Endometrial Natural Killer Cells Research Articles

Relaxin and the control of primate parturition.

In primate pregnancy, circulating relaxin, solely a product of the corpus luteum, peaks in the first trimester of pregnancy then declines and levels off for the remainder of pregnancy. Relaxin actions in pregnancy include increasing cervical pro-MMP-1 and pro-MMP-3 and decreasing TIMP-1, changes which soften the cervix. Relaxin, from early pregnancy, increases endometrial natural killer cells, macrophages and neutrophils, blood flow and arterial number. Hyperrelaxinemia correlates with preterm birth.

Expression of leukaemia inhibitory factor and interleukin 15 in endometrium of women with recurrent implantation failure after IVF; correlation with the number of endometrial natural killer cells

Several studies have suggested that endometrial interleukin 15 (IL-15) and the leukaemia inhibitory factor (LIF) may be important in embryo implantation. IL-15 is postulated to play a role in the control of uterine natural killer (uNK) cell proliferation and function, and uNK cells are also known to play a role in implantation. The aims of this study was to (1) compare endometrial levels of IL-15 and the LIF in women with recurrent implantation failure (RIF) after IVF with those in fertile women (controls) and (2) examine the relation of IL-15 and LIF levels to the uNK cell number. We investigated IL-15 and LIF in precisely timed endometrial biopsies (days LH + 7-LH + 9, where the day of the LH surge is LH + 0) obtained from control women (n = 15) and women with RIF (n = 45) by immunohistochemistry. A semi-quantitative analysis was performed by the H-score analysis of staining intensity in the stroma, glandular epithelium and luminal epithelium, separately. We also correlated expression of LIF and IL15 with uNK cell numbers (obtained in an earlier study of the same samples). The quantity of the LIF protein in endometrial glandular epithelium in women with RIF [median and range; 179 (70-365)] was lower (P = 0.01) than in control women [median and range; 247 (120-287)]. In contrast, the level of the IL-15 protein in the stroma in women with RIF [median and range; 90 (0-175)] was higher (P = 0.009) than in control women [median and range; 60 (15-150)]. There was a significant correlation between the uNK cell number and stromal expression of IL-15 (r = 0.427, P = 0.001). No correlation between the LIF expression in any compartment and the uNK cell number was seen. The results show an altered expression of LIF and IL-15 in the endometrium of women with RIF. Despite the limitation of not identifying uNK cells by phenotypic markers, the correlation between the uNK cell number and the stromal cell IL-15 suggests that IL-15 may play a role in the control of endometrial uNK cell function or proliferation.

Estradiol levels correlate with cytotoxic natural killer cell counts in implantation failure related to unexplained infertility

Hormone expression regulates the levels of endometrial Natural Killer (NK) cells during implantation window. Considering that supra-physiological levels of estradiol correlates with decreased embryo quality and a lower implantation rate, we investigated number and type of NK cells and cytokines IL-6, and VEGF according to estradiol and progesterone expression in unexplained infertility and implantation failure patients.

Immunological study of the quality of the endometrium in women with unexplained infertility and implantation failure

When you have ruled out the most common causes associated with infertility, it is considered that 80% of reproductive failure is related with immune imbalance. It is assumed that there must be a delicate balance between the expression of cytokines and subpopulations of endometrial natural killer cells (NK) during implantation. Based on these data we studied the ability of NK cells and regulatory cytokines IL-6 and VEGF as potential endometrial biomarkers for the diagnosis of immunological factor in infertility.

