Effect of endometrial biopsy method on ribonucleic acid quality and gene expression analysis in patients with leiomyoma.

Objective: To compare ribonucleic acid (RNA) quantity and purity in tissue collected with different endometrial sampling methods to establish the optimal tool for use in endometrial gene expression studies. Design: Observational study. Setting: University hospital. Patients: Fourteen patients with submucosal leiomyomas. Interventions: Unguided biopsies were obtained using a low-pressure suction device before hysteroscopy from 14 patients with submucosal leiomyomas followed by guided biopsy with a resectoscope loop. Fifty-seven samples were collected: 25 obtained using a suction device and 32 with a loop. Main Outcome Measures: Total biopsy weight, RNA purity, and RNA yield for each collection method. After complementary deoxyribonucleic acid synthesis, HOXA10 expression was measured by quantitative polymerase chain reaction in the endometrium overlying and remote from the leiomyoma, as similar expression throughout the cavity was a prerequisite for the use of unguided biopsy method. Results: The median weight of the samples was significantly larger when obtained with the low-pressure suction device than with the resectoscope loop (153 vs. 20 mg). The RNA yield was similar (suction curette, 1,625 ng/mg; resectoscope loop, 1,779 ng/mg). The A260-to-A280 ratio was satisfactory for 94.7 % of the samples, with no difference between the groups. The endometrial expression of HOXA10 was similar in areas overlying the leiomyoma compared with that in remote endometrial sites (2-ΔCt = 0.0224 vs. 0.0225). Conclusions: Low-pressure endometrial suction devices provide tissue samples with acceptable RNA purity and quantity for gene expression studies. The expression of HOXA10 did not differ between endometrial sampling sites even in the presence of leiomyomas.

Endometrial cytokines in patients with and without endometriosis evaluated for infertility.

OBJECTIVE: To evaluate whether endometrial molecular profiles distinguish subsets of patients according to clinical characteristics, and to infer dysregulated immune networks, by measuring cytokines, chemokines, and growth factors in endometrial biopsy specimens from a cohort of infertile women with a high incidence of endometriosis. DESIGN: Prospective cohort study. SETTING: Department of Gynecology at a university hospital. PATIENT(S): Patients undergoing laparoscopy for infertility assessment (n = 103). INTERVENTION(S): Endometrial biopsies were performed during surgery. Fertility outcome and clinical parameters were registered preoperatively and after 6 months. MAIN OUTCOME MEASURE(S): The concentrations of 48 factors in endometrial biopsy specimens were analyzed with respect to clinical status in univariate and multivariate frameworks. RESULT(S): The concentrations of 44 factors from endometrial tissues of 74 patients were suitable for analysis. Although the tissue concentrations of interleukin (IL)15, IL-7, and interferon γ-induced protein (IP)-10 were individually lower in patients with endometriosis than in those without endometriosis, the differences were not significant after multiple comparison. However, multivariate modeling incorporating covariation showed separation between subsets of endometriotic and nonendometriotic patients, based predominantly on IP-10, monocyte chemoattractant protein-1, IL-16, and IL-18; this result was independent of cycle and fertility status. Analysis restricted to endometrial tissues from the secretory phase separated endometriotic and nonendometriotic patients by a combination of IL-15, IP-10, monocyte chemoattractant protein-1, IL-16, and IL-18. This combination suggests a uterine natural killer cell defect. We found no significant correlations between endometrial cytokines and fertility outcome. CONCLUSION(S): A molecular signature in endometrial tissue was able to distinguish endometriotic from nonendometriotic patients, implicating uterine natural killer cells in endometriosis.

Ovulation induction in polycystic ovary syndrome.

The objective of this narrative review was to suggest a rational order of treatment choices in anovulatory women with polycystic ovary syndrome (PCOS), for whom a multitude of treatment options exist. In obese/overweight women with PCOS the importance of weight reduction should be stressed. Inositol, a dietary supplement with a documented effect on ovulation and without adverse effects in the doses recommended, may be suggested. Additional first-line medical alternatives include insulin sensitizers, selective estrogen receptor modulators, and aromatase inhibitors. Of these, the aromatase inhibitor letrozole and the combination of clomiphene citrate and metformin have the highest rates of ovulation and live birth. Second-line treatments are ovarian electrocautery and low-dose follicle-stimulating hormone stimulation. Controlled ovarian stimulation with in vitro fertilization, should be considered the last option as it carries a significant risk of ovarian hyperstimulation syndrome in patients with PCOS.

