading the arteries at day 17. By contrast in the rhesus monkey between days 24 and 35 of pregnancy and in human first trimester placenta, cyto- and syncytio-trophoblast in the villi but not cytotrophoblast in the shell were positively stained. The most intense staining for both IL-11 and IL-11Rα was present within the decidua in the maternal component of implantation sites in all three primates but moderate staining was also present in maternal vascular smooth muscle and glands perivascular cells and epithelial plaques. These results are consistent with a role for IL-11 both during decidualization and placentation in primates.

Subcellular localization of L-selectin ligand in the endometrium implies a novel function for pinopodes in endometrial receptivity

BackgroundApical surfaces of human endometrial epithelium and endothelium are key elements for the initiation of molecular interactions to capture the blastocyst or leukocyte, respectively. The L-selectin adhesion system has been strongly proposed to play an important role in the initial steps of trophoblast adhesion and promotion of integrin-dependent processes, ultimately culminating in the establishment of the embryo-maternal interface. On the basis of these facts, we hypothesized a novel role for pinopodes as the first embryo-fetal contact sites to contain the highest subcellular expression of L-selectin ligand suggesting its role in early adhesion as predicted. Thus, the objective of this study was therefore to determine the subcellular pattern of distribution of the L-selectin ligand (MECA-79) in human endometrial apical membrane region during the window of implantation.MethodsEndometrial biopsies of secretory phases from fertile females ranging in age between 25 and 42years were studied using several approaches, including scanning electron microscopy (SEM), immunostaining for light microscopy and transmission electron microscopy (TEM), and immunoblotting as well as statistical analysis of the area-related numerical densities of immunoreactive MECA-79-bound nanogolds to detect the expression pattern and the subcellular distribution pattern of L-selectin ligand (MECA-79) in human endometrium during the window of implantation.ResultsThe endometrial biopsies were scored according the dating criteria of Noyes et al. by an experienced histologist. The SEM images of the midluteal phase specimens revealed that fully developed pinopodes were abundant in our samples. HRP-immunostaining and immunofluorescent staining as well as immunoblotting revealed that MECA-79 was expressed in the midluteal phase specimens. The results of immunogold TEM illustrated the expression of MECA-79 in human pinopodes in the midluteal phase and a higher area-relate numerical density in pinopodes compared to that of the uterodome-free areas.ConclusionsThis is the first demonstration of the subcellular localization of MECA-79 in the human pinopodes which may indicate a novel role for pinopodes to be capable of shear-stress-dependent tethering-type adhesion in the initial phases of human embryo implantation.

525. ROLES FOR HUMAN CHORIONIC GONADOTROPHIN IN EMBRYO-ENDOMETRIAL CROSS-TALK DURING BLASTOCYST IMPLANTATION

Emerging evidence suggests an important role for the early embryo product human chorionic gonadotrophin (hCG) in embryo-endometrial interactions critical for successful embryo implantation1. The human endometrium is also a source of hCG, with maximal expression of hCG and its receptor, hCG/LHR, in endometrial epithelial cells during the window of implantation in vivo2,3, and in primary endometrial epithelial cells (EECs)3. Implantation is tightly regulated by growth and regulatory factors produced within the embryo-endometrial microenvironment. We hypothesise that embryo/endometrial-derived hCG mediates the molecular cross talk vital for successful implantation. The main objective of this study was to investigate the effect of hCG on the production of a selected cohort of 42 cytokines and growth factors by EECs. These included those with both known and previously unidentified roles during implantation. The secretory profile of cytokines/growth factors produced by EECs was also analysed. EECs (n=8 cultures) were isolated from biopsies collected from fertile cycling women. Cells were treated without or with recombinant hCG for 48 hr and conditioned media collected for quantitative analysis using LuminexTM multiplex technology. For the first time, a secretory profile of 42 cytokines and growth factors produced by EECs was established, as was the identification of fibroblast growth factor-2 (FGF-2) secretion by human endometrial epithelium. hCG (2 IU/ml) significantly increased the production of a number factors including those with known roles during trophoblast migration and adhesion (CX3CL1; 71±31%, CXCL10; 67±24%, CCL4; 87±12%), in trophoblast differentiation (IL-1α ; 68±31%) and with unidentified roles during implantation (CCL22; 78±40%, GM-CSF; 45±16%, FGF-2; 50±25%; all p<0.05). Upregulation of the known hCG regulated proteins, VEGF and LIF, validated this study. These findings clearly support roles for the embryo/endometrium via hCG in actively contributing to the molecular cross-talk during the early stages of implantation.

254. Interleukin-11 enhances endometrial stromal cell decidualisation via activation and inhibition of target genes

Differentiation of endometrial stromal cells into decidual cells is essential for successful embryo implantation. Interleukin (IL)-11 signalling is required for decidualisation in the mouse (1,2) and the expression pattern of IL-11 and its receptors during the menstrual cycle suggests a role for IL-11 in human decidualisation (3). Exogenous IL-11 has been shown to enhance hormone-induced decidualisation of human endometrial stromal cells in culture (4). This study aimed to determine the effects of IL-11 on downstream gene expression in endometrial stromal cells following 12 days of progesterone-induced decidualisation, and to examine the expression and functional significance of IL-11 target genes during this process. Stromal cells isolated from endometrial biopsies (n = 6) were decidualised with 17β-oestradiol and medroxyprogesterone acetate (EP) or EP with 100 ng/mL recombinant human IL-11. Medium was changed every 48 h, and total RNA extracted on Day 12 for gene expression analysis using custom-made 15K cDNA microarrays. Quantitative real-time RT-PCR was performed on the same samples to confirm gene expression levels. In subsequent experiments (n = 2), cells were cytocentrifuged onto glass slides for immunocytochemistry using specific antibodies. Microarray analysis revealed 16 upregulated and 11 downregulated cDNAs in EP + IL-11 compared to EP treated cells. Among these were IL-1β (6.1-fold upregulated) and insulin-like growth factor binding protein (IGFBP)-5 (3.6-fold downregulated). Using real-time RT-PCR, IL-11 was confirmed to increase IL-1β (fold change 1.3–107.1) and decrease IGFBP-5 (fold change 2.8–469.0) transcript abundance in 6 patients. Immunolocalisation of IL-1β in EP and EP + IL-11 treated cells revealed more intense vesicular cytoplasmic staining with IL-11 treatment, while staining intensity for IGFBP-5 was not affected. Interactions between IL-11 and its downstream targets IL-1β and IGFBP-5 are likely to have functional importance in early pregnancy, and may provide novel targets for the manipulation of human fertility. (1) Robb L, Li R, Hartley L, Nandurkar HH, Koentgen F, Begley CG (1998) Nat. Med. 4, 303–308. (2) Bilinski P, Roopenian D, Gossler A (1998) Gene Dev. 12, 2234–2243. (3) Dimitriadis E, Salamonsen LA, Robb L (2000) Mol. Hum. Reprod. 6, 907–914. (4) Dimitriadis E, Robb L, Salamonsen LA (2002) Mol. Hum. Reprod. 8, 636–643.