Controlled ovarian stimulation is affecting endometrial quality

It has been demonstrated that uterine receptivity is diminished during controlled ovarian stimulation (COS). Moreover, clinical evidence suggest that endometrial cytotoxic Natural Killer (NK) cell counts or activity were related to reproductive failure. Particularly, IL15 and IFNγ are associated with NK cell activation. The aim of this study was to compare the impact of rFSH or hMG COS protocols on endometrial NK cell counts and cytokine expression on fertile oocyte donors. Analytical, experimental, prospective study. Endometrial biopsy and peripheral blood of 10 fertile women were obtained 5-8 days post-ovulation during three consecutive cycles: 1.stimulated with long GnRH agonist protocol + rFSH, 2. natural cycle (NC) and 3.stimulated with long GnRH agonist protocol + hMG. Steroid hormones were measured in serum by RIA. NK cytotoxic subset (CD9+CD56+CD16+) were determined by flow cytometry. mRNA expression of IL15 and IFNy were determined by RT-qPCR. Statistical analysis were performed by ANOVA or Friedman, and Tukey or Dunn's test for media comparison. Both COS protocols increased the levels of estradiol (E2), progesterone (P4) and the proportion of cytotoxic NK cells (P<0.05) compared with NC. Moreover, we found a positive correlation between the proportion of cytotoxic NK cells and E2 (r = 0.4047, P<0.05) or P4 (r = 0.4323, P<0.05). Only the use of hMG increased local mRNA levels of IL15 and IFNy (P<0.05). Ovarian stimulation has a deleterious effect on fertile endometrium by increasing the proportion of cytotoxic NK cells. This effect seems to be due to the supra-physiological levels of E2 and P4. The use of hMG seems to be related to NK cell activation, since we found higher levels of IFNy in compare to rFSH.

Natural Killer Cells and Telomerase in the Endometrium of Patients with Endometriosis

Background Although endometriosis is a common cause of pelvic pain and infertility, the pathogenesis of the disease remains poorly understood. Several theories have been proposed to explain the mechanisms involved in the development of this disease, including the role of the immunological system. Objectives To evaluate the percentage of endometrial natural killer (eNK) cells and telomerase expression in the endometrium of patients with and without endometriosis. Materials and methods Endometrium samples were obtained during the mid-secretory phase from two groups of women: 12 women with endometriosis diagnosed by laparoscopy and confirmed by histological evaluation of the lesion, and 13 fertile women (control group) who underwent tubal sterilization at the same institution and in whom no signs of endometriosis were detected at surgery. Specific antibodies were used for the immunohistochemical assessment of eNK and telomerase. Results: eNK cells were significantly higher in the group of women without endometriosis (p&lt;0. 0001); however, telomerase expression in the endometrium was similar in the two study groups. Conclusions: Significantly fewer eNK cells were observed in the endometrium of women with endometriosis; however, there was no difference in telomerase expression. The finding of fewer eNK cells supports the hypothesis of a deficiency in the immune system facilitating the implantation of endometriotic tissue or interfering with implantation after fertilization.

Characterization of natural killer cells in implantation failure: effect of low-molecular weight heparin on endometrial natural killer cell counts

To compare the expression pattern of angiogenic cytokines in CD56+ uNK cells from peri-implantation endometrium in women with a history of recurrent miscarriage and fertile controls.28 women were recruited, from which 18 women were diagnosed as recurrent miscarriage and 10 women were of proven fertility. Endometrial biopsy samples were obtained precisely 7 days after luteinization hormone surge in a natural cycle. The angiogenic profile of isolated CD56+ uNK cells was determined by RayBio human angiogenesis antibody array G Series 1000. Differentially expressed angiogenic cytokines between groups were validated by ELISA kits.CD56+ uNK cells freshly isolated from peri-implantation endometrium were determined to be >90% pure. Angiogenic cytokine array demonstrated that CD56+ uNK cells are one of the angiogenic factors producers in endometrium around the time of embryo implantation. A differential angiogenic cytokine expression profile was found between two groups, with significantly higher expressions of angiogenin, VEGF-A and bFGF in CD56+ uNK cells from women with recurrent miscarriage, compared with fertile controls.Differential angiogenic cytokine profile of isolated CD56+ uNK cells suggested the role of uNK cells in the altered endometrial vascularity at the time of implantation, which may account for the endometrial contribution to recurrent miscarriage.

REVIEW ARTICLE: The Unique Properties of Uterine NK Cells

Natural killer (NK) cells are lymphocytes of the innate immunity system that are able to kill various hazardous pathogens and tumors. However, it is now widely accepted that NK cells also possess non-destructive functions, as has been demonstrated for uterine NK cells. Here, we review the unique properties of the NK cells in the uterine mucosa, prior to and during pregnancy. We discuss the phenotype and function of mouse and human endometrial and decidual NK cells and suggest that the major function of decidual NK cells is to assist in fetal development. We further discuss the origin of decidual NK cells and suggest several possibilities that might explain their accumulation in the decidua during pregnancy.