The prevalence of Type 2 diabetes is not increased in normal-weight women with PCOS.

STUDY QUESTION: Is oral glucose tolerance test (OGTT) needed in all women with polycystic ovary syndrome (PCOS)? SUMMARY QNSWER: OGTT is not routinely needed in women with PCOS and BMI < 25 kg/m2. WHAT IS KNOWN ALREADY: PCOS is associated with insulin resistance and increased prevalence of prediabetes and Type 2 diabetes (T2D) which is closely linked to obesity and possibly age, ethnicity and PCOS phenotype. Several guidelines recommend OGTT upon diagnosis of PCOS and during follow-up. STUDY DESIGN, SIZE, DURATION: A Nordic cross-sectional study including 876 women. PARTICIPANTS/MATERIALS, SETTING, METHODS: The 876 Nordic women with PCOS, aged 14-57 years, were examined for T2D and prediabetes (impaired glucose tolerance [IGT] or impaired fasting glucose (IFG) by OGTT. MAIN RESULT AND THE ROLE OF CHANCE: Of all study subjects 3% (23/876) had T2D, 23% (204/876) prediabetes and 74% (649/876) had normal glucose tolerance (NGT). Increased BMI and waist circumference were significantly (P < 0.001) associated with prevalence of prediabetes and T2D. No normal-weight woman (BMI < 25 kg/m2) was diagnosed with T2D. The prevalence of BMI ≥ 25 kg/m2 was 66% (578/ 876). 91% of women (21/23) with T2D had BMI ≥ 30 kg/m2. Testosterone levels and PCOS phenotype did not predict 2-h glucose levels during OGTT after adjustment for BMI and age. LIMITATIONS, REASONS FOR CAUTION: The present study included cross-sectional data and prospective studies are needed to confirm our results. These results may not apply to populations of other ethnic origin. WIDER IMPLICATIONS OF THE FINDINGS: Routine OGTT may not be indicated in normal-weight women with PCOS. STUDY FUNDING/COMPETING INTEREST(S): None. TRIAL REGISTRATION NUMBER: N/A.

Peritoneal fluid cytokines related to endometriosis in patients evaluated for infertility.

OBJECTIVE: Our aim was to characterize peritoneal cytokine profiles in patients with infertility, with and without endometriosis, to illuminate potential differences in immune profiles that may reflect mechanistic differences between these two patient populations. DESIGN: Cross-sectional study. SETTING: University hospital and research center. PATIENT(S): Women undergoing laparoscopy for infertility investigation (n = 107). INTERVENTION(S): Peritoneal fluid was collected during surgery. Clinical characteristics were registered preoperatively. MAIN OUTCOME MEASURE(S): We determined the concentration of 48 different cytokines from the peritoneal fluid with multiplex immunoassays. Associations between cytokines and clinical findings were assessed with logistic regression and partial least squares discriminant analyses (PLS-DA). RESULT(S): Concentrations of SCGF-ß, IL-8, HGF, and MCP-1 were significantly higher, while IL-13 was significantly lower in the endometriosis group compared with the group without endometriosis. Multiple stepwise logistic regression identified a combination of SCGF-ß, IL-13, and G-CSF concentrations that predicted the presence of endometriosis with 86% sensitivity and 67% specificity. PLS-DA identified a class of 11 cytokines (SCGF-ß, HGF, IL-13, MCP-1, CTACK, MCP-3, M-CSF, LIF, IL-5, IL-9, and IFN-a2) that were more characteristic of endometriosis than nonendometriosis patients. CONCLUSION(S): By combining univariate and multivariate analyses, profiles of cytokines more likely to be enriched or depleted in infertility patients with endometriosis compared with those without endometriosis were identified. These findings may inform future analyses of pathophysiological mechanisms of endometriosis in infertile patients, including dysregulated Th1/Th2 response and mobilization and proliferation of hematopoietic stem cells.

Endometriosis-associated infertility: aspects of pathophysiological mechanisms and treatment options.