ORIGINAL ARTICLE: Comparative Analysis of Peripheral Natural Killer Cells in the Two Phases of the Ovarian Cycle

ProblemChanges in endometrial Natural Killer (NK) cells during the luteal phase of the ovarian cycle are important in initiating/maintaining a subsequent pregnancy. In the present study it was investigated whether during the menstrual cycle changes occur also in peripheral blood (PB) NKs.Method of studyBlood samples during the follicular and the luteal phase were collected from 30 women without fertility problems. Samples were analyzed by flow‐cytometry for: (1) NK cells (CD3−CD16+CD56+) and (2) intracellular production of interferon‐γ (IFN‐γ) by NK cells. For the comparison and correlation of the two populations between the two phases, Wilcoxon signed‐rank test and Spearman’s Coefficient were used.ResultsThe differences in percentages of CD3−CD16+CD56+ cells and that of CD3−CD16+CD56+/IFN‐γ+ cells between the follicular and the luteal phase were not statistically significant (10.61 ± 5.11 versus 9.76 ± 4.57 and 6.48 ± 7.90 versus 7.30 ± 6.77, respectively, P &gt; 0.05). The correlation between the two variables (NK% and NK/IFN‐γ%) was weakly positive (P = 0.07) only in the follicular phase.ConclusionThe study did not reveal menstrual cycle‐depended changes in PB NK cells. Thus, a suggestion to measure these cells in a specific phase of the cycle in order to predict the outcome of a subsequent pregnancy in women with fertility problems is objected.

The effect of the in vitro fertilization (IVF) medication on endometrial natural killer cell (NK Cell), β3 integrin and Cyclin E

OBJECTIVE: The purpose of this pilot study is to see if the use of fertility medications in women undergoing IVF treatments have any significant effect on: 1) Natural Killer Cells at the level of the Endometrium and in peripheral blood 2) The Endometrial Expression of ß3 Integrin and Cyclin E.

Comparing effect of low molecular weight heparin and Vitamin E on endometrial Natural Killer cell counts

Comparing effect of low molecular weight heparin and Vitamin E on endometrial Natural Killer cell counts

ORIGINAL ARTICLE: Changes in Endometrial Natural Killer Cell Expression of CD94, CD158a and CD158b are Associated with Infertility

Problem Cycle‐dependent fluctuations in natural killer (NK) cell populations in endometrium and circulation may differ, contributing to unexplained infertility.Method of study NK cell phenotypes were determined by flow cytometry in endometrial biopsies and matched blood samples.Results While circulating and endometrial T cell populations remained constant throughout the menstrual cycle in fertile and infertile women, circulating NK cells in infertile women increased during the secretory phase. However, increased expression of CD94, CD158b (secretory phase), and CD158a (proliferative phase) by endometrial NK cells from infertile women was observed. These changes were not reflected in the circulation.Conclusion In infertile women, changes in circulating NK cell percentages are found exclusively during the secretory phase and not in endometrium; cycle‐related changes in NK receptor expression are observed only in infertile endometrium. While having exciting implications for understanding NK cell function in fertility, our data emphasize the difficulty in attaching diagnostic or prognostic significance to NK cell analyses in individual patients.

Accumulation of Uterine CD16(−) Natural Killer (NK) Cells: Friends, Foes, or Jekyll-and-Hyde Relationship for the Conceptus?

Human cycling endometrium and early pregnant decidua are infiltrated by a unique lymphocyte subset of CD16(−) natural killer (NK) cells, which are minor cells in circulating blood and other organs. The number of uterine (u) CD16(−) NK cells rises sharply after ovulation. If pregnancy occurs, uCD16(−) NK cells increase further in number, but are shed during the menstrual period. uCD16(−) NK cells have the potential to produce cytokines and growth factors that play important roles in embryo implantation and placentation, but they are armed with cytolytic cytoplasmic granules. In the mid-secretory phase endometrium of women with recurrent miscarriages, dense accumulations of uCD16(−) NK cells also occur, like those seen in first-trimester decidua of uncomplicated pregnancies. This finding complicates understanding the exact roles of these NK cells at implantation sites. uCD16(−) NK cells are likely to be a mixture of indigenous endometrial NK cells and immigrant NK cells from the circulation. However, it is not yet known if NK cells from these two different origins display similar or unique characteristics. In this review, the potential underlying mechanisms for accumulation of uCD16(−) NK cells in uncomplicated pregnancies and in pathological pregnancies, especially recurrent miscarriages, are discussed.

The Unique Properties of Human NK Cells in the Uterine Mucosa

Natural killer (NK) cells are lymphocytes of the innate immune system that are able to kill hazardous pathogens and tumours. It was recently recognized that NK cells also possess non-destructive functions. NK cells were shown to interact with T, B, DC cells and macrophages and consequently shape the adaptive immune response. In addition, activated NK cells were shown to be quite efficient antigen-presenting cells. Here we review the unique properties of human NK cells in the uterine mucosa prior to and during pregnancy. We discuss the role of decidual NK cells and suggest that their major function is to assist in fetal development. Further we discuss the function and origin of endometrial NK cells and define some questions that need to be addressed in future research.

Prednisolone reduces preconceptual endometrial natural killer cells in women with recurrent miscarriage

To test the hypothesis that high numbers of uterine natural killer (uNK) cells in the endometrium of women with recurrent miscarriage (RM) could be reduced with prednisolone. A before and after study. A tertiary referral teaching hospital. Eighty-five women with idiopathic RM recruited from all over the UK and 18 women attending for sterilization (controls). An endometrial sample was taken on day 21 +/- 2 of the menstrual cycle. Immunohistochemistry was used to identify uNK (CD56+, CD16-, CD3-). Twenty-nine women with RM and >5% uNK agreed to take 20 mg oral prednisolone daily from day 1 to 21 of their menstrual cycle, when a second biopsy was obtained and analyzed. The percentage of stromal cells that were uNK. The normal range was defined using control samples as <5%. Women with RM had significantly more uNK than the controls (P=.008). Prednisolone treatment significantly reduced the number of CD56 cells in the endometrium, from a median of 14% (before) to 9% (after) (P=.0004). We have demonstrated that high numbers of uNK in preimplantation endometrium of women with recurrent miscarriage can be reduced with administration of prednisolone.

Potential Selectin L Ligands Involved in Selective Recruitment of Peripheral Blood CD16(–) Natural Killer Cells into Human Endometrium1

Unique CD16(-) natural killer (NK) cells appear in the human cycling endometrium and acutely increase in number after ovulation. Selective recruitment from peripheral blood (PB) CD16(-) NK cells is a potential mechanism for the postovulatory increase of these NK cells. The interaction between selectin L, an adhesion molecule playing a critical role in leukocyte extravasation, and its ligands may be involved in this phenomenon. We investigated the menstrual cycle-dependent fluctuation of selectin L expression on PB CD16(-) NK cells and selectin L ligand expression in the human endometrial endothelium. The expression of selectin L on PB CD16(-) NK cells was constantly high throughout the menstrual cycle compared with other PB CD16(+) NK cells and non-NK lymphocytes. Among eight selectin L ligands examined, podocalyxin-like, mucosal addressin cell adhesion molecule-1 (MADCAM1) and chondroitin sulfate proteoglycan 2 (CSPG2) were localized in the endometrial endothelium. Semiquantitative score of immunostaining intensity in the endometrial endothelium for MADCAM1 was highest in the late secretory phase, whereas that for CSPG2 peaked throughout the secretory phase. There was a strong positive correlation between the number of endometrial NK cells and the semiquantitative score for CSPG2. Three active isoforms of CSPG2 mRNA were detected in the human endometrium. These findings support the idea that the interaction between selectin L and selectin L ligands functions in the postovulatory selective recruitment of PB CD16(-) NK cells into the human endometrium.

Role of the endometrial tripod interleukin-18, -15, and -12 in inadequate uterine receptivity in patients with a history of repeated in vitro fertilization–embryo transfer failure

To document in the endometrium the correlation among the interleukin (IL)-12, -15, and -18 mRNA and the correlation between cytokine levels, vascular status, and endometrial natural killer (NK) cell count in the context of recurrent implantation failure. A pilot study. Department of Reproductive Immunology. Women who failed to become pregnant after repeated IVF-embryo transfer and fertile control subjects. Ultrasonic evaluation and endometrial biopsy in luteal phase. Uterine artery Doppler, count of uterine CD56 bright cells/field, and quantification by real-time polymerase chain reaction (PCR) to monitor IL-12 family (IL-12p40, IL-12p35, EBI3, IL-23), the IL-18 system (IL-18, IL-18R, IL18BP), and the IL-15 mRNA ratio. The uterine artery Doppler and the CD56 bright cell counts were significantly different in fertile and infertile patients. The mean uterine artery pulsatility index correlated significantly negatively with the IL-18/actin ratio suggesting a defect of the cytokine-dependent vascular remodeling pathway. The number of uterine CD56 bright cells was significantly correlated with the IL-15/actin and IL-18/IL-18BP ratios. Thus, IL-18 and IL-15 seems to be involved in the local recruitment and the activation of uterine natural killer (uNK) cells. IL-18 was itself correlated with IL-15 and IL-12, suggesting a local control of uNK cells activation. The assessment of the tripod IL-12/-15/-18 shows distinct immune-related mechanisms that are involved in the broader context of inadequate uterine receptivity.