Endometriosis is a common condition in women of reproductive age. In addition to pain, endometriosis may also reduce fertility. The causes of infertility in women with endometriosis may range from anatomical distortions due to adhesions and fibrosis to endocrine abnormalities and immunological disturbances. In some cases, the various pathophysiological disturbances seem to interact through mechanisms so far not fully understood. Whether surgery should be offered as a treatment option in endometriosis-associated infertility has become controversial, partly due to its modest or undocumented effect. Medical or hormonal treatment alone has little or no effect and should only be used in conjunction with assisted reproductive technology (ART). Of the various methods of ART, intrauterine insemination, due to its simplicity, can be recommended in women with minimal or mild peritoneal endometriosis, even though insemination may yield a lower success rate than in women without endometriosis. In vitro fertilization (IVF) is an effective treatment option in less-advanced disease stages, and the success rates are similar to the results in other causes of infertility. However, women with more advanced stages of endometriosis have lower success rates with IVF.

Reversible RNA modifications in meiosis and pluripotency.

Post-transcriptional RNA modifications were discovered several decades ago, but the reversible nature of RNA modifications has only recently been discovered. Owing to technological advances, knowledge of epitranscriptomic marks and their writers, readers and erasers has recently advanced tremendously. Here we focus on the roles of the dynamic methylation and demethylation of internal adenosines in mRNA in germ cells and pluripotent stem cells.

Broad histone H3K4me3 domains in mouse oocytes modulate maternal-to-zygotic transition.

Maternal-to-zygotic transition (MZT) is essential for the formation of a new individual, but is still poorly understood despite recent progress in analysis of gene expression and DNA methylation in early embryogenesis. Dynamic histone modifications may have important roles in MZT, but direct measurements of chromatin states have been hindered by technical difficulties in profiling histone modifications from small quantities of cells. Recent improvements allow for 500 cell-equivalents of chromatin per reaction, but require 10,000 cells for initial steps or require a highly specialized microfluidics device that is not readily available. We developed a micro-scale chromatin immunoprecipitation and sequencing (µChIP-seq) method, which we used to profile genome-wide histone H3 lysine methylation (H3K4me3) and acetylation (H3K27ac) in mouse immature and metaphase II oocytes and in 2-cell and 8-cell embryos. Notably, we show that ~22% of the oocyte genome is associated with broad H3K4me3 domains that are anti-correlated with DNA methylation. The H3K4me3 signal becomes confined to transcriptional-start-site regions in 2-cell embryos, concomitant with the onset of major zygotic genome activation. Active removal of broad H3K4me3 domains by the lysine demethylases KDM5A and KDM5B is required for normal zygotic genome activation and is essential for early embryo development. Our results provide insight into the onset of the developmental program in mouse embryos and demonstrate a role for broad H3K4me3 domains in MZT.

Autotransplantation of cryopreserved ovarian tissue after treatment for malignant disease - the first Norwegian results.

INTRODUCTION: With increasing survival rates after treatment for cancer in prepubertal girls and women of reproductive age, an increasing focus on quality of life has emerged. Both irradiation and cytotoxic drugs can be detrimental to future fertility, consequently several treatment alternatives have been developed to spare or restore fertility in young females diagnosed with cancer. One of these options is cryopreservation of ovarian tissue before treatment and autotransplantation at a later time. MATERIAL AND METHODS: We present the Norwegian experience after 11 years of practice with ovarian tissue cryopreservation. A total of 164 patients have had ovarian tissue cryopreserved during the period 2004-2014. Fifteen patients died during the observation period. Six patients requested autotransplantation, which was performed in two women. RESULTS: Both patients conceived, one spontaneously and one after assisted reproduction due to a concomitant male factor. The pregnancies were uneventful and they each gave birth to a healthy child. CONCLUSIONS: Cryopreservation with later autotransplantation of ovarian tissue should be offered to a selected group of young women with cancer.

Maternal age and serum concentration of human chorionic gonadotropin in early pregnancy.

OBJECTIVE: To study whether maternal age is associated with serum concentration of human chorionic gonadotropin in early pregnancy. DESIGN: Cross-sectional study. SETTING: Oslo University Hospital in Oslo, Norway. POPULATION: All vital pregnancies in gestational week 8 conceived by in vitro fertilization between February 1996 and February 2013 (n = 4472). METHODS: Serum concentrations of human chorionic gonadotropin were measured on day 12 after embryo transfer/day 16 following ovulation induction. Trends in geometric means of human chorionic gonadotropin concentrations by maternal age group were tested by linear regression analysis. We also studied the association of maternal age (years) with log-transformed human chorionic gonadotropin concentrations, and adjustments were made for number of embryos transferred, method of in vitro fertilization and year (period) of embryo transfer. MAIN OUTCOME MEASURE: Serum concentration of human chorionic gonadotropin. RESULTS: Geometric mean concentrations of human chorionic gonadotropin decreased with increasing maternal age (p = 0.024, test for trend by weighted linear regression). Also, we estimated a significant negative association of maternal age with log-transformed human chorionic gonadotropin concentrations (adjusted regression coefficient -0.011, standard error 0.003, p < 0.001). CONCLUSIONS: Serum concentrations of human chorionic gonadotropin in very early pregnancy decreased with maternal age. Since human chorionic gonadotropin is synthesized in trophoblast cells only, the lower human chorionic gonadotropin concentrations in women of advanced age may reflect functional impairment or delayed proliferation of trophoblast cells in early pregnancy in these women.

Do endometriomas induce an inflammatory reaction in nearby follicles?

STUDY QUESTION: Do endometriomas induce an inflammatory reaction with increased cytokine concentrations in nearby follicles and thereby affect follicular development during controlled ovarian stimulation for in vitro fertilization (IVF)? SUMMARY ANSWER: With most endometriomas, there is no evidence of increased cytokine concentrations in the ipsilateral leading follicle. Infrequently, the concentration of inflammatory cytokines is increased in the follicular fluid (FF) and associated with diminished ovarian response. WHAT IS KNOWN ALREADY: The link between peritoneal endometriosis, inflammation and infertility is well established; however, the association between intraovarian inflammation and endometrioma is unknown. STUDY DESIGN, SIZE, DURATION: This prospective cohort study included 117 infertile women undergoing IVF in a tertiary infertility clinic at Oslo University Hospital Rikshospitalet, Norway, during the period May 2009 to September 2011. PARTICIPANTS, SETTING, METHODS: There were 47 patients with unilateral endometrioma and 17 patients with bilateral endometrioma, while the 53 control patients had unexplained or male factor infertility. Concentrations of IL-1ß, IL-6, IL-8, IL-10, IL-12 and TNF-α were measured in serum and in the fluid of the largest pre-ovulatory follicles from each ovary of each participant. MAIN RESULTS AND THE ROLE OF CHANCE: Cytokine levels in the follicular fluid from the two ovaries in women with unilateral endometriomas were comparable, and were not significantly altered compared with that of control groups with male factor infertility, unexplained infertility or bilateral endometriomas. Compared with serum levels, the follicular fluid levels of IL-8 and IL-6 were higher, suggesting a local production or recruitment. The follicular fluid IL-8 level varied considerably and showed an inverse relationship with IL-12, IL-10 and TNF-∝, suggesting a complex interaction between various immune cells. A small group of patients (n = 3) had increased levels of all follicular fluid cytokines combined with moderately to slightly elevated serum levels and these patients had a significantly lower ovarian response. LIMITATIONS, REASONS FOR CAUTION: For ethical reasons, the endometriomas were diagnosed indirectly by ultrasound rather than by histology. WIDER IMPLICATIONS OF THE FINDINGS: This paper reveals that endometriomas seldom induce inflammation in nearby follicles during IVF; therefore, routine cystectomy prior to IVF may not be necessary. Cytokine levels in the follicular fluid, nonetheless, show distinctive patterns and increased levels may be linked to reduced ovarian response independent of the cause of infertility.

Maternal body mass index and serum concentrations of human chorionic gonadotropin in very early pregnancy.