Spatial and temporal expression of ligands for CXCR3 and CXCR4 in human endometrium.

In this study, we investigated the expression of ligands for CXCR3 (Mig, IP-10, and I-TAC) and CXCR4 (SDF-1) in the human endometrium throughout the menstrual cycle. By immunohistochemistry, immunostaining for Mig and IP-10 was found in the surface epithelia, glandular epithelia, and stroma with some menstrual cycle-dependent fluctuation. By contrast, immunostaining for I-TAC or SDF-1 was not detected. ELISA demonstrated that the concentrations of Mig and IP-10 were higher in the secretory phase than in the proliferative phase, but I-TAC and SDF-1alpha was detected in only a few samples. Endometrial Mig and IP-10 concentrations strongly correlated with the number of endometrial natural killer cells. Progesterone significantly induced Mig secretion and tended to induce IP-10 secretion from the cultured endometrial stromal cells, whereas 17beta-estradiol had no significant effect. Neither I-TAC nor SDF-1alpha was detected in the supernatant of cultured endometrial stromal cells in the presence or absence of 17beta-estradiol or progesterone. The results suggest that Mig and IP-10 may be involved in the recruitment of natural killer cells or other phenomena in the human endometrium.

Expression of macrophage inflammatory protein-3β in human endometrium throughout the menstrual cycle

Objective To determine the expression of macrophage inhibitory protein-3β (MIP-3β), a potential chemoattractant for endometrial natural killer (NK) cells, in the human endometrium. Design An experimental study. Setting University department of obstetrics and gynecology. Patient(s) Thirty-seven fertile women with regular menstrual cycles and nonpathological endometrium, undergoing hysterectomy. Intervention(s) Endometrium was obtained from operative samples. Main outcome measure(s) Paraffin-embedded endometrium was immunostained to determine the localization of MIP-3β. The number of NK cells was counted in 10 nonoverlapping stromal areas. The MIP-3β concentration in the homogenized endometrium was determined by ELISA. Result(s) Immunoreactivity for MIP-3β was observed in the surface epithelia, glandular epithelia, and stroma with some menstrual cycle–dependent fluctuation. The MIP-3β concentration was significantly higher in the late secretory phase than in the other phases. It showed a trend toward correlation with the number of endometrial NK cells. Conclusion(s) MIP-3β was expressed in the human endometrium, but our results could not strongly support the hypothesis that MIP-3β is a potential chemoattractant for endometrial NK cells.

Fluctuation of 6Ckine expression in human endometrium during the menstrual cycle

Objective To clarify the expression of 6Ckine, a potential chemoattractant for endometrial natural killer (NK) cells, in the human endometrium. Design Experimental study. Setting Department of obstetrics and gynecology at a medical university. Patient(s) Fifty-seven fertile women 25 to 52 years of age who had regular menstrual cycles and normal endometrium and were undergoing hysterectomy. Intervention(s) Endometrium was obtained from operative samples. Main outcome measure(s) Tissue was immunostained to determine the localization of 6Ckine in the endometrium throughout the menstrual cycle. The number of NK cells was counted in 10 nonoverlapping stromal areas. The concentration of 6Ckine in homogenized endometrium was determined by enzyme-linked immunosorbent assay. Result(s) Endometrial surface, glandular epithelial cells, and perivascular stromal cells were immunoreactive for 6Ckine throughout the menstrual cycle with some fluctuation. In addition, some T cells, NK cells, and macrophages in the stroma were immunoreactive for 6Ckine. The 6Ckine concentration was low in the proliferative phase but elevated in the secretory phase. It showed a moderate positive correlation with the number of endometrial NK cells. Conclusion(s) 6Ckine may be a potential chemoattractant for endometrial NK cells.