OBJECTIVE: To study the association of maternal prepregnancy body mass index (BMI) with serum concentrations of hCG in early pregnancy. DESIGN: Cross-sectional study. SETTING: Oslo University Hospital, Norway, 1996-2010. PATIENT(S): Among 3,301 pregnancies with live-born offspring conceived after assisted reproductive techniques, 2,611 women had information on serum hCG concentrations on day 16 after ovulation induction and prepregnancy BMI: 2,110 mothers with singleton and 501 mothers with multiple pregnancy. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Human chorionic gonadotropin concentration. RESULT(S): Geometric mean hCG concentration was higher in multiple pregnancies (190 IU/L) than in singleton pregnancies (106 IU/L). In singleton pregnancies geometric mean serum concentration decreased from 117 IU/L in women with BMI <20 kg/m(2) to 86 IU/L in women with BMI ≥ 35 kg/m(2). In multiple pregnancies, the corresponding decrease was from 226 IU/L to 130 IU/L. There was a significant negative association of BMI with hCG concentrations log transformed in the study sample as a whole (regression coefficient -0.013), in singleton pregnancies (regression coefficient -0.012), and in multiple pregnancies (regression coefficient -0.03). CONCLUSION(S): Serum hCG concentrations were negatively associated with maternal prepregnancy BMI. One possible explanation may be an effect of adipose tissue-derived signaling molecules on hCG secretion by the implanting embryo.

Interaction between granulosa-lutein cells and monocytes regulates secretion of angiogenic factors in vitro.

BACKGROUND: Leukocyte infiltration and angiogenesis in the forming corpus luteum are prerequisites for normal ovarian function and may also underlie disorders like ovarian hyperstimulation syndrome. We examined whether ovarian angiogenesis could be affected by an interaction between granulosa-lutein (GL) cells and leukocytes. METHODS AND RESULTS: We found that GL cells isolated from the follicular fluid synthesize and secrete the chemokine interleukin-8 (IL-8), which activates IL-8-receptor-specific Ca(2+) and p38 mitogen-activated protein kinase signalling in monocytes and induces a directed migration of these cells towards the chemical gradient. Monocytes were found to further enhance IL-8 release, which suggests that these cells promote a massive leukocyte infiltration of the forming corpus luteum. A possible utility of leukocyte infiltration is the modulation of angiogenesis. We found that GL cells induce migration and capillary tube formation by endothelial cells in vitro. Furthermore, monocytes altered the profile of angiogenic factors released by GL cells, which supports the theory that an interaction between GL cells and leukocytes regulates ovarian angiogenesis. In addition, we found a correlation between increased secretion of pro-angiogenic cytokines and number of oocytes collected during IVF, which suggests that ovarian angiogenesis is related to the clinical response during ovarian stimulation. CONCLUSIONS: An intricate communication may exist between infiltrating leukocytes and ovarian GL cells during the formation of corpus luteum, affecting neo-vascularization of the luteal tissue.

Sustained fertility from 22 to 41 years of age in women with polycystic ovarian syndrome.

BACKGROUND: Subfertility due to chronic anovulation is common in women with polycystic ovary syndrome (PCOS) and is often treated with IVF. Women with PCOS have an increased ovarian follicle and oocyte count, increased ovarian reserve and/or a slower rate of follicle atresia. If so, one would expect women with PCOS to display a delayed reduction in fertility with advancing age as compared with eumenorrheic women. METHODS: To test this hypothesis, we compared oocyte count and live birth rates among two groups undergoing IVF, 500 women with PCOS and 500 eumenorrheic women with infertility due to tubal factor only. RESULTS: Across the age range of 22-41 years, oocyte count and live birth rates remained stable in women with PCOS. In the eumenorrheic comparison group, these parameters decreased significantly with age. CONCLUSIONS: Women with PCOS display sustained fertility with advancing age as compared with infertile eumenorrheic women.

Differential release of matrix metalloproteinases and tissue inhibitors of metalloproteinases by human granulosa-lutein cells and ovarian leukocytes.

Tissue reorganization during ovulation and corpus luteum formation involves a coordinated action of matrix metalloproteinases (MMPs) and tissue MMP inhibitors (TIMPs). In this study we investigated the cellular source of ovarian MMPs and TIMPs. Cells isolated from the preovulatory human follicle were cultured after immunobead depletion of CD45-expressing cells, which allowed differential assessment of leukocyte and granulosa-lutein cell fractions. Secretion of MMP-9 by follicular fluid-derived cells was associated with the presence of leukocytes. Granulosa-lutein cells synthesized low levels of MMP-9 but failed to secrete this enzyme that presumably accumulated in the cytoplasm, indicated by an increased MMP-9 expression of luteinized cells in sectioned midluteal phase corpora lutea. Synthesis and secretion of TIMP by follicular fluid-derived cells was associated with granulosa-lutein cells. TIMPs derived by granulosa-lutein cells failed to inhibit MMP-related pericellular proteolysis. The findings support a two-cell model of periovulatory MMP/TIMP release, in which leukocytes secrete MMPs and granulosa-lutein cells release TIMP, suggesting that there exists an intriguing interaction among cells that intertwingle during ovulation and corpus luteum formation.

Cellular interaction regulates interleukin-8 secretion by granulosa-lutein cells and monocytes/macrophages.

PROBLEM: Peri-ovulatory migration of leukocytes towards the follicle plays an important role during corpus luteum formation. In this study, we examined the secretion of the neutrophil chemoattractant interleukin (IL)-8 by ovarian GL cells and the role of monocytes in IL-8 secretion. METHOD OF STUDY: Granulosa-lutein cells were isolated from the pre-ovulatory follicle. After depletion of contaminating leukocytes, GL cells were co-cultured with the myelo-monocytic cell line THP-1. Intracellular IL-8 accumulation, IL-8 secretion, and chemotactic activity of cell culture media were examined. RESULTS: Intracellular IL-8 was predominantly localized in the endoplasmatic reticulum-Golgi both in GL cells and in THP-1 cells. In co-cultured cells, intracellular IL-8-specific immunofluorescence and IL-8 secretion were increased compared with either GL cells or THP-1 cells that were cultured alone. Conditioned cell culture media from GL cells and THP-1 cells induced directed cell migration by neutrophils. CONCLUSION: Human GL cells constitutively synthesize IL-8. An increased IL-8 secretion by co-cultured GL cells and THP-1 cells suggest that GL cells and monocytes mutually induce chemokine secretion. An initial interaction between GL cells and ovarian leukocytes may therefore contribute to an increased chemokine release and leukocyte recruitment to the forming corpus luteum.

[Gonadal function after cancer treatment in adult men]. / Gonadal funksjon etter kreftbehandling hos voksne menn.

BACKGROUND: Surgery, chemotherapy and radiation, but also long-term hormonal treatment may cause reduced gonadal function in male cancer patients. The germinal epithelium is more vulnerable to cytotoxic damage than the Leydig cells, which implies that subfertility/infertility is a more frequent side effect of cancer treatment than endocrine hypogonadism. MATERIAL AND METHODS: This review article is based on clinical experience and literature retrieved from PubMed. RESULTS AND INTERPRETATION: The degree of gonadal damage depends on the type of chemotherapy and the cumulative dose; with alkylating substances and procarbazine being the most gonadotoxic agents. The testicle is one of the most radiosensitive organs, and the damage depends on the radiation dose. Testicle damage may be caused by direct radiation of the testicles or scattered radiation from radiated adjacent tissue. Freezing of semen should be discussed with and offered to all men below 55 years that are about to undergo cancer treatment that may cause reduced fertility. Men surviving cancer who experience unwanted childlessness should be offered examination, advice and possibly assisted fertilization as part of the rehabilitation. Especially after intensive chemotherapy and high dose cranial radiation therapy the patient should be examined regularly throughout life with respect to premature endocrine hypogonadism.

Effects of leptin and leukemia inhibitory factor on preimplantation development and STAT3 signaling of mouse embryos in vitro.

Preimplantation mouse embryos simultaneously express receptors for leptin and leukemia inhibitory factor (LIF), both of which trigger activation of STAT3 (Signal Transducer and Activator of Transcription) protein. To examine the joint effects of leptin and LIF on embryonic development, we studied preimplantation development and activation of STAT3 signaling of mouse embryos after exposure to leptin and/or LIF in vitro. Two-cell mouse embryos (Day 2) were cultured in the presence of leptin and/or LIF. Significantly fewer leptin-exposed than control embryos hatched by Day 5 and by Day 6 of development. In addition, cells of leptin-exposed Day 5 blastocysts showed a higher rate of DNA fragmentation, which is a sign of apoptosis. Leukemia inhibitory factor alone had no effect on the rates of embryonic development or DNA fragmentation. Simultaneous exposure of embryos to leptin and LIF increased the proportion of hatching embryos and decreased the rate of apoptosis compared to embryos exposed to leptin only. Leptin treatment was associated with an increased phospho-STAT3-specific immunofluorescence in the cell membrane of blastocysts, which was not observed in LIF-exposed embryos. In conclusion, LIF modifies the effect of leptin during preimplantation embryo development in mice, presumably by interfering with activation of STAT3 signaling.